JP2016072438A - Reflective mask blank, reflective mask and method of manufacturing the same, and method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflective mask blank having a phase shift film of thin film, excellent in wash-resistance as a whole film, and shifting the phase of EUV light.SOLUTION: A phase shift film 15 of a reflective mask blank consists of a multilayer film including one or a plurality of first layers 15a and one or a plurality of second layers 15b. The first layer 15a contains a metal material (Ta, Cr, or the like) selected from metal materials having a refractive index n of 0.95 or less at a wavelength of 13.5 nm. The second layer 15b contains a metal material (Mo, Ru, Pt, Pd, Ag, Au, or the like) selected from metal materials having a refractive index n of 0.95 or less at a wavelength of 13.5 nm, different from those of the first layer 15a. On the interface of the first layer 15a and second layer 15b and in the vicinity thereof, a metal diffusion region R1 is formed at a ratio of 25% or more for the total thickness of one first layer 15a and one second layer 15b.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a reflective mask blank, a reflective mask, a manufacturing method thereof, and a manufacturing method of a semiconductor device, which are original plates for manufacturing an exposure mask used for manufacturing a semiconductor device.

  The types of light sources used in exposure apparatus in semiconductor manufacturing have evolved while gradually shortening the wavelength, such as g-line with a wavelength of 436 nm, i-line with 365 nm, KrF laser with 248 nm, and ArF laser with 193 nm. In order to realize a simple pattern transfer, EUV lithography using extreme ultraviolet (EUV) having a wavelength of around 13.5 nm has been proposed. In EUV lithography, a reflective mask is used because the difference in absorption rate between materials for EUV light is small. As the reflective mask, for example, a multilayer reflective film that reflects exposure light is formed on a substrate, and a phase shift film that absorbs exposure light is formed in a pattern on a protective film for protecting the multilayer reflective film. What has been formed is proposed. The light incident on the reflective mask mounted on the exposure machine (pattern transfer device) is absorbed by the part with the phase shift film pattern and reflected by the multilayer reflective film at the part without the phase shift film pattern. An image is transferred onto a semiconductor substrate through a reflective optical system. Part of the exposure light incident on the phase shift film pattern is reflected with a phase difference of about 180 degrees from the light reflected by the multilayer reflective film (phase shift), thereby obtaining contrast (resolution).

  Techniques relating to such a reflective mask for EUV lithography and a mask blank for producing the same are disclosed in Patent Documents 1 to 3 and the like.

  Patent Document 1 describes that a thin film (phase shift film) is a two-layer film in order to improve the transfer resolution by applying the principle of a halftone mask to EUV exposure. As a specific material for the two-layer film, a combination of a Mo layer and a Ta layer is described (see paragraphs 0007, 0008, and 0010 of the same document).

  In Patent Document 2, in order to improve the transfer resolution by applying the principle of a halftone mask to EUV exposure, a material of a halftone film (phase shift film) made of a single layer film, a refractive index and an extinction In FIG. 2, which is represented by plane coordinates having a coefficient as a coordinate axis, it is described that selection is made from an area surrounded by a square frame (□). As a specific material for the single layer film, TaMo (composition ratio 1: 1) is described (see paragraphs 0008 and 0022 of FIG. 2 and FIG. 2).

In Patent Document 3, in a halftone EUV mask, in order to reduce the projection effect (shadowing effect) and to have a high degree of freedom in reflectivity selectivity and a high cleaning resistance, the material of the halftone film is Ta. It is described that the composition range is defined as a compound of Ru and Ru (see claims of the same document, paragraphs 0013, 0015, and 0019).
Here, the shadowing effect means that, for example, in an exposure apparatus using a reflective mask, light is incident on the mask with a slight inclination from the vertical direction so that the optical axes of incident light and reflected light do not overlap. If the phase shift film pattern of the mask has a thickness due to such light inclination, a shadow based on the thickness is generated. This means that the size of the transfer pattern changes by the amount of the shadow.

JP 2004-207593 A JP 2006-228766 JP Patent No. 5332321

  As described above, along with the shortening of the wavelength of exposure light, the line width and pattern interval of a pattern forming a circuit on a semiconductor are continually miniaturized in order to increase the degree of integration. There is also a demand for miniaturization of the phase shift film pattern for a reflective mask used for transferring a pattern thereon. Further, simultaneously with the miniaturization of the pattern, it is required to reduce the thickness of the phase shift film pattern. In order to reduce the shadowing effect in response to such demands, further thinning is required.

  The problem of the shadowing effect has become serious due to an increase in aspect ratio (ratio of pattern film thickness to pattern line width) accompanying pattern miniaturization. In particular, in the case of EUV exposure, an absorber film (phase shift film) ) Is required to be 60 nm or less.

  As disclosed in Patent Documents 1 to 3, Ta has been conventionally used as a material for forming an absorber film (phase shift film) of a reflective mask blank, but EUV light (for example, wavelength 13.5 nm) is used. ) Has a refractive index n of about 0.943, and even if the phase shift effect is used, the limit of thinning the absorber film (phase shift film) formed only of Ta is 60 nm. In order to reduce the film thickness, it is necessary to use a metal material having a small refractive index n (having a large phase shift effect). For example, as a metal material having a small refractive index n at a wavelength of 13.5 nm, as described in, for example, FIG. 5 of Patent Document 3, Mo (n = 0.922) or Ru (n = 0.888). However, Mo is very easy to oxidize and there is a concern about cleaning resistance, and Ru has a low etching rate and is difficult to process and modify.

  The present invention has been made to solve the above-described problems, and is a reflective mask blank having a thin film phase shift film that is excellent in cleaning resistance and workability as a whole film and that shifts the phase of EUV light. Another object of the present invention is to provide a reflective mask patterned with the phase shift film, a method for manufacturing the same, and a method for manufacturing a semiconductor device using the reflective mask.

  In order to solve the above problems, the present invention has the following configuration.

(Configuration 1)
A reflective mask blank in which a multilayer reflective film and a phase shift film for shifting the phase of EUV light are formed in this order on a substrate,
The phase shift film is a multilayer film including one or more first layers and one or more second layers,
The first layer includes a metal material selected from metal materials having a refractive index n of 0.95 or less at a wavelength of 13.5 nm,
The second layer includes a metal material selected from a metal material different from the first layer among metal materials having a refractive index n of 0.95 or less at a wavelength of 13.5 nm,
A metal diffusion region is formed at a ratio of 25% or more with respect to the total film thickness of the first layer and the second layer at and near the interface between the first layer and the second layer. Reflective mask blank characterized by being made.

(Configuration 2)
The first layer includes a metal material of any one of Ta and Cr,
The reflective mask blank according to Configuration 1, wherein the second layer includes a kind of metal material having a refractive index n at a wavelength of 13.5 nm smaller than any of Ta and Cr.

(Configuration 3)
The reflective mask blank according to Configuration 2, wherein the second layer contains Mo.

(Configuration 4)
When the protective film is provided between the multilayer reflective film and the phase shift film, and the protective film is formed of a material containing Ru as a main component, the lowermost layer of the phase shift film is the second layer. The reflective mask blank according to Configuration 3, wherein the reflective mask blank is a layer.

(Configuration 5)
The reflective mask blank according to Configuration 2, wherein the second layer includes any one of Ru, Pt, Pd, Ag, and Au.

(Configuration 6)
When a protective film is provided between the multilayer reflective film and the phase shift film, and the protective film is formed of a material containing Ru as a main component, the lowermost layer of the phase shift film is the first layer 6. The reflective mask blank according to Configuration 5, wherein the reflective mask blank is a layer.

(Configuration 7)
The reflective mask blank according to any one of Structures 1 to 6, wherein the first layer is an uppermost layer of the phase shift film.

(Configuration 8)
8. The reflective mask blank according to any one of configurations 1 to 7, wherein the thickness of the phase shift film is 50 nm or less.

(Configuration 9)
A reflection type comprising a phase shift film pattern forming step of forming a phase shift film pattern by patterning the phase shift film formed of a multilayer film in the reflection type mask blank according to any one of configurations 1 to 8 Mask manufacturing method.

