JP2018031982A - REFLECTIVE MASK, REFLECTIVE MASK BLANK AND SEMICONDUCTOR DEVICE MANUFACTURING METHOD - Google Patents

Abstract

A method for manufacturing a reflective mask blank for manufacturing a reflective mask having a high contrast value is provided. SOLUTION: A method for manufacturing a reflective mask blank having a multilayer reflective film and an absorber film on a substrate in this order, wherein the film thickness of the absorber film and the reflectance on the surface of the absorber film are determined by simulation. and the reflectance Rabs on the surface of the absorber film having a thickness of D0, and the surface of the multilayer reflective film or the protective film on which the absorber film is removed to expose the multilayer reflective film or protective film. calculating a first contrast value C1 from the reflectance Rmulti; removing a part of the absorber film in the thickness direction having a second contrast value C2 higher than the first contrast value C1; forming the absorber film so as to have the total thickness D; A manufacturing method comprising the step of: [Selection drawing] Fig. 5

Description

  The present invention relates to a method for manufacturing a reflective mask blank, which is an original for manufacturing an exposure mask used for manufacturing a semiconductor device. The present invention also relates to a reflective mask that is an exposure mask manufactured using the reflective mask blank, and a method of manufacturing a semiconductor device using the reflective mask.

  In recent years, in the semiconductor industry, with the high integration of semiconductor devices, a fine pattern exceeding the transfer limit of the photolithography method has been required. For this reason, EUV lithography, which is an exposure technique using extreme ultraviolet (Extreme Ultra Violet: hereinafter abbreviated as EUV) light having a shorter wavelength, is promising. Here, EUV light refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, and specifically, light having a wavelength of about 0.2 to 100 nm. As a mask used in this EUV lithography, for example, an exposure reflective mask described in Patent Document 1 below has been proposed.

  A reflective mask is a substrate in which a multilayer reflective film that reflects exposure light is formed, a buffer film is formed on the multilayer reflective film, and an absorber film that absorbs exposure light is formed in a pattern on the multilayer reflective film. is there. The buffer film is provided between the multilayer reflective film and the absorber film for the purpose of protecting the multilayer reflective film in the pattern forming process and the correcting process of the absorber film. Light incident on a reflective mask mounted on an exposure machine (pattern transfer device) is absorbed in a part where the absorber film is present, and a light image reflected by the multilayer reflective film is reflected in a part where there is no absorber film. And transferred onto the semiconductor substrate.

JP-A-8-213303

In order to transfer a fine pattern onto a semiconductor substrate or the like with high accuracy using a reflective mask, it is important to improve the contrast value for exposure light such as EUV light. The contrast value is the reflection rate of the exposure light on the surface of the absorber film for absorbing the exposure light on the surface of the reflective mask, R _abs , and the reflection of the exposure light on the surface of the multilayer reflective film for reflecting the exposure light. The rate (reflectance at the surface of the protective film immediately below the absorber film when there is a protective film) can be expressed by the following equation, where _Rmulti is the ratio.
Contrast value = ( _{Rmulti- Rabs} ) / ( _Rmulti + _Rabs ) (1)

  Further, if the contrast values of the two reflective masks are the same value, the shadowing effect by the absorber film (absorber part pattern) can be produced in order to manufacture a semiconductor device having a fine and highly accurate transfer pattern. The smaller reflective mask is advantageous.

  In this specification, on the surface of the reflective mask, the part of the surface of the absorber film for absorbing exposure light is referred to as an absorber pattern, and the surface of the multilayer reflective film and the surface of the protective film for reflecting exposure light. Alternatively, the surface portion of the remaining film layer of the absorber film is referred to as a multilayer reflector pattern.

  Accordingly, an object of the present invention is to provide a manufacturing method of a reflective mask blank for manufacturing a reflective mask having a high contrast value. Another object of the present invention is to provide a reflective mask having a high contrast value. Another object of the present invention is to provide a method for manufacturing a semiconductor device having a fine and highly accurate transfer pattern by using a reflective mask having a high contrast value.

  An object of this invention is to provide the manufacturing method of the reflective mask blank for manufacturing the reflective mask with a small shadowing effect by the absorber film in which the absorber part pattern was formed. Another object of the present invention is to provide a reflective mask that has a small shadowing effect due to the absorber film on which the absorber pattern is formed. In addition, the present invention provides a method for manufacturing a semiconductor device having a fine and high-precision transfer pattern by using a reflective mask that has a small shadowing effect due to an absorber film in which an absorber pattern is formed. Objective.

According to equation (1) above, to obtain a high contrast value, generally, a higher reflectance R _multi multilayer reflective film surface for exposure light, low reflectivity R _abs of the absorber film surface It is required to do.

The present inventors have complete a reflectivity R _abs of the absorber film surface, than the contrast value obtained from the reflectance R _multi multilayer reflective film surface, and the reflectance R _abs of the absorber film surface, the absorber film It was found that the contrast value obtained from the reflectivity of the surface of the remaining film layer of the absorber film formed without removing the film was higher. By applying this knowledge, it has been found that a reflective mask blank for manufacturing a reflective mask having a high contrast value can be manufactured, leading to the present invention.

  In addition, the present inventors further apply the above knowledge to manufacture a reflective mask blank for manufacturing a reflective mask with a small shadowing effect by the absorber film in which the absorber part pattern is formed. Has been found to be possible to achieve the present invention.

  That is, in order to solve the above problems, the present invention has the following configuration. The present invention is a manufacturing method of a reflective mask blank having the following configurations 1 to 6, a reflective mask having the following configurations 7 to 12, and a manufacturing method of a semiconductor device having the following configuration 13.

(Configuration 1)
Configuration 1 of the present invention is a method for producing a reflective mask blank having a multilayer reflective film and an absorber film in this order on a substrate, or a multilayer reflective film, a protective film and an absorber film in this order,
The step of obtaining the relationship between the film thickness of the absorber film and the reflectance on the surface of the absorber film by simulation,
Based on the relationship between the film thickness of the absorber film and the reflectance on the surface of the absorber film, the reflectance R _{abs on the} surface of the absorber film having the film thickness D ₀ and the multilayer reflection film by removing the absorber film Alternatively, the first contrast value C ₁ , that is, the reflectance R _{multi on the} surface of the multilayer reflective film or the protective film with the protective film exposed, that is,
_{C 1 = (R multi -R abs} ) / (R multi + R abs) ··· (2)
Calculating
Based on the relationship between the film thickness of the absorber film and the reflectance on the surface of the absorber film, the reflectance R ′ _{abs on the} surface of the absorber film having the film thickness D and a part of the film thickness direction of the absorber film The second contrast value C ₂ higher than the first contrast value C ₁ is obtained from the reflectance R ′ _{multi on} the surface of the remaining film layer having the film thickness d when the film is removed to form the remaining film, that is,
_{C 2 = (R 'multi -R} ' abs) / (R 'multi + R' abs) ··· (3)
A step of obtaining a film thickness d of the remaining film layer and a total film thickness D = D ₁ (where D ₀ = D ₁ -d), or a film thickness of the absorber film and a reflectance on the surface of the absorber film based on the relationship between, remaining film thickness d in the case where the reflectance R _'abs in the absorber film surface with a thickness D, is residual film by removing part of the thickness direction of the absorber film From the reflectance R ′ _{multi on} the surface of the layer, the second contrast value C ₂ (= C ₁ ), which is the same as the _first contrast value C ₁ , that is,
_{C 2 = (R 'multi -R} ' abs) / (R 'multi + R' abs)
A step of obtaining a film thickness d of the remaining film layer and a total film thickness D = D ₂ (where D ₀ > D ₂ −d),
And a step of forming the absorber film so as to have the total film thickness D.

  According to Configuration 1 of the present invention, the reflective mask blank can be manufactured so that the absorber film of the reflective mask blank has the total film thickness D. If the reflective mask blank manufactured by the manufacturing method of the present invention is used, a residual film layer having a film thickness d can be left when manufacturing the reflective mask, so that a reflective mask having a high contrast value is manufactured. can do. Moreover, if the reflective mask blank manufactured by the manufacturing method of this invention is used, the reflective mask with a small shadowing effect by the absorber film | membrane which formed the absorber part pattern can be manufactured.

(Configuration 2)
Configuration 2 of the present invention is a method for manufacturing a reflective mask blank according to Configuration 1, wherein the difference between the total thickness D of the absorber film and the thickness d of the remaining film layer is 65 nm or less. .

  If a reflective mask is manufactured using the reflective mask blank manufactured by Configuration 2 of the present invention, the difference between the total film thickness D of the absorber film and the film thickness d of the remaining film layer is 65 nm or less. By doing so, it is possible to obtain a reflective mask that can reduce the shadowing effect of the absorber film on which the absorber pattern is formed.

(Configuration 3)
According to Structure 3 of the present invention, the remaining film layer of the absorber film is made of a material having a reflectance of 15% or less in the wavelength range of 190 nm to 400 nm. It is a manufacturing method of this reflective mask blank.

