JP2006147731A - Polishing cloth, wafer polishing device, and method of manufacturing wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing cloth that can supply a highly flat wafer by suppressing the occurrence of flaws and polishing marks, and to provide a wafer polishing device. <P>SOLUTION: The height of the surface of the outer periphery of the polishing cloth 12 used for polishing a wafer W is lowered by annularly grinding the outer periphery with a grinding plate 19 on which abrasive diamond grains are electrodeposited. Consequently, the highly flat wafer W which is reduced in plane dripping in the outer periphery can be manufactured, because the polishing resistance is reduced in the outer periphery of the polishing cloth 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for polishing a thin plate-like object, and in particular, a polishing cloth, a wafer polishing apparatus, and a wafer manufacturing method for polishing a surface of an object that requires a highly flat surface such as a semiconductor wafer. About.

  Conventionally, a semiconductor wafer used as a raw material wafer for manufacturing a semiconductor device is generally polished with a polishing cloth in order to obtain a wafer having a highly flat surface.

A wafer used as a raw material wafer for manufacturing a semiconductor device is a single crystal semiconductor ingot grown by the Czochralski method (CZ method) or the floating zone melting method (FZ method), and the outer periphery of the grown semiconductor ingot is It is formed by grinding with a cylindrical grinder or the like and slicing with a wire saw in a slicing step.
Thereafter, the wafer peripheral portion is chamfered in a chamfering process, and after a flattening process and an etching process in a lapping process, after primary polishing and secondary polishing, an epitaxial growth process is performed on the wafer surface to obtain a mirror wafer.

The mirror surface wafer obtained through such a process is formed with a circuit on its surface to become a semiconductor device.
However, when the surface flatness of the wafer manufactured through the above steps is low, the lens focus is not partially focused during exposure in the photolithography process for forming the circuit, and it becomes difficult to form a fine pattern of the circuit. .

Therefore, extremely high flatness is required in recent high-precision device fabrication.
In order to manufacture a wafer having such extremely high flatness, the surface polishing of the wafer is very important. In general, as a polishing apparatus for performing surface polishing of a wafer, a double-side polishing apparatus, a single-wafer single-side polishing apparatus, a batch-type single-side polishing apparatus, and the like are widely known.

FIG. 23 is a schematic view showing an example of a double-side polishing apparatus. FIG. 23A is a plan view schematically showing the carrier rotation mechanism of the double-side polishing apparatus, and FIG. 23B is a longitudinal sectional view of a part of the double-side polishing apparatus.
In the double-side polishing apparatus, the upper surface plate 1a and the lower surface plate 1b that form an annular shape when viewed from above are parallel with the surfaces to which the polishing cloth 2 is attached facing each other as shown in FIG. Hold on.

As shown in FIG. 23A, a substantially disc-shaped carrier 51 for holding a wafer is provided between an upper surface plate 1a and a lower surface plate 1b, and a sun gear 55 provided at the center of the lower surface plate 1b. Five centers are arranged at equal intervals.
Each carrier 51 is made of SK5 tool steel, SUS, or the like, and has a plurality of through-loading holes 52 that accommodate the wafer W on the plate surface. In order to allow the wafer W to rotate within the loading hole 52, the loading hole 52 is a circular hole having a diameter of 201 mm, for example, when a wafer W having a diameter of 200 mm is accommodated.

  FIG. 23A shows an example in which six loading holes 52 are provided radially at equal intervals in the carrier 51, but the number and arrangement of these loading holes 52 can be appropriately set for each double-side polishing apparatus. However, the present invention is not limited to these.

  A planet gear 53 is provided on the outer periphery of the carrier 51 and meshes with a sun gear 55 provided at the center of the lower surface plate 1b. The sun gear 55 can be rotated independently of the upper surface plate 1a and the lower surface plate 1b by driving means (not shown).

  An internal gear 54 is disposed around the lower surface plate 1 b with a certain gap from the outer periphery of the lower surface plate 1 b and meshes with the planet gear 53 of the carrier 51. The internal gear 54 has an inner peripheral surface concentric with the sun gear 55, and a gear portion is provided on the inner peripheral surface. This internal gear 54 can be rotated independently of the upper surface plate 1a and the lower surface plate 1b by driving means (not shown).

  Then, in a state where the wafer W is accommodated in the loading hole 52, both the sun gear 55 and the internal gear 54 or either one of the sun gear 55 or the internal gear 54 is rotated, so that the carrier 51 and the lower surface plate 1a are lowered. It rotates relative to the board 1b. At this time, either the upper surface plate 1a or the lower surface plate 1b or both the upper surface plate 1a and the lower surface plate 1b may be rotated.

  In this state, a polishing liquid such as a slurry is supplied to the upper surface of the carrier 51 and flows between the upper and lower surface plates 1 a and 1 b and the wafer W. As a result, the polishing cloth 2 provided on the upper surface plate 1a and the lower surface plate 1b and the wafer W slide relative to each other, and the surface of the wafer W is scraped and polished.

  FIG. 24 is a longitudinal sectional view showing an outline of a single-wafer single-side polishing apparatus. This polishing apparatus is roughly composed of a polishing surface plate 1, a polishing head 64, and a slurry tube 8.

The polishing surface plate 1 is provided with a flat surface having an area that is twice or more the diameter of the wafer W that is the object to be polished, and a polishing cloth 2 such as a non-woven fabric made of polyester resin is bonded to the flat surface. It is affixed with an agent or the like, and is configured to rotate around the surface plate rotation axis.
The polishing head 64 is positioned above the polishing surface plate 1, has a head rotation shaft disposed at a position deviated from the surface plate rotation axis of the polishing surface plate 1, and is configured to rotate around the head rotation axis. Yes.

The polishing head 64 includes a vacuum chuck mechanism 65 as a holding unit that holds the wafer W.
The vacuum chuck mechanism 65 includes a suction surface provided with a plurality of suction holes, a suction tube provided at the center of the head rotation axis of the polishing head 64, and a suction tube for sucking one surface of the wafer W. It consists of a connected suction pump.

  The configuration of the polishing head 64 that holds the wafer W is not necessarily a vacuum chuck mechanism, and is a configuration in which the wafer W is water-bonded using a backing pad made of a porous resin such as a polyurethane resin porous body. May be. In the case of the vacuum chuck mechanism 65, the wafer W is fixed to the polishing head 64 in a non-rotatable manner. However, in the case of applying water with a backing pad, the wafer W is held rotatably with respect to the polishing head 64. The

  A ring-shaped retainer 68 is provided on the outer periphery of the vacuum chuck mechanism 65. The retainer 68 serves to prevent lateral displacement of the wafer W and receives pressure from the polishing cloth 2 on the outer peripheral portion of the wafer W by the retainer 68 so that the surface pressure applied to the surface to be polished of the wafer W is uniform. To. The retainer 68 is not an essential component for the single-wafer single-side polishing apparatus, and the retainer 68 may not be provided.

  The slurry tube 8 supplies a polishing liquid (slurry) between the polishing cloth 2 and the wafer W in the vicinity of the center of rotation of the polishing platen 1. Then, by rotating the polishing platen 1 and the polishing head 64 while the wafer W is attracted to the vacuum chuck mechanism 65, the wafer W is displaced on the polishing cloth 2 and the surface of the wafer W is scraped off. Polished.

