A method for depositing a silicon carbide coating on a surface of quartz glass

Abstract

The application relates to a method for depositing a silicon carbide coating on a quartz glass surface, and the specific steps are as follows: 1) vacuumizing to reduce the pressure in a deposition cavity to below 10 Pa; 2) introducing hydrogen into the deposition cavity, adjusting the pressure in the deposition cavity to 200-2000 Pa, and loading a laser to etch the quartz glass surface; 3) vacuumizing the deposition cavity to below 10 Pa, introducing hexamethyldisilane and hydrogen, adjusting the pressure in the reaction cavity to 1000-4000 Pa, and loading a laser to deposit a silicon carbide coating on the quartz glass surface. The method for depositing a silicon carbide coating on a quartz glass surface provided by the application is relatively simple, the silicon carbide coating prepared on the quartz glass surface is free of cracks, and the adhesion between the coating and the substrate is significantly increased, so that the service life and stability of the quartz glass crucible are significantly improved, and the production of large-size high-purity single crystal silicon wafers is facilitated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of depositing carbide by chemical vapor deposition process, and particularly relates to a method for depositing a silicon carbide coating on a quartz glass surface. BACKGROUND

[0002] Monocrystalline silicon, as a basic material for the microelectronic industry, is widely used in the manufacture of integrated circuits and power electronic devices, and is a key basic material for the development and innovation of information technology in today's society. The Czochralski method is mature and stable, has low production cost, and the prepared monocrystalline has good mechanical properties and is easier to make large-diameter monocrystalline wafers, so it has become the mainstream technology for preparing monocrystalline silicon, with a market share of over 90%. The Czochralski method is to melt polycrystalline silicon into a molten state by heating with a hot field, control the temperature of the liquid surface at the critical point of crystallization by controlling the hot field, and then pull the monocrystalline seed crystal upward from the liquid surface, so that the molten liquid silicon rises with the pulling of the seed crystal and grows into a monocrystalline silicon rod according to the crystal direction of the seed crystal. The crucible, as a carrier container for molten liquid silicon during the growth process, is required to be able to work continuously for more than 50 hours at a temperature of more than 1500℃. Under the condition of long-term high-temperature work, the surface chemical elements of the crucible are easy to penetrate into the molten silicon, thereby increasing the defect density and impurity content of the monocrystalline silicon. Therefore, the material and structure of the crucible are important factors affecting the quality and yield of monocrystalline silicon.

[0003] Quartz crucibles have become the preferred container for preparing monocrystalline silicon by the Czochralski method due to their low cost, high stability and purity, low impurity content, and easy processing. Although the melting point of quartz crucible (1750℃) is higher than the temperature of molten liquid silicon (1500℃), a small amount of oxygen will still dissolve into the liquid silicon at a service temperature of 1500℃.

[0004] In order to avoid the reaction or adhesion of quartz glass crucible and molten silicon, and at the same time reduce the invasion of other impurities in the crucible, a coating with a certain thickness, high thermal coefficient, stable chemical properties and no effect on the quality of silicon is prepared on the inner wall of the crucible, which is used as a separation layer between the quartz glass crucible and the molten silicon, and is the most effective means to ensure the high purity of monocrystalline silicon. In current industrial production, silicon carbide has excellent properties such as high melting point, high hardness, high stability, thermal shock resistance and oxidation resistance, and has become the preferred material for the inner wall coating of the new generation of quartz crucible. However, due to the obvious difference between the thermal expansion coefficient and the lattice constant of quartz and silicon carbide, the silicon carbide coating grown on the surface of the quartz glass substrate is easy to crack or fall off, resulting in damage to the coating. SUMMARY

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a method for depositing a silicon carbide coating on the surface of quartz glass. The method employs specific process conditions to etch the surface of the quartz glass to give it an appropriate roughness, which allows for a tight bond with the subsequently deposited silicon carbide film. Furthermore, the deposited silicon carbide film has a certain porosity, which can alleviate stress concentration caused by thermal expansion mismatch during heating, and prevent the silicon carbide coating from cracking and peeling off, thus significantly improving its service life and stability.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0007] A method for depositing a silicon carbide coating on the surface of quartz glass is provided, the specific steps of which are as follows:

[0008] 1) Place the quartz glass substrate on the base inside the deposition chamber of the laser chemical vapor deposition equipment, and evacuate the chamber to reduce the pressure to below 10 Pa.

[0009] 2) Introduce hydrogen into the deposition chamber, adjust the pressure inside the deposition chamber to 200-2000 Pa, turn on the continuous laser, and apply the laser to the surface of the quartz glass substrate through the glass window on the deposition chamber to etch the quartz glass surface. After the etching is completed, turn off the laser and hydrogen.

