Composite process method for improving edge polishing sucker marks of silicon wafer

Abstract

The invention discloses a composite process method for improving edge polishing sucker marks of a silicon wafer. The processing technology comprises the following steps: (1) carrying out double-sided polishing on the silicon wafer subjected to alkali corrosion by using a double-sided polishing machine; (2) cleaning the silicon wafer after double-sided polishing by using a cleaning machine; (3) carrying out thermal oxidation on the silicon wafer subjected to double-sided polishing and cleaning, and growing a layer of compact silicon dioxide film with a stress buffering effect and a specific thickness range on the front surface of the silicon wafer; (4) carrying out edge polishing on the silicon wafer by taking the silicon dioxide film as a protective layer; (5) corroding the silicon dioxide film growing on the front surface of the silicon wafer by using hydrofluoric acid, and cleaning the silicon wafer; and (6) performing single-side fine polishing on the silicon wafer by using a final polishing machine. The invention provides a technical route and a processing flow for improving sucker marks generated on the front surface of the silicon wafer after edge polishing, and the front surface quality of the silicon polished wafer can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of silicon wafer processing technology, and in particular to a composite process method for improving edge polishing and suction cup printing on silicon wafers. Background Technology

[0002] A 12-inch silicon wafer is manufactured through multiple processes including single crystal growth, tumbling, slicing, grinding, etching, double-sided polishing, cleaning after double-sided polishing, edge polishing, cleaning after edge polishing, and final polishing. Edge polishing involves using a vacuum chuck to hold the front of the silicon wafer in place, with a polishing assembly positioned at the edge. The wafer is then driven to rotate relative to the polishing assembly, thus polishing the edge. However, because the front of the wafer is in contact with the chuck during edge polishing, prolonged contact with the vacuum chuck can cause adhesion marks on the front, known as edge polishing chuck marks.

[0003] Currently, to avoid the impact of suction cup marks on the quality of the front side of silicon wafers, two methods are usually adopted: one is to increase the amount of material removed during the final polishing to reduce damage to the front side of the silicon wafer caused by suction cup marks, but increasing the amount of material removed will affect the geometric parameters of the silicon wafer and the production capacity of the final polishing process; the other is to shorten the service life of the suction cup pads and replace the suction cup pads before the suction cup marks are generated, but there are certain differences in the usage of suction cup pads and each group of suction cup pads, and a uniformly specified service life cannot completely avoid this phenomenon. Summary of the Invention

[0004] The purpose of this invention is to provide a composite process method for improving the removal of suction cup marks on the edge of silicon wafers, thereby solving the technical problem of suction cup marks generated on the front side of silicon wafers during edge polishing in the prior art and improving the yield of processed products.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A composite process method for improving edge polishing and suction cup printing on silicon wafers includes the following steps: (1) Use a double-sided polishing machine to polish the silicon wafers after alkaline etching on both sides; (2) Clean the double-sided polished silicon wafers using a cleaning machine; (3) Thermal oxidation is performed on the silicon wafer that has been polished and cleaned on both sides to grow a dense silicon dioxide film with stress buffering effect and a specific thickness range on its front side. (4) Polish the edges of the silicon wafer using a silicon dioxide thin film as a protective layer; (5) Use hydrofluoric acid to etch away the silicon dioxide film grown on the front side of the silicon wafer and clean the silicon wafer; (6) Use a final polishing machine to perform single-sided fine polishing on the silicon wafer.

[0006] Preferably, in step (1), the polishing rate of double-sided polishing is 0.3-0.8 μm / min, and the removal amount of double-sided polishing is 10-20 μm.

[0007] Preferably, in step (2), SC1 is used to wash away the polishing liquid remaining on the silicon wafer after double-sided polishing, and the silicon wafer is dried.

[0008] Preferably, in step (3), thermal oxidation is performed under normal pressure conditions, with a temperature of 380-420°C and an atmosphere of silane and oxygen. The thickness of the silicon dioxide film grown on the front side of the silicon wafer is 1000-1500 Å. If the thickness is too thin (<1000 Å), the mechanical strength of the film is insufficient, and it is prone to plastic deformation or even cracking under the local high pressure of the suction cup, losing its protective function and having limited buffering capacity. The stress will be directly transmitted to the silicon substrate. If the thickness is too thick (>1500 Å), the stiffness of the film is too high, and its own deformation capacity decreases, and it begins to behave like a "hard shell". At this time, the local stress may not be effectively dispersed, and it may instead cause the film to undergo local brittle peeling under the shear force of edge polishing, generating new particulate contamination. In addition, an excessively thick oxide film requires a longer HF removal time, increasing the process cost and the risk of over-etching.

