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July 20, 2018 | News & Notices World's Highest Sensitivity Level for Laser-Induced Breakdown Spectroscopy Development of New Technology for Rapid Measurement of Metals in Semiconductor Wash Solutions

Shimadzu Corporation has developed a new technology for measuring trace quantities of metals using the principle of laser-induced breakdown spectroscopy (LIBS) that boasts the world’s highest level of sensitivity. Verification tests using a prototype system have already started.

Shimadzu has been developing a system that uses this new technology for measuring and monitoring trace quantities of copper, aluminum, titanium, and other metals contained in semiconductor wash solutions. The system is currently scheduled for release in 2020. It is anticipated that this new technology can be used in other fields besides semiconductors, and thus Shimadzu is also developing applications in such areas.

Background to the Development

In semiconductor manufacturing, the washing process to remove metals and other contaminants from wafer surfaces using wash solutions accounts for about 20 to 30 % of the overall process. Currently, the replacement frequency of the wash solutions is generally determined based on usage time. However, in recent years, the need to reduce manufacturing costs and reduce environmental impact has demanded the more efficient use of wash solutions. Consequently, it has become necessary to monitor the degree of contamination in real time.

To satisfy those needs, Shimadzu has been researching LIBS technology that takes advantage of the company’s extensive laser optics and spectrometry technologies. LIBS is a technique that can simultaneously measure multiple elements easily. When samples are irradiated with laser light, it generates a plasma by thermal vaporization of the sample surface. That plasma emits a characteristic light that is unique to the elements contained in the sample surface. Therefore, the elements can be measured by detecting the resulting light spectrum.

By using a laser manufactured by Shimadzu that features high output and stability and an optical system optimized based on Shimadzu's spectrometry technology, this newly developed technology enables trace quantities of metals to be measured extremely easily and quickly.
 

Overview and Features of the New Technology

Plasma is generated by laser irradiation of a sample that has been evaporated to dryness on a special plate. The light emitted from the plasma is then detected to identify and quantitate the metal elements contained in the sample. Detection limit is in the order of several ppm. The technology, which is based on LIBS measurement principles, offers the highest sensitivity levels in the world (as of July 2018, according to Shimadzu's survey).

The current prototype fits in a 1 m × 1 m footprint and can be linked to a semiconductor wafer cleaning system. The entire process from sampling to measuring the wash solution is fully automated, and achieves the simultaneous measurement of 12 trace metal components, such as copper, aluminum, and titanium, in about one minute.

Practical application of this technology is expected to offer benefits such as improved yield rates and lower manufacturing costs as a result of a better understanding of the most suitable wash solution replacement frequency.

Future Developments

Shimadzu plans to improve system usability by conducting verification testing at semiconductor and semiconductor manufacturing equipment companies and aims to release a practical system in 2020. Furthermore, we intend to develop new markets by studying the application of the new technology to other fields such as the inspection of public infrastructure and the inspection of factory effluents.