Silicon Germanium-on-Insulator Structure for Dislocation Reduction
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Solution Overview
Problem
Conventional methods for producing ultra-thin silicon-on-insulator (UTSOI) and silicon germanium-on-insulator (SGOI) substrates face challenges such as high threading dislocation densities and complex processing due to lattice mismatch between silicon and silicon germanium, leading to defects and non-uniformity in layer thickness.
Innovation Solution
A multilayer structure is created by etching a silicon-on-insulator substrate to a thickness of 0.5-4 nanometers, followed by germanium deposition and annealing to interdiffuse silicon and germanium, resulting in a strain-relaxed silicon germanium layer with reduced dislocations, using a simplified process flow that integrates top silicon layer thinning and silicon germanium growth in a single epitaxy step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to produce silicon germanium-on-insulator substrates, then silicon germanium layers can be formed, but high threading dislocation densities and defects occur due to lattice mismatch between silicon and silicon germanium
Solution Approach 1:
The process is segmented into distinct stages: first forming a silicon-on-insulator substrate with controlled thickness, then depositing germanium layer, and finally performing interdiffusion annealing. This segmentation allows each stage to be optimized independently, reducing cumulative defects
Solution Approach 2:
The silicon-on-insulator substrate is prepared in advance with precisely controlled thickness (0.5-4 nm) before germanium deposition. This preliminary preparation ensures the substrate is ready to accommodate the germanium layer with minimal strain, preventing dislocation formation
2Reliability
If conventional processing methods are used, then silicon germanium layers can be produced, but the process becomes complex due to multiple steps required to manage lattice mismatch
Solution Approach 1:
The patent merges the silicon layer thinning and silicon germanium growth into a single integrated process flow. The silicon-on-insulator substrate preparation, germanium deposition, and interdiffusion annealing are combined into one continuous process, eliminating intermediate handling steps and reducing process complexity
Solution Approach 2:
The silicon-on-insulator substrate serves multiple functions: it provides the base structure, controls the final layer thickness, and acts as a buffer to manage lattice mismatch. This multi-functionality reduces the need for additional dedicated layers or processes
3Manufacturing precision
If the silicon layer is made ultra-thin (0.5-4 nm), then the final silicon germanium layer achieves better uniformity, but the etching process becomes more challenging to control
Solution Approach 1:
The patent changes the thickness parameter of the silicon layer to an ultra-thin range (0.5-4 nm) to achieve better final uniformity. This parameter change is compensated by optimizing the etching process conditions, allowing precise control despite the reduced thickness
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 reduces threading dislocations and achieves a smooth, uniform silicon germanium layer with improved surface roughness, enhancing device performance and simplifying the manufacturing process by leveraging mature UTSOI technology.
Implementation Method 1
annealing to interdiffuse silicon and germanium
Implementation Method 2
annealing to interdiffuse silicon and germanium
Implementation Method 3
etching a silicon-on-insulator substrate to a thickness of 0.5-4 nanometers
Data Source
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AI summary
A multilayer structure comprising: a silicon-on-insulator substrate comprising (i) a single crystal semiconductor handle layer, (ii) a dielectric layer in interfacial contact with the front surface of the single crystal semiconductor handle layer, and (iii) a silicon layer in interfacial contact with the dielectric layer, wherein the silicon layer comprises a hydride-terminated surface; a first silicon germanium layer in interfacial contact with the hydride-terminated surface of the silicon layer, wherein the first silicon germanium layer comprises silicon and germanium and has a formula of SixGe1-x, wherein x is between about 0.2 and about 0.8, molar ratio; and a second silicon germanium layer in interfacial contact with the first silicon germanium layer, wherein the second silicon germanium layer comprises silicon and germanium and has a formula SiyGe1-y, wherein y is between about 0.3 and about 0.9, molar ratio.