Enhanced control of plasma etching parameters by optical emission spectroscopy

Laser interferometry and optical emission spectroscopy are well known techniques to characterize thin film etching during plasma processes. On one hand, laser interferometry allows the detection of end point and in situ etching rate, however it supposes using an external laser source. On the other hand, optical emission spectroscopy is useful for end point detection and also gives information on the plasma composition, if it works in a sufficient range of wavelength (for example 400-800 nm in our case) to find the characteristics plasma emission lines. As a result, this technique could also enable us to determine the etching rate in real time. The main topic of this paper is to show that, in a specific etching condition and geometrical configuration with the appropriated materials, Optical Emission Spectroscopy can gather the advantages of the two diagnostic techniques. This will be study on O2 etching plasma dedicated to polymers patterning in an optical integrated circuit process.