Preparation method and application of CVD-SiC focusing ring

Abstract

The invention relates to the field of ceramic materials, and discloses a preparation method and application of a CVD-SiC focusing ring. The preparation method comprises the following steps: 1) placing a graphite ring in a CVD furnace, and heating to 1050-1150 DEG C under the condition of introducing hydrogen; 2) introducing HCl and hydrogen to clean the surface of the graphite ring; 3) raising the temperature to 1250-1300 DEG C, keeping the temperature, introducing process gas comprising 5-9vol% of trichloromethylsilane, 86-91vol% of hydrogen and 2-6vol% of HCl, and reacting to obtain a graphite ring of which the surface is plated with a CVD-SiC layer; 4, machining, polishing and cleaning are conducted, and the CVD-SiC focusing ring is obtained.The CVD-SiC focusing ring prepared through the CVD method has the advantages of being high in purity, density and heat conductivity and can meet the use requirement of semiconductor etching equipment.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, and more particularly to a method for preparing a CVD-SiC focusing ring and its application. Background Technology

[0002] The focusing ring is a crucial ceramic component in plasma etching equipment. It is a vital part placed outside the wafer and in direct contact with it. By applying voltage to the ring, the plasma passing through it is focused onto the wafer, thereby improving processing uniformity. Since the focusing ring is in direct contact with the plasma within the vacuum reaction chamber, it must be made of a material resistant to plasma corrosion.

[0003] Traditional focusing rings are made of silicon or quartz. Conductive silicon is a commonly used focusing ring material, and its conductivity is almost the same as that of silicon wafers. However, its disadvantage is that it has poor resistance to etching in fluorine-containing plasma. The materials of etching machine components often show severe corrosion after a period of use, which seriously reduces its production efficiency.

[0004] Silicon carbide possesses electrical conductivity similar to silicon and excellent resistance to ion etching. With the advancement of integrated circuit miniaturization, the demand for and importance of etching processes in integrated circuit manufacturing are constantly increasing, and the power and energy of etching plasmas are continuously improving, especially the plasma energy required in capacitive coupling (CCP) plasma etching equipment. Therefore, the utilization rate of focusing rings made of silicon carbide materials is becoming increasingly higher.

[0005] However, most commonly used silicon carbide ceramic materials are prepared by reaction sintering (e.g., patent CN202510964800.3), which suffers from low purity, low density, and low thermal conductivity, making it difficult to meet the requirements of semiconductor etching equipment. Therefore, it is necessary to develop a silicon carbide focusing ring that simultaneously possesses high purity, high density, and high thermal conductivity to meet the needs of semiconductor etching equipment. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a CVD-SiC focusing ring and its application. The CVD-SiC focusing ring prepared by this invention using the CVD method possesses high purity, high density, and high thermal conductivity, meeting the requirements of semiconductor etching equipment.

[0007] The specific technical solution of the present invention includes: In a first aspect, the present invention provides a method for preparing a CVD-SiC focusing ring, comprising the following steps: 1) Place the graphite ring in a CVD furnace and heat it to 1050-1150℃ under hydrogen gas conditions.

[0008] Graphite is highly reactive at high temperatures, readily reacting with trace amounts of oxygen to produce carbon monoxide or carbon dioxide. This not only corrodes the substrate but also introduces impurities into the reaction chamber. Introducing hydrogen gas protects the graphite substrate from oxidation. More importantly, hydrogen reacts with the unstable, disordered carbon atoms on the graphite surface (forming methane), effectively "cleaning" and "stabilizing" the graphite surface, preventing the release of carbon particles that contaminate the film during subsequent deposition.

[0009] 2) Introduce HCl and hydrogen gas to clean the surface of the graphite ring.

[0010] HCl reacts efficiently with metallic impurities at high temperatures, generating gaseous products that are expelled with the gas flow, but it causes very little corrosion to the high-quality graphite matrix itself (high-purity graphite is very resistant to HCl corrosion). This selectivity allows it to remove contaminants without severely damaging the substrate.

[0011] 3) After heating and holding at that temperature, process gases including trichloromethylsilane, hydrogen and HCl are introduced to react and obtain graphite rings with a CVD-SiC layer on the surface.

