Development of pellicle for F2(157-nm) excimer laser

Because 157nm light energy is two or more times of C-C bonding energy, the main bonding of organic materials, pellicle membrane material decomposes if it absorbs light at 157nm. Therefore, in order to ensure the durability of the pellicle membrane, it is very important that the membrane material absorbs 157nm light as little as possible.We researched high transmittance polymers at 157nm by using simulation technology. In conclusion, we estimated that polymers with high transmittance at 157nm are possible, and several companies were asked to develop it. As a result, we obtained a polymer in which 157nm transmittance is 98.5% at 0.8 um [157nm absorbance is 0.008 um(-1),10base] from Asahi Glass Co., Ltd.We carried out various 157nm irradiation tests by using the above polymer, and obtained the result showing durability of 15J/cm(2) in nitrogen +1000ppm oxygen environment. Furthermore, we examined the environment during F-2 Excimer Laser irradiation and found that transmittance loss of membrane and also oxygen addition quantity to irradiation environment may be improved substantially by adopting irradiation environment of Helium.