JP4529359B2 - Ultraviolet exposure mask, blank and pattern transfer method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an extreme ultraviolet exposure mask used in a photolithography process using extreme ultraviolet exposure in a semiconductor manufacturing process, a blank for producing the mask, and a pattern transfer method using the mask. Is.
[Prior art]
[0002]
The miniaturization technology of semiconductor integrated circuits is constantly progressing, and the wavelength of light used in the photolithographic technology for miniaturization is gradually becoming shorter. As a light source, the KrF excimer laser (wavelength 248 nm) that 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) is proposed. Development with such deep ultraviolet rays (Deep UV, hereinafter referred to as DUV) has been carried out.
[0003]
However, even with an F2 excimer laser, it is not easy to apply as a lithography technique for manufacturing a device having a line width of 50 nm or less in the future because of exposure apparatus and resist problems. For this reason, research and development of EUV lithography using extreme ultraviolet (Extreme UV, hereinafter abbreviated as EUV) whose wavelength is one or more orders of magnitude shorter than excimer laser light (10-15 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 the value of vacuum, and the difference in light absorption between materials is also small. For this reason, in the EUV region, a conventional transmissive refractive optical system cannot be assembled, and a reflective optical system is formed. Therefore, the mask is also a reflective mask. Conventional EUV masks that have been developed so far have a highly reflective region, for example, a multi-layer film part in which about 40 layers of two layers of Mo and Si are laminated on a Si wafer or glass substrate. The metal film pattern was formed as a region (absorption region). In the high reflection region, two types of films having a steep interface, a large refractive index difference, and as small an absorption as possible are alternately laminated, and the thickness of a pair of two layers adjacent to each other is approximately one half of the exposure wavelength. About 40 pairs of two-layer films. As a result, a slight reflection component from each layer pair interferes and strengthens, and it is possible to obtain a relatively high reflectance for EUV light close to normal incidence.
[0005]
[Non-Patent Document 1]
Ogawa “Multilayer film for reflective masks for 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 blank as described above, reflected light by DUV is used because the line width is small. Therefore, the problem is the ratio of the reflectivity of the multilayer film part and the absorption film part to the DUV light, so-called contrast.
In the present invention, in order to improve the defect inspection capability by DUV exposure, a mask for EUV exposure in which an absorbing film material is defined so as to increase the DUV light reflectance ratio with the multilayer film, a blank for producing the mask, and the blank A pattern forming method using a mask is provided.
[0007]
The present invention according to claim 1 is an extreme ultraviolet exposure mask having a multilayer film that becomes a high reflection region of exposure light on a substrate, and an absorptive thin film pattern that becomes a low reflection region on the multilayer film. The thin film that becomes the low reflection portion is a single layer film of a metallic film, and the film thickness of the thin film that becomes the low reflection portion is in the range of 50 nm to 100 nm, and the thin film that becomes the low reflection portion is An extreme ultraviolet exposure mask characterized in that an extinction coefficient with respect to ultraviolet rays having a wavelength of 150 nm to 300 nm is in a range of 0.2 to 1.0.
[0008]
The present invention according to claim 2 is a high reflection region of exposure light on a substrate for producing the extreme ultraviolet exposure mask according to claim 1 by patterning an absorptive thin film that becomes the low reflection region. The ultra-violet exposure mask blank is characterized in that the 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.
[0009]
According to a third aspect of the present invention, the extreme ultraviolet exposure mask according to the first aspect is installed in an exposure apparatus, and exposure transfer is performed by lithography using the mask to perform pattern formation. This is a pattern transfer method.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. FIG. 1A is an explanatory view showing an example of an embodiment of an EUV exposure mask of the present invention in cross section, and FIG. 1B is a partially enlarged view of the multilayer film 2 in FIG. The EUV exposure mask of the present invention has an EUV exposure having a multilayer film 2 which becomes a high reflection area of exposure light on a substrate 1 and an absorptive thin film pattern 3 which becomes a low reflection area on the multilayer film 2. Presupposes a mask. And the absorptive thin film used as a low reflection part is characterized by the extinction coefficient with respect to the ultraviolet rays with a wavelength of 150 nm to 300 nm being in the range of 0.2 to 1.0.
[0012]
Here, under the pattern 3 of the absorbent thin film, there may be a buffer film that protects the multilayer film 2 serving as a highly reflective portion during patterning and defect correction. Furthermore, the multilayer film 2 that becomes a highly reflective region may be a thick film called “Capping Layer” only in its uppermost layer. However, since it does not affect the effect of the present invention, it is omitted in FIG.
[0013]
Moreover, FIG.1 (c) (d) is explanatory drawing which showed the example of embodiment of the mask blank for EUV exposure of this invention in the cross section. By patterning the blank absorbent thin film 3 ′ of FIG. 1C, the mask of FIG. 1A is obtained. FIG.1 (d) is a form before forming the absorptive thin film 3 'in the blank of FIG.1 (c).
Hereinafter, the EUV exposure mask of FIG. 1A will be described as a representative.
[0014]
That is, the absorptive thin film serving as the low reflection portion has an extinction coefficient with respect to ultraviolet rays having a wavelength of 150 nm to 300 nm in the range of 0.2 to 1.0, so that the reflectance ratio between the multilayer film and the absorptive thin film is maximized. become.
