Analysis of sidewall films formed during Si etching with photoresist and nitride mask

The trench sidewall passivation films produced with photoresist (PR) mask and nitride mask were examined in two different etching systems of helicon and inductively coupled plasma (ICP) types. Compared to the trench profiles obtained from the helicon etching system, under the ICP etching system, the trench profiles were observed to be more tapered with thicker sidewall films. X-ray Photoelectron Spectroscopy (XPS) analysis results indicated that N₂ addition to Cl₂ /HBr/O₂ plasma induced the formation of Si-N bonds in the sidewall films in addition to Si-O and Si-Br bonds. Moreover, the sidewall films formed in Cl₂/HBr/O₂ plasma showed higher oxygen intensities and higher binding energies compared to those formed in Cl₂/HBr/N₂/O₂ plasma. Nitride mask polymer films seem to be deposited thicker on the mask film for both helicon and ICP type etchers in comparison with the PR mask scheme. The oxygen component appeared more intensely on the silicon substrate in the helicon plasma etcher with the PR mask scheme, contrary to the nitride mask scheme. Cone-shaped microscopic Si defects were detected during Si trench etching regardless of etching system, but wafers etched with the nitride mask showed more defects than those etched with photoresist mask