Three-layer pixel structure of micro-bolometer

Abstract

A three-layer pixel structure of a micro-bolometer comprises a light absorption layer, a thermosensitive layer, an electrode layer and a substrate of the electrode layer. An optical resonant cavity is formed between the light absorption layer and the thermosensitive layer which are connected through a hollow bridge column, so that the microbridge heat capacity is reduced. The thermosensitive layer maximizes the absorptivity of a thermistor layer to infrared transmission light, and the electrode layer bends and arranges electrode bridge legs from two ends, so that the length of the bridge legs is increased, and the thermal conductivity is reduced. Passivation layers are laid above and below the thermosensitive layer and the electrode layer, and the electrode bridge legs are connected with the thermistor layer and the substrate respectively to achieve electrical communication and thermal communication. While time response constants are considered, a high infrared absorption rate and low thermal conductivity are achieved, the temperature rise of pixels is effectively improved, and high temperature response rate and high thermal sensitivity are achieved.

Description

technical field [0001] The invention belongs to the technical field of uncooled infrared detectors, and in particular relates to a three-layer pixel structure of a microbolometer. Background technique [0002] With the development of infrared imaging technology, the application range of infrared imaging system is getting wider and wider, including communication, medical treatment, chemistry, biology, and war, and low-cost commercialization has been realized. In terms of system application, the thermal imaging system’s Important parameters such as time response constant, infrared absorptivity and thermal sensitivity (equivalent noise temperature difference) have become the focus of research. Among them, the uncooled heat detector has the advantages of no need for refrigeration, light weight, miniaturization, and convenient use. Uncooled infrared detectors are also developing toward large arrays and miniaturized pixel sizes, and have been widely used in military, medical, agr...

AI Technical Summary

Problems solved by technology

[0004] The traditional microbolometer is composed of a single-layer pixel structure, in which the infrared absorbing layer and the heat-sensitive layer are on the same bridge surface, which causes the temperature of the infrared absorbing layer and the heat-sensitive layer to change at the same time, and it is difficult to reduce the temperature of the pixel. Guide while increasing the absorption rate of infrared light, thereby limiting the thermal sensitivity of the pixel

If the infrared absorption of the single-layer pixel is increased, the area of ​​the bridge surface needs to be continuously increased, which also limits the integration of the device, so the single-layer structure cannot meet the high performance requirements of the device, and the development of the single-layer micro-bridge has limitations.

[0005] There are roughly two types of existing double-layer microbolometers, one is a double-layer S-shaped structure, which is divided into two independent bridge decks, the light-absorbing layer and the heat-sensitive layer are on the upper bridge deck, and the lower deck is It consists of a single row of electrodes bent into an S shape and is hidden under the upper bridge surface. This structure reduces the thermal conductivity of the device, but the light-absorbing layer and the heat-sensitive layer are still not separated and cannot be changed independently, which limits the infrared of the device. Absorption rate, and its stability is not good, time response is slow

The other is a double-layer umbrella structure, which is characterized by the fact that the light-absorbing layer exists independently above the heat-sensitive layer, which increases the optical filling rate and overcomes the problem that the temperature of the light-absorbing layer and the heat-sensitive layer rise and fall at the same time in the traditional structure. Disadvantages, but the area of ​​the heat-sensitive layer is not maximized, and the length of the bridge legs is insufficient, resulting in a large thermal conductivity of the device, which affects its thermal sensitivity

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