NEW APPROACH TO PREPARING SMOOTH SI(100) SURFACES - CHARACTERIZATION BY SPECTROELLIPSOMETRY AND VALIDATION OF SI SIO2 INTERFACES PROPERTIESIN METAL-OXIDE-SEMICONDUCTOR DEVICES/

Wet chemical removal of thermally grown SiO2 layers on Si(100) substra tes 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 obtaine d at a 1:0.50:30 HF (49 wt %):H2SO4(98 wt%):H2O etch with a pH of appr oximately 0.5. Electrical characterization of metal-oxide-semiconducto r (MOS) capacitors fabricated on these surfaces with oxide layers prep ared by remote plasma enhanced chemical vapor deposition showed (i) th e lowest density of interface traps, D-it, (ii) the lowest tunneling c urrents, J(0), and that (iii) the highest breakdown fields, E(BD), occ urred at the same pH value that produced the smoothest surfaces. In co ntrast, MOS capacitors fabricated with high-temperature thermally grow n oxides were not significantly affected. (C) 1996 American Vacuum Soc iety.