Microelectromechanical system microhotplates for reliability testing of thin films and nanowires

摘要

Microelectromechanical system microhotplates fabricated using silicon-on-insulator wafers were designed and fabricated for accelerated lifetime testing of thin films and nanowires. Thin films of Cr/Ru/Au, Cr/Ru, and Ru were examined as well as nanowires of Ru and RuO_x. Rapid thermal cycling at a 1 kHz pulse frequency was employed for testing the thin films. Nanowires were characterized using 1 kHz and 500 Hz pulse frequencies. A 40 nm layer of sputtered Au deposited on 12 nm of sputtered Ru and 8 nm of sputtered Cr displayed a sheet resistance of 1.18 Ω/□ and a lifetime of 267 h before failure when cycled with a peak temperature of 692 K. Ru thin films with a thickness of 12 nm displayed a sheet resistance of 51 Ω/□ and a lifetime of 10 h under the same conditions. Sputtered Ru and RuO_x nanowires with thicknesses of 15 and 32 nm, respectively, displayed resistivities of 72 X 10~(-8) and 320 × 10~(-8) Ω m. It was found that the cycling frequency did not influence the nanowire lifetimes in air or in N_2. Ru nanowires tested in N_2 displayed lifetimes of 450 min followed by Ru nanowires tested in air with lifetimes of 340 min and finally by RuO_x. nanowires tested in air with lifetimes of 45 min. This latter behavior is attributed to a higher surface diffusion in RuO_x. compared to Ru. An activation energy of 0.29 eV was observed for failure of Ru nanowires tested in air conditions. Biased percolating behavior with critical exponents ranging from 0.5 to 0.7 was found to describe the electrical behavior for all the nanowires.