JP3779104B2 - Wafer polishing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wafer polishing apparatus for polishing the surface of a wafer or the like forming an integrated circuit.
[0002]
[Prior art]
The silicon wafer whose surface has been etched is subjected to mechanical chemical polishing on the surface in a polishing process. For example, the surface of the wafer is finished to a smooth and undistorted mirror surface by surface polishing.
A general double-side polishing wafer polishing apparatus is configured as follows. That is, an upper surface plate and a lower surface plate provided at opposite positions, a polishing cloth adhered to the surface of the upper surface plate and the lower surface plate, respectively, and a disk-like shape disposed on the polishing cloth on the surface of the lower surface plate A rotating shaft provided with a sun gear is arranged at the center of the lower surface plate, and an internal gear is provided around the outer periphery of the lower surface plate.
The carrier plate is provided with wafer holding holes for holding the wafer to be polished. A gear that meshes with the sun gear and the internal gear is provided around the outer periphery of the carrier plate, and the carrier plate revolves while rotating on the lower surface plate around the rotation axis by the rotation of the rotation shaft. .
[0003]
When polishing a wafer, a polishing liquid (slurry) containing abrasive grains such as baked silica or colloidal silica (silica sol) is supplied to the polishing cloth, while a predetermined load and relative speed are applied between the polishing cloth and each wafer. Give and polish. That is, in the case of single-side polishing, the wafer attached to the carrier is polished while rotating each carrier by each polishing head. In the case of double-side polishing, when the rotating shaft is driven to rotate the sun gear, the carrier plate revolves while rotating around the rotating shaft by the sun gear and the internal gear. Since the wafer is given a polishing load, the wafer is polished as the carrier plate rotates and revolves.
[0004]
[Problems to be solved by the invention]
Incidentally, the conventional wafer polishing apparatus has the following problems.
That is, when the wafer rotates, the rotation speed near the peripheral edge is faster than that near the center of the carrier. For this reason, the polishing amount of the wafer peripheral portion increases as compared with other portions, and a thin portion (so-called “sag”) having a thinner thickness than the central portion is formed at the peripheral portion. In particular, in an 8-inch wafer, the carrier has a large diameter of about 600 mm, and the amount of thin-walled portion formed is large. As a result, the flatness of the wafer surface indicated by TTV (Total Thickness Variation), SBIR (Site Back-side Ideal Range), etc. has been reduced.
Further, the wafer is pressed against the polishing cloth at the time of polishing, and the polishing cloth at that portion is elastically compressed and deformed. The state at this time is shown in FIG. In the drawing, the polishing cloths 25 and 26 that are elastically compressed and deformed give the wafer W a pressing force as a restoring force. Since this pressing force is particularly large at the peripheral portion of the wafer 4, a larger external pressure acts on the peripheral portion of the wafer W than at the central portion, and the polishing amount of the peripheral portion of the wafer W increases.
From the above, as shown in FIG. 17, the thinner the wafer periphery, the thinner the portion A is formed, and the surface of the wafer W becomes a convex curved surface as shown in FIG. There was a point.
[0005]
In view of the above circumstances, an object of the present invention is to provide a wafer polishing method and a wafer polishing apparatus that can improve the flatness of a wafer by preventing the generation of a thin portion at the periphery.
[0006]
[Means for Solving the Problems]
  The wafer polishing apparatus of the present invention includes an upper surface plate and a lower surface plate,
An upper polishing cloth provided on the upper surface plate, a lower polishing cloth provided on the surface of the lower surface plate,
A carrier plate provided with a wafer holding hole for holding a wafer to be polished, disposed on the lower polishing cloth on the lower surface of the lower platen surface, and in contact with the upper polishing cloth on the upper surface of the upper platen;
In a wafer polishing apparatus for double-side polishing having a carrier rotating mechanism for polishing a wafer by the upper polishing cloth and the lower polishing cloth by rotating the carrier plate,
The carrier plate is rotated when the carrier plate is rotated so that the total amount of time that the peripheral edge of the wafer held in the wafer holding hole passes through the region of the polishing cloth from the center thereof is reduced. The trajectory at the peripheral edge of the wafer holding hole is supported so as to pass outside the outer peripheral edge or the inner peripheral edge that is outside the polishing action region of at least one of the upper polishing cloth and the lower polishing cloth,
The upper polishing cloth and the lower polishing cloth are different in the size or shape of the outline in plan view, the polishing cloth is formed in an annular shape in plan view, and the outer peripheral outline shape or the inner peripheral outline shape is wavy or a saw blade. Formed into a non-circular shape,
The said subject was solved by the area of the said wafer peripheral part which passes the said grinding | polishing effect | action area | region being 10-30% of the whole wafer surface area.