[0009] Preferably, in step (4), the edge polishing pressure is 20-50 N, the rotation speed is 100-300 r / min, and the time is 90-120 s. Too low polishing pressure and rotation speed will affect the polishing effect of the silicon wafer edge; while under too high polishing pressure and rotation speed, the oxide film will be worn at a certain rate. Sufficient initial thickness must ensure that the oxide film has not been penetrated at the end of the entire edge polishing cycle, otherwise the silicon wafer will be directly damaged at the end.

[0010] Preferably, in step (5), the concentration of hydrofluoric acid is 0.3-0.5%, and the cleaning time is 40-80s.

[0011] Preferably, in step (6), the polishing rate of single-sided fine polishing is 0.1-0.3 μm / min, and the single-sided polishing removal amount is 0.3-0.8 μm.

[0012] The advantages of this invention are: This invention provides a composite process method for improving the edge polishing of silicon wafers with chuck marks. It utilizes a thermally oxidized SiO2 film as a "sacrificial stress buffer layer," actively managing and eliminating contact stress through its own elastic deformation and subsequent sacrificial removal, thereby fundamentally protecting the nanostructure (NT) of the silicon wafer's front side. A quantitative matching relationship between the thermal oxidation film thickness and edge polishing process parameters is established, providing a predictable and optimizable composite process window, achieving the optimal balance between edge polishing efficiency and front-side morphology protection. The thermal oxidation process also repairs subsurface damage at the silicon wafer edges, further improving the overall quality of the edge region. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the composite process of the present invention.

[0014] Figure 2 This is a surface particle diagram of the front side of the silicon wafer in Embodiment 1 of the present invention.

[0015] Figure 3 This is an NT (nanomorphic) image of the front side of the silicon wafer in Embodiment 1 of the present invention.

[0016] Figure 4 This is a surface particle diagram of the front side of the silicon wafer in Embodiment 2 of the present invention.

[0017] Figure 5 This is an NT (nanomorphic) image of the front side of the silicon wafer in Embodiment 2 of the present invention.

[0018] Figure 6 This is a surface particle diagram showing the suction cup marks on the front side of the silicon wafer in the comparative example.

[0019] Figure 7 This is an NT (nanomorphology) image showing the suction cup marks on the front side of the silicon wafer in the comparative example. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this does not imply any limitation on the scope of protection of the present invention.

[0021] like Figure 1 The diagram shows a flowchart of the polishing process of the present invention. The composite process for improving the edge polishing of silicon wafers with suction cup marks provided by the present invention includes the following steps: (1) Use a double-sided polishing machine to polish the silicon wafer after alkaline etching. The polishing rate of the double-sided polishing is 0.3-0.8μm / min, and the removal amount of the double-sided polishing is 10-20μm.

[0022] (2) Use a cleaning machine to clean the silicon wafer after double-sided polishing, use SC1 to wash away the polishing liquid remaining on the silicon wafer after double-sided polishing, and dry the silicon wafer; (3) The silicon wafer that has been polished and cleaned on both sides is thermally oxidized to grow a dense silicon dioxide film with stress buffering effect and a specific thickness range on its front side. The thermal oxidation is carried out under normal pressure conditions, the temperature is 380-420℃, the atmosphere is silane and oxygen, and the thickness of the silicon dioxide film is 1000-1500Å. (4) Use a silicon dioxide film as a protective layer to polish the edge of the silicon wafer. The pressure of edge polishing is 20-50N, the rotation speed is 100-400r / min, and the time is 60-180s.

[0023] (5) Use hydrofluoric acid to etch away the silicon dioxide film grown on the front side of the silicon wafer and clean the silicon wafer. The concentration of hydrofluoric acid is 0.3-0.5% and the cleaning time is 40-80s.

[0024] (6) Use a final polishing machine to perform single-sided fine polishing on the silicon wafer. The polishing rate of single-sided fine polishing is 0.1-0.3 μm / min, and the single-sided polishing removal amount is 0.3-0.8 μm.

[0025] Example 1 Experimental silicon wafer: 12-inch Czochralski lightly boron-doped silicon wafer; Model P; Crystal orientation <100> Resistivity 8-12 Ω·cm; Thickness 789µm; Quantity 15 pieces.