[0012] After introducing the aforementioned process gas, a CVD-SiC layer can be deposited on the surface of the graphite ring. The main reaction formula is CH3SiCl3(g) → SiC(s) + 3HCl(g). The actual reaction process is quite complex, and the intermediate steps involved mainly include: ① Decomposition of MTS: CH3SiCl3 (g) → :SiCl2(g) + :CH2(g) + HCl(g); This is a simplified representation, where : represents an active free radical. In reality, MTS undergoes homolytic cleavage to produce free radicals such as ·SiCl3 and ·CH3. Reduction reaction with H2: H2 is also activated at high temperatures, reacting with MTS fragments to generate more crucial intermediates.

[0013] The formation of silicon-active species: CH3SiCl3(g) + H2(g) → :SiCl2(g) + CH4(g) + HCl(g); SiCl2 (dichlorosilane) is considered one of the most important silicon-containing vapor precursors in SiC deposition.

[0014] Generates carbon-active species: The -CH3 group in MTS can react with H2 to generate methane (CH4), and CH4 can be further cracked or reacted at high temperatures to generate small molecule hydrocarbons such as ·CH3, C2H2 (acetylene), and C2H4 (ethylene), which serve as carbon sources.

[0015] ② Surface deposition reaction: The generated gaseous intermediates (such as SiCl2, CH4, C2H2, etc.) diffuse to the substrate surface, undergo adsorption and surface reactions, and form SiC. Surface reaction: SiCl2 (g) + H2 (g) → Si(s) + 2HCl(g) (Si atoms are released on the surface) C2H2(g) + 2H2(g) → 2C(s) + 3H2(g) or CH4(g) → C(s) + 2H2(g) (C atoms are released on the surface); ③Si combines with C to form SiC: Si and C atoms adsorbed on the surface migrate and bond, eventually forming SiC crystals.

[0016] Si(s) + C(s) → SiC(s) Traditionally, silicon carbide materials are prepared by reaction sintering, resulting in low purity, low density, low thermal conductivity, and an α-SiC crystal form. This invention utilizes a CVD-SiC focusing ring prepared by CVD, where the deposition process relies primarily on gas-phase reaction, avoiding the sintering aids required in solid-state sintering. The resulting CVD-SiC layer exhibits high purity (over 99.999%), high density (>3.19 g / cm³), and high thermal conductivity (>250 W / (m·k)). Its thickness is preferably 1.5-1.8 mm, and its crystal form is (111)-grown 3C-SiC (β-SiC), demonstrating excellent performance and fully meeting the requirements of semiconductor etching equipment. Compared to traditional α-SiC, the core and most crucial advantage of β-SiC in etching equipment lies in its isotropic etching. The etching reaction chamber contains extremely high-density, highly active plasma (containing fluorine- and chlorine-based free radicals and ions). The chemical bond strength and properties of β-SiC are almost identical in all crystal directions. When subjected to plasma attack, its corrosion rate is uniform in all directions.

[0017] 4) Machining, polishing, and cleaning are performed to obtain the CVD-SiC focusing ring.

[0018] Preferably, in step 3), the process gas includes 5-9 vol% trichloromethylsilane (MTS), 86-91 vol% hydrogen, and 2-6 vol% HCl.

[0019] This invention has found that the ratio of the above three gases in the process gas has a significant impact on the performance of the formed silicon nitride. Specifically: (1) When the MTS content is too low, the insufficient concentration of reactants may lead to difficulty in initial nucleation and discontinuous coating. When the MTS content is too high, it is easy to induce homogeneous nucleation in the gas phase, generating silicon clusters or silicon droplets, consuming reactants, which may reduce the effective deposition rate and contaminate the coating. At the same time, the gas phase nucleants block the pore inlet, severely hindering the transport of reactants to the interior, resulting in poor deep hole permeability and uneven coating thickness. (2) When the H2 content is too low, the deposition rate may decrease; MTS decomposition is insufficient. It is not conducive to the removal of chlorine-containing byproducts (such as HCl), which may affect the purity of the coating; it may promote the formation of hydrocarbons, leading to carbon enrichment in the coating. When the H2 content is too high, the strong reducing atmosphere helps to suppress carbon deposition, but excessive dilution of MTS will weaken all deposition effects. (3) HCl itself does not participate in the reaction, but only acts as a regulator. Adjustment in silicon-rich or carbon-rich conditions helps to control the C / Si stoichiometric ratio.

[0020] Preferably, in step 3), the heating temperature is 1250-1300℃.

