Extending Standard BSIM-BULK Model to Cryogenic Temperatures

In this work, we present a compact temperature-dependent model for bulk MOSFETs with applicability down to the cryogenic range of temperatures and validate it against the experimental data. The long-channel and low-threshold voltage MOSFET device is characterized by multiple bias conditions and temperatures. With decreasing temperature, the characteristics exhibit a positive temperature shift in threshold voltage, an increase in the low-field carrier mobility, higher mobility degradation, and subthreshold swing (SS) saturation. Furthermore, the transconductance shows a nonmonotonic behavior with respect to temperature. The observed temperature-dependent variations in the device characteristics have been thoroughly analyzed, incorporated into the temperature-dependent parameters of the BSIM-BULK model, and validated using our characterized data and experimental data from other recent publications. The accuracy of the model and physical correctness are effectively demonstrated by carrying out the Gummel symmetry test (GST), the slope ratio (SR) test, and the tree top test. This study also analyzes the behavior of the results of the SR and tree top tests at cryogenic temperature, presenting these findings for the first time.