Evaluation of Contaminants in the Cleanroom Atmosphere and on Silicon Wafer Surface (IV) -Evaluation and Prediction of Outgas Concentration from Construction Materials-

摘要

The quantitative and qualitative evaluation of outgassing compounds from cleanroom construction materials and polymers is very important, because the main sources of contaminants in cleanroom atmosphere are outgas released from cleanroom construction materials such as the floor, wall, etc. The outgas from wafer carrier cases is also a major source for organic contamination of wafers stored in the cases. This paper describes the comparison of five different outgassing methods for the evaluation of organic contaminants released from cleanroom construction materials and polymers. The dynamic headspace method was superior to the static headspace method regarding the detection ability for especially higher boiling compounds which adhere strongly to the wafer surface and cause trouble in semiconductor manufacturing process. The amount of outgas increases in proportion to the outgas processing time at fixed temperature. It was also found that the amount of outgas increased extremely with higher outgassing temperature and the logarithm of the outgassing amount shows a linear relationship with 1/T as follows, where M is the amount of outgas, T is the outgassing temperature (K), and A and B are constants. With the relationship of equation (1), the outgassing amount at room temperature could be estimated in spite of the low concentrations which could not be observed directly. For example, it was found that the outgassing amount of total organics and DOP from polypropylene at room temperature were 0.1 ng/g and 0.002ng/g, respectively.