  According to Configuration 3 of the present invention, the residual film layer of the absorber film is made of a material having a reflectance of 15% or less in the wavelength range of 190 nm or more and 400 nm or less. It becomes possible to suppress out-of-band light when used.

(Configuration 4)
Configuration 4 of the present invention is the reflective mask blank according to any one of Configurations 1 to 3, wherein the remaining film layer of the absorber film is made of a material having a reflectance of 30% or less with respect to inspection light for defect inspection. It is a manufacturing method.

  If the reflective mask blank obtained by the structure 4 of the present invention is used, the remaining film layer of the absorber film is made of a material having a reflectance of 30% or less with respect to inspection light for defect inspection, so that a highly accurate defect can be obtained. A reflective mask that can be inspected can be more reliably manufactured.

(Configuration 5)
According to Structure 5 of the present invention, in the structure 1 to 4, the absorber film has an etching stopper layer formed in a portion having a film thickness d corresponding to the film thickness of the remaining film layer of the absorber film. It is a manufacturing method of any reflective mask blank.

  According to the fifth aspect of the present invention, by having the predetermined etching stopper layer, it becomes easy to obtain the target film thickness of the absorber film by etching.

(Configuration 6)
The structure 6 of this invention is a manufacturing method of the reflective mask blank in any one of the structures 1-5 characterized by the said absorber film containing a tantalum and nitrogen.

  According to Configuration 6 of the present invention, the absorber film contains tantalum and nitrogen, so that expansion of crystal grains constituting the absorber film can be suppressed on the surface of the absorber film. Therefore, the pattern edge roughness when the absorber film is patterned can be reduced.

(Configuration 7)
Configuration 7 of the present invention is a reflective mask having a multilayer reflecting portion pattern for reflecting EUV light and an absorber portion pattern for absorbing EUV light on a substrate,
The multilayer reflector pattern has, on the substrate, the remaining film layers of the multilayer reflective film and the absorber film in this order, or the remaining film layers of the multilayer reflective film, the protective film, and the absorber film in this order,
The absorber pattern has a multilayer reflective film and an absorber film in this order on the substrate, or a multilayer reflective film, a protective film and an absorber film in this order,
The film thickness d of the remaining film layer of the absorber film is thinner than the total film thickness D of the absorber film,
A contrast value of the first contrast value C ₁ is the reference reflective mask, the multilayer reflective part pattern of the reference reflective mask does not have a residual layer of the absorber film, absorber section pattern of thickness D ₀ Having an absorber film,
When the second contrast value C ₂ is the contrast value of the reflection type mask,
C ₁ <C ₂ and D ₀ = D-d, or C ₁ = C ₂ and D ₀ > D-d
It is a reflection type mask characterized by being.

  According to Configuration 7 of the present invention, a reflective mask having a high contrast value can be obtained. Moreover, according to the structure 7 of this invention, the reflection type mask with a small shadowing effect by the absorber film in which the absorber part pattern was formed can be obtained.

(Configuration 8)
Configuration 8 of the present invention is the reflective mask according to Configuration 7, wherein a difference between the total thickness D of the absorber film and the thickness d of the remaining film layer is 65 nm or less.

  According to the configuration 8 of the present invention, the difference between the total film thickness D of the absorber film and the film thickness d of the remaining film layer is set to 65 nm or less, so that the shadow by the absorber film in which the absorber pattern is formed. A reflective mask capable of reducing the inging effect can be obtained.

(Configuration 9)
In the ninth aspect of the present invention, the remaining film layer of the absorber film is made of a material having a reflectance of 15% or less in the wavelength range of 190 nm to 400 nm. This is a reflective mask.

  According to Configuration 9 of the present invention, it is possible to suppress out-of-band light when a reflective mask is used.

(Configuration 10)
Configuration 10 of the present invention is the reflective mask according to any one of Configurations 7 to 9, wherein the remaining film layer of the absorber film is made of a material having a reflectance of 30% or less with respect to inspection light for defect inspection. is there.

  According to Configuration 10 of the present invention, a reflective mask capable of high-accuracy defect inspection is obtained because the remaining film layer of the absorber film is made of a material having a reflectance of 30% or less with respect to inspection light for defect inspection. Can be obtained.

(Configuration 11)
According to the structure 11 of the present invention, the multilayer reflective portion pattern includes a portion having a film thickness d corresponding to the film thickness of the remaining film layer of the absorber film, and an etching stopper layer formed on the remaining film layer. The reflective mask according to any one of configurations 7 to 10 characterized by the following:

  According to Configuration 11 of the present invention, when the reflective mask is manufactured, by having the predetermined etching stopper layer, it becomes easy to obtain the target film thickness of the remaining absorber film layer by etching. .

(Configuration 12)
Configuration 12 of the present invention is the reflective mask according to any one of Configurations 7 to 11, wherein the absorber film contains tantalum and nitrogen.

  According to the structure 12 of this invention, when an absorber film contains a tantalum and nitrogen, the expansion of the crystal particle which comprises an absorber film can be suppressed in the surface of an absorber film. Therefore, it is possible to obtain a reflective mask with reduced pattern edge roughness when the absorber film is patterned.

(Configuration 13)
According to a thirteenth aspect of the present invention, there is provided a semiconductor device manufacturing method including a pattern forming step of forming a pattern on a semiconductor substrate using the reflective mask according to any of the seventh to twelfth aspects.

  According to the thirteenth aspect of the present invention, since a reflective mask that can obtain a high contrast value can be used during exposure, a semiconductor device having a fine and highly accurate transfer pattern can be manufactured. . Further, according to the thirteenth aspect of the present invention, a reflective mask having a small shadowing effect due to the absorber film on which the absorber portion pattern is formed can be used, so that a semiconductor device having a fine and highly accurate transfer pattern can be obtained. Can be manufactured.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the reflective mask blank for manufacturing the reflective mask which has a high contrast value can be provided. In addition, according to the present invention, a reflective mask having a high contrast value can be provided. In addition, according to the present invention, by using a reflective mask having a high contrast value, a method for manufacturing a semiconductor device having a fine and highly accurate transfer pattern can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the reflective mask blank for manufacturing the reflective mask with a small shadowing effect by the absorber film in which the absorber part pattern was formed can be provided. In addition, according to the present invention, it is possible to provide a reflective mask having a small shadowing effect by the absorber film in which the absorber pattern is formed. In addition, according to the present invention, there is provided a method for manufacturing a semiconductor device having a fine and high-precision transfer pattern by using a reflective mask that has a small shadowing effect due to an absorber film on which an absorber pattern is formed. be able to.

It is a cross-sectional schematic diagram which shows an example of the reflective mask blank manufactured by the manufacturing method of this invention. It is a cross-sectional schematic diagram which shows another example of the reflective mask blank manufactured by the manufacturing method of this invention. It is a cross-sectional schematic diagram which shows another example of the reflective mask blank manufactured by the manufacturing method of this invention. It is a cross-sectional schematic diagram which shows an example of the conventional reflective mask. It is a cross-sectional schematic diagram which shows an example of Embodiment 1 of the reflective mask of this invention. It is a cross-sectional schematic diagram which shows an example of Embodiment 2 of the reflective mask of this invention. It is a cross-sectional schematic diagram which shows another example of Embodiment 2 of the reflective mask of this invention. It is a figure which shows an example of the relationship between the film thickness of an absorber film (TaN film), and a reflectance in a reflective mask.

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

  FIG. 1 shows a schematic cross-sectional view of an example of a reflective mask blank 10 (hereinafter simply referred to as “the reflective mask blank 10 of the present invention”) manufactured by the manufacturing method of the present invention. The present invention is a method for manufacturing a reflective mask blank 10 having a multilayer reflective film 13 and an absorber film 15 in this order on a substrate 12.

  In FIG. 2, the cross-sectional schematic diagram of another example of the reflective mask blank 10 manufactured by the manufacturing method of this invention is shown. As shown in FIG. 2, the reflective mask blank 10 can have a protective film 14 between the multilayer reflective film 13 and the absorber film 15.

  In the manufacturing method of the reflective mask blank 10 of the present invention, the absorber film 15 is formed to have a predetermined total film thickness D in consideration of the film thickness d of the remaining film layer 15b of the absorber film 15. There are features. Hereinafter, the manufacturing method of the reflective mask blank 10 of this invention is demonstrated.

  The manufacturing method of the reflective mask blank 10 of the present invention includes a step of obtaining the relationship between the film thickness of the absorber film 15 and the reflectance on the surface of the absorber film 15 by simulation.

