SiC Semiconductor Device with Recessed Contact Region
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Solution Overview
Problem
High dose implantation in silicon carbide (SiC) semiconductor devices introduces a high density of crystal defects, affecting reverse leakage current and long-term reliability, while methods to improve surge current, such as forming silicide on P-doped regions, add significant complexity to the process.
Innovation Solution
An offset is introduced between the masks of deep and shallow contact implants, recessing the edges of the shallow implant from the deep implant, preventing the depletion region from reaching crystal defects and allowing for increased implant dose without adding complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high dose implantation is performed to reduce contact resistance, then surge current capability is improved, but crystal defects increase causing higher reverse leakage current and reduced reliability
Solution Approach 1:
The implantation process is segmented into two distinct steps: a deep well implant and a shallow contact implant. The shallow implant is further segmented to have recessed edges relative to the deep implant, creating spatial separation between high-dose regions and depletion regions. This segmentation allows high dose implantation for low contact resistance while preventing crystal defects from entering the depletion region, thus reducing reverse leakage current.
Solution Approach 2:
Different implantation doses and depths are applied to different spatial regions. The center region receives high dose shallow implantation for low contact resistance, while the edge regions are recessed to prevent crystal defects from reaching the depletion region. This local differentiation of implantation quality optimizes both contact resistance and reverse leakage characteristics in their respective regions.
2Reliability
If high dose implantation is performed to reduce contact resistance, then surge current capability is improved, but long-term reliability deteriorates due to crystal defects
Solution Approach 1:
The implantation process is segmented into two distinct steps: a deep well implant and a shallow contact implant. The shallow implant is further segmented to have recessed edges relative to the deep implant, creating spatial separation between high-dose regions and depletion regions. This segmentation allows high dose implantation for low contact resistance while preventing crystal defects from entering the depletion region, thus reducing reverse leakage current.
Solution Approach 2:
Different implantation doses and depths are applied to different spatial regions. The center region receives high dose shallow implantation for low contact resistance, while the edge regions are recessed to prevent crystal defects from reaching the depletion region. This local differentiation of implantation quality optimizes both contact resistance and reverse leakage characteristics in their respective regions.
3Reliability
If silicide is formed on P-doped regions to improve surge current, then surge current capability is improved, but process complexity increases significantly
Solution Approach 1:
The invention extracts and eliminates the silicide formation step from the process. Instead of forming silicide on P-doped regions to improve surge current capability, the patent achieves the same effect through optimized implantation geometry alone, thereby removing the complex silicide formation process while maintaining surge current performance.
Solution Approach 2:
The recessed shallow implant structure serves multiple functions simultaneously: it provides low contact resistance through high dose implantation, prevents reverse leakage by keeping crystal defects out of the depletion region, and achieves surge current capability without requiring additional silicide formation processing. This multi-functional design simplifies the overall process.
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 approach effectively shields crystal defect damage sites from the reverse bias depletion region, reducing reverse leakage current and enhancing long-term reliability without increasing process complexity.
Implementation Method 1
implanting contact and well regions in the SiC epitaxial layer through the hardmask layer
Data Source
AI summary
A silicon carbide semiconductor device includes a silicon carbide (SiC) substrate having a SiC epitaxial layer disposed over a surface of the SiC substrate, the SiC substrate having a first conductivity and the SiC epitaxial layer having the first conductivity. A contact region and a well region are formed in the SiC epitaxial layer, the contact region and the well region have a doping level of a second conductivity opposite the first conductivity. The contact region lies completely within the well region, is not in contact with a region having the first conductivity and has edges recessed from edges of the well region.