(Configuration 10)
A reflection type mask having a phase shift film pattern in which the phase shift film formed of a multilayer film in the reflection type mask blank according to any one of configurations 1 to 8 is patterned.

(Configuration 11)
A method for manufacturing a semiconductor device, comprising a pattern forming step of forming a pattern on a semiconductor substrate using the reflective mask according to Configuration 10.

According to the reflective mask blank of the present invention, as described above, the phase shift film is a multilayer film using a metal material having a refractive index n of 0.95 or less at a wavelength of 13.5 nm. It becomes possible to form a phase shift film by reducing the thickness. For this reason, by changing the number of laminated phase shift films, optical characteristics such as phase difference can be adjusted in a wide film thickness range, so that the phase shift effect during EUV exposure can be obtained within that range. As a result, the reflective mask blank having the phase shift film can be used as a master for manufacturing a reflective mask having a phase shift film pattern with a small shadowing effect and improved resolution.
Further, since the phase shift film is a multilayer film including one or a plurality of first layers and one or a plurality of second layers, the thickness of each layer can be reduced. By reducing the thickness of each layer, even if the layer is made of a metal material that has a low etching rate and is difficult to process or modify, the thickness and thickness of the layer can be reduced and processing and modification can be performed easily. In the whole film, the influence of the processing difficulty of the metal material can be reduced, and the phase shift film as a whole can be made excellent in workability.
Further, the phase shift film is a multilayer film including one or more first layers and one or more second layers, and one layer of the first layer and one layer of the first layer are formed at and near the interface of each layer. Since the metal diffusion region is formed at a ratio of 25% or more with respect to the total film thickness of the two layers, the thin film layers containing different metal materials can be arranged adjacent to each other through the metal diffusion region. With this configuration, even a layer formed of a metal material that is easily oxidized and is feared for cleaning resistance, this layer is adjacent to a layer formed of a metal material that is not easily oxidized and has excellent cleaning resistance. Since the metal diffusion region can be formed between them and the cleaning resistance can be improved in the part, the influence of the cleaning resistance of the metal material concerned can be reduced in the entire phase shift film, and the entire phase shift film can be reduced. Can be made excellent in washing resistance.

According to the reflective mask manufacturing method of the present invention, the phase shift film pattern forming step of forming the phase shift film pattern by patterning the phase shift film formed of the multilayer film in the reflective mask blank described above is provided. Therefore, it is possible to manufacture a reflective mask having a thin phase shift film pattern with a small shadowing effect and improved resolution.
The phase shift film in the reflective mask blank is composed of a multilayer film in which thin film layers formed of different metal materials are arranged adjacent to each other. Therefore, in the phase shift film pattern forming process, the phase shift film is formed of the above-described difficult metal material. Even if the layer is a thin layer, since the film thickness is small, the influence of the processing difficulty can be reduced, the phase shift film can be easily processed, and the phase shift film pattern can be formed.
In the cleaning process in which the end face of the phase shift film pattern is exposed to the cleaning liquid, even if there is a thin film layer made of a metal material that is feared for cleaning resistance, this layer has excellent cleaning resistance. The thin film layer made of a metallic material is placed adjacent to each other, and the above-mentioned metal diffusion region is formed at and near the interface between the two layers. The effect on the end face of the phase shift film pattern can be suppressed, and the cleaning resistance of the entire phase shift film pattern can be improved.

According to the reflective mask according to the present invention, since the phase shift film formed of the multilayer film in the reflective mask blank described above has a patterned phase shift film pattern, the reflective mask has a shadowing effect. And a reflective mask having a thin phase shift film pattern with improved resolution.
In addition, since the phase shift film pattern is made of the above-described multilayer film, this reflective mask can be a reflective mask in which the entire phase shift film pattern is excellent in cleaning resistance.

  According to the method for manufacturing a semiconductor device according to the present invention, since it includes a pattern forming step of forming a pattern on a semiconductor substrate using the above-described reflective mask, a thin film comprising a multilayer film of the above-described reflective mask. With this phase shift film pattern, it is possible to manufacture a highly integrated semiconductor device with a small shadowing effect, high resolution, and fine pattern line width and spacing.

It is sectional drawing for demonstrating schematic structure of the reflective mask blank for EUV lithography by Embodiment 1 of this invention. It is sectional drawing which expands and shows the principal part (The phase shift film and protective film which consist of multilayer films) of the reflective mask blank shown in FIG. It is a graph which shows the characteristic of the extinction coefficient k and refractive index n of a metal material in EUV light (wavelength 13.5nm). It is a graph which shows the film thickness dependence of the phase difference of a phase shift film (Mo \ Ta) in EUV light (wavelength 13.5nm). It is a graph which shows the film thickness dependence of the reflectance of a phase shift film (Mo \ Ta) in EUV light (wavelength 13.5nm).

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In addition, the following embodiment is one form at the time of actualizing this invention, Comprising: This invention is not limited to the range.

<Structure of reflective mask blank and manufacturing method thereof>
FIG. 1 is a schematic diagram for explaining a configuration of a reflective mask blank for EUV lithography according to an embodiment of the present invention, and FIG. 2 is a schematic view of a main part (from a multilayer film) of the reflective mask blank shown in FIG. It is sectional drawing which expands and shows the phase shift film | membrane and protective film which become.
As shown in FIG. 1, the reflective mask blank 10 includes a substrate 12 having a back surface conductive film 11 for electrostatic chuck formed on a main surface on the back surface side, and a main surface (back surface conductive film 11) of the substrate 12. A multilayer reflection film 13 that reflects EUV light as exposure light, and protects the multilayer reflection film 13 on the multilayer reflection film 13. And a protective film 14 made of a material mainly composed of ruthenium (Ru), and formed on the protective film 14, absorbs EUV light, reflects a part of EUV light, and changes its phase. And a phase shift film 15 for shifting.

  Hereinafter, the structure of a board | substrate and each layer is demonstrated.

A substrate having a low thermal expansion coefficient within a range of 0 ± 5 ppb / ° C. is preferably used for the substrate 12 to prevent distortion of the absorber film pattern due to heat during exposure with EUV light. As a material having a low thermal expansion coefficient in this range, for example, SiO ₂ —TiO ₂ glass, multicomponent glass ceramics, or the like can be used.

Of the two main surfaces of the substrate 12, the main surface on the side where the phase shift film 15 is formed has at least pattern transfer accuracy and position accuracy because the phase shift film 15 becomes a transfer pattern of a reflective mask described later. Surface processing is performed so as to achieve high flatness from the viewpoint. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, particularly preferably in a 132 mm × 132 mm region of the main surface on the side where the transfer pattern of the substrate 12 is formed. 0.03 μm or less. Of the main surfaces of the substrate 12, the main surface opposite to the side on which the phase shift film 15 is formed is formed with a back surface conductive film 11 for electrostatic chucking when set in the exposure apparatus. In the area of 142 mm × 142 mm, the flatness is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less.
In this specification, the flatness is a value representing the warpage (deformation amount) of the surface indicated by TIR (Total Indicated Reading). A plane defined by the least square method with respect to the substrate surface is defined as a focal plane. It is the absolute value of the height difference between the highest position on the substrate surface above the plane and the lowest position on the substrate surface below the focal plane.

  In the case of EUV exposure, the surface smoothness required for the substrate 12 is that the surface roughness of the main surface of the substrate 12 on the side where the phase shift film 15 serving as a transfer pattern is formed is the root mean square roughness ( RMS) is preferably 0.1 nm or less. The surface smoothness can be measured with an atomic force microscope (AFM).

  Furthermore, the substrate 12 preferably has high rigidity in order to prevent deformation due to film stress of a film (such as the multilayer reflective film 13) formed thereon. In particular, those having a high Young's modulus of 65 GPa or more are preferable.

  The multilayer reflective film 13 provides a function of reflecting EUV light in a reflective mask for EUV lithography, and has a multilayer film structure in which elements having different refractive indexes are periodically stacked.

