Microtrench of oxynitride thin films in a C2F6 inductively coupled plasma

An etching of oxynitride (SiON) films was conducted using an inductively coupled plasma. The experimental ranges for the radio frequency source power, the bias power, the pressure, and the C2F6 flow rates were 400–1000 W, 30–90 W, 6–12 mTorr, and 30–60 sccm, respectively. The etch characteristics examined include etch rate, profile angle, and microtrench. Particular emphasis was placed on the investigation of microtrench etch mechanisms. For this, both etch rate and profile angle variations were correlated to microtrench variation. In general, microtrench variation was complex depending on process parameters or experimental ranges given a certain parameter. Microtrench variation with the bias power was opposite to the profile angle variation. Little relationship between them was noticed for the source power variation. In contrast, microtrench variation was highly correlated to the profile angle variation for C2F6 flow rates. For the pressure variation, microtrench variation was reasonably explained by the distribution of polymer deposition. The empirical relationships identified can be utilized for microtrench control.