JP2008109060A - Method for depositing reflective multilayer film of reflective mask blank for euv lithography and method for producing reflecting mask blank for euv lithography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for depositing a reflecting multilayer film of a reflective mask blank for EUV lithography which is capable of preventing deformation of a substrate to provide the substrate having proper flatness, even if stresses are applied to the substrate by deposition of the reflective multilayer film, and a method for producing the EUV mask blank which is capable of preventing deformation of a substrate to provide the substrate with proper flatness, even if stress is applied to the substrate by the deposition of a buffer layer and an absorption layer. <P>SOLUTION: A method for depositing on a substrate, a reflecting multilayer film of a reflecting mask blank for EUV lithography by sputtering comprises depositing a reflecting multilayer film, in a state where a substrate has been deformed so as to be subjected to a stress, which is directed in the direction opposite to the stress applied to the substrate by the implementation of deposition of the reflective multilayer film; and returning the substrate to the shape prior to deformation, after the deposition of the reflecting multilayer film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming a multilayer film on a substrate. More specifically, a reflective mask blank for EUV (Extreme Ultra Violet) lithography (hereinafter referred to as “EUV mask blank”) used for semiconductor manufacturing or the like is formed on a substrate. The present invention relates to a method and a method for manufacturing an EUV mask blank.

  2. Description of the Related Art Conventionally, in the semiconductor industry, a photolithography method using visible light or ultraviolet light has been used as a technique for transferring a fine pattern necessary for forming an integrated circuit having a fine pattern on a Si substrate or the like. However, while miniaturization of semiconductor devices is accelerating, the exposure limit of conventional light exposure has been approached. In the case of light exposure, the resolution limit of the pattern is about ½ of the exposure wavelength, and it is said that the exposure wavelength is about ¼ even if the immersion method is used. The immersion method of ArF laser (193 nm) is used. Even if it is used, the limit is expected to be about 45 nm. Therefore, EUV lithography, which is an exposure technique using EUV light having a wavelength shorter than that of an ArF laser, is promising as an exposure technique for 45 nm and beyond. In this specification, EUV light refers to light having a wavelength in the soft X-ray region or vacuum ultraviolet region, and specifically refers to light having a wavelength of about 10 to 20 nm, particularly about 13.5 nm ± 0.3 nm.

  Since EUV light is easily absorbed by any material and has a refractive index close to 1, conventional refractive optical systems such as photolithography using visible light or ultraviolet light cannot be used. For this reason, in the EUV light lithography, a reflective optical system, that is, a reflective photomask and a mirror are used.

The mask blank is a laminate before patterning for manufacturing a photomask. A mask blank for a reflective photomask has a structure in which a reflective layer that reflects EUV light and an absorption layer that absorbs EUV light are formed in this order on a glass substrate or the like. As a reflective layer, a film of a high refractive index material and a film of a low refractive index material are alternately laminated, so that the light reflectivity when irradiating the surface of the layer with light, more specifically EUV light is applied to the layer surface. A multilayer reflective film having an increased light reflectance upon irradiation is usually used. In such a multilayer reflective film, Mo is widely used as a high refractive index material, and Si is widely used as a low refractive material. Conventionally, a magnetron sputtering method has been used to form a multilayer reflective film (see Patent Document 1), but an ion beam sputtering method is becoming mainstream because a film with few defects and high accuracy can be obtained (patents). Reference 2).
On the other hand, a material having a high absorption coefficient for EUV light, specifically, for example, a material layer mainly composed of Cr or Ta is used for the absorption layer, and these are usually formed by a magnetron sputtering method (Patent Literature). 2-6).

When a thin film is formed on the substrate, a compressive stress or a tensile stress may be generated in the film after the film formation.
When these compressive stress and tensile stress are applied to the substrate, the substrate may be deformed. Since a substrate made of low expansion glass is usually used as a substrate for a photomask, the deformation of the substrate caused by the application of stress is slight, and thus has not been a problem in the past.
However, due to the demand for pattern miniaturization, a slight deformation of the substrate (deformation of the substrate caused by the application of stress), which has not been regarded as a problem in the past, has become a problem.
In Patent Document 7, even when the thin film itself has film stress, the flatness of the mask blank becomes a desired flatness, and pattern position deviation and pattern defects occur during pattern transfer of the mask and pattern transfer. A method for manufacturing a mask blank and a transfer mask, and a method for determining the flatness of a transparent substrate for an electronic device used therefor and a method for manufacturing the same are described. In the method described in Patent Document 7, the flatness of the mask blank is desired in consideration of the amount of flatness change caused by the film stress of the thin film formed on the main surface of the transparent substrate for electronic devices used for the mask blank. It has been proposed to adjust the flatness of the substrate by determining the flatness of the substrate so as to achieve flatness and polishing the surface of the substrate in a convex or concave shape accordingly.

  Further, in Patent Document 8, in order to correct the deflection caused by the stress imbalance between the EUV mask substrate made of a low thermal expansion material and the multilayer coating formed on the substrate, the back surface of the substrate is corrected. It has been proposed to provide a high dielectric coating on the side to facilitate electrostatic chucking of the substrate. In Patent Document 8, a stress balancing layer is formed between the substrate and the material layer in order to prevent deflection due to stress imbalance between the EUV mask substrate and the material layer formed on the substrate. It has been proposed to do.

Japanese Patent Laid-Open No. 2002-222864 JP 2004-246366 A JP 2002-319542 A Japanese Patent Laid-Open No. 2004-6798 JP 2004-6799 A JP 2004-39884 A JP 2004-29736 A Japanese translation of PCT publication No. 2003-501823

However, in the method described in Patent Document 7, it is difficult to grind the substrate surface into a predetermined shape (convex shape or concave shape) according to the amount of change in flatness due to the film stress of the thin film, and it is troublesome. Take it. In addition, when such polishing is performed, polishing is performed so that the flatness of the substrate is within the specification of the EUV mask blank and the wedge angle and local slope of the substrate are within the specification of the EUV mask blank. Is very difficult.
When manufacturing an EUV mask blank, a plurality of films having different compositions are formed on a substrate. For example, as the reflective layer, a multilayer reflective film in which high refractive index material films and low refractive material films are alternately laminated is used. As the absorption layer formed on the multilayer reflective film, a material layer having a high absorption coefficient for EUV light is used. The stress generated in these films is not necessarily the same tendency, and a film in which a tensile stress is generated and a film in which a compressive stress is generated may be laminated. . In such a case, it is practically impossible to polish the substrate surface so as to cope with the stress generated in all the films. Therefore, in the method described in Patent Document 7, the surface of the substrate is polished so as to correspond to the stress generated at the time when all the films are formed (the total stress generated in each film).

  Therefore, when the method described in Patent Document 7 is applied to an EUV mask blank, in the film formation process, the shape of the polished substrate surface may not correspond to the stress generated in the formed film. sell. For example, there may be a state in which compressive stress is generated in the formed film, even though the shape of the substrate surface is a shape corresponding to the situation in which tensile stress is generated in the film. If the substrate is removed from the fixing means such as the electrostatic chuck or the folder in this state, the stress generated in the formed film does not correspond to the shape of the polished substrate surface. There is a possibility that the deformation of the substrate due to the stress of the film may be accelerated rather than the case where the film is formed on the surface.

On the other hand, when a high dielectric coating is applied to the back side of the substrate according to the method described in Patent Document 8 to promote electrostatic chucking of the substrate, no deflection occurs in the substrate fixed by the electrostatic chuck. However, the stress imbalance between the substrate and the material layer is not improved. Therefore, when the substrate is removed from the electrostatic chuck, the substrate may bend due to an unbalance of stress between the substrate and the material layer.
Moreover, when manufacturing an EUV mask blank, the kind and thickness of the film | membrane formed on an EUV mask board | substrate are restrict | limited for reasons, such as an optical characteristic. For this reason, the kind of substance used as a stress balancing layer formed between the substrate and the substance layer and the thickness of the stress balancing layer are naturally limited. Therefore, it has been difficult to sufficiently improve the stress imbalance between the substrate and the material layer.