  FIG. 8 shows an example of the relationship between the film thickness of the absorber film 15 and the reflectance on the surface of the absorber film 15 obtained by simulation in the reflective mask 20. A method for obtaining the relationship as shown in FIG. 8 by simulation by specifying the refractive index n and the extinction coefficient k of the multilayer reflective film 13, the protective film 14, the absorber film 15, etc. is known to those skilled in the art. It is known. The structure of the reflective mask 20 used in the simulation shown in FIG. 8 is that a multilayer reflective film 13 (a multilayer film of Mo film and Si film, film thickness 284 nm) on the substrate 12 and a protective film 14 made of Ru as a material ( In this structure, the absorber film 15 having a thickness of 2.5 nm and a single TaN film is formed in this order. The wavelength of the exposure light used for the simulation is 13.5 nm. As shown in FIG. 8, the reflectance on the surface of the absorber film 15 tends to decrease as the thickness of the absorber film 15 increases. It can be seen that a vibration structure occurs in the film thickness dependence.

The manufacturing method of the reflective mask blank 10 of the present invention is based on the relationship between the film thickness of the absorber film 15 and the reflectance at the surface of the absorber film 15, and the surface of the absorber film 15 with the film thickness D ₀ is used. a reflectance _{R abs,} the reflectance _{R multi} the multilayer reflective film 13 surface or protective film 14 surface when exposing the multilayer reflective film 13 or the protective film 14 by removing the absorber film 15, a first comprising the step of calculating a contrast value C _1. The first contrast value C ₁ may be represented by the following formula.
_{C 1 = (R multi -R abs} ) / (R multi + R abs) ··· (2)

In FIG. 8, point A is the reflectance (R _A ) when the absorber film 15 is not present, and point a is the reflectance (R _a ) when the film thickness D ₀ of the absorber film 15 is present. Therefore, when the reflective mask 20 has the absorber film 15 having the film thickness D ₀ , the contrast value C ₁ is obtained as follows. C ₁ (A, a) indicates the contrast value C ₁ between point A and point a in FIG.
C ₁ (A, a) = (R _A −R _a ) / (R _A + R _a )
(Note that R _A = R _multi , R _a = R _abs .)

More specifically, in FIG. 4, when the incident light 30 having the light intensity I ₀ is incident, the intensity I _r-multi (= I ₀ · R _multi ) from the surface of the protective film 14 formed on the multilayer reflective film 13. The reflected light 31a is reflected, and the reflected light 31b having the intensity I _r-abs (= I ₀ · R _abs ) is reflected from the surface of the absorber film 15. 4, the thickness of the absorber film 15 is _{D 0.} In FIG. 4, a portion where the absorber film 15 does not exist is a multilayer reflector pattern 23 for reflecting EUV light, and a portion where the absorber film 15 exists is an absorber for absorbing EUV light. This is a part pattern 25. Therefore, the contrast value _{C 1} described above can be determined using the _{R multi} and _{R abs} 4, by the above equation (2).

  The manufacturing method of the reflective mask blank 10 of the present invention includes a step of obtaining the film thickness d of the remaining film layer 15 b of the absorber film 15 and the total film thickness D of the absorber film 15. This step can be any one of Embodiments 1 and 2 described below.

In the manufacturing method of the present invention, the steps of obtaining the film thickness d of the remaining film layer 15b of the absorber film 15 and the total film thickness D of the absorber film 15 of Embodiment 1 include the film thickness of the absorber film 15 and the absorber. Based on the relationship with the reflectance on the surface of the film 15, the reflectance R ′ _{abs on the} surface of the absorber film 15 having the film thickness D and a part of the absorber film 15 in the film thickness direction are removed to form a remaining film. and a reflectance R _'multi at the surface of the remaining film layer 15b having a thickness d when the has a first second contrast value _{C 2} is higher than the contrast value _{C 1,} Zanmakuso 15b thickness of d and a total film thickness D = D ₁ (where D ₀ = D ₁ -d). The second contrast value C ₂ can be expressed by the following equation.
_{C 2 = (R 'multi -R} ' abs) / (R 'multi + R' abs) ··· (3)

In FIG. 5, when the incident light 30 with the light intensity I ₀ is incident, the reflected light 31a with the intensity I _r-multi (= I ₀ · R ′ _multi ) is reflected from the surface of the absorber film 15 with the film thickness d. A state in which the reflected light 31b having the intensity I _r-abs (= I ₀ · R ′ _abs ) is reflected from the surface of the absorber film 15 having the film thickness D (= D ₁ ) is shown. In FIG. 5, the portion where the absorber film 15 having a film thickness d exists is a multilayer reflector pattern 23 for reflecting EUV light, and the absorber film 15 having a film thickness D (= D ₁ ) exists. The part to perform is the absorber part pattern 25 for absorbing EUV light.

The reflection of the exposure light of the reflective mask 20 having the structure shown in FIG. 5 will be described with reference to FIG. In FIG. 8, B point is when the film thickness of the absorber film 15 is d reflectance (in the case of the multilayer reflective part pattern ₂₃₎ (R B), b point of thickness d + D ₀ of the absorber film 15 This is the reflectance (R _b ) in the case (in the case of the absorber pattern 25). The contrast value C ₂ (B, b) in this case is obtained as follows. Note that C ₂ (B, b) indicates the contrast value C ₂ between point B and point b in FIG.
C ₂ (B, b) = (R _B −R _b ) / (R _B + R _b )
(Note that R _B = R ′ _multi and R _b = R ′ _abs .)

In the simulation shown in FIG. 8, the difference in film thickness between C ₁ (A, a) and C ₂ (B, b) is the film thickness D ₀ . In the conventional reflective mask 20, the film thickness D ₀ of the absorber film 15 is determined so that the absorber film 15 does not exist at the point A and the contrast value becomes C ₁ (A, a). . On the other hand, when the present inventors compare C ₁ (A, a) and C ₂ (B, b), C ₂ (B, b) is larger than C ₁ (A, a). I found out that there was a case. This is because, as shown in FIG. 8, a vibration structure is generated in the film thickness dependence of the reflectance due to the interference of the exposure light by the absorber film 15.

Based on the above knowledge, the present inventors, instead of the multilayer reflecting portion pattern 23 in which the absorber film 15 does not exist as shown by the point A, the multilayer reflecting portion pattern 23 in which the absorber film 15 having the film thickness d exists. As a result, it was found that the contrast value of the reflective mask 20 may be higher when using the method. Therefore, in Embodiment 1 of the manufacturing method of the present invention, the remaining film having a _second contrast value C ₂ higher than the first contrast value C ₁ is removed by removing a part of the absorber film 15 in the film thickness direction. In this case, the film thickness d and the total film thickness D = D ₁ (where D ₀ = D ₁ −d) of the remaining film layer 15 b are obtained. As shown in FIG. 8, the thickness of the absorber film 15, if the relationship is obtained between the reflectance at the absorber layer 15 surface, the contrast value in the case with a film thickness difference of D ₀ is easily because be calculated, it is possible to determine the thickness d of the residual film layer 15b of the case having a first second contrast value C ₂ is higher than the contrast value C ₁ easily.

In the case where the absorber layer 15 has a film thickness difference of D _0, the second contrast value C _2, the thickness d of the first higher becomes such Zanmakuso 15b than the contrast value C ₁ is more It is conceivable to take a value in the range. In the present invention, the second contrast value C _2, if the thickness d of the first higher becomes such Zanmakuso 15b than the contrast value C _1, it is possible to select any thickness d. However, in order to obtain a higher contrast value, it is preferable to select a higher second contrast value C ₂ to become such a film thickness d. Further, since it is economical that the absorber film 15 is thinner, it is also possible to select a thinner film thickness d from a range of a plurality of values of the film thickness d of the remaining film layer 15b.

In the manufacturing method of the present invention, the steps of obtaining the film thickness d of the remaining film layer 15b of the absorber film 15 and the total film thickness D of the absorber film 15 of Embodiment 2 include the film thickness of the absorber film 15 and the absorber. Based on the relationship with the reflectance on the surface of the film 15, the reflectance R ′ _{abs on} the surface of the absorber film 15 having the film thickness D and a part of the absorber film 15 in the film thickness direction are removed to leave the remaining film. From the reflectivity R ′ _{multi on} the surface of the remaining film layer 15b having the film thickness d in the case of the above, the remaining contrast having the second contrast value C ₂ (= C ₁ ) that is the same as the _first contrast value C ₁ In this step, the film thickness d and the total film thickness D = D ₂ (where D ₀ > D ₂ −d) are obtained. The second contrast value C ₂ can be expressed by the following equation.
_{C 2 = (R 'multi -R} ' abs) / (R 'multi + R' abs) ··· (3)

In FIG. 6, when incident light 30 having light intensity I ₀ is incident, reflected light 31 a having intensity I _r-multi (= I ₀ · R ′ _multi ) is reflected from the surface of the absorber film 15 having a film thickness d. A state in which the reflected light 31b having the intensity I _r-abs (= I ₀ · R ′ _abs ) is reflected from the surface of the absorber film 15 having the film thickness D (= D ₂ ) is shown. In FIG. 6, the portion where the absorber film 15 having a film thickness d exists is a multilayer reflector pattern 23 for reflecting EUV light, and the absorber film 15 having a film thickness D (= D ₂ ) exists. The part to perform is the absorber part pattern 25 for absorbing EUV light. In the second embodiment, the film thickness difference (D ₂ −d) of the absorber film 15 between the multilayer reflector pattern 23 and the absorber pattern 25 is the film used in the step of calculating the _first contrast value C _1. thinner than the thickness _{D 0.} Therefore, the reflective mask 20 that can be manufactured using the reflective mask blank 10 of Embodiment 2 has the same contrast value as that of the conventional reflective mask, but has a small film thickness difference (D ₂ −d). can do. As a result, the shadowing effect by the absorber film 15 in which the absorber part pattern 25 is formed can be reduced.

