Patent Application
20050009456
The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a polishing apparatus having a structure which can mount a polishing tool such as a fixed abrasive on a polishing table reliably.
As semiconductor devices have become more highly integrated in recent years, circuit interconnections become finer and dimensions of integrated devices become smaller. Therefore, there has been required a process for polishing and removing a film formed on a surface of a semiconductor wafer to planarize the surface of the semiconductor wafer. A polishing apparatus for performing chemical mechanical polishing (CMP) has been used for planarizing the surface of the semiconductor wafer.
This type of polishing apparatus comprises a polishing table having a polishing cloth (polishing pad) attached thereon, and a top ring for holding a workpiece, to be polished, such as a semiconductor wafer. The workpiece is disposed between the polishing pad and the top ring and pressed against the polishing pad under a certain pressure by the top ring while the polishing table and the top ring are being rotated. The workpiece is polished to a flat mirror finish while a polishing liquid (slurry) is being supplied onto the polishing pad.
As described above, the chemical mechanical polishing (CMP) process has been employed in a semiconductor device fabrication process to planarize irregularities on a surface of a semiconductor wafer which are formed in a deposition process of an insulating film or an interconnection metal film, for example. According to the chemical mechanical polishing process, a workpiece such as a semiconductor wafer is held by the top ring and pressed against a polishing pad made of hard polyurethane foam or the like. The workpiece is polished to a flat mirror finish while a polishing liquid (slurry) is being supplied onto the polishing pad. The polishing pad is attached on a polishing table by an adhesive tape or the like.
Depending on the type of films to be polished or slurry to be used, the polishing rate of a wafer or the uniformity of the polishing rates within a wafer can be improved by providing grooves of a lattice-like pattern or concentric grooves in the surface of the polishing pad. Once the adhesive tape which has been used to bond the polishing pad to the polishing table is peeled off, it cannot be reused because its adhesive strength is lowered. When the polishing pad is directly attached to the polishing table, the expensive polishing pad needs to be discarded each time the polishing pad is replaced according to the type of films to be polished or slurry to be used. Therefore, attempts have been made to reduce the cost of the polishing pads. Specifically, the polishing pad is bonded to a polishing pad attachment typified by a base which is made of a material having a high mechanical strength, such as metal or engineering plastics, and the base is fixed to the polishing table with a mechanism that allows the base to easily be attached to and detached from the polishing table. In such attempts, the polishing pad can be replaced many times.
In the chemical mechanical polishing process using a polishing liquid (slurry) as described above, a workpiece is polished while a polishing liquid containing a large amount of abrasive particles is being supplied onto a relatively soft polishing pad. Therefore, the problem of pattern dependence arises. The pattern dependence means that gentle irregularities are formed on a surface of a semiconductor wafer after the polishing process due to irregularities on the surface of the semiconductor wafer that has existed before the polishing process, thus making it difficult to planarize the surface of the semiconductor wafer to a completely flat surface. Specifically, the polishing rate is higher for irregularities having small pitches and is lower for irregularities having large pitches, and the existence of areas of the higher polishing rate and areas of the lower polishing rate causes gentle irregularities to be formed on the surface of the semiconductor wafer.
It has also been practiced to polish a semiconductor wafer with use of a fixed abrasive (grindstone) which comprises abrasive particles of cerium oxide (CeO2), TiO2, SiO2, Al2O3, ZrO2, MnO2, Mn2O3, or the like fixed by a binder such as a thermoplastic resin or a thermosetting resin (phenolic resin), instead of a polishing pad made of hard polyurethane foam or the like. The polishing process with use of the fixed abrasive is advantageous in that the polishing material, i.e., the fixed abrasive, is harder than the polishing pad used in the conventional CMP process, and tends to polish convexities of the irregularities more than concavities thereof, for thereby achieving a higher absolute level of planarity. Depending on the composition of the fixed abrasive, the fixed abrasive provides a self-stop function which considerably lowers the polishing rate and practically stops the polishing process when the convexities of the irregularities are polished to a flat surface. The polishing process with use of the fixed abrasive is also advantageous in that the environmental load can be reduced because of no use of a suspension liquid (slurry) containing a large amount of abrasive particles. Further, while most of the abrasive particles supplied to the polishing pad are discharged without contributing to the polishing process, the fixed abrasive polishes the workpiece by loosening a minimum amount of abrasive particles on the polishing surface with a dressing (conditioning) process. Therefore, the fixed abrasive has been expected to lower the cost and reduce the environmental load.
Such a hard fixed abrasive is more liable to crack under external shocks than the polishing pad made of hard polyurethane foam or the like. Therefore, more care should be given to handling the fixed abrasive. The fixed abrasive is heavy and difficult to be attached to the polishing table by an adhesive tape unlike the polishing pad. In order to protect the fixed abrasive and to facilitate the attachment of the fixed abrasive to the apparatus, the fixed abrasive is fixed to a fixed abrasive attachment (base) made of a material having a high mechanical strength, such as metal or engineering plastics, by an adhesive or the like. The base is fixed to the polishing table with a mechanism that allows the base to easily be attached to and detached from the polishing table.
Generally, the processing temperature rises during polishing due to the frictional heat produced between the workpiece and the polishing tool and the heat of the chemical reaction between chemical substances in the polishing liquid and the film being polished. If the temperature increases rapidly or drastically, then the base or the polishing tool is thermally expanded and deformed to such an extent that the polishing surface loses its planarity.
When the base 902 and the polishing tool 903 are deformed to such an extent that the polishing surface on the polishing tool 903 loses its planarity, the processing pressure (polishing pressure) periodically varies, i.e., components in the polishing apparatus vibrate, due to the lack of the planarity of the polishing surface. The vibration promotes the metal fatigue of components in the polishing apparatus. Therefore, the components in the polishing apparatus are frequently damaged, so that the maintenance cost of the polishing apparatus increases. Furthermore, when the processing pressure excessively increases by the vibration, a scratch may be caused on the workpiece such as a semiconductor wafer, thus resulting in a reduction in yield.
If the polishing tool 903 and the base 902 have largely different coefficients of thermal expansion from each other, then the polishing tool 903 and the base 902 are so distorted relatively to each other that the adhesive layer is broken by a produced shearing force, thus exfoliating the polishing tool 903 from the base 902.
Further, since the fixed abrasive has a low mechanical strength, it is difficult to mount the fixed abrasive directly on a conventional polishing table. Therefore, the fixed abrasive needs to be attached to a cartridge table (base table) having a sufficient strength. However, the cartridge table having a high strength and the fixed abrasive comprising fixed abrasive particles are heavy. Thus, the cartridge table having the fixed abrasive attached thereto is so heavy that the fixed abrasive is difficult to be moved and cannot be handled with ease. As a result, it is difficult to position the fixed abrasive with respect to the main table. Furthermore, it is very difficult to accomplish attachment of the heavy cartridge table on the main table.
Consequently, a fixed abrasive for polishing a semiconductor wafer has been composed of a base table which is made of a very light material and a thin fixed abrasive. Thus, it is practically difficult to increase the thickness of the fixed abrasive so as to prolong the service life thereof.
The present invention has been made in view of the above drawbacks. It is a first object of the present invention to provide a polishing apparatus having a structure which can minimize a distortion of a polishing surface due to thermal expansion of a polishing tool (a polishing pad, a fixed abrasive, or the like) and a base, and can prevent the polishing tool from being detached from the base.
A second object of the present invention is to provide a polishing tool assembly and a polishing apparatus having such a polishing tool assembly which can prevent a portion of a peripheral edge of a workpiece, such as a semiconductor wafer from being excessively polished, and can uniformly process the workpiece.
A third object of the present invention is to provide a polishing apparatus which can prolong the service life of a polishing tool, facilitate handling of a polishing tool, and improve the safety of the operator, and a method of assembling a cartridge table having a polishing tool on a main table.
According to a first aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a table; a base placed on the table; and a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece; wherein the base has at least a portion which is not fixed to the table for allowing the base to be deformed through the portion.
Since the base has at least a portion which is not fixed to the table, when the base is deformed due to thermal expansion, such a deformation is allowed to occur at the portion which is not fixed to the table. Thus, the polishing surface of the polishing tool can be kept flat.
According to a preferred aspect of the present invention, the polishing apparatus further comprises a fixing member for fixing the base to the table.
Since the polishing apparatus has the fixing member for fixing the base to the table, the base with the polishing tool fixed thereto can easily be mounted on and dismounted from the table.
According to a preferred aspect of the present invention, the polishing apparatus further comprises a transmission member provided on the table at a position where the base is not fixed to the table; wherein the table makes a motion, and the motion of the table is transmitted to the base through the transmission member.
Since the transmission member is provided for transmitting the motion of the table to the base at a position where the base is not fixed to the table, the deformation of the base and the polishing tool due to thermal expansion is allowed to occur at the portion of the base which is not fixed to the table. At the same time, the motion of the table can be transmitted to the base through the transmission member.