  In order to solve the above problems, an object of the present invention is to provide a method for forming a multilayer film in which even if stress is applied to the substrate by the formation of the multilayer film, the substrate is not deformed and the flatness is good. To do. More specifically, the present invention provides a method for forming a multilayer reflective film of an EUV mask blank that can improve the flatness without deformation of the substrate even when stress is applied to the substrate by forming the multilayer reflective film. For the purpose. It is another object of the present invention to provide a method for manufacturing an EUV mask blank that can improve the flatness without deformation of the substrate even when stress is applied to the substrate by forming the buffer layer and the absorption layer.

To achieve the above object, the present invention provides a method for forming a multilayer film on a substrate,
Forming the multilayer film in a state where the substrate is deformed so that the substrate has a stress in a direction opposite to the stress applied to the substrate by the multilayer film formation,
After the multilayer film is formed, the multilayer film is formed by returning the substrate to the shape before deformation.

Further, the present invention is a method of forming a multilayer reflective film of a reflective mask blank for EUV lithography on a substrate using a sputtering method,
Forming the multilayer reflective film in a state where the substrate is deformed so that the substrate has a stress in a direction opposite to the stress applied to the substrate by the formation of the multilayer reflective film;
After the multilayer reflective film is formed, the substrate is returned to its original shape before deformation. The method for forming a multilayer film of a reflective mask blank for EUV lithography (hereinafter referred to as “multilayer reflective of the present invention”). A film forming method ").
In the multilayer reflective film forming method of the present invention, it is preferable that the flatness of the substrate after returning to the shape before deformation is 100 nm or less.

In the multilayer reflective film formation method of the present invention, in order to perform the formation of the multilayer reflective film in a state where the substrate is deformed, a shape corresponding to the shape after deformation of the substrate is formed on the bonding surface with the substrate It is preferable to fix the substrate using a first electrostatic chuck having
In the multilayer reflective film forming method of the present invention, the first electrostatic chuck preferably has a chucking force of 0.5 kPa or more and a Young's modulus of 10 GPa or more.
In the multilayer reflective film forming method of the present invention, the substrate preferably has a specific rigidity of 3.0 × 10 ⁷ m ² / s ² or more and a Poisson's ratio of 0.16 to 0.25.

In addition, the present invention, after forming a multilayer reflective film on the substrate using the multilayer reflective film formation method of the present invention,
A method of manufacturing a reflective mask blank for EUV lithography by forming an absorption layer on the multilayer reflective film using a sputtering method,
The absorption layer is formed in a deformed state so that the substrate has a stress in a direction opposite to the stress applied to the substrate by the formation of the absorption layer,
Provided is a reflective mask blank manufacturing method for EUV lithography, wherein the substrate is returned to a shape before deformation after the absorption layer is formed.

In addition, the present invention, after forming a multilayer reflective film on the substrate using the multilayer reflective film formation method of the present invention,
A method of manufacturing a reflective mask blank for EUV lithography by forming a buffer layer and an absorption layer on the multilayer reflective film using a sputtering method,
The buffer layer and the absorption layer are formed in a deformed state so that the substrate has a stress in a direction opposite to the stress applied to the substrate by the formation of the buffer layer and the absorption layer,
Provided is a reflective mask blank manufacturing method for EUV lithography, wherein the substrate is returned to a shape before deformation after the absorption layer is formed.

  Hereinafter, in this specification, the manufacturing method of the reflective mask blank for EUV lithography described in [0015] and [0016] is generically referred to as “EUV mask blank manufacturing method”.

  In the manufacturing method of the EUV mask blank of this invention, it is preferable that the flatness of the said board | substrate after returning to the shape before a deformation | transformation is 100 nm or less.

  In the EUV mask blank manufacturing method of the present invention, in order to perform the film formation of the absorption layer, or the buffer layer and the absorption layer in a state where the substrate is deformed, the bonding surface with the substrate is formed after the deformation of the substrate. It is preferable to use a second electrostatic chuck having a shape corresponding to the shape.

  In the EUV mask blank manufacturing method of the present invention, the second electrostatic chuck preferably has a chucking force of 0.5 kPa or more and a Young's modulus of 10 GPa or more.

In the multilayer reflection film forming method of the present invention, the multilayer reflection film is formed by a stress in the direction opposite to the stress applied to the substrate by the formation of the multilayer reflection film (hereinafter referred to as “first stress” in this specification). The stress applied to the substrate is reduced by the film. As a result, there is no possibility that the substrate after the film formation is deformed by the stress applied to the substrate by the film formation of the multilayer reflective film. Thereby, a multilayer reflective film of an EUV mask blank having excellent flatness, specifically, a multilayer reflective film having a flatness of 100 nm or less can be obtained.
In the first embodiment of the EUV mask blank manufacturing method of the present invention, the absorption layer is subjected to stress in the direction opposite to the stress applied to the substrate by the formation of the absorption layer (hereinafter referred to as “second stress” in this specification). This reduces the stress applied to the substrate. As a result, there is no possibility that the substrate after film formation is deformed by the stress applied to the substrate by the film formation of the absorption layer. Thereby, an EUV mask blank excellent in flatness, specifically, an EUV mask blank having a flatness of 100 nm or less can be manufactured.
Furthermore, in the second embodiment of the EUV mask blank manufacturing method of the present invention, the stress (hereinafter referred to as the present specification) that is the sum of the stress applied to the substrate by the formation of the buffer layer and the stress applied to the substrate by the formation of the absorption layer. The buffer layer and the absorption by the stress in the opposite direction (hereinafter referred to as “third stress” in this specification) with respect to “the stress applied to the substrate by the film formation of the buffer layer and the absorption layer” in the document. The stress applied to the substrate is reduced by forming the layer. As a result, there is no possibility that the substrate after film formation is deformed by the stress applied to the substrate by the film formation of the buffer layer and the absorption layer. Thereby, an EUV mask blank excellent in flatness, specifically, an EUV mask blank having a flatness of 100 nm or less can be manufactured.

According to the multilayer reflective film forming method of the present invention, a multilayer reflective film having a flatness of 100 nm or less can be obtained by using a substrate having a flatness of more than 100 nm as a substrate for film formation.
According to the method for producing an EUV mask blank of the present invention, an EUV mask blank having a flatness of 100 nm or less can be produced using a substrate having a flatness of more than 100 nm as a film-forming substrate.
In addition, since the stress of the multilayer reflective film is roughly determined by the film thickness and the number of layers, when the film thickness and the number of layers of the multilayer reflective film to be formed are similar, The stress applied to the substrate is generally constant. Therefore, in the multilayer reflective film deposition method of the present invention, the first stress of the substrate during the multilayer reflective film deposition is also substantially constant. Therefore, when performing the multilayer reflective film forming method of the present invention, it is not necessary to change the first stress for each substrate, and specifically, it is not necessary to change the shape of the electrostatic chuck for each substrate. For this reason, it is excellent in productivity of a board | substrate with a multilayer reflective film.

The present invention is a method for forming a multilayer film on a substrate, wherein the substrate is deformed in a state in which the substrate has a stress in a direction opposite to a stress applied to the substrate by the multilayer film formation. A multilayer film is formed, and after the multilayer film is formed, the substrate is returned to a shape before deformation.
First, the multilayer reflective film forming method of the present invention will be described. In the multilayer reflective film forming method of the present invention, a multilayer reflective film of an EUV mask blank (hereinafter simply referred to as “multilayer reflective film”) is formed on a substrate using a sputtering method such as a magnetron sputtering method or an ion beam sputtering method. The film formation is the same as in the conventional method. However, in the multilayer reflective film forming method of the present invention, the multilayer reflective film is formed in a state where the substrate is deformed so that the substrate has the first stress.

