23 April 2001 Control of organic contamination in CMOS manufacturing
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Yield control in manufacturing of microelectronic devices is closely related to defect control and contamination control. For a proper definition of process windows, e.g. maximum sit time or minimum quality of used process materials, the impact of different kinds of contamination on device performance has to be determined. This paper describes the outline of a strategy that was used for an estimation of the impact of organic airborne molecular contamination (AMC) on a realistic device process on the basis of selected experimental results: A manufacturing process was performed using intentionally contaminated substrates, monitoring measures were installed and baseline-levels were determined, time-dependent effects were detected, and process windows were defined on the basis of calculations. A gate-oxide integrity test was performed using intentionally contaminated silicon wafers. Contamination was performed via the gas phase using individual organic compounds. This test indicates that, besides the overall concentration of organic airborne molecular contamination, also the additional presence of small amounts of individual organic compounds has an effect on gate-oxide quality. The installation of measures for the monitoring of organic contamination using Gas-Chromatography/Mass-Spectrometry (GC/MS) or Time-of-Flight -- Secondary-Ion-Mass-Spectrometry (ToF-SIMS) lead to the observation that the deposition of organic contamination onto wafer surfaces can be a very fast process. Especially the preparation of blank samples is a procedure which is complicated by this effect. For an adequate definition of process windows it is necessary to estimate the time that remains until a freshly cleaned wafer is covered by a monolayer or organic contamination. This estimation was made on the basis of calculations using gas kinetic theory. Under standard cleanroom conditions the calculated time is in the range of minutes and is strongly depending on the adsorption probability of individual organic compounds and their individual concentrations.
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Juergen H. Buegler, J. Frickinger, G. Zielonka, Lothar Pfitzner, Heiner Ryssel, M. Schottler, "Control of organic contamination in CMOS manufacturing", Proc. SPIE 4406, In-Line Characterization, Yield, Reliability, and Failure Analysis in Microelectronic Manufacturing II, (23 April 2001); doi: 10.1117/12.425279; https://doi.org/10.1117/12.425279

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