Method and apparatus for monitoring layer erosion in a dry-etching process

摘要

A method and apparatus for monitoring layer erosion in a dry-etching process. The apparatus has a first electrode that is electrically connected to a substrate to be etched, as well as a second electrode that is located above the first electrode. Both electrodes are situated inside a process chamber. An optical photometer is positioned outside of the process chamber and directed onto the substrate in the process chamber. Signals received from the optical photometer are amplified by an electrical circuit and are edited and displayed with a Fourier transformation. The etching process can be automatically interrupted when received periodic signals having essentially constant amplitude and frequency undergo a significant change during the etching process of the upper layer. That is, they are received as signals signficantly deviating from one another, this being identified by the electrical circuit as the passage from one layer to another layer of the substrate during the dry-etching process.