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KR-20260066469-A - Blankmask and Photomask for EUV lithography with Hardmask containing Chrome and Niobium

KR20260066469AKR 20260066469 AKR20260066469 AKR 20260066469AKR-20260066469-A

Abstract

A blank mask for EUV lithography has a structure in which a reflective film, a capping film, an absorption film, and a hard mask film are sequentially stacked on a substrate. The hard mask film is formed from a material containing chromium (Cr), niobium (Nb), oxygen (O), and nitrogen ( N ), so that a sufficient etching rate can be obtained even when using only a chlorine-based etching gas that does not contain oxygen ( O2 ). Accordingly, damage to the resist film caused by oxygen (O2) is prevented, and damage to the capping film is prevented because the capping film is not exposed to oxygen ( O2 ) during the process of removing the hard mask film.

Inventors

  • 윤종원
  • 양철규
  • 우미경
  • 박민규

Assignees

  • 주식회사 에스앤에스텍

Dates

Publication Date
20260512
Application Date
20241104

Claims (8)

  1. Substrate; A reflective film formed on the above substrate; A capping film formed on the above reflective film; An absorption film formed on the above capping film; and A hard mask film formed on the above absorption film, comprising chromium (Cr), niobium (Nb), oxygen (O), and nitrogen (N), and having an X-ray relectivity (XRR) measurement density of 5.0 to 6.5 g/cm³; A blank mask for extreme ultraviolet lithography characterized by including
  2. In Article 1, The above hard mask film is a blank mask for extreme ultraviolet lithography characterized by having a Full Width at Half Maximum (FWHM) of a main peak existing in a range of 2θ 40° or less as measured by X-ray Diffraction (XRD) of 2.0 or more.
  3. In Article 2, A blank mask for extreme ultraviolet lithography characterized by containing the above hard mask film in an at% ratio of Cr:Nb = 3:7 to 7:3.
  4. In Article 2, A blank mask for extreme ultraviolet lithography characterized by containing the above hard mask film in an at% ratio of Cr:Nb = 4:6 to 6:4.
  5. In any one of paragraphs 1 to 4, A blank mask for extreme ultraviolet lithography characterized in that the absorption film above is etched by a fluorine-based etching gas at least at its uppermost portion.
  6. In Article 5, The above absorption film includes an absorption layer disposed on the capping film and an inspection layer disposed on the absorption layer, and A blank mask for extreme ultraviolet lithography characterized in that the inspection layer is etched by a fluorine-based gas and the absorption layer is etched by a chlorine-based gas that does not contain oxygen ( O2 ).
  7. In Article 6, The above inspection layer comprises tantalum (Ta) and oxygen (O), and A blank mask for extreme ultraviolet lithography characterized in that the absorption layer contains tantalum (Ta) and does not contain oxygen (O).
  8. A photomask produced using a blank mask for extreme ultraviolet lithography according to any one of claims 1 to 4.

Description

Blank mask and photomask for EUV lithography with hardmask containing chrome and niobium The present invention relates to a blank mask and a photomask, and more specifically, to an EUV blank mask having a hard mask film and a photomask manufactured using the same. EUV lithography is a semiconductor device manufacturing technology that uses 13.5nm EUV exposure light. In EUV lithography, a reflective photomask is used in the wafer exposure process. A blank mask for fabricating an EUV photomask comprises two thin films on a substrate: a reflective film that reflects EUV light and an absorbing film that absorbs EUV light. The photomask is fabricated by patterning the absorbing film of this blank mask, utilizing the principle of forming a pattern on a wafer by using the contrast difference between the reflectance of the reflective film and the reflectance of the absorbing film. FIG. 1 is a diagram illustrating the structure of a blank mask for extreme ultraviolet lithography. The blank mask 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 absorption film (106) formed on the capping film (105), a hard mask film (108) formed on the absorption film (106), and a resist film (110) formed on the hard mask film (108). The reflective film (104) is generally formed as a multilayer structure in which layers of Mo material and Si material are alternately stacked 40 to 60 times. The capping film (105) is formed on the upper part of the reflective film (104) and functions to protect the reflective film (104). The capping film (105) is generally formed from a material containing ruthenium (Ru) and functions to protect the reflective film (204) during etching for patterning the absorption film (106). The absorption film (106) is generally formed from a material containing tantalum (Ta), and the hard mask film (108) is generally formed from a chromium compound, for example, a material containing nitrogen (N), oxygen (O), etc., in addition to chromium (Cr). The absorption film (106) may have a structure of two or more layers, wherein the uppermost layer of the absorption film (106) is composed of an inspection layer and the layer below the inspection layer is composed of an absorption layer. The inspection layer is a layer used to inspect a finished blank mask using inspection light, and is formed of a material containing oxygen (O) in tantalum (Ta), thereby increasing inspection sensitivity for the wavelength of 193 nm ArF inspection light. In order to produce a photomask, a resist film (110) is exposed to light to form a predetermined pattern, and then a hard mask film (108) is etched and patterned using this, and an absorption film (106) is patterned using the patterned hard mask film (108) as an etching mask. In the etching process for patterning a chromium (Cr)-based hard mask film (108), a chlorine ( Cl2 ) gas containing oxygen ( O2 ) is used. Compared to an etching process using a chlorine ( Cl2 ) gas that does not contain oxygen ( O2 ), this etching process causes greater damage to the thickness of the resist film (110). Considering this, the thickness of the resist film (110) must be increased, so there is a problem that it is difficult to thin the resist film (110) that is necessary for improving resolution. Additionally, in the patterning process of the absorption film (106) using the hard mask film (108), a fluorine (F)-based etching gas is used for etching the uppermost layer (inspection layer) of the absorption film (106), and a chlorine ( Cl2 )-based etching gas that does not contain oxygen ( O2 ) is used for etching the layer (absorption layer) below the uppermost layer of the absorption film (106). Since the hard mask film ( 108 ) is not etched when etching with a chlorine ( Cl2 ) gas that does not contain oxygen ( O2 ), a removal process using a chlorine ( Cl2 ) gas containing oxygen (O2) must be added separately to remove the hard mask film (108). The oxygen ( O2 ) contained in the gas used in the hard mask film (108) removal process causes oxidation of the capping layer, which causes a problem of reducing reflectivity. FIG. 1 is a drawing illustrating the thin film structure of a conventional blank mask for extreme ultraviolet lithography. FIG. 2 is a drawing illustrating the thin film structure of a blank mask for extreme ultraviolet lithography according to the present invention. The present invention will be described in more detail below with reference to the drawings. The blank mask of the present invention includes not only a binary type blank mask but also a phase-inversion blank mask. In a binary type blank mask, the absorption film functions to absorb EUV exposure light, while in a phase-inversion blank mask, the absorption film inverts the phase of the exposure light to cause destructive interference. In EUV reflective blank masks, it is common practice to refer to the