Study On The Readout Circuit Of The Microbolometer

Infrared detectors are devices that transform incoming infrared radiation signals into electrical signals.They are widely used in military and civilian fields.Infrared detectors are divided into photon infrared detector and thermal detector.Compared with the photon infrared detector,the sensitivity of the heat detector is low,but it has many advantages,such as small volume,light weight,low power consumption,low cost,wide bandwidth and so on,which has been gained wide range of attention.The microbolometer in heat detector has developed more rapidly because of its low power consumption,compatible with the silicon plane process,high performance price ratio and high sensitivity in the 8-12μm band.However,in our country,the research and production of the focal plane array of microbolometer are late,and the development lags behind by the industrial technology,so the read-out circuit in the focal plane array of the microcalorimeter is designed and realized in this paper.Based on the CSMC 0.18μm Mix Singal RF 1P6M Process,two kinds of microbolometer readout circuits are designed.A 160×160 focal plane array read-out circuit is designed according to the high resistance value and high TCR of the vanadium oxide microbolometer.The integral circuit adopts CTIA structure of low noise,high responsivity and high linearity,which is suitable for high and low background.The buffer output is made of nine tube buffer output structure of self bias,low power consumption,small area and high accuracy,and the circuit design is improved.The unit bias circuit adopts the point by point bias unit based on DAC to improve the uniformity of the detection array.The second is an aluminum microbolometer focal plane array.First,COMSOL Multiphysics software is used to design and simulate a single layer L leg aluminum microbolometer with 30μm×30μm.The simulation results show that the microbolometer structure is stable,and the response speed is moderate,but the detection sensitivity is low.The 26 x 100 focal plane array read-out circuit is designed for the aluminum microbolometer,which has the advantages of high speed,low noise and high linearity,according to the small resistance value of the thermistor and the small TCR.The total area of the chip is designed and fabricated for 2mm×2mm.After finishing the bare chip microbridge structure,we test it.The test results show that the nonlinearity of the vanadium microbolometer readout circuit is less than 0.1%,the readout rate is 2M/s,and the power consumption is 40mW.The readout circuit of the aluminum microbolometer is less than0.1%,the readout rate is 1M/s,and the power consumption is 0.356mW.Measurements of the aluminum microbolometer show that the thermistor temperature coefficient is 0.384%/K and the effective thermal time constant is 1.84ms,and the responsivity and detectivity is 260.32V/W and 1.46×10⁷cmHz^1/2/W.