TW202303729A - Processing method of wafer - Google Patents

Abstract

A processing method for a wafer includes detecting the bow of the wafer, wherein the wafer has a first surface and a second surface opposite to the first surface, wherein the first surface is a concave surface and the second surface is a convex surface; performing a medium-grinding process on the first surface and the second surface to obtain a medium-grinded first surface and a medium-grinded second surface; sequentially performing a fine-grinding process to the medium-grinded first surface and the medium-grinded second surface to obtain a fine-grinded first surface and a fine-grinded second surface.

Description

Wafer processing method

The present invention relates to a wafer, and in particular to a wafer processing method.

In the semiconductor industry, before the epitaxial layer or other film layers are formed on the wafer, the surface of the wafer needs to be ground, so as to adjust the thickness of the wafer and make the surface of the wafer more smooth. However, in the existing grinding process, after the wafer is ground, the surface of the wafer will be damaged, and the residual stress generated by the damage will increase the bow of the wafer (Bow). If the front and back sides of the wafer are ground many times, the wafer is prone to fatigue failure due to repeated changes in curvature.

The invention provides a wafer processing method, which can improve the problem of fatigue damage of the wafer after processing.

At least one embodiment of the present invention provides a wafer processing method, comprising: detecting the curvature of the wafer, wherein the wafer has a first surface and a second surface opposite to the first surface, wherein the first surface is a concave surface, and The second surface is a convex surface; the first surface and the second surface are subjected to an intermediate grinding process in order to obtain an intermediately ground first surface and an intermediately ground second surface, wherein the intermediate grinding process includes: grinding with a first grinding wheel The first side and the second side, wherein the grain size number of the first grinding wheel is #12000 to #15000, and the rotation speed of the first grinding wheel is 3500rpm to 4000rpm; A fine grinding process is performed on the medium ground second surface to obtain a fine ground first surface and a fine ground second surface, wherein the fine grinding process comprises: grinding the medium ground first surface and the The second surface of medium grinding, wherein the grain size number of the second grinding wheel is #27000 to #30000, and the rotation speed of the second grinding wheel is 2033rpm to 2133rpm.

At least one embodiment of the present invention provides a wafer processing method, comprising: detecting the curvature of the wafer, wherein the wafer has a first surface and a second surface opposite to the first surface, wherein the first surface is a concave surface, and The second surface is a convex surface; the first surface and the second surface are subjected to an intermediate grinding process in order to obtain an intermediately ground first surface and an intermediately ground second surface, wherein the intermediate grinding process includes: grinding with a first grinding wheel The first side and the second side, wherein the grain size number of the first grinding wheel is #12000 to #15000, and the rotation speed of the first grinding wheel is 3500rpm to 4000rpm; A fine grinding process is carried out on the second surface through the middle grinding, wherein the fine grinding process includes: fixing the wafer on the working platform, wherein the second surface through the middle grinding faces the working platform; grinding the first surface through the middle grinding with the second grinding wheel. face, to obtain a finely ground first face, wherein the grit number of the second grinding wheel is greater than that of the first grinding wheel, and the rotational speed of the second grinding wheel is 2033rpm to 2133rpm, and wherein the rotational speed of the working platform is 149rpm to 199rpm; overturn and re-fixing the wafer on the workbench with the finely ground first side facing the workbench; and grinding the center ground second side with a second grinding wheel to obtain the finely ground second side , wherein the rotational speed of the working platform is 149 rpm to 199 rpm, and the rotational speed of the working platform is not a factor of the rotational speed of the second grinding wheel.

1A to 1I are schematic cross-sectional views of a wafer processing method according to an embodiment of the present invention.

Referring to FIG. 1A , the wafer 10 has a first surface S1 and a second surface S2 opposite to the first surface S1 . The material of the wafer 10 includes, for example, silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), indium antimonide (InSb), gallium nitride (GaN), silicon carbide (SiC) or zinc selenide ( ZnSe).