[0010] 3) Evacuate the deposition chamber to below 10 Pa, then introduce hexamethyldisilane and hydrogen gas, adjust the pressure in the reaction chamber to 1000-4000 Pa, turn on the continuous laser again, apply the laser to the surface of the quartz glass substrate through the glass window on the deposition chamber to deposit a silicon carbide coating on the quartz glass surface, turn off the laser after deposition, turn off the hexamethyldisilane and hydrogen gas, then reduce the vacuum in the deposition chamber to below 10 Pa, wait for the substrate to cool naturally to room temperature, turn on the laser chemical vapor deposition equipment, and take out the sample.

[0011] According to the above scheme, the hydrogen flow rate in step 2) is 50-1000 sccm.

[0012] According to the above scheme, the laser wavelength in step 2) is 808-1060nm.

[0013] According to the above scheme, the process conditions for etching the quartz glass surface in step 2) are as follows: after the surface temperature of the quartz glass substrate reaches 1100-1300℃, continuous laser irradiation is performed for 2-30 minutes.

[0014] According to the above scheme, in step 3), the flow rate of hexamethyldisilane is 2-30 sccm, and the flow rate of hydrogen is 200-2000 sccm.

[0015] According to the above scheme, the process conditions for depositing a silicon carbide coating on the quartz glass surface in step 3) are as follows: after the surface temperature of the quartz glass substrate rises to 1000-1250℃, it is held at that temperature for 5-60 minutes. The temperature is kept constant by controlling the laser power through a computer program.

[0016] The present invention also includes a quartz glass crucible coated with silicon carbide prepared by the above method.

[0017] And the application of the aforementioned silicon carbide-coated quartz glass crucibles in the wafer manufacturing field.

[0018] This invention uses laser irradiation of quartz glass to induce efficient etching of the quartz glass surface by hydrogen gas through appropriate processes, forming a large number of micro-nano-scale uneven structures on the quartz glass surface. The above-mentioned uneven structures are beneficial to increasing the porosity of the subsequently grown silicon carbide coating and the uniform distribution of voids, and significantly improve the interlocking force between the silicon carbide coating and the quartz glass substrate, thereby avoiding the problem of coating cracking caused by thermal expansion mismatch between the coating and the substrate.

[0019] The beneficial effects of the present invention are as follows: the method for depositing silicon carbide coating on the surface of quartz glass provided by the present invention is relatively simple, the silicon carbide coating prepared on the surface of quartz glass is free of cracks, and the adhesion between the coating and the substrate is significantly increased, thus significantly improving the service life and stability of the quartz glass crucible, which is beneficial to the production of large-size, high-purity single crystal silicon wafers. Attached Figure Description

[0020] Figure 1 SEM images of the surface and cross-section (b) of the silicon carbide coating deposited on an unetched quartz glass substrate in Comparative Example 1 of this invention;

[0021] Figure 2 SEM images of the quartz glass substrate used in Example 1 before (a, b) and after (c, d) laser etching.

[0022] Figure 3 Atomic force microscopy images and roughness comparison diagrams of the surface of the quartz glass substrate before (a) and after (b) laser etching in Example 1.

[0023] Figure 4 The surface (a) of the silicon carbide coating grown on the etched quartz glass surface in Example 1.

[0024] SEM image of section (b);

[0025] Figure 5This image shows a comparison of the adhesion between the quartz glass substrate and the silicon carbide coating when the substrate is treated with un-laser-etched and etched quartz glass substrates at 1000℃, 1025℃, 1050℃, and 1075℃. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] Comparative Example 1

[0028] A method for depositing a silicon carbide coating on a quartz glass surface, comprising the following steps:

[0029] 1) Place the quartz glass substrate (12mm×15mm) on the base inside the deposition chamber of the laser chemical vapor deposition equipment, and evacuate to reduce the pressure inside the deposition chamber to below 10Pa;

[0030] 2) Without etching, the deposition chamber is directly evacuated to below 10 Pa, and then hexamethyldisilane and hydrogen are introduced. The flow rate of hexamethyldisilane is 5 sccm, and the flow rate of hydrogen is 500 sccm. The pressure in the reaction chamber is adjusted to 2500 Pa. The continuous laser is turned on, and the laser is applied to the surface of the quartz glass substrate through the glass window on the deposition chamber to deposit a silicon carbide coating on the quartz glass surface. After the substrate surface temperature rises to the set temperature of 1075℃, it is held for 10 min. After the deposition is completed, the laser is turned off, the hexamethyldisilane and hydrogen are turned off, and the vacuum in the deposition chamber is reduced to below 10 Pa. After the substrate cools naturally to room temperature, the laser chemical vapor deposition equipment is turned on and the sample is taken out.

