Grinding retaining ring and grinding wafer method

Abstract

This invention provides a polishing retaining ring and a method for polishing a wafer. The polishing retaining ring surrounds and secures the wafer to be polished. The retaining ring is made of a wear-resistant material and has a periodic undulating pattern on one or both sides of its surface. The period of the undulation corresponds to the distribution period of the crystal phases of the wafer to be polished. Specifically, the retaining ring of this invention exhibits a periodic undulating pattern on the surface facing the polishing pad, with the period of the undulation matching the distribution period of the crystal phases of the wafer to be polished. Due to the thickness correction effect of the retaining ring, thickness deviations caused by crystal phase issues can be compensated, resulting in a more flat surface globally.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and in particular to a polishing retaining ring and a method for polishing wafers. Background Technology

[0002] Chemical mechanical polishing, also known as chemical mechanical abrasion, is a processing technique that combines chemical corrosion with mechanical removal. It is a semiconductor processing technology that can achieve global surface planarization.

[0003] Chemical mechanical polishing (CMP) combines the advantages of both chemical and mechanical polishing. Chemical polishing alone offers high surface precision, low damage, and good integrity, with minimal surface / subsurface damage. However, it has a slower polishing rate, lower material removal efficiency, cannot correct surface profile accuracy, and exhibits poor polishing consistency. Mechanical polishing alone offers good polishing consistency, high surface smoothness, and high polishing efficiency, but it is prone to surface / subsurface damage and has a relatively low surface roughness. CMP combines the advantages of both methods, achieving a near-perfect surface while maintaining material removal efficiency. The resulting smoothness is 1-2 orders of magnitude higher than that achieved using either method alone, and it can achieve surface roughness from the nanometer to the atomic level.

[0004] As described above, the grinding process uses physical and chemical methods to achieve global surface planarization. Therefore, how to obtain a more flat surface on a global scale has always been a problem that existing technologies need to solve. Summary of the Invention

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

[0006] To address the aforementioned problems, the present invention provides a retaining ring for grinding, which surrounds and secures the wafer to be ground. The retaining ring is made of a wear-resistant material and has a periodic undulating pattern on one or both sides of its surface, the period of which is consistent with the distribution period of the crystal phases of the wafer to be ground.

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

[0008] Optionally, the wear-resistant material is an engineering plastic selected from polyetheretherketone, polyphenylene sulfide, polyimide, and polyterephthalic acid.

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

[0010] To address the aforementioned problems, the present invention provides a method for grinding a wafer, comprising: providing a wafer to be ground; surrounding and securing a retaining ring around the wafer to be ground, the retaining ring being made of a wear-resistant material and having a periodic undulating pattern on one or both sides of its surface, the period of which is consistent with the distribution period of the crystal phases of the wafer to be ground; and grinding the wafer to be ground with the retaining ring.

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

[0012] Optionally, the wear-resistant material is an engineering plastic selected from polyetheretherketone, polyphenylene sulfide, polyimide, and polyterephthalic acid.

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

[0014] The retaining ring of this invention exhibits a periodic undulating pattern on its surface facing the polishing pad, with the period of the undulations matching the distribution period of the crystal phases of the wafer to be polished. Due to the thickness correction effect of the retaining ring, thickness deviations caused by crystal phase issues can be compensated for, resulting in a more flattened surface globally. Attached Figure Description

[0015] Appendix Figure 1 The diagram shown is a structural schematic of the polishing equipment according to a specific embodiment of the present invention.

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

[0017] Appendix Figure 3 The diagram shown illustrates the periodic change in the relative thickness of the retaining ring according to a specific embodiment of the present invention.

[0018] Appendix Figure 4 The diagram shown is a structural schematic of the grinding equipment according to a specific embodiment of the present invention.

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

[0020] Appendix Figure 6 The diagram shows the implementation steps of the grinding method according to a specific embodiment of the present invention. Detailed Implementation

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

[0022] Appendix Figure 1The diagram shown is a structural schematic of the polishing equipment according to a specific embodiment of the present invention. Figure 2 The diagram shown is a schematic of the grinding head.

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

[0024] Continue to refer to the appendix Figure 2 As shown, a wafer 13 to be ground is positioned below the grinding head 12, and a retaining ring 14 is provided around and secures the wafer 13. In this specific embodiment, the retaining ring 14 has a periodic undulating shape on the surface facing the grinding pad 11, and the period of the undulation 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 has a (100) crystal phase, the retaining ring 14 has an undulation period of 90° central angle, and the lowest point is aligned with the positioning mark of the wafer. (See attached image) Figure 3 The diagram shows the periodic variation of the relative thickness of the retaining ring 14 along the circumferential direction, with the central angle starting from the alignment mark, ranging from 0° to 360°. Due to the thickness correction effect of the retaining ring 14, thickness deviations caused by crystal phase issues can be compensated, resulting in a more flattened surface globally.

[0025] The retaining ring 14 is preferably made of engineering plastic, including one of polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyimide (PAI), and polyterephthalic acid (PETP). These materials allow the retaining ring 14 to maintain a constant height during the grinding process, thereby correcting the thickness of the wafer 13 to be ground.

