Double-sided grinding device with convex polygonal grinding member

Abstract

A method and apparatus for simultaneous double sided grinding of semiconductor structures is disclosed. The double sided grinding apparatus may include first and second grinding wheels, each having an abrasive member shaped like a convex polygon (e.g., a convex pentagon).

Description

[Technical field]

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 180,481, filed April 27, 2021, which is incorporated by reference in its entirety.

[0002] The field of the disclosure relates generally to simultaneous double-sided grinding of semiconductor wafers, and more particularly to a double-sided grinding apparatus and method. [Background technology]

[0003] Semiconductor wafers are commonly used in the manufacture of integrated circuit (IC) chips with printed circuits. The circuits are first printed in miniaturized form on the surface of the wafer, and the wafer is then divided into circuit chips. However, this miniaturization of the circuits requires that the surface of the wafer be extremely flat and parallel so that the circuits can be properly printed across the entire surface of the wafer. To achieve this, after the wafer is cut from the ingot, a grinding process is commonly used to improve certain characteristics of the wafer (e.g., flatness and parallelism).

[0004] Simultaneous double-sided grinding simultaneously grinds both sides of a wafer, producing a wafer with a highly planarized surface, and is therefore the preferred grinding process. While this grinding process significantly improves the flatness and parallelism of the ground wafer surface, it can cause degradation of the topology and nanotopography (NT) of the wafer surface.

[0005] Poor nanotopography leads to uneven oxide removal during the subsequent polishing (CMP) step, which significantly reduces yields for wafer users such as IC manufacturers. As IC manufacturers move to smaller process technologies, nanotopography tolerances are expected to become tighter.

[0006] A need exists for a method for simultaneous double-sided grinding of semiconductor structures that improves the nanotopography of the wafer.

[0007] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to better understand the various aspects of the present disclosure. As such, it should be understood that these statements are to be read in this light, and not as admissions of prior art. Summary of the Invention

[0008] One aspect of the present disclosure relates to a method for double sided grinding of a semiconductor structure.

[0009] Resolving issues The semiconductor structure is positioned between first and second grinding wheels. Each grinding wheel includes a support wheel and a plurality of polishing members extending axially outward from the support wheel. Each polishing member has a wafer engaging surface. The wafer engaging surface is in the shape of a convex polygon having at least five sides. The semiconductor structure is ground by contacting the first and second grinding wheels with the semiconductor structure and rotating the first and second grinding wheels relative to one another.

[0010] Another aspect of the disclosure relates to a method for double sided grinding of a semiconductor structure. The semiconductor structure is disposed between first and second grinding wheels. Each wheel includes a support wheel and a plurality of abrasive members extending axially outward from the support wheel. Each abrasive member has a wafer engaging surface. The wafer engaging surface includes a base edge. The base edge is a first side of the wafer engaging surface. The wafer engaging surface includes a second side having a first end and a second end. The second side is connected to the base edge at its first end. The second side and the base edge form an obtuse angle. The wafer engaging surface includes a third side having a first end and a second end. The third side is connected to the base edge at its first end. The third side and the base edge form an obtuse angle. The semiconductor structure is ground by contacting the first and second grinding wheels with the semiconductor structure and rotating the first and second grinding wheels relative to one another.

[0011] A further aspect of the disclosure relates to a double sided grinding apparatus. The apparatus includes first and second grinding wheels. Each wheel has an axis of rotation and includes a support wheel and a plurality of abrasive members extending axially outward from the support wheel. Each abrasive member has a wafer engaging surface. The wafer engaging surface includes a base edge. The base edge is a first side of the wafer engaging surface. The wafer engaging surface includes a second side having a first end and a second end. The second side is connected to the base edge at the first end. The second side and the base edge form an obtuse angle. The wafer engaging surface includes a third side having a first end and a second end. The third side is connected to the base edge at the first end. The third side and the base edge form an obtuse angle. Each side of the wafer engaging surface has an average distance from the axis of rotation. The average distance of the base edge from the axis of rotation is less than the average distance of each of the other sides from the axis of rotation.

