> Read the August 2008 Solutions Update

A range of uses for the noble gas xenon have conspired to strain the worldwide supply and drive up prices for the rare gas. With that in mind, Air Products has developed XeCovery^SM, On-Site Xenon Recovery System, a new onsite service that provides a lower cost-of-ownership for customers using xenon within their manufacturing processes.

Xenon has a number of unique properties that have attracted a variety of industries to use this atom, including semiconductor manufacturing. Applications within integrated circuit fabrication include high aspect ratio etching, a possible excitation medium for EUV lithography, and a means to facilitate polymer cross-linking to enhance protection of photoresist during etching. Other uses for xenon include fuel for ion propulsion engines, an additive for very bright, low energy lamps for lighting and displays, as well as a delivery source for fluorine (XeF2) in MEMS processing. Future uses as an anesthetic and blanketing gas to reduce brain trauma after injuries are also beginning to emerge.

With demand and prices on the rise, there is a growing concern that cost will hamper its applicability. This is the situation within semiconductor manufacturing, where the price of xenon has risen while device prices have continued to drop. Besides higher costs, the potential impact to the industry is the need for additional R&D to mitigate the use of xenon in already established manufacturing processes, which compounds the cost issues.

The XeCovery recovery service is based on an Air Products' patented technology (US 7,285,154 B2) utilizing Vacuum Swing Adsorption (VSA). Because it is an on-site service, the customer's investment is limited to costs associated with installation and utilities to operate the equipment. Air Products assumes responsibility for owning, operating, and maintaining the units placed at a site. The process is capable of extracting from parts-per-million to percent levels of xenon from effluent streams. An enriched mixture of recovered xenon (typically in the percent levels) is compressed and stored. Full vessels are then transported offsite for distillation and certification as research grade xenon.

Figure 1 illustrates how a XeCovery system would be installed. Effluent gas from a process unit (e.g., a vacuum pump) is diverted towards the recovery system when xenon is present within the gas stream. This signal can either be from the customer (e.g., mass flow controller), or from an installed sensor. The extraction process can be designed so that either a single unit can be installed onto a process tool (i.e., for high xenon demand), or multiple tools can be interfaced into a single unit. This is especially attractive for processes that only periodically use xenon.

Figure 1

Conceptual depiction of the primary XeCovery components.

The ultimate customer benefit of the XeCovery service is a lower fixed price for the xenon used in the manufacturing processes. This price is determined by the length of time the service is contracted for, and the XeCovery unit's efficiency, which is based on the complexity of the process from which xenon is being recovered, and the volume available for capture by the system. The cost savings to the customer could be as much as 67%, without the need for an additional capital equipment outlay.

For additional information on our XeCovery offering, please contact Gene Karwacki, product manager.