Protective coatings of hafnium dioxide by atomic layer deposition for microelectromechanical systems applications

This work presents the investigation of HfO₂ deposited by atomic layer deposition (ALD) from either HfD-CO4 or TEMAHf and ozone for microelectromechanical systems (MEMS) applications, in particular, for environmental protection of aluminum micromirrors. This work shows that HfO₂ films successfully protect aluminum in moist environment and at the same time retain good reflectance properties of underlying material. In our experimental work, the chemical composition, crystal structure, electronic density and roughness of HfO₂ films remained the same after one week of humidity treatment (relative humidity of 85%, 85 °C). The reflectance properties underwent only minor changes. The observed shift in reflectance was only from 80-90% to 76-85% in 400-800 nm spectral range when coated with ALD HfO₂ films grown with Hf(NMeEt)₄ and no shift (remained in the range of 68-83%) for films grown from (CpMe)₂Hf(OMe)Me.