Method for improving surface roughness of SiC fine grinding sheet

Abstract

The invention relates to a method for improving the surface roughness of a SiC fine grinding sheet, which comprises the following steps of: performing cyclic etching and repair etching on the SiC fine grinding sheet to reduce the surface roughness Sa of the SiC fine grinding sheet to be below 2nm; the circular etching comprises a first etching step and a second etching step which are circularly carried out; working gas in the first etching step comprises first fluorine-based gas; working gas in the second etching step comprises chlorine-based gas and / or second fluorine-based gas. According to the method, through circular etching, continuous erosion of plasmas to the cavity is reduced, aging of cavity components is slowed down, and then the surface roughness Sa of the SiC fine grinding sheet can be reduced to 2 nm or below through repairing etching.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductors and relates to a method for improving the surface roughness of a SiC fine grinding sheet. BACKGROUND

[0002] Silicon carbide (SiC) is a third-generation semiconductor material with advantages such as high bandgap, high breakdown field and high thermal conductivity, and is widely used in power electronics, radio frequency devices and high-temperature sensors. However, SiC has extremely high hardness (Mohs hardness of 9.2, second only to diamond) and chemical inertness, making its thinning and polishing process a key difficulty in the manufacturing process. Currently, the thinning technology of silicon carbide is developing towards high efficiency, low damage and high precision, and mechanical polishing is still the mainstream process. However, the traditional fine grinding technology has obvious problems: during mechanical grinding / polishing, diamond abrasives can easily cause surface damage such as subsurface cracks (SSD) and scratches, and the material removal rate (MRR) is low, which not only wastes time but also increases costs. In addition, chemical mechanical polishing (CMP) also has limitations, such as dependence on strong oxidizing agents and expensive polishing liquid, and it is still difficult to completely eliminate the damage layer.

[0003] Dry etching has unique advantages in the SiC thinning process. Compared with traditional mechanical thinning, it has significant potential in precision control, damage suppression and processing of complex structures. Through the directional bombardment of active ions in the plasma on the SiC surface, dry etching can achieve nanoscale precision thickness control, avoiding the problems of overcutting or uneven thickness commonly seen in mechanical thinning. Moreover, dry etching has almost no mechanical stress and does not require the disposal of chemical waste, making it more in line with the trend of green manufacturing in the semiconductor industry.

[0004] In the development of dry etching, existing technologies have obvious limitations: reactive ion etching (RIE) has poor anisotropy, high sidewall roughness and is prone to introduce ion bombardment damage; electron cyclotron resonance (ECR) plasma etching has complex equipment and is difficult to implement large-scale production. Inductively coupled plasma (ICP) etching, with its high plasma density and independent ion energy control, is superior to other dry etching techniques in terms of etching rate, precision and damage control, and has become a key to solving the surface processing problem of SiC fine grinding sheets. SUMMARY

[0005] To overcome the deficiencies of the prior art, the purpose of the present application is to provide a method for improving the surface roughness of a SiC fine grinding sheet, which can reduce the surface roughness Sa of the SiC fine grinding sheet to below 2 nm.

[0006] To achieve this application purpose, the following technical solutions are adopted:

[0007] The application provides a method for improving the surface roughness of SiC fine grinding plate, which comprises the following steps:

[0008] The SiC fine grinding plate is subjected to cyclic etching and repair etching, so that the surface roughness Sa of the SiC fine grinding plate is reduced to below 2 nm.

[0009] The cyclic etching comprises cyclically performed first etching and second etching.

[0010] The working gas used in the first etching comprises a first fluorine-based gas.

[0011] The working gas used in the second etching comprises a chlorine-based gas and / or a second fluorine-based gas.

[0012] The conventional ICP etching process mainly uses a chlorine-based gas or a fluorine-based gas for single etching. The application combines the first etching and the second etching, and selects working gases with different compositions, so as to ensure the etching rate and realize the rapid removal of SiC materials. Meanwhile, the cyclic etching can avoid the lattice damage caused by the continuous heating of high-energy particles, and can also reduce the continuous erosion of the plasma on the cavity, and slow down the aging of the cavity components. Finally, the repair etching can reduce the surface roughness Sa of the SiC fine grinding plate to below 2 nm.

[0013] In an embodiment of the application, the composition of the first fluorine-based gas comprises SF6, O2 and Ar.

[0014] In an embodiment of the application, the volume ratio of the SF6 to the Ar is 5:200-10:200.

[0015] In an embodiment of the application, the volume ratio of the O2 to the Ar is 10:200-20:200.

[0016] In an embodiment of the application, the ICP power of the first etching is 800 W-1200 W.

[0017] In an embodiment of the application, the RF bias power of the first etching is 600 W-800 W.

[0018] In an embodiment of the application, the absolute pressure of the first etching is 8 mtorr-12 mtorr.

[0019] In an embodiment of the application, the time of the first etching is 0.5 min-1.5 min.

[0020] In an embodiment of the application, the chlorine-based gas comprises Cl2, BCl3, Ar and helium-oxygen mixed gas.

[0021] In one embodiment of the present application, the volume ratio of Cl2, BCl3, Ar and helium-oxygen mixture is 20: (3-5): (3-5): (6-8).

[0022] In one embodiment of the present application, the ICP power of the second etching step is 300-500 W.

[0023] In one embodiment of the present application, the RF bias power of the second etching step is 200-300 W.

[0024] In one embodiment of the present application, the absolute pressure of the second etching step is 6-10 mtorr.

[0025] In one embodiment of the present application, the time of the second etching step is 1.5-2.5 min.

[0026] In one embodiment of the present application, the second fluorine-based gas comprises SF6 and O2.

[0027] In one embodiment of the present application, the volume ratio of SF6 and O2 is 9: (3-5).

