Asymmetric Via Hole Wiring Structure for Electromigration Resistance
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Solution Overview
Problem
Conventional multilayer wiring structures in semiconductor apparatuses suffer from reduced electromigration resistance due to uneven thickness of second layer wiring within via holes, leading to increased current density and potential disconnection.
Innovation Solution
A wiring structure with a first interlayer dielectric film having a recessed region and a second interlayer dielectric film with an increasing opening width towards the upper end, allowing for improved coverage and thickness of subsequent wiring layers, reducing the effects of shadowing and current density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the via hole has the same opening width from lower end to upper end, then the manufacturing process is simple, but the second layer wiring has small thickness in the vicinity of the inner side surface due to shadowing effects
Solution Approach 1:
The patent applies asymmetry by designing the via hole with different opening widths at different heights. Specifically, the opening width at the upper end is larger than at the lower end, creating an asymmetric tapered structure. This asymmetric geometry compensates for the shadowing effect during wiring deposition, ensuring more uniform wiring thickness coverage on the inner side surface of the via hole.
Solution Approach 2:
The patent implements local quality by varying the via hole geometry at different locations. The upper portion of the via hole has a larger opening width compared to the lower portion, creating location-specific geometric properties. This local variation in opening width is specifically designed to address the shadowing effect that occurs during wiring deposition on the inner side surface.
2Device complexity
If the second layer wiring has small thickness on the inner side surface of the via hole, then the via hole structure is simple, but the coverage by second layer wiring is reduced
Solution Approach 1:
The asymmetric via hole geometry with larger upper opening width improves wiring coverage by ensuring that the wiring material can adequately cover the inner side surface during deposition, while still maintaining a relatively simple overall via hole structure that integrates into the existing manufacturing process.
3Ease of manufacture
If the coverage of second layer wiring is reduced, then the manufacturing process is simplified, but the current density is increased
Solution Approach 1:
The asymmetric via hole design maintains manufacturing simplicity while improving wiring coverage and thickness uniformity, thereby reducing current density and improving electromigration resistance without complicating the overall manufacturing process.
4Device complexity
If the current density is increased due to reduced wiring thickness, then the via hole structure remains simple, but the temperature increases and disconnection may occur
Solution Approach 1:
The asymmetric via hole geometry reduces current density by improving wiring coverage and thickness uniformity, thereby lowering operating temperature and preventing disconnection, while maintaining a relatively simple via hole structure that does not require complex additional manufacturing steps.
Data Source
AI summary
A wiring structure includes a first wiring, a first interlayer dielectric film having a first opening, a second wiring formed with a first recess portion on a region corresponding to the first opening, a second interlayer dielectric film having a second opening and a third wiring so formed as to cover the second interlayer dielectric film, wherein an inner side surface of the second opening is arranged on a region corresponding to the first recess portion and formed such that an opening width of a portion in the vicinity of an upper end increases from a lower portion toward an upper portion.