JP2004098264A - Method for dressing polishing cloth and method for polishing workpiece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for dressing polishing cloth for improving polishing speed, preventing outer peripheral sagging due to clogging of abrasive material and especially for stably obtaining a wafer of high flatness with efficiency by both-disc polishing using high hardness polishing cloth in polishing a work such as a silicon wafer with the polishing cloth. <P>SOLUTION: By this method, the polishing cloth is dressed in a polishing device for polishing the plate-like workpiece by rotating a lap adhered with the polishing cloth in a fixed direction. The dressing is performed by bringing a dressing surface of a dressing means 10 into contact with the polishing cloth 7 (8), while rotating the lap in the direction opposite to the rotating direction for polishing the workpiece. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to dressing of a polishing cloth in a polishing apparatus used for polishing a work such as a silicon wafer, and more particularly to a dressing method suitable for a high-hardness polishing cloth attached to a surface plate of a double-side polishing apparatus.
[0002]
[Prior art]
Conventionally, in the production of a silicon wafer, a single crystal silicon ingot is sliced to produce a silicon wafer, and then each step of chamfering, lapping, etching and the like is sequentially performed on the wafer, and then at least one principal surface of the wafer is mirror-finished. Polishing is performed. In the polishing step, in addition to a single-side polishing apparatus for polishing one side of the wafer, a double-side polishing apparatus for simultaneously polishing both sides of the wafer is used. Polishing is performed by bringing the surface of the wafer into contact with a polishing cloth.
[0003]
The double-side polishing apparatus usually includes an upper surface plate and a lower surface plate to which a polishing cloth made of a nonwoven fabric or the like is adhered. As shown in FIG. 8, a sun gear 101 is provided at the center and an internal gear is provided at the outer periphery. A so-called four-way type having a planetary gear structure in which 102 are arranged is used. When polishing a silicon wafer, a wafer is inserted and held in a plurality of wafer holding holes 104 formed in the carrier plate 103, polishing slurry is supplied to the wafer from above, and the upper and lower platens are rotated. By pressing the opposing polishing cloths of the upper and lower lapping plates against the front and back surfaces of the wafer, the carrier plate 103 is rotated between the sun gear 101 and the internal gear 102 so that both surfaces of each wafer can be polished simultaneously. it can.
[0004]
Also, as another form of double-side polishing apparatus, there is also known an apparatus which performs a double-side polishing by making a circular motion so as to draw a small circle without rotating a carrier plate sandwiched between upper and lower platens. (For example, see Japanese Patent Application Laid-Open No. 10-202511), with the increase in the diameter of the wafer, a double-side polishing apparatus having such a configuration has been used.
[0005]
On the other hand, a nonwoven fabric type polishing cloth (about 60 to 90 in Asker C hardness) has conventionally been used as the polishing cloth. However, recently, the flatness of the wafer has been further increased and fine irregularities on the wafer surface have been corrected. For this purpose, a high-hardness polishing cloth, for example, a polishing cloth having a Shore D hardness of about 40 to 100 is being used. The Shore D hardness is a value measured according to ASTM D 2240. The Asker C hardness is a value measured by an analog hardness tester (Asker Rubber Hardness Tester C type) commercially available from Kobunshi Keiki Co., Ltd., and is a hardness according to SRIS (Japan Rubber Association Standard) 0101.
[0006]
When the polishing is continued by using the same polishing cloth in the polishing apparatus, there is a problem that the wafer shape gradually changes. This is mainly due to the life of the polishing cloth, which is affected by changes in the compressibility and clogging of the polishing cloth.As the frequency of use increases, the wafer shape becomes different, and the outer peripheral portion of the wafer is excessively polished. As a result, so-called outer periphery sagging easily occurs. Therefore, in order to prevent such a change in the wafer shape, dressing of the polishing cloth surface is performed regularly or constantly.
[0007]
For example, in order to perform dressing of a polishing cloth used in a double-side polishing apparatus, as shown in FIG. 9, a dressing-dedicated carrier plate 9 having a plurality of holding holes 11 or a wafer used for polishing a wafer is generally used. The dressing plate 10 is set on the same carrier plate, and the dressing plate 10 is sandwiched between the upper surface plate 5 and the lower surface plate 6 to operate the apparatus in the same manner as in normal polishing, so that the upper and lower polishing cloths 7 and 8 are simultaneously formed. Dressed.
