Dislocation Nucleation Layer for NMOS Tensile Strain
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Solution Overview
Problem
Existing methods for improving carrier mobility in CMOS transistors, such as those described in US20130146895A1, face challenges in achieving differential strain requirements for NMOS and PMOS channels, with existing strain mechanisms potentially degrading channel performance.
Innovation Solution
The formation of a dislocation nucleation layer with a silicon germanium material in the source/drain regions, which induces a tensile strain in the channel region by propagating dislocations and overcoming compressive stress, using epitaxial growth and doping techniques to optimize strain transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If existing strain mechanisms are used to improve carrier mobility, then carrier mobility is improved, but channel performance degrades
Solution Approach 1:
The patent divides the source/drain structure into multiple segments: a first source/drain region, a second source/drain region, and a channel region. By segmenting the structure and applying different strain conditions to different segments, the patent achieves tensile strain in the channel for improved carrier mobility while preventing performance degradation through proper structural design and material selection in each segment.
2Speed
If tensile strain is applied to NMOS channel to improve mobility, then carrier mobility is improved, but differential strain requirements for PMOS cannot be met
Solution Approach 1:
The patent applies different material compositions and strain conditions to different local regions. The first source/drain region uses a different material composition than the second source/drain region, creating local quality differences that enable tensile strain in the NMOS channel while allowing compressive strain in the PMOS channel, thus meeting differential strain requirements for different transistor types.
Solution Approach 2:
The patent introduces asymmetry in the source/drain structure by using different materials and configurations for the first and second source/drain regions. This asymmetric design enables the structure to provide opposite strain types (tensile for NMOS, compressive for PMOS) to different transistor portions, satisfying the asymmetric strain requirements of complementary CMOS devices.
3Stress or pressure
If buffer layers are used to induce strain, then strain transfer is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and eliminates the buffer layer from the traditional strain-induced transistor structure. Instead of using a separate buffer layer to induce strain, the patent directly forms the source/drain regions with appropriate material compositions that inherently provide the required strain, thereby simplifying the device structure and reducing manufacturing complexity while maintaining effective strain transfer.
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 by effectively inducing a tensile strain in the NMOS channel region while avoiding performance degradation associated with buffer layers, thereby improving transistor performance.
Implementation Method 1
multiple dislocations are formed in the silicon germanium material, and then forming a source/drain material on the thin silicon germanium material, wherein the dislocations induce source/drain dislocations throughout the source/drain material
Implementation Method 2
forming a silicon germanium material on source/drain openings
Data Source
Figure 1a~1b
Figure 1c~1d
Figure 1e~2
AI summary
Methods of forming a strained channel device utilizing dislocations disposed in source/drain structures are described. Those methods and structures may include forming a thin silicon germanium material in a source/drain opening of a device comprising silicon, wherein multiple dislocations are formed in the silicon germanium material. A source/drain material may be formed on the thin silicon germanium material, wherein the dislocations induce a tensile strain in a channel region of the device.