EP-4738005-A2 - REFLECTIVE MASK BLANK AND METHOD FOR MANUFACTURING REFLECTIVE MASK

Abstract

A reflective mask blank is a material for a reflective mask used in EUV lithography using EUV light as exposure light. The reflective mask blank comprising: a substrate (1); a multilayer reflective film (2) that reflects the exposure light and is formed above one main surface of the substrate (1); a protective film (3) that protects the multilayer reflective film (2) and is formed above the multilayer reflective film (2); an absorption film (5) that absorbs the exposure light and is formed above the protective film (3); and an etch-stop film (4) that contains niobium (Nb) and is provided between the protective film (3) and the absorption film (5). The protective film (3) has at least one layer containing rhodium (Rh). A layer in contact with the protective film (3) in the multilayer reflective film (2) contains molybdenum (Mo).

Inventors

• INAZUKI, YUKIO
• KOSAKA, TAKURO
• OGOSE, Taiga
• SAKURAI, KEISUKE
• MIMURA, SHOHEI
• KANEKO, HIDEO

Assignees

• SHIN-ETSU CHEMICAL CO., LTD.

Dates

Publication Date

20260506

Application Date

20251030

Claims (6)

1. A reflective mask blank that is a material for a reflective mask used in EUV lithography using EUV light as exposure light, the reflective mask blank comprising: a substrate (1); a multilayer reflective film (2) that reflects the exposure light and is formed above one main surface of the substrate (1); a protective film (3) that protects the multilayer reflective film (2) and is formed above the multilayer reflective film (2); an absorption film (5) that absorbs the exposure light and is formed above the protective film (3); and an etch-stop film (4) that contains niobium (Nb) and is provided between the protective film (3) and the absorption film (5), wherein the protective film (3) has at least one layer containing rhodium (Rh), and a layer in contact with the protective film (3) in the multilayer reflective film (2) contains molybdenum (Mo).
2. The reflective mask blank according to claim 1, wherein the protective film (3) is made of rhodium (Rh).
3. The reflective mask blank according to claim 1, wherein the protective film (3) is a layer containing rhodium (Rh) and ruthenium (Ru).
4. The reflective mask blank according to claim 1, wherein the protective film (3) has a layer containing rhodium (Rh) and a layer containing ruthenium (Ru).
5. The reflective mask blank according to any one of claims 1 to 4, wherein the etch-stop film (4) is made of niobium (Nb), or a niobium (Nb) compound containing niobium (Nb) and oxygen (O).
6. A method for manufacturing a reflective mask from the reflective mask blank according to any one of claims 1 to 5.

Description

Technical Field The present invention relates to a reflective mask blank that is a material for a reflective mask used for manufacturing a semiconductor device such as an LSI, and a method for manufacturing a reflective mask from the reflective mask blank. Background Art In the manufacturing process of semiconductor devices, a photolithography technique for irradiating a transfer mask with exposure light and transferring a circuit pattern formed on the mask onto a semiconductor substrate (semiconductor wafer) via a reduction projection optical system is repeatedly used. In the related art, the wavelength of exposure light is mainly 193 nm, which is argon fluoride (ArF) excimer laser light, and a pattern having smaller dimensions than the exposure wavelength has been finally formed by adopting a process called multi-patterning in which an exposure process and a processing process are combined a plurality of times. However, it has been necessary to form even finer patterns due to continuous miniaturization of device patterns, and thus an EUV lithography technique using extreme ultraviolet (hereinafter, referred to as "EUV") light having a wavelength shorter than that of ArF excimer laser light as exposure light has been used. EUV light is light having a wavelength of about 0.2 to 100 nm, more specifically, light having a wavelength of around 13.5 nm. Since EUV light has extremely low transparency to substances, transmission type projection optical systems and masks of the related art cannot be used, and thus reflection type optical elements are used. Therefore, a reflective mask is also used as a mask for pattern transfer. In the reflective mask, a multilayer reflective film that reflects EUV light is formed on a substrate, and a pattern of an absorption film that absorbs EUV light is formed on the multilayer reflective film. Meanwhile, the material before patterning of the absorption film (including the material with a resist film formed thereon) is called a reflective mask blank, and the reflective mask blank is used as a material for the reflective mask. In general, the reflective mask blank has a basic structure including a low thermal expansion substrate, a multilayer reflective film that reflects EUV light and is formed on one of two main surfaces of the substrate, and an absorption film that absorbs EUV light and is formed on the multilayer reflective film. As the multilayer reflective film, a multilayer reflective film that obtains a necessary reflectivity for EUV light by alternately laminating a molybdenum (Mo) layer and a silicon (Si) layer is usually used. As the absorption film, tantalum (Ta) or the like having a relatively large extinction coefficient for EUV light is used (JP 2002-246299 A). Furthermore, as a protective film (capping film) for protecting the multilayer reflective film during washing of the reflective mask or the like, a ruthenium (Ru) film or a rhodium (Rh) film as disclosed in JP 2002-122981 A or JP 2005-516182 T is formed on the multilayer reflective film. In addition, as an etching mask for when a pattern is formed on the absorption film, a hard mask film containing chromium (Cr) may be formed on the absorption film. Meanwhile, a conductive film is formed on the other main surface of the substrate. As the conductive film, a metal nitride film is proposed for electrostatic chucking, and examples thereof include films mainly containing chromium (Cr) and tantalum (Ta). SUMMARY OF INVENTION PROBLEM TO BE SOLVED BY INVENTION The protective film is required to function to protect the multilayer reflective film. Specific examples of the function include a function of protecting the multilayer reflective film so that the multilayer reflective film is not exposed to an etching gas and a cleaning liquid in pattern processing of the absorption film, and a function of suppressing a decrease in reflectivity as exposure is repeated in exposure using a reflective mask. In the manufacturing process of a reflective mask using a reflective mask blank as a material, when a pattern is formed on the absorption film by dry etching, some degree of over-etching is usually performed to control a pattern shape. Since the over-etching is performed, the protective film is exposed to etching and damaged. In a case where the absorption film is formed of a material containing tantalum (Ta) and not containing oxygen (O), a gas containing chlorine (Cl) and not containing oxygen (O) is preferably used as an etching gas, and thus the protective film is required to have resistance to the dry etching using a gas containing chlorine (Cl) and not containing oxygen (O). In addition, in a case where a pattern of a hard mask film formed of a material containing chromium (Cr) is used as an etching mask when a pattern is formed on the absorption film, the pattern of the hard mask film is usually removed by dry etching using a gas containing chlorine (Cl) and oxygen (O) after formation of the pattern of the absorption