[0008]
As the dressing plate, for example, a disc-shaped dressing plate 41 as shown in FIG. 5 is generally used, and a front surface 44 and a rear surface 44 of which dressing is performed by contacting the upper and lower polishing cloths (hereinafter referred to as a “dress surface”). There is). As the material, for example, a hard material such as ceramics is used, and a material having minute irregularities formed on a dress surface is generally used. The shape and the like of the dressing plate include, for example, a donut-shaped dressing plate having a hole formed in the center, and various shapes.
[0009]
The purpose of the dressing for the non-woven type polishing cloth was to apply pressure and crush the dressing plate so as to reduce the elastic deformation of the non-woven fibers. That is, it is preferable that the wafer is polished in a state of creep deformation, and the dressing is performed with the rotation direction of the surface plate during dressing being the same as the rotation direction of the surface plate during polishing.
[0010]
On the other hand, for a polishing cloth of high hardness, in order to stably and improve the polishing ability, a dressing for the purpose of compression as in the case of a non-woven cloth polishing cloth is schematically shown in FIG. 2 rather than a dressing. Thus, it is important to sharpen the polishing cloth surface (generally referred to as "napping"). In order to perform such sharpening sufficiently, a polishing pad of high hardness having diamond pellets attached to both surfaces of a dressing plate may be used. The surface of the polishing pad is sharpened by rotating the platen as in the case of polishing.
[0011]
The dressing means is not limited to the above-mentioned dressing plate, and a dressing device or the like that performs dressing by holding a plate made of ceramics or the like with an arm and moving on a polishing cloth has also been proposed (for example, See JP-A-2000-42898).
[0012]
[Patent Document 1]
JP-A-2000-42898 (page 7, FIG. 6)
[0013]
[Problems to be solved by the invention]
For polishing a work such as a silicon wafer, the surface condition of the polishing cloth is particularly important. Dressing is performed to obtain a wafer with high flatness stably for a long period of time, and also to improve the life of the polishing cloth, but the dressing as described above is performed regularly or constantly. There is a problem that the outer periphery of the wafer is sagged. Particularly with high hardness polishing cloths, if the dressing is not performed sufficiently, the clogging of the polishing cloth with the abrasive proceeds quickly, and even after dressing, the outer peripheral sag of the wafer occurs immediately, and a wafer with high flatness is manufactured. Was difficult. Further, in the case of a hard polishing cloth, there is a problem that the polishing rate is low and the efficiency is low.
[0014]
The present invention has been made in view of the above problems, and when polishing a workpiece such as a silicon wafer with a polishing cloth, the polishing speed is improved, and the outer peripheral sag due to clogging of the abrasive is prevented, and in particular, high hardness polishing is performed. A main object of the present invention is to provide a dressing method capable of stably and efficiently obtaining a wafer having a high flatness by double-side polishing using a cloth.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided a method of dressing the polishing cloth in a polishing apparatus for polishing a plate-like work by rotating a platen to which a polishing cloth is attached in a fixed direction, A dressing method for a polishing cloth is provided, wherein dressing is performed by bringing a dress surface of a dressing means into contact with the polishing cloth while rotating the surface plate in a direction opposite to a rotation direction when polishing the work ( Claim 1).
[0016]
If the polishing pad is dressed by rotating the platen in the opposite direction to the direction of polishing the work in this way, it acts not in the direction of reducing the fuzz during polishing of the work, but in the direction of promoting the fuzz, thereby improving the efficiency. The surface of the polishing cloth can be well dressed. As a result, the holding power of the abrasive is improved, the polishing rate is improved, and the clogging of the abrasive due to insufficient sharpening is improved, so that a work with high flatness can be obtained stably and efficiently. Become.
[0017]
In this case, it is preferable that the polishing cloth to be dressed is a high hardness polishing cloth having a Shore D hardness of 40 or more (Claim 2).
While such a hard polishing cloth can polish a work to a high flatness, there is a problem that a polishing rate is slow, but as described above, the platen is rotated in a direction opposite to that of polishing the work. If the dressing is performed, the polishing cloth surface is sufficiently sharpened, the holding power of the polishing agent is increased, and the polishing rate can be improved.
