Patent Application
20200399089
The present invention relates to a tape attaching method of attaching an adhesive tape to a workpiece.
In a manufacturing process for device chips, there is used a wafer having respective devices formed in a plurality of regions demarcated by a plurality of division lines (streets). Such wafer is divided along the plurality of division lines into individual devices to obtain a plurality of device chips. The wafer is subjected to various processing by use of a processing apparatus. Examples of processing a wafer include grinding of grinding a wafer with a grinding apparatus to thin the wafer, cutting of cutting a wafer with a cutting apparatus to divide the wafer, or the like. Also, when a wafer is processed with a processing apparatus, an adhesive tape is attached to the wafer with a view to enhancing wafer handling, protecting a device formed in the wafer, or the like.
In recent years, a technique of automatically attaching an adhesive tape to a wafer has been widely used. For example, Japanese Patent Laid-Open No. H6-177243 discloses a tape attaching apparatus including a holding table for holding a wafer thereon and a movable roller for attaching an adhesive tape to the wafer. This tape attaching apparatus causes the movable roller to be rotated about its axis from one end of the wafer to the other end of the wafer in a state in which the adhesive tape is arranged on the wafer held on the holding table and to press the adhesive tape toward the wafer. Accordingly, the adhesive tape is automatically attached to the wafer.
In a wafer, fine dense devices such as devices configured through micro electro mechanical systems (MEMS) technology may be formed. In a case where the above-described tape attaching apparatus is used in attaching an adhesive tape to such a wafer formed with the devices described above, a device may be damaged due to a large pressing force applied by the movable roller. Accordingly, depending on a structure, a characteristic, or the like of a device formed in a wafer, there is demanded a method of attaching an adhesive tape to a wafer in such a manner that a load is not applied to the wafer as much as possible. In view of this, a technique of attaching an adhesive tape to a wafer by arranging the wafer onto the adhesive tape which is supported in a flat state may be used in some cases. In this technique, a wafer is not pressed excessively, and accordingly, damages or the like of a device formed in the wafer are less likely to occur.
However, when a method of arranging a wafer on an adhesive tape is used, gas is enclosed between the wafer and the adhesive tape, resulting in generation of bubbles, in some cases. The remaining bubbles prevent appropriate adhesion between the wafer and the adhesive tape, causing occurrence of processing defects upon processing the wafer. For example, the bubbles prevent the wafer from being held in a flat state, and as a result, it may be difficult to grind the entire wafer uniformly upon subjecting grinding processing on the wafer, in some cases. Also, when the wafer is cut and divided into a plurality of device chips, adhesion between each device chip and the adhesive tape is prevented due to the bubbles, resulting in scattering of the chip, in some cases.
The present invention has been made in view of such a problem, and it is therefore an object of the present invention to provide a tape attaching method in which bubbles remaining between an adhesive tape and a workpiece typified by a wafer formed with devices can be removed easily.
In accordance with an aspect of the present invention, there is provided a tape attaching method of attaching an adhesive tape to a workpiece, including a tape attaching step of attaching the adhesive tape to the workpiece in gas having a smaller molecular weight than an average molecular weight of the atmosphere, and a gas permeating step of causing the gas remaining between the workpiece and the adhesive tape to permeate the adhesive tape to thereby be removed, after the tape attaching step is carried out.
Preferably, in the gas permeating step, the adhesive tape may be heated. Preferably, in the gas permeating step, a pressure may be applied to one of or both the workpiece and the adhesive tape in a direction in which the workpiece and the adhesive tape come in close contact with each other. Still preferably, the gas may be helium.
The tape attaching method according to a preferred embodiment of the present invention includes a tape attaching step of attaching the adhesive tape to the workpiece in gas having a smaller molecular weight than the average molecular weight of the atmosphere, and a gas permeating step of causing the gas remaining between the workpiece and the adhesive tape to permeate the adhesive tape to thereby be removed. In this tape attaching method, since the gas entering between the workpiece and the adhesive tape is gas having a smaller molecular weight than the average molecular weight of the atmosphere, the gas is likely to permeate the adhesive tape. Accordingly, the bubbles remaining between the workpiece and the adhesive tape are likely to be easily removed.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing a preferred embodiment of the invention.