When a multilayer reflective film is formed on a substrate using a sputtering method such as magnetron sputtering or ion beam sputtering, stress (usually compressive stress) is generated in the multilayer reflective film after film formation, and this stress is applied to the substrate. To join. Such stress is hereinafter referred to as “stress applied to the substrate by forming the multilayer reflective film” or “stress by forming the multilayer reflective film”.
For example, using an ion beam sputtering method, as a multilayer reflective film on a substrate, a Si film (low refractive index layer, film thickness 4.5 nm), a Mo film (high refractive index layer, film thickness 2.3 nm), Are alternately formed to form a Si / Mo multilayer reflective film, a compressive stress of 400 to 500 MPa is usually applied to the substrate by the multilayer reflective film. When forming the multilayer reflective film, the substrate is fixed by an electrostatic chuck or a folder. In this state, even if a compressive stress of 400 to 500 MPa due to the formation of the multilayer reflective film is applied to the substrate, the substrate is not deformed thereby. However, when the substrate is removed from the electrostatic chuck or the folder, a compressive stress of 400 to 500 MPa due to the formation of the multilayer reflective film is applied, so that even a quartz glass substrate having high rigidity is deformed to some extent.
For example, as a substrate for an EUV mask blank, a commonly used SiO ₂ —TiO ₂ glass substrate (outer shape 6 inch (152.4 mm) square, thickness 6.3 mm, coefficient of thermal expansion 0.2 × 10 ^-7 / ° C., Young's modulus 67 GPa, specific rigidity 3.1 × 10 ⁷ m ² / s ² ), when a compressive stress of 400 to 500 MPa due to the formation of a multilayer reflective film is applied, It is deformed in a state where it is warped in a convex shape of about 1.9 to 2.1 μm. In the EUV mask blank, the flatness tolerance is 100 nm or less from end to end of the mask blank. The “flatness of the substrate after forming the multilayer reflective film” means the flatness on the multilayer reflective film.
Although it is possible to lower the flatness of the substrate after the multilayer reflective film is formed to be below the allowable limit value by heat treatment or the like, the optical characteristics of the EUV mask blank may be deteriorated when such treatment is performed. .

In the multilayer film forming method of the present invention, the multilayer reflective film is formed with the substrate deformed so that the substrate has the first stress. For example, in the above-described example, a compressive stress of 400 to 500 MPa is applied to the substrate by forming the multilayer reflective film, so the first stress is a tensile stress having a magnitude similar to this compressive stress.
As will be described in detail later, when the multilayer reflective film is formed with the substrate deformed so that the substrate has the first stress, the substrate after the multilayer reflective film is formed is returned to its original shape. At this time, the stress applied to the substrate by forming the multilayer reflective film is reduced to such an extent that the substrate is not deformed by being canceled by the first stress.
Here, the “first stress” is a stress in a direction opposite to the stress applied to the substrate by the formation of the multilayer reflective film, as described above. However, since the stress applied to the substrate by the formation of the multilayer reflective film is a two-dimensional stress, the first stress is generated by deforming the substrate. It is thought that. Therefore, when the above-mentioned definition of “first stress” is interpreted in a narrow sense, that is, when interpreted literally, it cannot be said that the stress is in the opposite direction to the stress applied to the substrate due to the formation of the multilayer reflective film. There is also. In this regard, in this specification, the definition relating to “first stress” is interpreted broadly. Specifically, as described above, when the stress applied to the substrate by the formation of the multilayer reflective film is a compressive stress, a tensile stress of the same magnitude or a three-dimensional stress corresponding thereto is applied. The first stress is assumed. The same applies to the second stress and the third stress described later.

As apparent from the above points, in the multilayer reflective film forming method of the present invention, the magnitude of the first stress varies depending on the magnitude of the stress applied to the substrate by the multilayer reflective film.
In the multilayer reflective film forming method of the present invention, the stress applied to the substrate by forming the multilayer reflective film is preferably reduced to 300 MPa or less by the first stress, more preferably reduced to 200 MPa or less, More preferably, the pressure is reduced to 100 MPa or less. In the multilayer reflective film forming method of the present invention, the magnitude of the first stress is more preferably equal to the magnitude of the stress applied to the substrate by forming the multilayer reflective film.

  In the multilayer reflective film forming method of the present invention, in order to cause the substrate to have the first stress by deformation, the direction opposite to the direction in which the substrate is deformed by applying compressive stress due to the formation of the multilayer reflective film. The substrate may be deformed. In the above-described example, by applying compressive stress due to the formation of the multilayer reflective film, about 1.9 to 2.1 μm, generally about 1.95 to 2.05 μm, The substrate is deformed in a warped state. Therefore, in order for the substrate 1 to have the first stress, it is warped in a concave shape of about 1.9 to 2.1 μm, preferably about 1.95 to 2.05 μm with respect to the film formation surface side. The substrate may be deformed so that

FIG. 1A to FIG. 1E are conceptual diagrams for explaining the multilayer reflective film forming method of the present invention, and show the shapes of the substrates before and after the multilayer reflective film is formed. FIG. 1A shows the substrate 1 before forming a multilayer reflective film. As shown in FIG. 1A, the flatness of the substrate 1 before forming the multilayer reflective film is targeted to be 0 μm by polishing. In FIG. 1A, a line 10 is a virtual horizontal line shown in order to clarify the presence / absence of deformation of the substrate 1. FIG. 1B shows the substrate 1 after the multilayer reflective film 2 is formed by sputtering according to the conventional procedure.
In FIG. 1B, compressive stress due to the formation of the multilayer reflective film 2 is applied to the substrate 1, whereby the substrate 1 is deformed in a convex shape on the film forming surface side.
FIG. 1C shows the substrate 1 deformed to have a first stress in order to prevent the substrate 1 after the multilayer reflective film 2 is formed from being deformed into the shape shown in FIG. Show. In FIG.1 (c), the board | substrate 1 is deform | transforming into the state which curved in the concave shape at the film-forming surface side. In the multilayer reflective film forming method of the present invention, the multilayer reflective film is formed by sputtering in a state where the substrate 1 is deformed into the shape shown in FIG. FIG. 1D shows a state in which a multilayer reflective film 2 is formed on the substrate 1 shown in FIG.

In the multilayer reflective film forming method of the present invention, as shown in FIG. 1D, after the multilayer reflective film 2 is formed in a state where the substrate 1 is deformed so as to have the first stress, the substrate 1 is formed. Return to the original shape.
In addition, what is necessary is just to cancel | release the force applied to the board | substrate 1 in order to deform | transform, in order to return the board | substrate 1 to the shape before a deformation | transformation from the state shown in FIG.1 (d). As a result, the substrate 1 returns to the shape before deformation by the restoring force.
FIG. 1E shows a state in which the substrate 1 is returned to the shape before deformation after the multilayer reflective film 2 is formed. In the state shown in FIG. 1E, the compressive stress applied to the substrate 1 by the formation of the multilayer reflective film is reduced to the extent that it is canceled out by the first stress and does not deform the substrate. As a result, the substrate 1 is prevented from being deformed by the compressive stress applied to the substrate 1 due to the formation of the multilayer reflective film.

