Manufacture of piezoelectric thin film resonator

Abstract

Abstract PURPOSE:To obtain a piezoelectric thin film resonator having high sharpness by making the lower electrode of an alkali resistant piezoelectric thin film resonator function as a stopping layer of etching when etching a supporting substrate made of a sintered body of zinc oxide by an alkaline etching solution. CONSTITUTION:To prevent deterioration of characteristic of a piezoelectric thin film made of zinc oxide 14 due to moisture absorption, a protective film 16 made of acid resistant and alkali resistant material is formed on the piezoelectric thin film and upper electrode 15. A mask 17 is formed by photoresist on a metallic layer 13 formed on the whole face of the main surface of a supporting substrate 11, and an area 13a of the metallic layer 3 slightly larger than an area facing the upper electrode 15 is removed by etching. Then, the supporting substrate 11 is etched by 30% caustic soda from removed area 13a of the metallic layer 13. This etching is stopped when arrived at a lower electrode 12 made of alkali resistant metal formed on a main face 11a of the supporting substrate 11. A protective film 20 is formed from the face of inner wall of a recessed part 18 to the metallic layer 13.

Inventors

• 👤 Tasuku Masuo
• 👤 増尾　翼

Bibliographic Details