In this embodiment, the method for manufacturing the wafer 10 includes forming an ingot first, and then dicing the ingot to obtain the wafer 10 . Crystal anchors are manufactured, for example, in a high-temperature environment. In some instances, an anchor may cause residual stress due to temperature differences at different locations during the manufacturing process. These residual stresses will bend the wafer 10 obtained after dicing the anchor.

In this embodiment, after the wafer 10 is obtained by dicing the anchor, the bow of the wafer 10 is detected. After inspection of the wafer 10 , it is found that the first surface S1 is concave, and the second surface S2 is convex. In some embodiments, the wafer 10 is a silicon carbide wafer, the first surface S1 is a silicon surface, and the second surface S2 is a carbon surface, but the invention is not limited thereto. In other embodiments, the second surface S2 is a silicon surface, and the first surface S1 is a carbon surface.

Referring to FIG. 1B to FIG. 1E , the first surface S1 and the second surface S2 are sequentially subjected to a medium grinding process to obtain a medium ground first surface S1' and a medium ground second surface S2'. The intermediate grinding process includes grinding the first surface S1 and the second surface S2 with the first grinding wheel 210 . The grain size number of the first grinding wheel 210 is #12000 to #15000 (the corresponding abrasive grain size is 140 microns to 130 microns), and the rotation speed of the first grinding wheel 210 is 3500 rpm to 4000 rpm. In this embodiment, when performing the middle grinding process, the feed rate applied by the first grinding wheel 210 to the wafer 10 is 0.15 microns to 0.17 microns.

Please refer to FIG. 1B and FIG. 1C , firstly, the wafer 10 is placed on the working platform 100 , wherein the second surface S2 faces the working platform 100 , and the first surface S1 faces away from the working platform 100 .

The first surface S1 is ground with the first grinding wheel 210 . For example, the first grinding wheel 210 is driven to rotate by the grinding head 200, and a force is applied to the first grinding wheel 210 toward the first surface S1, thereby grinding the first surface S1 to obtain a center-ground first surface S1'.

In this embodiment, both the first grinding wheel 210 and the working platform 100 can rotate. For example, the first grinding wheel 210 rotates clockwise or counterclockwise, and the rotation speed is 3500 rpm to 4000 rpm. The working platform 100 rotates clockwise or counterclockwise at a speed of 200 rpm to 250 rpm.

In this embodiment, the rotational speed of the first grinding wheel 210 is 3500rpm to 4000rpm, and the rotational speed of the first grinding wheel 210 is related to the force (pressure) applied to the wafer 10 by the first grinding wheel 210, and the first grinding wheel 210 is applied to the wafer 10 The smaller the pressure is, the faster the rotation speed of the first grinding wheel 210 is. If too much pressure is exerted on the surface of the wafer 10 , the rotation speed of the first grinding wheel 210 is too slow, and the curvature of the wafer 10 after grinding changes greatly, which makes the wafer 10 more prone to fatigue damage. If too little pressure is caused on the surface of the wafer 10, so that the rotating speed of the first grinding wheel 210 is too fast, then the total thickness variation (TTV) of the wafer 10 is insufficient, so that the surface of the wafer 10 is not smooth enough (the surface roughness (Ra) is too high. big).

In this embodiment, after the first surface S1 is ground by the first grinding wheel 210 , the thickness of the wafer 10 is reduced by tens of micrometers (eg, 20 micrometers), but the invention is not limited thereto. The desired reduced thickness of the wafer 10 after grinding can be changed according to requirements.

Please refer to FIG. 1D and FIG. 1E, then, flip the wafer 10, and re-fix the wafer 10 on the working platform 100, wherein the first side S1' of the center grinding is facing the working platform 100, and the second side S2 is facing away from the working platform. Work platform 100.

The second surface S2 is ground with the first grinding wheel 210 . For example, the first grinding wheel 210 is driven to rotate by the grinding head 200, and a force is applied to the first grinding wheel 210 toward the second surface S2, thereby grinding the second surface S2 to obtain a center-ground second surface S2'.

In this embodiment, both the first grinding wheel 210 and the working platform 100 can rotate. For example, the first grinding wheel 210 rotates clockwise or counterclockwise, and the rotation speed is 3500 rpm to 4000 rpm. The working platform 100 rotates clockwise or counterclockwise at a speed of 200 rpm to 250 rpm.

