Wafer polishing apparatus

Abstract

The application provides a wafer grinding device, which comprises a first grinding disc, a second grinding disc, an inner gear ring, a sun gear and at least one planetary gear; the planetary gear is provided with at least one limiting hole for limiting the wafer. The application limits the radial distance L of the limiting hole exposed to the first grinding disc to be greater than the radius R of the limiting hole, so that a part of the wafer is ground between the first grinding disc and the second grinding disc, and a part of the wafer is not ground outside the first grinding disc and the second grinding disc. Thus, the wafer is subjected to different forces on both sides, and a torque that can promote the rotation of the wafer is generated, the rotation rate of the wafer in the grinding process is increased, the wafer revolves under the action of the planetary gear on one side, and rotates under the action of the one-side torque on the other side in the grinding process, the edge warping of the wafer can be further repaired, the surface shape of the wafer is improved, and the planarization processing of the wafer is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wafer processing and manufacturing, in particular to a wafer grinding device. BACKGROUND

[0002] In the hard disk grinding process, the fixture revolves around the sun, and the upper and lower disks are ground at high speed. The abrasive particles uniformly grind and remove the unevenness and impurities on the surface of the wafer, and repair the flatness. However, the uniform grinding is difficult to repair the edge warpage and the surface shape of the wafer. Due to the warpage of the wafer, the height of the edge of the wafer is inconsistent. The uniform grinding of the wafer in the grinding process cannot effectively repair the high warpage position. SUMMARY

[0003] The purpose of the present application is to provide a wafer grinding device to improve the surface shape improvement and warpage repair capability of the wafer, and to realize the planarization processing of the wafer.

[0004] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0005] A wafer grinding device, comprising a first grinding disc, a second grinding disc, an inner gear ring, a sun gear and at least one planetary gear; wherein the planetary gears are respectively engaged with the inner teeth of the inner gear ring and the outer teeth of the sun gear, and the first grinding disc and the second grinding disc are respectively located on opposite sides of the planetary gears; at least one limiting hole is provided on the planetary gear for limiting the wafer; the radius of the limiting hole is set as R, and the radial distance of the limiting hole from the first grinding disc is L, wherein L>R.

[0006] In some embodiments, R

[0007] In some embodiments, the radial distance from the edge of the first grinding disc and / or the second grinding disc to the inner gear ring is set as the disc tooth spacing D, and the outer tooth length of the planetary gear is C; when the diameter of the wafer to be ground is 2 inches or 4 inches, R

[0008] In some embodiments, the radial distance from the edge of the first grinding disc and / or the second grinding disc to the inner gear ring is set as the disc tooth spacing D, and the outer tooth length of the planetary gear is C; when the diameter of the wafer to be ground is 6 inches, 0.75R

[0009] In some embodiments, the radial distance from the edge of the first grinding disc and / or the second grinding disc to the inner gear ring is set as the disc tooth spacing D, and the outer tooth length of the planetary gear is C; when the diameter of the wafer to be ground is 8 inches, 0.5R

[0010] In some embodiments, the radial distance between the edge of the first polishing plate and / or the second polishing plate and the inner ring gear is set to be a plate tooth spacing D, and the outer tooth length of the planetary gear is C; when the diameter of the wafer to be polished is 12 inches, 0.25R < D-2C < 0.5R.

[0011] In some embodiments, the rotation rate of the wafer is > 100 / Erpm, where the diameter of the wafer is E inches.

[0012] In some embodiments, the face type of the wafer converges to a concentric circle, and the concentric circle ratio is > 90%.

[0013] In some embodiments, the curvature of the wafer is within -3*E / 4 μm, where the diameter of the wafer is E inches.

[0014] In some embodiments, the warping of the wafer is less than 7*E / 4 μm, where the diameter of the wafer is E inches.

[0015] Compared with the prior art, the application has the following beneficial effects:

[0016] The application provides a wafer polishing device, which comprises a first polishing plate, a second polishing plate, an inner ring gear, a sun gear and at least one planetary gear; wherein the planetary gear is engaged with the inner teeth of the inner ring gear and the outer teeth of the sun gear, respectively, and the first polishing plate and the second polishing plate are located on opposite sides of the planetary gear; at least one limiting hole is arranged on the planetary gear for limiting the wafer. The application limits the radial distance L at which the limiting hole is exposed from the first polishing plate to be greater than the radius R of the limiting hole, so that, during the polishing process, a part of the wafer is polished between the first polishing plate and the second polishing plate, and a part of the wafer is not polished outside the first polishing plate and the second polishing plate. As a result, different forces are applied to the two sides of the wafer, and a torque that can promote the rotation of the wafer is generated, the rotation rate of the wafer during the polishing process is increased, and the wafer rotates around the sun gear under the action of the planetary gear and rotates by itself under the action of the single-side torque during the polishing process. Therefore, the edge warping of the wafer can be further repaired, the face type of the wafer can be improved, and the planarization processing of the wafer can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Figure 1a A conceptual diagram of a wafer in a saddle-like shape is shown; Figure 1bA conceptual diagram of a through-type wafer is shown; Figure 1c A conceptual diagram of a concentric elliptical wafer is shown; Figure 1d A conceptual diagram of a concentric circular wafer is shown;

[0019] Figure 2 A structural schematic diagram of a wafer grinding device in an embodiment of the present application is shown.

