Ultra-Thin Silicon On Sapphire For High-Density AMLCD Drivers

摘要

Single-crystal ultra-thin (< 100 nm) silicon on sapphire (UTSOS) has beenfabricated using solid-phase epitaxy and regrowth techniques to produce a high quality semiconductor material on a transparent substrate ideal for active-matrix liquid crystal display (AMLCD) applications. MOS devices fabricated in this material have lower leakages, smaller thresholds, and higher transconductances than those fabricated in conventional unimproved SOS. The low mobility and poor quality of amorphous and polysilicon materials currently being used for AMLCD's severely limit the performance of integrated drivers. UTSOS device characteristics and projected shift register performances are superior to those obtained by polysilicon and amorphous silicon processes. The higher speed of UTSOS devices allows one to exploit the advantages of ferroelectric liquid crystal (FLC) materials on a transparent substrate whose previous demonstrations were limited to bulk silicon devices. The higher speeds of the FLC's allow the use of time multiplexed gray levels and color generation with the corresponding increase in effective pixel density. Preliminary layouts and SPICE simulations for a 1000 X 1000 array of FLC pixels are described. Improvements obtained using UTSOS offer a viable alternative for AMLCD systems. Predicted aperture ratios and pixel sizes are applicable for efficient, small-size, high-density displays with integrated drive and signal processing circuitry. jg.