SiC Trench Structure Fabrication with Protection Layer
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Solution Overview
Problem
The challenge is to form a trench structure on a SiC substrate with a rounded bottom without roughening the surface, as high-temperature annealing processes used to achieve this often result in a roughened surface due to dry etching limitations.
Innovation Solution
A method involving the formation of a protection layer on the SiC substrate during annealing to prevent surface roughening, which includes depositing a protection layer and a resisting layer, patterning them to create an opening, using the resisting layer as a hard mask for dry etching, and then performing an annealing process to shape the trench bottom while maintaining the surface integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If high-temperature annealing process is performed to form a rounded bottom of the trench, then the trench bottom becomes rounded, but the surface of the SiC substrate becomes roughened
Solution Approach 1:
The SiC substrate surface is segmented into two regions: the trench bottom region (exposed to annealing for rounding) and the surface region (covered by protection layer to prevent roughening). This spatial segmentation allows different thermal treatments for different functional requirements.
Solution Approach 2:
A protection layer is introduced as an intermediary between the SiC substrate surface and the annealing environment. This layer mediates the thermal process by allowing heat transmission to the trench bottom while protecting the surface from direct exposure to annealing conditions that cause roughening.
2Manufacturing precision
If dry etching is used to process the trench structure, then high aspect ratio and vertical sidewalls are achieved, but a rounded bottom cannot be formed
Solution Approach 1:
Two different processing methods are merged in sequence: dry etching is first used to achieve high aspect ratio and vertical sidewalls, then high-temperature annealing is applied to form the rounded bottom. This combination leverages the strengths of both processes while mitigating their individual limitations.
Solution Approach 2:
The dry etching process is performed first to establish the trench structure with vertical sidewalls before the annealing process is applied. This preliminary action creates the foundation that subsequent annealing will modify at the bottom while preserving the sidewall characteristics.
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 effectively creates a trench structure with vertical lateral walls and a rounded bottom on the SiC substrate, protecting the surface from roughening during high-temperature processing, enabling precise and high-aspect-ratio trench formation without surface damage.
Implementation Method 1
the surface of the substrate is covered by a protection layer during the annealing process so as to avoid the surface of the substrate being roughened due to the annealing process
Implementation Method 2
performing an annealing process to form a rounded bottom of the trench
Implementation Method 3
The trench structure of SiC is usually processed by dry etching to obtain high aspect ratio and vertical sidewalls
Data Source
AI summary
A trench structure on a SiC substrate and method for fabricating thereof is provided. The fabricating method includes: providing a SiC substrate; forming a protection layer on the SiC substrate; forming an resisting layer on the protection layer; patterning the resisting layer and the protection layer to form an opening; patterning the SiC substrate by using the patterned resisting layer as a hard mask to form a trench; removing the patterned resisting layer; performing a high-temperature annealing process to form a rounded bottom of the trench; and removing the protection layer.