Cross Flow Conduit for Foam Prevention in Plating Cells
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Solution Overview
Problem
Existing electrochemical deposition processes face challenges in controlling electrolyte hydrodynamics, particularly in large feature size and high aspect ratio applications such as wafer level packaging and through silicon via technologies, leading to non-uniform plating and inefficiencies.
Innovation Solution
The development of an electroplating apparatus that includes a channeled ionically resistive plate with a cross flow region and a cross flow conduit, which creates a shear flow of electrolyte across the substrate, modulated by a flow restrictor to enhance plating uniformity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electroplating is used without cross flow control, then the process is simple, but plating uniformity is poor and air entrainment occurs
Solution Approach 1:
The electrolyte flow path is segmented into distinct regions: a cross-flow region for uniform distribution across the substrate, and a downward flow region for foam prevention. The channeled ionically resistive plate divides the cell into these functional zones, directing electrolyte laterally across the substrate before routing it downward through the cross-flow conduit, thereby achieving uniform plating without complex external control systems
Solution Approach 2:
The cross-flow conduit acts as an intermediary structure that receives electrolyte from the cross-flow region and redirects it downward below the fluid level. This intermediary component prevents direct air-electrolyte interaction at the outlet, eliminating foam generation and air entrainment while maintaining the beneficial cross-flow plating uniformity
2Productivity
If high convection is used to improve plating rate, then productivity increases, but foam generation and air entrainment worsen
Solution Approach 1:
The electrolyte outlet is positioned in a different spatial dimension - below the fluid level rather than at or above it. The cross-flow conduit routes electrolyte downward into the submerged region, changing the exit dimension from the air-electrolyte interface plane to a submerged depth, thereby enabling high convection rates for productivity while preventing foam and air entrainment
3Manufacturing precision
If electrolyte flows directly over the substrate without cross flow, then the system is simpler, but plating uniformity deteriorates
Solution Approach 1:
The channeled ionically resistive plate and cross-flow conduit structure enables the electrolyte to self-distribute uniformly across the substrate through the cross-flow region. The geometry of the channels and the hydrodynamics of the flowing electrolyte work together to automatically achieve uniform distribution without requiring external pumps, valves, or complex control mechanisms
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
This solution achieves highly uniform plating layers by controlling electrolyte hydrodynamics, improving filling capabilities for features with varying depths and widths, and reducing foam generation and air entrainment, thereby enhancing plating throughput and quality.
Implementation Method 1
controlling electrolyte hydrodynamics during electroplating
Implementation Method 2
creates a shear flow of electrolyte across the substrate
Implementation Method 3
Electrochemical deposition processes are well-established in modern integrated circuit fabrication
Data Source
AI summary
The embodiments herein relate to apparatuses and methods for electroplating one or more materials onto a substrate. Embodiments herein utilize a cross flow conduit in the electroplating cell to divert flow of fluid from a region between a substrate and a channeled ionically resistive plate positioned near the substrate down to a level lower than level of fluid in a fluid containment unit for collecting overflow fluid from the plating system for recirculation. The cross flow conduit can include channels cut into components of the plating cell to allow diverted flow, or can include an attachable diversion device mountable to an existing plating cell to divert flow downwards to the fluid containment unit. Embodiments also include a flow restrictor which may be a plate or a pressure relief valve for modulating flow of fluid in the cross flow conduit during plating.