Development of High TCR Platinum Thin Films

Abstract

High Temperature Coefficient of Resistance (TCR) platinum (Pt) thin films become increasingly attractive for devices with Micro Electro Mechanical Systems (MEMS) using high temperature. However, in annealing with high temperature, Pt thin films are degraded, and in comparison with bulk Pt, the TCR of Pt thin films are inferior. In this study, alumina (Al₂O₃) buffer layers were introduced between the silicon nitride (SiNx) films and Pt films. After annealing in the air, the structure of Pt thin films was observed by Scanning Electron Microscope (SEM) and analyzed by X-ray diffraction, and the depth-resolved elemental composition of interface between Pt thin films and Al₂O₃ buffer layers was observed by Secondary Ion Mass Spectrometry (SIMS). As the annealing temperature is higher, the grain size of Pt is larger. At the point of the largest grain size, the largest TCR could not obtain. In this paper, we discuss about the relationship between the structure of Pt thin film and annealing temperature, and about the effect of Al₂O₃ buffer layers.