Micro-sensors & actuators

N. Sandström (a), S. Braun (a), T. Grund (b), G. Stemme (a), M. Kohl (b), W. van der Wijngaart (a)
a Microsystem Technology Lab, KTH - Royal Institute of Technology, Stockholm, SWEDEN
b Institut für Mikrostrukturtechnik, Forschungszentrum Karlsruhe GmbH, Karlsruhe, GERMANY

Abstract

This paper demonstrates the concept of wafer-level fabrication and integration of robust bulk SMA microactuators based on adhesive bonding of cold-rolled SMA sheets to silicon wafers. Contact printing of an adhesive polymer ensures a selective bonding when transferring full SMA sheets to silicon structures on a patterned wafer. The induced stress of a thin dielectric film deposited on top of the SMA sheet ensures a stable and built-in reset mechanism of the actuators. The trimorph microactuators can be actuated by indirect resistive heating through a thin metal film. We report on the successful wafer-scale fabrication of actuator cantilevers and their characteristics. First test cantilevers show a cold-state deflection of 300 μm which, however, is limited by the silicon substrate. Upon heating, the cantilever shows a stroke of approx. 80 μm.

Carmen Moldovan (a), Sebastian Sosin (a), Oana Nedelcu (a), Ulrike Kaufmann (b), Hans-Joachim Ritzhaupt-Kleissl (b),
Stefan Dimov (c), Petko Petkov (c), Robert Dorey (d), Katrin Persson (e), David Gomez (f), Per Johander(g)
a National Institute for R&D in Microtechnologies, Erou Iancu Nicolae 32 B, Bucharest 077190, Romania
b Forschungszentrum Karlsruhe, Institut für Materialforschung III, P.O. Box 3640, 76021 Karlsruhe, Germany ;
c Manufacturing Engineering and Multidisciplinary Technology Centre, Cardiff University;
d Nanotechnology Group, Cranfield University, Cranfield, Bedfordshire, UK;
e IMEGO, Arvid Hedvalls Backe 4, SE 411 33 Goteborg, Sweden;
f Fundacion Tekniker
g IVF - Industrial Research and Development Corporation; Argongatan 30, S431 53 Molndal, Sweden

Abstract

The paper presents the development of a novel suspended membrane resistive gas sensor on a ceramic substrate. The sensor is designed and simulated to be fabricated by combining laser milling techniques, conductive ceramic technology, thin film technology, and semiconductor metal oxides. Trenches are created in the alumina substrate in order to define the geometry of the heater using laser processing of the substrate. The heater is completed by filling the trenches with conductive ceramic paste and then baking to remove the solvent from the paste. The next step consists of polishing the surface to obtain a surface roughness small enough for thin film technology. A dielectric (SiO2 or ceramic) material is then deposited, acting as hot plate and also as electrical isolation between the heater and sensing electrode. The sensing electrode consists of an interdigitated resistor made of Au or Pt with thickness in the range of 2000 -3000 Å. The gas sensitive layer (SnO2) is deposited by screen printing or spinning. When heated it react with gas molecules and changes its resistivity, thereby acting as a sensor. The final step involves releasing the sensor, enabling it to be suspended on four bridges, to minimise the dissipation of the heat in the substrate.

Dr. Dumitru Ulieru (a), Dr. Ileana Cernica (b)
(a) ROMES S.A., 126 A, Iancu Nicolae Str, 77190, Voluntari (Bucharest), Romania,
(b) IMT – Bucharest, 32B, Erou Iancu Nicolae Str., 77190, Voluntari (Bucharest), Romania

Abstract

Microsystems (MST) as MEMS, MOEMS, MCMs, microsensors and actuators uses the same techniques as microelectronics processing to create structural components that are essentially micronic or submicronic mechanical parts. These parts usually require high precision fabrication unless post-fabrication finishing. For various types of materials of which a great used for obtaining microsystems, micro and nanodevices the laser micro and nanoprocessing is the best solution for accuracy and roughness surface quality high precision technologies suitable for batch processing of ceramics and other MSN substrate materials.

• High precision microdrilling of microvias and different microholes configurations.
  Technical features of microprocessing for microsystems application with RF MCM detailed presented in the paper as
  shown on more tables with analyze of answers of more kind of support materials at laser radiation. The authors present also the detailed results of microprocessing of microholes realized by different lasers radiation as UV, Nd:YAG and CO2 for microvias of higher layers count for high density circuits ( HDI ) connection microholes as blind, through tapered holes, circular a/o squared areas etc.

• Microcutting and contouring processing by high precision laser technologies.
  On the paper are presented the experiments and results studies obtained by the authors on the basis of high precision laser for chips separation and / or singulation on ceramics wafer processed including as individual extraction possibility.
• Surface patterning generation by laser microprocessing
  The fine pattern generation of metal or alloy films on ceramic substrates can be structured directly with the laser direct patterning process. Our novel technology applications unless chemicals can resolve this problem by offering structuring processing of sensors and sensors systems able to fulfill these requirements.

Peter Shindov(a), Nasko Elektronov(b),Valery Serbezov(c), Franz Herbst(c)
a: Technical College-"John Atanasoff"
b: JN-Corp.
c: Multicoats Ltd.

Abstract

The development of new generations of laser source for fiber optic’s applications require more fast new photosensors with spectral characteristics in visible range. The idea of this work is development of technology and device – fast photosensor with spectral range adapted to modern lasers for the quickly increasing needs of optoelectronics and fiber optics communications. By pulsed laser deposition (PLD) usage UV N2 Laser for ablation λ=337.1 nm, energy per pulse 8 mJ and CW 60 W CO2 Laser for heating are produced thin CdSxSe1-x films on quartz substrate. Polycrystalline thin films with thickness from 0.5 to 2.0 μm and dominant orientation – (002) are formed by energy density 4.5 J/cm2 and repetition rate 20 Hz .The thin films are investigated by EDAX and SEM. The films are additional thermo treatment for increasing ratio photocurrent – dark current. This ratio reaches 107. By means of TEA UV N2 Laser with energy per pulse-0.3 mJ, pulse duration 2 ns are formed planar Ohm contacts from CdO directly onto thin film. The contacts are investigated by XRD. By means of coordinate table the contacts are formed on the backside of the structure. The dimension of photosensitive structure is 250x250 μm. The distance between contacts areas is 10 μm. The spectral response of devices is measured. The maximum spectral sensitive is at λ=575 nm. Lux ampere characteristics are measured. The increasable fronts and decreаsаble fronts at the structure are measured. They are 2 ns, at ratio 1000.

A. Boersma, R. de Zwart, R. Boot, P.J. Bolt
TNO Science and Industry, Eindhoven, The Netherlands

Abstract

Thin film actuators have been manufactured for application in small devices, such as valves and (micro)pump. These actuators are based on new materials especially suited to be used as electro-active dielectric elastomers. The properties of these elastomers are tuned to the specific requirements. It was found that the electric voltage required for operating could be lowered by a factor of three to five. The thin film actuators were processed into small valves and pumps for the manipulation of gasses and liquids. It was shown that the actuators could be operated when immersed in a liquid (e.g. water) and can be used as valves in microfluidic sensor array devices. The next step in the development is fine-tuning of the valve setting in order to minimize leakage and optimize performance and durability.