SiC Trench Plasma Etching With Rounded Corners for Breakdown Voltage
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Solution Overview
Problem
Current methods for fabricating compound semiconductor devices, such as silicon carbide (SiC) devices, face challenges in achieving high breakdown voltages due to micro-trenching and field bunching, which are exacerbated by the use of flat-based trenches with perpendicular sidewalls, requiring additional furnace or wet etch steps for corner rounding.
Innovation Solution
A plasma etching method involving multiple steps with controlled plasma etching and passivation material deposition to form trenches with rounded corners and edges, using fluorocarbon-based etchants and varying process parameters to disperse electric fields and prevent micro-trenching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flat-based trenches with perpendicular sidewalls are used, then manufacturing simplicity is improved, but breakdown voltage deteriorates due to micro-trenching and field bunching
Solution Approach 1:
The patent applies curvature by rounding the corners of trenches instead of using sharp perpendicular corners. This is achieved through a multi-step plasma etching process that creates rounded corner profiles, which disperses electric fields and prevents field bunching at corner locations, thereby improving breakdown voltage while maintaining manufacturing feasibility
Solution Approach 2:
The patent uses a periodic multi-step plasma etching process with alternating etching and passivation steps. The process cycles through different plasma chemistries and parameters to progressively shape the trench profile, achieving rounded corners through repeated controlled etching attacks rather than a single step
2Reliability
If furnace annealing processes are used to round trench corners, then breakdown voltage is improved, but manufacturing complexity and processing time increase
Solution Approach 1:
The patent replaces thermal furnace annealing processes with a plasma-based chemical etching approach. Instead of using high-temperature thermal diffusion to round corners, the invention uses controlled plasma chemistry and physics to achieve the same corner rounding effect directly during the etching process itself, eliminating the need for separate furnace steps
Solution Approach 2:
The patent merges the trench etching and corner rounding operations into a single integrated plasma etching process. The multi-step plasma process simultaneously creates the trench depth and shapes the corner profiles, combining what were previously separate manufacturing steps into one unified process flow
3Length of moving object
If micro-trenching occurs at trench corners, then etching depth is improved, but electric field concentration increases leading to reduced breakdown voltage
Solution Approach 1:
The patent applies local quality by creating different geometries at different locations within the trench structure. The corners are specifically rounded while the center and sidewalls maintain different characteristics. This localized geometric modification at corner regions disperses electric fields where they would otherwise concentrate, preventing field bunching while preserving overall trench depth
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 method enhances breakdown voltage by uniformly dispersing electric fields and preventing micro-trenching, achieving rounded corners and edges in SiC trenches without the need for furnace processes, thereby improving device performance.
Implementation Method 1
performing a first plasma etch step to anisotropically etch the substrate through the opening
Implementation Method 2
A plasma etching method involving multiple steps with controlled plasma etching and passivation material deposition
Implementation Method 3
performing a third plasma etch step to anisotropically etch the bottom surface of the partially-formed feature through the opening of the mask while depositing a passivation material onto the mask and the opening of the partially-formed feature
Data Source
AI summary
A method of plasma etching a compound semiconductor substrate forms a feature. A first plasma etch step anisotropically etches the substrate through an opening to produce a partially formed feature having an opening and a bottom surface with a peripheral region. A second plasma etch step removes a region of the mask adjacent to the opening of the partially formed feature thereby causing rounding of the edges of the substrate at the opening of the partially formed feature. A third plasma etch step anisotropically etches the bottom surface of the partially formed feature through the opening of the mask while depositing a passivation material onto the mask and the opening of the partially formed feature to reduce a dimension of the opening of the partially formed feature. A plasma etch apparatus can be used to perform the method.