Gate-Source/Drain Butted Contact Structure for Lower Resistance
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Solution Overview
Problem
Conventional gate-to-source/drain connections in multi-gate devices, such as FinFETs and MBC transistors, suffer from limited contact surfaces and high contact resistance due to butted contacts, which are not self-aligned and require high overlay accuracy, increasing manufacturing costs.
Innovation Solution
A butted contact structure with an extending portion that downwardly extends laterally between the gate structure and source/drain contact, providing additional contacting surfaces on sidewalls to reduce contact resistance and enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a butted contact structure is used to connect gate and source/drain, then the connection is achieved, but the contact surface area is limited and contact resistance is high
Solution Approach 1:
The contact structure extends vertically into multiple levels, transitioning from a single-plane contact to a multi-level structure. The first contact portion contacts the gate at one level while the second contact portion contacts the source/drain at a different vertical level, effectively increasing contact surface area by utilizing the vertical dimension rather than only horizontal expansion.
Solution Approach 2:
The contact structure is divided into distinct segments: a first contact portion for contacting the gate and a second contact portion for contacting the source/drain. This segmentation allows each portion to be optimized for its specific contact function while collectively providing increased total contact area and reduced resistance pathways.
2Reliability
If a butted contact is used for gate-to-source/drain connection, then connection is established, but overlay accuracy requirements increase manufacturing complexity and cost
Solution Approach 1:
The gate electrode is formed to extend beyond the gate dielectric edge, creating an exposed portion that protrudes into the source/drain region before subsequent processing steps. This preliminary extension of the gate electrode establishes a pre-defined contact location that simplifies later contact formation and reduces overlay sensitivity.
Solution Approach 2:
The extended gate electrode structure serves dual functions: it acts as both the functional gate electrode and provides a built-in contact surface for the source/drain connection. This self-providing contact surface eliminates the need for separate alignment-critical contact formation steps, allowing the structure to serve its own connection needs.
Data Source
AI summary
A semiconductor device according to the present disclosure includes first and second fins extending lengthwise in a first direction and first and second gate structures extending lengthwise in a second direction perpendicular to the first direction. The first gate structure engages the first fin in forming a first transistor, the second gate structure engages the second fin in forming a second transistor, and the second gate structure interfaces with a terminal end of the first fin. The semiconductor device further includes a source/drain feature of the first transistor, a source/drain contact in contact with the source/drain feature, and a contact structure interfacing with top surfaces of the source/drain contact and the second gate structure. The contact structure includes an extending portion laterally between sidewalls of the source/drain contact and the second gate structure.