In the multilayer reflection film forming method of the present invention, means for forming the multilayer reflection film 2 in a state where the substrate 1 is deformed to have the first stress, that is, the substrate 1 has the first stress. There are no particular limitations on the means for deforming. Therefore, for example, as shown in FIG. 1C, when the substrate 1 is deformed in a concave shape on the film forming surface side, both side surfaces of the substrate 1 shown in FIG. 1A are directed toward the center of the drawing. By pressing with a force of a specific magnitude, the film may be deformed into a concave shape on the film surface side. The magnitude of the force is preferably the same force toward the center.
In the multilayer reflective film forming method of the present invention, an electrostatic chuck having a specific shape is used to form the multilayer reflective film 2 while the substrate 1 is deformed to have the first stress. The substrate 1 is preferably fixed. In this case, the electrostatic chuck is a means for deforming the substrate 1 to have the first stress.
When forming a film on a substrate using a sputtering method such as a magnetron sputtering method or an ion beam sputtering method, an electrostatic chuck is most commonly used as a means for fixing the substrate. Therefore, when an electrostatic chuck is used as a means for deforming the substrate, it is not necessary to bring new means used only for the deformation of the substrate into the system for performing sputtering. When such a new means is brought into the system for performing sputtering, the sputtered particles adhering to the means may be peeled off to contaminate the substrate and the multilayer reflective film. Further, when an electrostatic chuck is used as means for deforming the substrate, the entire film formation surface of the substrate can be formed at a time.

In order to deform the substrate 1 so as to have the first stress using the electrostatic chuck, the first electrostatic chuck having a shape corresponding to the shape after deformation of the substrate is used. That's fine.
FIG. 2 is a conceptual diagram of a first electrostatic chuck used when the substrate 1 is deformed into the shape shown in FIG. Note that FIG. 2 also shows the substrate 1 of FIG. In the first electrostatic chuck 20 shown in FIG. 2, the bonding surface 20a with the substrate 1 corresponds to the shape of the substrate 1 after deformation shown in FIG. Specifically, the bonding surface 20a has a concave shape, and is a surface on the back side with respect to the film formation surface of the substrate 1 after deformation shown in FIG. This corresponds to the shape of “the back side of”. By fixing the substrate 1 to the first electrostatic chuck 20 having such a shape, the substrate 1 can be deformed into the shape shown in FIG. In FIG. 2, the bonding surface 20a of the electrostatic chuck itself has a concave shape, but the shaping surface has a concave shape between the electrostatic chuck and the substrate while the bonding surface of the electrostatic chuck remains horizontal. It is also possible to cope with this by inserting a member. This aspect is also the first electrostatic chuck described above, that is, the electrostatic chuck having a shape in which the bonding surface with the substrate corresponds to the shape after deformation of the substrate. included. When such a shaping member is used, it is necessary that the entire first electrostatic chuck including the shaping member satisfies the conditions described later.
When the first electrostatic chuck 20 has a shape corresponding to the deformed shape of the substrate 1, the shape of the bonding surface 20 a of the first electrostatic chuck 20 with the substrate 1 and the deformed shape of the substrate 1. It is preferable that the deviation from this shape is 2 mm or less, particularly 1 mm or less, more preferably 0.1 mm or less.

However, since the substrate used for manufacturing the EUV mask blank is a highly rigid substrate such as a quartz glass substrate, the substrate is deformed to have the first stress by using an electrostatic chuck. For this purpose, the first electrostatic chuck needs to satisfy the following conditions.
(A) It has higher rigidity (Young's modulus, Poisson's ratio) than the substrate used for film formation.
(B) The chucking force is sufficiently strong and the substrate can be deformed.
Regarding the above (a), the first electrostatic chuck preferably has Young's modulus and Poisson's ratio satisfying the following conditions, respectively.
Young's modulus: 10 GPa or more, preferably 50 GPa or more Poisson's ratio: 0.4 or less, preferably 0.3 or less When the rigidity of the first electrostatic chuck 20 is lower than the rigidity of the substrate 1, not the substrate 1 but the electrostatic chuck There is a possibility that 20 is deformed. Since the rigidity of the electrostatic chuck is also affected by the shape and size, it cannot be determined only by the Young's modulus and Poisson's ratio. It is preferable to increase the value.

In order for the first electrostatic chuck to satisfy the above Young's modulus and Poisson's ratio, it is necessary that the electrostatic chuck be made of a material having high hardness. The material of the surface portion of the electrostatic chuck that comes into contact with the substrate is required to be a high dielectric, and specifically, the relative dielectric constant at 1 MHz is 8 or more.
In order to satisfy such requirements, ceramic materials such as alumina, aluminum nitride, and silicon carbide are used as the material of the surface portion of the electrostatic chuck that contacts the substrate.

  Regarding the above (b), it is preferable to use a first electrostatic chuck having a chucking force of 0.5 kPa or more, more preferably a chucking force of 1.0 kPa or more. When the chucking force of the first electrostatic chuck is small, the substrate 1 may not be sufficiently deformed when the substrate 1 is fixed to the first electrostatic chuck 20. If the chucking force is within the above range, even a highly rigid substrate such as a quartz glass substrate can be deformed into a desired shape.

In the multilayer reflective film forming method of the present invention, the shape and dimensions of the first electrostatic chuck 20, more specifically, the planar shape and dimensions of the bonding surface 20 a of the first electrostatic chuck 20 are not particularly limited. . Therefore, the planar shape of the joint surface 20a may be a circle or an ellipse, a square or a rectangle, a hexagon, an octagon, or another polygon. However, the shape of the bonding surface 20a is preferably substantially the same as the planar shape of the substrate 1 fixed to the bonding surface 20a, in order to deform the substrate 1 fixed to the bonding surface 20a into a desired shape. .
The dimension of the bonding surface 20a may be larger or smaller than the dimension of the substrate 1 fixed to the bonding surface 20. However, when the bonding surface 20a is larger than the substrate 1, when the multilayer reflective film is formed using the sputtering method, the sputtered particles may adhere to the bonding surface 20a and become a contamination source. If the bonding surface 20a is too small than the substrate 1, the substrate 1 fixed to the bonding surface 20a may not be deformed into a desired shape. For this reason, it is preferable that the size of the bonding surface 20 a is slightly smaller than the size of the substrate 1.

In the multilayer reflective film forming method of the present invention, in order to deform the substrate 1 to have the first stress using the first electrostatic chuck 20, as in the method described in Patent Document 8, It is preferable to apply a high dielectric coating to the back surface of the substrate 1 to promote electrostatic chucking of the substrate 1. For such a purpose, the high dielectric coating applied to the back surface of the substrate 1 selects the electrical conductivity and thickness of the constituent material so that the sheet resistance is 100 Ω / □ 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 Patent Document 8, specifically, a coating made of silicon, TiN, molybdenum, chromium, CrN, or TaSi can be applied. The thickness of the high dielectric coating can be, for example, 10 to 1000 nm, in particular 10 to 100 nm.
The high dielectric coating can be formed using a known film forming method, for example, sputtering such as magnetron sputtering or ion beam sputtering, CVD, vacuum deposition, or electrolytic plating.

The substrate 1 used in the multilayer reflective film forming method of the present invention is required to satisfy the characteristics as a substrate for an EUV mask blank. Therefore, the substrate 1 preferably has a low thermal expansion coefficient (0 ± 1.0 × 10 ⁻⁷ / ° C., more preferably 0 ± 0.3 × 10 ⁻⁷ / ° C., and further preferably 0 ± 0.2. × 10 ⁻⁷ / ° C., more preferably 0 ± 0.1 × 10 ⁻⁷ / ° C., particularly preferably 0 ± 0.05 × 10 ⁻⁷ / ° C.), smoothness, flatness, and mask blank Or the thing excellent in the tolerance to the washing | cleaning liquid used for the washing | cleaning etc. of the photomask after pattern formation is preferable. Specifically, the substrate 1 is made of glass having a low thermal expansion coefficient, such as SiO ₂ —TiO ₂ glass, but is not limited to this. Crystallized glass, quartz glass, silicon, A substrate made of metal or the like can also be used. The substrate 1 is preferably a highly rigid substrate. Specifically, it is preferable that the specific rigidity is 3.0 × 10 ⁷ m ² / s ² or more and the Poisson's ratio is 0.16 to 0.25.
It is preferable that the substrate 1 has a smooth surface having an Rms of 0.15 nm or less and a flatness of 100 nm or less because a high reflectance and transfer accuracy can be obtained in a photomask after pattern formation. . On the other hand, the back surface of the substrate 1 is preferably a smooth surface having an Rms of 0.5 nm or less.
The size, thickness, etc. of the substrate 1 are appropriately determined according to the design value of the mask. As the substrate, a rectangular substrate having a side length of 140 to 160 mm square is preferably used, and a substrate having a thickness of 5 to 7 mm is preferably used. In the following examples, SiO ₂ —TiO ₂ glass having a side length of 6 inches (152.4 mm) and a thickness of 0.25 inches (6.3 mm) was used.

