BEOL Interconnect Aspect Ratio Variation for Cobalt Resistance
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Solution Overview
Problem
As semiconductor devices continue to scale, the conductivity of copper (Cu) in back-end-of-line (BEOL) interconnect structures decreases, leading to performance penalties when alternative materials like cobalt (Co) are used for wide lines, due to high resistance and capacitance issues.
Innovation Solution
The technique involves selectively increasing the aspect ratio of wide BEOL interconnect structures by varying their height while maintaining the aspect ratio of narrow lines, using a dual damascene structure or subtractive etching process, to minimize the impact on overall device performance without altering the width of power rails or other interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alternative materials like cobalt are used for wide BEOL interconnect structures, then the conductivity issue of copper at scaled dimensions is addressed, but resistance and capacitance increase leading to performance penalties
Solution Approach 1:
The patent applies different aspect ratios to different interconnect structures based on their width. Narrow interconnect structures maintain a first aspect ratio while wide interconnect structures use a second, different aspect ratio. This local differentiation optimizes each structure's electrical properties according to its specific dimensions, addressing the conductivity-resistance-c capacitance tradeoff without uniformly affecting all interconnects.
Solution Approach 2:
The invention changes the aspect ratio parameter of wide interconnect structures relative to narrow ones. By varying the height-to-width ratio specifically for wide structures while maintaining it for narrow structures, the patent optimizes electrical performance parameters (resistance and capacitance) for each category, thereby reducing the overall performance penalty of using alternative materials like cobalt.
2Reliability
If the aspect ratio of wide BEOL interconnect structures is increased, then the performance penalty from using cobalt is reduced, but the height of the interconnect structures must be varied which complicates the manufacturing process
Solution Approach 1:
The patent implements local quality by assigning different aspect ratios to different regions of the interconnect layer based on width criteria. Narrow interconnect structures receive one aspect ratio while wide structures receive another, allowing performance optimization without requiring complex variable geometry processing across the entire wafer.
Solution Approach 2:
The manufacturing approach segments interconnect structures into narrow and wide categories, each processed with appropriate aspect ratio specifications. This segmentation allows the complex performance optimization to be applied selectively rather than uniformly, simplifying the overall manufacturing process while achieving the desired performance benefits.
3Reliability
If narrow interconnect structures maintain their original aspect ratio, then their electrical performance is preserved, but wide interconnect structures require different aspect ratios to minimize resistance impact
Solution Approach 1:
The patent applies the local quality principle by specifying that narrow interconnect structures maintain a first aspect ratio while wide interconnect structures use a second aspect ratio. This localized differentiation ensures that narrow structures preserve their optimized electrical performance while wide structures independently optimize for reduced resistance through their different aspect ratio configuration.
Data Source
AI summary
A semiconductor structure includes an interlayer dielectric layer, a first set of back-end-of-line interconnect structures disposed in the interlayer dielectric layer, and a second set of back-end-of-line interconnect structures at least partially disposed in the interlayer dielectric layer. Each of the first set of back-end-of-line interconnect structures has a first width and a first height providing a first aspect ratio. Each of the second set of back-end-of-line interconnect structures has a second width and a second height providing a second aspect ratio different than the first aspect ratio. The second width is greater than the first width, and the second height is different than the first height.