According to a preferred aspect of the present invention, the base comprises a plurality of base segments.
In the case where the polishing tool and the base are large in size, since the base comprises a plurality of base segments, the base can easily be handled when the base is placed on and displaced from the table.
According to a preferred aspect of the present invention, the polishing tool comprises a fixed abrasive.
In the case where the polishing tool comprises the fixed abrasive as described above, the present invention can offer the following advantages: A flatness of the polishing surface can be maintained, the base can easily be attached to or detached from the table, the deformation of the polishing tool due to thermal expansion can be allowed to occur, and the motion of the table can be transmitted to the base.
According to a preferred aspect of the present invention, the base is made of a material whose coefficient of linear expansion ranges from {fraction (1/100)} to 100 times a coefficient of linear expansion of the polishing tool.
Since the base is made of a material whose coefficient of linear expansion ranges from {fraction (1/100)} to 100 times the coefficient of linear expansion of the polishing tool, the polishing tool and the base are deformed substantially equally to each other when thermal expansion occurs due to an increase in temperature caused by the polishing process. Therefore, shearing forces acting on the adhesive layer between the polishing tool and the base can be reduced, thus preventing the polishing tool from being detached from the base.
According to another aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a table; a base placed on the table and having an annular shape; a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece; and a fixing member for fixing the base to the table; wherein an inner circumferential portion of the base is fixed to the table by the fixing member and an outer circumferential portion of the base is not fixed to the table so as to allow the base to be deformed radially outwardly.
According to a preferred aspect of the present invention, the base comprises a plurality of base segments having a fan shape.
According to a preferred aspect of the present invention, a polishing apparatus further comprises a plurality of transmission members provided along a circumferential direction of the table; and a plurality of holes formed in the base and having an elongate shape extending in the radial direction of the base, the transmission members being inserted into the holes, respectively, for transmitting the motion of the table to the base.
According to still another aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a table; a base placed on the table and having an annular shape; a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece; and a fixing member for fixing the base to the table; wherein the base comprises a plurality of base segments, the polishing tool comprises a plurality of polishing tool segments which are fixed to the plurality of base segments, respectively, and an outer circumferential portion of the base is fixed to the table by the fixing member and an inner circumferential portion of the base is not fixed to the table so as to allow the base to be deformed radially inwardly.
According to a preferred aspect of the present invention, each of the base segments has a fan shape.
According to a preferred aspect of the present invention, a polishing apparatus further comprises a plurality of transmission members provided along a circumferential direction of the table; and a plurality of holes formed in the base and having an elongate shape extending in the radial direction of the base, the transmission members being inserted into the holes, respectively, for transmitting the motion of the table to the base. The elongate shape includes, for example, an elliptical shape and a rectangular shape.
According to still another aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a table which makes a motion; a base placed on the table; a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece; a plurality of transmission members provided along a circumferential direction of the table; and a plurality of holes formed in the base and having an elongate shape extending in the radial direction of the base, the transmission members being inserted into the holes, respectively, for transmitting the motion of the table to the base.
According to-still another aspect of the present invention, there is provided a polishing tool assembly for polishing a workpiece, comprising: a base positionable on a table; a polishing tool fixed to the base and having a polishing surface for polishing a surface of the workpiece, the polishing tool comprising a fixed abrasive; and a plurality of holes formed in the base and having an elongate shape extending in the radial direction of the base; wherein the holes are arranged to allow a plurality of transmission members provided along a circumferential direction of the table to be inserted therein when the polishing tool assembly is mounted on the table.
In order to achieve the second object, according to a second aspect of the present invention, there is provided a polishing tool assembly for polishing a workpiece, comprising: a plurality of polishing tool segments having a polishing surface for polishing a surface of the workpiece; and a polishing tool attachment for holding the polishing tool segments thereon in such a state that the circumferentially adjacent polishing tool segments are held in close contact with each other.
According to the present invention, the circumferentially adjacent polishing tool segments are held in close contact with each other. Therefore, when the workpiece is brought into sliding contact with the polishing surface across the polishing tool segments, a pressure acting on the surface of the workpiece does not change, and hence the surface of the workpiece can uniformly be processed. Since the polishing tool assembly comprises a plurality of polishing tool segments, each of the polishing tool segments can be made small in size, and the polishing tool assembly can be manufactured with small-scale equipments for forming the polishing tool assembly. Thus, initial investments and the manufacturing-cost of the polishing tool assembly can be reduced.
According to a preferred aspect of the present invention, the polishing tool segment comprises a fixed abrasive having abrasive particles fixed by a binder.
According to a preferred aspect of the present invention, each of the polishing tool segments is in a sectorial or fan-shaped form, and the circumferentially adjacent polishing tool segments are held in close contact with each other to form a disk or cylindrical shape as a whole.
Thus, each of the polishing tool segments is in a sectorial or fan-shaped form, and the circumferentially adjacent polishing tool segments are held in close contact with each other. Therefore, even though the polishing tool assembly comprises a plurality of polishing tool segments, the polishing tool segments can easily be positioned with respect to each other so as to form a disk or cylindrical shape as a whole when the polishing tool segments are mounted on the polishing tool attachment. Accordingly, the polishing tool can easily be assembled in a simple process.
According to a preferred aspect of the present invention, the polishing tool segments are mounted on the polishing tool attachment in such a state that the polishing tool segments are positioned with use of a positioning member mounted around the outer circumferential edges of the polishing tool segments.
According to a preferred aspect of the present invention, the polishing tool attachment has an outside diameter larger than the polishing tool segments. This arrangement can provide an attachment portion at a peripheral edge of the polishing tool attachment for attaching the polishing tool attachment to a polishing table.
According to a preferred aspect of the present invention, the polishing tool segments are mounted on a single polishing tool attachment.
According to a preferred aspect of the present invention, the polishing tool attachment is divided into a plurality of attachment segments so as to correspond to the polishing tool segments, and the polishing tool segments are mounted on the respective attachment segments.
In a CMP apparatus for polishing a 12-inch wafer, a polishing tool (fixed abrasive) has a diameter ranging from 700 to 800 mm and is heavy. Therefore, the polishing tool cannot be handled with ease at the time of replacement thereof. According to the present invention, the polishing tool segments are mounted on the attachment segments divided so as to correspond to the respective polishing tool segments. Therefore, even if the polishing tool assembly has a large diameter and is heavy, the polishing tool segments can easily be handled together with the respective attachment segments. Accordingly, a smaller space is required in a clean room for replacing the polishing tool assembly. Further, each of the polishing tool segments is so light in weight that it can easily be handled without any special device such as a crane or a lifter. As a result, the polishing tool assembly can be handled with ease in the clean room.
In order to achieve the second object, according to a third aspect of the present invention, there is provided a polishing apparatus for polishing a workpiece, comprising: a workpiece holding device for holding the workpiece; the aforementioned polishing tool assembly; and a polishing table on which the polishing tool is mounted.
In order to achieve the third object, according to a fourth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing tool having a polishing surface for polishing a surface of a workpiece; a cartridge table having a surface on which the polishing tool is mounted; a main table disposed so as to face a reverse surface of the cartridge table and having a support surface for supporting the cartridge table thereon; a moving mechanism mounted on the reverse surface of the cartridge table or the support surface of the main table for facilitating movement of the cartridge table along the main table; and a positioning member for positioning the cartridge table with respect to the main table. The support surface of the main table may support the cartridge table directly or may support the cartridge table through another member.
According to the present invention, as shown in, for example,
According to a preferred aspect of the present invention, the moving mechanism comprises a rolling element which rolls on the support surface of the main table, or the reverse surface of the cartridge table.
According to a preferred aspect of the present invention, the positioning member comprises a recess formed in the support surface of the main table or the reverse surface of the cartridge table for accommodating the rolling element.
As shown in
According to a preferred aspect of the present invention, a polishing apparatus further comprises a fastening member for securing the cartridge table to the main table.
According to a preferred aspect of the present invention, the moving mechanism is disposed in point symmetry with respect to a center of the surface on which the moving mechanism is mounted.
With the above arrangement, as shown in, for example,
According to a preferred aspect of the present invention, the polishing tool comprises a fixed abrasive.
In order to achieve the third object, according to a fifth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing tool having a polishing surface for polishing a surface of a workpiece; a cartridge table having a surface on which the polishing tool is mounted; a main table disposed so as to face a reverse surface of the cartridge table and having a support surface for supporting the cartridge table thereon; a rolling element mounted on the reverse surface of the cartridge table or the support surface of the main table and rolling on the support surface of the main table or the reverse surface of the cartridge table; and a recess formed in the support surface of the main table or the reverse surface of the cartridge table for accommodating the rolling element.
