SiGe Edge Reservoir Deposition for Lower Threading Dislocation Density
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Solution Overview
Problem
Existing methods for depositing silicon germanium (SiGe) layers on substrates face challenges with misfit dislocations (MD), threading dislocations (TD), and dislocation pile-ups (DP) due to lattice-mismatch, leading to surface roughening and high dislocation densities.
Innovation Solution
A method involving the deposition of a relaxed or partially relaxed silicon germanium layer as an edge reservoir on the substrate, providing a controlled nucleation site for dislocations to glide and reduce threading dislocation density (TDD) by forming long misfit dislocation segments, using a masking process to create an annular-shaped free surface for deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a SiGe layer is heteroepitaxially deposited on a silicon substrate, then a SiGe layer is formed for integration of SiGe channels, but misfit dislocations, threading dislocations, and dislocation pile-ups are formed due to lattice-mismatch
Solution Approach 1:
The patent applies preliminary action by depositing a relaxed or partially relaxed SiGe layer (edge reservoir) on the back side of the substrate before depositing the functional SiGe layer on the front side. This preliminary layer prepares dislocation loops in advance that will later serve as sinks for threading dislocations, preventing their formation in the functional layer
Solution Approach 2:
The patent uses an intermediary approach by introducing a stress compensating SiGe layer deposited on the back side of the substrate. This intermediary layer acts as a mediator that compensates for the lattice-mismatch stress, reducing the driving force for dislocation formation in the functional SiGe layer on the front side
2Object-generated harmful factors
If a stress compensating SiGe layer is deposited on the back side of the substrate, then dislocation formation is reduced, but the process complexity increases
Solution Approach 1:
The patent applies universality by making the back side of the substrate multi-functional. The back side not only serves as the substrate base but also hosts a stress compensating SiGe layer that actively participates in reducing dislocation formation. This allows one side of the substrate to perform multiple functions: structural support and stress compensation
Solution Approach 2:
The patent merges the stress compensation function with the substrate structure itself by depositing the compensating layer directly on the back side of the substrate. This combines the substrate and stress compensation mechanism into a single integrated structure, reducing the need for separate compensation structures
3Manufacturing precision
If threading dislocations are distributed uniformly across the surface, then dislocation pile-ups can form, but surface roughening occurs
Solution Approach 1:
The patent extracts threading dislocations from the functional SiGe layer by providing dislocation loops in the relaxed SiGe layer on the back side. These loops act as sinks that absorb and remove threading dislocations before they can reach the surface and cause roughening, effectively taking out the harmful dislocations from the functional layer
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
Reduces threading dislocation density and prevents dislocation bundle formation, improving surface uniformity and reducing surface roughness by allowing controlled relaxation of the SiGe layer.
Implementation Method 1
a SiGe layer is usually heteroepitaxially deposited atop a substrate
Implementation Method 2
depositing an edge reservoir consisting of a relaxed or partially relaxed silicon germanium layer atop the annular-shaped free surface of the substrate
Data Source
AI summary
A method heteroepitaxially deposits a silicon germanium layer on a substrate. The silicon germanium layer has a composition Si1-xGex, where 0.01≤x≤1. The substrate is a silicon single crystal wafer or a silicon-on-insulator wafer. The method includes: providing a mask layer atop the substrate; removing the mask layer in an edge region of the substrate to provide access to an annular-shaped free surface of the substrate in the edge region of the substrate surrounding a remainder of the mask layer; depositing an edge reservoir consisting of a relaxed or partially relaxed silicon germanium layer atop the annular-shaped free surface of the substrate; removing the remainder of the mask layer; and depositing the silicon germanium layer atop the substrate and atop the edge reservoir, the silicon germanium layer contacting an inner lateral surface of the edge reservoir.