21 May 2015 Fabrication of wear-resistant silicon microprobe tips for high-speed surface roughness scanning devices
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Abstract
Silicon microprobe tips are fabricated and integrated with piezoresistive cantilever sensors for high-speed surface roughness scanning systems. The fabrication steps of the high-aspect-ratio silicon microprobe tips were started with photolithography and wet etching of potassium hydroxide (KOH) resulting in crystal-dependent micropyramids. Subsequently, thin conformal wear-resistant layer coating of aluminum oxide (Al2O3) was demonstrated on the backside of the piezoresistive cantilever free end using atomic layer deposition (ALD) method in a binary reaction sequence with a low thermal process and precursors of trimethyl aluminum and water. The deposited Al2O3 layer had a thickness of 14 nm. The captured atomic force microscopy (AFM) image exhibits a root mean square deviation of 0.65 nm confirming the deposited Al2O3 surface quality. Furthermore, vacuum-evaporated 30-nm/200-nm-thick Au/Cr layers were patterned by lift-off and served as an etch mask for Al2O3 wet etching and in ICP cryogenic dry etching. By using SF6/O2 plasma during inductively coupled plasma (ICP) cryogenic dry etching, micropillar tips were obtained. From the preliminary friction and wear data, the developed silicon cantilever sensor has been successfully used in 100 fast measurements of 5- mm-long standard artifact surface with a speed of 15 mm/s and forces of 60–100 μN. Moreover, the results yielded by the fabricated silicon cantilever sensor are in very good agreement with those of calibrated profilometer. These tactile sensors are targeted for use in high-aspect-ratio microform metrology.
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Hutomo Suryo Wasisto, Hutomo Suryo Wasisto, Feng Yu, Feng Yu, Lutz Doering, Lutz Doering, Stefan Völlmeke, Stefan Völlmeke, Uwe Brand, Uwe Brand, Andrey Bakin, Andrey Bakin, Andreas Waag, Andreas Waag, Erwin Peiner, Erwin Peiner, } "Fabrication of wear-resistant silicon microprobe tips for high-speed surface roughness scanning devices", Proc. SPIE 9517, Smart Sensors, Actuators, and MEMS VII; and Cyber Physical Systems, 951723 (21 May 2015); doi: 10.1117/12.2179866; https://doi.org/10.1117/12.2179866
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