Substrate Etching Bath Concentration Control via Liquid Level Feedback
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Solution Overview
Problem
Existing substrate processing apparatuses face challenges in maintaining precise concentration control of etching solutions, such as phosphoric acid aqueous solutions, due to evaporation and concentration changes, which can lead to inconsistent processing results.
Innovation Solution
A substrate processing apparatus with a dual tub system, a concentration measurement and adjustment mechanism that uses a controller to calculate and adjust the liquid surface height based on concentration differences, and an adjusting liquid supply to maintain or change the concentration of the etching solution by controlling the supply of water, ensuring precise concentration control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water is supplied to compensate for evaporation, then the concentration of the etching solution can be maintained, but the liquid surface height becomes difficult to control precisely
Solution Approach 1:
The system employs a feedback control mechanism where the liquid surface height sensor continuously monitors the liquid level in the processing tub and sends signals to the water supply unit. This closed-loop feedback ensures that water is supplied only when the liquid surface height deviates from the target level, preventing over-supply while maintaining concentration through evaporation compensation.
Solution Approach 2:
The liquid surface height sensor acts as an intermediary between the water supply unit and the concentration maintenance goal. By measuring and reporting the actual liquid level, this intermediary enables precise control of water supply, ensuring that concentration is maintained without compromising liquid surface height accuracy.
2Adaptability or versatility
If the concentration of the etching solution is changed, then the processing characteristics can be adjusted, but the liquid surface height becomes unstable
Solution Approach 1:
The system performs preliminary action by calculating the required water supply amount based on the desired concentration change before actually supplying water. The controller determines the precise volume needed to achieve the target concentration and supplies exactly that amount, preventing liquid surface height instability that would result from arbitrary or excessive water addition.
Solution Approach 2:
The water supply system operates dynamically by continuously monitoring both liquid surface height and concentration, and adjusting the water supply rate accordingly. During concentration changes, the system adapts the supply rate to maintain liquid surface height stability while achieving the desired concentration adjustment, demonstrating dynamic control rather than static operation.
3Device complexity
If evaporation is allowed to occur, then the concentration control can be simplified, but the processing consistency deteriorates
Solution Approach 1:
The system uses feedback control where a concentration sensor continuously monitors the etching solution concentration and sends signals to the water supply unit. This real-time feedback ensures that water is supplied to compensate for evaporation losses, maintaining consistent concentration and thus processing consistency, while the control logic remains relatively simple.
Solution Approach 2:
The system implements self-service by automatically detecting concentration changes due to evaporation and supplying the appropriate amount of water without manual intervention. The concentration sensor and controller work together to self-regulate the water supply, maintaining processing consistency while keeping the operation simple and automated.
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 allows for accurate and stable maintenance or adjustment of etching solution concentrations, ensuring consistent processing results and extending the lifespan of the etching solution by minimizing evaporation-related concentration fluctuations.
Implementation Method 1
a processing liquid in which a substrate is immersed to be processed, the processing liquid including a first component and a second component having a boiling point higher than a boiling point of the first component
Data Source
AI summary
A substrate processing apparatus includes a processing tub configured to store therein a processing liquid in which a substrate is immersed to be processed, the processing liquid including a first component and a second component having a boiling point higher than that of the first component; an adjusting liquid supply configured to supply an adjusting liquid configured to adjust a concentration of the second component into the processing tub, the adjusting liquid including the first component; and a controller configured to control the adjusting liquid supply. When changing the concentration, the controller calculates a liquid surface height in the processing tub corresponding to the concentration after being changed based on a concentration difference between the concentration after being changed and the concentration before being changed, and the controller controls a supply of the adjusting liquid into the processing tub based on the calculated liquid surface height.