Semiconductor Termination Structure Guard Ring Trenches
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Solution Overview
Problem
Conventional Schottky diode termination region designs for high voltage applications suffer from limited success due to non-ideal electric field distribution, leading to premature breakdown and variability in breakdown voltage caused by asymmetry and precision issues in metal field plate length during formation.
Innovation Solution
A termination structure incorporating additional trench cells as guard rings and an extended metal field plate covering both termination and guard ring trenches, which extends the electric field profile and reduces sensitivity to field plate length variations, thereby enhancing breakdown voltage and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional termination structures with metal field plates are used, then breakdown voltage can be improved, but manufacturing precision deteriorates due to sensitivity to field plate length variations
Solution Approach 1:
The termination structure is divided into multiple discrete guard ring trenches instead of using a continuous metal field plate. This segmentation eliminates the need for precise metal length control while maintaining electric field management functionality. Each guard ring trench is independently formed, removing the manufacturing precision bottleneck associated with metal field plate length variations.
Solution Approach 2:
The patent replaces the metal field plate system with a semiconductor-based guard ring trench system. This substitution transitions from a metal deposition process (prone to length variation) to a trench etching and filling process, which offers better dimensional control and eliminates the sensitivity to field plate length variations.
2Strength
If the drift region is optimized for high breakdown voltage, then reverse breakdown voltage is improved, but on-state resistance increases
Solution Approach 1:
The guard ring trenches are strategically positioned only in the termination region, allowing the drift region to be optimized for low on-state resistance while the termination region separately manages breakdown voltage. This local differentiation enables independent optimization of both parameters without mutual compromise.
Solution Approach 2:
The guard ring trenches act as an intermediary structure between the active region and the device edge, managing electric field distribution in the termination region. This allows the drift region to maintain low resistance while the guard rings handle the breakdown voltage management function.
3Ease of manufacture
If termination region designs use conventional approaches, then manufacturing is simplified, but electric field distribution becomes non-ideal leading to premature breakdown
Solution Approach 1:
The guard ring trenches are formed and filled in the same processing steps as the active region trenches, merging the termination structure fabrication with the existing manufacturing flow. This integration maintains ease of manufacture while achieving ideal electric field distribution through the guard ring structure.
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 proposed structure achieves a maximum breakdown voltage of 94% of the ideal value, significantly reducing the impact of field plate length variations and improving the reliability of the device by stabilizing the electric field distribution.
Implementation Method 1
A metal layer or a metal silicide layer forms a Schottky contact with the lightly-doped drift region and forms the diode anode
Implementation Method 2
When reverse biased, the insulated conductive areas cause a lateral depletion of charge into the drift region, which modifies the distribution of the equipotential surfaces in this layer
Data Source
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AI summary
A termination structure is provided for a semiconductor device. The termination structure includes a semiconductor substrate having an active region and a termination region. A termination trench is located in the termination region and extends from a boundary of the active region toward an edge of the semiconductor substrate. A MOS gate is formed on a sidewall of the termination trench adjacent the boundary. At least one guard ring trench is formed in the termination region on a side of the termination trench remote from the active region. A termination structure oxide layer is formed on the termination trench and the guard ring trench. A first conductive layer is formed on a backside surface of the semiconductor substrate. A second conductive layer is formed atop the active region and the termination region.