Patent Application
20050260929
The present invention relates to a chemical mechanical polishing pad which can be advantageously used in a chemical mechanical polishing step and a chemical mechanical polishing method making use of the polishing pad.
In the manufacture of a semiconductor device, chemical mechanical polishing (CMP) is attracting much attention as a polishing technique capable of forming an extremely flat surface. Chemical mechanical polishing is a technique for polishing by letting an aqueous dispersion for chemical mechanical polishing, for example, an aqueous dispersion of abrasive grains flow down over the surface of a chemical mechanical polishing pad while the polishing pad and the surface to be polished are brought into slide contact with each other. It is known that the polishing result is greatly affected by the performance characteristic and properties of the polishing pad in this chemical mechanical polishing.
Heretofore, chemical mechanical polishing has been carried out by using polyurethane foam containing pores as a polishing pad to hold slurry in holes (to be referred to as “pores” hereinafter) which are open to the surface of the resin. It is known that the polishing rate and the polishing result are improved by forming grooves in the surface (polishing surface) of the chemical mechanical polishing pad (JP-A 11-70463, JP-A 8-216029 and JP-A 8-39423) (the term “JP-A” as used herein means an “unexamined published Japanese patent application”).
However, due to the improvement of the performance and the downsizing of a semiconductor device, the wiring pattern is becoming finer, the number of wiring layers is increasing and the performance required for chemical mechanical polishing and a chemical mechanical polishing pad is becoming higher. Although the design of a chemical mechanical polishing pad is described in detail in the above patent document 1, the polishing rate and the state of the polished surface are still unsatisfactory. There is a case where a surface defect like a scratch (to be referred to as “scratch” hereinafter) occurs, and the improvement of this defect is desired.
It is an object of the present invention which has solved the above problems of the prior art to provide a chemical mechanical polishing pad which fully suppresses the occurrence of a scratch on the polished surface and has an excellent polishing rate and a chemical mechanical polishing method making use of the polishing pad.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by a chemical mechanical polishing pad (may be referred to as “first polishing pad of the present invention” hereinafter) having a polishing surface, a non-polishing surface opposite to the polishing surface, and a side surface for defining these surfaces, the polishing surface having at least two groups of grooves, wherein
the two groups of grooves consist of (i) a first group of grooves which intersect a single virtual straight line extending from the center portion toward the peripheral portion of the polishing surface and do not cross one another and (ii) a second group of grooves which extend from the center portion toward the peripheral portion of the polishing surface, intersect the first group of grooves and do not cross one another.
According to the present invention, secondly, the above objects and advantages of the present invention are attained by a chemical mechanical polishing pad (may be referred to as “second polishing pad of the present invention” hereinafter) having a polishing surface, a non-polishing surface opposite to the polishing surface, and a side surface defining these surfaces, the polishing surface having (i) a single first spiral groove which expands gradually from the center portion toward the peripheral portion of the polishing surface and (ii) a second group of grooves which extend from the center portion toward the peripheral portion of the polishing surface, intersect the above spiral groove and do not cross one anther.
According to the present invention, thirdly, the above objects and advantages of the present invention are attained by a chemical mechanical polishing method making use of the above chemical mechanical polishing pad of the present invention.
The present invention will be described in detail hereniunder with reference to the accompanying drawings. A description is first given of the first polishing pad.
Although the grooves of the first group formed in the polishing surface are not limited to a particular shape, they may be, for example, two or more spiral grooves which expand gradually from the center portion toward the peripheral portion of the polishing surface, or annular or polygonal grooves which do not cross one another and are arranged concentrically. The annular grooves may be circular or elliptic, and the polygonal grooves may be tetragonal, hexagonal, etc.
The grooves of the first group do not cross one another.
The grooves of the first group are formed in the polishing surface in such a manner that they intersect a single virtual straight line extending from the center portion toward the peripheral portion of the polishing surface a plurality of times. For example, when the grooves are annular and the number of the annular grooves is 2, the number of intersections is 2, when the number of the annular grooves is 3, the number of intersections is 3, and when the number of the annular grooves is “n”, the number of intersections is “n”. When there are two spiral grooves, the number of intersections is 2 before the second turn (one turn is 360°), 3 after the start of the second turn and (n+1) after the start of the “n”-th turn.
When the grooves are polygonal, the same can be said.
When the grooves are annular or polygonal, they are arranged not to cross one another and may be arranged concentrically or eccentrically but preferably concentrically. A polishing pad having annular or polygonal grooves which are arranged concentrically is superior in the above functions to other polishing pads. The annular grooves are preferably circular grooves, more preferably circular grooves which are arranged concentrically. When the circular grooves are arranged concentrically, the obtained polishing pad is excellent in the above functions and the formation of the grooves is easy.
The sectional form in the width direction, that is, a direction perpendicular to the groove direction of the grooves is not particularly limited. It may be, for example, polygonal with three or more sides consisting of flat sides and a bottom side, U-shaped or V-shaped.
The number of the grooves (annular grooves) which differ from one another in diameter and are arranged concentrically may be, for example, 20 to 400 and the number of the spiral grooves may be, for example, 2 to 10.
