SiC Junction Termination Structure with Mesa Edge and Guard Rings
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Solution Overview
Problem
Conventional edge termination techniques for high voltage silicon carbide (SiC) devices, such as field plate terminations, are unsuitable due to high electric fields at the oxide-semiconductor interface, leading to reliability issues, and existing junction termination extension (JTE) methods are complex and costly with increased area requirements.
Innovation Solution
A semiconductor device with a junction termination structure featuring a lightly doped region and guard rings, where the lightly doped region extends further than the guard rings, and supplemental floating guard ring segments are used to reduce electric field vulnerability and leakage current, without increasing the device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If field plate termination is used, then device cost is reduced, but reliability deteriorates due to high electric fields at the oxide-semiconductor interface
Solution Approach 1:
The patent extracts the problematic oxide layer from the termination structure by using a mesa edge termination design where the semiconductor device is separated from the substrate at the periphery, eliminating the oxide-semiconductor interface that causes high electric field stress and reliability issues in conventional field plate structures
Solution Approach 2:
Instead of placing metal plates on the surface as in conventional field plate termination, the patent inverts the approach by creating a physical separation (mesa structure) where the device edge is elevated or separated from the substrate, fundamentally changing how the electric field is managed at the termination region
2Reliability
If conventional JTE methods are used, then breakdown voltage is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies local quality by creating a mesa structure specifically at the termination region while keeping the active device region conventional, allowing the termination area to have enhanced breakdown characteristics through physical separation without affecting the overall device complexity or requiring complex doping profiles throughout the entire device
Solution Approach 2:
The patent segments the device into distinct regions: an active region and a termination region separated by a mesa structure. This segmentation allows independent optimization of each region, with the termination region achieving higher breakdown voltage through the mesa configuration without complicating the active region design
3Reliability
If guard rings are added to reduce sensitivity to implant dose variation, then reliability is improved, but device area increases significantly
Solution Approach 1:
The patent transitions from a two-dimensional planar termination structure to a three-dimensional mesa structure by vertically separating the termination region from the substrate. This dimensional change provides enhanced reliability and reduced sensitivity to implant variations without requiring additional lateral area, as the key mechanism occurs in the vertical dimension through the mesa configuration
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
This configuration reduces leakage current and enhances breakdown voltage, improving device reliability and yield while maintaining a compact die size.
Implementation Method 1
The purpose of the JTE region is to reduce or prevent the electric field crowding at the edges
Implementation Method 2
The implants used to form the JTE region may be aluminum, boron, or any other suitable p-type dopant
Data Source
AI summary
An electronic device includes a semiconductor layer, a primary junction in the semiconductor layer, a lightly doped region surrounding the primary junction and a junction termination structure in the lightly doped region adjacent the primary junction. The junction termination structure has an upper boundary, a side boundary, and a corner between the upper boundary and the side boundary, and the lightly doped region extends in a first direction away from the primary junction and normal to a point on the upper boundary by a first distance that is smaller than a second distance by which the lightly doped region extends in a second direction away from the primary junction and normal to a point on the corner. At least one floating guard ring segment may be provided in the semiconductor layer outside the corner of the junction termination structure. Related methods are also disclosed.