Retaining ring for polishing and method for polishing wafer

Abstract

The invention provides a holding ring for polishing and a method of polishing a wafer. The retaining ring for grinding surrounds and fastens a wafer to be ground, the retaining ring is made of a wear-resistant material, the surface of one side or two sides of the retaining ring is in a periodic fluctuating shape, and the fluctuating period is consistent with the crystal phase distribution period of the wafer to be ground. The surface of the side, facing the grinding pad, of the retaining ring is in a periodic fluctuating shape, and the fluctuating period is consistent with the crystal phase distribution period of the wafer to be ground. Due to the correction effect of the thickness of the retaining ring, the thickness deviation caused by the crystal phase problem can be compensated, and a flatter surface can be obtained in a global range.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor processing, and in particular to a grinding retaining ring and a method for grinding a wafer. Background Art

[0002] Chemical mechanical grinding, also known as chemical mechanical polishing, is a processing technology that combines chemical corrosion and mechanical removal. It is a technology in semiconductor processing technology that can achieve global surface flattening.

[0003] Chemical mechanical polishing technology combines the advantages of chemical polishing and mechanical polishing. Pure chemical polishing has high surface accuracy, low damage, good integrity, and is not prone to surface / subsurface damage, but the polishing rate is slow, the material removal efficiency is low, the surface profile accuracy cannot be corrected, and the polishing consistency is relatively poor; pure mechanical polishing has good polishing consistency, high surface flatness, and high polishing efficiency, but it is prone to surface layer / subsurface layer damage and the surface roughness value is relatively low. Chemical mechanical polishing absorbs the advantages of both, and can obtain a more perfect surface while ensuring material removal efficiency. The flatness obtained is 1-2 orders of magnitude higher than that of using these two types of polishing alone, and can achieve surface roughness from nanometer level to atomic level.

[0004] As can be seen from the above description, the grinding process uses physical and chemical methods to achieve global surface flatness. Therefore, how to obtain a flatter surface on a global scale has always been a problem that needs to be solved in the prior art. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a grinding retaining ring and a method for grinding a wafer, which can obtain a flatter surface in the global range.

[0006] In order to solve the above problems, the present invention provides a grinding retaining ring, which is arranged around and tightly fixes the wafer to be ground. The retaining ring is made of wear-resistant material and has periodic undulations on one or both sides of the surface, and the period of the undulations is consistent with the distribution period of the crystal phase of the wafer to be ground.

[0007] Optionally, the wafer to be ground is in (100) crystal phase, the retaining ring has an undulation period of 90° at the central angle, and the lowest point is aligned with a positioning mark of the wafer.

[0008] Optionally, the wear-resistant material is an engineering plastic selected from one of polyetheretherketone, polyphenylene sulfide, polyimide, and polyethylene terephthalate.

[0009] Optionally, the grinding is chemical mechanical polishing.

[0010] In order to solve the above problems, the present invention provides a method for grinding wafers, comprising: providing a wafer to be ground; surrounding and tightening a retaining ring around the wafer to be ground, wherein the retaining ring is made of wear-resistant material and has periodic undulations on one side or both sides of the surface, and the period of the undulations is consistent with the distribution period of the crystal phase of the wafer to be ground; grinding the wafer to be ground with the retaining ring.

[0011] Optionally, the wafer to be ground is in (100) crystal phase, and the retaining ring has an undulation period of 90° at the central angle.

[0012] Optionally, the wear-resistant material is an engineering plastic selected from one of polyetheretherketone, polyphenylene sulfide, polyimide, and polyethylene terephthalate.

[0013] Optionally, the grinding is chemical mechanical polishing.

[0014] The surface of the retaining ring on the side facing the grinding pad of the present invention presents periodic undulations, and the period of the undulations is consistent with the distribution period of the crystal phase of the wafer to be ground. Due to the correction effect of the thickness of the retaining ring, the thickness deviation caused by the crystal phase problem can be compensated, and a flatter surface can be obtained in the global range. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Attached Figure 1 Shown is a schematic structural diagram of a polishing device according to a specific embodiment of the present invention.