[0021] At excessively low temperatures, MTS decomposes incompletely, resulting in a slow reaction rate and extremely low deposition rate, leading to poor production efficiency. Reactant atoms or groups reaching the substrate surface lack sufficient energy to migrate and find the most stable locations (such as lattice sites) for nucleation and growth. This results in random atomic stacking, forming amorphous or nanocrystalline SiC coatings. Such coatings are typically non-dense, porous, and have poor mechanical properties (hardness, strength) and chemical stability. At excessively high temperatures, precursors react with each other in the gas phase before reaching the substrate surface, generating silicon clusters or carbon nanoparticles. These particles deposit as powder on the coating surface, making the coating rough, loose, porous, and with extremely poor adhesion. This also consumes a large amount of reactants, reducing the effective deposition rate and potentially contaminating the reaction chamber.

[0022] Preferably, in step 1), the selected graphite ring is formed by isostatic pressing, with an impurity content of <20ppm and a coefficient of thermal expansion of 3.9×10⁻⁶. -6 ~4.8×10 -6 / K(CTE RT-400℃), specific gravity is 1.6-1.9g / cm³ 3 .

[0023] To ensure the final purity of the prepared silicon carbide material reaches 99.9995%, the ash content of the graphite substrate needs to be less than 20 ppm; to minimize cracking during annealing and processing after coating, the selected graphite material should have a coefficient of thermal expansion similar to that of the silicon carbide material (4.0~4.8) × 10⁻⁶. -6 / K(CTE RT-400℃); In order to ensure that the crystal orientation during coating is not affected, the graphite material surface must not have defects such as pores. At this specific gravity, the graphite material is basically free of pores.

[0024] Preferably, in step 1), before heating, the CVD furnace is evacuated and repressurized twice, including: first evacuation followed by nitrogen repressurization; second evacuation followed by hydrogen repressurization.

[0025] Further preferred, in step 1), the two consecutive vacuuming and repressurization processes include: First vacuuming: The gas inside the CVD furnace is extracted until the vacuum level reaches 1.0 × 10⁻⁶. -2 Kpa, maintain pressure for 5-15 minutes; Nitrogen repressurization: Introduce N2 until the furnace pressure is greater than 115 kPa, and maintain the pressure for 5-15 minutes; Second vacuuming: Repeat the first vacuuming process; Hydrogen gas is repressurized, and H2 is introduced until the pressure inside the furnace is greater than 115 kPa, and the pressure is maintained for 5-15 minutes.

[0026] Preferably, in step 1), the heating rate is 3-7℃ / min; after heating, the temperature is maintained for 20-40min.

[0027] Preferably, in step 2), the volume ratio of HCl to hydrogen is 8-12:1.

[0028] Preferably, in step 2), the cleaning time is 20-40 minutes.

[0029] Preferably, in step 3), the heating rate is 3-7℃ / min; and the holding time is 20-40min.

[0030] Preferably, in step 3), the reaction time is 50-60 hours.

[0031] Preferably, the purity of the nitrogen gas is >99.999%, the purity of the hydrogen gas is >99.999%, the purity of the trichloromethylsilane is >98%, and the purity of the HCl is >99.999%.

[0032] Secondly, the present invention provides the application of the CVD-SiC focusing ring obtained by the above preparation method in semiconductor etching equipment.

[0033] Compared with the prior art, the beneficial effects of the present invention are: This invention uses the CVD method to generate a CVD-SiC layer on the surface of a graphite ring. It has high purity (above 99.999%), high density (>3.2g / cm), high thermal conductivity (>250W / (m·k)), and crystal form of (111) grown 3C-SiC (β-SiC). It has excellent performance and can fully meet the requirements of semiconductor etching equipment. Attached Figure Description

[0034] Figure 1 This is a sample image of the CVD-SiC focusing ring prepared in Example 1 of the present invention; Figure 2 This is a SEM image of the CVD-SiC focusing ring sample prepared in Example 1 of this invention; Figure 3 The image shows the XRD pattern of the CVD-SiC focusing ring sample prepared in Example 1 of this invention. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments.

[0036] General Implementation Examples In a first aspect, the present invention provides a method for preparing a CVD-SiC focusing ring, comprising the following steps: 1) Place the graphite ring in a CVD furnace and heat it to 1050-1150℃ under hydrogen gas conditions.

