Shared Contact Structure for High-Aspect-Ratio Stacked FETs
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Solution Overview
Problem
Current technologies face challenges in forming effective electrical connections between stacked field effect transistor (FET) devices, particularly in high aspect ratio structures, which hinders the development of efficient and scalable integrated circuits.
Innovation Solution
The solution involves creating a shared contact structure between a top and bottom FET device using a conductive trench spacer and sacrificial plug, allowing for electrical connection between source/drain regions across multiple device layers, facilitated by a method that includes forming a contact trench, depositing a conductive trench spacer, and bonding dielectric layers to secure the top active device layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact trench is formed through multiple device layers to create a shared contact, then electrical connectivity between stacked FET devices is improved, but the aspect ratio of the contact trench increases making formation difficult
Solution Approach 1:
The contact formation process is segmented into multiple stages: first forming a shallow contact trench in the lower ILD layer and filling it with conductive material, then forming a separate upper contact trench through the upper device layers. This segmentation avoids the need to form a single deep high aspect ratio trench, making the manufacturing process feasible while achieving electrical connectivity between stacked devices.
Solution Approach 2:
The invention transitions from a vertical high aspect ratio contact approach to a multi-level horizontal approach. By creating contacts at different depth levels (lower ILD layer contact and upper device layer contact) and connecting them through shared contact structures, the solution distributes the connectivity function across multiple dimensions rather than relying on a single deep vertical trench.
2Reliability
If the top contact dimension is increased to ensure reliable electrical connection, then connectivity reliability is improved, but the device area and scalability are reduced
Solution Approach 1:
The electrical connection path is segmented into multiple contact points at different levels. Instead of relying on a single large top contact, the invention creates multiple smaller contact regions (lower contact in ILD layer, upper contact through device layers) that collectively provide reliable connectivity while minimizing the area occupied by any single contact structure.
Solution Approach 2:
The contact structures are nested across multiple device layers, with the lower contact structure embedded in the lower ILD layer and the upper contact structure formed through the upper device layers. This nesting allows efficient use of vertical space and achieves reliable connectivity without requiring excessive horizontal area expansion.
Data Source
AI summary
A stacked device is provided. The stacked device includes a reduced height active device layer, and a plurality of lower source/drain regions in the reduced height active device layer. The stacked device further includes a lower interlayer dielectric (ILD) layer on the plurality of lower source/drain regions, and a conductive trench spacer in the lower interlayer dielectric (ILD) layer, wherein the conductive trench spacer is adjacent to one of the plurality of lower source/drain regions. The stacked device further includes a top active device layer adjacent to the lower interlayer dielectric (ILD) layer, and an upper source/drain section in the top active device layer. The stacked device further includes a shared contact in electrical connection with the upper source/drain section, the conductive trench spacer, and the one of the plurality of lower source/drain regions.