Segmented Contact Ring for Electroplating Current Stability
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Solution Overview
Problem
As microelectronic devices become smaller, existing electrical contacts in electro-processing systems fail to meet the increased performance specifications, leading to issues with current path variations and heating during electroplating or electropolishing processes.
Innovation Solution
A contact ring assembly with multiple contact fingers on a ring base, clamped in place by a shield ring, which allows for precise positioning and high-density contact points, reducing current path variations and heating by providing a large number of contacts and using a shield to minimize metal deposition on the fingers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrical contacts are used, then the device structure is simple, but current path variations and heating occur during electroplating
Solution Approach 1:
The contact ring is segmented into multiple discrete contact fingers (typically 16-32 fingers) distributed around the ring circumference. Each finger is an independent conductive element that can be individually positioned and adjusted. This segmentation allows the current to be distributed across multiple parallel paths, reducing current density at any single point and eliminating hot spots while maintaining overall current path stability.
Solution Approach 2:
The contact fingers are nested within a ring structure that provides both mechanical support and electrical connection. The fingers are positioned radially inward from the ring outer circumference, with their bases attached to the ring inner circumference. This nested arrangement allows the contact fingers to be integrated into the ring structure while maintaining their individual functionality, achieving both simplicity and reliability.
2Manufacturing precision
If more contact fingers are added to reduce current path variations, then current distribution improves, but manufacturing complexity increases
Solution Approach 1:
Multiple contact fingers are combined into a single ring assembly where all fingers share common mounting features and alignment references. The ring structure provides a unified base with pre-formed attachment points, holes, and alignment features that simplify the manufacturing of individual fingers. This merging approach allows standardized fabrication processes to be applied to the entire contact assembly, improving precision while maintaining ease of manufacture.
Solution Approach 2:
The contact ring assembly is designed with universal features that serve multiple functions: the ring structure provides mechanical support, electrical connection, alignment reference, and mounting interface simultaneously. The contact fingers serve both as electrical contacts and as positioning elements for the workpiece. This multi-functionality reduces the number of separate components needed, simplifying manufacturing while achieving precise contact positioning.
3Duration of action of stationary object
If contact fingers are made of precious metal for extended life, then contact durability improves, but cost increases
Solution Approach 1:
Precious metal material is applied selectively only to the contact surfaces and critical wear areas of the contact fingers, rather than using it for the entire finger structure. The bases and non-contact portions of the fingers can be made from less expensive materials. This local application of precious metal extends contact life at the critical interfaces while significantly reducing overall material cost and precious metal consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables improved electrical contact performance by reducing current path variations and heating, allowing for uniform plating on thin seed layers and extending the contact life of precious metal fingers, while simplifying manufacturing and maintenance.
Implementation Method 1
A shield ring may be attached to the ring base, to clamp the contact fingers in place, and/or to provide an electric field shield over at least part of the contact fingers
Data Source
AI summary
An electro-processing apparatus includes a rotor in a head, and a contact ring assembly on the rotor. The contact ring assembly may have one or more strips of contact fingers on a ring base, with contact fingers clamped into position on the ring base. The strips may have spaced apart projection openings, with the projections on the ring base extending into or through the projection openings. A shield ring may be attached to the ring base, to clamp the contact fingers in place, and/or to provide an electric field shield over at least part of the contact fingers. The contact fingers may be provided as a plurality of adjoining forks, with substantially each fork including at least two contact fingers.