Polyimide membrane for micro-heated gas sensor array

Presented here is the fabrication of a polyimide (PI) membrane for potential use as a low loss microheated metal oxide (MOS) gas sensor array. Such membranes are often made from dielectric layers of silicon nitride or silicon oxide on bulk etched silicon (1 0 0) to fabricate low power sensors. Due to the fragility of these types of membranes, the yield is not good and the dielectric thickness and active area is limited. The area of PI membrane is not limited by the fragility of the material due to its rugged nature. The thickness of polyimide membrane used is in the region of 1-10 mum. The elastic modulus of the material enables it to be used in any number of applications ranging from heated sensor support to a microwave antenna array in the communication field. The application described here uses the thin rugged polyimide membrane to reduce the power consumption of a metal oxide gas sensor. Along with the fabrication of the polyimide membrane, an array of micro heaters is integrated on top of the membrane. A sputtered platinum (Pt) meander is resistively used to heat up the sensing layer to its elevated temperature of up to 350 degreesC. (C) 2004 Elsevier B.V. All rights reserved.