Laconte J., Flandre D., Raskin J.-P. Micromachined Thin-Film Sensors for SOI-CMOS Co-Integration

Dordrecht: Springer. – 2006. – 290 p. While in some applications such as gas-flow sensors, the co-integration of a sensor with its surrounding electronics on a single chip is just an asset, co-integration is inescapable in other cases such as transistors-based pressure sensors or low-loss microwave circuits insulated from the substrate, on a membrane. Moreover, co-integration performed in the most advanced of the Complementary-Metal-Oxide-Semiconductor (CMOS) technologies to date -namely Silicon-on-Insulator (SOI) technology- provides many significant benefits regarding the performance, reliability, miniaturization and processing easiness without significantly increasing the final cost. Thin dielectric membranes constitute the starting material for a large number of sensors thanks to their ability to act as a mechanical support or an electrical and thermal insulator. We particularly focused on the thermal insulation feature to build fully CMOSSOI co-integrated gas-flow sensors. A one-μm-thick robust and flat dielectric multilayered membrane has been built taking precisely into account the residual stresses in each constitutive layer. A novel loop-shape polysilicon microheater implementing the basic heating cell of new simple gas-flow sensors has been designed and produced in a CMOS-SOI standard process. High thermal uniformity, low power consumption and high working temperature have been targeted and confirmed by extensive measurements. Finally, transistors integrated in small silicon islands located in the middle of our dielectric membrane have been studied and presented as a concluding demonstrator of the co-integration in SOI technology. Such devices open the door to numerous new applications where integrated circuits and sensors are merged in order to target higher performance in harsh environments.Introduction: Context and motivations
Techniques and materials
Silicon bulk micromachining with TMAH
Thin dielectric films stress extraction
Microsensors
Low power microhotplate as basic cell
Microheater based flow sensor
Gas Sensors on microhotplate
SOI-CMOS compatibility validation
Conclusions and outlook
Silicon crystallography
About Interferometry
About ReflectometryPublications originated from this work