The wafer polishing apparatus of the present invention includes an upper surface plate and a lower surface plate,
An upper polishing cloth provided on the upper surface plate, a lower polishing cloth provided on the surface of the lower surface plate,
A carrier plate provided with a wafer holding hole for holding a wafer to be polished, disposed on the lower polishing cloth on the lower surface of the lower platen surface, and in contact with the upper polishing cloth on the upper surface of the upper platen;
In a wafer polishing apparatus for double-side polishing having a carrier rotating mechanism for polishing a wafer by the upper polishing cloth and the lower polishing cloth by rotating the carrier plate,
The carrier plate is rotated when the carrier plate is rotated so that the total amount of time that the peripheral edge of the wafer held in the wafer holding hole passes through the region of the polishing cloth from the center thereof is reduced. The trajectory at the peripheral edge of the wafer holding hole is supported so as to pass outside the outer peripheral edge or the inner peripheral edge that is outside the polishing action region of at least one of the upper polishing cloth and the lower polishing cloth,
The upper polishing cloth and the lower polishing cloth are different in the size or shape of the outline in plan view, the polishing cloth is formed in a ring shape in plan view, and the outer peripheral outline shape or the inner peripheral outline shape is an ellipse or a polygon. Formed in a non-circular shape
The said subject was solved by the area of the said wafer peripheral part which passes the said grinding | polishing effect | action area | region being 10-30% of the whole wafer surface area.
The wafer polishing apparatus of the present invention includes an upper surface plate and a lower surface plate,
An upper polishing cloth provided on the upper surface plate, a lower polishing cloth provided on the surface of the lower surface plate,
A carrier plate provided with a wafer holding hole for holding a wafer to be polished, disposed on the lower polishing cloth on the lower surface of the lower platen surface, and in contact with the upper polishing cloth on the upper surface of the upper platen;
In a wafer polishing apparatus for double-side polishing having a carrier rotating mechanism for polishing a wafer by the upper polishing cloth and the lower polishing cloth by rotating the carrier plate,
The carrier plate is rotated when the carrier plate is rotated so that the total amount of time that the peripheral edge of the wafer held in the wafer holding hole passes through the region of the polishing cloth from the center thereof is reduced. The trajectory at the peripheral edge of the wafer holding hole is supported so as to pass outside the outer peripheral edge or the inner peripheral edge that is outside the polishing action region of at least one of the upper polishing cloth and the lower polishing cloth,
The upper polishing cloth and the lower polishing cloth have different sizes or shapes in outline in plan view. The polishing cloth is formed in an annular shape in plan view, and the outline shape of the outer peripheral edge or the outline shape of the inner peripheral edge is non-circular. As described above, at least one notch is provided on the outer periphery or the inner periphery of the polishing cloth,
As the shape of the notch, when provided on the outer peripheral edge of the polishing cloth, a wave shape or a wedge shape in which the width in the circumferential direction of the notch is narrower than the width of the outer peripheral edge of the polishing cloth. of In the case of providing the shape and the peripheral edge of the polishing cloth, as a wave shape or a wedge shape such that the outer periphery of the polishing cloth is narrow,
The said subject was solved by the area of the said wafer peripheral part which passes the said grinding | polishing effect | action area | region being 10-30% of the whole wafer surface area.
The wafer polishing apparatus of the present invention is the above-described wafer polishing apparatus,
A plurality of the notches may be provided discretely and periodically in the circumferential direction of the polishing pad.
  The present inventionThe wafer polishing apparatus includes an upper surface plate and a lower surface plate, an upper polishing cloth provided on the upper surface plate, a lower polishing cloth provided on the surface of the lower surface plate, and a wafer holding hole for holding a wafer to be polished. A carrier plate disposed on the lower polishing cloth of the lower platen surface and in contact with the upper polishing cloth of the upper platen surface; and rotating the carrier plate to rotate the wafer to move the wafer to the upper polishing cloth and the lower polishing cloth. In the wafer polishing apparatus having a carrier rotating mechanism for polishing by the carrier plate, when the carrier plate is rotated, the locus at the peripheral edge of the wafer holding hole is at least one of the upper polishing cloth and the lower polishing cloth. It is supported so that it passes outside one of the polishing regions, and the area of the peripheral edge of the wafer that passes outside the polishing region is Characterized by comprising been 10 to 30% of the whole Doha surface area.
[0007]
In this wafer polishing apparatus, when the polishing head and the carrier plate are rotated, a part of the peripheral edge of the wafer is outside the polishing action area of at least one of the upper polishing cloth and the lower polishing cloth, for example, outside the outer periphery or May pass through the inner periphery.
For this reason, the total amount of time that the peripheral portion of the wafer passes through the polishing action region of the polishing cloth is smaller than the central portion thereof. Accordingly, as described above, when the peripheral edge of the wafer passes through the polishing region of the polishing cloth, it is polished more than the central portion, but since the total amount of time passing through the polishing region is small, the polishing amount is offset as a result. The Rukoto.
Note that at least a part of the peripheral edge of the wafer may always pass outside the polishing area of the polishing cloth, or the peripheral edge of the wafer may temporarily pass outside the polishing area of the polishing cloth.
