Cyclic Cl-2/H-2 Quasi-Atomic Layer Etching Approach For Tin And Tan Patterning Using Organic Masks

A plasma-enhanced cyclic etch process utilizing sequential cycles of Cl-2 (deposition) and He/H-2 (etch) chemistries separated by purge steps was used to pattern TiN and TaN lines using an organic planarization layer mask at a 100 nm critical dimension and a 200 nm pitch. Etch rates (ERs) were found to vary from 3.5 to 7 nm per cycle for TaN and 5-7.3 nm per cycle for TiN, depending on the addition of H-2 to the etch step. The cyclic etch process displayed several key advantages over a continuous wave plasma process, such as no residual material in TiN patterning and reduced veiling due to redeposition in the TaN features. Analysis of the optical emission spectra collected indicated a key mechanistic difference between etching of the two materials, with TiN etching mainly controlled by the residence time of Cl species and TaN etching rate-limited by physical bombardment to facilitate Ta-Cl formation. Tailoring of the feature profiles and control of the etch rate per cycle (ER/cycle) were demonstrated through manipulation of the Cl and H-2 residence times. (C) 2017 American Vacuum Society.