Titanium Hydride Formation in Current-Biased Titanium Microbolometer and Nanobolometer Devices

• Main Authors: S. F. GILMARTIN, K. ARSHAK, D. COLLINS, B. LANE, D. BAIN, S. B. NEWCOMB, B. McCARTHY, A. ARSHAK
• Format: Article
• Language: English
• Published: IFSA Publishing, S.L. 2009-04-01
• Series: Sensors & Transducers
• Subjects: Microbolometer; Nanobolometer; IR; MEMS; CMOS; Titanium; Hydride
• Online Access: http://www.sensorsportal.com/HTML/DIGEST/april_09/P_415.pdf

This paper presents a study on the impact of current-bias heating on the material properties and electrical characteristics of titanium (Ti) microbolometer and nanobolometer devices. We present TEM, electron microdiffraction, SIMS and SEM data showing the interaction effects of hydrogen present within the device fabrication process layers on the bolometer resistor layer. Under high current stress conditions, hydrogen present in the Ti resistor layer can react with the Ti to form a Ti hydride phase. We show that the formation of Ti hydride within the resistor meander affects sensor resistance, and under extreme temperature/bias conditions can compromise the integrity of surrounding dielectric layers, resulting in warped pixel structures. We also show that the use of hydrogen-limiting SiN encapsulating layers around the Ti bolometer layer can limit Ti hydride formation, and reduce stress-related defects and resistance drift affects at high bias currents.