New analytical models of subthreshold surface potential and subthreshold current of fully depleted short-channel silicon-on-insulator MOSFETs with halo or pocket implantation

Abstract

New analytical models of the subthreshold surface potential, threshold voltage and subthreshold current of fully depleted (FD) silicon on insulator MOSFETs with halo or pocket implants are presented. The subthreshold surface potential model is based on the solutions of the quasi-two-dimensional (2D) Poisson’s equation, which rigorously satisfy the boundary conditions of the continuity of the potential and electric field in the lateral direction along the channel surface of halo MOS transistors. Closed-form model equations without any fitting empirical formula correctly and efficiently generate the surface potential distribution between the source and drain regions. The drain-induced barrier lowering effect of deep-submicrometer halo MOSFETs is also addressed in the present models. On the basis of the subthreshold surface potential, analytical models of the threshold voltage and subthreshold current are also developed for deep-submicrometer halo MOSFETs. The subthreshold current model is derived using the conventional drift-diffusion current theory considering the nonuniform doping profiles of a silicon film of fully-depleted silicon-on-insulator (SOI) MOS devices with halo implants. The results obtained using the model have been compared with those obtained using the device simulation software Medici to show the validity of the proposed model, and good agreement is achieved between the two. The use of the presented models can be treated as an alternative to 2D numerical analysis and used for the design of deep-submicrometer FD SOI MOSFETs with halo or pocket implants.