Measurement Based Electro-Thermal Modeling of LDMOSFETs

This paper presents a new approach for the electro-thermal characterization and modeling of LDMOSFETs without using pulsed-IV and pulsed-RF measurement data. The characterization method, which relies on an infrared thermometer to measure the device surface temperature, automatically follows the constant LDMOSFET power contours in order to efficiently acquire in a single sweep of the substrate temperature the targeted iso-thermal IV and microwave measurements. The comparison of the acquired iso-thermal IV´s with pulsed-IVs and also with the extracted microwave gm reveals the presence of a relatively small low-frequency dispersion in LDMOSFETS. The temperature and bias dependence of the equivalent circuit model parameters is extracted from the small-signal microwave data acquired. Optimized tensor-product B-splines that distribute knots to minimize fitting errors are then used to represent the equivalent-circuit model parameters and extract the large signal model as a function of voltages and temperature. The accuracy of this measurement-based LDMOSFET model which is implemented in ADS is then verified by comparing the simulated and measured harmonic and IMD large-signal response of a power amplifier.