Reaction Co-Product Removal System

The exhaust system often contains a vacuum pump (for low pressure systems) and scrubbers to reduce the exhaust vapors to acceptable local environmental standards. Processes operating at ambient atmospheric pressure do not require vacuum pumps or pressure control. At reduced pressures, however, a diverse variety of pumps is available. Additionally, for low pressure systems, a means of pressure control must be employed. 

In many CVD processes, toxic, explosive, and corrosive materials are produced as one component of the vapor phase reaction co-product. In order to remove them prior to atmospheric venting, scrubbers are employed, which must be appropriate for the process used. For example, halides frequently are neutralized in a water scrubber. Carbon monoxide and hydrogen often are burnt. Arsine generally is removed by heating the exhaust gas in a cracking furnace. Charcoal canisters often are used to absorb vapor phase species. Sulfur has been employed to getter thallium. Very fine particle filters also are used to catch a diversity of solids entrained within the exhaust stream. 

The vapor phase co-products from a CVD reactor frequently have highly unpleasant properties. They cannot, therefore, be vented directly to the atmosphere, but must be trapped and disposed of in a safe and environmentally-friendly manner. Chemical and physical methods of removal of the product gas and any excess reactor gases often must be employed. For example, dry absorption, wet chemical scrubbers and pyrolysis 

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