TW202245033A - Double side grinding apparatus having convex polygon-shaped abrasive members - Google Patents

Abstract

Methods and apparatus for simultaneous double-side grinding semiconductor structures are disclosed. The double-side grinding apparatus may include first and second grinding wheels each having abrasive members that are shaped as a convex polygon (e.g., convex pentagon).

Description

Double-sided grinding device with convex polygonal abrasive members

The field of the invention relates generally to simultaneous double-side grinding of semiconductor wafers, and more particularly to double-side grinding apparatus and methods for double-side grinding.

Semiconductor wafers are commonly used in the production of integrated circuit (IC) chips for printed circuits. Circuitry is first printed in miniature form on the surface of the wafer, and the wafer is then diced into circuit chips. But this smaller circuit requires the wafer surface to be extremely flat and parallel to ensure that the circuit can be printed correctly across the entire surface of the wafer. To achieve this, after the wafers are diced from an ingot, a grinding process is typically used to improve certain characteristics of the wafers (eg, flatness and parallelism).

Simultaneous double-side grinding operates on both sides of the wafer simultaneously and produces wafers with highly planarized surfaces. Therefore, this is a desirable grinding process. Although this polishing process significantly improves the flatness and parallelism of the polished wafer surface, it also causes degradation of the topography and nanosurface topography (NT) of the wafer surface.

Poor nano-surface topography leads to non-uniform oxide removal in a subsequent polishing (CMP) process. This can result in substantial loss of yield for wafer users such as IC manufacturers. As IC manufacturers move to smaller process technologies, the tolerances for nanometer surface topography are expected to become tighter.

There is a need for a method of grinding semiconductor structures on both sides simultaneously to improve the nanometer surface topography of the wafer.

This section is intended to introduce the reader to various aspects of technology that may be related to various aspects of the invention, which are described and/or claimed below. This discussion is considered helpful in providing the reader with background information in order to better understand aspects of the invention. Accordingly, it should be understood that such statements are to be read in this light, and not as admissions of prior art.

One aspect of the present invention is directed to a method for double-sided grinding of a semiconductor structure. The semiconductor structure is located between the first and second grinding wheels. Each grinding wheel includes a support wheel and a plurality of abrasive components extending axially outward from the support wheel. Each abrasive member has a wafer bonding surface. The wafer bonding surface is shaped to have a convex polygon with 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 each other.

Another aspect of the invention is directed to a method for double-sided grinding of a semiconductor structure. The semiconductor structure is located between the first and second grinding wheels. Each grinding wheel includes a support wheel and a plurality of abrasive components extending axially outward from the support wheel. Each abrasive member has a wafer bonding surface. The wafer bonding includes a substrate. The substrate is a first side of the wafer bonding surface. The wafer bonding surface includes a second face having a first end and a second end. The second face is connected to the base at its first end. The second surface and the base form an obtuse angle. The wafer bonding surface includes a third surface having a first end and a second end. The third face is connected to the base at its first end. The third surface and the base 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 each other.

Another aspect of the present invention is directed to a double-sided grinding device. The device includes first and second grinding wheels. Each grinding wheel has a rotating shaft, and includes a supporting wheel and a plurality of abrasive components axially extending outward from the supporting wheel. Each abrasive member has a wafer bonding surface. The wafer bonding surface includes a base. The substrate is a first side of the wafer bonding surface. The wafer bonding surface includes a second face having a first end and a second end. The second face is connected to the base at its first end. The second surface and the base form an obtuse angle. The wafer bonding surface includes a third surface having a first end and a second end. The third face is connected to the base at its first end. The third surface and the base form an obtuse angle. Each face of the wafer bonding surface has an average distance from the axis of rotation. The average distance of the base from the axis of rotation is smaller than the average distance of each of the other faces from the axis of rotation.

There are various modifications of the features noted in the above aspects of the invention. Other features may also be incorporated into the above-described aspects of the invention. These improvements and additional functionality may exist alone or in any combination. For example, various features discussed below in relation to any illustrated embodiment of the invention may be incorporated into any of the above aspects of the invention alone or in any combination.