[0018]
The form of the polishing apparatus is not particularly limited, such as a single-side polishing apparatus, a double-side simultaneous polishing apparatus, and the polishing apparatus includes a carrier plate having a hole for holding the work, an upper platen, and a lower platen. A double-side polishing apparatus (Claim 3) for simultaneously polishing both sides of the work by sandwiching the work held in the holes between the polishing cloths respectively adhered to the upper and lower surface plates, and particularly, the carrier plate is rotated. It is preferable to use a double-side polishing apparatus for simultaneously polishing both sides of the work by performing a circular motion (claim 4).
[0019]
If the dressing is performed on the upper and lower polishing cloths in the double-side polishing apparatus as described above, the effect of polishing both surfaces of the work at high speed and with high flatness can be enhanced, and in particular, the carrier plate moves circularly without rotating. A double-side polishing apparatus is advantageous in that a large-diameter wafer can be polished to a very high degree of flatness even with a small apparatus.
[0020]
Further, the dressing means is not particularly limited, but a disk-shaped dressing plate can be suitably used (claim 5).
By using such a dressing plate, dressing can be performed in the same manner as in the case of polishing a wafer, except that the platen is rotated in a direction opposite to the direction in which the workpiece is polished.
[0021]
Further, as the dressing means, it is preferable to use a dressing surface provided with diamond abrasive grains (claim 6), and it is particularly preferable to use diamond abrasive grains of # 200 or less (claim). Item 7).
When the diamond abrasive grains are provided on the dress surface as described above, the dressing action is enhanced, and in particular, sharpening of a high-hardness polishing cloth can be more effectively performed. In particular, when a diamond abrasive grain of # 200 or less is provided, the surface roughness of the polishing pad can be increased, and the holding power of the abrasive can be reliably increased.
[0022]
It is preferable that the dressing is performed until the surface roughness of the polishing cloth satisfies RMS ≧ 1 μm.
By roughening the surface roughness of the polishing cloth until RMS ≧ 1 μm, clogging of the abrasive hardly occurs, the holding power of the abrasive is improved, and the polishing ability can be reliably increased. . The upper limit is not particularly limited, but RMS is about 10 μm.
[0023]
Furthermore, according to the present invention, in a method of polishing a plate-like work by rotating a platen to which a polishing cloth is attached in a polishing apparatus in a fixed direction, a direction opposite to a rotation direction when polishing the platen with the work After the dressing is performed by rotating the workpiece, the workpiece is polished, and the method for polishing the workpiece is provided (claim 9).
After the dressing is performed by rotating the platen in the opposite direction to the direction of polishing the workpiece, if the workpiece such as a silicon wafer is polished, the sharpening direction of the polishing cloth surface acts in a direction that promotes fuzzing. Since the holding power of the polishing agent is improved, the polishing rate is increased and the workpiece can be polished with a high flatness.
[0024]
In this case, it is preferable that the polishing cloth is a high-hardness polishing cloth having a Shore D hardness of 40 or more.
If the wafer is polished after dressing by rotating the surface of such a high-hardness polishing cloth in a direction opposite to the direction of polishing, minute irregularities on the wafer surface can be removed at a high speed, so that extremely high flatness is achieved. The wafer can be obtained efficiently.
[0025]
As the polishing device, a carrier plate having a hole for holding a work, an upper surface plate, and a lower surface plate, a polishing cloth attached to the work held in the hole of the carrier plate to the upper surface plate and the lower surface plate, respectively. It is preferable to use a double-side polishing apparatus for simultaneously polishing both surfaces of the work by sandwiching them between them.
For example, when a wafer polishing process is performed in multiple stages, double-side polishing is often performed in the first stage, and it is desired to improve the polishing rate because the polishing allowance is relatively large. If dressing is performed by rotating the platen in the direction opposite to the direction of rotation of the wafer, and then polishing of the wafer, the holding power of the polishing agent is improved and the polishing rate can be increased.
[0026]
In particular, in the case of a double-side polishing apparatus for simultaneously polishing both surfaces of a work by making a circular motion without rotation of the carrier plate (claim 12), for example, even a large-diameter wafer as large as 300 mm in diameter can be relatively used. Polishing can be performed with high flatness using a small polishing apparatus.