[0028] In one embodiment of the present application, the ICP power of the second etching step is 1400-1600 W.

[0029] In one embodiment of the present application, the RF bias power of the second etching step is 70-80 W.

[0030] In one embodiment of the present application, the absolute pressure of the second etching step is 15-25 mtorr.

[0031] In one embodiment of the present application, the time of the second etching step is 0.5-1.5 min.

[0032] In one embodiment of the present application, the cycle number of the first etching step and the second etching step is 4-8 times.

[0033] In one embodiment of the present application, the working gas of the repair etching comprises SF6, N2 and Ar.

[0034] In one embodiment of the present application, the volume ratio of SF6, N2 and Ar is 8: (4-6): (85-95).

[0035] In one embodiment of the present application, the ICP power of the repair etching is 100-150 W.

[0036] In one embodiment of the present application, the RF bias power for repairing the etching is 8W-12W.

[0037] In one embodiment of the present application, the time for repairing the etching is 4min-6min.

[0038] The numerical range of the present application includes not only the above-mentioned point values, but also any point values between the above-mentioned numerical ranges that are not mentioned, and the present application does not list the specific point values included in the range for the sake of brevity and simplicity.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] The conventional ICP etching process mainly uses chlorine-based gas or fluorine-based gas for single etching, and the present application combines the first etching step and the second etching step, selects different working gases, ensures the etching rate, and can realize the rapid removal of SiC material; at the same time, the cyclic etching can avoid the lattice damage caused by the continuous heating of high-energy particles, and can also reduce the continuous erosion of the plasma to the cavity, and slow down the aging of the cavity components; finally, through the repair etching, the surface roughness Sa of the SiC fine grinding piece can be reduced to below 2nm. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 With Figure 2 is an atomic force microscope surface morphology diagram of a SiC fine grinding piece with unimproved surface roughness;

[0042] Figure 3 With Figure 4 is an atomic force microscope surface morphology diagram of a SiC fine grinding piece with improved surface roughness in Example 1;

[0043] Figure 5 With Figure 6 is an atomic force microscope surface morphology diagram of a SiC fine grinding piece with improved surface roughness in Example 12;

[0044] Figure 7 With Figure 8 is an atomic force microscope surface morphology diagram of a SiC fine grinding piece with improved surface roughness in Comparative Example 1. DETAILED DESCRIPTION

[0045] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0046] In the ICP etching process, the synergistic effect of various process parameters realizes efficient thinning, the ICP power source controls the ion flux by generating high-density plasma, the increase of power can increase the density of ions and active groups to improve the etching rate, but too high power will affect the uniformity and increase the thermal load; the RF bias power source is used to regulate the ion bombardment energy, increasing the RF bias power can significantly improve the etching rate and improve the step angle, but will cause the selectivity to decrease, and too high bias may cause step effect; the gas pressure parameter affects the mean free path of ions, the ion directionality is better at lower gas pressure and is beneficial to product desorption, and higher gas pressure can increase the density of active groups, thereby improving the etching rate and selectivity.

[0047] The working gas in the ICP etching process includes fluorine-based gas and chlorine-based gas, the fluorine-based gas at least includes SF6, and the chlorine-based gas at least includes Cl2 and / or BCl3.

[0048] When SF6 reacts with SiC, fluorine radicals (F·) react with SiC to generate volatile SiF4 (boiling point -86℃), but carbon residues may form non-volatile polymers. When Cl2 and / or BCl3 react with SiC, chlorine radicals (Cl·) react with SiC to generate SiCl4 (boiling point 57.6℃), the volatility of SiCl4 is lower than that of SiF4, and higher temperature or ion bombardment assisted desorption is required, in addition, BCl3 dissociation generates BCl x (x=1 or x=2) will form a passivation layer on the sidewall. The normal progress of SiC etching is affected.

[0049] An embodiment of the present application provides a method for improving the surface roughness of a SiC fine grinding plate, the method comprising the following steps:

[0050] The SiC fine grinding plate is subjected to cyclic etching and repair etching, so that the surface roughness Sa of the SiC fine grinding plate is reduced to below 2nm;

[0051] The cyclic etching comprises cyclically performed first etching steps and second etching steps;

[0052] The working gas of the first etching step comprises a first fluorine-based gas;

[0053] The working gas of the second etching step comprises a chlorine-based gas and / or a second fluorine-based gas.

[0054] The conventional ICP etching process mainly uses chlorine-based gas or fluorine-based gas for single etching, the present application combines the first etching step and the second etching step, selects different working gas compositions, ensures the etching rate, and can realize the rapid removal of SiC material; at the same time, the cyclic etching can avoid the lattice damage caused by the continuous heating of high-energy particles, and also can reduce the continuous erosion of the plasma to the cavity, and slow down the aging of the cavity components; finally, through the repair etching, the surface roughness Sa of the SiC fine grinding sheet can be reduced to below 2nm.

[0055] In some embodiments, the surface roughness Sa of the SiC fine grinding sheet is 3nm-5nm.

[0056] In some embodiments, the composition of the first fluorine-based gas includes SF6, O2 and Ar.

[0057] In some embodiments, the volume ratio of SF6 to Ar is 5:200-10:200, for example, it can be 5:200, 6:200, 7:200, 8:200, 9:200 or 10:200, but is not limited to the listed values, and the remaining values within the value range are also applicable.

[0058] In some embodiments, the volume ratio of O2 to Ar is 10:200-20:200, for example, it can be 10:200, 12:200, 15:200, 18:200 or 20:200, but is not limited to the listed values, and the remaining values within the value range are also applicable.

[0059] In some embodiments, the ICP power of the first etching step is 800W-1200W, for example, it can be 800W, 900W, 1000W, 1100W or 1200W, but is not limited to the listed values, and the remaining values within the value range are also applicable, and the preferred value is 1000W.

