JP2020106721A - Substrate for mask blank, substrate with multilayer reflection film, reflective mask blank, reflective mask, transmissive mask blank, transmissive mask, and method for producing semiconductor device - Google Patents

Abstract

To provide a substrate for a mask blank with which the flatness of a main surface can be measured accurately and with high reproductivity, a substrate with a multilayer reflection film, a reflective mask blank, a reflective mask, a transmissive mask blank, a transmissive mask, and a method for producing a semiconductor device.SOLUTION: A substrate 10 for a mask blank comprises: a pair of opposite main surfaces 12a, 12b; and four end surfaces 14a-14d adjacent to outer edges of the pair of main surfaces 12a, 12b. When a value of a root-mean-square surface roughness as measured in a longer direction of the end surface is RqA, and a value of a root-mean-square surface roughness as measured in a vertical direction of the longer direction is RqB, a relationship of RqA>RqB is satisfied in at least part of the four end surfaces 14a-14d.SELECTED DRAWING: Figure 1

Description

The present invention relates to a mask blank substrate, a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask, a transmissive mask blank, a transmissive mask, and a method for manufacturing a semiconductor device.

Generally, in a manufacturing process of a semiconductor device, a fine pattern is formed by using a photolithography method. In order to form this fine pattern, a number of transfer masks usually called photomasks are used. This transfer mask generally has a fine pattern made of a metal thin film or the like provided on a translucent glass substrate, and the photolithography method is also used in the manufacture of this transfer mask.

A mask blank having a thin film (for example, a light-shielding film) for forming a transfer pattern (mask pattern) on a transparent substrate such as a glass substrate is used for manufacturing a transfer mask by a photolithography method. A method of manufacturing a transfer mask using this mask blank is performed by a drawing step of drawing a desired pattern on a resist film formed on the mask blank, and after drawing, developing the resist film to develop a desired resist pattern. A developing step of forming a film, an etching step of etching the thin film using the resist pattern as a mask, and a step of peeling and removing the remaining resist pattern. In the developing step, a desired pattern is drawn on the resist film formed on the mask blank, and then a developing solution is supplied. As a result, the portion of the resist film that is soluble in the developing solution is dissolved, so that a resist pattern is formed. In the etching step, the resist pattern is used as a mask to perform dry etching or wet etching to remove the exposed portion of the thin film which is not covered with the resist pattern. Thereby, a desired mask pattern is formed on the transparent substrate.

As a type of transfer mask, a phase shift mask is known in addition to a binary mask having a light-shielding film pattern made of a chromium-based material on a conventional transparent substrate. This phase shift mask has a transparent substrate and a phase shift film formed on the transparent substrate. This phase shift film has a predetermined phase difference and is formed of, for example, a material containing a molybdenum silicide compound. Further, a binary mask using a material containing a silicide compound of a metal such as molybdenum as a light shielding film has also been used. These binary type masks and phase shift type masks are collectively referred to as a transmission type mask in this specification. In addition, the binary type mask blank and the phase shift type mask blank, which are the original plates used for the transmission type mask, are collectively referred to as a transmission type mask blank.

Further, in recent years, with the increase in integration of semiconductor devices in the semiconductor industry, fine patterns exceeding the transfer limit of the conventional photolithography method using ultraviolet light have been required. In order to enable the formation of such a fine pattern, EUV lithography, which is an exposure technique using extreme ultra violet (hereinafter referred to as “EUV”) light, is considered promising. Here, the 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. A reflective mask has been proposed as a transfer mask used in this EUV lithography. In such a reflective mask, a multilayer reflective film that reflects exposure light is formed on a substrate, and an absorber film that absorbs exposure light is formed on the multilayer reflective film. A transfer pattern is formed on the absorber film.

Patent Document 1 discloses a low-expansion glass substrate which is a base material of a reflective mask used in a lithography process of a semiconductor manufacturing process. A low-expansion glass substrate for a reflective mask is described, in which the flatness of each of the two side surfaces facing each other is 25 μm or less, and the parallelism of the two side surfaces is 0.01 mm/inch or less.

Patent No. 5640744

The main surface of the mask blank substrate is required to have extremely high flatness so that the distortion of the pattern formed on the mask blank falls within an allowable range. The flatness of the main surface of the mask blank substrate is measured by a flatness measuring device.

When measuring the flatness of the substrate with the flatness measuring device, the substrate is substantially upright (for example, the substrate is tilted by 2° with respect to the vertical direction) in order to reduce distortion of the substrate due to gravity. The measurement is done at. At this time, of the four end faces adjacent to the main surface of the substrate, for example, two end faces facing each other are held by the holder. When the flatness of the substrate is measured by the flatness measuring device, the substrate may be rotated in, for example, four directions while holding the end surface of the substrate by the holder. Further, while holding the end surface of the substrate by the holder, the inclination angle of the substrate in the upright state may be changed.

As described above, in the conventional mask blank substrate, when the flatness of the substrate is measured by the flatness measuring device, the substrate held by the holder may be moved. For this reason, the position of the substrate with respect to the holder may be slightly moved, and the measured value of the flatness of the substrate may vary.

