Technological process and resonator design optimization of Ir/LGS high temperature SAW devices

Abstract

Photolithography together with ion beam etching was used for fabrication of high temperature SAW devices. Ir thin film of 0.3 µm thick was deposited by magnetron sputtering without additional adhesion layers and than Ir film was annealed after electrode patterning in different conditions. The resistivity of magnetron sputtered thick Ir films drops noticeably after annealing. However, this process requires special care in order to avoid delaminating of the film due to developing high stress during such procedures. We have annealed the substrates with Ir films in different regimes and in different gas/vacuum conditions. The results of these studies have shown that annealing in air up to about 500 °C decreases the Ir film resistivity 1.5-2 times. Vacuum annealing did not show much improvement in comparison to open air annealing. Magnetron sputtered thin Ir films have somewhat porous structure allowing oxygen to diffuse from the substrate surface through Ir films. Resonator structures with thick Ir electrodes were prepared and tested. Examples of the resonator structures show very promising properties, such as high conductance and high Q-factor.

Novel Multilayer SAW Temperature Sensor for Ultra-High Temperature Environments

“…Micromachines 2021, 12, 643 2 of 8 et al [14] and Aubert et al [15,16] prepared Ir-based composite electrodes and demonstrated their stable operation above 800 °C. Alternatively, Moulzolf et al [17] prepared Pt-ZrO2 and Pt-HfO2 composite electrodes that operated stably for 4 h at 1000 °C.…”

“…For example, Thompson [13] found that metal films agglomerate at high temperatures, resulting in a loss of electrical conductivity. In addition, Sakharov et al [14] and Aubert et al [15,16] prepared Ir-based composite electrodes and demonstrated their stable operation above 800 • C. Alternatively, Moulzolf et al [17] prepared Pt-ZrO 2 and Pt-HfO 2 composite electrodes that operated stably for 4 h at 1000 • C. In addition, Aubert et al [18][19][20][21] used Ta as the adhesive layer in the electrode to prepare a SAW device capable of stable operation at 1000 • C for at least 30 min.…”

High-Temperature SAW Resonator Sensors: Electrode Design Specifics

“…All these problems are waiting to be taken care of. However, greater conductance of thicker electrodes is obvious and better device properties, such as a larger resonator Q-factor have already been demonstrated [22].…”

High‐Temperature Conductive Stability of ITO/Pt Bilayer‐Film Electrode for Applications in High‐Temperature SAW Devices

“…Except for their important roles in nanocatalyst, [18,19] the multilayer metal films and alloys present their effect on high-temperature film electrodes. For example, alloys of different compositions have been found to have more stable conductivity at high temperatures [20][21][22][23][24]. In addition, Ti or Ta adhesion layers, [25][26][27][28][29][30] capping layers, [31] buffer layers, [15] and diffusion barriers [32][33][34] have also been applied to promote the hightemperature stability of electrode resistivity.…”