Stacked Transistor Contact Layout for Flexible Semiconductor Routing
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Solution Overview
Problem
The increasing density of integrated circuits leads to design and fabrication challenges due to the complexity of connecting conductive features across multiple layers and transistors, requiring innovative solutions to enhance routing flexibility and reduce the number of conductive trace layers.
Innovation Solution
The semiconductor device incorporates a contact that electrically isolates from the source/drain of one transistor while connecting to another, allowing for flexible routing without additional stacked conductive traces or vias, by extending over conductive segments and connecting to features across or offset from gates at different elevations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional conductive trace layers and vias are used to connect transistors across multiple layers, then electrical connectivity is achieved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The contact extends in the vertical dimension to pass over the second source/drain region, enabling connection to conductive features at different elevations without requiring additional horizontal trace layers. This dimensional approach reduces the number of conductive trace layers needed while maintaining electrical connectivity.
Solution Approach 2:
The contact serves as an intermediary element that bridges the second source/drain region of the first transistor with conductive features of the second transistor. By extending over the source/drain region and making electrical connection, it facilitates connectivity without requiring traditional via structures through the source/drain area.
2Reliability
If deep vias are used to connect conductive features across layers, then electrical connection is established, but manufacturing risk increases
Solution Approach 1:
Instead of forming deep vertical vias through multiple layers, the contact extends horizontally over the source/drain region to reach conductive features at different elevations. This approach avoids the manufacturing challenges of deep via formation while achieving the same electrical connection function.
Solution Approach 2:
The contact is extracted from the traditional via structure and repositioned to extend over the source/drain region. This extraction eliminates the need for deep via formation through the source/drain area, reducing manufacturing risk while maintaining electrical connectivity.
3Adaptability or versatility
If additional stacked conductive traces are added to increase routing flexibility, then connectivity options improve, but device area increases
Solution Approach 1:
The contact extends in the vertical dimension to provide routing flexibility by connecting to conductive features at different elevations. This eliminates the need for additional stacked conductive traces in the horizontal plane, maintaining routing versatility without increasing device area.
Solution Approach 2:
The contact structure serves multiple functions: it provides electrical connection, enables routing flexibility, and connects transistors across different layers. This multi-functionality replaces the need for additional dedicated conductive trace layers, reducing device area while maintaining adaptability.
Data Source
AI summary
A semiconductor device includes a first transistor, a second transistor, a third transistor, and a contact. The first transistor includes a first source/drain (S/D), a second S/D, and a first gate between the first S/D and the second S/D. The first transistor and the second transistor are stacked over the third transistor. The contact covers the second S/D of the first transistor. The contact is electrically connected to the second transistor and electrically isolated from the second S/D.