  Next, an example of a batch type single-side polishing apparatus is shown in FIG. FIG. 21A is a longitudinal sectional view of a batch type single-side polishing apparatus, and FIG. 21B is an enlarged cross-sectional view of a main part of the batch type single-side polishing apparatus. A batch-type single-side polishing apparatus is an apparatus that polishes only one side of a wafer by one polishing, and can polish a plurality of wafers simultaneously.

  In FIG. 21, reference numeral 1 is a surface plate having a disk shape that can rotate in a predetermined direction (for example, counterclockwise when viewed from above), and reference numeral 2 is a non-woven fabric stuck on the surface of the surface plate 1. Polishing cloth for polishing, reference numeral 4 is a polishing head arranged above the polishing cloth 2 and rotates around the support shaft 3, reference numeral 9 is a carrier plate arranged on the lower surface of the polishing head 4, and reference numeral 6 is a carrier plate A template that is fixed to the lower surface of 9 and holds the wafer W in the wafer positioning hole 6 a, and 8 is a slurry tube that supplies slurry toward the surface of the polishing cloth 2.

The carrier plate 9 is a carrier for holding a wafer, and is formed of a porous resin such as a polyurethane resin porous body. The template 6 is formed from a glass epoxy resin, a polycarbonate sheet, a polyester sheet, or the like.
Further, the template 6 has five wafer positioning holes 6a for holding five wafers W. As shown in FIG. 21B, the diameter of the wafer positioning hole 6a is larger than the wafer diameter, and when the polishing head 4 is rotated, the wafer W freely rotates in the wafer positioning hole 6a.

  In the batch-type single-side polishing apparatus shown in FIGS. 21A and 21B, the template 6 is provided on the carrier plate 9 so that the wafer W can freely rotate. The wafer W may be attached to the lower surface of the carrier plate 9 and fixed.

  With the wafer W held by the carrier plate 9, the polishing liquid is supplied from the slurry tube 8 to the upper surface of the surface plate 1, and the surface plate 1 and the polishing head 4 are rotated so that the wafer W moves over the polishing cloth 2. The surface of the wafer W is scraped off and polished.

  As described above, various apparatuses such as a double-side polishing apparatus, a single-wafer single-side polishing apparatus, and a batch-type single-side polishing apparatus are known as polishing apparatuses that perform polishing of a wafer surface using a polishing cloth.

  In a polishing apparatus that polishes the surface of a wafer using a polishing cloth as described above, since the polishing cloth is generally elastic, if the polishing is performed while pressing the wafer against the polishing cloth, the wafer slightly sinks into the polishing cloth. . Then, as shown in FIG. 19, since the elastic stress from the polishing cloth 2 is concentrated on the front end portion (broken line circle portion) of the wafer W relative to the polishing cloth 2, the wafer W is compared with the center portion of the wafer W. The pressure applied to the outer periphery of the wafer W increases, and the outer periphery of the wafer W is excessively polished.

  For this reason, the polished wafer has a problem that surface sagging occurs at the outer peripheral portion of the wafer, and the SFQR value of that portion deteriorates.

In addition, there is a polishing device that uses a polishing method that prevents free rotation of the wafer with a polishing block. In this type of polishing device, the wafer is affixed under the polishing block, so that the wafer is polished without rotating. Is done.
When a plurality of wafers are arranged so as not to rotate under the polishing block in this way, the distance between adjacent wafers varies depending on the position of the outer periphery, so the wafers are affected by the dynamic viscoelasticity of the polishing cloth. It was difficult to ensure a uniform SFQR at the outer peripheral portion of each.

16 and 17 are schematic views showing the relationship between the distance between the wafers and the dynamic viscoelasticity of the polishing cloth. FIG. 16 is a schematic diagram showing a case where the distance between the wafers is small, and FIG. 17 is a schematic diagram showing a case where the distance between the wafers is large.
The polishing cloth 2 is made of an elastic nonwoven fabric, and when pressure is applied by the wafer W, the surface is temporarily recessed. When the polishing cloth 2 is released from the pressure received from the wafer W, the polishing cloth has a property of returning to the original state. The viscosity and elasticity of the polishing cloth at this time are referred to as dynamic viscoelasticity.

For example, in FIG. 17, the distance L ₁ between the wafer Wa and the wafer Wb is sufficiently large, and after the previous wafer Wa passes through the polishing cloth 2, the polishing cloth 2 until the next wafer Wb reaches the same place. The dent has recovered to its original state. Thus wafer Wa and is sufficiently wide distance L ₁ between the wafer Wb, when the time recovery by the viscoelasticity of the polishing cloth 2 is sufficient, the distal end portion of the moving direction of the wafer Wb the same peak as when the wafer Wa The stress which has is generated.

In Figure 16, on the other hand, the distance L ₂ is narrow between the wafer Wc and the wafer Wd, after previous wafer Wc passes the polishing cloth 2, the polishing cloth 2 on the next wafer Wd reaches the same location The dent has not recovered to its original state. Thus wafer Wc and the distance L ₂ is narrow and the wafer Wd, if the recovery time by the viscoelasticity of the polishing cloth 2 is not sufficient, since the polishing cloth 2 is not recovered to the original state, the moving direction of the wafer Wd Only a stress having a smaller peak than that in the case of the wafer Wb in FIG.

  Therefore, when the distance between the wafers is large, a large peak stress is generated, so the amount of polishing increases. When the distance between the wafers is small, the peak value of the stress is lowered and only a small stress is generated. It can be seen that the polishing amount decreases.

Reference is now made to FIG. FIG. 18A is a plan view showing a part of the polishing block and a part of the wafer, and FIG. 18B is a graph showing the change in the arc distance L between the wafers in a wafer having a diameter of 200 mm.
FIG. 18A shows the arc distance L between the wafers W at an arbitrary angle θ by taking the parameter θ counterclockwise from the center of the semicircular wafer W drawn on the left side shown in FIG. 18 (B).

As shown in FIGS. 18A and 18B, the arc distance L between adjacent wafers W on the polishing block 9 is not uniform over the entire periphery of the adjacent wafers W. For example, as the distance from the outer periphery of the polishing block 9 toward the center of the polishing block 9, the arc distance L between adjacent wafers W gradually decreases from the maximum distance L _1, passes through the minimum distance L ₂ , and further reaches the center of the polishing block 9. gradually spread now from _{L 2} to _{L 3} as it goes.

For example, wafer-to-wafer arc distance L ₁ shown in FIG. 18 (A) is much larger than the wafer between the arc distance L _2. As described above, since the arc distance L increases in the vicinity of the outer periphery of the polishing block 9, a stress having a large peak is generated as shown in FIG. As a result, the outer peripheral portion of the wafer W tends to be excessively polished.

FIG. 13 is a graph showing the relationship between the arc distance L between adjacent wafers and the amount of surface sag (ROA). As shown in FIG. 13, there is a correlation between the arc distance L between wafers and the amount of surface sag, and the amount of surface sag is the smallest at L ₂ where the arc distance L between wafers is minimum, and the arc distance L between wafers. The amount of surface sag is maximized at L ₁ where the maximum is. Incidentally, the graph is a two-step, the easily accumulate slurry toward the center of the polishing block 9, liable dullness occurs at the site where the arc distance L between the wafer becomes L ₃ at the inner peripheral side It is.