[0012] Advantageous Effects of the Invention There are various refinements of the features noted in relation to the above-mentioned aspects of the present disclosure. Additional features may also be incorporated into the above-mentioned aspects of the present disclosure as well. These refinements and additional features may exist individually or in any combination. For example, the various features described below in relation to any of the illustrated embodiments of the present disclosure may be incorporated alone or in any combination into any of the above-mentioned aspects of the present disclosure. [Brief description of the drawings]

[0013] [Figure 1] FIG. [Diagram 2] FIG. 2 is a cross-sectional view of a grinding wheel of a double-sided grinding device. [Diagram 3] FIG. 2 is a top view of the support wheel of the grinding wheel. [Figure 4] FIG. [Diagram 5] FIG. 2 is a detailed top view of the grindstone showing the abrasive members. [Figure 6] FIG. 2 is a top view of the grinding member of the grindstone. [Figure 7] FIG. 13 is a top view of another embodiment of a grinding wheel. [Figure 8] FIG. 2 is a detailed top view of the grindstone showing the abrasive members. [Figure 9] FIG. 2 is a top view of the grinding member of the grindstone. [Figure 10] 1 shows peak-to-valley box plots of nanotopography of semiconductor structures simultaneously double-sided ground by a convex polygon polishing member and a conventional polishing member. [Figure 11] 1 shows a box plot of peak-to-valley nanotopography in a 10 mm×10 mm window of semiconductor structures simultaneously double-sided polished by a convex polygon polishing member and a conventional polishing member. [Figure 12] 1 shows wafer images of semiconductor structures simultaneously double-sided ground by a convex polygon polishing member and a conventional polishing member. [Figure 13] 1 shows a box plot of the BOW of a semiconductor structure after simultaneous double-sided grinding by a convex polygon polishing member and a conventional polishing member. [Figure 14] 1 shows a box plot of the change (delta) in BOW before and after double-sided polishing of semiconductor structures before and after simultaneous double-sided polishing with a convex polygon polishing member and a conventional polishing member. [Figure 15] 1 is a time series plot of left wheel current for semiconductor structures simultaneously double-sided ground with a convex polygon abrasive member and a conventional abrasive member. [Figure 16] 1 is a time series plot of right wheel current for semiconductor structures simultaneously double-sided ground with a convex polygon abrasive member and a conventional abrasive member. [Figure 17] 1 shows the cumulative percentage of particle counts with count 0 (DIC mode) for simultaneous double-sided grinding of semiconductor structures simultaneously double-sided ground by a convex polygon polishing member and a conventional polishing member. [Figure 18] 1 shows an image of a convex polygonal abrasive member along its height showing porosity. [Figure 19] 1 is a time series plot of CRING values ​​for a convex polygonal abrasive member and a conventional abrasive member.

[0014] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An exemplary double-sided grinding apparatus 100 for use in embodiments of the present disclosure is shown in FIG. The double-sided grinding apparatus 100 (also referred to herein as a "simultaneous double-sided grinding apparatus") includes a pair of hydrostatic pads 105, 110 that form a water cushion or "pocket" 113 via a water source 111. A semiconductor structure W is guided between the water cushion 113, thereby "clamping" the wafer W in a generally vertical orientation. The wafer is secured to a carrier ring 122. The carrier ring 122 (and the wafer W secured thereto) rotates within hydrostatic guide rollers 136. A pair of first and second grinding wheels 133, 135 ("left" and "right" grinding wheels) extend through the hydrostatic pads 105, 110. The pair of grinding wheels 133, 135 rotate in opposite directions relative to each other. The grinding wheels 133, 135 may be coupled to air spindles 141, 142, and an electric motor rotates the grinding wheels 133, 135. The grinding wheels 133, 135 may include full peripheral contact with the semiconductor structure as they rotate.

[0016] In general, the double sided grinding apparatus 100 can be adapted to process semiconductor structures of any size, such as structures having diameters of 200 mm or more, 300 mm or more, or 450 mm or more. The semiconductor structure may be a single crystal silicon wafer. In other embodiments, the semiconductor structure is silicon carbide, sapphire, or Al2O3. The semiconductor structure may be a layered structure or a bulk wafer.