[0037] In some preferred embodiments, in step 1), the selected graphite ring is formed by isostatic pressing, with an impurity content of <20ppm and a coefficient of thermal expansion of 3.9×10⁻⁶. -6 ~4.8×10 -6 / K(CTE RT-400℃), specific gravity is 1.6-1.9g / cm³ 3 .

[0038] In some preferred implementations, in step 1), before heating, the CVD furnace is evacuated and repressurized twice, including: first evacuation followed by nitrogen repressurization; second evacuation followed by hydrogen repressurization.

[0039] In some preferred embodiments, the two consecutive vacuuming and repressurization processes include: First vacuuming: The gas inside the CVD furnace is extracted until the vacuum level reaches 1.0 × 10⁻⁶. -2 Kpa, maintain pressure for 5-15 minutes; Nitrogen repressurization: Introduce N2 until the furnace pressure is greater than 115 kPa, and maintain the pressure for 5-15 minutes; Second vacuuming: Repeat the first vacuuming process; Hydrogen gas is repressurized, and H2 is introduced until the pressure inside the furnace is greater than 115 kPa, and the pressure is maintained for 5-15 minutes.

[0040] In some preferred embodiments, in step 1), the heating rate is 3-7℃ / min; after heating, the temperature is maintained for 20-40min.

[0041] 2) Introduce HCl and hydrogen gas to clean the surface of the graphite ring.

[0042] In some preferred embodiments, in step 2), the volume ratio of HCl to hydrogen is 8-12:1.

[0043] In some preferred embodiments, the cleaning time in step 2) is 20-40 minutes.

[0044] 3) Heat to 1250-1300℃, hold for a period of time, and then introduce process gas including 5-9 vol% trichloromethylsilane, 86-91 vol% hydrogen and 2-6 vol% HCl to react and obtain a graphite ring with a CVD-SiC layer on the surface; wherein, the CVD-SiC layer is 1.5~1.8 mm thick, the crystal form is (111) grown 3C-SiC (β-SiC), the density is >3.19 g / cm and the thermal conductivity is >250 W / (m·k).

[0045] In some preferred embodiments, in step 3), the heating rate is 3-7℃ / min; the holding time is 20-40min.

[0046] In some preferred embodiments, in step 3), the reaction time is 50-60 hours.

[0047] In some preferred embodiments, the purity of the nitrogen is >99.999%, the purity of the hydrogen is >99.999%, the purity of the trichloromethylsilane is >98%, and the purity of the HCl is >99.999%.

[0048] 4) Machining, polishing, and cleaning are performed to obtain the CVD-SiC focusing ring.

[0049] Secondly, the present invention provides the application of the CVD-SiC focusing ring obtained by the above preparation method in semiconductor etching equipment.

[0050] Specific embodiments and comparative examples The following cases use the following gas purities: N2 purity > 99.999%, H2 purity > 99.999%, methyltrichlorosilane (MTS) purity > 98%, and HCl purity > 99.999%.

[0051] Example 1 The flow rates of various gases during deposition in a CVD-SiC focusing ring for semiconductor etching equipment are shown in Table 1. Table 1 Its preparation method includes the following steps: (1) Place the graphite jig tower, rotating shaft, and high-purity graphite ring substrate into the CVD reactor. The graphite ring substrate is formed by isostatic pressing, with an impurity content of <20ppm and a thermal expansion coefficient of 4.3×10. -6 / K(CTE RT-400℃), specific gravity is 1.77g / cm³ 3 .

[0052] (2) First vacuuming: All gas in the furnace body is extracted until the vacuum level inside the furnace reaches 1.0 × 10⁻⁶. -2 Kpa, pressure maintained for 9 minutes, vacuum degree maintained at 4.0 × 10 -2 Anything below kPa is acceptable.

[0053] (3) N2 repressurization: fill the furnace with N2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0054] (4) Vacuuming is performed a second time, and step (2) is repeated.

[0055] (5) H2 repressurization: fill the furnace with H2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0056] (6) Start heating. Increase the temperature inside the furnace from room temperature to 1100℃ at a heating rate of 5℃ / min. During the heating process, continuously introduce H2 and keep it at that temperature for 30min.

[0057] (7) HCl treatment: H2 and HCl are introduced at a ratio of 10:1 when the temperature reaches 1100℃ to clean the surface of the graphite ring substrate for 30 minutes.

