Double-sided grinding device having a convex polygonal polishing 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 Apr. 27, 2021, which is hereby incorporated by reference in its entirety.

[0002] The field of the present disclosure generally relates to simultaneous double-sided grinding of semiconductor wafers, and more particularly to double-sided grinding apparatuses and methods.

Background Art

[0003] Semiconductor wafers are commonly used in the manufacture of integrated circuit (IC) chips on which circuits are printed. The circuits are first printed in a miniaturized form on the surface of the wafer, and then the wafer is diced into circuit chips. However, in order to miniaturize the circuits in this way, it is necessary to make the surface of the wafer extremely flat and parallel so that the circuits can be properly printed over the entire surface of the wafer. To achieve this, after cutting the wafer from an ingot, a grinding process is commonly used to improve certain characteristics of the wafer, such as flatness and parallelism.

[0004] Simultaneous double-sided grinding grinds both sides of the wafer simultaneously to produce a wafer with a highly planarized surface. Thus, it is a desirable grinding process. This grinding process significantly improves the flatness and parallelism of the ground wafer surface while potentially causing degradation of the topography and nanotopography (NT) of the wafer surface.

[0005] Poor nanotopography results in non-uniform removal of the oxide film in subsequent chemical mechanical polishing (CMP) processes. This significantly reduces the yield of wafer users such as IC manufacturers. As IC manufacturers transition to smaller process technologies, the tolerance for nanotopography is expected to become more stringent.

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

[0007] This section is intended to introduce to the reader various aspects of the technology that may relate to the various aspects of the disclosure described and / or claimed below. This discussion is intended to be useful in providing the reader with background information to better understand the various aspects of the disclosure. Accordingly, these descriptions should be read in this context and should be understood not as an admission of prior art. [Overview of the project]

[0008] One aspect of this disclosure relates to a method for double-sided grinding of semiconductor structures.

[0009] Solving the problem The semiconductor structure is positioned between the 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 engagement surface. The wafer engagement surface has the shape of a convex polygon with at least five sides. The semiconductor structure is ground by bringing the first and second grinding wheels into contact with the semiconductor structure and rotating the first and second grinding wheels relative to each other.

[0010] Another aspect of the present disclosure relates to a method for double-sided grinding a semiconductor structure. The semiconductor structure is positioned between first and second grinding wheels. Each grinding wheel includes a support wheel and a plurality of abrasive members extending axially outward from the support wheel. Each abrasive member has a wafer engagement surface. The wafer engagement surface includes a base. The base is the first edge of the wafer engagement surface. The wafer engagement surface includes a second edge having a first end and a second end. The second edge connects to the base at its first end. The second edge and the base form an obtuse angle. The wafer engagement surface includes a third edge having a first end and a second end. The third edge connects to the base at its first end. The third edge and the base form an obtuse angle. The semiconductor structure is ground by bringing the first and second grinding wheels into contact with the semiconductor structure and rotating the first and second grinding wheels relative to each other.

[0011] Further aspects of the present disclosure relate to a double-sided grinding apparatus. The apparatus includes first and second grinding wheels. Each grinding wheel has a rotation axis and includes a support wheel and a plurality of abrasive members extending axially outward from the support wheel. Each abrasive member has a wafer engagement surface. The wafer engagement surface includes a base. The base is the first side of the wafer engagement surface. The wafer engagement surface includes a second side having a first end and a second end. The second side connects to the base at its first end. The second side and the base form an obtuse angle. The wafer engagement surface includes a third side having a first end and a second end. The third side connects to the base at its first end. The third side and the base form an obtuse angle. Each side of the wafer engagement surface has an average distance from the rotation axis. The average distance of the base from the rotation axis is less than the average distance of each of the other sides from the rotation axis.