[0016] Attached Figure 2 Shown is a schematic structural diagram of a grinding head according to a specific embodiment of the present invention.

[0017] Attached Figure 3 A schematic diagram showing the periodic variation of the relative thickness of the retaining ring according to a specific embodiment of the present invention is shown.

[0018] Attached Figure 4 Shown is a schematic structural diagram of a grinding device according to a specific embodiment of the present invention.

[0019] Attached Figure 5 Shown is a schematic diagram of the relative structure between a wafer to be ground and a retaining ring according to a specific embodiment of the present invention.

[0020] Attached Figure 6 Shown is a schematic diagram of the implementation steps of the grinding method described in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0021] The specific implementation of the grinding retaining ring and the method for grinding a wafer provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Attached Figure 1FIG. 1 is a schematic diagram of the structure of a polishing device according to a specific embodiment of the present invention, Figure 2 Shown is a schematic diagram of the structure of the grinding head.

[0023] Reference Figure 1 As shown, the polishing equipment is a single-sided polishing machine, including a platform 10, a grinding pad 11 and a grinding head 12. The grinding pad 11 is laid on the surface of the platform 10 and can rotate or remain stationary. The grinding head 12 contacts the grinding pad 12 in the form of a certain pressure, and the grinding head 12 can rotate and revolve on the surface of the platform 10. The wafer to be polished is placed between the grinding pad 11 and the grinding head 12. Polishing liquid is further dripped between the grinding pad 11 and the grinding head 12 for chemical mechanical polishing.

[0024] Continue to refer to the attached Figure 2 As shown, a wafer 13 to be ground is disposed below the grinding head 12, and a retaining ring 14 is disposed around and fastened to the wafer 13 to be ground. In this specific embodiment, the retaining ring 14 presents periodic undulations on the surface facing the grinding pad 11, and the period of the undulations is consistent with the distribution period of the crystal phase of the wafer 13 to be ground. In this specific embodiment, the wafer 13 to be ground is a (100) crystal phase, and the retaining ring 14 has an undulation period of 90° at the central angle, and the lowest point is aligned with the positioning mark of the wafer. Figure 3 The diagram shows the periodic variation of the relative thickness of the retaining ring 14 along the circumferential direction, with the center angle of the circle starting from the alignment mark, from 0° to 360°. Due to the thickness correction effect of the retaining ring 14, the thickness deviation caused by the crystal phase problem can be compensated, and a flatter surface can be obtained in the global range.

[0025] The material of the retaining ring 14 is preferably engineering plastic, including one of polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyimide (PAI), and polyethylene terephthalate (PETP). The above materials can keep the retaining ring 14 at a constant height during the grinding process, so as to correct the thickness of the wafer 13 to be ground.

[0026] Attached Figure 4 FIG. 1 is a schematic diagram of the structure of a grinding device according to a specific embodiment of the present invention. Figure 5 The figure shows the relative structure between the wafer to be ground and the retaining ring. Figure 4 As shown, the polishing device is a double-sided grinding machine, including an upper polishing plate 21, a lower polishing plate 22, a center wheel 23 and an outer gear 24. A planetary wheel 25 is arranged between the upper polishing plate 21 and the lower polishing plate 22, and a wafer 26 to be polished is placed in the inner cavity of the planetary wheel 25. A retaining ring 27 is arranged around and fastened to the wafer 26 to be polished.

[0027] An upper grinding pad 211 and a lower grinding pad 221 are respectively arranged on the two opposite surfaces of the upper throwing disc 21 and the lower throwing disc 22. The upper throwing disc 21, the lower throwing disc 22, the center wheel 23 and the outer gear 24 rotate at a set angular speed. The upper throwing disc 21 and the lower throwing disc 22 rotate in opposite directions, and the center wheel 23 and the outer gear 24 rotate in opposite directions. Polishing liquid is further dripped between the upper throwing disc 21 and the lower throwing disc 22 for chemical mechanical grinding. The above device can perform double-sided grinding and thinning on the wafer 26 to be ground.