  In general, a thin film (high refractive index layer) of a light element or a compound thereof, which is a high refractive index material, and a thin film (low refractive index layer) of a heavy element or a compound thereof, which is a low refractive index material, are alternately 40 A multilayer film laminated for about ˜60 periods is used as the multilayer reflective film 13. The multilayer film may be laminated in a plurality of periods, with a laminated structure of a high refractive index layer / low refractive index layer in which a high refractive index layer and a low refractive index layer are laminated in this order from the substrate 12 side. Alternatively, a low-refractive index layer and a high-refractive index layer in which the low-refractive index layer and the high-refractive index layer are stacked in this order may be stacked in a plurality of periods. The outermost layer of the multilayer reflective film 13, that is, the surface layer opposite to the substrate 12 of the multilayer reflective film 13, is preferably a high refractive index layer. In the multilayer film described above, when the high refractive index layer / low refractive index layer stacking structure in which the high refractive index layer and the low refractive index layer are stacked in this order from the substrate 12 is stacked for a plurality of periods, the uppermost layer has a low refractive index. In this case, if the low refractive index layer constitutes the outermost surface of the multilayer reflective film 13, it is easily oxidized and the reflectance of the reflective mask is reduced. Further, it is preferable to form a multilayer reflective film 13 by forming a high refractive index layer. On the other hand, in the multilayer film described above, when the low-refractive index layer and the high-refractive index layer stacked in this order from the substrate 12 side are stacked in a plurality of periods, the stack structure is one cycle. Since the upper layer is a high refractive index layer, it can be left as it is.

  In the embodiment, a layer containing Si can be adopted as the high refractive index layer. The material containing Si may be Si compound containing B, C, N, and O in addition to Si alone. By using a layer containing Si as the high refractive index layer, a reflective mask for EUV lithography having excellent EUV light reflectivity can be obtained. Further, since a glass substrate is preferably used as the substrate 12 in the embodiment, Si is excellent in adhesion to it. For the low refractive index layer, a single metal selected from Mo, Ru, Rh, and Pt, or an alloy thereof is used. For example, as the multilayer reflective film 13 for EUV light having a wavelength of 13 to 14 nm, a Mo / Si periodic laminated film in which Mo films and Si films are alternately laminated, for example, about 40 to 60 periods is preferably used. A high refractive index layer that is the uppermost layer of the multilayer reflective film 13 is formed of silicon (Si), and a silicon oxide layer containing silicon and oxygen is formed between the uppermost layer (Si) and the protective film 14. You may make it form. Thereby, the mask cleaning resistance (resistance to peeling of the phase shift film pattern) can be improved.

  The reflectance of the multilayer reflective film 13 alone is, for example, 65% or more, and the upper limit is preferably 73%. The film thickness and the number of periods of each constituent layer of the multilayer reflective film 13 may be appropriately selected according to the exposure wavelength, and are selected so as to satisfy Bragg's law. The multilayer reflective film 13 includes a plurality of high refractive index layers and low refractive index layers, but the film thicknesses of the high refractive index layers and the low refractive index layers may not be the same. The film thickness of the outermost Si layer of the multilayer reflective film 13 can be adjusted within a range in which the reflectance is not lowered. The film thickness of the outermost surface Si (high refractive index layer) can be, for example, 3 to 10 nm.

  A method of forming the multilayer reflective film 13 is known in the art, but can be formed by depositing each layer by, for example, ion beam sputtering. In the case of the Mo / Si periodic multilayer film described above, an Si film having a film thickness of about 4 nm is first formed on the substrate 12 using an Si target, for example, by ion beam sputtering, and then a film thickness of about 3 nm is formed using the Mo target. A multilayer reflection film 13 is formed by laminating a total of 40 to 60 periods with this period as one period (the uppermost layer is a Si layer).

  As shown in FIGS. 1 and 2, the protective film 14 is formed on the multilayer reflective film 13 in order to protect the multilayer reflective film 13 from dry etching and cleaning liquid in the manufacturing process of the reflective mask for EUV lithography described later. Is done. The protective film 14 is made of, for example, a material containing Ru (ruthenium) as a main component (main component: 50 atomic% or more), and may be a Ru metal alone, or Ru may include Nb, Zr, Y, B, Ti, La Ru alloy containing a metal such as Mo, Co, Re, etc., and may contain N (nitrogen). Further, the protective film 14 has a laminated structure of three or more layers, the lowermost layer and the uppermost layer are made of a material containing the above Ru, and a metal or alloy other than Ru is placed between the lowermost layer and the uppermost layer. It does not matter if they are interposed.

  The film thickness of the protective film 14 composed of such Ru or an alloy thereof is not particularly limited as long as it can function as the protective film, but is preferably 1 from the viewpoint of the reflectance of EUV light. .5 to 8.0 nm, more preferably 1.8 to 6.0 nm.

  As a method for forming the protective film 14, a method similar to a known film forming method can be employed without any particular limitation. Specific examples include a sputtering method and an ion beam sputtering method.

  As shown in FIG. 2, the phase shift film 15 formed on the protective film 14 is a multilayer film including a first layer 15a and a second layer 15b. The multi-layered phase shift film 15 has a structure in which one first layer 15a and one second layer 15b are alternately stacked in a plurality of numbers. In the phase shift film 15 shown in FIG. 2, the lowermost layer is the second layer 15b, and the uppermost layer is the first layer 15a. In the following description, one first layer 15a and one second layer 15b may be indicated as one period (P). The number of stacked layers in such a stacked structure is not particularly limited as long as it is two or more, and may be an even layer or an odd layer. Examples of even layers include 20 layers shown in 10 cycles in FIGS. 4 and 5 to be described later, but are not limited thereto.

The metal material for forming the first layer 15a is selected from metal materials having a refractive index n at a wavelength of 13.5 nm of 0.95 or less as shown in FIG. 3, for example, Ta (refractive index n at a wavelength of 13.5 nm). = About 0.943, extinction coefficient k = about 0.041), or Cr (refractive index n = about 0.932, extinction coefficient k = about 0.039).
For example, Ta is a phase shift film material that has a low extinction coefficient of EUV light and can be easily dry-etched with a fluorine-based gas or a chlorine-based gas, and thus has excellent workability. Further, by adding B, Si, Ge or the like to Ta, an amorphous material can be easily obtained, and the smoothness of the phase shift film 15 can be improved. Further, if N or O is added to Ta, the resistance of the phase shift film 15 to oxidation is improved, so that the effect of being excellent in cleaning resistance and improving stability over time can be obtained.
In addition, as a forming material of the 1st layer 15a, it is preferable that a kind of metal material is selected, However, It is not limited to this, A 2 or more types of metal material may be selected.

The metal material forming the second layer 15b is selected from metal materials different from the first layer 15a among metal materials having a refractive index n of 0.95 or less at a wavelength of 13.5 nm shown in FIG. For example, Mo (the refractive index n = about 0.921, extinction coefficient k = about 0.006), Ru (the refractive index n = about 0.888, extinction coefficient k = about 0.017), Pt (The refractive index n = about 0.891, extinction coefficient k = about 0.060), Pd (the refractive index n = about 0.876, extinction coefficient k = about 0.046), Ag (the refractive index) n = about 0.890, extinction coefficient k = about 0.079) or Au (the refractive index n = about 0.899, extinction coefficient k = about 0.052).
For example, Mo has a concern about washing resistance by itself, but the washing resistance can be improved by forming a metal diffusion region by forming a multilayer film in combination with the layer containing Ta or Cr described above. . Moreover, since the refractive index n in EUV light is smaller than 0.95, it is possible to obtain a phase shift effect with a thin film thickness. Furthermore, since the extinction coefficient k is small, it is a film material that has a high EUV light reflectivity and can easily obtain contrast (resolution) due to the phase shift effect.
In addition, Ru alone has a low etching rate with respect to various etching gases and has a high processing difficulty, but it forms a multilayer film in combination with the layer containing Ta or Cr described above to form a metal diffusion region. Thus, the workability of the entire phase shift film 15 can be improved. Further, since the refractive index n in EUV light is smaller than 0.95, it is possible to obtain a phase shift effect with a thin film thickness, and since the extinction coefficient k is small, the reflectivity of EUV light is high and the phase shift effect is obtained. It is a film material that easily obtains contrast (resolution).
Pt and Pd are film materials having a low etching rate and difficulty in processing. However, since the refractive index n in EUV light is smaller than 0.95, a phase shift effect can be obtained with a thin film thickness.
As a material for forming the second layer 15b, a kind of metal material is preferably selected, but the material is not limited to this, and two or more kinds of metal materials may be selected.

