Nanosheet Backside Contact Layout With Enlarged Placeholder
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Solution Overview
Problem
Conventional backside contact and placeholder fabrication techniques result in reduced backside contact size due to placeholder trimming during substrate removal, posing challenges for nanosheet transistor structures.
Innovation Solution
The semiconductor structure incorporates a backside contact structure with a faceted profile, an enlarged placeholder directly beneath a source drain region, and a dielectric liner surrounding the bottom portion of the placeholder, enabling enhanced backside contact size and effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional backside contact and placeholder fabrication techniques are used, then the manufacturing process is simple, but the backside contact size is reduced
Solution Approach 1:
The placeholder is enlarged before substrate removal to compensate for the trimming that occurs during the process. By performing the enlargement action in advance, the final backside contact size is maintained at the desired dimension despite the subsequent trimming operation.
Solution Approach 2:
The placeholder is intentionally enlarged beyond the desired final contact size to counteract the harmful effect of trimming during substrate removal. This preliminary over-sizing acts as a compensation mechanism that ensures the final contact dimensions meet specifications.
2Productivity
If placeholder trimming is performed during substrate removal, then the substrate removal process is completed, but the backside contact size is reduced
Solution Approach 1:
The placeholder enlargement is performed as a preliminary step before substrate removal and trimming. This ensures that even after the trimming operation completes the substrate removal process, the backside contact retains adequate size.
Solution Approach 2:
The placeholder dimensions are changed (enlarged) to a specific parameter value that compensates for the expected trimming loss. This parameter adjustment ensures the final contact size meets requirements after the substrate removal process completes.
3Reliability
If backside contact size is increased, then resistance is reduced and performance is improved, but the device footprint increases
Solution Approach 1:
The backside contact structure utilizes the vertical dimension by extending beneath the gates, rather than only expanding in the lateral plane. This dimensional transition allows increased contact area and reduced resistance without proportionally increasing the device footprint.
Solution Approach 2:
The backside contact structure is nested beneath the gates and extends into the vertical space under the channel region. This nesting arrangement allows the contact to occupy space that would otherwise be unused, improving electrical performance without increasing the planar footprint.
Data Source
AI summary
A nanosheet semiconductor structure including a backside contact structure, where the backside contact structure has a faceted profile extending beneath one or more gates, a placeholder adjacent to the backside contact structure and directly beneath a source drain region, and a dielectric liner surrounding a bottom portion of the placeholder.