MICRO: Extreme Silicon - Sun (March 2000)

Peng Sun and Martin Adams, formerly of Because their effects on semiconductor devices are numerous and destructive, organic contaminants on wafer surfaces must be monitored and controlled. It has been reported that the presence of organic contamination can change surface hydrophobicity, lower breakdown voltage, form silicon carbide, affect oxide growth and quality, cause unintentional doping, contribute to degradation haze formation, and generate post-CVD defects. To prevent such effects, various techniques have been used to analyze organic contaminants on silicon wafer surfaces, including Fourier transform infrared spectroscopy, ion mobility spectrometry, time-of-flight ion mass spectrometry, x-ray photoelectron spectroscopy, and thermal desorption gas chromatography­mass spectrometry. However, all these methods have limitations. They either lack the capability to identify specific contaminants or are unable to quantify total organics accurately. This article describes a new technique that uses thermal desorption gas chromatography (TD-GC) coupled with a mass spectrometry detector (MSD) and an atomic emission detector (AED) for organic contaminant analysis. By combining the superior separation ability of GC, the accurate compound-identification ability of an MSD, and the sensitive elemental-analysis ability of an AED, TD-GC-MSD/AED can provide simultaneous qualitative and quantitative measurements of organic contaminants on silicon wafers. The article also discusses the use of this combined technique to monitor organic contamination in wafer manufacturing processes and environments at the MEMC Electronic Materials facility (St. Peters, MO), detailing the detection procedures and their capabilities. The TD-GC-MSD/AED system used in the work described in this article consists of a Model 6890 GC interfaced with a Model 5970 MSD and a Model G2350 AED, all from Hewlett-Packard (Palo Alto, CA). The MSD is employed for the identification of organic contaminants, and the AED is used for the quantification of total organic carbon, total organophosphorus, and other elements of interest. Samples are introduced into the GC separation column