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10 Apr 2006
Lithography is just one of the applications set to benefit from an ammonia detector operating at parts-per-billion levels.
Picarro of the US has started commercial shipment of its ammonia ESP-1000 trace gas measurement instrument. The latest device, according to the firm, has applications in lithography, where part-per-billion levels of ammonia can lead to wafer yield loss and failure of critical lithography equipment.
Picarro says the ESP-1000, which is based on the company's patented Cavity Ring Down Spectroscopy (CRDS) technology, offers higher sensitivity and speed, and lower operating costs. This is compared to mainstream techniques for detection such as gas chromatography, mass spectroscopy, and optical spectroscopy.
The firm has already tested the ESP-1000 range for other gases, including CO2 and isotopic CO2, H2O and isotopic H2O, and H2S. With ammonia, however, the company has addressed particular challenges associated with the molecule's chemical properties.
At trace levels, ammonia is a very 'sticky' gas: it easily adsorbs onto surfaces that it contacts. This means small variations in temperature or ambient moisture can alter ammonia's adsorption or desorption rate, causing erroneous measurements.
Picarro's director of business development, Kathleen Hartnett, told Optics.org, "The ESP-1000 overcomes these challenges through careful design of its internal gas handling system, precise control of internal temperature, acquisition and analysis of multiple ammonia absorption peaks, and simultaneous measurement of and compensation for moisture content."
The ESP-1000 detects gases at well-below 1 part per billion by volume. It does this, its makers say, in a much shorter measurement time than other techniques: on the order of minutes. The device can also make its measurements in situ, directly on the gas stream, skipping the complex sampling processes used elsewhere.
As a result, says Picarro, the ammonia ESP-1000 has performance advantages that allow lithographers and lithography equipment manufacturers to control ammonia risk areas before they harm production.
"The ESP-1000, began shipments in February this year and to date we have shipped instruments for semiconductor, atmospheric, and emissions applications," added Hartnett. "We're expanding the platform to measure new compounds such as H2S, H2O, CH4, CO2, and isotopic CO2. The platform is also extendable to simultaneous measurement of multiple compounds and we expect to demonstrate that capability by the end of the year."
Author
Darius Nikbin is Science/Technology Reporter on Optics.org and Opto & Laser Europe magazine.
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