[0028] In this specific embodiment, the surfaces on both sides of the retaining ring present periodic undulations, and the undulation period is consistent with the distribution period of the crystal phase of the wafer 26 to be ground. In this specific embodiment, the wafer 26 to be ground is a (100) crystal phase, and the retaining ring 27 has an undulation period of 90° at the central angle, and the lowest point is aligned with the positioning mark of the wafer. The undulation state is the same as that in the attached figure. Figure 3 The situation shown in the figure is the same on both sides. A schematic diagram of the periodic change of the relative thickness of the retaining ring 27 along the circumferential direction, with the center angle of the circle starting from the alignment mark, from 0° to 360°. Due to the correction effect of the thickness of the retaining ring 27, the thickness deviation caused by the crystal phase problem can be compensated, and a flatter surface can be obtained in the global range.

[0029] The material of the retaining ring 27 is preferably engineering plastic, including one of polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyimide (PAI), and polyethylene terephthalate (PETP). The above materials can keep the retaining ring 27 at a constant height during the grinding process, so as to correct the thickness of the wafer 26 to be ground.

[0030] Next, the specific implementation of the grinding method of the present invention is given in conjunction with the accompanying drawings. Figure 6 The figure is a schematic diagram of the implementation steps of the present specific embodiment, including: step S10, providing a wafer to be ground; step S11, surrounding and fastening a retaining ring around the wafer to be ground, wherein the retaining ring is made of wear-resistant material and has a periodic undulation on the surface of at least one side, and the period of the undulation is consistent with the distribution period of the crystal phase of the wafer to be ground; and step S12, grinding the wafer to be ground with the retaining ring.

[0031] Step S10, providing a wafer to be ground. In this specific embodiment, the wafer to be ground is in a (100) crystal phase, and the grinding is preferably performed by chemical mechanical polishing (CMP).

[0032] Step S11, surround and tighten a retaining ring around the wafer to be ground, the retaining ring is made of wear-resistant material, and the surface on one or both sides presents periodic undulations, and the period of undulations is consistent with the distribution period of the crystal phase of the wafer to be ground. Single-sided polishing corresponds to single-sided polishing, and double-sided polishing corresponds to double-sided polishing. The retaining ring has an undulation period of 90° at the central angle, and the lowest point is aligned with the positioning mark of the wafer.

[0033] Step S12, grinding the wafer to be ground with the retaining ring. In this step, due to the correction effect of the thickness of the retaining ring, the thickness deviation caused by the crystal phase problem can be compensated, and a flatter surface can be obtained in the global range.

[0034] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A grinding retaining ring, characterized in that: The retaining ring is arranged to surround and fasten the wafer to be ground. The retaining ring is made of wear-resistant material and has a surface on one side or both sides that presents periodic undulations. The period of the undulations is consistent with the distribution period of the crystal phase of the wafer to be ground.

2. The grinding retaining ring according to claim 1, characterized in that: The wafer to be ground is in (100) crystal phase, the retaining ring has an undulation period of 90° at the central angle, and the lowest point is aligned with the positioning mark of the wafer.

3. The grinding retaining ring according to claim 1, characterized in that: The wear-resistant material is engineering plastic, selected from one of polyetheretherketone, polyphenylene sulfide, polyimide and polyethylene terephthalate.

4. The grinding retaining ring according to claim 1, characterized in that: The grinding is chemical mechanical polishing.

5. A method for grinding a wafer, characterized in that: include: Providing a wafer to be ground; A retaining ring is surrounded and fastened around the wafer to be ground, wherein the retaining ring is made of wear-resistant material and has a surface with periodic undulations on at least one side, and the period of the undulations is consistent with the distribution period of the crystal phase of the wafer to be ground; Grinding the wafer to be ground with the retaining ring.

6. The method for grinding a wafer according to claim 5, characterized in that: The wafer to be ground is in (100) crystal phase, and the retaining ring has an undulation period of 90° at the central angle.

7. The method for grinding a wafer according to claim 5, characterized in that: The wear-resistant material is engineering plastic, selected from one of polyetheretherketone, polyphenylene sulfide, polyimide and polyethylene terephthalate.

8. The method for grinding a wafer according to claim 5, characterized in that: The grinding is chemical mechanical polishing.

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