Semiconductor Structure with Graded Buffer for Dislocation Reduction
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Solution Overview
Problem
Integration of lattice mismatched semiconductor materials, such as germanium on silicon, often results in epitaxial defects like threading dislocations due to lattice mismatch, which can hinder the performance of semiconductor devices like CMOS FETs and optoelectronic devices.
Innovation Solution
The formation of multidimensionally arranged recesses in the substrate allows for the growth of epitaxial layers with reduced lattice mismatch, trapping threading dislocations and enabling the growth of high-quality epitaxial layers with varying lattice parameters, thereby reducing defects and improving device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lattice mismatched semiconductor materials are integrated, then device performance is improved, but threading dislocations increase
Solution Approach 1:
A silicon-germanium buffer layer is introduced as an intermediary between the silicon substrate and the germanium layer. This buffer layer has a graded composition that transitions from lower germanium content near the substrate to higher germanium content near the germanium layer, serving as a mediator that reduces lattice mismatch and prevents threading dislocation formation.
Solution Approach 2:
The germanium content parameter is gradually changed through the buffer layer thickness, creating a composition gradient. This parameter change strategy allows the lattice constant to transition smoothly, reducing the abrupt mismatch that causes threading dislocations while still enabling high-performance device operation.
2Reliability
If germanium heteroepitaxy is performed on silicon, then carrier mobility is improved, but epitaxial defects increase
Solution Approach 1:
The silicon-germanium buffer layer acts as an intermediary structure that enables the integration of germanium on silicon while minimizing epitaxial defects. By providing a gradual transition in lattice constant, it allows high carrier mobility germanium to be grown on silicon substrates without the severe defect formation that would otherwise occur.
Solution Approach 2:
A composite structure consisting of silicon substrate, silicon-germanium buffer layer with graded composition, and germanium layer is created. This composite material approach combines the advantages of both materials while mitigating their incompatibility, resulting in low-defect epitaxial layers with high carrier mobility.
3Adaptability or versatility
If germanium surface is obtained for substitution, then application versatility is improved, but manufacturing cost increases
Solution Approach 1:
The invention enables the use of conventional silicon substrates, which are inexpensive and widely available, to produce germanium surfaces. Instead of requiring expensive germanium wafers, the method grows germanium layers on cheap silicon substrates, making germanium-based devices more cost-effective while maintaining application versatility.
Solution Approach 2:
By controlling the germanium content parameter through the buffer layer and epitaxial growth conditions, high-quality germanium surfaces can be produced on silicon substrates. This parameter control enables cost-effective production of germanium surfaces for various applications including photovoltaics and light-emitting diodes without requiring expensive germanium wafers.
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 effectively reduces threading dislocations and enhances the quality of epitaxial layers, leading to improved performance and integration of high-performance semiconductor devices like CMOS FETs and optoelectronic devices.
Implementation Method 1
Integration of lattice mismatched semiconductor materials is one path to high performance semiconductor devices
Implementation Method 2
germanium (Ge) heteroepitaxy on silicon (Si) is promising both for, for example, high-performance p-channel metal-oxide-semiconductor field-effect transistors (p-channel MOSFETs)
Data Source
AI summary
A semiconductor structure includes a substrate, at least one first epitaxial layer, and at least one second epitaxial layer. The substrate has a plurality of recesses multidimensionally arranged therein. The first epitaxial layer is disposed at least in the recesses of the substrate. The second epitaxial layer is disposed on the first epitaxial layer.