JP2010045211A - Method of manufacturing reflective mask for euv lithography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a reflective mask for EUVL which is excellent in size controllability of a resist pattern. <P>SOLUTION: The method of manufacturing the reflective mask for EUV lithography (EUVL) includes: a step of manufacturing a reflective mask for EUVL which has a portion where a reflective layer for reflecting EUV light is formed and an absorber layer for absorbing the EUV light is formed on the reflective layer and a portion where the absorber layer is not formed on the reflective layer, on a substrate, the portion having the absorber layer formed on the reflective layer is the non-opening of a mask pattern and the portion not having the absorber layer formed on the reflective layer is the opening of the mask pattern; a step of forming a resist pattern on a wafer using the reflective mask for EUVL; a step of measuring the space width (or line width) of the resist pattern; a step of comparing the measured value of the space width (or line width) of the resist pattern with a design value; and a step of locally heating part of the opening of the mask pattern of the reflective mask for EUVL. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a reflective mask for EUV lithography.

Conventionally, in lithography technology, an exposure apparatus for manufacturing an integrated circuit by transferring a fine circuit pattern onto a wafer has been widely used. As integrated circuits become highly integrated, faster, and more functional, miniaturization of integrated circuits advances, and the exposure apparatus is required to image a high-resolution circuit pattern on the wafer surface with a deep focal depth. The wavelength of the exposure light source is being shortened. As an exposure light source, an ArF excimer laser (wavelength 193 nm) has started to be used further from the conventional g-line (wavelength 436 nm), i-line (wavelength 365 nm), and KrF excimer laser (wavelength 248 nm). Further, in order to cope with next-generation integrated circuits whose circuit line width is 100 nm or less, it is considered promising to use an F ₂ laser (wavelength 157 nm) as an exposure light source. It can only be covered.

  In such a technical trend, a lithography technique using EUV light as an exposure light source for the next generation is considered to be applicable over a plurality of generations of 45 nm and after, and has attracted attention. EUV light refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, specifically, light having a wavelength of about 0.2 to 100 nm. At present, the use of 13.5 nm as a lithography light source is being studied. The exposure principle of this EUV lithography (hereinafter abbreviated as “EUVL”) is the same as that of conventional lithography in that the mask pattern is transferred using a projection optical system, but light is transmitted in the EUV light energy region. Since there is no material to be used, the refractive optical system cannot be used, and a reflective optical system is used.

  The EUVL mask is formed using a mask blank having a structure in which a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed in this order on a substrate such as glass. Specifically, it is created by patterning the absorber layer of the mask blank (by removing a part of the absorber layer to form a mask pattern). Here, a portion where the absorber layer is removed and the reflective layer is exposed forms an opening portion of the mask pattern, and a portion where the absorber layer is not removed forms a non-opening portion of the mask pattern.

As the reflective layer of the EUVL mask, the peak reflectivity in the EUV wavelength region when the layer surface is irradiated with light in the wavelength region of EUV light is increased by alternately laminating high refractive layers and low refractive layers. A multilayer reflective film is usually used. For the absorber layer, a material having a high absorption coefficient for EUV light, specifically, a material mainly composed of Cr or Ta, for example, is used.
The EUVL mask may have only a reflective layer and an absorber layer, but usually further includes other layers. For example, a protective layer for preventing oxidation of the reflective layer surface may be formed on the reflective layer. In addition, a buffer layer may be provided on the reflective layer in order to prevent the reflective layer from being damaged by an etching process performed for the purpose of patterning the absorber layer. Note that in the case where the protective layer can serve as a buffer layer, a single film may be provided as a protective layer that also serves as the buffer layer. When these layers are included, the reflective portion of the EUVL mask is in a state where the protective layer and the buffer layer are exposed instead of the reflective layer.
Further, in order to increase the contrast at the time of inspection of the mask pattern, that is, the reflectance difference between the opening portion and the non-opening portion of the mask for EUVL in the wavelength region of the inspection light of the mask pattern, In some cases, an antireflection layer having a low reflectance is formed on the absorber layer. When the EUVL mask has an antireflection layer, the antireflection layer becomes the uppermost layer of the non-reflection portion.

Using such an EUVL mask and a reflective exposure apparatus, when the mask pattern of the EUVL mask is transferred to a resist film formed on a silicon wafer, the mask pattern is formed on the resist film. There has been a problem in that a dimension of a transfer pattern (hereinafter referred to as a “resist pattern”) (space width (or line width) of the resist pattern) may deviate from a design value.
One of the causes of the deviation of the resist pattern dimension from the design value is flare in the projection optical system of the EUVL exposure apparatus. Patent Document 1 points out the influence of flare on a transferred image and proposes an improvement method. In Patent Document 1, the influence of flare on a transferred image is described as follows.
Flare is generated by the undulation of the surface shape of the mirror constituting the exposure machine. The space width (or line width) of the resist pattern varies depending on the flare, and if there is flare, the space width (or line width) of the resist pattern increases. However, the amount of flare depends on the mask pattern density, and there is almost no flare in the case of a mask in which there is almost no reflection pattern (a portion where there is no absorption layer and the protective layer is exposed). For this reason, the deviation of the pattern dimension due to flare depends on the reflection pattern density. Within the surface of the reticle, there are a mixture of reflective patterns (parts where there is no absorbing layer and the protective layer is exposed) and non-reflective patterns (parts where the absorbing layer or its anti-reflection film is exposed covering the reflective layer and protective layer), The area ratio is not constant throughout the surface, and a portion where the ratio of the reflection pattern is large and a portion where the reflection pattern is small are mixed, resulting in a distribution in the amount of flare. That is, where the reflection pattern ratio is large, the flare is large and the deviation of the space width (or line width) of the resist pattern is large. On the other hand, the flare is small in the portion where the reflection pattern ratio is small, and the deviation of the space width (or line width) of the resist pattern is small. As a result, the amount of change in the space width (or line width) of the resist pattern due to flare differs within the exposure field, which is a problem.
As a method for improving such a change in the space width (or line width) of the resist pattern, Patent Document 1 proposes to provide a reflectance adjustment means in the reflective pattern portion. Specifically, it has been proposed to adjust the reflectance by two methods so that the dimensional change due to flare is minimized after pattern formation with a reticle having a conventional configuration. That is, (1) forming a reflectance adjustment layer (reflectance attenuation layer) in the reflection pattern portion, and (2) adjusting the thickness of the absorber layer (scraping the absorber layer from the surface layer with an ion beam or the like). is suggesting.

JP 2007-201306 A

  However, for the purpose of improving the change in the resist pattern dimension (resist pattern space width (or line width)) due to flare, it is necessary to form a reflectance adjustment layer locally on the EUVL mask, and to absorb the absorber layer. It is difficult to adjust the thickness locally in terms of practicality or production efficiency.

  As another cause, when patterning the absorber layer of the EUVL mask blank, a mask pattern having dimensions as designed is formed due to some variation (for example, overetching or overdevelopment). That was not. The deviation of the resist pattern dimension (resist pattern space width (or line width)) due to such a cause is irrelevant to the flare in the projection optical system of the EUVL exposure apparatus. Can not do it.

  SUMMARY OF THE INVENTION In order to solve the above-described problems of the prior art, an object of the present invention is to provide a method for manufacturing an EUVL mask having excellent controllability of resist pattern dimensions (space width (or line width) of a resist pattern). And

In order to achieve the above object, the present invention provides a substrate on which a reflective layer that reflects EUV light is formed, and an absorber layer that absorbs EUV light is formed on the reflective layer; A portion where the absorber layer is not formed on the reflective layer, and a portion where the absorber layer is formed on the reflective layer forms a non-opening portion of the mask pattern, and the absorber is formed on the reflective layer. A step of manufacturing a reflective mask for EUV lithography (EUVL) in which a portion where a layer is not formed forms an opening of a mask pattern;
Measuring the width of the opening of the mask pattern;
A step of comparing the measured value of the width of the opening of the mask pattern with a design value;
Based on the result obtained in the step of comparing the measured value of the width of the opening of the mask pattern and the design value, a part of the opening of the mask pattern of the reflective mask for EUVL is locally heated. And a process for producing a reflective mask for EUVL (a process for producing an EUVL mask according to the present invention (1)).

  In the EUVL mask manufacturing method (1) of the present invention, when there is a portion where the measured value of the width of the opening of the mask pattern is larger than the design value, the portion of the opening of the mask pattern is locally heated. Is preferred.

According to the present invention, a reflective layer that reflects EUV light is formed on a substrate, an absorber layer that absorbs EUV light is formed on the reflective layer, and the absorption layer is formed on the reflective layer. A portion where the body layer is not formed, a portion where the absorber layer is formed on the reflective layer forms a non-opening portion of the mask pattern, and no absorber layer is formed on the reflective layer Producing a reflective mask for EUV lithography (EUVL) in which a portion forms an opening of a mask pattern;
Measuring the width of the non-opening portion of the mask pattern;
A step of comparing the measured value of the width of the non-opening portion of the mask pattern with a design value;
Based on the result obtained in the step of comparing the measured value of the width of the non-opening portion of the mask pattern with the design value, a part of the opening portion of the mask pattern of the reflective mask for EUVL is locally heated. There is provided a method for manufacturing a reflective mask for EUVL (a method for manufacturing a mask for EUVL of the present invention (2)).

  In the EUVL mask manufacturing method (2) of the present invention, when there is a portion where the measured value of the width of the non-opening portion of the mask pattern is smaller than the design value, it is adjacent to the portion of the non-opening portion of the mask pattern. It is preferable to locally heat the opening portion of the mask pattern.

According to the present invention, a reflective layer that reflects EUV light is formed on a substrate, an absorber layer that absorbs EUV light is formed on the reflective layer, and the absorption layer is formed on the reflective layer. A portion where the body layer is not formed, a portion where the absorber layer is formed on the reflective layer forms a non-opening portion of the mask pattern, and no absorber layer is formed on the reflective layer Producing a reflective mask for EUV lithography (EUVL) in which a portion forms an opening of a mask pattern;
Forming a resist pattern on the wafer using the EUVL reflective mask;
Measuring the space width of the resist pattern;
A step of comparing the measured value of the space width of the resist pattern with the design value;
A step of locally heating a part of the opening of the mask pattern of the reflective mask for EUVL based on a result obtained by comparing a measured value of the space width of the resist pattern with a design value; A method for manufacturing a reflective mask for EUVL (a method for manufacturing a mask for EUVL of the present invention (3)) is provided.

  In the EUVL mask manufacturing method (3) of the present invention, when the resist film on the wafer is a positive resist and there is a portion where the measured value of the space width in the resist pattern is larger than the design value, the portion It is preferable that the portion of the opening portion of the mask pattern of the reflective mask for EUVL corresponding to is locally heated.

  In the EUVL mask manufacturing method (3) of the present invention, when the resist film on the wafer is a negative resist and there is a portion where the measured value of the space width in the resist pattern is smaller than the design value, the portion It is preferable that the portion of the opening portion of the mask pattern of the reflective mask for EUVL corresponding to is locally heated.