[0060] In some embodiments, the RF bias power of the first etching step is 600W-800W, for example, it can be 600W, 650W, 700W, 750W or 800W, but is not limited to the listed values, and the remaining values within the value range are also applicable, and the preferred value is 700W.

[0061] In some embodiments, the absolute pressure of the first etching step is 8mtorr-12mtorr, for example, it can be 8mtorr, 9mtorr, 10mtorr, 11mtorr or 12mtorr, but is not limited to the listed values, and the remaining values within the value range are also applicable, and the preferred value is 10mtorr.

[0062] In some embodiments, the first etching step has a time of 0.5-1.5 minutes, for example, 0.5, 0.6, 0.8, 1, 1.2 or 1.5 minutes, but not limited to the listed values, and the remaining values in the range are also applicable. Preferably, the time is 1 minute.

[0063] In some embodiments, the chlorine-based gas includes Cl2, BCl3, Ar and helium-oxygen mixture.

[0064] For example, the helium-oxygen mixture has an oxygen volume percentage of 25-35%, for example, 25%, 28%, 30%, 32% or 35%, but not limited to the listed values, and the remaining values in the range are also applicable. In the embodiments of the present application, the oxygen volume percentage in the helium-oxygen mixture is taken as an example for illustration.

[0065] In some embodiments, the volume ratio of Cl2, BCl3, Ar and helium-oxygen mixture is 20:(3-5):(3-5):(6-8).

[0066] For example, the volume ratio of Cl2 and BCl3 is 20:3, 20:4 or 20:5, but not limited to the listed values, and the remaining values in the range are also applicable.

[0067] For example, the volume ratio of Cl2 and Ar is 20:3, 20:4 or 20:5, but not limited to the listed values, and the remaining values in the range are also applicable.

[0068] For example, the volume ratio of Cl2 and Ar is 20:3, 20:4 or 20:5, but not limited to the listed values, and the remaining values in the range are also applicable.

[0069] In some embodiments, when the working gas of the second etching step is a chlorine-based gas, the ICP power of the second etching step is 300-500 W, for example, 300 W, 350 W, 400 W, 450 W or 500 W, but not limited to the listed values, and the remaining values in the range are also applicable. Preferably, the ICP power is 400 W.

[0070] In some embodiments, when the working gas of the second etching step is a chlorine-based gas, the RF bias power of the second etching step is 200-300 W, for example, 200 W, 210 W, 240 W, 250 W, 270 W, 280 W or 300 W, but not limited to the listed values, and the remaining values in the range are also applicable. Preferably, the RF bias power is 250 W.

[0071] In some embodiments, when the working gas of the second etching step is a chlorine-based gas, the absolute pressure of the second etching step is 6mtorr to 10mtorr, for example, it can be 6mtorr, 7mtorr, 8mtorr, 9mtorr or 10mtorr, but is not limited to the listed values, and the remaining values in the value range are also applicable, and preferably 8mtorr.

[0072] In some embodiments, when the working gas of the second etching step is a chlorine-based gas, the time of the second etching step is 1.5min to 2.5min, for example, it can be 1.5min, 1.6min, 1.8min, 2min, 2.1min, 2.4min or 2.5min, but is not limited to the listed values, and the remaining values in the value range are also applicable, and preferably 2min.

[0073] In some embodiments, the second fluorine-based gas includes SF6 and O2.

[0074] In some embodiments, the volume ratio of SF6 to O2 is 9:(3-5), for example, it can be 9:3, 9:4 or 9:5, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0075] In some embodiments, when the working gas of the second etching step is a second fluorine-based gas, the ICP power of the second etching step is 1400W to 1600W, for example, it can be 1400W, 1450W, 1500W, 1550W or 1600W, but is not limited to the listed values, and the remaining values in the value range are also applicable.

[0076] In some embodiments, when the working gas of the second etching step is a second fluorine-based gas, the RF bias power of the second etching step is 70W to 80W, for example, it can be 70W, 72W, 75W, 78W or 80W, but is not limited to the listed values, and the remaining values in the value range are also applicable, and preferably 75W.

[0077] In some embodiments, when the working gas of the second etching step is a second fluorine-based gas, the absolute pressure of the second etching step is 15mtorr to 25mtorr, for example, it can be 15mtorr, 16mtorr, 18mtorr, 20mtorr, 21mtorr, 24mtorr or 25mtorr, but is not limited to the listed values, and the remaining values in the value range are also applicable, and preferably 20mtorr.

[0078] In some embodiments, when the working gas of the second etching step is a second fluorine-based gas, the time of the second etching step is 0.5 min to 1.5 min, for example, can be 0.5 min, 0.8 min, 1 min, 1.2 min or 1.5 min, but not limited to the listed values, the remaining values in the value range are also applicable, and preferably 1 min.

[0079] In some embodiments, the number of cycles of the first etching step and the second etching step is 4 to 8 times, for example, can be 4 times, 5 times, 6 times, 7 times or 8 times.

[0080] In some embodiments, the working gas of the repair etching includes SF6, N2 and Ar.

[0081] In some embodiments, the volume ratio of SF6, N2 and Ar is 8:(4-6):(85-95).

[0082] In some embodiments, the volume ratio of SF6 and N2 is 8:(4-6), for example, can be 8:4, 8:5 or 8:6, but not limited to the listed values, the remaining values in the value range are also applicable.

[0083] In some embodiments, the volume ratio of SF6 and Ar is 8:(85-95), for example, can be 8:85, 8:86, 8:88, 8:90, 8:92, 8:94 or 8:95, but not limited to the listed values, the remaining values in the value range are also applicable, and preferably 8:90.

