一、Introduction

Silicon carbide (SiC) coatings are high-end materials with excellent etching resistance, corrosion resistance, and thermal conductivity. In recent years, they have been widely applied in various industries. As shown in Figure 1, SiC coatings have become a key protective technology for critical components in semiconductor manufacturing, aerospace, and industrial sectors. Although the manufacturing cost is relatively high, SiC coating has demonstrated significant effectiveness in extending the service life of components and reducing maintenance frequency, leading to increased adoption across various industries. Particularly in semiconductor and precision machining sectors, SiC coating has become an indispensable technology in the production of key components.

Figure 1. Application fields of silicon carbide (SiC) [1]

二、Silicon Carbide Manufacturing Technologies

There are various methods for manufacturing silicon carbide (SiC) materials. Depending on the specific application requirements, this article introduces three key techniques: Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), and Sintering. As shown in Table 1, this article compares the differences in key characteristics of each processing technology, including process temperature, applicable substrates, coating speed, surface roughness, environmental and safety considerations, corrosion resistance, and application areas.

Physical Vapor Deposition (PVD) typically produces SiC coatings with amorphous or nanocrystalline structures. The resulting films exhibit highly dense microstructures with extremely low porosity, smooth surfaces, and excellent mechanical integrity. These coatings generally demonstrate high hardness, outstanding wear resistance, and exceptional chemical inertness. PVD-deposited SiC films are well-suited for applications requiring high-temperature resistance, corrosion protection, and superior surface hardness. This technology offers several key advantages, including low processing temperatures, high deposition rates, and excellent film density. Free from toxic byproducts, PVD strikes an ideal balance between high performance and environmental sustainability."

Chemical Vapor Deposition (CVD) is currently the most widely used technique for producing high-purity, high-density silicon carbide (SiC) coatings. In this process, gaseous precursors containing silicon and carbon are introduced into a high-temperature reaction chamber, where they react on the substrate surface to form a SiC coating. CVD enables precise control of film thickness, composition, and crystallinity, and can uniformly coat substrates with complex geometries. Therefore, CVD is extensively utilized in applications such as semiconductor parts, thermal protection systems, and corrosion-resistant layers.

Sintering is a process in which SiC powder is first compacted into a desired shape and then subjected to high temperatures to achieve solid-state or liquid-phase sintering. During this process, diffusion and rearrangement occur at the interfaces between powder particles, resulting in a high-density bulk material. Traditional solid-state sintering of SiC requires extremely high temperatures; therefore, small amounts of sintering aids are often added to promote liquid-phase sintering, thereby reducing the required temperature and improving forming efficiency. SiC components produced through sintering exhibit excellent mechanical strength, wear resistance, and thermal shock stability, making them widely used in applications such as mechanical seal rings, wear-resistant liners, and high-temperature structural parts.

三、Introduction to SiC Coating Properties

• High Hardness

SiC coatings have a Mohs hardness close to 9 and a Vickers hardness exceeding 2000 HV, making them highly effective at resisting mechanical wear and particle impact.

• Resistance to Plasma Bombardment and Etching

SiC materials demonstrate outstanding resistance to etching and ion energy damage in high-density plasma environments, making them especially suitable for use in semiconductor etching chambers and protective components.

• Excellent Chemical Resistance

SiC offers excellent resistance to corrosive gases, including fluorine- and chlorine-based compounds, providing reliable protection in harsh chemical environments.

• High Thermal Stability

SiC has an extremely high thermal decomposition temperature. Regardless of the structure formed during different processes (such as polycrystalline, amorphous, or sintered bodies), the material can withstand operating temperatures of at least >1200°C without significant degradation.

四、Applications for SiC Coatings

Etching Resistance Applications
In semiconductor etching processes, chambers and components such as focus rings and inner shields are often exposed to fluorocarbon plasma environments for extended periods. This exposure frequently leads to rapid material degradation due to plasma bombardment, resulting in particle contamination, uneven etching, and increased maintenance frequency, which poses significant challenges to yield and process stability.
Research has shown [2] that high-purity silicon carbide (SiC) exhibits excellent resistance to etching in fluorocarbon plasma environments (e.g., CF₄, CHF₃). Compared to traditional silicon materials, SiC coatings have an etching rate reduced by approximately 2 to 3 times under fluorocarbon plasma conditions. The primary reason for this is the formation of a fluorocarbon layer on the surface, which further enhances the protective effect and effectively suppresses substrate erosion, significantly extending the lifespan of the components.

Figure 2. Etching rates of Si and SiC in CF₄ or CHF₃ plasma as a function of oxygen flow rate [2]

High-Temperature Corrosion Resistance Applications
Research has shown [3] that in advanced nuclear systems such as Molten Salt Reactors (MSRs), graphite (e.g., IG-110) is commonly used as structural support or neutron moderator material. However, graphite, being a porous structure, is highly susceptible to absorbing molten salts at high temperatures, leading to volumetric expansion, mechanical degradation, and chemical corrosion, which severely affects the material's lifespan and reactor operation safety. Therefore, a high purity SiC coating is applied to the surface of graphite, successfully forming a dense and intact protective layer. Experimental results indicate that after soaking SiC-coated samples for 24 hours at 650°C and 5 atm, the weight change was only 1.1 wt.%, significantly lower than the 14.8 wt.% observed in uncoated graphite. The primary reason for this is that the SiC coating reduces the porosity of the graphite surface, effectively preventing the infiltration and corrosion of active ions from the molten salts, thereby maintaining the structural integrity of the otherwise vulnerable graphite material in high-temperature molten salt environments, enhancing its corrosion resistance and service life.

Figure 3: Weight increase ratio of graphite (IG-110) and SiC-coated samples after molten salt immersion [3]

五、References

[1] HE, Rujie, et al. Progress and challenges towards additive manufacturing of SiC ceramic. *Journal of Advanced Ceramics*, 2021, 10: 637-674.

[2] JANG, Mi-Ran; PAEK, Yeong-Kyeun; LEE, Sung-Min. Plasma resistance and etch mechanism of high purity SiC under fluorocarbon plasma. *Journal of the Korean Ceramic Society*, 2012, 49.4: 328-332.

[3] HE, Xiujie, et al. SiC coating: An alternative for the protection of nuclear graphite from liquid fluoride salt. *Journal of Nuclear Materials*, 2014, 448.1-3: 1-3.