Without considering the relationship between the distance between the arcs of adjacent wafers W and the dynamic viscoelasticity of the polishing cloth, if the wafer W is polished with the polishing block 9 preventing free rotation of the wafer W, the wafer W A large sag is generated on the outer periphery of the substrate. FIG. 14A is a three-dimensional view of the wafer after the wafer is polished using a conventional wafer polishing apparatus, and the front side of the drawing is a portion arranged toward the outer periphery of the polishing block 9.
In the three-dimensional view of FIG. 14A, it can be seen that surface sagging occurs on the entire outer periphery of the wafer.

In view of the above problems, recently, as disclosed in Patent Document 2, the outer periphery of the surface plate is inclined, and the outer periphery of the polishing cloth is inclined so as to be separated from the wafer. As disclosed in References 3 and 4, the diameter of the polishing cloth is made smaller than the outer diameter of the movement locus of the wafer, and the outer periphery of the wafer is projected outside the polishing cloth during polishing. A technique for reducing the amount of polishing at the outer peripheral portion of the wafer and suppressing the occurrence of surface sag is considered.
JP-A-11-285963 JP 2002-252191 A JP 2001-138225 A JP 2001-326197 A JP 2004-160603 A

  However, when the outer peripheral portion of the surface plate is inclined as in Patent Document 2 described above, an existing general surface plate or polishing cloth cannot be used, and the outer periphery is inclined. A problem arises that a specially shaped polishing cloth conforming to the surface plate must always be attached to the surface plate.

  Further, as in Patent Documents 3 and 4 described above, when the outer periphery of the wafer is temporarily ejected from the polishing cloth, the outer periphery of the wafer temporarily ejected from the polishing cloth is returned to the polishing cloth again. In addition, there is a new problem that a high pressure is locally applied from the end surface of the polishing cloth, and the polishing surface of the wafer is easily scratched or polished. In particular, when the wafer is polished with the polishing block preventing the wafer from rotating freely, such scratches and polishing marks appear remarkably.

In addition, the polishing cloth has changes such as variations in physical properties such as its thickness and viscoelasticity, and deterioration and clogging of the polishing cloth due to long-term use. For this reason, the polishing surface of the wafer being processed cannot receive a completely uniform pressure from the polishing cloth.
However, in the conventional polishing apparatus, no consideration is given to the change in the physical properties of the polishing cloth, and as a result, the flatness of the polished wafer varies depending on the manufacturing lot of the polishing cloth.
In addition, since the center and outermost portions of the polishing cloth have a small amount of wafer travel, there is little degradation of the polishing cloth, and the processing characteristics change as the cumulative usage time increases, resulting in a partial change in the polishing amount of the wafer. Was also seen.

  The invention according to the present application has been made to solve the above-described problems, and a first object thereof is a polishing cloth, a wafer polishing apparatus, and a wafer capable of supplying a wafer with high flatness. It is to provide a manufacturing method.

  A second object of the invention according to the present application is to provide a polishing cloth, a wafer polishing apparatus, and a wafer manufacturing method capable of supplying a wafer with less surface sagging at the outer periphery of the wafer.

  A third object of the invention according to the present application is to provide a polishing cloth, a wafer polishing apparatus, and a wafer manufacturing method capable of suppressing generation of scratches and polishing marks and supplying a wafer with high flatness. is there.

In order to achieve the above object, a first invention according to the present application provides a polishing cloth that polishes the surface to be polished by sliding the surface to be polished and the surface of the cloth together, and has an outer periphery of the polishing cloth. The polishing cloth is characterized in that the height of the cloth surface in the part is lowered.
According to the above invention, by subjecting the polishing object to an appropriate location on the polishing cloth so that the polishing object can be uniformly polished as a whole, partial overpolishing of the polishing object due to the viscoelasticity of the polishing cloth is performed. Can be reduced.

Further, in the second invention according to the present application, the cloth surface is processed so that the height thereof decreases stepwise toward the outer peripheral end. Cross.
According to the above invention, the contact pressure between the cross surface of the polishing cloth and the surface to be polished of the object to be polished can be controlled stepwise.

Further, in a third invention according to the present application, the cloth surface is processed into a taper shape such that the height decreases toward the outer peripheral edge, and the polishing according to the first invention is characterized in that Cross.
According to the above invention, the contact pressure between the cross surface of the polishing cloth and the surface to be polished can be set more finely in consideration of the viscoelasticity of the polishing cloth.

According to a fourth aspect of the present invention, there is provided a grinding plate for grinding a polishing cloth, wherein a plurality of diamond particles are fixed to a base metal and at least a metal portion is coated with a fluorine-based resin or rhodium. It is.
According to said invention, it can prevent that a metal ion elutes from a grinding plate, and can reduce the metal contamination in wafer grinding | polishing.

Further, a fifth invention according to the present application is a grinding plate for grinding a polishing cloth, wherein a plurality of diamond particles are fixed to a base, and the size or contact area of the diamond particles is the base. It is a grinding plate characterized by becoming larger stepwise or gradually in at least one direction.
According to the above invention, the polishing cloth can be ground so that the contact pressure between the cloth surface of the polishing cloth and the surface to be polished of the object to be polished decreases toward the outer periphery of the polishing cloth.

According to a sixth aspect of the present application, there is provided a polishing cloth in which the height of the cloth surface in the outer peripheral portion is lowered, a surface plate holding the polishing cloth, a rotating mechanism for rotating the surface plate, and an object to be polished. Holding means for bringing the object to be polished into contact with the polishing cloth in a state where the polishing cloth is held.
According to said invention, generation | occurrence | production of a damage | wound, a polishing mark, etc. with respect to a to-be-polished object can be suppressed, and a to-be-polished object with high flatness can be supplied.

Further, a seventh invention according to the present application includes a step of attaching an abrasive cloth to a surface plate, a step of processing the outer peripheral portion so that the height of the cloth surface in the outer peripheral portion of the abrasive cloth is reduced, and at least And polishing the wafer by relatively displacing the polishing cloth and the wafer in a state where one wafer is pressed against the polishing cloth.
According to said invention, generation | occurrence | production of a damage | wound, a polishing mark, etc. with respect to a wafer can be suppressed, and a wafer with high flatness can be supplied.

According to an eighth aspect of the present invention, a wafer is polished using the step of processing the outer peripheral portion so that the height of the cloth surface at the outer peripheral portion of the polishing cloth is reduced, and the ground polishing cloth. A wafer manufacturing method comprising the steps of:
According to the above-described invention, it is possible to obtain a polishing cloth that uniformly polishes the wafer as a whole by using the existing polishing cloth, and a partial excess of the wafer due to the viscoelasticity of the polishing cloth. Polishing can be reduced.

  According to the polishing cloth, the wafer polishing apparatus, and the wafer manufacturing method of the present invention, it is possible to supply a highly flat wafer with less surface sagging at the outer peripheral portion of the wafer.

Next, a polishing cloth and a wafer polishing apparatus according to the present invention will be described with reference to the drawings.
The present invention is characterized in that the polishing cloth is processed so that the height of the cloth surface at the outer peripheral portion of the polishing cloth is reduced in the technique of polishing by sliding an object to be polished on the polishing cloth.
Various types of processing to such a polishing cloth can be considered. In the following description, as an example of processing to be performed on the polishing cloth, a case of grinding with a grinding plate will be described as an example. As processing for obtaining the same effect as that of the present application, other processing by polishing is also possible. However, since the polishing only replaces the grinding plate with a polishing tool, description thereof is omitted.

