Using the “Dual Zone” filter for FFU Ionization
Since the ionizer in a front end is located right under the filter and in fact the airflow carries the ions to the wafer plane, it is natural to see the ionizer integrated into the Fan Filter Unit (FFU). In typical applications the wafer plane is some 12 or more inches below the silicon tips of the Simco-Ion 5635 ionizer.
However with space being so critical in the newest generation of process tools it can also be the case where the wafer plane extends to within millimeters of the face of the filter media. In this case we use a technique where the ionizer is integrated into an inverted channel in the filter face . We call this type of filter a Dual Zone filter.
Additionally the need for a recessed ion channel may exist alongside the need for an integrated LED light in the FFU’s filter face. In this case the Dual zone filter can also be fitted with the integral “Lumifilter’ light.