REACTIVE SPUTTERING OF INP IN N2 AND N2/O2 PLASMAS

The plasma etching of InP using nontoxic, fluorocarbon free, N2 and N2/O2 mixtures has been demonstrated. The etch rates as a function of pressure, power, and O2 content have been studied. Reactive sputtering appears to be the principal etching mechanism for both plasmas. These plasmas react with the InP substrate forming In2O3, InPO4 and probably nitride and oxynitrides of indium. N2+ and N+ ions are the dominant sputtering species in the N2 plasma, while addition of small quantities of O2(< 2%) to the plasma appears to promote the formation of heavier ions like NO+ and NO2+ and easily sputterable NO compounds thereby dramatically increasing the etch rates. At higher O2 contents (greater-than-or-equal-to 4%) strong surface oxidation and formation of compounds containing the NO2 radical limit the sputtering rate. Both gas mixtures exhibit low etch rates but form very smooth surfaces.