In precision industries such as semiconductor manufacturing and microelectronics processing, etching and cleaning are core process steps. The accurate control of chemical solution levels directly determines product yield and process stability. Etching/cleaning machines frequently handle highly corrosive chemicals like hydrofluoric acid and concentrated sulfuric acid, operating under complex conditions involving high temperatures, turbulence, and crystallization. Standard liquid level measurement devices are prone to corrosion and inaccuracies, making specialized level sensors a critical support for ensuring efficient process operation. Their performance and selection directly impact production safety and product quality.
The core requirements for liquid level measurement in etching/cleaning machines are corrosion resistance, high precision, and high stability. For different operating conditions, mainstream sensor types have their respective suitable applications. The static pressure liquid level sensor is widely used due to its simple structure and lack of moving parts. Based on the proportional relationship between hydrostatic pressure and liquid level height, it employs corrosion-resistant materials such as PTFE and PFA, paired with a ceramic piezoresistive core, enabling it to withstand highly corrosive media like 49% hydrofluoric acid. Within a small range of 0-1mH₂O, it achieves a precision of 0.25%FS, allowing precise control of chemical solution ratios and meeting the depth requirements of semiconductor tanks from 200mm to 600mm.
The magnetic flap level gauge is more suitable for etching/cleaning scenarios with high cleanliness requirements. Its main body uses electrolytically polished 316L EP tubes, and the float is made of smooth, pore-free PFA material. Assembled in an ISO Class 4 cleanroom, it avoids secondary contamination such as metal ion shedding and sealant exudates. Additionally, it achieves local and remote level indication through magnetic coupling principles. Some models can be linked to laser particle counters to monitor real-time solution particle size, helping improve wafer yield rates.
Non-contact sensors provide effective solutions for extreme operating conditions. Ultrasonic level gauges eliminate the need for contact with the liquid, avoiding damage to the core caused by high temperatures and strong corrosion, making them suitable for scenarios with intense turbulence or high temperatures (＞130°C) in the tank. Laser level gauges, with their exceptional precision, are ideal for liquid level measurement in confined spaces, but their performance can be affected by steam or transparent liquids, necessitating careful selection based on the application scenario.
The proper selection and standardized application of sensors are crucial to their performance. During selection, priority should be given to confirming the medium characteristics, specifying the type of solution and maximum temperature, and ensuring the wetted material is a fully PTFE/PFA + ceramic structure to avoid the risk of permeation corrosion caused by PTFE-coated stainless steel diaphragms. Cables should be PFA-sheathed shielded cables to prevent embrittlement and cracking due to acid and alkali fogs. Installation typically adopts a top-insertion method, with preference for structures featuring anti-deposition and easy disassembly for cleaning, facilitating regular maintenance and calibration to address solution crystallization issues.
With the advancement of semiconductor processes toward refinement and efficiency, liquid level sensors are evolving toward intelligent and integrated solutions. They enable data calibration and diagnostics via RS485 interfaces and transmit data to MES systems using SECS/GEM protocols to meet compliance requirements. Proper selection of suitable liquid level sensors not only prevents wafer contamination and equipment damage caused by abnormal levels but also enhances process stability and reduces maintenance costs. In the future, with the iteration of corrosion-resistant materials and sensing technologies, sensors will further adapt to more extreme operating conditions, providing more reliable support for precise control of etching/cleaning processes.