The present invention has been made in view of the above circumstances, a mask blank substrate capable of measuring the flatness of the main surface precisely and with high reproducibility, a substrate with a multilayer reflective film, a reflective mask blank, An object of the present invention is to provide a method for manufacturing a reflective mask, a transmissive mask blank, a transmissive mask, and a semiconductor device.

In order to solve the above problems, the present invention has the following configurations.
(Structure 1)
A pair of main surfaces facing each other, a mask blank substrate having an end face adjacent to the outer edge of the pair of main surfaces,
The value of the root mean square surface roughness measured along the longitudinal direction of the end surface in at least a part of the end face is Rq _A , and the value of the root mean square surface roughness measured along the direction perpendicular to the longitudinal direction. the when the Rq _B, satisfy the relationship of Rq a> Rq _B, a substrate for a mask blank.

(Configuration 2)
The end surface includes a side surface and a chamfered surface formed between the side surface and the main surface,
The mask blank substrate according to Configuration 1, wherein the relationship of Rq _A >Rq _B is satisfied in at least one of the side surface and the chamfered surface.

(Structure 3)
The chamfered surface includes a ridge portion adjacent to the main surface,
3. The mask blank substrate according to Configuration 2, wherein the ridge portion satisfies the relationship of Rq _A >Rq _B.

(Structure 4)
The mask blank substrate according to any one of Configurations 1 to 3, wherein Rq _A is 0.1 nm or more on at least a part of the end face.

(Structure 5)
The mask blank substrate according to any one of configurations 1 to 4, wherein Rq _A /Rq _B is 1.1 or more on at least a part of the end face.

(Structure 6)
6. The mask blank substrate according to any one of configurations 1 to 5, a multilayer reflective film that reflects EUV light formed on the one main surface of the mask blank substrate, and formed on the multilayer reflective film. And a multilayered reflective film-coated substrate.

(Structure 7)
A reflective mask blank, comprising: the substrate with a multilayer reflective film according to configuration 6; and an absorber film which is a transfer pattern formed on a protective film of the substrate with a multilayer reflective film.

(Structure 8)
A reflective mask, comprising: the substrate with a multilayer reflective film according to configuration 6; and an absorber film pattern formed on a protective film of the substrate with a multilayer reflective film.

(Configuration 9)
A transmissive mask blank comprising: the mask blank substrate according to any one of configurations 1 to 5; and a light-shielding film which is a transfer pattern formed on the one main surface of the mask blank substrate.

(Configuration 10)
A transmission type mask, comprising: the mask blank substrate according to any one of configurations 1 to 5; and a light-shielding film pattern formed on the one main surface of the mask blank substrate.

(Configuration 11)
A method for manufacturing a semiconductor device, comprising the step of performing a lithography process using an exposure apparatus, using the reflective mask according to configuration 8, to form a transfer pattern on a transfer target.

(Configuration 12)
A method of manufacturing a semiconductor device, comprising the step of performing a lithographic process using an exposure apparatus, using the transmission mask according to the structure 10, to form a transfer pattern on a transfer target.

According to the present invention, a mask blank substrate, a substrate with a multilayer reflective film, a reflective mask blank, a reflective mask, a transmissive mask blank, a transmissive type capable of accurately measuring the flatness of the main surface with high reproducibility. A mask and a method for manufacturing a semiconductor device can be provided.

It is a perspective view of the mask blank substrate. It is a fragmentary sectional view of a mask blank substrate. It is a top view of the mask blank substrate mounted on the stage of the flatness measuring apparatus. It is a side view of the mask blank substrate mounted on the stage of the flatness measuring apparatus. It is a bottom view of the mask blank substrate mounted on the stage of the flatness measuring apparatus. FIG. 5 is an enlarged view of part A of the mask blank substrate shown in FIG. 4. It is an enlarged view of the B section of the mask blank substrate shown in FIG. It is a figure showing the state where the substrate mounted on the stage of the flatness measuring device was made almost upright. It is a schematic diagram which shows the board|substrate with a multilayer reflective film. It is a schematic diagram which shows a reflective mask blank. It is a schematic diagram which shows a reflective mask. It is a schematic diagram which shows a transmissive mask blank. It is a schematic diagram which shows a transmissive mask. It is a schematic diagram which shows the aspect at the time of polishing the side surface (T surface) of a glass substrate with a substrate finishing apparatus. It is a schematic diagram which shows the aspect at the time of polishing the chamfered surface (C surface) and ridgeline part of a glass substrate with a substrate finishing apparatus.

Hereinafter, embodiments of the present invention will be described in detail.
[Mask blank substrate]
First, the mask blank substrate of this embodiment will be described.
FIG. 1 is a perspective view showing a mask blank substrate 10 according to this embodiment. FIG. 2 is a partial cross-sectional view of the mask blank substrate 10 of this embodiment.

