A method of fabricating and the structure of a micro-electromechanical switch device provided with self-aligned spacers or bumps is described. By applying a dither voltage and a correction voltage to a voltage-controlled oscillator, electron density of a plasma processing system may be measured and controlled as part of a plasma-based process. At the prism holding portion, an opening is formed. A second driving circuit for the second bidirectional switch is input with the PWM control signal and generates a second PWM signal, in phase opposition to the first PWM signal, applied between control and conduction terminals of the second bidirectional switch. Other aspects are provided herein. The method also determines the proper grip size for the handle of the shaft.