Microassembly with Nanometer Resolution

Assembly of Terahertz Frequency Mixers


Fig.1: The superconducting detector within the wave-guide. Click to see a movie of the gripper taking a substrate bar.

Fig. 2: The KOSMA assembly stage

Fig. 3: Principle of the KOSMA detector

Fig. 4: Setup of the assembly stage

The “Superconducting Devices and Mixers Group” at KOSMA (Kölner Observatorium für Submillimeter Astronomie), I. Department of Physics at the University of Cologne, designs, develops and fabricates superconducting devices. They are used as heterodyne frequency detectors and local oscillators for highly sensitive receivers for spectroscopic analysis in astro-physics. The assembly of these devices requires very sensible and precise manufacturing techniques that have been realized by the use of a Nanomotor-based assembly stage.

In order to minimize the loss of 800 GHz RF-Power inside of the receiving waveguide, the total dimensions of the fused quartz mixer substrates have to be 80 µm by only 2 µm (width x height) and 1600 µm long. The manual mounting of these devices into the substrate channel is rather difficult, not reproducible and ends mostly by breaking the device. For array and satellite applications on the other hand, a reliable and reproducible mounting procedure is of utmost importance. The requirements for the coming 1.9 THz receiver for the SOFIA-aeroplane will be even higher. Another point of concern is the sensitivity of some of the devices against electrostatic discharge, being much higher than the sensitivity of semiconductor devices.

That is why the KOSMA group used a Klocke Nanotechnik microassembly stage. The main problem is gripping the fragile device. The two fingers of the gripper are just 200 µm by 300 µm strong. Any standard stepper motor would break the device or even bend the tiny fingers as soon as they try to grip.

For further information, please download the application paper (see right).

SEM picture of the assembled device: It is centered and precisely aligned parallel to the waveguide.

The assembly of substrate
bars with a profile of 35 µm x 80 µm could only be done with the
Nanomotor-based devices.
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