Isothermal DC and microwave characterizations of power RF silicon LDMOSFETs

Abstract

Presented in this paper are two new approaches for the acquisition of both iso-thermal dc current-voltage (-) characteristics and microwave-parameters of power RF LD-MOSFETs. In the first approach, three-dimensional (3-D) tensor product B-spline representation is used to extract iso-thermal dc-characteristics from dc-characteristics measured at various substrate temperatures. The average device surface temperature is measured using an infrared sensor. A single effective thermal resistance is found to map the entire electrothermal profile of the device justifying the iso-thermal dc-definition used. In the second approach, iso-thermal-and microwave data are directly measured with an efficient procedure that keeps the average device surface temperature constant. Excellent agreement is obtained between the numerical extraction and the direct measurement approach. Finally, the comparison of the transconductance extracted from the iso-thermal dc-and microwave data confirms the presence of a small low-frequency dispersion in LDMOSFET not due to self-heating.

RF electro-thermal modeling of LDMOSFETs for power-amplifier design

“…A novel approach to directly measure iso-thermal IVs has been implemented under computer control [13]. In this approach, the substrate is set to the lowest temperature (in this case, cooled to 18 C) and is set to its highest value.…”