Although the size of the grooves is not particularly limited, the width of the grooves of the first group may be 0.1 mm or more, preferably 0.1 to 5 mm, more preferably 0.2 to 3 mm. The depth of the grooves may be 0.1 mm or more, preferably 0.1 to 2.5 mm, more preferably 0.2 to 2.0 mm. As for the interval between grooves, the shortest distance between adjacent intersections between the above virtual straight line and the grooves of the first group may be 0.05 mm or more, preferably 0.05 to 100 mm, more preferably 0.1 to 10 mm. A chemical mechanical polishing pad having the excellent effect of reducing the number of scratches on the polished surface and a long service life can be facilely manufactured by forming grooves having the above ranges.
The above preferred ranges may be combined in various ways. For example, the width of the grooves may be set to 0.1 mm or more, the depth of the grooves may be set to 0.1 mm or more, and the interval between adjacent grooves may be set to 0.05 mm or more. Preferably, the width of the grooves is set to 0.1 to 5 mm, the depth of the grooves is set to 0.1 to 2.5 mm, and the interval between adjacent grooves is set to 0.15 to 105 mm. More preferably, the width of the grooves is set to 0.2 to 3 mm, the depth of the grooves is set to 0.2 to 2.0 mm, and the interval between adjacent grooves is set to 0.6 to 13 mm.
Although the sectional form of the grooves, that is, the shape of the cut plane obtained when the grooves are cut in the normal direction is not particularly limited, it is, for example, polygonal or U-shaped. Examples of the polygonal shape include triangle, tetragon and pentagon.
The pitch which is the sum of the width of the grooves and the distance between adjacent grooves is preferably 0.15 mm or more, more preferably 0.15 to 105 mm, much more preferably 0.5 to 13 mm, particularly preferably 0.5 to 5.0 mm, ideally 0.5 to 2.2 mm.
The surface roughness (Ra) of the inner wall of each of the above grooves of the first group is preferably 20 μm or less, more preferably 0.05 to 15 μm, particularly preferably 0.05 to 10 μm. A scratch which may occur on the polished surface in the chemical mechanical polishing step can be prevented more effectively by setting this surface roughness to 20 μm or less.
The above surface roughness (Ra) is defined by the following equation (1):
Ra=Σ|Z−Zav|/N (1)
wherein N is the number of measurement points, Z is the height of a roughness profile and Zav is the average height of the roughness profile.
The above second group of grooves consists of a plurality of grooves extending from the center portion toward the peripheral portion of the polishing surface. The expression “center portion” as used herein means an area surrounded by a circle having a radius of 50 mm from the center of gravity on the surface of the chemical mechanical polishing pad as the center thereof. The grooves of the second group may extend from any point within this “center portion” toward the peripheral portion and may be linear or arcuate, or a combination thereof.
The grooves of the second group may or may not reach the peripheral end. Preferably, at least one of them reaches the peripheral end, that is, the side surface of the pad. For example, the second group of grooves may consist of a plurality of linear grooves extending from the center portion toward the peripheral portion and at least one of them may reach the side surface of the pad, or the second group of grooves may consist of a plurality of linear grooves extending from the center portion toward the peripheral portion and a plurality of linear grooves extending from a halfway portion between the center portion and the peripheral portion toward the peripheral portion and at least one of them may reach the side surface of the pad. Further, the second group of grooves may consist of pairs of two parallel linear grooves.
The number of the grooves of the second group is preferably 4 to 65, more preferably 8 to 48.
The grooves of the second group existent on the surface of the chemical mechanical polishing pad may or may not be in contact with one another but do not cross one another. Preferably, 2 to 32 out of the grooves of the second group are in contact with other grooves of the second group in the area of the above center portion. More preferably, 2 to 16 out of the grooves of the second group are in contact with other grooves of the second group. Some of the second grooves may be in contact with other grooves of the second group and other grooves at positions other than the center portion of the surface of the pad.
The preferred width and depth of the grooves of the second group are the same as those of the first group. The preferred range of the surface roughness (Ra) of the inner wall of each of the grooves of the second group is the same as that of the first group.
The grooves of the second group are preferably arranged as equally as possible on the surface of the chemical mechanical polishing pad.
The grooves of the second group formed in the polishing surface of the chemical mechanical polishing pad of the present invention may be arranged as shown in the diagrams of FIGS. 1 to 7.
The second polishing pad of the present invention has a single first spiral groove which expands gradually from the center portion toward the peripheral portion of the polishing surface in place of the first group of grooves of the above first polishing pad.
The number of turns of the first spiral groove may be 20 to 400. 360° corresponds to one turn.
The first spiral groove has a width of 0.1 mm or more and a depth of 0.1 mm or more and the shortest distance between intersections between the first spiral groove and a single virtual straight line extending from the center portion toward the peripheral portion of the polishing surface may be 0.05 mm or more.
As for what is not described of the second polishing pad, it should be understood that what has been described of the first polishing pad can be applied to the second polishing pad as it is or with modifications obvious to those skilled in the art.
Examples of the arrangement of the grooves of the chemical mechanical polishing pad of the present invention will be described with reference to the accompanying drawings.
