Research On Integrated Multi-Channel Infrared Spectrum Detector For Multi-Gas Sensing

Due to its unique advantages,infrared spectrum detection technology has been widely used in food inspection,environmental engineering,biomedicine,etc.With the gradual mature of Micro-Electro-Mechanical System(MEMS)technology,as the core devices of infrared spectroscopy detection systems,infrared detectors have gradually developed towards the direction of high integration,miniaturization and multi-function while their performances continue to be improved.In the fields of storage,transportation and fresh-keeping of fruits and vegetables,there are strong demands for the simultaneous detection of various gases including ethylene,so as to efficiently control the maturity of fruits and vegetables to avoid premature ripening or rot of them.In response to this application requirement,this thesis proposed an integrated scheme of multi-channel infrared spectrum detector by bonding of three-layer structural chips.Four infrared peaks including three absorption wavelengths of gases which are ethanol 3.5μm,ammonia 9.7μm and ethylene 10.6μm and a reference wavelength 3.9μm can be effectively detected by this detector.Through the research on the chip structure,process preparation,integration method and performance test of integrated devices,some valuable results have been achieved.The specific research contents of this thesis are as follows:(1)A design scheme of three-layer structure of integrated multi-channel infrared spectrum detector was proposed,and the overall model of the device was established.The structure description and parameter simulation of the top-layer optical chip,the middle-layer spacer chip and the bottom-layer detector chip were carried out respectively.The narrow-band filtering characteristics of the metal hole array and the focusing performance of the metasurface structure were analyzed.At the same time,the design of absorption structure of four detection units on the bottom-layer detector chip was carried out.The results showed that the absorption rate of detection units could reach about 90% at the above four wavelengths.(2)Design of process flow and preparation of the bottom-layer detector chip and the middle-layer spacer chip were carried out respectively,and the integrated solution of whole three-layer chip was put forward.The preparation processes of the chips were introduced in detail starting with the chip renderings and the design of mask layout,and then the parameters of the main process steps and the micrograph of the chips were given.The prepared chips have good morphological characteristics,and the structure and size meet the design requirements.Finally,the integration process of the device was introduced.(3)The infrared absorption spectrum,blackbody response sensitivity,noise and blackbody detectivity of different detection units of the bottom-layer detector chip were tested.Experiments have shown that the blackbody response sensitivity of different detection units reached 104V/W,the blackbody detectivity was of the order of 108cm·Hz1/2/W and the smaller detection unit had a higher sensitivity performance.The characterization of the relevant parameters of the performance of the detector chip was established,which provides a guidance to the future optimization of the device.