Engineered Substrates for Semiconductor Devices
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Solution Overview
Problem
The proliferation of solid state transducer devices like LEDs is hindered by stresses caused by dissimilar coefficients of thermal expansion (CTE) and lattice structures during epitaxial growth, leading to bowing, warping, and delamination issues, which reduce device uniformity and increase manufacturing costs due to substrate destruction.
Innovation Solution
Engineered substrates composed of materials with matched CTE and lattice parameters, potentially including sapphire and aluminum nitride, are designed to minimize stresses through miscutting and pre-straining, and can be patterned or include buffer structures to enhance epitaxial growth and remain intact as part of the final device, allowing for reduced substrate wastage and improved device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional substrates with dissimilar CTE are used for epitaxial growth, then manufacturing process is simpler, but stresses cause bowing, warping, and delamination reducing device uniformity
Solution Approach 1:
The patent employs a composite substrate structure consisting of a first substrate material (e.g., sapphire) and a second substrate material (e.g., aluminum nitride) with different properties. The first material provides mechanical strength while the second material's CTE is matched to the epitaxial film, reducing thermal stresses and preventing bowing, warping, and delamination during manufacturing.
Solution Approach 2:
The patent changes the thermal expansion parameter by selecting and combining materials with specific CTE values. The second substrate material is specifically chosen to have a CTE that matches the epitaxial film, thereby compensating for the CTE mismatch between the first substrate material and the film, reducing thermal stresses during temperature cycling.
2Reliability
If substrate thickness is increased to reduce CTE mismatch effects, then stress resistance improves, but manufacturing cost increases due to material waste
Solution Approach 1:
The composite substrate structure allows each layer to be optimized for its specific function. The first substrate can be thinner since it only needs to provide mechanical support, while the second substrate layer is optimized for CTE matching. This reduces overall material usage compared to using a single thick substrate, decreasing waste and manufacturing cost.
Solution Approach 2:
The patent applies different material properties to different regions/layers of the substrate. The first substrate material provides mechanical strength where needed, while the second substrate material provides CTE matching in the region interfacing with the epitaxial film. This localized optimization reduces overall material requirements while maintaining stress resistance.
3Ease of manufacture
If conventional substrates are used, then fabrication process is simpler, but substrates are destroyed or sacrificed in manufacturing increasing device cost
Solution Approach 1:
The composite substrate is designed so that the first substrate material (e.g., sapphire) can be reused after the epitaxial growth process. The second material layer is optimized for CTE matching and can be selectively removed or retained, allowing the expensive first substrate to be recovered and reused multiple times, reducing material waste and device cost.
Solution Approach 2:
The patent enables recovery and reuse of the first substrate material after epitaxial growth. The second substrate material layer can be selectively removed, allowing the first substrate to be cleaned and reused for subsequent growth processes, thereby reducing material waste and manufacturing cost.
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 engineered substrates effectively reduce stresses during epitaxial growth, enhance device uniformity, and allow for the reuse of substrate materials, thereby improving the efficiency and cost-effectiveness of semiconductor device manufacturing.
Implementation Method 1
the substrate and the epitaxial film are composed of different materials having dissimilar coefficients of thermal expansion (CTE). Under high temperature manufacturing conditions, the distinct CTEs of the differing materials can cause the substrate and the epitaxial film to expand or contract at significantly differing rates
Implementation Method 2
engineered substrates composed of materials with matched CTE and lattice parameters
Data Source
AI summary
Engineered substrates for semiconductor devices are disclosed herein. A device in accordance with a particular embodiment includes a transducer structure having a plurality of semiconductor materials including a radiation-emitting active region. The device further includes an engineered substrate having a first material and a second material, at least one of the first material and the second material having a coefficient of thermal expansion at least approximately matched to a coefficient of thermal expansion of at least one of the plurality of semiconductor materials. At least one of the first material and the second material is positioned to receive radiation from the active region and modify a characteristic of the light.