[0026] (1) A double-sided polishing machine was used to polish 15 silicon wafers after alkaline etching. The polishing rate of the double-sided polishing was 0.5 μm / min, and the removal amount of the double-sided polishing was 15 μm. (2) Clean the silicon wafers using a double-sided polishing cleaning machine, use SC1 to wash away the polishing liquid remaining on the silicon wafers after double-sided polishing, and dry the silicon wafers; (3) The silicon wafer that has been polished and cleaned on both sides is thermally oxidized to grow a dense silicon dioxide film with stress buffering effect and a specific thickness range on its front side. The thermal oxidation is carried out under normal pressure conditions, the temperature is 400℃, the atmosphere is silane and oxygen, and the thickness of the silicon dioxide film is 1200Å. (4) When the edge polishing suction cup pad has been used for 7 days, the silicon wafer is edge polished. The edge polishing pressure is 30 N, the rotation speed is 300 r / min, and the time is 120 s. (5) Use hydrofluoric acid to etch away the silicon dioxide film grown on the front side of the silicon wafer and clean the silicon wafer. The concentration of hydrofluoric acid is 0.4% and the cleaning time is 80s. (6) Use a final polishing machine to perform single-sided fine polishing on the silicon wafer. The polishing rate of single-sided fine polishing is 0.2 μm / min, and the single-sided polishing removal amount is 0.5 μm.

[0027] After all 15 wafers were polished, the geometric parameters of the front side of the silicon wafers were measured using a parameter measuring instrument (Wafersight 2+). The test results are shown in Table 1. Following the parameter testing, the silicon wafers were cleaned using a final cleaning machine, and then the surface particles were tested using a particle detector (SP5 XP). All test results were satisfactory, and no particles were found in fixed positions at the edges. Figure 2 As shown.

[0028] Table 1 The test results show that, using the optimized processing technology, when the lifespan of the edge-polishing suction cup pad reaches 7 days, it does not affect the NT (non-nuclear) surface area on the silicon wafer. Figure 3 As shown.

[0029] Example 2 Experimental silicon wafer: 12-inch Czochralski lightly boron-doped silicon wafer; Model P; Crystal orientation <100> Resistivity 8-12 Ω·cm; Thickness 789µm; Quantity 15 pieces.

[0030] (1) A double-sided polishing machine was used to polish 15 silicon wafers after alkaline etching. The polishing rate of the double-sided polishing was 0.5 μm / min, and the removal amount of the double-sided polishing was 15 μm. (2) Clean the silicon wafers using a double-sided polishing cleaning machine, use SC1 to wash away the polishing liquid remaining on the silicon wafers after double-sided polishing, and dry the silicon wafers; (3) The silicon wafer that has been polished and cleaned on both sides is thermally oxidized to grow a dense silicon dioxide film with stress buffering effect and a specific thickness range on its front side. The thermal oxidation is carried out under normal pressure conditions, the temperature is 400℃, the atmosphere is silane and oxygen, and the thickness of the silicon dioxide film is 1200Å. (4) When the edge polishing suction cup pad has been used for 30 days, the silicon wafer is polished at the edge with a pressure of 30 N, a rotation speed of 300 r / min, and a time of 120 s. (5) Use hydrofluoric acid to etch away the silicon dioxide film grown on the front side of the silicon wafer and clean the silicon wafer. The concentration of hydrofluoric acid is 0.4% and the cleaning time is 80s. (6) Use a final polishing machine to perform single-sided fine polishing on the silicon wafer. The polishing rate of single-sided fine polishing is 0.2 μm / min, and the single-sided polishing removal amount is 0.5 μm.

[0031] After all 15 wafers were polished, the geometric parameters of the front side of the silicon wafers were measured using a parameter measuring instrument (Wafersight 2+). The test results are shown in Table 2. Following the parameter testing, the silicon wafers were cleaned using a final cleaning machine, and then the surface particles were tested using a particle detector (SP5 XP). All test results were satisfactory, and no particles were found in fixed positions at the edges. Figure 4 As shown.

[0032] Table 2 The test results show that, even with the optimized processing technology, when the lifespan of the edge-polishing suction cup pad reaches 30 days, it still does not affect the NT (non-nitrous oxide) on the front side of the silicon wafer. Figure 5 As shown.

[0033] Comparative Example Experimental silicon wafer: 12-inch Czochralski lightly boron-doped silicon wafer; Model P; Crystal orientation <100> Resistivity 8-12 Ω·cm; Thickness 789µm; Quantity 15 pieces.

