Self-heating effects in SOI MOSFETs and their measurement by small signal conductance techniques

Self-heating is an important issue for SOI CMOS, and hence, so is its characterization and modeling. This paper sets out how the critical parameters for modeling, i.e., thermal resistance and thermal time-constants, may be obtained using purely electrical measurements on standard MOS devices. A summary of the circuit level issues is presented, and the physical effects contributing to thermally related MOSFET behavior are discussed. A new thermal extraction technique is presented, based on an analytically derived expression for the electro-thermal drain conductance in saturation. Uniquely, standard MOSFET structures can be used, eliminating errors due to additional heat flow through special layouts. The conductance technique is tested experimentally and results are shown to be in excellent agreement with thermal resistance values obtained from noise thermometry and gate resistance measurements using identical devices. It is demonstrated that the conductance technique can be used confidently over a wide range of bias conditions, with both fully and partially depleted devices.