193-nm excimer laser-assisted etching of polysilicon was studied in vacuum and in the presence of Ar, CF3 Br, CF2 Cl2, and NF3. In inert atmospheres (vacuum, Ar) exposure to the laser led to jagged profiles at high fluences (>350 mJ/(cm2-pulse)) resulting from surface temperature gradients. At lower fluences, a resolidified Si-SiO2 lump was formed by thermal and surface tension gradients induced by laser heating. In the presence of 193-nm radiation, CF3Br showed some propensity to etch polysilicon, while CF2Cl2 did not show any appreciable etching.
Etch experiments were also performed in the presence of NF3 Maximum etch rates of 0.6 A/pulse were obtained for pressures greater than 500 torr and fluences exceeding 200 mJ/(cm2-pulse). An adsorptive etch mechanism is proposed, where NF3 molecules diffuse to the surface, adsorb and then react after absorbing laser radiation. Etching of micron profiles in polysilicon was also examined.