  The multilayer reflective film formed on the substrate 1 using the multilayer reflective film deposition method of the present invention is not particularly limited as long as it has desired characteristics as the multilayer reflective film of the EUV mask blank. Here, the characteristic particularly required for the multilayer reflective film is a film having a high EUV light reflectance. Specifically, when the multilayer reflective film surface is irradiated with light in the wavelength region of EUV light, the maximum value of light reflectance near the wavelength of 13.5 nm is preferably 60% or more, and is 65% or more. It is more preferable.

  As the multilayer reflective film satisfying the above characteristics, a Si / Mo multilayer reflective film in which Si films and Mo films are alternately laminated, a Be / Mo multilayer reflective film in which Be and Mo films are alternately laminated, and a Si compound Si compound / Mo compound multilayer reflective film, Si film, Mo film and Ru film laminated in this order, Si film, Ru film, A Si / Ru / Mo / Ru multilayer reflective film in which a Mo film and a Ru film are laminated in this order can be mentioned.

The procedure for forming the multilayer reflective film described above may be a procedure that is normally performed when the multilayer reflective film is formed using a sputtering method such as a magnetron sputtering method or an ion beam sputtering method. For example, in the case where a Si / Mo multilayer reflective film is formed by using ion beam sputtering, an Si target is used as a target and Ar gas (gas pressure 1.3 × 10 ⁻² Pa as a sputtering gas). ˜2.7 × 10 ⁻² Pa) is used to form a Si film so as to have a thickness of 4.5 nm at an ion acceleration voltage of 300 to 1500 V and a deposition rate of 0.03 to 0.30 nm / sec. , then, using a Mo target as the target, using an Ar gas (gas pressure ^{1.3 × 10 -2 Pa~2.7 × 10 -2} Pa), an ion acceleration voltage 300 to 1,500 V, formed It is preferable to form the Mo film so as to have a thickness of 2.3 nm at a film speed of 0.03 to 0.30 nm / sec. With this as one period, the Si / Mo multilayer reflective film is formed by laminating the Si film and the Mo film for 40 to 50 periods. The film thickness of the multilayer reflective film is preferably 250 to 300 nm from the viewpoint of obtaining a suitable EUV light reflectance.
The method for forming the multilayer reflective film 2 is not particularly limited as long as it is a sputtering method, and may be either a magnetron sputtering method or an ion beam sputtering method. However, it is preferable to form the film by ion beam sputtering because a film with few defects and high accuracy can be obtained.

  When forming a multilayer reflective film by using a sputtering method, in order to obtain a uniform film formation, the film formation is generally performed while rotating the substrate using a rotating body. Also in the multilayer reflective film forming method of the present invention, it is preferable to perform film formation while rotating the substrate using a rotating body in order to obtain uniform film formation.

  In the multilayer reflective film forming method of the present invention, the uppermost layer of the multilayer reflective film is preferably made of a material that is difficult to oxidize in order to prevent oxidation of the surface of the multilayer reflective film after film formation. The layer of the material that is not easily oxidized functions as a cap layer of the multilayer reflective film. As a specific example of the layer of a material that hardly functions to be oxidized and functions as a cap layer, a Si layer can be exemplified. When the multilayer reflective film is a Si / Mo film, the uppermost layer can be made to function as a cap layer by making the uppermost layer an Si layer. In that case, the thickness of the cap layer is preferably 11.0 ± 1 nm.

As described with reference to FIGS. 1D and 1E, in the multilayer film forming method of the present invention, after the multilayer reflective film 2 is formed, the shape of the substrate 1 is returned to the shape before deformation. When the substrate 1 is deformed to the shape shown in FIG. 1C by being fixed to the first electrostatic chuck 20 shown in FIG. 2, the first shape is used to return the shape of the substrate 1 to the shape before deformation. The substrate 1 may be removed from the first electrostatic chuck 20 by releasing the chucking force of the electrostatic chuck 20. The substrate 1 removed from the first electrostatic chuck 20 returns to the shape before deformation by the restoring force.
As described with reference to FIG. 1 (e), in the multilayer reflective film forming method of the present invention, after the multilayer reflective film 2 is formed, the multilayer reflective film 2 is returned in a state in which the substrate 1 is returned to its original shape. The stress applied to the substrate by the film formation is canceled by the first stress and reduced to such an extent that the substrate is not deformed. As a result, the substrate 1 is prevented from being deformed by the stress applied to the substrate 1 by the formation of the multilayer film. For this reason, the board | substrate 1 after film-forming of the multilayer reflective film 2, and the board | substrate 1 after returning to the shape before a deformation | transformation more specifically are excellent in flatness. The flatness of the substrate 1 after returning to the shape before deformation is preferably 100 nm or less, more preferably 75 nm or less, still more preferably 50 nm or less, and particularly preferably 30 nm or less. The “flatness of the substrate after forming the multilayer reflective film” means the flatness on the multilayer reflective film.
As a result, an EUV mask blank multilayer reflective film having excellent flatness, specifically, a multilayer reflective film having a flatness of 100 nm or less can be obtained.

Next, a first embodiment of a method for manufacturing an EUV mask blank of the present invention will be described.
In the first embodiment of the manufacturing method of the EUV mask blank of the present invention, a multilayer reflective film is formed on a substrate using the multilayer reflective film forming method of the present invention, and then the multilayer reflective film is formed on the multilayer reflective film using a sputtering method. In this method, an EUV mask blank is produced by forming an absorption layer on the substrate.

In the first embodiment of the manufacturing method of the EUV mask blank of the present invention, the absorption layer is formed on the multilayer reflective film by using a sputtering method such as a magnetron sputtering method or an ion beam sputtering method. is there.
However, in the first embodiment of the manufacturing method of the EUV mask blank of the present invention, the absorption layer is formed in a state where the substrate is deformed so that the substrate has the second stress.
As will be described in detail later, when the absorption layer is formed with the substrate deformed so that the substrate has the second stress, when the substrate after the absorption layer is formed is returned to the original shape. The stress applied to the substrate by the formation of the absorption layer is canceled by the second stress, and is reduced to the extent that the substrate is not deformed.

Similarly to the case where a multilayer reflective film is formed on a substrate, when an absorption layer is formed on the multilayer reflective film using a sputtering method such as a magnetron sputtering method or an ion beam sputtering method, Stress is generated and this stress is applied to the substrate. Such stress is hereinafter referred to as “stress applied to the substrate by the formation of the absorption layer” or “stress due to the formation of the absorption layer” in the present specification.
However, since the constituent materials and the film formation conditions of the multilayer reflective film and the absorption layer are different, the stress applied to the substrate by the multilayer reflective film formation and the stress applied to the substrate by the absorption layer deposition are expressed as follows: The size is different. For example, when a TaN film having a thickness of 70 nm is formed as an absorption layer on a multilayer reflective film using an ion beam sputtering method, a compressive stress of 100 to 400 MPa due to the formation of the absorption layer is applied to the substrate.
The stress applied to the substrate by the formation of the absorption layer is usually a compressive stress. However, in the case of the absorption layer, the stress applied to the substrate by the formation of the absorption layer may be a tensile stress.
As a result, the first stress in the multilayer reflective film deposition method of the present invention and the second stress in the EUV mask blank manufacturing method of the present invention are usually different in magnitude and have different attributes. There is.

