Abstract
The intrinsic stress behavior and microstructure evolution of Molybdenum thin films were investigated to evaluate their applicability as a metallization in high temperature microelectronic devices. For this purpose, 100 nm thick Mo films were sputter-deposited without or with an AlN or SiO2 cover layer on thermally oxidized Si substrates. The samples were subjected to thermal cycling up to 900 °C in ultrahigh vacuum; meanwhile, the in-situ stress behavior was monitored by a laser based Multi-beam Optical Sensor (MOS) system. After preannealing at 900 °C for 24 h, the uncovered films showed a high residual stress at room temperature and a plastic behavior at high temperatures, while the covered Mo films showed an almost entirely elastic deformation during the thermal cycling between room temperature and 900 °C with hardly any plastic deformation, and a constant stress value during isothermal annealing without a notable creep. Furthermore, after thermal cycling, the Mo films without as well as with a cover layer showed low electrical resistivity (≤10 μΩ·cm).
Highlights
Accurate in-situ real-time temperature monitoring has become a key requirement to control and optimize processes in several industrial fields requiring high temperatures
Mo-La2 O3 [15] material systems were investigated regarding their suitability for applications in high temperature Surface acoustic wave (SAW) devices, and the results showed their applicability as electrode materials for high temperatures
AlN or SiO2 cover layer was studied during thermal cycling up to 900 ◦ C as well as during an
Summary
Accurate in-situ real-time temperature monitoring has become a key requirement to control and optimize processes in several industrial fields requiring high temperatures. The development of wireless and passive (i.e., operating without a battery) measurement systems has been strongly demanded to enable measurements at locations that cannot be connected by a wired sensor. Such parts are moving or rotating objects like turbine blades, which are exposed to an elevated temperature. One of the main issues for a SAW sensor to be used above 350 ◦ C is the development of a suitable material for the IDTs that is able to withstand these high temperatures without degradation due to thermally induced processes like diffusion, agglomeration, oxidation, corrosion, and stress-induced defects. For the temperature range above 350 ◦ C, platinum has attained interests due to its remarkable noble character and higher melting point Tm of 1768 ◦ C, as compared to
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