Measuring the effective channel length of the deep submicron MOSFET and channel broadening effect

This paper investigates the channel broadening effect by the n-LDD (n-Lightly Doped Drain) doping on the n-channel MOSFET. The n-LDD L/sub eff/ modulation is due to charge density distribution by the gate bias and the carrier distribution 'spill out' of the source and drain into the channel. In this work, we present deep submicron silicon n-LDD experimental results with a comparison of several well-known L/sub eff/ measurement techniques. Low n-LDD implant concentration modulates L/sub eff/. As the n-LDD doping level increases, the channel length modulation effect is reduced, providing optimum device performance. Several MOSFET effective channel length, i.e., L/sub eff/, extraction methods with constant gate drive were used to observe n-LDD L/sub eff/ modulation. It is found that a constant gate drive is required to provide accurate results particularly when severe SCE or RSCE are observed. The L/sub eff/ measurements indicate that several different methods investigated provide matching results only when constant gate drive is used.