Hydrogen radical cleaning using the hot-wire (HW) method is considered the future technology for the optical system of extreme ultraviolet lithography (EUVL). However, the optical system of EUVL has a low heat resistance. Therefore, it is necessary to reduce the radiant heat from the HW method. It is crucial to separate the hydrogen radical source from the cleaning site and to control the transportation of hydrogen radicals. However, the inactivation of hydrogen radicals on the surface of a transportation tube poses the problem hydrogen radical inactivation. In this work, we examined the inner surface materials of transportation tubes in order to improve the transportation efficiency of hydrogen radicals. It was found that the transportation efficiency of hydrogen radicals was in the following order: silicon carbon nitride (SiCN) film-coated = quartz > Au-coated > stainless steel (SUS) = Inconel. Furthermore, the sample surface temperature could be lowered from 160 degrees C to 70 degrees C by using a transportation tube. (C) 2014 Elsevier B. V. All rights reserved.