Application of class D resonant inverter to titanium thin film sputtering on glass slide

Thin film sputtering on the desired substrate is one of an industrial application that needs to split atoms of sputter gas, such as Argon (Ar), to ions and electrons. This can be done by plasma driven circuit that delivers a high frequency sinusoidal current waveform to the sputtering machine. For the reason of high efficiency (more than 70% at 100 - 500 W) with high frequency sinusoidal current waveform, this paper presents an application of half-bridge class D series-parallel-resonant inverter for plasma-driven circuit. In order that the inverter can operate at zero voltage turn-on switches (ZVS), the resonant frequency (f_o) of resonant tank is set below switching frequency (f). However, the vacuumed chamber of sputtering system has a complicated physical structure, so that a simply load model is used together with an ideal model of matching impedance transformer. The design concept is realized by 373 W of prototype with 80.7% of efficiency at 100 kHz switching frequency. Under environment of Argon gas, the experimental results verify that the prototype can sputter thin film of material target; which here is Titanium, on glass slide.