The design, fabrication and measurement of asymmetrical LDD transistors

A method for fabricating asymmetric lightly doped drain (LDD) transistors was developed. These transistors were measured, and a range of precisely known asymmetries was determined. These transistors were measured to investigate how asymmetry affects the performance. Measurements suggest that asymmetrical transistors are no more susceptible to hot electrons than normal LDD devices. However, the asymmetry of the LDD regions has an effect on the drive current of the device. This was shown by a difference in the drive currents on swapping the source-drain terminals. This was especially noticeable when LDD regions of the devices were shadowed by the polysilicon gate. The analysis includes a comparison between measured results and computer simulations