The development of high brightness LEDs is being studied worldwide due to the expectation to replace present light sources because of the higher efficiency and estimated lifetime. The deposition of the epitaxial layers is the most critical step of the LED manufacturing process and has to be carried-out in well controlled conditions to get the necessary uniformity of the epitaxial layers and the proper cleanliness. The most common technology to grow the epitaxial layers is MOVPE, a technology that requires a large quantity of gas to transport the precursors into the process reactor. Control of the cleanliness of the gases used during the process (hydrogen, ammonia, arsine, etc) is necessary to obtain highly efficient and reproducible devices. However, even the use of the cleanest gas source cannot avoid the introduction of impurities when the gas is used in the process reactor. In fact there are several causes that can degrade the actual purity level: the degree of emptiness of the source cylinder, improper procedures during the change out of the cylinder or outgassing from the components in the gas distribution system. These effects can be even worse in research centers where the gas consumption is low and not continuous. A common way to get rid of the above mentioned problems is the adoption of point of use purifiers. Results showing the improvements in the gas quality by adopting point of use purifiers will be presented and discussed. The differences between some widely used hydrogen purification technologies in the compound semiconductor applications will also be evaluated.

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The use of purified carbon dioxide (CO 2 ) has become a reality for leading edge 193 nm immersion lithography scanners. Traditionally, both dry and immersion 193 nm lithographic processes have constantly purged the optics stack with ultrahigh purity compressed dry air (UHPCDA). CO 2 has been utilized for a similar purpose as UHPCDA. Airborne molecular contamniation (AMC) purification technologies and analytical measurement methods have been extensively developed to support the Lithography Tool Manufacturers purity requirements. This paper covers the analytical tests and characterizations carried out to assess impurity removal from 3.0 N CO 2 (beverage grade) for its final utilization in 193 nm and EUV scanners.

Abstract:Hydrogen is the most common gas used to operate FCs (fuel cells). The performance of proton exchange membrane FCs is sensitive to the hydrogen gas purity. Of particular concern are specific gaseous contaminants such as carbon monoxide, sulphur compounds, and ammonia that are known to drastically reduce the FC efficiency even when present at low concentrations (in the ppb range). To eliminate efficiency losses due to hydrogen purity, dedicated hydrogen gas purifiers are now available specifically for FCs; their adoption protects the FCs and guarantees that consistent gas purity is supplied throughout their lifetime. Different purification technologies have been developed to match the wide variety of applications and to manage various impurities that are dependent on the H 2 source. For gas sources where nitrogen is present above the acceptable limit, palladium membrane purifiers can be used to reduce the nitrogen concentration to the desired level. At the same time, the other impurities like carbon monoxide, sulphur compounds, ammonia, hydrocarbons, etc. are also removed. For applications where the main concern is the presence of reactive gases, such as carbon monoxide and sulphur compounds, adsorber purifiers can eliminate these impurities down to the single digit ppb range or better. This technology is suitable to cover a very broad range of flow rates, from a few sccm up to 1,000 m 3 /h. The purity performance of both technologies has been proven with state-of-the-art analyzers and will be discussed in the paper.