[0084] In some embodiments, the ICP power of the repair etching is 100 W to 150 W, for example, can be 100 W, 110 W, 120 W, 130 W, 140 W or 150 W, but not limited to the listed values, the remaining values in the value range are also applicable, and preferably 120 W.

[0085] In some embodiments, the RF bias power of the repair etching is 8 W to 12 W, for example, can be 8 W, 9 W, 10 W, 11 W or 12 W, but not limited to the listed values, the remaining values in the value range are also applicable, and preferably 10 W.

[0086] In some embodiments, the time of the repair etching is 4 min to 6 min, for example, can be 4 min, 5 min or 6 min, but not limited to the listed values, the remaining values in the value range are also applicable, and preferably 5 min.

[0087] In some embodiments, the cyclic etching and the repair etching are carried out in an etching chamber, and the etching chamber is cleaned before use.

[0088] In some embodiments, the cleaning process includes introducing SF6 and O2 in a volume ratio of 6:1-9:1 into the etching chamber.

[0089] In some embodiments, the temperature of the cyclic etching and the repair etching is 58-62℃, for example, it can be 58℃, 59℃, 60℃, 61℃ or 62℃, but is not limited to the listed values, and the remaining values in the value range are also applicable, and the preferred temperature is 60℃.

[0090] As one of the preferred technical solutions of the method provided by the present application, the method comprises the following steps:

[0091] (1) introducing SF6 and O2 in a volume ratio of (6-9):1 into the etching chamber for cleaning, then placing the substrate into the etching chamber and fixing it by the electrostatic chuck, setting the temperature of the electrostatic chuck to 58-62℃, and then placing the SiC fine grinding sheet on the substrate;

[0092] (2) cyclically etching the SiC fine grinding sheet;

[0093] The cyclic etching includes a first etching step and a second etching step, and the number of cycles of the first etching step and the second etching step is 4-8 times.

[0094] The working gas of the first etching step is a first fluorine-based gas; the composition of the first fluorine-based gas is SF6, O2 and Ar in a volume ratio of (5-10):(10-20):200;

[0095] The ICP power of the first etching step is 800-1200W, the RF bias power is 600-800W, the absolute pressure is 8-12mtorr, and the time is 0.5-1.5min;

[0096] The working gas of the second etching step is a chlorine-based gas; the chlorine-based gas is Cl2, BCl3, Ar and helium-oxygen mixed gas in a volume ratio of 20:(3-5):(3-5):(6-8);

[0097] The ICP power of the second etching step is 300-500W, the RF bias power is 200-300W, the absolute pressure is 6-10mtorr, and the time is 1.5-2.5min.

[0098] (3) performing repair etching after the cyclic etching to reduce the surface roughness Sa of the SiC fine grinding sheet to below 2nm;

[0099] The working gas for the repair etching is SF6, N2 and Ar with a volume ratio of 8:(4-6):(85-95); the ICP power for the repair etching is 100-150 W, the RF bias power is 8-12 W, and the time is 4-6 min.

[0100] As the second preferred technical solution of the method provided by the present application, the method comprises the following steps:

[0101] (1) SF6 and O2 with a volume ratio of (6-9):1 are introduced into the etching chamber for cleaning treatment, then the substrate is placed in the etching chamber and fixed by the electrostatic chuck, the temperature of the electrostatic chuck is set to 58-62℃, and then the SiC lapping plate is placed on the substrate;

[0102] (2) the SiC lapping plate is subjected to cyclic etching;

[0103] The cyclic etching comprises a first etching step and a second etching step which are cyclically performed, and the number of cycles of the first etching step and the second etching step is 4-8 times;

[0104] The working gas for the first etching step is a first fluorine-based gas; the first fluorine-based gas comprises SF6, O2 and Ar with a volume ratio of (5-10):(10-20):200;

[0105] The ICP power for the first etching step is 800-1200 W, the RF bias power is 600-800 W, the absolute pressure is 8-12 mtorr, and the time is 0.5-1.5 min;

[0106] The working gas for the second etching step is a second fluorine-based gas; the second fluorine-based gas comprises SF6 and O2 with a volume ratio of 9:(3-5);

[0107] The ICP power for the second etching step is 1400-1600 W, the RF bias power is 70-80 W, the absolute pressure is 15-25 mtorr, and the time is 0.5-1.5 min.

[0108] (3) after the cyclic etching, repair etching is performed to reduce the surface roughness Sa of the SiC lapping plate to below 2 nm;

[0109] The working gas for the repair etching is SF6, N2 and Ar with a volume ratio of 8:(4-6):(85-95); the ICP power for the repair etching is 100-150 W, the RF bias power is 8-12 W, and the time is 4-6 min.

[0110] Example 1

[0111] The embodiment provides a method for improving the surface roughness of a SiC fine grinding disc, which comprises the following steps:

[0112] (1) SF6 and O2 with a volume ratio of 7.5:1 are introduced into the etching chamber for cleaning treatment, then the substrate is placed into the etching chamber and fixed through an electrostatic chuck, the temperature of the electrostatic chuck is set to 60 DEG C, and then the SiC fine grinding disc (the surface roughness Sa is 3.998 nm) is placed on the substrate;

[0113] Exemplarily, as shown in FIG. 1 and FIG. 2, the surface roughness Sa of the SiC fine grinding disc is 3.998 nm. Figure 1 Figure 2

[0114] (2) The SiC fine grinding disc is subjected to cyclic etching;

[0115] The cyclic etching comprises a first etching step and a second etching step which are cyclically performed, and the cyclic times of the first etching step and the second etching step are 6 times;

[0116] The working gas of the first etching step is a first fluorine-based gas; the first fluorine-based gas comprises SF6, O2 and Ar with a volume ratio of 8:15:200;

[0117] The ICP power of the first etching step is 1000 W, the RF bias power is 700 W, the absolute pressure is 10 mtorr, and the time is 1 min;

[0118] The working gas of the second etching step is a chlorine-based gas; the chlorine-based gas comprises Cl2, BCl3, Ar and helium-oxygen mixed gas with a volume ratio of 20:4:4:7;

[0119] The ICP power of the second etching step is 400 W, the RF bias power is 250 W, the absolute pressure is 8 mtorr, and the time is 2 min.

