Self-Aligned Backside Gate Via Structure for Nanosheet Isolation
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Solution Overview
Problem
Nanosheet technology faces challenges in forming backside gate contacts as devices scale down, leading to interference and difficulty in creating effective connections.
Innovation Solution
A self-aligned structure is developed with a gate protrusion and dielectric liners flush against sidewalls, along with a contact via and metal lines, forming a continuous barrier to prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If nanosheet devices are scaled down and placed closer together to increase device density, then the number of devices per area increases, but interference between adjacent devices increases and backside gate contact formation becomes difficult
Solution Approach 1:
The patent divides the gate structure into a frontside gate portion and a backside gate protrusion portion, with the protrusion extending through the shallow trench isolation layer. This segmentation allows the gate to access both frontside and backside contacts independently, enabling proper electrical connection even when devices are densely packed and interfering with each other.
Solution Approach 2:
The patent extends the gate structure in the vertical dimension by creating a backside gate protrusion that penetrates through the shallow trench isolation layer. This dimensional extension allows the gate to reach the backside surface for contact formation without increasing horizontal device footprint, thus maintaining device density while avoiding interference.
2Reliability
If a backside gate contact structure is formed in densely packed nanosheet devices, then gate contact can be established, but the process becomes increasingly difficult and reliability decreases due to interference
Solution Approach 1:
The patent forms the backside gate protrusion and its associated dielectric liner structure before final contact formation. The protrusion is created by extending the gate through the shallow trench isolation layer in advance, and the dielectric liner is deposited on the protrusion sidewalls beforehand. This preliminary structuring simplifies subsequent contact formation and ensures reliable electrical connection.
Solution Approach 2:
The patent introduces a dielectric liner as an intermediary structure that coats the sidewalls of the gate protrusion. This liner acts as a barrier between the gate protrusion and surrounding materials, preventing short circuits while allowing the gate to maintain its extended configuration for reliable backside contact formation.
3Reliability
If dielectric liners are added to prevent short circuits between gate protrusion and metal lines, then electrical isolation is improved, but manufacturing steps increase
Solution Approach 1:
The patent combines the dielectric liner formation with the gate protrusion creation process. The dielectric liner is deposited conformally on the gate protrusion sidewalls as part of the same processing sequence, rather than as a separate subsequent step. This merging approach provides necessary electrical isolation while minimizing the increase in manufacturing complexity.
Data Source
AI summary
A structure including a plurality of nanosheet transistors each comprising a gate. A gate protrusion extends from the gate towards the backside of one of the plurality of electronic devices. A first dielectric liner is located flush against the sidewalls of the gate protrusion. A contact via connected to a backside surface of the gate protrusion. A second dielectric liner located flush again the sidewalls of the contact via.