Press Release: K-Patents announced today a significant installation project of its industry-leading inline refractive index sensor for wet chemical composition monitoring in spray solvent tools. The well-received Process Refractometer PR-33-S sensor offers an optical design for improved measurement stability in process conditions of tools using wet etch and post etch residue removal chemistries. A drift-free digital output allows connection to the programmable logic controller or fab network through an Ethernet connector.

“Like other aspects of wafer processing, monitoring feed-in chemicals has become fast paced and unforgiving. When an error occurs, be it human or in a tool, an inline refractometer can provide instant fault detection or feedback for chemical spiking functions in wet strip spinning tools for metal etch and etch residue removal,” said Marcus Kavaljer, Manager of K-Patents’ semiconductor operations.

The emergence of sensors, MEMS, and other IoT devices is driving the revival of legacy equipment using new processes and different chemistries relative to conventional CMOS devices. But without accurate monitoring, fabs cannot know the composition of a given chemical stream. Errors may not be detected until the etch rate drops below specification, the particle counter spikes, or a lithography or CMP step fails to deliver the desired results.
Few technologies can deliver accurate measurements at a reasonable cost, and across a wide range of chemistries. For example, titration — the gold standard for measurement accuracy — requires consumable reagents, creates a new waste stream of sampled chemicals and their reaction products, and introduces possible contamination through the probe used to collect samples. Conductivity, pH, and IR spectroscopy methods can be useful, but are not universally applicable across the many compositions encountered in a semiconductor fab.
In situ refractive index measurements are a cost-effective tool for fast and accurate measurement of chemical composition. Light from a calibrated LED source reflects off the interface between the liquid being measured and an optical window. A CCD camera detects the position of the reflected light in order to determine the so-called “critical angle” at which the light demonstrates total reflection. This critical angle in turn yields the index of refraction of the fluid. This method can be used with opaque fluids and is not affected by bubbles and other flow irregularities. Overlapping refractive index values are rare; even very similar mixtures generally have unique index values.
About Process Refractometers
K-Patents provides Process Refractometers for real-time concentration monitoring in wet chemical process applications in semiconductor and microelectronics fabrication. The K-Patents Semicon Refractometer is designed to be used in bulk chemical distribution, mixing, blending and dilution, and in point-of-use in the fab. If the chemical is out of specifications, an alarm prevents wrong chemicals or wrong concentrations from being dispensed on to the process and thus helps avoid very costly production problems. 

About K-Patents Process Instruments
Headquartered in Finland, with subsidiaries in the US and China, K-Patents designs and supplies specialized in-line liquid analysers and process refractometers for industrial process instrumentation and control. The company combines innovations in several technical fields to offer superior design and process-specific expertise across a wide range of industries, from semiconductor manufacturing to pharmaceuticals and biorefining. For more information, please visit
Press contact:
Mona Kokkonen, Communications Manager. Email: mona.kokkonen[at]
Customer contact:
Marcus Kavaljer, Area Manager. Email: marcus.kavaljer[at]