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Industry  Gases


Setting a new benchmark for hydrogen delivery


Purified hydrogen is an essential ingredient in the MOCVD processes used to manufacture LEDs,power devices and photovoltaics.Moves toward larger reactors and bigger


wafers are increasing the demand for more and more ultra-pure hydrogen from increasingly reliable,compact sources. Fulfilling this need is a novel palladium technology developed by Power and Energy, says the company’s Stuart Bestrom.


S


ales of MOCVD tools have exploded over the last twenty years, leading to a vast increase in the number of chips produced by this technique. But the approach for purifying the hydrogen gas that supports this form of epitaxial growth – a palladium membrane purification technology – has stood still.


This lack of progress on the hydrogen front is a significant concern for LED chipmakers, who continue to migrate to more complex and demanding processes involving ever-larger chambers and ever-bigger wafers. Sensitivity to oxygen and carbon contamination goes up and up, hydrogen flow rates have recently tripled for the largest MOCVD reactors, and flow changes during the process recipe runs can surge from 0 to 300 standard litres per minute (slpm) with no transition period. The traditional palladium purifiers were never designed to handle these new process recipes and they have a number of inherent limitations in durability, quality and cost. This has prompted some users, particularly those in large fabs in China and Taiwan that are particularly keen to cut costs and work with higher flow rates, to


consider alternative purification technologies. These chipmakers are finding a solution to their needs in a palladium membrane technology developed by Power and Energy of Ivyland, PA, in cooperation with the US Department of Defense (DoD). The DoD pursued this development to serve its needs for pure hydrogen to power fuel cells (see box “Hydrogen fuel cells”), but the results of the project have proven successful in semiconductor applications as well.


The resulting palladium membrane technology that we have developed at P+E is the most significant innovation in gas purification in over 20 years. One of the biggest breakthroughs is a doubling-to-trebling of capacity per purifier compared to traditional palladium purifiers. This larger capacity means that a new LED fab requiring 12,000 (slpm) of hydrogen to support 50 MOCVD reactors needs only three of our gas cabinet- sized purifiers. If traditional purifiers were used, six would be needed, and each would have a much bigger footprint.


Reducing size also has additional benefits, because it January/February 2012 www.compoundsemiconductor.net 37


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