It will be described below that the reflectance ratio is maximized 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 absorbent thin film, and the vertical axis represents the reflectance ratio R / R ₀ (%). here,
R: reflectivity of absorption film portion R ₀ : reflectivity of 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. Included. Moreover, in order to ensure the absorbability with respect to EUV light and fine workability, the film thickness of an absorption film is appropriate from 500 to 1000 mm.
[0016]
FIG. 2 is a graph when the refractive index is used as a parameter (0.8, 2.0), the inspection light wavelength is 257 nm, and the absorption film thickness is 1000 mm. Similarly, in FIG. 3, the inspection light wavelength is 257 nm and the absorption film thickness is 500 mm, the inspection light wavelength is 193 nm and the absorption film thickness is 1000 mm, and the inspection light wavelength is 193 nm and the absorption film thickness is 500 mm in FIG. is there.
[0017]
As can be seen from the figure, in most absorption films having a refractive index (n) in the range of 0.8 to 2.0, R / R _O has one minimum value, and at this time, the reflectance contrast becomes maximum. . Then k is approximately in the range of 0.2 to 1.0. This relationship holds even if the wavelength or film thickness is changed.
[0018]
The multilayer film 2 is formed by alternately laminating two kinds of films, and the two kinds of films are a film containing Mo as a main component and a film containing Si as a main component. As a result, the interface is steep, the refractive index difference is large, slight reflection components from each pair of layers interfere and strengthen each other, and a multilayer film with as little absorption as possible can be obtained, thereby increasing the reflectance.
[0019]
The EUV mask of the present invention can be manufactured according to a conventional mask manufacturing process. That is, a multilayer film made of, for example, Mo and Si is laminated on a Si wafer or glass substrate 1 by a normal magnetron sputtering method, an ion beam sputtering method, or the like to form a highly reflective region 2. . On top of that, a thin film is produced as a low reflection (absorption) region 3 ′ by a normal magnetron sputtering method or the like, and the blank for EUV halftone mask of the present invention is completed.
[0020]
Hereinafter, in accordance with a normal mask manufacturing process, the thin film is patterned to manufacture the EUV halftone mask of the present invention. That is, an electron beam resist is applied on the blank and baked, followed by normal electron beam drawing and development to form a resist pattern. Thereafter, using this resist pattern as a mask, dry etching of the low-reflection double-layer film is performed, and then the resist is removed to complete the halftone mask of the present invention.
[0021]
In the pattern transfer method using the photomask according to the present invention, for example, first, a photoresist layer is provided on a substrate on which a layer to be processed is formed, and then the extreme ultraviolet rays reflected through the photomask according to the present invention are selectively selected. Irradiate.
[0022]
Next, an unnecessary portion of the photoresist layer is removed in the development step, and a pattern of the etching resist layer is formed on the substrate. Then, the layer to be processed is etched using the pattern of the etching resist layer as a mask. In this method, a pattern faithful to the photomask pattern is transferred onto the substrate by removing the pattern of the etching resist layer.
[0023]
【The invention's effect】
In the present invention, since it has the above-described configuration and function, the absorption film material can increase the DUV light reflectivity contract with the multilayer film, and the EUV exposure mask that improves the defect inspection capability by DUV exposure and the same are manufactured. Therefore, a pattern forming method using the blank and the mask can be used.
[Brief description of the drawings]
FIG. 1A is an explanatory view showing, in section, an example of an embodiment of an EUV exposure mask of the present invention.
(B) is the elements on larger scale 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 the cross section.
FIG. 2 is a graph showing a reflectance ratio with respect to an extinction coefficient.
FIG. 3 is another graph showing the reflectance ratio with respect to the extinction coefficient.
FIG. 4 is another graph showing the reflectance ratio with respect to the extinction coefficient.
FIG. 5 is another graph showing the reflectance ratio with respect to the extinction coefficient.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... High reflection multilayer film 3 ... Low reflection thin film pattern 3 '... Low reflection thin film (absorbing thin film)

Claims (3)

In an extreme ultraviolet exposure mask having a multilayer film that becomes a high reflection region of exposure light on a substrate, and an absorptive thin film pattern that becomes a low reflection region on the multilayer film,
The thin film serving as the low reflection portion is a single layer film of a metallic film,
The film thickness of the thin film serving as the low reflection portion is in the range of 50 nm to 100 nm,
The extreme ultraviolet exposure mask, wherein the thin film serving as the low reflection portion has an extinction coefficient with respect to ultraviolet rays having a wavelength of 150 nm to 300 nm in a range of 0.2 to 1.0.   The multilayer film serving as a high reflection region for exposure light is formed on a substrate for producing the extreme ultraviolet exposure mask according to claim 1 by patterning an absorptive thin film serving as the low reflection region, A mask blank for extreme ultraviolet exposure, characterized in that the absorptive thin film serving as a low reflection region is formed on the entire surface of the multilayer film.   A pattern transfer method comprising: setting an extreme ultraviolet exposure mask according to claim 1 in an exposure apparatus, performing exposure transfer by lithography using the mask, and performing pattern formation.

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