Authors : Franck Amiet, Damien Bazin
To ensure people’s safety and a good repeatability of industrial process, near real-time risk management and the continuous monitoring are crucial. In the semiconductor fabrication process, particle control is an essential part. Clean room technology, which relies on the use of HEPA and ULPA filtration, has in the past exclusively focused on the control of micro- and nano-particles. Nevertheless, as a consequence of device reduction, Airborne Molecular Contaminations (AMCs) has also become a key detractor of yield. Especially in photolithography area where a variety of molecules can impact the process (ammonia, Silicon Volatile organic compounds, acids).1 The nature and concentration of AMCs can be different depending on the chemical process and can also vary rapidly. These AMCs can impact the process and reduce the lifetime of equipment. Among the AMCs, silicon compounds are very problematic because they combine with oxygen to create amorphous silicon dioxide on optical surfaces, leading to non-reversible lens damages. These optical tools are very expensive and need to be protected
The concentrations of VOCs are usually assessed using sorbent tubes or canisters for the sample collection. The samples are then taken to a laboratory for GC–MS analyses. Some of these methods are well established and have been published by the US Environmental Protection Agency (US EPA) as compendium methods, which are known as TO-14A or TO-15 methods. These methods for sampling and analysis are inherently for time-averaged concentrations. Although rapid sampling is possible when using canisters, it is too expensive to analyze a large number of samples if real-time concentration trends need to be profiled.
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