According to the present invention, a reflective layer that reflects EUV light is formed on a substrate, an absorber layer that absorbs EUV light is formed on the reflective layer, and the absorption layer is formed on the reflective layer. A portion where the body layer is not formed, a portion where the absorber layer is formed on the reflective layer forms a non-opening portion of the mask pattern, and no absorber layer is formed on the reflective layer Producing a reflective mask for EUV lithography (EUVL) in which a portion forms an opening of a mask pattern;
Forming a resist pattern on the wafer using the EUVL reflective mask;
Measuring the line width of the resist pattern;
A step of comparing the measured value of the line width of the resist pattern with the design value;
A step of locally heating a part of the opening of the mask pattern of the reflective mask for EUVL based on a result obtained by comparing a measured value of the line width of the resist pattern with a design value; A method for producing a reflective mask for EUVL (a method for producing an EUVL mask according to the present invention (4)) is provided.

In the manufacturing method (4) of the EUVL mask of the present invention,
The resist film on the wafer is a positive resist,
When there is a portion where the measured value of the line width in the resist pattern is smaller than the design value, it is preferable that the portion of the opening portion of the mask pattern of the reflective mask for EUVL corresponding to the portion is locally heated.

In the manufacturing method (4) of the EUVL mask of the present invention,
The resist film on the wafer is a negative resist,
When there is a portion where the measured value of the line width in the resist pattern is larger than the design value, it is preferable to locally heat the portion of the mask pattern opening portion of the EUVL reflective mask corresponding to the portion.

  In the EUVL mask manufacturing methods (1) to (4) of the present invention, it is preferable to use laser beam or electron beam irradiation for the local heating.

  In the EUVL mask manufacturing methods (1) to (4) of the present invention, it is preferable to use a minute heating member for the local heating.

  Moreover, this invention provides the reflective mask for EUVL manufactured by the manufacturing method (1)-(4) of the EUVL mask of this invention.

  The present invention also provides a semiconductor integrated circuit manufacturing method for manufacturing a semiconductor integrated circuit by exposing an object to be exposed using the EUVL mask of the present invention.

  According to the manufacturing method of the present invention, an EUVL mask having excellent controllability of resist pattern dimensions (resist pattern space width (or line width)) can be obtained.

Hereinafter, the manufacturing method of the mask for EUVL of this invention is demonstrated.
First, the manufacturing method (1) of the EUVL mask of the present invention will be described first.
In the EUVL mask manufacturing method (1) of the present invention, first, a reflective layer for reflecting EUV light is formed on a substrate, and an absorber layer for absorbing EUV light is formed on the reflective layer. An EUVL mask (hereinafter referred to as a “base mask”) having a portion thus formed and a portion where the absorber layer is not formed on the reflective layer is manufactured. FIG. 1 is a schematic cross-sectional view showing an embodiment of a base mask. In the base mask 1 shown in FIG. 1, a reflective layer 3 is formed on a substrate 2. The base mask 1 includes a portion 10 where the absorber layer 4 is formed on the reflective layer 3 and a portion 20 where the absorber layer 4 is not formed on the reflective layer 3. In the part 20, since the absorber layer 4 is not formed, the reflective layer 3 is exposed. In the base mask 1, the arrangement of the part 10 and the part 20 forms a mask pattern. Here, the part 20 forms an opening part of the mask pattern, and the part 10 forms a non-opening part of the mask pattern.

The base mask can be manufactured according to a conventional EUVL mask manufacturing procedure. That is, an EUVL mask blank in which a reflective layer and an absorber layer are formed in this order on a substrate is manufactured, and then the absorber layer of the EUVL mask blank is patterned to absorb on the reflective layer. An EUVL mask having a portion where the body layer is not formed (that is, the mask pattern opening) and a portion where the absorber layer is formed on the reflective layer (that is, the mask pattern non-opening) is obtained.
The base mask may have only the reflective layer and the absorber layer on the substrate, but may further have layers other than those usually provided in the EUVL mask. For example, a protective layer for preventing oxidation of the reflective layer surface may be formed on the reflective layer. In addition, a buffer layer for preventing the reflective layer from being damaged by an etching process performed for the purpose of patterning the absorber layer may be formed on the reflective layer. Further, in order to increase the contrast at the time of inspection of the mask pattern, an antireflection layer having a low reflectance in the wavelength region of the inspection light of the mask pattern may be formed on the absorber layer.

[substrate]
The substrate is required to satisfy the characteristics of the EUVL mask as a substrate. Therefore, the substrate preferably has a low thermal expansion coefficient (average thermal expansion coefficient is 0 ± 30 ppb / ° C., particularly 0 ± 20 ppb / ° C., more preferably 0 ± 15 ppb / ° C., and the overall spatial variation of the thermal expansion coefficient ( Total spatial variation) is 0 ± 10 ppb / ° C., in particular 0 ± 6 ppb / ° C., further 0 ± 4 ppb / ° C.), and smoothness, flatness, and cleaning liquid used for mask blank manufacturing or after patterning The thing excellent in tolerance to is preferable. As the substrate, specifically, glass having a low thermal expansion coefficient, for example, SiO ₂ —TiO ₂ glass or the like is used. However, the substrate is not limited thereto, and crystallized glass, quartz glass, silicon or metal on which β quartz solid solution is precipitated is used. A substrate such as can also be used. A film such as a stress correction film may be formed on the substrate.
It is preferable that the substrate has a smooth surface of 0.15 nm rms or less and a flatness of 100 nm or less because high reflectivity and high transfer accuracy can be obtained in the EUVL mask after manufacture.
The size, thickness, and the like of the substrate are appropriately determined depending on the design value of the manufactured EUVL mask. For example, an example is a substrate having an outer shape of 6 inches (152.4 mm) square and a thickness of 0.25 inches (6.3 mm).
It is preferable that no defects exist on the surface (film formation surface) of the substrate on which the multilayer reflective film is formed. However, even if it exists, the depth of the concave defect and the height of the convex defect are not more than 2 nm so that the phase defect does not occur due to the concave defect and / or the convex defect. It is preferable that the half width (FWHM (full width of half maximum)) of the defect and the convex defect is 60 nm or less.

[Reflective layer]
The reflective layer is not particularly limited as long as it has desired characteristics as the reflective layer of the EUVL mask. Here, the characteristic particularly required for the reflective layer is that the peak reflectance in the EUV wavelength region is high. Specifically, the peak reflectivity in the EUV wavelength region is preferably 60% or more and preferably 64% or more when the reflection layer surface is irradiated with light in the EUV light wavelength region at an incident angle of 6 degrees. Is more preferable.

  Since the reflective layer can achieve a high EUV light reflectance, a multilayer reflective film in which a high refractive layer and a low refractive index layer are alternately laminated a plurality of times is usually used. In the multilayer reflective film as the reflective layer, Si (refractive index at a wavelength of 13.5 nm = 0.999) is widely used for the high refractive index layer, and Mo (same refractive index = 0.924) for the low refractive index layer. Is widely used. That is, the Mo / Si multilayer reflective layer is the most common. However, the multilayer reflective film is not limited to this, and Ru / Si multilayer reflective film, Mo / Be multilayer reflective film, Rh / Si multilayer reflective film, Pt / Si multilayer reflective film, Mo compound / Si compound multilayer reflective film, Si / Mo / Ru multilayer reflective film, Si / Mo / Ru / Mo multilayer reflective film, Si / Ru / Mo / Ru multilayer reflective film, and the like can also be used.

  The thickness of each layer constituting the multilayer reflective film and the number of repeating units of the layers can be appropriately selected according to the film material to be used and the peak reflectance in the EUV wavelength region required for the multilayer reflective film. Taking a Mo / Si multilayer reflective film as an example, in order to obtain a multilayer reflective film having a peak reflectivity in the EUV wavelength region of 60% or more, a Si layer having a thickness of 4.5 ± 0.1 nm, and a thickness of 2. What is necessary is just to laminate | stack Mo layer of 3 +/- 0.1nm in this order so that a repeating unit number may be set to 30-60.

In addition, what is necessary is just to form each layer which comprises the multilayer reflective film which comprises a reflective layer so that it may become desired thickness using well-known film-forming methods, such as a magnetron sputtering method and an ion beam sputtering method. For example, when forming a Mo / Si multilayer reflective film by using an ion beam sputtering, using a Si target as the target, as a sputtering gas, an inert gas, such as argon (Ar) gas (gas pressure 1.3 × 10 ^{- 2} Pa to 2.7 × 10 ⁻² Pa), and an Si acceleration film having a thickness of 4.5 nm at an ion acceleration voltage of 300 to 1500 V and a film formation rate of 0.03 to 0.30 nm / sec. and film, then using using a Mo target as the target and an inert gas as a sputtering gas, e.g., argon (Ar) gas (gas pressure ^{1.3 × 10 -2 Pa~2.7 × 10 -2} Pa) Then, it is preferable to form the Mo film so that the thickness is 2.3 nm at an ion acceleration voltage of 300 to 1500 V and a film formation rate of 0.03 to 0.30 nm / sec. With this as one period, the Mo / Si multilayer reflective film is formed by laminating the Si film and the Mo film for 40 to 50 periods.

[Protective layer]
A protective layer can be provided on the multilayer reflective film in order to prevent the surface of the multilayer reflective film forming the reflective layer and the vicinity thereof from being naturally oxidized during storage or oxidized during cleaning. As the protective layer, Si, Ru, Rh, C, SiC, a mixture of these elements, or a material obtained by adding nitrogen, boron, or the like to these elements can be used. The use of Ru as the protective layer is particularly preferable because it can also function as a buffer layer described later. When Si is used as the protective layer, when the multilayer reflective film is made of Mo / Si, the uppermost layer can be made to function as a protective layer by making the uppermost layer an Si film. In that case, the thickness of the uppermost Si film that also serves as a protective layer is preferably 5 to 15 nm, which is thicker than the usual 4.5 nm. Further, after forming a Si film as a protective layer, a Ru film serving as both a protective layer and a buffer layer may be formed on the Si film.
The film such as the multilayer reflective film or the protective layer is not necessarily one layer, and may be two or more layers.
When a protective layer is provided on the multilayer reflective film, the peak reflectance in the EUV wavelength region in the protective layer needs to satisfy the above range.

[Buffer layer]
An etching process, usually a dry etching process, is used when patterning the absorber layer of the mask blank to create a base mask. In order to prevent the multilayer reflective film as the reflective layer from being damaged by this etching process, a buffer layer that serves as an etching stopper is provided as a multilayer reflective film (when a protective layer is formed on the multilayer reflective film) You may provide between a protective layer) and an absorber layer. Therefore, as the material of the buffer layer, a material that is not easily affected by the etching process of the absorber layer, that is, the etching rate is slower than that of the absorber layer and is not easily damaged by the etching process is selected. Examples of the material satisfying this condition include Cr, Al, Ru, Ta, and nitrides thereof, and SiO ₂ , Si ₃ N ₄ , Al ₂ O _3, and mixtures thereof. Among these, Ru, CrN and SiO ₂ are preferable, CrN and Ru are more preferable, and Ru is particularly preferable because it has the functions of a protective layer and a buffer layer.
The thickness of the buffer layer is preferably 1 to 60 nm.

