Dry plasma etching of GaAs vias using BCl 3 /Ar and Cl 2 /Ar plasmas

Abstract

We report the development and characterizations of GaAs via hole processes using BCl<SUB>3</SUB>/Ar and Cl<SUB>2</SUB>/Ar plasmas generated by an electron cyclotron resonance (ECR) system. The effect of the in- and out-diffuse of the reactive species and etch by-products, of the BCl<SUB>3</SUB>/Ar plasma, on the etch rate of the GaAs vias has been studied. The average GaAs etch rate was found to increase with increasing of both BCl<SUB>3</SUB> and Cl<SUB>2</SUB> flow rates. Under similar conditions, namely 800W microwave power, 150W RF power, 10sccm Ar flow rate, same flow rate, the etch rates of Cl<SUB>2</SUB>/Ar plasma were found to be 7-16 times higher than those of BCl<SUB>3</SUB>/Ar plasma. As the microwave power increased from 0 to 1500W, the etch rate increased by a factor of as large as 124 for the Cl<SUB>2</SUB>/Ar process. Etch rate as high as 6.7micrometers /min was observed from sample etched in Cl<SUB>2</SUB>/Ar plasma using a microwave power, RF power and process pressure of 800W, 150W and 50mTorr, respectively. Compared to the BCl<SUB>3</SUB>/Ar plasma, Cl<SUB>2</SUB>/Ar plasma is a better candidate, as this process gives higher etch rate and smoother etched surface.