As is apparent from the above points, in the first embodiment of the manufacturing method of the EUV mask blank of the present invention, the magnitude of the second stress varies depending on the magnitude of the stress applied to the substrate by the formation of the absorption layer.
In the first embodiment of the EUV mask blank manufacturing method of the present invention, the stress applied to the substrate by the formation of the absorption layer is preferably reduced to 300 MPa or less by the second stress, and is reduced to 200 MPa or less. Is more preferable, and it is further preferable that the pressure is reduced to 100 MPa or less.

  In the first embodiment of the EUV mask blank manufacturing method of the present invention, the concept for deforming the substrate so as to have the second stress and the means for deforming the substrate are as follows: This is basically the same as described for the case where the substrate is deformed to have the first stress. However, the stress applied to the substrate by the formation of the absorption layer may be a tensile stress. Therefore, when the stress applied to the substrate due to the formation of the absorption layer is a tensile stress, the idea for deforming the substrate to have the second stress and the means for deforming the substrate will be described below.

FIGS. 3A to 3E are conceptual diagrams for explaining the first embodiment of the manufacturing method of the EUV mask blank of the present invention, and show the shapes of the substrates before and after the formation of the absorption layer. In FIG. 3, the stress applied to the substrate by the formation of the absorption layer is tensile stress.
FIG. 3A shows the substrate 1 before the absorption film is formed. In FIG. 3A, a multilayer reflective film 2 is formed on a substrate 1. As shown in FIG. 3A, the substrate 1 before the formation of the absorption layer has a flatness of 0 μm. In FIG. 3A, a line 10 is a virtual horizontal line shown in order to clarify the presence / absence of deformation of the substrate 1.
FIG. 3B shows the substrate after the absorption layer 3 is formed on the multilayer reflective film 2 according to the conventional procedure. The substrate 1 shown in FIG. 3B is deformed in a state of warping in a concave shape on the film forming surface side due to tensile stress due to film formation of the absorption layer 3.
FIG. 3C shows a substrate deformed to have a second stress in order to prevent the substrate 1 after the absorption layer 3 is formed from being deformed into the shape shown in FIG. 1 is shown. In FIG.3 (c), the board | substrate 1 has deform | transformed into the state which curved in convex shape at the film-forming surface side. In the first embodiment of the manufacturing method of the EUV mask blank of the present invention, the absorption layer is formed using the sputtering method in a state where the substrate 1 is deformed into the shape shown in FIG. FIG. 3D shows a state in which the absorption layer 3 is formed on the multilayer reflective film 2 of the substrate 1 shown in FIG.

  In the first embodiment of the EUV mask blank manufacturing method of the present invention, as shown in FIGS. 3C and 3D, the substrate 1 is deformed so as to have the second stress. After the absorption layer 3 is formed, the EUV mask blank is manufactured by returning the substrate 1 to the shape before deformation. In addition, what is necessary is just to cancel | release the force applied in order to deform | transform the board | substrate 1 in order to return the board | substrate shown in FIG.3 (d) to the shape before a deformation | transformation. The substrate 1 returns to its original shape by the restoring force. FIG. 3E shows a state in which the substrate 1 is returned to the shape before deformation after the absorption layer 3 is formed. In the state shown in FIG. 3E, the stress applied to the substrate 1 by the formation of the absorption layer 3 is canceled by the second stress, and is reduced to the extent that the substrate is not deformed. As a result, the substrate 1 after the absorption layer 3 is formed is prevented from being deformed by the stress applied to the substrate 1 by the formation of the absorption layer 3.

In the first embodiment of the EUV mask blank manufacturing method of the present invention, in order to deform the substrate 1 into the shape shown in FIG. 3C, the shape of the joint surface with the substrate is changed to the shape after the deformation of the substrate. The substrate 1 may be fixed to a second electrostatic chuck having a corresponding shape. FIG. 4 is a conceptual diagram of a second electrostatic chuck used when the substrate 1 is deformed into the shape shown in FIG. FIG. 4 also shows the substrate 1 of FIG. In the second electrostatic chuck 20 ′ shown in FIG. 4, the shape of the bonding surface 20 a ′ with the substrate 1 corresponds to the shape of the substrate 1 after deformation shown in FIG.
In the second electrostatic chuck 20 ′ shown in FIG. 4, the bonding surface 20a ′ with the substrate 1 corresponds to the shape of the substrate 1 after deformation shown in FIG. Specifically, the joint surface 20a ′ has a convex shape, and corresponds to the shape of the back surface of the substrate 1 after deformation shown in FIG. The substrate 1 can be deformed into the shape shown in FIG. 3C by fixing the substrate 1 to the second electrostatic chuck 20 ′ having such a shape. In FIG. 4, the joining surface of the electrostatic chuck itself has a convex shape, but the shaping member having a convex shape between the electrostatic chuck and the substrate while the joining surface of the electrostatic chuck remains horizontal. It is also possible to cope with this by inserting, and this mode is included in the above mode of the electrostatic chuck.
When the second electrostatic chuck 20 ′ has a shape corresponding to the deformed shape of the substrate 1, the shape of the bonding surface 20 a ′ of the second electrostatic chuck 20 ′ with the substrate 1 and the substrate 1 It is preferable that the deviation from the deformed shape is 2 mm or less, particularly 1 mm or less, more preferably 0.1 mm or less.

In the first embodiment of the EUV mask blank manufacturing method of the present invention, the Young's modulus, Poisson's ratio, chucking force, shape, dimensions, etc. of the second electrostatic chuck (including the case where a shaping member is used) are as follows. This is the same as the first electrostatic chuck in the multilayer reflective film forming method of the invention.
In the first embodiment of the manufacturing method of the EUV mask blank of the present invention, the second electrostatic chuck has a size between the first stress and the second stress as described above. This is because they are usually different and may have different attributes. In short, the electrostatic chuck (first electrostatic chuck) 20 used when the substrate 1 is deformed so as to have the first stress and the electrostatic chuck used when the substrate 1 is deformed so as to have the second stress. The chuck (second electrostatic chuck) 20 ′ is because the shapes of the joint surfaces 20 a and 20 a ′ with the substrate 1 are usually different. Therefore, when the first stress and the second stress have the same magnitude and attribute, the first electrostatic chuck 20 and the second electrostatic chuck 20 ′ may be the same. .

  In the first embodiment of the EUV mask blank manufacturing method of the present invention, the constituent material of the absorption layer 3 formed on the multilayer reflective film 2 is a material having a high absorption coefficient for EUV light, specifically, Cr, Ta and nitrides thereof are mentioned. Among these, TaN is preferable because it is amorphous and the surface shape is smooth. The thickness of the absorption layer 3 is preferably 50 to 150 nm. The method for forming the absorption layer 3 is not particularly limited as long as it is a sputtering method, and may be either a magnetron sputtering method or an ion beam sputtering method.

The procedure for forming the absorption layer described above may be a procedure that is normally performed when forming the absorption layer using a sputtering method such as a magnetron sputtering method or an ion beam sputtering method. For example, when a TaN layer is formed as an absorption layer using an ion beam sputtering method, a Ta target is used as a target, and an N ₂ gas (gas pressure 5 × 10 ⁻³ Pa to ³ × 10 ⁻² Pa) as a sputtering gas. ) Is preferably used to form a film having a thickness of 50 to 150 nm at a voltage of 200 to 600 V and a film formation speed of 0.05 to 0.3 nm / sec.

  When forming the absorption layer using the sputtering method, it is preferable to perform the film formation while rotating the substrate using a rotating body in order to obtain a uniform film formation.