The buffer layer is formed using a known film formation method such as a magnetron sputtering method or an ion beam sputtering method. When forming the Ru film by a magnetron sputtering method, using a Ru target as the target, the inert gas as a sputtering gas, such as argon (Ar) gas (gas pressure ^{1.0 × 10 -1 Pa~10 × 10 -1} Pa ) Is preferably used to form a film having a film thickness of 2 to 5 nm at an input power of 30 to 500 W and a film formation speed of 5 to 50 nm / min.

[Absorber layer]
The characteristic particularly required for the absorber layer is that the reflectance in the EUV wavelength region is somewhat low. Specifically, it is preferable that the peak reflectance in the EUV wavelength region is 5% or less when light in the wavelength region of EUV light is irradiated onto the absorber layer surface at an incident angle of 6 to 8 degrees.
The absorber layer is made of a material having a high absorption coefficient for EUV light. Specifically, the absorber layer contains a film containing Cr or Ta, for example, a film containing a nitride of Cr or Ta, or contains Ta and Hf. Examples thereof include a film (TaBN film or TaHf film).
The film thickness of the absorber layer is such that the reflected light from the absorber layer and the reflected light from the multilayer reflective film forming the reflective layer (if a protective layer is formed on the multilayer reflective film, the reflected light from the protective layer) ) May be suitably adjusted so as to ensure the strength ratio, and is preferably 10 to 100 nm. The absorber layer may be a single layer or a plurality of layers.

The absorber layer is not particularly limited as long as the above characteristics are satisfied. Among them, a film containing Ta, preferably a TaHf film or a TaN film, has an amorphous crystal state and excellent surface smoothness of the absorber layer. To preferred. When the surface roughness of the absorber layer is large, the edge roughness of the mask pattern formed on the absorber layer increases, and not only the dimensional accuracy of the resist pattern formed using the EUVL mask deteriorates, but also scattering. Light (commonly referred to as flare) and pattern contrast in EUVL, that is, the peak reflectance in the EUV wavelength region in the non-opening 10 and the EUV in the opening 20 when the base mask 1 shown in FIG. The contrast with the peak reflectance in the wavelength region is lowered. This also deteriorates the dimensional accuracy of the resist pattern formed using the EUVL mask. Since these problems become conspicuous as the mask pattern becomes finer, the surface of the absorber layer is required to be smooth.
If the absorber layer is a film containing Ta (for example, TaHf film, TaN film, etc.), it becomes a film having an amorphous structure or a microcrystalline structure. Therefore, the surface roughness of the surface of the absorber layer is 0.5 nm rms or less. Since the layer surface is sufficiently smooth, there is no risk that the dimensional accuracy of the resist pattern formed using the EUVL mask will be deteriorated due to the effect of edge roughness, and scattering due to the surface roughness of the absorber layer surface Light can be suppressed to an extent that there is no problem. The surface roughness of the absorber layer surface is more preferably 0.4 nm rms or less, and further preferably 0.3 nm rms or less.

Note that in this specification, the phrase “crystalline state is amorphous” includes a microcrystalline structure other than an amorphous structure having no crystal structure. If it is a film having an absorption film body layer, an amorphous structure or a microcrystalline structure, the surface of the absorber layer is excellent in smoothness.
In addition, it can be confirmed by an X-ray diffraction (XRD) method that the crystalline state of the absorber layer is amorphous, that is, an amorphous structure or a microcrystalline structure. If the crystalline state of the absorber layer is an amorphous structure or a microcrystalline structure, a sharp peak is not observed in a diffraction peak obtained by XRD measurement.

When the absorber layer is a TaHf film, it is preferable to contain Ta and Hf in specific ratios described below.
It is preferable that the content of Hf in the absorber layer is 20 to 60 at% because the crystalline state of the absorber layer is likely to be amorphous and the surface of the absorber layer is excellent in smoothness. In addition, it has excellent characteristics as an absorber layer of an EUVL mask, such that the reflectance in the EUV wavelength region and the reflectance in the wavelength region of pattern inspection light can be made relatively low with a thinner film thickness.
As for the content rate of Hf of an absorber layer, it is more preferable that it is 30-50 at%, and it is further more preferable that it is 30-45 at%.

  In the absorber layer, the remainder excluding Hf is preferably Ta. Therefore, the Ta content in the absorber layer is preferably 40 to 80 at%. As for the content rate of Ta in an absorber layer, it is more preferable that it is 50-70 at%, and it is further more preferable that it is 55-70 at%.

  In the absorber layer, the composition ratio of Ta and Hf is more preferably 7: 3 to 4: 6, further preferably 6.5: 3.5 to 4.5: 5.5, 6 : It is more preferable that it is 4-5: 5.

The TaHf film can be formed by performing a sputtering method using a TaHf compound target, for example, a magnetron sputtering method or an ion beam sputtering method, in an inert gas (eg, argon (Ar) gas) atmosphere.
The TaHf compound target has a composition of Ta = 30 to 70 at% and Hf = 70 to 30 at%, so that an absorber layer having a desired composition can be obtained, and variations in film composition and film thickness are avoided. It is preferable in that it can be performed.

In order to form the TaHf film by the above-described method, specifically, it may be carried out under the following film formation conditions.
Sputtering gas: Ar gas (gas pressure ^{1.0 × 10 -1 Pa~50 × 10 -1} Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably 1.0 × 10 ^-1 Pa to 30 x 10 ^-1 Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 2.0-60 nm / min, preferably 3.5-45 nm / min, more preferably 5-30 nm / min

When the absorber layer is a TaN film, it is preferable to contain Ta and N at a specific ratio described below.
The N content of the TaN film is preferably 10 at% or more and less than 50 at%. In the present invention, when the TaN film contains Ta and N at a specific ratio, the crystalline state becomes amorphous.

[Antireflection layer]

In the mask blank used for manufacturing the base mask, an antireflection layer having a low reflectance in the wavelength region of the inspection light used for inspection of the mask pattern may be provided on the absorber layer.
After manufacturing the EUVL mask, it is inspected whether the mask pattern is formed as designed. In the inspection of the mask pattern, it is expected that an inspection machine that uses ultraviolet light having a normal wavelength of 257 nm as inspection light and in the future using ultraviolet light having a wavelength of 190 to 200 nm will be used. That is, the inspection is performed using the difference in reflectance between the opening portion and the non-opening portion of the mask pattern in the wavelength region of the inspection light. Hereinafter, in this specification, inspection light used for inspection of a mask pattern is referred to as pattern inspection light.
If the difference in reflectance between the opening portion and the non-opening portion of the mask pattern in the wavelength region of the pattern inspection light is small, the contrast at the time of inspection deteriorates and accurate inspection cannot be performed.
As shown in FIG. 1, in the opening 20 of the mask pattern, the absorber layer 4 is not formed on the reflective layer 3, and the reflective layer (multilayer reflective film) 3 is exposed. However, when a protective layer is formed on the reflective layer 3, the protective layer is exposed. Therefore, the reflectance at the opening 20 of the mask pattern is the reflectance at the reflective layer (multilayer reflective film) 3, and when the protective layer is formed on the reflective layer 3, the reflectance at the protective layer. . On the other hand, the reflectance at the non-opening portion 10 of the mask pattern is the reflectance at the absorber layer 4, and when the antireflection layer is formed on the absorber layer 4, the reflectance at the antireflection layer.

  The absorber layer containing Ta has a relatively low reflectance in the EUV wavelength region and has excellent characteristics as an absorber layer of the EUVL mask blank, but the reflectance in the wavelength region of the pattern inspection light is not necessarily limited. It's not low enough. As a result, the difference in reflectance between the opening portion and the non-opening portion of the mask pattern in the wavelength region of the pattern inspection light becomes small, and there is a possibility that sufficient contrast at the time of inspection cannot be obtained. Therefore, it is preferable to form an antireflection layer having a low reflectance in the wavelength region of the inspection light on the absorber layer containing Ta. If the antireflection layer is formed on the absorber layer, the reflectance in the wavelength region of the pattern inspection light at the non-opening portion of the mask pattern becomes extremely low, and the contrast at the time of inspection becomes good. In addition, it is preferable that the contrast of the reflectance of the opening part of a mask pattern in a wavelength range of pattern inspection light and a non-opening part is 30% or more.

In this specification, the contrast can be obtained using the following equation.
Contrast (%) = ((R ₂ −R ₁ ) / (R ₂ + R ₁ )) × 100
Here, R ₂ is the reflectance at the opening 20 of the mask pattern, and is the reflectance at the reflective layer (multilayer reflective film) 3 in the case of the base mask 1 shown in FIG. When a protective layer is formed on the reflective layer 3, the reflectance is the protective layer. R ₁ is the reflectance at the non-opening portion 10 of the mask pattern, and is the reflectance at the absorber layer 4 in the case of the base mask 1 shown in FIG. When an antireflection layer is formed on the absorber layer 4, the reflectance is the antireflection layer. In order to obtain the contrast of the base mask 1, when the reflective layer (multilayer reflective film) 3 is formed on the substrate 2 in the process of creating the mask blank, the reflectance at the reflective layer 3 is measured. R ₂ may be obtained. When a protective layer is formed on the reflective layer 3, R ₂ may be obtained by measuring the reflectance at the time when the protective layer is formed. Then, when the absorber layer 4 is formed, R ₁ may be obtained by measuring the reflectance at the absorber layer 4. Further, after patterning the absorber layer of the mask blank to form a base mask, the reflectance at the non-opening portion 10 of the mask pattern and the reflectance at the opening portion 20 of the mask pattern are respectively measured, R ₁ , R ₂ may be obtained.
In the present invention, the contrast represented by the above formula in the wavelength region of the pattern inspection light is more preferably 45% or more, further preferably 60% or more, and particularly preferably 80% or more.

  The reflectance (peak reflectance) in the wavelength region of the pattern inspection light when the surface of the reflection layer (multilayer reflective film) is irradiated with light in the wavelength region of the pattern inspection light at an incident angle of about 10 degrees depends on the material. 60 to 70%. Even when a protective layer is formed on the reflective layer, the reflectance in the wavelength region of the pattern inspection light in the protective layer is within the above range. Therefore, in order to set the contrast represented by the above formula in the wavelength region of the pattern inspection light to 30% or more, the reflectance (peak reflectance) in the wavelength region of the pattern inspection light in the antireflection layer is 20% or less. It is preferable that it is 10% or less.

  When the antireflection layer is formed on the absorber layer, the total film thickness of the absorber layer and the antireflection layer is preferably 20 to 100 nm. However, if the film thickness of the antireflection layer is larger than the film thickness of the absorber layer, the EUV light absorption characteristics of the absorber layer may be lowered. In general, the etching rate of the antireflection layer is the etching rate of the absorber layer. Since the etching of the antireflection layer becomes rate-determining later when the absorber layer is patterned, the thickness of the antireflection layer is preferably smaller than that of the absorber layer and as thin as possible. For this reason, it is preferable that the film thickness of an antireflection layer is 1-30 nm, and it is more preferable that it is 2-10 nm.

  In order to achieve the above characteristics, the antireflection layer is preferably made of a material having a higher refractive index in the wavelength region of pattern inspection light than a film containing Ta, and its crystal state is preferably amorphous.

