KR20090132305A - Method for fabricating extreme ultra violet lithography mask - Google Patents

Abstract

PURPOSE: A method for forming a mask for extreme ultraviolet lithography is provided to simplify a process and a structure of a mask by arranging a buffer silicon film and a buffer molybdenum film to a top part of a reflective layer. CONSTITUTION: A reflective layer(215) is formed on a substrate(200). A first buffer film and a second buffer film are deposited on the reflective layer. An absorbing layer is formed on the first buffer film and the second buffer film. An absorbing layer pattern(235) is formed by patterning the absorbing layer, and selectively exposes the first buffer film and the second buffer film. A repair process is performed in order to remove a defect generated at a process for forming the absorbing layer pattern. A surface of the reflective layer is exposed by etching an exposing part of the first buffer film and the second buffer film. A cleaning process is performed on the substrate.

Description

Method for fabricating extreme ultra violet lithography mask

The present invention relates to a photomask, and more particularly to a method for forming a mask for extreme ultraviolet lithography.

A photomask transmits light onto a mask pattern formed on a transparent substrate so that the transmitted light is transferred to the wafer to form a desired pattern on the wafer. On the other hand, an electron beam is mainly used as an exposure process applied on a photomask. However, as the degree of integration of semiconductor devices increases, the size of the pattern becomes fine, and thus there is a limit in forming a mask pattern.

One lithography method to overcome this limitation is a lithography process using Extreme Ultra Violet (EUV). The extreme ultraviolet lithography (EUVL) process uses extreme ultraviolet (EUV) shorter than the light source of KrF or ArF wavelength used in the conventional exposure process as a light source. In this case, the extreme ultraviolet wavelength region has a photon energy near 100 eV or a wavelength of 10 nm to 15 nm. When such extreme ultraviolet light is used as a light source, the extreme ultraviolet light source is absorbed in most materials, which makes it difficult to use the exposure method using current transmission. Accordingly, a method of reflecting and exposing light is being studied, not an exposure method using transmission.

1 is a view schematically showing a general extreme ultraviolet blank mask.

Referring to FIG. 1, in the extreme ultraviolet blank mask, a reflective layer 115 is formed on a substrate 100, and a capping layer 120, a buffer layer 125, an absorbing layer 130, and a resist film 135 are formed on the reflective layer 115. ) Is made of a laminated structure. The reflective layer 115 is made of a material capable of reflecting extreme ultraviolet rays to be irradiated on the extreme ultraviolet lithography mask. Reflective layer 115 reflects 70 percent of the injected energy. In this case, the reflective layer 115 is formed of a multilayer in which different material layers 105 and 110 are stacked to cross each other. The capping layer 120 formed on the reflective layer 115 prevents damage of the reflective layer 115 in an etching process that is performed to form a pattern while preventing oxidation of the reflective layer 115 and is formed of a silicon (Si) film. Subsequently, the buffer layer 125 formed on the capping layer 120 protects the reflective layer 115 during the etching process or the modification process, and is formed of a silicon oxide film (SiO ₂ ). Next, the absorbing layer 130 absorbs the light source to be injected into the mask, and the resist layer 135 serves as an etching mask in the process of forming the mask pattern. A patterning process is performed on the extreme ultraviolet blank mask of this structure to form a mask pattern (not shown), and then irradiated with ultraviolet rays to the absorbing layer and the reflecting layer. Then, the ultraviolet light is absorbed from the absorbing layer, and the extreme ultraviolet rays irradiated to the reflective layer exposed in the patterning process are reflected to perform exposure.

Meanwhile, in the process of manufacturing the extreme ultraviolet photomask using the blank mask, defect correction or foreign matter may occur in the state where the absorbing layer 130, the reflecting layer 115, or the capping layer 120 exist. In this case, since the selectivity between the thin films is relatively high, there is little surface damage by the corrosive gas at the interface of the thin film during the modification process. However, in the case of an extreme ultraviolet photomask, the reflective layer 115 is formed of multiple layers in which thin layers 105 and 110 of different materials cross each other and are stacked, and the gaps between the layers 105 and 110 are corrosive at the interface. The surface damage by gas is large. In addition, when the capping film 120 is damaged or foreign matter occurs, there is a problem that subsequent processing is difficult.

