Effect of Oxygen Precipitation in Nitrogen-Doped Annealed Silicon Wafers on Thermal Strain Induced by Rapid Thermal Processing

We have studied the effect of oxygen precipitation in annealed silicon wafers on the thermal strain induced during rapid thermal processing (RTP), focusing on the density of oxygen precipitates. It was found that the strain decreased with an increase in the precipitate density. Furthermore, the strain was drastically suppressed when the density of oxygen precipitates (average size: 80 nm) was greater than 1.5 ×1010 cm-3. This is interpreted as "precipitation hardening" against dislocation movements during RTP.