  The antireflection layer formed on the absorber layer containing Ta is preferably an oxide film, an oxynitride film, or a nitride film. Specifically, when a TaHf film is used as the absorber layer, it is preferable to use a TaHfO film as the antireflection layer, and it is preferable to contain Ta, Hf and O in a specific ratio described below.

  The TaHfO film preferably has a total content of Ta and Hf of 30 to 80 at% and a composition ratio of Ta and Hf of 8: 2 to 4: 6. When the total content of Ta and Hf is less than 30 at%, the conductivity of the TaHfO film is lowered, and there is a possibility that a charge-up problem occurs when drawing an electron beam. When the total content of Ta and Hf is more than 80 at%, the reflectance (peak reflectance) in the wavelength region of the pattern inspection light cannot be sufficiently lowered. Further, when Hf is lower than the above composition ratio, the crystalline state is unlikely to be amorphous. When Hf is higher than the above composition ratio, the etching characteristics may be deteriorated and the required etching selectivity may not be satisfied.

  The O content in the TaHfO film is preferably 20 to 70 at%. When the O content is lower than 20 at%, the reflectance (peak reflectance) in the wavelength region of the pattern inspection light may not be sufficiently lowered. When the content of O is higher than 70 at%, the acid resistance is lowered, the low anti-insulation property is increased, and there is a possibility that problems such as charge-up occur when drawing an electron beam.

  The total content of Ta and Hf in the TaHfO film is more preferably 35 to 80 at%, and further preferably 35 to 75 at%. The composition ratio of Ta and Hf is more preferably Ta: Hf = 7: 3 to 4: 6, further preferably 6.5: 3.5 to 4.5: 5.5, More preferably, it is 6: 4-5: 5. The content of O is more preferably 20 to 65 at%, and further preferably 25 to 65 at%.

The TaHfO film may contain elements other than Ta, Hf, and O as necessary. In this case, the element to be included in the TaHfO film needs to satisfy suitability as a mask blank, such as EUV light absorption characteristics.
An example of an element that can be included in the TaHfO film is N. In this case, it is considered that the surface smoothness is improved when the TaHfO film contains N.
When the TaHfO film contains N (that is, a TaHfON film), the total content of Ta and Hf is 30 to 80 at%, and the composition ratio of Ta and Hf is Ta: Hf = 8: 2 to 4: 6, the total content of N and O is preferably 20 to 70 at%, and the composition ratio of N and O is preferably 9: 1 to 1: 9. If the total content of Ta and Hf is less than 30 at%, the conductivity is lowered, and there is a possibility that a charge-up problem occurs when drawing an electron beam. When the total content of Ta and Hf is more than 80 at%, the reflectance (peak reflectance) in the wavelength region of the pattern inspection light cannot be sufficiently lowered. When Hf is lower than the above composition ratio, the crystal state may not be amorphous. When Hf is higher than the above composition ratio, the etching characteristics may be deteriorated and the required etching selectivity may not be satisfied. Further, when the N and O content is lower than 20 at%, there is a possibility that the reflectance (peak reflectance) in the wavelength region of the pattern inspection light cannot be sufficiently lowered. When the content ratio of N and O is higher than 70 at%, the acid resistance is lowered, the insulation property is increased, and there is a possibility that problems such as charge-up occur when drawing an electron beam.

  In the TaHfON film, the total content of Ta and Hf is more preferably 35 to 80 at%, and further preferably 35 to 75 at%. The composition ratio of Ta and Hf is more preferably Ta: Hf = 7: 3 to 4: 6, further preferably 6.5: 3.5 to 4.5: 5.5, More preferably, it is 6: 4-5: 5. The total content of N and O is more preferably 20 to 65 at%, and further preferably 25 to 65 at%.

Since the TaHfON film has the above-described configuration, its crystal state is amorphous and its surface is excellent in smoothness. Specifically, the surface roughness (rms) is 0.5 nm or less.
As described above, the surface of the absorber layer is required to be smooth in order to prevent deterioration of the dimensional accuracy of the resist pattern formed using the EUVL mask due to the influence of edge roughness. The TaHfON film formed as an antireflection layer on the absorber layer is required to have a smooth surface.
If the surface roughness (rms) of the TaHfON film surface is 0.5 nm or less, the surface is sufficiently smooth, and the dimensional accuracy of the resist pattern formed using the EUVL mask deteriorates due to the influence of edge roughness. Or scattered light due to surface roughness is not increased. The surface roughness (rms) of the TaHfON layer surface is more preferably 0.4 nm or less, and further preferably 0.3 nm or less.

  Note that whether the TaHfON film is in an amorphous state, that is, an amorphous structure or a microcrystalline structure can be confirmed by an X-ray diffraction (XRD) method. If the crystal state of the TaHfON film is an amorphous structure or a microcrystalline structure, a sharp peak is not observed in a diffraction peak obtained by XRD measurement.

The TaHfO film and the TaHfON film can be formed by performing a sputtering method using a TaHf compound target, for example, a magnetron sputtering method or an ion beam sputtering method.
In the case of a TaHfO film, the film is formed by discharging a TaHf compound target in an oxygen (O ₂ ) atmosphere diluted with an inert gas (eg, argon (Ar) gas). Alternatively, after a TaHf compound target is discharged in an inert gas (eg, argon (Ar) gas) atmosphere to form a film containing Ta and Hf, the film is exposed to, for example, oxygen plasma, or an ion beam using oxygen The film formed may be oxidized by irradiating with a TaHfO film.
On the other hand, a TaHfON film is formed by discharging a TaHf compound target in an oxygen (O ₂ ) / nitrogen (N ₂ ) mixed gas atmosphere diluted with an inert gas (for example, argon (Ar) gas). Alternatively, a TaHf compound target is discharged in a nitrogen (N ₂ ) atmosphere diluted with an inert gas (eg, argon (Ar) gas) to form a film containing Ta, Hf, and N, and then, for example, oxygen plasma A TaHfON film may be formed by oxidizing the formed film by exposing the film to the inside or irradiating an ion beam using oxygen.
The TaHf compound target has a composition of Ta = 30 to 70 at% and Hf = 70 to 30 at%, so that a TaHfO film and a TaHfON film having a desired composition can be obtained, and variations in film composition and film thickness can be obtained. Is preferable in that it can be avoided. The TaHf compound target may contain 0.1 to 5.0 at% of Zr.

In order to form the TaHfO film and the TaHfON film by the above-described method, specifically, the following film-forming conditions may be used.
If <br/> sputtering gas to deposit a TaHfO film: mixed gas of Ar and O ₂ (O ₂ gas concentration 3~80vol%, preferably 5~60vol%, more preferably 10~40vol%; gas pressure 1. ^{0 × 10 -1 Pa~50 × 10 -1} Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably ^{1.0 × 10 -1 Pa~30 × 10 -1} Pa )
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 2.0-60 nm / min, preferably 3.5-45 nm / min, more preferably 5-30 nm / min
If <br/> sputtering gas to deposit a TaHfON film: Ar, O ₂ and a mixed gas of N ₂ (O ₂ gas concentration 5~40vol%, N ₂ gas concentration 5~40vol%, preferably O ₂ gas concentration: 6 ~35vol%, N ₂ gas concentration 6~35vol%, more preferably O ₂ gas concentration 10 to 30 vol%, N ₂ gas concentration 10 to 30 vol%; gas pressure 1.0 × 10 ^-1 Pa~50 × 10 ^-1 Pa, preferably ^{1.0 × 10 -1 Pa~40 × 10 -1} Pa, more preferably ^{1.0 × 10 -1 Pa~30 × 10 -1} Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 2.0-60 nm / min, preferably 3.5-45 nm / min, more preferably 5-30 nm / min

The mask blank used for manufacturing the base mask may have other functional layers known in the field of EUVL mask blanks in addition to the above configuration. As a specific example of such a functional layer, for example, as described in JP-A-2003-501823, in order to promote electrostatic chucking of the substrate, the back side of the substrate (with respect to the film formation surface) And a high dielectric coating applied. For the high dielectric coating applied to the back surface of the substrate for such a purpose, the electrical conductivity and thickness of the constituent material are selected so that the sheet resistance is 100Ω / □ or less. The constituent material of the high dielectric coating can be widely selected from those described in known literature. For example, a high dielectric constant coating described in JP-A-2003-501823, specifically, a coating made of silicon, TiN, molybdenum, chromium, or TaSi can be applied. The thickness of the high dielectric coating can be, for example, 10 to 1000 nm, preferably 50 to 200 nm.
The high dielectric coating can be formed using a known film forming method, for example, a sputtering method such as a magnetron sputtering method or an ion beam sputtering method, a CVD method, a vacuum evaporation method, or an electrolytic plating method.

A base mask is obtained by patterning the absorber layer of the mask blank obtained by the above procedure. The patterning of the absorber layer can be performed by the following procedure.
(1) A resist film having a predetermined thickness by applying a resist on the mask blank (specifically, on the absorber layer, or on the low reflection layer when a low reflection layer is formed on the absorber layer) Form. The resist coating method can be selected from a wide variety of known coating methods used when manufacturing EUVL masks, such as spin coating, roller coating, bar coating, slit coating, spraying, and vapor phase coating. Can do. Among these, the spin coat method is preferable because the resist can be applied uniformly. The resist film thickness is preferably 1000 to 5000 mm, and particularly preferably 1000 to 3500 mm.
(2) After pre-baking at a temperature of 80 to 150 ° C. for 5 to 15 minutes for the purpose of removing the solvent remaining in the resist film, the resist film is subjected to pattern exposure in order to print a desired resist pattern on the resist film. In manufacturing an EUVL mask, exposure using a mask is not usually used, and a resist pattern is directly printed on a resist film by scanning an electron beam. Or the method of irradiating only a desired part with ultraviolet light using a direct mirror device etc. is taken.
(3) When a positive resist is used for the resist film, a desired resist pattern is obtained by removing the resist film at a portion irradiated with an electron beam or ultraviolet light using a developer. On the other hand, when a negative resist is used for the resist film, a desired resist pattern is obtained by removing the resist film at a portion not irradiated with an electron beam or ultraviolet light using a developer. After obtaining a desired resist pattern, post-baking may be performed as necessary for the purpose of removing the developer or cleaning liquid remaining on the resist film and for improving the adhesion of the resist film to the substrate.
(4) The portion of the absorber layer not covered with the resist film of the mask blank (if the low reflection layer is formed on the absorber layer, the low reflection layer) is removed using an etching process. Thus, a mask pattern is formed. In manufacturing an EUVL mask, a fine mask pattern having a mask pattern opening width of 150 nm or less is formed. Therefore, as an etching process, plasma etching, sputter etching, ion beam etching, gas cluster ion beam etching, or the like is used. Such an anisotropic dry etching process is usually used. After performing the etching process, the resist film that is no longer needed is removed using a highly oxidizing chemical such as a mixture of sulfuric acid and hydrogen peroxide, or ozone water, and then the surface is rinsed with ion-exchanged water. By cleaning and drying, a base mask having a desired mask pattern can be obtained.

