Cleanrooms with low molecular organic contamination (MOC): From material classification measurements to different assessment methods regarding organic condensables

In such fields as cleanroom technology for space applications, semiconductor and optics, the indoor air quality (IAQ) in these controlled environments need to be assessed for the presence of molecular organic contaminants (MOC) in order to permit clean device surfaces during the entire construction and assembly period. Especially high boiling MOC such as phthalates, organic esters, siloxanes and hydrocarbons may emit constantly from building and construction materials and later condense on critical surfaces. Therefore, extensive MOC material emission screening measurements of different types of cleanroom building products according to a new standard ISO/WD 14644-15 were performed. All obtained surface specific emission rates are entered into a public available database in order to enable a material selection already in the planning phase of a low-emission controlled environment. Therefore, a simulation model for cleanroom settings predicts the expected level of MOC of the environment to be constructed. New cleanroom settings for space applications and research with a very high IAQ regarding MOC are planned and built based on a targeted material selection using the database values and the simulation tool. The presence of critical condensables was quantified on selected cleanroom settings using especially designed condensation witness samples which are later analysed by transmission Fourier transform infrared spectroscopy (FTIR) purged with ultrapure VOC-filtered air based on EN 16602-70-05. As a result, a condensation rate is calculated for the individual sampling sites. A more detailed species analysis of the collected condensables is done by thermal extraction of witness samples in a micro emission chamber and subsequent analysis using automated thermodesorption coupled with gas chromatography and mass spectrometry (ATD-GC/MS) based on a slightly adapted method described in ISO 16000-25. Additional VOC/SVOC onsite measurements according ISO 16017-1 are used a) to predict the indoor air quality (IAQ) regarding condensables and b) to verify as root cause analysis the measured MOC condensation rate by transmission FTIR. the described method using witness samples and subsequent FTIR analysis is very cost effective, standardized and easy-to-use and can be a valuable tool for initial IAQ screening applications regarding SVOC and condensables.