High‐temperature kinetic study for the reactive ion etching of InP in BCl3/Ar/O2

Abstract

AbstractThe reactive ion etching kinetics of InP studied uses BCl3/Ar and BCl3/Ar/O2 as etchants. High‐temperature etching using BCl3 and Ar increases the etch rate negligibly. However, the addition of 30% oxygen in the gas feed increases etch rates by a factor of 10,000 up to 1.5 micron/min at wafer temperatures of 250°C. X‐ray photoelectron spectroscopy analysis reveals that oxygen removes the boron species adsorbing on the InP surface by scavenging the boron to form volatile boron oxides. To study the gas‐phase chemistry, optical emission spectroscopy is used to monitor atomic chlorine intensity at different gas mixtures. The chlorine intensity shows a Gaussian‐type dependence with oxygen addition, which is similar to the etch rate dependence. Two regimes of etching found are: at temperatures below 150°C, the etching is limited by the removal of indium chlorides; above 180°C, the etching is reaction‐limited. The surface morphology shows that the etch profile becomes rougher as a result of increased chemical etching. At high power densities (0.21 W/cm2) and intermediate temperatures (150°C), near vertical wall shapes are obtained. A kinetic model for the high‐temperature etching is developed, as well as a rate law based on the InCl formation reaction. The rate law compares favorably with experimental etch rate results.