To simplify the preparation of sacrificial layer in micro-electromechanical system structure, new processes have been developed. By using lift-off technology, sacrificial layer was selectively deposited into the pit that prepared for sacrificial layer releasing. Then a short time polishing process was used to remove the burrs around the pit. This method offers several advantages including reducing the difficulty of polishing and hence processing cost. Methods and apparatuses to provide a continuously smoothly sacrificial layer surface in the pit were disclosed. However, it is important to control the homogeneity of filling and avoid the shadow effect at the corner of the pit. The unpadded regions would form a steep step and cause the cracking of structure layer. This problem was discussed and solved by rotating the tilted wafer during sacrificial material deposition. The surface roughness after the preparation process of sacrificial layer was measured. The root mean square roughness of sacrificial layer was 1.247 nm and reduced to 0.861 nm after a short time polishing process. Finally, a film bulk acoustic wave resonator with stacked Mo/AlN/Mo films had been fabricated on the sacrificial layer based on this method.
展开▼