[0020] Explanation of reference signs:

[0021] 1, inner gear ring; 2, first grinding disc; 3, second grinding disc; 4, planetary gear; 5, limiting hole. DETAILED DESCRIPTION

[0022] The technical solutions of the specific embodiments of the present application will be further described in detail below with reference to the drawings. These embodiments are only used to illustrate the present application, and are not a limitation on the present application.

[0023] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is usually placed, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0024] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the term "connection" should be understood broadly, for example, it can be a fixed connection, or a detachable connection, or an integral connection; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a communication inside two elements. For those skilled in the art, the specific meaning of the above-mentioned term in the present application can be understood according to the specific circumstances.

[0025] A wafer, also known as a substrate or wafer substrate, in the prior art, the uneven stress distribution of the wafer causes bending, warping or distortion, which usually makes the wafer exhibit different surface shapes. The surface shape of the wafer in the prior art is shown in Figures 1a to 1d If the bending directions of the wafer in two perpendicular directions are opposite, the wafer exhibits a horse-saddle-like shape as shown in Figure 1a Therefore, such a wafer surface shape is usually called a horse-saddle shape. As shown in Figure 1bAs shown, if the wafer is relatively flat in one direction and is curved to a greater extent in another direction, the wafer surface type presenting this type of curvature is generally referred to as a through type. As shown, Figure 1c As shown, if the wafer is curved in the same direction in different directions but the wafer is curved to different extents in different directions, the wafer surface type presents a concentric ellipse shape. Figure 1d A concentric circular wafer is shown. Since the stress distribution of the concentric circular wafer is relatively uniform, the wafer is curved to the same extent in different directions, and the convergence of the wafer curvature is good.

[0026] In order to solve the problems in the prior art, the present application provides a wafer grinding device, which will be described in detail below in combination with the drawings.

[0027] Figure 2 A wafer grinding device in an embodiment of the present application is shown. As shown, Figure 2 The wafer grinding device includes an inner gear ring 1, a sun gear (not shown in the figure), a first grinding disc 2, a second grinding disc 3, and a plurality of planetary gears 4. The body of each planetary gear 4 is provided with a plurality of limiting holes 5 for placing wafers. The limiting holes 5 are circular through holes, and the size of the limiting holes 5 is comparable to the size of the wafers, so that the wafers can be placed in or taken out of the limiting holes 5, and the wafers are limited to avoid horizontal movement during grinding. In some embodiments, the aforementioned wafers can be gallium nitride wafers. The outer teeth of each planetary gear 4 are engaged with the inner teeth of the inner gear ring 1 and the outer teeth of the sun gear, respectively. The first grinding disc 2 and the second grinding disc 3 are located on opposite sides of the planetary gears 4, respectively, and each planetary gear 4 is in the same plane.

[0028] The rotation direction of the first grinding disc 2 is opposite to the rotation direction of the second grinding disc 3, and the rotation direction of the inner gear ring 1 is opposite to the rotation direction of the sun gear. The rotation axis of the grinding device is generally perpendicular to the horizontal plane, i.e., the first grinding disc 2 can be an upper grinding disc located above the planetary gears 4, and the second grinding disc 3 can be a lower grinding disc located below the planetary gears 4. The first grinding disc 2 applies pressure to the wafers placed in the limiting holes 5 by using a pressure applying device connected to the grinding disc and the gravity of the first grinding disc 2. In one embodiment, the pressure applying device can be a pneumatic cylinder, a hydraulic cylinder, etc.

[0029] In the semiconductor wafer manufacturing process, the polishing process is indispensable. In the free abrasive polishing, the planet wheel carries the wafer in the double-sided polishing process, and makes planetary motion under the driving of the inner and outer gear rings, i.e. the rotation and revolution motion. When the free abrasive is used for polishing, the wafer is difficult to rotate in the clamp, and the edge warpage is difficult to repair. Therefore, the existing free abrasive polishing cannot effectively process the wafer flat. The applicant finds that in the existing polishing device, the planet wheel 4 is difficult to rotate during the wafer polishing process due to the consistency grinding of the first polishing disc 2 and the second polishing disc 3, the space of the disc surface is compact, and the characteristics of the polishing device make it impossible to set a combined clamp to strengthen the wafer rotation. Therefore, the wafer surface type of the existing polishing device is prone to have insufficient flatness as shown in Figures 1a to 1c .

[0030] Based on this, the wafer polishing device provided by the embodiments of the present application can improve the flatness processing capability of the wafer by improving the rotation rate of the wafer during the polishing process, thereby improving the surface type of the wafer.

