Application of a PEM Hydrogen Gas Generator as Reliable Gas Source for Hydrogen Implantation

This paper focuses on the integration of a longliving multilayer PEM (proton exchange membrane) hydrogen gas generator as source of ultra clean hydrogen in the VIISTA 1500H, a single wafer high energy spot beam implanter with an energy range up to 1500 keV. In modern Insulated Gate Bipolar Transistors (IGBTs) and other power devices, light ions are used to form n-doped layers. With the reduction of the drift region of the IGBTs a so-called field stop or soft punch-through layer between the drift region and the collector contact was introduced to shorten the tail current and to prohibit the punch-through of the space-charge region into the collector. In comparison to the widely used VIISTA 3000 the beamline of the VIISTA 1500H is optimized to accelerate light ions and to fulfill the radiation safety requirements. Most of the components of both tool types, however, are identical in order to reduce the development effort, also including the indirectly heated cathode (IHC) ion source. Compared to other source types, the gas consumption for stable source operation of the used IHC ion source is quite high. Therefore, the lifetime of an installed gas bottle is limited, resulting in increased scheduled downtime. For safety and cost reasons, neither an external hydrogen gas supply nor a high capacity gas cylinder is an option compared to the multilayer PEM hydrogen gas generators which are widely used in analytical services and in medicine. These gas generators fulfill all the safety and purity requirements and can be integrated easily in the gas rack of existing tools. The results have shown that multilayer PEM hydrogen gas generators can be used inside the gas box to enable a stable source operation in a production environment.