According to another aspect of the present invention, there is provided a method of forming a mask for extreme ultraviolet lithography, comprising: forming a reflective layer on which a first reflective film and a second reflective film are laminated while reflecting an extreme ultraviolet light source; Depositing the first buffer layer and the second buffer layer on the reflective layer by crossing the first buffer layer and the second buffer layer; Forming an absorption layer on the first buffer layer and the second buffer layer; Patterning the absorber layer to form an absorber layer pattern for selectively exposing the first buffer layer and the second buffer layer; Performing a repair process to remove a defective element caused in the process of forming the absorber layer pattern; Etching the exposed portions of the first buffer layer and the second buffer layer damaged in the repair process using the absorbing layer pattern as an etch mask to expose a surface of the reflective layer; And performing a cleaning process on the substrate to form a mask for extreme ultraviolet lithography comprising a reflective region set by the exposed reflective layer and an absorbing region set by an absorbing layer pattern disposed on the reflective layer. It is done.

In the present invention, it is preferable that the first reflecting film contains molybdenum (Mo), and the second reflecting film includes silicon (Si).

The absorbing layer is preferably formed of a tantalum boron nitride (TaBN) film or tantalum boron nitride oxide (TaBNO).

The repair process is preferably carried out using a corrosive gas.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

2 to 8 are diagrams for explaining a method for forming a mask for extreme ultraviolet lithography according to an embodiment of the present invention.

Referring to FIG. 2, an Extreme Ultra Violet Blank mask having a structure in which a reflective layer 215, an absorbing layer 220, and a resist layer 225 are stacked is formed on a substrate 200. In detail, the reflective layer 215 is formed on the substrate 200. Herein, the substrate 200 is made of a material having a low thermal expansion coefficient, and may be made of an opaque material. However, since it absorbs the energy supplied in the manufacturing of the mask for the extreme ultraviolet lithography, it is preferable to use a material having an extremely low coefficient of thermal expansion for the minimum expansion and contraction of the mask patterns to be formed later.

Next, the reflective layer 215 formed on the substrate 200 serves to reflect a light source of 13.4 nm, which is an extreme ultraviolet wavelength irradiated with a mask, in a subsequent exposure process. The reflective layer 215 may have a structure in which a molybdenum (Mo) film 205 or a silicon (Si) film 210 crosses each other and is stacked. In this case, the molybdenum (Mo) film 205 or the silicon (Si) film 210 is formed in a multilayer structure cross-deposited into 40 layers in order to realize high reflectance. In this case, the buffer molybdenum film 205a and the buffer silicon film 210a are alternately stacked on top of the reflective layer 215 that is stacked in 40 layers to form two layers. The buffered molybdenum film 205a and the buffer silicon film 210a stacked at the intersection protect the lower reflective layer 215 and serve as a buffer film to prevent oxidation in the subsequent etching process. Next, the absorbing layer 220 formed on the reflective layer 215 absorbs and quenches 90% or more of incident light incident on the mask in an exposure process to be performed later in correspondence with the reflective layer 215. The absorption layer 220 may include a tantalum boron nitride (TaBN) film or tantalum boron nitride oxide (TaBNO). The resist layer 225 then serves as an etching mask in the process of patterning the lower layers. The resist film 225 is formed of a photosensitive material whose physical properties change when exposed to an electron beam of a writing device of a mask. The extreme ultraviolet blank mask of this structure is simply composed of the structure of the reflective layer 215, the absorbing layer 220 and the resist film 225 instead of the general extreme ultraviolet blank mask (see FIG. 1) in which the buffer film and the capping film are formed on the reflective layer.

Referring to FIG. 3, the resist film 225 is patterned to form a resist film pattern 230 that selectively exposes the surface of the absorber layer 220. Next, the exposed portion of the absorber layer 220 is etched using the resist layer pattern 230 as an etch mask to form the absorber layer pattern 235. The surface of the buffer molybdenum film 205a or the buffer silicon film 210a positioned on the top of the reflective layer 215 is selectively exposed by the absorbing layer pattern 235.

Referring to FIG. 4, the resist film pattern 230 is removed by a strip process and a cleaning process is performed to remove residues. Then, the absorption layer pattern 235 selectively exposes the surface of the buffer molybdenum film 205a or the buffer silicon film 210a.

