Metalhyphen;oxidehyphen;semiconductor fieldhyphen;effect transistors and a ring oscillator fabricated in laserhyphen;recrystallized polycrystalline silicon islands

摘要

Directions of grain boundaries in laserhyphen;recrystallized polycrystalline silicon (polysilicon) islands are found to be arranged along with the laser scan direction, and are connected to the electrical characteristics of metalhyphen;oxidehyphen;semiconductor fieldhyphen;effect transistors (MOSFETrsquo;s) fabricated in polysilicon islands. When the laser scan is parallel to the channel direction, grain boundaries work as fasthyphen;diffusion paths of arsenic from source and drain into the channel and a decrease of effective channel length of the MOSFET results. But when the laser scan is perpendicular to the channel direction, few grain boundaries are contributed to diffusion paths of arsenic. A maximum electron mobility of 590 cm2/V s approaching that of a single crystalline silicon can be obtained in devices with a channel length of 3 mgr;m, though grain boundaries work as additional potential barriers for carriers. A ninehyphen;stage ring oscillator is fabricated by applying these results. A minimum propagation delay of 38 ns is obtained.