A thermopile detector array with scaled TE elements for use in an integrated IR microspectrometer

J. Micromech. Microeng.

et al. 2009

Self Cite

The spectral resolution of a MEMS-based IR microspectrometer critically depends on the thermal cross-talk between adjacent TE elements in the detector array. Thermal isolation between elements is realized by using bulk micromachining directly following CMOS processing. This paper reports on the characterization results of bridge-shaped TE detector elements that are cut out of a membrane. Elements with dimensions of 650 × 36 μm 2 are separated by 10 μm wide gaps in order to minimize the thermal cross-talk by heat conduction through the support structure. The static and dynamic aspects of thermal cross-talk have been evaluated with an emphasis on the effect of the thermal conductivity of air as a function of the package pressure.

Section: Introductionmentioning

confidence: 99%

Characterization of thermal cross-talk in a MEMS-based thermopile detector array

Grabarnik

J. Micromech. Microeng.

et al. 2009

Self Cite

“…The process used for the fabrication of the uncoated TE elements has been described in detail in previous work 2 . This section is focused on the fabrication of absorber and realizing of bridge structure.…”

Section: Fabrication Of the Absorbermentioning

confidence: 99%

“…Optical microspectrometers based on IC-compatible MEMS technologies offer significant benefits due to: small sample volume, fast response, small dimensions, weight and integrated circuits for signal pre-processing 1 . The structure of the IR microspectrometer discussed in this paper comprises slit, planar imaging diffraction grating and TE detector array 2 . The dispersed IR spectrum is projected onto a 1-dimensional detector array.…”

Section: Introductionmentioning

confidence: 99%

Thin film encapsulated 1D thermoelectric detector in an IR microspectrometer

Optical Sensing and Detection

Graaf

et al. 2010

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 μm 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 μm wavelength range makes a complete on-chip microspectrometer possible.

“…The difference would be in the choice of dielectric materials for the LVOF filter and suitable detector array. For near-infra red region, for example PolySi and SiO 2 are to be used as dielectric materials [10] and MEMS fabricated thermopile arrays as detectors [11].…”

Section: Introductionmentioning

confidence: 99%

CMOS-compatible LVOF-based visible microspectrometer

Graaf

et al. 2010

SPIE Proceedings

This paper reports on a CMOS-Compatible Linear Variable Optical Filter (LVOF) visible micro-spectrometer. The CMOS-compatible post process for fabrication of the LVOF has been used for integration of the LVOF with a CMOS chip containing a 128-element photodiode array and readout circuitry. Fabrication of LVOF involves a process for fabrication of very small taper angles, ranging from 0.001° to 0.1°, in SiO 2 . These layers can be fabricated flexibly in a resist layer by just one lithography step and a subsequent reflow process. The 3D pattern of the resist structures is subsequently transferred into SiO 2 by appropriate etching. Complete LVOF fabrication involves CMOS-compatible deposition of a lower dielectric mirror using a stack of dielectrics on the wafer, tapered layer formation and deposition of the top dielectric mirror. The LVOF has been optimized for 580 nm -720 nm spectral operating range and has also been mounted on a CCD camera for characterization. The design of LVOF micro-spectrometer, the fabrication and characterization results are presented.