[0027]
Further, it is preferable that the work is polished after dressing is performed until the surface roughness of the polishing cloth becomes RMS ≧ 1 μm.
If the wafer is polished after reliably increasing the surface roughness of the polishing cloth, minute irregularities on the wafer surface can be removed at high speed, and a wafer with high flatness can be reliably obtained. .
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings, but the present invention is not limited thereto.
As a result of the inventor's intense study of dressing of the polishing cloth and repeated experiments, as shown in FIG. 1 (A), the rotation direction of the platen during dressing was changed to a platen during wafer polishing as shown in FIG. If the rotation direction is the same, the fluffing of the dressed portion of the polishing pad 7 (8) will fall, and the polishing capability will decrease due to a decrease in the ability to hold the abrasive when polishing the wafer. It turned out to be. Therefore, the inventor of the present invention rotates the surface plate in the direction opposite to the direction of rotation when polishing the wafer as shown in FIG. 1B, that is, while rotating the surface plate in a direction that promotes the fluffing of the polishing pad 7 (8). As a result of the dressing, it has been found that the polishing ability of the polishing pad 7 (8) can be significantly improved, and the present invention has been completed.
[0029]
The present invention can be applied to any type of polishing apparatus that can rotate the surface plate to which the polishing cloth is attached and polishes a plate-like work without any particular limitation. As an example, a description will be given of a case where a dressing method according to the present invention is applied to a double-side polishing apparatus using a high-hardness polishing cloth used for polishing a silicon wafer.
[0030]
FIGS. 6A and 6B show an example of a double-side polishing apparatus. The double-side polishing machine 61 includes an upper surface plate 5 and a lower surface plate 6. The upper surface plate 5 has a cylinder rod 12 a that rotates while applying a polishing load to the upper surface plate 5, and the load is determined. A housing 13 and the like to be transmitted to the board are attached. Cooling means for controlling the temperature and a slurry supply pipe 14 for supplying the slurry are provided in the surface plate 5. When a silicon wafer or a dressing plate is supplied to and discharged from the carrier plate 9, the upper platen 5 can be moved vertically by a lifting device (not shown).
[0031]
On the other hand, in addition to the rotating rod 12b, a thrust bearing 15 for supporting the load of the surface plate 6 and the like are attached to the lower surface plate 6, and a cooling means for controlling the temperature is provided inside the surface plate 6. I have.
When the wafer is polished or dressed, the upper and lower platens 5, 6 are rotated in a horizontal plane by a motor or a speed reducer (not shown) so that the rotation speed and the like can be controlled.
[0032]
Polishing cloths 7 and 8 are attached to the respective platens 5 and 6, respectively. In addition, as described above, the present invention can be applied without being limited to the material of the polishing cloth and the like, and a conventionally used nonwoven fabric, furthermore, a nonwoven fabric obtained by impregnating and curing a urethane resin can be used. Any form of polishing cloth can be used, but a hard polishing cloth other than a nonwoven fabric, particularly a high-hardness polishing cloth having a Shore D hardness of 40 or more is preferred.
[0033]
As such a high-hardness polishing cloth, for example, a hard water-insoluble thermoplastic polymer or a crosslinked elastomer as disclosed in JP-A-2000-34416 or JP-A-2002-134445 is used. A polishing cloth formed by dispersing a water-soluble substance having a small particle size can be used. In such a polishing cloth, the particulate water-soluble substance exposed on the surface of the polishing cloth elutes to form fine pores on the surface, and the water-soluble substance remains therein to form pores. And a polishing pad having high hardness. In addition, a polishing cloth having an independent foam structure, for example, a polishing cloth having a foamed polyurethane sheet as a base material independently having fine cells may be used. Such a polishing cloth becomes an extremely hard polishing cloth and has a micro-pore on a polished surface, so that it has a relatively high polishing ability and is preferable. It should be noted that the higher the hardness of the polishing cloth, the greater the effect of improving minute irregularities, but considering the polishing ability and the like, the upper limit is suitably about 100 Shore D hardness.
