Aluminum Nitride Buffer Layers by Physical Vapor Deposition
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Solution Overview
Problem
The challenge in manufacturing high-quality Group III-V semiconductor devices, such as power devices, LEDs, and laser diodes, lies in the difficulty of growing Group III-nitride layers on foreign substrates without forming crystalline defects or cracks, due to material differences like lattice constants and thermal expansion coefficients, which affects device performance.
Innovation Solution
The use of cluster tools with physical vapor deposition (PVD) chambers to form high-quality aluminum nitride (AlN) buffer layers with precise crystalline orientation and smooth surfaces, promoting the growth of low-defect-density Group III-nitride layers by controlling process conditions like substrate temperature, gas composition, and electrode biasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If MOCVD or HVPE methods are used to deposit Group III-nitride layers, then the layers can be formed on foreign substrates, but crystalline defects and cracks form due to lattice constant and thermal expansion coefficient mismatches
Solution Approach 1:
The patent introduces an aluminum nitride (AlN) buffer layer as an intermediary between the foreign substrate and the Group III-nitride device layers. This buffer layer serves as a transition medium that accommodates the lattice mismatch and thermal expansion differences between the substrate and the active layers, thereby reducing crystalline defects and cracks while enabling deposition on foreign substrates
Solution Approach 2:
The patent employs physical vapor deposition (PVD) instead of chemical vapor deposition (MOCVD/HVPE) to deposit the AlN buffer layer, changing the deposition method parameters. This PVD process operates at lower temperatures and provides better control over buffer layer thickness and crystalline structure, improving the interface quality and reducing defect formation
2Reliability
If buffer layers are added to reduce defects and improve device functionality, then device performance improves, but the process becomes more complex and sensitive to deposition conditions
Solution Approach 1:
The AlN buffer layer acts as a mediator that simplifies the overall process by providing a stable, defect-reducing interface that is less sensitive to variations in subsequent deposition conditions. The buffer layer's robust crystalline structure compensates for process variations, making the overall manufacturing process more reliable despite the added layer
Solution Approach 2:
The buffer layer is deposited in advance before the sensitive Group III-nitride device layers are formed. This preliminary action prepares a stable, low-defect substrate surface that protects subsequent layers from defects, reducing the sensitivity of the overall process to deposition condition variations
3Device complexity
If conventional deposition methods are used, then the process is simpler, but the quality of Group III-nitride layers is not well controlled leading to thickness variation and poor film properties
Solution Approach 1:
The patent replaces chemical vapor deposition (MOCVD/HVPE) with physical vapor deposition (PVD) for buffer layer formation. This substitution changes the deposition mechanism from chemical reactions to physical processes, providing better control over film thickness, composition, and crystalline structure with improved uniformity and reduced sensitivity to process variations
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 method results in improved device performance and reliability by reducing film defects, enhancing crystalline quality, and reducing processing time and costs, while eliminating the need for complex MOCVD growth steps.
Implementation Method 1
a target comprising aluminum is sputtered by plasma to form an aluminum nitride buffer layer on a surface of one or more substrates
Implementation Method 2
a target comprising aluminum is sputtered by plasma to form an aluminum nitride buffer layer
Data Source
AI summary
Embodiments of the invention described herein generally relate to an apparatus and methods for forming high quality buffer layers and Group III-V layers that are used to form a useful semiconductor device, such as a power device, light emitting diode (LED), laser diode (LD) or other useful device. Embodiments of the invention may also include an apparatus and methods for forming high quality buffer layers, Group III-V layers and electrode layers that are used to form a useful semiconductor device. In some embodiments, an apparatus and method includes the use of one or more cluster tools having one or more physical vapor deposition (PVD) chambers that are adapted to deposit a high quality aluminum nitride (AlN) buffer layer that has a high crystalline orientation on a surface of a plurality of substrates at the same time.