Anisotropic Etching of n+-Polysilicon Using Beam Plasmas Generated by Gas Puff Plasma Sources

Generation of pulsed chlorine beam plasmas using a nozzle beam system generated from an electron cyclotron resonance (ECR) discharge plasma source with a high-speed gas puff valve (gas puff plasma source) has been studied. Simulations of gas flow, and measurements of plasma parameters and their etching properties have also been discussed, comparing the experimental results with those of conventional ECR plasmas using an almost identical reactor. The time-averaged electron temperatures around a wafer were lower than those in the ECR plasmas for time-averaged pressure of 0.1-2 mTorr. The instantaneous ion energy distributions of the beam plasmas incident on the wafer had wider high-energy tails than those in the ECR plasmas. Thus, anisotropic etching profiles of n+-polysilicon were obtained at the position of the wafer (B z ∼200 G) where notching phenomena were observed in the ECR plasmas.