Process Flow and Design Optimization of a Microbolometer

Microbolometers using a-Si
0.15
Ge
0.85
O
0.0236
thin films were fabricated using radio frequency magnetron sputtering and lift of technique. When a 200 nm-thick and 40 × 40 μm
²
Si
0.15
Ge
0.85
O
0.0236
pixels on top of the electrode arm was used, it was observed that the electrode arms and the pixels were wrapped after they were subjected to the surface micromachining process. In order to fix this problem, the design and process flow of the microbolometer array were optimized to obtain mechanically stable microbolometers. We used Ge
x
Si
1-x
O
y
, silicon nitride, NiCr and silicon nitride to provide mechanical strength and stability to the microbolometer pixels. With the modified structure and process flow optimization it was found that the detectors of bridge structure were suspended on top of the substrate. We performed forming gas passivation at 250
^o
C for seven hours to minimize the 1/f-noise. A temperature coefficient of resistance (TCR) of 4.8%/K was obtained at 295 K. We obtained the highest detectivity and responsivity values 1 × 10
⁴
V/W and 8.3 × 10
⁶
cm-Hz
^1/2
/W.