This application claims priority to U.S. Provisional Patent Application No. 63/180,481, filed April 27, 2021, the disclosure of which is incorporated herein by reference.

Figure 1 shows an example double-sided grinding device 100 for use in an embodiment of the present invention. Double-sided lapping device 100 (which may also be referred to herein as a "simultaneous double-sided lapping device") includes a pair of hydrostatic pads 105, 110 that generate water pads or "pockets" 113 through a water source 111. The semiconductor structure W is guided between the water pads 113, thereby "clamping" the wafer W in a generally vertical alignment. The wafer is fixed in a carrier ring 122 . Carrier ring 122 (and wafer W held therein) rotates within a hydrostatic guide roller 136 . A pair of first and second grinding wheels 133 , 135 (“left” and “right” grinding wheels) extend across the hydrostatic pads 105 , 110 . The pair of grinding wheels 133, 135 rotate in opposite directions relative to each other. Grinding wheels 133,135 may be connected to air spindles 141,142 and an electric motor rotates grinding wheels 133,135. Grinding wheels 133, 135 may include contact with the full perimeter of the semiconductor structure as they rotate.

In general, the double-side grinding apparatus 100 may be suitable for processing 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 can be a single crystal silicon wafer. In other embodiments, the semiconductor structure is made of silicon carbide, sapphire, or Al ₂ O ₃ . The semiconductor structure may be a layered structure, or may be a bulk wafer.

Figure 2 shows an example of a grinding wheel 200 of the device. Grinding wheel 200 can be used as the first and second grinding wheels of device 100 because the first and second grinding wheels are typically identical. The grinding wheel 200 has an axis of rotation A around which the grinding wheel rotates. The grinding wheel 200 includes a support wheel 208 and a plurality of abrasive members 212 extending axially outward from the support wheel 208 . A plurality of abrasive members 212 extend circumferentially around the support wheel 208 (around circumference C (FIG. 3)).

Abrasive member 212 comprises an abrasive grit material, such as diamond grit or cubic boron nitride (CBN) grit. In some embodiments, the abrasive member comprises vitrified diamond.

The support wheel 208 includes a circumferential groove 215 (eg, formed by a single shoulder or two shoulders formed in the support wheel 208). A plurality of abrasive members 212 are disposed in the circumferential groove 215 . Abrasive member 212 may be attached to support wheel 208 by any method that allows the abrasive wheel to function as described herein. In some embodiments, abrasive member 212 is attached to support wheel 208 by an adhesive. In other embodiments, abrasive member 212 is attached to support wheel 208 by a die. In other embodiments, the abrasive member is attached to a collar (not shown) seated within the circumferential groove.

Referring now to FIGS. 4 to 5 , a grinding wheel 200 according to an embodiment of the present invention is shown. Grinding wheel 200 includes abrasive members 212 each having a wafer bonding surface 225 ( FIG. 6 ) that contacts one of the semiconductor structures during grinding. A gap 219 (FIG. 4) may be formed between abrasive members 212. In other embodiments, no gaps are formed between abrasive members 212 (ie, wafer bonding surface 225 is uniform).

In the illustrated embodiment, the wafer bonding surface 225 is shaped to have a convex polygon with at least five sides. For example, the convex polygon can be a pentagon as shown in the depicted embodiment, or, in other embodiments, a hexagon, heptagon, octagon, or other convex polygon. The convex polygon can be a regular polygon or an irregular polygon.

In some embodiments, as shown in FIG. 6 , the wafer bonding surface 225 includes a base 235 (e.g., the side whose height can be measured, which is generally closest or farthest from the axis of rotation A ( FIG. 4 ) of the grinding wheel 200 ). The second side 239 and the third side 243 extend from the base 235 (also referred to herein as a “first side” of the wafer bonding surface 225 ). The second surface 239 includes a first end 241 and a second end 242 . The second face 239 is connected to the base 235 at its first end 241 . The second surface 239 and the base 235 form an angle λ ₁ . The third surface 243 includes a first end 261 and a second end 263 . The third face 243 is connected to the base 235 at its first end 261 . The third surface 243 and the base 235 form an angle λ ₂ . In some embodiments, each of the first angle λ1 and the _second angle _λ2 is an obtuse angle.

