What generally affects the thickness of CVD films?

The thickness of CVD (Chemical Vapor Deposition) films is influenced by various factors, which collectively determine the final thickness and quality of the films. Here are some of the main influencing factors:
1. Sedimentation time
Influence mode: The thickness of CVD film increases with the increase of deposition time. Generally, the longer the deposition time, the thicker the film obtained.
Attention: However, when the deposition time is too long, problems such as grain size increase and defect increase may occur, affecting the performance of the film.
2. Sedimentation temperature
Influence mode: Deposition temperature is one of the key factors affecting the thickness of CVD thin films. As the temperature increases, the deposition rate and film thickness also increase. An increase in temperature can enhance reaction activity and diffusion rate, accelerating the formation and deposition rates of sediments.
Application example: In the preparation of diamond thick films, an increase in substrate temperature will improve the crystal shape of the diamond film, tending to expose the (111) surface, thereby increasing the density and growth rate of the film (source: Docin. com).
3. Reaction gas pressure
Influence mode: The pressure of the reaction gas has a significant impact on the deposition rate and film thickness of CVD. Higher reaction gas pressure can increase the number of excited molecules, enhance the rate of accumulation, and thus increase the deposition rate and film thickness.
Example analysis: In the preparation of diamond thick films, changes in chamber pressure play a dominant role in the growth of diamond films. When the room pressure is high, it is beneficial to increase the growth rate and secondary nucleation rate of diamond films, thereby improving the density of the film (source: Docin. com).
4. Bottom plate material (or substrate)
Influence mode: The choice of substrate material and surface state have a significant impact on the thickness of CVD films. The smaller the surface roughness of the substrate material, the higher the uniformity of the film, and the more stable the thickness. In addition, the type of substrate also affects the growth mechanism and quality of the thin film.
Application examples: In CVD graphene preparation, transition metals (such as Fe, Ru, Co, Rh, IR, Ni, PD, Pt, Cu, AU) and alloys (such as Co Ni, AU Ni, Ni Mo, stainless steel) can be used as base metals for graphene preparation. The selection of these metals is based on their melting points, the amount of dissolved carbon, and the presence of stable metal carbides (source: Mobile Sohu).
5. Precursor (or reactant gas)
Influence mode: The type and concentration of precursor directly affect the deposition rate and thickness of the film. Different precursors have different decomposition temperatures and rates, which affect the growth process of thin films.
Application example: In the preparation of CVD diamond thick films, changes in methane concentration can affect the grain size, growth rate, and purity of the diamond film (source: Docin.com).
6. Growth conditions
Comprehensive factors: In addition to the above factors, growth conditions also include carrier gas type, gas flow rate, reaction chamber design, etc., which indirectly affect the thickness and quality of the film.
In summary, the thickness of CVD films is a result of a combination of multiple factors. During the preparation process, it is necessary to optimize these parameters based on specific application requirements and material properties to obtain the desired thickness and quality of the film.