[0058] (8) After completing (7), continue to heat up to 1300℃ and keep warm for 30 minutes.

[0059] (9) MTS:H2:HCl were simultaneously introduced into the CVD reactor at a gas flow rate ratio of 7:89:4 and continued for 55 hours to obtain a CVD-SiC focusing ring (CVD-SiC layer thickness 1.6 mm).

[0060] (10) The deposited CVD-SiC focusing ring is machined, polished and cleaned as needed to obtain CVD-SiC products.

[0061] like Figure 1The image shown is a sample diagram of the CVD-SiC focusing ring prepared in Example 1 of this invention; as shown Figure 2 The image shown is a SEM image of the CVD-SiC focusing ring sample prepared in Example 1 of this invention; from Figure 2 The silicon carbide layer is very dense and without voids; as shown in the image. Figure 3 The image shown is the XRD pattern of the CVD-SiC focusing ring sample prepared in Example 1 of this invention; from Figure 3 It can be seen that the material has a crystal form of 3C (β-SiC) and the growth direction is only the (1,1,1) plane and the (2,2,2) plane.

[0062] Example 2 The flow rates of various gases during deposition in a CVD-SiC focusing ring for semiconductor etching equipment are shown in Table 2. Table 2 Its preparation method includes the following steps: (1) Place the graphite jig tower, rotating shaft, and high-purity graphite ring substrate into the CVD reactor. The graphite ring substrate is formed by isostatic pressing, with an impurity content of <20ppm and a thermal expansion coefficient of 4.3×10. -6 / K(CTE RT-400℃), specific gravity is 1.77g / cm³ 3 .

[0063] (2) First vacuuming: All gas in the furnace body is extracted until the vacuum level inside the furnace reaches 1.0 × 10⁻⁶. -2 Kpa, pressure maintained for 9 minutes, vacuum degree maintained at 4.0 × 10 -2 Anything below kPa is acceptable.

[0064] (3) N2 repressurization: fill the furnace with N2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0065] (4) Vacuuming is performed a second time, and step (2) is repeated.

[0066] (5) H2 repressurization: fill the furnace with H2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0067] (6) Start heating. Increase the temperature inside the furnace from room temperature to 1100℃ at a heating rate of 5℃ / min. During the heating process, continuously introduce H2 and keep it at that temperature for 30min.

[0068] (7) HCl treatment: H2 and HCl are introduced at a ratio of 10:1 when the temperature reaches 1100℃ to clean the surface of the graphite ring substrate for 30 minutes.

[0069] (8) After completing (7), continue to heat up to 1300℃ and keep warm for 30 minutes.

[0070] (9) MTS:H2:HCl were simultaneously introduced into the CVD reactor at a gas flow rate ratio of 6:90:4 and continued for 55 hours to obtain a CVD-SiC focusing ring (CVD-SiC layer thickness 1.6 mm).

[0071] (10) The deposited CVD-SiC focusing ring is machined, polished and cleaned as needed to obtain CVD-SiC products.

[0072] Example 3 The flow rates of various gases during deposition in a CVD-SiC focusing ring for semiconductor etching equipment are shown in Table 3. Table 3 (1) Place the graphite jig tower, rotating shaft, and high-purity graphite ring substrate into the CVD reactor. The graphite ring substrate is formed by isostatic pressing, with an impurity content of <20ppm and a thermal expansion coefficient of 4.3×10. -6 / K(CTE RT-400℃), specific gravity is 1.77g / cm³ 3 .

[0073] (2) First vacuuming: All gas in the furnace body is extracted until the vacuum level inside the furnace reaches 1.0 × 10⁻⁶. -2 Kpa, pressure maintained for 9 minutes, vacuum degree maintained at 4.0 × 10 -2 Anything below kPa is acceptable.

[0074] (3) N2 repressurization: fill the furnace with N2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0075] (4) Vacuuming is performed a second time, and step (2) is repeated.

[0076] (5) H2 repressurization: fill the furnace with H2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0077] (6) Start heating. Increase the temperature inside the furnace from room temperature to 1100℃ at a heating rate of 5℃ / min. During the heating process, continuously introduce H2 and keep it at that temperature for 30min.

[0078] (7) HCl treatment: H2 and HCl are introduced at a ratio of 10:1 when the temperature reaches 1100℃ to clean the surface of the graphite ring substrate for 30 minutes.