[0026] Appendix Figure 4 The diagram shown is a structural schematic of the grinding equipment according to a specific embodiment of the present invention. (Attached) Figure 5 The diagram shows the relative structure between the wafer to be ground and the retaining ring. (See attached reference.) Figure 4 As shown, the polishing equipment is a double-sided polishing machine, including an upper polishing disc 21, a lower polishing disc 22, a central wheel 23, and an external gear 24. A planetary gear 25 is arranged between the upper polishing disc 21 and the lower polishing disc 22, and the wafer 26 to be polished is placed in the inner cavity of the planetary gear 25. A retaining ring 27 is arranged around and secures the wafer 26 to be polished.

[0027] Upper polishing pad 211 and lower polishing pad 221 are respectively disposed on their opposite surfaces. Upper polishing pad 21, lower polishing pad 22, center wheel 23, and external gear 24 rotate at a set angular velocity. The upper polishing pad 21 and lower polishing pad 22 rotate in opposite directions, as do the center wheel 23 and external gear 24. Polishing slurry is further dripped between the upper polishing pad 21 and lower polishing pad 22 for chemical mechanical polishing. This apparatus enables double-sided polishing and thinning of the wafer 26 to be polished.

[0028] In this specific embodiment, the surfaces on both sides of the retaining ring exhibit a periodic undulation pattern, and the period of the undulation is consistent with the distribution period of the crystal phase of the wafer 26 to be polished. In this specific embodiment, the wafer 26 to be polished has a (100) crystal phase, the retaining ring 27 has an undulation period of 90° central angle, and the lowest point is aligned with the positioning mark of the wafer. The undulation state is the same as in the attached figure. Figure 3 The diagram illustrates the situation where both sides are identically configured. It shows the periodic variation of the relative thickness of the retaining ring 27 along the circumferential direction, with the central angle starting from the alignment mark, ranging from 0° to 360°. Due to the thickness correction effect of the retaining ring 27, thickness deviations caused by crystal phase issues can be compensated for, resulting in a more flattened surface globally.

[0029] The retaining ring 27 is preferably made of engineering plastic, including one of polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyimide (PAI), and polyterephthalic acid (PETP). These materials allow the retaining ring 27 to maintain a constant height during the grinding process, thereby correcting the thickness of the wafer 26 to be ground.

[0030] The following describes a specific embodiment of the grinding method of the present invention with reference to the accompanying drawings. Figure 6 The diagram shows the implementation steps of this specific embodiment, including: step S10, providing a wafer to be polished; step S11, surrounding and fastening a retaining ring around the wafer to be polished, the retaining ring being made of a wear-resistant material and having a periodic undulating shape on at least one side of its surface, the period of the undulation being consistent with the distribution period of the crystal phase of the wafer to be polished; and step S12, polishing the wafer to be polished with the retaining ring.

[0031] Step S10: Provide a wafer to be polished. In this specific embodiment, the wafer to be polished is a (100) crystal phase, and the polishing is preferably chemical mechanical polishing (CMP).

[0032] Step S11: A retaining ring is wrapped around and secured around the wafer to be polished. The retaining ring is made of a wear-resistant material and has a periodic undulating pattern on one or both sides of its surface. The period of the undulation is consistent with the distribution period of the crystal phases of the wafer to be polished. Single-sided polishing corresponds to single-sided polishing, and double-sided polishing corresponds to double-sided polishing. The retaining ring has a 90° central angle as its undulation period, and the lowest point is aligned with the positioning mark on the wafer.

[0033] Step S12: Grind the wafer to be ground with the retaining ring. In this step, due to the correction effect of the retaining ring thickness, the thickness deviation caused by the crystal phase problem can be compensated, and a more flat surface can be obtained globally.

[0034] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A retaining ring for grinding, characterized in that, The retaining ring is set around and secures the wafer to be ground. The retaining ring is made of wear-resistant material and has a periodic undulation on one or both sides of the surface. The period of the undulation is consistent with the distribution period of the crystal orientation of the wafer to be ground. The wafer to be ground has a (100) crystal orientation. The retaining ring has an undulation period of 90° central angle and the lowest point is aligned with the positioning mark of the wafer.

2. The grinding retaining ring according to claim 1, characterized in that, The wear-resistant material is an engineering plastic selected from one of polyetheretherketone, polyphenylene sulfide, polyimide, and polyterephthalic acid.

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

4. A method for grinding wafers, characterized in that, include: A wafer to be polished is provided, wherein the wafer to be polished has a (100) crystal orientation; A retaining ring is wrapped around and fastened around the wafer to be ground. The retaining ring is made of wear-resistant material and has a periodic undulation on at least one side of its surface. The period of the undulation is consistent with the distribution period of the crystal orientation of the wafer to be ground. The retaining ring has an undulation period of 90° central angle. Grind the wafer to be ground, which has a retaining ring.

5. The method for grinding wafers according to claim 4, characterized in that, The wear-resistant material is an engineering plastic selected from one of polyetheretherketone, polyphenylene sulfide, polyimide, and polyterephthalic acid.

6. The method for grinding wafers according to claim 4, characterized in that, The grinding process is chemical mechanical polishing.

Images