Impurity detection in Nitrous Oxide (N₂O) manufacturing in the Chinese Semiconductor market by ECO PHYSICS’s nCLD844CMhr N2O edition

"Special gases" consist of high-purity, electronic and standard gases. Especially the electronic gases are a vital raw material for the electronic industrial production, such as integrated circuits, display devices or solar cells. Besides being a weak anesthetic gas, for instance in the context of dentistry, Nitrous Oxide (N₂O) is also essential for the Semiconductor production process. It is the main Oxygen source for Silicon Oxide in the Chemical Vapor Deposition (CVD) process and is used in the high-tech thin film industries and LCD-display manufacturing. In combination with Gas Chromatography (GC) analysers for the direct detection of N₂O concentrations, the producers of high purity gases are also on need of impurity detection. In the Semiconductor industry a purity level of up to 5N N₂O is a demand. High purity and ultra-high purity materials range from 99.999% (5N) to 99.9999% (6N). The method to collect highly pure N₂O gas is to split Ammonia Nitrate ([NH₄NO₃]) into N₂O and H₂O ([NH₄NO₃] = N₂O + 2H₂O) at a reaction temperature of 220°C. As a side product, Ammonia (NH3), is quickly formed, because Ammonia Nitrate is merely a complex formation, not a covalent bonding. Even on the pure 5N level of the N₂O product, Ammonia (NH₃) is still emerging on ppb to ppm level.

On the current customer site, the Ammonia concentration lays between 30ppb and 2ppm. Ammonia (NH₃) will damage the Semiconductor surface material, which makes the detection critical. The nature of the chemiluminescence based Ammonia detection implies, that Ammonia is being converted by a special catalyst to Nitrogen Monoxide (NO). Dinitrogen monoxide or Nitrous Oxide (N₂O) also always carries low levels of Nitrogen Monoxide. Therefore, the calibration gas purity is crucial. It needs as little Nitrogen Monoxide (NO) in Nitrous Oxide (N₂O) as possible. To check the purity levels of N₂O, the nCLD844CMhr “N₂O-Edition” is installed. With adapted gas flow and converter configuration, this model is the first chemiluminescence analyser, that is able to detect Ammonia impurities in Nitrous Oxide (N₂O). Range and resolution are identical to the standard nCLD844CMhr.

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