July/August 2018 • www.cemag.us 5
Table 1: Vibration Criteria for Sensitive Equipment
Amplitude1 Detail Size2 Description of Use
μin/s μm/s μm
Workshop (ISO) 32,000 800 N/A Distinctly perceptible vibration. Appropriate in workshops and non-sensitive areas.
Office (ISO) 16,000 400 N/A Perceptible vibration. Appropriate for offices and non-sensitive areas.
Residential Day (ISO) 8,000 200 75 Mildly perceptible vibration. Appropriate for daytime residences, quiet offices,
Residential Night (ISO) 5,600 150 50 Barely perceptible vibration. Appropriate to sleep areas in most instances. Usually
adequate for hospital recovery rooms, semiconductor probe test equipment, and
microscopes less than 40x.
Operating Rooms (ISO) 4,000 100 25 Vibration not perceptible. Suitable in most instances for surgical suites, microscopes
to 100X, and for other equipment of low sensitivity.
VC-A 2,000 50 8 Adequate in most instances for optical microscopes to 400X, microbalances, optical
balances, proximity and projection aligners, etc.
VC-B 1,000 25 3 Appropriate for inspection and lithography (including steppers) to 3 μm line widths.
VC-C 500 12.5 1 - 3 Appropriate standard for optical microscopes to 1000X, inspection and lithography
inspection equipment (including moderately sensitive electron microscopes) to 1 μm
detail size, TF T-LCD stepper/scanner processes.
VC-D 250 6.25 0.1 - 0.3 Suitable in most instances for the most demanding equipment including electron
microscopes (TEMs and SEMs) and E-Beam systems.
VC-E 125 3. 12 < 0.1 A challenging criterion to achieve. Assumed to be adequate for the most demanding
of sensitive systems including long path, laser-based, small target systems, E-Beam
lithography systems working at nanometer scales, and other systems requiring
extraordinary dynamic stability.
Appropriate for extremely quiet research spaces; generally difficult to achieve in
most instances, especially cleanrooms. Generally, not recommended for use as a
design criterion, only for evaluation.
NIS T-A NIST-A criterion is identical to the VC-E curve at frequencies above 20 Hz but maintains constant displacement at frequencies below this. 0.025 μm or 25 nm between
1 and 20 Hz; 3.1 μm /s (125 μ in /s) between 20 and 100 Hz.
NIS T-A1 NIST-A1 criterion requires an RMS velocity of 3 μm/sec (118 μin./sec) for frequencies less than 4 Hz, and 0.75 μm/sec (29.5 μin./sec) velocity for frequencies 4 Hz <
f < 100 Hz.
1. As measured in one-third octave bands of frequency over the frequency range 8 to 80 Hz (VC-A and VC-B)
or 1 to 80 Hz (VC-C through VC-G)
2. The detail size refers to line width in the case of microelectronics fabrication, the particle (cell) size in the case
of medical and pharmaceutical research, etc. It is not relevant to imaging associated with probe technologies,
AFMs, and nanotechnology.