  In the following description of the embodiments, a batch type single-side polishing apparatus will be described as a model as the wafer polishing apparatus of the present invention. However, the present invention is applicable to any polishing apparatus using a polishing cloth, and is a double-side polishing apparatus. Of course, the present invention can also be applied to other polishing apparatuses such as single-sided single-side polishing apparatuses.

A polishing cloth and a wafer polishing apparatus of the present invention will be described with reference to the drawings.
[Device configuration]
1 and 2 show the wafer polishing apparatus of the present invention, FIG. 1A is a schematic perspective view of the wafer polishing apparatus of the present invention, FIG. 1B is a perspective view of the polishing cloth of the present invention, and FIG. It is a top view of the wafer polish device of the present invention.

  1A, a wafer polishing apparatus according to the present invention includes a surface plate 1 that can rotate in a predetermined direction (for example, counterclockwise direction in the drawing), and a polishing cloth 12 that is bonded and fixed to the upper surface of the surface plate 1. And a rotating shaft 3 that is attached to the center of the bottom surface of the surface plate 1 and rotates the surface plate 1 integrally with the polishing cloth 12 by power transmission of a rotational drive device (not shown), and a weight by a center roller 26 (see FIG. 2). A plurality of polishing heads 4 whose rotation is controlled in a predetermined direction (for example, counterclockwise direction in the figure) with the support shaft 5 as a rotation center, and a polishing block which is disposed on the bottom surface of the polishing head 4 and is disposed opposite to the polishing cloth 12 9 and a guide roller 18 (see FIG. 2) for assisting the polishing block 9 from the side surface.

As shown in FIG. 2, the polishing cloth 12 is a standard cloth in which the height of the cross surface of a predetermined passing area E on the outer peripheral side with respect to the wafer W is positioned on the inner side (inner peripheral side area) of the outer peripheral passing area E. A recessed cross surface 12b that is lower than the height of the surface 12a is formed.
Specifically, the polishing cloth 12 is formed of a nonwoven fabric having a diameter of about 1400 mm and a compressive displacement of about 30 μm at a surface pressure of 0 to 300 kg / cm ² , and an inner peripheral side region from the rotation center to a radius of 640 to 650 mm. The height of the recessed cross surface 12b of the predetermined passing region E on the outer peripheral side from the radius of 640 to 650 mm to the outer diameter is 2 to 25 μm with respect to the height of 0.8 to 1.5 mm of the standard cross surface 12a corresponding to It is so low.

  In the polishing cloth having a displacement amount smaller than the compression displacement amount of the polishing cloth 12, that is, a hard polishing cloth, the difference in height between the 12a surface and the 12b surface may be smaller. Further, in the polishing cloth having a displacement amount larger than the compressive displacement amount of the polishing cloth 12, that is, a soft polishing cloth, the height difference between the 12a surface and the 12b surface needs to be increased.

  3A to 3C are longitudinal sectional views of the outer peripheral portion of the polishing cloth. As shown in FIGS. 3A and 3B, the concave cross surface 12b is obtained by subjecting a predetermined passing region E on the outer peripheral side of the existing polishing cloth 12 to a grinding process with a depth D of about 2 to 25 μm. Form. In FIG. 3 (B), the recessed cross surface 12b has one stage. However, as shown in FIG. 3 (C), for example, a multi-stage configuration having two or more stages is provided so as to become lower than the standard cross surface 12a toward the outer periphery. May be.

  As described above, since the level difference between the standard cross surface 12a and the concave cross surface 12b of the polishing cloth 12 is an extremely small level of about 2 to 25 μm, scratches and polishing marks are hardly generated on the wafer W to be polished.

Further, as shown in FIGS. 4A and 4B, a continuous inclined cross surface 12c that is inclined downward in the cross section toward the outer periphery of the polishing cloth 12 may be used. 4A to 4D are longitudinal sectional views of the outer peripheral portion of the polishing cloth.
In FIG. 4B, the inclined cross surface 12c is a flat inclined surface. However, for example, as shown in FIG. 4C, the inclined cross surface is composed of two or more stages so that the inclination angle becomes gentler toward the outer periphery. Anyway.

Further, as shown in FIG. 4D, the inclined cross surface may be formed in two or more stages, and the inclination angle may be steeper as it goes toward the outer periphery.
Of course, you may incline in circular arc shape from the standard cross surface 12a.
In this way, by making the inclined cross surface 12c having a gentle inclination continuous with the standard cross surface 12a of the polishing cloth 12, it is possible to prevent the polishing cloth 12 from being stepped, and scratches or polishing marks on the wafer W to be polished. Can be suppressed.

  Of course, the concave cross surface 12b and the inclined cross surface 12c can be used in combination, and the standard cross surface 12a and the concave cross surface 12b of the polishing cloth 12 may be smoothly connected by the inclined cross surface 12c.

  As shown in FIG. 1B, the concave cross surface 12b and the inclined cross surface 12c are ground on the surface of the polishing cloth 12 by using a grinding plate 19 whose apex is directed toward the center of the polishing cloth 12. It is formed by doing. The position of the grinding plate 19 is fixed, and the cross surface of the polishing cloth 12 is ground by rotating the polishing cloth 12 while being pressed against the polishing cloth 12. Therefore, the recessed cross surface 12 b and the inclined cross surface 12 c are formed in an annular shape on the outer peripheral side of the polishing cloth 12.

  Further, by grinding the cross surface of the polishing cloth 12 while swinging the grinding plate 19 in the direction approaching and leaving the center of the polishing cloth 12, the concave cross surface 12b and the inclined cross surface 12c are made into a perfect circle. It can also be formed in a wave shape. Thus, the recessed cross surface 12b and the inclined cross surface 12c do not necessarily need to be formed in an annular shape.

  FIG. 5 shows a specific example of the grinding plate 19, FIG. 5 (A) is a plan view showing the main part in a state where the grinding plate is arranged on the polishing cloth, and FIG. 5 (B) is a diagram in which diamond particles of uniform size are electrodeposited. FIG. 5C is an enlarged longitudinal sectional view showing a state where the ground side of the ground plate is disposed with the ground side facing downward, and FIG. 5C shows the ground side surface of the ground plate on which non-uniformly sized diamond particles are electrodeposited. It is an enlarged vertical sectional view which shows the state arrange | positioned toward.

As shown in FIGS. 5A and 5B, a grinding plate 19 is used in which a large number of diamond particles 19b are evenly dispersed and electrodeposited on the ground side of the base metal 19a. As the diamond particles 19b, those having a count of about # 100 to # 300 can be used. Particularly, the diamond particles of the count # 100 are used for rough grinding and the count # 200 is used for finish grinding. Is good.
Further, the base need not be a metal base 19a, but may be made of other materials such as ceramics.

Usually, the diamond particles 19b are electrodeposited by evenly scattering particles of almost the same size on the base metal 19a, but the diamond particles 19b do not necessarily have the same size. For example, as shown in FIG. 5C, diamond particles with small particles are arranged on the center side of the polishing cloth of the base metal 19a, and gradually or gradually as it goes to the outer peripheral side of the polishing cloth of the base metal 19a. Diamond particles having large particles may be arranged.
Thus, by appropriately changing the size of the diamond particles 19b arranged on the base metal 19a, the grinding amount in the grinding plate 19 is changed, and the grinding amount on the center side of the polishing cloth is larger than the grinding amount on the outer peripheral side. You may adjust so that it may also decrease.