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The arrangement of the grooves on the polishing surface of the polishing pad of the present invention is preferably symmetric about the center, for example, point symmetrical, line symmetrical or plane symmetrical as understood from FIGS. 1 to 10.
The first polishing pad and the second polishing pad of the present invention may have a recessed portion on the non-polishing surface (rear side of the pad) as required. This recessed portion has the function of dispersing a local pressure rise caused by the pressure of the polishing head in the chemical mechanical polishing step and contributes to the further reduction of the number of scratches on the polished face. The position of the recessed portion is not particularly limited but preferably located in the center portion of the pad. The expression “located in the center portion” means not only that the recessed portion is located at the center in the mathematically strict sense but also that the center of the non-polishing surface of the polishing pad may be located within the area of the above recessed portion.
The above recessed portion is not limited to a particular shape but preferably circular or polygonal, particularly preferably circular. When the recessed portion is circular, the upper limit of its diameter is preferably 100%, more preferably 75%, particularly preferably 50% of the diameter of a wafer as an object to be polished. When the recessed portion is circular, the lower limit of its diameter is preferably 1 mm, more preferably 5 mm irrespective of the size of the wafer as the object to be polished.
The shape of the chemical mechanical polishing pad of the present invention is not particularly limited. It may be shaped like a disk or polygonal pole. The shape of the chemical mechanical polishing pad of the present invention may be suitably selected according to a polishing machine to be used with the chemical mechanical polishing pad of the present invention.
For example, when the chemical mechanical polishing pad is shaped like a disk, its circular top surface and circular under surface serve as the polishing surface and the non-polishing surface, respectively.
The size of the chemical mechanical polishing pad is not particularly limited. For example, a disk-like chemical mechanical polishing pad has a diameter of 150 to 1,200 mm, particularly preferably 500 to 800 mm and a thickness of 0.5 to 5.0 mm, preferably 1.0 to 3.0 mm, particularly preferably 1.5 to 3.0 mm.
The chemical mechanical polishing pad of the present invention may be made of any material if it has the above grooves. For example, the chemical mechanical polishing pad may be a pad comprising a water-insoluble matrix and water-soluble particles dispersed in the water-insoluble matrix or a pad having fine pores in a water-insoluble matrix.
In the former material, the water-soluble particles dissolve or swell upon their contact with an aqueous medium of slurry containing an aqueous medium and solid matter at the time of polishing to be eliminated, and slurry can be held in pores formed by elimination. In the latter material, the slurry can be held in the pores formed as cavities.
The material for forming the above “water-insoluble matrix” is not particularly limited but an organic material is preferably used because it is easily molded to have a predetermined shape and predetermined properties and can provide suitable hardness and suitable elasticity. Examples of the organic material include thermoplastic resins, elastomers, rubbers such as crosslinked rubbers, and curable resins such as thermally or optically curable resins and resins cured by heat or light. They may be used alone or in combination.
Out of these, the above thermoplastic resins include 1,2-polybutadiene resin, polyolefin resins such as polyethylene, polystyrene resins, polyacrylic resins such as (meth)acrylate-based resins, vinyl ester resins (excluding acrylic resins), polyester resins, polyamide resins, fluororesins such as polyvinylidene fluoride, polycarbonate resins and polyacetal resins.
The above elastomers include diene elastomers such as 1,2-polybutadiene, polyolefin elastomer (TPO), styrene-based elastomers such as styrene-butadiene-styrene block copolymer (SBS) and hydrogenated block copolymers thereof (SEBS), thermoplastic elastomers such as thermoplastic polyurethane elastomers (TPU), thermoplastic polyester elastomers (TPEE) and polyamide elastomers (TPAE), silicone resin elastomers and fluororesin elastomers. The above rubbers include conjugated diene rubbers such as butadiene rubber (high cis-butadiene rubber, low cis-butadiene rubber, etc.), isoprene rubber, styrene-butadiene rubber and styrene-isoprene rubber, nitrile rubbers such as acrylonitrile-butadiene rubber, acrylic rubber, ethylene-α-olefin rubbers such as ethylene-propylene rubber and ethylene-propylene-diene rubber, butyl rubber, silicone rubber and fluorine rubber.
The above curable resins include urethane resins, epoxy resins, acrylic resins, unsaturated polyester resins, polyurethane-urea resins, urea resins, silicon resins, phenolic resins and vinyl ester resins.
These organic materials may be modified by an acid anhydride group, carboxyl group, hydroxyl group, epoxy group or amino group. The affinity for the water-soluble particles to be described hereinafter and slurry can be adjusted by modification.
These organic materials may be used alone or in combination of two or more.
The organic material may be a partially or wholly crosslinked polymer or non-crosslinked polymer. Therefore, the water-insoluble matrix may be composed of a crosslinked polymer alone, a mixture of a crosslinked polymer and a non-crosslinked polymer, or a non-crosslinked polymer alone. It is preferably composed of a crosslinked polymer alone or a mixture of a crosslinked polymer and a non-crosslinked polymer. When a crosslinked polymer is contained, elastic recovery force is provided to the water-insoluble matrix and displacement caused by shear stress applied to the polishing pad during polishing can be reduced. Further, it is possible to effectively prevent the pores from being filled by the plastic deformation of the water-insoluble matrix when it is excessively stretched at the time of polishing and dressing and the surface of the polishing pad from being excessively fluffed. Therefore, the pores are formed efficiently even during dressing, whereby the deterioration of the holding properties of the slurry during polishing can be suppressed and further the polishing pad is rarely fluffed, thereby not impairing polishing flatness. The method of crosslinking the above material is not particularly limited. For example, chemical crosslinking making use of an organic peroxide, sulfur or sulfur compound, or radiation crosslinking by applying an electron beam may be employed.
