Composite Substrate Structure for Stress-Relaxed GaN Epitaxy
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Solution Overview
Problem
The challenge in growing high-quality Gallium Nitride films on silicon substrates lies in significant lattice and thermal mismatches, leading to poor crystal quality and warpage issues, which existing technologies struggle to address effectively.
Innovation Solution
A composite substrate is created by stacking a first substrate with protruding structures and grooves, a bonding layer that covers these structures, and a second substrate, where all materials are made of N-type doped semiconductor materials, with the bonding layer and second substrate being made of SiC or SiCN, to enhance mechanical strength and epitaxial crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon substrate is used for GaN heteroepitaxial growth, then the substrate conductivity can be controlled by doping and thermal conductivity is high, but there is a large lattice mismatch (16.9%) leading to penetrating dislocations and poor crystal quality
Solution Approach 1:
The invention introduces a composite substrate structure with a first substrate, bonding layer, and second substrate stacked sequentially. The first substrate includes protruding structures that segment the bonding interface, creating localized bonding regions that reduce overall stress while maintaining electrical control capabilities.
Solution Approach 2:
The invention uses a composite substrate composed of different materials (first substrate, bonding layer, second substrate) to combine the advantages of silicon substrates (controllable conductivity, high thermal conductivity) with reduced lattice mismatch effects, thereby improving both electrical control and epitaxial crystal quality.
2Reliability
If a silicon substrate is used for GaN heteroepitaxial growth, then the substrate is cost-effective and has high thermal conductivity, but there is a huge thermal mismatch (54%) causing epitaxial warpage and edge cracking
Solution Approach 1:
The protruding structures on the first substrate create a segmented bonding interface with the second substrate. This segmentation allows for localized stress distribution, preventing the propagation of thermal stress across the entire substrate area, thereby reducing warpage and edge cracking while maintaining high thermal conductivity.
Solution Approach 2:
The bonding layer is configured to cover specific regions (protruding structures) rather than the entire substrate surface. This local bonding approach concentrates mechanical strength where needed while allowing stress relief in other regions, addressing the thermal mismatch problem without compromising overall thermal conductivity.
3Stability of the object's composition
If AlN layers are introduced to compensate for thermal mismatch stress, then compressive stress compensates for tensile stress during high-temperature epitaxial growth, but the device structure becomes more complex and manufacturing steps increase
Solution Approach 1:
The invention extracts the stress compensation function from the epitaxial layer structure (AlN layers) and transfers it to the substrate structure (protruding structures on the first substrate). This separation allows stress compensation to be achieved at the substrate level, simplifying the overall device structure and reducing manufacturing complexity.
Solution Approach 2:
The protruding structures are pre-formed on the first substrate before epitaxial growth begins. This preliminary structural configuration establishes the stress compensation mechanism in advance, eliminating the need for additional AlN compensation layers and reducing the number of manufacturing steps.
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 configuration improves the mechanical strength and epitaxial crystal quality of the semiconductor structure by attenuating stress and preventing plastic deformation during epitaxial growth, thereby enhancing the performance of subsequent semiconductor devices.
Implementation Method 1
a bonding layer, and a second substrate which are stacked sequentially
Implementation Method 2
the first substrate includes a plurality of protruding structures disposed on a side close to the second substrate, and a groove formed between at least two protruding structures
Implementation Method 3
the first substrate, the bonding layer, and the second substrate are all made of an N-type doped semiconductor material
Data Source
AI summary
Disclosed are a composite substrate, a manufacturing method thereof and a semiconductor device. The composite substrate includes a first substrate, a bonding layer, and a second substrate which are stacked sequentially, where the first substrate comprises a plurality of protruding structures disposed on a side close to the second substrate, and a groove formed between at least two protruding structures of the plurality of protruding structures. The composite substrate provided by the present disclosure, by setting a bonding layer, a bond strength between the first substrate and the second substrate may be improved, and a mechanical strength of the composite substrate is enhanced. By setting the groove, a stress transmitted from the second substrate to the first substrate may be attenuated, so as to improve the mechanical strength of the composite substrate and avoid a plastic deformation in a subsequent epitaxial process.