300-mm Abatement: The Devil is in the Details
Van Gompel, Joe
(BOC Edwards, Austin TX)
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Exhaust gas management of 300-mm processes is complicated both by the larger flows over 200-mm as well as the development of new processes. A survey of several problematic 300-mm processes will be discussed; how a process is different from the analogous 150- and 200-mm wafers, and empirical solutions will be presented. For example, tungsten deposition uses about 2.5x more WF6 and 3x the H2 for 300-mm. Similarly, new processes such as WPNL (tungsten pulsed nucleation layer) introduce gases that challenge both vacuum pumps and abatement. LPCVD nitride processes using DCS and NH3 are less effectively abated with cold traps, due both to higher process gas flows as well as higher N2 purges required to keep the vacuum pumps clear. Very high flows of DCS or SiH4 in poly furnaces lead to significant buildup of ultrafine silica in the ductwork. H2, SiH4, and TEOS in flows high enough to exceed their lower flammable limits require special attention for safety. And HF levels from NF3 chamber cleans hydraulically threaten fab water treatment facilities; point-of-use water treatment is introduced. Each of these process challenges will be discussed, and safe and practical solutions will be presented.