[0031] As shown in Figure 2 , the radius of the limiting hole is R, the radial distance from the edge of the first polishing disc 2 to the inner gear ring 1 is referred to as the disc-tooth distance D, the maximum exposure length L of the limiting hole, and the outer tooth length of the planet wheel 4 is C. Among them, the maximum exposure length L of the limiting hole can be understood as the radial distance of the limiting hole 5 exposed to the first polishing disc 2. Since the size of the wafer matches the size of the limiting hole 5, the maximum exposure length L of the limiting hole can be approximately equal to the radial length of the wafer exposed to the first polishing disc 2; the outer tooth length of the planet wheel 4 can be understood as the vertical length of the outer tooth. It can be understood that since the first polishing disc 2 and the second polishing disc 3 are placed symmetrically, the radial distance from the edge of the first polishing disc 2 to the inner gear ring 1 and the radial distance from the edge of the second polishing disc 3 to the inner gear ring 1 represent the same meaning; the maximum radial distance of the limiting hole 5 exposed to the first polishing disc 2 and the radial distance of the limiting hole 5 exposed to the second polishing disc 3 represent the same meaning. It should be noted that since the radius of the limiting hole is usually about 0.1 mm larger than the radius of the corresponding wafer to be polished in actual polishing of the wafer, in the present application, the wafer radius is approximately equal to the limiting hole radius.

[0032] In some embodiments, in order to increase the self-rotation rate of the wafer while avoiding too large total thickness variation (TTV) after the wafer is polished, the exposed length of the wafer at the edge of the first polishing plate 2 can be greater than the radius of the wafer, i.e. L>R. During the polishing process, if the wafer is exposed too much, the stability of the wafer will be affected, and the flatness of the wafer after polishing will be reduced. Therefore, the relationship between the wafer and the wafer polishing device is R

[0033] Further, in some embodiments, the relationship between the size of the wafer and other components of the wafer polishing device can be determined according to the specific use scenario. Based on the stability during wafer polishing, different sizes of wafers need to correspond to different relationships between the disc teeth. For example, when the diameter of the wafer is 2 inches or 4 inches, the relationship between the limiting hole 5 or the wafer and other components of the wafer polishing device is R

[0034] Using the wafer polishing device of the embodiments of the present application, the self-rotation rate of the wafer (with a diameter of E inches) during the polishing process can reach 100 / Erpm, the warpage repair capability is improved, the surface profile of the wafer is improved, the surface profile of the wafer converges to a concentric circle, and the proportion of the concentric circle reaches more than 90%. The curvature of the wafer is within -3*E / 4 μm, and the proportion of the warpage value warp less than 7*E / 4 μm is 100%, and the planarization processing of the wafer is realized.

[0035] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and replacements can be made, and these improvements and replacements should also be considered as the protection scope of the present application.

Claims

1. A wafer polishing apparatus characterized by comprising: The first grinding disc, the second grinding disc, the inner ring gear, the sun gear and at least one planetary gear are included. The planetary gear is respectively engaged with the inner teeth of the inner ring gear and the outer teeth of the sun gear, and the first grinding disc and the second grinding disc are respectively located on the opposite sides of the planetary gear. At least one limiting hole is arranged on the planetary gear for limiting the wafer. The radius of the limiting hole is set as R, and the radial distance of the limiting hole from the first grinding disc is L, wherein R 2. The wafer polishing apparatus of claim 1, wherein The radial distance of the edge of the first grinding disc and / or the second grinding disc from the inner ring gear is set as the disc-tooth spacing D, and the length of the outer teeth of the planetary gear is C. When the diameter of the wafer to be ground is 2 inches or 4 inches, R 3. The wafer polishing apparatus of claim 1, wherein The radial distance of the edge of the first grinding disc and / or the second grinding disc from the inner ring gear is set as the disc-tooth spacing D, and the length of the outer teeth of the planetary gear is C. When the diameter of the wafer to be ground is 6 inches, 0.75R 4. The wafer polishing apparatus of claim 1, wherein The radial distance of the edge of the first grinding disc and / or the second grinding disc from the inner ring gear is set as the disc-tooth spacing D, and the length of the outer teeth of the planetary gear is C. When the diameter of the wafer to be ground is 8 inches, 0.5R 5. The wafer polishing apparatus of claim 1, wherein The radial distance of the edge of the first grinding disc and / or the second grinding disc from the inner ring gear is set as the disc-tooth spacing D, and the length of the outer teeth of the planetary gear is C. When the diameter of the wafer to be ground is 12 inches, 0.25R 6. The wafer polishing apparatus according to any one of claims 1 to 5, wherein The self-rotation rate of the wafer is greater than 100 / Erpm, wherein the diameter of the wafer is E inches.

7. The wafer polishing apparatus according to any one of claims 1 to 5, wherein The face type of the wafer converges to a concentric circle, and the proportion of the concentric circle is greater than 90%.

8. The wafer polishing apparatus according to any one of claims 1 to 5, wherein The curvature of the wafer is within -3*E / 4 μm, wherein the diameter of the wafer is E inches.

9. The wafer polishing apparatus according to any one of claims 1 to 5, wherein The warping degree of the wafer is less than 7*E / 4 μm, wherein the diameter of the wafer is E inches.

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