150-200 V Split-Gate Trench Power MOSFETs with Multiple Epitaxial Layers

A rating voltage of 150 and 200 V split-gate trench (SGT) power metal-oxide- semiconductor field-effect transistor (Power MOSFET) with different epitaxial layers was proposed and studied. In order to reduce the specific on-resistance (R_on,sp) of a 150 and 200 V SGT power MOSFET, we used a multiple epitaxies (EPIs) structure to design it and compared other single-EPI and double-EPIs devices based on the same fabrication process. We found that the bottom epitaxial (EPI) layer of a double-EPIs structure can be designed to support the breakdown voltage, and the top one can be adjusted to reduce the R_on,sp. Therefore, the double-EPIs device has more flexibility to achieve a lower R_on,sp than the single-EPI one. When the required voltage is over 100 V, the on-state resistance (R_on) of double-EPIs device is no longer satisfying our expectations. A triple-EPIs structure was designed and studied, to reduce its R_on, without sacrificing the breakdown voltage. We used an Integrated System Engineering-Technology Computer-Aided Design (ISE-TCAD) simulator to investigate and study the 150 V SGT power MOSFETs with different EPI structures, by modulating the thickness and resistivity of each EPI layer. The simulated R_on,sp of a 150 V triple-EPIs device is only 62% and 18.3% of that for the double-EPIs and single-EPI structure, respectively.