Stacked Source/Drain Contacts for Low-Resistance GAA Transistors
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Solution Overview
Problem
The semiconductor industry faces challenges in creating smaller and more complex circuits due to limitations in semiconductor structure design and fabrication processes, particularly in forming efficient gate structures and source/drain contacts that enhance device performance and reliability.
Innovation Solution
The process involves forming parallel channel members with a gate structure wrapping around them, using a silicide layer on source/drain features, and creating a two-staged source/drain contact structure with a first contact based on the silicide layer and a second contact separate from it, which reduces contact resistance and improves reliability without the need for additional lining or seed layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-stage source/drain contact structure is used, then the fabrication process is simpler, but the contact resistance is higher and reliability is reduced
Solution Approach 1:
The source/drain contact structure is divided into two distinct stages: a first source/drain contact formed directly on the silicide layer, and a second source/drain contact formed on the first contact. This segmentation allows each contact layer to be optimized for specific functions, reducing overall contact resistance while maintaining fabrication feasibility through sequential processing steps.
Solution Approach 2:
The contact structure transitions from a conventional planar single-layer design to a vertical multi-layer stacked architecture. By adding the vertical dimension with stacked contact layers, the patent achieves lower contact resistance and improved reliability without significantly increasing lateral footprint, enabling better electrical performance in scaled devices.
2Reliability
If additional lining or seed layers are added to reduce contact resistance, then contact resistance decreases, but the number of fabrication steps increases
Solution Approach 1:
The patent merges the function of contact formation with the existing silicide layer structure. The first source/drain contact is formed directly on the silicide layer without requiring separate lining or seed layers, combining multiple functions into fewer processing steps while achieving low contact resistance through the direct silicide-contact interface.
Solution Approach 2:
The silicide layer serves a dual function: as the active contact region and as the foundation for the first source/drain contact. This self-service approach eliminates the need for additional lining or seed layers that would otherwise be required, reducing fabrication steps while maintaining low contact resistance through the inherent properties of the silicide layer.
3Reliability
If conventional contact formation processes are used, then the process is simpler, but damage to the silicide layer occurs during processing
Solution Approach 1:
The first source/drain contact is formed on the silicide layer before subsequent processing steps that could cause damage. This preliminary formation establishes a protective interface and allows for optimized processing conditions that preserve silicide layer integrity, preventing damage from later fabrication steps while maintaining manufacturing simplicity.
Data Source
AI summary
A semiconductor device includes parallel channel members, a gate structure, source/drain features, a silicide layer, and a source/drain contact. The parallel channel members are spaced apart from one another. The gate structure is wrapping around the channel members. The source/drain features are disposed besides the channel members and at opposite sides of the gate structure. The silicide layer is disposed on and in direct contact with the source/drain features. The source/drain contact is disposed on the silicide layer, wherein the source/drain contact includes a first source/drain contact and a second source/drain contact stacked on the first source/drain contact, and the second source/drain contact is separate from the silicide layer by the first source/drain contact.