Low-temperature anodic oxidation of silicon using a wave resonance plasma source

A rf wave resonance plasma (WARP) source has been used to plasma oxidize Si at temperatures below 100 degrees C. Oxidation under positive substrate bias in constant current mode gives an oxidation rate of 1-8 nm/min for current densities of 0.4-5.5 mA/cm(2). This corresponds to an ionic (O-) current of about 10% of the total current, which is 2-5 times higher than previously reported, due to the high plasma density of 10(12)-10(13) cm(-3) achieved by the WARP source. The breakdown field of similar to 10 MV/cm and the etch rate of 60 nm/min of the oxide are independent of the oxidation rate and similar to those of the thermal oxide. Results from capacitance-voltage measurements, Fourier transform infrared absorbance spectroscopy, null ellipsometry, and Rutherford backscattering spectroscopy suggest that the oxide grown at low rates (< 2 nm/min) is very close to stoichiometric SiO2 while the oxide grown at high rates (> 3 nm/min) is Si rich (35%-40% atomic Si). (C) 1999 American Institute of Physics. [S0003-6951(99)02930-7].