Damage-free metal-oxide-semiconductor gate electrode patterning on thin HfSiON film using neutral beam etching

The charging damage of metal-oxide-semiconductor (MOS) capacitors and the degradation of HfSiON dielectric films during gate electrode etching were compared with neutral beam etching and conventional plasma etching. Furthermore, residual flux of charged particles (positive/negative ions and electrons) in the neutral beam was analyzed and the relationship between the residual charge flux and the charging damage induced in SiO₂ and/or HfSiON gate dielectrics was investigated. Although the residual charge flux and its composition varied depending on the neutral beam acceleration method (dc or rf biasing), the amounts were noticeably lower than that with the plasma etching system. The gate leakage currents of the MOS capacitors etched using the neutral beam were sufficiently lower than those in the plasma etching, which was consistent with the charge flux during the gate electrode etching. On the neutral beam irradiated surface of the HfSiON film, there were no changes in the x-ray photoelectron spectrometry spectra, while large decreases in Hf composition were observed on the plasma-irradiated surface.