Abstract
Why is the development of a deep trench superjunction (SJ) MOSFET above 600 V and under 8.0 mohm · cm2 difficult? A deep trench SJ MOSFET is expected to have a low turn-on resistance because the post thermal process after the epitaxial process, which is normally used in a multi-step epitaxy structure, is unnecessary. When designing a deep trench SJ MOSFET, the trench angle is the most important factor because this determines the breakdown voltage (BV) and BV variations. In this paper, we investigated how the trench angle affects the BV and BV window as a condition of the possible thermal process. By employing a physical concept, ΔCharge, we explained why the maximum BV is decreased and the BV window is increased as the trench angle decreases. Also, we systematically scrutinized the transition of the vertical electric field by varying the trench angle. Furthermore, in a real case, the principle of the trench angle which contributes to the deviation of the charge imbalance and specific resistance of SJ is described. Finally, we discuss the challenge of SJ MOSFET development in the industry.
Published Version
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