[0120] (3) After the cyclic etching, repair etching is performed;

[0121] The working gas of the repair etching is SF6, N2 and Ar with a volume ratio of 8:5:90; the ICP power of the repair etching is 120 W, the RF bias power is 10 W, and the time is 5 min.

[0122] As shown in FIG. 3 and FIG. 4, the atomic force microscope surface topography of the SiC fine grinding disc after the surface roughness is improved through the method provided in the embodiment. Figure 3 Figure 4

[0123] Embodiment 2

[0124] ​​​​The embodiment provides a method for improving the surface roughness of a SiC fine grinding piece, and comprises the following steps:

[0125] (1) SF6 and O2 in a volume ratio of 7.5:1 are introduced into an etching chamber for cleaning treatment, then a substrate is placed into the etching chamber and fixed through an electrostatic chuck, the temperature of the electrostatic chuck is set to 58 DEG C, and then a SiC fine grinding piece (the surface roughness Sa is 3.880 nm) is placed on the substrate;

[0126] (2) the SiC fine grinding piece is subjected to cyclic etching;

[0127] The cyclic etching comprises cyclically performed first etching steps and second etching steps, and the cyclic times of the first etching steps and the second etching steps are 8 times;

[0128] The working gas of the first etching step is a first fluorine-based gas; the first fluorine-based gas is composed of SF6, O2 and Ar in a volume ratio of 5:20:200;

[0129] The ICP power of the first etching step is 800 W, the RF bias power is 600 W, the absolute pressure is 8 mtorr, and the time is 1.5 min;

[0130] The working gas of the second etching step is a chlorine-based gas; the chlorine-based gas is Cl2, BCl3, Ar and helium-oxygen mixed gas in a volume ratio of 20:3:3:8;

[0131] The ICP power of the second etching step is 300 W, the RF bias power is 200 W, the absolute pressure is 6 mtorr, and the time is 2.5 min.

[0132] (3) after the cyclic etching, repair etching is performed;

[0133] The working gas of the repair etching is SF6, N2 and Ar in a volume ratio of 8:4:95; the ICP power of the repair etching is 100 W, the RF bias power is 8 W, and the time is 6 min.

[0134] Embodiment 3

[0135] The embodiment provides a method for improving the surface roughness of a SiC fine grinding piece, and comprises the following steps:

[0136] (1) SF6 and O2 in a volume ratio of 7.5:1 are introduced into an etching chamber for cleaning treatment, then a substrate is placed into the etching chamber and fixed through an electrostatic chuck, the temperature of the electrostatic chuck is set to 62 DEG C, and then a SiC fine grinding piece (the surface roughness Sa is 4.016 nm) is placed on the substrate;

[0137] (2) the SiC fine grinding piece is subjected to cyclic etching;

[0138] The cyclic etching comprises a first etching step and a second etching step which are cyclically performed, and the number of cycles of the first etching step and the second etching step is 8 times;

[0139] The working gas of the first etching step is a first fluorine-based gas; the composition of the first fluorine-based gas is SF6, O2 and Ar with a volume ratio of 10:10:200;

[0140] The ICP power of the first etching step is 1200W, the RF bias power is 800W, the absolute pressure is 12mtorr, and the time is 0.5min;

[0141] The working gas of the second etching step is a chlorine-based gas; the chlorine-based gas is Cl2, BCl3, Ar and helium-oxygen mixed gas with a volume ratio of 20:5:5:6;

[0142] The ICP power of the second etching step is 500W, the RF bias power is 300W, the absolute pressure is 10mtorr, and the time is 1.5min.

[0143] (3) After the cyclic etching, repair etching is performed;

[0144] The working gas of the repair etching is SF6, N2 and Ar with a volume ratio of 8:6:85; the ICP power of the repair etching is 150W, the RF bias power is 12W, and the time is 4min.

[0145] Example 4

[0146] The embodiment provides a method for improving the surface roughness of a SiC fine grinding piece, and the ICP power of the first etching step is 600W, and the rest is the same as that in example 1.

[0147] Example 5

[0148] The embodiment provides a method for improving the surface roughness of a SiC fine grinding piece, and the ICP power of the first etching step is 1500W, and the rest is the same as that in example 1.

[0149] Example 6

[0150] The embodiment provides a method for improving the surface roughness of a SiC fine grinding piece, and the RF bias power of the first etching step is 500W, and the rest is the same as that in example 1.

[0151] Example 7

[0152] The embodiment provides a method for improving the surface roughness of a SiC fine grinding piece, and the RF bias power of the first etching step is 1000W, and the rest is the same as that in example 1.

[0153] Example 8

[0154] This embodiment provides a method for improving the surface roughness of SiC precision-ground wafers. Except for the ICP power of 200W in the second etching step, the rest is the same as in Embodiment 1.

[0155] Example 9

[0156] This embodiment provides a method for improving the surface roughness of SiC precision-ground wafers. Except for the ICP power of 600W in the second etching step, the rest is the same as in Embodiment 1.

[0157] Example 10

[0158] This embodiment provides a method for improving the surface roughness of SiC precision-ground wafers. Except for the RF bias power of 100W in the second etching step, the rest is the same as in Embodiment 1.

