Effects of Gas Flow Rate on Particulate Contamination in a PECVD Reactor

The effects of gas flow rate on the contamination by dust particles in an RF plasma reactor were studied experimentally. A mixture of tetraethylorthosilicate vapor, oxygen and nitrogen were fed into the reactor to fabricate SiO2 thin film. Dust particles generated in the plasma were visualized by a laser light scattering technique. Particle size was measured by a laser particle counter, and particle deposition for the film was observed by a scanning electron microscope. The dust particles were found to be trapped in a certain region in the reactor. The amount and size of the trapped particles decreased with increasing gas flow rate. The particle contamination on the film surface also decreased with increasing gas flow rate. At a high flow rate, however, dust particles embedded into the film were observed. In addition, high gas flow rate degraded the film uniformity. It is considered from the above results that a proper selection of gas flow rate is important to decrease particulate contamination as much as possible.