In the EUVL mask manufacturing method (1) of the present invention, first, the width of the opening of the mask pattern of the base mask obtained by the above procedure is measured. In the base mask 1 shown in FIG. 1, the width of the opening 20 of the mask pattern is indicated by W.
The method of measuring the width of the opening of the mask pattern is not particularly limited as long as it is a measuring method or measuring apparatus that can measure the width of the opening of 150 nm or less with high accuracy with an error of 20 nm or less. Specific examples of such a measuring apparatus include CD-SEM (Critical dimension SEM), three-dimensional AFM (Atomic Force Microscope), and the like.

Next, the measured value of the width of the opening obtained by the above procedure is compared with the design value, and whether or not there is a deviation of the measured value with respect to the design value is confirmed.
If there is no deviation from the design value, or if the deviation from the design value is within an allowable range, the base mask produced by the above procedure can be used as it is as a final product EUVL mask. There is no need to implement.
On the other hand, when a deviation exceeding the allowable range is found with respect to the design value, a part of the opening of the mask pattern is locally localized according to the procedure described later based on the comparison result between the measured value obtained in the above procedure and the design value. Heat. An EUVL mask of the final product is obtained by locally heating a part of the opening of the mask pattern based on the comparison result between the measured value and the design value regarding the width of the opening of the mask pattern. As will be described in detail later, in the resist pattern formed using the EUVL mask of the final product thus obtained, the resist generated due to deviation from the design value of the width of the opening of the mask pattern in the EUVL mask Misalignment of the pattern has been corrected.

  The allowable range of deviation from the design value of the width of the opening of the mask pattern is the shape and size of the target mask pattern, the portion where the mask pattern exists, the process factor (k1 factor) of the lithography process, the resist The details are described in International Technology Roadmap for Semiconductors, etc. For example, if the mask pattern consists of an opening with a width of 150 nm and a non-opening with a width of 150 nm, The allowable dimensional error is 10 nm or less.

  In the EUVL mask manufacturing method (1) of the present invention, when a deviation exceeding the allowable range with respect to the design value is found in the width of the opening, a part of the opening of the mask pattern of the base mask is locally heated. The reason is based on the knowledge of the present inventors described below.

As described above, the opening of the mask pattern is a portion where the absorber layer is not formed on the reflective layer, and the reflective layer is exposed. When a protective layer is formed on the reflective layer, the protective layer is exposed at the opening of the mask pattern. Therefore, in this specification, when it says that a part of opening part of a mask pattern is locally heated, it means that a part of reflective layer or protective layer exposed in this opening part is locally heated.
The inventors of the present application have found that when the multilayer reflective film forming the reflective layer is heated, the peak reflectance in the EUV wavelength region when the surface of the multilayer reflective film is irradiated with EUV light is reduced. When the reflectance spectrum in the EUV wavelength region when the EUV light is irradiated on the surface of the multilayer reflective film is measured, the reflectance value differs depending on the wavelength to be measured and has a maximum value R _max as shown in FIG. In this specification, this maximum value R _max is referred to as a peak reflectance in the EUV wavelength region. Hereinafter, when simply referred to as peak reflectance in this specification, it refers to peak reflectance in the EUV wavelength region. In FIG. 2, as will be described later, EUV is formed on the surface of the protective film of the multilayer reflective film in which the Mo / Si multilayer reflective film and the Ru film serving as the protective film and the buffer film are formed on the substrate, and the substrate with the protective film. It is a reflectance spectrum of the EUV wavelength region when light is irradiated.

When the multilayer reflective film is heated, the high refractive material and the low refractive material forming the multilayer reflective film diffuse and react with each other to form a diffusion layer. As a result, when the EUV light is irradiated on the surface of the multilayer reflective film after heating, the peak reflectance in the EUV wavelength region is lowered. When EUV light is irradiated on the surface of the multilayer reflective film after heating, the center wavelength of the reflected light in the EUV wavelength region also decreases (shifts to the short wavelength side). In the present specification, the center wavelength of the reflected light in the EUV wavelength region, the reflectivity spectrum in the EUV wavelength region, the wavelength corresponding to the half width of the peak reflectivity (FWHM (full width of half maximum )) λ 1 and When λ ₂ , the wavelength is the median value of these wavelengths ((λ ₁ + λ ₂ ) / 2). In this specification, when the central wavelength of reflected light is simply referred to, it means the central wavelength of reflected light in the EUV wavelength region.

When the protective layer is formed on the multilayer reflective film forming the reflective layer, the inventors of the present application heated the protective layer, and the peak reflection in the EUV wavelength region when the protective layer surface was irradiated with EUV light. It has also been found that the rate and the central wavelength of reflected light are reduced.
When the protective layer is heated, the material that forms the surface layer of the multilayer reflective film and the material that forms the protective layer diffuse and react with each other to form a diffusion layer. As a result, when EUV light is irradiated on the surface of the protective layer after heating, the peak reflectance in the EUV wavelength region and the center wavelength of the reflected light are reduced. Alternatively, when the protective layer is heated, the high refractive material and the low refractive material forming the multilayer reflective film under the protective layer diffuse and react with each other to form a diffusion layer. As a result, when EUV light is irradiated on the surface of the protective layer after heating, the peak reflectance in the EUV wavelength region and the center wavelength of the reflected light are reduced.

3 and 4, 40 layers of Si films (film thickness 4.5 nm) and Mo films (film thickness 2.3 nm) are alternately laminated in this order on a substrate (made of SiO ₂ —TiO ₂ glass). After forming the multilayer reflective film, a Si film (film thickness: 4.5 nm) is formed as a protective layer on the multilayer reflective film, and a Ru film (film thickness 2) serving as a protective layer and a buffer layer is formed on the Si film. .5 nm) was irradiated with EUV light on the surface of the Ru film of the multilayer reflective film and the substrate with the protective layer when the multilayer reflective film and the substrate with the protective layer were heated for 10 minutes using a hot plate in the atmosphere. The heating temperature dependence of the central wavelength reduction amount and the peak reflectance reduction amount in the EUV wavelength region is shown. In FIG. 3, the vertical axis represents the amount of decrease in the center wavelength of reflected light (Decrease in CWL) (nm), and the horizontal axis represents 1000 / T (bake temperature) (1 / K). In FIG. 4, the vertical axis represents the peak reflectivity reduction amount (Decrease in Peak% R), and the horizontal axis represents 1000 / T (bake temperature) (1 / K).

First, in the heating temperature dependence of the central wavelength decrease amount of the reflected light shown in FIG. 3, since the multilayer reflective film is a kind of Bragg reflection mirror, the central wavelength decrease amount of the reflected light is almost linear to the thickness of the diffusion layer to be generated. And its heating temperature dependence follows the Arrhenius equation, which is the temperature dependence of the general reaction rate. Further, since the thickness of the diffusion layer increases in proportion to the reaction time (= heating time), the heating temperature and heating time dependency of the amount of decrease in the center wavelength of the reflected light follows the following equation (2a). In the case of the example shown in FIG. 3, the expression (2a) is expressed by the expression (2b).
Decrease in center wavelength of reflected light
加熱 Heating time × exp (a + b / heating temperature (K))
(Where a and b are constants) Equation (2a)
Center wavelength decrease amount of reflected light (nm) = 4120 × heating time (min)
Xexp (-6380 / heating temperature (K))
Formula (2b)

図４および表１から明らかなように、多層反射膜または保護層を加熱することにより、これらの層表面にＥＵＶ光を照射した際のＥＵＶ波長域におけるピーク反射率を低下させることができる。この際、反射光の中心波長も低下する（短波長側にシフトする）が、ピーク反射率の低下に比べて反射光の中心波長の低下は僅かであるため、反射光の中心波長の低下を問題ないレベルに維持しつつ、ピーク反射率を所望のレベルまで下げることは比較的容易であることが判明した。 On the other hand, the peak reflectivity decrease amount is not as simple as the center wavelength decrease amount because the dependency on the thickness of the diffusion layer to be generated is relatively complicated, but as clearly shown in FIG. As a result, according to the Arrhenius equation, the heating temperature and heating time dependency of the peak reflectance reduction amount follows the following equation (3a). In the case of the example shown in FIG. 4, the formula (3a) is expressed by the formula (3b).
Peak reflectivity drop ∝ Diffusion layer thickness
加熱 Heating time × exp (a + b / heating temperature (K))
(Where a and b are constants) Equation (3a)
Peak reflectance decrease (%) = 9130 × heating time (min)
Xexp (-4370 / heating temperature (K))
Formula (3b)
Table 1 shows the temperature dependence of the peak reflectance and the amount of change (amount of decrease) in the center wavelength of reflected light by heating obtained from FIGS. 3 and 4.

As apparent from FIG. 4 and Table 1, by heating the multilayer reflective film or the protective layer, the peak reflectance in the EUV wavelength region when EUV light is irradiated onto the surface of these layers can be reduced. At this time, the central wavelength of the reflected light also decreases (shifts to the short wavelength side), but since the decrease in the central wavelength of the reflected light is slight compared to the decrease in the peak reflectance, the central wavelength of the reflected light is decreased. It has been found that it is relatively easy to reduce the peak reflectivity to the desired level while maintaining a problem-free level.

In the EUVL mask blank, the required value regarding the in-plane uniformity of the central wavelength of the reflected light on the surface of the multilayer reflective film forming the reflective layer is within ± 0.03 nm, and preferably within ± 0.01 nm. Here, the required value regarding the in-plane uniformity of the center wavelength is an allowable value of the difference between the largest center wavelength and the smallest center wavelength when the center wavelength is measured over the entire surface of the multilayer reflective film. When a protective layer is formed on the reflective layer, the required value regarding the in-plane uniformity of the center wavelength is applied to the reflected light in the EUV wavelength region when the protective layer is irradiated with EUV light. . The required value of the in-plane uniformity of the peak reflectance is preferably within ± 1.2%, particularly within ± 0.6%, and more preferably within ± 0.3%.
The EUVL mask created from the mask blank is also required to have the in-plane uniformity of the central wavelength of the reflected light satisfying the above-mentioned required value for the reflected light in the EUV wavelength region at the opening of the mask pattern. Accordingly, in the EUVL mask manufacturing method (1) of the present invention, the peak reflectance can be lowered to a desired level while the in-plane uniformity of the center wavelength at the opening of the mask pattern satisfies the required value. Thus, the conditions for locally heating a part of the opening may be selected.

  As is clear from the above points, the peak reflectance and the central wavelength of the reflected light are in the EUV wavelength range when EUV light is irradiated on the surface of the target (multilayer reflective film or protective layer) to be examined. It can be determined by measuring the reflectance spectrum. The method for measuring the reflectance spectrum in the EUV wavelength region will be described below, taking as an example the case where the surface of the multilayer reflective film is irradiated with EUV light. In addition, what is necessary is just to read the place described as a multilayer reflective film as a protective layer about the case where EUV light is irradiated to the protective layer surface.

