A novel two-step etching process for reducing plasma-induced oxide damage

During plasma etching, a large amount of charging current due to plasma can flow through the gate oxide near the endpoint, resulting in the degradation of thin gate oxide. In this paper, a two-step etching process using reactive ion etching (RIE) following wet etching is proposed to reduce the gate oxide charging current. The characteristics of the proposed process for gate oxide protection are characterized by time-dependent dielectric breakdown (TDDB), high-frequency capacitance-voltage (HFCV), and quasistatic capacitance-voltage (QSCV) measurements. From measurement results, it is shown that degradation of the gate oxide is dramatically eliminated by the proposed two-step etching method as compared with that using pure RIE. Therefore, the proposed two-step etching process can replace the pure dry etching process to reduce the plasma-induced gate oxide damage.