Out of these, chemical crosslinking is preferred. In the case of chemical crosslinking, an organic peroxide is preferably used as a crosslinking agent because it is easy to handle and does not contaminate an object to be polished. Examples of the organic peroxide include dicumyl peroxide, diethyl peroxide, di-t-butyl peroxide, diacetyl peroxide and diacyl peroxide. For chemical crosslinking, the amount of the crosslinking agent is preferably 0.01 to 5.0 parts by mass, more preferably 0.2 to 4.0 parts by mass based on 100 parts by mass of the crosslinkable polymer contained in the water-insoluble member. A chemical mechanical polishing pad which suppresses the occurrence of a scratch in the chemical mechanical polishing step can be obtained by setting the amount of the crosslinking agent to the above range. All of the material constituting the water-insoluble member may be crosslinked at a time, or part of the material constituting the water-insoluble member is crosslinked and then mixed with the rest of the material. Alternatively, several different types of specially crosslinked products may be mixed together.
For chemical crosslinking, a mixture of organic materials some of which the water-insoluble member are crosslinked and the other are not can be easily obtained with a single crosslinking operation by adjusting the amount of the crosslinking agent and crosslinking conditions. For radiation crosslinking, by adjusting the dose of radiation, the same effect as described above can be easily obtained.
Out of the above organic materials, a crosslinked rubber, curable resin, crosslinked thermoplastic resin or crosslinked elastomer may be used as the crosslinked polymer. A crosslinked thermoplastic resin and/or crosslinked elastomer all of which are stable to a strong acid or strong alkali contained in many kinds of slurry and are rarely softened by water absorption are/is preferred. Out of the crosslinked thermoplastic resin and crosslinked elastomer, what is crosslinked with an organic peroxide is more preferred, and crosslinked 1,2-polybutadiene is particularly preferred.
The amount of the crosslinked polymer is not particularly limited but preferably 30 vol % or more, more preferably 50 vol % or more, particularly preferably 70 vol % or more and may be 100 vol % of the water-insoluble matrix. When the amount of the crosslinked polymer contained in the water-insoluble matrix is smaller than 30 vol %, the effect obtained by containing the crosslinked polymer may not be fully obtained.
The residual elongation after breakage (to be simply referred to as “residual elongation at break” hereinafter) of the above water-insoluble matrix containing a crosslinked polymer can be 100% or less when a specimen of the above water-insoluble matrix is broken at 80° C. in accordance with JIS K 6251. That is, the total distance between bench marks of the specimen after breakage becomes 2 times or less the distance between the bench marks before breakage. This residual elongation at break is preferably 30% or less, more preferably 10% or less and particularly preferably 5% or less. When the above residual elongation at break is more than 100%, fine pieces scraped off from the surface of the polishing pad or stretched at the time of polishing and surface renewal tend to fill the pores disadvantageously. The “residual elongation at break” is an elongation obtained by subtracting the distance between bench marks before the test from the total distance between each bench mark and the broken portion of the broken and divided specimen in a tensile test in which a dumbbell-shaped specimen No. 3 is broken at a tensile rate of 500 mm/min and a test temperature of 80° C. in accordance with the “vulcanized rubber tensile test method” specified in JIS K 6251. The test is carried out at 80° C. because heat is generated by slide contact at the time of actual polishing.
The above “water-soluble particles” are particles which are eliminated from the water-insoluble matrix upon their contact with slurry as an aqueous dispersion in the polishing pad. This elimination may occur when they dissolve in water contained in the slurry upon their contact with water or when they swell and gel by absorbing this water. Further, this dissolution or swelling is caused not only by their contact with water but also by their contact with an aqueous mixed medium containing an alcohol-based solvent such as methanol.
The water-soluble particles have the effect of increasing the indentation hardness of the polishing pad in addition to the effect of forming pores in the polishing pad. For example, the shore D hardness of the polishing pad of the present invention can be set to preferably 35 or more, more preferably 50 to 90, particularly preferably 50 to 80 and generally 100 or less by adding the water-soluble particles. When the shore D hardness is 35 or more, pressure applied to the object to be polished can be increased, and the polishing rate can be thereby improved. In addition, high polishing flatness is obtained. Therefore, the water-soluble particles are particularly preferably made of a solid substance which can ensure sufficiently high indentation hardness for the polishing pad.
