Method for predicting the lifetime of euv pellicles

A method for predicting the lifetime of an EUV pellicle, the method comprising:

• a) acquiring transmittance data of an EUV pellicle over a wavelength band ranging from an infrared region to an ultraviolet region;
• b) acquiring complex refractive index data of the EUV pellicle over the wavelength band ranging from the infrared region to the ultraviolet region;
• c) acquiring information on a relationship between density and transmittance of the EUV pellicle as a function of wavelength by performing optical modeling using the transmittance data and the complex refractive index data;
• and
• d) measuring the transmittance of the EUV pellicle for at least one measurement beam having a wavelength within the wavelength band ranging from the infrared region to the ultraviolet region, extracting an estimated density of the EUV pellicle on the basis of the measured transmittance and the information on the relationship between density and transmittance acquired in the step c), and predicting a remaining lifetime of the EUV pellicle on the basis of the estimated density.