Piezoresistive cantilevers in a commercial CMOS technology for intermolecular force detection

✍ Scribed by Guillermo Villanueva; Francesc Pérez-Murano; Martin Zimmermann; Jan Lichtenberg; Joan Bausells

• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 212 KB
• Volume: 83
• Category: Article
• ISSN: 0167-9317
• DOI: 10.1016/j.mee.2006.01.223

✦ Synopsis

We report the development of piezoresistive cantilevers for intermolecular force detection in biochemical sensing, by using a commercial CMOS technology. The detection of the small forces involved in molecular recognition requires cantilevers with a small spring constant and high force sensitivity. We have fabricated polycrystalline silicon cantilevers by using the two polysilicon layers of a commercial CMOS process with minimum design rule widths. The cantilevers have been released by post-process micromachining. The upper polysilicon layer has been used as a piezoresistor. CMOS amplifying circuits have been integrated on-chip with the cantilever structures. The cantilevers have small spring constants ranging from 1.5 to 12 mN/m. The complete system has been successfully tested by applying a known transverse displacement with an AFM tip. A force sensitivity of 8 lV/pN and resolution of 50 pN has been obtained. This high resolution is obtained with CMOS polysilicon, which has a relatively low piezoresistive coefficient, but this is compensated by the integration of signal-processing circuitry.