  The manufacturing method of the reflective mask blank 10 of this invention includes the process of forming the absorber film | membrane 15 so that it may become the total film thickness D obtained as mentioned above. By adjusting the film formation time when the absorber film 15 is formed, the film thickness of the absorber film 15 can be controlled to form the absorber film 15 having the total film thickness D. As a method for forming the absorber film 15, ion beam sputtering, DC sputtering, RF sputtering, or the like can be used.

  According to the present invention, the reflective mask blank 10 can be manufactured such that the absorber film 15 of the reflective mask blank 10 has a total film thickness D in consideration of the film thickness d of the remaining film layer 15b. If the reflective mask blank 10 of the present invention is used, the residual film layer 15b having a film thickness d can be left when the reflective mask 20 is manufactured. Therefore, the reflective mask 20 or the absorber having a high contrast value is used. The reflective mask 20 having a small shadowing effect by the absorber film 15 in which the part pattern 25 is formed can be manufactured.

  In the manufacturing method of the reflective mask blank 10 of the present invention, the difference between the total film thickness D of the absorber film 15 and the film thickness d of the remaining film layer 15b is preferably 65 nm or less, more preferably 60 nm. preferable. By reducing the difference between the total film thickness D of the absorber film 15 and the film thickness d of the remaining film layer 15b to 65 nm or less, the shadowing effect by the absorber film 15 in which the absorber pattern 25 is formed is reduced. Thus, a reflective mask 20 capable of achieving the above can be obtained.

  In the manufacturing method of the reflective mask blank 10 of the present invention, the remaining film layer 15b of the absorber film 15 may be made of a material that has a reflectance of the remaining film layer 15b of 15% or less in a wavelength range of 190 nm or more and 400 nm or less. preferable.

  When EUV light is used as an exposure source, it is known that vacuum ultraviolet light and ultraviolet light (wavelength: 190 to 400 nm) called out-of-band (OoB) light are generated. For example, in a reflective mask for EUV lithography that digs into a multilayer reflective film, the substrate 12 is exposed in the shading zone region, so out-of-band light generated from the exposure source is reflected on the substrate surface, Reflection is caused by the back conductive film 11 that is transmitted through the substrate 12 and provided on the back surface of the substrate 12. Since adjacent circuit pattern regions are exposed a plurality of times, the integrated light amount of the reflected out-of-band light has a non-negligible size, which causes a problem of affecting the dimensions of the wiring pattern. Suppressing out-of-band light when the reflective mask 20 is used by using a material in which the reflectance of the remaining film layer 15b of the absorber film 15 is 15% or less in a wavelength range of 190 nm to 400 nm. Is possible.

  In the manufacturing method of the reflective mask blank 10 of the present invention, the remaining film layer 15b of the absorber film 15 is preferably made of a material having a reflectance with respect to inspection light for defect inspection of 30% or less.

  By using the reflective mask blank 10 made of a material whose remaining film layer 15b of the absorber film 15 has a reflectance of 30% or less with respect to inspection light for defect inspection, a reflective mask 20 capable of highly accurate defect inspection is provided. It can be manufactured more reliably.

<Configuration of Reflective Mask Blank 10>
1 and 2 are schematic cross-sectional views for explaining the configuration of a reflective mask blank 10 for EUV lithography manufactured by the manufacturing method of the present invention. The reflective mask blank 10 of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, a reflective mask blank 10 of the present invention includes a substrate 12 having a back surface conductive film 11 for an electrostatic chuck formed on a main surface on the back surface side of a substrate 12, and a main surface of the substrate 12. A multilayer reflective film 13 that is formed on the front surface (main surface opposite to the side on which the back surface conductive film 11 is formed) and reflects EUV light as exposure light, and is formed on the multilayer reflective film 13. And an absorber film 15 for absorbing EUV light. The reflective mask blank 10 shown in FIG. 2 further includes a protective film 14 for protecting the multilayer reflective film 13 between the multilayer reflective film 13 and the absorber film 15.

  In this specification, for example, the description “a multilayer reflective film 13 formed on the main surface of the substrate 12” means that the multilayer reflective film 13 is disposed in contact with the surface of the substrate 12. In addition, a case where it means that another film is provided between the substrate 12 and the multilayer film 26 for mask blank is included. The same applies to other films. In addition, in this specification, for example, “the film A is disposed on the film B” means that the film A and the film B are not interposed between the film A and the film B without interposing another film. It means that it is arranged so that it touches directly.

  Hereinafter, the configuration of the substrate 12 and each layer will be described.

(Substrate 12)
In order to prevent distortion of the absorber pattern 25 due to heat during exposure with EUV light, a substrate having a low thermal expansion coefficient within the range of 0 ± 5 ppb / ° C. is preferably used. As a material having a low thermal expansion coefficient in this range, for example, SiO ₂ —TiO ₂ glass or multicomponent glass ceramics can be used.

  Of the two main surfaces of the substrate 12, the main surface on the side where the absorber film 15 to be the transfer pattern of the reflective mask 20 is formed has high flatness from the viewpoint of obtaining at least pattern transfer accuracy and position accuracy. The surface is processed. In the case of EUV exposure, the flatness is preferably 0.1 μm or less, more preferably 0.05 μm or less, particularly preferably in a 132 mm × 132 mm region of the main surface on the side where the transfer pattern of the substrate 12 is formed. 0.03 μm or less. Further, of the main surfaces of the substrate 12, the main surface opposite to the side on which the absorber film 15 is formed is formed with the back surface conductive film 11 for electrostatic chucking when being set in the exposure apparatus. The surface. The flatness of the surface on which the back conductive film 11 is formed is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less in a 142 mm × 142 mm region.

  In the present specification, the flatness is a value representing the warpage (deformation amount) of the surface indicated by TIR (Total Indicated Reading). This value is determined by taking the plane defined by the least square method with respect to the surface of the substrate 12 as a focal plane, and the highest position of the surface of the substrate 12 above the focal plane and the surface of the substrate 12 below the focal plane. This is the absolute value of the difference in height from the lowest position.

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

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

(Multilayer reflective film 13)
The multilayer reflective film 13 has a function of reflecting EUV light in the reflective mask 20 for EUV lithography. The multilayer reflective film 13 is a multilayer film in which elements having different refractive indexes are periodically stacked.

  In general, a thin film (high refractive index layer) of a light element or a compound thereof, which is a high refractive index material, and a thin film (low refractive index layer) of a heavy element or a compound thereof, which is a low refractive index material, are alternately 40 A multilayer film laminated for about ˜60 periods is used as the multilayer reflective film 13. The multilayer film can have a structure in which a plurality of high-refractive index layers / low-refractive index layers are stacked in this order from the substrate 12 side and a plurality of periods are stacked. In addition, the multilayer film can have a structure in which a low refractive index layer and a high refractive index layer laminated in this order from the substrate 12 side are laminated in a plurality of periods with a laminated structure of a low refractive index layer / high refractive index layer as one period. . The outermost layer of the multilayer reflective film 13, that is, the surface layer opposite to the substrate 12 of the multilayer reflective film 13, is preferably a high refractive index layer. In the multilayer film described above, when the high refractive index layer / low refractive index layer stacking structure in which the high refractive index layer and the low refractive index layer are stacked in this order from the substrate 12 is stacked for a plurality of periods, the uppermost layer has a low refractive index. Become a rate layer. For this reason, it is preferable to form a multilayer reflective film 13 by further forming a high refractive index layer on the uppermost low refractive index layer.

  In the reflective mask blank 10 of the present invention, a layer containing Si can be adopted as the high refractive index layer. As a material containing Si, Si compound containing B, C, N and / or O in addition to Si alone may be used. By using a layer containing Si as a high refractive index layer, a reflective mask 20 for EUV lithography having excellent EUV light reflectivity can be obtained. In the reflective mask blank 10 of the present invention, a glass substrate is preferably used as the substrate 12. Si is also excellent in adhesion to the glass substrate. As the low refractive index layer, a single metal selected from Mo, Ru, Rh, and Pt, and alloys thereof are used. For example, as the multilayer reflective film 13 for EUV light having a wavelength of 13 to 14 nm, a Mo / Si periodic laminated film in which Mo films and Si films are alternately laminated, for example, about 40 to 60 periods is preferably used. A high refractive index layer, which is the uppermost layer of the multilayer reflective film 13, is formed of silicon (Si), and a silicon oxide layer containing silicon and oxygen is interposed between the uppermost layer (Si) and the protective film 14. You may make it form. Thereby, mask cleaning tolerance (film peeling tolerance of absorber part pattern 25 grade) can be improved.

