Metal-oxide sensors compatible

The heater material is a crucial point for the stability of this type of device during operation. Driven by CMOS compatibility, Poly-Si was first used but it suffers from an inappropriate drift of its electrical resistivity at high temperature (Ehmann et al, 2001). Platinum is the material that has been implemented for the heater for improved reliability. It is used in most micromachined metal-oxide sensors on the market at the time of writing, not only for the heater, but also for the electrodes. Courbat et al (2008) showed that adding a small amount of another refractory metal (such as iridium) to the platinum can improve its resistance to electromigration. However, Mo exhibited superior performances to platinum, allowing higher operational temperatures (Mele et a/., 2012). 

Four main concerns need to be addressed when integrating metal-oxide sensors in a CMOS-compatible process ... 

Complementary metal-oxide semiconductor (CMOS)-compatible metal-oxide gas sensors... 

The operation of metal-oxide gas sensors on plastic foil was successfully demonstrated. However, to make them fully compatible with large-scale fabrication techniques, additional work is required. So far, inkjet and gravure printing have been applied for the deposition of the gas sensing layer. However, the full printing of the transducers including the sensing layer still needs to be demonstrated. 

In addition, polymers are relatively open materials that allow ingress of gases into their interior. Moreover, conducting polymers can be deposited over defined areas of electrodes, hi addition, unlike metal and metal oxide semiconductor materials, there is no need for special clean room, high-temperature, or special high-cost process techniques to fabricate sensor devices using polymers. This means that polymers can be readily incorporated into miCTofabricated structures and therefore CPs are inherently compatible with solid-state integrated gas sensors. 

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