GaN Bonded Intermediate Substrate for Thermal Management
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Solution Overview
Problem
The production of nitride semiconductor structures on sapphire substrates is hindered by low thermal conductivity, electrical insulation, and mismatched thermal expansion coefficients, leading to device degradation, high production costs, and limitations in scaling to larger substrate sizes, while freestanding GaN substrates are costly and difficult to thin without damaging the device structure.
Innovation Solution
A method involving ion implantation to create a weak interface in a GaN source substrate, bonding it to a handle substrate, exfoliating a thin GaN layer, depositing a capping layer, and annealing in a nitrogen atmosphere to reduce in-plane strain, enabling the use of a bonded intermediate substrate for improved crystalline quality and thermal coupling, allowing for larger substrate sizes and reduced substrate thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sapphire substrates are used for growing nitride semiconductor structures, then device fabrication is enabled, but thermal conductivity is low and thermal expansion mismatch causes device degradation
Solution Approach 1:
The patent introduces an intermediate substrate layer between the sapphire substrate and the nitride semiconductor structure. This intermediate layer serves as a mediator that provides better thermal conductivity and thermal expansion matching, thereby improving heat dissipation and reducing thermal stress while maintaining device functionality
Solution Approach 2:
The patent employs a composite substrate structure combining sapphire with an intermediate material layer. This composite approach leverages the optical properties of sapphire while adding the thermal management capabilities of the intermediate material, resolving the contradiction between device fabrication enablement and thermal management
2Ease of manufacture
If sapphire substrates are used, then device growth is possible, but electrical insulation limits device functionality
Solution Approach 1:
The intermediate substrate layer acts as an intermediary that provides electrical conductivity pathways while maintaining the mechanical and optical support functions of the sapphire substrate, thereby enabling both device growth and enhanced electrical functionality
3Reliability
If post-growth sapphire substrate removal is attempted, then device functionality may be improved, but device layer damage and low yields occur
Solution Approach 1:
The patent extracts or removes the problematic sapphire substrate portion after device growth while retaining the beneficial intermediate layer and device structure. This selective extraction approach improves device performance by eliminating thermal and electrical limitations without causing damage to the device layer or reducing yields
4Productivity
If larger substrate sizes are used, then production cost may decrease, but CTE mismatch challenges increase
Solution Approach 1:
The composite substrate structure with the intermediate layer provides improved thermal expansion compatibility across larger substrate areas. The intermediate material acts as a buffer that accommodates CTE differences, enabling the use of larger substrates for cost-effective production while maintaining reliability
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 enhances the crystalline quality of nitride semiconductor structures, reduces strain, and enables the use of larger substrates, improving the efficiency and cost-effectiveness of light-emitting device production by minimizing strain and thermal mismatch issues.
Implementation Method 1
forming a weak interface in a GaN source substrate by implanting ions into an N-terminated surface of the GaN source substrate
Implementation Method 2
annealing the thin GaN single crystal layer in a nitrogen containing atmosphere after depositing the capping layer. The in-plane strain present in the thin GaN single crystal layer after the annealing is reduced
Data Source
AI summary
A method of making a bonded intermediate substrate includes forming a weak interface in a GaN source substrate by implanting ions into an N-terminated surface of the GaN source substrate, bonding the N-terminated surface of the GaN source substrate to a handle substrate, and exfoliating a thin GaN single crystal layer from the source substrate such that the thin GaN exfoliated single crystal layer remains bonded to the handle substrate and a Ga-terminated surface of the thin GaN single crystal layer is exposed. The method further includes depositing a capping layer directly onto the exposed surface of the thin GaN single crystal layer, and annealing the thin GaN single crystal layer in a nitrogen containing atmosphere after depositing the capping layer. The in-plane strain present in the thin GaN single crystal layer after the annealing is reduced relative to an in-plane strain present in said layer prior to the annealing.