Raman spectroscopy characterization of a thermal bimorph actuator used in a bio-MEMS device

Devising a MEMS (Micro Electro Mechanical System) sensor is a very challenging task. When movement is required, a transducer has to be integrated, capable to convert electrical into mechanical energy. Different types of actuators can be selected, using electrostatic forces, magnetic fields or thermal expansion, and reliability of actuators has proven to be a critical element in MEMS devices. In this paper we have demonstrated that the Raman spectroscopy technique (using the Raman peaks shift) is a suitable tool to assess the temperature of a thermal actuator in a MEMS device. The technique used is a spectrometric characterization, benefitting from the Raman peaks shift caused by an increase in temperature. This method shows that it is possible to map areas with a resolution of a few microns and a temperature accuracy of around 0.01 %/full scale. This technique provides good resolution and accuracy and allows several analyses: from simple thermal mapping to determination of the system’s thermal physical parameters and constant thermal resistance variation at a micrometric scale.