Page 45 - Vol.06

陳錦村 C.T. Chen
人生，是個不斷
學習的過程

Location:F3, FA 1ab=partition=EW=n0.75, Ti=0, Tf=48, Avg. No.:45
a) Time History
0.15

0.1

0.05
Velocity (cm/s) 0

-0.05

-0.1

-0.15
0 16 32
Time
Figure1. Beating phenomenon

induced by the footfall of “Tae Bo” Microscope), deviation of electron beam (E-beam writer),
exercisers, and the footfall frequency alignment of scanner and particle issue, all of them will affect
is the same with the building’s natural yield.
frequency results in resonance.
• The vibration induced by two low power Vibration Criteria
(1/2 HP) motors in a laboratory let the There’re various vibration criteria in different fields and
people feel uncomfortable while working
countries, for example, JIS1510 is acceleration-based criteria for
on the desk. high speed railway, DIN4150 is velocity-based criteria, ISO2631
The Fig ure 1 shows the beati ng adopts both acceleration-based and velocity-based criteria;
phenomenon, which is caused by regarding the semiconductor field, the widely used vibration
two rotating machines with almost criteria is called generic vibration criteria, the criteria are
same power and running at very close given in terms of RMS velocity amplitude as processed in one-
frequency; then there will be another third-octave bands of frequency. The vibration criteria curves
very low frequency induced, from time are as shown in Figure 2 and definition in Table 1
domain the peak and trough is very
obvious. The beating frequency is equal
to the difference of two waves’ frequency.
The beating phenomenon will result in Background
negative effect on machine and people
working nearby. There’re two assessment methods discussed in this report.
• The impacts of floor vibration on One is AISC steel design guide series 11: “Floor Vibrations Due
semiconductor Fab include image blur of to Human Activity”; and the other is “Improved methodologies
SEM (Scanning Electron Microscope), for the prediction of footfall-induced vibration” by Arup
measurement quality of CD-SEM Consulting Engineering. The formula by Colin Gordon is
(Critical Dimension- Scanning Electron described also though there’s little information about this

NEW FAB TECHNOLOGY JOURNAL APRIL 2012 45