Trench Field Electrode Layout for Low-Resistance MOSFET Contact
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Solution Overview
Problem
Existing trench field-plate MOSFETs face challenges in achieving a low resistance electrical connection to the buried field electrode, which is crucial for efficient charge coupling and rapid switching in high-frequency applications.
Innovation Solution
The proposed semiconductor device features a trench field electrode termination structure with a first section of the field electrode buried below the gate electrode and a second section transitioning upward, ensuring a low resistance connection. The separation between the second section of the field electrode and the gate electrode is greater than or equal to the separation between the first section and the gate electrode, maintaining robust dielectric breakdown characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the field electrode is buried deep below the gate electrode to achieve low resistance connection, then the electrical connection quality improves, but the dielectric breakdown robustness deteriorates
Solution Approach 1:
The field electrode is configured with a first section extending vertically below the gate electrode and a second section extending horizontally at a intermediate depth. This dimensional transition allows the electrode to achieve both close vertical proximity to the gate (improving electrical connection) and sufficient horizontal separation (maintaining dielectric breakdown robustness).
Solution Approach 2:
The field electrode is divided into two distinct sections: a first vertical section for establishing low-resistance connection to the gate, and a second horizontal section for providing robust dielectric breakdown characteristics. This segmentation allows each section to optimize its function independently.
2Reliability
If the field electrode is accessed beneath the gate electrode in the same trench to form ohmic connection, then the electrical connection quality improves, but the manufacturing complexity increases
Solution Approach 1:
Instead of accessing the field electrode vertically beneath the gate electrode (which would require complex processing), the second section extends horizontally at an intermediate depth. This allows connection through the trench sidewall using standard planar processing techniques, significantly reducing manufacturing complexity while maintaining low-resistance connection.
Solution Approach 2:
The second horizontal section of the field electrode acts as an intermediary structure that bridges the vertical gate electrode and the external connection point. This intermediate configuration enables simple planar access for forming ohmic connections without requiring complex vertical etching or deep trench access processes.
3Strength
If the separation between field electrode and gate electrode is increased to maintain dielectric breakdown characteristics, then the breakdown robustness improves, but the electrical connection quality deteriorates
Solution Approach 1:
The field electrode transitions from a vertical configuration (first section) to a horizontal configuration (second section). This dimensional change allows the electrode to maintain small vertical separation from the gate for good electrical connection while achieving large horizontal separation for robust dielectric breakdown characteristics.
Solution Approach 2:
The field electrode is segmented into a first vertical section that provides close proximity to the gate electrode for low-resistance connection, and a second horizontal section that provides sufficient separation distance for dielectric breakdown robustness. Each segment optimizes a different aspect of performance.
Data Source
AI summary
A semiconductor device includes: a trench formed in a surface of a semiconductor substrate and extending lengthwise in a direction parallel to the surface; a body region adjoining the trench; a source region adjoining the trench above the body region; a drift region adjoining the trench below the body region; a field electrode in a lower part of the trench and separated from the substrate; and a gate electrode in an upper part of the trench and separated from the substrate and the field electrode. A first section of the field electrode is buried below the gate electrode in the trench. A second section of the field electrode transitions upward from the first section in a direction toward the surface. The separation between the second section and the gate electrode is greater than or equal to the separation between the first section and the gate electrode.