Controlled two-step solid-phase crystallization for high-performance polysilicon TFT's

Solid-phase crystallization for polysilicon thin-film transistors (TFT's) is generally limited by a tradeoff between throughput and device performance. Larger grains require lower crystallization temperatures, and hence, longer crystallization times. In this letter, a novel crystallization technique is presented which increases both throughput and device performance, using a two-step process, controlled using an in situ acoustic temperature/crystallinity sensor. A high-temperature rapid thermal annealing (RTA) nucleation step is followed by a low-temperature grain growth step to grow large-grain polysilicon. TFT's have been fabricated with a substantial improvement in throughput and device performance. This promises a high-throughput, high-performance, spatially uniform TFT process.