Alternative dielectric films for rf MEMS capacitive switches deposited using atomic layer deposited Al₂O₃/ZnO alloys

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• 作者：Cari F. Herrmann ; Frank W. DelRio ; David C. Miller ; Steven M. George ; Victor M. Bright ; Jack L. Ebel ; Richard E. Strawser ; Rebecca Cortez ; Kevin D. Leedy
• 关键词：Atomic layer deposition ; Capacitive shunt switch ; Dielectric layer ; rf MEMS
• 刊名：Sensors and Actuators A: Physical
• 出版年：2007
• 出版时间：30 March 2007
• 年：2007
• 卷：135
• 期：1
• 页码：262-272
• 全文大小：948 K

文摘

Atomic layer deposition (ALD) was used to deposit an alternative dielectric barrier layer for use in radio frequency microelectromechanical systems (rf MEMS). The layer is an alloy mixture of Al₂O₃ and ZnO and is proposed for use as charge dissipative layers in which the dielectric constant is significant enough to provide a large down-state capacitance while the resistivity is sufficiently low to promote the dissipation of trapped charges. This paper investigates Al₂O₃/ZnO ALD alloys deposited at 100 and 177 °C and compares their material properties. Auger electron spectroscopy was used to determine the Zn concentrations in the alloy films, which was lower than expected. Atomic force microscopy images revealed an average surface roughness of 0.27 nm that was independent of deposition temperature and film composition. The dielectric constants of the Al₂O₃/ZnO ALD alloys films were calculated to be similar to pure Al₂O₃ ALD, being 7. Indentation was used to ascertain the modulus and hardness of the ALD films. Both the modulus and hardness were found to increase for the greater deposition temperature. ALD-coated rf MEMS switches showed a low insertion loss, 0.35 dB, and a high isolation, 55 dB at 14 GHz. Mechanical actuation of the ALD-coated devices showed lifetimes of over 1 billion cycles.