JP2004260050A - Extreme ultraviolet light exposure mask and blank and pattern transfer method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EUV light exposure mask having a multilayer film 2 formed on a substrate 1 and becoming a high reflection area of exposure light, and a pattern 3 of absorbent thin film formed on the multilayer film 2 and becoming a low reflection area in which the material of an absorption film 3' is specified to increase the DUV light reflectivity contract with the multilayer film 2 in order to enhance defect inspection capability by DUV exposure, and to provide a blank for producing the mask and a patterning method employing that mask. <P>SOLUTION: The thin film 3' becoming the low reflection area has an extinction coefficient in the range of 0.2-1.0 for ultraviolet light having a wavelength from 150 nm to 300 nm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mask for extreme ultraviolet exposure used in a photolithography process using extreme ultraviolet exposure during a semiconductor manufacturing process, a blank for producing the mask, and a pattern transfer method using the mask. Things.
[Prior art]
[0002]
The miniaturization technology of semiconductor integrated circuits is constantly progressing, and the wavelength of light used for photolithography technology for miniaturization is gradually becoming shorter. As a light source, the KrF excimer laser (wavelength 248 nm), which has been used so far, is being switched to an ArF excimer laser (wavelength 193 nm), and then the use of an F2 excimer laser (wavelength 157 nm) has been proposed. Such deep ultraviolet (DUV) has been developed.
[0003]
However, even with an F2 excimer laser, it is not easy to apply it as a lithography technique for fabricating a device having a line width of 50 nm or less in the future due to problems with an exposure machine and a resist. For this reason, research and development of EUV lithography using extreme ultraviolet (Extreme UV, hereinafter abbreviated as EUV) whose wavelength is shorter than the excimer laser beam by one digit or more (10 to 15 nm) is being promoted.
[0004]
In EUV exposure, since the wavelength is short as described above, the refractive index of a substance is almost close to a vacuum value, and the difference in light absorption between materials is small. For this reason, in the EUV region, a conventional transmissive refraction optical system cannot be assembled, and a reflection optical system is used. Therefore, the mask is also a reflection mask. A typical EUV mask that has been developed is a high-reflection region consisting of, for example, a multilayer film in which about 40 layers of two layers of Mo and Si are stacked on a Si wafer or a glass substrate, and a low-reflection region is formed thereon. The structure was such that a pattern of a metallic film was formed as a region (absorption region). The high-reflection region has a steep interface, a large difference in refractive index, and alternately stacks two types of films having as small an absorption as possible. The thickness of a pair of two adjacent layers is set to approximately one half of the exposure wavelength. About 40 pairs of two-layer films. As a result, slight reflection components from each layer pair interfere with each other and reinforce each other, so that it is possible to obtain a relatively high reflectance with respect to EUV light near normal incidence.
[0005]
[Non-patent document 1]
Ogawa, "Multilayer film for reflective mask of EUV lithography" (Optical Technology Contact, Vol. 39, No. 5, 2001, Japan Opto-Mechatronics Association) p. 292
[0006]
[Problems to be solved by the invention]
In the defect inspection of the EUV mask or the blank as described above, light reflected by DUV is used because the line width is small. What is problematic is the ratio of the reflectance of the multilayer film and the absorption film to DUV light, that is, the so-called contrast.
In the present invention, in order to improve the defect inspection capability by DUV exposure, an EUV exposure mask in which an absorption film material is defined so that the DUV light reflectance ratio with a multilayer film can be increased, a blank for producing the same, and a blank thereof Provided is a pattern forming method using a mask.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 of the present invention provides an extreme ultraviolet exposure mask having a multilayer film on a substrate, which is a high reflection area of exposure light, and a pattern of an absorbing thin film on the multilayer film, which is a low reflection area. In the above, the thin film serving as the low reflection portion is an extreme ultraviolet exposure mask, wherein the extinction coefficient for ultraviolet light having a wavelength of 150 nm to 300 nm is in the range of 0.2 to 1.0.
