Sacrificial aluminum etching for CMOS microstructures

This paper reports recent advances in surface micromachining by sacrificial aluminum etching (SALE). This method is applied to standard CMOS substrates in a single-mask, or even maskless, post-processing scheme. Underetching distances of several hundred microns are feasible. Design issues and technological steps such as protection of contact pads, etching, rinsing, and drying are discussed. The combination of SALE with other micromachining techniques, e.g., silicon bulk micromachining or material deposition is reported. New devices include thermal, capacitive, and mechanical structures for thermal microfluidics, the measurement of pressures and inertial forces, and the evaluation of mechanical thin film properties.