Actuator for Out-of-Plane MEMS Devices

摘要

Two major problems from phase I were solved during phase II. The step-coverage problem of TiNi thin film on the polysilicon structure was solved by introducing silicon-on-insulator (SOI) wafers. Also the out-of-plane devices were fabricated completely in-house to eliminate the problem of long turn-around time at the Microelectronics Center of North Carolina (MCNC). In a novel approach, the micromirrors were fabricated from the thin silicon membrane layer of the SOI wafer. Hinge structures were fabricated from SU-8 photoresist. Since the mirrors and the actuator beams were made on same silicon plane, the sharp step and thus the problem of step-coverage was eliminated. TiNi thin film was sputter deposited on silicon beams to form actuators. Silicon oxide and OCG 825 photoresist were used as sacrificial layers for releasing the mirrors and hinges respectively. The mechanical functionality of hinges made in-house was verified and demonstrated by tilting the silicon mirrors from horizontal to vertical position. Magnetic actuation was investigated as an alterative method for actuating the mirrors. A magnetic alloy, Permalloy, was successfully plated on the spacer dies from MCNC. Spacer devices were chemically released from the substrate and tested for the actuation. Displacement of the released spacer devices magnetically was demonstrated.