Design of a Low-Cost Infrared Sensor Array Through Thermal System Modeling

The responsivity, sensitivity (signal-to-noise ratio), and cross talk of pyroelectric infrared sensor arrays are directly related to the thermal performance of the interconnect between sensor elements and readout electronics. Conventional low-cost designs, employing a film of sensor material like polyvinylidenefluoride (PDVF) layered on top of a silicon substrate, function by reading the electronic signal generated in the sensor when infrared radiation causes the sensor to heat up proportional to the radiation intensity. However, the change in temperature of the sensor material, and therefore signal generated, is highly dependent on the thermal properties of the interconnect material between the sensor and silicon substrate. A numerical framework for evaluating the effect of thermal conductivity and specific heat on sensor responsivity, sensitivity, and cross talk is developed. This allows us to analyze the relationships between feature size, thermal properties, and system performance. Using this model, a selection of materials from epoxies and other conventional solutions to emerging material systems such as nanoporous silica (aerogel) can be analyzed. Aerogel is most interesting since its thermal properties are 1–3 orders-of-magnitude better than conventional interconnect materials. Recent developments have also shown its compatibility with low-cost microelectronics fabrication and packaging techniques. The numerical model illustrates the potential of highly miniaturized pyroelectric infrared sensor arrays that have comparable performance at dramatically lower fabrication cost compared to conventional infrared sensor array technology.Copyright © 2003 by ASME