Silicon oxidation studies - Measurement of the diffusion of oxidant in SiO2 films

A method for the measurement of the diffusion of oxidant through a growing SiO2 film is presented. The procedure is based on so-called lag-time diffusion methods, in which the time to achieve steady-state oxidation is measured using in situ ellipsometry. Two different modes of oxidant transport were observed over the range of temperatures investigated (600-1000 C). At temperatures of 900 C and below, no lag-time was observed, and steady-state oxidation was seen at the outset of oxidation. At 1000 C, a lag-time was measured which yielded a value for the diffusion constant of 2.3 x 10 to the -13th sq cm/sec for dry O2, and this value increased to 2.4 x 10 to the -12th sq cm/sec for 1000 ppm H2 in O2. This study provides clear evidence for different dominant modes of oxidation at higher and lower oxidation temperatures.