The mask blank substrate 10 (hereinafter may be simply referred to as the substrate 10) is made of a substantially quadrangular plate-shaped body, and has two main surfaces 12 (12a, 12b) and four end faces 14 (14a to 14d). Have. The two main surfaces 12 a and 12 b facing each other form the upper surface and the lower surface of the substrate 10. At least one of the two main surfaces 12a and 12b is a surface on which a thin film serving as a transfer pattern is formed.
In addition, in this specification, "upper" does not necessarily mean an upper side in the vertical direction. In addition, “down” does not necessarily mean a lower side in the vertical direction. These terms are merely used for convenience to describe the positional relationship between members and parts.

The four end surfaces 14a to 14d are respectively adjacent to the four sides that are the outer edges of the substantially quadrangular main surfaces 12a and 12b.
Each of the four end surfaces 14 (14a to 14d) has a side surface 16 and two chamfered surfaces 18a and 18b (see FIG. 2) formed between the side surface 16 and the main surfaces 12a and 12b. ..

The side surface 16 is a surface that is substantially perpendicular to the two main surfaces 12a and 12b, and is sometimes called a "T surface".
The chamfered surfaces 18a and 18b are surfaces formed between the two main surfaces 12a and 12b and the side surface 16, and are surfaces that are formed by being chamfered obliquely. The chamfered surfaces 18a and 18b are sometimes referred to as "C surfaces".

In the mask blank substrate 10 of the present embodiment, the root mean square surface roughness value measured along the longitudinal direction of the end faces of at least a part of the four end faces 14a to 14d is Rq _A , which is perpendicular to the longitudinal direction. the value of the root mean square surface roughness measured along the direction when the Rq _B, satisfy the relationship of Rq _a> Rq _B. Here, the "longitudinal direction" means the direction along the long sides of the substantially rectangular end surfaces 14a to 14d. Taking one end surface 14b as an example, the "longitudinal direction" of the end surface 14b means the vertical direction in FIG.

The root mean square surface roughness Rq _A and Rq _B mean the surface roughness represented by Rq (root mean square roughness) specified in JIS B 0601. The root mean square roughness Rq is the square root of the value obtained by averaging the squares of the deviations from the mean line to the measurement curve. The root mean square roughness Rq can be measured using, for example, an atomic force microscope. The root mean square roughness Rq is expressed by the following equation (1), for example.

The mask blank substrate 10 of the present embodiment preferably satisfies the relationship of Rq _A >Rq _{B on} at least one of the side surface 16 and the chamfered surfaces 18 a and 18 b.

As shown in FIGS. 1 and 2, each of the four end faces 14 (14a to 14d) includes two ridge line portions 20a and 20b. The two ridge line portions 20a and 20b are linear portions formed at the boundaries between the chamfered surfaces 18a and 18b and the main surfaces 12a and 12b. The mask blank substrate 10 of the present embodiment preferably satisfies the relationship of Rq _A >Rq _B in at least one of the two ridge lines 20 a and 20 b. The reason will be described later.

In the mask blank substrate 10 of the present embodiment, Rq _A is preferably 0.1 nm or more, more preferably 0.2 nm or more, and 0.3 nm in at least a part of the four end faces 14 a to 14 d. It is more preferable that the above is satisfied. Further, Rq _A is preferably 1.0 nm or less, more preferably 0.7 nm or less, and further preferably 0.5 nm or less.

In the mask blank substrate 10 of the present embodiment, Rq _A /Rq _B (ratio of Rq _{A to} Rq _B ) is preferably 1.1 or more in at least a part of the four end faces 14a to 14d, and 1.2. The above is more preferable. Rq _A /Rq _B is preferably 2.0 or less, and more preferably 1.5 or less.

3 to 5 show the mask blank substrate 10 placed on the stage 102 of the flatness measuring apparatus 100. 3 is a plan view, FIG. 4 is a side view, and FIG. 5 is a bottom view.

As shown in FIGS. 3 to 5, the flatness measuring apparatus 100 includes a stage 102 on which the substrate 10 is placed. Three holders 104 a to 104 c for holding the substrate 10 are fixed on the upper surface of the stage 102. The three holders 104a to 104c are made of synthetic resin. The mask blank substrate 10 carried by the robot arm from the previous step (for example, the cleaning step) is placed on the three holders 104a to 104c.

Of the three holders 104a to 104c, the two holders 104a and 104b support the end surface 14b on the left side (the left side in FIGS. 3 to 5) of the substrate 10. The other holder 104c supports the end surface 14d on the right side (the right side in FIGS. 3 to 5) of the substrate 10.

The two holders 104a and 104b located on the left side in FIGS. 3 to 5 have a substantially conical cone portion 106 and a spherical ball portion 108 connected to the upper portion of the cone portion 106.

The holder 104c located on the right side in FIGS. 3 to 5 has a pedestal portion 110 fixed to the upper surface of the stage 102. A taper surface 112 that is inclined with respect to the upper surface of the stage 102 is formed on the pedestal portion 110.

