Experimental and theoretical analysis of energy capability of RESURF LDMOSFETs and its correlation with static electrical safe operating area (SOA)

Thermal and electrical destruction of 55 V single and double reduced surface field (RESURF) lateral double-diffused MOSFETs (LDMOSFETs) in smart power ICs are investigated by experiments, simulations, and theoretical modeling. Static safe operating area (SOA) and single pulse dynamic SOA (energy capability) have been studied and correlated. Single RESURF device failure and hence the energy capability is controlled by electrical phenomenon for drain to source voltage near breakdown voltages, whereas the energy capability of the double RESURF device is shown to be controlled by thermal phenomenon for voltage ranges up to about 5 V below the breakdown voltage. Measured energy capability data have been used to obtain critical temperatures for device failure, which decreases with an increase in drain to source voltage. We have empirically shown using experimental data that if the dynamic SOA of the device comes within about 2-5× of the static SOA boundary, the device failure is strongly influenced by avalanche multiplication. An analytical model based on Green´s function formulation is derived and proposed which can predict energy capability of LDMOSFETs for a wide range of device geometry. The calculated data show excellent matching with the measurements and are within ±10%. A new technique of distributing power within a device by applying less power at the center and more at the edges is proposed, which realizes significant improvement in energy capability by optimizing the temperature distribution within the device