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

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

(Protective film 14)
The reflective mask blank 10 of the present invention preferably has a protective film 14 between the multilayer reflective film 13 and the absorber film 15.

  As shown in FIG. 2, the protective film 14 is formed on the multilayer reflective film 13 in order to protect the multilayer reflective film 13 from dry etching or cleaning liquid in the manufacturing process of the reflective mask 20 for EUV lithography described later. . The protective film 14 is made of, for example, a material (main component: 50 atomic% or more) containing Ru (ruthenium) as a main component. The material containing Ru as a main component is Ru metal alone, Ru alloy containing a metal such as Nb, Zr, Y, B, Ti, La, Mo, Co, and / or Re in Ru, or N in these materials. It may be a material containing (nitrogen). Further, the protective film 14 has a laminated structure of three or more layers, the lowermost layer and the uppermost layer are made of a material containing the above Ru, and a metal or alloy other than Ru is placed between the lowermost layer and the uppermost layer. It can be interposed.

  The thickness of the protective film 14 is not particularly limited as long as it can function as the protective film 14. From the viewpoint of the reflectivity of EUV light, the thickness of the protective film 14 is preferably 1.5 to 8.0 nm, more preferably 1.8 to 6.0 nm.

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

(Absorber membrane 15)
As shown in FIGS. 1 and 2, the reflective mask blank 10 of the present invention includes an absorber film 15 on a multilayer reflective film 13. As shown in FIG. 1, the absorber film 15 can be formed on and in contact with the multilayer reflective film 13. As shown in FIG. 2, when the protective film 14 is formed, the protective film 14 can be formed in contact with the protective film 14.

  The absorber film 15 may be a single layer or a laminated structure. In the case of a laminated structure, either a laminated film of the same material or a laminated film of different materials may be used. The laminated film may have a material or composition that is changed stepwise and / or continuously in the film thickness direction.

  The material of the absorber film 15 is not particularly limited. For example, it has a function of absorbing EUV light, and it is preferable to use a material containing Ta (tantalum) alone or Ta as a main component. The material mainly composed of Ta is usually an alloy of Ta. The crystalline state of the absorber film 15 preferably has an amorphous or microcrystalline structure from the viewpoint of smoothness and flatness. Examples of the material containing Ta as a main component include a material containing Ta and B, a material containing Ta and N, a material containing Ta and B, and further containing at least one of O and N, and a material containing Ta and Si. A material selected from a material containing Ta, Si and N, a material containing Ta and Ge, a material containing Ta, Ge and N can be used. Further, for example, by adding at least one selected from B, Si, Ge, and the like to Ta, an amorphous structure can be easily obtained and the smoothness can be improved. Furthermore, if N and / or O is added to Ta, the resistance to oxidation is improved, so that the stability over time can be improved. In order to make the surface of the absorber film 15 suitable for the reflective mask 20 while maintaining the surface form of the substrate 12 or the substrate 12 on which the multilayer reflective film 13 is formed, the absorber film 15 is It is preferable to have a microcrystalline structure or an amorphous structure. The crystal structure can be confirmed by an X-ray diffractometer (XRD).

  Specifically, as a material containing tantalum that forms the absorber film 15, for example, tantalum metal, tantalum contains one or more elements selected from nitrogen, oxygen, boron, and carbon, and substantially contains hydrogen. The material etc. which are not contained in are mentioned. For example, Ta, TaN, TaON, TaBN, TaBON, TaCN, TaCON, TaBCN, TaBOCN and the like can be mentioned. About the said material, you may contain metals other than a tantalum in the range with which the effect of this invention is acquired. When boron is contained in the material containing tantalum that forms the absorber film 15, the absorber film 15 can be easily controlled to have an amorphous structure (amorphous).

  The absorber film 15 of the reflective mask blank 10 of the present invention is preferably formed of a material containing tantalum and nitrogen. The nitrogen content in the absorber film 15 is preferably 50 atomic percent or less, preferably 30 atomic percent or less, more preferably 25 atomic percent or less, and 20 atomic percent or less. Further preferred. The nitrogen content in the absorber film 15 is preferably 5 atomic% or more.

  In the reflective mask blank 10 of the present invention, the absorber film 15 contains tantalum and nitrogen, and the nitrogen content is preferably 10 atomic% or more and 50 atomic% or less, more preferably 15 atomic%. The content is preferably 50 atomic percent or less and more preferably 30 atomic percent or more and 50 atomic percent or less. Since the absorber film 15 contains tantalum and nitrogen and the nitrogen content is 10 atomic% or more and 50 atomic% or less, the expansion of the crystal particles constituting the absorber film 15 can be suppressed. Pattern edge roughness when patterning 15 can be reduced.

  In the reflective mask blank 10 of the present invention, the film thickness of the absorber film 15 is the total film thickness D obtained as described above.

  Further, the material of the absorber film 15 may be a material other than Ta. Materials other than Ta include Ti, Cr, Ni, Nb, Mo, Ru, Rh, Te, Pd, and W. Further, an alloy containing two or more elements of Ta, Ti, Cr, Ni, Nb, Mo, Ru, Rh, Te, Pd and W can be used as a material, and a layer stack using these elements as a material is used. It can be a membrane. These materials may contain one or more elements selected from nitrogen, oxygen, and carbon. In particular, by using a material containing nitrogen, the root mean square roughness (Rms) of the surface of the absorber film 15 can be reduced, and pseudo defects can be detected in defect inspection using a high-sensitivity defect inspection apparatus. Since the reflective mask blank 10 which can be suppressed is obtained, it is preferable.

  When the absorber film 15 is a laminated film, it may be a laminated film of layers of the same material or a laminated film of layers of different materials. In this case, the lower layer serving as the remaining film layer of the absorber film may be formed of a material that suppresses out-of-band light. For example, the lower layer of the absorber film can be a tantalum compound (TaO, TaON, etc.) containing oxygen (O). The oxygen content is preferably 50 atomic% or more. Further, when the absorber film 15 is a laminated film of layers of different materials, the absorber film 15 having an etching mask function may be formed by using materials having different etching characteristics as materials constituting the plurality of layers.

  Further, in the reflective mask blank 10 of the present invention, the absorber film 15 has a phase shift having a desired phase difference between the reflected light 31a from the multilayer reflecting portion pattern 23 and the reflected light 31b from the absorbing portion pattern 25. Can have a function. In that case, a reflective mask blank 10 which is an original for the reflective mask 20 with improved transfer resolution by EUV light is obtained. In addition, since the thickness of the absorber necessary for achieving the phase shift effect necessary for obtaining the desired transfer resolution can be made thinner than before, the reflective mask blank having a reduced shadowing effect. 10 is obtained. The material of the absorber film 15 having a phase shift function is not particularly limited, and can be the material of the above-described absorber film.

  The absorber film 15 is preferably formed continuously from the start of film formation to the end of film formation without exposure to the atmosphere. For example, the absorber film 15 is preferably formed by ion beam sputtering. However, it can also be formed by a known method such as DC sputtering or RF sputtering. By adjusting the film formation time when the absorber film 15 is formed, the film thickness of the absorber film 15 can be controlled to form the absorber film 15 having the total film thickness D. The total film thickness D is preferably 20 to 100 nm.

  As shown in FIG. 3, in the reflective mask blank 10 of the present invention, the absorber film 15 is an etching stopper layer formed in a portion having a film thickness d corresponding to the film thickness of the remaining film layer 15 b of the absorber film 15. 16 is preferable.

  FIG. 7 shows an example of a reflective mask 20 manufactured using the reflective mask blank 10 shown in FIG. The reflective mask 20 shown in FIG. 7 has an etching stopper layer 16 formed in a portion having a film thickness d corresponding to the film thickness of the remaining film layer 15 b of the absorber film 15. Since the absorber film 15 of the reflective mask blank 10 has the predetermined etching stopper layer 16, when the absorber film 15 is etched, the progress of the etching is not significantly dependent on the etching time, and the etching stopper layer 16. Can be stopped by. Therefore, it becomes easy to obtain the target film thickness d of the remaining film layer 15b of the absorber film 15 by etching.

  The material of the etching stopper layer 16 is formed of a material having etching selectivity with an etching gas for the absorber film 15. Specifically, Ru and / or Cr can be used as the material of the etching stopper layer 16.

  The film thickness of the etching stopper layer 16 is preferably 1 to 20 nm, and preferably 2 to 10 nm.

In the example shown in FIG. 7, (the absorber part pattern 25 of thickness D _2, the thickness difference between the multilayer reflective portion pattern 23 is D ₂ -d) Embodiment 2 of the present invention showed. In FIG. 7, the reflective mask blank 10 shown in FIG. 3 is obtained by setting the film thickness of the multilayer reflective part pattern 23 to D ₁ and the film thickness difference between the multilayer reflective part pattern 23 and the absorber part pattern 25 to D ₀ . Can be used to manufacture the reflective mask 20 of the first embodiment of the present invention.