As a method for measuring the reflectance spectrum, (1) after the light in the EUV wavelength region is dispersed, the multilayer reflective film surface is irradiated at an incident angle of 6 to 8 degrees, and the reflected light intensity is measured by a photodiode or a charge coupled device (Charged Coupled). (2) After the light in the EUV wavelength range is dispersed, the multilayer reflective film surface is irradiated at an incident angle of 6 to 8 degrees, and the reflected light in the EUV wavelength range is applied to a scintillator or the like. An indirect method in which the light is converted into light in other wavelength ranges (for example, visible light, ultraviolet light, etc.) and the intensity thereof is measured with a photomultiplier tube, etc. (3) After incident light in the EUV wavelength range, the incident angle The reflected light when irradiated on the surface of the multilayer reflective film at 6 to 8 degrees is dispersed, and each reflected light intensity dispersed at each wavelength is converted into a multi-channel photodiode array or multi-channel. Method such as measured using a CCD array, and the like. In these methods, a reflectance spectrum can be obtained by actually measuring using a so-called spectrophotometer.
Specifically, as a spectrophotometer, an EUV reflectometer manufactured by US EUV technology using the method (1), an EUV-mask blank reflectometer (MBR) manufactured by AIXUV using the method (3), and the like. Can be mentioned. As a light source that emits light in the EUV wavelength range, capillary discharge in the presence of light emitted from plasma generated by irradiating a target such as xenon gas or tin with YAG laser light, or xenon gas or tin. For example, light emitted from plasma generated by discharging by pinch discharge or the like can be used.

As a specific example, a method for measuring a reflectance spectrum using an EUV-mask blank reflectometer (MBR) manufactured by AIXUV, Germany will be described below.
The EUV light emitted from the plasma generated by the discharge by the xenon gas pinch discharge is passed through the slit, and the multilayer reflection film and the reference mirror (reflectance (= R _ref (λ)) in the EUV wavelength region are known. The surface of the mirror formed on the substrate is irradiated at an incident angle of 6 to 8 degrees. After the reflected light from the multilayer reflective film and the reference mirror is dispersed with a grating mirror, it is projected onto a multi-channel CCD (Charged Coupled Device) array, and reflected from the multilayer reflective / protective film and the reference mirror at each wavelength. The light intensity (I (λ), I _ref (λ)) is measured, and the reflectance spectrum R (λ) of the multilayer reflective film is obtained by Equation (1).
R (λ) = R _ref (λ) × I (λ) / I _ref (λ) Equation (1)
An example of the reflectance spectrum obtained by the above series of procedures is shown in FIG. In FIG. 2, the vertical axis represents reflectivity (%), and the horizontal axis represents wavelength (nm). However, FIG. 2 shows a multilayer reflection in which 50 layers of Si films (film thickness 4.5 nm) and Mo films (film thickness 2.3 nm) are alternately laminated in this order on a substrate (made of SiO ₂ —TiO ₂ glass). After forming the film, a Si film (film thickness: 4.5 nm) is formed as a protective film on the multilayer reflective film, and a Ru film (film thickness: 2. nm) serving as a protective film and a buffer film is formed on the Si film. 5 nm) is a reflectance spectrum in the EUV wavelength region (12.5 to 14.5 nm) when EUV light is irradiated at an incident angle of 6 degrees on the Ru film surface of the multilayer reflective film and the protective film-coated substrate.

  As described above, by heating the multilayer reflective film or the protective layer, the peak reflectance in the EUV wavelength region when these surfaces are irradiated with EUV light can be reduced. Therefore, by locally heating a part of the opening of the mask pattern where the multilayer reflective film or the protective layer is exposed, the peak reflectance of the locally heated portion can be locally reduced. When a mask pattern is transferred to a resist film formed on the wafer using an EUVL mask in which a part of the opening is locally heated, the resist is applied from the locally heated portion of the opening of the mask pattern. The amount of exposure to the film is reduced. In short, in the present invention, by using a mask for EUVL in which a part of the opening is locally heated, the mask pattern is transferred to the resist film formed on the wafer, whereby the exposure amount to the resist film is locally increased. Can be adjusted. Then, by locally adjusting the exposure amount to the resist film, it is possible to correct a deviation in the dimension of the resist pattern caused by a deviation from the design value of the width of the opening of the mask pattern in the EUVL mask. Hereinafter, in this specification, the deviation of the resist pattern dimension caused by deviation from the design value of the width of the opening of the mask pattern in the EUVL mask is referred to as “resist pattern dimension deviation caused by the mask”. . It should be noted that the resist pattern dimension shift caused by a shift from the design value of the width of the non-opening portion of the mask pattern in the EUVL mask in the EUVL mask manufacturing method (2) of the present invention to be described later is also referred to as “mask. This is referred to as “the displacement of the dimension of the resist pattern caused by“.

  However, locally heating a part of the opening of the mask pattern on the principle of correcting the deviation of the resist pattern dimension caused by the mask by reducing the exposure amount to the resist film from the locally heated portion. Therefore, the deviation of the resist pattern dimension caused by the mask can be corrected when the measured dimension value of the resist pattern corresponding to the opening of the mask pattern is larger than the design value. is there. That is, in the EUVL mask manufacturing method (1) of the present invention, when there is a portion where the measured value of the width of the opening of the mask pattern is larger than the design value, the portion is locally heated. In this case, the resist pattern dimensional deviation caused by the mask is corrected by locally reducing the exposure amount from the portion to the resist film.

The heating method used for the local heating is not particularly limited as long as it is a method that can locally heat only a portion of the opening of the base mask where it is desired to reduce the peak reflectance in the EUV wavelength region.
As an example of a suitable heating method used for local heating, a portion of the base mask opening where the peak reflectance in the EUV wavelength region is to be lowered is locally irradiated with a high-energy light beam using a laser or a lamp as a light source, A method of performing local heating by locally irradiating an electron beam can be mentioned.
When irradiating a light beam using a laser or a lamp as a light source, it is necessary to select a light beam in a wavelength region having absorption in the material constituting the multilayer reflective film, the protective layer, or the buffer layer that is the target of local heating. Specific examples of such a light source that can irradiate light include: an F ₂ laser (wavelength: about 157 nm), an ArF excimer laser (about 193 nm), a KrF excimer laser (about 248 nm), and a YAG laser quadruple harmonic. (About 266 nm), XeCl excimer laser (about 308 nm), Ar laser (about 488 nm), YAG laser (about 1064 nm), CO ₂ laser (about 10.6 um), xenon arc lamp (about about 266 nm) 300 to about 1000 nm) and halogen lamps (about 600 to about 6000 nm).

  As another example of a suitable heating method used for local heating, a minute heating member by resistance heating or induction heating is brought close to a portion where the peak reflectance in the EUV wavelength region of the opening of the base mask is to be lowered, A method of locally heating by radiation or heat conduction through gas is mentioned. Specifically, a heating member by resistance heating using a filament such as tungsten or carbon, and a heating member by induction heating using a magnetic material such as carbon, iron, or stainless steel can be exemplified. In addition, an atomic force microscope (AFM) having a heatable probe, a scanning tunneling microscope (STM), or a stylus-type step meter can be mentioned. As a commercial product, local thermal analysis of nano-TA manufactured by Anasys Instruments of the United States. There are systems.

The local heating conditions, i.e., heating temperature and heating time, are the conditions of the part to be locally heated, i.e., the constituent material of the multilayer reflective film, the number of repeated layers and the thickness of each layer, or the constituent material and thickness of the protective layer, etc. It can be selected as appropriate according to the conditions. Alternatively, the level may be appropriately selected according to the degree to which the peak reflectance in the EUV wavelength region is desired to be reduced and the amount of the peak reflectance to be reduced. However, as described above, when the local heating is performed, not only the peak reflectance in the EUV wavelength region at the locally heated portion is lowered, but also the central wavelength of the reflected light in the EUV wavelength region from the portion is lowered. Therefore, care must be taken not to cause an unacceptable shift in the center wavelength of reflected light due to local heating.
In addition, the environment which implements local heating is not specifically limited, You may implement in air | atmosphere and may implement in inert gas like a noble gas or nitrogen gas. However, in order to prevent an increase in surface roughness due to surface oxidation, it is preferable to carry out in an inert gas such as a rare gas or nitrogen gas.

Next, the manufacturing method (2) for the EUVL mask of the present invention will be described.
The basic concept of the EUVL mask manufacturing method (2) of the present invention is the same as that of the EUVL mask manufacturing method (1) of the present invention. However, it is not the width of the opening portion of the mask pattern of the base mask but the width of the non-opening portion that is to be compared with the measured and designed values. In the base mask 1 shown in FIG. 1, the width of the non-opening portion 10 of the mask pattern is indicated by w.
That is, in the EUVL mask manufacturing method (2) of the present invention, after measuring the width w of the non-opening portion 10 of the mask pattern of the base mask 1, the measured value of the width w of the non-opening portion 10 is compared with the design value. Then, the presence or absence of a deviation of the measured value from the design value is confirmed. When a deviation exceeding the allowable range with respect to the design value is found in the width w of the non-opening portion 10, the portion of the opening portion 20 of the mask pattern adjacent to the portion of the non-opening portion 10 of the mask pattern is locally heated.
As described above, the knowledge of the inventors of the present application is that the peak reflectance in the EUV wavelength region can be reduced by irradiating these surfaces with EUV light by heating the multilayer reflective film or the protective layer. is there. On the other hand, the non-opening part of the mask pattern is a part where the absorber layer is formed on the multilayer reflective film or the protective layer. Even if a part of the non-opening is locally heated, a part of the absorber layer is locally heated. Therefore, the peak reflectance in the EUV wavelength region cannot be reduced. A portion of the opening 20 of the mask pattern adjacent to is locally heated.
For example, in FIG. 1, when the width w of the non-opening portion 10 of the mask pattern located on the left side is measured, if a deviation exceeding the allowable range is found with respect to the design value, it is adjacent to the portion of the non-opening portion 10 The site | part of the opening part 20 (opening part 20 located in the left side in a figure) is heated locally. Further, in FIG. 1, when the width w of the non-opening portion 10 of the mask pattern located at the center is measured, if a deviation exceeding the allowable range is found with respect to the design value, it is adjacent to the portion of the non-opening portion 10. The part of the opening 20 on both sides or one of the two adjacent openings 20 is locally heated.

  However, locally heating a part of the opening of the mask pattern on the principle of correcting the deviation of the resist pattern dimension caused by the mask by reducing the exposure amount to the resist film from the locally heated portion. Can correct the deviation of the dimension of the resist pattern caused by the mask when the measured value of the dimension of the resist pattern corresponding to the non-opening part of the mask pattern is smaller than the design value. It is. That is, in the EUVL mask manufacturing method (2) of the present invention, when there is a portion where the measured value of the width w of the non-opening 10 of the mask pattern is smaller than the design value, the non-opening 10 By locally heating the portion of the opening 20 adjacent to the portion, the exposure amount from the portion of the opening 20 to the resist film is locally reduced, and the deviation of the resist pattern dimension caused by the mask is corrected. To do.