FIG. 6 is an enlarged view of part A of the mask blank substrate 10 shown in FIG. However, in FIG. 6, the stage 102 is omitted for simplification.
As shown in FIG. 6, when the substrate 10 is held by the three holders 104 a to 104 c, the outer peripheral surfaces of the cone portions 106 of the two left holders 104 a and 104 b are the same as the lower main surface 12 b of the substrate 10. It is in contact with the ridge line portion 20b formed at the boundary with the chamfered surface 18b. The outer peripheral surfaces of the ball portions 108 of the holders 104 a and 104 b are in contact with the side surface 16 of the substrate 10.

FIG. 7 is an enlarged view of part B of the mask blank substrate 10 shown in FIG. However, in FIG. 7, the stage 102 is omitted for simplification.
As shown in FIG. 7, when the substrate 10 is held by the three holders 104 a to 104 c, the tapered surface 112 of the right holder 104 c is located at the boundary between the lower main surface 12 b of the substrate 10 and the chamfered surface 18 b. It is in contact with the formed ridge line portion 20b.

FIG. 8 shows a state in which the substrate 10 placed on the stage 102 of the flatness measuring apparatus 100 is substantially upright.
As shown in FIG. 8, when the flatness of the substrate 10 is measured by the flatness measuring apparatus 100, the substrate 10 is substantially upright (for example, the substrate 10 is placed upright in order to reduce distortion of the substrate 10 due to gravity). The measurement is performed in a state of being inclined by 2° with respect to the vertical direction. The flatness measuring apparatus 100 is provided with a driving device (not shown), and by rotating the stage 102 with this driving device, the substrate 10 can be erected from a horizontal state to a substantially upright state.

When measuring the flatness of the substrate 10 by the flatness measuring device 100, the substrate 10 may be rotated in, for example, four directions while holding the end surfaces 14b and 14d of the substrate 10 by the holders 104a to 104c.

Further, when the flatness of the substrate 10 is measured by the flatness measuring device 100, the tilt angles of the substrate 10 in the upright state are changed while holding the end surfaces 14b and 14d of the substrate 10 by the holders 104a to 104c. Sometimes.

As described above, when the flatness of the substrate 10 is measured by the flatness measuring device 100, the substrate 10 held by the holders 104a to 104c may be moved. In this case, the position of the substrate 10 slightly moves with respect to the holders 104a to 104c, which causes variation in the flatness measurement value.
In the present specification, “flatness” is a value representing the warp (deformation amount) of the surface indicated by TIR (Total Indicated Reading), and a plane defined by the least squares method with the substrate surface as a reference. Is the absolute value of the height difference between the highest position on the substrate surface above the focal plane and the lowest position on the substrate surface below the focal plane.

The present inventors have determined that the value of the root mean square surface roughness measured along the longitudinal direction of the end faces of at least a part of the four end faces 14a to 14d of the substrate 10 is Rq _A , in the direction perpendicular to the longitudinal direction. It has been found that the position of the substrate 10 with respect to the holders 104a to 104c can be prevented from moving by satisfying the relationship of Rq _A >Rq _B , where Rq _B is the value of the root mean square surface roughness measured along. It was

According to the mask blank substrate 10 of the present embodiment, when the flatness of the substrate 10 is measured by the flatness measuring apparatus 100, it is possible to prevent the position of the substrate 10 from moving with respect to the holders 104a to 104c. It is possible to prevent variations in the flatness measurement values.

The mask blank substrate 10 of the present embodiment preferably satisfies the relationship of Rq _A >Rq _{B on} at least one of the side surface 16 and the chamfered surfaces 18 a and 18 b. Further, the mask blank substrate 10 of the present embodiment preferably satisfies the relationship of Rq _A >Rq _{B in} the ridge portions 20a and 20b. That is, it is preferable to satisfy the relationship of Rq _A >Rq _{B at} the portions where the holders 104a to 104c and the four end surfaces 14a to 14d may actually contact each other. Accordingly, when the flatness of the substrate 10 is measured by the flatness measuring device 100, the position of the substrate 10 with respect to the holders 104a to 104c can be prevented from moving. As a result, it is possible to more reliably prevent variations in the measured flatness of the substrate 10.

Although the flatness measuring apparatus 100 of the present embodiment holds the mask blank substrate 10 by the three holders 104a to 104c, it is also possible to hold it by four or more holders. Further, in the present embodiment, the two end faces 14b and 14d are held, but the four end faces 14a to 14d may be held. Further, the holders 104a to 104c are not limited to such a shape, and may have a shape that comes into contact with any of the side surface 16, the chamfered surfaces 18a and 18b, and the ridge line portions 20a and 20b. That is, regardless of the shape and number of holders, Rq _A >Rq at a portion where the holder may contact the four end surfaces 14a to 14d (side surface 16, chamfered surfaces 18a and 18b, ridge line portions 20a and 20b). It is preferable to satisfy the relationship of _B.

The surface roughness of the main surface of the mask blank substrate 10 can be controlled by root mean square roughness (Rq). For example, a multilayer reflective film, a protective film, an absorption film formed on the main surface of the substrate 10 can be used. It is preferable from the viewpoint of improving the optical characteristics such as the reflectance of the body film and the light-shielding film. The surface roughness of the main surface of the substrate 10 is preferably Rq≦0.13 nm, more preferably Rq≦0.10 nm, and further preferably Rq≦0.08 nm.

