Vertical MOSFET Split Gate Reduces Gate Charge
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Solution Overview
Problem
Existing semiconductor transistors face challenges in reducing Figure-of-Merit (FOM) values such as FOMoss and FOMG, which affect power dissipation and switching losses, often requiring trade-offs with other device parameters like on-state resistance and gate charge, making it difficult to achieve high performance and efficiency, especially at higher switching frequencies.
Innovation Solution
The design incorporates a semiconductor body with a field electrode trench extending deeper than a gate electrode trench, featuring two electrodes separated by a dielectric structure, which reduces gate charge while maintaining or improving on-state resistance, achieved through a split gate structure and needle-like field electrode design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If gate oxide thickness is increased to reduce gate charge, then gate charge is reduced, but MOSFET performance deteriorates due to increased DIBL
Solution Approach 1:
The gate structure is segmented into a conventional gate electrode and an additional field plate electrode arranged in parallel. This segmentation allows the gate charge to be reduced by optimizing the field plate configuration while the conventional gate maintains proper channel control and prevents DIBL effects.
Solution Approach 2:
The field plate is positioned in a different spatial dimension (parallel to the gate electrode but offset laterally), creating a three-dimensional electric field distribution. This dimensional change allows the field plate to influence the electric field without directly interfering with the gate-channel interaction, thereby reducing gate charge while maintaining performance.
2Quantity of substance
If thick trench bottom oxide is used to lower gate charge, then gate charge is reduced, but cost and complexity of MOSFET are increased
Solution Approach 1:
The field plate structure extracts the charge reduction function from the trench bottom oxide, eliminating the need for thick trench bottom oxide. By placing the field plate laterally offset from the gate electrode, the invention achieves gate charge reduction through a simpler structural modification rather than increasing oxide thickness.
3Quantity of substance
If more driver ICs are used to handle high gate charge, then gate charge capability is improved, but power density requirements and layout challenges increase
Solution Approach 1:
The field plate configuration provides dynamic control over the electric field distribution, allowing optimization of gate charge characteristics without requiring additional driver ICs. This dynamic field control reduces the burden on driver circuits while maintaining compact layout.
Data Source
AI summary
A vertical semiconductor field-effect transistor includes a semiconductor body having a front side, and a field electrode trench extending from the front side into the semiconductor body. The field electrode trench includes a field electrode and a field dielectric arranged between the field electrode and the semiconductor body. The vertical semiconductor field-effect transistor further includes a gate electrode trench arranged next to the field electrode trench, extending from the front side into the semiconductor body, and having two electrodes which are separated from each other and the semiconductor body. A front side metallization is arranged on the front side and in contact with the field electrode and at most one of the two electrodes.