[0008]
Examples of the wafer include a silicon wafer and a gallium arsenide wafer. As polishing cloth, for example, hard urethane pad, CeO₂Examples include pads.
As the polishing liquid, for example, a mixture of baked silica, colloidal silica (abrasive grains), amine (processing accelerator), organic polymer (haze suppression material), or the like can be used. Colloidal silica is present by forming a transparent or opaque milky white colloidal solution dispersed in water as primary particles without condensation of silicic acid fine particles.
The area of the peripheral edge of the wafer that passes outside the polishing area of the polishing pad is preferably 10 to 30%, particularly 20 to 25% of the entire wafer surface area. If it is less than 10%, there is a disadvantage that the wafer shape is not changed (thinning of the peripheral edge cannot be eliminated). On the other hand, if it exceeds 30%, there is an inconvenience that the peripheral edge of the wafer may be rounded up.
[0009]
  The present inventionThe wafer polishing equipmentthe aboveIn the wafer polishing apparatus of claim 1, when the carrier plate is rotated, the locus at the peripheral edge of the wafer holding hole is outside or inside the outer peripheral edge of at least one of the upper polishing cloth and the lower polishing cloth. The polishing cloth is supported so as to pass through the inner periphery, and the polishing cloth is formed in an annular shape in plan view, and the outer peripheral contour shape or the inner peripheral contour shape is noncircular. .
[0010]
  Also,The present inventionThe wafer polishing equipmentthe aboveIn the wafer polishing apparatus, at least one notch is provided on the outer peripheral edge or the inner peripheral edge of the polishing cloth.
[0011]
As the shape of the notch, for example, when provided on the outer periphery of the polishing cloth, the width in the circumferential direction of the notch is such that the width closer to the center is narrower than the width of the outer periphery of the polishing cloth. When it is provided on the outer periphery of the polishing pad, the shape of the polishing cloth is narrower at the outer periphery. Specifically, it is a notch such as a wave shape or a wedge shape, but the shape may be various. By providing such a notch, the outer peripheral edge or the inner peripheral edge of the polishing pad has a non-circular contour. The number of notches may be at least one, and a plurality of notches may be provided discretely and periodically in the circumferential direction of the polishing pad.
In addition, the configuration in which the outer peripheral edge or inner peripheral edge of the polishing cloth is non-circular is not limited to the above-described notch, and for example, the polishing cloth has a wavy shape or a saw blade shape, or the polishing cloth has an elliptical shape. It may be formed in a polygonal shape.
This configuration has the following effects.
That is, when the contour shape of the polishing cloth is circular as described above and the locus at the peripheral edge of the wafer is supported so that it passes through the outer peripheral edge of the polishing cloth or the inner peripheral edge as shown in FIG. The amount of polishing of the peripheral portions 35 and 36 is reduced, and the sagging of the wafer W is eliminated.
However, in some cases, a step B as shown in FIG. 20 appears at the boundary between the wafer peripheral portions 35 and 36 and the wafer central portion that does not leave the polishing region at all. As the invention according to claims 4 and 5 of the present invention, for example, with the configuration shown in FIGS. 12 and 13, the boundary between the portion that protrudes outside the polishing region of the polishing cloth and the portion that does not protrude is smooth, The step as indicated by the symbol B in FIG. Specifically, for example, when the notch is provided on the outer peripheral edge of the polishing cloth, the notch is formed narrower near the center of the polishing cloth. The amount can be reduced and the polishing amount closer to the center can be relatively increased. That is, a difference can be given to the polishing amount in the peripheral portion of the wafer, and the polishing amount can be controlled. Therefore, the step B can be made gentle and the flatness of the wafer can be improved. .
[0012]
  The present inventionThe wafer polishing equipmentthe aboveIn the wafer polishing apparatus according to any one of the above, when the carrier plate is rotated, the locus at the peripheral edge of the wafer holding hole is outside the polishing area of the upper and lower polishing cloths. The upper polishing cloth and the lower polishing cloth are supported so as to pass through, and the size or shape of the outline in plan view is different.
[0013]
In this wafer polishing apparatus, when the carrier plate rotates, a part of the peripheral edge of the wafer holding hole may be located outside the polishing area of the polishing cloth, for example, the outer peripheral edge or the inner peripheral edge.
For this reason, the total amount of time that the peripheral part of the wafer held in the wafer holding hole passes through the region of the polishing cloth from the central part thereof decreases. Therefore, when the wafer passes through the region of the polishing cloth, the peripheral portion is more polished as described above, but since the total amount of time passing through the region is small, the polishing amount is offset.
Further, since the upper polishing cloth and the lower polishing cloth have different sizes or shapes of the contours in plan view, the polishing state of the wafer peripheral portion is different between the upper surface and the lower surface of the wafer. Therefore, different polishing can be performed on the upper and lower surfaces of the wafer.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. First, the prerequisite technology of the present invention will be described.
