SiGe Strain-Relaxed Buffer for Thinner Superlattice Growth
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Solution Overview
Problem
Existing methods for growing strain relaxed buffer (SRB) layers in semiconductor devices are costly and time-consuming, often requiring thick layers that introduce defects and mechanical stress, which can lead to substrate cracking and increased processing times.
Innovation Solution
A method involving the epitaxial deposition of a silicon germanium layer with a germanium concentration gradient, followed by a capping layer with a uniform germanium concentration, to form a strain relaxed buffer layer on a substrate, which reduces defect density and processing time while minimizing substrate stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thick SRB layers are grown to reduce defect density, then manufacturing precision improves, but productivity deteriorates due to increased processing time and cost
Solution Approach 1:
The patent applies local quality by creating a non-uniform germanium concentration distribution within the SRB layer. The gradient structure transitions from lower germanium content near the substrate interface to higher germanium content toward the top surface, allowing different regions to serve different functions: the lower-germanium region manages strain accumulation while the higher-germanium region provides lattice matching for subsequent superlattice growth, achieving defect reduction without requiring excessive thickness
Solution Approach 2:
The patent utilizes parameter changes by varying the germanium concentration as a continuous gradient through the SRB layer thickness. This gradual parameter transition enables controlled strain relaxation and lattice constant adjustment, allowing the layer to accommodate misfit dislocations progressively rather than abruptly, thereby reducing defect density while maintaining thinner overall thickness and shorter processing time
2Manufacturing precision
If thick SRB layers are grown to reduce defect density, then manufacturing precision improves, but loss of substance increases due to costly materials
Solution Approach 1:
The patent applies local quality by creating a non-uniform germanium concentration distribution within the SRB layer. The gradient structure transitions from lower germanium content near the substrate interface to higher germanium content toward the top surface, allowing different regions to serve different functions: the lower-germanium region manages strain accumulation while the higher-germanium region provides lattice matching for subsequent superlattice growth, achieving defect reduction without requiring excessive thickness
Solution Approach 2:
The patent utilizes parameter changes by varying the germanium concentration as a continuous gradient through the SRB layer thickness. This gradual parameter transition enables controlled strain relaxation and lattice constant adjustment, allowing the layer to accommodate misfit dislocations progressively rather than abruptly, thereby reducing defect density while maintaining thinner overall thickness and shorter processing time
3Manufacturing precision
If thick SRB layers are grown to reduce defect density, then manufacturing precision improves, but device complexity increases due to substrate stress and cracking
Solution Approach 1:
The patent utilizes parameter changes by varying the germanium concentration as a continuous gradient through the SRB layer thickness. This gradual parameter transition enables controlled strain relaxation and lattice constant adjustment, allowing the layer to accommodate misfit dislocations progressively rather than abruptly, thereby reducing defect density while maintaining thinner overall thickness and shorter processing time
Solution Approach 2:
The graded SRB layer acts as an intermediary transition region between the silicon substrate and the superlattice structure. The gradual germanium concentration gradient serves as a buffer that mediates the lattice mismatch and thermal expansion differences, progressively adapting the crystal structure from the substrate to the superlattice composition, thereby reducing misfit dislocations and mechanical stress
4Productivity
If thinner SRB layers are used to reduce processing time, then productivity improves, but manufacturing precision deteriorates due to increased defect density
Solution Approach 1:
The patent applies local quality by creating a non-uniform germanium concentration distribution within the SRB layer. The gradient structure transitions from lower germanium content near the substrate interface to higher germanium content toward the top surface, allowing different regions to serve different functions: the lower-germanium region manages strain accumulation while the higher-germanium region provides lattice matching for subsequent superlattice growth, achieving defect reduction without requiring excessive thickness
Solution Approach 2:
The graded SRB layer acts as an intermediary transition region between the silicon substrate and the superlattice structure. The gradual germanium concentration gradient serves as a buffer that mediates the lattice mismatch and thermal expansion differences, progressively adapting the crystal structure from the substrate to the superlattice composition, thereby reducing misfit dislocations and mechanical stress
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 proposed method enables the formation of thinner SRB layers with reduced defect density and processing costs, improving the efficiency and reliability of semiconductor device manufacturing by minimizing substrate stress and optimizing superlattice structure processing.
Implementation Method 1
a monocrystalline film is deposited on a monocrystalline substrate from gaseous or liquid precursors. During deposition, the substrate acts as a seed crystal, the deposited film takes on a lattice structure and orientation identical to those of the substrate
Implementation Method 2
In epitaxy, a monocrystalline film is deposited on a monocrystalline substrate from gaseous or liquid precursors
Implementation Method 3
mechanical stress and thermal stress may be generated due to a difference in lattice constants and thermal expansion coefficients causing the silicon substrate to bow and the epitaxial SiGe material and even the silicon substrate to crack
Data Source
AI summary
A method and apparatus for forming strain relaxed buffers that may be used in semiconductor devices incorporating superlattice structures are provided. The method includes epitaxially depositing a first silicon germanium layer over the substrate. The first silicon germanium layer has a first surface that contacts a frontside surface of the substrate and a second surface opposite the first surface. The first silicon germanium layer has a first thickness and a germanium concentration gradient that increases from the first surface to the second surface. The method further includes epitaxially depositing a silicon germanium capping layer on the first silicon germanium layer. The silicon germanium capping layer has a second thickness and a substantially uniform germanium concentration that is equal to, substantially equal to, or greater than a maximum germanium concentration of the germanium concentration gradient.