[0034] (1) A double-sided polishing machine was used to polish 15 silicon wafers after alkaline etching. The polishing rate of the double-sided polishing was 0.5 μm / min, and the removal amount of the double-sided polishing was 15 μm. (2) Clean the silicon wafers using a double-sided polishing cleaning machine, use SC1 to wash away the polishing liquid remaining on the silicon wafers after double-sided polishing, and dry the silicon wafers; (3) When the edge polishing suction cup pad has been used for 7 days, the silicon wafer is polished at the edge with a pressure of 40 N, a rotation speed of 300 r / min and a time of 120 s. (4) Use hydrofluoric acid to clean the silicon wafer. The concentration of hydrofluoric acid is 0.3% and the cleaning time is 80s. (5) Use a final polishing machine to perform single-sided fine polishing on the silicon wafer. The polishing rate of single-sided fine polishing is 0.2 μm / min, and the single-sided polishing removal amount is 0.5 μm.

[0035] After all 15 wafers were polished, the geometric parameters of the front side of the silicon wafers were measured using a parameter measuring instrument (Wafersight 2+). The test results are shown in Table 3. After the parameter testing was completed, the silicon wafers were cleaned using a final cleaning machine, and then the surface particles were tested using a particle detector (SP5 XP). The particle map showed a ring of particles near the edge of the silicon wafer, as shown in the image. Figure 6 As shown.

[0036] Table 3 The test results show that, using conventional polishing processes, when the lifespan of the edge-polished suction cup pad reaches 7 days, the NT (Nickel Torque) already begins to deteriorate. Furthermore, Wafersight 2+ patterning reveals a ring of suction cup marks appearing near the edge of the silicon wafer. Figure 7 As shown.

[0037] As can be seen from the comparison of the embodiments and comparative examples, the present invention utilizes a thermally oxidized SiO2 film as a "sacrificial stress buffer layer," actively managing and eliminating contact stress through its own elastic deformation and subsequent sacrificial removal, thereby fundamentally protecting the nanostructure (NT) and surface particle quality of the silicon wafer's front side. The present invention establishes a quantitative matching relationship between the thermal oxidation film thickness and edge polishing process parameters, providing a predictable and optimizable composite process window, achieving the optimal balance between edge polishing efficiency and front-side morphology protection.

[0038] In summary, as demonstrated by the examples and comparative performance tests, the method provided by this invention can extend the service life of the edge-spraying suction cup pad while ensuring that no suction cup marks are generated.

Claims

1. A composite process method for improving edge polishing and suction cup printing on silicon wafers, characterized in that, Includes the following steps: (1) Use a double-sided polishing machine to polish the silicon wafers after alkaline etching on both sides; (2) Clean the double-sided polished silicon wafers using a cleaning machine; (3) Thermal oxidation is performed on the silicon wafer that has been polished and cleaned on both sides to grow a dense silicon dioxide film with stress buffering effect and a specific thickness range on its front side. (4) Polish the edges of the silicon wafer using a silicon dioxide thin film as a protective layer; (5) Use hydrofluoric acid to etch away the silicon dioxide film grown on the front side of the silicon wafer and clean the silicon wafer; (6) Use a final polishing machine to perform single-sided fine polishing on the silicon wafer.

2. The composite process method for improving edge polishing and suction cup printing on silicon wafers according to claim 1, characterized in that, In step (1), the polishing rate of double-sided polishing is 0.3-0.8 μm / min, and the removal amount of double-sided polishing is 10-20 μm.

3. The composite process method for improving edge polishing and suction cup printing on silicon wafers according to claim 1, characterized in that, In step (2), after double-sided polishing, SC1 is used to wash away the polishing liquid remaining on the silicon wafer after double-sided polishing, and the silicon wafer is dried.

4. The composite process method for improving edge polishing and suction cup printing on silicon wafers according to claim 1, characterized in that, In step (3), thermal oxidation is performed under normal pressure conditions, with a temperature of 380-420°C and an atmosphere of silane and oxygen. The thickness of the silicon dioxide film grown on the front side of the silicon wafer is 1000-1500 Å.

5. The composite process method for improving edge polishing and suction cup printing on silicon wafers according to claim 1, characterized in that, In step (4), the edge polishing pressure is 20-50 N, the rotation speed is 100-400 r / min, and the time is 60-180 s.

6. The composite process method for improving edge polishing and suction cup printing on silicon wafers according to claim 1, characterized in that, In step (5), the concentration of hydrofluoric acid is 0.3-0.5%, and the cleaning time is 40-80 seconds.

7. The composite process method for improving edge polishing and suction cup printing on silicon wafers according to claim 1, characterized in that, In step (6), the polishing rate of single-sided fine polishing is 0.1-0.3 μm / min, and the single-sided polishing removal amount is 0.3-0.8 μm.

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