Structure of film thermoelectric converter based on micro bridge resonator and fabricating method thereof

Abstract

The invention discloses a structure of a film thermoelectric converter based on a micro bridge resonator and a fabricating method thereof. The film thermoelectric converter mainly comprises a heating resistor (1), the micro bridge resonator (2) and a sealing ring (3). Heat of the heating resistor 1 after the temperature rises leads the temperature of the micro bridge resonator (2) to rise through ways of convection, radiation, or heat exchange and the like. Because the heat expansion coefficients of materials made into the micro bridge resonator (2) are different, the axial crushing stress of the heated micro bridge resonator increases or pulling stress reduces, the resonance frequency is lowered, and the temperature information of the heating resistor (1) can be reflected through measuring the change of the resonance frequency. The film thermoelectric converter based on the micro bridge resonator (2) has high sensitivity of measuring the heating resistor (1) by using the micro bridge resonator (2), little heat of conducting to an underlayer through the micro bridge resonator (2), and small error of converting alternative current into direct current; meanwhile, the heating resistor (1) can be flexibly designed.

Description

technical field [0001] The invention relates to a structure and a manufacturing method of a thermoelectric transducer, in particular to a structure and a manufacturing method of a thin-film thermoelectric transducer based on a micro-bridge resonator, and belongs to the field of micro-electromechanical systems (MEMS). Background technique [0002] The AC-DC conversion standard is one of the basic electrical standards. Through this standard, the 10Hz-1MHz AC voltage (or current) can be derived from the corresponding DC flow, and traced to the Josephson DC quantum voltage reference (uncertainty better than 10 -8 ). At present, the most accurate AC-DC conversion standard system in the world is realized by thermoelectric converters. A thermoelectric converter consists of a heating resistor and a temperature sensor. AC voltage (or current) and DC voltage (or current) are applied to the heating resistor in turn. The temperature sensor measures the temperature of the heating resis...

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Problems solved by technology

[0007] However, this kind of thermoelectric converter using thermopile as temperature sensitive element has the following disadvantages: (1) From the perspective of improving the sensitivity of thermopile temperature sensor, thermocouple material needs to have high Seebeck coefficient, low resistivity, low thermal conductivity and other characteristics, but according to the Wedman-Franze law, the product of thermal conductivity and resistivity of the material is a constant, it is difficult to reduce thermal conductivity and resistivity at the same time, CuNi widely used at present 44 -Cu, CuNi-NiCr, and Bi-Sb thermocouples have relatively large thermal conductivity, and the heat insulation is not ideal. The heat transferred to the substrate through the thermocouple wire is one of the main sources of AC-DC conversion errors.

(2) The sensitivity of the thermocouple temperature sensitive element is relatively low

In order to improve the temperature measurement sensitivity (or the responsivity of the thermoelectric converter), more than 100 pairs of thermocouples are usually used to form the thermopile sensitive element. The size of the device is very large, and a large-area Si 3 N 4 / SiO 2 / Si 3 N 4 Heat insulation film, the film is easy to wrinkle or break, and it is difficult to achieve stress balance

(3) Thermopile materials with high responsivity (such as Bi, Sb, Bi 2 Te 3 、Bi 0.5 Sb 1.5 Te 3 , Sb 2 Te 3 ) processes such as deposition, corrosion, and stripping are poorly compatible with standard integrated circuit processes and yields are low

(4) The size of the thermopile composed of a large number of thermocouples is large, which limits the degree of freedom in the design of the heating resistor. Usually, only two-wire heating resistors can be used. When measuring small AC signals, the temperature of the heating resistor is low, so that the thermoelectric converter The response rate is small and the conversion error is large

The disadvantage is that system integration, structural optimization design and necessary electromagnetic shielding measures have not been realized; limited by the packaging structure of commercial infrared detectors, the distance between infrared detectors and heating resistors cannot be approached; the performance is comparable to that of thin-film thermoelectric transducers based on thermopile temperature measurement methods There is still a big gap; the use of photon detectors requires refrigeration equipment, which is costly, while the responsivity and detection rate of thermopile infrared detectors are relatively low

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