Referring to FIG. 5, an inspection process for detecting a defect a caused in the process of forming the absorber layer pattern 235 is performed, and a repair process for supplementing the detected defect a is performed. Specifically, in the process of forming the absorption layer pattern 235 by removing the resist layer pattern 230 by performing an etching process using the resist layer pattern 230 as an etch mask, or the residue of the resist remains. Defect (a) may occur. If a subsequent process is performed in a state where such a defect (a) is generated, a mask defect may be caused, and as a result, a pattern defect transferred to a wafer may be caused, so that a defect is detected and a repair process is performed. remove a) In this case, the repair process may proceed in such a way that the residue is desorbed by supplying a corrosive gas to remove the resist residue. The reflective layer 215 is blocked by the buffer molybdenum film 205a or the buffer silicon film 210a and is not affected by the repair process.

Referring to FIG. 6, an additional etching process is performed on the substrate 200 subjected to the repair process to etch exposed portions of the buffer molybdenum film 205a or the buffer silicon film 210a to form an upper surface of the reflective layer 215. Expose The buffer molybdenum film 205a or the buffer silicon film 210a is in a state where the surface of the buffer molybdenum film 205a is damaged by the corrosive gas supplied during the repair process described above. Accordingly, an additional etching process is performed to etch exposed portions of the damaged buffer molybdenum film 205a or the buffer silicon film 210a. Then, the surface of the reflective layer 215 including a molybdenum (Mo) film or a silicon (Si) film cross-deposited into 40 layers exhibiting reflective properties is selectively exposed. The buffer molybdenum film 205a or the buffer silicon film 210a under the absorption layer pattern 235 is not etched.

Referring to FIG. 7, an additional cleaning process is performed on the substrate 200 to remove the defective element b generated during the etching of the damaged buffer molybdenum film 205a or the buffer silicon film 210a.

Next, as shown in FIG. 8, final inspection is performed to verify the suitability of the mask for extreme ultraviolet lithography. Accordingly, a mask for extreme ultraviolet lithography is formed by a reflection region set by the reflective layer 215 formed on the substrate 200 and an absorption region set by the absorption layer pattern 235 spaced apart by a predetermined interval on the reflective layer.

In the method for forming a mask for extreme ultraviolet lithography according to the present invention, a structure of a mask for extreme ultraviolet lithography is provided by disposing a buffer molybdenum film and a buffer silicon film on top of the reflective layer instead of a buffer film and a capping film, which are protective films protecting the lower reflective layer. The process can be simplified. The patterned mask can be easily processed without affecting the characteristics of the reflective layer by removing only the buffer molybdenum film and the buffer silicon film damaged by the modification process and foreign matter generation.

1 is a view schematically showing a general extreme ultraviolet blank mask.

2 to 8 are diagrams for explaining a method for forming a mask for extreme ultraviolet lithography according to an embodiment of the present invention.

Claims (4)

Forming a reflective layer on which a first reflective film and a second reflective film are laminated while reflecting an extreme ultraviolet light source on the substrate; Depositing the first buffer layer and the second buffer layer on the reflective layer by crossing the first buffer layer and the second buffer layer; Forming an absorption layer on the first buffer layer and the second buffer layer; Patterning the absorber layer to form an absorber layer pattern for selectively exposing the first buffer layer and the second buffer layer; Performing a repair process to remove a defective element caused in the process of forming the absorber layer pattern; Etching the exposed portions of the first buffer layer and the second buffer layer damaged in the repair process using the absorbing layer pattern as an etch mask to expose a surface of the reflective layer; And Performing a cleaning process on the substrate to form a mask for extreme ultraviolet lithography comprising a reflective region set by the exposed reflective layer and an absorbing region set by an absorbing layer pattern disposed on the reflective layer. How to form a mask for the dragon. The method of claim 1, The first reflective film comprises molybdenum (Mo), and the second reflective film is formed of silicon (Si) mask for extreme ultraviolet lithography. The method of claim 1, And the absorbing layer comprises a tantalum boron nitride (TaBN) film or tantalum boron nitride oxide (TaBNO). The method of claim 1, The repair process is a mask forming method for extreme ultraviolet lithography using a corrosive gas.

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