(293g) Design of a Dual Purpose Air Filter for Semiconductor Clean Rooms

Authors: 
Sothen, R. A. - Presenter, Auburn University


In the semiconductor industry, the need for quality control is critical for success. Beginning in the Seventies with ten micron gates-lengths, the smallest feature size on semiconductor chips has continuously shrunk by a factor of two every five years. Released in 2004, the Pentium 4 Prescott utilizes gate-lengths of 0.09 microns (90 nm). Following the trend in reduction, the use of 30 nm gates has already been demonstrated in the next generation of chips. With gate dimensions on this order of magnitude, particulate matter as well as airborne molecular contaminants (AMCs) must be controlled in order to prevent defections. The destructive effects of AMCs have been studied for years; however, chip dimensions have only recently entered a range were the effects are pronounced. AMCs in the semiconductor environment primarily consist of various acidic and basic vapors in addition to siloxanes, phthalates, amines, and dopants. The objective of this study is to design and construct a single filtration unit that can remove both particulate matter and AMCs. The filter is comprised of HEPA media combined with a novel filter material, microfibrous sorbent-supported media, developed at Auburn University. The HEPA media is capable of capturing particulate matter (0.3 micron in diameter) to 99.99% efficiency while the microfibrous layer removes AMCs. The final design will be able to filter all AMCs to a concentration of less than 1ppb while producing no more than 2? H2O pressure drop. The novel filter material, microfibrous media, is a sinter-locked matrix composed of fibers with diameters ranging from one to twenty microns. Through a traditional wet-laid paper manufacturing process, fiber matrixes are constructed with metal, ceramic, or polymer material. The microfibrous framework is capable of entrapping particles as small as ten microns. The resulting composite structure is known as microfibrous sorbent-supported media (MSSM). This novel filter technology can easily be tailored to the appropriate environment by selecting and entrapping a variety of sorbents and catalysts. Initial studies indicate activated carbon as a good sorbent for organic vapors, while zeolites and activated alumina are utilized for acidic and basic gases. In order to minimize cost and optimize efficiency of the filter, the study examined the following factors: breakthrough plots of contaminant concentrations versus time, interactions between various sorbents , effect of sorbent loading, bed depth, and pressure drop.