Real-time measurement and evaluation of wall deposition behavior of gaseous organic contaminants

摘要

It is widely recognized that wall contamination by airborne molecular contaminants (AMC) may lead to serious problems in various gas-phase manufacturing processes of materials. In this study, a new device is developed for measuring the amount of AMC deposited onto a wall based on the quartz crystal microbalance method. First, performance evaluation of the device is made experimentally by using test gases including toluene, dibutylphthalate (DBP), or dioctylphthalate (DOP). The measured mass change of deposited AMC with time of exposure to the test gases indicated that real-time monitoring of deposited mass can be achieved at the order of 10 nanograms. The device also revealed the difference of deposited mass among test gases. Next, the measured results are analyzed with an existing theoretical model that considers simultaneous adsorption and desorption of gaseous matters on a wall. The model suggested that the adsorption rates of DBP and DOP are 2-3 orders of magnitude larger than that of toluene. Finally, the device is brought to work in an actually operating clean room. The device is proved to be capable of detecting deposited mass change which is considered to be caused by daily variation of gas-phase AMC concentration.