Abstract
An analytical model for the electro-thermal feedback effect in a microbolometer infrared focal plane array is presented. The presented model is the integrated optical-electro-thermal model, in which the electro-thermal feedback effect incorporated with the response of incident IR can be described. In addition, since the model is based on physics, the model parameters also have their own physical meaning. This analytical model can be easily utilized to describe the temperature increase caused by the applied heat sources and has a unique feature describing capability of optical-electro-thermal analysis in a quasi-steady-state, which can hardly be performed with thermal analysis tools based on the finite element method. The model shows that the temperature of the microbolometer in this study can be increased 7.1% to 18.6% more by the electro-thermal feedback effect.
Highlights
IntroductionUncooled microbolometer infrared focal plane array (IRFPA) technology has extended its application to the small-size, low-weight, low-power, and low-cost IR systems.[1,2,3] As the density of IRFPA has rapidly increased, several technical challenges, such as process technology, optical fill-factor, thermal isolation, and the thermal drift of their characteristics, have emerged.[4,5,6,7,8,9,10,11] The accurate performance prediction of the high-density microbolometer IRFPA is one of the emerging challenges.[8,9,10,11,12,13,14,15,16] In order to make a reasonable performance prediction of a highly optimized and high-density microbolometer IRFPA, the correct understanding of the electro-thermal phenomena that occur in a microbolometer IRFPA is essentially required
In order to demonstrate the utilization of two analytical models for describing the electro-thermal feedback effect, the feedback amplifier gain (FAG) model of Eq (4), the effective thermal conductance (ETC) model of Eq (8), and the conventional linear (CL) model of Eq (2) were applied to a typical microbolometer infrared focal plane array (IRFPA)
It is assumed that the microbolometer IRFPA has a columnwise readout with a capacitive transimpedance amplifier as a column amplifier, as indicated in Table 1.19,21 The IR response signals from the FAG and ETC models, in which the incident IR radiation incorporated with the electro-thermal feedback effect are considered, are larger than that from CL, in which only the IR radiation is considered
Summary
Uncooled microbolometer infrared focal plane array (IRFPA) technology has extended its application to the small-size, low-weight, low-power, and low-cost IR systems.[1,2,3] As the density of IRFPA has rapidly increased, several technical challenges, such as process technology, optical fill-factor, thermal isolation, and the thermal drift of their characteristics, have emerged.[4,5,6,7,8,9,10,11] The accurate performance prediction of the high-density microbolometer IRFPA is one of the emerging challenges.[8,9,10,11,12,13,14,15,16] In order to make a reasonable performance prediction of a highly optimized and high-density microbolometer IRFPA, the correct understanding of the electro-thermal phenomena that occur in a microbolometer IRFPA is essentially required. The correct understanding of the electro-thermal effect leads to a more accurate signal prediction in the development, and to the proper use of an IRFPA in the application period.[13,14,15,16,17,18]. The electro-thermal feedback effect starts when the bias is applied to read the resistance change of the microbolometer in IRFPA. Once the bias is applied, the bias heat, which is inversely proportional to the resistance of the microbolometer for a constant voltage bias, is produced in a sensing material. This bias heat leads to a rapid temperature increase in the microbolometer. Since the negative temperature coefficient of resistance (NTCR) of IR sensing materials such as VOx and a-Si is used for most microbolometer technology,
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