The metal material that can be used as the material for forming the first layer 15a and the second layer 15b is preferably a single metal, but does not affect the characteristics of the phase shift film 15 such as the phase shift effect. As a condition, a material containing the metal can be used.
Examples of a material containing Ta used as a material for forming the first layer 15a include a TaB alloy containing Ta as a main component and containing B, a TaSi alloy containing Ta as a main component, and Si as a main component, and Ta as a main component. In addition, it may be a Ta alloy containing a transition metal (for example, Pt, Pd, Ag), or a Ta compound in which N, O, H, C, or the like is added to Ta metal or an alloy thereof. Examples of the material containing Cr include a CrSi alloy containing Cr as a main component and containing Si, a Cr alloy containing Cr as a main component and other transition metals (for example, Pt, Pd, Ag), a Cr metal and an alloy thereof. It may be a Cr-based compound to which N, O, H, C or the like is added.
In addition, as a material containing Mo used as a material for forming the second layer 15b, Mo containing Mo as a main component and containing a metal such as Nb, Zr, Y, B, Ti, La, Ru, Co, and Re. An alloy or the like may be used. The Ru-containing material may be a Ru alloy containing Ru as a main component and a metal such as Nb, Zr, Y, B, Ti, La, Mo, Co, or Re. Further, a Ru compound obtained by adding N, H, C, or the like to a Ru metal or an alloy thereof may be used. The material containing Pt may be a Pt alloy containing a metal such as Nb, Zr, Y, B, Ti, La, Mo, Co, Re, etc. containing Pt as a main component. The material containing Pd may be a Pd alloy containing a metal such as Nb, Zr, Y, B, Ti, La, Mo, Co, Re, etc. containing Pd as a main component. The material containing Ag may be an Ag alloy containing a metal such as Nb, Zr, Y, B, Ti, La, Mo, Co, Re, etc. containing Ag as a main component. The material containing Au may be an Au alloy containing a metal such as Nb, Zr, Y, B, Ti, La, Mo, Co, Re, etc. with Au as a main component.

The lowermost layer of the phase shift film 15 and the layer thereon are the first layer 15a or the second layer 15b containing another metal material that does not overlap with the material for forming the protective film 14 formed thereunder ( Ru protective film \ Other than Ru \ ...). For example, when the lowermost layer of the phase shift film 15 is the second layer 15b containing Ru and the protective film 14 is formed of a material mainly containing Ru (Ru protective film \ Ru ...), both are common. This combination should be avoided because it forms and overlaps with Ru. In this case, the lowermost layer of the phase shift film 15 is, for example, a first layer 15a containing Ta having high etching selectivity with respect to Ru of the protective film 14 or a second layer 15b containing Mo (Ru). Protective film \ Ta or Mo \ Mo or Ta ...), high-definition patterning is possible, and damage to the protective film 14 can be suppressed.
The uppermost layer of the phase shift film 15 is the first layer 15a or the first layer 15a containing a metal material determined according to the etching resistance determined by the relationship between the cleaning resistance and the formation material when the etching mask film is formed. 2 layers 15b. For example, the uppermost layer of the phase shift film 15 including the first layer 15a containing Ta or Cr and the second layer 15b containing Mo is the first layer 15a containing Ta or Cr (Ru protective film). \ Ta \ Mo \ Ta \ Mo ... \ Ta or Ru protective film \ Cr \ Mo \ Cr \ Mo ... \ Cr), improving the cleaning resistance before pattern formation of the entire phase shift film 15 be able to.
Thus, when the phase shift film 15 including the first layer 15a containing Ta and the second layer 15b containing Mo is formed on the protective film 14 containing Ru as a main component, the outermost layer of the phase shift film 15 is formed. For example, the lower layer is a first layer 15a containing Ta having high etching selectivity with respect to Ru of the protective film 14 or a second layer 15b containing Mo, and the uppermost layer of the phase shift film 15 is a first layer containing Ta. 1 layer 15a (Ru protective film \ Ta or Mo \ Mo or Ta ... \ Ta) enables high-definition patterning and damages the protective film 14 as described above. And the resistance to cleaning before and after pattern formation can be improved.
When the lowermost layer of the phase shift film 15 is the first layer 15a containing Ta (Ru protective film \ Ta \ Mo \ Ta \ Mo ... \ Ta), the number of stacked phase shift films 15 is an odd number. When the lowermost layer of the phase shift film 15 is the second layer 15b containing Mo (Ru protective film \ Mo \ Ta \ Mo \ Ta ... \ Ta), the number of stacked phase shift films 15 is an even number. It becomes.

  The first layer 15a constituting the phase shift film 15 may be formed of a plurality of layers. Each first layer 15a in the phase shift film 15 is preferably formed of the same metal material, but may be formed of different metal materials. Also, the second layer 15b constituting the phase shift film 15 may be formed of a plurality of layers, like the first layer 15a. Each second layer 15b is desirably formed of the same metal material, but may be formed of different metal materials. In the latter case, the phase shift film 15 can be composed of, for example, a first layer 15a containing Ta, a second layer 15b containing Mo, and a second layer 15b containing Ru (Ru protective film). \ Ta \ Mo \ Ru \ Ta \ Mo \ Ru \ ... \ Ta or Ru protective film \ Ta \ Mo \ Ta \ Ru \ ... \ Ta). In this case, since the former can reduce the content ratio of the Ta layer in the phase shift film 15, the phase shift effect can be easily obtained, and the latter can reduce the content ratio of the Ru layer, so that the workability can be improved. .

Further, in the phase shift film 15, there are metal components contained in the first layer 15 a and the second layer 15 b in the vicinity of the interface between the first layer 15 a and the second layer 15 b in contact with the first layer 15 a. A metal diffusion region R1 in which another metal component contained in the metal diffuses is formed. In the metal diffusion region R1, the metal component of the second layer 15b diffuses into a part of the first layer 15a on the first layer 15a side, and the second layer 15b side of the second layer 15b side. The metal component of the first layer 15a is diffused in part. Therefore, the metal diffusion region R1 has a metal component concentration gradient on the first layer 15a side and the second layer 15b side, but the metal component of the first layer 15a and the metal component of the second layer 15b. Since both are included, it is an area | region which shows the characteristic of both metal components. Since the sudden characteristic change can be reduced between the first layer 15a and the second layer 15b, the entire phase shift film 15 is not affected by the sudden characteristic change, and the phase shift is performed. The characteristics of the entire film 15 can be made constant.
The formation ratio of the metal diffusion region R1 with respect to the total film thickness of the first layer 15a and the second layer 15b is 25% or more, and the upper limit is less than 100%, preferably 80% or less. When the formation ratio of the metal diffusion region R1 is 100%, the metal diffusion region R1 occupies the first layer 15a and the second layer 15b. In this case, since the first layer 15a and the second layer 15b become one layer, the optical characteristics of the first layer 15a and the optical characteristics of the second layer 15b are equal or approximate, and the first layer 15a And the significance of dividing into the second layer 15b is lost. For example, in the case of the phase shift film 15 in which the first layer 15a is Ta, the second layer 15b is Mo, and the uppermost layer is the first layer 15a, the outermost surface of the uppermost layer has excellent cleaning resistance. In addition to Ta, Mo, whose cleaning resistance is a concern, is mixed, so that the cleaning resistance of the phase shift film 15 is deteriorated. In consideration of this point, in order for Ta to remain on the outermost surface and its excellent cleaning resistance contribute to the cleaning resistance of the phase shift film 15, the upper limit of the formation ratio is 80% as described above. The following is preferable.

