Backside Source/Drain Contacts With Sacrificial Gate Protection
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Solution Overview
Problem
Existing semiconductor devices face challenges in forming backside source/drain contacts with precise alignment, as they are prone to damage due to overlay shifts during photolithographic processes, which can result in unintended contact with gate electrodes or spacers, limiting their tolerance for overlay errors.
Innovation Solution
The implementation of sacrificial dielectric structures on gate regions or metal gate electrodes that protect the gate areas during the formation of backside source/drain contacts, allowing for a self-aligned and enlarged patterning window that can accommodate overlay shifts, ensuring the contacts land on epitaxial source/region regions even if the patterning window is slightly misaligned.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If backside source/drain contacts are formed without sacrificial dielectric structures, then the manufacturing process is simpler, but the contacts are prone to damage from overlay shifts during photolithographic processes
Solution Approach 1:
A sacrificial dielectric structure is introduced as an intermediary element between the gate electrode and the backside source/drain contact formation process. This sacrificial layer acts as a protective mediator that absorbs the impact of overlay shifts, preventing direct damage to the gate electrode while allowing the contact to be formed. The sacrificial dielectric is temporarily present during the critical alignment process and is subsequently removed, having served its protective function.
Solution Approach 2:
The sacrificial dielectric structure is deposited beforehand on the gate electrode to create a protective cushion layer before the backside source/drain contact formation process begins. This pre-established protective layer compensates for potential alignment errors by providing a buffer zone that prevents the contact opening from directly exposing or damaging the gate electrode, thereby cushioning against the harmful effects of overlay shifts.
2Manufacturing precision
If the patterning window is enlarged to accommodate overlay shifts, then the tolerance for overlay errors increases, but the risk of unintended contact with gate electrodes or spacers increases
Solution Approach 1:
The sacrificial dielectric structure serves as an intermediary protective layer that allows the patterning window to be enlarged for better overlay tolerance. By having this protective layer in place, the process can use a larger, less precise patterning window without risking direct contact between the backside source/drain contact and the gate electrode, as the sacrificial dielectric prevents such harmful interactions.
Solution Approach 2:
The sacrificial dielectric structure functions as a thin film protective shell that covers the gate electrode during the contact formation process. This flexible protective film allows for variations in alignment (enlarged patterning window) while maintaining protection of the underlying gate structure, effectively decoupling the precision requirements of the patterning process from the actual alignment accuracy.
3Reliability
If sacrificial dielectric structures are used to protect gate regions, then damage to gate structures is prevented, but the device complexity increases
Solution Approach 1:
The sacrificial dielectric structure is a temporary, disposable protective element that is deposited, serves its protective function during the critical contact formation process, and then completely removed afterward. This discard-and-recover approach allows the system to gain the benefits of protection and relaxed alignment tolerances without permanently incorporating the additional structural complexity into the final device.
Solution Approach 2:
The sacrificial dielectric structure is a low-cost, temporary protective layer that is intentionally designed to be short-lived - present only during the specific manufacturing step where protection is needed. This disposable protective layer provides essential gate protection and enables relaxed alignment tolerances, but is subsequently removed so that it does not add permanent complexity to the device structure.
Data Source
AI summary
A device includes semiconductor device structure includes a first dielectric layer. A first plurality of nanostructures are disposed on the first dielectric layer, with the first plurality of nanostructures overlying one another. A first source/drain region is disposed laterally adjacent to a first side of the first plurality of nanostructures. A second dielectric layer is on a first side of the first source/drain region. A front side source/drain contact is disposed on a second side of the first source/drain region that is opposite the first side, and a backside source/drain contact is disposed on the first side of the first source/drain region. The backside source/drain contact extends through the second dielectric layer.