The material for forming the water-soluble particles is not particularly limited. They are, for example, organic water-soluble particles or inorganic water-soluble particles. Examples of the material of the organic water-soluble particles include saccharides (polysaccharides such as starch, dextrin and cyclodextrin, lactose, mannitol, etc.), celluloses (such as hydroxypropyl cellulose, methyl cellulose, etc.), protein, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, polyethylene oxide, water-soluble photosensitive resins, sulfonated polyisoprene and sulfonated polyisoprene copolymers. Examples of the material of the inorganic water-soluble particles include potassium acetate, potassium nitrate, potassium carbonate, potassium hydrogencarbonate, potassium chloride, potassium bromide, potassium phosphate and magnesium nitrate. These water-soluble particles may be used alone or in combination of two or more. The water-soluble particles may be made of a predetermined single material, or two or more different materials.
The water-soluble particles have an average particle diameter of preferably 0.1 to 500 μm, more preferably 0.5 to 100 μm. The pores are as big as preferably 0.1 to 500 μm, more preferably 0.5 to 100 μm. When the average particle diameter of the water-soluble particles is smaller than 0.1 μm, the formed pores become smaller in size than the abrasive grains in use, whereby a polishing pad capable of holding slurry completely may be hardly obtained. When the average particle diameter is larger than 500 μm, the formed pores become too big, whereby the mechanical strength and polishing rate of the obtained polishing pad may lower.
The amount of the water-soluble particles is preferably 2 to 90 vol %, more preferably 2 to 60 vol %, particularly preferably 2 to 40 vol % based on 100 vol % of the total of the water-insoluble matrix and the water-soluble particles. When the amount of the water-soluble particles is smaller than 2 vol %, pores are not fully formed in the obtained polishing pad and the polishing rate may lower. When the amount of the water-soluble particles is larger than 90 vol %, it may be difficult to completely prevent the water-soluble particles existent in the interior of the obtained polishing pad from swelling or dissolving, thereby making it difficult to maintain the hardness and mechanical strength of the obtained chemical mechanical polishing pad at appropriate values.
It is preferred that the water-soluble particles should dissolve in water only when they are exposed to the surface layer of the polishing pad and should not absorb moisture or swell when they are existent in the interior of the polishing pad. Therefore, the water-soluble particles may have an outer shell for suppressing moisture absorption on at least part of their outermost portion. This outer shell may be physically adsorbed to the water-soluble particle, chemically bonded to the water-soluble particle, or in contact with the water-soluble particle by physical adsorption and chemical bonding. The outer shell is made of epoxy resin, polyimide, polyamide or polysilicate. Even when it is formed on only part of the water-soluble particle, the above effect can be fully obtained.
The above water-insoluble matrix may contain a compatibilizing agent to control its affinity for the water-soluble particles and the dispersibility of the water-soluble particles in the water-insoluble matrix. Examples of the compatibilizing agent include homopolymers, block copolymers and random copolymers modified by an acid anhydride group, carboxyl group, hydroxyl group, epoxy group, oxazoline group or amino group, nonionic surfactants and coupling agents.
The water-insoluble matrix material constituting the polishing pad comprising the latter water-insoluble matrix material (foam, etc.) containing cavities dispersed therein is, for example, a polyurethane, melamine resin, polyester, polysulfone or polyvinyl acetate.
The average size of the cavities dispersed in the above water-insoluble matrix material is preferably 0.1 to 500 μm, more preferably 0.5 to 100 μm.
The process for manufacturing the chemical mechanical polishing pad of the present invention is not particularly limited, and the methods of forming the grooves of the chemical mechanical polishing pad and the optional recessed portion in the rear surface of the chemical mechanical polishing pad (both will be generally referred to as “grooves” hereinafter) are not particularly limited as well. For example, after a composition for forming a chemical mechanical polishing pad which will become a chemical mechanical polishing pad is prepared and molded into a substantially desired form, grooves may be formed by cutting. Alternatively, a metal mold having a groove pattern is used to mold the composition for forming a chemical mechanical polishing pad, thereby making it possible to form groves simultaneously with the manufacture of a desired form for the chemical mechanical polishing pad. The surface roughness of the inner wall of each of the grooves can be easily set to 20 μm or less by molding.
The method of obtaining the composition for forming a chemical mechanical polishing pad is not particularly limited. For example, the composition can be obtained by kneading together required materials including a predetermined organic material by means of a kneader. A conventionally known kneader may be used, such as a roll, kneader, Banbury mixer or extruder (single-screw, multiple-screw).
The composition for forming a chemical mechanical polishing pad, which comprises water-soluble particles for obtaining a polishing pad containing the water-soluble particles, can be obtained, for example, by kneading together a water-insoluble matrix, water-soluble particles and other additives. In general, they are kneaded together under heating so that they can be easily processed at the time of kneading. The water-soluble particles are preferably solid at this kneading temperature. When they are solid, they can be dispersed with the above preferred average particle diameter irrespective of their compatibility with the water-insoluble matrix. Therefore, the type of the water-soluble particles is preferably selected according to the processing temperature of the water-insoluble matrix in use.
The chemical mechanical polishing pad of the present invention may be a multi-layer pad having a base layer formed on the non-polishing surface of the above pad.