[0017] An example of a grinding wheel 200 of the present apparatus is shown in FIG. 2. Grinding wheel 200 can be used as the first and second grinding wheels of apparatus 100 since the first and second grinding wheels are typically identical. Grinding wheel 200 has an axis of rotation A about which the grinding wheel rotates. Grinding wheel 200 includes a support wheel 208 and a plurality of abrasive members 212 that extend axially outwardly from support wheel 208. The plurality of abrasive members 212 extend circumferentially about support wheel 208 (centered about circumference C (FIG. 3)).

[0018] The abrasive member 212 comprises an abrasive material such as diamond grit or cubic boron nitride (CBN) grit, in some embodiments, the abrasive member comprises vitrified diamond.

[0019] The support wheel 208 includes a circumferential recess 215 (e.g., formed from a single shoulder or two shoulders formed in the support wheel 208). A plurality of abrasive members 212 are disposed within the circumferential recess 215. The abrasive members 212 can be connected to the support wheel 208 by any method that enables the grindstone to function as described herein. In some embodiments, the abrasive members 212 are connected to the support wheel 208 by an adhesive. In other embodiments, the abrasive members 212 are connected to the support wheel 208 by a mold. In other embodiments, the abrasive members are connected to a collar (not shown) that is disposed within the circumferential recess.

[0020] 4-5, a grinding wheel 200 according to an embodiment of the present disclosure is shown. The grinding wheel 200 includes polishing members 212 each having a wafer-engaging surface 225 (FIG. 6) that contacts the semiconductor structure during grinding. Gaps 219 (FIG. 4) may be formed between the polishing members 212. In other embodiments, no gaps are formed between the polishing members 212 (i.e., the wafer-engaging surfaces 225 are coincident).

[0021] In the illustrated embodiment, the wafer engaging surface 225 is in the shape of a convex polygon having at least five sides. For example, the convex polygon may be a pentagon as shown in the illustrated embodiment, or a hexagon, heptagon, octagon, or other convex polygon as in other embodiments. The convex polygon may be a regular polygon or an irregular polygon.

[0022] In some embodiments, and as shown in FIG. 6, the wafer-engaging surface 225 includes a base side 235 (e.g., a side from which a height can be measured that is generally closest or farthest from the axis of rotation A (FIG. 4) of the grinding wheel 200). Second and third sides 239, 243 extend from the base side 235 (also referred to herein as the "first side" of the wafer-engaging surface 225). The second side 239 includes a first end 241 and a second end 242. The second side 239 is connected to the base side 235 at its first end 241. The second side 239 and the base side 235 form an angle λ1. The third side 243 includes a first end 261 and a second end 263. The third side 243 is connected to the base side 235 at its first end 261. The third side 243 and the base side 235 form an angle λ2. In some embodiments, the first and second angles λ1, λ2 are each obtuse angles.

[0023] The wafer engaging surface 225 includes a fourth side 250 that connects to the first side 239 at a first end 267 of the fourth side 250. The wafer engaging surface 225 includes a fifth side 255 that connects to the second end 243 at a first end 272 of the fifth side 255. In embodiments where the convex polygon is a pentagon, the fourth and fifth sides 250, 255 connect at second sides 270, 275 of the fourth and fifth sides 250, 255.

[0024] The sides 235, 239, 243, 250, 255 of the convex polygon can have any length that enables the polishing member 212 to function as described herein. In the illustrated embodiment, the second and third sides 239, 243 are each shorter than the base side 235 and the fourth and fifth sides 250, 255, respectively.

[0025] As shown in the illustrated embodiment, one or more corners formed between the sides may be rounded corners (e.g., having one or more radii of curvature). For example, the corner 286 formed between the second side 239 and the fourth side 250 is rounded, and the corner 288 formed between the third side 243 and the fifth side 255 is rounded. In the illustrated embodiment, the corner 290 formed between the fourth side 250 and the fifth side 255 is also rounded (e.g., the apex opposite the base side 235 is rounded). The ends of the various sides of a convex polygon that terminate in a rounded corner may generally correspond to the midpoint of the rounded corner, unless otherwise noted herein.

