Reliability study of power RF LDMOS device under thermal stress

This paper presents the results of comparative reliability study of two accelerated ageing tests for thermal stress applied to power RF LDMOS: Thermal Shock Tests (TST, air-air test) and Thermal Cycling Tests (TCT, air-air test) under various conditions (with and without DC bias, TST cold and hot, different extremes temperatures ΔT). The investigation findings of electrical parameter degradations after various ageing tests are discussed. On-state resistance (R_{ds_on}) is reduced by 12% and feedback capacitance (C_rss) by 24%. This means that the tracking of these parameters enables to consider the hot carrier injection as dominant degradation phenomenon. To reach a better understanding of the physical mechanisms of parameter's shift after thermal stress, a numerical device model (2D, Silvaco-Atlas) was used to confirm degradation phenomena.