[0031] Figure 1 The SEM images of the coating (a) surface and (b) cross section of the comparative sample show that when the quartz glass substrate is not etched by laser irradiation, the subsequently grown silicon carbide coating is relatively dense, but there are many cracks on the surface, and the coating thickness is about 27.8 μm.

[0032] Example 1

[0033] A method for depositing a silicon carbide coating on a quartz glass surface, comprising the following steps:

[0034] 1) Place the quartz glass substrate (12mm×15mm) on the base inside the deposition chamber of the laser chemical vapor deposition equipment, and evacuate to reduce the pressure inside the deposition chamber to below 10Pa;

[0035] 2) Introduce hydrogen into the deposition chamber, set the hydrogen flow rate to 500 sccm, adjust the pressure in the deposition chamber to 500 Pa, turn on the continuous laser with a laser wavelength of 1000 nm, apply the laser to the surface of the quartz glass substrate through the glass window on the deposition chamber to etch the quartz glass surface, and continue laser irradiation for 20 minutes after the substrate surface temperature reaches the set temperature of 1200℃, and then turn off the laser and hydrogen.

[0036] 3) Evacuate the deposition chamber to below 10 Pa, then introduce hexamethyldisilane and hydrogen gas. The flow rate of hexamethyldisilane is 5 sccm, and the flow rate of hydrogen gas is 500 sccm. Adjust the pressure in the reaction chamber to 2500 Pa. Turn on the continuous laser again and apply the laser to the surface of the quartz glass substrate through the glass window on the deposition chamber to deposit a silicon carbide coating on the quartz glass surface. After the substrate surface temperature rises to the set temperature of 1075℃, hold it at that temperature for 10 min. After the deposition is completed, turn off the laser, turn off the hexamethyldisilane and hydrogen gas, and then reduce the vacuum in the deposition chamber to below 10 Pa. After the substrate cools naturally to room temperature, turn on the laser chemical vapor deposition equipment and take out the sample.

[0037] Figure 2 The images show SEM images of the quartz glass substrate before and after laser etching in this embodiment. a and b are before etching, and c and d are after etching. The images show that after etching, a large number of micro-nano-sized depressions and protrusions are formed on the substrate surface, and they are evenly distributed.

[0038] Figure 3 The images show atomic force microscopy (AFM) images and roughness comparisons of the quartz glass substrate before (a) and after (b) laser etching in this embodiment. The roughness parameter Sa is 0.0429 μm before etching and 3.34 μm after etching, showing that the surface roughness of the substrate increases significantly after etching.

[0039] Figure 4 The images show SEM images of the surface (a) and cross-section (b) of the coating in this embodiment. The surface SEM image shows a large number of hemispherical granular silicon carbide clusters on the coating surface; the cross-section SEM image shows that silicon carbide is densely grown on the uneven quartz glass surface, and the silicon carbide clusters are composed of rod-shaped nano-sized grains with pores between them. The total thickness of the silicon carbide coating is approximately 47.3 μm. The figures show that after laser etching of the quartz glass substrate, a silicon carbide coating was grown using the same deposition parameters as in Comparative Example 1. No cracks were observed on the coating surface, indicating that etching can increase the porosity of the silicon carbide coating and effectively eliminate cracks caused by thermal expansion mismatch.

[0040] Using untreated quartz glass substrates and quartz glass substrates treated with laser etching (step 2) of this embodiment as substrates, silicon carbide coatings were deposited at 1000℃, 1025℃, and 1050℃ respectively using the method in step 3) of this embodiment, with other conditions the same as in step 3) of this embodiment. The adhesion between the obtained samples and the silicon carbide coating on the quartz glass substrates in Comparative Example 1 and the samples of this embodiment was tested. The test results are as follows: Figure 5 As shown, the adhesion between the coating and the substrate is significantly enhanced after laser etching.

[0041] Example 2

[0042] A method for depositing a silicon carbide coating on a quartz glass surface, comprising the following steps:

[0043] 1) Place the quartz glass substrate on the base inside the deposition chamber of the laser chemical vapor deposition equipment, and evacuate the chamber to reduce the pressure to below 10 Pa.

[0044] 2) Introduce hydrogen into the deposition chamber, set the hydrogen flow rate to 50 sccm, adjust the pressure in the deposition chamber to 2000 Pa, turn on the continuous laser with a laser wavelength of 808 nm, apply the laser to the surface of the quartz glass substrate through the glass window on the deposition chamber to etch the quartz glass surface, and continue laser irradiation for 30 min after the substrate surface temperature reaches the set temperature of 1100℃, and then turn off the laser and hydrogen after the end.

