Conductance technique in MOSFETs: Study of interface trap properties in the depletion and weak inversion regimes

Abstract

A new and accurate approach to a.c. conductance measurements on MOSFETs is presented. It is shown that the conductance technique can be used to study interface trap properties in most of the silicon band-gap by direct measurement on a single MOSFET. The equivalent circuit is analyzed and the influence of the channel length on the inversion layer response is discussed in detail. It is shown that the channel time constant is mainly determined by the channel length. For small channel lengths L < 5 <m the channel time constant is generally, smaller than 10 −8 s. Thus, as a result of such rapid response, the interface traps can easily interact with the minority carrier band in inversion. Therefore, such traps can be studied in a similar way as those interacting with the majority carrier band in depletion.