In this embodiment, after the second surface S2 is ground by the first grinding wheel 210 , the thickness of the wafer 10 is reduced by tens of micrometers (eg, 20 micrometers), but the invention is not limited thereto. The desired reduced thickness of the wafer 10 after grinding can be changed according to requirements.

Please refer to FIG. 1E to FIG. 1I. After the medium grinding process, the medium ground first surface S1' and the medium ground second surface S2' are subjected to a fine grinding process in order to obtain a finely ground first surface. S1'' and a finely ground second surface S2''. The fine grinding process includes grinding the center-ground first surface S1' and the center-ground second surface S2' with the second grinding wheel 210a. The grain size number of the second grinding wheel 210a is #27000 to #30000 (the corresponding abrasive grain size is 60 microns to 50 microns), and the rotation speed of the second grinding wheel 210a is 2033 rpm to 2133 rpm. In this embodiment, when the fine grinding process is performed, the feed amount applied to the wafer 10 by the second grinding wheel 210 a is 0.1 micron to 0.12 micron.

In this embodiment, the rotational speed of the second grinding wheel 210a during the fine grinding process is lower than that of the first grinding wheel 210 during the medium grinding process, and the rotational speed of the working platform 100 during the fine grinding process is lower than that of the working platform 100 during the medium grinding process.

Referring to FIG. 1F and FIG. 1G , the wafer 10 is fixed on the working platform 100 . The middle-ground second surface S2' faces the working platform 100, and the middle-ground first surface S1' faces away from the working platform 100.

The medium-ground first surface S1' is ground with the second grinding wheel 210a to obtain a fine-ground first surface S1''. For example, the second grinding wheel 210a is driven to rotate by the grinding head 200, and a force is applied to the second grinding wheel 210a toward the first surface S1' that is ground through the middle, thereby grinding the first surface S1' through the middle grinding to obtain the through-grinding surface S1'. Finely ground first side S1''.

In this embodiment, both the second grinding wheel 210a and the working platform 100 can rotate. For example, the second grinding wheel 210a rotates clockwise or counterclockwise, and the rotation speed is 2033 rpm to 2133 rpm. The working platform 100 rotates clockwise or counterclockwise at a speed of 149 rpm to 199 rpm. In this embodiment, the rotation speed of the second grinding wheel 210a cannot be divided by the rotation speed of the working platform 100, that is, the rotation speed of the working platform 100 is not a factor of the rotation speed of the second grinding wheel 210a, thereby improving the fineness of the wafer 10 after grinding.

In this embodiment, the thickness of the wafer 10 is reduced by tens of micrometers (for example, 10 micrometers) after the center-ground first surface S1' is ground by the second grinding wheel 210a, but the invention is not limited thereto. The desired reduced thickness of the wafer 10 after grinding can be changed according to requirements.

Please refer to FIG. 1H and FIG. 1I, turn over the wafer 10, and re-fix the wafer 10 on the working platform 100, wherein the finely ground first side S1'' faces the working platform 100, and the middle ground second side S2 ′ faces away from the working platform 100 .

The medium-ground second surface S2' is ground with the second grinding wheel 210a to obtain a fine-ground second surface S2''. For example, the second grinding wheel 210a is driven to rotate by the grinding head 200, and a force is applied to the second grinding wheel 210a toward the second surface S2' through the middle grinding, thereby grinding the second surface S2' through the middle grinding to obtain the second grinding wheel 210a. Finely ground second side S2''.

In this embodiment, both the second grinding wheel 210a and the working platform 100 can rotate. For example, the second grinding wheel 210a rotates clockwise or counterclockwise, and the rotation speed is 2033 rpm to 2133 rpm. The working platform 100 rotates clockwise or counterclockwise at a speed of 149 rpm to 199 rpm. In this embodiment, the rotation speed of the second grinding wheel 210a cannot be divided by the rotation speed of the working platform 100, that is, the rotation speed of the working platform 100 is not a factor of the rotation speed of the second grinding wheel 210a, thereby improving the fineness of the wafer 10 after grinding.

