Vertical-Trench Source-Drain Structures for Lower Contact Resistance
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Solution Overview
Problem
Conventional integrated circuit fabrication processes face challenges in scaling to sub-10 nanometer nodes due to variability in source and drain contact resistance, which limits transistor performance and efficiency.
Innovation Solution
The implementation of conformal epitaxial source and drain structures with vertical trenches, where dopant concentration is homogeneous in the bulk and higher on the growth surface, allowing for selective etching and increased contact area with metal, thereby reducing external resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fabrication processes are used for scaling, then manufacturing simplicity is maintained, but source and drain contact resistance variability increases, limiting transistor performance
Solution Approach 1:
The patent applies local quality by creating a non-uniform dopant distribution within the source and drain regions. Specifically, the dopant concentration is higher at the growth surface and lower in the bulk, forming a graded structure that optimizes local electrical properties. This local variation in dopant concentration reduces contact resistance variability while maintaining manufacturing feasibility through selective etching processes.
Solution Approach 2:
The patent changes the dopant concentration parameter by creating a vertical gradient from the growth surface into the bulk of the source and drain regions. This parameter change is achieved through selective etching that removes dopant-rich material from the surface while preserving the bulk structure. The resulting dopant concentration profile optimizes electrical contact properties and reduces resistance variability, directly addressing the technical contradiction.
2Productivity
If feature size is reduced to increase device density, then capacity increases, but fabrication process variability worsens, limiting extension to sub-10 nanometer nodes
Solution Approach 1:
The patent transitions from two-dimensional planar source and drain structures to three-dimensional structures with vertical trenches. By introducing the vertical dimension and creating trenches that extend into the substrate, the patent achieves better process control at sub-10 nanometer nodes. The vertical trench geometry provides additional degrees of freedom for process optimization and reduces variability inherent in conventional planar scaling.
Solution Approach 2:
The patent segments the source and drain regions by creating vertical trenches that divide the continuous structure into discrete segments. This segmentation allows for independent optimization of different regions and improves manufacturing precision by enabling selective processing. The trench structure breaks down the complex doping process into manageable segments that can be controlled more precisely at sub-10 nanometer dimensions.
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 significantly enhances source and drain contact area and reduces contact resistivity, improving transistor performance and control, especially for low power applications, by leveraging the directional merging of epitaxial growth and selective etching techniques.
Implementation Method 1
epitaxially growing a silicon material in the recess, the silicon material including a Group V dopant impurity. The epitaxially growing includes forming a Group V dopant impurity-rich region centered in the silicon material
Implementation Method 2
The Group V dopant impurity-rich region is then removed to form a vertical trench centered in the silicon material
Data Source
AI summary
Integrated circuit structures having source or drain structures with vertical trenches are described. In an example, an integrated circuit structure includes a fin having a lower fin portion and an upper fin portion. A gate stack is over the upper fin portion of the fin, the gate stack having a first side opposite a second side. A first source or drain structure includes an epitaxial structure embedded in the fin at the first side of the gate stack. A second source or drain structure includes an epitaxial structure embedded in the fin at the second side of the gate stack. The epitaxial structures of the first and second source or drain structures have a vertical trench centered therein. The first and second source or drain structures include silicon and a Group V dopant impurity.