What Is a Chemical Vapor Deposition (CVD)?
Chemical vapor deposition (CVD) is a process for forming thin films on various surfaces, including metals. It is used for surface hardening of molds and cutting tools, and for forming insulating and protective films on semiconductor wafers. The process involves heating a substrate inside a furnace, introducing a precursor gas containing film-forming material, and applying energy to trigger chemical reactions that form the film.
Energy sources for CVD include heat, plasma, and light, leading to different CVD types: thermal CVD, plasma-enhanced CVD (PECVD), photochemical CVD (PCVD), and metal organic CVD (MO CVD).
Uses of CVD
CVD is widely used for coating metals, tools, and semiconductor wafers, enhancing their hardness, resistance to damage, and electrical properties. It’s particularly important in semiconductor manufacturing for insulating and protective film formation.
Principles of CVD
CVD involves placing a substrate in a furnace, introducing a precursor gas, and applying energy to trigger reactions that create a film on the substrate’s surface. This differs from vacuum deposition and sputtering methods, offering uniform film creation on complex substrates without large vacuum facilities.
Types of CVD
Types of CVD include:
1. Thermal CVD
Uses high heat to deposit substances like titanium carbide or nitride on substrates, ideal for molds and parts needing high hardness and resistance to friction and corrosion.
2. Plasma CVD
Applies high-frequency electrical power to precursor gas, turning it into plasma for film deposition at lower temperatures, widely used in semiconductor manufacturing.
3. Photochemical CVD
Shines intense light to photodecompose precursor gas, with the radicals recombining on the substrate to form a film. Used in semiconductor manufacturing, this method avoids damage caused by plasma CVD.
4. MO CVD
Uses organometallic compounds as precursor gases, forming films through high-frequency heating. It’s effective for large, uniform films but requires caution due to the toxicity of some compounds.
How to Choose CVD
When selecting a CVD method, consider the specific combination of substrate and precursor gas, as well as the desired film properties. Each CVD type has its own advantages and limitations, making the choice dependent on the application’s specific requirements.