Hereinafter, a detailed description will be given regarding a preferred embodiment of the present invention with reference to the drawings. First, there will be described a configuration example of a workpiece to which an adhesive tape is attached in a tape attaching method according to the preferred embodiment of the present invention.
The workpiece 11 is a disc-shaped silicon wafer, for example, and has a front surface 11a and a back surface 11b. The workpiece 11 is demarcated into a plurality of regions by a plurality of division lines (streets) 13 which are arrayed in a grid pattern so as to cross each other, and each region on the front surface 11a side has a device 15 including a MEMS device formed therein. In other words, the workpiece 11 is a MEMS wafer including a plurality of MEMS devices. It is to be noted that, however, the workpiece 11 is not limited in material, shape, structure, size, or the like. For example, the workpiece 11 may be formed of a material such as a semiconductor other than silicon (gallium arsenide (GaAs), indium phosphide (InP), gallium nitride (GaN), silicon carbide (SiC), or the like), glass, ceramic, resin, or metal. In addition, the devices 15 are not limited in kind, number, shape, structure, size, and layout, for example. For example, the device 15 may be an integrated circuit (IC), a large scale integration (LSI), or the like. Moreover, the workpiece 11 may not have any of the devices 15 formed therein.
When the workpiece 11 is divided along the division lines 13, a plurality of device chips are obtained, and each device chip includes each of the devices 15. Note that, in the case of dividing the workpiece 11, used are a cutting apparatus which cuts the workpiece 11 with an annular blade and a laser processing apparatus which processes the workpiece 11 with irradiation of a laser beam, for example. In addition, with a view to thinning the device chips, the workpiece 11 before being divided may be thinned, in some cases. In the case of thinning the workpiece 11, used are a grinding apparatus which grinds the workpiece 11 with grindstones and a polishing apparatus which polishes the workpiece 11 with a polishing pad, for example.
When various types of processing apparatuses described above are used to process the workpiece 11, with a view to enhancing a handling property of the workpiece 11, protecting the devices 16 formed in the workpiece 11, or the like, an adhesive tape is attached to the workpiece 11. For example, in order to facilitate transfer and holding of the workpiece 11, the workpiece 11 may be supported by an annular frame through the adhesive tape.
When the adhesive tape 17 is attached to the workpiece 11, gas is enclosed between the workpiece 11 and the adhesive tape 17, and bubbles may be formed therebetween. For example, when attachment of the adhesive tape 17 is carried out in the atmosphere, the air enters a gap between the workpiece 11 and the adhesive tape 17, and after the adhesive tape 17 is attached to the workpiece 11, bubbles containing the air may remain between the workpiece 11 and the adhesive tape 17. These remaining bubbles prevent appropriate adhesion between the workpiece 11 and the adhesive tape 17, causing occurrence of processing defects upon processing the workpiece 11. For example, there may be a case in which the workpiece 11 is not held in a flat state due to the bubbles and it becomes difficult to grind the entire workpiece 11 uniformly in carrying out grinding processing on the workpiece 11. Also, when the workpiece 11 is cut to be divided into a plurality of device chips, adhesion between each device chip and the adhesive tape 17 is hindered by the bubbles, causing a risk of scattering of the chips. To cope with this problem, it is desirable to remove the bubbles remaining between the workpiece 11 and the adhesive tape 17.
Removal of the bubbles is carried out, for example, by heating the adhesive tape 17 to increase gas permeability of the gas contained in the bubbles with respect to the adhesive tape 17. Accordingly, the gas is more likely to permeate the adhesive tape 17, and as a result, the gas easily goes out from between the workpiece 11 and the adhesive tape 17. It is to be noted that, however, in a case in which the gas contained in the bubbles is air, even if the heating process described above is carried out, the bubbles may not be sufficiently removed, or it may take a long period of time to remove the bubbles.
In view of this, in the preferred embodiment of the present invention, the adhesive tape 17 is attached to the workpiece 11 in the gas having a smaller molecular weight than the average molecular weight of the atmosphere. Note that the average molecular weight of the atmosphere corresponds to an average value of the molecular weight of gas contained in the atmosphere (air) on the ground. When the adhesive tape 17 is attached to the workpiece 11 in this gas, in a case in which the bubbles remain between the workpiece 11 and the adhesive tape 17, the molecular weight of the gas contained in the bubbles becomes smaller than the average molecular weight of the atmosphere.