[0034]
As another form of the polishing cloth, a multi-layer polishing cloth of two or more layers obtained by laminating polishing cloths made of a plurality of materials may be used. Also in such a case, it is preferable that the hardness of the surface polishing cloth serving as the polishing surface is high.
The use of the polishing cloth having high hardness as described above can improve minute irregularities on the wafer surface.
[0035]
The carrier plate 9 is held by a carrier holder 16, and four bearings 17 projecting outward are provided at equal intervals on the outer periphery of the holder 16. An eccentric arm 18 is rotatably inserted into each bearing 17, and a rotating shaft 19 is attached to the center of the lower surface of each eccentric arm 18. Then, by rotating the sprocket provided on the rotation shaft 19 of each eccentric arm 18 by the timing chain 20, all the eccentric arms 18 rotate in a horizontal plane around the rotation shaft 19 in synchronization. Accordingly, the carrier plate 9 held by the carrier holder 16 can perform a circular motion without drawing a small circle in a horizontal plane.
[0036]
The material of the carrier plate 9 and the number of the holding holes are not particularly limited. For example, the carrier plate 9 is made of glass epoxy or vinyl chloride, and the number of the holding holes is, for example, five holding holes 64 as shown in FIG. By using a carrier plate 63 having the same, a wafer W can be put into each holding hole 64 to perform double-side polishing.
In such a double-side polishing apparatus 61, all points on the carrier plate 9 draw a locus of small circles of the same size as shown by C in FIG. 6 (B) due to the circular motion without rotation. There is an advantage that the wafer W can be uniformly polished.
[0037]
When dressing is performed on such a double-side polishing apparatus 61 using a dressing plate, the dressing plate, which is rotatably inserted and held in the wafer holding hole of the carrier plate, is attached to the upper surface plate 5 and the lower surface plate 6, respectively. Between the polished polishing cloths 7 and 8. Then, in the present invention, dressing of the polishing cloth surface is performed by rotating each of the platens 5 and 6 in a direction opposite to the rotation direction when polishing the silicon wafer W.
[0038]
The shape and material of the dressing plate to be used are not particularly limited, and the diameter and thickness of the dressing plate may be appropriately set according to the size of the double-side polishing apparatus, for example, as shown in FIG. Such a dressing plate 1 can be suitably used. The dressing plate 1 has a diamond pellet 3 provided on one surface (dress surface) of a ceramic dressing plate body 2. The diamond pellet 3 is formed by pelletizing diamond abrasive grains by nickel electrodeposition or the like. As the diamond abrasive grains, for example, those having a count of # 30 to 24000 can be used according to the polishing cloth. However, if the count is # 200 or less, particularly, the count of # 60 to 200, a hard polishing cloth is required. In addition, it is good for hanging and can effectively fluff the surface.
[0039]
The dressing according to the present invention can be performed in the same manner as the polishing of the silicon wafer except for the rotation direction of the surface plate. Therefore, even if the same carrier plate 63 as the polishing of the wafer W as shown in FIG. Good, but it is preferable that the dressing is performed wider than the area for polishing the wafer W. Therefore, for the purpose of dressing, for example, as shown in FIG. 7B, a dedicated carrier plate 73 having a holding hole 74 larger than that of the wafer is prepared, and the dressing plate 10 is also dressed by using a plate larger than the wafer W. Is preferably performed.
[0040]
When performing dressing, specifically, as shown in FIG. 4, the dressing plate 1 is put into the holding holes 74 of the carrier plate 73, and the polishing cloths 7 and 8 adhered to the upper platen 5 and the lower platen 6, respectively. The dressing liquid is supplied in between, and the upper platen 5 and the lower platen 6 are each rotated in the direction opposite to the rotation direction when polishing the silicon wafer. That is, when the upper platen 5 is rotated in the CCW direction and the lower platen 6 is rotated in the CW direction at the time of polishing a wafer, the upper platen 5 is rotated in the CW direction as shown in FIG. The lower platen 6 is rotated in the CCW direction (direction of b in FIG. 4) in the directions indicated by arrows. If both the upper and lower bases 5, 6 are rotated in the CW direction during polishing, both the upper and lower bases 5, 6 are rotated in the CCW direction during dressing, and both the upper and lower bases 5, 6 are rotated in the CCW direction during polishing. For example, if the upper and lower stools 5 and 6 rotate in the CW direction during dressing, and the upper stool 5 rotates in the CW direction and the lower stool 6 rotates in the CCW direction during polishing, the upper stool 5 is dressed during dressing. The CCW direction and the lower surface plate 6 are respectively rotated in the CW direction.
