Cross-Coupled Contact Structure for SRAM Cell Reliability
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Solution Overview
Problem
The existing cross-coupled contact structures in semiconductor devices, such as SRAM cells, face challenges in maintaining robust and reliable connections between merged doped source/drain regions and conductive gate structures, which affects the stability and performance of memory devices due to limited surface area contact.
Innovation Solution
The proposed solution involves forming a cross-coupled contact structure with a first portion positioned within a contact trench laterally adjacent to and conductively coupled to the side surfaces and a second portion positioned vertically above the upper surface of the merged doped source/drain region, ensuring conductive coupling to the conductive gate structure, thereby increasing the contact area and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional contact structure is used to connect merged doped source/drain regions and conductive gate structures, then the device complexity is reduced, but the contact area is limited which worsens the reliability of charge storage and data retention
Solution Approach 1:
The contact structure transitions from a conventional planar contact to a multi-dimensional configuration by extending laterally along the side surfaces of the merged doped source/drain regions. This dimensional expansion increases the contact area without proportionally increasing device footprint, thereby improving reliability of charge storage and data retention.
Solution Approach 2:
The contact structure is positioned within a contact trench that is formed in the isolation structure, creating a nested configuration where the contact is embedded within the existing device architecture. This nesting approach increases contact area while maintaining compact device layout and avoiding additional lateral expansion.
2Reliability
If the contact structure is extended to increase contact area, then the reliability improves, but the manufacturing complexity increases due to additional contact trench formation
Solution Approach 1:
The contact trench is formed in the isolation structure before the final contact material deposition. This preliminary action allows the trench to be integrated into the existing fabrication sequence, and the contact structure to be formed in a single deposition step, reducing overall manufacturing complexity despite the enhanced contact configuration.
3Stability of the object's composition
If a larger contact area is formed by extending the contact structure laterally, then the stability enhances, but the manufacturing precision requirements increase for aligning the contact with side surfaces
Solution Approach 1:
The contact structure uses the isolation structure as an intermediary medium to achieve lateral extension along the side surfaces of the merged doped source/drain regions. The isolation structure provides a controlled interface that simplifies alignment, as the contact trench can be defined relative to the isolation structure rather than requiring direct alignment with the small features of the source/drain regions.
Data Source
AI summary
An IC product disclosed herein includes a first merged doped source/drain (MDSD) region having an upper surface, a first side surface and a second side surface that intersect one another at a corner of the first merged doped source/drain region, a second MDSD region and a contact trench in an isolation structure positioned between the first and second MDSD regions. The product also includes a conductive gate structure positioned above at least the second MDSD region and a cross-coupled contact structure that comprises a first portion positioned within the contact trench laterally adjacent to and conductively coupled to at least one of the first side surface and the second side surface, and a second portion that is positioned above and conductively coupled to the upper surface of the MDSD region, wherein the cross-coupled contact structure is conductively coupled to the conductive gate structure.