In this embodiment, the thickness of the wafer 10 is reduced by tens of micrometers (for example, 10 micrometers) after the second grinding wheel 210a is used to grind the center-ground second surface S2', but the invention is not limited thereto. In this embodiment, the thickness of the wafer 10 removed by the fine grinding process is less than the thickness of the wafer 10 removed by the medium grinding process.

Based on the above, since the present embodiment starts grinding from the concave surface (the first surface S1 ), it can reduce the variation of the curvature of the wafer 10 after the grinding process, thereby reducing the problem of fatigue failure of the wafer 10 after grinding. In addition, the present embodiment begins to grind the wafer 10 with the medium grinding process, which is compared with the coarse grinding process (the grain size of the grinding wheel is #12000 to #15000, and the corresponding abrasive particle size is 140 microns to 130 microns) The processing damage caused to the surface of the wafer 10 is smaller, so it can reduce the damage difference between the first surface S1 and the second surface S2 of the wafer 10 after processing, and further avoid the damage caused by the first surface S1 and the second surface S2. The difference is too large to cause the problem of wafer 10 bowing.

FIG. 2A is a flowchart of a wafer processing method according to an embodiment of the present invention. FIG. 2B is a schematic cross-sectional view of a wafer according to an embodiment of the invention. FIG. 2C is a schematic cross-sectional view of a wafer according to an embodiment of the invention.

Please refer to FIGS. 2A , 2B and 2C to detect the curvature of the wafers 20 and 30 . In this embodiment, the silicon side SiS of the wafers 20 and 30 faces up, and the carbon side CS faces down.

If the curvature of the wafer 20 is positive, as shown in FIG. 2B . The silicon side SiS of the wafer 20 is convex, and the carbon side CS is concave. The carbon-surface CS and the silicon-surface SiS are medium-polished sequentially, and then the carbon-surface CS and the silicon-surface SiS are finely ground sequentially.

If the curvature of the wafer 30 is a negative value, as shown in FIG. 2C . The silicon surface SiS of the wafer 30 is concave, and the carbon surface CS is convex. The silicon surface SiS and the carbon surface CS are subjected to intermediate grinding in sequence, and then the silicon surface SiS and the carbon surface CS are subjected to fine grinding in sequence.

Based on the above, since the present embodiment starts grinding from the concave surface first, the variation of the curvature of the wafers 20 and 30 after the grinding process can be reduced, thereby reducing the problem of fatigue damage of the wafers 20 and 30 after grinding.

FIG. 3 is a broken line diagram of tortuosity of wafer processing methods according to some embodiments of the present invention and some comparative examples. The vertical axis of Fig. 3 represents the curvature of the wafer (unit: micron). The horizontal axis of Fig. 3 represents different times of grinding. For example, for the first medium grinding, refer to the relevant descriptions of Fig. 1B and Fig. 1C, for the second medium grinding, refer to the relevant descriptions of Fig. For the second fine grinding, refer to the related descriptions of FIG. 1F and FIG. 1G , and for the second fine grinding, refer to the related descriptions of FIG. 1H and FIG. 1I .

Please refer to FIG. 3 , in the first embodiment, before the grinding process, the curvature of the wafer during inspection is a positive value. For example, referring to FIG. 2B for the wafer of the first embodiment, the wafer 20 is silicon carbide, and the carbon surface CS is concave and the silicon surface SiS is convex. In Embodiment 1, the first medium grinding grinds the carbon surface CS, the second medium grinding grinds the silicon surface SiS, the first fine grinding grinds the medium ground carbon surface CS, and the second fine grinding grinds the medium ground SiS. Silicon surface SiS.

In the second embodiment, before the grinding process, the curvature of the wafer during detection is a negative value. For example, referring to FIG. 2C for the wafer of the second embodiment, the wafer 30 is silicon carbide, and the carbon surface CS is convex and the silicon surface SiS is concave. In Example 2, the first medium grinding grinds the silicon surface SiS, the second medium grinding grinds the carbon surface CS, the first fine grinding grinds the medium ground silicon surface SiS, and the second fine grinding grinds the medium ground CS. Carbon Surface CS.