[0026] In some embodiments, some or all of the corners are not rounded (i.e., some or all are sharp). In the illustrated embodiment, the corner 282 formed between the base 235 and the second side 239 is not rounded, and the corner 284 formed between the base 235 and the third side 243 is not rounded. In general, the selection of rounded and sharp corners (and the radius or radii of the rounded corners) can be made based on the performance of the polishing member 212.

[0027] Each side 235, 239, 243, 250, 255 of the wafer engagement surface 225 has an average distance from the axis of rotation A (FIG. 4). In the illustrated embodiment, the average distance D 235 of the base side 235 from the axis of rotation A is less than the average distance of each of the other sides 239, 243, 250, 255 from the axis of rotation (i.e., the base side 235 is closer to the axis of rotation A than the other sides of the convex polygon).

[0028] Another embodiment of the grinding wheel 300 is shown in Figures 7-8. Components shown in Figures 7-8 that are similar to those in Figures 4-5 are numbered with the corresponding reference numbers in Figures 4-5 plus "100" (e.g., member 212 becomes 312). In the embodiment of Figures 7-8, the orientation of the grinding member 312 is rotated 180° from the grinding member 212 of Figures 4-6 (compare Figures 6 and 9). In this illustrated embodiment, the average distance D335 of the base side 335 from the axis of rotation A is greater than the average distance of each of the other sides 239, 243, 250, 255 from the axis of rotation A (i.e., the base side 235 is farther from the axis of rotation A than the other sides of the convex polygon). Other than the orientation of the grinding member 312, the grinding member 312 may be the same as the grinding member 212 of Figures 4-6.

[0029] According to an embodiment of the present disclosure, a semiconductor structure may be double-sided ground by positioning the semiconductor structure between first and second grinding wheels (FIG. 1). The semiconductor structure is ground by contacting the first and second grinding wheels with the semiconductor structure and rotating the first and second grinding wheels relative to one another (i.e., in opposite directions).

[0030] Compared with conventional methods of simultaneous double-sided grinding of semiconductor structures, the disclosed method has several advantages. The convex polygon-shaped polishing member has more polishing surface area than conventional polishing members to hold the semiconductor structure. This reduces horizontal vibration and tilting due to contacting grindstones. The rotating semiconductor structure is ground under more balanced conditions, which may improve the nanotopography. In addition, the sharp step along the edge of the semiconductor structure may be improved, reducing distorted areas on the ground wafer. The convex polygon-shaped polishing member can generate less surface damage with less polishing current. Different shapes or orientations of the convex polygon polishing member can be used to create different BOW effects on the wafer. The convex polygon polishing member has a relatively consistent porosity over its length, which may increase the consistency of the polishing process.

[0031] Working Example

[0032] The processes of the present disclosure are further illustrated by the following examples, which should not be construed in a limiting sense.

[0033] Example 1: Improvement of nanotopography by using a convex polygonal abrasive member

[0034] A first set of semiconductor structures (single crystal silicon wafers) were simultaneously double-sided polished by a grindstone having abrasive members as shown in Figures 4-7 of U.S. Patent No. 6,692,343. A second set of semiconductor structures (single crystal silicon wafers) were simultaneously double-sided ground by a grindstone having a convex polygonal (convex pentagonal) abrasive member. Figure 10 shows the peak to valley of the nanotopography, and Figure 11 shows the peak to valley of a 10 mm x 10 mm window in the wafer. As shown in Figures 10-11, the pentagonal shaped abrasive member results in improved nanotopography.

[0035] Example 2: Reduction of distortion area by using a convex polygonal polishing member

[0036] FIG. 12 shows wafer images of wafers ground by the grindstone of FIGS. 4-6 of the present application having a pentagonal polishing member "(1)" and the grindstone having the polishing member shown in FIGS. 4-7 of U.S. Pat. No. 6,692,343 having a central pattern "(2)" and an end pattern "(3)". The pentagonal polishing member was able to apply a holding force toward the rotating wafer surface and could maintain the inclination without changing the grinding sequence. As shown in FIG. 12, the wafer ground using the pentagonal polishing member was less likely to have distorted portions in the ground wafer, and the nanotopography was improved.

