Porous Semiconductor Buffer Structure for Lattice-Mismatch Epitaxy
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Solution Overview
Problem
The deposition of semiconductor layers with different material parameters through heteroepitaxy leads to stresses and crystal defects in both the semiconductor layers and the substrate, reducing material quality, particularly in applications like photovoltaic solar cells.
Innovation Solution
A method involving the formation of a semiconductor structure with a highly porous layer, functional intermediate layer, and closed growth template layer between the semiconductor substrate and layer, using etching to create these layers from the substrate material, and adjusting lattice constants through heat treatment and gas incorporation to reduce stress and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If heteroepitaxial deposition is used to deposit semiconductor layers with different material parameters on a semiconductor substrate, then the semiconductor structure can be formed with layers of different materials, but stresses and crystal defects occur in both the semiconductor layers and the substrate, reducing material quality
Solution Approach 1:
The patent introduces an intermediate buffer layer between the semiconductor substrate and the semiconductor layer with different material parameters. This buffer layer acts as a mediator that gradually transitions the lattice constant from the substrate to the final layer, reducing the abrupt mismatch that causes stresses and crystal defects. The buffer layer composition is gradually changed along its thickness to accommodate the lattice constant transition.
Solution Approach 2:
The patent changes the composition parameter of the buffer layer gradually through its thickness. The buffer layer starts with a composition closer to the substrate and progressively transitions to a composition closer to the final semiconductor layer. This gradual parameter change allows the lattice constant to transition smoothly, reducing dislocation formation and maintaining material quality while enabling deposition of layers with different material parameters.
2Adaptability or versatility
If heteroepitaxial deposition is used to deposit semiconductor layers with different lattice constants, then multi-layer semiconductor structures can be created, but the process causes stresses and crystal defects in the epitaxially grown layers
Solution Approach 1:
The buffer layer serves as an intermediary structure between substrates with different lattice constants. It provides a gradual transition zone that reduces the abrupt lattice mismatch, thereby minimizing the generation of misfit dislocations and maintaining higher crystal quality in the epitaxially grown layers.
Solution Approach 2:
The buffer layer can be divided into multiple sub-layers with progressively changing compositions. Each sub-layer has a slightly different composition that steps gradually from the substrate toward the final layer composition. This segmentation approach allows better control over dislocation propagation and enables the formation of high-quality epitaxial layers on substrates with significantly different lattice constants.
3Ease of manufacture
If heteroepitaxial deposition is used on a semiconductor substrate, then semiconductor layers can be formed, but stresses and crystal defects occur in the semiconductor substrate itself
Solution Approach 1:
The buffer layer protects the semiconductor substrate from direct interaction with the epitaxially grown layer that has different material parameters. This intermediary layer absorbs the lattice mismatch stresses and prevents them from propagating into the substrate, thereby maintaining substrate material quality while still enabling the formation of the desired semiconductor 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
The method significantly reduces the risk of material impairment and defects by allowing better compensation of thermal expansion and lattice constant differences, maintaining high material quality and enabling efficient deposition of semiconductor layers with different properties.
Implementation Method 1
at least the porous layers are formed from the semiconductor substrate material by etching
Implementation Method 2
the closed growth template layer is formed from a sub-region of the porous growth template layer facing away from the semiconductor substrate by means of heat treatment
Implementation Method 3
adjusting lattice constants through heat treatment and gas incorporation to reduce stress and defects
Implementation Method 4
The process of depositing several successive layers with different material parameters, particularly different lattice constants, is called heteroepitaxy
Data Source
Figure 1
AI summary
The invention relates to a semiconductor structure for a semiconductor component, said structure comprising a semiconductor layer (2) for forming at least one semiconductor component, which layer is disposed indirectly on a semiconductor substrate (1). Essential features are that: disposed between the semiconductor substrate (1) and the semiconductor layer (2), starting from the semiconductor substrate (1), are at least the following layers in the sequence A, B, C, with or without the interposition of additional layers, A. a highly porous layer (3) having a porosity greater than 50% and a thickness of 0.1-1 µm, B. a functional interlayer (4) having a porosity of 5-90% and a thickness of 0.1-5 µm, and a porous growth template layer (5) having a porosity less than 50% and a thickness of 0.5-5 µm, and C. a solid growth template layer (6) having a porosity less than 5%, in particular less than 1%, and a thickness of 1-100 nm, the solid growth template layer (6) having a lattice constant which differs from the lattice constant of the semiconductor layer (2) by less than 10%; the semiconductor substrate (1) and the semiconductor layer (2) have a material composition that differs by at least 1 wt%; the semiconductor substrate (1) and the semiconductor layer (2) have a different lattice constant; and the semiconductor substrate (1) and the semiconductor layer (2) are electrically conductively connected via the layers positioned therebetween. The invention also relates to a method producing such a semiconductor structure.