Si Substrate Buffer Structure for Nitride Semiconductor Growth
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Solution Overview
Problem
Direct growth of AlN on a Si substrate via PVD often results in an amorphous silicon oxide layer, leading to poor quality AlN layers with inconsistent stress release, cracks, and substrate corrosion, degrading semiconductor performance.
Innovation Solution
A multi-layer buffer structure comprising a metal protective layer, a metal oxide protective layer, and a transition layer is formed on the Si substrate to prevent amorphous layer formation and reduce lattice differences, improving crystal quality of the III-V-group buffer layer, which includes oxygen-doped AlN layers deposited via PVD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If AlN layer is directly grown on Si substrate via PVD, then buffer layer can be deposited with high density and good bonding, but an amorphous silicon oxide layer forms at the contact surface, leading to poor crystal quality and device performance
Solution Approach 1:
An Al2O3 intermediate layer is introduced between the Si substrate and the AlN buffer layer. This intermediate layer acts as a mediator that prevents direct reaction between Si and AlN, thereby avoiding the formation of amorphous silicon oxide layer while maintaining good lattice matching and crystal quality of the AlN layer.
2Stress or pressure
If AlN layer is deposited via PVD to minimize lattice mismatch and thermal mismatch, then stress can be eased, but cracks form due to inconsistent stress release ability in the amorphous silicon nitride contact layer
Solution Approach 1:
The Al2O3 intermediate layer serves as a stress buffer that enables consistent stress release. By preventing the formation of the amorphous silicon nitride contact layer, the intermediate layer ensures uniform stress distribution and release, thereby preventing crack formation in the AlN buffer layer and improving device reliability.
3Ease of manufacture
If low density AlN layer is deposited, then deposition process is simpler, but holes are generated that allow Gallium to corrode the Si substrate in subsequent CVD processes
Solution Approach 1:
The Al2O3 intermediate layer acts as a protective barrier that prevents Gallium from reaching and corroding the Si substrate. This intermediate layer maintains the integrity of the substrate during subsequent CVD processes, eliminating the need for complex deposition processes to achieve high density AlN layers.
4Manufacturing precision
If multi-layer buffer structure is introduced to prevent amorphous layer formation, then crystal quality is improved, but device structure becomes more complex
Solution Approach 1:
The buffer structure is segmented into distinct functional layers: an Al2O3 intermediate layer for preventing amorphous layer formation, an AlN buffer layer for lattice matching, and optionally an AlGaN transition layer for stress management. This segmentation allows each layer to perform its specific function optimally while maintaining overall structural simplicity.
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 solution prevents cracks and substrate corrosion, enhances crystal quality, and reduces dislocation and defect density, resulting in improved performance and reliability of nitride semiconductor devices with increased luminous efficiency and electron mobility.
Implementation Method 1
Physical vapor deposition (PVD) is an easy-to-operate process that consumes little raw material and causes little environmental pollution
Implementation Method 2
the transition layer reduces lattice difference between the metal oxide protective layer and the III-V-group buffer layer, thus improving crystal quality of the III-V-group buffer layer
Implementation Method 3
atoms sputtered from PVD have higher energy (in general 10 ̃20 eV) and migration ability
Data Source
AI summary
A semiconductor element has a metal protective layer and a metal oxide protective layer formed on the substrate to prevent the Si substrate surface from forming an amorphous layer; and a transition layer to reduce lattice difference between the metal oxide protective layer and the III-V-group buffer layer, thus improving crystal quality of the III-V-group buffer layer. A fabrication method can avoid formation of amorphous layers and cracks surrounding the Si substrate surface. A light-emitting diode (LED) element or a transistor element can be formed by depositing a high-quality multi-layer buffer structure via PVD and forming a GaN, InGaN or AlGaN epitaxial layer thereon.