Small, deep, steep? – This is no longer a problem!

Micro-optical components often include steep and simultaneously deep structure which are difficult or even impossible to access for conventional profilometers, optical microscopes and scanning force microscopes. Besides the geometrical dimensions, also the roughness of such surfaces is highly interesting. The new device allows traceable dimensional measurements on and in structures with high aspect ratio or in nozzles. Its core component is a long silicon bending beam with an integrated tip and a piezoresistive measuring bridge for deflection detection. The sensor was developed in cooperation with the Forschungsinstitut für Mikrosensorik und Photovoltaik (Microsensor systems and photovoltaics research institute – CiS) in Erfurt and the Institute of Semiconductor Technology (Institut für Halbleitertechnologie – IHT) of Braunschweig Technical University. Sensors are available in different lengths (1.5 mm, 3 mm, 5 mm) and widths (30 μm, 100 μm, 200 μm) at tip heights of up to 70 μm and a noise of 6 nm at a bandwidth of 20 kHz. For the measurement of soft surfaces, the measuring force of the stylus tip can be adjusted down to values of 1 μN. The tactile microsensor is affixed to a 3D piezo table and can be displaced over a positioning range of 800 μm × 800 μm × 250 μm. One of the advantages of this microsensor is its light weight which allows extremely high displacement rates – and, thus, short measuring times. Microsensors with displacement rates of up to 1 mm/s have been tested successfully in experiments on technical surfaces at PTB. Hereby, the sensor proved to be very robust. The measuring head of the device contains, besides the microsensor, also three laser interferometers which are arranged vertically to each other and have a resolution of 1 nm to guarantee the direct traceability of the measurements to the SI unit “metre”. The measuring beams of the interferometers intersect on the stylus tip of the sensor at one point to ensure practically Abbeerror-free measurements. With the measurement and control software of the device (LabWindows), operating the device is easy. The complete surface scanner is equipped with a coarse positioning table of 12.5 mm × 12.5 mm × 12 mm, a rotating range of 360° and the possibility of measuring very large test objects with dimensions up to 80 mm × 100 mm × 100 mm. The sensor and the device were presented to the interested public at the trade fair “Control” in Stuttgart in May 2012.