The above “base layer” is a layer formed on the rear surface to support the chemical mechanical polishing pad. Although the characteristic properties of this base layer are not particularly limited, the base layer is preferably softer than the pad body. When the pad has a soft base layer, if the pad body is thin, for example, 1.0 mm or less, it is possible to prevent the pad body from rising during polishing or the surface of the polishing layer from curving, whereby polishing can be carried out stably. The hardness of the base layer is preferably 90% or less, more preferably 50 to 90%, much more preferably 50 to 80%, particularly preferably 50 to 70% of the hardness of the pad body.
The base layer may be made of a porous material such as foam or a non-porous material. The planar shape of the base layer is not particularly limited and may be the same or different from that of the polishing layer. The planar shape of the base layer may be circular or polygonal, for example, tetragonal. Its thickness is not particularly limited but preferably 0.1 to 5 mm, more preferably 0.5 to 2 mm.
Although the material of the base layer is not particularly limited, an organic material is preferably used because it can be easily molded to have a predetermined shape and predetermined properties and can provide suitable elasticity.
The above-described chemical mechanical polishing pad of the present invention can provide an excellent polished surface at a high polishing rate and has a long service life.
The mechanism that the chemical mechanical polishing pad of the present invention reduces the number of scratches on the polished surface of an object is not made clear yet. Since a phenomenon that an aqueous dispersion for chemical mechanical polishing and polishing chips are remained in the center portion of the conventionally known chemical mechanical polishing pad is observed in the chemical mechanical polishing step, it is assumed that the above holdup serves as the source of a scratch. Meanwhile, since the above phenomenon is not observed in the chemical mechanical polishing step when the chemical mechanical polishing pad of the present invention is used, it is considered that the remains are effectively removed by the formation of the above grooves in the polishing surface, thereby obtaining the effect of reducing the number of scratches.
The chemical mechanical polishing method of the present invention is characterized by making use of the chemical mechanical polishing pad of the present invention. The chemical mechanical polishing pad of the present invention can be used for chemical mechanical polishing by means of known processes when it is set in a commercially available polishing machine.
The type of the surface to be polished and the type of the aqueous dispersion for chemical mechanical polishing in use are not particularly limited.
(1) Manufacture of Chemical Mechanical Polishing Pad
80 parts by volume (equivalent to 72 parts by mass) of 1,2-polybutadiene (manufactured by JSR Corporation, trade name of JSR RB830) which would be crosslinked to become a water-insoluble matrix and 20 parts by volume (equivalent to 28 parts by mass) of β-cyclodextrin (manufactured by Bio Research Corporation of Yokohama, trade name of Dexy Pearl β-100, average particle diameter of 20 μm) as water-soluble particles were kneaded together by an extruder set at 160° C. Thereafter, 1.0 part by volume (equivalent to 1.1 parts by mass) of dicumyl peroxide (manufactured by NOF Corporation, trade name of Percumyl D) was added to and kneaded with the above kneaded product at 120° C. to obtain a pellet. The resulting kneaded product was then heated in a metal mold at 170° C. for 18 minutes to be crosslinked so as to obtain a disk-like molded product having a diameter of 600 mm and a thickness of 2.5 mm. Concentrically circular grooves having a width of 0.5 mm and a depth of 1.0 mm were formed in the polishing surface of this molded product at a pitch of 2.0 mm by using a cutting machine manufactured by Kato Machinery Co., Ltd. (first group of grooves). Further, 16 linear grooves (having a width of 1.0 mm and a depth of 1.0 mm) extending from the center to the peripheral end of the pad were formed in the polishing surface in such a manner that they were in contact with one another at the center of the polishing surface of the pad and the angle between adjacent linear grooves was 22.5° (second group of grooves). The arrangement of the formed grooves is shown in the diagram of
(2) Evaluation of Polishing Rate and the Number of Scratches
The above manufactured chemical mechanical polishing pad was set on the platen of a polishing machine (EPO112 of Ebara Corporation), and a wafer (diameter of 8 inches) having an SiO2 film (PETEOS film: SiO2 film formed from tetraethyl orthosilicate (TEOS) by chemical vapor deposition using plasma as a promoting condition) and no pattern was polished by using the CMS-1101 (trade name, manufactured by JSR Corporation) diluted 3 times as chemical mechanical polishing slurry under the following conditions to evaluate the polishing rate and the number of scratches. As a result, the polishing rate was 210 nm/min and no scratch was observed on the polished surface.
The above polishing rate was calculated from the difference in film thickness by measuring the thickness of the film before and after polishing with an optical film thickness meter. The number of scratches on the entire polished surface of the SiO2 film wafer after polishing was counted with a wafer defect inspection device (KLA2351 of KLA-Tencor Co., Ltd.).
A chemical mechanical polishing pad was manufactured in the same manner as in Example 1 except that 4 linear grooves (having a width of 1.0 mm and a depth of 1.0 mm) were formed from the center to the peripheral end of the pad as a second group of grooves in such a manner that they were in contact with one another at the center of the polishing surface of the pad and the angle between adjacent linear grooves was 90° and that 28 linear grooves were formed from a portion 25 mm away from the center of the pad to the peripheral end in such a manner that the angle between adjacent linear grooves was 11.25°. The arrangement of the formed grooves is shown in the diagram of
The polishing rate and the number of scratches were evaluated in the same manner as in Example 1 except that the above polishing pad was used. As a result, the polishing rate was 220 nm/min and no scratch was observed.