(Etching mask film)
In the reflective mask blank 10 of the present invention, an etching mask film (not shown) can be further formed on the absorber film 15. The etching mask film is formed of a material having etching selectivity with respect to the uppermost layer of the multilayer reflective film 13 and capable of being etched with an etching gas with respect to the absorber film 15 (having no etching selectivity). Specifically, the etching mask film is formed of a material containing Cr or Ta, for example. Examples of the material containing Cr include Cr metal alone and Cr-based compounds obtained by adding one or more elements selected from elements such as O, N, C, H, and B to Cr. Materials containing Ta include Ta metal alone, TaB alloy containing Ta and B, Ta alloy containing Ta and other transition metals (for example, Hf, Zr, Pt, and W), Ta metal, and their alloys And Ta-based compounds in which N, O, H and / or C are added. Here, when the absorber film 15 contains Ta, a material containing Cr is selected as a material for forming the etching mask film. Moreover, when the absorber film 15 contains Cr, it is preferable to select a material containing Ta as a material for forming the etching mask film.

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

  The thickness of the etching mask film is preferably 5 nm or more from the viewpoint of ensuring the function as a hard mask. In the manufacturing process of the reflective mask 20, the etching mask film is removed simultaneously with the absorber film 15 by the fluorine-based gas used in the etching process of the absorber film 15. Therefore, it is preferable that the etching mask film has substantially the same thickness as the absorber film 15. Considering the film thickness of the absorber film 15, the film thickness of the etching mask film is 5 nm or more and 20 nm or less, preferably 5 nm or more and 15 nm or less.

(Back conductive film 11)
As shown in FIGS. 1 and 2, a back surface conductive film 11 for an electrostatic chuck is formed on the back surface side of the substrate 12 (on the side opposite to the formation surface of the multilayer reflective film 13). The electrical characteristics required for the back surface conductive film 11 for the electrostatic chuck are normally a sheet resistance of 100Ω / sq or less. The back surface conductive film 11 can be formed by, for example, a magnetron sputtering method or an on-beam sputtering method using a target of a metal such as chromium or tantalum, or an alloy thereof. When the back surface conductive film 11 is formed of, for example, CrN, it can be formed by the above sputtering method in a gas atmosphere containing N such as nitrogen gas using a Cr target. Although the film thickness of the back surface conductive film 11 is not specifically limited as long as the function for an electrostatic chuck is satisfied, it is usually 10 to 200 nm.

  The configuration of the reflective mask blank 10 according to the embodiment has been described above for each layer.

  The reflective mask blank 10 of the present invention is not limited to the above-described embodiment. For example, the reflective mask blank 10 of the present invention can include a resist film having a function as an etching mask on the absorber film 15. In addition, the reflective mask blank 10 of the present invention can include the absorber film 15 in contact with the multilayer reflective film 13 without providing the protective film 14 on the multilayer reflective film 13.

<Reflective mask 20>
Next, the reflective mask 20 of the present invention will be described with reference to FIGS.

  As shown in FIG. 5 to FIG. 7, the reflective mask 20 of the present invention has a multilayer reflecting portion pattern 23 for reflecting EUV light and an absorber portion pattern 25 for absorbing EUV light on a substrate 12. Have.

  As shown in FIG. 5 and FIG. 6, the multilayer reflective portion pattern 23 of the reflective mask 20 of the present invention has the multilayer reflective film 13 and the remaining film layer 15 b of the absorber film 15 on the substrate 12 in this order, or The multilayer reflective film 13, the protective film 14, and the remaining film layer 15b of the absorber film 15 are provided in this order. Also, as shown in FIGS. 5 and 6, the absorber pattern 25 of the reflective mask 20 of the present invention has a multilayer reflective film 13 and an absorber film 15 on the substrate 12 in this order, or a multilayer reflective film. 13, the protective film 14 and the absorber film 15 are provided in this order. The film thickness d of the remaining film layer 15 b of the absorber film 15 is smaller than the total film thickness D of the absorber film 15. The total film thickness D is preferably 20 to 100 nm, and the film thickness d is preferably 4 to 40 nm. FIG. 7 shows another example of the reflective mask 20 of the present invention. In the example shown in FIG. 7, an etching stopper layer 16 is further provided on the remaining film layer 15b.

In the present invention, the first and the contrast value C _1, the contrast value of the reference reflective mask 20a. The reference reflective mask 20a is a reflective mask 20a as shown in FIG. That is, the multilayer reflective portion pattern 23 of the reference reflective mask 20 a does not have the remaining film layer 15 b of the absorber film 15. Further, the absorber part pattern 25 of the reference reflective mask 20a includes an absorber layer 15 having a thickness _{D 0.}

In the first embodiment of the reflection type mask 20 of the present invention, a contrast value of the reflection type mask 20, the second and the contrast value C _2, the first contrast value C ₁ and the second contrast value C ₂ is, C ₁ <a relationship _{C 2,} and the thickness _{D 0} of the absorber film 15 of the reference reflective mask 20a, the thickness d of the total thickness D and Zanmakuso 15b of the absorber film 15 of the reflective mask 20 Is a relationship of D ₀ = D−d.

FIG. 5 shows the reflective mask 20 of the first embodiment. In FIG. 5, when incident light 30 with light intensity I ₀ is incident, reflected light 31 a with intensity I _r-multi (= I ₀ · R ′ _multi ) is reflected from the surface of the absorber film 15 with film thickness d, A state in which the reflected light 31b having the intensity I _r-abs (= I ₀ · R ′ _abs ) is reflected from the surface of the absorber film 15 having the film thickness D (= D ₁ ) is shown. In FIG. 5, the portion where the absorber film 15 having a film thickness d exists is a multilayer reflector pattern 23 for reflecting EUV light, and the absorber film 15 having a film thickness D (= D ₁ ) exists. The part to perform is the absorber part pattern 25 for absorbing EUV light.

  According to Embodiment 1 of the reflective mask 20 of the present invention, the reflective mask 20 having a high contrast value can be obtained.

In the second embodiment of the reflection type mask 20 of the present invention, a contrast value of the reflection type mask 20, the second and the contrast value C _2, the first contrast value C ₁ and the second contrast value C ₂ is, C ₁ = C ₂ , and the film thickness D ₀ of the absorber film 15 of the reference reflective mask 20a, the total film thickness D of the absorber film 15 of the reflective mask 20, and the film thickness d of the remaining film layer 15b. Is a relationship of D ₀ > D−d.

FIG. 6 shows a reflective mask 20 according to the second embodiment. In FIG. 6, when incident light 30 with light intensity I ₀ is incident, reflected light 31 a with intensity I _r-multi (= I ₀ · R ′ _multi ) is reflected from the surface of the absorber film 15 with film thickness d, A state in which the reflected light 31b having the intensity I _r-abs (= I ₀ · R ′ _abs ) is reflected from the surface of the absorber film 15 having the film thickness D (= D ₂ ) is shown. In FIG. 6, the portion where the absorber film 15 having a film thickness d exists is a multilayer reflector pattern 23 for reflecting EUV light, and the absorber film 15 having a film thickness D (= D ₂ ) exists. The part to perform is the absorber part pattern 25 for absorbing EUV light. In the second embodiment, the film thickness difference (D ₂ −d) between the multilayer reflector pattern 23 and the absorber pattern 25 is thinner than the film thickness D ₀ used in the step of calculating the _first contrast value C _1. . Therefore, the reflective mask 20 of Embodiment 2 can reduce the film thickness difference (D ₂ −d) while having the same contrast value as the conventional reflective mask. As a result, the shadowing effect by the absorber film 15 in which the absorber part pattern 25 is formed can be reduced.

  In the reflective mask 20 of the present invention, the difference between the total film thickness D of the absorber film 15 and the film thickness d of the remaining film layer 15b is preferably 65 nm or less. By reducing the difference between the total film thickness D of the absorber film 15 and the film thickness d of the remaining film layer 15b to 65 nm or less, the shadowing effect by the absorber film 15 in which the absorber pattern 25 is formed is reduced. Thus, a reflective mask 20 capable of achieving the above can be obtained.

  In the reflective mask 20 of the present invention, the remaining film layer 15b of the absorber film 15 is preferably made of a material that provides a reflectance of 15% or less for the remaining film layer 15b in the wavelength range of 190 nm to 400 nm. By setting the reflectance of the remaining film layer 15b to a value within a predetermined range, it is possible to suppress out-of-band light when the reflective mask 20 is used.

  In the reflective mask 20 of the present invention, the remaining film layer 15b of the absorber film 15 is preferably made of a material having a reflectance of 30% or less with respect to inspection light for defect inspection. Since the remaining film layer 15b of the absorber film 15 is made of a material having a reflectance of 30% or less with respect to inspection light for defect inspection, the reflective mask 20 capable of highly accurate defect inspection can be obtained.

