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Hal Amick, Ph.D., P.E., Michael Gendreau, INCE.Bd.Cert, Colin Gordon & Associates, San Bruno, CA, USA

ABSTRACT

Vibration surveys are carried out for a variety of reasons over the lifetime of a facility for semiconductor fabrication (fab) or other advanced technology process.1 Evaluations may take place as part of the site selection effort, during construction, or during the productive life of the facility. Generally, there should be a reason for a vibration survey-a question or set of questions that need to be answered. That reason will likely suggest an appropriate time at which a survey should be carried out. However, it is not unusual for a survey to be scheduled at an inappropriate time, which may lead to useless data, or data that lead to an incorrect conclusion. The question or questions providing the reason for the survey may not even be answered. For example, suppose the object of the survey is to assess whether the vibration design goals of a facility have been met. In essence, the survey is intended to predict the quality of the vibration environment in a fab after it becomes operational. When operational, the vibration environment is some combination of ambient site vibrations, vibrations generated by the facility’s mechanical systems (fans and air handling systems, pumps and liquid circulation systems, etc.), and those generated by personnel activities. Will the survey objective be met by a site survey carried out during the construction phase, in the middle of the night (to avoid construction activities), prior to turning on the mechanical systems? Most likely not. Ambient site vibrations will likely be at their lowest during the night, and there will be no contribution from the ubiquitous mechanical systems. The intent of this article is to identify some of the reasons for vibration surveys and discuss the appropriate timing for those surveys. This will necessarily involve some discussion of the IEST/ISO operational states of a fab as well as some aspect of measurement protocols. The issue of facility “maturation” will be touched upon, but a detailed presentation of that phenomenon is beyond our present scope. Measured data from multiple surveys taken over periods of many months (or several years) will be used to illustrate the discussions.