A planetary wheel and wafer polishing device for wafer polishing

Abstract

The application provides a planet wheel for wafer grinding, and a wafer grinding device comprising the planet wheel. The planet wheel is provided with a limiting hole, and a flow guide groove is arranged on the limiting hole for guiding the grinding liquid in or out. The flow guide groove is provided with an opening on the outer periphery of the limiting hole, and the included angle between the straight line where the opening is located and the projection of the side wall of the flow guide groove on the plane of the limiting hole is less than 90°. Based on the fluidity of the grinding liquid, when the wafer is performing the grinding operation, one side of the wafer will revolve with the planet wheel. During the revolution, the grinding liquid is forced to spin out. Since the spinning-out path is along the direction of the flow guide groove, the grinding liquid spins out along the tangential direction of the wafer, and then generates a reaction force on the wafer, so that the wafer is forced to rotate. The edge warping of the wafer can be further repaired, and the surface shape of the wafer can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wafer processing and manufacturing, in particular to a planetary wheel for wafer grinding and 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, uniform grinding is difficult to repair the edge warpage and surface profile of the wafer. Due to the warpage of the wafer, the height of the edge of the wafer is inconsistent, and the uniform grinding of the wafer during the grinding process cannot effectively repair the high warpage position. SUMMARY

[0003] The purpose of the present application is to provide a planetary wheel for wafer grinding and a wafer grinding device to improve the surface profile of the wafer, improve the warpage repair capability, and 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 planetary wheel for wafer grinding, comprising: a main body; at least one limiting hole provided on the main body; a flow guide groove provided on the main body, the flow guide groove is provided with an opening on the outer periphery of the limiting hole and is in communication with the limiting hole; the projection of the two side walls of the flow guide groove on the main body is parallel or intersects; the opening is divided into a first opening point and a second opening point, the projection line of the flow guide groove on the plane where the limiting hole is located is the first long side and the second long side of the flow guide groove, the length of the first long side is L, the first opening point is on the second long side, and the second opening point is on the second long side; the included angle between the first long side and the tangent line of the limiting hole at the first opening point is less than 90 degrees; the included angle between the second long side and the tangent line of the limiting hole at the second opening point is less than 90 degrees.

[0006] In some embodiments, the limiting hole is circular, the radius of the limiting hole is R, and the relationship between the limiting hole and the flow guide groove is 0.01R

[0007] In some embodiments, the straight line distance between the first opening point and the second opening point is W, and the relationship between the limiting hole and the flow guide groove is 0.1L

[0008] In some embodiments, the included angle between the second long side and the tangent line of the limiting hole at the second opening point is θ, and the relationship between the limiting hole and the flow guide groove is 10°

[0009] In some embodiments, the plurality of flow guide grooves are arranged symmetrically around the center of the limiting hole.

[0010] In some embodiments, the rotation rate of the wafer is greater than 100 / Erpm, where E is the diameter of the wafer.

[0011] In some embodiments, the wafer has a face type converging to a concentric circle, and the proportion of the concentric circle is greater than 90%.

[0012] In some embodiments, the wafer has a curvature within -3*E / 4 μm, where E is the diameter of the wafer.

[0013] In some embodiments, the wafer has a warpage less than 7*E / 4 μm, where E is the diameter of the wafer.

[0014] The second aspect of the present application provides a wafer grinding device, comprising an inner ring gear, a sun gear, a first grinding disc, a second grinding disc and a plurality of planetary gears as described in the first aspect of the present application; wherein each of the planetary gears is engaged with the inner ring gear and the sun gear, and the first grinding disc and the second grinding disc are respectively located on opposite sides of the planetary gears.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] The present application provides a planetary gear for wafer grinding, and a wafer grinding device comprising the same. The planetary gear is provided with a limiting hole, and a flow guide groove is arranged on the limiting hole for guiding the grinding liquid in or out. The flow guide groove is provided with an opening on the outer periphery of the limiting hole, and the included angle between the straight line on which the opening is located and the projection of the side wall of the flow guide groove on the plane of the limiting hole is less than 90°. Based on the fluidity of the grinding liquid, when the wafer is being ground, it will revolve with the planetary gear, and the grinding liquid will be thrown out under the action of force during the revolution. Since the throwing-out path is along the flow guide groove, the grinding liquid will generate a reaction force on the wafer to generate a torque that can promote the rotation of the wafer, thereby increasing the rotation rate of the wafer during the grinding process. In this way, the wafer revolves under the action of the planetary gear and rotates under the action of the torque generated by the throwing-out of the grinding liquid during the grinding process, which can further repair the edge warpage of the wafer and improve the face type of the wafer, thereby achieving the planarization processing of the wafer. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present 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 present application, and therefore should not be regarded as a limitation on 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 showing a saddle-like shape is shown; Figure 1b A conceptual diagram of a wafer showing a through-type wafer is shown; Figure 1c A conceptual diagram of a wafer showing a concentric oval shape is shown; Figure 1d A conceptual diagram of a wafer showing concentric circular rows is shown;