[0079] (8) After completing (7), continue to heat up to 1300℃ and keep warm for 30 minutes.

[0080] (9) MTS:H2:HCl were simultaneously introduced into the CVD reactor at a gas flow rate ratio of 5:91:4 and continued for 55 hours to obtain a CVD-SiC focusing ring (CVD-SiC layer thickness 1.6 mm).

[0081] (10) The deposited CVD-SiC ceramic focusing ring is mechanically processed, polished and cleaned as needed to obtain CVD-SiC products.

[0082] Comparative Example 1 Compared to Example 1, the only difference is that the content of methyltrichlorosilane in the process gas is too low, and the flow rates of each gas during deposition are shown in Table 4: Table 4 Its preparation method includes the following steps: (1) Place the graphite jig tower, rotating shaft, and high-purity graphite ring substrate into the CVD reactor. The graphite ring substrate is formed by isostatic pressing, with an impurity content of <20ppm and a thermal expansion coefficient of 4.3×10. -6 / K(CTE RT-400℃), specific gravity is 1.77g / cm³ 3 .

[0083] (2) First vacuuming: All gas in the furnace body is extracted until the vacuum level inside the furnace reaches 1.0 × 10⁻⁶. -2 Kpa, pressure maintained for 9 minutes, vacuum degree maintained at 4.0 × 10 -2 Anything below kPa is acceptable.

[0084] (3) N2 repressurization: fill the furnace with N2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0085] (4) Vacuuming is performed a second time, and step (2) is repeated.

[0086] (5) H2 repressurization: fill the furnace with H2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0087] (6) Start heating. Increase the temperature inside the furnace from room temperature to 1100℃ at a heating rate of 5℃ / min. During the heating process, continuously introduce H2 and keep it at that temperature for 30min.

[0088] (7) HCl treatment: H2 and HCl are introduced at a ratio of 10:1 when the temperature reaches 1100℃ to clean the surface of the graphite ring substrate for 30 minutes.

[0089] (8) After completing (7), continue to heat up to 1300℃ and keep warm for 30 minutes.

[0090] (9) MTS:H2:HCl were simultaneously introduced into the CVD reactor at a gas flow rate ratio of 3:89:8 and continued for 55 hours to obtain a CVD-SiC focusing ring (CVD-SiC layer thickness 1.6 mm).

[0091] (10) The deposited CVD-SiC focusing ring is machined, polished and cleaned as needed to obtain CVD-SiC products.

[0092] Comparative Example 2 Compared to Example 1, the only difference is that the content of methyltrichlorosilane in the process gas is too high, and the flow rates of each gas during deposition are shown in Table 5: Table 5 Its preparation method includes the following steps: (1) Place the graphite jig tower, rotating shaft, and high-purity graphite ring substrate into the CVD reactor. The graphite ring substrate is formed by isostatic pressing, with an impurity content of <20ppm and a thermal expansion coefficient of 4.3×10. -6 / K(CTE RT-400℃), specific gravity is 1.77g / cm³ 3 .

[0093] (2) First vacuuming: All gas in the furnace body is extracted until the vacuum level inside the furnace reaches 1.0 × 10⁻⁶. -2 Kpa, pressure maintained for 9 minutes, vacuum degree maintained at 4.0 × 10 -2 Anything below kPa is acceptable.

[0094] (3) N2 repressurization: fill the furnace with N2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0095] (4) Vacuuming is performed a second time, and step (2) is repeated.

[0096] (5) H2 repressurization: fill the furnace with H2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0097] (6) Start heating. Increase the temperature inside the furnace from room temperature to 1100℃ at a heating rate of 5℃ / min. During the heating process, continuously introduce H2 and keep it at that temperature for 30min.

[0098] (7) HCl treatment: H2 and HCl are introduced at a ratio of 10:1 when the temperature reaches 1100℃ to clean the surface of the graphite ring substrate for 30 minutes.

[0099] (8) After completing (7), continue to heat up to 1300℃ and keep warm for 30 minutes.

[0100] (9) MTS:H2:HCl were simultaneously introduced into the CVD reactor at a gas flow rate ratio of 10:89:1 and continued for 55 hours to obtain a CVD-SiC focusing ring (CVD-SiC layer thickness 1.6 mm).

[0101] (10) The deposited CVD-SiC focusing ring is machined, polished and cleaned as needed to obtain CVD-SiC products.

