Trends in polycrystalline-silicon thin-film transistor technologies for AMLCDs

Polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) offer significantly improved performance compared to amorphous-silicon TFTs and are therefore advantageous for application as pixel-switching elements as well as for integration of peripheral driver circuitry in high-density AMLCDs. The domain of applications for poly-Si TFT-AMLCD technology can potentially expand to cover a wide range of LCD products, from small projection displays to large direct-view displays, provided the low-cost fabrication of poly-Si TFTs on large-area substrates is realized. In order to lower manufacturing cost, reductions in thermal-processing budget and improvements in process-module throughput are needed. This paper reviews the technological approaches to meeting these requirements. In particular, process-development trends for channel-film formation, gate-dielectric formation, source/drain doping and defect passivation are discussed, as well as device-architecture and associated process-integration issues.