In addition, in order to improve the transfer accuracy and/or the position accuracy of the pattern, the main surface of the mask blank substrate 10 of the present embodiment on the side where the transfer pattern is formed is surface-processed to have high flatness. Is preferred. In the case of a reflective mask blank substrate for EUV exposure, the flatness is 0.1 μm or less in a 132 mm×132 mm area or a 142 mm×142 mm area of the main surface of the substrate 10 on which the transfer pattern is formed. The thickness is preferably 0.05 μm or less. Further, the main surface on the side opposite to the side on which the transfer pattern is formed is a surface to be electrostatically chucked when set in the exposure apparatus, and has a flatness of 0.1 μm or less, particularly in a region of 142 mm×142 mm. It is preferably 0.05 μm or less. In the case of the mask blank substrate 10 used for the transmission type mask blank for ArF excimer laser exposure, the flatness is measured in a 132 mm×132 mm area or a 142 mm×142 mm area of the main surface on the side where the transfer pattern of the substrate is formed. Is preferably 0.3 μm or less, and particularly preferably 0.2 μm or less.

The mask blank substrate 10 of the present embodiment may be a transmissive mask blank substrate or a reflective mask blank substrate.

Any material may be used as the material of the substrate for a transmission type mask blank for ArF excimer laser exposure as long as it has a light transmitting property with respect to the exposure wavelength. Generally, synthetic quartz glass is used. Other materials may be aluminosilicate glass, soda lime glass, borosilicate glass, and alkali-free glass.

As a material for the reflective mask blank substrate for EUV exposure, a material having a property of low thermal expansion is preferable. For example, SiO ₂ —TiO ₂ system glass (binary system (SiO ₂ —TiO ₂ ) and ternary system (SiO ₂ —TiO ₂ —SnO ₂ etc.)), for example, SiO ₂ —Al ₂ O ₃ —Li ₂ O system. The so-called multi-component glass such as the crystallized glass of 1. can be used. In addition to the above glass, a substrate made of silicon or metal can be used. Examples of the metal substrate include Invar alloy (Fe—Ni based alloy).

As described above, in the case of a mask blank substrate for EUV exposure, a low thermal expansion property is required for the substrate, so a multi-component glass material is used, but higher smoothness is obtained as compared with synthetic quartz glass. There is a problem that it is difficult. In order to solve this problem, a thin film (underlayer) made of a metal, an alloy, or a material containing at least one of oxygen, nitrogen, and carbon in any of these is formed on a substrate made of a multi-component glass material. It may be formed.

As the material of the thin film, for example, Ta (tantalum), an alloy containing Ta, or a Ta compound containing at least one of oxygen, nitrogen and carbon in any of these is preferable. Examples of the Ta compound include TaB, TaN, TaO, TaON, TaCON, TaBN, TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO, TaSiN, TaSiON, TaSiON, TaSiON, TaSiON, TaSiON, TaSiON, TaSiON, TaSiON, TaSiON, TaSiON it can. Among these Ta compounds, TaN containing nitrogen (N), TaON, TaCON, TaBN, TaBON, TaBCON, TaHfN, TaHfON, TaHfON, TaHfON, TaHfCON, TaSiN, TaSiON, TaSiCONCON, TaSiN, TaSiON, TaSiCONCON, TaSiN, TaSiON , TaSiCONCON, TaSiN, TaSiON, TaSiCON are more preferable.

In the mask blank substrate 10 of the present embodiment, the processing method for satisfying the relation of surface roughness Rq _A >Rq _B defined above is not particularly limited. The mask blank substrate 10 of the present embodiment has a surface such that at least a part of the end faces 14a to 14d, which are portions that can contact the holders 104a to 104c of the flatness measuring apparatus 100, satisfy the relationship of Rq _A >Rq _B. The feature is that the roughness is set. Such surface roughness can be realized, for example, by the processing method as illustrated in Examples 1 and 2 described later.

[Substrate with multilayer reflective film]
Next, the substrate with a multilayer reflective film of this embodiment will be described.
FIG. 9 is a schematic view showing the substrate 30 with a multilayer reflective film of this embodiment.

The substrate 30 with a multilayer reflection film of the present embodiment has a structure in which a multilayer reflection film 32 is formed on the main surface of the mask blank substrate 10 on the side where the transfer pattern is formed. The multilayer reflective film 32 has a function of reflecting EUV light in a reflective mask for EUV lithography, and includes a multilayer film in which elements having different refractive indexes are periodically laminated.

The material of the multilayer reflective film 32 is not particularly limited as long as it reflects EUV light, but the reflectance alone is usually 65% or more, and the upper limit is usually 73%. In such a multilayer reflective film 32, generally, a thin film (high refractive index layer) made of a material having a high refractive index and a thin film (low refractive index layer) made of a material having a low refractive index are alternately arranged. It includes a multilayer reflective film that is laminated for about 60 cycles.

