Thermal stability of Pt/Cr and Pt/Cr2O3 thin-film layers on a SiNx/Si substrate for thermal sensor applications

• We studied two types of adhesion layers for Pt layers on SiNx/Si substrates.
• We report that Cr adhesion layer induces a drift of thermoresistive properties.
• Cr2O3 adhesion layer leads to more stable thermoresistive properties.
• Pt/Cr2O3 thin films can withstand up to 300 °C without properties weakening.

In this paper, we have studied the influence of the adhesion layer on the thermal stability of Pt/SiNx thin-film suspended resistors over a cavity etched in silicon with a KOH solution. Two types of adhesion layers are investigated: one made of metal (Cr) and the other one made of metal oxide (Cr2O3). Crystallographic properties of Pt are shown to be independent of the adhesion layer nature contrary to the electrical properties. In fact, we show that in Pt/Cr layers, there is an evolution of the thermoresistive properties with temperature as well as a resistance drift with large operating powers. On the other hand, Pt/Cr2O3 layers present no evolution of their thermoresistive properties up to 300 °C and no upper limit in operating power is found that could induce a resistance drift.