IR uncooled bolometers based on amorphous Ge/sub x/Si/sub 1-x/O/sub y/ on silicon micromachined structures

In this work, we present the fabrication of bulk micromachined microbolometers made of amorphous germanium-silicon-oxygen compounds (Ge/sub x/Si/sub 1-x/O/sub y/) grown by reactive sputtering of a Ge/sub 0.85/Si/sub 0.15/ target. We describe the complete procedure for fabricating thermally isolated microbolometers consisting of Ge/sub x/Si/sub 1-x/O/sub y/ sensing films deposited on sputtered silicon dioxide membranes suspended over a silicon substrate. The electrical properties of the sensitive material are set by controlling the deposition parameters of the sputtering technique. Under optimum deposition conditions, Ge/sub x/Si/sub 1-x/O/sub y/ layers with moderate electrical resistivity and thermal coefficient at room temperature as high as -4.2% /spl middot/ K/sup -1/ can be obtained. Isolated structures measured at atmospheric pressure in air have a thermal conductance of 3 /spl times/ 10/sup -6/ W /spl middot/ K/sup -1/ and a thermal capacitance of 6/spl middot/10/sup -9/ W /spl middot/ s /spl middot/ K/sup -1/, yielding a response time of 1.8 ms. Bolometers with an IR responsivity of 380 V /spl middot/ W/sup -1/ and a NEDT of 3.85 K at 100 nA bias current are obtained. The use of sputtered films allows designing a fully low-temperature fabrication process, wholly compatible with silicon integrated circuit technologies.

[1]  Robert E. Higashi,et al.  Monolithic two-dimensional arrays of micromachined microstructures for infrared applications , 1998, Proc. IEEE.

[2]  E. Monticone,et al.  Properties of metal bolometers fabricated on porous silicon , 1999 .

[3]  X. Yi,et al.  Linear uncooled microbolometer array based on VOx thin films , 2001 .

[4]  M. Clement,et al.  Amorphous GexSi1−xOy sputtered thin films for integrated sensor applications , 2001 .

[5]  P. Richards.  Bolometers for infrared and millimeter waves , 1994 .

[7]  P. Fiorini,et al.  Characterization of bolometers based on polycrystalline silicon germanium alloys , 1998, IEEE Electron Device Letters.

[8]  G. Karunasiri,et al.  Performance of microbolometer focal plane arrays under varying pressure , 2000, IEEE Electron Device Letters.

[9]  Y. Watabe,et al.  A high performance amorphous Si/sub 1-x/C/sub x/:H thermistor bolometer based on micro-machined structure , 1997, Proceedings of International Solid State Sensors and Actuators Conference (Transducers '97).

[10]  Olaf Reinhold,et al.  Design and fabrication of thin film monolithic uncooled infrared detector arrays , 1994, Defense, Security, and Sensing.

[11]  Roman Sobolewski,et al.  Investigation of semiconducting YBaCuO thin films: A new room temperature bolometer , 1996 .

[12]  Ernst Obermeier,et al.  A thin-film bolometer for radiation thermometry at ambient temperature , 1990 .

[13]  A. Navarro,et al.  High sensitivity bolometers development , 1992 .

[14]  K. Liddiard.  Thin-film resistance bolometer IR detectors—II , 1984 .

[15]  M. Clement,et al.  Ge:Si:O evaporated alloys as a thermosensitive layer for large area bolometers , 1999 .

[16]  Jin-Shown Shie,et al.  Characterization and modeling of metal-film microbolometer , 1996 .

[17]  J. Piotrowski,et al.  Micromachined silicon bolometers as detectors of soft X-ray, ultraviolet, visible and infrared radiation , 1997 .

[18]  V. G. Malyarov,et al.  Amorphous silicon and germanium films for uncooled microbolometers , 1997 .

[19]  K. C. Liddiard,et al.  Application of interferometric enhancement to self-absorbing thin film thermal IR detectors , 1993 .

[20]  R. Andrew Wood,et al.  Micromachined bolometer arrays achieve low-cost imaging , 1993 .

[21]  Robert Mertens,et al.  Structural and mechanical properties of polycrystalline silicon germanium for micromachining applications , 1998 .

[22]  Mahmoud Almasri,et al.  Self-supporting uncooled infrared microbolometers with low-thermal mass , 2001 .