Backside Contact Liner for Stacked Transistor Short Isolation
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Solution Overview
Problem
The fabrication of backside BEOL networks in semiconductor IC devices is challenging due to the difficulty in connecting backside contacts to upper and lower transistor regions, particularly in stacked transistors, which increases the risk of electrical shorting.
Innovation Solution
The semiconductor IC device includes an upper transistor with a recessed sidewall connected to a backside contact, and a lower transistor with a recessed sidewall covered by a dielectric contact liner, allowing for self-aligned formation of backside contact openings and reducing the risk of shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If backside contacts are placed closer to lower S/D regions to improve device scaling, then device area is reduced and scaling is enabled, but the risk of electrical shorting between backside contacts and lower transistor regions increases
Solution Approach 1:
A dielectric contact liner is introduced as an intermediary layer between the backside contact and the lower S/D region. This liner provides electrical isolation, preventing shorting while allowing the backside contact to be positioned close to the lower S/D region for improved device scaling and reduced area.
Solution Approach 2:
The structure is segmented into distinct functional layers: the backside contact, the dielectric contact liner, and the lower S/D region. This segmentation allows each component to perform its specific function independently - the contact provides electrical connection, the liner provides isolation, and the S/D region provides transistor function - enabling close placement without shorting.
2Adaptability or versatility
If multi-layer components are used to connect backside wires with active regions, then routing flexibility and power distribution are improved, but fabrication difficulty increases
Solution Approach 1:
The dielectric contact liner is formed preliminarily before the backside contact is deposited. This preliminary action establishes the isolation structure in advance, guiding subsequent contact formation and simplifying the overall fabrication process by pre-defining the interface between contact and lower S/D region.
Solution Approach 2:
The dielectric contact liner serves multiple functions simultaneously: it provides electrical isolation, defines the contact interface geometry, and guides the formation of subsequent layers. This self-service capability reduces the need for additional dedicated isolation structures and simplifies manufacturing.
Data Source
AI summary
A semiconductor IC structure includes a dielectric contact liner between an upper S/D region backside contact and a lower S/D region. As a result of the dielectric contact liner, the overlap between the upper transistor and the lower transistor may be increased, which may lead to further device scaling. To achieve these benefits, material that later forms the dielectric contact liner is deposited within an associated upper S/D region backside contact opening and has etch selectivity that may result in a later self-aligned reformation of the backside contact opening with reduced risk of that opening extending into the neighboring lower S/D region. The ability to self-align the formation of the backside contact opening may allow for the placement of such opening to be relatively closer to lower S/D region. The dielectric contact liner material may remain between and adequately electrically isolate the backside contact and the lower S/D region.