For example, the multilayer reflective film 32 for EUV light having a wavelength of 13 to 14 nm is preferably a Mo/Si periodic laminated film in which Mo films and Si films are alternately laminated for about 40 cycles. In addition, examples of the multilayer reflective film used in the EUV light region include Ru/Si periodic multilayer film, Mo/Be periodic multilayer film, Mo compound/Si compound periodic multilayer film, Si/Nb periodic multilayer film, Si/Mo. /Ru periodic multilayer film, Si/Mo/Ru/Mo periodic multilayer film, and Si/Ru/Mo/Ru periodic multilayer film.

The multilayer reflective film 32 can be formed by a method known in the art. For example, each layer can be formed by a magnetron sputtering method, an ion beam sputtering method, or the like. In the case of the above-mentioned Mo/Si periodic multilayer film, for example, an Si target having a thickness of several nm is first formed on the substrate 10 by an ion beam sputtering method, and then a Mo target is used to form a film. It is possible to form a Mo film having a thickness of about several nm, and stack the film for 40 to 60 cycles, and form the multilayer reflective film 32.

A protective film 34 (see FIG. 10) is formed on the multilayer reflective film 32 formed above to protect the multilayer reflective film 32 from dry etching and wet cleaning in the manufacturing process of the reflective mask for EUV lithography. May be done.

Examples of the material of the protective film 34 include Ru, Ru-(Nb, Zr, Y, B, Ti, La, Mo), Si-(Ru, Rh, Cr, B), Si, Zr, Nb, La, and Examples of the material include at least one selected from the group consisting of B. When a material containing ruthenium (Ru) is used among these, the reflectance characteristic of the multilayer reflective film is improved. Specifically, Ru and Ru-(Nb, Zr, Y, B, Ti, La, Mo) are preferable as the material of the protective film 34. Such a protective film is particularly effective when the absorber film contains a Ta-based material and the absorber film is patterned by dry etching with a Cl-based gas.

A back conductive film 36 (see FIG. 10) may be formed on the surface of the substrate 10 opposite to the surface in contact with the multilayer reflective film 32 for the purpose of electrostatic chuck. The electrical characteristics (sheet resistance) required for the back surface conductive film 36 are usually 100Ω/□ or less. The back conductive film 36 can be formed by a known method. For example, the back surface conductive film 36 can be formed by a magnetron sputtering method or an ion beam sputtering method using a target of a metal such as Cr or Ta or an alloy thereof.

The base layer described above may be formed between the substrate 10 and the multilayer reflective film 32. The underlayer can be formed for the purpose of improving the smoothness of the main surface of the substrate 10, reducing defects, improving the reflectance of the multilayer reflective film 32, and reducing the stress of the multilayer reflective film 32.

[Reflective mask blank]
Next, the reflective mask blank of this embodiment will be described.
FIG. 10 is a schematic view showing the reflective mask blank 40 of this embodiment.
The reflective mask blank 40 of the present embodiment has a structure in which an absorber film 42 that serves as a transfer pattern is formed on the protective film 34 of the substrate 30 with the multilayer reflective film described above.

The material of the absorber film 42 is not particularly limited as long as it has a function of absorbing EUV light. For example, Ta (tantalum) alone or a material containing Ta as a main component is preferably used. The material containing Ta as a main component is, for example, an alloy of Ta. Alternatively, as an example of a material containing Ta as a main component, a material containing Ta and B, a material containing Ta and N, a material containing Ta and B, and a material containing at least one of O and N, Ta and Si are used. Examples thereof include a material containing Ta, a material containing Si and N, a material containing Ta and Ge, and a material containing Ta, Ge, and N.

The reflective mask blank of this embodiment is not limited to the configuration shown in FIG. For example, a resist film serving as a mask for patterning the absorber film 42 may be formed on the absorber film 42. The resist film formed on the absorber film 42 may be a positive type or a negative type. The resist film formed on the absorber film 42 may be for electron beam writing or laser writing. Further, a hard mask (etching mask) film may be formed between the absorber film 42 and the resist film.

[Reflective mask]
Next, the reflective mask 50 of this embodiment will be described.
FIG. 11 is a schematic view showing the reflective mask 50 of this embodiment.

The reflective mask 50 of the present embodiment has an absorber film pattern 52 obtained by patterning the absorber film 42 of the reflective mask blank 40 described above. In the reflective mask 50 of the present embodiment, the exposure light is absorbed in a portion where the absorber film pattern 52 is present, and in the portion where the multilayer reflective film 32 (or the protective film 34) is exposed by removing the absorber film 42. The exposure light is reflected. Thereby, the reflective mask 50 of the present embodiment can be used as a reflective mask for lithography that uses EUV light as exposure light, for example.

[Transmissive mask blank]
Next, the transmissive mask blank 60 of this embodiment will be described below.
FIG. 12 is a schematic diagram showing the transmission-type mask blank 60 of this embodiment.

The transmissive mask blank 60 of the present embodiment has a configuration in which a light-shielding film 62 serving as a transfer pattern is formed on the main surface of the mask blank substrate 10 on the side where the transfer pattern is formed.

The transmissive mask blank 60 may be, for example, a binary mask blank or a phase shift mask blank. The light blocking film 62 may include a light blocking film having a function of blocking exposure light. Alternatively, the light shielding film 62 may include a halftone film that attenuates the exposure light and shifts the phase of the exposure light.

