Piezoresistive gauge factor of hydrogenated amorphous carbon films

• Published in: Journal of micromechanics and microengineering 2006-06, Vol.16 (6), p.S75-S81
• Main Authors: Tibrewala, A, Peiner, E, Bandorf, R, Biehl, S, Lüthje, H
• Format: Article
• Language: English
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Microelectronic fabrication (materials and surfaces technology); Micromechanical devices and systems; Physics; Precision engineering, watch making; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/16/6/S12

In this paper we report on the transport properties of hydrogenated amorphous carbon (a-C:H) which is an attractive material for strain gauges and can also be used in flow meters, accelerometers and vibrational sensors. The a-C:H films were deposited at -350 V bias voltage on silicon (Si) substrates using plasma assisted chemical vapor deposition (PACVD). Current-voltage characteristics of a-C:H/n-Si heterojunctions show ohmic behavior within operating voltages of +/-1 V. In the higher voltage range the Frenkel-Poole mechanism is dominant. Conduction is thermally activated at temperatures ranging from 23 deg C to 150 deg C. The activation energy amounts to 0.48 eV. A-C:H resistors are successfully integrated as strain gauges in Si bulk micromachined force sensors. Piezoresistive gauge factors are measured for the a-C:H strain gauge resistors in the temperature range 23-60 deg C. The measured piezoresistive gauge factors are in between 40 and 90 for a-C:H with resistivities in the range 100-700 MOmega cm.