An exposure mask includes a substrate, and a plurality of first films and a plurality of second films located alternately over each other over selected portions of the substrate. The exposure mask further includes a third film selectively located over the first and second films. At least one first pattern is located over the substrate and does not include any of the first, second or third films. At least one second pattern is located over the substrate and includes the first and second films and does not include the third film. At least one third pattern is located over the substrate and includes the first, second and third films.

An exposure mask includes a substrate, and a plurality of first films and a plurality of second films located alternately over each other over selected portions of the substrate. The exposure mask further includes a third film selectively located over the first and second films. At least one first pattern is located over the substrate and does not include any of the first, second or third films. At least one second pattern is located over the substrate and includes the first and second films and does not include the third film. At least one third pattern is located over the substrate and includes the first, second and third films.

A reflective mask blank includes a substrate and, on or above the substrate in order, a reflective layer for reflecting EUV light, a protective layer for protecting the reflective layer, and an absorbent layer for absorbing EUV light. The absorbent layer has a reflectance for a wavelength of 13.53 nm of from 2.5% to 10%. A film thickness d of the absorbent layer satisfies a relationship of:

[00001]$d_{MAX}-\left(i\times 6+1\right)\mathrm{nm}\le d\le d_{MAX}-\left(i\times 6-1\right)\mathrm{nm}$

where the integer i is 0 or 1, and d.sub.MAX is represented by:

[00002]$d_{MAX}\left(\mathrm{nm}\right)=\frac{13.53}{2n\cos 6°}\left\{\mathrm{INT}\left(\frac{0.58}{1-n}\right)+\frac{1}{2\pi }\left({\tan }^{-1}\left(\frac{-k}{1-n}\right)+0.64\right)\right\}$

where n is a refractive index of the absorbent layer, k is an absorption coefficient of the absorbent layer, and INT(x) is a function of returning an integer value obtained by truncating a decimal part.

A reflective mask blank includes a substrate and, on or above the substrate in order, a reflective layer for reflecting EUV light, a protective layer for protecting the reflective layer, and an absorbent layer for absorbing EUV light. The absorbent layer has a reflectance for a wavelength of 13.53 nm of from 2.5% to 10%. A film thickness d of the absorbent layer satisfies a relationship of:

[00001]$d_{MAX}-\left(i\times 6+1\right)\mathrm{nm}\le d\le d_{MAX}-\left(i\times 6-1\right)\mathrm{nm}$

where the integer i is 0 or 1, and d.sub.MAX is represented by:

[00002]$d_{MAX}\left(\mathrm{nm}\right)=\frac{13.53}{2n\cos 6°}\left\{\mathrm{INT}\left(\frac{0.58}{1-n}\right)+\frac{1}{2\pi }\left({\tan }^{-1}\left(\frac{-k}{1-n}\right)+0.64\right)\right\}$

where n is a refractive index of the absorbent layer, k is an absorption coefficient of the absorbent layer, and INT(x) is a function of returning an integer value obtained by truncating a decimal part.

A reflective mask blank includes, on/above a substrate in the following order from the substrate side a multilayer reflective film which reflects EUV light and an absorber film which absorbs EUV light. The absorber film is a tantalum-based material film containing a tantalum-based material. The absorber film provides a peak derived from the tantalum-based material in an X-ray diffraction pattern, the peak having a peak diffraction angle (2θ) of 36.8 degrees or more and a full width at half maximum of 1.5 degrees or more.

A reflective mask blank includes, on/above a substrate in the following order from the substrate side a multilayer reflective film which reflects EUV light and an absorber film which absorbs EUV light. The absorber film is a tantalum-based material film containing a tantalum-based material. The absorber film provides a peak derived from the tantalum-based material in an X-ray diffraction pattern, the peak having a peak diffraction angle (2θ) of 36.8 degrees or more and a full width at half maximum of 1.5 degrees or more.

A method for generating an electromagnetic radiation includes the following operations. A target material is introduced in a chamber. A light beam is irradiated on the target material in the chamber to generate plasma and an electromagnetic radiation. The electromagnetic radiation is collected with an optical device. A gas mixture is introduced in the chamber. The gas mixture includes a first buffer gas reactive to the target material, and a second buffer gas to slow down debris of the target material and/or plasma by-product, so as to increase an reaction efficiency of the target material and the first buffer gas, and to reduce deposition of the debris of the target material and/or the plasma by-product on the optical device.

A method for generating an electromagnetic radiation includes the following operations. A target material is introduced in a chamber. A light beam is irradiated on the target material in the chamber to generate plasma and an electromagnetic radiation. The electromagnetic radiation is collected with an optical device. A gas mixture is introduced in the chamber. The gas mixture includes a first buffer gas reactive to the target material, and a second buffer gas to slow down debris of the target material and/or plasma by-product, so as to increase an reaction efficiency of the target material and the first buffer gas, and to reduce deposition of the debris of the target material and/or the plasma by-product on the optical device.

A mask blank glass substrate having a maximum value of a circularly averaged power spectral density of 1,000 nm.sup.4 or less at a spatial frequency of 0.1 μm.sup.−1 or more and 20 μm.sup.−1 or less, the maximum value being obtained by measuring a surface morphology of a region of 10 μm×10 μm with an atomic force microscope.

An extreme ultraviolet (EUV) mask blank is provided. The EUV mask blank includes a substrate having a first surface and a second surface opposed to each other, a reflective layer having first reflective layers and second reflective layers alternately stacked on the first surface of the substrate, a capping layer on the reflective layer, and a hydrogen absorber layer between the reflective layer and the capping layer, the hydrogen absorber layer configured to store hydrogen and being in contact with the capping layer.