[0019] Figure 2 A schematic diagram showing the basic structure of a planetary wheel for wafer grinding is shown;

[0020] Figure 3 A schematic diagram showing the structure of a limiting hole in an embodiment of the present application is shown.

[0021] BRIEF DESCRIPTION OF DRAWINGS

[0022] 1. Planetary wheel; 2. Limiting hole; 3. Flow guide groove. DETAILED DESCRIPTION

[0023] The technical solutions of the embodiments of the present application will be described in further detail below with reference to the drawings, which are only used to illustrate the present application and not limit the present application.

[0024] 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 limiting 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.

[0025] 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 connection between two elements inside. 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.

[0026] 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 opposite directions are opposite, the wafer exhibits aFigure 1a The wafer surface shown is saddle-shaped. Therefore, such a wafer surface is generally referred to as a saddle type. As shown in Figure 1b If the wafer is relatively flat in one direction and is curved to a greater extent in another direction, the wafer surface showing this type of curvature is generally referred to as a through type. As shown in Figure 1c If the wafer is curved in different directions in the same direction, but the wafer is curved to different extents in different directions, the wafer surface shows a concentric ellipse type. Figure 1d A concentric circle type wafer is shown. Since the stress distribution of the concentric circle type wafer is relatively uniform, the curvature is the same in all directions, and the convergence of the wafer curvature is good.

[0027] In order to solve the problems in the prior art, the present application provides a planetary wheel for wafer grinding and a wafer grinding device, which will be described in detail below in combination with the drawings.

[0028] The wafer grinding device provided by the present application comprises an inner ring gear, a sun gear, a first grinding disc, a second grinding disc and a plurality of planetary wheels 1. The main body of each planetary wheel 1 is provided with at least one limiting hole 2 for placing a wafer, and the limiting hole 2 is a circular through hole which limits the wafer. In some embodiments, the aforementioned wafer can be a gallium nitride wafer. Each planetary wheel 1 is 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 opposite sides of the planetary wheel 1. Each planetary wheel 1 is in the same plane.

[0029] The self-rotation direction of the first grinding disc is opposite to the self-rotation direction of the second grinding disc, and the self-rotation direction of the inner ring gear is opposite to the self-rotation direction of the sun gear. The rotation axis of the grinding device is generally perpendicular to the horizontal plane, that is, the first grinding disc can be a lower grinding disc located below the planetary wheel, and the second grinding disc can be an upper grinding disc located above the planetary wheel. The second grinding disc applies pressure to the wafer placed in the limiting hole 2 by using a pressure applying device connected to the grinding disc and its own gravity. In one embodiment, the pressure applying device can be, for example, a pneumatic cylinder, a hydraulic cylinder or the like.

[0030] Figure 2 A structural schematic diagram of a planetary wheel for wafer grinding is shown. As shown in Figure 2 As shown in the present application, 18 limiting holes 2 can be provided in the planetary wheel 1 for wafer grinding. The size of the limiting hole 2 is slightly larger than the size of the wafer to be ground, so that the wafer can be smoothly placed in the corresponding limiting hole 2 and can rotate in the limiting hole 2. It should be noted that the number of limiting holes 2 provided in the planetary wheel can be determined according to actual needs and production capacity, that is, the number of limiting holes 2 in each planetary wheel 1 can also be other values, and the present application does not specially limit the number of limiting holes 2 in each planetary wheel 1.

[0031] The outer teeth of each of the foregoing planetary gears 1 are respectively meshed with the inner teeth of the inner ring gear and the outer teeth of the sun gear, and then the wafer is placed in the limiting hole 2 of each planetary gear 1, the second grinding disc is placed, the second grinding disc is pressed by the pressing device matched with the second grinding disc such as the air cylinder, the grinding liquid is added dropwise, and then the grinding process is started. The specific processing parameters, types and amounts of grinding liquid can be determined according to the demand index of the wafer.