  As the absorber film 15 of the reflective mask 20 of the present invention, those described as the absorber film 15 of the reflective mask blank 10 of the present invention can be used. The absorber film 15 of the reflective mask 20 of the present invention preferably contains tantalum and nitrogen. When the absorber film 15 contains tantalum and nitrogen, expansion of crystal grains constituting the absorber film 15 can be suppressed on the surface of the absorber film 15. Therefore, it is possible to obtain the reflective mask 20 with reduced pattern edge roughness when the absorber film 15 is patterned.

  The reflective mask 20 of the present invention can be produced using the reflective mask blank 10 of the present invention described above. For the production of the reflective mask 20 for EUV lithography, a photolithography method that can perform high-definition patterning is most suitable.

  A method of manufacturing the reflective mask 20 using the photolithography method will be described by taking as an example the case of manufacturing the reflective mask 20 of the first embodiment shown in FIG. 6 using the reflective mask blank 10 shown in FIG.

  First, a resist film (not shown) is formed on the outermost surface of the reflective mask blank 10 shown in FIG. 2 (the outermost surface of the absorber film 15). The film thickness of the resist film can be set to 100 nm, for example. Next, a desired pattern is drawn (exposed) on the resist film, and further developed and rinsed to form a predetermined resist pattern (not shown).

Next, the absorber film 15 is dry-etched with an etching gas containing a fluorine-based gas such as SF ₆ using a resist pattern (not shown) as a mask, so that the predetermined absorber pattern 25 and the multilayer are formed. The reflection part pattern 23 is formed. That is, the etching of the absorber film 15 is performed so that the film thickness of the remaining film layer 15b of the multilayer reflective pattern 23 becomes the film thickness d. In this step, the resist pattern (not shown) is removed. In the case of the second embodiment shown in FIG. 7 as well, the reflective mask 20 of the second embodiment can be manufactured by etching so that the film thickness d of the remaining film layer 15b is obtained.

  Here, the etching rate of the absorber film 15 depends on conditions such as a material for forming the absorber film 15 and an etching gas. In the case of the absorber film 15 made of a multilayer film of different materials, the etching rate varies somewhat for each layer of different materials. However, since the thickness of each layer is small, the etching rate in the entire absorber film 15 is considered to be substantially constant. The remaining film layer 15b having a film thickness d can be formed by adjusting the film formation time of the absorber film 15 in consideration of the etching rate.

  In the reflective mask 20 of the present invention, the multilayer reflector pattern 23 is formed of a portion having a film thickness d corresponding to the film thickness of the remaining film layer 15b of the absorber film 15, and an etching stopper layer formed on the remaining film layer 15b. 16 is preferable.

  FIG. 7 shows an example of the reflective mask 20 in which the etching stopper layer 16 is formed in a portion having a film thickness d corresponding to the film thickness of the remaining film layer 15 b of the absorber film 15. Since the absorber film 15 has the predetermined etching stopper layer 16, the etching progress can be stopped by the etching stopper layer 16 regardless of the etching time when the absorber film 15 is etched. Therefore, it becomes easy to obtain the target film thickness d of the remaining film layer 15b of the absorber film 15 by etching. The material and film thickness of the etching stopper layer 16 are as described in the reflective mask blank 10 of the present invention.

  By the above process, the absorber film pattern (the multilayer reflection portion pattern 23 and the absorber portion pattern 25) is formed. In the case of the absorber film 15 made of a multilayer film, it can be continuously etched by dry etching with one kind of etching gas. By performing dry etching with one kind of etching gas, the effect of simplifying the process can be obtained. Next, wet cleaning using an acidic or alkaline aqueous solution is performed to obtain a reflective mask 20 for EUV lithography that has achieved high reflectivity.

As an etching gas for the absorber film 15, in addition to SF ₆ , CHF ₃ , CF ₄ , C ₂ F ₆ , C ₃ F ₆ , C ₄ F ₆ , C ₄ F ₈ , CH ₂ F ₂ , CH ₃ A fluorine-based gas such as F, C ₃ F ₈ , and F, and a mixed gas containing these fluorine gas and O ₂ at a predetermined ratio can be used. When the absorber film 15 is etched, another gas may be used as long as it is a gas useful for processing. As another gas, for example, a chlorine-based gas selected from Cl ₂ , SiCl ₄ , CHCl ₃ , CCl ₄ , BCl ₃ , and the like, and a mixed gas thereof, a mixed gas containing a chlorine-based gas and He at a predetermined ratio Selected from the group consisting of a mixed gas containing chlorine-based gas and Ar at a predetermined ratio, a halogen gas containing at least one selected from fluorine gas, chlorine gas, bromine gas and iodine gas, and a hydrogen halide gas At least one kind or more may be mentioned. Furthermore, the mixed gas containing these gas and oxygen gas etc. are mentioned.

  In addition, when the absorber film 15 is formed of a multilayer film, when the lower layer is formed of a material having etching resistance with respect to the uppermost layer of the absorber film 15, two types of etching gases described above are used to perform two-stage dryness. It is also possible to perform etching.

<Manufacture of semiconductor devices>
The present invention is a method for manufacturing a semiconductor device, including a pattern forming step of forming a pattern on a semiconductor substrate using the above-described reflective mask 20 of the present invention.

  Using the above-described reflective mask 20 of the present invention, a transfer pattern based on the absorber film pattern (multilayer reflector pattern 23 and absorber pattern 25) of the reflective mask 20 is formed on a semiconductor substrate by EUV lithography. can do. Thereafter, through various other processes, a semiconductor device in which various patterns and the like are formed on the semiconductor substrate can be manufactured. A known pattern transfer apparatus can be used for forming the transfer pattern.

  According to the method for manufacturing a semiconductor device of the present invention, since a high contrast value can be obtained during exposure, a semiconductor device having a fine and highly accurate transfer pattern can be manufactured. In addition, according to the method for manufacturing a semiconductor device of the present invention, the reflective mask 20 having a small shadowing effect by the absorber film 15 in which the absorber part pattern 25 is formed can be used. A semiconductor device having a pattern can be manufactured.

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

<Example 1>
By the method described below, the contrast value of the reflective mask 20 of Example 1 was obtained by simulation. The reflective mask 20 of Example 1 had a structure of CrN back surface conductive film 11 \ substrate 12 \ MoSi multilayer reflective film 13 \ protective film 14 \ absorber film 15. Table 1 shows the film thicknesses of the absorber film 15, the protective film 14, and the multilayer reflective film 13 of the reflective mask 20 of Example 1 and the corresponding reference reflective mask 20a. By specifying the refractive index n and the extinction coefficient k of the material constituting each film, the relationship between the film thickness of the absorber film 15 and the reflectance was obtained by simulation. FIG. 8 shows the relationship between the thickness of the absorber film 15 obtained by simulation and the reflectance in the reflective mask 20 having the structure of the first embodiment.

The substrate 12 of Example 1 was a SiO ₂ —TiO ₂ glass substrate 12 having a thickness of 6.35 mm. Further, the back surface conductive film 11 made of CrN having a thickness of 20 nm is disposed on the back surface of the substrate 12.

  The multilayer reflective film 13 of Example 1 has a Si film with a film thickness of 4.2 nm and a film thickness of 2.8 nm on the surface opposite to the surface (back surface) on which the back surface conductive film 11 of the substrate 12 is disposed. The Mo film was arranged, and this was used as one period, and 40 periods were stacked. Finally, the Si film was arranged with a film thickness of 4.0 nm. Therefore, the total film thickness of the multilayer reflective film 13 is 284 nm.

  As shown in Table 1, the protective film 14 of Example 1 has a structure in which the protective film 14 made of Ru is disposed on the uppermost Si film of the multilayer reflective film 13 with a film thickness of 2.5 nm. .

  As shown in Table 1, the absorber film 15 of Example 1 has a structure in which a single-layer TaN film is disposed on the protective film 14. In the reference reflective mask 20a corresponding to the reflective mask 20 of Example 1, the thickness of the absorber film 15 of the absorber pattern 25 is 62 nm, and the absorber film 15 is provided in the multilayer reflector pattern 23. The reflective mask 20a is not formed. The film thickness of the absorber film 15 of the absorber pattern 25 of the reflective mask 20 of Example 1 is 76 nm, and the film thickness of the absorber film 15 (residual film layer 15b) of the multilayer reflector pattern 23 is 14 nm. The film thickness difference of the absorber film 15 between the absorber part pattern 25 and the multilayer reflector part pattern 23 is the same as the film thickness 62 nm of the absorber film 15 of the absorber part pattern 25 of the reference reflective mask 20a. In FIG. 8, points corresponding to the film thickness (= 0 nm) of the absorber film 15 of the multilayer reflective part pattern 23 of the reference reflective mask 20a and the film thickness of the absorber film 15 of the absorber part pattern 25 are respectively A. Shown as point and point a. FIG. 8 shows points corresponding to the film thicknesses of the multilayer reflective portion pattern 23 of the reflective mask 20 and the absorber film 15 of the absorber portion pattern 25 as point B and point b, respectively.