[0102] Comparative Example 3 Compared to Example 1, the only difference is that the hydrogen content in the process gas is too low, and the flow rates of each gas during deposition are shown in Table 6: Table 6 Its preparation method includes the following steps: (1) Place the graphite jig tower, rotating shaft, and high-purity graphite ring substrate into the CVD reactor. The graphite ring substrate is formed by isostatic pressing, with an impurity content of <20ppm and a thermal expansion coefficient of 4.3×10. -6 / K(CTE RT-400℃), specific gravity is 1.77g / cm³ 3 .

[0103] (2) First vacuuming: All gas in the furnace body is extracted until the vacuum level inside the furnace reaches 1.0 × 10⁻⁶. -2 Kpa, pressure maintained for 9 minutes, vacuum degree maintained at 4.0 × 10 -2 Anything below kPa is acceptable.

[0104] (3) N2 repressurization: fill the furnace with N2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0105] (4) Vacuuming is performed a second time, and step (2) is repeated.

[0106] (5) H2 repressurization: fill the furnace with H2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0107] (6) Start heating. Increase the temperature inside the furnace from room temperature to 1100℃ at a heating rate of 5℃ / min. During the heating process, continuously introduce H2 and keep it at that temperature for 30min.

[0108] (7) HCl treatment: H2 and HCl are introduced at a ratio of 10:1 when the temperature reaches 1100℃ to clean the surface of the graphite ring substrate for 30 minutes.

[0109] (8) After completing (7), continue to heat up to 1300℃ and keep warm for 30 minutes.

[0110] (9) MTS:H2:HCl were simultaneously introduced into the CVD reactor at a gas flow rate ratio of 7:84:9 and continued for 55 hours to obtain a CVD-SiC focusing ring (CVD-SiC layer thickness 1.6 mm).

[0111] (10) The deposited CVD-SiC focusing ring is machined, polished and cleaned as needed to obtain CVD-SiC products.

[0112] Comparative Example 4 Compared to Example 1, the only difference is that the hydrogen content in the process gas is too high, and the flow rates of each gas during deposition are shown in Table 7: Table 7 Its preparation method includes the following steps: (1) Place the graphite jig tower, rotating shaft, and high-purity graphite ring substrate into the CVD reactor. The graphite ring substrate is formed by isostatic pressing, with an impurity content of <20ppm and a thermal expansion coefficient of 4.3×10. -6 / K(CTE RT-400℃), specific gravity is 1.77g / cm³ 3 .

[0113] (2) First vacuuming: All gas in the furnace body is extracted until the vacuum level inside the furnace reaches 1.0 × 10⁻⁶. -2 Kpa, pressure maintained for 9 minutes, vacuum degree maintained at 4.0 × 10 -2 Anything below kPa is acceptable.

[0114] (3) N2 repressurization: fill the furnace with N2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0115] (4) Vacuuming is performed a second time, and step (2) is repeated.

[0116] (5) H2 repressurization: fill the furnace with H2 until the furnace pressure is greater than 115 kPa. Hold the pressure for 9 minutes until the furnace pressure is greater than 112 kPa.

[0117] (6) Start heating. Increase the temperature inside the furnace from room temperature to 1100℃ at a heating rate of 5℃ / min. During the heating process, continuously introduce H2 and keep it at that temperature for 30min.

[0118] (7) HCl treatment: H2 and HCl are introduced at a ratio of 10:1 when the temperature reaches 1100℃ to clean the surface of the graphite ring substrate for 30 minutes.

[0119] (8) After completing (7), continue to heat up to 1300℃ and keep warm for 30 minutes.

[0120] (9) MTS:H2:HCl were simultaneously introduced into the CVD reactor at a gas flow rate ratio of 7:92:1 and continued for 55 hours to obtain a CVD-SiC focusing ring (CVD-SiC layer thickness 1.6 mm).

[0121] (10) The deposited CVD-SiC focusing ring is machined, polished and cleaned as needed to obtain CVD-SiC products.

