Semiconductor Contact Structure With Air Gap for Overlay-Limited Scaling
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Solution Overview
Problem
The aggressive scaling of semiconductor IC dimensions leads to densely spaced gate structures and source/drain contacts, posing challenges in forming accurate gate contacts and source/drain contact vias due to high overlay precision requirements, which can result in electrical shorts and increased parasitic capacitance.
Innovation Solution
The method involves forming a contact structure with a reduced thickness spacer structure to create sufficient space between adjacent gate structures, allowing for the formation of an air gap between the contact and the gate, which reduces parasitic capacitance while maintaining control over the contact structure profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gate structures and source/drain contacts are densely packed to improve production efficiency and lower costs, then productivity increases, but manufacturing precision requirements increase due to high overlay precision needs to avoid electrical shorts and leakage
Solution Approach 1:
The patent introduces a mandrel structure as an intermediary element between the gate structure and the contact opening. This mandrel serves as a sacrificial placeholder that defines the contact opening position and dimensions, acting as a mediator that simplifies the patterning process and reduces overlay precision requirements while enabling dense packing of gate structures and source/drain contacts
Solution Approach 2:
The patent performs preliminary actions by forming the mandrel structure and spacer layers before defining the final contact openings. The mandrel is formed as a preliminary structure that guides subsequent etching processes, allowing the contact openings to be precisely defined relative to the gate structure without requiring high overlay precision in later alignment-critical steps
2Device complexity
If conventional contact formation techniques are used in densely packed structures, then manufacturing process remains simple, but parasitic capacitance increases and electrical shorts occur due to misalignment
Solution Approach 1:
The mandrel structure acts as an intermediary that enables precise contact opening formation in densely packed structures. By using the mandrel as a template, the method achieves reliable electrical isolation and proper contact alignment without significantly increasing manufacturing process complexity, thus improving reliability while maintaining process simplicity
Solution Approach 2:
The patent extracts the alignment-critical function from the final contact opening step by using the mandrel structure to pre-establish the correct geometry and position. This separation of functions allows the contact opening etch to proceed with standard precision while the mandrel ensures proper alignment, reducing parasitic capacitance and preventing electrical shorts
Data Source
AI summary
Methods and devices including an air gap adjacent a contact element extending to a source/drain feature of a device are described. Some embodiments of the method include depositing a dummy layer, which is subsequently removed to form the air gap. The dummy layer and subsequent air gap may be formed after a SAC dielectric layer such as silicon nitride is formed over an adjacent metal gate structure.