Next, the manufacturing method (3) for the EUVL mask of the present invention will be described.
In the EUVL mask manufacturing method (3) of the present invention, first, a base mask is prepared in the same procedure as the EUVL mask manufacturing method (1) of the present invention.
Next, a resist pattern is formed on the wafer using the created base mask. This procedure is the same as that normally performed when transferring a mask pattern to a silicon wafer on which a resist film is formed using an EUVL mask. That is, a test wafer on which a resist film is formed (hereinafter referred to as “test wafer”) is placed on a stage, and a base mask is placed on a reflective EUVL exposure apparatus configured by combining a reflecting mirror. Then, the EUV light is irradiated from the light source to the base mask through the reflecting mirror, and the EUV light is reflected by the base mask and irradiated to the test wafer. Thereby, a resist pattern is baked on the resist film of the test wafer. Next, the latent image formed in the resist film is developed with a developer to form a resist pattern.

The EUVL exposure apparatus used in this procedure is actually used when a semiconductor integrated circuit is manufactured by forming a resist pattern on a wafer using an EUVL mask as a final product (hereinafter referred to as “semiconductor integrated circuit manufacturing”). It is preferable to use an EUVL exposure apparatus.
As described above with respect to Patent Document 1, as one of the causes of deviation of the resist pattern dimensions from the design value, there is a flare in the projection optical system of the EUVL exposure apparatus. Hereinafter, in this specification, the resist pattern dimension deviation caused by flare in the projection optical system of the EUVL exposure apparatus is referred to as “resist pattern dimension deviation caused by the exposure apparatus”. Such a shift in the dimension of the resist pattern caused by the exposure apparatus inevitably occurs as long as an exposure apparatus having a flare problem is used. When an EUVL exposure apparatus having a flare problem is used in the procedure for forming a resist pattern on a test wafer using a base mask, the resist pattern formed on the test wafer is a resist pattern caused by the exposure apparatus. Including dimensional deviation. If an EUVL exposure apparatus for manufacturing a semiconductor integrated circuit is used in a procedure for forming a resist pattern on a test wafer, a deviation in the dimension of the resist pattern caused by the exposure apparatus can be corrected.
However, the EUVL mask manufacturing method (3) of the present invention mainly corrects the dimensional deviation of the resist pattern caused by the mask, similarly to the EUVL mask manufacturing methods (1) and (2). .

The resist used to form the resist film on the test wafer is a resist actually used when a semiconductor integrated circuit is manufactured by forming a resist pattern on the wafer using an EUVL mask as a final product. Although not limited to the same thing, the thing of the same kind at the time of EUV light irradiation is used for the reason mentioned later. That is, when a semiconductor integrated circuit is manufactured, when a resist film is formed with a positive resist on a wafer, it is necessary to form a resist film with a positive resist on a test wafer. When forming a resist film with a negative resist on a wafer, it is necessary to form a resist film with a negative resist on a test wafer. However, considering the reactivity of the resist film during EUV light irradiation and development, it is preferable to use the same resist as that actually used when manufacturing a semiconductor integrated circuit.
On the other hand, the test wafer has a dimension of a resist pattern formed thereon (in the EUVL mask manufacturing method (3) of the present invention, the resist pattern space width. In the EUVL mask manufacturing method (4) of the present invention described later) Unlike the wafer used when actually manufacturing a semiconductor integrated circuit, a metal layer that serves as various functional films of a semiconductor integrated circuit is used on a silicon wafer, because it is used only for measuring the line width of a resist pattern. It is not always necessary to form an oxide layer. That is, in this procedure, a resist film directly formed on a test wafer made of a silicon wafer can be used.

In the EUVL mask manufacturing method (3) of the present invention, next, the space width of the resist pattern formed on the test wafer is measured. FIG. 5 is a diagram showing a correspondence relationship between the base mask shown in FIG. 1 and a test wafer on which a resist pattern is formed using the base mask when a positive resist is used for the resist film. is there. FIG. 6 is a diagram showing a correspondence relationship between the base mask shown in FIG. 1 and a test wafer on which a resist pattern is formed using the base mask when a negative resist is used for the resist film. is there. 5 and 6, the space width of the resist pattern is the width of the opening 20 'of the resist pattern and is indicated by W' in the drawings.
The method for measuring the space width of the resist pattern is not particularly limited as long as it is a measurement method or a measurement apparatus that can measure a space width of 100 nm or less with high accuracy with an error of 10 nm or less. As such a measuring apparatus, the apparatus described as the measuring apparatus for the width of the opening of the mask pattern in the EUVL mask manufacturing method (1) of the present invention can be used.

Next, the measured value of the space width of the resist pattern obtained by the above procedure is compared with the design value, and whether or not there is a deviation of the measured value from the designed value is confirmed.
If there is no deviation from the design value, or if the deviation from the design value is within an allowable range, the base mask produced by the above procedure can be used as it is as a final product EUVL mask. There is no need to implement.
On the other hand, when a deviation exceeding the allowable range is found with respect to the design value, a part of the opening of the mask pattern is locally localized according to the procedure described later based on the comparison result between the measured value obtained in the above procedure and the design value. By heating, a final product EUVL mask is obtained.

  The allowable range of deviation of the resist pattern space width with respect to the design value varies depending on the shape and size of the target resist pattern or the portion where the resist pattern exists, and details are described in International Technology Roadmap for Semiconductors. However, for example, when the space width of the resist pattern is 50 nm and the line width is 50 nm, the allowable range of deviation from the design value of the space width of the resist pattern is 5 nm or less.

  As apparent from the above points, in the EUVL mask manufacturing method (1) of the present invention, the measured value of the width of the opening of the mask pattern is compared with the design value for the base mask, and the result is obtained. Whereas part of the opening of the mask pattern of the base mask is locally heated, in the EUVL mask manufacturing method (3) of the present invention, the resist pattern formed on the test wafer using the base mask Then, the measured value of the space width is compared with the design value, and based on the result, a part of the opening of the mask pattern of the base mask is locally heated.

  In the manufacturing method (3) of the EUVL mask of the present invention, the idea of locally heating a part of the opening of the mask pattern of the base mask based on the comparison result between the measured value of the space width and the design value is a test. It differs depending on whether the resist used for the resist film formed on the wafer is a positive resist or a negative resist. Each case will be described below.

[When positive resist is used for resist film]
As described above, FIG. 5 shows the correspondence between the base mask shown in FIG. 1 and the test wafer on which a resist pattern is formed using the base mask when a positive resist is used for the resist film. FIG. As shown in FIG. 5, the test wafer portion corresponding to the opening 20 of the base mask 1 is irradiated with EUV light from the opening 20, so that the resist film 6 is removed by development and the test wafer (silicon Wafer) 5 is exposed. That is, the resist pattern opening 20 'is formed. On the other hand, the portion of the test wafer corresponding to the non-opening portion 10 of the base mask 1 is not irradiated with EUV light. Therefore, the resist film 6 is not removed by development and becomes a non-opening portion 10 ′ of the resist pattern. That is, when the resist film is a positive resist, the opening 20 and the non-opening 10 of the base mask correspond to the opening 20 ′ and the non-opening 10 ′ of the resist pattern formed on the test wafer, respectively.
Therefore, a part of the opening can be locally heated by the same idea as the EUVL mask manufacturing method (1) of the present invention. That is, when there is a portion on the test wafer where the measured value of the resist pattern space width W ′ (the width of the resist pattern opening 20 ′) is larger than the design value, the measured value of the resist pattern space width W ′. By locally heating the part of the opening 20 of the mask pattern corresponding to the part where is larger than the design value, the exposure amount from the part to the resist film is locally reduced, and the design value of the space width in the resist pattern Correct the deviation from.
On the other hand, when there is a portion on the test wafer where the measured value of the space width W ′ of the resist pattern is smaller than the design value, the space in the resist pattern can be obtained by locally heating a part of the opening 20 of the mask pattern. It is difficult to correct the deviation of the width from the design value.

[When negative resist is used for resist film]
As described above, FIG. 6 shows the correspondence between the base mask shown in FIG. 1 and the test wafer on which a resist pattern is formed using the base mask when a negative resist is used for the resist film. FIG. As shown in FIG. 6, the portion of the test wafer corresponding to the opening 20 of the base mask 1 is irradiated with EUV light from the opening 20, so that the resist film 7 is not removed by development and the resist pattern is not opened. Part 10 '. On the other hand, the portion of the test wafer corresponding to the non-opening portion 10 of the base mask 1 is not irradiated with EUV light. Therefore, the resist film 7 is removed by development, and the test wafer (silicon wafer) 5 is exposed to form a resist pattern. It becomes an opening 20 '. That is, when the resist film is a positive resist, the relationship between the opening and the non-opening is reversed between the mask pattern of the base mask and the resist pattern.
Therefore, a part of the opening is locally heated based on the concept opposite to the case where a positive resist is used for the resist film described above. That is, when there is a portion where the measured value of the resist pattern space width W ′ (the width of the resist pattern opening 20 ′) is smaller than the design value on the test wafer, the measured value of the resist pattern space width W ′ is By locally heating the portion of the opening 20 of the mask pattern corresponding to a portion smaller than the design value, the exposure amount from the portion to the resist film is locally reduced, and the space width with respect to the design value of the resist pattern is reduced. Correct the misalignment. Here, as is apparent from FIG. 6, when a negative resist is used for the resist film, the mask pattern non-opening 10 directly corresponds to the opening 20 ′ of the resist pattern. Therefore, the portion of the opening 20 of the mask pattern corresponding to the portion where the measured value of the space width W ′ (width of the opening 20 ′) of the resist pattern is smaller than the design value is the relevant of the opening 20 ′ of the resist pattern. This is a part of the opening part 20 of the mask pattern adjacent to the part of the non-opening part 10 of the mask pattern that directly corresponds to the part.
On the other hand, when there is a portion on the test wafer where the measured value of the space width W ′ of the resist pattern is larger than the design value, the space in the resist pattern may be obtained by locally heating a part of the opening 20 of the mask pattern. It is difficult to correct the deviation of the width W ′ from the design value.

Next, the manufacturing method (4) of the EUVL mask of the present invention will be described.
The basic concept of the EUVL mask manufacturing method (4) of the present invention is the same as that of the EUVL mask manufacturing method (3) of the present invention. However, it is not the space width W ′ in the resist pattern but the line width w ′ in the resist pattern (the width of the non-opening 10 ′) that is to be compared with the measured and designed values.
Also in the EUVL mask manufacturing method (4) of the present invention, a part of the opening 20 of the mask pattern of the base mask is locally heated based on the comparison result between the measured value and the design value of the line width w ′ in the resist pattern. The way of thinking depends on whether the resist used for the resist film formed on the test wafer is a positive resist or a negative resist. Each case will be described below.

