Substrate-Effect of Chemically Amplified Resist.

SiN, Bare Si, and SiO2 substrate-effects in chemically amplified (CA) resist have been investigated by surface analysis and evaluating the pattern profile of CA negative tone resist. It is considered that substrate-effects are distinguished from adhesion, optics and substrate components. It is found that the undercut profile of negative tone resist on SiN substrate can not be due to adhesion and optics. Fine profile can be replicated on SiN substrate treated with oxygen plasma optimized condition. Undercut profile can not be affected mainly by adsorbed materials on SiN substrate from Thermal Desorption Spectroscopy (TDS) analysis results. From the results of Electron Spectroscopy for Chemical Analysis (ESCA), it is found that Si-N bonding is replaced to Si-O bonding while SiN substrate is treated with oxygen plasma. The pattern profile on SiN substrate by oxygen plasma treatment is improved by the thin SiO2 layer formed on SiN substrate. Relations between footing length and oxygen plasma treatment condition suggest that undercut profile is caused by the atom content of nitrogen on the surface of SiN substrate. Excessive oxygen plasma treatment of SiN substrate occurs the footing profile for the negative tone resist because of surface damage. At the interface between the SiN substrate and the CA resist, the SiN substrate works as base existing H2O, and quenches photo- generated acids. Additionally, it is considered that the NHx on SiN substrate quenches the photo-generated acids directly. The mechanism of substrate-effect is clarified.