[0037] Example 3: Change in BOW by using a convex polygonal polishing member

[0038] The central profile (BOW best fit, CRING) measured without adjusting the tilt of the grinding wheel for the pentagonal grinding member with the base closest to the rotation axis of the grinding wheel (FIGS. 4-5 of the present application), the pentagonal grinding member with the base farthest from the rotation axis (FIGS. 7-8 of the present application), and the grinding member shown in FIGS. 4-7 of U.S. Patent No. 6,692,343 ("US6,692,343") is shown in FIGS. 13-14. FIG. 13 shows the measured value of the BOW after double-sided grinding, and FIG. 14 shows the difference in the BOW before and after double-sided grinding. The pentagonal grinding members have different removal amounts, and the grinding wheels have different BOW capabilities.

[0039] Example 4: Reduction of surface damage by using a convex polygonal abrasive member

[0040] Figure 17 shows the cumulative percentage of particle counts (DIC mode) for a grinding wheel having an abrasive member as shown in Figures 4-7 of U.S. Patent No. 6,692,343 (left column) and a grinding wheel having a pentagonal shaped abrasive member (right column). As shown in Figure 17, the pentagonal shaped abrasive member produced less surface damage at lower grinding currents (Figures 15-16).

[0041] Example 5: Grinding stability using a convex polygonal abrasive member

[0042] The convex polygonal grinding wheel had stable grinding performance from the top to the bottom layer of the convex polygonal structure. As shown in Figure 18, the porosity of the convex polygonal grinding wheel was constant over its entire length. This is also evident from Figure 19, where the CRING value changed (from low to high and back to low) for the grinding members in Figures 4-7 of U.S. Patent No. 6,692,343, while the pentagonal grinding member showed a constant value.

[0043] As used herein, the terms "about," "substantially," "essentially," and "approximately" when used in conjunction with a dimension, concentration, temperature, or other physical or chemical property or range of properties are meant to cover variations that may exist at the upper and / or lower limits of the property or range of properties, including, for example, variations due to rounding, measurement methodology, or other statistical variations.

[0044] When introducing elements of the disclosure or embodiments thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," "containing," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of specific directional terms (e.g., "top," "bottom," "side," etc.) is for convenience of description and does not require a particular orientation of the items being described.

[0045] Since various changes may be made in the above structures and methods without departing from the scope of the present disclosure, it is intended that all matter contained in the above description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

Claims

1. 1. A method for double sided polishing a semiconductor structure, comprising: Positioning the semiconductor structure between first and second grinding wheels, each grinding wheel comprising: A support wheel; and a plurality of abrasive members extending axially outwardly from the support wheel, each abrasive member having a wafer engaging surface, the wafer engaging surface being in the shape of a convex polygon having at least five sides; and contacting first and second grinding wheels with the semiconductor structure and rotating the first and second grinding wheels relative to one another to grind the semiconductor structure.

2. The method of claim 1 , wherein the convex polygon has one or more rounded corners.

3. 3. The method of claim 2, wherein one of the sides of the polygon includes a base and a plurality of sides other than the base, and each corner formed between two sides of the polygon other than the base is rounded.

4. 4. The method of claim 3, wherein each corner formed with the base is an acute angle.

5. The method of claim 1 , wherein the polishing member comprises diamond abrasive grains.

6. The method of claim 5 , wherein the abrasive member comprises vitrified diamond.

7. 10. The method of claim 1, wherein each abrasive member is attached to the support wheel by an adhesive or a mold.

8. The method of claim 1 , wherein the support wheel defines a circumferential recess and the abrasive member is disposed within the circumferential recess.

9. The method of claim 1 , wherein the convex polygon is a convex pentagon.

10. The method of claim 1 , wherein the semiconductor structure is secured by first and second hydrostatic pressure pads.

