Development of pellicle for ArF excimer laser

We have conducted a series of test under practical conditions with low fluence of ArF excimer laser to check membrane longevity of a fluoropolymer, a candidate for membrane material for the ArF excimer laser. According to the test results, the causes of the membrane longevity deterioration with ArF excimer laser exposure are: (1) Due to deviation from anti-reflection conditions caused by physical reduction of the membrane thickness. (2) Due to creation of substances causing light absorption. Also, we have found out that the environment inside a stepper/scanner can influence the test results to a large extent. Under air environment conditions, only phenomenon (1) above is noticed, and comparatively longer membrane longevity can be achieved; however, under nitrogen environment conditions, both phenomena (1) and (2) take place, and lesser membrane longevity is achieved compared to under air environment conditions. Under nitrogen environment conditions, we notice that phenomenon (2) can be avoided by adding a small amount of oxygen into a stepper/scanner. In this case, the membrane longevity can be improved to the same level as under air environment conditions. We analyzed by XPS, the surface status of the fluoropolymer membrane that was exposed with ArF excimer laser under nitrogen environment conditions. According to our findings, we presume that the substance causing light absorption is created by a chemical reaction between carbon structure causing light absorption is created by a chemical reaction between carbon structure without fluorine and nitrogen or water or both in the environment.