GaN Seed Substrate Honeycomb Dislocation Pattern for Peeling
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Solution Overview
Problem
The existing flux method for growing Group III nitride semiconductors faces challenges with warpage and dislocation density issues, leading to poor peeling properties and reduced mass productivity, especially when using large-area substrates, which complicates the grinding and quality of GaN crystals.
Innovation Solution
A seed substrate with a base layer having a two-dimensional periodic dislocation density distribution, featuring high and low dislocation density regions arranged in a honeycomb pattern, is used, where the high dislocation density region is melted back during initial growth to create cavities, allowing for improved peeling and reducing warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If trenches are formed on the GaN layer to improve peeling property, then peeling ease is improved, but crystal quality deteriorates due to warpage and dislocation density issues
Solution Approach 1:
The invention applies local quality by creating regions with different dislocation densities within the base layer. Specifically, it forms a patterned structure where some regions have high dislocation density and others have low dislocation density, allowing different areas to serve different functions: high dislocation density regions facilitate peeling while low dislocation density regions maintain crystal quality.
Solution Approach 2:
The invention employs the melting back process during initial crystal growth to selectively remove high dislocation density regions. By controlling the growth conditions, the high dislocation density areas are melted back and removed, while low dislocation density regions are preserved, thus skipping the problematic high dislocation density areas before they can cause warpage.
2Productivity
If large-area substrates are used to increase productivity, then mass productivity is improved, but warpage increases making grinding difficult
Solution Approach 1:
The invention segments the base layer into multiple regions with different dislocation densities arranged in a periodic pattern. This segmentation allows large-area substrates to be used for increased productivity while the distributed pattern of high and low dislocation density regions prevents cumulative stress that would cause warpage, enabling easier grinding of large wafers.
3Manufacturing precision
If dislocation density is drastically decreased at initial growth stage, then dislocation density is reduced, but warpage occurs due to large dislocation density difference
Solution Approach 1:
Instead of uniformly decreasing dislocation density across the entire base layer, the invention creates local variations with both high and low dislocation density regions distributed in a periodic pattern. This local quality approach maintains overall low average dislocation density while preventing warpage through the balanced distribution of stress-relieving high dislocation density regions.
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 enhances the peeling property and reduces warpage in GaN crystals, enabling the production of high-quality, large-area wafers with low dislocation density and narrow off-angle distribution, facilitating easier grinding and increased yield.
Implementation Method 1
the high dislocation density region is melted back at an initial stage of growth
Data Source
AI summary
The seed substrate comprises a base substrate and a base layer comprising a Group III nitride semiconductor formed on the base substrate, which has a high dislocation density region and a low dislocation density region. The planar pattern of the high dislocation density region is a honeycomb pattern. A hollow exists between the base substrate and the low dislocation density region. The object layer is grown through a flux method using the seed substrate. The high dislocation density region is melted back at an initial stage of crystal growth, and thereafter, the object layer is grown on the top surface of the low dislocation density region. A cavity remains between the high dislocation density region and the object layer. The presence of the cavity and the hollow makes easy to peel the object layer from the seed substrate.