Elsevier Science 1 Piezoresistive cantilevers in a commercial CMOS technology for intermolecular force detection Guillermo Villanueva a , Francesc Pérez-Murano a , Martin Zimmermann b , Jan Lichtenberg b , Joan Bausells a* a Centro Nacional de Microelectrónica (IMB-CSIC), Campus UAB, 08193 Bellaterra (Barcelona), Spain b Physical Electronics Laboratory, ETH Zurich, Hönggerberg,HPT H 6,CH-8093 Zurich, Switzerland Elsevier use only: Received date here; revised date here; accepted date here Abstract 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 μV/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. © 2006 Elsevier Science. All rights reserved Keywords: Piezoresistive cantilever; CMOS cantilever; force detection. ——— * Corresponding author. Tel.: +34-93-5947700; fax: +34-93-5801496; e-mail: Joan.Bausells@cnm.es. 1. Introduction Silicon microcantilevers, originally developed for atomic force microscopy (AFM), have been increasingly used for (bio)chemical sensing [1,2]. A high sensitivity can be obtained by detecting the intermolecular forces between a functionalized AFM tip and a functionalized surface [3]. This technique has been used for the measurement of the unfolding of proteins [4,5], forces in DNA molecules [6] and antibody-antigen binding [7]. We are interested in detecting proteins by molecular binding between a cantilever and a substrate in a portable instrument. The standard optical measurement of the deflection of an AFM cantilever is difficult to implement in a portable low-cost instrument or for small cantilevers. Journal logo