Single-crystalline AlN/sapphire and composite electrode based ultra-high temperature surface acoustic wave devices

Abstract

Single crystalline AlN material is very attractive for the development of high temperature electronic devices owing to its high temperature resistance. However, at ultrahigh temperatures, AlN film still will be oxidized and metal electrodes used for the devices will aggregate and vaporize. The deterioration of the material and metal electrodes eventually fails the AlN-based devices. Here, we report a single crystalline AlN film-based ultrahigh temperature surface acoustic wave (SAW) device. By using a thin alumina (Al2O3) protection layer on surface, oxidation of the AlN piezoelectric film was effectively inhibited at high temperatures. A composite electrode based on multilayer structure of Pt-Rh and Al2O3 was designed and fabricated, with the Al2O3 layer as the diffusion barrier layers to suppressed inter-diffusion, agglomeration and vaporization of the metals. The results showed that the developed AlN SAW devices can withstand high temperatures, and work well at temperatures up to 1400 °C.

Study of the Long-Term High-Temperature Structural Stability of RuAl Electrodes for Microelectronic Devices

“…Depending on the applied metallization and substrate, additional barrier and cover layers might be required to prevent a chemical reaction between the substrate and the metallization or the metallization and the surrounding atmosphere. In contrast to investigations reported in the literature, which are mainly restricted to electrode materials based on noble metals such as Pt, Pd, or Ir [1][2][3][4][5][6][7][8][9][10], we developed high-temperature stable electrode systems made of the intermetallics TiAl [11,12] or RuAl on Ca 3 TaGa 3 Si 2 O 14 (CTGS) substrates [13][14][15]. In combination with suited cover layers, these metallizations provide sufficient oxidation resistance at high temperatures.…”