Multilayer Embedded Stressor Graded Dopant Profile
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Solution Overview
Problem
Existing embedded stressor technologies in semiconductor devices face challenges in achieving a balance between stress proximity and short channel effects, and often result in defect generation during the formation of deep source/drain regions.
Innovation Solution
A multilayer embedded stressor with a graded dopant profile and a conformal epitaxial semiconductor layer is introduced, which is formed within recessed regions of the semiconductor substrate to induce strain on the channel region of field effect transistors, eliminating defects and improving stress proximity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If embedded stressors are formed close to the channel region to enhance stress proximity, then device performance is improved, but short channel effects worsen
Solution Approach 1:
The patent transitions from planar stressor geometry to a three-dimensional structure by forming stressors in recessed regions that extend vertically into the substrate. This vertical dimension allows the stressor to be positioned close to the channel for enhanced stress proximity while the recessed geometry confines the stressor laterally, preventing excessive lateral spread that would cause short channel effects.
Solution Approach 2:
The patent applies different doping concentrations at different locations within the stressor structure. The stressor region adjacent to the channel has optimized dopant concentration to maximize stress effect, while regions farther from the channel have different doping to control electrical characteristics and minimize harmful effects on channel performance.
2Reliability
If deep source/drain regions are formed using deep implants to create embedded stressors, then stress proximity is improved, but defect generation increases
Solution Approach 1:
The patent replaces the mechanical impact process of ion implantation with a chemical deposition process. Epitaxial silicon layers are grown conformally to fill recessed regions, eliminating the high-energy ion bombardment that causes lattice damage and defects. The stressor is formed through controlled epitaxial growth rather than mechanical implantation.
Solution Approach 2:
The patent introduces recessed regions as an intermediary structure that enables close proximity between the stressor and channel without requiring deep ion implantation. The recessed geometry provides a physical template that guides epitaxial growth, allowing the stressor to be formed close to the channel through low-damage chemical deposition rather than high-energy implantation.
3Stress or pressure
If embedded stressors are formed with high dopant concentration to enhance stress effect, then stress magnitude is improved, but dopant diffusion into the channel increases
Solution Approach 1:
The patent uses vertical recessed structures to confine high-concentration dopants in the depth dimension, allowing high dopant concentration to generate sufficient stress magnitude while the vertical confinement prevents lateral diffusion into the channel region. The recessed geometry acts as a physical barrier to dopant migration.
Solution Approach 2:
The patent creates a composite structure with multiple epitaxial layers having different dopant concentrations. The stressor region contains high dopant concentration to generate stress, while adjacent regions have lower or graded doping to act as diffusion barriers, preventing dopant migration into the channel while maintaining stress generation.
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 solution achieves a good balance between stress proximity and short channel effects, reducing defects and enhancing the performance of semiconductor devices by maintaining high channel stress with minimal dopant diffusion.
Implementation Method 1
Mechanical stresses within a semiconductor device substrate have been widely used to modulate device performance
Implementation Method 2
at least a first epitaxial (epi) semiconductor layer that is conformal
Data Source
AI summary
A multilayer embedded stressor having a graded dopant profile for use in a semiconductor structure for inducing strain on a device channel region is provided. The inventive multilayer stressor is formed within areas of a semiconductor structure in which source/drain regions are typically located. The inventive multilayer stressor includes a first conformal epi semiconductor layer that is undoped or lightly doped and a second epi semiconductor layer that is highly dopant relative to the first epi semiconductor layer. The first and second epi semiconductor layers each have the same lattice constant, which is different from that of the substrate they are embedded in. The structure including the inventive multilayer embedded stressor achieves a good balance between stress proximity and short channel effects, and even eliminates or substantially reduces any possible defects that are typically generated during formation of the deep source/drain regions.