KRISS Develops Non-contact Flow Sensor for Real-time Monitoring of Semiconductor Fabrication Process

Korea Research Institute of Standards and Science (KRISS, President Hyun-Min Park) developed a non-contact flow sensor capable of measuring the amount of epoxy used in the semiconductor fabrication process in real time. Through accurate monitoring of the discharge amount during the dispensing process, the sensor can enhance semiconductor yield.

The dispenser used in the fabrication of electronic products plays the role of discharging epoxy. Epoxy is used as an adhesive in cellphone assembly due to its high viscosity and hardening property, or as an underfill resin to protect chips from stress. Devices are growing smaller thanks to the advances in semiconductor technology, and the accurate dispensing of resins in smaller volumes has become increasingly important.

Before introducing dispensers into the electronic packaging process, the discharge amount is checked using a balance. This prevents issues such as epoxy hardening, inaccurate discharge amount, and blockage of nozzles. Non-contact flowmeters are required for real-time monitoring of discharge amount without stopping the process, but small traces can be difficult to measure with existing ultrasonic flowmeters.

The sensor developed by the KRISS Flow Rate Measurement Team is based on the infrared absorption method, which allows real-time measurement of flow rate without cutting tubes or stopping the fabrication process. A local spot of the epoxy supply tube is heated using infrared, and an infrared absorption-based temperature sensor measures the flow from outside the tube.

By comparing real-time measurements of discharge amounts to weights obtained using a balance, the team showed that the new sensor is capable of measuring small traces up to an accuracy of 1 µg (microgram; one millionth of a gram) for shots dispensed at 300 Hz. The sensor can be used to measure discharge amounts in the range of 10 µg to tens of mg in the actual semiconductor fabrication process.

The team is the first to develop a sensor capable of measuring discharge amounts of a dispenser during the semiconductor fabrication process in a non-contact manner and in real time. The advantages include higher yield from improved accuracy and non-interference of processes by clamp-on mounting.

Currently, the team is conducting follow-up research aimed at commercialization. Korea has relied on foreign-made ultrasonic flowmeters for non-contact measurements of flow rate. If commercialization is successful, the Korean market will see the launch of non-contact flow sensors using domestic technology alone.

Seok Hwan Lee, Senior Research Scientist of the Flow Rate Measurement Team at KRISS, said, “Our technology can be applied to measure the flow rate of sulfuric acid and other liquid chemicals used in cleaning and etching in a non-contact manner. We hope to improve semiconductor yield while enhancing safety and efficiency.” 

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As the representative institute in the national measurement standards, the Korea Research Institute of Standards and Science (KRISS) has been setting the highest measurement standards and ensuring their international equivalence since its inception in 1975. Thereby, we help build solid foundations for the national development in science and technology and for industrial advancements

This study, funded by the joint research support program between the Ministry of Science and ICT and the European Union, was published online in the international journal Optics and Lasers in Engineering (IF: 5.67) in October.