[0012] Advantageous effects of the present invention Various improvements to the features pointed out in relation to the above-described embodiments of this disclosure exist. Further features may also be incorporated into the above-described embodiments of this disclosure. These improvements 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 this disclosure may be incorporated individually or in any combination into any of the above-described embodiments of this disclosure. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view of a double-sided grinding machine. [Figure 2] This is a cross-sectional view of the grinding wheel of a double-sided grinding machine. [Figure 3] This is a top view of the support wheel for the grinding wheel. [Figure 4] This is a top view of a whetstone. [Figure 5] This is a detailed top view of a grinding wheel, which is an abrasive component. [Figure 6] This is a top view of the abrasive component of a grinding wheel. [Figure 7] This is a top view of another embodiment of the grinding wheel. [Figure 8] This is a detailed top view of a grinding wheel, which is an abrasive component. [Figure 9] It is a top view of the grinding member of the grindstone. [Figure 10] Shows a box plot from peak to valley of the nanotopography of a semiconductor structure simultaneously double-sided lapped by a convex polygon grinding member and a conventional grinding member. [Figure 11] Shows a box plot from peak to valley of the nanotopography in a 10 mm × 10 mm window of a semiconductor structure simultaneously double-sided polished by a convex polygon grinding member and a conventional grinding member. [Figure 12] Shows a wafer image of a semiconductor structure simultaneously double-sided lapped by a convex polygon grinding member and a conventional grinding member. [Figure 13] Shows a box plot of the BOW of a semiconductor structure after simultaneous double-sided lapping by a convex polygon grinding member and a conventional grinding member. [Figure 14] Shows a box plot of the change (delta) in BOW before and after double-sided polishing of a semiconductor structure before and after simultaneous double-sided polishing by a convex polygon grinding member and a conventional grinding member. [Figure 15] It is a time series plot of the current of the left grindstone of a semiconductor structure simultaneously double-sided lapped by a convex polygon grinding member and a conventional grinding member. [Figure 16] It is a time series plot of the current of the right grindstone of a semiconductor structure simultaneously double-sided lapped by a convex polygon grinding member and a conventional grinding member. [Figure 17] Shows the cumulative percentage (DIC mode) of the particle count at count 0 of simultaneous double-sided lapping of a semiconductor structure simultaneously double-sided lapped by a convex polygon grinding member and a conventional grinding member. [Figure 18] Shows an image of a convex polygon grinding member along the height indicating the porosity. [Figure 19] It is a time series plot of the CRING values of a convex polygon grinding member and a conventional grinding member.

[0014] Corresponding reference numerals indicate corresponding parts throughout the drawings.

Embodiments for Carrying Out the Invention

[0015] An exemplary dual-sided grinding apparatus 100 for use in embodiments of the present disclosure is shown in FIG. 1. The dual-sided grinding apparatus 100 (also referred to herein as a “simultaneous dual-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 cushions 113, thereby “clamping” the wafer W in a generally vertical direction. The wafer is fixed to a carrier ring 122. The carrier ring 122 (and the wafer W fixed thereto) rotates within a hydrostatic guide roller 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 connected to air spindles 141, 142, and an electric motor rotates the grinding wheels 133, 135. The grinding wheels 133, 135 can include complete peripheral contact with the semiconductor structure when rotating.

[0016] Generally, the dual-sided grinding apparatus 100 can be adapted to process semiconductor structures of any size, such as structures having a diameter 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. Since the first and second grinding wheels are usually the same, the grinding wheel 200 can be used as the first and second grinding wheels of the apparatus 100. The grinding wheel 200 has a rotation axis A about which the grinding wheel rotates. The grinding wheel 200 includes a support wheel 208 and a plurality of polishing members 212 extending axially outward from the support wheel 208. The plurality of polishing members 212 extend circumferentially about a center of the support wheel 208 (about a circumference C (FIG. 3)).

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

[0019] The support wheel 208 includes a circumferential recess 215 (formed, for example, from a single shoulder or two shoulders formed in the support wheel 208). Multiple abrasive members 212 are arranged within the circumferential recess 215. The abrasive members 212 can be attached to the support wheel 208 in any way that enables the grinding wheel to function as described herein. In some embodiments, the abrasive members 212 are attached to the support wheel 208 by adhesive. In other embodiments, the abrasive members 212 are attached to the support wheel 208 by mold. In other embodiments, the abrasive members are attached to a collar (not shown) located within the circumferential recess.