The binary mask blank is a mask blank substrate 10 on which a light-shielding film that blocks exposure light is formed. By patterning this light-shielding film, a desired transfer pattern can be formed. Examples of the light-shielding film include a Cr film, a Cr alloy film that selectively contains oxygen, nitrogen, carbon, and fluorine in Cr, a laminated film of these, a MoSi film, and a MoSi alloy that selectively contains oxygen, nitrogen, and carbon in MoSi. A film and a laminated film of these films can be used. An antireflection layer having an antireflection function may be formed on the surface of the light shielding film.

The phase shift mask blank is formed by forming a phase shift film for changing the phase of exposure light on the mask blank substrate 10. A desired transfer pattern can be formed by patterning this phase shift film. An example of the phase shift film is a SiO ₂ film having a phase shift function. In addition, as an example of the phase shift film, a metal silicide oxide film, a metal silicide nitride film, a metal silicide oxynitride film, a metal silicide oxynitride carbide film, a metal silicide oxynitride carbide film (metal Are transition metals such as Mo, Ti, W, and Ta), CrO films, CrF films, and halftone films such as SiON films. The light shielding film may be formed on the phase shift film.

The transmissive mask blank of this embodiment is not limited to the configuration shown in FIG. For example, a resist film serving as a mask for patterning the light shielding film 62 may be formed on the light shielding film 62.
The resist film formed on the light shielding film 62 may be a positive type or a negative type. The resist film formed on the light shielding film 62 may be for electron beam writing or laser writing. Further, a hard mask (etching mask) film may be formed between the light shielding film 62 and the resist film.

[Transparent mask]
Next, the transmissive mask of this embodiment will be described.
FIG. 13 is a schematic diagram showing the transmissive mask 70 of this embodiment.

The transmissive mask 70 of the present embodiment has a light shielding film pattern 72 obtained by patterning the light shielding film 62 of the above transmission mask blank 60. The transmission type mask 70 of this embodiment may be a binary type mask or a phase shift type mask.

In the binary mask, the exposure light is blocked at the portion where the light shielding film pattern 72 is present. The exposure light is transmitted through the portion where the mask blank substrate 10 is exposed by removing the light shielding film 62. Thereby, the transmission mask 70 can be used as a transmission mask for lithography that uses ArF excimer laser light as exposure light, for example.

In the halftone type phase shift mask which is one of the phase shift type masks, the exposure light is transmitted through the portion where the mask blank substrate 10 is exposed by removing the light shielding film 62. At a portion where the light shielding film pattern 72 is present, the exposure light is attenuated and the phase of the exposure light is shifted. Thereby, the transmission type mask 70 can be used as a phase shift type mask for lithography that uses, for example, ArF excimer laser light as exposure light.

[Semiconductor Device Manufacturing Method]
A semiconductor device can be manufactured by the lithography process using the reflective mask 50 or the transmissive mask 70 described above and the exposure apparatus. Specifically, the absorber pattern 52 of the reflective mask 50 or the light shielding film pattern 72 of the transmissive mask 70 is transferred onto the resist film formed on the semiconductor substrate. After that, a semiconductor device having a pattern (circuit pattern or the like) formed on a semiconductor substrate can be manufactured by passing through necessary steps such as a developing step and a washing step.

[Example 1]
First, Example 1 regarding a mask blank substrate for EUV exposure, a substrate with a multilayer reflective film, a reflective mask blank for EUV exposure, and a reflective mask according to the present invention will be described.

<Production of mask blank substrate>
As the mask blank substrate 10, a SiO ₂ —TiO ₂ glass substrate having a size of 152 mm×152 mm and a thickness of 6.4 mm was prepared. Using a double-sided polishing machine, the front and back surfaces of the glass substrate were polished step by step with cerium oxide abrasive grains and colloidal silica abrasive grains. After that, the surface of the glass substrate was treated with a low concentration of hydrofluoric acid. The surface roughness of the obtained glass substrate was measured with an atomic force microscope. As a result, the root mean square roughness (Rq) of the surface of the glass substrate was 0.15 nm. Similarly, an area of 10 μm×10 μm was measured with an atomic force microscope at a resolution of 512×512 pixels. As a result, Rq _{A in} the longitudinal direction of the side surface (T surface) of the glass substrate was 0.65 nm, and Rq _{B in the} direction perpendicular to the longitudinal direction was 0.65 nm, which were the same.

The shapes (surface morphology and flatness) of the front surface and the back surface of the glass substrate were measured using a flatness measuring device (UltraFlat200 manufactured by Tropel). The surface shape was measured at 1024×1024 points in a 148 mm×148 mm region excluding the peripheral region of the glass substrate. As a result, the flatness of the front and back surfaces of the glass substrate was 290 nm (convex shape). The measurement result of the shape (flatness) of the surface of the glass substrate was stored in the computer as the information of the height with respect to a certain reference plane for each measurement point. In addition, for each measurement point, the height information was compared with a reference value of surface flatness of 50 nm (convex shape) required for the glass substrate, and the difference (required removal amount) was calculated by a computer. Similarly, the height information was compared with the reference value of the back surface flatness of 50 nm, and the difference (required removal amount) was calculated by a computer.

