A Microbolometer detector based on a sol-gel technology

Dervişoğlu, Özgecan
The objective of this study is to develop a high performance bolometric material for microbolometers. The bolometric material to be developed was chosen as vanadium oxide due to its high temperature coefficient of resistance (TCR), low 1/f noise performance, and read out integrated circuit (ROIC) compatible resistivity. Among various deposition techniques, sol-gel method was decided to be implemented because of its various advantages such as simpler instrumentation, attainability of good chemical homogeneity, high deposition rate, etc. The route of dissolving metallic vanadium powder in hydrogen peroxide was determined as the sol-gel route to be followed. Having conducted various experimental runs, the sol formation and VOx thin film deposition steps were optimized and successful coatings on Si/SiNx substrates could be obtained. The sheet resistance, thickness, resistivity, morphology, and phase of VOx thin films heat treated at different temperatures upto 400ºC were characterized and then, successful microresistor structures could be fabricated by utilizing vanadium pentoxide gel (V2O5.nH2O with n≤1.8) among the VOx phases as the bolometric material due its low enough resistivity (i.e. below 20 Ω.cm). This is the first time in literature that V2O5.nH2O phase was used as an IR active material for microbolometers. The resistance values could be maintained below 100 kΩ for microresistors that can be fit into a 35 µm pixel pitch. The TCR of V2O5.nH2O thin films was measured to be ranging between -1.7 and -2.4 %/ºC. The lowest 1/f noise parameter (C_(1/f)) that could be achieved is 1.6x10^-11. After microresistor fabrication, suspended single pixels having 35 µm pitch were fabricated successfully by implementing the developed sol-gel deposited V2O5.nH2O thin film as the bolometric material. The responsivity, thermal conductance, thermal time constant, and absorptance of a single pixel were measured to be 50,569 V/W, 3.37x10-8 W/K, 20.9 ms, and 87 %, respectively. These performance values encourage to implement the sol-gel deposited V2O5.nH2O thin film into the large format microbolometer arrays, thus, a 384x288 microbolometer array on a ROIC in which the developed sol-gel deposited V2O5.nH2O was used as the IR active material was fabricated successfully.


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Citation Formats
Ö. Dervişoğlu, “A Microbolometer detector based on a sol-gel technology,” Ph.D. - Doctoral Program, Middle East Technical University, 2013.