When manufacturing an EUV mask blank, a buffer layer may be formed between the multilayer reflective film and the absorption layer. Also in the manufacturing method of the EUV mask blank of the present invention, a buffer layer may be formed between the multilayer reflective film and the absorption layer. In the second embodiment of the method for producing an EUV mask blank of the present invention, a multilayer reflective film is formed on a substrate using the multilayer reflective film deposition method of the present invention, and then the multilayer reflective film is formed on the multilayer reflective film using a sputtering method. In this method, an EUV mask blank is manufactured by forming a buffer layer on the buffer layer and forming an absorption layer on the buffer layer.
The second embodiment of the manufacturing method of the EUV mask blank of the present invention is the same as that of the EUV mask blank of the present invention except that a buffer layer is formed between the multilayer reflective film and the absorption layer using a sputtering method. It is the same as that of 1st Embodiment of a manufacturing method.

In the second embodiment of the manufacturing method of the EUV mask blank of the present invention, examples of the material constituting the buffer layer include Cr, Al, Ru, Ta and nitrides thereof, and SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ is mentioned. The buffer layer is preferably 10 to 60 nm thick.
The method for forming the buffer layer is not particularly limited as long as it is a sputtering method, and may be either a magnetron sputtering method or an ion beam sputtering method.
The procedure for forming the buffer layer may be a procedure that is normally performed when forming the buffer layer using a sputtering method such as a magnetron sputtering method or an ion beam sputtering method. For example, it is preferable to form a SiO ₂ film by ion beam sputtering. When an SiO ₂ film is formed as a buffer layer using ion beam sputtering, an Si target (boron doping) is used as a target, and Ar gas and O ₂ gas (gas pressure 2.7 × 10 ⁻² ) are used as sputtering gases. It is preferable to form a film at a voltage of 1200 to 1500 V, a film formation rate of 0.01 to 0.03 nm / sec, and a thickness of 4 to 60 nm using Pa to 4.0 × 10 ⁻² Pa).
When forming the buffer layer using the sputtering method, it is preferable to perform the film formation while rotating the substrate using a rotating body in order to obtain a uniform film formation.

In the second embodiment of the manufacturing method of the EUV mask blank of the present invention, the absorption layer is formed in a state where the substrate is deformed so that the substrate has the third stress.
In the second embodiment of the manufacturing method of the EUV mask blank of the present invention, a buffer layer is formed in a state where the substrate is deformed so that the substrate has the third stress, and the absorption layer is formed on the buffer layer. After filming, the EUV mask blank is manufactured by returning the substrate to its original shape.
In the second embodiment of the manufacturing method of the EUV mask blank of the present invention, when the substrate is returned to the original shape after the absorption layer is formed, the stress applied to the substrate by the formation of the buffer layer and the formation of the absorption layer are reduced. The total stress added to the substrate by the film is canceled out by the third stress, and is reduced to the extent that the substrate is not deformed. As a result, it is possible to prevent the substrate after the buffer layer and the absorption layer are formed from being deformed by the stress applied to the substrate by the formation of the buffer layer and the absorption layer.

In the manufacturing method (first embodiment and second embodiment) of the EUV mask blank of the present invention, the substrate 1 after the absorption layer 3 is formed, more specifically, the shape before the deformation after the absorption layer 3 is formed. The substrate 1 after being returned to has excellent flatness. After the absorption layer 3 is formed, the flatness of the substrate 1 after returning to the shape before deformation is preferably 100 nm or less, more preferably 75 nm or less, further preferably 50 nm or less, and 30 nm or less. It is particularly preferred. Here, “the flatness of the substrate after the absorption layer is formed” means the flatness on the absorption layer.
As a result, an EUV mask blank excellent in flatness, specifically, an EUV mask blank having a flatness of 100 nm or less can be manufactured.

According to the multilayer reflective film forming method of the present invention, a multilayer reflective film for EUV mask blanks having a flatness of 100 nm or less can be obtained by using a substrate having a flatness of more than 100 nm as a substrate for film formation. it can. In addition, according to the method for manufacturing an EUV mask blank of the present invention, an EUV mask blank having a flatness of 100 nm or less can be manufactured using a substrate having a flatness of more than 100 nm as a substrate for film formation.
In order to obtain a multilayer reflective film for an EUV mask blank with a flatness of 100 nm or less using a substrate having a flatness of more than 100 nm, the state shown in FIG. 1E, that is, after the multilayer reflective film 2 is formed The shape of the substrate 1 in a state where the substrate 1 is returned to the shape before deformation is predicted by calculation or the like, so that the flatness of the substrate 1 in the state shown in FIG. ), The substrate 1 is deformed to have the first stress.
Similarly, in the case of manufacturing an EUV mask blank having a flatness of 100 nm or less using a substrate having a flatness of more than 100 nm, the substrate 1 is formed after the state shown in FIG. The shape of the substrate 1 (EUV mask blank) in a state where the shape is returned to the shape before deformation is predicted by calculation or the like, and the flatness of the substrate 1 (EUV mask blank) in the state shown in FIG. Thus, in the state shown in FIG. 3C, the substrate 1 is deformed so as to have the second stress.

The present invention will be further described below using examples.
(Comparative Example 1)
In Comparative Example 1, the Si / Mo multilayer film is formed without deforming the substrate.
As a substrate for film formation, a SiO ₂ —TiO ₂ glass substrate (outer diameter 6 inches (152.4 mm) square, thickness 6.3 mm) is used. This glass substrate has a thermal expansion coefficient of 0.2 × 10 ⁻⁷ / ° C., a Young's modulus of 67 GPa, a Poisson's ratio of 0.17, and a specific rigidity of 3.07 × 10 ⁷ m ² / s ² . This glass substrate is polished to form a smooth surface with an Rms of 0.15 nm or less and a flatness of 100 nm or less.
On the back side of the glass substrate, a high dielectric coating having a sheet resistance of 100Ω / □ is applied by forming a Cr film having a thickness of 100 nm by using a magnetron sputtering method.
A glass substrate (outer dimensions 6 inches (152.4 mm) square, thickness 6.3 mm) is fixed to a flat electrostatic chuck having a flat plate shape, and an ion beam sputtering method is used to form Si on the surface of the glass substrate. By alternately forming the film and the Mo film for 40 cycles, a Si / Mo multilayer reflective film having a total film thickness of 272 nm ((4.5 nm + 2.3 nm) × 40) is formed. The uppermost layer of the Si / Mo multilayer reflective film is a Si layer (film thickness 11.0 nm) to provide a cap layer.

The film forming conditions for the Si film and the Mo film are as follows.
Conditions for forming the Si film Target: Si target (boron doped)
Sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 700V
Deposition rate: 0.077 nm / sec
Film thickness: 4.5nm
Conditions for forming the Mo film Target: Mo target Sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 700V
Deposition rate: 0.064 nm / sec
Film thickness: 2.3 nm

  When the chucking force of the electrostatic chuck is released and the substrate is removed from the electrostatic chuck after the film formation is completed, the substrate is deformed in a convex shape toward the film formation surface as shown in FIG. To do. When the amount of deformation of the most warped portion of the substrate is measured using a laser interferometer, it is confirmed to be 2 μm.

(Example 1)
In this embodiment, the Si / Mo multilayer reflection is performed in the same procedure as in Comparative Example 1 except that the first electrostatic chuck 20 having the concave surface of the film forming surface 20a shown in FIG. 2 is used as the electrostatic chuck. A film is formed. The first electrostatic chuck 20 has a film-forming surface 20a in a shape in which the substrate 1 after the multilayer reflective film 2 is formed in Comparative Example 1 is deformed (a state in which the substrate 1 is warped in a concave shape on the film-forming surface side). ) Is a shape deformed in the opposite direction, that is, a concave shape. On the film forming surface 20a, the depth of the concave surface is 2 μm.
At the time of forming the Si / Mo multilayer reflective film, the substrate 1 fixed to the electrostatic chuck 20 is deformed into a state in which it is warped in a concave shape on the film forming surface side as shown in FIGS. After forming the Si / Mo multilayer reflective film, the chucking force of the first electrostatic chuck 20 is released, and the substrate 1 is detached from the first electrostatic chuck 20. The substrate 1 returns to its original shape by the restoring force, and no deformation of the substrate is recognized. When the flatness of the substrate 1 is measured using a laser interferometer, it is confirmed to be 0.1 μm.

