Inverted Damascene Interconnects for Overlay Accuracy
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Solution Overview
Problem
The existing damascene processes for forming back-end-of-line (BEOL) interconnect structures face challenges in accurately overlaying patterns for trenches and via openings as device dimensions shrink, leading to inaccuracies in interconnect formation.
Innovation Solution
A method involving the formation of a mandrel, etch mask, and subsequent recessing to create conductive vias and lines that reproduce the mandrel's shape, allowing for accurate reproduction and removal to form an inverted damascene interconnect structure, which addresses the overlay issues by using selective etching and deposition techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional damascene processes are used to form interconnect structures, then the process can be implemented with standard fabrication techniques, but the overlay accuracy of trenches and via openings deteriorates as device dimensions shrink
Solution Approach 1:
The patent inverts the conventional damascene approach by forming conductive lines and vias simultaneously through a single etching process that patterns both features at once, eliminating the sequential patterning steps that cause overlay errors. Instead of forming trenches first then via openings, the method uses an inverted mandrel structure where both conductive features are created in one operation, directly resolving the overlay accuracy problem.
Solution Approach 2:
The patent segments the mandrel structure into different sections (first section for vias, second section for lines) that can be selectively recessed and filled. This segmentation allows independent optimization of via and line formation while maintaining precise spatial relationships, enabling accurate reproduction of both feature types without overlay errors.
2Productivity
If device dimensions are reduced to increase integration density, then the number of interconnects per chip increases, but the ability to accurately form and align interconnect features deteriorates
Solution Approach 1:
By inverting the conventional approach and forming both via openings and trenches simultaneously in a single etching step, the patent eliminates cumulative alignment errors that would otherwise accumulate with each additional patterning step. This enables continued scaling to higher integration densities while maintaining precise feature alignment.
Solution Approach 2:
The patent performs preliminary recessing of the mandrel structure before filling with conductive material, creating precise cavities that guide subsequent material deposition. This preliminary structuring ensures that even at reduced dimensions, the interconnect features are formed with accurate geometry and alignment.
3Manufacturing precision
If selective etching and deposition techniques are used to form accurate interconnect structures, then manufacturing precision improves, but process complexity increases
Solution Approach 1:
The patent merges the formation of via openings and trenches into a single etching operation, and combines the filling of both feature types in a unified deposition process. This consolidation reduces the number of separate process steps compared to conventional dual-damascene methods, thereby decreasing overall process complexity while maintaining high manufacturing precision.
Solution Approach 2:
The inverted mandrel structure serves multiple functions simultaneously: it defines both via and line patterns, provides self-alignment references, and creates the necessary cavities for conductive material filling. This multi-functionality reduces the need for additional specialized process steps.
Data Source
AI summary
Interconnect structures and methods of fabricating an interconnect structure. A first section of a mandrel is covered with a feature of an etch mask. A top surface of a second section of the mandrel is exposed by the feature of the etch mask and is recessed with an etching process. A conductive via is formed that reproduces a shape of the first section of the mandrel, and a conductive line is formed that reproduces a shape of the second section of the mandrel. The mandrel is removed to release the conductive via and the conductive line.