Micro fabrication of lead-free (K,Na)NbO3 piezoelectric thin films by dry etching

Micro fabrication has been conducted for sodium potassium niobate [(K,Na)NbO₃, KNN] thin films by dry etching and Pt/KNN/Pt unimorph micro cantilevers have been fabricated as a lead-free piezoelectric micro electro mechanical system (MEMS). KNN etching by Ar/C₄F₈ plasma showed a high etching rate of about 60 nm/min and KNN/Cr selectivity of over 5. Tip displacement of the Pt/KNN/Pt micro cantilevers was measured and the frequency response and piezoelectric properties were evaluated. Young s modulus and piezoelectric coefficients d₃₁ of the KNN thin film were estimated to be 115 GPa and 99 to 219 pm/V, respectively. These results indicate that Ar/C₄F₈ plasma etching does not degrade the piezoelectric properties of KNN thin films and enables one to fabricate various lead-free piezoelectric MEMS applications.