Silicon Carbide Plasma Etching for Rounded Trench Corners
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Solution Overview
Problem
Current methods for fabricating compound semiconductor devices, such as silicon carbide (SiC) devices, are inefficient and require many processing steps, leading to issues like micro-trenching, electric field concentration, and reduced breakdown voltages due to uncontrolled trench corner angles.
Innovation Solution
A plasma etching method involving multiple steps with controlled plasma etching and passivation material deposition to form trenches with rounded corners, minimizing micro-trenching and field bunching, using fluorocarbon-based etchants and varying process parameters to achieve rounded profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional plasma etching methods are used to create trenches with perpendicular sidewalls, then manufacturing simplicity is maintained, but micro-trenching occurs at the corners causing electric field concentration and reduced breakdown voltage
Solution Approach 1:
The etching process is divided into multiple sequential steps with different parameters: a first etch step creates the initial trench structure, while subsequent etch steps with modified conditions round the corners and remove micro-trenching. This segmentation allows each step to optimize for its specific function, achieving rounded corners and high breakdown voltage without requiring furnace annealing or wet etching.
Solution Approach 2:
The patent modifies plasma etching parameters including gas composition, power levels, and pressure conditions between etch steps to transition from creating perpendicular sidewalls to rounding corners. By changing etch chemistry and physical conditions, the process achieves corner rounding and micro-trenching removal purely through plasma-based methods, eliminating the need for thermal or wet processing steps.
2Reliability
If furnace annealing or wet etch steps are used to round trench corners, then breakdown voltage is improved, but the number of processing steps increases and manufacturing complexity rises
Solution Approach 1:
The patent combines corner rounding and micro-trenching removal into the same plasma etching sequence that also defines the trench profile. By merging multiple functions (trench formation, corner rounding, and defect removal) into a single integrated plasma process, the method eliminates separate furnace annealing or wet etching steps, reducing total processing time while maintaining high breakdown voltage through rounded corners.
Solution Approach 2:
The patent replaces thermal processing (furnace annealing) and chemical processing (wet etching) with plasma-based physical and chemical etching. This substitution uses plasma chemistry and ion bombardment to achieve corner rounding and defect removal, eliminating the need for high-temperature thermal fields or liquid chemical baths, thereby reducing processing complexity and time.
3Manufacturing precision
If multiple plasma etch steps are used to round both base and top corners, then micro-trenching is avoided and breakdown voltage increases, but process complexity increases
Solution Approach 1:
The patent employs dynamic adjustment of plasma parameters during sequential etching steps. By varying gas flow rates, power levels, and pressure conditions between and during etch steps, the process dynamically transitions from creating sharp corners to rounding them precisely. This dynamic control achieves high corner rounding precision while managing process complexity through automated parameter sequencing.
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 prevents micro-trenching, achieving higher quality semiconductor devices with fewer processing steps.
Implementation Method 1
performing a first plasma etch step to anisotropically etch the substrate through the opening
Implementation Method 2
performing a first plasma etch step to anisotropically etch the substrate through the opening to produce a partially-formed feature
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
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AI summary
A method of plasma etching a compound semiconductor substrate to form a feature and plasma etch apparatus for plasma etching a substrate to form a feature are provided.