Investigation And Preparation Of Pyroelectric Line Array Infrared Sensor Based On Lithium Tantalate

As an important branch of uncooled infrared detector, pyroelectric infrared sensor has been dicussed a lot. Lithium tantalate single crystal is a typical pyroelectric material. It has high Curie temperature, low dielectric loss and high figure of merit, which makes it the perfect candidate material for making pyroelectric infrared single-element detector, linear array and focal plane array. Since the production of domestic pyroelectric infrared detectors has complicated process and low detecting performance, the related researches are requisite. In this thesis, we use lithium tantalate single crystal as pyroelectric material in sensor, study on photolithography of UV sensitive ink and ultraviolet laser cutting on lithium tantalate sensitive element. The current mode single-element detectors and line array detector have been designed and fabricated. All the detectors have been measured by the pyroelectric infrared test system. The main contents and results are as follows:1. Based on circuit design, sensitive element design and packaging design, a variety of current mode single-element detectors were designed and fabricated by photolithography of UV sensitive ink, laser cutting process, ultrasonic wire bonding and automatic dispenser techniques.2. The current mode single-element detectors were measured by pyroelectric infrared test system. When the testing frequency was between 1Hz and 2Hz, the detectors have peak voltage responsivity, the magnitude of voltage responsivity was between 104V/W and 105V/W. The magnitude of detector’s noise equivalent power was between 10-7W and 10-9W, The magnitude of detector’s specific detectivity was between 107cmHz1/2W-1 and 109cmHz1/2W-1. The detectors had3. According to the test and linear regression calculating, the thermal time constant of each detector was between 160ms and 190ms.This indicated that the thermal time constant is irrelevant with circuit, only depends on the material itself. The electric time constant is proportional to the feedback electric capacity and inversely proportional to the feedback resistance. The electric time constant defines detector’s response range.4. Using photolithography process and laser etching process, we successfully fabricated variety lithium tantalate sensitive line array. The linewidth of each single element is 300μm and the pitch is 400μm. The ink absorber has clear edge and a spot of cavities, the array is compact. The depth of laser etching has been controlled exactly. When the cutting was repetead 8 times, the depth and width of the etching pitch was below 10μm. The material has no broken or damaged.5. When the testing frequency is 5.3Hz, the voltage responsivity of the line array’s each detecting element was 2.3×105V/W, the specific detectivity was about 108cmHz1/2W-1, the maximum of the specific detectivity was 7×108cmHz1/2W-1. The result showed that the line array producted by laser etching process has high performence. When the testing frequency is up to 1000Hz, the voltage responsivity, the noise, the specific detectivity decreased with the increase in frequency. The noise equivalent power increased with the increase in frequency. This indicated that the sensor’s detecting performance in extremly low frequency is much better than in higher frequency.