Inverted Trapezoidal Trench Gate for MOSFET Oxide Breakdown
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Solution Overview
Problem
Conventional trench MOSFETs experience gate oxide breakdown and leakage current due to the concentration of electric field at the right-angled base of the gate structure.
Innovation Solution
A semiconductor structure with a gate structure having an inverted trapezoidal cross-sectional profile, where the width of the bottom surface is less than the width of the top surface, and the side wall and bottom surface of the trench form an obtuse angle, reducing the electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional trench MOSFET with a right-angled gate base is used, then the vertical channel structure is achieved to reduce on-state resistance, but the electric field concentrates at the gate base angle causing gate oxide breakdown and leakage current
Solution Approach 1:
The patent applies asymmetry by changing the gate structure from a conventional right-angled profile to an inverted trapezoidal profile with an obtuse angle at the gate base. This asymmetric design redistributes the electric field lines, preventing concentration at sharp corners and reducing the risk of gate oxide breakdown while maintaining the vertical channel structure for low on-state resistance
Solution Approach 2:
The patent introduces curvature by forming an inclined surface at the gate base with an obtuse angle rather than a sharp right angle. This curved/rounded transition smooths the electric field distribution, eliminating the field concentration effect that occurs at sharp corners and preventing gate oxide breakdown
2Ease of manufacture
If a right-angled gate base is used in trench MOSFET, then the manufacturing process is simple, but leakage current is generated due to electric field concentration
Solution Approach 1:
The inverted trapezoidal gate structure with obtuse angle base provides an asymmetric design that effectively reduces leakage current by preventing electric field concentration, while the fabrication process remains straightforward using standard photolithography and etching techniques with appropriately designed masks
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The reduced electric field concentration at the base angle of the gate structure prevents gate oxide breakdown and leakage current, enhancing the stability of trench MOSFETs.
Implementation Method 1
oxidizing the stepped side wall to form a surface oxide layer
Data Source
AI summary
A semiconductor structure includes a substrate, a gate structure, a first oxide layer, and a second oxide layer. The substrate has a trench. An inclined surface and a bottom surface of the trench have an obtuse angle therebetween. The gate structure is located in the trench. A width of a bottom surface of the gate structure is less than a width of a top surface of the gate structure. A cross-sectional profile of the gate structure is inverted trapezoid. The first oxide layer is located between the gate structure and the substrate. The second oxide layer is located on the top surface of the gate structure.