New approach to preparing smooth Si(100) surfaces: Characterization by spectroellipsometry and validation of Si/SiO2 interfaces properties in metal-oxide-semiconductor devices

Wet chemical removal of thermally grown SiO2 layers on Si(100) substrates has been studied as a function of the pH of the etching solutions in the range of -0.32-1.6 by adding controlled amounts of H2SO4 to a 1:30 HF:H2O mixture. Characterization of the stripped Si(100) surfaces by spectroellipsometry showed that the smoothest surfaces were obtained at a 1:0.50:30 HF (49 wt %):H2SO4(98 wt%):H2O etch with a pH of approximately 0.5. Electrical characterization of metal-oxide-semiconductor (MOS) capacitors fabricated on these surfaces with oxide layers prepared by remote plasma enhanced chemical vapor deposition showed (i) the lowest density of interface traps, D-it, (ii) the lowest tunneling currents, J(0), and that (iii) the highest breakdown fields, E(BD), occurred at the same pH value that produced the smoothest surfaces. In contrast, MOS capacitors fabricated with high-temperature thermally grown oxides were not significantly affected. (C) 1996 American Vacuum Society.