FIG. 1 is an enlarged cross-sectional view of a main part of a wafer polishing apparatus according to a first prerequisite technology. FIG. 2 is a plan view of a polishing surface plate according to the first prerequisite technology. This technique is a wafer polishing apparatus for single-side polishing.
In FIG. 1, 10 is a batch type silicon wafer polishing apparatus. This polishing apparatus 10 has a polishing surface plate 12 on which a polishing cloth 11 made of a hard urethane pad is stretched, and 4 disposed above this. A polishing head 13 is provided.
[0015]
As the polishing cloth 11, a hard non-woven urethane pad ("suba800", manufactured by Rodel Nitta Co., Ltd.) having a diameter of 200 mm and a thickness of 1.3 mm is employed. In addition, an annular groove 11a having a width of 25 mm and a depth of 0.6 mm is cut out at the peripheral edge of the polishing pad 11 as a non-polishing region. This groove width is a width that allows the silicon wafer W to be polished by polishing a part of the peripheral edge of each rotating wafer outside the polishing area of the polishing pad 11 during wafer polishing. Since the annular groove 11a is formed thinner than the polishing area, a part of the peripheral edge of the wafer that protrudes from the polishing area comes into contact with the polishing cloth (annular groove 11a) with a smaller pressing force than the polishing area.
On the lower surface of the polishing head 13, five silicon wafers W having a diameter of 8 inches and a thickness of 725 μm are attached by wax at intervals of 72 degrees centering on the center of the head. Each silicon wafer W has a notch w1 formed on the peripheral edge of each silicon wafer, facing the outside in the radial direction of the carrier. The rotation direction of the polishing surface plate 12 and each polishing head 13 is the same direction (see FIG. 2).
[0016]
It should be noted that all the prerequisite technologies shown here and the wafer polishing apparatus according to the present invention to be described later may be a waxless type that does not use wax.
Waxless mount polishing equipment uses a template with a suction pad (such as a suede pad) placed in a hole slightly larger than the wafer diameter. The foam layer (nap part) on the surface of this suction pad and the back of the wafer Pure water or the like is supplied to the wafer, and the wafer is handled using the surface tension of the pure water.
However, in this apparatus, since the wafer is only adsorbed to the adsorption pad by the surface tension of water, the adhesion force of the wafer to the mounting block (carrier) side is weak. Therefore, during rotation of the mounting block, when a part of the wafer peripheral part that once protrudes outside the polishing cloth is pressed against the polishing surface of the polishing cloth again, the wafer peripheral part may be rolled up, possibly damaging the wafer. is there.
[0017]
Next, a method for polishing the silicon wafer W using the polishing apparatus 10 will be described.
As shown in FIGS. 1 and 2, first, five silicon wafers W are wax-adhered to each carrier 14 at intervals of 72 degrees, and then each carrier 14 is fixed to the lower surface of the corresponding polishing head 13.
Then, by lowering each polishing head 13, 0.3 kgf / cm²Each silicon wafer W is pressed against the polishing surface of the polishing pad 11 stretched on the polishing surface plate 12 with the pressure of. While maintaining this state and supplying the polishing liquid onto the polishing pad 11 at 2.0 ± 0.5 liter / min, the polishing surface plate 12 is rotated at 35 ± 2 rpm in the direction of the solid line arrow in FIG. At the same time, each polishing head 13 is rotated at 35 ± 2 rpm in the direction of the two-dot chain line in FIG. Thereby, the polishing surface (surface) of each silicon wafer W is polished. The polishing time is, for example, 10 minutes.
[0018]
By the way, in this first prerequisite technique, an annular groove 11 a is formed at the peripheral edge of the polishing pad 11. For this reason, during the polishing, each silicon wafer W rotates by protruding a part of the peripheral edge of the wafer on the annular groove 11a. That is, the periphery of the silicon wafer passes through the annular groove 11a having a smaller pressing force than when the silicon wafer W is rotated by a predetermined angle.
That is, in the conventional polishing apparatus, the polishing of the formation part of the notch w1 proceeds as compared with the central part of the wafer, and the thin part is generated in the notch formation part. The amount of polishing at the peripheral edge of the wafer is suppressed by the grooves 11a. Therefore, the flatness (TTV or the like) of the silicon wafer W is increased.
[0019]
Next, a wafer polishing apparatus according to the second prerequisite technique of the present invention will be described with reference to FIGS.
FIG. 3 is an enlarged cross-sectional view of a main part of the wafer polishing apparatus according to the second prerequisite technology. FIG. 4 is a plan view of a polishing surface plate according to the second prerequisite technology.
As shown in FIGS. 3 and 4, the wafer polishing apparatus 20 according to the second prerequisite technique replaces the polishing cloth 11 having the annular groove 11 a of the first prerequisite technique with a regular hexagonal polishing cloth 11 </ b> A in plan view. This is an example of adopting. Thus, six moon-shaped notches (non-abrasive action region) 11b are disposed on the peripheral edge of the polishing pad 11A.