(Comparative Example 2)
In Comparative Example 2, an EUV mask blank is produced by forming an absorption layer by fixing the substrate on which the Si / Mo multilayer reflective film is formed in Example 1 to a flat electrostatic chuck. As a film forming method, an ion beam sputtering method is used, and a Cr film having a thickness of 70 nm is formed.
The deposition conditions for the Cr film are as follows.
Conditions for forming Cr film Target: Cr target Sputtering gas: Ar gas (gas pressure 3.3 × 10 ⁻² Pa)
Voltage: 700V
Deposition rate: 0.082 nm / sec
Film thickness: 70nm

  After the Cr film is formed, when the chucking force of the electrostatic chuck is released and the substrate is removed from the electrostatic chuck, the substrate is deformed into a convex shape on the film forming surface side (see FIG. 1B). It is deformed to the same shape as shown.) When the amount of deformation of the most warped portion of the substrate is measured using a laser interferometer, it is confirmed to be 2 μm.

(Example 2)
In this embodiment, a Cr film is formed in the same procedure as in Comparative Example 2 except that the electrostatic chuck 20 having a concave surface as the film forming surface 20a shown in FIG. 2 is used as the second electrostatic chuck. To do. The electrostatic chuck 20 has a film-formed surface in which the substrate 1 after the absorption layer 3 is formed in Comparative Example 2 is deformed (deformed in a state of being convexly curved toward the film-formed surface side of the substrate 1). The shape is deformed in the opposite direction, that is, a concave shape. The film-forming surface 20a of the electrostatic chuck 20 has a concave shape depth of 2 μm.
At the time of film formation of the Cr film, the substrate fixed to the electrostatic chuck 20 is deformed so as to be warped in a concave shape on the film forming surface side (deformed into a shape similar to the shape shown in FIGS. 1C and 1D). To do.) After forming the Cr film, the substrate is removed from the electrostatic chuck. The substrate returns to its original shape due to the restoring force, and deformation of the substrate is not recognized. When the flatness of the substrate is measured using a laser interferometer, it is confirmed to be 0.1 μm.

FIG. 1A to FIG. 1E are conceptual diagrams for explaining the multilayer reflective film forming method of the present invention, and show the shapes of the substrates before and after the multilayer reflective film is formed. FIG. 1A shows the substrate before the multilayer reflective film is formed. FIG. 1B shows the substrate after the multilayer reflective film is formed according to the conventional procedure. FIG. 1C shows a substrate deformed so as to have the first stress. FIG. 1D shows a state where a multilayer reflective film is formed on the substrate shown in FIG. FIG. 1E shows a state in which the substrate is returned to the shape before deformation after the multilayer reflective film is formed. FIG. 2 is a conceptual diagram of a first electrostatic chuck used when the substrate is deformed into the shape shown in FIG. FIGS. 3A to 3E are conceptual diagrams for explaining the method for manufacturing the EUV mask blank of the present invention, and show the shape of the substrate before and after the formation of the absorption layer. FIG. 3A shows the substrate before the absorption film is formed. FIG. 3B shows the substrate after the absorption layer is formed on the multilayer reflective film according to the conventional procedure. FIG. 3C shows the substrate deformed to have the second stress. FIG. 3D shows a state where an absorption layer is formed on the multilayer film of the substrate shown in FIG. FIG. 3E shows a state where the substrate is returned to the shape before deformation after the absorption layer is formed. FIG. 4 is a conceptual diagram of a second electrostatic chuck used when the substrate is deformed into the shape shown in FIG.

Explanation of symbols

1: Substrate 2: Multilayer reflective film 3: Absorbing layer 10: Virtual horizontal line 20, 20 ': Electrostatic chuck 20a, 20a': Bonding surface with substrate

Claims (12)

A method of forming a multilayer film on a substrate,
Forming the multilayer film in a state where the substrate is deformed so that the substrate has a stress in a direction opposite to the stress applied to the substrate by the multilayer film formation,
After the multilayer film is formed, the multilayer film is formed by returning the substrate to the shape before deformation. A method of forming a multilayer reflective film of a reflective mask blank for EUV lithography on a substrate using a sputtering method,
Forming the multilayer reflective film in a state where the substrate is deformed so that the substrate has a stress in a direction opposite to the stress applied to the substrate by the formation of the multilayer reflective film;
A method of forming a multilayer reflective film of a reflective mask blank for EUV lithography, wherein the substrate is returned to a shape before deformation after the multilayer reflective film is formed.   3. The method for forming a multilayer reflective film of a reflective mask blank for EUV lithography according to claim 2, wherein the flatness of the substrate after returning to the shape before deformation is 100 nm or less.   In order to form the multilayer reflective film in a state where the substrate is deformed, a first electrostatic chuck having a shape corresponding to the shape after deformation of the substrate is used for the bonding surface with the substrate. 4. The method for forming a multilayer reflective film of a reflective mask blank for EUV lithography according to claim 2, wherein the substrate is fixed.   5. The multilayer reflective film of the reflective mask blank for EUV lithography according to claim 4, wherein the first electrostatic chuck has a chucking force of 0.5 kPa or more and a Young's modulus of 10 GPa or more. Membrane method. 6. The reflective type for EUV lithography according to claim 2, wherein the substrate has a specific rigidity of 3.0 × 10 ⁷ m ² / s ² or more and a Poisson's ratio of 0.16 to 0.25. A method for forming a multilayer reflective film of a mask blank. After forming the multilayer reflective film on the substrate using the multilayer reflective film formation method of the reflective mask blank for EUV lithography according to any one of claims 2 to 6,
A method of manufacturing a reflective mask blank for EUV lithography by forming an absorption layer on the multilayer reflective film using a sputtering method,
The absorption layer is formed in a deformed state so that the substrate has a stress in a direction opposite to the stress applied to the substrate by the formation of the absorption layer,
A method of manufacturing a reflective mask blank for EUV lithography, wherein the substrate is returned to a shape before deformation after the absorption layer is formed. After forming the multilayer reflective film on the substrate using the multilayer reflective film formation method of the reflective mask blank for EUV lithography according to any one of claims 2 to 6,
A method of manufacturing a reflective mask blank for EUV lithography by forming a buffer layer and an absorption layer on the multilayer reflective film using a sputtering method,
The buffer layer and the absorption layer are formed in a deformed state so that the substrate has a stress in a direction opposite to the stress applied to the substrate by the formation of the buffer layer and the absorption layer,
A method of manufacturing a reflective mask blank for EUV lithography, wherein the substrate is returned to a shape before deformation after the absorption layer is formed.   The method of manufacturing a reflective mask blank for EUV lithography according to claim 7 or 8, wherein the flatness of the substrate after returning to the shape before deformation is 100 nm or less. .   In order to perform the film formation of the absorption layer in a state where the substrate is deformed, a bonding surface with the substrate is used using a second electrostatic chuck having a shape corresponding to the shape after deformation of the substrate. The method for producing a reflective mask blank for EUV lithography according to claim 7 or 9, wherein the substrate is fixed.   In order to perform the film formation of the buffer layer and the absorption layer in a state where the substrate is deformed, a second electrostatic chuck having a shape corresponding to a shape after deformation of the substrate is formed on the bonding surface with the substrate. The method of manufacturing a reflective mask blank for EUV lithography according to claim 8 or 9, wherein the substrate is fixed by using.   The method of manufacturing a reflective mask blank for EUV lithography according to claim 10 or 11, wherein the second electrostatic chuck has a chucking force of 0.5 kPa or more and a Young's modulus of 10 GPa or more.

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