GaN Substrate Stress Management via SOI Notches
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Solution Overview
Problem
The challenge lies in manufacturing large-size gallium nitride semiconductor substrates due to significant lattice and thermal mismatches with silicon substrates, leading to stress-induced defects, warping, and cracking, which limits the production of high-quality, cost-effective GaN devices.
Innovation Solution
A method involving a silicon-on-insulator substrate with a nitride semiconductor layer, where notches are formed to expose the top silicon layer, followed by removing the top silicon layer and forming protrusions and recesses on the buried silicon dioxide layer, allowing for epitaxial growth of a second nitride semiconductor layer, thereby alleviating stress mismatch and enabling the creation of a self-supporting nitride semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a large-size silicon substrate is used to prepare gallium nitride semiconductor substrate, then the cost is reduced and applicability is improved, but stress-induced defects, warping, and cracking occur due to lattice and thermal mismatch
Solution Approach 1:
The invention divides the continuous nitride semiconductor layer into segmented regions by forming notches, which allows stress to be released in a controlled manner. This segmentation prevents the accumulation of stress that would otherwise lead to warping and cracking, while still maintaining the integrity of the substrate for large-size manufacturing
Solution Approach 2:
The invention introduces a buffer layer as an intermediary between the silicon substrate and the nitride semiconductor layer. This buffer layer acts as a stress-absorbing intermediate structure that mitigates the lattice and thermal mismatch between silicon and gallium nitride, enabling large-size substrate manufacturing without compromising substrate quality
2Productivity
If a large-size gallium nitride semiconductor substrate is manufactured on silicon substrate, then cost is reduced, but stress causes defects and prevents large-size production
Solution Approach 1:
The invention performs preliminary stress management by forming notches in the nitride semiconductor layer before completing the epitaxial growth process. This preliminary action creates stress release pathways that prevent subsequent warping and cracking, enabling the manufacturing of large-size substrates with high precision and low defect rates
Solution Approach 2:
The invention applies local quality changes by creating notches with specific geometries and distributions in the nitride semiconductor layer. These localized structural modifications are strategically placed to manage stress concentration points, allowing the overall substrate to maintain high manufacturing precision while achieving large size
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 reduces defects and radio frequency loss, facilitates the production of large-size nitride semiconductor substrates with improved quality and reduces manufacturing costs by alleviating stress mismatch and enabling the transfer of the substrate for further processing.
Implementation Method 1
the buried silicon dioxide layer is etched by HF acid solution so as to separate the self-supporting nitride semiconductor substrate from the underlying silicon layer
Implementation Method 2
epitaxially growing a second nitride semiconductor layer on the first nitride semiconductor layer, such that the first nitride semiconductor layer and the second nitride semiconductor layer form a nitride semiconductor substrate
Data Source
AI summary
A method of manufacturing nitride semiconductor substrate, comprising: providing silicon-on-insulator substrate which comprises an underlying silicon layer, a buried silicon dioxide layer and a top silicon layer; forming a first nitride semiconductor layer on the top silicon layer; forming, in the first nitride semiconductor layer, a plurality of notches which expose the top silicon layer; removing the top silicon layer and forming a plurality of protrusions and a plurality of recesses on an upper surface of the buried silicon dioxide layer, wherein each of the plurality of protrusions is in contact with the first nitride semiconductor layer, and there is a gap between each of the plurality of recesses and the first nitride semiconductor layer; and epitaxially growing a second nitride semiconductor layer on the first nitride semiconductor layer, such that the first nitride semiconductor layer and the second nitride semiconductor layer form a nitride semiconductor substrate.