[When positive resist is used for resist film]
As described in the EUVL mask manufacturing method (3) of the present invention, when the resist film is a positive resist, the opening 20 and the non-opening 10 of the base mask are respectively formed on the test wafer. This corresponds to the opening 20 ′ and the non-opening 10 ′ of the resist pattern.
When there is a portion where the measured value of the resist pattern line width w ′ (width of the non-opening portion 10 ′ of the resist pattern) is smaller than the design value on the test wafer, the measured value of the resist pattern line width w ′ is By locally heating the part of the opening 20 of the mask pattern corresponding to a part smaller than the design value, the exposure amount from the part to the resist film is locally reduced, and the space width in the resist pattern is compared with the design value. Correct the misalignment. Here, as is apparent from FIG. 5, when a positive resist is used for the resist film, the non-opening 10 of the mask pattern directly corresponds to the non-opening 10 'of the resist pattern. Therefore, the portion of the opening portion 20 of the mask pattern corresponding to the portion where the measured value of the line width w ′ (width of the non-opening portion 10 ′) of the resist pattern is smaller than the design value is the non-opening portion 10 ′ of the resist pattern. This is a portion of the opening portion 20 of the mask pattern adjacent to the portion of the non-opening portion 10 of the mask pattern that directly corresponds to the portion.
On the other hand, when there is a portion on the test wafer where the measured value of the line width w ′ of the resist pattern is larger than the design value, a space in the resist pattern may be obtained by locally heating a part of the opening 20 of the mask pattern. It is difficult to correct the deviation of the width from the design value.

[When negative resist is used for resist film]
As described in the manufacturing method (3) of the EUVL mask of the present invention, when the resist film is a negative resist, the opening 20 and the non-opening 10 of the base mask are respectively formed on the test wafer. This corresponds to the non-opening 10 'and the opening 20' of the resist pattern.
When there is a portion on the test wafer where the measured value of the resist pattern line width w ′ (width of the non-opening portion 10 ′ of the resist pattern) is larger than the design value, the measured value of the resist pattern line width w ′ is By locally heating the part of the opening 20 of the mask pattern corresponding to the part larger than the design value, the exposure amount from the part to the resist film is locally reduced, and the space width with respect to the design value of the resist pattern is reduced. Correct the misalignment.
On the other hand, when there is a portion on the test wafer where the measured value of the line width w ′ of the resist pattern is smaller than the design value, a space in the resist pattern can be obtained by locally heating a part of the opening 20 of the mask pattern. It is difficult to correct the deviation of the width from the design value.

  In the EUVL mask manufacturing methods (3) and (4) of the present invention, as a method of locally heating a part of the opening of the mask pattern of the EUVL mask, the EUVL mask manufacturing method (1) of the present invention is used. Then, the method mentioned as the method for locally heating a part of the opening of the mask pattern can be preferably used.

In the manufacturing methods (3) and (4) of the EUVL mask of the present invention, based on the comparison result between the design value and the measured value of the space width or line width of the resist pattern formed on the test wafer. The EUVL mask that is the final product is obtained by locally heating a part of the opening of the mask, but the above-described procedure is further performed on the EUVL mask after partially heating the opening. That is, a resist pattern is formed on a new test wafer using the EUVL mask, a space width (or line width) of the formed resist pattern is measured, and a space width (or line width) of the resist pattern is measured. Based on the comparison result between the measured value and the design value of the resist pattern, and the measured value of the space width (or line width) of the resist pattern and the designed value By locally heating a part of the opening of the EUVL mask one or more times, the deviation of the resist pattern space width (or line width) from the design value is further corrected, and the final product A certain EUVL mask may be obtained.
Further, the EUVL mask manufacturing method (3) of the present invention is different from the EUVL mask in which a part of the opening of the mask pattern is locally heated in the EUVL mask manufacturing method (1) and (2) of the present invention. , (4) may be performed. That is, a resist pattern is formed on a test wafer by using the EUVL mask in which a part of the opening of the mask pattern is locally heated in the manufacturing method (1) and (2) of the EUVL mask of the present invention. Measuring the space width (or line width) of the resist pattern, comparing the measured value of the space width (or line width) of the resist pattern with the design value, and the space width (or line width of the resist pattern). ) By locally heating a part of the opening of the EUVL mask based on the comparison result between the measured value and the design value of 1) or a plurality of times, so that the space width (or line width) of the resist pattern is achieved. The deviation from the design value may be further corrected to obtain a final product EUVL mask.

  The EUVL mask obtained by the above procedure can be applied to a method of manufacturing a semiconductor integrated circuit by a photolithography method using EUV light as an exposure light source. Specifically, a substrate such as a silicon wafer coated with a resist is placed on a stage, and the EUVL mask of the present invention is installed in a reflective exposure apparatus configured by combining a reflecting mirror. Then, EUV light is irradiated from the light source to the EUVL mask through a reflecting mirror, and the EUV light is reflected by the EUVL mask and irradiated onto the resist-coated substrate. By this pattern transfer process, the circuit pattern is transferred onto the substrate. The substrate on which the circuit pattern has been transferred is subjected to development to etch the photosensitive portion or the non-photosensitive portion, and then the resist is peeled off. A semiconductor integrated circuit is manufactured by repeating such steps.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a base mask. FIG. 2 is a reflectance spectrum in the EUV wavelength region when EUV light is irradiated on the protective film surface of a substrate with a multilayer reflective film (Mo / Si multilayer reflective film) and a protective film (Si film, Ru film). FIG. 3 shows the heating temperature of the decrease in central wavelength when a substrate with a multilayer reflective film (Mo / Si multilayer reflective film) and a protective film (Si film, Ru film) is heated for 10 minutes using a hot plate in an air atmosphere. It is the graph which showed the dependence. FIG. 4 shows the heating of the decrease in peak reflectance when a substrate with a multilayer reflective film (Mo / Si multilayer reflective film) and a protective film (Si film, Ru film) is heated for 10 minutes using a hot plate in an air atmosphere. It is the graph which showed temperature dependence. FIG. 5 is a diagram showing a correspondence relationship between the base mask shown in FIG. 1 and a test wafer on which a resist pattern is formed using the base mask when a positive resist is used for the resist film. is there. FIG. 6 is a diagram showing a correspondence relationship between the base mask shown in FIG. 1 and a test wafer on which a resist pattern is formed using the base mask when a negative resist is used for the resist film. is there.

Explanation of symbols

1: Base mask 2: Substrate 3: Reflective layer 4: Absorber layer 5: Test wafer 6, 7: Resist film 10, 10 ′: Non-opening 20, 20 ′: Opening

Claims (14)

A reflective layer that reflects EUV light is formed on a substrate, a portion where an absorber layer that absorbs EUV light is formed on the reflective layer, and the absorber layer is formed on the reflective layer. A portion where the absorber layer is formed on the reflective layer forms a non-opening portion of the mask pattern, and a portion where the absorber layer is not formed on the reflective layer is an opening of the mask pattern Manufacturing a reflective mask for EUV lithography (EUVL) forming a part;
Measuring the width of the opening of the mask pattern;
A step of comparing the measured value of the width of the opening of the mask pattern with a design value;
Based on the result obtained in the step of comparing the measured value of the width of the opening of the mask pattern and the design value, a part of the opening of the mask pattern of the reflective mask for EUVL is locally heated. A process for producing a reflective mask for EUVL, comprising the steps of:   2. The reflective type for EUVL according to claim 1, wherein when there is a portion where the measured value of the width of the opening of the mask pattern is larger than a design value, the portion of the opening of the mask pattern is locally heated. Mask manufacturing method. A reflective layer that reflects EUV light is formed on a substrate, a portion where an absorber layer that absorbs EUV light is formed on the reflective layer, and the absorber layer is formed on the reflective layer. A portion where the absorber layer is formed on the reflective layer forms a non-opening portion of the mask pattern, and a portion where the absorber layer is not formed on the reflective layer is an opening of the mask pattern Manufacturing a reflective mask for EUV lithography (EUVL) forming a part;
Measuring the width of the non-opening portion of the mask pattern;
A step of comparing the measured value of the width of the non-opening portion of the mask pattern with a design value;
Based on the result obtained in the step of comparing the measured value of the width of the non-opening portion of the mask pattern with the design value, a part of the opening portion of the mask pattern of the reflective mask for EUVL is locally heated. And a process for producing a reflective mask for EUVL, comprising the step of:   When there is a portion where the measured value of the width of the non-opening portion of the mask pattern is smaller than a design value, the portion of the opening portion of the mask pattern adjacent to the portion of the non-opening portion of the mask pattern is locally heated. A method for manufacturing a reflective mask for EUVL according to claim 3. A reflective layer that reflects EUV light is formed on a substrate, a portion where an absorber layer that absorbs EUV light is formed on the reflective layer, and the absorber layer is formed on the reflective layer. A portion where the absorber layer is formed on the reflective layer forms a non-opening portion of the mask pattern, and a portion where the absorber layer is not formed on the reflective layer is an opening of the mask pattern Manufacturing a reflective mask for EUV lithography (EUVL) forming a part;
Forming a resist pattern on the wafer using the EUVL reflective mask;
Measuring the space width of the resist pattern;
A step of comparing the measured value of the space width of the resist pattern with a design value;
A step of locally heating a part of the opening of the mask pattern of the reflective mask for EUVL based on a result obtained by comparing a measured value of the space width of the resist pattern with a design value; A process for producing a reflective mask for EUVL, comprising: The resist film on the wafer is a positive resist,
When there is a portion where the measured value of the space width in the resist pattern is larger than a design value, the portion of the opening portion of the mask pattern of the reflective mask for EUVL corresponding to the portion is locally heated. The manufacturing method of the reflective mask for EUVL of Claim 5. The resist film on the wafer is a negative resist,
When there is a portion where the measured value of the space width in the resist pattern is smaller than a design value, the portion of the opening portion of the mask pattern of the reflective mask for EUVL corresponding to the portion is locally heated. The manufacturing method of the reflective mask for EUVL of Claim 5. A reflective layer that reflects EUV light is formed on a substrate, a portion where an absorber layer that absorbs EUV light is formed on the reflective layer, and the absorber layer is formed on the reflective layer. A portion where the absorber layer is formed on the reflective layer forms a non-opening portion of the mask pattern, and a portion where the absorber layer is not formed on the reflective layer is an opening of the mask pattern Manufacturing a reflective mask for EUV lithography (EUVL) forming a part;
Forming a resist pattern on the wafer using the EUVL reflective mask;
Measuring the line width of the resist pattern;
A step of comparing the measured value of the line width of the resist pattern with the design value;
A step of locally heating a part of the opening of the mask pattern of the reflective mask for EUVL based on a result obtained by comparing a measured value of the line width of the resist pattern with a design value; A process for producing a reflective mask for EUVL, comprising: The resist film on the wafer is a positive resist,
When there is a portion where the measured value of the line width in the resist pattern is smaller than a design value, the portion of the mask pattern opening portion of the EUVL reflective mask corresponding to the portion is locally heated. The manufacturing method of the reflective mask for EUVL of Claim 8. The resist film on the wafer is a negative resist,
When there is a portion where the measured value of the line width in the resist pattern is larger than a design value, the portion of the opening portion of the mask pattern of the reflective mask for EUVL corresponding to the portion is locally heated. The manufacturing method of the reflective mask for EUVL of Claim 8.   The method of manufacturing a reflective mask for EUVL according to claim 1, wherein irradiation with a laser beam or an electron beam is used for the local heating.   The method for manufacturing a reflective mask for EUVL according to claim 1, wherein a minute heating member is used for the local heating.   The reflective mask for EUVL manufactured by the manufacturing method in any one of Claims 1-12.   A method for manufacturing a semiconductor integrated circuit, wherein a semiconductor integrated circuit is manufactured by exposing an object to be exposed using the EUVL reflective mask according to claim 13.

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