Co-Optimization of Si Thin-Film Deposition and Excimer Laser Anneal Processes for Fabrication of High-Performance p-Si TFTs

In this work we have co-optimized the deposition and excimer laser crystallization processes for formation of high quality, low-temperature, p-Si films (LPS). We have found that the post-ELA polysilicon structure is very sensitive to deposition process adjustments, collectively expressed by the deposition rate. At low rates the PECVD Si-film is deposited in the microcrystalline phase (µc-Si). Comparing µc-Si and a-Si film precursors, we have shown that at equivalent annealing conditions (laser energy density) polysilicon films obtained from µc-Si precursor demonstrate improved crystallinity (grain size, defect density). Polysilicon thin film transistors (p-Si TFTs) have been fabricated and characterized using this material and compared to our standard process. We have found that the performance of µc-Si precursor exceeds by 20-50% that of a-Si precursor. Use of µc-Si precursor may also have important implications in reducing substrate damage during ELA process and for widening the ELA process window.