GaN Substrate Growth via Patterned Mask Ammonothermal Process
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Solution Overview
Problem
Current methods for growing GaN crystals suitable for C-plane GaN substrates face challenges in achieving high-quality substrates with controlled dislocation arrays and efficient growth processes, particularly in producing substrates with reduced dislocation defects and improved electrical properties for nitride semiconductor devices.
Innovation Solution
A method involving a GaN seed with a nitrogen polar surface, a pattern mask with a periodic opening pattern, and ammonothermal growth using mineralizers like NH4F and NH4I to promote GaN crystal growth, forming gaps between the crystal and the mask, which reduces orientation disorder and dislocation defects, and results in a substrate with periodic dislocation arrays and improved electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a pattern mask is used during ammonothermal growth to control crystal orientation, then orientation disorder is reduced and dislocation defects decrease, but the device complexity and manufacturing process complexity increase
Solution Approach 1:
The pattern mask is divided into multiple regions with different opening patterns (first region with first pattern, second region with second pattern) to control dislocation propagation in different areas independently. This segmentation allows precise control of crystal orientation and dislocation reduction while managing the overall complexity through modular design.
Solution Approach 2:
Different regions of the pattern mask provide different local structures (different opening patterns) to address local requirements for dislocation control. The first region has a pattern optimized for controlling dislocations in one direction, while the second region has a pattern optimized for another direction, achieving local quality optimization throughout the crystal substrate.
2Manufacturing precision
If ammonothermal growth is used to produce GaN crystals, then high-quality substrates with reduced dislocation defects are achieved, but the growth time and production cost increase
Solution Approach 1:
A GaN seed crystal with predetermined orientation and structure is prepared before the main growth process. This preliminary action establishes the foundation for high-quality crystal growth, reducing the time needed during the actual ammonothermal growth phase while ensuring the final substrate meets the required quality standards.
Solution Approach 2:
The pattern mask design creates periodic structures that guide dislocation propagation and crystal growth in a controlled manner. This periodic action allows the system to manage dislocation density and crystal quality efficiently, optimizing the balance between growth time and substrate quality.
3Reliability
If the pattern mask has intersections with specific orientation relative to M-plane, then dislocation arrays are controlled and electrical properties improve, but the manufacturing precision requirements and process complexity increase
Solution Approach 1:
The pattern mask utilizes asymmetric intersection designs where the first and second regions have different pattern orientations relative to the M-plane. This asymmetry is deliberately introduced to control dislocation propagation directions and achieve optimal electrical properties, while the specific angular relationships (within ±5° or ±10°) provide clear manufacturing guidelines.
Solution Approach 2:
The invention specifies particular parameter ranges for mask orientation (±5° or ±10° relative to M-plane) to optimize the balance between dislocation control and manufacturing feasibility. By defining these parameter ranges, the system achieves reliable electrical properties while accommodating reasonable manufacturing tolerances.
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 enables the production of high-quality C-plane GaN substrates with reduced dislocation defects and enhanced electrical properties, suitable for nitride semiconductor devices, by promoting the closure of through-holes and relieving stress during growth, thus improving substrate quality and performance.
Implementation Method 1
a third step of ammonothermally growing a GaN crystal on the nitrogen polar surface of the GaN seed through the pattern mask
Implementation Method 2
NH4F and one or more ammonium halides selected from NH4Cl, NH4Br, and NH4I are used as mineralizers
Data Source
AI summary
A method for growing a GaN crystal suitable as a material of GaN substrates including C-plane GaN substrates includes: a first step of preparing a GaN seed having a nitrogen polar surface; a second step of arranging a pattern mask on the nitrogen polar surface of the GaN seed, the pattern mask being provided with a periodical opening pattern comprising linear openings and including intersections, the pattern mask being arranged such that longitudinal directions of at least part of the linear openings are within ±3° from a direction of an intersection line between the nitrogen polar surface and an M-plane; and a third step of ammonothermally growing a GaN crystal through the pattern mask such that a gap is formed between the GaN crystal and the pattern mask.