FinFET Epitaxial Source/Drain Contact Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As semiconductor devices, particularly FinFETs, are scaled down, the shrinking electrode contact area on the source/drain (S/D) increases contact resistance, necessitating improvements in the S/D structure to maintain performance and efficiency.
Innovation Solution
The implementation of an epitaxial source/drain structure with voids, where a first epitaxial layer with a lower Ge concentration is formed, followed by a second epitaxial layer with a higher Ge concentration, creating a void between them, and a capping layer, to enhance the interfacial area for contact and reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the FinFET size is scaled down, then the device density and integration are improved, but the electrode contact area on the source/drain shrinks and contact resistance increases
Solution Approach 1:
The patent introduces a vertical dimension to the contact structure by forming an epitaxial source/drain structure with multiple layers at different heights. The contact structure extends vertically into the source/drain region, creating a three-dimensional contact interface that increases the contact area without increasing the lateral footprint, thus maintaining high device density while reducing contact resistance.
Solution Approach 2:
The contact structure is nested within the source/drain region by forming an epitaxial structure that grows into the source/drain area. The contact opening is formed within the interlayer dielectric and extends down to contact the epitaxial source/drain structure, creating a nested configuration where the contact is embedded within the source/drain region rather than being a separate surface element.
2Ease of manufacture
If a single-layer epitaxial source/drain structure is used, then the manufacturing process is simple, but the interfacial area for contact is limited and resistance remains high
Solution Approach 1:
The epitaxial source/drain structure is segmented into multiple layers with different germanium concentrations. The first epitaxial layer has a lower Ge concentration (e.g., 0-10%) and the second epitaxial layer has a higher Ge concentration (e.g., 15-30%). This segmentation allows each layer to contribute differently to the contact properties, with the higher Ge concentration layer providing better lattice matching and the lower Ge concentration layer providing mechanical support, thereby reducing contact resistance while maintaining manufacturing feasibility.
Solution Approach 2:
Different regions of the epitaxial source/drain structure have different germanium concentrations optimized for their specific functions. The first epitaxial layer has a lower Ge concentration suitable for providing mechanical support and reducing stress, while the second epitaxial layer has a higher Ge concentration optimized for lattice matching with the silicon channel and reducing misfit dislocations. This local quality variation improves the overall contact interface without requiring complex manufacturing processes.
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 configuration decreases contact resistance and improves the efficiency of the FinFET by increasing the interfacial area between the contact layer and the epitaxial source/drain layers, leading to better performance and reduced variations in contact resistance values.
Implementation Method 1
a first epitaxial layer is formed at a source/drain region of a fin structure for the FinFET. A second epitaxial layer is formed over the first epitaxial layer. The second epitaxial layer has a material composition different from the first epitaxial layer
Data Source
AI summary
A semiconductor device includes a gate structure formed over a channel region of the semiconductor device, a source/drain region adjacent the channel region, and an electrically conductive contact layer over the source/drain region. The source/drain region includes a first epitaxial layer having a first material composition and a second epitaxial layer formed over the first epitaxial layer. The second epitaxial layer has a second material composition different from the first composition. The electrically conductive contact layer is in contact with the first and second epitaxial layers. A bottom of the electrically conductive contact layer is located below an uppermost portion of the first epitaxial layer.