In order to achieve the third object, according to a sixth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing tool having a polishing surface for polishing a surface of a workpiece; a cartridge table having a surface on which the polishing tool is mounted; and a main table disposed so as to face a reverse surface of the cartridge table and having a support surface for supporting the cartridge table thereon; wherein the cartridge table is coupled to a carrier device for carrying the cartridge table onto the support surface of the main table when the cartridge table is to be mounted on the main table and carrying the cartridge table upwardly above the support surface when the cartridge table is dismounted from the main table.
According to the present invention, as shown in, for example,
According to a preferred aspect of the present invention, a polishing apparatus further comprises a jig attached to the cartridge table and having a coupling member through which the cartridge table is coupled to the carrier device.
With the above arrangement, the cartridge table 316 is coupled to the carrier device 501 by the coupling member. If the carrier device 501 holds the cartridge table 316 and carries the cartridge table 316 upwardly, then the portion of the cartridge table 316 which is held by the carrier device 501 serves as the coupling member. If the carrier device 501 grips and carries the cartridge table 316 upwardly, then the portion of the cartridge table 316 which is gripped serves as the coupling member. The cartridge table 16 may be directly coupled to the carrier device 501 or may be indirectly coupled to the carrier device 501 through the coupling member 337.
According to a preferred aspect of the present invention, the polishing apparatus has a space to allow the carrier device to access the main table.
With the above arrangement, as shown in, for example,
As shown in
According to a preferred aspect of the present invention, a polishing apparatus further comprises a fastening member for securing the cartridge table to the main table.
With the above arrangement, as shown in, for example,
In order to achieve the third object, according to a seventh aspect of the present invention, there is provided a method of assembling a cartridge table, comprising: preparing a cartridge table having a surface on which a polishing tool is mounted, the polishing tool having a polishing surface for polishing a surface of a workpiece; attaching a jig having a coupling member to the cartridge table; coupling the jig attached to the cartridge table through the coupling member to a carrier device; carrying the cartridge table to a position above a support surface of a main table for supporting the cartridge table by the carrier device, and lowering the cartridge table to place the cartridge table onto the support surface by the carrier device; removing the jig from the cartridge table; moving the cartridge table along the support surface of the main table by a moving mechanism which is mounted on a reverse surface of the cartridge table or the support surface of the main table; and positioning the cartridge table with respect to the main table by a positioning member.
According to a preferred aspect of the present invention, the moving mechanism comprises a rolling element which rolls on the support surface of the main table or the reverse surface of the cartridge table.
According to a preferred aspect of the present invention, the positioning member comprises a recess, and the positioning is performed by accommodating the rolling element into the recess.
A polishing apparatus according to embodiments of the present invention will be described below with reference to the drawings.
The polishing tool 10 comprises a polishing pad made of hard polyurethane foam or the like, or a fixed abrasive. In this embodiment, the disk-shaped fixed abrasive is used as the polishing tool 10. The polishing tool 10 is fixed to an upper surface of the base 20 by an adhesive or the like. The base 20 comprises a disk-shaped member and serves to protect the polishing tool 10 comprising the fixed abrasive and also to allow the polishing tool 10 to easily be mounted on the polishing table 30. The base 20 is made of a material, such as metal or engineering plastics, which has a high mechanical strength and a high chemical resistance. The base 20 has a bolt insertion hole 21 which passes therethrough at a central portion of the base 20. A bolt 40 is inserted through the bolt insertion hole 21 and is screwed into the polishing table 30, so that the base 20 is fastened to the polishing table 30.
The base 20 has an outside diameter slightly larger than that of the polishing tool 10, and hence has a flange projecting radially outwardly from an outer circumferential edge of the polishing tool 10. The flange of the base 20 has a plurality of drive pin insertion holes 22 disposed at substantially equal intervals along the circumferential direction of the base 20, and drive pins 41 are inserted into the drive pin insertion holes 22, respectively, and fixed to the polishing table 30. Each of the drive pin insertion holes 22 has an elongate shape such as an elliptical shape extending in the radial direction of the base 20. Specifically, the width of the drive pin insertion hole 22 in the circumferential direction of the base 20 is slightly larger than the diameter of the drive pin 41, and the length of the drive pin insertion hole 22 in the radial direction of the base 20 is several times longer than the diameter of the drive pin 41. In the portions of the drive pin insertion holes 22, the flange of the base 20 is not fixed in the radial direction thereof with respect to the polishing table 30. Therefore, the base 20 and the polishing tool 10 can be deformed in the radial direction of the polishing table 30 due to thermal expansion thereof caused by the frictional heat and the heat of chemical reaction which are produced by the polishing process. As a result, the polishing surface, i.e., upper surface, of the polishing tool 10 can be kept flat.
One or more drive pins 41 are provided on an upper surface 31 of the polishing table 30 at positions corresponding to positions of the drive pin insertion holes 22 formed in the base 20. Rotation of the polishing table 30 is transmitted to the base 20 and the polishing tool 10 by the bolt 40 and the drive pins 41. Since the drive pins 41 serve to transmit the rotation of the polishing table 30, a load applied to the bolt 40 for transmitting the rotation of the polishing table 30 is reduced.
In the case where the polishing tool 10 has a diameter of up to about 600 mm, the base 20 may be made of a material having a high mechanical strength such as aluminum alloy or engineering plastics so as to provide a sufficient mechanical strength and such a light weight that the base 20 can be handled with ease. Generally, the base 20 having a single integral structure may be used for the purpose of polishing an 8-inch semiconductor wafer.
However, in the case of polishing a semiconductor wafer having a diameter of 12 inches or larger, the polishing tool 10 is required to have a diameter of 700 mm or larger. If the base 20 having such a single integral structure is used for polishing the semiconductor wafer having a diameter of 12 inches or larger, then the base 20 is too heavy to be handled with ease.
In such a case, polishing tool segments as shown in
The fan-shaped base segment 20-1 has one or more bolt insertion holes 23 (two bolt insertion holes in the present embodiment) formed in an inner circumferential portion thereof. The base segment 20-1 is fastened by bolts 24 inserted through the bolt insertion holes 23 into a plate 50, which is secured by the bolt 40 to the central portion of the upper surface 31 of the polishing table 30. Since a plurality of the bolts 24 are used to fasten the respective base segments 20-1 to the polishing table 30, the base segments 20-1 are fixed to the polishing table 30 more firmly than in the case where the respective base segments 20-1 are fixed only by the single bolt 40. The base 20 having the single integral structure as shown in
The fan-shaped base segment 20-1 may be fastened directly to the polishing table 30 by bolts screwed into bolt insertion holes formed in the polishing table 30, without the plate 50. As with the base 20 shown in
The adjacent base segments 20-1 are spaced from each other by a gap having a width represented by {(outer circumferential length of the base 20 or the polishing tool 10 (mm))×(coefficient of linear expansion of the base segment 20-1 or the polishing tool segment 10-1 (1/° C.))×(increase in temperature due to polishing (°C))/(the number of the base segments 20-1) }. The gap is designed so as not to cause the wafer to be polished excessively on the peripheral edge of the wafer by corners of the polishing segments. The gaps and the drive pin insertion holes 22 allow the base segments 20-1 and the polishing tool segments 10-1 to be deformed due to thermal expansion not only in the radial direction of the base 20 or the polishing tool 10 but also in the circumferential direction of the base 20 or the polishing tool 10. As a result, more complete flatness of the polishing surface can be obtained. The width of the gap should preferably be larger than the larger one of the calculated value for the base segments 20-1 and the calculated value for the polishing tool segments 10-1.
The polishing tool 10, which is the assembly of the polishing tool segments 10-1, comprises a polishing pad made of hard polyurethane foam, or a fixed abrasive. The fixed abrasive is produced as follows: First, fine abrasive particles and a binder are mixed with fixed abrasive additives for thereby producing a fixed abrasive material powder. The fixed abrasive additives include an abrasive particle dispersant such as a surface-active agent, a process stabilizer such as a buffer, a process accelerator typified by a pH controller such as KOH, and a mirror finish improver such as a polymeric agent. Each of the materials to be mixed may be in the powder state or in the liquid state. If necessary, pure water may be added to the fixed abrasive material powder, thus producing a mixture. The materials in the mixture are dispersed by an agitator, an ultrasonic dispersing unit, or the like.
Next, the mixture is dried and granulated by a drying device typified by a spray dryer, and thus granulated powdery substance which is formed by uniformly mixing the above materials and has an average diameter of about 50 μm is produced.
The material for the abrasive particles as the materials of the fixed abrasive may be in the powder state or in the slurry state. However, it is preferable to use slurry-like abrasive particles as an abrasive particle material. Since the slurry-like abrasive particles contain fine abrasive particles in a stable state, when the slurry-like abrasive particles are used as the abrasive particle material, the ratio of compositions contained in the granulated powdery substance as an intermediate product can be uniformized, and the homogeneity of the fixed abrasive can be improved. Furthermore, in order to polish a semiconductor wafer with less metal contamination, the amount of any metals contained in the abrasive particle material should preferably be as small as possible. For example, the amount of metals contained in the abrasive particle material should be 100 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less, although such amount of the metals depends on the type of the abrasive particle material and the ratio of compositions contained in the abrasive particle material.