[0020] Next, referring to Figures 4-5, a grinding wheel 200 of an embodiment of the present disclosure is shown. The grinding wheel 200 includes each abrasive member 212 having a wafer engagement surface 225 (Figure 6) that contacts the semiconductor structure during grinding. A gap 219 (Figure 4) may be formed between the abrasive members 212. In other embodiments, no gap is formed between the abrasive members 212 (i.e., the wafer engagement surfaces 225 coincide).

[0021] In the illustrated embodiment, the wafer engagement surface 225 has 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 it may be 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 Figure 6, the wafer engagement surface 225 includes a base 235 (for example, the side from which the height closest or furthest from the rotation axis A of the grinding wheel 200 (Figure 4) can be measured). Second and third sides 239, 243 extend from the base 235 (also referred herein as the “first side” of the wafer engagement 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 235 at its first end 241. The second side 239 and the base 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 235 at its first end 261. The third side 243 and the base 235 form an angle λ2. In some embodiments, the first and second angles λ1 and λ2 are obtuse angles, respectively.

[0023] The wafer engagement surface 225 is at the first end 267 of the fourth side 250. 2nd The wafer engagement surface 225 includes a fourth side 250 connected to side 239. Third side It includes a fifth side 255 that connects to 243. In embodiments where the convex polygon is a pentagon, the fourth and fifth sides 250, 255 are connected by the second sides 270, 275 of the fourth and fifth sides 250, 255.

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

[0025] As shown in the illustrated embodiments, one or more corners formed between 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 embodiments, the corner 290 formed between the fourth side 250 and the fifth side 255 is also rounded (e.g., the vertex opposite the base side 235 is rounded). The ends of various sides of a convex polygon terminating within a rounded corner may generally correspond to the midpoint of the rounded corner, unless otherwise stated herein.

[0026] In some embodiments, some or all of the corners are not rounded (i.e., some or all are acute). 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. Generally, the choice between rounded and sharp corners (and one or more radii of the rounded corners) can be made based on the performance of the abrasive member 212.

[0027] Each side 235, 239, 243, 250, and 255 of the wafer engagement surface 225 has an average distance from the axis of rotation A (Figure 4). In the illustrated embodiment, the average distance D235 of the base side 235 from the axis of rotation A is smaller than the average distances of the other sides 239, 243, 250, and 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. Among the components shown in Figures 7-8, those similar to the components in Figures 4-5 are numbered by adding "100" to the corresponding reference number in Figures 4-5 (for example, component 212 becomes 312). In the embodiment of Figures 7-8, the orientation of the polishing member 312 is rotated by 180° from the polishing member 212 in Figures 4-6 (compare Figure 6 and Figure 9). In this illustrated embodiment, the average distance D335 of the base 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 335 (This side is further from the axis of rotation A than the other sides of the convex polygon). Except for the orientation of the polishing member 312, the polishing member 312 may be the same as the polishing member 212 in Figures 4-6.

[0029] In accordance with embodiments of the present disclosure, a semiconductor structure may be double-sided ground by positioning the semiconductor structure between first and second grinding wheels (Figure 1). The semiconductor structure is ground by bringing the first and second grinding wheels into contact with the semiconductor structure and rotating the first and second grinding wheels relative to each other (i.e., in opposite directions).

[0030] Compared to conventional methods for simultaneously grinding both sides of a semiconductor structure, the method of this disclosure offers several advantages. The convex polygonal polishing member has a larger polishing surface area than conventional polishing members for holding the semiconductor structure. This reduces horizontal vibration and inclination caused by the contacting grinding wheel. The rotating semiconductor structure is ground under more balanced conditions, potentially improving nanotopography. Furthermore, abrupt steps along the edges of the semiconductor structure are improved, potentially reducing distorted areas on the ground wafer. The convex polygonal polishing member can generate less surface damage with less polishing current. Different shapes or orientations of the convex polygonal polishing member can be used to produce different BOW effects on the wafer. The convex polygonal polishing member has relatively consistent porosity over its length, which can improve the consistency of the polishing process.

[0031] Examples

[0032] The processes described herein are further illustrated by the following embodiments, which should not be taken as limiting.

