Implementing ALD Layers in MEMS Processing

Abstract

Layers manufactured by the ALD technique have many interesting applications in microelectromechanical systems (MEMS), for example as protective layers for biocompatible coating, high-dielectric-constant layers, or low-temperature conformal insulating layers. Before an ALD process can be successfully implemented in MEMS processing, several practical issues have to be solved, starting from patterning the layers and characterizing their behaviour in various chemical and thermal environments. Stress issues may not be forgotten. We have recently implemented two ALD processes, namely the trimethylaluminium/water process to deposit Al2O3 and the titanium tetrachloride/water process to deposit TiO2 in our MEMS processing line and carried out the necessary characterization, details of which are reported here. For us, ALD has been a truly enabling technology in the processing of a three-dimensional micromechanical compass based on the Lorentz force, where Al2O3 acted as a pinhole-free electrical insulation grown at low temperature.