Study On Preparation Of Uncooled Infrared Detector And Its Electrical、Thermal Properties

VOxis used as the sensitive material in uncooled infrared detectors and reachesto practical level for reasons as follows: it has high temperature coefficient ofresistance(TCR), moderate resistance, lower deposition temperature and it can formgood ohmic contact with metal materials. Noise and thermal conductance are veryimportant technical indicators for infrared detectors based on VOx.Device noise is closely related to material preparation, device structure andcontact conditions. The purpose of study in this paper is to obtain a detector structurewith low noise. So we added different types of metal buffer layers between electrodeand thermal sensitive layers. After that, Tests, comparisons and analyses are carriedout to get an improved scheme for electrode contacts in infrared detectors.When testing the thermal conductance of VOxmicrobridge pixel using the1/R—(-αI2) curve method, certain deviation occurs if we ignore temperature changingand take TCR as a fixed number. The test on the microbridge thermal conductance ofthe uncooled detector is carried out by using the TCR corrected1/R—(-αI2) curvemethod. This test method is more precise and more practically available.The research contents and results in this dissertation are summarized as follows:(1) Aiming at uncooled infrared detectors based on VOxthermal sensitivematerial, Pt is used as the electrode and metal materials of V、Ti、Al、Cr are addedbetween electrode and thermal sensitive layers. Then we carried out tape-out work ofinfrared detectors. According to the design, final thickness of the microbridge pixel is0.75μm, and the whole area of bridge is80μm×77μm. The length-width ratio reachesto40/1.(2) A noise test bench based on SR830Lock-in Amplifier is established. Thelock-in amplifying technique was applied to test the response and noise, through thisway, the technical problems of small signal extraction were overcome. Dataacquisition and display program written with Labview is used in this test bench.Synchronous communication is available between the program and intelligent instruments via serial port. This test bench is a integration of test, acquisition and dataanalysing. Noise test evaluations are performed according to all detector devices. Andresults showed that adding of the buffer layer has a significant effect on reducing thenoise amplitude. And the degree of noise reduction is V＞Cr＞Ti＞Al.(3) Responsivity, noise equivalent power and detectivity were calculated basedon response voltage and noise data tested above. And it was found that under DC biasconditions, the response voltage reached a maximum value at a certain current. That isto say, there is a perfect match value between the matching resistance and thermalsensitive resistance.(4) A modified bolometer microbridge thermal conductance testing method israised. Thermal conductance parameter gained by this method is more precise andwith more practical value. Besides that, effective thermal conductance is analysed toguide performance evaluation within experimental process.