In the semiconductor manufacturing process, liquid leakage may cause equipment failure, wafer contamination, and even production interruption. Traditional detection methods such as manual inspection or mechanical float sensors have problems with slow response and low accuracy. The capacitive leakage sensor uses non-contact detection principle and utilizes the difference between the dielectric constant of liquid and air. When the liquid contacts the surface of the sensor, it causes a change in capacitance value, thereby triggering an alarm. Its core advantages lie in:
High sensitivity: capable of detecting trace liquid leaks (such as 0.1ml/min), meeting the stringent cleanliness requirements of the semiconductor industry;
Anti interference: not affected by ambient light and electromagnetic noise, suitable for high-density electronic equipment areas;
Quick response: millisecond level reaction speed, can be linked to control system emergency shutdown to avoid chemical reagent diffusion.
For example, a 12 inch wafer fab successfully reduced downtime caused by acid leakage by 90% after deploying capacitive sensors on etching machines. In the critical process of semiconductor manufacturing, capacitive leakage sensors have become the core equipment to ensure production safety by accurately detecting the risk of liquid leakage. Its typical application scenarios include:
Chemical mechanical polishing (CMP) equipment
In CMP process, leakage of abrasive and cleaning agents can cause scratches on the wafer surface. Capacitive sensors are embedded at the bottom of the device to monitor liquid leakage in real-time. For example, a certain chip factory successfully detected a slight leak of 0.5mm/min after deploying non flush mounted sensors on the polishing machine, avoiding the mass scrapping of wafers worth millions of dollars.
Photoresist coating system
The adhesive liquid leakage of photoresist can contaminate precision optical components. The sensor adopts a PTFE shell design, which is corrosion-resistant and can penetrate non-metallic pipelines for detection. When the adhesive liquid contacts the sensing area, the system automatically triggers the vacuum recovery device to control the leakage within 0.1ml.
Etching and cleaning process
The leakage of strong acids (such as hydrofluoric acid) or organic solvents is extremely dangerous. Capacitive sensors upload data to the central control system through IO Link function for remote monitoring. A semiconductor company has used this technology to lock in the leakage source and initiate neutralization procedures within 3 seconds, resulting in an 85% increase in efficiency compared to traditional methods.
Ultra pure water transportation pipeline
Leakage of high-purity water may cause a short circuit in the circuit. The sensor adopts distributed fiber optic assisted design to form a continuous monitoring network in long-distance pipelines. Through cross validation of capacitance changes and optical signals, the false alarm rate is less than 0.01%.
These cases demonstrate that capacitive sensors effectively address the unique needs of the semiconductor industry for micro, fast, and accurate leak detection through customized installation solutions, such as flush type for closed containers and non flush type for open tanks. Although capacitive leakage sensors have shown significant advantages in the semiconductor industry, their practical applications still face multiple challenges. Firstly, environmental interference issues are prominent: high-purity water or solvents with low dielectric constants (such as isopropanol) may cause weak changes in capacitance, which can be easily confused with signals generated by equipment vibration or temperature fluctuations. Secondly, the complexity of installation constrains promotion – in wafer fabs with limited space, sensors need to be deployed close to pipelines or equipment gaps, and the cleanliness requirements of semiconductor workshops may pose a risk of particle contamination during drilling installation. In addition, maintenance costs cannot be ignored: long-term exposure to corrosive liquids (such as hydrofluoric acid) can accelerate the aging of sensor electrodes, requiring regular calibration or replacement. A company has reported that the average annual maintenance cost accounts for 12% of the total equipment cost.
To overcome these bottlenecks, the industry is optimizing solutions through technological innovation:
Intelligent algorithm upgrade: adopting differential pulse width modulation (PWM) circuit, by comparing the charging and discharging time difference between the reference capacitor and the detection capacitor, the signal resolution is increased to 0.01pF, effectively distinguishing liquid leakage from background noise;
Material Innovation: Develop sensors with PTFE coating or ceramic substrate, which can withstand strong acid and alkali environments and extend their lifespan by more than three times;
Integrated design: Integrating sensors and MOSFET semiconductor circuits on the same chip to reduce external interference and achieve miniaturization, suitable for precision equipment such as lithography machines.
For example, the “Intelligent Capacitor Array” system launched by a leading manufacturer works together with 16 micro sensor units and combines machine learning to analyze capacitor change patterns. It not only reduces the false alarm rate to 0.001%, but also predicts leakage trends and provides early warnings. These advances mark the evolution of capacitive sensors from “passive detection” to “active protection”, providing more reliable security for the semiconductor industry.