A micro thermal conductivity detector with integrated filter structure and its preparation method

Abstract

The invention discloses a micro thermal conductivity detector with an integrated filtering structure and a manufacturing method. A micro filtering structure is integrated structurally, bent air flow channels and thermistors are suspended, and a cavity structure is adopted for a substrate, so that the problems of great thermal losses of the thermistors and pollution in a manufacturing process are solved, and the thermal response of the thermistors is enhanced; and meanwhile, a dielectric film which can be directly bonded with glass is prepared on the substrate, so that the problem of difficulty in encapsulating the thermistors is solved. The manufacturing method comprises the following steps: preparing a layer of dielectric film on a silicon wafer; performing photoetching in sequence to obtain the thermistors, electrodes, two air flow channels, support beams in the air flow channels and the micro filtering structure; suspending the thermistors in the air flow channels; aging the thermistors under the condition of inert gas; and performing etching on the surface of the glass to obtain an air flow channel appearance which is the same as the surface position and shape of the silicon wafer, performing bonding and sealing in alignment with the silicon wafer, and cutting to obtain the micro thermal conductivity detector.

Description

technical field [0001] The invention relates to the field of gas detection, in particular to a micro thermal conductivity detector with an integrated filter structure and a preparation method. Background technique [0002] On-site gases such as ambient air quality monitoring, equipment internal environment monitoring, smart grid fault diagnosis, and oil exploration (mainly CO, CO 2 , SO 2 , NO 2 、H 2 S, C 1 ~C 6 In the rapid detection of low-carbon hydrocarbons, etc.), a large number of miniature thermal conductivity detectors are needed to realize on-site analysis or on-line monitoring. [0003] Thermal conductivity detector is a very important and widely used detector in the field of chromatography. This detector responds to almost all gases, which cannot be replaced and compared with other types of detectors. With the increasing maturity of micro-electromechanical system (MEMS) technology, the micro-thermal conductivity detector (Micro-TCD) based on MEMS technology ...

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Problems solved by technology

[0005] Such as a miniature thermal conductivity detector developed by JanM.Lysko, such as figure 1 As shown, although the cell volume of the thermal conductivity cell is reduced by 1 to 2 orders of magnitude, due to too many support points of the thermistor, a large amount of substrate heat loss is caused, which reduces the thermal response characteristics of the thermistor; in addition, The thermistor is directly prepared on the silicon surface without being suspended, so that the heat generated on the thermistor is transferred by the substrate

Therefore, the thermal isolation of the thermistor is poor

[0006] In addition, the biggest feature of MEMS technology is mass production. During the preparation process, a slicer must be used to separate dozens or even hundreds of individual chips. Silicon and glass powder, some powder will enter the thermal conductivity pool with the cooling water or air flow, cover the surface of the thermistor and contaminate the thermistor, resulting in a decrease in the thermal response characteristics of the thermistor

[0007] At the same time, since the chip uses a silicon substrate, the general silicon material has a certain conductivity, and a layer of insulating material needs to be grown on the silicon surface. Generally, SiN prepared by LPCVD is used as the insulating layer, but the SiN prepared by this method will hinder the silicon substrate. Bonding to the glass substrate presents the problem of difficult packaging of thermistors

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