[0041]
When dressing is performed, it is preferable to supply a dressing liquid such as pure water or an alkaline polishing slurry used for polishing from the slurry supply pipe 14 or a dedicated supply pipe. In particular, if the dressing liquid is pure water, the cost is lower than that of the polishing slurry, and debris and the like existing in the polishing cloth are easily removed. The supply amount of the dressing liquid varies depending on the size of the polishing apparatus (carrier plate) and the like, but is usually about 5 to 15 liters / minute. However, the type and supply amount of the dressing liquid are not limited to the above.
[0042]
The rotation speed of each platen and the pressing force on the wafer and the dressing plate are not particularly limited. However, when polishing the wafer, the rotation speed is usually 5 to 30 rpm, and the pressing force (load) on the wafer is 100 to 350 g / cm. ² On the other hand, when dressing a high-hardness polishing cloth (for example, Shore D hardness of 40 or more), it is preferable that the polishing be performed at a lower rotation speed and a lower load than the polishing conditions, for example, a rotation speed of 5 to 20 rpm and a load. 10 to 300 g / cm ² Do about.
[0043]
The dressing may be performed in a plurality of stages. In addition, it may be performed in a single step with a dressing plate having diamond pellets on both sides, for example, by attaching diamond pellets only on one side, and separately dressing the polishing cloth attached to the upper surface plate and the lower surface plate good. In the case of a double-side polishing machine, it is common to reverse the rotation directions of the upper and lower stools. Since the dressing plate is rotatably inserted into the holding hole of the carrier plate, the dressing plate rotates in the same direction as one of the surface plates (this is called co-rotation), and is rotated in the opposite direction to the other surface plate. Will rotate. Even in such a state, since the rotation speed (rotation speed) of the dressing plate and the rotation speed (rotation speed) of the surface plate are different, it is possible to dress both upper and lower polishing cloths.
[0044]
However, it is preferable to dress the upper and lower polishing cloths as uniformly as possible. For example, if a diamond pellet having a large dressing action is attached to only one of the above-mentioned surfaces and a dressing plate having one flat surface is used, The dressing plate can be rotated so as to rotate in the rotation direction of the upper stool during dressing, and to rotate in the rotation direction of the lower stool during dressing of the lower stool. Therefore, it is possible to dress the polishing cloth stuck on the upper and lower platens uniformly under substantially the same conditions. If the polishing is performed by rotating the platen in the direction opposite to the direction of the dressing using the dressing-made polishing cloth, polishing with high polishing ability can be performed.
[0045]
In addition, when the polishing cloth is hard and the dressing surface (diamond abrasive grains) does not catch well on the polishing cloth during dressing, or when the dressing effect cannot be sufficiently obtained by using a dressing plate with a low diamond abrasive grain. There is. In that case, the diamond abrasive grains of the dressing plate may be gradually changed from a high count to a low count and applied. That is, in the first stage, processing is performed using a dressing plate provided with a good-numbered diamond abrasive grain, and at a later stage, a dressing plate provided with a lower-numbered diamond abrasive grain is used. Thus, stable dressing can be performed. More specifically, in the first stage, fine dressing is performed using a dressing plate with a higher count of diamond abrasive grains than # 200, and in the later stage, coarse dressing is performed using a dressing plate with a low count of # 200 or lower. I do. It is also possible to perform such a two-stage dressing.
[0046]
The surface roughness of the polishing cloth after the dressing is not particularly limited. However, if the dressing is performed until the surface roughness of the polishing cloth becomes RMS ≧ 1 μm, the holding power of the polishing agent is surely improved, and the polishing agent is used. Clogging can be further suppressed.
The upper limit of the surface roughness of the polishing pad is not particularly limited, but RMS = 10 μm or less is appropriate in consideration of the dressing time, the life of the polishing pad, and the like.
