H

H. Lehr

Technische Universität Berlin

Publishes on Particle Accelerators and Free-Electron Lasers, Advancements in Photolithography Techniques, 3D IC and TSV technologies. 81 papers and 1.3k citations.

81Publications
1.3kTotal Citations

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Top publicationsby citations

Fabrication of photonic crystals by deep x-ray lithography
Gregor Feiertag, W. Ehrfeld, H. Freimuth et al.|Applied Physics Letters|1997
Cited by 140

We have developed a new microfabrication technique for the construction of three-dimensional photonic crystals. In particular, we used multiple tilted x-ray lithography exposures in order to construct structures with photonic band gaps in the infrared region. First polymethylmethacrylate (PMMA) resist layers with a thickness of 500 μm were irradiated, then the holes in the resist structure were filled with preceramic polymer and subsequent pyrolysis converts the preceramic polymer into a SiCN ceramic. Theoretical results with fitted values of the dielectric constant are in good agreement with the transmission measurements.

Micro gear pumps for dosing of viscous fluids
J. Döpper, Markus Clemens, W. Ehrfeld et al.|Journal of Micromechanics and Microengineering|1997
Cited by 75

Gear pumps using micro gear wheels with diameters of 596 and and a height of have been realized at IMM by means of a combination of LIGA technology and precision engineering. Using oil as pumping medium the pumps achieve back pressures of more than 1200 hPa and flow rates of up to . The self-filling pumps tolerate air bubbles and particles contained in the working medium. The gear pumps displace 82 and 213 nl respectively per revolution, i.e. they offer the possibility of very precise dosing of viscous fluids, such as oil.

<title>Micromolding: a powerful tool for large-scale production of precise microstructures</title>
Lutz Weber, W. Ehrfeld, H. Freimuth et al.|Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE|1996
Cited by 66

In recent years a number of micro machining processes have been developed suitable for the realization of industrial process applications, whereby the LIGA technique is considered to be one of the most promising and flexible technologies for the large scale fabrication of three- dimensional microstructure products. LIGA is based on the combination of deep lithography, and electroforming to realize mold inserts with high accuracy for the mass fabrication of microcomponents made from plastic material. The present report deals with the development of micromolding technologies which are applied at IMM. Specifically they are focused on the small dimensions of the molded microstructures, the high aspect ratio, and the demand for sub-micron precision. This includes the technical implementation of molding processes, the production of suitable micro mold inserts, the investigation in simulation software, the screening of polymer materials, ceramics, metallic powders or preceramic polymers and the development of quality qualification systems. The potential of micro molding processes will be demonstrated by presenting a variety of applications like micro gear wheels, micro pumps, micro optical components, splices and connectors, waveguides, optical gratings and components for chemical and biological micro reactors.