Wet chemical etching method for BST thin films annealed at high temperature

As a traditional etchant, pure buffered hydrofluoric acid (BHF), does not possess the ability to etch BST thin films annealed at high temperature, even though it works greatly on as-deposited Ba0.5Sr0.5TiO3 (BST) films. In this paper, we developed an etchant by mixing BHF and strong acid (HNO3, HCl, H2SO4 and H3PO4) and use it successfully on BST films annealed with high temperature. The experimental results show that a 1-8 wt% of strong acid acts as an efficient catalyst and the etching speed is significantly improved. The etched BST films show little distortions and smooth etching edges were recorded.