  Further, metal diffusion in which the metal component contained in the protective film 14 and the metal component contained in the lowermost layer of the phase shift film 15 are diffused at and near the interface between the protective film 14 and the lowermost layer of the phase shift film 15. Region R2 is formed. This metal diffusion region R <b> 2 has a function of improving the adhesion between the protective film 14 and the lowermost layer of the phase shift film 15.

The phase shift film 15 can be formed by a known film formation method such as an ion beam sputtering method. For example, in the case of the ion beam sputtering method, two targets formed of the metal materials of the first layer 15a and the second layer 15b are prepared, and the two targets are formed in an atmosphere of an inert gas such as Ar gas. Of these, the first layer 15a and the second layer 15b can be formed by alternately irradiating one beam at a time. At this time, the metal diffusion region R1 can be formed by controlling the power of the ion beam emitted from the ion beam generator. When the power of the ion beam is increased, the ratio of the metal diffusion region R1 can be increased.
Further, the metal diffusion region R1 may be formed by adjusting the incident angle (incident angle with respect to the normal line of the substrate) of sputtered particles generated when the ion beam emitted from the ion beam generator enters the target. As the incident angle approaches 0 °, the ratio of the metal diffusion region R1 can be increased.
The metal diffusion region R2 can also be formed by a known film formation method such as an ion beam sputtering method. As will be described later, when forming the phase shift film 15 using the ion beam sputtering method, when the protective film 14 and the second layer 15b are formed of the same metal material (for example, Ru), for example, a Ru target And the Ta target, the protective film 14 and the phase shift film 15 are continuously formed, and the metal diffusion region R2 can be formed by controlling the power of the ion beam emitted from the ion beam generator.

The phase shift film 15 made of such a multilayer film has a reflectance of 1 to 30% with respect to EUV light, and a phase difference between the reflected light from the phase shift film 15 and the reflected light from the multilayer reflective film 13 is 170 to 190 degrees. It is formed to become.
The film thickness of the phase shift film 15 is set in accordance with the type of metal material used for each layer and the design value of the reflectance of EUV light, and so that the phase difference falls within the above range. Yes, preferably 50 nm or less. With the phase shift film 15 formed with such a thin film thickness, for example, in the case of EUV exposure, the shadowing effect can be reduced. In addition, the thickness of each of the first layer 15a and the second layer 15b in the phase shift film 15 made of a multilayer film is the wavelength of EUV light, the number of layers of the multilayer film, the type of material of each layer, the cleaning resistance, It is determined by an appropriate combination of film thickness in consideration of characteristics such as workability.
The film thickness ratio between the first layer 15a and the second layer 15b is determined in consideration of characteristics such as cleaning resistance and workability of the material type of each layer. The film thickness ratio between the first layer 15a and the second layer 15b can be appropriately determined according to the metal material used, and is not particularly limited. For example, in the case of Ta: Mo, 20: 1 to 1: 5 is preferable. When the Ta layer is thick and the Mo layer is too thin, there is an inconvenience that the entire thickness of the phase shift film 15 for obtaining the phase shift effect is increased. Further, when the Ta layer is thin and the Mo layer is too thick, Mo is easily oxidized, so that there is a disadvantage that the cleaning resistance of the entire phase shift film 15 is lowered.

The phase shift film 15 made of a multilayer film is preferably formed continuously from the start of film formation to the end of film formation without being exposed to the atmosphere. For example, each phase (first layer 15a, second layer 15b) of the phase shift film 15 is continuously formed with a very thin film thickness, and the metal diffusion region is formed at the interface between the layers and the vicinity thereof. Although it is preferable to form by an ion beam sputtering method useful for forming R1, other than the said method, it can also form by well-known methods, such as sputtering methods, such as DC sputtering method and RF sputtering method.
At least the surface of the target used in the sputtering method is preferably formed of a single metal or a metal oxide thereof that forms the first layer 15 a and the second layer 15 b of the phase shift film 15.
For example, when an ion beam sputtering method is used, each layer of the phase shift film 15 such as Ta \ Mo (first layer) is formed after the formation of the MoSi multilayer reflective film 13, the protective film 14 of Ru. 15a and the second layer 15b) can be formed without coming out of the sputtering apparatus and are not exposed to the air, which is advantageous in that the number of defects in each film can be suppressed.

  If the surface or the like of the phase shift film 15 thus formed is not smooth, the edge roughness of the phase shift film pattern increases, and the dimensional accuracy of the pattern may deteriorate. For this reason, the surface roughness of the phase shift film 15 is a root mean square roughness (RMS), which is 0.5 nm or less, more preferably 0.4 nm or less and 0.3 nm or less.

An etching mask film (not shown) may be further formed on the phase shift film 15. The etching mask film has etching selectivity with respect to the uppermost layer of the multilayer reflective film 13, and the uppermost layer of the phase shift film 15 can be etched with an etching gas for the first layer 15a or the second layer 15b. It is made of a material (having no etching selectivity). Specifically, for example, it is formed of a material containing Cr or Ta. Examples of the material containing Cr include a Cr metal simple substance, and a Cr compound in which one or more elements selected from elements such as O, N, C, H, and B are added to Cr. Materials containing Ta include Ta metal alone, TaB alloy containing Ta and B, Ta alloy containing Ta and other transition metals (for example, Hf, Zr, Pt, W), Ta metal and their alloys And Ta compounds obtained by adding N, O, H, C, etc. to Here, when the uppermost layer of the phase shift film 15 is the first layer 15a and the first layer 15a contains Ta, a material containing Cr is selected as a material for forming the etching mask film, and When the uppermost layer of the phase shift film 15 is the second layer 15b, and the second layer 15b includes any one metal material of Mo, Ru, Pt, Pd, Ag, and Au, the etching mask film As the forming material, any metal material including Ta or Cr is selected.
As an etching gas applicable to an etching mask film formed of a material containing Cr, a mixed gas of a chlorine-based gas such as Cl ₂ and an oxygen gas can be used. As an etching gas applicable to an etching mask film formed of a material containing Ta, a chlorine-based gas such as Cl ₂ can be used. In particular, since a material containing Ta used as an etching mask film exists on the outermost surface of the reflective mask blank 10, the surface is easily oxidized by natural oxidation or cleaning. When the material containing Ta is oxidized, the etching mask film is not removed at the same time when the metal material constituting the phase shift film 15 is etched with a chlorine-based gas such as Cl ₂ . For this reason, it is preferable that the material containing Ta used as the etching mask film has a material and composition with high oxidation resistance that are not easily oxidized. Furthermore, considering simplification of the process of the reflective mask, it is preferable to use a material and composition having a higher etching rate than a metal material constituting the phase shift film 15 in a chlorine-based gas such as Cl ₂ . A preferable material is preferably a material containing Ta and N, and the content of N is desirably 10 atomic% or more. From the viewpoint of suppressing pseudo defects in defect inspection of the reflective mask blank 10, the etching mask film surface is preferably smooth, and in this case, the N content is desirably 75 atomic% or less. The preferable N content in the etching mask film is 10 to 75 atomic%, more preferably 10 to 60 atomic%, and 15 to 50 atomic%.
In consideration of the etching rate of the etching mask film, it is preferably amorphous.

  The etching mask film can be formed by a known method such as a sputtering method such as a DC sputtering method or an RF sputtering method.

  The thickness of the etching mask film is preferably 5 nm or more from the viewpoint of ensuring the function as a hard mask. In the reflective mask manufacturing process, the etching mask film is removed at the same time as the phase shift film 15 by the fluorine-based gas during the etching process of the phase shift film 15, so that the film is almost the same as the phase shift film 15. It may be formed with a thickness. Considering the film thickness of the phase shift film 15, the film thickness of the etching mask film is 5 nm to 20 nm, preferably 5 nm to 15 nm.

  As shown in FIG. 1, a back surface conductive film 11 for an electrostatic chuck is formed on the back surface side of the substrate 12 (opposite the surface on which the multilayer reflective film 13 is formed). The electrical characteristics required for the back surface conductive film 11 for the electrostatic chuck are usually 100Ω / sq or less. The back surface conductive film 11 can be formed, for example, by a magnetron sputtering method or an ion beam sputtering method, using a target of a metal or alloy such as chromium or tantalum. When the back surface conductive film 11 is formed of, for example, CrN, it can be formed by the above sputtering method in a gas atmosphere containing N such as nitrogen gas using a Cr target. Although the film thickness of the back surface conductive film 11 is not specifically limited as long as the function for an electrostatic chuck is satisfied, it is usually 10 to 200 nm.

