Micromachined thermoelectric IR sensors fabricated by a self-aligned process

Abstract

In this paper, we report the fabrication and characterization of micromachined thermoelectric IR sensors through a self-aligned technique. Unlike most conventional front-etched thermoelectric IR sensors, etching windows in the self-aligned process are determined by the spacing between polysilicon thermocouple legs. Due to etching windows for structure release being patterned by a self-aligned process rather than as a last photolithography step, the fabrication complication is reduced and narrow etching windows can be patterned. Using the self-aligned process, three types of thermoelectric IR sensors are fabricated and characterized. With SiO 2 /Si 3 N 4 as absorber layer, the sensor with rectangular structure shows the highest responsivity of 43.5 V W −1 , and the circular-shaped sensor with polysilicon strips patterned in the absorber area shows the fastest response and the highest specific detectivity of 3.41 × 10 7 cm √ Hz W −1 . This self-aligned technique is also directly applicable to other MEMS devices with polysilicon as the structure material, and also makes it possible to manufacture ultrasmall gaps.

Bi2Te3 and Sb2Te3 Thin Films with Enhanced Thermoelectric Properties for Flexible Thermal Sensors

“…= 1 considering the internal reflections inside the thermopile case, and therefore, the whole structure behaves as a cavity blackbody with high emissivity [6]. The responsivity (Rs) is obtained by the slope of the output voltage as a function of absorbed heat radiation power [2], and is 0.19 V W −1 for our sensor. Specific detectivity (D*) can be calculated by [2]…”

“…The responsivity (Rs) is obtained by the slope of the output voltage as a function of absorbed heat radiation power [2], and is 0.19 V W −1 for our sensor. Specific detectivity (D*) can be calculated by [2]…”

“…where A is area of sensor (25 mm 2 ) and NEP is the noise equivalent power which is the quotient of RMS of the voltage ( ) and Rs [2]. A = 3.9 nV was obtained taking in account the = 1 Hz, = 298 K and = 910 Ω. NEP value was estimated to be 20 nW.…”

“…Thermoelectric (TE) technology appears as a green energy source due to their direct transformation of small thermal gradients into electric power, and vice-versa, in a renewable manner and without CO2 emissions. Telluride alloys have attracted a great deal of interest because of their potential applications as TE generators, TE coolers and thermal sensors [1,2]. The performance of TE devices is highly dependent on TE properties of constituent materials, namely the Seebeck coefficient ( ), the electrical conductivity( ) and the thermal conductivity ( ), according to the figure of merit ( ), = 2 / , where 2 is related to the power factor, .…”

Design, fabrication, and characterization of a high-performance CMOS-compatible thermopile infrared detector with self-test function

“…However, these two materials are not compatible with complementary metal oxide semiconductor (CMOS) fabrication, which makes it difficult for mass production and low cost. To solve this problem, thermopile IR detectors composed of polysilicon and Al have been presented [7][8][9], such devices can be fabricated by using CMOS-compatible process. In terms of etching method, early researchers often chose backside wet anisotropic micromachining to release their thermopile structures [4,10,11].…”