| In modern mobile communication systems, the devices working underhigh power and electromagnetic interference in the radio frequencytransceiver often encounter reliability problems. This article mainly focuseson the reliability problems of multi-physics fields of laterally diffused metaloxide semiconductor field effect transistor (LDMOSFET) under the injectionof high power microwave (HPM) pulses, and issues an improving scheme.The values of thermal breakdown power, under HPM pulses withdifferent number of pulses, pulse widths and pulse repetition frequencies, areobtained by our HPM pulses test of LDMOSFET-based power amplifiers.Then an integral structure model including the silicon-substrate active regionand interconnection passive region is established.Based on such a structure model, the profiles of multi-physics fieldswith the measured HPM pulse failure power are figured out through thecoupled finite element method (FEM)-based electro-thermal-stress (E-T-S)FORTRAN code, and the results are compared with the commercial softwareof COMSOL.Furthermore, the heat transfer equation of the passive via, withboundaries of constant heat source and constant temperature, is analyticallyderived to efficiently achieve the thermal and stress reliabilities of the device,and the results are validated by the FEM code.At last, a theoretical structure model of LDMOSFET with a novelmaterial, few layer graphene, is issued to improve its reliabilities. Analyticalapproach combined with the FEM code is used to calculate its transientthermal and mechanical responses. Conclusion is that the thermal failure temperature is determined to be604K, which is located at the drain, and the metal via with unrecoverabledeformation is also analyzed by comparing the thermal stress with its yieldstrength. And the most temperature of the hot spot under1μs HPM pulse isable to be decreased by35K, and the thermal stress of the mechanical failurevia spot can be reduced by16MPa. |
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