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In-line monitoring of silicon dioxide film properties using non-contact or non-destructive techniques is quickly gaining industry acceptance as an alternative to conventional electrical and analytical methods. Mobile ion measurement in oxides using the corona temperature stress (CTS) technique was first discussed in the early 1970's. However, CTS measurements have only recently become available in a new generation of measurement tools. The CTS method may be applied immediately following film growth and does not depend on the fabrication of electrical test structures. This paper addresses the sensitivity and repeatability of the CTS approach with results of measurements performed, using a Semiconductor Diagnostics, Inc. mobile charge/plasma damage monitor system, on a variety of intentionally contaminated oxides. All oxide growth and characterization was performed on 200 mm diameter silicon wafers in a state- of-the-art manufacturing facility. Both chlorinated and non- chlorinated oxides were tested in addition to the effects of growth conditions that resulted in high charge density at the silicon-silicon dioxide interface. Water solutions containing sodium in the range from 10 to 1 ppba were used to introduce the contamination to the oxides. Photovoltage measurements, conventional C-V (capacitance-voltage) testing, and SIMS analysis were also performed to assess the quality of the oxides and to provide correlation to the corona mobile charge measurements.
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