Improved short-channel characteristics in boron-implanted n-channel MOSFETs

This paper describes the results of a study of short- and narrow-channel effects in boron-implanted n-channel MOS transistors. Discrete devices with a wide range of single and double implants have been assessed, and many characteristics examined in detail. Whenever possible, the experimental results are compared with appropriate models. In particular, a relatively simple numerical model has been developed to account for the threshold voltages of small geometry transistors with non-uniform channel doping profiles, and in general the predictions of this model are shown to be in excellent agreement with experiment. The limitations imposed on maximum circuit operating voltages by short-channel effects are illustrated, and the improvements achieved by the use of relatively deep implants are clearly shown. The disadvantages of such implants are also described, and the form of the relationships which will determine the choice of optimum implant conditions are demonstrated.