[0122] Performance testing Purity testing was performed using glow discharge mass spectrometry, and the equipment used was Astrunm. Density testing was performed using a precision density balance at a temperature of 25°C. Thermal conductivity was measured using a laser pulse thermal conductivity meter, specific heat was measured using a differential scanning calorimeter (DSC 8000), and finally calculated in combination with the sample density. Crystal form was measured using X-ray diffraction with a Bruker D8 ADVANCE instrument. The test results are shown in Table 8: Table 8 The data comparison in Table 8 shows that: The difference between Comparative Example 1 and Example 1 lies in the lower content of methyltrichlorosilane. The results show that the density is significantly lower than that of Example 1. This is because when the MTS content is too low, insufficient reactant concentration easily leads to difficulties in initial nucleation and discontinuous coating. Due to the lower coating density, its thermal conductivity also decreases significantly.

[0123] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 has a higher content of methyltrichlorosilane, and the results show that the purity is significantly lower than that of Example 1. This is because when the MTS content is too high, it is easy to induce homogeneous nucleation in the gas phase, generating silicon clusters or silicon droplets, consuming reactants, which may reduce the effective deposition rate and contaminate the coating.

[0124] The difference between Comparative Example 3 and Example 1 is the lower hydrogen content, which resulted in a significant decrease in purity. This is because when the H2 content is too low, the deposition rate decreases, and MTS decomposition is insufficient. This is detrimental to the removal of chlorine-containing byproducts (such as HCl), thus affecting the purity of the coating.

[0125] The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 has a higher hydrogen content, and the results show that the thermal conductivity is significantly lower than that of Example 1. This is because when the H2 content is too high, the strong reducing atmosphere will inhibit carbon deposition, resulting in an excess of silicon in the coating. Since the thermal conductivity of carbon is higher than that of silicon, the thermal conductivity of the coating decreases.

[0126] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0127] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a CVD-SiC focusing ring, characterized in that... include: 1) Place the graphite ring in a CVD furnace and heat it to 1050-1150℃ under hydrogen gas conditions; 2) The graphite rings were cleaned by introducing HCl and hydrogen gas; 3) Heat to 1250-1300℃, hold for a period of time, and then introduce process gas including 5-9 vol% trichloromethylsilane, 86-91 vol% hydrogen and 2-6 vol% HCl to react and obtain a graphite ring with a CVD-SiC layer on the surface; wherein, the CVD-SiC layer is β-SiC grown by (111), with a density > 3.19 g / cm and a thermal conductivity > 250 W / (m·k); 4) Machining, polishing, and cleaning are performed to obtain the CVD-SiC focusing ring.

2. The preparation method according to claim 1, characterized in that: In step 1), the selected graphite rings are formed by isostatic pressing, with an impurity content of <20ppm and a coefficient of thermal expansion of 3.9×10⁻⁶. -6 ~4.8×10 -6 / K, specific gravity is 1.6-1.9 g / cm³ 3 .

3. The preparation method according to claim 1 or 2, characterized in that: In step 1), before heating, the CVD furnace is evacuated and repressurized twice, including: first evacuation followed by nitrogen repressurization; second evacuation followed by hydrogen repressurization.

4. The preparation method according to claim 3, characterized in that: In step 1), the two consecutive vacuuming and repressurization processes include: First vacuuming: The gas inside the CVD furnace is extracted until the vacuum level reaches 1.0 × 10⁻⁶. -2 Kpa, maintain pressure for 5-15 minutes; Nitrogen repressurization: Introduce N2 until the furnace pressure is greater than 115 kPa, and maintain the pressure for 5-15 minutes; Second vacuuming: Repeat the first vacuuming process; Hydrogen gas is pressurized and H2 is introduced until the pressure inside the furnace is greater than 115 kPa, and the pressure is maintained for 5-15 minutes.

5. The preparation method according to claim 1 or 2, characterized in that: In step 1), The heating rate is 3-7℃ / min; Keep warm for 20-40 minutes after heating.

6. The preparation method according to claim 1, characterized in that: In step 2), The volume ratio of HCl to hydrogen is 8-12:1; The cleaning time is 20-40 minutes.

7. The preparation method according to claim 1, characterized in that: In step 3), The heating rate is 3-7℃ / min; The heat preservation time is 20-40 minutes.

8. The preparation method according to claim 1 or 6, characterized in that: In step 3), the reaction time is 50-60 hours.

9. The preparation method according to claim 4, characterized in that: The purity of the nitrogen gas is >99.999%, the purity of the hydrogen gas is >99.999%, the purity of the trichloromethylsilane is >98%, and the purity of the HCl is >99.999%.

10. The application of the CVD-SiC focusing ring obtained by the preparation method according to any one of claims 1-9 in a semiconductor etching apparatus.

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