CMP Slurry Supply Control for Freshness and Waste Reduction
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Solution Overview
Problem
The challenge of slurry freshness control in chemical mechanical polishing (CMP) processes is critical due to the impact of aged polishing slurry on removal rate and production efficiency, leading to waste and increased costs when slurry is discarded before reaching optimal quality.
Innovation Solution
Implementing continuous liquid level gauges and weight scales in supply and buffer tanks to adjust the refill level and mix-in amount of fresh polishing slurry in real-time, using data from wafer production levels to optimize slurry freshness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If polishing slurry is stored in supply tanks for extended periods, then production efficiency is improved by maintaining continuous supply, but slurry quality deteriorates due to aging leading to increased waste
Solution Approach 1:
The system dynamically adjusts the refill level and mix-in volume of fresh polishing slurry based on real-time data from liquid level sensors and weight scales. The controller continuously monitors slurry age and production consumption rates, adapting the replenishment strategy to optimize both continuous supply and slurry freshness, thereby reducing waste from premature discarding of aged slurry.
Solution Approach 2:
The system implements feedback control by continuously monitoring slurry level, weight, and age through sensors, then using this data to adjust the refill level and mix-in volume. This closed-loop control ensures that fresh slurry is added at optimal times and in optimal amounts, maintaining slurry quality while ensuring continuous production supply.
2Measurement precision
If real-time monitoring of slurry level and weight is implemented, then slurry quality control is improved, but device complexity increases due to additional sensors and control systems
Solution Approach 1:
The control system integrates multiple functions into a single controller that manages liquid level monitoring, weight measurement, slurry age tracking, and refill level adjustment. This multi-functional approach reduces overall system complexity by consolidating control operations rather than requiring separate dedicated systems for each function.
Solution Approach 2:
The system performs self-monitoring and self-adjustment through automated sensors and control algorithms that continuously track slurry conditions and modify refill parameters without human intervention. This automation reduces operational complexity while maintaining precise measurement and control of slurry quality parameters.
3Productivity
If the refill level is increased to ensure sufficient slurry supply, then production continuity is improved, but the amount of aged slurry in the tank increases leading to quality degradation
Solution Approach 1:
The system dynamically adjusts the refill level based on real-time monitoring of slurry age, consumption rate, and tank contents. Rather than using a fixed refill level, the controller adapts the refill parameters to balance maintaining sufficient slurry volume for continuous production with preserving slurry quality by avoiding excessive accumulation of aged slurry.
Solution Approach 2:
The system performs preliminary monitoring and calculation of slurry age and consumption patterns to predict when refilling is needed and how much fresh slurry should be added. This proactive approach allows the system to maintain optimal slurry composition by planning refills before quality degradation occurs, ensuring both continuous production and slurry freshness.
Data Source
AI summary
A method is provided. The method includes: determining a forecasted slurry consumption value; determining a refill line associated with the forecasted slurry consumption value; determining a mix-in volume associated with the forecasted slurry consumption value; and operating a supply tank containing polishing slurry, the operating being according to the refill line and the mix-in volume. The operating includes: determining whether liquid level of the polishing slurry is below the refill line by a continuous liquid level sensor assembly mounted on the supply tank; in response to the liquid level of the polishing slurry being below the refill line, adding the mix-in volume of fresh polishing slurry to the supply tank; and supplying the polishing slurry to a polishing apparatus that is operable to polish a surface of a semiconductor wafer.