Fabrication of laser-annealed poly-TFT by forming a Si/sub 1-x/Gex thermal barrier

Germanium is ion-implanted deeply into the bottom of a Si film before excimer laser annealing begins. During the solidification step, the implanted Ges form a high thermal resistive Si/sub 1-x/Ge/sub x/ alloy, which reduces the thermal extraction rate of laser energy and the grain growth rate. Laterally larger but double-stacked grains were achieved with a higher Ge implant dose and a slower grain growth. The performance of fabricated poly-TFTs has been enhanced with a Ge 5/spl times/10/sup 15//cm/sup 2/ at 80 keV implant but deteriorated at a higher dose. We attribute this enhancement to a laterally enlarged grain and show that the performance of TFT is deteriorated more dominantly by other Ge-related factors than by surface roughening and Ge-induced defect creation.