ON THE QUESTION OF OXYGEN DIFFUSION DURING OXYGEN RELATED THERMAL DONOR FORMATION IN SILICON.
In an attempt to decide the question whether enhanced oxygen diffusion is important for heat-treatments of silicon at approximately 450 degree C where thermal donors are formed the authors conducted two types of experiments aimed at providing a measure of the 'effective' oxygen diffusivity. First, the authors extensively measured the temperature dependence of the thermal donor introduction rate for very short heat treatment times (20min). This measurement provides the thermal activation energy of TD formation. Since effects of long range diffusion and formation of large oxygen clusters are negligible for such times and temperatures and, presumably, thermal donor formation at the lowest heat treatment temperatures is oxygen diffusion limited, it should be possible to interpret the obtained activation energy in terms of oxygen diffusivity. The change of the interstitial oxygen content is immeasureable for 20min heat treatment times. Therefore, the decay of the interstitial oxygen content was measured for longer heat treatments at 450 degree C (up to 500 hours). The two experiments are complementary in several ways: In one experiment the oxygen diffusion activation energy is extracted, while the other measurement provides the value of the diffusion coefficient at a given temperature.
