Comparison of plasma chemistries for inductively coupled plasma etching of InGaAlP alloys

Two plasma chemistries, i.e., CH4/H-2/Ar and Cl-2/Ar, were compared for the etching of InGaP, AlInP, and AlGaP under inductively coupled plasma (ICP) conditions. While the etching with CH4/H-2/Ar discharges appears to be ion driven, Cl-2/Ar discharges showed an additional strong chemical enhancement. The highest etch rate (similar to 1 mu m/min) for InGaP was achieved at high ICP source power (greater than or equal to 750 W) with the Cl-2/Ar chemistry. Cl-2/Ar discharges provided very smooth surfaces in all three materials with root-mean-square roughness measured by atomic force microscopy around 2 nm. This result may be due to the efficient ion-assisted product desorption in this chemistry. The etched near-surface region of InGaP (similar to 100 Angstrom) with Cl-2/Ar maintained almost the same stoichiometry as that of the unetched control. By contrast, the CH4/H-2/Ar plasma chemistry produced somewhat rougher surfaces and depletion of phosphorous (P) from the surface of InGaP. (C) 1998 American Vacuum Society.