Trench FET Mesa Doping Profile for Avalanche Robustness
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Solution Overview
Problem
Existing field effect transistors (FETs) face challenges in optimizing area-specific on-state resistance and reliability, particularly in terms of avalanche breakdown behavior, as device geometries shrink.
Innovation Solution
The proposed FET design includes a semiconductor substrate with a mesa structure between an electrode trench, a groove contact extending into the mesa, and a pn junction with a specific doping concentration profile that increases by a factor of 5 to 100 along the lateral direction from the electrode trench towards the center of the mesa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device geometries are shrunk to improve cost efficiency and increase device functionalities per unit area, then productivity and area utilization are improved, but reliability and avalanche breakdown behavior deteriorate
Solution Approach 1:
The patent applies local quality by implementing a non-uniform doping concentration profile in the body structure, where the doping concentration varies laterally from the electrode trench towards the center of the mesa. This creates regions with different electrical properties within the same device structure, allowing optimization of both conductivity and avalanche characteristics in different areas simultaneously.
Solution Approach 2:
The patent changes the doping concentration parameter by a factor of 5 to 100 along the lateral direction at a specific vertical level. This parameter change enables the body structure to maintain adequate conductivity while providing enhanced avalanche robustness, resolving the contradiction between device functionality and reliability in scaled geometries.
Data Source
AI summary
A FET includes a semiconductor substrate having a mesa arranged between an electrode trench structure along a first lateral direction. A groove contact extends into the mesa from a top surface of the mesa. A bottom of the groove contact is located at a first vertical reference level. The mesa includes a source region, a body structure, and a drift region. A pn junction between the drift region and body structure has a minimum vertical distance to the mesa top surface at a second vertical reference level and a maximum vertical distance to the mesa top surface at a third vertical reference level. At a fourth vertical reference level between the second and first vertical reference levels, a doping concentration of the body structure increases by a factor of 5 to 100 along the first lateral direction from the electrode trench structure towards the mesa center. The first vertical distance is by a factor of 1.5 to 10 larger than a second vertical distance from the fourth to the second vertical reference level.