The configuration of the reflective mask blank 10 according to the embodiment has been described above for each layer.
In addition, although the thing provided with the etching mask film | membrane mentioned above on the phase shift film 15 as the said reflection type mask blank was applied to this invention, it used as an etching mask on the phase shift film 15 as a reflection type mask blank. A film provided with a resist film that can be applied may be applied to the present invention. In addition, as the reflective mask blank, a protective film 14 provided on the multilayer reflective film 13 and a phase shift film 15 provided on the protective film 14 was applied to the present invention, but the protective film 14 was not provided. A film provided with the phase shift film 15 on the multilayer reflective film 13 may be applied to the present invention.

According to the reflective mask blank according to the embodiment, as described above, the phase shift film 15 is a multilayer film using a metal material having a refractive index n of 0.95 or less at a wavelength of 13.5 nm. The phase shift film 15 can be formed by reducing the film thickness. For this reason, since the optical characteristics such as phase difference can be adjusted in a wide film thickness range by changing the number of laminated phase shift films 15, the phase shift effect at the time of EUV exposure can be obtained in that range. . As a result, the reflective mask blank 10 having the phase shift film 15 can be used as a master for manufacturing a reflective mask having a phase shift film pattern with a small shadowing effect and improved resolution.
Further, since the phase shift film 15 is a multilayer film including the first layer 15a and the second layer 15b, the thickness of each layer can be reduced. By reducing the thickness of each layer, even if the layer is made of a metal material that has a low etching rate and is difficult to process or modify, the thickness and thickness of the layer can be reduced and processing and modification can be performed easily. In the entire film 15, the influence of the processing difficulty of the metal material can be reduced, and the phase shift film 15 as a whole can be made excellent in workability.
In addition, the phase shift film 15 is a multilayer film including the first layer 15a and the second layer 15b, and the total film thickness of one layer of the first layer and one layer of the second layer at and near the interface between the layers. Since the metal diffusion region R1 is formed at a ratio of 25% or more, the thin film layers containing different metal materials can be arranged adjacent to each other via the metal diffusion region R1. With this configuration, even a layer formed of a metal material (Mo or the like) that is easily oxidized and is feared for cleaning resistance is formed of a metal material (Ta or the like) that is not easily oxidized and has excellent cleaning resistance. Since the metal diffusion region R1 is formed between the adjacent layers and the cleaning resistance can be improved in the portion, the influence of the cleaning resistance which is a concern of the metal material is exerted on the entire phase shift film 15. Therefore, the entire phase shift film 15 can be made excellent in cleaning resistance.

<Reflective mask and manufacturing method thereof>
A reflective mask can be manufactured using the reflective mask blank 10 according to the embodiment. For the production of a reflective mask for EUV lithography, a photolithography method that can perform high-definition patterning is most suitable.

  In this embodiment mode, manufacturing of a reflective mask using a photolithography method is described.

First, a resist film (not shown) is formed on the outermost surface (uppermost layer of the phase shift film 15) of the reflective mask blank 10 shown in FIG. The film thickness of the resist film can be set to 100 nm, for example. Next, a desired pattern is drawn (exposed) on the resist film, and further developed and rinsed to form a predetermined resist film pattern (not shown).
Next, the phase shift film 15 made of a multilayer film is subjected to dry etching using an etching gas containing a fluorine-based gas such as SF ₆ by using a resist film pattern (not shown) as a mask, thereby obtaining a phase shift film pattern. (Not shown). In this step, the resist film pattern (not shown) is removed.
Here, the etching rate varies depending on conditions such as a material for forming the target phase shift film 15 and an etching gas. In the phase shift film 15 made of a multilayer film of different metal materials, the etching rate varies slightly for each layer of different metal materials, but the etching rate in the entire phase shift film 15 is substantially constant because the thickness of each layer is small. It is thought that it becomes.

The above process constitutes the phase shift film pattern forming process, and the layers (15a, 15b) of the multilayered phase shift film 15 are continuously etched by dry etching with a kind of etching gas. (Not shown) is formed, so that the effect of simplifying the process can be obtained. Then, wet cleaning using an acidic or alkaline aqueous solution is performed to obtain a reflective mask for EUV lithography that achieves high reflectivity.
Etching gases include SF ₆ , CHF ₃ , CF ₄ , C ₂ F ₆ , C ₃ F ₆ , C ₄ F ₆ , C ₄ F ₈ , CH ₂ F ₂ , CH ₃ F, and C ₃ F. _8. A fluorine-based gas such as F or a mixed gas containing these fluorine gas and O ₂ at a predetermined ratio can be used, but each layer (15a, 15b) of the phase shift film 15 formed of a multilayer film is useful for processing. Other gases may be used as long as they are correct gases. For example, a chlorine-based gas such as Cl ₂ , SiCl ₄ , CHCl ₃ , CCl ₄ , BCl _{3 and the} like, a mixed gas thereof, a mixed gas containing a chlorine-based gas and He at a predetermined ratio, a chlorine-based gas, and Ar are predetermined. At least one selected from the group consisting of mixed gas, oxygen gas, fluorine gas, chlorine gas, bromine gas, iodine gas, halogen gas containing at least one of them, and hydrogen halide gas The mixed gas containing the above and oxygen gas etc. are mentioned.

The reflective mask manufacturing method according to the embodiment includes a phase shift film pattern forming step of forming a phase shift film pattern by patterning the phase shift film 15 formed of the multilayer film in the reflective mask blank 10 described above. Therefore, a reflective mask having a thin phase shift film pattern with a small shadowing effect and improved resolution can be manufactured.
Since the phase shift film 15 in the reflective mask blank 10 is composed of a multilayer film in which thin film layers formed of different metal materials are arranged adjacent to each other, in the phase shift film pattern forming step, the above-described difficult metal material is processed. Even if the layer is formed by the above method, since the film thickness is small, the influence of the processing difficulty can be reduced, the phase shift film 15 can be easily processed, and the phase shift film pattern can be formed.
In the cleaning process in which the end face of the phase shift film pattern is exposed to the cleaning liquid, even if there is a thin film layer formed of a metal material that is feared for cleaning resistance in a part of the phase shift film 15 made of a multilayer film, this layer In addition, a thin film layer formed of a metal material having excellent cleaning resistance is disposed adjacent to each other, and the above-described metal diffusion region R1 is formed at and near the interface between the two layers. It is possible to suppress the influence of the cleaning resistance, which is a concern for a part of 15, on the end face of the phase shift film pattern, and to improve the cleaning resistance of the entire phase shift film pattern.

According to the reflection type mask according to the embodiment, the reflection type mask blank 10 has the phase shift film pattern (not shown) in which the phase shift film 15 made of the multilayer film is patterned. The mask (not shown) can be a reflective mask (not shown) having a thin phase shift film pattern (not shown) with a small shadowing effect and improved resolution.
Further, since the phase shift film pattern (not shown) is composed of the above-mentioned multilayer film, the entire phase shift film pattern (not shown) is excellent in cleaning resistance. A reflective mask (not shown) can be used.

<Manufacture of semiconductor devices>
By using the reflective mask according to the embodiment, a transfer pattern based on the phase shift film pattern of the reflective mask is formed on the semiconductor substrate by lithography, and various other processes are performed. A semiconductor device in which a pattern or the like is formed can be manufactured.

  A manufacturing method for manufacturing a semiconductor device by transferring a pattern to a semiconductor substrate with a resist film (not shown) by EUV light using a reflective mask according to the embodiment by a pattern transfer device (not shown) will be described. .

  A pattern transfer apparatus (not shown) on which a reflective mask (not shown) according to the embodiment is mounted includes an exposure light source such as a laser plasma X-ray source, a reflective mask, a reduction optical system, and the like. An X-ray reflecting mirror is used as the reduction optical system. An exposure light source with a power of, for example, 80 W is used based on the viewpoint of optimization of throughput.

