Neutral etching and shadowing in trench etching of semiconductors

Summary form only given, as follows. Etching profiles by neutral atoms in a plasma are analyzed for a semiconductor trench with neutral shadowing due to the trench acceptance angle. The etch rate is assumed proportional to the neutral flux incident on the semiconductor surface. Etch rates have been found to obey this relation for some substrates where the neutral species are depleted in the plasmas such that the ion energy flux is relatively large. The one-particle distribution function of the neutral species is modeled by a Maxwellian. The neutral flux to the semiconductor surface is found to be an exact analytical expression for the trench geometry. The vertical neutral flux reduces to the value for the midtrench already reported. The etching profiles are determined from points on the initial surface by numerical integration of trajectory equations with the exact analytical etch rates. The profiles are compared with etching profiles determined previously for neutral etching where the etch rate was a constant over the trench surface and for ion assisted etching where the etch rate was proportional to the ion energy flux.