[0159] Example 11

[0160] This embodiment provides a method for improving the surface roughness of SiC precision-ground wafers. Except for the RF bias power of 400W in the second etching step, the rest is the same as in Embodiment 1.

[0161] Comparative Example 1

[0162] This comparative example provides a method for improving the surface roughness of a finely ground SiC wafer, including the following steps:

[0163] (1) SF6 and O2 with a volume ratio of 7.5:1 are introduced into the etching chamber for cleaning. Then the substrate is placed into the etching chamber and fixed by an electrostatic chuck. The temperature of the electrostatic chuck is set to 60℃. Then the SiC precision-ground wafer (surface roughness Sa is 4.235nm) is placed on the substrate.

[0164] (2) The SiC precision-ground wafer undergoes the first etching step and the second etching step in sequence;

[0165] The working gas for the first etching step is a first fluorine-based gas; the first fluorine-based gas is composed of SF6, O2 and Ar in a volume ratio of 8:15:200.

[0166] The first etching step has an ICP power of 1000W, an RF bias power of 700W, an absolute pressure of 10mtorr, and a time of 6min.

[0167] The working gas for the second etching step is a chlorine-based gas; the chlorine-based gas is a mixture of Cl2, BCl3, Ar and helium-oxygen in a volume ratio of 20:4:4:7.

[0168] The ICP power of the second etching step is 400 W, the RF bias power is 250 W, the absolute pressure is 8mtorr, and the time is 12 min.

[0169] (3) performing repair etching after the second etching step;

[0170] The working gas of the repair etching is SF6, N2 and Ar with a volume ratio of 8:5:90. The ICP power of the repair etching is 120 W, the RF bias power is 10 W, and the time is 5 min.

[0171] The atomic force microscope surface topography of the SiC fine grinding sheet after the surface roughness is improved by the method provided in the present comparative example is shown in FIG. 2. Figure 7 and Figure 8 .

[0172] Comparative Example 2

[0173] The present comparative example provides a method for improving the surface roughness of a SiC fine grinding sheet, which is the same as that of Example 1 except that repair etching is not performed.

[0174] The surface roughness of the SiC fine grinding sheet after the method is improved is measured for the SiC fine grinding sheets provided in Examples 1-11 and Comparative Examples 1-2, and the results are shown in Table 1.

[0175] Table 1

[0176] Surface roughness Sa (nm) Example 1 1.347 Example 2 1.759 Example 3 1.499 Example 4 2.725 Example 5 2.061 Example 6 2.987 Example 7 2.263 Example 8 2.157 Example 9 2.121 Example 10 2.568 Example 11 2.709 Comparative Example 1 3.139 Comparative Example 2 3.235

[0177] As can be seen from Table 1, when the working gas used in the first etching step is a first fluorine-based gas, the working gas used in the second etching step is a chlorine-based gas, and the first etching step and the second etching step are cyclically performed, the surface roughness of the SiC fine grinding sheet can be improved to below 2 nm. When repair etching or cyclic etching is not performed, the surface roughness of the SiC fine grinding sheet is above 3 nm.

[0178] As can be seen from the comparison of Examples 4, 5 and 1, when the ICP power of the first etching step is too low or too high, although the surface roughness of the SiC fine grinding sheet can be improved, it cannot be reduced to below 2 nm. As can be seen from the comparison of Examples 6, 7 and 1, when the RF bias power of the first etching step is too low or too high, although the surface roughness of the SiC fine grinding sheet can be improved, it cannot be reduced to below 2 nm.

[0179] From the comparison of Example 8, Example 9 and Example 1, it can be seen that when the ICP power of the second etching step is too low or too high, although the surface roughness of the SiC polishing plate can be improved, it cannot be reduced to below 2 nm. From the comparison of Example 10, Example 11 and Example 1, it can be seen that when the RF bias power of the second etching step is too low or too high, although the surface roughness of the SiC polishing plate can be improved, it cannot be reduced to below 2 nm.

[0180] Example 12

[0181] The present embodiment provides a method for improving the surface roughness of a SiC polishing plate, comprising the following steps:

[0182] (1) SF6 and O2 with a volume ratio of 7.5:1 are introduced into the etching chamber for cleaning treatment, then the substrate is placed in the etching chamber and fixed by an electrostatic chuck, and the temperature of the electrostatic chuck is set to 60°C, then the SiC polishing plate (surface roughness Sa is 3.916 nm) is placed on the substrate;

[0183] (2) The SiC polishing plate is subjected to cyclic etching;

[0184] The cyclic etching comprises a first etching step and a second etching step which are cyclically performed, and the number of cycles of the first etching step and the second etching step is 6 times;

[0185] The working gas of the first etching step is a first fluorine-based gas; the composition of the first fluorine-based gas is SF6, O2 and Ar with a volume ratio of 8:15:200;

[0186] The ICP power of the first etching step is 1000 W, the RF bias power is 700 W, the absolute pressure is 10 mtorr, and the time is 1 min;

[0187] The working gas of the second etching step is a second fluorine-based gas; the second fluorine-based gas is SF6 and O2 with a volume ratio of 9:4;

[0188] The ICP power of the second etching step is 1500 W, the RF bias power is 75 W, the absolute pressure is 20 mtorr, and the time is 1 min.

[0189] (3) After the cyclic etching, repair etching is performed;

[0190] The working gas of the repair etching is SF6, N2 and Ar with a volume ratio of 8:5:90; the ICP power of the repair etching is 120 W, the RF bias power is 10 W, and the time is 5 min.

[0191] The atomic force microscope surface topography of the SiC polishing plate after the surface roughness is improved by the method provided in the present embodiment is shown in Figure 5 andFigure 6 as shown.

