HIGH-TEMPERATURE KINETIC-STUDY FOR THE REACTIVE ION ETCHING OF INP INBCL3 AR/O-2/

The reactive ion etching kinetics of InP studied uses BCl3/Ar and BCl3 /Ar/O-2 as etchants. High-temperature etching using BCl3 and Ar increa ses the etch rate negligibly. However, the addition of 30% oxygen in t he gas feed increases etch rates by a factor of 10,000 up to 1.5 micro n/min at wafer temperatures of 250 degrees C. X-ray photoelectron spec troscopy analysis reveals that oxygen removes the boron species adsorb ing on the InP surface by scavenging the boron to form volatile boron oxides. To study the gas-phase chemistry, optical emission spectroscop y is used to monitor atomic chlorine intensity at different gas mixtur es. The chlorine intensity shows a Gaussian-type dependence with oxyge n addition, which is similar to the etch rate dependence. Two regimes of etching found are: at temperatures below 150 degrees C, the etching is limited by the removal of indium chlorides; above 180 degrees C, t he 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/cm(2)) and intermediate temperatures (150 degrees C), near vertical wall shapes are obtained. A kinetic mo del for the high-temperature etching is developed as well as a rate la w based on the InCl formation reaction. The rate law compares favorabl y with experimental etch rate results.