Use of focused-ion-beam and modeling to optimize submicron MOSFET characteristics

An asymmetrical MOSFET structure is formed by using a focused-ion-beam implanter to create a p(+) channel doping next to the source. This work builds on previous efforts by providing a uniquely tailored doping profile through the use of localized beams. An investigation shows that the output resistance improves, detrimental hot-electron effects diminish, and threshold voltage stabilizes as channel length is reduced. The improved output resistance is especially beneficial to analog applications where enhanced current source characteristics often lead to significantly better circuit operation. Improvements in device performance are attributed to the reduction of the pinchoff region, which is clarified with the help of detailed hydrodynamic device simulations. A two-transistor equivalent circuit model has been developed which reflects the device structure.