Current-Source-Type Pulse Current Generator with Reduced Waveform Distortion for Capacitively Coupled Plasma Systems

Plasma application systems can be classified as an inductive-coupled plasma (ICP) system and a capacitive coupled plasma (CCP) system. Generally, a voltage-source-type pulse generator (VST-PG) is utilized in ICP systems. The VST-PG has the intrinsic problem of spike currents and voltage ringing in CCP systems. A filter inductor and damping circuit have been employed to mitigate this problem. However, this solution degrades the dynamic performance and increases the system cost, particularly for a CCP system with a large power rating. This article proposes a current-source-type pulse generator (CST-PG) to solve the problem of current spike and voltage ringing in a CCP system. The proposed circuit structure provides the output voltage and current waveform of the enhanced waveform fidelity. In the proposed system, two current sources of different scales are connected in parallel to generate the output current with high precision. The entire system consists of four major functional blocks: a bias current generator, a bias current modulator, a slope current generator, and a slope current modulator. The proposed solution also employs a SiC mosfet-type power semiconductor switch of 1200 V/90 A to meet the fast transient requirement. The proposed converter system successfully satisfies the specification of an output voltage of 1.6 kV and an output current of 35 A with a fundamental frequency of 100 kHz. The experimental validation result confirms the superior performance of CST-PG with a reduced crest factor of 1.12 for a laboratory prototype.