[0045] 3) Evacuate the deposition chamber to below 10 Pa, then introduce hexamethyldisilane and hydrogen gas. The flow rate of hexamethyldisilane is 2 sccm, and the flow rate of hydrogen gas is 200 sccm. Adjust the pressure in the reaction chamber to 1000 Pa, turn on the continuous laser again, and apply the laser to the surface of the quartz glass substrate through the glass window on the deposition chamber to deposit a silicon carbide coating on the quartz glass surface. After the substrate surface temperature rises to the set temperature of 1000℃, hold it at that temperature for 60 min. After the deposition is completed, turn off the laser, turn off the hexamethyldisilane and hydrogen gas, and then reduce the vacuum in the deposition chamber to below 10 Pa. After the substrate cools naturally to room temperature, turn on the laser chemical vapor deposition equipment and take out the sample.

[0046] Example 3

[0047] A method for depositing a silicon carbide coating on a quartz glass surface, comprising the following steps:

[0048] 1) Place the quartz glass substrate on the base inside the deposition chamber of the laser chemical vapor deposition equipment, and evacuate the chamber to reduce the pressure to below 10 Pa.

[0049] 2) Introduce hydrogen into the deposition chamber, set the hydrogen flow rate to 1000 sccm, adjust the pressure in the deposition chamber to 200 Pa, turn on the continuous laser with a laser wavelength of 1060 nm, apply the laser to the surface of the quartz glass substrate through the glass window on the deposition chamber to etch the quartz glass surface, and continue laser irradiation for 2 minutes after the substrate surface temperature reaches the set temperature of 1300℃, and then turn off the laser and hydrogen after the end.

[0050] 3) Evacuate the deposition chamber to below 10 Pa, then introduce hexamethyldisilane and hydrogen gas. The flow rate of hexamethyldisilane is 30 sccm, and the flow rate of hydrogen gas is 2000 sccm. Adjust the pressure in the reaction chamber to 4000 Pa. Turn on the continuous laser again and apply the laser to the surface of the quartz glass substrate through the glass window on the deposition chamber to deposit a silicon carbide coating on the quartz glass surface. After the substrate surface temperature rises to the set temperature of 1250℃, hold it at that temperature for 5 minutes. After the deposition is completed, turn off the laser, turn off the hexamethyldisilane and hydrogen gas, and then reduce the vacuum in the deposition chamber to below 10 Pa. After the substrate cools naturally to room temperature, turn on the laser chemical vapor deposition equipment and take out the sample.

[0051] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be within the protection scope of the present invention.

Claims

1. A method of depositing a silicon carbide coating on a surface of quartz glass, characterized by, The specific steps are as follows: 1) Place the quartz glass substrate on the base in the deposition cavity of the laser chemical vapor deposition device, and vacuumize the deposition cavity to a pressure below 10 Pa; 2) Introduce hydrogen into the deposition cavity at a flow rate of 50-1000 sccm, adjust the pressure in the deposition cavity to 200-2000 Pa, turn on the continuous laser, and load the laser onto the surface of the quartz glass substrate through the glass window on the deposition cavity to etch the surface of the quartz glass, the process conditions for etching the surface of the quartz glass being: after the surface temperature of the quartz glass substrate reaches 1100-1300 °C, continuously irradiate with the laser for 2-30 min, and then turn off the laser and hydrogen after etching is completed; 3) Vacuumize the deposition cavity to below 10 Pa, introduce hexamethyldisilane and hydrogen, adjust the pressure in the reaction cavity to 1000-4000 Pa, turn on the continuous laser again, load the laser onto the surface of the quartz glass substrate through the glass window on the deposition cavity to deposit a silicon carbide coating on the surface of the quartz glass, turn off the laser after deposition is completed, turn off the hexamethyldisilane and hydrogen, vacuumize the deposition cavity to below 10 Pa again, cool the substrate to room temperature naturally, turn on the laser chemical vapor deposition device, and take out the sample.

2. The method of claim 1, wherein the method further comprises: In step 3), the flow rate of hexamethyldisilane is 2-30 sccm, and the flow rate of hydrogen is 200-2000 sccm.

3. The method of claim 1, wherein the method further comprises: In step 3), the process conditions for depositing a silicon carbide coating on the surface of the quartz glass are: after the surface temperature of the quartz glass substrate is raised to 1000-1250 °C, heat for 5-60 min.

4. A quartz glass crucible coated with a silicon carbide coating prepared by the method of any one of claims 1-3.

5. Use of the quartz glass crucible of claim 4 in the field of wafer production.

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