The material for the binder, which is one of the materials of the fixed abrasive, may be in the powder state or in the slurry state. However, it is preferable to use a latex suspension as a binder material. Since the latex suspension contains its components dispersed uniformly therein, when the latex suspension is used as the binder material, the ratio of compositions contained in the granulated powdery substance as an intermediate product can be uniformized, and the homogeneity of the fixed abrasive can be improved. Moreover, in order to polish a semiconductor wafer with less metal contamination, the amount of any metals contained in the binder material should preferably be as small as possible. For example, the amount of metals contained in the binder material should be 100 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less, although such amount of the metals depends on the type of the binder material and the ratio of compositions contained in the binder material.
Preferably, a synthetic resin, i.e., a synthetic micromolecular compound (polymer), is selected as the binder. The synthetic micromolecular compound (polymer) is produced by polymerization of a number of monomers. A process for producing the synthetic micromolecular compound comprises various polymerization processes including addition polymerization, copolymerization, condensation polymerization, addition condensation, and the like. The above polymerization processes use water and various chemicals including a polymerization catalyst such as an organometallic compound and an inorganometallic compound, a polymerization inhibitor, a dispersant, an activator, a solvent, a catalyst deactivator, a stabilizer, an emulsifier, an antioxidant, and the like. In this manner, the binder is produced through complex processes. In order to reduce a metallic element mixed in the binder for use in the fixed abrasive, it is preferable to reduce the amount of any metal compounds contained in chemicals and water used in the above various polymerization processes. For example, the amount of metal compounds should be 100 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less, although allowable amount of the metal compounds depends on the polymerization processes, the type of chemicals, and the amount of chemicals remaining in the binder as the product. Pure water or ultrapure water should preferably be used as the above water.
Furthermore, the amount of any metals contained in the fixed abrasive additives as part of the materials of the fixed abrasive should also preferably be as small as possible. The fixed abrasive additives include a process accelerator (amine or the like) including a microcapsule chemical, a process stabilizer (buffer), a mirror finish improver (water-soluble polymer), a polishing auxiliary such as an abrasive particles aggregation inhibitor (organic polymer), an abrasive particle self-generation regulator (resolvent for binder), a fixed abrasive formation auxiliary, and the like. For example, the amount of metals contained in such additives should be 100 ppm or less, preferably 10 ppm or less, and more preferably 1 ppm or less, although allowable amount the metals depends on the type of the additives, the ratio of addition, or the like. Pure water or ultrapure water should preferably be used.
In
The workpiece W held by the top ring 70 is pressed against the polishing surface on the polishing tool 10, and the polishing table 30 and the top ring 70 are rotated relatively to each other, thereby bring the lower surface of the workpiece W into sliding contact with the polishing surface on the polishing tool 10. At the same time, ultrapure water and a chemical liquid are supplied from a polishing liquid supply nozzle 90 onto the polishing surface of the polishing tool 10 for thereby polishing the workpiece W.
After or while the workpiece W is polished, the dressing tool 81 is pressed against the polishing surface on the polishing tool 10 under a predetermined pressure while the dressing member 80 and the polishing table 30 are being rotated. At this time, water is supplied from the polishing liquid supply nozzle 90 onto the polishing surface of the polishing tool 10 for thereby dressing the polishing surface on the polishing tool 10. In this manner, the workpiece W such as a semiconductor wafer is polished by the polishing apparatus 100. The polishing apparatus 100 shown in
The embodiments described above are merely preferred embodiments, and various other embodiments can be made without departing from the scope of the present invention. Specifically, various changes and modifications can be made therein within the scope of the inventions described in the claims and also within the scope of technical ideas described in the specification and the drawings. For example, although the polishing table which is rotatable about its own axis is illustrated as a polishing table in the above embodiments, the polishing table is not limited to the illustrated polishing table. For example, the polishing table may perform a reciprocating motion or an eccentric motion. Specifically, the structure of the polishing table is not limited insofar as the workpiece can be polished by a relative motion between the workpiece and the polishing tool mounted on the polishing table.
As described above, according to one aspect of the present invention, since at least a portion of the base is not fixed to the table, even when the base and/or the polishing tool is deformed due to thermal expansion, the deformation is allowed to occur by a portion of the base which is not fixed to the table. Therefore, the polishing surface of the polishing tool can be kept flat.
According to the present invention, since the polishing apparatus has a fixture for fixing the base to the table, the base with the polishing tool fixed thereto can easily be mounted on and dismounted from the table.
According to the present invention, a transmitting member is provided for transmitting movement of the table to the base. With this arrangement, the base and the polishing tool is allowed to be deformed due to thermal expansion at the portion of the base which is not fastened to the table, and the motion of the table can be transmitted to the base.
According to the present, since the base is divided into a plurality of segments, in the case where the polishing tool and the base are large in size, the base with the polishing tool fixedly mounted thereon can easily be handled when the base together with the polishing tool is mounted on and dismounted from the table.
According to the present invention, the above advantages can more efficiently be obtained in the case where the polishing tool comprises the fixed abrasive.
According to the present invention, since the base is made of a material whose coefficient of linear expansion ranges from {fraction (1/100)} to 100 times the coefficient of linear expansion of the polishing tool, the polishing tool and the base are deformed substantially equally to each other when thermal expansion occurs due to an increase in temperature caused by the polishing process. Therefore, shearing force acting on the adhesive layer between the polishing tool and the base can be reduced, thus preventing the polishing tool from being detached from the base.
According to the polishing process using the fixed abrasive, generally, the workpiece is polished under a constant pressure to achieve a uniform polishing rate. As described in the second and third embodiments, a polishing tool may have a fixed abrasive divided into a plurality of segments fixedly mounted on a base with predetermined gaps being formed between the segments in a circumferential direction.
With such a polishing tool, large steps are formed on the polishing surface of the fixed abrasive by the gaps. Therefore, when the semiconductor wafer pressed against the polishing surface of the fixed abrasive is brought into sliding contact with the polishing surface over the steps, the contacting areas of the semiconductor wafer with the polishing surface change. In this case, a surface pressure applied to the semiconductor wafer is greatly changed, so that a strong pressure is locally produced. Accordingly, an edge first phenomenon in which a portion of the peripheral edge of the semiconductor wafer is excessively polished may occur to make it difficult to control the polished film at a uniform film thickness within the surface of the semiconductor wafer.
As shown in
The polishing tool segments 110-1 through 110-6 have the same shape in a fan-shaped form and the same dimension. The side edges 111 of the circumferentially adjacent polishing tool segments 110-1 through 110-6 are held in close contact with and fixed to each other, for thereby forming the cylindrical polishing tool 110 as a whole. Specifically, the polishing tool segments 110-1 through 110-6 are divided radially at equal angles around the center of the polishing tool 110 so as to have the same shape and dimension. In the present embodiment, the polishing tool segments 110-1 through 110-6 are in a fan-shaped form having the same central angle.
Each of the polishing tool segments 110-1 through 110-6 is produced as follows: First, fine abrasive particles and a binder are mixed with fixed abrasive additives (as needed) for thereby producing a fixed abrasive material powder. The fixed abrasive additives include an abrasive particle dispersant such as a surface-active agent, a process stabilizer such as a buffer, a process accelerator typified by a pH controller such as KOH, and a mirror finish improver such as a polymeric agent. Each of the materials to be mixed may be in the powder state or in the liquid state. If necessary, pure water may be added to the fixed abrasive material powder, thus producing a mixture. The materials in the mixture are sufficiently dispersed by an agitator, an ultrasonic dispersing unit, or the like.
Next, the mixture is dried and granulated by a drying device typified by a spray dryer, and thus granulated powdery substance which is formed by uniformly mixing the above materials and has an average diameter of about 50 μm is produced. Alternatively, particles may be formed in the liquid and then filtered to produce a powder to be formed.
The material for the abrasive particles as the materials of the fixed abrasive may be in the powder state or in the slurry state. However, it is preferable to use slurry-like abrasive particles as an abrasive particle material. Since the slurry-like abrasive particles contain fine abrasive particles in a stable state, when the slurry-like abrasive particles are used as the abrasive particle material, the ratio of compositions contained in the granulated powdery substance as an intermediate product can be uniformized, and the homogeneity of the fixed abrasive can be improved. Furthermore, in order to polish a semiconductor wafer with less metal contamination, the amount of any metals contained in the abrasive particle material should preferably be as small as possible.
The material for the binder, which is one of the materials of the fixed abrasive, may be in the powder state or in the slurry state. However, it is preferable to use a latex suspension as a binder material. Since the latex suspension contains its components dispersed uniformly therein, when the latex suspension is used as the binder material, the ratio of compositions contained in the granulated powdery substance as an intermediate product can be uniformized, and the homogeneity of the fixed abrasive can be improved. Moreover, in order to polish a semiconductor wafer with less metal contamination, the amount of any metals contained in the binder material should preferably be as small as possible.
