Etching of poly-Si with atomic scale accuracy in inductively coupled Ar and He plasmas

Atomic scale etching of poly-Si, which can give atomic scale accuracy, was investigated in inductively coupled Ar and He plasmas. Atomic scale etching used a cyclic operation of gas adsorption and ion beam irradiation, which is the same concept as atomic layer etching of single crystal substrates. Cl₂ was used as etchant gas, and ions generated from inductively coupled Ar and He plasmas were used as an ion beam. The etch rates gradually increased, reached the saturated region, and then rapidly increased with increasing bias voltage in both Ar and He plasmas. This saturation region offered a process window for the realization of atomic scale etching. Angular dependence of etch yields in atomic scale etching process showed that ion-induced chemical etching was dominant at the bias voltage within the process window, confirming that atomic scale etching was achieved in this regime. On the contrary, at the bias voltage outside the process window, physical sputtering was dominant so that atomic scale etching was not obtained