Applications of ion chromatography in the semiconductor industry II. Determination of basic airborne contaminants in a cleanroom

Since the geometry of semiconductors and integrated circuits has been shrunk to well below sub-micron dimensions, there is a great demand for precise and reliable analytical techniques to measure and monitor the contaminants in all areas related to the fabrication process. Special concerns about the air cleanliness in a Fab lead to the necessity for developing analytical techniques to perform this task. In this research, basic airborne contaminants in a cleanroom were adsorbed onto a collection tube, subsequently extracted with deionized water and analyzed by ion chromatography. Such a method is capable of simultaneously measuring the concentrations of ammonia and cations (e.g., sodium, potassium, calcium, magnesium, etc.) present in the cleanroom air samples. The optimal sample preparation method was determined and the analyte concentrations at various locations in the cleanroom were measured. The results showed significant variations from one location to another. The long-term fluctuations in the contaminant levels were also significant. Data obtained using this method compared well with data from inductively coupled plasma analysis of the same materials. Copyright (C) 1999 Elsevier Science B.V.