Carbon removal from trenches on EUV reticles

We report on our investigation of dry cleaning of reticles with a microwave induced hydrogen plasma on dummy reticles. The dummy reticles were manufactured with 70 nm ALD grown TaN on a Ru surface and test structures were patterned with lines and spaces ranging between 250 and 400 nm. After processing the test structures were contaminated with e-beam grown carbon and exposed in our plasma facility to remove the carbon with the aid of a hydrogen plasma. Analysis of the samples was performed with SEM/EDX and with SIMS-SPM to verify the complete removal of carbon from the bottom of the trench. Analysis showed that there are small traces of carbon still present on the samples. This can be contributed to contamination which has occurred during transport and storage or that the grown carbon has some edges which are higher due to localized high intensity in the focus of the e-beam.