Charge-free etching process using positive and negative ions in pulse-time modulated electron cyclotron resonance plasma with low-frequency bias

Charge build-up on a substrate is greatly reduced by using a pulse-time modulated electron cyclotron resonance generated plasma of more than 50 μs with 600 kHz radio frequency (RF) substrate bias. Negative ions are generated in the afterglow plasma due to decay in electron temperature. Low-frequency RF bias directly accelerates both negative and positive ions from the plasma onto the substrate and reduces self-bias voltage, thus reducing charge accumulation on the substrate. This method shows promise for charge-free etching processes in the production of ultra large scale integrated circuits.