Pulse-time modulated electron cyclotron resonance plasma etching for highly selective, highly anisotropic, and less-charging polycrystalline silicon patterning

Abstract

Highly selective, highly anisotropic, notch-free and charge build-up damage-free polycrystalline silicon etching is achieved using an electron cyclotron resonance plasma modulated at a pulse time in the range of 10–20 μs. In this plasma, the selectivity ratio of the polycrystalline silicon etching rate to the SiO2 etching rate is increased significantly by the same etching rate as that attained using a continuous discharge. Additionally, vertical and notch-free phosphorus-doped polycrystalline silicon etching profiles and suppressing charge build-up damage can be achieved. These results are attained by controlling the ion energy distribution through the duty ratio, maintaining a high ion current density, generating a collimated ion flux, and eliminating surface charge with the pulsed discharge.