Agitator Design for High Mass Transfer in Microfeature Processing
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Solution Overview
Problem
Existing paddle-type plating tools fail to achieve sufficient high velocity fluid flows at the surface of microfeature workpieces, leading to inadequate mass-transfer rates, non-uniform plating, and inefficiencies in processing, particularly in plating alloys and recessed features, while also occupying large footprints and struggling with bubble and particulate removal.
Innovation Solution
The development of agitators with dividers and intermediate sections that form moveable confinements to contain high-energy fluid flows, creating vortices and tangential flows, which enhance ion concentration and mixing uniformity across the workpiece surface, allowing for controlled high-velocity fluid flows and efficient processing in a compact footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If open-type paddle plating tools are used, then the structure is simple and easy to manufacture, but the flow velocities at the wafer surface are insufficient and mass transfer rate is limited
Solution Approach 1:
The paddle structure is segmented into multiple blades arranged in a circular pattern, with each blade contributing to fluid agitation. The segmentation allows for distributed flow generation across the wafer surface, improving mass transfer without requiring a single complex moving component
Solution Approach 2:
A stationary screen with apertures is introduced as an intermediary element between the rotating paddle and the wafer. The screen modulates the fluid flow generated by the paddle, creating controlled jet streams that impinge on the wafer surface. This intermediary structure enables high mass transfer rates while keeping the paddle design relatively simple
2Productivity
If paddle blades are positioned close to the wafer surface, then mass transfer rate increases, but bubbles and particulates become trapped under the workpiece
Solution Approach 1:
The paddle blades are designed with asymmetric geometry, having different heights or profiles on opposite sides. This asymmetry creates asymmetric flow patterns that generate both downward impinging jets for mass transfer and lateral flows that sweep bubbles and particulates away from trapped regions under the wafer
Solution Approach 2:
The paddle rotates continuously to maintain constant fluid agitation and flow generation. This continuous motion ensures that fresh processing solution is constantly delivered to the wafer surface while simultaneously preventing bubble and particulate accumulation through ongoing lateral flow sweeps
3Area of stationary object
If large footprint reactors are used, then sufficient processing space is available, but device complexity and operating costs increase
Solution Approach 1:
The system transitions from horizontal fluid flow generation to vertical jet stream generation. By directing fluid flow perpendicular to the wafer surface through the screen apertures, the system achieves effective processing in a compact vertical space, reducing the horizontal footprint while maintaining adequate processing volume
Solution Approach 2:
The system uses hydraulic principles to generate high-velocity fluid jets through the screen apertures. The rotating paddle creates pressure differentials that drive processing solution through the screen in controlled jets, achieving intense local mixing and mass transfer in a compact configuration without requiring large reactor volume
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 high-quality surfaces and efficient wet chemical processes by maintaining high mass-transfer rates, uniform plating, and effective bubble and particulate removal, while reducing the tool's footprint and operating costs.
Implementation Method 1
creating vortices and tangential flows, which enhance ion concentration and mixing uniformity across the workpiece surface
Implementation Method 2
The agitator is coupled to an actuator that moves the base and the features along the face of the workpiece in a manner that agitates the processing fluid at the surface of the workpiece
Implementation Method 3
A diffusion layer forms adjacent to a process surface of a workpiece... The thickness of the diffusion layer dictates the mass-transfer rate of components/reactants to the surface
Implementation Method 4
increase the relative velocity between the processing solution and the surface of the workpiece... flows that impinge upon the workpiece
Data Source
AI summary
Reactors with agitators and methods for processing microfeature workpieces with such reactors. The agitators are capable of obtaining high, controlled mass-transfer rates that result in high quality surfaces and efficient wet chemical processes. The agitators generate high flow velocities in the fluid and contain the high energy fluid proximate to the surface of the workpiece to form high quality surfaces when cleaning, etching and/or depositing materials to/from a workpiece. The agitators also have short stroke lengths so that the footprints of the reactors are relatively small. As a result, the reactors are efficient and cost effective to operate. The agitators are also designed so that electrical fields in the processing solution can effectively operate at the surface of the workpiece.