Preferably, a synthetic resin, i.e., a synthetic micromolecular compound (polymer), is selected as the binder. The synthetic micromolecular compound (polymer) is produced by polymerization of a number of monomers. A process for producing the synthetic micromolecular compound comprises various polymerization processes including addition polymerization, copolymerization, condensation polymerization, addition condensation, and the like. The above polymerization processes use water and various chemicals including a polymerization catalyst such as an organometallic compound and an inorganometallic compound, a polymerization inhibitor, a dispersant, an activator, a solvent, a catalyst deactivator, a stabilizer, an emulsifier, an antioxidant, and the like. In this manner, the binder is produced through complex processes. In order to reduce a metallic element mixed in the binder for use in the fixed abrasive, it is preferable to reduce the amount of any metal compounds contained in chemicals and water used in the above various polymerization processes.
Furthermore, the amount of any metals contained in the fixed abrasive additives as part of the materials of the fixed abrasive should also preferably be as small as possible. The fixed abrasive additives include a process accelerator (amine or the like) including a microcapsule chemical, a process stabilizer (buffer), a mirror finish improver (water-soluble polymer), a polishing auxiliary such as an abrasive particles aggregation inhibitor (organic polymer), an abrasive particle self-generation regulator (resolvent for binder), a fixed abrasive formation auxiliary, and the like.
The granulated powdery substance produced by the above process are formed into the polishing tool segments 110-1 through 110-6, which constitute the polishing tool 110, by a compression molding process, typically, a hot pressing process. The size of a compression molding machine used in the compression molding process is determined by the size of a polishing tool to be produced. Therefore, the divided polishing tool segments 110-1 through 110-6 can be produced with a smaller compression molding machine in comparison with a compression molding machine producing an unseparated polishing tool, i.e., a disk-shaped or cylindrical polishing tool. Accordingly, incidental equipments and equipments in subsequent processes can be made smaller in size, and hence initial investments and manufacturing cost of the polishing tool can be reduced.
As described above, the side edges 111 of the circumferentially adjacent polishing tool segments 110-1 through 110-6 are held in close contact with each other to form the cylindrical polishing tool 110. In this state, the polishing tool 110 composed of the polishing tool segments 110-1 through 110-6 is fixedly mounted on the base 120 by an adhesive or the like in such a manner that certain pressures are uniformly applied to the respective polishing tool segments 110-1 through 110-6, for thereby producing the polishing tool assembly 101. The polishing tool segments 110-1 through 110-6 mounted on the base 120 become a cylindrical shape as a whole. The side edges 111 of the polishing tool segments 110-1 through 110-6 are held in close contact with each other so that gaps are not intentionally formed between the polishing tool segments 110-1 through 110-6. If the side edges 111 do not have perfectly flat surfaces, the entire surfaces of the side edges 111 cannot be held in contact with each other. The entire surfaces of the side edges 111 of the adjacent polishing tool segments 110-1 through 110-6 may not be held in contact with each other as long as at least a portion of the side edge 111 of the polishing tool is held in contact with at least a portion of the side edge 111 of the adjacent polishing tool.
The base 120 has a single integral cylindrical shape and serves to protect the polishing tool segments 110-1 through 110-6 of the polishing tool 110 and also to facilitate the attachment of the polishing tool 110 to a CMP apparatus. The base 120 is made of a material having a high mechanical strength, such as metal or engineering plastics. The base 120 has a hole 121 formed in the central portion thereof for inserting a bolt therethrough. The base 120 has an outside diameter slightly larger than the polishing tool 110 (the polishing tool segments 110-1 through 110-6), and thus a radially outwardly projecting portion 123 is provided at a peripheral edge of the base 120. The radially outwardly projecting portion 123 serves as an attachment portion for attaching the base 120 to a polishing table 150, which will be described later.
In the case where the polishing tool 110 comprises many polishing tool segments or the polishing tool segments have complicated shapes, it is difficult to position the polishing tool segments 110-1 through 110-6 with respect to each other. If the polishing tool segments 110-1 through 110-6 are inaccurately positioned with respect to each other, then, in mounting the polishing tool segments 110-1 through 110-6 on the base 120, the adhesive applied to bond the polishing tool segments 110-1 through 110-6 to the base 120 may ooze out from the gaps between the opposed side edges 111 of the adjacent polishing tool segments 110-1 through 110-6 and thus leak onto the polishing surface of the polishing tool 110. The adhesive on the polishing surface prevents the polishing of a semiconductor wafer or causes a scratch on a surface of a semiconductor wafer. According to the present invention, the adhesive is not applied to the side edges 111 of the polishing tool segments 110-1 through 110-6, but is applied only to the contacting surfaces of the polishing tool segments 110-1 through 110-6 and the base 120.
Further, gaps formed between the polishing tool segments 110-1 through 110-6 would change contacting areas of the semiconductor wafer with the polishing surface on the polishing tool 110. Because it is difficult to instantaneously change a pressure applied to the semiconductor wafer during the polishing process, the change of the contacting areas of the semiconductor wafer with the polishing surface on the polishing tool 110 changes a surface pressure (polishing pressure) applied to the semiconductor wafer, thus causing change of the processing rate (polishing rate) of the semiconductor wafer. Particularly, since large forces are applied to the semiconductor wafer when the peripheral edge of the semiconductor wafer crosses the gaps between the polishing tool segments 110-1 through 110-6, the peripheral edge portion of the semiconductor wafer is excessively polished.
According to the present embodiment, since the polishing tool segments 110-1 through 110-6 are in a fan-shaped form, the polishing tool segments 110-1 through 110-6 are assembled radially inwardly on the base 120 and fixed thereon so as to form outer circumferential edges of the polishing tool segments 110-1 through 110-6 into a circular shape. Therefore, the polishing tool segments 110-1 through 110-6 can easily be positioned with respect to each other. For example, as shown in
The polishing tool segments 110-1 through 110-6 assembled on the base 120 may be positioned by various positioning members other than the annular positioning ring 130. Any positioning member may be used as long as it can support the fan-shaped (or sectorial) polishing tool segments 110-1 through 110-6 so as to form the outer circumferential edges of the polishing tool segments 110-1 through 110-6 into a circular shape. For example, a clamp mechanism shown in
When the polishing tool 110 comprises a plurality of polishing tool segments 110-1 through 110-6, it is not necessary to handle a large piece of polishing tool, which tends to crack in the manufacturing process, and air bubbles are less introduced into the adhesive layer applied to bond the polishing tool segments 110-1 through 110-6 to the base 120 than in the case where a single integral piece of polishing tool is employed. The air bubbles introduced into the adhesive layer tend to produce unbonded areas below the polishing surface of the polishing tool. Such air bubbles prevent the polishing tool from being firmly fixed to the base 120, and are liable to allow the polishing tool to be broken under frictional forces produced when the polishing tool is brought into sliding contact with the semiconductor wafer.
The polishing tool assembly 101 is fastened to the polishing table 150 as follows: The polishing tool assembly 101 is placed on the polishing table 150, and a bolt 170 is inserted through a central hole 113 in the polishing tool 110 and the bolt insertion hole 121 in the base 120 and screwed into the fixing portion 153 in the polishing table 150. Three clamp members 175 having an inverted L-shaped cross section are placed respectively on the attachment portion 123 at the peripheral edge of the base 120. Bolts 179 are inserted through two bolt insertion holes 177 formed in each of the clamp members 175 and screwed into the fixing portions 155 in the polishing table 150. Thus, the clamp members 175 press the base 120 downwardly against the polishing table 150 with upper holding portions 176 thereof.
The bolt insertion hole 121 in the base 120 has an inside diameter smaller than the hole 113 in the polishing tool 110 so as to provide a step between the upper surface of the polishing tool 110 and the upper surface of the base 120. The step is used to accommodate the head of the bolt 170 which fastens the base 120 to the polishing table 150.
Since the polishing tool assembly 101 is fastened at the central portion and the circumferential portions, the polishing tool assembly 101 is easily and reliably positioned on the polishing table 150 for axial alignment, and is firmly secured to the polishing table 150.
When the polishing tool 110 has a diameter of up to about 600 mm, the base 120 may be made of a material such as aluminum alloy or engineering plastics so as to provide a sufficient mechanical strength and such a light weight that the base 120 can be handled with ease. Generally, a rotatable thick polishing tool for polishing an 8-inch semiconductor wafer can be manufactured by the above process.
When a material preparing step including mixing and dispersing materials, a granulating step, a forming step, and steps of mounting and bonding components are performed in an environment into which clean air is supplied through a filter installed in a clean room, a clean booth, or the like, it is possible to manufacture a highly clean polishing tool (fixed abrasive).
With the polishing tool assembly manufactured by the above process, a semiconductor wafer can be processed with high quality. Further, this polishing tool assembly can easily and inexpensively be manufactured and can be handled with ease.
