Analysis of temperature effects on high-frequency characteristics of RF lateral-diffused metal-oxide-semiconductor transistors

In this work, the effects of temperature on the DC and RF characteristics of lateral-diffused metal-oxide-semi conductor (LDMOS) transistors were studied. Devices with different layout structures were fabricated using a 40 V LDMOS process. The temperature coefficients of the threshold voltage and channel mobility are negative and their values are similar for devices with fishbone and ring structures. In addition, we found that both the cutoff frequency (f(T)) and the maximum oscillation frequency (f(max)) decrease with increasing temperature. The variations of f(T) with different temperatures are not only affected by the change in transconductance but also affected by the drain resistance. Finally, the temperature behaviors of S-parameters were measured, and the ring structure showed less S-22 variation with different temperatures than the fishbone structure. We extracted the model parameters of the devices to explain this observation.