Patterned AlN/AlGaN Seed Layer for Epitaxial Stress Relief
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Solution Overview
Problem
The surface of an epitaxial layer in semiconductor structures is difficult to flatten due to large stress, which is not effectively addressed by existing nano-scale patterned sapphire substrate technologies.
Innovation Solution
A semiconductor structure is developed with a patterned AlN/AlGaN seed layer, including a superlattice structure or graded composition, and an AlGaN epitaxial layer, where the patterned seed layer provides stress relief through holes or alternating layers, and impurities like In or Mg are incorporated to enhance flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AlGaN material is regrown on nPSS substrate with AlN template, then the epitaxial layer can be formed on heterogeneous substrate, but the surface is not easy to flatten due to large stress
Solution Approach 1:
The patent divides the continuous AlN template layer into a patterned structure with periodic holes or recesses. This segmentation allows the AlGaN epitaxial layer to relax stress at the hole regions while maintaining structural integrity in the AlGaN layer, thereby improving surface flatness despite the inherent stress in heteroepitaxial growth
Solution Approach 2:
The patterned AlN template creates a porous or hollow structure beneath the AlGaN epitaxial layer. These voids act as stress relief zones, allowing the overlying AlGaN layer to flatten by redistributing stress away from the heterogeneous interface, solving the flatness problem while maintaining reliable epitaxial formation
2Shape
If patterned structure is introduced to reduce stress, then surface flatness is improved, but the device complexity increases
Solution Approach 1:
The patterned AlN template uses simple periodic hole structures rather than complex geometries. This segmentation approach achieves stress relief through regular, easily manufacturable patterns that can be created with standard lithography and etching processes, minimizing the increase in device complexity
Solution Approach 2:
The patent optimizes parameters such as hole diameter, spacing, and depth to achieve effective stress relief. By carefully controlling these geometric parameters, the pattern achieves the desired flatness improvement while keeping the structure simple and compatible with existing manufacturing capabilities
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 patterned seed layer effectively reduces stress concentration, improving the flatness of the epitaxial layer and promoting healing, resulting in a more uniform and performant semiconductor structure.
Implementation Method 1
the patterned seed layer provides stress relief through holes or alternating layers
Implementation Method 2
impurities like In or Mg are incorporated to enhance flatness
Data Source
AI summary
Disclosed are a semiconductor structure and a manufacturing method therefor, solving a problem that a surface of an epitaxial layer is not easy to flatten as the epitaxial layer has a large stress. The semiconductor structure includes: a substrate; a patterned AlN/AlGaN seed layer on the substrate; and an AlGaN epitaxial layer formed on the patterned AlN/AlGaN seed layer.