Plasma monitoring of chrome dry etching for mask making

Abstract

As a photomask feature size shrinks, chrome (Cr) dry etching process is one of the most critical steps which define the performance of critical dimensions (CDs). In consequence, plasma conditions should be maintained stable in a etch chamber. In this work, advanced methodologies using plasma monitoring tools are introduced; Optical Emission Spectroscopy (OES) and the Self-Excited Electron Resonance Spectroscopy (SEERS). After an etch chamber was monitored with these tools, plasma conditions could be categorized with respect to the three parameters; the spectra, the electron collision rate, and the electron density distributions. Finally, it is possible to predict the CD performance of the chamber by checking the specific plasma parameters.