Hannes Mehner

Variation of the intrinsic stress gradient in thin aluminum nitride films

The intrinsic stress gradient variation of thin aluminum nitride (AlN) films is the central objective in this paper. For the first time, significant influence parameters on the stress gradient are identified and varied during the deposition process. The process power induced in the plasma and the gas flow ratio of the sputter gases argon and nitrogen are the two major parameters for controlling the stress gradient of deposited AlN films. The controlled avoidance as well as the controlled generation of positive and negative gradients is shown. The stress gradient was investigated by analysis of released one-side clamped cantilever test structures.

Linear micromechanical stepping drive for pinhole array positioning

A compact linear micromechanical stepping drive for positioning a 7 × 5.5 mm2 optical pinhole array is presented. The system features a step size of 13.2 µm and a full displacement range of 200 µm. The electrostatic inch-worm stepping mechanism shows a compact design capable of positioning a payload 50% of its own weight. The stepping drive movement, step sizes and position accuracy are characterized. The actuated pinhole array is integrated in a confocal chromatic hyperspectral imaging system, where coverage of the object plane, and therefore the useful picture data, can be multiplied by 14 in contrast to a non-actuated array.

Linear stepping microactuator for hyperspectral systems

We present an electrostatic inch-worm stepping drive for optical filter alignment in hyperspectral imaging systems requiring a large displacement range of about 140 μm and a step size of 10 μm. The shifted pinhole filter greatly improves the optical resolution of an innovative hyperspectral imaging system [1]. The fabrication is based on SOI (silicon on insulator) technology. The pinhole array is separately mounted into the driving frame.

Process flow to integrate nanostructures on silicon grass in surface micromachined systems

The process flow to integrate metallic nanostructures in surface micromachining processes is presented. The nanostructures are generated by evaporation of microstructured silicon grass with metal. The process flow is based on the lift-off of a thin amorphous silicon layer deposited using a CVD process. All steps feature a low temperature load beneath 120 °C and high compatibility with many materials as only well-established chemicals are used. As a result metallic nanostructures usable for optical applications can be generated as part of multilayered microsystems fabricated in surface micromachining.

MEMS gas ionization sensor with palladium nanostructures for use at ambient pressure

A microfabricated gas ionization sensor with integrated field enhancing silicon- palladium nanostructures is presented. The sensor can be used to determine the ambient gas by its specific breakdown voltage. Technological details of the fabrication and the assembly of the sensor are presented too.

2D stepping microdrive for hyperspectral imaging

In a novel hyperspectral imaging concept based on confocal chromatic microscopy, a pinhole array (matrix of pinholes) has to be scanned across an intermediate image plane to capture the full object plane. In this paper a two-axis stepping microdrive is presented for the pinhole array (6×7.5×0.2 mm3 of glass, weight 20 mg), featuring a 10 μm step size and a 200 μm displacement range in each direction. With the two-axis stepwise actuation of the pinhole array, the imaged area of the object plane is increased from 7% (fixed pinhole array) up to 89% with actuated array. The two-axis positioning is implemented with a three-axis inchworm motion driven by electrostatic forces. A combination of horizontal and vertical electrostatic actuators are arranged to achieve a precise in-plane actuation of the pinhole array. The microdrive is fabricated with established MEMS technologies and features a size about 1 cm2 with 1 mm thickness. The microdrive is capable to position the pinhole array over the displacement range. The array size enables a 1:1 optical imaging on an 8 mm diagonal size CCD. The presented stepping microdrive outperforms existing microsystem solutions with a combination of high payload, large step size, displacement range, and the large optical aperture. Furthermore, the device concept enables the positioning of milligram weights with a highly integrated microsystem.

2D stepping drive for hyperspectral systems

We present the design, fabrication and characterization of a compact 2D stepping microdrive for pinhole array positioning. The miniaturized solution enables a highly integrated compact hyperspectral imaging system. Based on the geometry of the pinhole array, an inch-worm drive with electrostatic actuators was designed resulting in a compact (1 cm2) positioning system featuring a step size of about 15 µm in a 170 µm displacement range. The high payload (20 mg) as required for the pinhole array and the compact system design exceed the known electrostatic inch-worm-based microdrives.