Continuous Slurry Mixing via Recirculation Loops
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Solution Overview
Problem
Conventional slurry manufacturing processes, both batch and continuous, fail to meet the stringent demands of producing CMP slurries with tight property specifications due to high variations, low throughput, and high production costs, especially as semiconductor wafers become more advanced with finer and more complex features.
Innovation Solution
An Advanced Continuous Process (ACP) that involves mixing multiple continuous material flows in a single mixing tank, eliminating in-line static or dynamic mixers, and using a recirculation loop to maintain a steady flow rate and quality control without interrupting the process, allowing for turbulent mixing and mechanical agitation to form a consistent chemical composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional batch process is used for slurry manufacturing, then equipment simplicity is maintained, but productivity is low and manufacturing precision is poor
Solution Approach 1:
The batch process is segmented into multiple continuous flow paths, each handling specific slurry components. Material tanks are divided into separate units for different chemicals and abrasives, with dedicated pumps and flow controllers for each stream. This segmentation enables parallel processing while maintaining precise control over each component's flow rate and mixing ratio.
Solution Approach 2:
Components are pre-prepared and held in separate material tanks before mixing. Each component undergoes preliminary filtration and flow stabilization through recirculation loops. This preliminary action ensures that when components are combined in the mixing chamber, they are already in optimal condition for consistent mixing, eliminating the need for lengthy batch preparation times.
2Manufacturing precision
If conventional continuous process with in-line mixers is used, then productivity increases, but manufacturing precision deteriorates due to high back pressures and flow control issues
Solution Approach 1:
A central mixing chamber serves as an intermediary between component storage tanks and the final product line. This chamber provides a controlled environment where all components converge and mix under optimized conditions, acting as a buffer that decouples the high-throughput requirement from the precise mixing requirement. The mixing chamber's design eliminates back pressure issues by providing adequate volume and optimized flow paths.
Solution Approach 2:
The system incorporates feedback control through flow sensors and controllers that monitor each component's flow rate in real-time. These sensors feed back to pump controllers, automatically adjusting flow rates to maintain precise mixing ratios. This closed-loop feedback ensures consistent slurry properties even when throughput requirements fluctuate, eliminating the property variations seen in conventional continuous processes.
3Manufacturing precision
If batch process with large tanks is used, then manufacturing precision can be achieved, but loss of time increases and productivity decreases
Solution Approach 1:
The system maintains continuous flow of all slurry components through the mixing chamber, eliminating the start-stop nature of batch processing. Pumps operate continuously, delivering components at controlled rates, and the mixing chamber continuously produces output slurry. This continuous operation eliminates idle times between batch additions and mixing operations, dramatically reducing total manufacturing time while maintaining precision through controlled flow rates.
Solution Approach 2:
Components are pre-prepared, filtered, and held in ready-to-use material tanks with recirculation systems that maintain component stability. This preliminary preparation eliminates time-consuming on-site mixing and filtration operations during the manufacturing process. When production is needed, pre-prepared components can be immediately pumped and mixed, reducing addition and mixing times while ensuring consistent quality.
4Manufacturing precision
If in-line static or dynamic mixers are used in continuous process, then productivity increases, but manufacturing precision worsens due to flow control issues
Solution Approach 1:
Multiple component streams are merged in a single, well-designed mixing chamber rather than using sequential in-line mixers. This consolidation simplifies the flow control system by reducing the number of mixing zones and interconnections. The unified mixing chamber provides a controlled environment where all components converge simultaneously, ensuring consistent chemical composition without the flow control complexities of multiple in-line mixing stages.
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 ACP process significantly reduces product variations, increases manufacturing efficiency and yields, and lowers costs by achieving high throughput and product consistency, with total lot-to-lot variations of less than 1% in weight, meeting the stringent requirements of advanced semiconductor node applications.
Implementation Method 1
The mixing process in the at least one mixing tank includes at least one mixing method selected from the group consisting of turbulent mixing of the material flows
Implementation Method 2
the mixing tank optionally includes a recirculation loop in fluid communication with the mixing tank
Data Source
AI summary
The disclosure features a system that includes a plurality of material tanks, each of which includes at least one material for forming a chemical composition and includes a first recirculation loop; at least one mixing tank in which the materials from the material tanks are mixed to form a chemical composition, the mixing tank including a second recirculation loop; and at least one holding tank configured to continuously receive the chemical composition from the mixing tank, the holding tank including a third recirculation loop. The system may further include a plurality of fluid flow controller units and be configured to form material and chemical composition flows in an in-process steady state.