Patterning and bonding of TiNi shape memory thin film for fabrication of micropump

Eiji Makino; Takashi Mitsuya; Tae Nakatsuji; Takayuki Shibata

doi:10.1117/12.341172

10 March 1999 Patterning and bonding of TiNi shape memory thin film for fabrication of micropump

Eiji Makino, Takashi Mitsuya, Tae Nakatsuji, Takayuki Shibata

Proceedings Volume 3680, Design, Test, and Microfabrication of MEMS and MOEMS; (1999) https://doi.org/10.1117/12.341172
Event: Design, Test, and Microfabrication of MEMS/MOEMS, 1999, Paris, France

Abstract

In order to develop a micropump driven by shape memory actuation, we require a TiNi diaphragm structure with a cap to act as a chamber for applying bias pressure to the diaphragm. With the purpose of realizing such a structure, we studied the photoetching of TiNi thin film on a Si substrate and two bonding processes-diffusion bonding and anodic bonding- for patterning and assembling. TiNi thin film deposited on Si substrates by flash evaporation was etched in HF/HNO₃/H₂O solutions using negative photoresist masks. HF:HNO₃:H₂O equals 1:1:4 solution proved capable of etching it at a rate of about 30 nm/s without etching of the Si substrate. Patterned TiNi thin film of 6 micrometers in thickness on a Si substrate was diffusion bonded to another Si substrate coated with the same TiNi thin film at a thickness of 300 nm. Bonding was conducted in a vacuum at a bonding pressure of 210 MPa. TiNi-TiNi diffusion bonding was obtained at temperatures of more than 300 degrees C. A 4-point bending test revealed that the bond strength of specimens bonded at 400 degrees C was 15-20 MPa. Anodic bonding was conducted between TiNi thin film on a Si substrate and a Pyrex 7740 glass substrate at an applied voltage of 600 V. Two substrates were bonded in nitrogen ambient at temperatures of more than 350 degrees C, giving a bond strength of about 15 MPa at 400 degrees C bonding.

Citation Download Citation

Eiji Makino, Takashi Mitsuya, Tae Nakatsuji, and Takayuki Shibata "Patterning and bonding of TiNi shape memory thin film for fabrication of micropump", Proc. SPIE 3680, Design, Test, and Microfabrication of MEMS and MOEMS, (10 March 1999); https://doi.org/10.1117/12.341172

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KEYWORDS

Silicon

Thin films

Etching

Diffusion

Optical lithography

Glasses

Shape memory alloys

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