What conditions affect the deposition rate of plasma enhanced PECVD coating electric furnace?

The deposition rate of plasma enhanced PECVD coating electric furnace is mainly affected by the following conditions:

1.Reaction gas flow rate: The reaction gas flow rate directly affects the amount of chemical substances involved in the deposition reaction. For example, when depositing silicon nitride thin films, silane (SiH ₄) and ammonia (NH3) are commonly used reaction gases. Increasing the flow rate of silane may lead to a relative increase in the silicon content in the film, thereby affecting the deposition rate under other constant conditions. At the same time, an appropriate gas flow ratio is also important for the equilibrium of chemical reactions, which can affect the chemical composition and structure of the film, thereby affecting the deposition rate.

2.RF power: RF power is a key factor in exciting plasma. Higher RF power can generate more high-energy electrons, which collide with reaction gas molecules, making them easier to ionize and decompose, increasing the concentration of reactive species, and thus accelerating the deposition rate. However, excessive power may cause plasma damage to the thin film, leading to a decrease in its quality; If the power is too low, it may lead to a slow deposition rate and insufficient film density, affecting the electrical and mechanical properties of the film.

3.Deposition temperature: Deposition temperature affects the adsorption, diffusion, and chemical reaction rate of reaction gas molecules on the substrate surface. For some PECVD processes, increasing the temperature appropriately can promote the decomposition and reaction of reaction gases, resulting in better crystallization quality of the film and potentially increasing the deposition rate. However, excessively high temperatures may cause mutual diffusion between the film and substrate, or result in the loss of certain volatile components, affecting the chemical composition and structure of the film, and may actually reduce the deposition rate or affect the quality of the film.

4.Reaction chamber pressure: The reaction chamber pressure affects the diffusion of reaction gases and the characteristics of plasma. At lower pressures, the average free path of reaction gas molecules is longer, and ions and active groups in the plasma can more effectively reach the substrate surface, which is beneficial for the uniform deposition of thin films, but may affect the deposition rate. Higher pressure may cause changes in the density distribution of the plasma, affecting the growth rate and uniformity of the thin film. For example, as the reaction pressure increases, the concentration of the reaction gas increases, and the concentration of related substances in the reaction products also increases accordingly. However, as the reaction pressure in the chamber increases, more gas molecules participate in the reaction, resulting in more collisions between ions. Without sufficient time to obtain the energy required for ionization, frequent collisions will cause a decrease in plasma density and limit the reaction rate.

5.Gas ratio: Different ratios of raw material gases can promote reaction kinetics and achieve rapid and uniform deposition. For example, the flow ratio of silane to oxidant is a key parameter determining the film stoichiometry and deposition rate when depositing silicon dioxide thin films. A higher oxidant flow rate can enhance the oxidation degree of the film, improve its dielectric properties and chemical stability, but excessive oxidant flow rate may lead to oxygen defects or other structural defects in the film, thereby affecting the deposition rate, uniformity, and mechanical properties of the film.

6.Electrode spacing and reaction chamber size: The selection of electrode spacing should consider the relationship between the starting voltage, electrode spacing, and chamber pressure. The selection of spacing should make the starting voltage as low as possible to reduce the plasma potential and minimize damage to the substrate; When the electrode spacing is large, the damage to the substrate is relatively small, but the spacing should not be too large, otherwise it will aggravate the edge effect of the electric field, affect the uniformity of deposition, and may affect the deposition rate. The size of the reaction chamber can increase productivity, but it can also affect the uniformity of thickness, which may indirectly affect the evaluation of deposition rate and application effectiveness.

7.The working frequency of RF power supply: RF PECVD usually uses RF power supply in the frequency range of 50kHz~13.56MHz. When the frequency is high, the ion bombardment effect in the plasma is strong, and the deposited thin film is denser. Moreover, the uniformity of high-frequency deposited thin film is better than that of low-frequency (because the electric field near the edge of the electrode is weak at low frequencies, the deposition rate is lower than that in the central area, and the time difference between high frequencies decreases), which may have a certain impact on the deposition rate.