[0032] In the process of manufacturing semiconductor wafers, the polishing process is indispensable. In free abrasive grinding, the planetary gear carries the wafer during double-sided grinding and makes planetary motion under the drive of the inner and outer ring gears, i.e. rotation and revolution. When using free abrasive for grinding, the wafer is difficult to rotate in the clamp, and the edge warpage is difficult to repair. Therefore, the existing free abrasive grinding cannot effectively process the wafer flat. The applicant found that the planetary gear 1 of the existing grinding device is difficult to rotate during the wafer grinding process due to the consistency of the grinding surface of the first grinding disc and the second grinding disc. The space of the grinding surface is compact, and the characteristics of the grinding device make it impossible to set a combined clamp to strengthen the rotation of the wafer. Therefore, the wafer surface of the existing grinding device is prone to have insufficient flatness as shown in Figures 1a to 1c .

[0033] Based on this, the embodiment of the present application provides a planetary gear 1 for wafer grinding, which can improve the flatness processing capability of the wafer by improving the rotation rate of the wafer during the grinding process, thereby improving the surface shape of the wafer.

[0034] Figure 3 The structure of the limiting hole of the planetary gear for wafer grinding is shown. As shown in Figure 3 , the outer periphery of the limiting hole 2 is provided with a plurality of flow guide grooves 3, and the plurality of flow guide grooves 3 are uniformly distributed relative to the limiting hole 2, so as to improve the stress uniformity of the wafer during the grinding process.

[0035] In some embodiments, the radius of the limiting hole 2 is R, the length of the flow guide groove 3 is L, the width of the flow guide groove 3 is W, and the angle between the flow guide groove 3 and the limiting hole 2 is θ. The flow guide groove 3 is provided with an opening on the outer periphery of the limiting hole 2 for guiding the polishing liquid in or out, and the adjacent points of the opening and the outer periphery of the limiting hole 2 are called the first opening point and the second opening point. The length of the flow guide groove 3 can be understood as the length of the first long side of the flow guide groove 3, which is the length of the side wall of the flow guide groove 3 at the first opening point in the plane of the limiting hole 2; the width of the flow guide groove 3 can be understood as the opening width of the flow guide groove 3 on the outer periphery of the limiting hole 2, that is, the straight line distance between the first opening point and the second opening point; the second long side of the flow guide groove 3 is the side at the second opening point. It should be noted that, in actual polishing of wafers, the radius of the limiting hole is usually about 0.1 mm larger than the radius of the corresponding wafer to be polished, so in this application, the wafer radius is approximately equal to the limiting hole radius.

[0036] For ease of understanding, the first long side and the second long side are set to be arranged from outside to inside, and the outer side (i.e. the left side facing the paper) is the first long side, and the inner side (i.e. the right side facing the paper) is the second long side, as shown in FIG. 1. Figure 3 The angle θ between the flow guide groove 3 and the limiting hole 2 can be understood as the angle between the second long side of the flow guide groove 3 and the tangent line of the outer periphery of the limiting hole 2 at the second opening point, which is a non-right angle. It can also be said that the side wall of the flow guide groove 3 is not perpendicular to the straight line where the width of the flow guide groove 2 is located. The angle between the first long side and the tangent line of the limiting hole 2 at the first opening point is less than 90°, and the angle between the second long side and the tangent line of the limiting hole 2 at the first opening point is less than 90°.

[0037] Based on the flowability of the polishing liquid, when the wafer is being polished, one side will revolve with the planetary wheel, and the polishing liquid will be thrown out during the revolution due to the force. Since the throwing path is along the flow guide groove 3, the polishing liquid will generate a reaction force on the wafer, causing the wafer to rotate, further repairing the edge warpage of the wafer during polishing, and improving the surface profile of the wafer.

[0038] In some embodiments, the length, width and depth of the flow guide groove 3 can be determined according to the specific use scenario, such as the amount of polishing liquid required for wafer polishing. In other embodiments, the first long side and the second long side of the flow guide groove 3 can be in a parallel state, and the extension line of the first long side and the extension line of the second long side can also be in an intersecting state.

[0039] In some embodiments, in order to improve the self-rotation rate of the wafer during the grinding process, the length L of the guide groove 3 and the radius R of the limiting hole 2 satisfy the relationship 0.01R < L < 0.05R, the width W of the guide groove 3 and the length L of the guide groove 3 satisfy the relationship 0.1L < W < 0.5L, and the included angle θ between the guide groove 3 and the limiting hole 2 satisfies 10° < included angle θ < 45°. The included angle θ can be understood as the acute angle between the second long side of the guide groove 3 and the tangent line of the outer periphery of the limiting hole at the second opening point. By using the wafer grinding device of the embodiments of the present application, the self-rotation rate of the wafer (with a diameter of E inches) during the grinding 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 / 4μm, the proportion of the warpage value warp less than 7*E / 4μm is 100%, and the planarization processing of the wafer is realized.

