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EP-4738004-A1 - BLANKMASK AND PHOTOMASK FOR EUV LITHOGRAPHY WITH HARD MASK FILM CONTAINING CHROME AND NIOBIUM

EP4738004A1EP 4738004 A1EP4738004 A1EP 4738004A1EP-4738004-A1

Abstract

The blank mask for EUV lithography has a structure in which a reflective film, a capping film, an absorber film, and a hard mask film are sequentially stacked on a substrate. The hard mask film is formed of a material containing chromium (Cr), niobium (Nb), oxygen (O), and nitrogen (N), allowing sufficient etching speed to be obtained even using only chlorine-based etching gas without oxygen (O 2 ). Accordingly, damage to the resist film caused by oxygen (O 2 ) is prevented, and damage to the capping film is prevented since the capping film is not exposed to oxygen (O 2 ) during the process of removing the hard mask film.

Inventors

  • YUN, JONG-WON
  • YANG, CHUL-KYU
  • WOO, MI-KYUNG
  • PARK, MIN-KYU

Assignees

  • S&S Tech Co., Ltd.

Dates

Publication Date
20260506
Application Date
20250717

Claims (8)

  1. A blankmask for extreme ultraviolet lithography comprising: a substrate; a reflective film formed on the substrate; a capping film formed on the reflective film; an absorber film formed on the capping film; and a hard mask film formed on the absorber film, containing chromium (Cr), niobium (Nb), oxygen (O), and nitrogen (N), and having an XRR (X-ray reflectivity) measured density of 5.0-6.5g/cm 3 .
  2. The blankmask of claim 1, wherein the hard mask film is characterized in that an FWHM (Full Width at Half Maximum) of main peak existing in a range of 2θ 40° or less as measured by XRD (X-ray Diffraction) is 2.0 or more.
  3. The blankmask of claim 2, wherein the hard mask film contains Cr:Nb = 3:7 - 7:3 at% ratio.
  4. The blankmask of claim 2, wherein the hard mask film contains Cr:Nb = 4:6 - 6:4 at% ratio.
  5. The blankmask of any one of claims 1 to 4, wherein at least an uppermost part of the absorber film is etched by fluorine-based etching gas.
  6. The blankmask of claim 5, wherein the absorber film includes an absorber layer disposed on the capping film and an inspection layer disposed on the absorber layer, and the inspection layer is etched by fluorine-based gas and the absorber layer is etched by chlorine-based gas without oxygen (O 2 ).
  7. The blankmask of claim 6, wherein the inspection layer contains tantalum (Ta) and oxygen (O), and the absorber layer contains tantalum (Ta) and does not contain oxygen (O).
  8. A photomask manufactured using the blankmask of any one of claims 1 to 7.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based on and claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2024-0154514 filed on November 4, 2024 in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. BACKGROUND Field The present invention relates to a blankmask for EUV lithography with hard mask film and a photomask manufactured with the same. Description of the Related Art EUV Lithography is a semiconductor device manufacturing technology that uses 13.5nm EUV exposure light. In EUV lithography, reflective type photomasks are used in the wafer exposure process. A blankmask for manufacturing EUV photomasks has two films on a substrate: a reflective film that reflects EUV light and an absorber film that absorbs EUV light. The photomask is manufactured by patterning the absorber film of this blankmask, and is used to form patterns on the wafer using the contrast difference between the reflectance of the reflective film and the reflectance of the absorber film. Figure 1 illustrates the structure of a blankmask for extreme ultraviolet lithography. The blankmask for extreme ultraviolet lithography comprises a substrate 102, a reflective film 104 formed on the substrate 102, a capping film 105 formed on the reflective film 104, an absorber film 106 formed on the capping film 105, a hard mask film 108 formed on the absorber film 106, and a resist film 110 formed on the hard mask film 108. The reflective film 104 is generally formed in a multilayer structure where Mo material layers and Si material layers are alternately stacked 40 to 60 times. The capping film 105 is formed on top of the reflective film 104 and functions to protect the reflective film 104. The capping film 105 is generally formed of a material containing ruthenium (Ru) and functions to protect the reflective film 104 during etching for patterning of the absorber film 106. The absorber film 106 is generally formed of a material containing tantalum (Ta), and the hard mask film 108 is generally formed of a material containing chromium compounds, for example, chromium (Cr) with nitrogen (N), oxygen (O), etc. The absorber film 106 can have a structure of two or more layers, where the uppermost layer of the absorber film 106 consists of an inspection layer and the layer below the inspection layer consists of an absorber layer. The inspection layer is used for inspecting the completed blankmask using inspection light, and by being formed of a material containing tantalum (Ta) with oxygen (O), the inspection sensitivity to the wavelength of 193nm ArF inspection light is increased. To manufacture a photomask, the resist film 110 is exposed to form a predetermined pattern, then used to etch and pattern the hard mask film 108, and the patterned hard mask film 108 is used as an etching mask to pattern the absorber film 106. In the etching process for patterning the chromium (Cr)-based hard mask film 108, chlorine-based gas containing oxygen (O2) is used. This etching process causes greater damage to the resist film 110 compared to etching processes using chlorine-based gas without oxygen (O2). Considering this, the thickness of the resist film 110 must be increased, making it difficult to achieve the thinning of the resist film 110 needed for resolution improvement. Also, in the process of patterning the absorber film 106 using the hard mask film 108, fluorine (F)-based etching gas is used for etching the inspection layer, which is the uppermost layer of the absorber film 106, and chlorine-based etching gas without oxygen (O2) is used for etching the absorber layer, which is the layer below the uppermost layer of the absorber film 106. Since the hard mask film 108 is not etched when using chlorine-based gas without oxygen (O2), an additional removal process using chlorine-based gas containing oxygen (O2) is required to remove the hard mask film 108. In this case, the oxygen (O2) contained in the etching gas causes oxidation of the capping film 105, resulting in decreased reflectance. SUMMARY The present invention was devised to solve the above problems, and it is the object of the invention to enable etching of the hard mask film using etching gas without oxygen in the process of manufacturing photomasks using EUV blankmasks equipped with an absorber film and hard mask film, thereby enabling thinning of the resist film and consequently achieving high resolution. Another object of the invention is to eliminate the need for additional etching process to remove the hard mask film pattern by ensuring that the hard mask film pattern is removed during the etching of the absorber film. Still another object of the invention is to prevent damage to the capping film that occurs when using etching gas containing oxygen (O2), thereby achieving high image contrast. According to the present invention, sufficient hard mask film etching speed can be obtained using only ch