In-situ chamber clean for chromium etch application

As technology advances with feature size shrinking for the state-of-the-art integrated circuit (IQ fabrication, the degree of reduction in critical dimension (CD) features on a photomask shrinks at a faster pace, thanks to the ever aggressive optical proximity correction (OPC) design. In addition to stringent CD requirement, defect control has also become one of the most difficult challenges for advanced photomask manufacturing as a result of reduction in printable defect size. Therefore, keeping a photomask etching chamber at an optimal condition becomes very critical for controlling in both defectivity and CD fidelity. In the present study, analyses on optical emission spectrum (OES) collected in an Applied Materials' Tetra (TM) chronic etch module have been performed to understand (1) the impact of Cr etching on the chamber condition, and (2) the effectiveness of in-situ chamber dry clean for chamber condition control and potential particle reduction. Results showed that, with the right selection of chamber materials (to be compatible with process chemistry and etching condition), the main impact of Cr etching on chamber condition and particle performance is from resist etch-by-products. Various plasma dry clean chemistries have been explored to address the effectiveness for the removal of such etch-by-products. As a result, an in-situ chamber clean (ICC) procedure is developed and has been validated to be product] on-worthy for desired particle control and chamber stability control.