Regulation of plasma discharge using fuzzy logic and an in-situ plasma sensor

Abstract

A new strategy for regulating a plasma discharge is presented. This is accomplished by using a fuzzy logic and a non-invasive in-situ plasma sensor. Using the sensor, fundamental plasma characteristics were collected and these characteristics include plasma density, ion flux, and electron temperature. For the collected data, fuzzy logic was used to identify the relationship between the process parameters and plasma characteristics. The process parameters of concern include a radio frequency source power, SiH4 flow rate, and N2 flow rate. For each of the plasma characteristics, a fuzzy logic model was developed. Another fuzzy controller was then applied to regulate the plasma characteristics as a function of the process parameters. Evaluation of the presented control model shows an error of less than 3% in most of the plasma characteristics. The performance of the plasma regulator under noisy environments provided information useful for regulator design, such as the existence of a minimum level of noises and the high sensitivity of fuzzy logic models to noises in a regulation system with high regulation errors.