The semiconductor wafer W held by the top ring 210 is pressed against the upper polishing surface on the polishing tool assembly 101, and the polishing tool assembly 101 and the top ring 210 are rotated independently of each other to bring the lower surface of the semiconductor wafer W into sliding contact with the upper polishing surface on the polishing tool 110. At the same time, a polishing liquid (abrasive liquid) is supplied onto the upper polishing surface of the polishing tool assembly 101 from a polishing liquid supply nozzle 230 to thus polish the semiconductor wafer W.
After or while the semiconductor wafer W is polished, the dressing process is preformed as follows. While the dressing member 220 and the polishing tool assembly 101 are being rotated, the dressing tool 221 is pressed against the polishing surface on the polishing tool 110 under a predetermined pressure. At the same time, water is supplied from a water supply nozzle 223 onto the polishing surface, for thereby dressing the polishing surface on the polishing tool 110. In this manner, the semiconductor wafer W is polished with the polishing apparatus 200 incorporating the polishing tool assembly 101 according to the present invention. The polishing apparatus according to the present invention is not limited to the polishing apparatus 200 shown in
Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various other embodiments may be made without departing from the scope of the present invention. Specifically, it should be understood that various changes and modifications may be made within the scope of the inventions described in the appended claims and also within the scope of technical concepts described in the specification and the drawings. Any shapes, structures, and materials which are not described directly in the specification and the drawings may fall within the scope of technical concepts of the present invention as long as they provide operations and advantages according to the present invention.
As described in detail above, the present invention provides the following advantages:
(1) According to the present invention, the circumferentially adjacent polishing tool segments are held in close contact with each other. Therefore, when the workpiece is brought into sliding contact with the polishing surface across the polishing tool segments, a pressure acting on the surface of the workpiece does not change, and hence the surface of the workpiece can uniformly be processed.
(2) Since the polishing tool assembly comprises a plurality of polishing tool segments, each of the polishing tool segments can be made small in size, and the polishing tool assembly can be manufactured with small-scale equipments for forming the polishing tool assembly. Thus, initial investments and the manufacturing cost of the polishing tool assembly can be reduced. Since each of the polishing tool segments is small in size, it can be handled with ease, and the polishing tool assembly can easily be manufactured with high cleanliness and high quality.
(3) Each of the polishing tool segments is in a sectorial or fan-shaped form, and the circumferentially adjacent polishing tool segments are held in close contact with and fixed to each other. Therefore, even though the polishing tool assembly comprises a plurality of polishing tool segments, the polishing tool segments can easily be positioned with respect to each other so as to form a disk or cylindrical shape as a whole when the polishing tool segments are fixedly mounted on the polishing tool attachment. As a result, the polishing tool assembly can be replaced with a small expenditure of labor and time in a simple process.
(4) According to the present invention, the polishing tool attachment on which the polishing tool segments are mounted is divided into a plurality of attachment segments so as to correspond to the polishing tool segments. Therefore, even if the polishing tool assembly has a large diameter and is heavy, the polishing tool segments can easily be handled together with the respective attachment segments. Accordingly, a smaller space is required in a clean room for replacing the polishing tool assembly, and the polishing tool assembly can be handled with ease in the clean room.
An eighth embodiment of the present invention will be described below with reference to
The polishing apparatus 401 comprises a flanged cartridge table 316 to which a fixed abrasive 315 serving as a polishing tool is attached, a main table 305 on which the cartridge table 316 is mounted, a top ring 301 for holding a semiconductor wafer 304 as a workpiece to be polished, rotating the semiconductor wafer 304, and pressing the semiconductor wafer 304 against the main table 305, and a liquid supply nozzle 310 for supplying water or a chemical L to the fixed abrasive 315 during polishing. The fixed abrasive 315 is attached to a surface 316A of the cartridge table 316. The main table 305 is disposed so as to face a reverse surface 316B of the cartridge table 316 opposite to the surface 316A thereof.
The fixed abrasive 315 is in the form of a disk having a diameter of about 60 cm, and bonded to the surface 316A of the cartridge table 316 made of aluminum or the like by an adhesive. The cartridge table 316 has a flange 316C on its outer circumferential edge. When clamp members 318 serving as fastening members are fixed to the main table 305 by bolts, the clamp members 318 press the flange 316C against the main table 305 for thereby securing the cartridge table 316 to a surface 305A of the main table 305. Specifically, the bolts 319 are screwed into internally threaded holes 320 formed in the main table 305, and hence the cartridge table 316 is fixed to the main table 305 by the clamp members 318. At this time, the reverse surface 316B of the cartridge table 316 is held in contact with the surface 305A of the main table 305 which supports the cartridge table 316. Thus, the surface 305A of the main table 305 serves as a support surface for supporting the cartridge table 316.
As shown in
The flange 316C of the cartridge table 316 has circumferentially spaced projections 329 projecting radially outwardly therefrom. Each of the projections 329 has an internally threaded hole 330 formed therethrough for the insertion of a pusher bolt 331 (or suspension bolt (not shown)) therein. The internally threaded holes 330 are used to insert the respective pusher bolts 331 therethrough for removing the cartridge table 316 from the main table 305. Specifically, in order to remove the cartridge table 316 from the main table 305, the pusher bolts 331 are inserted into the internally threaded holes 330 and turned until tip ends 331A of the pusher bolts 331 are brought into contact with the bottoms 342A of grooves 342 formed in the main table 305. When the pusher bolts 331 are further turned, the torque of the pusher bolts 331 is converted into forces by which the cartridge table 316 is removed from the main table 305. The grooves 342 are formed in the surface 305A of the main table 305 so as to be positioned directly below the internally threaded holes 330 of the cartridge table 316. The grooves 342 serve to receive the tip ends 331A of the pusher bolts 331 (or suspension bolt) for protecting the surface 305A of the main table 305 so as not to be damaged.
In the present embodiment, the polishing apparatus 401 has four clamp members 318 and four projections 329. However, in view of usage conditions such as the pressing load applied by the clamp members 318, an annular clamp member 318 may be used to press the entire circumference of the cartridge table 316. The number of projections 329 may be increased or decreased in view of the weight of the cartridge table 316 and the adhesion strength between the cartridge table 316 and the main table 305. The cartridge table 316 to which the fixed abrasive 315 is attached may be made of ceramics, stainless steel, titanium, synthetic resin, or the like as well as aluminum for corrosion resistance.
As shown in
As shown in
As shown in
As shown in
m:(R2+h2)1/2=r:R
hence, m=r·(R2+h2)1/2/R
When the ball bearing 324 actually enters the recess 333, the ball bearing 324 either floats from the recess 333 as shown in
In the case of
If the distance from the surface 305A (the reverse surface 316B) to the upper surface 323A is represented by S and the distance from the surface 305A (the reverse surface 316B) to the uppermost end (in
In the case of
Since the distance from the surface 305A (the reverse surface 316B) to the upper surface 323A of the holder 323 is represented by S and the distance from the surface 305A (the reverse surface 316B) to the uppermost end (in
For example, if the shapes and dimensions of the holder 323 and the recess 333 are determined to satisfy the expressions (1), (2) and (3), then the cartridge table 316 and the main table 305 can be positioned in order to keep the surface 305A and the reverse surface 316B in close contact with each other. When the cartridge table 316 and the main table 305 are thus positioned, the reverse surface 316B is not caused to float off from the surface 305A by the ball bearing 324.
Referring back to
An arrangement for suspending the cartridge table 316 will be described below.
As shown in
The suspension jig 335 is fastened to the flange 316C of the cartridge table 316 by hexagon socket head cap bolts 339 which are screwed into the internally threaded holes 338 and 334. Instead of the hexagon socket head cap bolts 339, the pusher bolts 331 (see
As shown in
The semiconductor wafer 304 is held on the lower surface of the resilient pad 302 attached to the lower surface of the top ring 301, and is pressed by the top ring 301 against the fixed abrasive 315 on the cartridge table 316 fixed to the main table 305. The main table 305 and the top ring 301 are rotated in one direction independently of each other at respective predetermined rotational speeds, whereby the fixed abrasive 315 and the semiconductor wafer 304 cause relative motion for thereby polishing the semiconductor wafer 304. At this time, water or a chemical L is supplied from the liquid supply nozzle 310 onto the fixed abrasive 315.
The water or the chemical is supplied onto the polishing surface of the fixed abrasive 315 in order to lubricate the polishing surface when the semiconductor wafer 304 is polished and also to cool the polishing surface for thereby removing heat generated when the semiconductor wafer 304 is polished. In an example, water is supplied at a rate of about 200 ml/min to the polishing surface on the fixed abrasive 315. The water may comprise ultrapure water free of impurities. A chemical such as an acid or alkali solution may be supplied instead of water.