Other configurations are substantially the same as those of the first prerequisite technology, and thus description thereof is omitted.
In the base technology, since the notch portion 11b is provided, each silicon wafer W rotates by protruding a part of the peripheral edge portion of the wafer from the polishing region of the polishing pad 11 during polishing. Therefore, the periphery of the silicon wafer passes through the non-polishing region each time the silicon wafer W rotates by a predetermined angle. Since the wafer W is not polished in the non-polishing region, the amount of polishing at the peripheral edge of the wafer is suppressed and the flatness (TTV or the like) of the silicon wafer W is increased as in the first premise technique.
[0020]
Here, referring to FIG. 5 and FIG. 6, a comparison experiment when actually polishing a silicon wafer using the wafer polishing apparatus 10 according to the first premise technique and a conventional polishing apparatus of the same type is performed. The results of the flatness (SBIR) of each silicon wafer surface when performed are described.
FIG. 5 is a perspective view showing contour lines of a silicon wafer polished using the wafer polishing apparatus according to the first prerequisite technology. FIG. 6 is an explanatory diagram showing the partial flatness of the surface of the silicon wafer polished using the wafer polishing apparatus according to the first prerequisite technique. FIG. 7 is a perspective view showing a silicon wafer polished with a conventional polishing apparatus by contour lines. FIG. 8 is an explanatory diagram showing the partial flatness of the surface of a silicon wafer polished using a conventional polishing apparatus.
The numerical value in each area is an SBIR value for evaluating the flatness. Among these, the shaded portion is 0.4 μm or more.
[0021]
As apparent from FIG. 7 and FIG. 8, in the polishing with the conventional polishing apparatus, a thin portion is generated in a part of the peripheral edge portion of the wafer. On the other hand, as shown in FIGS. 5 and 6, in the polishing by the polishing apparatus 10 according to the first prerequisite technique, there was almost no area where the SBIR value exceeded 0.4 μm, and the flatness was improved.
[0022]
Next, a first embodiment according to the present invention will be described.
In FIG. 9, reference numeral 21 denotes a wafer polishing apparatus for polishing a silicon wafer, which is attached to the upper surface plate 22 and the lower surface plate 23 provided at opposite positions, and the upper surface plate 22 and the lower surface plate 23, respectively. An abrasive cloth (upper abrasive cloth) 25, an abrasive cloth (lower abrasive cloth) 26, and a disk-shaped carrier plate 24 disposed on the abrasive cloth 26 on the surface of the lower surface plate 23. A rotating shaft 29 provided with a sun gear 28 is disposed at the center of the lower surface plate 23, and an internal gear 30 is provided around the outer periphery of the lower surface plate 23. The sun gear 28, the rotating shaft 29, and the internal gear 30 constitute a carrier plate rotating mechanism 31.
FIG. 10 shows a perspective view of the wafer polishing apparatus 21. The upper surface plate 22 is omitted.
As shown in FIG. 10, the carrier plate 24 is provided with wafer holding holes 32 for holding the wafer W to be polished. A gear 33 that meshes with the sun gear 28 and the internal gear 30 is provided around the outer periphery of the carrier plate 24, and the carrier plate 24 rotates on the lower surface plate 23 around the rotary shaft 29 by the rotation of the rotary shaft 29. However, it has come to revolve.
[0023]
Each of the polishing cloths 25 and 26 is annular in plan view, and the outer peripheral contour shape and the inner peripheral contour shape are circular. However, the outer diameter is smaller and the inner diameter is larger than that of the conventional polishing cloth. As shown in FIG. 11, the movement trajectory of the peripheral edge portion of the wafer holding hole 32 indicated by reference numeral 35 is the polishing cloth 25, 26 passes the outside of the polishing action region, that is, the outer periphery and the inner periphery.
Similarly, with respect to the wafer W held in the wafer holding hole 32, the movement locus of the peripheral edge 36 passes outside the polishing area of the polishing cloths 25 and 26, that is, outside the outer peripheral edge and the inner peripheral edge. It has become.
Hereinafter, the radial width of the wafer peripheral portion 36 is referred to as an offset amount d.
[0024]
In general, the higher the hardness of the polishing cloth, the smaller the compression deformation, so that the thin portion at the peripheral edge of the wafer W becomes inconspicuous. Further, the degree of occurrence of the thin portion varies depending on the polishing load and the polishing rate. Therefore, although the extent of the area of the wafer peripheral portion 36 is not uniquely determined, the surface area of the wafer is as described above for each of the inner and outer peripheral edges of the outer peripheral edge in consideration of the hardness of the polishing cloth actually used. 10 to 30% of the whole, especially 20 to 25% is preferable. The offset amount d is about 5 to 50 mm. Although the offset amount d for the outer peripheral edge is shown in the figure, the inner peripheral edge is also set under the same conditions.
[0025]
The wafer polishing apparatus 21 configured as described above operates as follows.
