Sub-part-per-trillion detection and analysis of submicrometer particles in integrated circuit processing chemicals
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Sub-part-per-trillion detection and analysis of submicrometer particles in integrated circuit processing chemicals D. Xu and R. F. Pinizzotto Department of Materials Science, University of North Texas, Denton, Texas 76203
J. A. Sees Texas Instruments Inc., P.O. Box 655012, MS 301, Dallas, Texas 75265 (Received 22 November 1996; accepted 10 June 1997)
We have developed a new technique for the analysis of particulate contaminants in liquids (or gases) with an elemental detectability limit as low as 0.1 parts per trillion, and a particle concentration detectability limit as low as 1 particleyml for particles greater than 0.2 mm in diameter. Samples are prepared using extraction replication and analyzed using analytical transmission electron microscopy. The methodology has been applied to the analysis of H2 O2 and HF, important chemicals in integrated circuit fabrication. The new methodology should become an important tool in the identification of submicron-sized particles which adversely affect integrated circuit fabrication.
I. INTRODUCTION A. Particle contamination in the semiconductor industry
As processes become increasingly sophisticated and critical device geometries continue to shrink, the effects of microcontamination on defect density and product yield have become important concerns in semiconductor fabrication facilities. One major type of microcontamination is particle contamination. It is believed that more than half the defects on wafers are due to particulate matter.1 Particle contaminants can adversely affect device integrity2–4 by creating pinholes, microvoids, and shorts, and can act as masks during photolithography or etching steps. Particle contaminants in wet chemicals can adversely affect the wet chemical cleaning process. To generate particle-free processes, one must be able to detect, characterize, and identify the particles. Other required information includes the particle sources, how the particles form, and how they can be eliminated. Optical particle counters, spectrometers,5–7 and the scanning electron microscope8,10 (SEM) are commonly used for particle detection and characterization, but their use is limited when the particle size is very small (,0.2 mm). Optical particle counters cannot provide chemical composition or crystal structure information. SEM cannot provide crystal structure information. An SEM equipped with an x-ray energy dispersive spectrometer (XEDS) cannot give accurate chemical information for submicron sized particles. Transmission electron microscopy11 (TEM) is an excellent technique for small particle analysis. TEM has excellent spatial resolution and can simultaneously provide accurate chemical composition and crystal structure data for particles as small as 1 nm. These capabilities J. Mater. Res., Vol. 13, No. 3, Mar 1998
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will make particle and particle source identification much easier. The major disadvantage of the TEM technique is the difficulty of sample prepa
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