  The pattern reflected by the reflective mask is usually reduced to about ¼ by the reduction optical system. For example, a wavelength band of 13 to 14 nm is used as the exposure wavelength, and the optical path is preset in vacuum. In such a state, EUV light obtained from an exposure light source is incident on a reflective mask, and the light reflected here is transferred to a resist film on a semiconductor substrate with a resist film through a reduction optical system.

  The EUV light incident on the reflective mask is absorbed and not reflected by the phase shift film 15 in the portion where the phase shift film 15 remains, while the multilayer reflective film 13 is present in the portion where the phase shift film 15 does not remain. EUV light is incident on and reflected from the light. In this way, the image formed by the light reflected from the reflective mask enters the reduction optical system, and the exposure light passing through the reduction optical system forms a transfer pattern on the resist layer on the semiconductor substrate with the resist film. Form. Note that a part of the EUV light is reflected by the phase shift film 15, and the phase of the light is shifted by 180 degrees with respect to the light reflected from the multilayer reflective film 13, thereby increasing the contrast of the image. Then, by developing this exposed resist layer, a resist pattern can be formed on the semiconductor substrate with a resist film. Then, by performing etching or the like using this resist pattern as a mask, for example, a predetermined wiring pattern can be formed on the semiconductor substrate. A semiconductor device is manufactured through such a pattern formation process and other necessary processes.

  According to the method of manufacturing a semiconductor device according to the embodiment, since the structure includes the pattern forming step of forming a pattern on the semiconductor substrate using the above-described reflective mask, a thin film made of a multilayer film of the above-described reflective mask. With this phase shift film pattern, it is possible to manufacture a highly integrated semiconductor device with a small shadowing effect, high resolution, and fine pattern line width and spacing.

  Hereinafter, the present invention will be described based on each example.

Example 1.
<Production of reflective mask blank (CrN back surface conductive film \ substrate \ MoSi multilayer reflective film \ Ru protective film \ phase shift film)>
First, a SiO ₂ —TiO ₂ glass substrate 12 was prepared.
A back conductive film 11 made of CrN was formed on the back surface of the substrate 12 by the magnetron sputtering method under the following conditions.
Back surface conductive film formation conditions: Cr target, Ar + N ₂ gas atmosphere (Ar: N ₂ = 90%: N: 10%), film thickness 20 nm.

  Next, the multilayer reflective film 13 was formed on the main surface of the substrate 12 opposite to the side on which the back conductive film 11 was formed. As the multilayer reflective film 13 formed on the substrate 12, a Mo / Si periodic multilayer reflective film suitable for 13.5 nm EUV light was employed. The multilayer reflective film 13 was formed by alternately stacking Mo layers and Si layers on the substrate 12 by ion beam sputtering (Ar gas atmosphere) using a Mo target and a Si target. First, a Si film was formed with a film thickness of 4.2 nm, and then a Mo film was formed with a film thickness of 2.8 nm. This was set as one period, and 40 periods were laminated in the same manner. Finally, a Si film was formed with a film thickness of 4.0 nm to form a multilayer reflective film 13 (total film thickness: 284 nm).

  Subsequently, a protective film 14 containing Ru was formed to a thickness of 2.5 nm on the uppermost Si film of the multilayer reflective film 13 by ion beam sputtering (Ar gas atmosphere) using a Ru target.

Next, a phase shift film 15 made of a multilayer film was formed on the protective film 14 by the following method.
First, a Mo layer (second layer 15b) is formed to a thickness of 2.4 nm by ion beam sputtering (Ar gas atmosphere) using a Mo target and a Ta target, and then a Ta layer (first layer) Layer 15a) was deposited to a thickness of 2.4 nm (thickness ratio 1: 1). The phase shift film 15 having a total film thickness of 48 nm (film configuration: Mo \ Ta \ Mo) is formed with this period as one period, 10 periods being continuously formed, and the uppermost layer being a Ta layer (first layer 15a). \ Ta \ ... \ Ta). The metal diffusion region R1 was formed by controlling the power of the ion beam emitted from the ion beam generator.

The metal diffusion region R1 formed in the phase shift film 15 thus obtained has a total film thickness of one Mo layer (second layer 15b) and one Ta layer (first layer 15a). It was formed at a ratio of about 40%.
The reflectance of the multilayered phase shift film 15 at a wavelength of 13.5 nm was 7.5%. The measured value of the reflectivity acts while changing the phase because the reflectivity of each layer of the Ta layer (first layer 15a) and the Mo layer (second layer 15b) of 10 periods in the phase shift film 15 overlaps. Therefore, it is considered that this is a result of reducing the reflectance at the uppermost layer of the phase shift film 15.
The phase difference of the phase shift film 15 at a wavelength of 13.5 nm was 180 degrees.

  After the prepared reflective mask blank 10 was cleaned by supplying ozone water while irradiating UV, it was confirmed that the reflectance and the phase difference did not change.

<Production of reflective mask>
Next, after forming a resist film with a film thickness of 100 nm on the phase shift film 15 of the reflective mask blank 10 and forming a resist pattern by drawing / development, this resist pattern is used as a mask, and a fluorine-based SF ₆ gas is used. Was used to dry-etch the phase shift film 15 to form a phase shift film pattern. Thereafter, the resist pattern was removed to produce a reflective mask.
After the prepared reflective mask is cleaned by supplying ozone water while irradiating UV, the reflectance and the phase difference are not changed, and the side wall of the phase shift film pattern before and after the cleaning. It was confirmed that there was no change.
Further, when a defect inspection on the surface of the reflective mask was performed on a 132 nm × 132 nm region excluding the peripheral region of the mask using a mask defect inspection apparatus (Teron610: manufactured by KLA-Tencor), a defect was found. The number was three. The defect inspection was carried out under inspection sensitivity conditions capable of detecting a defect of 70 nm size in terms of SEVD (Sphere Equivalent Volume Diameter). SEVD is the length of the diameter when the defect is assumed to be hemispherical.

Reference Example 1
A reflective mask blank was produced in the same manner as in Example 1 except that the metal diffusion region was not formed in the phase shift film.
When forming the Mo layer (second layer 15b), the beam is irradiated only to the Mo target, and when forming the Ta layer (first layer 15a), the beam is irradiated only to the Ta target, and the total film thickness is 48 nm. Then, a phase shift film was formed. The reflectance of the phase shift film at a wavelength of 13.5 nm was 7.5%, and the phase difference of the phase shift film 15 at the wavelength of 13.5 nm was 180 degrees.

Next, a reflective mask was produced by the same method as in Example 1 using the obtained reflective mask blank.
The manufactured reflective mask was cleaned by supplying ozone water while irradiating UV, and then subjected to defect inspection under the same inspection conditions using the same mask defect inspection apparatus as in Example 1. The number of defects was 8. In Reference Example 1, the number of defects increased compared to Example 1 because the metal diffusion region was hardly formed near the interface between the Mo layer and the Ta layer in the phase shift film. In this case, the cleaning resistance of Mo which is easily oxidized cannot be improved by Ta having excellent cleaning resistance. Therefore, Mo is dissolved by the cleaning liquid, and the dissolved matter is minutely formed on the phase shift film. It is thought that it became a foreign body.

Example 2
A reflective mask blank is produced by the same method as in Example 1 except that the formation ratio of the metal diffusion region formed in the phase shift film is 25%, and the reflective mask is used by using this reflective mask blank. Was made.
The processability during the production of the reflective mask was good.
Further, when the defect inspection of the surface of the reflective mask was performed by the same method as in Example 1, the number of defects was 5.

Example 3
A reflective mask blank is produced by the same method as in Example 1 except that the formation ratio of the metal diffusion region formed in the phase shift film is 80%, and the reflective mask is used by using this reflective mask blank. Was made.
The processability during the production of the reflective mask was good.
Further, when the defect inspection of the surface of the reflective mask was performed by the same method as in Example 1, the number of defects was one.