  Alternatively, as described later, the contact area where the grinding plate 19 contacts the polishing cloth may be increased stepwise or gradually from the center side to the outer periphery side of the polishing cloth. Thus, the grinding amount on the outer peripheral side of the polishing cloth can be made larger than the grinding amount on the center side by adjusting the contact area between the grinding plate and the polishing cloth.

  In addition, in order to prevent metal contamination of the wafer W due to metal powder falling from the metal portion of the grinding plate 19 to the polishing cloth or metal ions eluting from the grinding plate, the metal portion of the grinding plate 19 has a polytetra Coating with fluororesin such as fluoroethylene or rhodium.

FIG. 6A is a perspective view of the grinding plate 19, and FIG. 6B is a side view of the grinding plate 19. As shown in FIG. 6 (A), the grinding plate 19 has an isosceles triangle shape with the base H ₂ = 100 mm and the height H ₁ = 60 mm as viewed from above, and the thickness is T ₁ = triangular prism shape of 10 mm. By arranging the apex angle of the isosceles triangle-shaped grinding plate 19 so as to face the center side of the polishing cloth 12, a larger contact area with the grinding plate 19 is ensured as the polishing cloth 12 approaches the outer periphery.
As a result, the grinding cloth 12 has a larger amount of grinding by the grinding plate 19 as it goes to the outer periphery, and a continuous inclined cloth that inclines downward as it goes to the outer periphery of the polishing cloth 12 as shown in FIG. This is convenient for forming the surface 12c.

Further, as shown in FIG. 6B, the grinding side surface of the grinding plate 19 is cut off so that the apex arranged on the center side of the polishing cloth becomes an extremely loose inclined surface 19c.
For example, when the grinding plate 19 does not have such an inclined surface 19c, when the polishing cloth 12 is ground, the corner of the grinding plate 19 hits as shown in FIG. Or a step that is perpendicular to the boundary between the standard cross surface 12a and the concave cross surface 12b. In particular, when this level difference is large, scratches or polishing marks may occur on the wafer W to be polished.

On the other hand, when the polishing cloth 12 is ground by the grinding plate 19 having the inclined surface 19c as shown in FIG. 22B, the boundary between the standard cross surface 12a and the recessed cross surface 12b is a gentle slope. Tied together. As a result, scratches and polishing marks on the polished wafer W can be effectively suppressed.
As a method for obtaining the same effect, when the grinding plate 19 does not have the inclined surface 19c, the grinding plate 19 itself may be inclined and the polishing cloth 12 may be ground as shown in FIG.

  FIG. 7 shows a state in which the grinding plate 19 is mounted on the guide roller body 20 that holds the existing guide roller 18. 7A is a side view of the guide roller body 20 in a normal use state, FIG. 7B is a side view of the guide roller body 20 with the grinding plate 19 mounted, and FIG. 7C is a grinding plate 19. It is a top view of the guide roller main body 20 of the state which mounted | wore.

  As shown in FIG. 2, the guide roller 18 is disposed in contact with the outer peripheral side surface of each polishing block 9. Each polishing block 9 is in contact with the center roller 26 provided at the center of the polishing cloth 12 on the outer peripheral side surface, and is given a driving force by the rotation of the center roller 26. The guide roller 18 supports the side surface of each polishing block 9 and prevents the polishing block 9 from revolving on the polishing cloth 12.

As shown in the side view of FIG. 7A, the guide roller body 20 includes a base 21, a bracket 22 fixed on the base 21 and having a through hole 22a, and a bracket 22 centered on a support shaft 23a. The arm 23 is pivotally supported at one end so that it can be swung. At the tip of this arm 23, there is provided a guide roller 18 rotatably held by a rotating shaft 18a.
An active driving force is not applied to the guide roller 18, and the guide roller 18 is passively rotated according to the rotation of the polishing block 9. During normal polishing operation, as shown in FIG. 7A, the guide roller 18 abuts on the side surface of the rotating polishing block 9 to support the side surface of the polishing block 9.

When grinding the outer periphery of the polishing cloth 12, a grinding plate 19 is installed instead of the guide roller 18.
First, as shown in FIG. 7B, the arm 23 of the guide roller body 20 is turned about 180 ° so as to be retracted from the polishing cloth 12 around the support shaft 23a.
Next, a crank-shaped arm 24 having a grinding plate 19 at the tip is attached to the bracket 22.

The arm 24 is mounted in a state where the tip of the arm 24 can swing around the pin 24a through the pin 24a through the through hole 22a of the bracket 22.
Further, the bracket 22 has a slide mechanism for moving back and forth toward the center of the polishing cloth or away from the polishing cloth by a driving force or a spring.

A weight 25 that presses the grinding plate 19 toward the polishing cloth 12 is placed on the tip of the arm 24. Thus, since the tip of the arm 24 can swing around the pin 24a, and the bracket 22 has a slide mechanism that slides back and forth, the grinding of the polishing cloth 12 by the grinding plate 19 is fixed point grinding. And the occurrence of a step can be prevented.
The grinding plate 19 may be attached to at least one of the plurality of guide roller bodies 20.

[Description of operation]
Next, a procedure for grinding the polishing cloth 12 with the grinding plate 19 to form the recessed cloth surface 12b and the inclined cloth surface 12c on the outer peripheral portion will be described with reference to the flowchart of FIG.

(Step S1)
In step S <b> 1, the polishing cloth 12 is attached to the surface plate 1. As the polishing cloth 12, a generally flat one that is generally sold is used. The polishing cloth 12 is particularly preferably a nonwoven cloth impregnated with urethane. However, since the material, hardness, thickness, etc. of the polishing cloth 12 are design matters, various selections can be made.
In this embodiment, a polishing cloth having a thickness of 0.8 to 1.5 mm and a displacement of about 30 μm with a load of 300 g / cm ² is used.

(Step S2)
In step S2, in at least one of the plurality of guide roller bodies 20, the arm 23 is swung so as to retract from the polishing cloth 12 as shown in FIG. Then, the arm 24 provided with the grinding plate 19 is attached to the through hole 22a of the bracket 22 through the pin 24a.
In this embodiment, in order to reduce the surface roughness of the polishing cloth 12, two-stage grinding is performed using two types of grinding plates 19 provided with diamond particles having different counts. Here, in order to perform rough grinding first, a grinding plate 19 having a coarse grinding count # 100 (diamond grain size of 180 μm) is mounted.

(Step S3)
In step S <b> 3, with the polishing cloth 12 rotated, the grinding plate 19 for rough grinding is brought into contact with the polishing cloth 12, and grinding of a predetermined passing region E on the outer peripheral side of the polishing cloth 12 is started.
The range of the passing area E may be set according to the size of the polishing cloth 12 and the diameter of the wafer W to be polished. In the present embodiment, as the passing region E, grinding is performed in a range of 50 to 60 mm from the outermost periphery of the polishing cloth 12 toward the center.

For example, as shown in FIG. 20, when the concave cross surface 12b and the inclined cross surface 12c are formed in a large region including the vicinity of the center of the wafer W, the flatness of the entire wafer is prevented more than preventing the outer periphery of the wafer from sagging. Becomes worse.
Therefore, the recessed cross surface 12b and the inclined cross surface 12c are desirably regions of 60 mm or less from the outer periphery of the polishing cloth 12 or the outer periphery of the region through which the wafer W passes toward the center side of the polishing cloth 12.

