Composition of metal layers in CMOS-MEMS micromachining process

In this work some representative mechanical and materials-related issues in the design and fabrication of CMOS-MEMS devices are reviewed, especially those appearing in the further on-chip micromachining process needed to release MEMS structures within conventional CMOS integrated circuits. CMOS-MEMS is a micro-sensor and micro-actuator development technique consisting in applying either an etching or deposition process to previously designed and fabricated CMOS circuitry, in order to enhance its mechanical, optical, chemical or so properties achieving a micro-electromechanical behavior. In the case of material removal, also known as micromachining, a surface or bulk process, usually a wet chemical etching, is used to release metallic structures embedded in insulating glass layers. Nevertheless, the composition of those metallic structures may vary from a CMOS fabrication technology to another and should not be neglected during the etching process.