Impurity detection in Nitrous Oxide (N2O) manufacturing in the Chinese Semiconductor market

"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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