The wafer bonding surface 225 includes a fourth side 250 connected to the first side 239 at a first end 267 of the fourth side 250 . The wafer bonding surface 225 includes a fifth side 255 connected to the second end 243 at a first end 272 of the fifth side 255 . In an embodiment where the convex polygon is a pentagon, the fourth face 250 and the fifth face 255 are connected at the second face 270 , 275 of the fourth face 250 and the fifth face 255 .

The faces 235, 239, 243, 250, 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 side 239 and the third side 243 are each shorter than the base 235 , and the fourth side 250 and the fifth side 255 are each shorter than the base 235 .

As shown in the depicted embodiment, the one or more corners formed between the faces can be rounded (eg, have one or more radii of curvature). For example, the corner 286 formed between the second surface 239 and the fourth surface 250 is rounded, and the corner 288 formed between the third surface 243 and the fifth surface 255 is rounded. In the illustrated embodiment, the corner 290 formed between the fourth side 250 and the fifth side 255 is also rounded (eg, rounded with respect to an apex of the base 235 ). Unless otherwise stated herein, the ends of the various faces of a convex polygon that terminate within a corner may generally correspond to the midpoints of the corner.

In some embodiments, some or even none of the corners are rounded (ie, some or all of the corners 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, a choice between rounded corners and sharp corners (and one or more radii of the rounded corners) can be selected based on the performance of the abrasive member 212 .

Each face 235, 239, 243, 250, 255 of the wafer bonding 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 235 from the axis of rotation A is less than the average distance from the axis of rotation of each of the other faces 239, 243, 250, 255 (i.e., the base 235 is shorter than the other sides of the convex polygon). The plane is closer to the axis of rotation A).

Another embodiment of the grinding wheel 300 is shown in FIGS. 7-8 . Components shown in FIGS. 7-8 that are analogous to those in FIGS. 4-5 are indicated by the corresponding element numbers of FIGS. 4-5 plus "100" (eg, component 212 becomes component 312). In the embodiment of FIGS. 7-8, the orientation of the abrasive member 312 is rotated 180° from the abrasive member 212 of FIGS. 4-6 (compare FIGS. 6 and 9). In the embodiment shown here, the average distance D ₃₃₅ of the base 335 from the axis of rotation A is greater than the average distance from each of the other faces 239, 243, 250, 255 from the axis of rotation A (i.e., the base 235 is larger than the convex polygon). The other faces are farther from the axis of rotation A). Abrasive member 312 may be the same as abrasive member 212 in FIGS. 4-6 except for the orientation of abrasive member 312 .

According to an embodiment of the present invention, a semiconductor structure can be double-sidedly ground by positioning the semiconductor structure between first and second grinding wheels (FIG. 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 (ie, in opposite directions).

The method of the present invention has several advantages over conventional methods for simultaneous double-sided grinding of semiconductor structures. Convex polygonal abrasive members have more abrasive surface area relative to conventional abrasive members used to hold semiconductor structures. This reduces vibration in the horizontal direction and on the slope by the contact grinding wheel. Rotating semiconductor structures can be ground under more balanced conditions and can improve nanoscale surface topography. In addition, steep slope stages along edge regions of semiconductor structures can be improved, and warped regions on lapped wafers can be reduced. Convex polygonal abrasive members can produce less surface damage using less abrasive current. Different shapes or orientations of the convex polygonal abrasive members can be used to create different bending effects in the wafer. The convex polygonal abrasive member can have a relatively uniform porosity over its length, which increases the consistency of the abrasive process. example

The process of the present invention is further illustrated by the following examples. These examples should not be viewed as limiting. Example 1: Modification of Nanosurface Topography by Using a Convex Polygonal Abrasive Member

