Self-Heat Characterizations and Modeling of Multifinger nMOSFETs for RF-CMOS Applications

The purpose of this paper is to characterize and model the self-heating effect (SHE) of multifinger n-channel MOSFETs (nMOSFETs). The amount of SHE is small enough not to be analyzed for single-finger bulk CMOS devices. However, SHE should be considered for multifinger nMOSFETs that are mainly used for RF-CMOS applications. The SHE mechanism was analyzed based on a 2-D device simulator. SHE model equations are derived and implemented in the BSIM6 model with Verilog-A language used in a SPICE simulator. The model improves speed and accuracy of multifinger nMOSFETs simulations. To extract thermal resistance and capacitance, an advanced ac conductance method using a vector network analyzer is developed to obtain I
_ds
-V
_ds
measurement without increasing temperatures with the proposed model and extracted parameters, excellent agreement has been obtained between measurements and simulations in dc and S-parameter domain, whereas the original BSIM6 shows inconsistency between the static dc and the small signal ac simulations due to the lack of SHE. Unlike the widely used subcircuits-based SHE models, including Silicon-On-Insulator MOSFET and power MOSFET models, the proposed SHE model can converge in large-scale circuits even for transient simulations.