MEMS Tilt Sensor Fabricated Utilizing Anodic Bonding of Thin Silicon Film on Glass Substrate

Abstract

This paper reports on a new type of a tilt sensor fabricated using silicon MEMS processing technologies. The sensor consists of a ring shaped movable electrode, an extremely thin (15 μm) spiral spring connected with the movable electrode and eight surrounding lower electrodes. When a gravitational acceleration 1 G (9.80 m/s2) is applied to the movable electrode, it moves and makes a short circuit between itself and a pair of the lower electrodes. The movable electrode comes in contact with different surrounding electrodes depending on the tilt angle of the chip. Therefore, it is possible to detect the tilt. The tilt sensor was fabricated utilizing the following MEMS processes including anodic bonding of an extremely thin 60 μm-thick silicon wafer on a glass substrate, photolithography on the silicon film and dry etching the silicon film using an inductively coupled plasma (ICP) dry etcher. Then, the underneath glass was selectively etched off using a hydrofluoric (HF) solution to release the movable parts. Since the device layers were fabricated on a single-crystal silicon, it enables to fabricate stress free silicon spring. The sensor successfully detected the tilt of the chip.