Thermal analysis of fingerprint sensor having a microheater array

For the purpose of properties security, in particular of information systems, demands for portable fingerprint sensors are increasing. We proposed a new type of fingerprint sensor having an arrayed microheater, and successfully fabricated one-dimensional array of sensor elements on a silicon wafer using micromachining technologies. Electric resistance of each heater element is measured as signals of temperature difference between elements that are in contact or non-contact with ridges of the fingerprints. In this paper, we analyzed thermal characteristics of our sensor device using computer modeling. Effects of the following parameters were investigated; cavity under heater, SiO₂ film between heater and sensor base, heater size, input power and pulse time duration applied to the heater, material properties contacting to sensor surface etc. We concluded that making cavities under the microheater elements and having SiO₂ film layer between heater element and sensor base both for the purpose of thermal insulation, is necessary to realize the performance of the proposed sensor system. From the simulation results, it was clarified that such a miniaturized heater element will work quite effective for detecting fingerprint patterns