Fabrication of (K,Na)NbO₃ lead-free piezoelectric films deposited by sputtering

Abstract

Recently, the applications of MEMS devices fabricated using piezoelectric films have widely been extended to inkjet-printer heads and angular-rate sensors. Most of the piezoelectric films used in the present products are Pb (Zr,Ti)O₃ films with a high fraction of lead (Pb), and it is seen as an environmental problem. However, there has been no report regarding high-performance lead-free piezoelectric films that are sufficient for substituting Pb (Zr,Ti)O₃ films. Under these circumstances, we developed technologies for preparing fine (K,Na)NbO₃ films with (001) orientation deposited by sputtering and successfully obtained a high piezoelectric coefficient d₃₁ of more than 100 pm/V on 4-inch Si wafers. The d₃₁ value was comparable to those of the best commercially available Pb(Zr,Ti)O₃ films.