Effect of rapid thermal plus conventional annealing on the microstructure of oxygen implanted SOI material

Rapid thermal annealing (RTA) plus conventional annealing has been used to examine heating rate effects on microstructure for higher temperature implanted SIMOX (separation by implanted oxygen). Material used for this study was a (100) wafer of SIMOX material that was implanted at 200 keV to a dose of 1.8×10¹⁸ at 620°C. It was rapidly thermal annealed in a lamp annealer for 1 min at 1320°C. The heating rate was about 100°C s^-1. A portion of this sample was then conventionally annealed in a tube furnace for 5 h at 1320°C in an atmosphere of argon plus 1/2% oxygen. The heating rate was 1°C s^-1. A TEM (transmission electron microscope) image of the RTA+CA sample is shown. There is a dramatic difference in this sample compared to one which has only been conventionally annealed. Defects are seen in the top Si layer and plan view images give a density of 10⁹ cm^-2. This is three orders of magnitude greater than a typical CA sample. These defects were first formed during the RTA and were retained during the CA step. This indicates that the high rate of heating in the RTA step can increase the defect density