Limitations of rapid thermal processing on ultra-shallow junctions for sub-0.25 mu m MOSFETs

Very shallow ( approximately 0.1 mu m) junctions are needed for sub-0.25 mu m MOSFET devices. These junctions can be made by implanting dopants into silicides and then drive out by RTA. Compared to furnace processed junctions, however, the RTA processed junctions show a higher leakage current, coupled with a non-ideal diode behavior. In addition, good junctions processed by furnace annealing showing ideal behavior and low leakage current are converted to leakier non-ideal diodes after an additional RTA. On the other hand, leaky junctions processed by RTA can be ´cured´ by an additional furnace annealing. The authors conclude that Rapid Thermal Processing has to be carefully engineered to produce useful shallow junctions for 0.25 mu m and sub-0.25 mu m devices.