Asymmetric Source/Drain Layout for Backside Source Contact Alignment
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Solution Overview
Problem
As technology nodes shrink, accurately aligning backside source contacts in semiconductor devices becomes increasingly difficult, leading to performance degradation and fabrication challenges in field-effect transistors.
Innovation Solution
The formation of asymmetric source and drain structures is achieved by extending the recess for the source structure deeper into the substrate, forming a dummy source contact, and then replacing it with a real contact, improving alignment and electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If technology nodes are shrunk to increase functional density, then production efficiency and cost are improved, but manufacturing precision and alignment accuracy deteriorate
Solution Approach 1:
The patent applies preliminary action by forming a dummy source contact region before the actual source contact formation. This dummy region serves as a placeholder that guides subsequent alignment processes, ensuring that when the real source contact is formed, it can be accurately aligned to the channel structure despite the challenges of scaled dimensions. The dummy contact is formed in advance to establish a reference point for precise alignment.
Solution Approach 2:
The dummy source contact region acts as an intermediary element between the patterning process and the final contact formation. It mediates the alignment process by providing a visible and measurable reference structure that facilitates precise positioning of the source contact relative to the channel, thereby resolving the alignment accuracy issue at scaled technology nodes.
2Reliability
If asymmetric source and drain structures are formed with extended source recess, then alignment and electrical connectivity are improved, but device complexity increases
Solution Approach 1:
The patent directly applies asymmetry by forming an asymmetric source and drain structure where the source region has an extended recess compared to the drain region. This asymmetric configuration allows the source contact to be formed deeper, improving electrical connectivity and alignment with the channel structure. The asymmetry is strategically designed to optimize contact resistance and alignment without requiring complex additional structures.
Solution Approach 2:
The extended source recess represents a local modification to the otherwise symmetric source-drain structure. By concentrating the structural variation in the source region only, where it is most needed for alignment and connectivity, the patent achieves improved electrical properties without unnecessarily complicating the entire device structure. The drain region maintains its standard configuration.
Data Source
AI summary
A semiconductor structure includes a dielectric layer, a backside contact feature embedded in the dielectric layer, a semiconductor layer disposed over the dielectric layer, a first source/drain feature disposed on a top surface of the backside contact feature and adjacent to the semiconductor layer, a second source/drain feature disposed over the semiconductor layer, a channel member disposed between the first source/drain feature and the second source/drain feature, and a gate structure disposed over the channel member.