EP-4738006-A2 - REFLECTIVE MASK BLANK AND METHOD FOR MANUFACTURING REFLECTIVE MASK

Abstract

A reflective mask blank comprises: 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 (6) that absorbs the exposure light and is formed above the protective film (3); and an intermediate film provided between the protective film (3) and the absorption film (6). The intermediate film includes a first intermediate film (4) containing niobium (Nb) and a second intermediate film (5) that is provided closer to the absorption film (6) than the first intermediate film (4) and is made of a material that can be dry-etched with an oxygen-containing gas. The absorption film (6) is made of a material that can be dry-etched with a fluorine-containing gas.

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 (8)

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 (6) that absorbs the exposure light and is formed above the protective film (3); and an intermediate film provided between the protective film (3) and the absorption film (6), wherein the intermediate film includes a first intermediate film (4) containing niobium (Nb) and a second intermediate film (5) that is provided closer to the absorption film (6) than the first intermediate film (4) and is made of a material that can be dry-etched with an oxygen-containing gas, and the absorption film (6) is made of a material that can be dry-etched with a fluorine-containing gas.
2. The reflective mask blank according to claim 1, wherein the first intermediate film (4) is a film made of niobium (Nb) alone, a niobium (Nb) compound containing niobium (Nb) and oxygen (O), or combination thereof.
3. The reflective mask blank according to claim 1 or 2, wherein the second intermediate film (5) contains at least one selected from ruthenium (Ru), chromium (Cr), vanadium (V), and molybdenum (Mo).
4. The reflective mask blank according to any one of claims 1 to 3, wherein the absorption film (6) contains at least one selected from tantalum (Ta), rhodium (Rh), platinum (Pt), iridium (Ir), and gold (Au).
5. The reflective mask blank according to any one of claims 1 to 4, wherein the second intermediate film (5) contains ruthenium (Ru), and wherein the absorption film (6) contains platinum (Pt).
6. The reflective mask blank according to any one of claims 1 to 4, wherein the second intermediate film (5) contains chromium (Cr), and wherein the absorption film (6) contains platinum (Pt).
7. The reflective mask blank according to any one of claims 1 to 6, wherein an etching mask film containing chromium (Cr) is provided on the absorption film (6).
8. A method for manufacturing a reflective mask from the reflective mask blank according to any one of claims 1 to 7 comprising: patterning the absorption film (6) by dry etching using a fluorine-containing gas; patterning the second intermediate film (5) by dry etching using an oxygen-containing gas; and patterning the first intermediate film (4) by a sulfuric acid/hydrogen peroxide mixture (SPM).

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 In a mask for EUV exposure, a Ta-based absorption film of about 70 nm or 60 nm is used as a light shielding film in the related art. However, the absorption film is required to be thin to reduce the mask 3D effect during EUV exposure, and various materials are proposed. However, even in a case where a film exhibiting optically better characteristics than the Ta-based absorption film of the related art was used, problems arose such as damage to the protective film during mask processing due to a low etching rate during mask processing. The present invention has been made to solve the problems, and an object thereof is to provide a reflective mask blank in which a protective film is not damaged during mask processing, and a method for manufacturing a reflective mask using the reflective mask blank. The inventors of the present application have conducted intensive studies to solve the problems, and as a result, found that, when an absorption film that can be etched with a fluorine-containing gas is used, the problems can be solved by providing, between a protective film and the absorption film, at least two layers of intermediate films having a layer containing niobium (Nb) on the protective film side and a layer made of a material that can be etched with an oxygen-containing gas on the absorption film side, and completed the present invention. MEANS FOR SOLVING PROBLEM Therefore, the present invention provides the following reflective mask blank and method for