(Step S4)
In step S4, whether or not the polishing cloth 12 in the predetermined outer peripheral region E has been ground to a predetermined depth is determined based on the surface pressure by the weight 25, the rotational speed and time of the polishing cloth 12, and the like. When the polishing cloth 12 is ground to a predetermined depth, it is determined that the rough grinding has been completed, the grinding plate 19 is retracted from the polishing cloth 12, and the rotation of the polishing cloth 12 is stopped.
And the pin 24a is extracted from the through-hole 22a of the bracket 22, and the arm 24 provided with the grinding plate 19 for rough grinding is removed.

(Step S5)
In step S5, the arm 24 equipped with the grinding plate 19 for finish grinding is mounted through the pin 24a through the through hole 22a of the bracket 22 this time. Here, in order to perform finish grinding, a grinding plate 19 of finish count # 200 is mounted.

(Step S6)
In step S <b> 6, with the polishing cloth 12 rotated, the grinding plate 19 for finish grinding is brought into contact with the polishing cloth 12, and finish grinding of a predetermined passing region E on the outer peripheral side of the polishing cloth 12 is started.

(Step S7)
In step S7, it is determined whether or not the polishing cloth 12 in the outer peripheral side predetermined passing region E has been ground to a predetermined depth based on the surface pressure by the weight 25, the rotational speed and time of the polishing cloth 12, and the like. However, since the finish grinding is different from the rough grinding and places importance on the surface roughness of the ground surface rather than the grinding depth, it is better to actually measure the surface roughness of the ground surface of the polishing cloth 12. good.
When the polishing cloth 12 is ground to the desired surface roughness, it is determined that the finish grinding is finished, the grinding plate 19 is retracted from the polishing cloth 12, and the rotation of the polishing cloth 12 is stopped.

(Step S8)
In step S8, after confirming the end of finish grinding, the arm 24 is detached from the bracket 22. The pin 24a is extracted from the through hole 22a of the bracket 22, and the arm 24 including the grinding plate 19 for finish grinding is removed.
Then, the guide roller body 20 is turned to the original state shown in FIG.

(Step S9)
In step S9, the wafer W is polished.
As shown in FIG. 1, five wafers W are stuck under a polishing block 9 with wax or an adhesive, and pressure is applied by the polishing head 4 while the polishing cloth 12 is rotated.

1 and 2 disclose an example in which four polishing heads 4 are arranged on one polishing cloth 12, the number of polishing heads 4 is not particularly limited.
Further, by arranging a plurality of polishing heads 4 for one surface plate 1, the rotation center thereof is shifted from the rotation center of the surface plate 1. However, even if there is only one polishing head. The rotation center of the polishing head and the rotation center of the surface plate 1 are not coaxially arranged.

  Further, the polishing block 9 may be fixed to the lower surface of the polishing head 4, or may not be fixed only by being pressed by the pressure from the polishing head 4. When the polishing block 9 is not fixed, the polishing block 9 is fixed to the lower surface of the polishing head 4 by frictional force only by contacting the lower surface of the polishing head 4 by the pressure from the polishing head 4.

Although an example in which five wafers W are arranged below the polishing block 9 is shown, the number of wafers W to be arranged is not particularly limited.
Further, the wafer W does not have to be adhered and fixed to the lower surface of the polishing block 9 with an adhesive such as wax, and the frictional force can be obtained simply by contacting the lower surface of the polishing block 9 by the pressure from the polishing head 4. Thus, the position may be fixed with respect to the lower surface of the polishing block 9.
Alternatively, a soft chuck such as affixing water with a backing pad may be used to make contact with the lower surface of the polishing block 9 by pressurization from the polishing head 4. When the soft chuck is used, the wafer W itself also rotates under the polishing block 9.

  The polishing block 9 is a carrier for holding the wafer W. In particular, in the present application, the shape and structure of the polishing block 9 are not limited. For example, a recess or a recess for fitting the wafer W in accordance with the shape of the wafer W It may have a loading hole or a vacuum chuck mechanism. Moreover, as shown in FIG. 21, the structure which provided the template 6 in the lower surface of the grinding | polishing block may be sufficient.

  In such a configuration, a desired load is applied to the polishing block 9 while controlling the load by the polishing head 4 by the weight support shaft 5 in a state where five wafers W are arranged under each polishing block 9. The load at this time does not need to be positively applied by the weight support shaft 5 but may be due to the weight of the polishing head 4.

When the center roller 26 is rotated from this state, the polishing block 9 rotates integrally with the polishing head 4. The four polishing blocks 9 are rotated on the spot by the rotational driving of the center roller 26 with the side surfaces supported by the guide rollers 18. As a result, the five wafers W pressed against the polishing cloth 12 by the polishing block 9 also revolve around the weight support shaft 5 together with the polishing block 9. Note that the wafer W does not rotate.
On the other hand, the polishing cloth 12 rotates as the surface plate 1 rotates. A polishing liquid such as a slurry is supplied onto the polishing cloth 12.

  In this way, due to the rotation action of the polishing block 9 and the rotation action of the polishing cloth 12, the surface to be polished of the wafer W is rubbed against the surface of the polishing cloth 12, and the wafer W is polished.

The wafer W that slides on the polishing cloth 12 is polished by passing through the standard cross surface 12a and the concave cross surface 12b or the inclined cross surface 12c of the polishing cloth 12.
At this time, when the outer peripheral portion of the wafer W passes the outer peripheral side of the polishing cloth 12, it is not polished without contacting the concave cross surface 12b or the inclined cross surface 12c at all, or is not polished on the concave cross surface 12b or the inclined cross surface 12c. Polished with low polishing pressure in contact.

[Experimental example]
9 to 12 show a case where the wafer W is polished using the polishing cloth 12 in which the concave cross surface 12b is formed in the predetermined passing region E on the outer peripheral side, and a conventional polishing in which the concave cross surface 12b is not formed. A comparative example when the wafer W is polished using the cloth 2 will be described.
Here, the polishing cloth 12 of the present invention has a diameter of about 1400 mm, a surface pressure of 50 g / cm ² using a grinding plate 19, a surface plate rotation speed of 40 rpm, a grinding time of 20 minutes, and diamond particle counts # 100 and # 200. Grinding was performed to form a concave cross surface 12b. The recessed cross surface 12b was formed with a width of about 60 mm from the outermost periphery of the polishing cloth 12 toward the center.

The change in the thickness of the surface of the polishing cloth 12 at this time is shown in FIG. FIG. 9 is a graph in which the horizontal axis represents each measurement point from the outer periphery to the center of the polishing cloth, and the vertical axis represents the thickness of the polishing cloth 12. The measurement point of 0 (cm) on the horizontal axis is the outermost peripheral position of the polishing cloth 12, and the measurement point moves toward the center of the polishing cloth 12 as the numerical value of the measurement point increases.
From the graph of FIG. 9, the polishing cloth 12 becomes thinner toward the outer periphery, and the thickness of the recessed cloth surface 12b after grinding the polishing cloth 12 under the above-described conditions is 57 μm thinner than the standard cloth surface 12a. You can see that

  FIG. 10 shows an experimental result when the wafer W is actually polished by the above-described polishing cloth 12. FIG. 10A is a plan view showing the ratio of the wafer W passing through the recessed cross surface 12b, and FIG. 10B is a graph showing the thickness of the outer peripheral portion after the wafer W is polished. is there.

