Thomas Theiler

Low-temperature processing of semiconductor surfaces by use of a high-density microwave plasma

The required temperature in semiconductor process technology is going into two extreme directions. Either very high temperatures up to 1300 °C with very short durations in the order of a millisecond or even shorter for highest dopant activation is required, or extremely low temperatures near room temperature or slightly above are needed for forming high-quality dielectrics with minimum dopant deactivation and redistribution. This letter describes a new microwave plasma oxidation apparatus with unique features addressing the aforementioned low-temperature process. With this new technique the oxide growth rate was studied as a function of time, gaseous ambient, pressure, applied microwave power and silicon substrate parameters to determine crystallographic oxidation rate anisotropy and dopant concentration-dependent oxidation at temperatures much below 400 °C. Some tests have also been performed on doped and undoped SiGe material and on patterned structures. The plasma oxides grown on silicon have been electrically characterized regarding fixed charges, interface state densities and breakdown strength. In addition the selective oxidation regimes in the presence of various metals such as W, TiN and TaN were evaluated and determined.