Development of a thermopile infrared sensor using stacked double polycrystalline silicon layers based on the CMOS process

Abstract

A stacked double-layer (SDL) thermopile-based infrared sensor, which comprised of 96 thermocouples on a suspended membrane, has been designed and fabricated with a CMOS-compatible process. The thermoelectric properties were characterized, and responsivity (R s) of 202.8 V W −1 and detectivity (D *) of 2.85 * 10 8 cm Hz 1/2 W −1 for a SDL thermopile were derived.

CMOS Compatible Midinfrared Wavelength-Selective Thermopile for High Temperature Applications

“…Since the Seebeck coefficient of poly-Si varies with the temperature of the device and the micro-heater will inevitably affect the temperature of the device, it is crucial to make sure that the temperature rise caused by the micro-heater will be minimized and not affect the performance of the thermopile too much. Our previous work [42] shows that the output voltage at different temperatures is linear with the applied input power. Therefore it can be concluded that the testing results of the test key are still reasonable.…”

“…The detailed analysis is shown in our previous work [42]. Another significant parameter, D * is defined as:…”

“…The implantation conditions of the poly-Si test structures used in the experiment are the same as we did in previous work [42]. The thickness of the poly-Si is 300nm.…”

“…In order to optimize the performance of the thermopile IR sensor, we use a thermopile structure of a stacked double layer (SDL), which was reported in our previous work [42]. 6(a) shows a cross-beam-like thermopile structure which comprises an interferometric absorber.…”

“…The absorber is formed with three layers: 7nm Titanium Nitride (TiN) on the top, 250nm amorphous Silicon (A-Si) in the second layer and 300nm Aluminum at the bottom. According the our previous work [42] the optimal dimension parameters are as follows: the length of the thermopile equals to 600 μm, the width of the thermopile equals to 12 μm and the number of thermopile equals to 96. The thickness of the poly-Si strips are 300nm and the thickness of the SiO 2 electrical isolation layer is 150nm.…”