The gas having a smaller molecular weight than the average molecular weight of the atmosphere is more likely to permeate the adhesive tape 17 than the air. Accordingly, even if this gas enters the gap between the workpiece 11 and the adhesive tape 17 and the bubbles are formed therein upon attachment of the adhesive tape 17, these bubbles are likely to permeate the adhesive tape 17 going out from the gap between the workpiece 11 and the adhesive tape 17. As a result, the gas remaining between the workpiece 11 and the adhesive tape 17 is easily removed. Examples of the gas having a smaller molecular weight than the average molecular weight of the atmosphere include hydrogen, helium (monatomic molecule), nitrogen, neon (monatomic molecule), methane, ammonia, hydrogen fluoride, acetylene, carbon monoxide, ethylene, or the like. In particular, since helium has a small molecular weight (atomic weight) and high safety, helium is preferable as gas (gaseous atmosphere) to be used in attachment between the workpiece 11 and the adhesive tape 17.
Note that the attachment of the adhesive tape 17 to the workpiece 11 may be carried out with hands or by use of a dedicated apparatus (tape attaching apparatus).
The tape attaching apparatus 2 includes a cylindrical chamber 4 capable of accommodating the workpiece 11 and the adhesive tape 17 attached to the workpiece 11. The chamber 4 includes a cylindrical main body portion 6 which is opened on an upper side thereof, and a lid portion 8 which opens/closes the opening of the main body portion 6. Inside the chamber 4, there are formed a tape holding portion 4a in which the adhesive tape 17 is held, and a workpiece holding portion 4b on which the workpiece 11 is held. The tape holding portion 4a is a cylindrical space formed inside the chamber 4. Also, the workpiece holding portion 4b is a cylindrical space (recess) formed downward from a bottom of the tape holding portion 4a. Note that the workpiece holding portion 4b is smaller in diameter than the tape holding portion 4a, and a T-shaped space in cross-sectional view is formed inside the chamber 4.
An annular frame supporting portion 10 is provided in the tape holding portion 4a to support the annular frame 19 with the adhesive tape 17 being attached thereto. The frame supporting portion 10 includes a circular opening 10a vertically extending in a central portion of the frame supporting portion 10, and the opening 10a is arranged so as to overlap with the workpiece holding portion 4b. Note that a diameter of the opening 10a is set substantially equal to the diameter of the opening 19a of the annular frame 19, for example. In addition, the workpiece holding portion 4b has a holding table 12 holding the workpiece 11 provided therein. The holding table 12 is formed so as to have a diameter substantially equal to the diameter of the workpiece holding portion 4b. The holding table 12 is accommodated in the workpiece holding portion 4b in such a state as to be movable in a vertical direction and supported by the main body portion 6 of the chamber 4. Note that a height of the holding table 12 is smaller than a height of the workpiece holding portion 4b, and a gap is secured on a lower side of the holding table 12. Also, an upper surface of the holding table 12 constitutes a holding surface 12a for holding the workpiece 11.
The tape holding portion 4a is connected to a gas supplying source 18 through a flow path 14a formed in the main body portion 6 and a valve 16a. The gas supplying source 18 supplies gas having a smaller molecular weight than the average molecular weight of the atmosphere to the tape holding portion 4a through the valve 16a and the flow path 14a. Also, the tape holding portion 4a is connected to a valve 16b through a flow path 14b formed in the main body portion 6. When the valve 16b is opened, the tape holding portion 4a is opened to the atmosphere. A lower region of the holding table 12 of the workpiece holding portion 4b is connected to an air supplying source 20 through a flow path 14c formed in the main body portion 6 and a valve 16c. The air supplying source 20 supplies air to the workpiece holding portion 4b through the valve 16c and the flow path 14c. In addition, the lower region of the holding table 12 of the workpiece holding portion 4b is connected to a valve 16d through a flow path 14d formed in the main body portion 6. When the valve 16d is opened, the workpiece holding portion 4b is opened to the atmosphere. Note that the tape holding portion 4a and the lower region of the holding table 12 of the workpiece holding portion 4b are separated from each other by the holding table 12. Thus, communication of the gas between these two regions is blocked.