64 parts by volume (equivalent to 58 parts by mass) of 1,2-polybutadiene (manufactured by JSR Corporation, trade name of JSR RB830), 16 parts by volume (equivalent to 14 parts by mass) of a block copolymer of 1,2-polybutadiene and polystyrene (manufactured by JSR Corporation, trade name of TR2827) and 20 parts by volume (equivalent to 28 parts by mass) of β-cyclodextrin (manufactured by of Bio Research Corporation of Yokohama, trade name of Dexy Pearl β-100, average particle diameter of 20 μm) as water-soluble particles were kneaded together by an extruder set at 160° C. Thereafter, 0.5 part by volume (equivalent to 0.56 part by mass) of dicumyl peroxide (manufactured by NOF Corporation, trade name of Percumyl D) was added to and kneaded with the above kneaded product at 120° C. to obtain a pellet. The resulting kneaded product was then heated in a metal mold at 180° C. for 10 minutes to be crosslinked so as to obtain a disk-like molded product having a diameter of 600 mm and a thickness of 2.5 mm. Concentrically circular grooves having a width of 0.5 mm and a depth of 1.0 mm were formed in the polishing surface of this molded product at a pitch of 1.5 mm by using a cutting machine manufactured by Kato Machinery Co., Ltd. (first group of grooves). Further, 8 linear grooves (having a width of 1.0 mm and a depth of 1.0 mm) were formed from the center to the peripheral end of the pad in such a manner that they were in contact with one another at the center of the polishing surface of the pad and the angle between adjacent linear grooves was 45° (second group of grooves), and further 56 linear grooves were formed from a portion 25 mm away from the center of the pad to the peripheral end in such a manner that the angle between adjacent linear grooves was 5.625° (second group of grooves). The arrangement of the formed grooves is shown in the diagram of
The polishing rate and the number of scratches were evaluated in the same manner as in Example 1 except that the above polishing pad was used. As a result, the polishing rate was 185 nm/min and no scratch was observed.
56 parts by volume (equivalent to 48 parts by mass) of 1,2-polybutadiene (manufactured by JSR Corporation, trade name of JSR RB830), 14 parts by volume (equivalent to 12 parts by mass) of polystyrene (manufactured by A and Enstyrene Co., Ltd., trade name of GPPS HF55) and 30 parts by volume (equivalent to 40 parts by mass) of β-cyclodextrin (manufactured by of Bio Research Corporation of Yokohama, trade name of Dexy Pearl β-100, average particle diameter of 20 μm) as water-soluble particles were kneaded together by an extruder set at 160° C. Thereafter, 0.5 part by volume (equivalent to 0.56 part by mass) of dicumyl peroxide (manufactured by NOF Corporation, trade name of Percumyl D) was added to and kneaded with the above kneaded product at 120° C. to obtain a pellet. The resulting kneaded product then was heated in a metal mold at 180° C. for 10 minutes to be crosslinked so as to obtain a disk-like molded product having a diameter of 600 mm and a thickness of 2.8 mm. Concentrically circular grooves having a width of 0.5 mm and a depth of 1.4 mm were formed in the polishing surface of this molded product at a pitch of 2.0 mm by using a cutting machine manufactured by Kato Machinery Co., Ltd. (first group of grooves). Further, a second group of grooves were formed in the same manner as in Example 2 except that the depth of the grooves was changed to 1.4 mm. The surface roughness of the inner wall of each of the formed grooves was 3.5 μm.
A chemical mechanical polishing pad was manufactured in the same manner as in Example 1 except that 4 linear grooves (having a width of 1.0 mm and a depth of 1.0 mm) were formed from the center to the periphery of the pad as a second group of grooves in such a manner that they were in contact with one another at the center of the polishing surface of the pad and the angle between adjacent linear grooves was 90°, that 28 linear grooves were formed from a portion 25 mm away from the center to the peripheral end of the pad in such a manner that the angle between adjacent linear grooves was 11.25° and that 32 linear grooves were formed from a portion 75 mm away from the center to the peripheral end of the pad in such a manner that the angle between adjacent linear grooves was 5.625°. The arrangement of the formed grooves is shown in the diagram of
When the polishing rate and the number of scratches were evaluated in the same manner as in Example 1 except that the above polishing pad was used, the polishing rate was 225 nm/min and no scratch was observed.
80 parts by volume (equivalent to 72 parts by mass) of 1,2-polybutadiene (manufactured by JSR Corporation, trade name of JSR RB830) and 20 parts by volume (equivalent to 28 parts by mass) of β-cyclodextrin (manufactured by Bio Research Corporation of Yokohama, trade name of Dexy Pearl β-100, average particle diameter of 20 μm) as water-soluble particles were kneaded together by an extruder set at 160° C. Thereafter, 0.12 part by volume (equivalent to 0.13 part by mass) of dicumyl peroxide (manufactured by NOF Corporation, trade name of Percumyl D) was added to and kneaded with the above kneaded product at 120° C. to obtain a pellet. The resulting kneaded product was then heated in a metal mold at 170° C. for 18 minutes to be crosslinked so as to obtain a disk-like molded product having a diameter of 800 mm and a thickness of 2.5 mm. The same grooves as in Example 1 were formed in this molded product. The surface roughness of the inner wall of each of the formed grooves was 3.5 μm. A center portion having a diameter of 600 mm was cut out from this polishing pad having a diameter of 800 mm to evaluate the polishing rate and the number of scratches in the same manner as in Example 1. As a result, the polishing rate was 254 nm/min and no scratch was observed.