FIG. 4 is a broken line diagram of the tortuosity of wafer processing methods according to some embodiments of the present invention and some comparative examples. The vertical axis of Fig. 4 represents the curvature of the wafer (unit: micron). The horizontal axis of Figure 4 represents different times of grinding. For example, the first rough grinding and the second rough grinding use grinding wheels with grit numbers of #6000 to #8000 to grind both sides of the wafer respectively, and the first The fine grinding and the second fine grinding are respectively used to grind both sides of the wafer with a grinding wheel with a grit number of #27000 to #30000.

In Comparative Example 1, before the grinding process, the curvature of the wafer during inspection is a positive value. For example, referring to FIG. 2B for the wafer of Comparative Example 1, the wafer 20 is silicon carbide, and the carbon surface CS is concave and the silicon surface SiS is convex. In Comparative Example 1, the first coarse grinding grinds the carbon surface CS, the second rough grinding grinds the silicon surface SiS, the first fine grinding grinds the coarsely ground carbon surface CS, and the second fine grinding grinds the coarsely ground SiS. Silicon surface SiS.

In Comparative Example 2, before the grinding process, the curvature of the wafer during inspection is positive. For example, referring to FIG. 2B for the wafer of Comparative Example 2, the wafer 20 is silicon carbide, and the carbon surface CS is concave and the silicon surface SiS is convex. In Comparative Example 2, the first coarse grinding grinds the silicon surface SiS, the second rough grinding grinds the carbon surface CS, the first fine grinding grinds the coarsely ground silicon surface SiS, and the second fine grinding grinds the coarse ground CS. Carbon Surface CS.

Comparing Example 1, Example 2, Comparative Example 1 and Comparative Example 2, it can be seen that in Example 1 and Example 2, the middle grinding process is used instead of the rough grinding process, which can reduce the variation of the curvature of the wafer, thereby avoiding the There is a problem of fatigue damage. In some embodiments, the curvature of the wafer varies by less than 30 microns before and after performing the grinding process. In some embodiments, the curvature of the wafer varies by less than 15 microns before and after performing the fine grinding process.

In addition, if both the intermediate grinding process and the coarse grinding process are omitted, that is, the silicon surface SiS and the carbon surface CS are directly processed by the fine grinding process, more repeated fine grinding processes are required. Specifically, due to the smaller removal amount of the fine grinding process, in the case of the same amount of unevenness on the wafer 20, more fine grinding processes need to be performed compared to the medium grinding process and the coarse grinding process. To remove the uneven area on the wafer 20 . Based on the foregoing, if the wafer 20 is directly processed by a fine grinding process, more repeated processing of the silicon surface SiS and the carbon surface CS will be required, resulting in repeated bending of the wafer 20 . Therefore, directly processing the wafer 20 through the fine grinding process will not only make the processing time longer, but also the wafer 20 will be easily broken due to more repeated bending times.

10:Wafer 100: work platform S1: the first surface (concave) S1': the second side that is medium ground S1'': Finely ground first side S2: second side (convex) S2': The second side of the medium ground S2'': Second side finely ground 200: grinding head 210: The first grinding wheel 210a: second grinding wheel

1A to 1I are schematic cross-sectional views of a wafer processing method according to an embodiment of the present invention. FIG. 2A is a flowchart of a wafer processing method according to an embodiment of the present invention. FIG. 2B is a schematic cross-sectional view of a wafer according to an embodiment of the invention. FIG. 2C is a schematic cross-sectional view of a wafer according to an embodiment of the invention. FIG. 3 is a broken line diagram of tortuosity of wafer processing methods according to some embodiments of the present invention and some comparative examples. FIG. 4 is a broken line diagram of the tortuosity of wafer processing methods according to some embodiments of the present invention and some comparative examples.