  A notch 27 that is a notch for indicating the crystal orientation of the wafer W is formed in a black square portion shown in the wafer W in FIG. In the experiment shown in FIG. 10A, each wafer W is arranged so that the notch 27 comes to the outermost peripheral side of the polishing block 9. As shown in FIG. 10A, when the recessed cross surface 12b is formed in the polishing cloth 12 having a diameter of about 1400 mm in the passing region E having a diameter of 60 mm from the outer periphery, the polishing block 9 having a diameter of 570 mm is rotated once in the portion of the notch 27. As a result, it passes over the concave cross surface 12b by ¼ rotation. Therefore, if it is assumed that the wafer W is not polished while passing through the concave cross surface 12b, the portion of the notch 27 may be less polished by ¼ than the other outer peripheral portion.

FIG. 10B is a graph in which each measurement point taken on the center line of the wafer is taken on the horizontal axis and the thickness of the wafer is taken on the vertical axis. The measurement point of 0 (mm) on the horizontal axis is the center position of the wafer W, and the measurement point moves toward the outer peripheral side of the wafer W as the absolute value of the measurement point increases. The measurement point of −100 on the horizontal axis is the portion of the notch 27.
When the wafer W was actually polished with a polishing margin of 3 μm using the polishing cloth 12, the notch 27 portion of the wafer W was cut off by about 0.9 μm.

  Considering that the portion of the notch 27 is less polished by ¼ than the other outer peripheral portion, it has a shape that is cut by about 0.75 μm (= 3 ÷ 4) in the calculation, and the numerical value and the actual measurement value are calculated. Almost the same result was obtained.

  In this experiment, it was confirmed that by grinding the outer peripheral portion of the polishing cloth 12 with the grinding plate 9, the polishing amount of the wafer W can be partially changed and the shape of the wafer can be controlled.

  FIG. 14B is a three-dimensional view of the wafer after the wafer is polished using the polishing cloth of the present application, and the front side of the drawing is a portion arranged toward the outer periphery of the polishing block 9. In the three-dimensional view of FIG. 14B, it can be seen that surface sagging is prevented particularly in a portion surrounded by a broken line as compared with FIG.

FIG. 11 is a comparison graph when the wafer W is polished using the conventional polishing cloth 2 and when the wafer W is polished using the polishing cloth 12 of the present invention.
FIG. 11A is a graph when the wafer W is polished with the conventional polishing cloth 2 in which the concave cross surface 12b is not formed, and FIG. 11B is the polishing cloth 12 of the present invention in which the concave cross surface 12b is formed. It is a graph figure at the time of grind | polishing the wafer W in FIG. In FIG. 11B, a grinding cloth having a width of 60 mm ground to a depth of about 5 μm from the outermost periphery of the polishing cloth is used.

  The graph in the figure shows the number of wafers W acquired with respect to SFQR (horizontal axis) after the wafer W is polished. A specific numerical value is omitted for the number of acquired sheets on the vertical axis, and it is displayed as a bar graph showing only the ratio. Also, the black circle plot in the figure represents the ratio of the cumulative number.

  In FIG. 11A, the peak value of the bar graph is at the position of 0.15 in SFQR, but in FIG. 11B, the peak value of the bar graph is at the position of 0.12 in SFQR, and the flatness is improved. You can see that Further, the average value of SFQR was 0.148 in the graph shown in FIG. 11A, but was improved to 0.125 in the graph shown in FIG.

FIG. 12 shows the SFQR for each site at each planar position of the wafer W as a numerical value.
FIG. 12A is an explanatory diagram of SFQR distribution for each chip when the wafer W is polished with the conventional polishing cloth 2 in which the concave cross surface 12b is not formed, and FIG. 12B shows the concave cross surface 12b formed. FIG. 12C is an explanatory diagram of SFQR distribution for each chip when the wafer W is polished by the polishing cloth 12 of the present invention. FIG. 12C shows the wafer W polished by the conventional polishing cloth 2 in which the recessed cloth surface 12b is not formed. It is explanatory drawing of distribution of the difference value at the time of grind | polishing the wafer W with the grinding | polishing cloth 12 of this invention in which the concave cross surface 12b was formed.
12A to 12C, the lower side of the drawing is a portion disposed on the outermost peripheral side of the polishing block 9.

  As is clear from FIG. 12C, since the numerical value of the portion surrounded by the broken line is large, it can be seen that the flatness improvement rate in the portion arranged on the outermost peripheral side of the polishing block 9 is high.

In the above embodiment, the shape of the grinding plate 19 is an isosceles triangle and the apex angle thereof is arranged toward the center side of the polishing cloth 12. However, the shape of the grinding plate 19 does not always need to be an isosceles triangle. .
For example, as shown in FIG. 15 (A), a trapezoidal shape with the upper base facing the center side of the polishing cloth 12, and one corner portion on the center side of the polishing cloth 12 as shown in FIG. 15 (B). The shape such as a rhombus or a square shape disposed toward the surface, a rectangular shape disposed such that the short sides are positioned on the center side and the outer peripheral side of the polishing cloth 12, as shown in FIG. Is not limited.

15C is advantageous when forming the concave cross surface 12b of the polishing cloth 12 shown in FIGS. 3A and 3B.
When the inclined cross surface 12c of the polishing cloth 12 shown in FIGS. 4 (A) and 4 (B) is formed by the rectangular grinding plate 19 shown in FIG. 15 (C), it is shown in FIG. 5 (C). As described above, the diameter of the diamond particles 19b may be increased stepwise or gradually toward the outer peripheral side, or the grinding plate 19 may be inclined.

  In the present application, by grinding the polishing cloth of the portion through which the outer peripheral portion of the wafer is likely to cause surface sagging of the wafer, the amount of polishing of that portion is reduced, The influence of viscoelasticity due to the difference in distance between adjacent wafers can also be reduced.

  Various types of processing to the polishing cloth are conceivable in addition to grinding, and processing by polishing is also possible. For polishing, the above-described grinding plate may be replaced with a polishing tool.

  In addition, since the grinding amount and grinding area (width) of the polishing cloth can be freely changed, it is possible to cope with different compression characteristics for each polishing cloth.

  Furthermore, by making the grinding plate into a triangular shape, a grinding ratio can be provided from the outer peripheral portion of the polishing cloth toward the central portion, and a step between the ground portion and the unground portion can be eliminated. As a result, the generation of scratches and polishing marks due to steps can be suppressed, and a wafer with high flatness can be supplied.

In particular, since the present application processes the polishing cloth afterwards, it is possible to perform grinding according to the difference in the compression characteristics of the polishing cloth generated for each production lot.
In addition, since the center and outermost portions of the polishing cloth have a small amount of wafer travel, there is little degradation of the polishing cloth, and the processing characteristics change as the cumulative usage time increases, resulting in a partial change in the polishing amount of the wafer. However, since the present application grinds afterwards, it is possible to perform grinding according to the degree of deterioration.

  In the above embodiment, a batch type single-side polishing apparatus is described. However, the present invention can be applied to any polishing apparatus using a polishing cloth, and other types such as a double-side polishing apparatus and a single-wafer type single-side polishing apparatus. Of course, the present invention can also be applied to a polishing apparatus.

In the above embodiment, a semiconductor wafer is described as an example of an object to be polished. However, the object to be polished is not limited to a semiconductor wafer, but can be applied to a wafer (thin plate-like object) made of other materials. .
The shape of the object to be polished is not limited to a disk-shaped wafer, but can be applied to a square or polygonal wafer.

  Further, the invention according to the present application is not limited to a thin plate-like wafer, and can be applied to an object to be polished having any shape.