First, the wafer W is held in the wafer holding hole 32, and the wafer W is pressed by the upper surface plate 22 and the lower surface plate 23, and 100 to 500 g / cm.²A polishing load of about a degree is given.
When the rotating shaft 29 is driven and the sun gear 28 is rotated in this state, the carrier plate 24 revolves around the rotating shaft 29 by the sun gear 28 and the internal gear 30 as shown in FIG. At this time, the polishing liquid is supplied to the polishing cloths 25 and 26.
When the rotation shaft 29 rotates, the wafer W rotates in the wafer holding hole 32 and revolves around the rotation center axis of the carrier plate 24. Further, since the carrier plate 24 itself revolves around the rotation axis 29, the wafer W moves relative to the polishing cloths 25 and 26. The speed is 5-50 m / s.
[0026]
Due to the polishing load, the polishing cloths 25 and 26 in contact with the wafer W are compressively deformed. For this reason, in the wafer peripheral part 36 pressed against the polishing cloths 25 and 26, the restoring force of the polishing cloths 25 and 26 causes a larger external pressure than the central part, and the polishing amount increases.
However, as described above, the movement trajectory of the wafer peripheral portion 36 passes outside the polishing action area of the polishing cloths 25 and 26, so that part of the wafer is temporarily polished as the wafer W moves. Since the regions of the cloths 25 and 26 are removed and pass through the outer peripheral edge or the inner peripheral edge, the total amount of time polished by the polishing cloths 25 and 26 is different between the peripheral edge 36 and the vicinity of the center.
As a result, the difference in polishing amount between the central portion and the peripheral portion 36 is canceled out. Therefore, the occurrence of a thin portion at the wafer peripheral portion 36 is prevented, and the flatness of the wafer W can be increased.
The wafer polished by this embodiment is shown in FIG. According to this, it can be seen that the flatness is higher than that of the wafer polished by the conventional polishing apparatus shown in FIG.
[0027]
By the way, in the wafer polishing apparatus 21, as shown in FIG. 20, a step B may appear as a boundary between the wafer peripheral portion 36 and the wafer central portion that does not leave the polishing region at all.
In this case, by cutting the peripheral edges of the polishing cloths 25 and 26 in a wavy manner as shown in FIG. 12, the boundary between the peripheral edge portion 36 and the central portion becomes gentle, so this step can be eliminated.
[0028]
This step B can also be eliminated in the following second and third embodiments.
That is, as a second embodiment of the present invention, as shown in FIG. 13A, a plurality of wedge-shaped notches 25a and 26a are provided on the outer peripheral edges of the polishing cloths 25 and 26 at predetermined intervals in the circumferential direction. Provide. Other configurations are the same as those of the third embodiment.
In this polishing apparatus, when the wafer W passes through the vicinity of the peripheral edges of the polishing cloths 25 and 26, the peripheral edge portion 36 of the wafer W is polished by the notches 25a and 26a of the polishing cloths 25 and 26, that is, the polishing action of the polishing cloths 25 and 26. It will pass outside the area. That is, as in the first embodiment, the wafer peripheral portion 36 is polished more than the central portion when passing through the region of the polishing cloths 25 and 26, but the total amount of time passing through the region is small. As a result, the difference in the polishing amount is offset. Therefore, the occurrence of a thin portion at the wafer peripheral portion 36 is prevented, and the flatness of the wafer W can be increased.
Further, since the boundary between the wafer peripheral portion 36 and the central portion becomes gentle, the occurrence of the step B as shown in FIG. 20 is suppressed.
[0029]
In addition, the shape of the said notches 25a and 26a is not restricted to the said embodiment, The number is also arbitrary. For example, it may be one as shown in FIG. 13B, or may be a wave-shaped notch as shown in FIG.
Further, as shown in FIG. 13 (d), it is needless to say that the notch portion may be provided not on the outer periphery but on the inner periphery.
[0030]
Next, a third embodiment of the present invention will be described.
As shown in FIG. 14, in the wafer polishing apparatus 21 according to the present embodiment, the periphery of the outer periphery of the upper and lower polishing cloths 25 and 26 is a non-circular shape that is cut into a wave shape. Other configurations are the same as those of the first embodiment.
In this polishing apparatus, when the wafer W passes near the periphery of the polishing cloths 25 and 26, the peripheral part 36 of the wafer W crosses the cut portions of the polishing cloths 25 and 26, that is, outside the polishing action region of the polishing cloths 25 and 26. Will pass. That is, as in the first embodiment, the wafer peripheral portion 36 is polished more than the central portion when passing through the region of the polishing cloths 25 and 26, but the total amount of time passing through the region is small. As a result, the difference in the polishing amount is offset. Therefore, the occurrence of a thin portion at the wafer peripheral portion 36 is prevented, and the flatness of the wafer W can be increased.
Also in this embodiment, since the boundary between the wafer peripheral portion 36 and the central portion becomes gentle, the occurrence of the step B as shown in FIG. 20 can be suppressed.
