SUCCESS STORY – Vibration Isolation for Industry, Laboratory and Research-- Steffen Arnold --Vibration Isolation for Industry, Laboratory and Research
Piezo Actuators Improve Effectiveness, Reliability and Lifetime

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

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SUCCESS STORY – Vibration Isolation for Industry, Laboratory and Research-- Steffen Arnold --If a disturbance knocks a system off balance, this can result invibrations. Since every vibration is damped by the effect of its
surroundings, any system will eventually come to a standstillagain by itself. Many applications cannot wait this long,
however, especially since what usually happens is that several
disturbances temporally superimpose producing a more orless confusing vibration pattern with very different
frequencies.
The vibration must then be dampened passively in a suitable
way or, even better, the system must be isolated from thesource of the disturbances. Active vibration isolation isparticularly good at reducing the settling times significantly,
the precision of measuring or production processes improvesand higher throughputs are possible. Laboratory setups, laser
technology, mechanical engineering and optical metrology,
microscopy and micromachining, for example, all benefit
from this.

Fig. 1

Test pattern with a line width of 45 nm, without (a) and with (b)STACIS vibration isolation (image: Sematech)

The usual methods of vibration isolation used until now are
no longer sufficient for many of today's technologies.
Movements and jolts caused by footfall, fans, coolingsystems, motors, machining processes etc. can distortpatterns for micromachining, for example, to such an extent
that the result is unusable. In addition, conventional
pneumatic decouplers are ineffective at interference
frequencies below 2 Hz. Fig. 1 shows a typical example:
When a lithography device does not have sufficient vibration
isolation, the 45 nm wide lines are practically not discernable(a).

The picture next to it (b) shows the result when the vibration
isolation uses active methods which not only dampen thevibration but actively oppose it.

Fig. 2Piezoelectric active STACIS vibration isolators with controller(image: TMC)

The problem solver here was an active isolation system fromthe STACIS range developed by TMC Technical Manufacturing
Corporation (Fig. 2). It makes it possible to isolate very low
oscillation frequencies starting at the sub-hertz range andthus prevents the vibrations having a detrimental effect on
the machine installed on it. This not only improves themachining or testing quality but at the same time reduces thesettling times (Fig. 3). The cycle times are shortened and thethroughput increases.

Fig. 3

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

Settling time as a reaction to the on-board perturbation whenloading a microscopy table with the substrate (image: TMC)

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SUCCESS STORY – Vibration Isolation for Industry, Laboratory and Research-- Steffen Arnold --Detect and Compensate Vibrationsin Six Degrees of Freedom
The active vibration isolators use integrated acceleration
sensors to detect vibrations occurring in six degrees offreedom. The counter-movements necessary for thecompensation are generated by piezo actuators which arecontrolled by a real time digital signal processor. This provides
the computing power required for the extremely fastcalculations of the vibration compensation.

The isolator can also work well with existing conventional
pneumatic isolators, supplement them in the lower frequency
range, and can even be retrofitted with ease in many
applications. Suitable versions are also available for scanningelectron microscopy (Fig. 4), and their compact size means
they can be integrated well in the comparably compact
microscopes.

Fast, strong actuators for highly
precise motion
The driving force behind the isolators is provided by piezo
actuators. Their specific characteristics make them optimallysuited to the application in isolators:
They operate with response times of only a few microseconds
and resolutions in the sub-nanometer range. At the sametime, high accelerations of more than 10,000 g can beachieved and loads up to several tonnes can be moved. Since
the piezo effect is based on electric fields, piezo actuators do
not generate magnetic fields, neither are they affected bythem. Changing ambient temperatures do not affect thepiezoelectric effect.

Fig. 5

Fig. 4

STACIS isolation is also possible for smaller equipment, e.g. forscanning electron microscopes (image: TMC)

Their great stiffness, high load capacity and clean operation
without compressed air make the piezo-based active isolators
suitable for integration as OEM components in ultramodern
tools and also for installation in isolation platforms for
metrology devices or optical lithography systems, which now
write with line widths in the nanometer range thanks tomodern laser technology.