Next, an operational example of the tape attaching apparatus 2 in a tape attaching step of attaching the adhesive tape 17 to the workpiece 11 in the tape attaching method according to the preferred embodiment of the present invention will be described. Note that a case in which helium is supplied from the gas supplying source 18 will be described below by way of example. However, the gas to be supplied from the gas supplying source 18 (the gas having a smaller molecular weight than the average molecular weight of the atmosphere) can be changed appropriately.
First, the lid portion 8 is opened, and the workpiece 11 is held on the holding table 12 in such a way that a surface of the workpiece 11 to which the adhesive tape 17 is attached is exposed upward. For example, in a case in which the adhesive tape 17 is attached to the back surface 11b side of the workpiece 11, the workpiece 11 is arranged onto the holding table 12 such that the front surface 11a of the workpiece 11 faces the holding surface 12a. In addition, the annular frame 19 with the adhesive tape 17 being attached thereto is supported on the frame supporting portion 10. The annular frame 19 is supported such that a surface to which the adhesive tape 17 is not attached comes in contact with the frame supporting portion 10. Note that the workpiece 11 and the annular frame 19 are arranged such that a center of the workpiece 11 and a center of the opening 19a of the annular frame 19 overlap with each other in plan view.
Next, the lid portion 8 is closed to hermetically seal the tape holding portion 4a. Then, the valves 16a and 16b are opened, and helium gas is supplied by a predetermined flow rate to the tape holding portion 4a from the gas supplying source 18, while the atmosphere remaining inside the tape holding portion 4a is discharged through the flow path 14b and the valve 16b. Accordingly, the tape holding portion 4a is filled with helium gas. Next, with the valve 16d being closed, the valve 16c is opened, so that air is supplied by a predetermined flow rate to the workpiece holding portion 4b from the air supplying source 20. Accordingly, a pressure in the lower region of the holding table 12 of the workpiece holding portion 4b increases, so that the holding table 12 is pushed upward. As a result, the workpiece 11 moves toward the adhesive tape 17. Then, the back surface 11b side of the workpiece 11 and the adhesive tape 17 come in contact with each other under helium gas, and then, the adhesive tape 17 is attached to the workpiece 11.
Subsequently, the valve 16c is closed while the valve 16d is opened, so that the workpiece holding portion 4b is opened to the atmosphere. Accordingly, the pressure in the lower region of the holding table 12 of the workpiece holding portion 4b decreases, so that the holding table 12 is lowered. At this time, the workpiece 11 is kept being attached to the adhesive tape 17 and held thereon.
Note that, although
As described above, in the tape attaching step of the preferred embodiment of the present invention, the adhesive tape 17 is attached to the workpiece 11 in the gas having a smaller molecular weight than the average molecular weight of the atmosphere.
When the adhesive tape 17 is attached to the workpiece 11, the air enters a gap between the workpiece 11 and the adhesive tape 17, and bubbles 21 may be formed between the workpiece 11 and the adhesive layer 17b of the adhesive tape 17, in some cases. In the preferred embodiment of the present invention, attachment of the workpiece 11 and the adhesive tape 17 is carried out in the gas having a smaller molecular weight than the average molecular weight of the atmosphere. Accordingly, the gas contained in the bubbles 21 is gas having a smaller molecular weight than the average molecular weight of the atmosphere. In addition, this gas is more likely to permeate the adhesive tape 17 than the air, the gas is easily removed from between the workpiece 11 and the adhesive tape 17.
For example, after the tape attaching step is carried out, the workpiece 11 and the adhesive tape 17 are left for a given period of time in a state in which the workpiece 11 is arranged onto the adhesive tape 17 (see
Note that, in order to enhance removal of the bubbles 21 in the gas permeating step, a predetermined process may be carried out. For example, the adhesive tape 17 is heated, thereby causing the gas contained in the bubbles 21 to easily permeate the adhesive tape 17.
