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Purification and Recovery of Fluids in Processing Applications Disclosure Number: IPCOM000035615D
Publication Date: 2005-Jan-27

Publishing Venue

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Background of Invention

Field of Invention

The present invention pertains to purification and recovery of fluids in processing applications.  In particular, the present invention relates to systems and methods for supplying, purifying and recovering fluids such as carbon dioxide in semiconductor cleaning and other processing applications.

Related Art

The use of supercritical fluids such as carbon dioxide in cleaning operations (e.g., dry cleaning and cleaning parts and components) has been on the rise in recent years as a replacement for organic solvents and other potentially toxic and environmentally unfriendly chemicals.  In particular, supercritical carbon dioxide (SCCO2) has zero surface tension and very high diffusivity, which makes this fluid very attractive for use in semiconductor fabrication processes such as cleaning of wafers and photoresist removal.  Carbon dioxide is in a supercritical state at a temperature of about 31°C or greater and a pressure of about 1080 pounds per square inch gauge (psig) (about 74.46 bar) or greater.

In semiconductor cleaning operations, it is important to provide the supercritical carbon dioxide at a high purity level to reduce or eliminate the presence of undesirable contaminants contacting the substrate surface in a semiconductor process chamber.  Accordingly, the carbon dioxide stream is typically purified in one or more purification steps prior to being delivered to the process chamber for cleaning of the semiconductor component. 

In a typical semiconductor cleaning process, carbon dioxide is drawn from a supply source (e.g., a storage or feed tank), where the carbon dioxide is stored at a liquid state (e.g., at a temperature of about -20°C to about -10°C and a pressure of about 300 psig or 20.68 bar).  The liquefied carbon dioxide is pressurized and heated to achieve a supercritical state prior to delivery to the process chamber for cleaning the semiconductor substrate.  After the cleaning step, the carbon dioxide is treated in one or more purification units to remove contaminants (e.g., photoresist and/or other compounds) and/or additives such as co-solvents from the carbon dioxide.  The carbon dioxide can be purified to a desired level and recycled for further use in the process chamber or, alternatively, vented to the atmosphere.  If the carbon dioxide is recycled for further use, the carbon dioxide stream is typically purified and processed in a gaseous state.  At some point prior to re-use, the carbon dioxide must be re-pressurized from the gaseous state to achieve a supercritical state. 

The problem with re-pressurizing carbon dioxide during a recycle process is that considerable energy and equipment costs are required to convert the carbon dioxide from gaseous back to liquid and supercritical states.  In addition, re-pressurization of the carbon dioxide may result in the addition of impurities to the carbon dioxide...