Ion Energy Control with High-Voltage Bipolar Tailored Waveforms and Droop Compensation

In plasma etching, the ion energy and flux can be independently controlled with the use of multiple power systems. Traditionally, a high-frequency RF generator is used for plasma production while a low-frequency RF generator is used for wafer bias. Broad ion energy distributions (IEDs) at the wafer surface are produced with RF wafer bias systems. EHT Semi has developed a high-voltage bipolar waveform generator for precision control of the IED at the wafer surface. This power system is being tested in an experimental plasma chamber with a 60 MHz capacitively coupled plasma source and a pedestal that can be biased. EHT will present IED measurements collected using a retarding field energy analyzer (RFEA) with energies up to 2.5 kV. Additionally, we will show IED calculations from bias waveforms for ions over 5 kV when the voltage exceeds the limits of the RFEA. Future plans will also be discussed.