TECHNICAL PAPER Simple fabrication of an uncooled Al/SiO 2 microcantilever IR detector based on bulk micromachining Hassan Abdollahi • Hassan Hajghassem • Shams Mohajerzadeh Received: 22 March 2013 / Accepted: 7 June 2013 / Published online: 19 June 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract A simple microfabrication process to make an uncooled aluminum/silicon dioxide bi-material microcan- tilever infrared (IR) detector using silicon bulk microma- chining technology is presented in this work. This detector is based on high banding of the microcantilever due to the large dissimilar in thermal expansion coefficients between the two materials. It consists of a 1 lm SiO 2 layer depos- ited by 200 nm thin Al layer. Since no sacrificial layer is used in this process, complexity related to releasing sac- rificial layer is avoided. Moreover Al is protected in Si etchant using dual-doped tetramethyl ammonium hydrox- ide. The other advantage of this process is that only three masks are used with four photolithography process. Ther- mal and thermal mechanical behaviors of this structure are obtained using finite element analysis, and the maximum temperature and displacement at the end of cantilever at 100 pW/lm 2 absorbed IR power density on top surface are 7.82°K and 1.924 lm, respectively. Abbreviations FEA Finite element analysis IR Infrared TMAH Tetramethyl ammonium hydroxide MEMS Micro electromechanical system SEM Scanning electron microscope CTE Thermal expansion coefficients Al Aluminum Au Gold BOE Buffered hydrofluoric acid Cr Chromium DI De-ionized HF Hydrofluoric acid Si Silicon SiN x Silicon nitride SiO 2 Silicon dioxide A Cross-section area of leg A ab IR absorbed area L One of the folded lengths of leg t 1 Thickness of Al layer t 2 Thickness of SiO 2 layer T Element temperature DT Temperature rise DT s Blackbody target temperature change G Total Total thermal conduction between the detector structure and the surroundings regain G air Air thermal conductance G rad Thermal radiative conductance G leg Thermal leg’s conductance V Volume of film W s Absorbed IR power density n Ratio of Al and SiO 2 Young’s modulus x Al and SiO 2 thickness ratio c Heat capacity r Stefan–Boltzmann constant q Density of the material e Al Al emissivity e SiO 2 SiO 2 emissivity k Thermal conductivity coefficient H. Abdollahi (&)  H. Hajghassem Department of Electrical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran e-mail: hassan_abdollahi@yahoo.com S. Mohajerzadeh Nano-Electronic Center of Excellence, Nano-Electronic and Thin Film Laboratory, University of Tehran, Tehran, Iran S. Mohajerzadeh Department of Electrical and Computer Engineering, University of Tehran, Tehran, Iran 123 Microsyst Technol (2014) 20:387–396 DOI 10.1007/s00542-013-1854-4