High-rate electron cyclotron resonance etching of GaAs via holes

We report a high-rate etching of GaAs via holes using Cl2/Ar plasma generated by an electron cyclotron resonance system. Ni, with a thickness of 200 nm, was used as the etch mask. The effects of the chuck temperature, process pressure, r.f. power, gas flow rate, and microwave power on the etch rate and the resultant etch profiles were investigated. The GaAs etch rate was found to increase as the process pressure, Cl2 flow rate, and the r.f. power or the microwave power increased. An etch rate as high as 6.7 μm min−1 was observed from a sample etched using a microwave power, r.f. power and process pressure of 800 W, 150 W and 50 mTorr, respectively. An etch profile, suitable for monolithic microwave integrated circuits via hole applications, has been achieved using the process developed.