Backside Source/Drain Contact Layout for Gate-Safe Alignment
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Solution Overview
Problem
Existing semiconductor devices face challenges in forming backside source/drain contacts without damaging gate electrodes due to overlay shifts during photolithographic processes, leading to potential damage to underlying structures.
Innovation Solution
Incorporation of sacrificial dielectric structures on gate regions or metal gate electrodes that protect the gate regions during the formation of backside source/drain contacts, allowing for self-aligned contact formation even with patterning window shifts, and enabling the contacts to fully land on epitaxial source/drain regions.
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 gate electrodes may be damaged due to overlay shifts during photolithographic processes
Solution Approach 1:
A sacrificial dielectric structure is introduced as an intermediary element between the gate electrode and the etching process. This mediator absorbs the impact of overlay shifts by providing a buffer layer that prevents direct contact between the etchant and the gate electrode, thus protecting the gate while enabling contact formation.
Solution Approach 2:
The sacrificial dielectric structure is formed in advance before the backside source/drain contact formation process. This preliminary action prepares the structure to accommodate potential overlay shifts during subsequent photolithographic steps, ensuring gate electrode protection is already in place before damage can occur.
2Reliability
If sacrificial dielectric structures are used to protect gate regions, then gate electrode damage is prevented, but the device structure becomes more complex
Solution Approach 1:
The sacrificial dielectric structure serves as a temporary element that is discarded after fulfilling its protective function. It is removed after the backside source/drain contacts are successfully formed, leaving no permanent trace in the final device. This approach adds complexity only during the manufacturing process, not in the final product.
Solution Approach 2:
The sacrificial dielectric structure is designed as a disposable, low-cost component that exists only temporarily during fabrication. Its temporary presence enables complex protective functionality during manufacturing, but it is completely removed before the device is finalized, so the complexity does not persist in the end product.
3Manufacturing precision
If patterning windows are enlarged to tolerate overlay shifts, then manufacturing precision is improved, but the risk of damaging underlying structures increases
Solution Approach 1:
The sacrificial dielectric structure acts as a pre-positioned cushioning layer that absorbs the harmful effects of overlay shifts. By placing this protective buffer beforehand, the structure can tolerate larger patterning window variations without transmitting damage to the gate electrode or other underlying sensitive structures.
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.