Example 4
The Mo layer constituting the phase shift film is replaced with a Ru layer. First, a Ta layer (first layer 15a) is formed to a thickness of 1.9 nm, and then a Mo layer (second layer 15b) is formed. The film was formed with a film thickness of 1.9 nm (film thickness ratio 1: 1). With this as one cycle, the film structure of the phase shift film 15 having a total film thickness of 39.9 nm, in which a Ta layer (first layer 15a) is formed as the uppermost layer after film formation for 10 cycles, is Ta \ Ru. A reflective mask blank was produced in the same manner as in Example 1 except that \ Ta \ Ru \ ... \ Ta.

The total film thickness of one Ta layer (first layer 15a) and one Ru layer (second layer 15b) in the metal diffusion region R1 formed in the phase shift film 15 thus obtained. Formed at a ratio of about 40%.
The reflectance of the multilayered phase shift film 15 at a wavelength of 13.5 nm was 7.5%.
The phase difference of the phase shift film 15 at a wavelength of 13.5 nm was 180 degrees.

Next, a reflective mask was produced by the same method as in Example 1 using the obtained reflective mask blank.
The etching rate by dry etching during the production of the reflective mask was 10 nm / min, and the workability was good.

Reference Example 2
A reflective mask blank was produced in the same manner as in Example 2 except that the metal diffusion region was not formed in the phase shift film.
When the Ru layer (second layer 15b) is formed, the beam is irradiated only to the Ru target, and when the Ta layer (first layer 15a) is formed, the beam is irradiated only to the Ta target. A phase shift film was formed at .9 nm. The reflectance of the phase shift film at a wavelength of 13.5 nm was 7.5%, and the phase difference of the phase shift film 15 at the wavelength of 13.5 nm was 180 degrees.

Next, a reflective mask was produced by the same method as in Example 1 using the obtained reflective mask blank.
The etching rate by dry etching during the production of the reflective mask was 0.5 nm / min, and the workability was poor.

Example 5 FIG.
A reflective mask blank is produced by the same method as in Example 4 except that the formation ratio of the metal diffusion region formed in the phase shift film is 25%, and the reflective mask is used by using this reflective mask blank. Was made.
The etching rate by dry etching during the production of the reflective mask was 5 nm / min, and the workability was good.

<Thickness dependence of retardation and reflectivity of phase shift film (Mo \ Ta)>
For a reflective mask blank having the same phase shift film (Mo \ Ta \ Mo \ Ta ... \ Ta: 10 cycles) as in Example 1 above, the phase shift film (film) in EUV light (wavelength 13.5 nm) (Thickness: 40 nm to 60 nm) and the film thickness dependence of the reflectivity was examined. The result is indicated by “10P” in FIGS. 4 and 5.
On the other hand, EUV light (wavelength) is also applied to the reflective mask blank by the same method as in Reference Example 1 except that the phase shift film has a single cycle (Mo \ Ta, film thickness ratio of 1: 1). 13.5 nm), the phase difference of the phase shift film (film thickness: 40 nm to 60 nm) and the film thickness dependence of the reflectance were examined. The result is indicated by “1P” in FIGS. 4 and 5. “1P” is assumed to be “a two-layer film composed of a Mo layer and a Ta layer” disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2004-207593).

First, referring to FIG. 4, whether “10P” and “1P” have the film dependency of the phase difference is confirmed.
The phase difference graph of “10P” shows a gentle waveform with little undulation in the film thickness range of 40 nm to 60 nm. In particular, at a phase difference of 180 degrees, the film thickness is between about 47 nm and about 50 nm. A linear flat region A was confirmed in a range of about 3 nm. The flat region A indicates that the phase difference does not depend on the film thickness. In particular, the phase shift film set in the film thickness range of the flat region A obtains an excellent phase shift effect with the phase difference 180. It also shows that you can.
On the other hand, the phase difference graph of “1P” shows a waveform with a larger waviness than the graph of phase difference of “10P” in the film thickness range of 40 nm to 60 nm. The change area of the shape could not be confirmed.
Such a difference in effect between the two is considered to be based on a difference in configuration between the two.

Next, referring to FIG. 5, the presence / absence of the dependency of reflectance on the film is confirmed for “10P” and “1P”.
The reflectance graph of “10P” shows a gentle waveform with little undulation in the film thickness range of 40 nm to 60 nm. In particular, in the narrow range of the reflectance of 8% or less, the film thickness about the flat region A is about. In the range of about 3 nm, 47 nm and film thickness of about 50 nm, a substantially flat region B having a gentle curved shape close to the linear shape was confirmed although it was not a linear shape. This substantially flat region B indicates that the reflectance does not depend on the film thickness. In particular, the phase shift film set in the film thickness range of the substantially flat region B has a very narrow range with a reflectance of 8% or less. However, the reflectivity is almost constant.
On the other hand, the phase difference graph of “1P” shows a waveform with a larger waviness than the graph of phase difference of “10P” in the film thickness range of 40 nm to 60 nm. A linear change region could not be confirmed. Further, in the film thickness range of the substantially flat region B, the reflectance that varies greatly between 7% and 10% is shown.
Such a difference in effect between the two is considered to be based on a difference in configuration between the two.

  As described above, “10P” has a flat region A that does not depend on the film thickness at a phase difference of 180 degrees, and a substantially flat region B that does not depend on the film thickness in a very narrow range with a reflectance of 8% or less. Have. From this result, “10P” having the same film configuration as in Example 1 indicates that the reflective mask blank according to the present invention has excellent optical characteristics in EUV light (wavelength 13.5 nm). Yes.

  DESCRIPTION OF SYMBOLS 10 ... Reflective type mask blank, 12 ... Substrate, 13 ... Multi-layer reflective film, 14 ... Protective film, 15 ... Phase shift film, 15a ... First layer, 15b ... Second layer, R1, R2 ... Metal diffusion region, A: flat region, B: substantially flat region.

Claims (11)

A reflective mask blank in which a multilayer reflective film and a phase shift film for shifting the phase of EUV light are formed in this order on a substrate,
The phase shift film is a multilayer film including one or more first layers and one or more second layers,
The first layer includes a metal material selected from metal materials having a refractive index n of 0.95 or less at a wavelength of 13.5 nm,
The second layer includes a metal material selected from a metal material different from the first layer among metal materials having a refractive index n of 0.95 or less at a wavelength of 13.5 nm,
A metal diffusion region is formed at a ratio of 25% or more with respect to the total film thickness of the first layer and the second layer at and near the interface between the first layer and the second layer. Reflective mask blank characterized by being made. The first layer includes a metal material of any one of Ta and Cr,
2. The reflective mask blank according to claim 1, wherein the second layer includes a kind of metal material having a refractive index n at a wavelength of 13.5 nm smaller than any of Ta and Cr.   The reflective mask blank according to claim 2, wherein the second layer contains Mo.   When the protective film is provided between the multilayer reflective film and the phase shift film, and the protective film is formed of a material containing Ru as a main component, the lowermost layer of the phase shift film is the second layer. The reflective mask blank according to claim 3, wherein the reflective mask blank is a layer.   3. The reflective mask blank according to claim 2, wherein the second layer includes any one metal material of Ru, Pt, Pd, Ag, and Au.   When a protective film is provided between the multilayer reflective film and the phase shift film, and the protective film is formed of a material containing Ru as a main component, the lowermost layer of the phase shift film is the first layer The reflective mask blank according to claim 5, wherein the reflective mask blank is a layer.   The reflective mask blank according to claim 1, wherein the first layer is an uppermost layer of the phase shift film.   The reflective mask blank according to any one of claims 1 to 7, wherein the thickness of the phase shift film is 50 nm or less.   A reflection comprising a phase shift film pattern forming step of forming a phase shift film pattern by patterning the phase shift film formed of the multilayer film in the reflective mask blank according to claim 1. Mold mask manufacturing method.   A reflective mask having a phase shift film pattern in which the phase shift film formed of a multilayer film in the reflective mask blank according to claim 1 is patterned.   A method for manufacturing a semiconductor device, comprising: a pattern forming step of forming a pattern on a semiconductor substrate using the reflective mask according to claim 10.

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