Low bias dry etching of tungsten and dielectric layers on GaAs

Microwave-enhanced SF 6 /O 2 discharges with low ion energies (<or=100 eV) were examined for dry etching of W, SiN x and SiO 2 films on GaAs. The etch rates of W and SiN x peak at 10% O 2 flow rates, which produce higher atomic fluorine densities in the discharges. Undercutting of W features is minimized when using Ti masks because of a sidewall passivant mechanism. Tungsten films may also be anisotropically etched in BCl 3 /Ar discharges at somewhat lower rates than with the SF 6 -based chemistry. Fluorine residues on the GaAs surface after dry etching were removed by NH 4 OH/H 2 O wet chemical cleaning, while an H 2 plasma treatment at room temperature was also effective in removing dry etch residues.