HEMT Epitaxy with Split Nitride Layers for Crack Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional High Electron Mobility Transistors (HEMTs) face defects such as cracks, bowing, and breakages due to thermal expansion differences in material layers, affecting their breakdown voltage performance.
Innovation Solution
A method for epitaxy of HEMT involving the formation of a substrate, nucleation, buffer, first nitride, and second nitride layers with carbon doping, where the second nitride layer has a lower growth temperature and greater film thickness than the first nitride layer, forming a channel layer and barrier layer to reduce defects and enhance epitaxial structure quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different formation materials with different coefficients of thermal expansion are used in different layers, then the HEMT can achieve high electron mobility and high breakdown voltage, but thermal stress during temperature changes causes cracks, bowing, and breakages
Solution Approach 1:
The patent divides the nitride layer into multiple sub-layers (first nitride layer, second nitride layer, third nitride layer) with different thicknesses and compositions. This segmentation allows each sub-layer to accommodate thermal stress differently, preventing crack propagation through the entire structure while maintaining the overall high breakdown voltage performance.
Solution Approach 2:
Different regions of the nitride layer are assigned different properties: the first nitride layer has specific thickness and composition optimized for stress management, the second nitride layer has carbon doping for enhanced mobility, and the third nitride layer has different thickness for protective functions. This local differentiation resolves the contradiction between strength and reliability.
2Device complexity
If a single nitride layer is used, then the structure is simpler, but it cannot effectively reduce defects such as cracks and bowing caused by thermal expansion differences
Solution Approach 1:
The nitride layer is segmented into multiple sub-layers with specific thickness ratios and compositions. This segmentation transforms a simple single-layer structure into a complex multi-layer structure that can effectively manage thermal stress and reduce defects like cracks and bowing, thereby improving manufacturing precision.
Solution Approach 2:
The patent uses composite material structure where the nitride layer is composed of multiple sub-layers with different properties (thickness, composition, carbon doping). This composite structure provides both mechanical strength to prevent defects and electrical properties for high electron mobility, resolving the contradiction between device complexity and manufacturing precision.
3Ease of manufacture
If the nitride layer has uniform thickness, then the manufacturing process is simpler, but it cannot optimize both stress distribution and electron mobility
Solution Approach 1:
The uniform nitride layer is segmented into multiple sub-layers with different thicknesses. This segmentation allows each sub-layer to be optimized for specific functions (stress management, electron mobility, protection) while maintaining a controlled epitaxy process, thereby improving reliability without excessively complicating manufacturing.
Solution Approach 2:
Different thicknesses and compositions are assigned to different sub-layers of the nitride structure. This local quality differentiation enables optimal stress distribution and electron mobility in each region, improving defect density while keeping the epitaxy process manageable through standardized multi-layer fabrication.
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 effectively reduces defects and improves the breakdown voltage of HEMT epitaxial structures by optimizing the nitride layer thickness and growth conditions, resulting in improved structural integrity and performance.
Implementation Method 1
perform carbon doping on the second nitride layer
Implementation Method 2
Method for epitaxy of a high electron mobility transistor
Data Source
AI summary
A method for epitaxy of a high electron mobility transistor includes: provide a substrate; form a nucleation layer on the substrate; form a buffer layer on the nucleation layer; form a first nitride layer being in contact with the buffer layer on the buffer layer; form a second nitride layer being in contact with the first nitride layer on the first nitride layer, and perform carbon doping on the second nitride layer; form a channel layer on the second nitride layer; and form a barrier layer on the channel layer; a two-dimensional electron gas is formed in the channel layer along an interface between the channel layer and the barrier layer; a growth temperature of the second nitride layer is less than a growth temperature of the first nitride layer; a film thickness of the first nitride layer is less than a film thickness of the second nitride layer.