Self-Aligned Top Vias for Metal Line End Resistance Scaling
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Solution Overview
Problem
Conventional subtractive patterning techniques for forming top vias over metal lines result in rounding at the ends, leading to increased resistance and reduced via size, which limits the scalability of interconnect designs.
Innovation Solution
The development of interconnect structures with top vias self-aligned to metal line ends using a metal fill or selective metal growth process, avoiding the issues of rounding and resistance by employing a dielectric fill material with curved sidewalls and trimming to enhance via size and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional subtractive patterning is used to form top vias over metal lines, then the via formation process is simple, but rounding occurs at the ends of metal lines leading to reduced via size and increased interconnect resistance
Solution Approach 1:
The patent inverts the conventional subtractive approach by using an additive process: forming a dielectric material over the metal line ends, then selectively removing portions to create vias. This reversal eliminates the rounding problem because the dielectric is deposited conformally before via formation, preserving sharp metal line endings and enabling precise via alignment.
Solution Approach 2:
The dielectric material is deposited in advance over the metal line structures before via formation. This preliminary deposition creates a protective layer that defines the via locations and prevents rounding during subsequent processing steps, ensuring precise via placement at metal line ends.
2Manufacturing precision
If the via location is moved in from the ends of metal lines to accommodate rounding, then the via size is maintained, but the distance between vias over adjacent metal lines cannot be scaled down
Solution Approach 1:
By inverting the process sequence and using additive dielectric formation followed by selective removal, the patent enables vias to be positioned exactly at metal line ends without rounding. This maintains maximum via size while allowing minimal spacing between vias on adjacent lines, thereby enabling continued interconnect scaling.
3Reliability
If top vias are formed at the ends of metal lines, then interconnect resistance is minimized, but conventional patterning causes rounding that reduces via size
Solution Approach 1:
The dielectric material is deposited conformally over the metal line structures before via formation. This preliminary step creates a protective layer that maintains sharp metal line endings and enables precise via placement at the ends, minimizing interconnect resistance while preserving via size through the additive process.
Solution Approach 2:
The patent reverses the conventional approach by using additive dielectric formation and selective removal instead of subtractive patterning. This inversion eliminates rounding at metal line ends, allowing vias to be formed precisely at line ends with optimal size, thereby minimizing interconnect resistance.
Data Source
AI summary
Interconnect structures having top vias self-aligned to metal line ends and techniques for formation thereof are provided. In one aspect, an interconnect structure includes: at least one metal line disposed on a substrate; at least one top via over the at least one metal line, wherein the at least one top via is aligned with an end of the at least one metal line, and wherein a sidewall of the at least one top via is curved. A dielectric fill material can be disposed adjacent to the at least one top via having sidewalls that are also curved. A method of fabricating an interconnect structure is also provided.