Composite AlN Substrate Structure for High-Temperature Power Devices
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Solution Overview
Problem
Existing silicon on insulator (SOI) substrates face limitations in high-temperature and high-power applications due to poor thermal conductivity, parasitic capacitance, and crosstalk issues, which affect device performance and reliability.
Innovation Solution
A composite substrate is developed with a high-resistance layer composed of stacked single crystal AlN layers and a growth substrate, featuring a first low-temperature AlN layer to reduce tensile stress, a high-temperature AlN layer for improved crystal quality, and a second low-temperature AlN layer as a protective layer, along with optional insertion and dielectric layers to enhance bonding and reduce parasitic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a traditional SiO2 insulator layer is used in SOI substrate, then the substrate can be manufactured with conventional processes, but the thermal conductivity is poor leading to high-temperature operation limitations
Solution Approach 1:
The patent employs a composite substrate structure combining SiC substrate with AlN high-resistance layer. SiC provides superior thermal conductivity compared to traditional SiO2 insulators, enabling effective heat dissipation at high temperatures while maintaining device reliability through the high thermal conductivity pathway from active devices through AlN to SiC substrate.
2Manufacturing precision
If a simple single-layer high-resistance layer is used, then the manufacturing process is simple, but the crystal quality is insufficient with many dislocations
Solution Approach 1:
The high-resistance layer is segmented into multiple AlN sub-layers with different thicknesses and growth conditions. This segmentation allows each layer to serve specific functions: improving overall crystal quality, reducing dislocation density, and enabling better stress management while maintaining manufacturability through standardized deposition processes.
Solution Approach 2:
Different regions of the AlN high-resistance layer have different local qualities with varying thicknesses and growth temperatures. The first AlN layer uses lower temperature for initial nucleation, the second layer uses higher temperature for improved crystal quality, and the third layer uses lower temperature again for stress management, creating locally optimized properties throughout the structure.
3Manufacturing precision
If high-temperature AlN layer is grown to improve crystal quality, then dislocation density is reduced, but tensile stress increases causing holes and defects
Solution Approach 1:
The patent applies beforehand cushioning by growing low-temperature AlN layers before and after the high-temperature AlN layer. The first low-temperature layer serves as a buffer that accommodates initial stress, while the second low-temperature layer provides stress relief after the high-temperature layer, preventing hole formation and maintaining layer integrity throughout the structure.
Solution Approach 2:
The patent utilizes parameter changes by varying the growth temperature of AlN layers. The temperature is changed from low to high and back to low across different layers, allowing optimization of crystal quality in the high-temperature layer while using low-temperature layers to manage stress and prevent structural defects.
4Reliability
If ion doping is performed to create high-resistance layer, then the resistivity is increased, but lattice damage occurs requiring additional repair steps
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical vapor deposition approach to form the AlN high-resistance layer. This substitution eliminates lattice damage associated with ion bombardment while achieving the desired high resistivity through the intrinsic properties of AlN and controlled doping during deposition, avoiding the need for additional lattice repair 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
The composite substrate improves thermal conductivity, reduces dislocations, enhances mechanical strength, and provides superior radiation resistance, ensuring stable operation in high-temperature and high-power environments while minimizing crosstalk and signal loss.
Implementation Method 1
a first low-temperature aluminum nitride (AlN) layer, a high-temperature AlN layer, and a second low-temperature AlN layer which are stacked in sequence
Implementation Method 2
the high-resistance layer including a first low-temperature aluminum nitride (AlN) layer, a high-temperature AlN layer, and a second low-temperature AlN layer which are stacked in sequence
Data Source
AI summary
A composite substrate includes a substrate, a high-resistance layer located on the substrate, the high-resistance layer comprising a first low-temperature aluminum nitride (AlN) layer, a high-temperature AlN layer and a second low-temperature AlN layer which are stacked in sequence, and a growth substrate located on a side, away from the substrate, of the high-resistance layer. Under the action of the first low-temperature AlN layer, a tensile stress on the high-temperature AlN layer may be reduced, to reduce a dislocation, and further improve a crystal quality of the high-temperature AlN layer and ensure resistivity of the high-temperature AlN layer; and an element of Al in the high-temperature AlN layer is prevented from diffusing into the growth substrate, to protect the crystal quality of the high-temperature AlN layer and improve a bonding effect between the high-resistance layer and the growth substrate. Thus, stability and reliability of the composite substrate are greatly improved.