Abstract
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 (Ron,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 Ron,sp. Therefore, the double-EPIs device has more flexibility to achieve a lower Ron,sp than the single-EPI one. When the required voltage is over 100 V, the on-state resistance (Ron) of double-EPIs device is no longer satisfying our expectations. A triple-EPIs structure was designed and studied, to reduce its Ron, 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 Ron,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.
Highlights
Trench power MOSFETs have become a superior device in the medium-to-low voltage power application field
Because the stepped gate electrode plays a role as an extended field plate (FP) to modulate the electric field (EF) around it, this structure reduces the feedback capacitance and the Ron, by using a low-resistivity epitaxial layer
Split-gate trench (SGT) devices overcame that problem by adding a source electrode located between the gate and drain [5,6,7,8,9]
Summary
Trench power MOSFETs have become a superior device in the medium-to-low voltage power application field. In order to reduce the device-switching losses, many studies, such as a thick-bottom oxide layer (TBOX) design, W-gated, and RESURF stepped oxide (RSO) MOSFET, were proposed [1,2,3,4]. Because the stepped gate electrode plays a role as an extended field plate (FP) to modulate the electric field (EF) around it, this structure reduces the feedback capacitance and the Ron, by using a low-resistivity epitaxial layer. There are two parts in the trenches for a split-gate structure: The upper electrode is the gate, and the lower one is connected by a separate contact to the source, to play as a field plate to balance the charge in the n- drift epitaxy region. For a device structure with a rating voltage below 200 V, Si SGT power MOSFET dominates and plays an important role in reducing the device Ron,sp in power applications. The Ron,sp of a triple-epitaxial-layer structure is much lower than those applied with a single- or double-epitaxial layer based on the same fabrication process
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