ECR plasma deposited a-SiCN:H as insulating layer in piezoceramic modules

Highly resistive and sufficiently stiff insulation layers are an important prerequisite for the direct integration of piezoceramic modules into microstructured aluminium alloy sheets to produce smart adaptronic metal parts. In this study, we evaluate the mechanical and electrical properties of amorphous, hydrogenated silicon carbonitride films (a-SiCN:H) deposited by electron cyclotron resonance plasma CVD. First, we find the optimal process parameters for silicon substrates which we then transfer to electroded lead zirconate titanate (PZT) plates. Deposition rate, Young's modulus, stoichiometry and resistivity of a-SiCN:H films are determined by stylus profilometry, nanoindentation, X-ray photoelectron spectroscopy, elastic recoil detection analysis and current-voltage measurements, respectively. Under a 100 kHz bipolar pulsed substrate bias, 2 … 3 μm thick, well insulating films with Young's modulus ≈100 GPa are deposited at high rate of up to 7 μm/h. The electrical performance of a-SiCN:H films on PZT substrates is, to large extent, governed by the size and number of PZT roughness peaks, locally enhancing the field strength. Furthermore, we briefly address the deposition of the electrode layer on PZT. The selected material, sputter-deposited CuCr1Zr alloy, considerably improves the fracture strength of PZT substrates.