Strained Seed Layer Lattice Parameter Adaptation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for adapting the lattice parameter of seed layers in semiconductor materials are inadequate for achieving complete strain relaxation and matching thermal expansion coefficients, leading to defects and surface roughness issues in epitaxially grown layers.
Innovation Solution
A method involving a seed layer of strained material, a low-viscosity layer, and an intermediate substrate, followed by a heat treatment and transfer onto a support substrate with carefully chosen thermal expansion coefficients to achieve complete relaxation and alignment of the lattice parameter with the desired application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-viscosity layer is used to relax strained material layers through heat treatment, then strain relaxation is achieved, but the strained layer may be pulled off the structure and surface roughness increases
Solution Approach 1:
The patent introduces an intermediate substrate with specifically selected thermal expansion properties as a mediator between the seed layer and the final support substrate. This intermediate substrate acts as a controlled stressor during heat treatment, enabling strain relaxation while maintaining layer adhesion through its intermediate mechanical properties that bridge the seed layer and support substrate.
Solution Approach 2:
The patent systematically changes the thermal expansion coefficient parameter by selecting specific intermediate substrates with CTE values between those of the seed layer and support substrate. This parameter optimization allows controlled strain relaxation during heat treatment while preventing excessive stress that would cause layer delamination or surface roughness.
2Reliability
If heat treatment is applied above the glass transition temperature of the low-viscosity layer, then strain relaxation occurs, but the structure deteriorates and surface roughness increases
Solution Approach 1:
The patent optimizes the thermal expansion coefficient parameter of the intermediate substrate to fall within a specific range between the seed layer and support substrate CTE values. This parameter control enables effective strain relaxation at reduced heat treatment temperatures while preventing the structural deterioration and surface roughness that occur with conventional high-temperature treatment.
3Productivity
If the lattice parameter of the seed layer is not adapted to match the material to be grown, then epitaxial growth can proceed, but defects such as dislocations and cracks develop
Solution Approach 1:
The patent changes the lattice parameter of the seed layer by selecting an intermediate substrate with specific thermal expansion properties. During heat treatment, the thermal expansion mismatch between the intermediate substrate and seed layer induces controlled strain that adjusts the seed layer's lattice parameter to match the material to be grown, enabling defect-free epitaxial growth.
Solution Approach 2:
The patent exploits thermal expansion effects by choosing an intermediate substrate whose thermal expansion coefficient creates controlled stress during heat treatment. This stress adjusts the seed layer's lattice parameter in situ, transforming it from a mismatched state to a matched state for the target material, thereby preventing dislocation and crack formation during epitaxial growth.
4Reliability
If compressively strained material is relaxed elastically, then strain is reduced, but the material wrinkles and surface roughness increases
Solution Approach 1:
The patent optimizes the thermal expansion coefficient of the intermediate substrate to a specific value between those of the seed layer and support substrate. This optimized parameter enables progressive, controlled strain relaxation that prevents the sudden release causing wrinkles, maintaining surface flatness while reducing strain.
5Reliability
If tensilely strained material is relaxed, then strain is reduced, but cracks form and surface roughness increases
Solution Approach 1:
The patent selects an intermediate substrate with a thermal expansion coefficient specifically optimized to control the relaxation of tensilely strained material. This parameter optimization enables gradual strain reduction that prevents crack formation, maintaining structural integrity while achieving the desired strain relaxation.
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 adaptation of the lattice parameter of seed layers, reducing defects and surface roughness, enabling the growth of materials with low defect density and improved crystalline quality for electronic, optoelectronic, or photovoltaic applications.
Implementation Method 1
By applying a heat treatment at or above the glass transition temperature of the low-viscosity layer, it is then possible to relax the strained layer
Implementation Method 2
it is then possible to relax the strained layer
Implementation Method 3
the intermediate substrate and the support substrate being chosen so that: An and CTE1≤CTE3 and CTE5>CTE1 or An<A1 and CTE1≥CTE3 and CTE5<CTE3
Data Source
AI summary
The invention relates to a method of adapting the lattice parameter of a seed layer of a strained material, comprising the following successive steps: a) a structure is provided that has a seed layer of strained material, of lattice parameter A1, of nominal lattice parameter An and of thermal expansion coefficient CTE3, a low-viscosity layer and an intermediate substrate of thermal expansion coefficient CTE1; b) a heat treatment is applied so as to relax the seed layer of strained material; and c) the seed layer is transferred onto a support substrate of thermal expansion coefficient CTE5, the intermediate substrate and the support substrate being chosen so that A1<An and CTE1≦̸CTE3 and CTE5>CTE1 or A1>An and CTE1≧CTE3 and CTE5<CTE1.