GaN Epitaxy Dislocation Control via Interlaced Hard Masks
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Solution Overview
Problem
The challenge in epitaxial growth of gallium nitride on silicon substrates is the high dislocation density due to lattice mismatch and thermal expansion coefficient differences, leading to defects that reduce device efficiency and potentially break the semiconductor substrate.
Innovation Solution
The use of at least two interlaced patterned hard mask layers during epitaxial growth of gallium nitride layers blocks dislocations, preventing them from extending into the surface layer, thereby reducing defects and enhancing device efficiency and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gallium nitride is epitaxially grown on silicon substrate, then the device can be manufactured with wide band gap properties, but high dislocation density occurs due to lattice mismatch and thermal expansion coefficient differences
Solution Approach 1:
The patent divides the continuous gallium nitride layer into multiple segments by introducing patterned hard mask layers at different depths. These hard mask layers create discrete growth regions that segment the dislocation propagation paths, preventing dislocations from continuously extending through the entire layer thickness. This segmentation approach directly reduces the effective dislocation density in the functional surface layer.
Solution Approach 2:
The patterned hard mask layers serve as intermediary structures between the silicon substrate and the surface gallium nitride layer. These intermediaries block dislocation propagation by creating physical barriers that dislocations cannot penetrate, thereby mediating the stress and defect transmission from the substrate to the active device layer.
2Ease of manufacture
If dislocations are allowed to grow continuously, then the epitaxial growth process is simpler, but device efficiency significantly decreases due to high dislocation density
Solution Approach 1:
The patent applies preliminary action by introducing patterned hard mask layers during the epitaxial growth process itself, rather than adding them after growth. This allows the hard masks to be integrated into the layer structure in advance, blocking dislocation propagation before defects can accumulate in the functional layer, thereby maintaining both manufacturing simplicity and device reliability.
3Manufacturing precision
If multiple patterned hard mask layers are used to block dislocations, then dislocation density decreases, but device structure becomes more complex
Solution Approach 1:
The patent addresses dislocation control not just in the vertical dimension but by introducing a lateral dimension through patterned hard mask layers. The interlaced patterns create a two-dimensional network of dislocation barriers that extend laterally, blocking defect propagation from multiple directions and providing more comprehensive protection with potentially fewer layers.
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 significantly decreases dislocation density in the gallium nitride layer, resulting in more perfect crystals closer to the surface and improving the efficiency and reliability of subsequent manufacturing steps.
Implementation Method 1
epitaxial growth of gallium nitride layers... at least two interlaced patterned hard mask layers are used when gallium nitride layers are epitaxially grown
Data Source
AI summary
A semiconductor substrate structure includes a seed layer on a substrate, a first gallium nitride layer on the seed layer, and a patterned first hard mask layer on the first gallium nitride layer, wherein the patterned first hard mask layer includes a first opening. The semiconductor substrate structure also includes a second gallium nitride layer in the first opening and on the patterned first hard mask layer, a patterned second hard mask layer on the second gallium nitride layer, wherein the patterned second hard mask layer includes a second opening, and at least a portion of a projection on the substrate of the first opening and a projection on the substrate of the second opening are non-overlapped. The semiconductor substrate structure further includes a third gallium nitride layer in the second opening and on the patterned second hard mask layer.