The strong effect on MEMS switch reliability of film deposition conditions and electrode geometry

• Autores: Changho Oh, Charles B. Stovall, Wassim Dhaouadi, Robert W. Carpick, Maarten P. de Boer
• Localización: Microelectronics reliability, ISSN 0026-2714, Nº. 98, 2019, págs. 131-143
• Idioma: inglés
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• Resumen

  • Microelectromechanical systems (MEMS) or nanoelectromechanical systems (NEMS) switches are of interest for applications ranging from radio frequency (RF) communication circuitry to power surge protection to low power computing. Reliable operation of the switch contacts is critical. Many researchers have investigated the effect of different materials on reliability, but little work has been reported on the effects of process conditions. In this study, the effects of the angle of deposition incidence, the microstructure, the interface adhesion, the base pressure, and the process transferability have been evaluated in Pt-coated MEMS switches. Among them, base pressure attained prior to deposition was most important, while an interaction between electrode geometry and film microstructure was also identified to play a role. A lower base pressure (2•10−6 Torr) improved cycle count significantly while a higher base pressure (8•10−6 Torr) resulted in low cycle counts (106 or less). Failure analysis indicated surface wear due to damage at a corner junction, where films deposited at different angles of deposition incidence meet. Mass spectroscopy analysis detected higher carbon content in Pt films with high base pressure. This suggests that grain boundaries weakened by impurity segregation exacerbated the geometric effect. Switches tested in a follow-up experiment, in which the base pressure was 5•10−7 Torr, again resulted in high cycle counts (330•106), reinforcing the importance of achieving low base pressure in improving the mechanical reliability of the corner junction.