[0031]
As long as the same effect can be obtained, the polishing cloths 25 and 26 may have any shape, and may be a wave shape, a saw blade shape, an elliptical shape as shown in FIG. Further, the peripheral edge portion 36 of the wafer W may pass outside the polishing action area of the polishing cloths 25 and 26 at least one of the outer peripheral edge of the polishing cloths 25 and 26 and the inner peripheral edge.
[0032]
Next, a fourth embodiment of the present invention will be described.
As shown in FIG. 16, in the wafer polishing apparatus 21 according to this embodiment, the inner diameters of the polishing cloth 25 and the polishing cloth 26 and the outer diameters of the polishing cloth 25 and the polishing cloth 26 are different from each other. Other configurations are the same as those of the first embodiment.
In the wafer polishing apparatus 21, the offset amount d of the wafer W is different between the polishing cloth 25 side and the polishing cloth 26 side. That is, when performing double-side polishing of the wafer W, the width of the wafer peripheral portion 36 that passes outside the polishing area of the polishing cloth differs between the upper surface and the lower surface of the wafer W. Accordingly, the polishing state of the peripheral edge portion 36 can be different between the upper surface and the lower surface of the wafer W.
[0033]
In addition, the magnitude | size or shape of the outer periphery outline and inner periphery outline of polishing cloth 25 and 26 is each arbitrary. That is, abrasive cloths of various sizes and shapes used in the first to third embodiments may be freely combined.
In each of the above embodiments, the wafer peripheral portion may pass outside the polishing area of the polishing cloth on at least one of the outer peripheral edge of the polishing cloth and the inner peripheral edge.
Moreover, the shape of the polishing cloth shown in each embodiment can take various forms. For example, the annular groove 11a provided in the polishing cloth shown in the first prerequisite technique can be used for the polishing cloth of the first to fourth embodiments.
[0034]
【The invention's effect】
As described above, in the wafer polishing apparatus according to the present invention, since the peripheral edge of the wafer holding hole is configured to pass outside the polishing area of the polishing pad, the occurrence of a thin portion at the peripheral edge of the wafer is prevented. The flatness of the wafer can be increased.
[Brief description of the drawings]
FIG. 1 is an enlarged view of a main part of a wafer polishing apparatus shown as a first prerequisite technique of the present invention.
FIG. 2 is a plan view of a polishing surface plate used in the polishing apparatus.
FIG. 3 is an enlarged cross-sectional view of a main part of a wafer polishing apparatus according to a second prerequisite technique of the present invention.
FIG. 4 is a plan view of a polishing surface plate used in the polishing apparatus.
FIG. 5 is a perspective view of a silicon wafer polished by using the wafer polishing apparatus according to the first premise technique, represented by contour lines.
FIG. 6 is an explanatory diagram showing each partial flatness of the surface of a silicon wafer polished by using a wafer polishing apparatus as a first prerequisite technology.
FIG. 7 is a perspective view showing contours of a silicon wafer polished using a conventional polishing apparatus.
FIG. 8 is an explanatory diagram showing the partial flatness of the surface of a silicon wafer polished using a conventional polishing apparatus.
FIG. 9 is a cross-sectional view of the wafer polishing apparatus shown as the first embodiment of the present invention.
FIG. 10 is a schematic perspective view of the wafer polishing apparatus.
FIG. 11 is a view showing a peripheral edge portion of the wafer holding hole of the wafer polishing apparatus.
FIG. 12 is a view showing a peripheral edge portion of a wafer holding hole of a wafer polishing apparatus shown as another embodiment of the present invention.
FIG. 13 is a plan view of a polishing cloth used in the wafer polishing apparatus shown as the second embodiment of the present invention.
FIG. 14 is a view showing a peripheral edge portion of a wafer holding hole of a wafer polishing apparatus shown as a third embodiment of the present invention.
FIG. 15 is a view showing a peripheral edge portion of a wafer holding hole of a wafer polishing apparatus shown as another embodiment of the present invention.
FIG. 16 is a sectional view of a wafer polishing apparatus shown as a fourth embodiment of the present invention.
FIG. 17 is a cross-sectional view showing a polishing state of a conventional wafer polishing apparatus.
FIG. 18 is a perspective view showing contours of a silicon wafer polished by using a conventional wafer polishing apparatus, and a graph showing a cross-sectional height.
FIG. 19 is a perspective view showing a silicon wafer polished by using the wafer polishing apparatus of the present invention with contour lines, and a graph showing a cross-sectional height.
FIG. 20 is a view showing a stepped portion formed on a wafer.
