P Type Polysilicon Shield for Trench MOSFET Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Shielded gate trench MOSFETs face reliability and fabrication challenges due to thick shielded gate structures, particularly with regards to shield oxide and related reliability issues, which affect their performance and efficiency in high voltage applications.
Innovation Solution
The introduction of a P type polysilicon PN junction type shield structure that is laterally confined by insulators, replacing traditional shielded MOS gates, to enhance reliability and fabrication processes, including specific masking steps and ion implantation processes to form polysilicon shield regions that improve the device's breakdown voltage and switching performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick shielded gate structure is used in trench MOSFETs, then the breakdown voltage is improved, but shield oxide reliability issues worsen
Solution Approach 1:
The patent extracts and removes the problematic shield oxide layer from the trench gate structure, replacing it with a metal shield layer that does not suffer from oxide reliability issues. This extraction of the harmful element (oxide) while maintaining the shielding function resolves the contradiction between achieving high breakdown voltage and ensuring shield oxide reliability.
Solution Approach 2:
The patent changes the material parameter of the shield layer from oxide-based materials to metal materials. This parameter change fundamentally alters the reliability characteristics while maintaining the electrical shielding function, thereby resolving the contradiction between breakdown voltage performance and shield oxide reliability.
2Strength
If a thick shielded gate structure is used, then the breakdown voltage is enhanced, but fabrication complexity increases
Solution Approach 1:
The patent extracts the complex multi-layer oxide structure and replaces it with a simpler metal shield layer. This simplification of the shield structure reduces fabrication steps and complexity while maintaining the necessary breakdown voltage enhancement, thereby resolving the contradiction between enhanced breakdown voltage and reduced fabrication complexity.
3Loss of energy
If traditional shielded MOS gate structures are used, then low on resistance is achieved, but switching performance at high frequencies deteriorates
Solution Approach 1:
The patent employs a composite structure combining metal shield layers with doped semiconductor regions (such as P+ or N+ regions). This composite approach maintains the low on-resistance characteristic of traditional shielded gates while the metal component enables faster switching performance at high frequencies, resolving the contradiction between low on resistance and high-frequency switching capability.
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 P type polysilicon PN junction shield structure improves the reliability and efficiency of trench MOSFETs and IGBTs by reducing shield oxide-related issues, enhancing breakdown voltage, and optimizing switching performance, making them more robust for high current and high voltage applications.
Implementation Method 1
The introduction of a P type polysilicon PN junction type shield structure that is laterally confined by insulators
Implementation Method 2
including specific masking steps and ion implantation processes to form polysilicon shield regions
Data Source
AI summary
A shield trench power device such as a trench MOSFET or IGBT employs a gate structure with an underlying polysilicon shield region that contacts a shield region in an epitaxial or crystalline layer of the device.