Sub-nanometer scale measurements of silicon oxide thickness by spectroscopic ellipsometry

Possibility and limitation of sub-nanometer thickness measurements with spe ctroscopic ellipsometry (SE) of ultrathin silicon oxide on hydrogen-termina ted silicon were investigated, in comparison with X-ray photoelectron spect roscopic (XPS) measurements of the same sample. Experimental results obtain ed from SE showed ultraslow growth of the oxide with the increase of time i n air t (hours) at the rate of 0.7 . log(10) t (nm) up to 100 hours. During the hydrogen termination prevented from the oxidation for 4 hours by XPS o bservation, the 'oxide thickness' remained at 0.3 nm at the initial stage o f the oxidation by SE measurements.