11. 1. A method for double sided grinding of a semiconductor structure, comprising: Positioning the semiconductor structure between first and second grinding wheels, each grinding wheel comprising: A support wheel; and A plurality of abrasive members extending axially outwardly from the support wheel, each abrasive member having a wafer engaging surface, the wafer engaging surfaces including: a base side which is a first side of the wafer engaging surface; a second side having a first end and a second end, the second side being connected to the base at the first end, the second side and the base forming an obtuse angle; and a third side having a first end and a second end, the third side being connected to the base at the first end, the third side and the base forming an obtuse angle; and contacting first and second grinding wheels with the semiconductor structure and rotating the first and second grinding wheels relative to one another to grind the semiconductor structure.

12. The method of claim 11 , wherein the wafer engaging surface includes a fourth side and a fifth side.

13. 12. The method of claim 11, wherein each grinding wheel has an axis of rotation, each side of the wafer engaging surface has an average distance from the axis of rotation, the average distance of the bottom side from the axis of rotation being greater than the average distance of each of the other sides from the axis of rotation.

14. 12. The method of claim 11, wherein each grinding wheel has an axis of rotation, each side of the wafer engaging surface having an average distance from the axis of rotation, the average distance of the bottom side from the axis of rotation being less than the average distance of each of the other sides from the axis of rotation.

15. The method of claim 11 , wherein the wafer engaging surface has one or more rounded corners.

16. 16. The method of claim 15, wherein a corner formed between the base and the second side is not rounded, and a corner formed between the base and the third side is not rounded.

17. The method of claim 11 , wherein the wafer engaging surface is pentagonal in shape and includes a fourth side and a fifth side.

18. The method of claim 11 , wherein the polishing member comprises diamond abrasive grains.

19. The method of claim 18, wherein the abrasive member comprises vitrified diamond.

20. 12. The method of claim 11, wherein each abrasive member is connected to a support wheel by an adhesive or a mold.

21. The method of claim 11 , wherein the support wheel defines a circumferential recess and the abrasive member is disposed within the circumferential recess.

22. The method of claim 11 , wherein the semiconductor structure is secured by first and second hydrostatic pressure pads.

23. first and second grinding wheels, each having an axis of rotation; A support wheel; and A plurality of abrasive members extending axially outwardly from the support wheel, each abrasive member having a wafer engaging surface, the wafer engaging surfaces including: a base edge, the first edge of the wafer engaging surface; a second side having a first end and a second end, the second side being connected to the base at the first end such that the second side and the base form an obtuse angle; and a third side having a first end and a second end, the third side being connected to the base at the first end, the third side forming an obtuse angle with the base; A double sided grinding apparatus, wherein each side of the wafer engaging surface has an average distance from the axis of rotation, the average distance of the bottom side from the axis of rotation being less than the average distance of each of the other sides from the axis of rotation.

24. 24. The double sided grinding apparatus of claim 23, wherein the wafer engaging surface includes a fourth side and a fifth side.

25. 24. The double sided grinding apparatus of claim 23, wherein the wafer engaging surface has one or more rounded corners.

26. 26. The double sided grinding apparatus of claim 25, wherein a corner formed between the base and the second side is not rounded, and a corner formed between the base and the third side is not rounded.

27. 24. The double sided grinding apparatus of claim 23, wherein the wafer engaging surface is pentagonal in shape and includes a fourth side and a fifth side.

28. 24. The double-sided grinding apparatus according to claim 23, wherein the polishing member includes diamond abrasive grains.

29. 30. The double sided grinding apparatus of claim 28, wherein the abrasive member comprises vitrified diamond.

30. 24. The double sided grinding apparatus of claim 23, wherein the support wheel defines a circumferential recess, and the abrasive member is disposed within the circumferential recess.

31. 24. The double sided grinding apparatus of claim 23, wherein the support wheel defines a circumferential recess, the collar being disposed within the circumferential recess.

32. 24. The double sided grinding apparatus of claim 23, further comprising first and second hydrostatic pads for securing the semiconductor structure.

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