Gate Extension Structure for FEOL Source/Drain Connection
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Solution Overview
Problem
Conventional gate-to-source/drain connections in multi-gate devices require additional lithography steps and space, increasing manufacturing costs and complexity, particularly due to the need for MEOL or BEOL contact structures.
Innovation Solution
An FEOL contact structure is formed by depositing a cladding layer over a fin-shaped structure, allowing self-aligned exposure of source/drain features and direct electrical coupling with a gate electrode, eliminating the need for MEOL or BEOL contact structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional MEOL or BEOL contact structures are used to connect gate and source/drain, then reliable electrical connection is achieved, but manufacturing complexity and cost increase due to additional lithography steps
Solution Approach 1:
The gate electrode is extended into the source/drain region during the front-end-of-line process, before the formation of interlayer dielectric and metal contacts. This preliminary extension creates direct electrical connection between gate and source/drain, eliminating the need for subsequent MEOL/BEOL contact structures and reducing manufacturing complexity while maintaining connection reliability
2Reliability
If butted contacts are used to connect gate and source/drain, then electrical connection is established, but space is consumed in metal line layer affecting routing
Solution Approach 1:
Instead of using lateral butted contacts in the metal line layer, the gate electrode is extended vertically into the source/drain region. This dimensional change from lateral to vertical connection eliminates the need for additional metal line layer space, freeing up routing area while maintaining reliable electrical connection
3Manufacturing precision
If additional lithography steps are performed for gate-to-source/drain connection, then precise alignment is achieved, but manufacturing cost increases
Solution Approach 1:
The gate electrode extension structure serves dual purposes: it provides the gate function and simultaneously creates the electrical connection to source/drain. This self-service approach eliminates the need for separate alignment-critical lithography steps for contact formation, reducing manufacturing cost while maintaining precision through the inherent alignment of the extension structure
Data Source
AI summary
A semiconductor device according to the present disclosure includes a gate extension structure, a first source/drain feature and a second source/drain feature, a vertical stack of channel members extending between the first source/drain feature and the second source/drain feature along a direction, and a gate structure wrapping around each of the vertical stack of channel members. The gate extension structure is in direct contact with the first source/drain feature.