Metal foundation construction to consolidate electroplated structures for successful removal of SU-8 mould

Cao, Feng; Chen, W.-Y.; Zhao, Xianghui; Jing, Xiangmeng; Wu, Xiaojiang

doi:10.1049/el:20060751

Cited by 11 publications

(8 citation statements)

References 3 publications

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“…Then, using surface micromachining process, thin film electrodes and interconnections, nickel stoppers, solder in positioning pits, and alumina passivation film are fabricated through photolithography, electroplating, sputtering and etching. Like the top glass wafer, on the bottom glass wafer, the thin film electrodes and interconnections, nickel stoppers and foundations of later electroformed thick structures [ 26 ], and alumina dielectric passivation film are fabricated by surface micromachining processes. Then, the alumina passivation film is patterned to expose the foundations and thick nickel structures, such as lateral electrodes, connecting pillars and pads, are electroformed through the patterned SU-8 thick resist mold.…”

Section: Fabrication Processes Of the Designed Esmamentioning

confidence: 99%

Design, Fabrication and Levitation Experiments of a Micromachined Electrostatically Suspended Six-Axis Accelerometer

Cao

Liu

Chen

et al. 2011

Sensors

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A micromachined electrostatically suspended six-axis accelerometer, with a square plate as proof mass housed by a top stator and bottom stator, is presented. The device structure and related techniques concerning its operating principles, such as calculation of capacitances and electrostatic forces/moments, detection and levitation control of the proof mass, acceleration measurement, and structural parameters design, are described. Hybrid MEMS manufacturing techniques, including surface micromachining fabrication of thin film electrodes and interconnections, integration fabrication of thick nickel structures about 500 μm using UV-LIGA by successful removal of SU-8 photoresist mold, DRIE of silicon proof mass in thickness of 450 μm, microassembly and solder bonding, were employed to fabricate this prototype microdevice. A levitation experiment system for the fabricated microaccelerometer chip is introduced, and levitation results show that fast initial levitation within 10 ms and stable full suspension of the proof mass have been successfully demonstrated.

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Section: Fabrication Processes Of the Designed Esmamentioning

confidence: 99%

Design, Fabrication and Levitation Experiments of a Micromachined Electrostatically Suspended Six-Axis Accelerometer

Cao

Liu

Chen

et al. 2011

Sensors

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“…The embedded metal foundations made contributions to consolidating the adhesion of the electroplated nickel structures to the substrate [9], and the electroplated structures became stronger to resist interfacial stress between nickel structures and SU-8 mould, which was helpful during SU-8 removal.…”

Section: Continuous Etchingmentioning

confidence: 99%

“…The authors in our research group have reported a wet chemical method which uses fuming sulphuric acid to remove SU-8 mould for fabrication of a micromachined gyroscope stator [9,10]. Fuming sulphuric acid was used to remove thick SU-8 resist mould by oxidizing and breaking the dense chemical bonding of SU-8.…”

Section: Introductionmentioning

confidence: 99%

Investigation on removal of SU-8 electroplating mould using fuming sulphuric acid

Cao

Chen

Zhang

2011

Proceedings of the Institution of Mechanical Engineers, Part C:

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In some microelectromechanical system device fabrication, using fuming sulphuric acid to remove crosslinked SU-8 mould from integrated thick metal structures is an inexpensive and effective wet etching technique. The fabrication of stator for a suspended rotational microgyroscope, which has surface-micromachined structures integrated, was investigated to study the removal process of 250-mm thick SU-8 plating mould. Immersion time in the acid was a critical factor for complete removal of SU-8 mould without detectable damage to the nickel structures. Variation of etch rate was investigated every 0.5 h in the range from 0.5 to 6 h; 5 h was found to be a suitable time setting to remove 250-mm thick SU-8 mould. During the process, etch rate was measured slowing down from 110 mm/h in the first 0.5 h to 18 mm/h in the last 0.5 h. It was better to finish the whole removal process in a consistent manner because although taking sample out of the acid, cleaning, and immersing it back into the acid again was able to accelerate subsequent etch rate, metal structures were likely to be etched black. The etch rate which slowed down with the increase of etch time based on continuous etching provided useful reference for time control during SU-8 application for ultra-thick integrated microstructure fabrication.

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“…Generally, to provide electrical connection between bonding pads and MEMS components, interconnections are usually microfabricated on the common substrate. Based on surface micromachining technique, a metal foundation construction method, that is compatible with multilevel interconnections microfabrication, has been proposed (Cui et al 2006). The metal foundation, on which the thick metal structure is electroplated, is mainly formed along with Cu lines and vias, and then be tamped by interlevel dielectric to withstand the internal induced stress during SU-8 removal process.…”

Section: Microfabrication Process Of the Bottom Statormentioning

confidence: 99%

Design and fabrication of an electrostatically suspended microgyroscope using UV-LIGA technology

et al. 2009

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A micromachined electrostatically suspended gyroscope, with a wheel-like rotor housed by top stator and bottom stator, using UV-LIGA microfabrication technology, was presented. The designed structure and basic operating principle of the gyroscope are described. The key steps in the fabrication process, such as wet etching of Pyrex glass pits for soldering, and integration of thick nickel structures by removal of SU-8 mold, were considered in detail and well solved. Cr/Pt/photoresist was used as etching mask and the etched pits, in depth of near 30 lm, with aspect ratio (depth to undercutting) of 0.75, were obtained. With metal foundations constructed for consolidation, successful integration of the nickel structures, in thickness of 200 lm, was achieved by successful removal of the SU-8 mold using oleum. After the two stators and the rotor were fabricated separately, they were assembled and soldering bonded to form axial and radial small gaps, hence, the initial prototype of the microgyroscope was realized. The key techniques described in this paper can be applied to fabrication of other micro devices. The metal foundation method, associated with removal of SU-8 mold by oleum, is expected to make SU-8 wider applications in making integrated microstructures with fabricated circuitry on the same chip.

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Metal foundation construction to consolidate electroplated structures for successful removal of SU-8 mould

Cited by 11 publications

References 3 publications

Design, Fabrication and Levitation Experiments of a Micromachined Electrostatically Suspended Six-Axis Accelerometer

Design, Fabrication and Levitation Experiments of a Micromachined Electrostatically Suspended Six-Axis Accelerometer

Investigation on removal of SU-8 electroplating mould using fuming sulphuric acid

Design and fabrication of an electrostatically suspended microgyroscope using UV-LIGA technology

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