The semiconductor wafer 304 is rotated by the drive shaft 308 in the direction indicated by the arrow X1 while being pressed against the fixed abrasive 315 through the resilient pad 302 by the top ring 301. The main table 305 to which the cartridge table 316 having the fixed abrasive 315 attached thereto is fixed is also rotated in the direction indicated by the arrow X2 independently of the semiconductor wafer 304. The surface 304A, to be polished, of the semiconductor wafer 304 is now polished by being brought into sliding contact with the surface 315A of the fixed abrasive 315.
The fixed abrasive 315 comprises a grindstone having a self-stop function which does not polish the surface 304A after surface irregularities of the surface 304A have been planarized by the polishing action thereof. The fixed abrasive 315 comprises abrasive particles of cerium oxide (CeO2) or the like having an average particle diameter of 2 μm or less, and a binder of a synthetic resin such as polyimide or the like. The abrasive particles may alternatively be made of SiO2, Al2O3, ZrO2, MnO2, Mn2O3, TiO2, or the like. The binder may alternatively be phenolic resin, urethane resin, epoxy resin, polyvinyl alcohol resin, acrylic resin, or the like. As materials for the abrasive particles and the binder, suitable materials are selected from the above materials in view of the type of films formed on the semiconductor wafer to be polished and the affinity between the abrasive particles and the binder.
The semiconductor wafer 304 is polished under conditions of, for example, a wafer surface pressure of 3×104 Pa (300 g/cm2), rotational speeds of 30 and 35 rpm for the table and the wafer, respectively, and a supply rate of 200 ml/min of pure water (containing 1 wt % or less of a surface active agent). Alternatively, the semiconductor wafer 304 may be polished under conditions of a wafer surface pressure of 5×104 Pa (500 g/cm2), rotational speeds of 25 and 10 rpm for the table and the wafer, respectively, and a supply rate of 200 ml/min of pure water (containing 1 wt. % or less of a surface active agent).
A process of mounting the cartridge table 316 with the fixed abrasive 315 attached thereto on the main table 305 will be described below with reference to
Then, the hexagon socket head cap bolts 339 by which the suspension jig 335 is attached to the flange 316C of the cartridge table 316 are removed, and hence the suspension jig 335 is detached from the flange 316C. The clamp members 318 are attached to the flange 316C of the cartridge table 316, and fastened to the main table 305 by the bolts 319. In this manner, the process of mounting the cartridge table 316 on the main table 305 is completed.
Next, a process of removing the cartridge table 316 from the main table 305 will be described below. The bolts 319 are removed from the clamp members 318, and hence the clamp members 318 are detached from the flange 316C. The pusher bolts 331 are screwed into the internally threaded holes 330 in the projections 329 to cause the tip ends 331A of the pusher bolts 331 to engage the bottoms 342A of the grooves 342, thereby removing the cartridge table 316 from the main table 305. After the pusher bolts 331 are removed, the suspension jig 335 is placed on the flange 316C of the cartridge table 316. Then, the suspension jig 335 is positionally adjusted to align the internally threaded holes 338 of the suspension jig 335 with the internally threaded holes 334. Thereafter, the hexagon socket head cap bolts 339 are screwed into the internally threaded holes 338 and 334 to fasten the suspension jig 335 to the flange 316C of the cartridge table 316. A process of suspending the cartridge table 316 with the suspension jig 335 will be described later on.
A cartridge table 516 and a main table 505 of a polishing apparatus 403 according to a ninth embodiment of the present invention will be described below with reference to
The cartridge table 516 incorporates a bearing member 522 disposed centrally in a reverse surface 516B thereof. The bearing member 522 comprises a holder 523, a ball bearing 524, and a bearing retainer plate, and the like. The main table 505 has a recess 533 formed therein which is disposed centrally in a surface 505A thereof.
According to the polishing apparatus 403 of the present embodiment, the cartridge table 516 with a fixed abrasive 515 attached thereto is placed on the surface 505A of the main table 505. Thereafter, the center of the cartridge table 516 is aligned with the center of the main table 505 for thereby placing the ball bearing 524 in the recess 533, so that the cartridge table 516 is positioned with respect to the main table 505. It is therefore not necessary to angularly align the cartridge table 516 with the main table 505 for positioning of the cartridge table 516 with respect to the main table 505.
When the cartridge table 516 is placed on the main table 505, because only one bearing 524 is used, the bearing 524 is normally brought into contact with the surface 505A, and a point on the outer edge of the reverse surface 516B contacts the surface 505A. A reaction force which the bearing 524 receives from the surface 505A is much greater than a reaction force which the point on the outer edge of the reverse surface 516B receives. Therefore, the resistance due to friction at the point is small, and hence the cartridge table 516 can be easily moved manually on the main table 505.
A cartridge table 616 and a main table 605 of a polishing apparatus 404 according to a tenth embodiment of the present invention will be described below with reference to
The cartridge table 616 has on a reverse surface 616B thereof a ridge 643 in the form of a rectangular parallelepiped, and the ridge 643 has a height h1 from the reverse surface 616B. The ridge 643 extends in the radial direction of the cartridge table 616. The height h1 is smaller than a downward projecting distance h2 of a bearing 624 from a surface 605A of the main table 605. The surface 605A has a groove 644 formed therein as a directional member in which the ridge 643 enters. The groove 644 extends in the radial direction of the main table 605, and has such a width that the bearing 624 enters in the groove 644 with a small play.
Since the height h1 of the ridge 643 is smaller than the projecting distance h2 of the bearing 624, when the cartridge table 616 is placed on the main table 605, the bearing 624 and a point on the outer edge of the reverse surface 616B (or a point on the ridge 643) normally contact the surface 605A. A reaction force which the bearing 624 receives from the surface 605A is much greater than a reaction force which the above point receives. Therefore, the cartridge table 616 can easily be moved manually on the main table 605. The main table 605 has a recess 633 which is disposed centrally in the surface 605A of the main table 605. The recess 633 has a depth h4 and the groove 644 has a depth h3, and the depth h4 is greater than the depth h3. The recess 633 is located adjacent to an end 644B of the groove 644 which is opposite to an end 644A located at the outer edge of the surface 605A. When the bearing 624 enters the recess 633, the bearing 624 also enters the end 644B of the groove 644.
The cartridge table 616 is placed on the main table 605, and the center of the cartridge table 616 is aligned with the center of the main table 605. The bearing 624 enters the recess 633 and the ridge 643 enters the groove 644, thus positioning the cartridge table 616 with respect to the main table 605. At this time, if the bearing 624 initially enters the recess 633, then the cartridge table 616 is turned to angularly align itself with the main table 605, whereby the ridge 643 is brought into the groove 644 to position the cartridge table 616 with respect to the main table 605.
If the bearing 624 initially enters the groove 644, then the bearing 624 is moved on the bottom of the groove 644 toward the recess 633 to directionally align the cartridge table 616 with the main table 605. After the bearing 624 reaches the recess 633, the cartridge table 616 is turned to angularly align itself with the main table 605 for thereby bringing the ridge 643 into the groove 644, thus positioning the cartridge table 616 with respect to the main table 605. Alternatively, the cartridge table 616 may first be angularly aligned and then directionally aligned with the main table 605.
According to the present embodiment, the bearing 624 and the ridge 643 allow the cartridge table 616 to be positioned accurately with respect to the main table 605, and also prevent the cartridge table 616 and the main table 605 from rotating relatively to each other. If the cartridge table 616 is fastened to the main table 605 by the clamp members 318 (see
The polishing system 402 shown in
The lower one of the two hands of the transport robot 424 is used only to take out a semiconductor wafer 304 (see
Two cleaning machines 425 and 426 are disposed in the opposite side of the wafer cassettes 421 with respect to the transport mechanism 423. Each of the cleaning machines 425 and 426 is located in a position that can be accessed by the hands of the transport robot 424. A wafer station 470 having four placement stages 427, 428, 429 and 430 for placing semiconductor wafers 304 (see
The cleaning machines 425 and 426 and the placement stages 427, 428, 429 and 430 are disposed in an area AB, and the wafer cassettes 421 and the transport robot 424 are disposed in an area AA. A partition wall 484 is disposed to provide different levels of cleanliness in the areas AA and AB. The partition wall 484 has an opening at which a shutter 431 is provided for delivering semiconductor wafers 304 therethrough between the areas AA and AB. A transport robot 480 having two hands is located in a position where the transport robot 480 can access the cleaning machine 425 and the three placement stages 427, 429 and 430, and a transport robot 481 having two hands is located in a position where the transport robot 481 can access the cleaning machine 426 and the three placement stages 428, 429 and 430.
The placement stage 427 is used to transfer semiconductor wafers 304 (see
The placement stages 429 and 430 are disposed in a common water-resistant cover, and a shutter 497 is provided at an opening of the cover which allows semiconductor wafers to be delivered therethrough. The placement stage 429 is disposed above the placement stage 430. A semiconductor wafer 304 which has been cleaned is placed on the placement stage 429, and a semiconductor wafer 304 to be cleaned is placed on the placement stage 430, thereby preventing the semiconductor wafers from being contaminated due to droplets of rinsing water. In
The upper hands of the transport robot 480 and the transport robot 481 are used to deliver semiconductor wafers 304 which have been cleaned once to the cleaning machines 425, 426, 482 and 483 or the placement stages in the wafer station 470. The lower hands of the transport robot 480 and the transport robot 481 are used to deliver semiconductor wafers 304 which have never been cleaned, and semiconductor wafers 304 to be polished. The lower hands are used to transfer semiconductor wafers 304 to and from a reversing machine for thereby preventing the upper hands from being contaminated by droplets of the rinsing water from an upper wall of the reversing machine.
