A New Emitter Switched Thyristor (EST) employing Trench Segmented p-base

Abstract

A new emitter switched thyristor (EST) employing trench segmented p-base, which successfully improves the forward I–V and switching characteristics with decreasing the device active area, is proposed and verified experimentally with using shallow trench process of novel junction termination extension (JTE) method. The latching current of EST is determined by the p-base resistance of upper npn transistor. Floating n+emitter of conventional EST is enlarged to obtain large base resistance. However, the proposed EST increases the p-base resistance with shorter floating n+ emitter than that of conventional one. Shallow trench in floating emitter region forms the highly resistive p-base region under the bottom of trench. The experimental results show that the shortened floating n+ emitter and lowered latching current of proposed EST decrease experimentally the forward voltage drop by 17.7% and snap-back phenomenon with small active area. The breakdown voltage of series lateral MOSFET of proposed EST is increased from 7 to 14 V due to the trench filled with oxide which results in vertical redistribution of electric field, therefore current saturation capability and forward biased safe operating area (FBSOA) of proposed EST are enhanced. The simulation results show that the switching operation is performed successfully at the blocking voltage of 600 V and Eoff of the proposed one is reduced by 3.7%. The measured inductive load switching characteristics also shows that Eoff of proposed one is improved by 7.2%.