Defects introduced in silicon wafers during rapid isothermal annealing: Thermoelastic and thermoplastic effects

The temperature and stress distribution induced in silicon wafers during ‘‘rapid isothermal’’ annealing have been calculated for two commonly used heating methods: (a) by a strip heater and (b) by uniform irradiation with an energy flux. Analytical expressions have been obtained for the temperature and stress profiles which show that thermoelastic effects, originated by the temperature drop at the sample edge, are much higher in case (b). The conditions of plastic deformation and consequent damage introduction have been established by comparing the yield stress with the value of stress resolved on the {111} planes in the 〈110〉 slip directions. As a result, the topographic distribution of the slip lines, the extension of the peripheral damaged region, and the temperature threshold for damage introduction have been evaluated for 2- and 4-in. wafers. Rapid isothermal annealing experiments have been performed to check the results of the calculations. Two-inch silicon wafers were irradiated uniformly for 15 sec in the temperature range from 930 to 1400 °C by using a shuttered electron gun. The threshold temperature for damage onset was found to lie in the interval 1030–1090 °C; the observed geometrical distribution of the slip lines and their extension were consistent with theoretical estimates.