Platinum metallization for MEMS application: Focus on coating adhesion for biomedical applications

The adherence of Platinum thin film on Si/SiO(2) wafer was studies using Chromium, Titanium or Alumina (Cr, Ti, Al(2)O(3)) as interlayer. The adhesion of Pt is a fundamental property in different areas, for example in MEMS devices, which operate at high temperature conditions, as well as in biomedical applications, where the problem of adhesion of a Pt film to the substrate is known as a major challenge in several industrial applications health and in biomedical devices, such as for example in the stents.(1)(-)(4) We investigated the properties of Chromium, Titanium, and Alumina (Cr, Ti, and Al(2)O(3)) used as adhesion layers of Platinum (Pt) electrode. Thin films of Chromium, Titanium and Alumina were deposited on Silicon/Silicon dioxide (Si/SiO(2)) wafer by electron beam. We introduced Al(2)O(3) as a new adhesion layer to test the behavior of the Pt film at higher temperature using a ceramic adhesion thin film. Electric behaviors were measured for different annealing temperatures to know the performance for Cr/Pt, Ti/Pt, and Al(2)O(3)/Pt metallic film in the gas sensor application. All these metal layers showed a good adhesion onto Si/SiO(2) and also good Au wire bondability at room temperature, but for higher temperature than 400 °C the thin Cr/Pt and Ti/Pt films showed poor adhesion due to the atomic inter-diffusion between Platinum and the metal adhesion layers.(5) The proposed Al(2)O(3)/Pt ceramic-metal layers confirmed a better adherence for the higher temperatures tested.