Thin film MOSFET’s fabricated in laser-annealed polycrystalline silicon

Abstract

Both depletion- and enhancement-mode MOSFET’s have been fabricated with the active transistor channels in laser-annealed polycrystalline-silicon films. A dose of 3×1012 31P/cm2 was implanted at 100 keV into 0.5-μm-thick poly-silicon films for the depletion-mode device, and a dose of 3×1011 11B/cm2 was used for the enhancement-mode device. The transistors fabricated in the poly-silicon films show electrical characteristics comparable to those of devices in single-crystal silicon. In the depletion-mode device, an electron mobility of ∼450 cm2/Vsec was obtained, and approximately 80% of the phosphorus was electrically active. The surface mobility of electrons was about 340 cm2/V sec in the enhancement-mode device, and a threshold voltage of approximately 2.5 V was obtained.