[0008]
The invention according to claim 2 of the present invention is characterized in that the multilayer film is formed by alternately stacking two types of films, and the two types of films are a film mainly containing Mo and a film mainly containing Si. The mask for extreme ultraviolet exposure according to claim 1 is provided.
[0009]
The invention according to claim 3 of the present invention is directed to forming the extreme ultraviolet exposure mask according to claim 1 or 2 by patterning the absorptive thin film on a substrate, which becomes a high reflection area of exposure light. A mask blank for extreme ultraviolet exposure, wherein a multilayer film is formed, and the absorptive thin film serving as a low reflection region is formed on the entire surface of the multilayer film.
[0010]
The invention of claim 4 of the present invention is characterized in that the extreme ultraviolet exposure mask according to claim 1 or 2 is installed in an exposure apparatus, and exposure and transfer are performed by lithography using the mask to form a pattern. This is a pattern transfer method.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1A is an explanatory view showing a cross section of an embodiment of the EUV exposure mask of the present invention, and FIG. 1B is a partially enlarged view of the multilayer film 2 of FIG. The EUV exposure mask of the present invention has an EUV exposure mask having, on a substrate, a multilayer film serving as a high-reflection region of exposure light, and a pattern 3 of an absorbing thin film serving as a low-reflection region on the multilayer film. Assume a mask for use. The absorptive thin film serving as the low reflection portion is characterized in that the extinction coefficient for ultraviolet light having a wavelength of 150 nm to 300 nm is in the range of 0.2 to 1.0.
[0012]
Here, a buffer film for protecting the multilayer film 2 serving as a highly reflective portion may be present below the pattern 3 of the absorptive thin film during patterning or defect correction. Further, the multilayer film 2 serving as a high-reflection region may be a thick film called “Capping Layer” only in its uppermost layer. However, none of them has any effect on the effect of the present invention, and thus is omitted in FIG.
[0013]
FIGS. 1C and 1D are explanatory views showing a cross section of an embodiment of a mask blank for EUV exposure according to the present invention. The mask shown in FIG. 1A is obtained by patterning the blank absorbent thin film 3 ′ shown in FIG. 1C. FIG. 1D shows the blank of FIG. 1C before the formation of the absorbent thin film 3 ′.
Hereinafter, the EUV exposure mask of FIG. 1A will be described as a representative.
[0014]
That is, by setting the extinction coefficient of ultraviolet light having a wavelength of 150 nm to 300 nm in the range of 0.2 to 1.0, the reflectance ratio between the multilayer film and the absorbing thin film is maximized. become.
It will be described below that the reflectance ratio becomes maximum by adopting such a configuration.
[0015]
FIG. 2 is a graph showing the reflectance ratio with respect to the extinction coefficient. The horizontal axis represents the extinction coefficient k of the absorptive thin film, and the vertical axis represents the reflectance ratio R / R ₀ (%). here,
R: the reflectance of the absorption film portion R ₀ : the reflectance of the multilayer film portion Since the absorption film is a metallic film, the refractive index (n) for DUV light is almost between 0.8 and 2.5. Case included. Further, in order to secure the absorbability to EUV light and the fine workability, the thickness of the absorbing film is appropriately from 500 ° to 1000 °.
[0016]
FIG. 2 is a graph in which the refractive index is a parameter (0.8, 2.0), the inspection light wavelength is 257 nm, and the absorption film thickness is 1000 °. Similarly, FIG. 3 shows the case where the inspection light wavelength is 257 nm and the absorption film thickness is 500 °, FIG. 4 shows the case where the inspection light wavelength is 193 nm and the absorption film thickness is 1000 °, and FIG. is there.
[0017]
As can be seen, in most of the absorbing films having a refractive index (n) in the range of 0.8 to 2.0, R / R _O has one minimum value, and the reflectance contrast becomes maximum at this time. . Then k is generally in the range of 0.2 to 1.0. This relationship holds even when the wavelength or the film thickness is changed.