A first set of semiconductor structures (single crystal silicon wafers) are simultaneously ground on both sides by a grinding wheel with an abrasive member, as shown in FIGS. 4-7 of US Pat. No. 6,692,343. A second set of semiconductor structures (single crystal silicon wafers) are simultaneously ground on both sides by a grinding wheel having a convex polygonal (convex pentagonal) abrasive member. Figure 10 shows the peak-to-valley nanosurface topography, and Figure 11 shows the peak-to-valley of a 10 mm x 10 mm window of one of the wafers. As shown in Figures 10-11, the pentagonal abrasive members have modified nanosurface topography. Example 2: Reduction of Deformed Area by Using a Convex Polygonal Abrasive Member

Figure 12 shows an image of a wafer ground by one of the grinding wheels of Figures 4 through 6 of the present application, the grinding wheel has a pentagonal abrasive member "(1)" and the grinding wheel has the features of US Patent No. 6,692,343 Figures 4 through 6 The abrasive member shown in 7, where "(2)" is a center pattern and "(3)" is an edge pattern. The pentagonal abrasive member is better able to apply a holding force to the rotating wafer surface and maintain the resulting slope without changing the grinding sequence. As shown in FIG. 12, wafers ground with pentagonal abrasive members prevent the generation of distorted regions on the ground wafer, thereby improving nanometer surface topography. Example 3: Varying the Curvature by Using a Convex Polygonal Abrasive Member

For pentagonal abrasive members having one of the bases closest to the axis of rotation of the grinding wheel (“FIGS. 4-5 of the application”), for pentagonal abrasive members with one of the bases farthest 7 to 8") and for the abrasive members shown in Figures 4 to 7 of U.S. Patent No. 6,692,343 ("US 6,692,343"), the center profile (curvature best fits the , CRING) as shown in Figures 13 to 14. Figure 13 shows the measured curvature after double-side grinding, and Figure 14 shows the difference in curvature before and after double-side grinding. The pentagonal abrasive members have different removals, and the grinding wheels have different bending capabilities. Example 4: Reducing Surface Damage by Using a Convex Polygonal Abrasive Member

17 shows cumulative particle count percentages (DIC mode) for the grinding wheel with abrasive members (left row) and the grinding wheel with pentagonal abrasive members (right row) shown in FIGS. 4-7 of US Patent No. 6,692,343. As shown in Figure 17, the pentagonal abrasive members resulted in less surface damage with less grinding current (Figures 15-16). Example 5: Grinding Stability by Using a Convex Polygonal Abrasive Member

Convex polygon wheels involve stable grinding capabilities from the top layer to the bottom layer of the convex polygon structure. As shown in Figure 18, the porosity of the convex polygonal wheel is uniform throughout its length. This is evidenced by Figure 19, which shows that the CRING values for the abrasive members in Figures 4 through 7 of U.S. Patent No. 6,692,343 vary (from low to high and back to low), while the pentagonal abrasive members show consistent values .

As used herein, the terms "about", "substantially", "essentially" and "approximately" when used in connection with a range of size, concentration, temperature or other physical or chemical property or characteristic are meant to encompass Variations in the upper and/or lower bounds of a property or characteristic range, including, for example, changes resulting from rounding, measurement methodologies, or other statistical changes.

When introducing elements of the invention or its embodiment(s), the terms "a/an" and "the/said" are intended to mean that there are one or more of the elements. The terms "comprising", "comprising", "containing" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. The use of terms indicating a particular orientation (eg, "top," "bottom," "side," etc.) is for convenience of description and does not require any particular orientation of the item being described.

As various changes could be made in the above structures and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawing(s) be interpreted as illustrative non-restrictive.