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

[0034] A first set of semiconductor structures (single-crystal silicon wafers) were simultaneously polished on both sides using a grinding wheel with abrasive members as shown in Figures 4-7 of U.S. Patent No. 6,692,343. A second semiconductor structure (single-crystal silicon wafer) was simultaneously ground on both sides using a grinding wheel with convex polygonal (convex pentagonal) abrasive members. Figure 10 shows the peaks and valleys of the nanotopography, and Figure 11 shows the peaks and valleys of a 10 mm × 10 mm window on the wafer. As shown in Figures 10-11, the pentagonal abrasive members improve the nanotopography.

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

[0036] Figure 12 shows wafer images of wafers ground with the grinding wheel shown in Figures 4-6 of the present application, which has a pentagonal polishing member "(1)", and the grinding wheel shown in Figures 4-7 of U.S. Patent No. 6,692,343, which has a polishing member "(2)" as the central pattern and "(3)" as the edge pattern. The pentagonal polishing member was able to apply holding force toward the rotating wafer surface and maintain the inclination without changing the grinding sequence. As shown in Figure 12, wafers ground using the pentagonal polishing member were less prone to distortion and showed improved nanotopography.

[0037] Example 3: Change in BOW due to the use of a convex polygonal polishing member

[0038] Figures 13-14 show the central profile (BOW best fit, CRING) measured without adjusting the tilt of the grinding wheel for a pentagonal grinding member having the base closest to the rotation axis of the grinding wheel ("Figures 4-5 of this application"), a pentagonal grinding member having the base furthest from the rotation axis ("Figures 7-8 of this application"), and the grinding member shown in Figures 4-7 of U.S. Patent No. 6,692,343 ("US6,692,343"). Figure 13 shows the measured BOW after double-sided grinding, and Figure 14 shows the difference in 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 polishing member

[0040] Figure 17 shows the cumulative particle count (DIC mode) for grinding wheels with abrasive members as shown in Figures 4-7 of U.S. Patent No. 6,692,343 (left column) and grinding wheels with pentagonal abrasive members (right column). As shown in Figure 17, the pentagonal abrasive members resulted in less surface damage with less grinding current (Figures 15-16).

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

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

[0043] In this specification, the terms “about,” “substantially,” “essentially,” and “approximately,” when used with dimensions, concentrations, temperatures, or other physical or chemical properties or ranges of properties, mean to cover any variations that may exist in the upper and / or lower limits of a property or range of properties, including, for example, variations resulting from rounding, measurement methods, or other statistical variations.

[0044] When describing elements or embodiments of the present disclosure, the articles “a,” “an,” “the,” and “said” are intended to mean that there is one or more elements. The terms “comprising,” “including,” “containing,” and “having” are intended to mean comprehensive and that there may be additional elements other than those listed. The use of terms indicating a particular direction (e.g., “top,” “bottom,” “side”) is for explanatory convenience and does not require a specific direction for the items described.

[0045] Various modifications can be made to the above configurations and methods without departing from the scope of this disclosure, so all matters included in the above description and shown in the accompanying drawings are intended to be illustrative and not to be construed in a restrictive sense.

Claims

1. A method for grinding both sides of a semiconductor structure, A step of positioning a semiconductor structure between a first and a second grinding wheel, wherein each grinding wheel has a rotation axis and, Support wheels; and, A plurality of polishing members extending axially outward from a support wheel, each polishing member having a wafer engagement surface, the wafer engagement surface having the shape of a convex polygon with at least five sides, the sides of the polygon including a base and a plurality of other sides, the base being the side closest to or furthest from the rotation axis of the grinding wheel, Each corner formed between two sides of a polygon other than the base is rounded. The process involves ensuring that each angle formed between the base and the other is a sharp angle, and A method comprising the step of grinding a semiconductor structure by bringing first and second grinding wheels into contact with the semiconductor structure and rotating the first and second grinding wheels relative to each other.

2. The method according to claim 1, wherein the abrasive member includes diamond abrasive grains.

3. The method according to claim 2, wherein the abrasive member comprises vitrified diamond.

4. The method according to claim 1, wherein each polishing member is connected to a support wheel by adhesive or mold.

5. The method according to claim 1, wherein the support wheel has a circumferential recess and the polishing member is arranged within the circumferential recess.