[Explanation of symbols]
10, 20 Wafer polishing equipment
11, 11A Abrasive cloth
11a annular groove
11b Notch
12 Polishing surface plate
13 Polishing head
14 Carrier
21 Wafer polishing equipment
22 Upper surface plate
23 Lower surface plate
24 Carrier plate
25 Abrasive cloth (upper abrasive cloth)
26 Abrasive cloth (lower abrasive cloth)
28 Sun Gear
29 Rotating shaft
30 Internal gear
31 Carrier plate rotation mechanism
32 Wafer holding hole
35 Edge of wafer holding hole
36 Wafer edge
W Silicon wafer (wafer)

Claims (4)

Upper and lower surface plates;
An upper polishing cloth provided on the upper surface plate, a lower polishing cloth provided on the surface of the lower surface plate,
A carrier plate provided with a wafer holding hole for holding a wafer to be polished, disposed on the lower polishing cloth of the lower surface plate surface, and in contact with the upper polishing cloth of the upper surface plate surface;
In a wafer polishing apparatus for double-side polishing having a carrier rotating mechanism for polishing a wafer by the upper polishing cloth and the lower polishing cloth by rotating the carrier plate,
The carrier plate is rotated when the carrier plate is rotated so that the total amount of time that the peripheral edge of the wafer held in the wafer holding hole passes through the region of the polishing cloth from the center thereof is reduced. The trajectory at the peripheral edge of the wafer holding hole is supported so as to pass outside the outer peripheral edge or the inner peripheral edge that is outside the polishing action region of at least one of the upper polishing cloth and the lower polishing cloth,
The upper polishing cloth and the lower polishing cloth are different in the size or shape of the outline in plan view, the polishing cloth is formed in an annular shape in plan view, and the outer peripheral outline shape or the inner peripheral outline shape is wavy or a saw blade. Formed into a periodic non-circular shape,
The wafer polishing apparatus, wherein an area of the peripheral edge of the wafer passing outside the polishing action region is 10 to 30% of the entire wafer surface area. Upper and lower surface plates;
An upper polishing cloth provided on the upper surface plate, a lower polishing cloth provided on the surface of the lower surface plate,
A carrier plate provided with a wafer holding hole for holding a wafer to be polished, disposed on the lower polishing cloth of the lower surface plate surface, and in contact with the upper polishing cloth of the upper surface plate surface;
In a wafer polishing apparatus for double-side polishing having a carrier rotating mechanism for polishing a wafer by the upper polishing cloth and the lower polishing cloth by rotating the carrier plate,
The carrier plate is rotated when the carrier plate is rotated so that the total amount of time that the peripheral edge of the wafer held in the wafer holding hole passes through the region of the polishing cloth from the center thereof is reduced. The trajectory at the peripheral edge of the wafer holding hole is supported so as to pass outside the outer peripheral edge or the inner peripheral edge that is outside the polishing action region of at least one of the upper polishing cloth and the lower polishing cloth,
The upper polishing cloth and the lower polishing cloth are different in the size or shape of the outline in plan view, the polishing cloth is formed in a ring shape in plan view, and the outer peripheral outline shape or the inner peripheral outline shape is an ellipse or a polygon. Formed into a periodic non-circular shape,
The wafer polishing apparatus, wherein an area of the peripheral edge of the wafer passing outside the polishing action region is 10 to 30% of the entire wafer surface area. Upper and lower surface plates;
An upper polishing cloth provided on the upper surface plate, a lower polishing cloth provided on the surface of the lower surface plate,
A carrier plate provided with a wafer holding hole for holding a wafer to be polished, disposed on the lower polishing cloth of the lower surface plate surface, and in contact with the upper polishing cloth of the upper surface plate surface;
In a wafer polishing apparatus for double-side polishing having a carrier rotating mechanism for polishing a wafer by the upper polishing cloth and the lower polishing cloth by rotating the carrier plate,
The carrier plate is rotated when the carrier plate is rotated so that the total amount of time that the peripheral edge of the wafer held in the wafer holding hole passes through the region of the polishing cloth from the center thereof is reduced. The trajectory at the peripheral edge of the wafer holding hole is supported so as to pass outside the outer peripheral edge or the inner peripheral edge that is outside the polishing action region of at least one of the upper polishing cloth and the lower polishing cloth,
The upper and the polishing cloth and the lower polishing cloth, different size or shape in plan view the outline, the polishing cloth is formed in plan view ring, is non-circular contour of the contour shape or inner periphery of the outer peripheral edge As described above, at least one notch is provided on the outer periphery or the inner periphery of the polishing cloth,
As the shape of the notch, when provided on the outer peripheral edge of the polishing cloth, a wave shape or a wedge shape in which the width in the circumferential direction of the notch is narrower than the width of the outer peripheral edge of the polishing cloth. In the case where it is provided on the inner periphery of the polishing cloth, as a wave shape or a wedge shape such that the outer periphery of the polishing cloth becomes narrower ,
The wafer polishing apparatus, wherein an area of the peripheral edge of the wafer passing outside the polishing action region is 10 to 30% of the entire wafer surface area. The wafer polishing apparatus according to claim 3, wherein
A wafer polishing apparatus , wherein a plurality of the notches are provided discretely and periodically in the circumferential direction of the polishing pad.

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