The reflectance with respect to the exposure light having a wavelength of 13.5 nm in the absorber pattern 25 and the multilayer reflective pattern 23 of the reflective mask 20 of Example 1 and the reference reflective mask 20a corresponding thereto was determined by simulation. From the reflectance, the contrast value C ₁ of the reference reflective mask 20a was calculated based on the formula (2), and the contrast value C ₂ of the reflective mask 20 of Example 1 was calculated based on the formula (3). . The results are shown in Table 1.
_{C 1 = (R multi -R abs} ) / (R multi + R abs) ··· (2)
_{C 2 = (R 'multi -R} ' abs) / (R 'multi + R' abs) ··· (3)

  As is clear from Table 1, the contrast value of the reflective mask 20 of Example 1 of the present invention is larger than the contrast value of the reference reflective mask 20a which is a conventional reflective mask. Therefore, according to the present invention, it can be said that the reflective mask 20 having a high contrast value can be obtained.

<Example 2>
The contrast value of the reflective mask 20 of Example 2 was obtained by simulation by the method described below. The reflective mask 20 of Example 2 had a structure of CrN back surface conductive film 11 \ substrate 12 \ MoSi multilayer reflective film 13 \ protective film 14 \ absorber film 15. Table 2 shows the film thicknesses of the absorber film 15, the protective film 14, and the multilayer reflective film 13 of the reflective mask 20 of Example 2 and the corresponding reference reflective mask 20a. The substrate 12, the back surface conductive film 11, the multilayer reflective film 13 and the protective film 14 of Example 2 are the same as those of Example 1.

  As shown in Table 2, the absorber film 15 of Example 2 is different from Example 1 in that the upper layer of the TaN layer (layer opposite to the protective film 14) and the lower layer of the TaO layer (layer in contact with the protective film 14). , The remaining film layer). Table 2 shows the film thickness and the like of the absorber film 15 of the reference reflective mask 20a corresponding to the reflective mask 20 of Example 2.

The reflectance for the exposure light having a wavelength of 13.5 nm in the absorber pattern 25 and the multilayer reflective pattern 23 of the reflective mask 20 of Example 2 and the reference reflective mask 20a corresponding thereto was determined by simulation. Further, the contrast value C ₁ of the reference reflective mask 20a and the contrast value C 2 of the reflective mask 20 of Example ₂ were calculated from these reflectances based on the equations (2) and (3). The results are shown in Table 2.

  As is clear from Table 2, the contrast value of the reflective mask 20 of Example 2 of the present invention is larger than the contrast value of the reference reflective mask 20a which is a conventional reflective mask. Therefore, according to the present invention, it can be said that the reflective mask 20 having a high contrast value can be obtained.

<Manufacture of semiconductor devices>
The reflective mask 20 of Examples 1 and 2 can be actually manufactured and set in an EUV scanner, and EUV exposure can be performed on a wafer on which a processed film and a resist film are formed on a semiconductor substrate. Then, by developing the exposed resist film, a resist pattern can be formed on the semiconductor substrate on which the film to be processed is formed.

  Since the reflective mask 20 of Examples 1 and 2 is larger than the contrast value of the reference reflective mask 20a which is a conventional reflective mask, a semiconductor device having a fine and highly accurate transfer pattern can be manufactured.

  This resist pattern is transferred to the film to be processed by etching, and through various processes such as formation of an insulating film, conductive film, introduction of dopant, or annealing, a semiconductor device having desired characteristics is manufactured at a high yield. can do.

DESCRIPTION OF SYMBOLS 10 Reflective mask blank 11 Back surface conductive film 12 Substrate 13 Multilayer reflective film 14 Protective film 15 Absorber film 15a Absorber film body 15b Residual film layer 16 Etching stopper layer 20 Reflective mask 20a Reflective mask (reference reflective mask)
23 multilayer reflector pattern 25 absorber pattern 30 incident light 31a reflected light (reflected light in multilayer reflector pattern)
31b Reflected light (reflected light at the absorber pattern)

Claims (13)

A method for producing a reflective mask blank having a multilayer reflective film and an absorber film in this order on a substrate, or a multilayer reflective film, a protective film and an absorber film in this order,
The step of obtaining the relationship between the film thickness of the absorber film and the reflectance on the surface of the absorber film by simulation,
Based on the relationship between the film thickness of the absorber film and the reflectance on the surface of the absorber film, the reflectance R _{abs on the} surface of the absorber film having the film thickness D ₀ and the multilayer reflection film by removing the absorber film Alternatively, the first contrast value C ₁ , that is, the reflectance R _{multi on the} surface of the multilayer reflective film or the protective film with the protective film exposed, that is,
_{C 1 = (R multi -R abs} ) / (R multi + R abs)
Calculating
Based on the relationship between the film thickness of the absorber film and the reflectance on the surface of the absorber film, the reflectance R ′ _{abs on the} surface of the absorber film having the film thickness D and a part of the film thickness direction of the absorber film The second contrast value C ₂ higher than the first contrast value C ₁ is obtained from the reflectance R ′ _{multi on} the surface of the remaining film layer having the film thickness d when the film is removed to form the remaining film, that is,
_{C 2 = (R 'multi -R} ' abs) / (R 'multi + R' abs)
A step of obtaining a film thickness d of the remaining film layer and a total film thickness D = D ₁ (where D ₀ = D ₁ -d), or a film thickness of the absorber film and a reflectance on the surface of the absorber film based on the relationship between, remaining film thickness d in the case where the reflectance R _'abs in the absorber film surface with a thickness D, is residual film by removing part of the thickness direction of the absorber film From the reflectance R ′ _{multi on} the surface of the layer, the second contrast value C ₂ (= C ₁ ), which is the same as the _first contrast value C ₁ , that is,
_{C 2 = (R 'multi -R} ' abs) / (R 'multi + R' abs)
A step of obtaining a film thickness d of the remaining film layer and a total film thickness D = D ₂ (where D ₀ > D ₂ −d),
Forming the absorber film so as to have the total film thickness D. A method for manufacturing a reflective mask blank, comprising:   2. The method of manufacturing a reflective mask blank according to claim 1, wherein the difference between the total thickness D of the absorber film and the thickness d of the remaining film layer is 65 nm or less.   3. The reflective mask according to claim 1, wherein the remaining film layer of the absorber film is made of a material having a reflectance of 15% or less in the wavelength range of 190 nm to 400 nm. Blank manufacturing method.   The manufacturing method of the reflective mask blank according to any one of claims 1 to 3, wherein the remaining film layer of the absorber film is made of a material having a reflectance of 30% or less with respect to inspection light for defect inspection. Method.   The said absorber film | membrane has an etching stopper layer formed in the part of the film thickness d equivalent to the film thickness of the remaining film layer of an absorber film | membrane, The any one of Claims 1-4 characterized by the above-mentioned. Method for manufacturing a reflective mask blank.   The said absorber film contains a tantalum and nitrogen, The manufacturing method of the reflective mask blank of any one of Claims 1-5 characterized by the above-mentioned. A reflective mask having a multilayer reflection part pattern for reflecting EUV light and an absorber part pattern for absorbing EUV light on a substrate,
The multilayer reflector pattern has, on the substrate, the remaining film layers of the multilayer reflective film and the absorber film in this order, or the remaining film layers of the multilayer reflective film, the protective film, and the absorber film in this order,
The absorber pattern has a multilayer reflective film and an absorber film in this order on the substrate, or a multilayer reflective film, a protective film and an absorber film in this order,
The film thickness d of the remaining film layer of the absorber film is thinner than the total film thickness D of the absorber film,
A contrast value of the first contrast value C ₁ is the reference reflective mask, the multilayer reflective part pattern of the reference reflective mask does not have a residual layer of the absorber film, absorber section pattern of thickness D ₀ Having an absorber film,
When the second contrast value C ₂ is the contrast value of the reflection type mask,
C ₁ <C ₂ and D ₀ = D-d, or C ₁ = C ₂ and D ₀ > D-d
A reflective mask characterized by the above.   The reflective mask according to claim 7, wherein a difference between the total film thickness D of the absorber film and the film thickness d of the remaining film layer is 65 nm or less.   9. The reflective mask according to claim 7, wherein the remaining film layer of the absorber film is made of a material having a reflectance of 15% or less in the wavelength range of 190 nm to 400 nm. .   The reflective mask according to any one of claims 7 to 9, wherein the remaining film layer of the absorber film is made of a material having a reflectance of 30% or less with respect to inspection light for defect inspection.   8. The multilayer reflective portion pattern includes a portion having a film thickness d corresponding to the film thickness of the remaining film layer of the absorber film, and an etching stopper layer formed on the remaining film layer. The reflective mask of any one of 10-10.   The reflective mask according to claim 7, wherein the absorber film contains tantalum and nitrogen.   A method for manufacturing a semiconductor device, comprising: a pattern forming step of forming a pattern on a semiconductor substrate using the reflective mask according to claim 7.