Claims (11)

A method for processing a wafer, comprising: detecting curvature of a wafer, wherein the wafer has a first surface and a second surface opposite the first surface, wherein the first surface is concave and the second surface is convex; Sequentially performing a grinding process on the first surface and the second surface to obtain a medium ground first surface and a medium ground second surface, wherein the medium grinding process includes: Grinding the first surface and the second surface with a first grinding wheel, wherein the grain size of the first grinding wheel is #12000 to #15000, and the rotation speed of the first grinding wheel is 3500rpm to 4000rpm; After the medium grinding process, a fine grinding process is performed on the medium ground first surface and the medium ground second surface in order to obtain a finely ground first surface and a finely ground second surface , wherein the fine grinding process includes: Grinding the center-ground first surface and the center-ground second surface with a second grinding wheel, wherein the grain size of the second grinding wheel is #27000 to #30000, and the rotation speed of the second grinding wheel is 2033rpm to 2133rpm . The processing method of wafer as described in claim 1, wherein the grinding process comprises: fixing the wafer on a working platform, wherein the second side faces the working platform; Grinding the first surface with the first grinding wheel to obtain the center-ground first surface, wherein the rotating speed of the working platform is 200rpm to 250rpm; flipping the wafer over and re-mounting the wafer on the workbench with the center ground first side facing the workbench; and Grinding the second surface with the first grinding wheel to obtain the center-ground second surface, wherein the rotating speed of the working platform is 200 rpm to 250 rpm. The processing method of wafer as described in claim 1, wherein the fine grinding process comprises: fixing the wafer on a working platform, wherein the center-ground second side faces the working platform; Grinding the mid-ground first surface with the second grinding wheel to obtain the finely ground first surface, wherein the rotating speed of the working platform is 149rpm to 199rpm; flipping the wafer over and re-mounting the wafer on the workbench with the finely ground first side facing the workbench; and Grinding the middle-ground second surface with the second grinding wheel to obtain the fine-ground second surface, wherein the rotating speed of the working platform is 149 rpm to 199 rpm. The wafer processing method as claimed in claim 3, wherein the rotation speed of the working platform is not a factor of the rotation speed of the second grinding wheel. The wafer processing method according to claim 1, wherein the wafer is a silicon carbide wafer, the first surface is a silicon surface, and the second surface is a carbon surface. The wafer processing method according to claim 1, wherein the wafer is a silicon carbide wafer, the second surface is a silicon surface, and the first surface is a carbon surface. The wafer processing method according to claim 1, wherein when performing the middle grinding process, the feed rate applied to the wafer by the first grinding wheel is 0.15 microns to 0.17 microns. The wafer processing method according to claim 1, wherein when performing the fine grinding process, the feed rate applied to the wafer by the second grinding wheel is 0.1 micron to 0.12 micron. The wafer processing method as claimed in claim 1, wherein the variation of the curvature of the wafer before and after performing the grinding process is less than 30 microns. The wafer processing method as claimed in claim 1, wherein the variation of the curvature of the wafer before and after the fine grinding process is less than 15 microns. A method for processing a wafer, comprising: detecting curvature of a wafer, wherein the wafer has a first surface and a second surface opposite the first surface, wherein the first surface is concave and the second surface is convex; Sequentially performing a grinding process on the first surface and the second surface to obtain a medium ground first surface and a medium ground second surface, wherein the medium grinding process includes: Grinding the first surface and the second surface with a first grinding wheel, wherein the grain size of the first grinding wheel is #12000 to #15000, and the rotation speed of the first grinding wheel is 3500rpm to 4000rpm; After the medium grinding process, a fine grinding process is performed on the medium ground first surface and the medium ground second surface in sequence, wherein the fine grinding process includes: fixing the wafer on a work platform, wherein the center ground second side faces the work platform; Grinding the intermediate ground first side with a second grinding wheel having a larger grit number than the first grinding wheel to obtain a finely ground first side, and the second grinding wheel having a rotational speed of 2033 rpm to 2133rpm, and wherein the rotational speed of the working platform is from 149rpm to 199rpm; flipping the wafer over and re-mounting the wafer on the workbench with the finely ground first side facing the workbench; and grinding the mid-ground second surface with the second grinding wheel to obtain a finely ground second surface, wherein the rotational speed of the working platform is 149 rpm to 199 rpm, and the rotational speed of the working platform is not the rotational speed of the second grinding wheel factor.

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