Thin-Film Polyimide Membrane Actuators Fabricated by Etching a Substrate by DRIE (Bosch Process)

Abstract

This paper deals with thin-film polyimide membrane actuators. The membranes were fabricated by deep-RIE using the Bosch process for etching a silicon substrate up to the polyamide layer, since we found that the polyimide layer was scarcely etched in this process. Membranes that were 5 mm in diameter and 2-10 µm thick were fabricated. The characteristics of membrane deflection were experimentally and analytically investigated by applying static pressure. The membranes could produce displacement on the order of a hundred micrometers in an experiment. We chose thermal expansion to actuate the membranes as actuators. Applying electricity to an aluminum layer deposited on the membrane deflected the membrane due to the thermal expansion of the aluminum layer. The experiments demonstrated that membranes 3-10 µm thick produced displacements at the membrane centers in a range from 10-20 µm by applying 1 V and the actuators worked periodically by turning the supply of electricity on and off.

Fundamental characteristics of a MEMS‐diaphragm actuator using a thermal expansion drive composed of a conductive polymer

“…The diaphragm part of the Si substrate (a tip of 15 mm × 15 mm cut from a Si wafer) was etched by deep reactive ion etching (RIE). The details of the fabrication processes of the PI layer and the Si etching are described in . The PI layer of the diaphragm has sufficient adhesive strength to the silicon substrate.…”