[0018]
The multilayer film 2 is formed by alternately laminating two types of films, and the two types of films are a film mainly composed of Mo and a film mainly composed of Si. As a result, the interface is steep, the refractive index difference is large, and slight reflection components from each pair of layers interfere with each other to reinforce each other.
[0019]
The EUV mask of the present invention can be manufactured according to a conventional mask manufacturing process. That is, a high-reflection region 2 is formed by laminating a multilayer film made of, for example, Mo and Si on a Si wafer or a glass substrate 1 by a desired number of layers by a normal magnetron sputtering method, an ion beam sputtering method, or the like. . A thin film is formed thereon as a low-reflection (absorption) region 3 'by a usual magnetron sputtering method or the like to complete the EUV halftone mask blank of the present invention.
[0020]
Hereinafter, the thin film is patterned according to a normal mask manufacturing process to manufacture the EUV halftone mask of the present invention. That is, after applying an electron beam resist on the blank and performing baking, normal electron beam drawing is performed and developed to form a resist pattern. Thereafter, using this resist pattern as a mask, the low-reflection two-layer film is dry-etched, and then the resist is peeled off to complete the halftone mask of the present invention.
[0021]
The pattern transfer method using the photomask according to the present invention includes, for example, first providing a photoresist layer on a substrate on which a layer to be processed is formed on the surface, and then selectively exposing the ultimate ultraviolet light reflected through the photomask according to the present invention. Irradiation.
[0022]
Next, in the developing step, unnecessary portions of the photoresist layer are removed, and after forming a pattern of the etching resist layer on the substrate, the layer to be processed is etched using the pattern of the etching resist layer as a mask, This is a method of transferring a pattern faithful to a photomask pattern onto a substrate by removing the pattern of the etching resist layer.
[0023]
【The invention's effect】
In the present invention, because of the above configuration and function, the EUV exposure mask and the manufacturing of the EUV exposure mask which can increase the DUV light reflectance contract between the absorbing film material and the multilayer film and improve the defect inspection capability by DUV exposure And a pattern forming method using the mask.
[Brief description of the drawings]
FIG. 1A is an explanatory view showing a cross section of an example of an embodiment of an EUV exposure mask of the present invention.
(B) is a partially enlarged view of the multilayer film 2 of (a).
(C), (d) is explanatory drawing which showed the example of embodiment of the mask blank for EUV exposure of this invention in cross section.
FIG. 2 is a graph showing a reflectance ratio with respect to an extinction coefficient.
FIG. 3 is another graph showing a reflectance ratio with respect to an extinction coefficient.
FIG. 4 is another graph showing a reflectance ratio with respect to an extinction coefficient.
FIG. 5 is another graph showing a reflectance ratio with respect to an extinction coefficient.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... High reflection multilayer film 3 ... Low reflection thin film pattern 3 '... Low reflection thin film (absorbing thin film)

Claims (4)

On a substrate, a multilayer film serving as a high-reflection region of exposure light, and an extreme ultraviolet exposure mask having a pattern of an absorptive thin film serving as a low-reflection region on the multilayer film, wherein the thin film serving as the low-reflection portion is An extinction coefficient for ultraviolet light having a wavelength of 150 nm to 300 nm is in the range of 0.2 to 1.0. 2. The extreme ultraviolet light according to claim 1, wherein two kinds of films are alternately stacked in the multilayer film, and the two kinds of films are a film containing Mo as a main component and a film containing Si as a main component. Exposure mask. The multilayer film to be a high reflection area of exposure light is formed on a substrate for producing the extreme ultraviolet exposure mask according to claim 1 or 2 by patterning an absorptive thin film to be the low reflection area. A mask blank for extreme ultraviolet exposure, wherein the absorptive thin film serving as a low reflection region is formed on the entire surface of the multilayer film. 3. A pattern transfer method, comprising: installing the mask for extreme ultraviolet exposure according to claim 1 or 2 in an exposure apparatus, performing exposure transfer by lithography using the mask, and forming a pattern.

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