6. The method according to claim 1, wherein the convex polygon is a convex pentagon.

7. The method according to claim 1, wherein the semiconductor structure is fixed by first and second hydrostatic pads.

8. A method for grinding both sides of a semiconductor structure, A step of positioning a semiconductor structure between a first and a second grinding wheel, wherein each grinding wheel has a rotation axis and, Support wheels; and, A plurality of polishing members extending axially outward from a support wheel, each polishing member having a wafer engaging surface, and the wafer engaging surface having one or more rounded corners, The first edge of the wafer engagement surface, which is the base edge that is closest to or furthest from the rotation axis of the grinding wheel, A second side having a first end and a second end, wherein the second side is connected to the base at its first end, the second side and the base form an obtuse angle, the second side and the base form a corner, and the corner of the second side is not rounded; and A process comprising: a third side having a first end and a second end, wherein the third side is connected to the base at its first end, the third side and the base form an obtuse angle, the third side and the base form a corner, and the corner of the third side is not rounded; and A method comprising the step of grinding a semiconductor structure by bringing first and second grinding wheels into contact with the semiconductor structure and rotating the first and second grinding wheels relative to each other.

9. The method according to claim 8, wherein the wafer engagement surface includes a fourth edge and a fifth edge.

10. The method according to claim 8, wherein each side of the wafer engagement surface has an average distance from the axis of rotation, and the average distance of the bottom side from the axis of rotation is greater than the average distance of each other side from the axis of rotation.

11. The method according to claim 8, wherein each side of the wafer engagement surface has an average distance from the axis of rotation, and the average distance of the bottom side from the axis of rotation is smaller than the average distance of each other side from the axis of rotation.

12. The method according to claim 8, wherein the wafer engagement surface is pentagonal in shape and includes a fourth side and a fifth side.

13. The method according to claim 8, wherein the abrasive member includes diamond abrasive grains.

14. The method according to claim 13, wherein the polishing member comprises vitrified diamond.

15. The method according to claim 8, wherein each polishing member is connected to a support wheel by adhesive or mold.

16. The method according to claim 8, wherein the support wheel forms a circumferential recess, and the polishing member is arranged within the circumferential recess.

17. The method according to claim 8, wherein the semiconductor structure is fixed by first and second hydrostatic pads.

18. First and second grinding wheels, each grinding wheel having a rotation axis, Support wheels; and, A plurality of polishing members extending axially outward from a support wheel, each polishing member having a wafer engaging surface, the wafer engaging surface is The first edge of the wafer engagement surface, which is the base edge and is the edge closest to the rotation axis of the grinding wheel; The vertex opposite the base; A second side having a first end and a second end, the second side being connected to the base at its first end, and 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 its first end, and the third side and the base forming an obtuse angle; A double-sided grinding apparatus in which each side of the wafer engagement surface has an average distance from the axis of rotation, and the average distance from the axis of rotation of the bottom side is smaller than the average distance from the axis of rotation of each other side.

19. The double-sided grinding apparatus according to claim 18, wherein the wafer engagement surface includes a fourth side and a fifth side.

20. The double-sided grinding apparatus according to claim 18, wherein the wafer engagement surface has one or more rounded corners.

21. The double-sided grinding apparatus according to claim 20, wherein the corner formed between the base and the second side is not rounded, and the corner formed between the base and the third side is not rounded.

22. The double-sided grinding apparatus according to claim 18, wherein the wafer engagement surface is pentagonal in shape and includes a fourth side and a fifth side.

23. The double-sided grinding apparatus according to claim 18, wherein the abrasive member includes diamond abrasive grains.

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

25. The double-sided grinding apparatus according to claim 18, wherein the support wheel forms a circumferential recess, and the polishing member is arranged within the circumferential recess.

26. The double-sided grinding apparatus according to claim 18, wherein the support wheel has a circumferential recess and the collar is disposed within the circumferential recess.

27. ​​The double-sided grinding apparatus according to claim 18, further comprising first and second hydrostatic pads.

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