Sensitivity of frequency characteristics of semiconductor devices to random doping fluctuations

Abstract

A novel technique for the analysis of fluctuations of frequency characteristics of semiconductor devices induced by random doping fluctuations is presented. This technique is based on the computation of "superposition" coefficients of admittance matrix elements that show how the fluctuations of admittance matrix elements (y-parameters) are sensitive to the fluctuations of the doping concentrations at different locations inside the semiconductor device. It is shown that by using the superposition coefficients of y-parameters one can easily deduce the fluctuations of other small-signal parameters (hybrid parameters, voltage and current gain, cut-off frequencies, etc.) through the use of the appropriate algebra of superposition coefficients. This technique is based on the linearization of transport equations and it is computationally much more efficient then purely "statistical" methods that are based on the simulation of a large number of devices with different doping realizations. The sensitivity coefficients can be directly used for the design of dopant fluctuation-resistant structures of semiconductor devices. The numerical implementation of this technique is discussed and numerous computational results are presented for MOSFET devices. These results demonstrate that frequency characteristics are very sensitive to doping fluctuations in the source and drain regions, and, therefore, cannot be easily remedied by the presence of epitaxial layer. © 2003 Elsevier Ltd. All rights reserved.