[0192] Embodiment 13

[0193] The embodiment provides a method for improving surface roughness of a SiC fine grinding disc, which comprises the following steps:

[0194] (1) SF6 and O2 in a volume ratio of 7.5:1 are introduced into an etching chamber for cleaning treatment, then a substrate is placed into the etching chamber and fixed through an electrostatic chuck, the temperature of the electrostatic chuck is set to 58℃, and then a SiC fine grinding disc (surface roughness Sa is 3.942 nm) is placed on the substrate;

[0195] (2) the SiC fine grinding disc is subjected to cyclic etching;

[0196] The cyclic etching comprises cyclically performed first etching steps and second etching steps, and the cyclic number of the first etching steps and the second etching steps is 8 times.

[0197] The working gas of the first etching step is a first fluorine-based gas; the first fluorine-based gas is composed of SF6, O2 and Ar in a volume ratio of 5:20:200;

[0198] The ICP power of the first etching step is 800 W, the RF bias power is 600 W, the absolute pressure is 8mtorr, and the time is 1.5 min;

[0199] The working gas of the second etching step is a second fluorine-based gas; the second fluorine-based gas is SF6 and O2 in a volume ratio of 9:3;

[0200] The ICP power of the second etching step is 1400 W, the RF bias power is 70 W, the absolute pressure is 15mtorr, and the time is 1.5 min.

[0201] (3) repair etching is performed after the cyclic etching;

[0202] The working gas of the repair etching is SF6, N2 and Ar in a volume ratio of 8:4:95; the ICP power of the repair etching is 100 W, the RF bias power is 8 W, and the time is 6 min.

[0203] Embodiment 14

[0204] The embodiment provides a method for improving surface roughness of a SiC fine grinding disc, which comprises the following steps:

[0205] (1) SF6 and O2 in a volume ratio of 7.5:1 are introduced into an etching chamber for cleaning treatment, then a substrate is placed into the etching chamber and fixed through an electrostatic chuck, the temperature of the electrostatic chuck is set to 62℃, and then a SiC fine grinding disc (surface roughness Sa is 3.719 nm) is placed on the substrate;

[0206] (2) SiC fine grinding sheet is subjected to cyclic etching;

[0207] The cyclic etching comprises a first etching step and a second etching step which are cyclically performed, and the number of cycles of the first etching step and the second etching step is 8 times;

[0208] The working gas of the first etching step is a first fluorine-based gas; the first fluorine-based gas is composed of SF6, O2 and Ar in a volume ratio of 10:10:200;

[0209] The ICP power of the first etching step is 1200W, the RF bias power is 800W, the absolute pressure is 12mtorr, and the time is 0.5min;

[0210] The working gas of the second etching step is a second fluorine-based gas; the second fluorine-based gas is SF6 and O2 in a volume ratio of 9:5;

[0211] The ICP power of the second etching step is 1600W, the RF bias power is 80W, the absolute pressure is 25mtorr, and the time is 0.5min.

[0212] (3) After the cyclic etching, repair etching is performed;

[0213] The working gas of the repair etching is SF6, N2 and Ar in a volume ratio of 8:6:85; the ICP power of the repair etching is 150W, the RF bias power is 12W, and the time is 4min.

[0214] Example 15

[0215] The method for improving the surface roughness of the SiC fine grinding sheet provided in this embodiment is the same as that in Example 12, except that the ICP power of the first etching step is 600W.

[0216] Example 16

[0217] The method for improving the surface roughness of the SiC fine grinding sheet provided in this embodiment is the same as that in Example 12, except that the ICP power of the first etching step is 1500W.

[0218] Example 17

[0219] The method for improving the surface roughness of the SiC fine grinding sheet provided in this embodiment is the same as that in Example 12, except that the RF bias power of the first etching step is 500W.

[0220] Example 18

[0221] The embodiment provides a method for improving the surface roughness of a SiC fine grinding disc, wherein, except that the RF bias power of the first etching step is 1000W, the rest is the same as that in the embodiment 12.

[0222] Embodiment 19

[0223] The embodiment provides a method for improving the surface roughness of a SiC fine grinding disc, wherein, except that the ICP power of the second etching step is 1200W, the rest is the same as that in the embodiment 12.

[0224] Embodiment 20

[0225] The embodiment provides a method for improving the surface roughness of a SiC fine grinding disc, wherein, except that the ICP power of the second etching step is 1800W, the rest is the same as that in the embodiment 12.

[0226] Embodiment 21

[0227] The embodiment provides a method for improving the surface roughness of a SiC fine grinding disc, wherein, except that the RF bias power of the second etching step is 60W, the rest is the same as that in the embodiment 12.

[0228] Embodiment 22

[0229] The embodiment provides a method for improving the surface roughness of a SiC fine grinding disc, wherein, except that the RF bias power of the second etching step is 100W, the rest is the same as that in the embodiment 12.

[0230] Comparative example 3

[0231] The comparative example provides a method for improving the surface roughness of a SiC fine grinding disc, comprising the following steps:

[0232] (1) SF6 and O2 with a volume ratio of 7.5:1 are introduced into the etching chamber for cleaning treatment, then the substrate is placed into the etching cavity and fixed through the electrostatic chuck, and the temperature of the electrostatic chuck is set to 60 DEG C, then the SiC fine grinding disc (the surface roughness Sa is 3.871 nm) is placed on the substrate;

[0233] (2) the SiC fine grinding disc is sequentially subjected to the first etching step and the second etching step;

[0234] The working gas of the first etching step is the first fluorine-based gas; the composition of the first fluorine-based gas is SF6, O2 and Ar with a volume ratio of 8:15:200;

[0235] The ICP power of the first etching step is 1000W, the RF bias power is 700W, the absolute pressure is 10mtorr, and the time is 6min;

[0236] The working gas of the second etching step is a second fluorine-based gas; the second fluorine-based gas is SF6 and O2 at a volume ratio of 9:4;

[0237] The ICP power of the second etching step is 1500 W, the RF bias power is 75 W, the absolute pressure is 20 mtorr, and the time is 6 min.

