Strained Source/Drain Epitaxial Layers for Carrier Mobility
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Solution Overview
Problem
Existing methods for manufacturing strained source/drain structures in semiconductor devices, such as MOSFETs, are not entirely satisfactory in enhancing carrier mobility and device performance, particularly due to limitations in forming raised source and drain features using epitaxial semiconductor materials.
Innovation Solution
A method involving the formation of a semiconductor device with epitaxially grown layers in trenches, where a first layer with a specific dopant concentration is grown along the bottom and sidewalls of the trenches, and a second layer with a different dopant concentration is grown over the first layer to enhance carrier mobility and strain the channel region, thereby improving device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epitaxial semiconductor materials are used to form raised source and drain features, then carrier mobility is enhanced and device performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent divides the source/drain structure into multiple epitaxial layers with different compositions and doping concentrations. The first layer has a first composition and doping concentration, while the second layer has a second composition and doping concentration, creating a segmented structure that optimizes both carrier mobility and manufacturing control
Solution Approach 2:
Different regions of the source/drain structure are assigned different material compositions and doping concentrations tailored to local requirements. The first epitaxial layer uses one set of parameters while the second layer uses different parameters, optimizing performance in each specific region
2Reliability
If dopant concentration is increased to improve device performance, then carrier mobility enhances, but short channel effects worsen
Solution Approach 1:
The patent applies different doping concentrations in different layers: the first epitaxial layer has a first doping concentration optimized for carrier mobility, while the second epitaxial layer has a second doping concentration that addresses short channel effects, allowing local optimization without compromise
Solution Approach 2:
The source/drain structure comprises composite epitaxial layers with different material compositions and doping concentrations. This composite structure enables simultaneous optimization of carrier mobility in one layer and short channel effect suppression in another layer
3Object-affected harmful factors
If junction depth is reduced to improve device performance, then short channel effects improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent segments the junction formation into two distinct epitaxial growth stages, where each layer can be precisely controlled independently. This segmentation allows precise junction depth control without requiring single-step precision
Solution Approach 2:
The first epitaxial layer is formed with specific composition and doping concentration as a preliminary step, establishing a foundation that enables subsequent precise formation of the second layer with different parameters, making the overall precision requirement more manageable
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 enhances carrier mobility, improves short channel effects, and reduces contact resistance, resulting in improved device performance with precise control over dopant distribution and junction depth.
Implementation Method 1
epitaxially grown layers in trenches, where a first layer with a specific dopant concentration is grown along the bottom and sidewalls of the trenches, and a second layer with a different dopant concentration is grown over the first layer
Implementation Method 2
a first layer with a specific dopant concentration is grown along the bottom and sidewalls of the trenches, and a second layer with a different dopant concentration is grown over the first layer
Data Source
AI summary
A method includes forming a gate structure over a semiconductor substrate. The gate structure defines a channel region in the semiconductor substrate. Trenches are formed in the semiconductor substrate, and the trenches are interposed by the channel region. A first semiconductor layer is epitaxially grown in the trenches, and the first semiconductor layer has a first dopant with a first dopant concentration. A second semiconductor layer is epitaxially grown over the first semiconductor layer, and the second semiconductor layer has a second dopant with a second dopant concentration. The second dopant has an electrical carrier type opposite to an electrical carrier type of the first dopant.