The effect of plasma conditions on reactive ion etching of GaAs in Cl/sub 2//Ar

Summary form only given. The parameters of the plasma used for GaAs/Cl/sub 2/ RIE were studied by means of emission spectroscopy. The different behavior was observed for different types of emitting species. For the main plasma species (Cl/sub 2/, Cl/sub 2//sup +/, Cl, Ar) a non-monotonical dependence of the emission intensity on the discharge power P was found, with fast fall of emission for P>50 Watts. For some of the etch products observed near the electrode, i.e. Al, Si, SiCl, Ga (Al and Si products originated from the electrode and sample holder materials) the emission intensity increased rapidly (monotonically) with P. The GaAs etch rate showed the same power dependence as the main plasma species. The similar behavior of Ar line emission proves, that the observed effect can not be attributed to the depletion of reagents in plasma. The fall of the etch rate E/sub etch/ with P was accompanied by remarkable changes in the other etching properties: the sample surface changed from smooth to rough, both the anisotropy factor and photoresist removal rates decreased, in spite of the substantial rise of the self-bias. A simple kinetic model has been developed to describe the observed features of GaAs etching in Cl/sub 2//Ar.