[0238] (3) After the second etching step, repair etching is performed;

[0239] The working gas of the repair etching is SF6, N2 and Ar at a volume ratio of 8:5:90; the ICP power of the repair etching is 120 W, the RF bias power is 10 W, and the time is 5 min.

[0240] Comparative Example 4

[0241] This comparative example provides a method for improving the surface roughness of a SiC fine grinding plate, which is the same as Example 12 except that repair etching is not performed.

[0242] The surface roughness of the SiC fine grinding plate after the method improvement provided in Examples 12-22 and Comparative Examples 3-4 is measured, and the results are shown in Table 2.

[0243] Table 2

[0244] Surface roughness Sa (nm) Example 12 1.420 Example 13 1.496 Example 14 1.754 Example 15 2.475 Example 16 2.418 Example 17 2.775 Example 18 2.308 Example 19 2.674 Example 20 2.340 Example 21 2.855 Example 22 2.935 Comparative Example 3 3.353 Comparative Example 4 3.304

[0245] As can be seen from Table 2, when the working gas used in the first etching step is a first fluorine-based gas, the working gas used in the second etching step is a second fluorine-based gas, and the first etching step and the second etching step are cycled, the surface roughness of the SiC fine grinding plate can be improved to below 2 nm. When no cyclic etching or repair etching is performed, the surface roughness of the SiC fine grinding plate is above 3 nm.

[0246] As can be seen from the comparison of Examples 15, 16 and 12, when the ICP power of the first etching step is too low or too high, although the surface roughness of the SiC fine grinding plate can be improved, it cannot be reduced to below 2 nm. As can be seen from the comparison of Examples 17, 18 and 12, when the RF bias power of the first etching step is too low or too high, although the surface roughness of the SiC fine grinding plate can be improved, it cannot be reduced to below 2 nm.

[0247] From the comparison of Example 19, Example 20 and Example 12, it can be known that when the ICP power of the second etching step is too low or too high, although the surface roughness of the SiC fine grinding sheet can be improved, it cannot be reduced to below 2nm. From the comparison of Example 21, Example 22 and Example 12, it can be known that when the RF bias power of the second etching step is too low or too high, although the surface roughness of the SiC fine grinding sheet can be improved, it cannot be reduced to below 2nm.

[0248] In summary, the conventional ICP etching process mainly uses chlorine-based gas or fluorine-based gas for single etching, the present application combines the first etching step and the second etching step, selects different working gases to ensure the etching rate, and can realize the rapid removal of SiC material; at the same time, the cyclic etching can avoid the lattice damage caused by the continuous heating of high-energy particles, and can also reduce the continuous erosion of the plasma to the cavity, and slow down the aging of the cavity components; finally, through the repair etching, the surface roughness Sa of the SiC fine grinding sheet can be reduced to below 2nm.

[0249] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by any person skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for improving the surface roughness of finely ground SiC wafers, characterized in that, The method includes the following steps: The SiC precision-polished wafer is subjected to cyclic etching and repair etching to reduce the surface roughness Sa of the SiC precision-polished wafer to below 2nm. The cyclic etching includes a first etching step and a second etching step performed cyclically. The working gas used in the first etching step includes a first fluorine-based gas; The working gas used in the second etching step includes chlorine-based gas and / or a second fluorine-based gas.

2. The method according to claim 1, characterized in that, The first fluorine-based gas comprises SF6, O2, and Ar; And / or, the volume ratio of SF6 to Ar is 5:200 to 10:200; And / or, the volume ratio of O2 to Ar is 10:200 to 20:

200.

3. The method according to claim 1, characterized in that, The ICP power of the first etching step is 800W to 1200W; And / or, the RF bias power of the first etching step is 600W to 800W; And / or, the absolute pressure of the first etching step is 8 mtorr to 12 mtorr; And / or, the time for the first etching step is 0.5 min to 1.5 min.

4. The method according to claim 1, characterized in that, The chlorine-based gas includes Cl2, BCl3, Ar, and a helium-oxygen mixture; And / or, the volume ratio of the Cl2, BCl3, Ar and the helium-oxygen mixture is 20:(3-5):(3-5):(6-8).

5. The method according to claim 4, characterized in that, The ICP power for the second etching step is 300W to 500W; And / or, the RF bias power of the second etching step is 200W to 300W; And / or, the absolute pressure of the second etching step is 6 mtorr to 10 mtorr; And / or, the time for the second etching step is 1.5 min to 2.5 min.

6. The method according to claim 1, characterized in that, The second fluorine-based gas includes SF6 and O2; And / or, the volume ratio of SF6 to O2 is 9:(3-5).

7. The method according to claim 6, characterized in that, The ICP power for the second etching step is 1400W to 1600W; And / or, the RF bias power of the second etching step is 70W to 80W; And / or, the absolute pressure of the second etching step is 15 mtorr to 25 mtorr; And / or, the time for the second etching step is 0.5 min to 1.5 min.

8. The method according to claim 1, characterized in that, The first etching step and the second etching step are repeated 4 to 8 times.

9. The method according to any one of claims 1 to 8, characterized in that, The working gases for the repair etching include SF6, N2, and Ar; And / or, the volume ratio of SF6, N2 and Ar is 8:(4-6):(85-95).

10. The method according to claim 9, characterized in that, The ICP power for the repair etching is 100W to 150W; And / or, the RF bias power for the repair etching is 8W to 12W; And / or, the repair etching time is 4 min to 6 min.

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