100: double-sided grinding device 105: hydrostatic pad 110: hydrostatic pad 111: water source 113: water pad 122: bearing ring 133: first grinding wheel 135: second grinding wheel 136: hydrostatic guide roller 141: air core Shaft 142: Air Mandrel 200: Grinding Wheel 208: Support Wheel 212: Abrasive Member 215: Circumferential Groove 219: Gap 225: Wafer Bonding Surface 235: Base 239: Second Side 241: First End 242: Second End 243 : Third surface 250: Fourth surface 255: Fifth surface 261: First end 263: Second end 267: First end 270: Second surface 272: First end 275: Second surface 282: Corner 284: Corner 286: Corner 288: Corner 290: Corner 300: Grinding wheel 312: Abrasive member 335: Base A: Rotation axis C: Circumference D ₂₃₅ : Average distance D ₃₃₅ : Average distance W: Wafer λ ₁ : First Angle λ ₂ : second angle

Fig. 1 is a perspective exploded view of a double-sided grinding device;

Fig. 2 is a cross-sectional view of one of the grinding wheels of the double-sided grinding device;

Fig. 3 is a top view of one of the support wheels of the grinding wheel;

One top view of Fig. 4 series grinding wheel;

Figure 5 is a detailed top view of a grinding wheel showing an abrasive member;

Figure 6 is a top view of one of the abrasive components of the grinding wheel;

Fig. 7 is a top view of another embodiment of a grinding wheel;

Figure 8 is a detailed top view of a grinding wheel showing an abrasive member;

Figure 9 is a top view of one of the abrasive members of the grinding wheel;

10 shows a box diagram of the peak-to-valley nanometer surface topography of a semiconductor structure that is simultaneously polished on both sides by a convex polygonal abrasive member and by a conventional abrasive member;

11 shows a box diagram of the peak-to-valley nanosurface topography of a semiconductor structure that is simultaneously polished on both sides by a convex polygonal abrasive member and by a conventional abrasive member in a window of 10 mm x 10 mm;

12 shows a wafer image of a semiconductor structure that is simultaneously ground on both sides by a convex polygonal abrasive member and by a conventional abrasive member;

13 shows a box diagram of a semiconductor structure that is simultaneously ground on both sides by a convex polygonal abrasive member and by a conventional abrasive member;

Fig. 14 shows the box diagram (difference) before and after the change of the curvature of the semiconductor structure that is simultaneously ground on both sides by a convex polygonal abrasive member and by a conventional abrasive member;

Fig. 15 is a time-series diagram of the current of the left grinding wheel of the semiconductor structure of the double-sided grinding by the convex polygon abrasive member and the conventional abrasive member simultaneously;

Fig. 16 is a time-series diagram of the current of the right grinding wheel of the semiconductor structure which is simultaneously ground double-sided by a convex polygonal abrasive member and by a conventional abrasive member;

Figure 17 shows cumulative particle count percentage (DIC mode) for count 0 for a semiconductor structure double sided polished simultaneously by a convex polygonal abrasive member and by a conventional abrasive member;

Figure 18 depicts an image of a convex polygonal abrasive member along its height, demonstrating its porosity; and

Figure 19 is a time series plot of CRING values for convex polygonal abrasive members and conventional abrasive members.

Corresponding element symbols indicate corresponding parts throughout the drawings.

212: Abrasive member

225: Wafer bonding surface

235: base

239: second side

241: first end

242: second end

243: third side

250: The fourth side

255: fifth side

261: first end

263:Second end

267: first end

270: second side

272: first end

275: second side

282: Corner

284: Corner

286: Corner

288: Corner

290: Corner

λ ₁ : first angle

λ ₂ : second angle

Claims (32)