[0040] When the acute angle is complementary to the obtuse angle, the inclination direction of the guide groove 3 is opposite to that when the acute angle is present, and the inclination direction of the guide groove 3 is opposite to that when the acute angle is present. It can be understood that the inclination direction of the guide groove 3 is related to the rotation direction of the planetary gear 1, for example, when the planetary gear 1 rotates clockwise, the guide groove 3 is inclined in the clockwise direction. When the inclination direction of the guide groove 3 is consistent with the rotation direction of the planetary gear 1, it is beneficial to realize the application of the counteracting force of the grinding liquid to the wafer, so as to provide the self-rotation force of the wafer during the grinding process, and improve the self-rotation rate of the wafer during the grinding process.

[0041] The second aspect of the present application provides a wafer grinding device, which comprises the planetary gear 1 for wafer grinding provided by the first aspect of the present application, and an inner ring gear, a sun gear, a first grinding disc and a second grinding disc. Each planetary gear 1 is engaged with the inner teeth of the inner ring gear and the outer teeth of the sun gear, respectively, and the first grinding disc and the second grinding disc are located on opposite sides of the planetary gear 1, respectively, and each planetary gear 1 is in the same plane.

[0042] The self-rotation direction of the first grinding disc is opposite to that of the second grinding disc, and the self-rotation direction of the inner ring gear is opposite to that of the sun gear. The rotation axis of the grinding device is generally perpendicular to the horizontal plane, that is, the first grinding disc can be a lower grinding disc located below the planetary gear, and the second grinding disc can be an upper grinding disc located above the planetary gear. The second grinding disc applies pressure to the wafer placed in the limiting hole 2 by using the pressure applying device connected to the grinding disc and its own gravity.

[0043] 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 planetary wheel for wafer polishing, characterized by, The utility model relates to a kind of planetary gear mechanism, including: Main body; At least one limiting hole is arranged on the main body; Flow guide ditch is arranged on the main body, the opening is provided on the outer periphery of the limiting hole, and the flow guide ditch is communicated with the limiting hole;The extension line of the projection of the two side walls of the flow guide ditch on the main body is parallel or intersects; The opening is divided into first opening point and second opening point, the projection line of the flow guide ditch in the plane where the limiting hole is located is defined as the first long side and the second long side of the flow guide ditch, the length of the first long side is the length L of flow guide ditch, the first opening point is on the second long side, and the second opening point is on the second long side;The straight-line distance between the first opening point and the second opening point is the width W of flow guide ditch, and the relationship between the width W of flow guide ditch and the length L of flow guide ditch is 0.1L The angle between the first long side and the tangent of the limiting hole at the first opening point is less than 90 degrees; The angle between the second long side and the tangent of the limiting hole at the second opening point is less than 90 degrees.

2. The planetary gear of claim 1, wherein, The limiting hole is circular, and the radius of the limiting hole is defined as R, and the relationship between the limiting hole and the flow guide ditch is 0.01R 3. The planetary gear of claim 1, wherein, The angle between the second long side and the tangent of the limiting hole at the second opening point is defined as θ, and the relationship between the limiting hole and the flow guide ditch is 10°<θ<45°.

4. The planetary gear of claim 1, wherein, The flow guide ditch is arranged as a plurality, and the plurality of flow guide ditches are uniformly distributed along the limiting hole.

5. A planetary gear as claimed in any one of claims 1 to 4, characterised in that, The self-rotation rate of the wafer is greater than 100 / Erpm, where the diameter of the wafer is E inches.

6. A planetary gear as claimed in any one of claims 1 to 4, characterised in that, The face type of the wafer converges to a concentric circle, and the proportion of the concentric circle is greater than 90%.

7. A planetary gear as claimed in any one of claims 1 to 4, characterised in that, The bending degree of the wafer is within -3*E / 4 μm, where the diameter of the wafer is E inches.

8. A planetary gear as claimed in any one of claims 1 to 4, characterised in that, The warping degree of the wafer is less than 7*E / 4 μm, where the diameter of the wafer is E inches.

9. A wafer polishing apparatus characterized by comprising: It includes inner gear ring, sun gear, first grinding disc, second grinding disc and several planetary gears as claimed in any one of claims 1 to 8. Wherein, each of the planetary gears is 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 the opposite sides of the planetary gears.

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