Study Of The Neutral Gas Flow On Discharges Of Capacitively Coupled Plasma In A PECVD Reactor

PECVD (plasma enhanced chemical vapor deposition) is a process of the deposited film. The process uses microwave, RF or DC to generate plasma, in which high-energy electrons collide with the working gas molecules and release the radicals. These radicals proliferation to the surface of the substrate. Then After a series of chemical reactions, it would form a new film on the substrate surface.The uniformity of the deposited film is extremely important in PECVD. And it influenced by the plasma density distribution is directly related to many factors such as discharge power, frequency, pressure, and neutral gas flow rate, reactor structure and size, etc.. Thus, in order to find the optimal parameters of the deposition of uniform films, it is necessary to clarify the relationship between these factors and discharge characteristics. Therefore, a two-dimensional fluid discharge model would be used to carry out a detailed study on this issue.The preface introduces the use of low-temperature plasma in the PECVD process. Then we introduce the the PECVD working principle, and current research progress.In Chapter2, We use computational fluid dynamics software to simulate the neutral gas inthe distribution of different types of reactor. The simulation results showed that the gas flow rate and pressure are proportional to the neutral gas density distribution. The reactor structure for the distribution of neutral gas flow also has a significant effect in given three structures.In the first kind of reactor, the gas density and pressure distribution is fairly uniform in the discharge chamber. Because only part of the work gas would enter into this part due to diffusion. In the2nd kind of reactor, the inlet velocity increases the radial density of neutral gas. In the3rd kind of reactor, the density distribution is very uniform in the discharge chamber due to the effect of the board and holes in the top electrode. Gas inlet velocity and gas pressure almost no effect on the gas density distribution.In Chapter III, the two-dimensional fluid program was used to study the relationship between the various elements and discharge characteristics. The simulation results show that in the different structure of the reactor, the gas inlet flow rate and pressure increases could both increase the ion density. But the change of the inlet velocity can change the ion uniformity. In the first kind of reactor, the inlet velocity increase would undermine the right side of the density peak. In the second kind of reactor, when the inlet velocity increased, the ion density peak in the left side of chamber was weakened; the ion peak in the other side was strengthened. Then the ion density uniformity was improved. In the third kind of reactor, the inlet velocity and gas pressure would not change the ion density uniformity.