Effects Of Edge Roughness On Surface Charging In Plasma Etching

In the plasma etching technique, acquiring a high-quality transfer from the mask pattern onto the substrate under the suppression of the charging effects is of great significance. Most previous publications only focus on studying the charging phenomena on smooth round mask holes. This work shifted the target to an isolated mask hole with a rough edge using a classical particle simulation program, to examine the effects of edge roughness on surface charging for a mask hole. This study adopted the CF4 plasmas, due to the widely used fluorocarbon plasmas for the contact-holes. Simulated results indicate that the mask holes with various shapes present differences in electric field (E-field) strength distribution, etching rate and profile evolution, relying on some condition parameters (roughness and reflection probability on the mask surface). The larger the dominant wavelength (DW), the more uniform the E-field distribution around the edge of the mask hole will be. The simulation of the profile evolution further confirmed that the deformation is in keeping with the distribution of the E-field. It was further found that the root mean square (RMS) of roughness increases with time in cases of the relatively small values of wavelength (10 and 35 nm) and decreases for other cases. Possible mechanisms behind have been discussed in detail. The findings of this work would shed light on an approach to maintain the pattern integrity.