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 3×10^{12 31}P/cm² was implanted at 100 keV into 0.5‐μm‐thick poly‐silicon films for the depletion‐mode device, and a dose of 3×10^{11 11}B/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.