Etch Pit Dielectric Blocking for Lattice-Mismatched Semiconductor Films
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Solution Overview
Problem
The challenge lies in reducing dislocation defects in semiconductor heterostructures, particularly when growing lattice-mismatched materials like germanium on silicon substrates, which leads to poor material quality and performance due to misfit dislocations and thermal expansion coefficient mismatch, limiting the thickness and functionality of devices such as solar cells and transistors.
Innovation Solution
The approach involves creating etch pits in the first epitaxial film where threading dislocations intersect the surface, filling these pits with a dielectric material to block dislocation propagation, and then growing a second epitaxial film through selective epitaxial lateral overgrowth (ELO) over the dielectric material, thereby reducing dislocation density and improving film quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If heteroepitaxial growth is used to grow lattice-mismatched materials, then device functionality and material diversity are improved, but dislocation defect density increases
Solution Approach 1:
The patent segments the continuous epitaxial growth process into two distinct stages: initial growth of the first epitaxial film containing dislocations, followed by selective lateral overgrowth to form a second defect-free film. This segmentation allows the harmful dislocations to be confined to the first layer while the second layer remains defect-free, resolving the contradiction between achieving lattice-mismatched material functionality and maintaining low dislocation density.
Solution Approach 2:
The patent extracts and removes the harmful threading dislocations from the growth path by using selective lateral overgrowth that bypasses the dislocation-containing first epitaxial film. The second epitaxial film is grown laterally over a sacrificial layer, effectively taking out the dislocation defects from the final device structure while preserving the desired lattice-mismatched material composition.
2Productivity
If epitaxial layer thickness is increased to improve device performance, then device functionality is improved, but dislocation defects propagate through the structure
Solution Approach 1:
The patent divides the thick epitaxial structure into two segments: a first epitaxial film that contains the dislocation defects and a second epitaxial film that is dislocation-free. By segmenting the structure, the patent enables the second film to achieve the necessary thickness for device performance without inheriting the dislocation propagation problem that would occur in a single continuous thick layer.
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary between the substrate and the second epitaxial film. This sacrificial layer mediates the growth process by providing a template for selective lateral overgrowth, allowing the second epitaxial film to form without direct contact with and propagation of dislocations from the first epitaxial film.
3Adaptability or versatility
If selective heteroepitaxy is used to combine multiple materials, then device functionality is improved, but control of surface morphology and defect density becomes more difficult
Solution Approach 1:
The patent segments the heteroepitaxial process into distinct stages with different materials: a first epitaxial film grown on the substrate, a sacrificial layer, and a second epitaxial film grown via selective lateral overgrowth. This segmentation allows each layer to be optimized independently, enabling control of surface morphology and defect density in the final film while combining multiple lattice-mismatched materials.
Solution Approach 2:
The sacrificial layer acts as an intermediary that enables the combination of multiple lattice-mismatched materials while maintaining surface morphology control. It provides a controlled interface for selective lateral overgrowth, allowing the second epitaxial film to form with improved surface quality despite the complexity of combining dissimilar materials.
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 method effectively blocks a significant percentage of threading dislocations, resulting in a substantial reduction of dislocation density and defect density in the second epitaxial film, enhancing the performance and reliability of semiconductor devices by preventing dislocation propagation and promoting continuous, high-quality film growth.
Implementation Method 1
The dielectric material can block at least some of the threading dislocations (TDs) in the first epitaxial film from propagating into the second epitaxial film
Implementation Method 2
epitaxial growth of a semiconductor material over a semiconductor substrate, for example, by chemical vapor deposition ('CVD') or molecular beam epitaxy ('MBE'), where the semiconductor material, when fully relaxed, has a different lattice constant than the underlying substrate
Implementation Method 3
This lattice-mismatch between the starting substrate and subsequent layer(s) creates stress during material deposition that generates dislocation defects in the semiconductor structure. Misfit dislocations form at the mismatched interface to relieve the misfit strain
Data Source
AI summary
Lattice-mismatched semiconductor devices having a substrate, a first epitaxial film disposed thereon, a dielectric material, and a second epitaxial film. The first epitaxial film contains etch pits that extend from the outer surface of the first epitaxial film into the first epitaxial film. The dielectric material is disposed within the etch pits and blocks at least some of the threading dislocations in the first epitaxial film from propagating into the second epitaxial film. Semiconductor devices containing a silicon (Si) substrate or a silicon germanium (SiGe) substrate, a germanium (Ge) film disposed over the substrate, and a dielectric material. Methods for producing such semiconductor devices.