Investigation of Pt/Ti bilayer on $SiNx/Si$ substrates for thermal sensor applications

Pt/Ti thin films on $SiNx/Si$ substrates have been investigated for thermal sensor applications on $SiNx$ membrane. Therefore, Pt/Ti adhesion during KOH etching of silicon and high temperature coefficient of resistance (TCR) are the principal aims of this study. ac sputtering and electron beam evaporation have been investigated for metal deposition. Vacuum annealing is used to improve the Pt/Ti characteristics. Stress characterizations and adhesion strength are evaluated by an x-ray diffraction pattern and adhesive tape test, respectively. TCR and resistivity were finally measured to confirm the compatibility with good thermal sensor sensitivity. Pt/Ti films elaborated by electron beam evaporation and vacuum annealed present the best characteristics for thermal sensor applications: good adhesion is obtained even after 5 h in KOH etching solution, electrical resistivity is about 15 μΩ cm and TCR is $3.3×10−3/°C.$ Finally, by using these platinum thin films, a thermal accelerometer has been manufactured and tilt measurements have been achieved.