A Polymer-Rich Re-deposition Technique for Non-volatile Etching By-products in Reactive Ion Etching Systems

Re-deposition is a non-volatile etching by-product in reactive ion etching systems that is well known to cause dirt on etching work. In this study, we propose a novel etching method called the polymer-rich re-deposition technique, used particularly for improving the etched sidewall where the re-deposition is able to accumulate. This technique works by allowing the accumulated re-deposition on the etched sidewall to have a higher polymer species than the new compounds in the non-volatile etching by-product. The polymer-rich re-deposition is easy to remove along with the photo-resist mask residual at the photo-resist strip step using an isopropyl alcohol-based solution. The traditional, additional cleaning process step used to remove the re-deposition material is not required anymore, so this reduces the overall processing time. The technique is demonstrated on an Al₂O₃-TiC substrate by C₄F₈ plasma, and the EDX spectrum confirms that the polymer re-deposition has C and F atoms as the dominant atoms, suggesting that it is a C—F polymer re-deposition.