A method for double-sided grinding of a semiconductor structure, the method comprising: The semiconductor structure is positioned between first and second grinding wheels, each grinding wheel comprising: a support wheel; and a plurality of abrasive members extending axially outward from the support wheel, each abrasive member having a wafer engaging surface shaped as a convex polygon having at least five sides; and 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 each other. The method of claim 1, wherein the convex polygon has one or more rounded corners. The method of claim 2, wherein one of the faces of the polygon includes a base and a plurality of faces other than the base, wherein the corners formed between two faces of the polygon other than the base Each of the angles is round. The method according to claim 3, wherein each of the corners formed with the base is an acute corner. The method of claim 1, wherein the abrasive members comprise diamond grit. The method of claim 5, wherein the abrasive members comprise vitrified diamond. The method of claim 1, wherein each abrasive member is connected to the support wheel by an adhesive or a mold. The method of claim 1, wherein the support wheel forms a circumferential groove, and the abrasive members are disposed in the circumferential groove. The method of claim 1, wherein the convex polygon is a convex pentagon. The method of claim 1, wherein the semiconductor structure is fixed by first and second hydrostatic pads. A method for double-sided grinding of a semiconductor structure, the method comprising: The semiconductor structure is positioned between first and second grinding wheels, each grinding wheel comprising: a support wheel; and A plurality of abrasive members extending axially outward from the support wheel, each abrasive member having a wafer engaging surface comprising: a substrate, the substrate being a first side of the wafer bonding surface; a second face having a first end and a second end, the second face being connected to the base at its first end, the second face and base forming an obtuse angle; and a third face having a first end and a second end, the third face being connected to the base at its first end, the third face and base forming an obtuse angle; and 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 each other. The method of claim 11, wherein the wafer bonding surface includes a fourth surface and a fifth surface. The method of claim 11, wherein each grinding wheel has an axis of rotation, each face of the wafer bonding surface has an average distance from the axis of rotation, wherein the average distance of the substrate from the axis of rotation is greater than that of the other faces the average distance of each from the axis of rotation. The method of claim 11, wherein each grinding wheel has an axis of rotation, and each face of the wafer bonding surface has an average distance from the axis of rotation, wherein the average distance of the base from the axis of rotation is less than that of the other faces the average distance of each from the axis of rotation. The method of claim 11, wherein the wafer bonding surface has one or more rounded corners. The method of claim 15, wherein the corner formed between the base and the second face is not rounded, and the corner formed between the base and the third face is not rounded. The method according to claim 11, wherein the wafer bonding surface is pentagonal and includes a fourth surface and a fifth surface. The method of claim 11, wherein the abrasive members comprise diamond grit. The method of claim 18, wherein the abrasive members comprise vitrified diamond. The method of claim 11, wherein each abrasive member is connected to the support wheel by an adhesive or a mold. The method of claim 11, wherein the support wheel forms a circumferential groove, and the abrasive members are disposed in the circumferential groove. The method of claim 11, wherein the semiconductor structure is fixed by first and second hydrostatic pads. A double-sided grinding device, comprising: First and second grinding wheels, each grinding wheel having an axis of rotation, and comprising: a support wheel; and A plurality of abrasive members extending axially outward from the support wheel, each abrasive member having a wafer engaging surface comprising: a substrate, the substrate being a first side of the wafer bonding surface; a second face having a first end and a second end, the second face being connected to the base at its first end, the second face and the base forming an obtuse angle; and a third face having a first end and a second end, the third face being connected to the base at its first end, the third face and base forming an obtuse angle; and Each face of the wafer bonding surface has an average distance from the axis of rotation, wherein the average distance of the substrate from the axis of rotation is less than the average distance of each of the other faces from the axis of rotation. The double-sided grinding device according to claim 23, wherein the wafer bonding surface includes a fourth surface and a fifth surface. The double-sided lapping device according to claim 23, wherein the wafer bonding surface has one or more rounded corners. The double-sided grinding device according to claim 25, wherein the corner formed between the base and the second surface is not rounded, and the corner formed between the base and the third surface is not rounded. The double-sided grinding device according to claim 23, wherein the wafer bonding surface is pentagonal and includes a fourth surface and a fifth surface. The double-sided grinding device according to claim 23, wherein the abrasive members include diamond grit. The double-sided grinding device of claim 28, wherein the abrasive members include vitrified diamond. The double-sided grinding device according to claim 23, wherein the support wheel forms a circumferential groove, and the abrasive members are placed in the circumferential groove. The double-sided grinding device according to claim 23, wherein the support wheel forms a circumferential groove, and the collar is placed in the circumferential groove. The double-sided polishing device according to claim 23, further comprising first and second hydrostatic pads for fixing the semiconductor structure.

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