| Focused Ion Beam (FIB) has been used for channel engineering for high-performance Metal Oxide Semiconductor Field Effect Transistor (MOSFET) fabrication. Focused Ion Beam Metal Oxide Semiconductor (FIBMOS) with a special narrow doping region implanted with FIB in the source side of the channel has been proposed and it shows higher output resistance, reduced hot electron effect, more stable threshold voltage (VT) upon device scaling and higher operation frequency. Due to the nature of the asymmetric doping profile within the channel, classical VT equations do not work for the device. VT is a complex function of step doping width and step doping density. A sophisticated optimization technique for FIBMOS using two dimensional device simulations and three dimensional VT contour mapping has been developed. This method enables us to design a FIBMOS with a certain VT and the best performance in consideration of drain current, hot-electron degradation, VT stability and maximum operation frequency. A multi-step-doped FIBMOS (MSFIBMOS), which has a multi step FIB implantation looking like a down step from source to drain, is also proposed. This device takes advantage of the built-in electric field between doping steps, which aids drift of electrons. In the course of this study, it has been found that the FIBMOS, has higher drain current than a normal MOSFET and MSFIBMOS has an even higher drain current. High drain current, in addition to the advantages that Shen, Murguia, Goldsman, Peckerar, Melngailis and Antoniadis found, leads to low-power high-performance MOSFETs. The advantages of FIBMOSs and MSFIBMOSs are presented through bench-marking against normal MOSFETs in the core device performance area.; Since the FIB-implanted area is as narrow as 40nm tunneling through the channel barrier is of concern. A new computational method, based on the calculation for resonant tunneling diodes, was developed to take the potential energy profile from the FIBMOS simulation and to calculate the tunneling coefficient and current. It shows that the FIBMOS does not exhibit a noticeable tunneling current at 0.25mum channel length. |