[0047]
When the wafer is polished after the dressing, as shown in FIG. 6 (A), the wafer W is put into the holding holes of the carrier plate 9 and held, and the wafer W is attached to the upper platen 5 and the lower platen 6, respectively. Both surfaces of the wafer W are simultaneously polished by rotating the platens 5, 6 in the direction opposite to the direction of dressing while sandwiching the polishing pad between the polishing cloths 7, 8. At this time, since the sharpening direction of the surface of the polishing cloth acts not in the direction of suppressing fluffing in polishing the wafer but in the direction of promoting fluffing, the holding power of the abrasive is improved and the polishing rate is increased. Further, the abrasive is hardly clogged, and the time until the abrasive cloth is clogged with the abrasive is extended, so that the sharpening effect is maintained for a long time. As a result, the sag on the outer periphery of the wafer is extremely reduced, and a wafer with high flatness can be obtained extremely efficiently.
[0048]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.
(Example)
A polishing cloth made of an independently foamed polyurethane sheet as a polishing cloth (Shore D hardness 98: Example 1) as shown in FIG. 6 and a polishing cloth of a type obtained by adding a water-soluble substance to a crosslinked elastomer (Shore D hardness) 45: Polishing was performed using the two types of polishing cloths of Example 2).
First, dressing of the polishing cloth was performed. As the dressing plate, a dressing plate body having ceramics and diamond # 100 diamond abrasive grains (pellets) concentrically provided on one of the dress surfaces was used.
[0049]
The above dressing plate was set on a carrier plate having four holding holes. First, the dressing surface having diamond pellets is set so that it is on the upper platen side, the upper platen is rotated in the CCW direction at a rotation speed of 10 rpm, and the lower platen is rotated in the CW direction at a rotation speed of 10 rpm. Was. The load at this time is 100 g / cm ² The polishing was performed with a load lower than the load at the time of polishing, and pure water was supplied at a flow rate of 10 L / min during the dressing. Next, the dressing plate was turned upside down, set so that a dress surface having diamond pellets was placed on the lower platen side, and dressing was performed under the same conditions.
[0050]
After dressing, both sides of a silicon wafer having a diameter of 300 mm were polished. For polishing, five etched silicon wafers are set on a carrier plate having five holding holes. The upper platen is in the CW direction (the direction opposite to the direction of dressing), and the lower platen is in the CCW direction (the opposite direction of the dressing). Direction), the rotation speed is 20 rpm, and the load is 250 g / cm. ² An alkaline solution containing colloidal silica was used as an abrasive.
As a result, both of the polishing cloths of Example 1 and Example 2 were able to obtain wafers having a polishing allowance (removal allowance) of 5 μm or more on one side and a high flatness (GBIR = 0.5 μm or less).
In addition, it was found that the polishing rate was improved by 10 to 30% compared to the related art.
[0051]
Note that the present invention is not limited to the above embodiment. The above embodiment is merely an example, and any embodiment having substantially the same configuration as the technical idea described in the claims of the present invention and having the same function and effect will be described. It is included in the technical scope of the invention.
[0052]
For example, the present invention can be applied not only to the above-described double-side polishing apparatus but also to another type of polishing apparatus, for example, a conventional 4-way double-side polishing apparatus or a single-side polishing apparatus. . Further, the dressing means is not limited to a dressing plate having diamond pellets on one surface, but may be a dressing plate having diamond pellets on both surfaces. May be used.
The dressing of the polishing cloth may be performed periodically, or may be performed for each polishing of the wafer or for each batch.
[0053]
【The invention's effect】
According to the present invention, dressing is performed by bringing the dressing surface of the dressing means into contact with the polishing cloth while rotating the platen to which the polishing cloth is attached in a direction opposite to the rotation direction when polishing the work. Thereby, when polishing the work, the work acts on the polishing cloth so as to promote fluffing, the holding power of the abrasive increases, and the polishing rate (polishing ability) in polishing the work improves. In addition, since the clogging state of the polishing agent due to insufficient sharpening of the polishing cloth surface layer is also improved, the sagging of the outer periphery of the wafer is reduced, and a wafer having a high flatness can be efficiently obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing the rotation direction of a surface plate during dressing and wafer polishing.
(A) Conventional technology
(B) The present invention
FIG. 2 is an explanatory diagram showing a surface state before and after dressing of a high hardness polishing cloth.
FIG. 3 is a schematic sectional view showing an example of a dressing plate.
