Thin film encapsulated 1D thermoelectric detector in an IR microspectrometer

Thin film encapsulated 1D thermoelectric detector in an IR microspectrometer

Wu, H.
Emadi, A.
De Graaf, G.
Wolffenbuttel, R.F.

Electrical Engineering, Mathematics and Computer Science

Department of ME/EI

2010-05-07

A thermopile-based detector array for use in a miniaturized Infrared (IR) spectrometer has been designed and fabricated using CMOS compatible MEMS technology. The emphasis is on the optimal of the detector array at the system level, while considering the thermal design, the dimensional constraints of a design on a chip and the CMOS compatibility. The resolving power is maximized by spacing the Thermo-Electric (TE) elements at an as narrow as possible pitch, which is limited by processing constraints. The large aspect ratio of the TE elements implies a large cross-sectional area between adjacent elements within the array and results in a relatively large lateral heat exchange between micromachined elements by thermal diffusion. This thermal cross-talk is about 10% in case of a gap spacing of 10 ?m between elements. Therefore, the detector array should be packaged (and operated) in vacuum in order to reduce the cross-talk due to the air conduction through the gap. Thin film packaging is a solution to achieve an operating air pressure at 1.3 mBar, which reduces the cross-talk to 0.4%. One of other advantages of having low operating pressure is the increased sensitivity of single TE element. An absorber based on an optical interference filter design is also designed and fabricated as an IC compatible post-process on top the detector array. The combination of the use of CMOS compatible materials and processing with high absorbance in 1.5 - 5 ?m wavelength range makes a complete on-chip microspectrometer possible.

microspectrometer
thermopile
IR detector araay
interference IR absorber
surface micromachining

http://resolver.tudelft.nl/uuid:1965c89c-c31d-409c-9d8e-a4ef30931e77

SPIE

0277-786X

Proceedings of SPIE, 2010, vol. 7726

Institutional Repository

conference paper

(c)2010 Wu, H., Emadi, A., De Graaf, G., Wolffenbuttel, R.F.