Self-Aligned SRAM Contact Process Window Expansion
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Solution Overview
Problem
The scaling down of semiconductor devices has resulted in a smaller contact process window, leading to restrictive processing and design issues, such as poor device performance due to minimum spacing requirements between contact openings and device features, causing contact/gate structure short and open issues.
Innovation Solution
A method incorporating a selective etch back process and protective layer formation to enlarge the contact module process window, reducing the space between contacts and gates, allowing for zero spacing and eliminating performance issues like shorting, while significantly reducing semiconductor device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device geometry is scaled down to increase functional density, then production efficiency and cost are improved, but contact process window decreases leading to manufacturing precision issues
Solution Approach 1:
The method performs preliminary actions by forming a mandrel structure and spacer before contact opening formation. The spacer is deposited and patterned to define the contact opening location with high precision, enabling self-aligned contact formation that eliminates overlay errors and enlarges the contact process window despite scaled-down dimensions
Solution Approach 2:
The patent introduces intermediate structures (mandrel and spacer) as mediators between the gate structure and contact openings. The spacer acts as a self-aligned mask that precisely defines contact opening positions, serving as an intermediary element that enables accurate contact formation without requiring tight overlay control between separate lithography steps
2Reliability
If minimum spacing between contact openings and gate structures is enforced, then device reliability is improved, but design flexibility and functional density decrease
Solution Approach 1:
The method employs self-aligned contact formation where the spacer automatically positions the contact opening relative to the gate structure. This self-service mechanism ensures precise spatial relationship control without requiring external alignment procedures, enabling contact openings to be formed at optimal positions that maintain reliability while maximizing design flexibility
Solution Approach 2:
The patent transitions from planar alignment control to three-dimensional self-aligned formation. By using vertical spacer deposition and patterned etching, the contact position is determined by the spacer thickness and pattern rather than lateral overlay, adding a vertical dimension to the alignment process that enables precise control while improving design adaptability
3Volume of moving object
If contact-gate structure spacing is reduced to zero, then device size is minimized, but shorting and open issues occur reducing reliability
Solution Approach 1:
The spacer serves as a protective intermediary between the contact opening and gate structure during fabrication. It prevents direct contact between potentially damaging processes and the gate structure, acting as a buffer that enables zero spacing while preventing shorting and open issues that would otherwise occur
Solution Approach 2:
The method applies beforehand cushioning by forming the spacer structure prior to contact opening formation. This pre-formed protective layer cushions the gate structure against potential damage during subsequent processing steps, enabling aggressive spacing reduction while maintaining structural integrity and preventing reliability issues
Data Source
AI summary
A method for fabricating an integrated circuit providing an enlarged contact process window while reducing device size is disclosed. The method comprises providing a substrate including a first region and a second region, the first and second regions having one or more gate structures including a dummy gate layer; removing the dummy gate layer from at least one of the one or more gate structures in the first and second regions to form one or more trenches in the first and second regions; filling the one or more trenches in the first and second regions with a conductive layer; selectively etching back the conductive layer of the one or more gate structures in the second region of the substrate; forming a protective layer over the etched back conductive layer of the one or more gate structures in the second region; and forming one or more contact openings in the first and second regions.