Metamorphic Buffer Layer Strain Relaxation via HVPE
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Solution Overview
Problem
The challenge lies in growing substrates with lattice parameters that are not attainable using commercial substrates, particularly in achieving strain relaxation and low threading dislocation density in metamorphic buffer layer structures, which often results in residual strain and warping, complicating the growth of high-quality semiconductor devices.
Innovation Solution
The development of virtual substrates with a metamorphic buffer layer structure grown via hydride vapor phase epitaxy, where the lattice constant transitions from the substrate's lattice constant to a different value, and the thickness of the buffer layer is optimized to prevent warping, allowing for strain relaxation and reduced threading dislocation density, enabling the growth of high-quality semiconductor devices with varying lattice mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the metamorphic buffer layer structure is made thick to achieve strain relaxation and reduce threading dislocation density, then the strain relaxation and dislocation reduction are improved, but warping of the buffer layer structure occurs
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the metamorphic buffer layer structure to a specific range (at least 10 μm but below the warping threshold) and controlling the composition grading parameters during HVPE growth. This resolves the contradiction by finding the optimal thickness parameter that achieves strain relaxation and dislocation reduction without causing warping.
Solution Approach 2:
The patent implements local quality through compositionally graded metamorphic buffer layers where the lattice constant transitions gradually from the substrate lattice constant to a different value. This gradual composition change allows different regions of the buffer layer to have different properties, enabling strain relaxation while maintaining planarity and preventing warping.
2Stress or pressure
If misfit dislocations are introduced to relieve strain in the metamorphic buffer layer, then strain relaxation is improved, but threading dislocations are concurrently introduced which increase defect density
Solution Approach 1:
The patent uses parameter changes by controlling the composition gradient parameters and growth conditions during HVPE to achieve strain relaxation through a controlled mechanism that minimizes threading dislocation formation. The gradual composition change and optimized growth parameters allow strain relief without significant TD introduction.
Solution Approach 2:
The metamorphic buffer layer structure acts as an intermediary between the GaAs substrate and the InxGa1-xAs device layer. This intermediate structure with gradually changing composition provides a transition zone that relieves strain through misfit dislocations in the buffer layer itself rather than allowing them to propagate as threading dislocations into the device layer.
3Manufacturing precision
If the composition of the metamorphic buffer layer is graded to achieve the desired lattice constant, then the lattice parameter control is improved, but residual strain remains in the completed structure
Solution Approach 1:
The patent applies parameter changes by optimizing the composition grading parameters and thickness parameters of the metamorphic buffer layer during HVPE growth. By carefully controlling these parameters, the lattice constant is precisely controlled while the thickness is optimized to allow complete strain relaxation, minimizing residual strain in the final structure.
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 allows for the growth of high-quality semiconductor devices with reduced residual strain and threading dislocation density, facilitating the production of devices like quantum cascade lasers, and enables the reuse of virtual substrates due to the thick, strain-relaxed metamorphic buffer layers.
Implementation Method 1
The metamorphic buffer layer structure is compositionally graded such that the lattice constant of the metamorphic buffer layer structure transitions from a lattice constant at the interface with the growth substrate that is substantially the same as the first lattice constant to a second lattice constant at a surface opposite the interface that is different from the first lattice constant
Implementation Method 2
growing a substantially strain-relaxed metamorphic buffer layer structure comprising one or more layers of a semiconductor alloy on a semiconductor growth substrate via hydride vapor phase epitaxy
Implementation Method 3
relaxation of the MBL structure requires the introduction of misfit dislocations (MDs) to relieve strain
Data Source
AI summary
Virtual substrates made by hydride vapor phase epitaxy are provided comprising a semiconductor growth substrate and a substantially strain-relaxed metamorphic buffer layer (MBL) structure comprising one or more layers of a semiconductor alloy on the growth substrate. The MBL structure is compositionally graded such that its lattice constant transitions from a lattice constant at the interface with the growth substrate that is substantially the same as the lattice constant of the growth substrate to a lattice constant at a surface opposite the interface that is different from the lattice constant of the growth substrate. The virtual substrates comprise relatively thick MBL structures (e.g., >20 μm) and relatively thick growth substrates (e.g., >0.5 mm).