FIG. 1A is a schematic perspective view of a wafer polishing apparatus of the present invention, and FIG. 1B is a perspective view of a polishing cloth of the present invention. It is a top view of the wafer polish device of the present invention. 3A is a vertical cross-sectional view of the main part of the wafer polishing apparatus, FIG. 3B is an enlarged vertical cross-sectional view of the main part of the polishing cloth, and FIG. 3C is an enlarged main part of a modification of the polishing cloth. It is a longitudinal cross-sectional view. 4A is a longitudinal cross-sectional view of the main part of the wafer polishing apparatus, FIG. 4B is an enlarged vertical cross-sectional view of the main part of the polishing cloth, and FIGS. 4C and 4D are modified examples of the polishing cloth. It is an expanded vertical sectional view of the principal part. 5A is a plan view showing the positional relationship between the polishing cloth and the grinding plate, FIG. 5B is an enlarged longitudinal sectional view of the main part of the grinding plate, and FIG. 5C is a main part of a modification of the grinding plate. FIG. 6A is a perspective view of the grinding plate of the present invention, and FIG. 6B is a side view of the grinding plate of the present invention. 7A is a side view showing the usage state of the guide roller, FIG. 7B is a side view showing a state where the grinding plate is attached, and FIG. 7C is a plan view showing a state where the grinding plate is attached. is there. It is a flowchart which shows the process process of the grinding | polishing cloth of this invention. It is a graph which shows the thickness change of the abrasive cloth of this invention. It is a figure which shows the experimental result when a wafer is actually grind | polished with the grinding | polishing cloth of this invention, FIG. 10 (A) is a top view which shows the ratio which a wafer passes a concave cross surface, FIG.10 (B) is a wafer. It is the graph which graphed the thickness of the outer peripheral part after grinding | polishing. FIG. 11A is a comparative graph when a wafer is polished using a conventional polishing cloth and when a wafer is polished using the polishing cloth of the present invention. FIG. 11A is a polishing cloth that does not form a concave cloth surface. FIG. 11B is a graph when a wafer is polished with a polishing cloth having a concave cross surface, and FIG. 11B is a graph when the wafer is polished. FIG. 12A is an explanatory diagram of the SFQR distribution for each site when the wafer is polished with a polishing cloth that does not form a concave cross surface. FIG. ) Is an explanatory diagram of SFQR distribution for each site when a wafer is polished with a polishing cloth having a concave cross surface. FIG. 12C is a case where the wafer W is polished with a polishing cloth having no concave cross surface. It is explanatory drawing which shows distribution of the difference value at the time of grind | polishing a wafer with the grinding | polishing cloth which formed the concave cross surface. It is a graph which shows the relationship between the distance between wafers, and a surface sagging amount. 14A is a three-dimensional view of the wafer when polished using a conventional polishing cloth, and FIG. 14B is a three-dimensional view of the wafer when polished using the polishing cloth of the present invention. FIG. 15A is a plan view of a trapezoidal grinding plate, FIG. 15B is a plan view of a diamond-shaped grinding plate, and FIG. 15C is a rectangular grinding. It is a top view of a plate. It is explanatory drawing of the elastic stress by the dynamic viscoelasticity accompanying the separation distance of a wafer, and is explanatory drawing which shows the elastic stress of the polishing cloth when the separation distance of a wafer is narrow. It is explanatory drawing of the elastic stress by the dynamic viscoelasticity accompanying the separation distance of a wafer, and is explanatory drawing which shows the elastic stress of the polishing cloth when the separation distance of a wafer is wide. FIG. 18A is a plan view showing a part of the polishing block and a part of the wafer, and FIG. 18B is a graph showing the relationship of the arc distance between adjacent wafers. It is explanatory drawing for demonstrating the elastic stress by the dynamic viscoelasticity of the grinding | polishing cloth accompanying a movement of a wafer, and the graph of the elastic stress which matched this explanatory drawing and position. It is a top view which shows the example of the grinding | polishing cloth with a large area | region of a concave cross surface and an inclination cross surface. A batch type single-side polishing apparatus is shown, (A) is a longitudinal sectional view of the batch type single-side polishing apparatus, and (B) is an enlarged sectional view of a main part of the batch type single-side polishing apparatus. 22 (A) to 22 (C) are enlarged longitudinal sectional views of main parts showing a state in which the polishing cloth is ground by the grinding plate. The double-side polishing apparatus is shown, is a plan view schematically showing the carrier rotation mechanism of the double-side polishing apparatus, and (B) is an enlarged vertical sectional view of a part of the double-side polishing apparatus. It is a longitudinal cross-sectional view which shows the outline of a single-wafer | sheet-fed single-side polish apparatus.

Explanation of symbols

W ... wafer (object to be polished) Wa, Wb, Wc, Wd ... wafer E ... predetermined passing area on the outer peripheral side 1 ... surface plate 1a ... upper surface plate 1b ... lower surface plate 2 ... polishing cloth 3 ... rotary shaft 4 ... polishing Head 5 ... Weight support shaft 6 ... Template 6a ... Wafer positioning hole 8 ... Slurry tube 9 ... Polishing block 12 ... Polishing cross 12a ... Standard cross surface 12b ... Recessed cross surface 12c ... Inclined cross surface 18 ... Guide roller 18a ... Rotating shaft 19 ... Grinding plate 19a ... Base metal 19b ... Diamond particles 19c ... Inclined surface 20 ... Guide roller body 21 ... Base 22 ... Bracket 22a ... Through hole 23 ... Arm 23a ... Support shaft 24 ... Arm 24a ... Pin 25 ... Weight 26 ... Center Roller 27 ... Notch 51 ... Carrier 52 ... Loading hole 53 ... Planet gear 54 ... Inter Narugiya 55 ... sun gear 64 ... polishing head 65 ... vacuum chuck mechanism 68 ... retainer.

Claims (8)

In the polishing cloth that polishes the surface to be polished by rubbing the surface to be polished and the surface of the cloth,
A polishing cloth characterized in that a height of a cloth surface in an outer peripheral portion of the polishing cloth is lowered.   2. The polishing cloth according to claim 1, wherein the cloth surface is processed so that a height thereof is gradually reduced toward an outer peripheral end. 3.   2. The polishing cloth according to claim 1, wherein the cloth surface is processed into a taper shape such that the height of the cloth surface decreases toward the outer peripheral end.   A grinding plate for grinding a polishing cloth, wherein a plurality of diamond particles are fixed to a base metal and at least a metal portion is coated with a fluorine-based resin or rhodium. A grinding plate that grinds the polishing cloth, with a plurality of diamond particles fixed to the base,
A grinding plate, wherein the size or contact area of the diamond particles increases stepwise or gradually toward at least one direction of the base. A polishing cloth having a reduced cloth surface height at the outer periphery,
A surface plate holding the polishing cloth;
A rotating mechanism for rotating the surface plate;
Holding means for contacting the object to be polished with the polishing cloth while holding the object to be polished;
A polishing apparatus comprising: A step of attaching an abrasive cloth to a surface plate;
Processing the outer peripheral portion so that the height of the cloth surface at the outer peripheral portion of the polishing cloth is reduced;
Polishing the wafer by relatively displacing the polishing cloth and the wafer while pressing at least one wafer against the polishing cloth;
A wafer polishing method comprising: Processing the outer peripheral portion so that the height of the cloth surface at the outer peripheral portion of the polishing cloth is reduced;
Polishing the wafer using the ground polishing cloth;
A wafer manufacturing method comprising:

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