Recrystallisation of amorphous silicon films by rapid isothermal and transient annealing

Abstract

Undoped amorphous silicon films have been produced by the implantation of 70 keV 8*1014 28Si ions cm-2 into (100) silicon wafers. These layers have been recrystallised by rapid isothermal annealing at 600 degrees C and transient thermal annealing for 400 mu s in the temperature range 800-1100 degrees C. The annealing has been carried out in an optical annealing furnace consisting of a bank of tungsten-halogen lamps below the specimen, with which the rapid isothermal anneals were performed, and a bank of linear flashlamps above the specimen for the transient annealing. After annealing, the thickness and quality of the recrystallised layers have been assessed by ellipsometry and transverse TEM. In the RIA material the average rate of recrystallisation has been calculated by carrying out constant temperature anneals for different times and measuring the remaining film thickness. Using these results in conjunction with published data on the temperature dependence of the recrystallisation rates the annealing temperature has been calculated and compared with the temperature measured by a thermocouple. This technique provides a valuable tool with which isothermal annealing temperatures may be calibrated. Measurements have been made of the total recrystallisation that occurred in the flash annealed material. This data has been compared with the temperature profiles that are predicted by a one-dimensional heat-flow simulation program that models the absorption and heat flow within the wafer during flash annealing.