Fabrication and Characterization of a SU-8 Epoxy Membrane-Based Thermopile Detector With an Integrated Multilayered Absorber Structure for the Mid-IR Region

This paper reports on the fabrication and characterization of a thermopile detector with an integrated midinfrared absorber structure. The fabricated absorber structure has shown an absorption of more than 95% in the wavelength range of 3.2-5.47 μm. The detector was fabricated with standard cleanroom process techniques and equipments. The serial resistance was measured at about 315 kQ at room temperature. The photosensitivity of the detector was characterized for a signal wavelength (4.26 μm) and a band of wavelength ranging from 2.5-5.5 μm through two different measurement setups. In the first measurement setup, the photosensitivity was estimated at 57.5 V · mm
²
· W
^-1
through a MEMS-based infrared radiation source and with an optical band-pass filter of wavelength 4.26 μm. The following characterization was performed to characterize the photosensitivity of the detector in a broader wavelength range. This measurement was taken using a monochromator setup utilizing a reference photodetector for calculations of the optical power of the infrared source. The photosensitivity and the specific detectivity (D*) of the fabricated detector were measured to values of 30-92 V · W
^-1
and 8.0 × 10
⁷
- 2.4 × 10
⁸
cm · Hz
^1/2
· W
^-1
, respectively, in the wavelength range of 2.8-5 μm. The time constant was estimated to around 21 ms.