In addition, in the gas permeating step, a pressure may be applied to one of or both the workpiece 11 and the adhesive tape 17 in a direction in which the workpiece 11 and the adhesive tape 17 come in close contact with each other. For example, in a state in which the workpiece 11 is supported by the annular frame 19 (see
In addition, applying the pressure on the workpiece 11 can be also carried out by use of a holding table for holding under suction the workpiece 11.
The holding table 40 is formed into a cylindrical shape larger in diameter than the workpiece 11, for example, and its upper surface constitutes a holding surface 40a for holding the workpiece 11. In addition, the holding table 40 includes a porous member 42 which is formed of a porous ceramic material or the like on the holding surface 40a side. The porous member 42 is formed into a disc shape smaller in diameter than the holding table 40, for example, and is fit in the holding surface 40a of the holding table 40. Note that an upper surface of the porous member 42 constitutes part of the holding surface 40a. The porous member 42 is connected to a suction source 46 such as an ejector through a flow path 40b formed inside the holding table 40 and a valve 44. In addition, a plurality of clamps 48 for gripping the annular frame 19 which supports the workpiece 11 to be fixed thereto are provided in the periphery of the holding table 40.
The workpiece 11 is arranged on the holding table 40 in such a way that the surface of the workpiece 11 to which the adhesive tape 17 is attached (the back surface 11b side) faces the holding surface 40a. In addition, the annular frame 19 is fixed with the plurality of clamps 48. In this state, a negative pressure from the suction source 46 is applied to the holding surface 40a through the valve 44, the flow path 40b, and the porous member 42. Then, a suction force is applied to the workpiece 11 through the adhesive tape 17, and accordingly, a pressure toward the adhesive tape 17 side (holding surface 40a side) is applied to the workpiece 11. As a result, the bubbles 21 (see
Also, the holding table 40 may further include a heater for heating the adhesive tape 17.
After the gas permeating step is carried out, subsequent processes such as processing with a processing apparatus or cleaning with a cleaning apparatus are carried out on the workpiece 11 held on the annular frame 19 through the adhesive tape 17. Note that details of processing on the workpiece 11 are not limited. For example, the workpiece 11 is processed by a cutting apparatus which cuts the workpiece 11 with an annular blade, by a grinding apparatus which grinds the workpiece with grindstones, by a polishing apparatus which polishes the workpiece 11 with a polishing pad, by a laser processing apparatus which processes the workpiece 11 by irradiation of a laser beam, or the like.
As described above, the tape attaching method according to the preferred embodiment of the present invention includes the tape attaching step of attaching the adhesive tape 17 to the workpiece 11 in the gas having a smaller molecular weight than the average molecular weight of the atmosphere, and the gas permeating step of causing the gas remaining between the workpiece 11 and the adhesive tape 17 to permeate the adhesive tape 17 and to be removed. In this tape attaching method, the gas entering between the workpiece 11 and the adhesive tape 17 is gas having a smaller molecular weight than the average molecular weight of the atmosphere, and accordingly, the gas is likely to permeate the adhesive tape 17. As a result, the bubbles remaining between the workpiece 11 and the adhesive tape 17 are likely to be easily removed.
Note that, after the gas permeating step is carried out, the minute bubbles 21 may remain between the workpiece 11 and the adhesive tape 17 in a range not affecting processing or cleaning of the workpiece 11. In other words, in the gas permeating step, gas is removed from between the workpiece 11 and the adhesive tape 17 and the bubbles 21 are decreased to such an extent that there is no bad influence on processing or cleaning of the workpiece 11. For example, the tape attaching step is preferably carried out under gaseous atmosphere only containing gas having a smaller molecular weight than the average molecular weight of the atmosphere (first gas). However, in practice, the adhesive tape 17 may be attached to the workpiece 11 under the gaseous atmosphere in which a small amount of another gas (second gas) is mixed into the first gas, in some cases. In such cases, the bubbles 21 may contain the first gas and the second gas. However, if the second gas contained in the bubbles 21 is in small amounts, the first gas is removed properly in the gas permeating step, so that the size of each of the bubbles 21 can be efficiently reduced.
Besides, a structure, a method, and the like according to the above embodiment may be appropriately modified, and various modifications can be implemented without departing from the scope of the object of the present invention.
The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-112537 | Jun 2019 | JP | national |
