Abstract: A system and process for analyzing the plasma discharge for various frequency components that can be correlated to wafer, chamber or equipment conditions. This system and process monitors (step 210), by using optical or electrical signals from the plasma, the low frequency plasma variations (step 220) generated during the wafer manufacturing process. For example, in endpoint detection applications, the amplitude variations of the plasma glow at a selected audio frequency, chosen for sensitivity to the etched material, is used to generate the endpoint signal (step 230). This endpoint signal has a potential response time equal to one cycle of the selected frequency plus minimal filtering due to noise reduction. To extract the vital parameters from the plasma glow, DSPs for frequency analysis or simple frequency filtering methods can be used.