Backside Source/Drain Contact Structure for Lower Resistance
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Solution Overview
Problem
As integrated circuit technologies progress towards smaller technology nodes, existing source/drain contacts face challenges in maintaining performance due to parasitic resistance, which is exacerbated by the recessing of epitaxial layers to increase landing area, adversely impacting the volume of the source/drain features.
Innovation Solution
A method is employed to increase contact area between the backside silicide layer and the source/drain feature by forming a dielectric layer to block the top surface during epitaxial growth, followed by etching processes to expose the bottom surface, allowing the silicide layer to fill voids and enhance contact area without reducing the source/drain feature volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If epitaxial layers are recessed to increase landing area, then contact area is improved, but source/drain feature volume is reduced
Solution Approach 1:
The patent transitions from a planar contact geometry to a three-dimensional cup-shaped contact structure by forming an overhang configuration. The dielectric layer is patterned to create lateral overhangs that extend beyond the underlying source/drain feature, allowing the conductive layer to wrap around and contact the source/drain feature from multiple directions, thereby increasing contact area without reducing the source/drain feature volume.
Solution Approach 2:
The conductive layer is formed to wrap around and nest within the space created by the overhanging dielectric layer, creating a nested configuration where the conductive material contacts the source/drain feature from multiple surfaces. This nested structure maximizes the contact interface between the conductive layer and source/drain feature while preserving the source/drain feature volume.
2Reliability
If contact area is increased to reduce parasitic resistance, then electrical connectivity is improved, but device complexity increases
Solution Approach 1:
The dielectric layer serves multiple functions: it acts as an insulating barrier, defines the overhang geometry through its patterned top surface, and provides structural support for the conductive layer. This multi-functional dielectric layer simplifies the overall contact structure by consolidating several roles into a single material layer, reducing device complexity while maintaining improved electrical connectivity.
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 reduces parasitic resistance and improves the overall performance of the semiconductor structure by increasing contact area and minimizing void formation, thereby enhancing the electrical connectivity of the source/drain contacts.
Implementation Method 1
epitaxial growth, followed by etching processes to expose the bottom surface
Data Source
AI summary
In an embodiment, an exemplary method includes forming a source/drain opening extending into a substrate, forming a semiconductor layer in a bottom portion of the source/drain opening, forming a dielectric feature in the source/drain opening and on the semiconductor layer, epitaxially growing a source/drain feature in the source/drain opening, wherein the source/drain feature is in direct contact with the dielectric feature, removing the semiconductor layer and a portion of the substrate disposed directly under the semiconductor layer to form a trench, selectively removing the dielectric feature to enlarge the trench, after the selectively removing of the dielectric feature, forming a silicide layer in the enlarged trench, and depositing a conductive layer in the enlarged trench and in direct contact with the silicide layer.