A chemical mechanical polishing pad was manufactured in the same manner as in Example 2 except that 28 pairs of linear grooves were formed with an interval between the grooves of each pair of 2 mm in place of the 28 linear grooves in Example 2. The grooves are shown in the diagram of
Since the paired linear grooves were formed from the center portion to the peripheral portion of the pad with an interval between the grooves of each pair of 2 mm, it is understood that the paired linear grooves slightly shifted from the diameter direction of the pad though they started from the center portion of the pad.
28.2 parts by mass of polytetramethylene glycol having two hydroxyl groups at both terminals of the molecule and a number average molecular weight of 650 (manufactured by Mitsubishi Chemical Co., Ltd., trade name of PTMG650) and 21.7 parts by mass of 4,4′-diphenylmethane diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., trade name of Sumidule 44S) were fed to a reactor and maintained at 90° C. for 3 hours under agitation to carry out a reaction, and then cooled to obtain a prepolymer having an isocyanate group at both terminals.
14.5 parts by mass of β-cyclodextrin (manufactured by Bio Research Corporation of Yokohama, trade name of Dexy Pearl β-100, average particle diameter of 20 μm) as water-soluble particles was dispersed into 21.6 parts by mass of polypropylene glycol having three hydroxyl groups and a number average molecular weight of 330 (manufactured by NOF Corporation, trade name of Uniol TG300, addition reaction product of glycerin and propylene oxide) and 6.9 parts by mass of the PTMG650 polytetramethylene glycol as crosslinking agents by agitation, and further 0.1 part by mass of 2-methyl triethylenediamine (manufactured by Sankyo Air Products Co., Ltd., trade name of Me-DABCO) was dissolved in the obtained dispersion as a reaction accelerator by agitation. The resulting mixture was added to the reactor of the above prepolymer having an isocyanate group at both terminals.
Further, 21.6 parts by mass of the Sumidule 44S 4,4′-diphenylmethane diisocyanate was added to the above reactor of the prepolymer having an isocyanate group at both terminals, stirred at 200 rpm at room temperature for 2 minutes and defoamed under reduced pressure to obtain a raw material mixture.
This raw material mixture was injected into a metal mold having a diameter of 60 cm and a thickness of 3 mm and maintained at 80° C. for 20 minutes to carry out the polymerization of polyurethane and further post-cured at 110° C. for 5 hours to obtain a molded product having a diameter of 600 mm and a thickness of 2.5 mm. Thereafter, the same grooves as in Example 1 were formed in this molded product. The surface roughness of the inner wall of each of the formed grooves was 3.0 μm.
The polishing rate and the number of scratches were evaluated in the same manner as in Example 1 except that the above polishing pad was used. As a result, the polishing rate was 231 nm/min and no scratch was observed.
A disk-like molded product as large as that of Example 1 was produced in the same manner as in Example 1 in order to manufacture a chemical mechanical polishing pad in the same manner as in Example 1 except that only concentrically circular grooves (first group of grooves) having a width of 0.5 mm, a pitch of 2.0 mm and a depth of 1.0 mm were formed in the polishing surface by using a commercially available cutting machine. The surface roughness of the inner wall of each of the formed grooves was 4.8 μm.
The polishing rate and the existence of scratches were evaluated in the same manner as in Example 1 except that this polishing pad was used. As a result, the polishing rate was 200 nm/min and 15 scratches were seen.
A disk-like molded product as large as that of Example 1 was produced in the same manner as in Example 1 in order to manufacture a chemical mechanical polishing pad in the same manner as in Example 1 except that the first group of concentrically circular grooves were not formed and only the second group of grooves were formed in the polishing surface. The surface roughness of the inner wall of each of the formed grooves was 4.5 μm.
The polishing rate and the existence of scratches were evaluated in the same manner as in Example 1 except that this polishing pad was used. As a result, the polishing rate was 120 nm/min and 25 scratches were seen.
A disk-like molded product as large as that of Example 1 was produced in the same manner as in Example 1 in order to manufacture a chemical mechanical polishing pad in the same manner as in Example 1 except that grooves having a width of 1.0 mm and a depth of 1.0 mm were formed in a lattice in the polishing surface at a pitch of 10.0 mm by using a commercially available cutting machine. The surface roughness of the inner wall of each of the formed grooves was 5.5 μm.
The polishing rate and the existence of scratches were evaluated in the same manner as in Example 1 except that this polishing pad was used. As a result, the polishing rate was 150 nm/min and 50 scratches were seen.
As described above, the chemical mechanical polishing pad of the present invention fully suppresses the occurrence of a scratch on the polished surface and has an excellent polishing rate, and the chemical mechanical polishing method making use of the polishing pad of the present invention provides a polished object having an excellent surface state at a high polishing rate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-149884 | May 2004 | JP | national |
