Group III Nitride Composite Substrate Bonding for Crystal Quality
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Solution Overview
Problem
Existing group III nitride substrates face challenges such as high manufacturing costs, cracking issues, and difficulty in increasing diameter and decreasing thickness, leading to high cost and low yield in semiconductor device production, particularly due to large thickness variations and crystal quality degradation during the growth of semiconductor layers.
Innovation Solution
A group III nitride composite substrate with a diameter of 75 mm or more, featuring a support substrate and a group III nitride film with a thickness of 50 nm to 10 μm, bonded with specific thickness and off-angle variations, and a thermal expansion coefficient ratio within certain limits, to facilitate high crystal quality growth and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a free-standing group III nitride substrate is used, then the substrate can be manufactured with sufficient mechanical strength, but the manufacturing cost increases and the substrate is likely to crack, making it difficult to increase diameter and decrease thickness
Solution Approach 1:
The substrate is divided into two functional parts: a support substrate providing mechanical strength and a thin group III nitride film providing semiconductor functionality. This segmentation allows each component to be optimized independently - the support substrate can be thick and strong while the nitride film is thin and low-cost.
Solution Approach 2:
The group III nitride layer is extracted from the bulk substrate structure and formed as a thin film on a separate support substrate. This extraction eliminates the need to manufacture expensive free-standing thick nitride substrates while maintaining the necessary mechanical support function.
2Productivity
If the thickness of the group III nitride substrate is decreased to enable semiconductor device formation, then the device can be formed with fewer process steps, but the manufacturing cost increases due to additional process steps such as grinding of the rear surface
Solution Approach 1:
The support substrate is prepared in advance with appropriate thickness and surface properties before the nitride film is formed. This preliminary preparation eliminates the need for subsequent grinding or thickening steps that would be required if a free-standing nitride substrate were used.
3Manufacturing precision
If ion implantation is performed to form a GaN thin film, then the film can be formed with controlled thickness, but the crystal quality of the GaN thin film is degraded
Solution Approach 1:
A joint layer is introduced as an intermediary between the support substrate and the nitride film. This joint layer serves as a buffer that accommodates lattice mismatches and reduces stress, enabling high-quality epitaxial growth without the need for ion implantation damage.
4Productivity
If the diameter of the substrate is increased, then more devices can be produced per substrate, but the variation in thickness of the group III nitride film increases, reducing manufacturing precision
Solution Approach 1:
The support substrate is designed with specific physical properties (thermal expansion coefficient, Young's modulus, thermal conductivity) that compensate for the increased stress and thermal gradients present in large-diameter substrates. These parameter optimizations maintain film uniformity across the larger substrate area.
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 enables the production of low-cost, large-diameter group III nitride composite substrates with small thickness variations, allowing for high-yield semiconductor devices with improved crystal quality and reduced manufacturing expenses.
Implementation Method 1
a support substrate and a group III nitride film with a thickness of 50 nm or more and less than 10 μm that are bonded to each other
Implementation Method 2
a ratio αIII-N/αS of a thermal expansion coefficient αIII-N of the group III nitride film to a thermal expansion coefficient αS of the support substrate may be 0.75 or more and 1.25 or less
Data Source
AI summary
A group III nitride composite substrate with a diameter of 75 mm or more includes a support substrate and a group III nitride film with a thickness of 50 nm or more and less than 10 μm that are bonded to each other. A ratio st/mt of a standard deviation st of the thickness of the group III nitride film to a mean value mt of the thickness thereof is 0.01 or more and 0.5 or less, and a ratio so/mo of a standard deviation so of an absolute value of an off angle between a main surface of the group III nitride film and a plane of a predetermined plane orientation to a mean value mo of the absolute value of the off angle is 0.005 or more and 0.6 or less.