Trench Semiconductor Device with Multiple Active Depths
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Solution Overview
Problem
Existing Schottky devices face challenges in achieving higher efficiency with higher power density, lower power dissipation, and smaller die size while maintaining cost-effectiveness and ease of integration, due to issues like higher leakage current and forward voltage drop, which hinders their performance in applications such as unclamped inductive switching, electro-static discharge, and surge non-repetitive forward current.
Innovation Solution
The approach involves forming semiconductor devices with trench structures where the active trenches and termination trenches have different depths, allowing for thinner epitaxial layers and higher dopant concentrations, which reduces forward voltage drop and leakage current, and includes a method to form these trenches in a way that minimizes the area occupied in the active region while maintaining desired breakdown voltage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional Schottky device designs are used, then device structure is simple and manufacturing is easy, but leakage current is high and forward voltage drop is high
Solution Approach 1:
The device is divided into multiple trenches (first active trenches and second active trenches) with different depths extending into the semiconductor layer. This segmentation allows different regions to have optimized electrical characteristics, reducing overall leakage current and forward voltage drop while maintaining manageable manufacturing complexity through systematic patterning.
Solution Approach 2:
Different regions of the device are given different trench depths and configurations tailored to their specific functional requirements. First active trenches have one depth configuration while second active trenches have another depth, allowing local optimization of electrical properties in high-stress versus low-stress regions, thereby reducing overall power dissipation.
2Loss of energy
If trench depth is increased to reduce leakage current, then leakage current decreases, but forward voltage drop increases
Solution Approach 1:
The trench structure is segmented into multiple depth levels with first active trenches extending to a first depth and second active trenches extending to a second depth. This segmentation allows the device to achieve low leakage current through deeper trenches in critical regions while maintaining lower forward voltage drop through shallower trenches in other regions, thus resolving the trade-off between these two parameters.
Solution Approach 2:
Different trench depths are applied locally based on functional requirements: deeper trenches in regions requiring low leakage current and shallower trenches in regions where low forward voltage drop is prioritized. This local differentiation allows simultaneous optimization of both leakage current and forward voltage drop across different device regions.
3Power
If epitaxial layer thickness is reduced to increase power density, then power density increases, but breakdown voltage decreases
Solution Approach 1:
Instead of relying solely on epitaxial layer thickness to control breakdown voltage, the invention transitions to a vertical dimension solution by implementing trenches at different depths. This dimensional shift allows thin epitaxial layers (high power density) to coexist with high breakdown voltage through the trench depth configuration, which provides electrical isolation and field control without requiring thick layers.
Solution Approach 2:
The trench structure provides localized field control and electrical isolation at specific depths within the semiconductor layer, allowing thin epitaxial regions to achieve high power density while the trench configuration locally manages electric field distribution to maintain adequate breakdown voltage characteristics.
4Reliability
If multiple trench depths are implemented to optimize performance, then breakdown voltage increases by up to 8%, but manufacturing complexity increases
Solution Approach 1:
The trench formation process is segmented into systematic steps: forming first active trenches to a first depth, then forming second active trenches to a second depth. This segmentation of the manufacturing process into discrete, repeatable steps makes the complex multi-depth structure achievable through standard semiconductor fabrication techniques, balancing manufacturing ease with improved breakdown voltage.
Data Source
AI summary
A method of forming a semiconductor device includes providing a region of semiconductor material comprising a major surface. A termination trench is provided extending from a first portion of the major surface into the region of semiconductor material to a first depth and has a first width. A first active trench is provided extending from a second portion of the major surface into the region of semiconductor material to a second depth and has a second width less than the first width. A second active trench is provided extending from a third portion of the major surface into the region of semiconductor material to a third depth and has a third width less than the first width. A first conductive material is provided adjoining a fourth portion of the major surface, which is configured as a Schottky barrier. The selected trench depth difference alone or in combination with other features provides a semiconductor device having improved performance characteristics.