SiC Semiconductor Surge Protection via Selective Etching
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Solution Overview
Problem
Existing semiconductor devices in silicon carbide (SiC) face challenges with surge current protection due to insufficient conductivity modulation and residual implantation damage, and mesa edge termination techniques are difficult to apply effectively in SiC due to etching complexities and damage removal.
Innovation Solution
A method involving selective etching to form a mesa structure with raised regions of n-type and p-type SiC semiconductor materials, followed by thermal oxidation and dielectric layer formation, allowing for the creation of ohmic contacts and Schottky metal deposition, which enhances conductivity modulation and protects against high electric fields using mesa edge termination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation is used to form heavily doped p-type regions, then surge current protection is improved, but residual implantation damage reduces minority carrier lifetime
Solution Approach 1:
The patent extracts the harmful residual implantation damage from the system by using selective etching to remove damaged material, while preserving the beneficial heavily doped p-type regions that provide surge current protection and conductivity modulation.
Solution Approach 2:
The device is segmented into distinct regions: heavily doped p-type regions for surge protection, etched trenches to remove damage, and drift regions for conductivity modulation. This segmentation allows each region to be optimized independently for its specific function.
2Reliability
If mesa edge termination is applied to SiC devices, then electric field management is improved, but etching complexities and damage removal difficulties increase
Solution Approach 1:
The patent applies local quality by creating heavily doped p-type regions at specific locations (anode contact regions) rather than uniformly throughout the device. This localized doping provides surge protection where needed while avoiding unnecessary complexity in other regions.
Solution Approach 2:
The patent performs preliminary selective etching to remove damaged material and define trenches before subsequent processing steps. This preliminary action eliminates etching damage early in the process, preventing propagation of defects through later manufacturing steps.
3Reliability
If low doping of p-type regions is used, then conductivity modulation is reduced, but surge current protection capability is insufficient
Solution Approach 1:
The patent changes the doping parameter by creating heavily doped p-type regions with high dopant concentrations specifically in the anode contact regions. This parameter change enables both surge current protection and adequate conductivity modulation in the drift region.
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 approach results in improved semiconductor devices with enhanced surge current handling and efficient electric field management, reducing residual damage and fabrication complexities, leading to higher yield and lower costs compared to traditional edge termination methods.
Implementation Method 1
thermally oxidizing the device to form an oxide layer on unetched surfaces of p-type SiC semiconductor material and on etched surfaces of the device including the sidewalls of the raised region of n-type semiconductor material
Data Source
AI summary
A wide bandgap semiconductor device with surge current protection and a method of making the device are described. The device comprises a low doped n-type region formed by plasma etching through the first epitaxial layer grown on a heavily doped n-type substrate and a plurality of heavily doped p-type regions formed by plasma etching through the second epitaxial layer grown on the first epitaxial layer. Ohmic contacts are formed on p-type regions and on the backside of the n-type substrate. Schottky contacts are formed on the top surface of the n-type region. At normal operating conditions, the current in the device flows through the Schottky contacts. The device, however, is capable of withstanding extremely high current densities due to conductivity modulation caused by minority carrier injection from p-type regions.