SiC Device Trench Gate Protection Against Avalanche Breakdown
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In silicon carbide (SiC) semiconductor devices, the application of reverse bias voltage can cause avalanche breakdown beneath the trench, leading to the breakdown of the gate insulating film, which existing technologies fail to reliably prevent due to insufficient protection of the electric field shielding regions.
Innovation Solution
A silicon carbide semiconductor device design incorporating a drift region, a base region, trench gate structure, a protection region, and an avalanche breakdown-inducing region, where the width ratio of the protection region to the avalanche breakdown-inducing region satisfies specific conditions to divert avalanche current away from the trench bottom, preventing gate insulating film breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electric field shielding region is formed beneath the trench to protect the gate insulating film, then the gate insulating film is protected from breakdown, but avalanche current may still flow into the bottom of the trench causing film breakdown
Solution Approach 1:
The invention divides the electric field shielding function into two separate regions: (1) an electric field shielding region formed beneath the trench bottom, and (2) an electric field shielding region formed beneath the base region between adjacent trenches. This segmentation allows each region to perform its specific function - the first region protects the gate insulating film while the second region induces avalanche breakdown away from the trench bottom, preventing harmful current flow.
Solution Approach 2:
The invention introduces an intermediary electric field shielding region beneath the base region that acts as a mediator to redirect avalanche current. This intermediate region with specific impurity concentration and depth creates a controlled avalanche breakdown path that prevents current from reaching the trench bottom, thus protecting the gate insulating film without compromising overall device performance.
2Ease of manufacture
If both electric field shielding regions are formed with arbitrary dimensions and impurity concentrations, then device fabrication is simplified, but sufficient protection against avalanche current cannot be achieved
Solution Approach 1:
The invention specifies precise parameter ranges for both electric field shielding regions, including impurity concentrations (first region: 1×10^18 to 1×10^19 atoms/cm³, second region: 1×10^17 to 1×10^18 atoms/cm³) and depth relationships (second region bottom surface deeper than first region bottom surface by 0.1 to 1.0 μm). These controlled parameter changes ensure optimal electric field distribution that prevents avalanche current from reaching the trench bottom while maintaining fabrication feasibility.
Solution Approach 2:
The invention applies different local qualities to different regions: the first electric field shielding region beneath the trench has higher impurity concentration to provide strong local protection, while the second electric field shielding region beneath the base region has lower impurity concentration to induce controlled avalanche breakdown. This local quality differentiation optimizes both protection effectiveness and current redirection functionality.
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 design effectively avoids the flow of avalanche current into the trench bottom, thereby reliably protecting the gate insulating film from breakdown, ensuring the semiconductor device's operational integrity.
Implementation Method 1
a high voltage is applied between the drain and the source. This high voltage sometimes causes avalanche breakdown to occur beneath the trench
Data Source
AI summary
A silicon carbide semiconductor device includes an n-type drift region made of SiC, n-type base regions, gate electrodes formed inside trenches with gate insulating films interposed therebetween, n-type source regions formed in upper portions of the base regions, an n-type drain region formed on the bottom of the drift region, p-type protection regions formed beneath the trenches, and p-type avalanche breakdown-inducing regions (first under-contact base regions) formed at the same depth as the protection regions and having the same impurity concentration as the protection regions. The width wcb of the avalanche breakdown-inducing regions and the width wtb of the protection regions satisfy the relationship wtb/wcb>4/3.