Limiting Si/SiO2 interface roughness resulting from thermal oxidation

The changes effected by oxidation on purposely roughened and initially smooth Si surfaces are followed via atomic force microscopy and spectroscopic ellipsometry and a technique called spectroscopic immersion ellipsometry. Initially, rough and smooth Si surfaces yield opposite roughening trends upon thermal oxidation. Rough surfaces become smoother, and smooth surfaces become rougher, ultimately yielding a limiting roughness of about 0.3 nm root-mean square. A consideration of the distribution of surface roughness features plus the thermodynamics of small features are used to explain these trends. It is also reported that the changes of interface roughness are primarily the result of the oxidation reaction and not from the high temperatures. (C) 1999 American Institute of Physics. [S0021-8979(99)04415-1].