A monolithic integrated circuit fabricated in laser-annealed polysilicon

An integrated-circuit (IC) fabrication process has been used to construct small-geometry MOS transistors and a ring oscillator with the active transistor channels in a thin layer of laser-annealed polysilicon. Both enhancement-mode and depletion-mode n-channel, silicon-gate transistors have been fabricated with dimensions compatible with high-performance MOS technology (gate lengths as short as 3 µm). A modified LOCOS process was used to fabricate the devices so that each transistor was contained within a pocket of silicon completely isolated from adjacent elements by dielectrics. The transistors were well behaved, with mobilities approaching those in single-crystal silicon, reasonably abrupt subthreshold characteristics, and low leakage current. An operating, nine-stage ring oscillator was also fabricated, and its behavior suggests the approach for further optimization. The technology offers the possibility of high-performance IC´s on poteno tially inexpensive substrates, as well as the possibility of additional levels of devices on monolithic silicon IC´s.