FIG. 4 is a schematic explanatory view of a case where dressing is performed using the dressing plate of FIG. 3;
FIG. 5 is a view schematically showing an example of the shape of a general dressing plate.
(A) Plan view
(B) Sectional view
FIG. 6 is a view schematically showing an example of a double-side polishing apparatus.
(A) Side view
(B) Plan view
FIG. 7 is a schematic plan view of a carrier plate.
(A) Five holding holes
(B) Three holding holes
FIG. 8 is a schematic view showing a four-way type planetary gear structure of the double-side polishing apparatus.
FIG. 9 is a schematic diagram showing a state where a dressing plate is set in a double-side polishing apparatus.
[Explanation of symbols]
1 ... dressing plate, 2 ... dressing plate body,
3 ... diamond pellet, 4 ... dress surface, 5 ... upper platen, 6 ... lower platen, 7, 8 ... polishing cloth, 9 ... carrier plate, 10 ... dressing plate, 11 ... holding hole, 12a, 12b ... cylinder rod , 13 ... housing, 14 ... slurry supply pipe, 15 ... thrust bearing, 16 ... carrier holder,
17 ... bearing part, 18 ... eccentric arm, 19 ... rotating shaft,
20: timing chain, 41: dressing plate,
44: Dress surface, 61: Double-side polishing machine, 63, 73 ... Carrier plate,
64, 74: holding hole, 101: sun gear, 102: internal gear,
103: Carrier plate, 104: Holding hole, W: Work (wafer).

Claims (13)

A method of dressing the polishing cloth in a polishing apparatus for polishing a plate-like work by rotating a surface plate to which a polishing cloth is attached in a fixed direction, and the rotation direction when polishing the work with the surface plate A dressing method for a polishing cloth, wherein dressing is performed by bringing a dress surface of a dressing means into contact with the polishing cloth while rotating in the opposite direction. The polishing cloth dressing method according to claim 1, wherein the polishing cloth to be dressed is a high hardness polishing cloth having a Shore D hardness of 40 or more. The polishing apparatus comprises a carrier plate having holes for holding the work, an upper surface plate, and a lower surface plate, and the work held in the holes of the carrier plate is affixed to the upper surface plate and the lower surface plate, respectively. The dressing method for a polishing cloth according to claim 1 or 2, wherein the polishing apparatus is a double-side polishing apparatus for simultaneously polishing both sides of the work sandwiched between cloths. The dressing method for a polishing cloth according to claim 3, wherein the double-side polishing apparatus is a double-side polishing apparatus for simultaneously polishing both surfaces of a work by making the carrier plate make a circular motion without rotation. The method according to claim 1, wherein a disc-shaped dressing plate is used as the dressing unit. The dressing method for a polishing pad according to any one of claims 1 to 5, wherein the dressing means is a dress surface provided with diamond abrasive grains. 7. The dressing method for a polishing pad according to claim 6, wherein the diamond abrasive grains are # 200 or less. The dressing method for a polishing cloth according to any one of claims 1 to 7, wherein dressing is performed until the surface roughness of the polishing cloth satisfies RMS ≧ 1 μm. In a method of polishing a plate-like work by rotating a platen on which a polishing cloth is adhered in a polishing apparatus in a fixed direction, dressing is performed by rotating the platen in a direction opposite to a rotation direction when polishing the work. And polishing the workpiece after the polishing. The method according to claim 9, wherein the polishing cloth is a high-hardness polishing cloth having a Shore D hardness of 40 or more. As the polishing device, a carrier plate having a hole for holding a work, an upper surface plate, and a lower surface plate, a polishing cloth attached to the work held in the hole of the carrier plate to the upper surface plate and the lower surface plate, respectively. The method for polishing a work according to claim 9, wherein a double-side polishing apparatus for simultaneously polishing both sides of the work with the work piece interposed therebetween is used. The method of polishing a work according to claim 11, wherein the double-side polishing apparatus is a double-side polishing apparatus for simultaneously polishing both surfaces of the work by making the carrier plate make a circular motion without rotation. The method according to any one of claims 9 to 12, wherein the work is polished after dressing is performed until the surface roughness of the polishing cloth becomes RMS ≧ 1 μm.

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