The cleaning machine 482 is disposed so as to be adjacent to the cleaning machine 425 in a position that is accessible by the hand of the transport robot 480. The cleaning machine 483 is disposed so as to be adjacent to the cleaning machine 426 in a position that is accessible by the hand of the transport robot 481.
The cleaning machines 425, 426, 482 and 483, the placement stages 427, 428, 429 and 430 in the wafer station 470, and the transport robots 480 and 481 are disposed in the area AB. The air pressure in the area AB is adjusted so as to be lower than the air pressure in the area AA. The cleaning machines 482 and 483 are capable of cleaning both sides of semiconductor wafers 304.
The polishing system 402 has a housing 466 so as to enclose the constituent units or components thereof. The interior of the housing 466 is divided into a plurality of chambers (including the areas AA and AB) by the partition wall 484 and partition walls 485, 486, 487 and 467. A polishing chamber separate from the area AB is defined by the partition wall 487, and the polishing chamber is divided into two areas AC and AD by the partition wall 467. In each of the two areas AC and AD there are provided two main tables and a top ring for holding one semiconductor wafer 304 (see
Specifically, in the area AC, there are provided the main tables 454 and 456 and the top ring 452, and in the area AD, there are provided the main tables 455 and 457 and the top ring 453. In the area AC, there are provided a polishing liquid nozzle 460 for supplying a polishing liquid to the main table 454, and a dresser 458 for dressing the main table 454.
In the area AD, there are provided a polishing liquid nozzle 461 for supplying a polishing liquid to the main table 455, and a dresser 459 for dressing the main table 455. A dresser 468 for dressing the main table 456 is disposed in the area AC, and a dresser 469 for dressing the main table 457 is disposed in the area AD. Wet-type wafer thickness measuring devices may be installed in place of the respective main tables 456 and 457. The wet-type wafer thickness measuring devices are capable of measuring the thickness of a film of a semiconductor wafer 304 immediately after it has been polished, and allow the semiconductor wafer 304 to be additionally polished. Further, a polishing process of a next semiconductor wafer 304 can be controlled based on the measured values by the thickness measuring devices.
Semiconductor wafers 304 (see
The polishing system 402 also has a hand lifter 501 (see
A structure of the hand lifter 501 serving as a carrier device for delivering the cartridge table 316 suspended by the suspension jig 335 will be described below with reference to
The hand lifter 501 comprises a horizontal base 502, wheels 503 mounted on the base 502, a lifter body 504 connected to one end of the base 502 and extending vertically from the base 502, and two suspension bars 507 vertically movable along the lifter body 504. The two suspension bars 507 extend horizontally and are parallel to each other. The hand lifter 501 has a hand wheel (not shown) for vertically moving the suspension bars 507 along the lifter body 504. When the hand wheel is manually turned in a given direction, the two suspension bars 507 are vertically moved along the lifter body 504. Since the hand lifter 501 has the wheels 503, the hand lifter 501 can be manually moved in the direction indicated by the arrow P1 toward the polishing system 402 on a floor 506 on which the polishing system 402 is installed.
As shown in
The hand lifter 501 which has lifted the cartridge table 316 moves in the direction indicated by the arrow P1, approaches the polishing system 402, and the base 502 of the hand lifter 501 enters a cavity 472 defined as a space in a side 471A of the base 471 of the polishing system 402 (see
As shown in
Thereafter, as described above, the cartridge table 316 is manually moved on the main table 454 until the bearings 324 (see
In the case where the cartridge table 316 is removed from the main table 454, the bolts 319 are loosened and the clamp members 318 are detached, and then the suspension jig 335 is carried from the outside of the polishing system 402 to a position over the main table 454 by the hand lifter 501. After the suspension jig 335 is attached to the flange 316C of the cartridge table 316 as described above, the hand lifter 501 with the suspension bars 507 positioned lower than the flange 337 approaches the cartridge table 316. When the base 502 enters the cavity 472 and the tip ends of the suspension bars 507 reach a position directly below the flange 337, the hand lifter 501 stops. The non-illustrated hand wheel is turned in the given direction to lift the suspension bars 507. Thus, the tip ends of the suspension bars 507 are brought into contact with the flange 337, thus lifting the cartridge table 316. The bearings 324 are positioned above the surface 454A of the main table 454 and are brought out of the recesses 333. The hand lifter 501 is moved in the direction opposite to the direction indicated by the arrow P1 (see
According to the polishing system 402 of the present embodiment, the cartridge table 316 with the fixed abrasive 315 attached thereto can manually be moved and placed on the main table 454 by the hand lifter 501. The cartridge table 316 can manually be moved over the main table 454 to put the bearings 324 (see
The cartridge table 316 can manually be lifted and removed from the main table 454 by the hand lifter 501. The cartridge table 316 with the fixed abrasive 315 attached thereto can thus be handled with ease. Because the cartridge table 316 with the heavy fixed abrasive 315 attached thereto can be carried, lifted, or lowered by the hand lifter 501, the safety of the operator can be ensured. Even if the cartridge table 316 with the fixed abrasive 315 attached thereto is heavy, the cartridge table 316 can manually be handled without its handling capability being affected. Therefore, the fixed abrasive 315 can sufficiently be increased in thickness, and hence the service life of the fixed abrasive 315 can be prolonged.
As shown in
The hand lifter 501 may be replaced with a crane device as a carrier device. The crane device may be an industrial machine such as a crane, a chain block, a hoist, or the like for suspending an object with a wire. If a crane arm, a crane body, a lifter, and the like are incorporated in advance in the base 471 of the polishing system 402 or are easily detachably combined with the base 471, then the cavity 472 does not need to be formed in the base 471 of the polishing system 402, and the crane device may be used to replace the main tables 454 and 455 with new ones. With this arrangement, the possibility of bringing particles from the exterior space into the polishing system is reduced to thus allow operations to be made in a clean environment. If the crane device is used, then the suspension jig 335 does not need the flange 337, but may have at least one member, preferably three members such as the pusher bolts 331 (see
As shown in
The crane device 701 includes a moving unit 703, a take-up unit 704, a rope 707, and a hook 706. The moving unit 703 engages the rail 702 and moves horizontally along the rail 702 in the direction indicated by the arrow P2 or the direction opposite to the direction indicated by the arrow P2. The take-up unit 704 is mounted on the moving unit 703, and winds or unwinds the rope 707. The hook 706 is connected to the end of the rope 707. The hook 706 is lifted in the direction opposite to the direction indicated by the arrow Q2 (see
The polishing system 405 also has a suspension jig 735, a cartridge table 716, and a main table 705. The rail 702 is mounted on a ceiling 405A of the polishing system 405, and permits the crane device 701 to move from the side 405B of the polishing system 405 to at least a position directly above the main table 705. For moving the cartridge table 716 onto the main table 705, the suspension jig 735 is fastened to the cartridge table 716 by hexagon socket head cap bolts 739. Then, the hook 706 engages a flange 737 of the suspension jig 735 attached to the cartridge table 716. Thereafter, the take-up unit 704 winds the rope 707 to lift the hook 706, and hence the cartridge table 716 is suspended by the crane device 701.
Then, as shown in
Next, as shown in
After the cartridge table 716 is placed on the main table 705, the hexagon socket head cap bolts 739 are removed, and the suspension jig 735 is detached from the cartridge table 716. The suspension jig 735 is suspended by the crane device 701, and carried out of the polishing system 405 in the direction opposite to the direction indicated by the arrow P2.
Because the polishing system 405 has the crane device 701, the handling of the cartridge table 716 can be improved and the safety of the operator can be improved. The cartridge table 716 can be made heavy, the fixed abrasive (see
As shown in
The embodiments described above are only preferred embodiments of the present invention, and various changes and modifications may be made therein without departing from the scope of the invention.
According to the present invention, as described above, since the moving mechanism and the positioning member are provided, the cartridge table can be moved easily on the main table by the moving mechanism, and can be positioned with respect to the main table by the positioning member. The polishing tool can thus be handled with ease, and the safety of the operator can be increased. Further, the polishing tool can be increased in thickness for a longer service life.
The present invention is applicable to a polishing apparatus having a polishing tool for polishing a workpiece such as a semiconductor wafer to a flat mirror finish.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2001-336783 | Nov 2001 | JP | national |
| 2002-9989 | Jan 2002 | JP | national |
| 2002-208468 | Jul 2002 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP02/11466 | 11/1/2002 | WO |