PI piezo actuators have gone through several billion cycles inendurance tests without measurable changes in their behavior(image: PI)

The technology does not suffer from wear and tear either,because there are no gearwheels, bearings or othermechanical parts. The motion is based on crystalline solidstate effects. Piezo actuators from PI Ceramic/Germany havegone through several billion cycles in endurance tests without
measurable changes in their behavior (Fig. 5).
At the same time, piezos can also score in terms of energy
consumption: In static mode they require almost no energy,
even if heavy loads are held permanently. The behavior canbe compared to that of an electrical capacitor.

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

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SUCCESS STORY – Vibration Isolation for Industry, Laboratory and Research-- Steffen Arnold --Piezos for Active VibrationIsolation
The piezo actuators used by TMC are from the PICA series(Fig. 6) and originate from PI Ceramic, a subsidiary of Physik
Instrumente (PI), the Karlsruhe specialist for precision
positioning. The actuators are manufactured in a high-tech
production plant and supplied in a large range of diameters
and overall lengths.
They can be used for almost all actuator applications and are
optimally suited to the isolators as well, because they aresuitable for high loads and resonant frequencies above
10 kHz, at scanning ranges of more than 100 µm and ablocking force of more than 75 kN.

Fig. 6

Fig. 7

Patented technology for maximum operating hours and life time:
PICMA (Image: PI)

The so-called piezo stepping drives (Fig. 8) are also of interest
for applications in the field of vibration isolation. They cancover large travel ranges for adjustment, on the one hand,and on the other can act like conventional piezo actuators,
i.e. they can isolate vibrations thanks to their high stiffness ofa few micrometers. In the semiconductor industry they are
therefore used in conjunction with lithographic methods tofabricate structure widths of only a few 10 nm without
interference and reproducibly. Piezo actuators thus open up
interesting possibilities for active vibration isolation in a large
variety of application fields.

Different standard and special versions of PICA piezo stackactuators (image: PI)

In principle these actuators consist of a stack of piezo ceramic
disks separated by metal electrodes. For the PICA versions thelayers are around 5 mm thick. The thinner the individuallayers in the stack, the lower the drive voltage.
Multilayer actuators, where the thickness of the individual
layers is only around 60 µm, are thus very attractive forindustrial applications (Fig. 7). These actuators alreadyachieve their nominal displacement at operating voltages
significantly below 150 V. They are also considered to be very
robust. The full-ceramic encapsulation protects them fromhumidity and failure caused by an increase in the leakage
current.

Fig. 8

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

In the semiconductor industry, piezo step actuators are
therefore often used in conjunction with lithographic methods tomanufacture structure widths of only a few 10 nm without
interference and with high reproducibility (Image: PI)

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SUCCESS STORY – Vibration Isolation for Industry, Laboratory and Research-- Steffen Arnold --About TCM

Author

TMC Technical Manufacturing Corporation was established in1969. Its headquarters are in Peabody, Massachusetts andthe company is now considered to be the technology leader
for products in the field of vibration isolation. Isolationdevices from TMC were already in place when the firsttransistors were manufactured at Western Electric.
The spectrum now ranges from simple, low-cost desktop
microscopes with vibration-isolated base right through to theactive vibration systems of the STACIS range, which areequipped with sensors, piezo actuators and digital controllers
and are supplied in a large variety of sizes. Customers include
large research centers, OEM and end users in the field ofsemiconductor manufacture and many companies working in
the field of nanotechnology, e.g. in microscopy andmicrobiology.

Dipl.-Phys. Steffen Arnold, Head of "Marketing and Products"
at PI (Physik Instrumente)

About PI
In the past four decades, PI (Physik Instrumente) with
headquarters in Karlsruhe, Germany has become the leading
manufacturer of nanopositioning systems with accuracies inthe nanometer range. With four company sites in Germany
and fifteen sales and service offices abroad, the privately
managed company operates globally. Over 850 highly
qualified employees around the world enable the PI Group tomeet almost any requirement in the field of innovative
precision positioning technology. All key technologies aredeveloped in-house. This allows the company to control every
step of the process, from design right down to shipment:
precision mechanics and electronics as well as positionsensors.
The required piezoceramic elements are manufactured by its
subsidiary PI Ceramic in Lederhose, Germany, one of the
global leaders for piezo actuator and sensor products.
PI miCos GmbH in Eschbach near Freiburg, Germany, is a
specialist for positioning systems for ultrahigh vacuum
applications as well as parallel-kinematic positioning systems
with six degrees of freedom and custom-made designs.

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

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