Next, conditions for local surface processing according to the required removal amount were set for each processing spot area on the surface of the glass substrate. The dummy substrate was previously spot-processed for a certain period of time without moving the substrate, as in the actual processing, using the dummy substrate. The shape of the dummy substrate was measured by the same device as that used when measuring the above-mentioned front and back surfaces. The processing volume of the spot per unit time was calculated. Then, the scanning speed for raster-scanning the glass substrate was determined according to the required removal amount obtained from the information on the spot and the information on the surface shape of the glass substrate.

According to the set processing conditions, the flatness of the front surface and the back surface of the glass substrate is measured by a magnetic viscoelastic fluid polishing (MRF) processing method using a magnetic fluid substrate finishing device (manufactured by QED Technologies). The surface shape was adjusted by performing local surface processing so that the surface shape was not more than the reference value. The magnetic viscoelastic fluid used at this time contained an iron component. The polishing slurry was an aqueous alkaline solution+polishing agent (about 2 wt %), and cerium oxide was used as the polishing agent. The maximum machining allowance was 150 nm, and the machining time was 30 minutes.

Next, four side surfaces (T surface) of the glass substrate were polished by a magnetic viscoelastic fluid polishing (MRF) processing method using the substrate finishing apparatus (manufactured by QED Technologies).
FIG. 14 is a schematic diagram showing an aspect in which the side surface (T surface) of the glass substrate is polished by the substrate finishing apparatus. As shown in FIG. 14, the substrate finishing apparatus 200 includes a supply nozzle 202, a recovery nozzle 204, and a wheel 206. From the supply nozzle 202, a fluid 208 containing a fine magnetic substance and an abrasive is supplied. The supplied fluid 208 flows through the apex of the wheel 206 rotating in the right direction, and then is recovered by the recovery nozzle 204. Since a magnetic field exists near the apex of the wheel 206, the fluid 208 flows while maintaining viscoelasticity. By bringing the side surface (T surface) of the glass substrate into contact with the apex portion, polishing can proceed in the contact region. When the side surface (T surface) of the glass substrate was polished, the longitudinal direction of the side surface was set in the same direction as the rotation axis of the wheel 206.

Then, the glass substrate was immersed in a cleaning tank containing a hydrochloric acid aqueous solution having a concentration of about 10% (temperature of about 25° C.) for about 10 minutes, followed by rinsing with pure water and drying with isopropyl alcohol (IPA).

When the surface shape (surface morphology, flatness) of the obtained glass substrate was measured, the flatness of the front surface and the back surface was about 20 to 30 nm. In addition, the surface roughness of the glass substrate was measured using an atomic force microscope in an area of 1 μm×1 μm in an arbitrary portion of the transfer pattern forming area (132 mm×132 mm). As a result, the root mean square roughness (Rq) of the surface of the glass substrate was 0.37 nm. From this result, it was found that the surface after the local surface processing by MRF was in a rougher state than before the local surface processing by MRF. Similarly, when an area of 10 μm×10 μm was measured using an atomic force microscope with a resolution of 512×512 pixels, the Rq _{A in} the longitudinal direction of the four side surfaces (T plane) was 0.45 to 0.48 nm, and Rq _{B in the} direction was 0.34 to 0.36 nm.

Next, finish polishing of the front surface and the back surface of the glass substrate was performed under the following conditions.
Processing liquid: Alkaline aqueous solution (NaOH) + Abrasive (concentration: about 2 wt%)
Abrasive: colloidal silica, average particle size: about 70 nm
Polishing plate rotation speed: about 1 to 50 rpm
Processing pressure: About 0.1-10kPa
Polishing time: about 1-10 minutes

Then, the glass substrate was washed with an alkaline aqueous solution (NaOH) to obtain a mask blank substrate 10 for EUV exposure.

The flatness of the front surface and the back surface of the obtained mask blank substrate 10 was measured 10 times each. The flatness measuring device used for the measurement supported the end surface of the glass substrate by the three holders 104a to 104c shown in FIG. As a result, the flatness of the front surface was 21 nm±2 nm, and the flatness of the back surface was 23 nm±2 nm, showing small variations.

Further, with respect to the obtained mask blank substrate 10, an area of 1 μm×1 μm at an arbitrary position of the transfer pattern forming area (132 mm×132 mm) was measured by an atomic force microscope. As a result, the root mean square roughness (Rq) of the surface of the mask blank substrate 10 was 0.13 nm. Similarly, an area of 10 μm×10 μm was measured with an atomic force microscope at a resolution of 512×512 pixels. As a result, the Rq _{A in} the longitudinal direction of the four side surfaces (T surface) of the mask blank substrate 10 is 0.45 to 0.48 nm, the Rq _{B in} the vertical direction is 0.34 to 0.36 nm, and Rq _A >. It was Rq _{B. Further,} Rq A / Rq _B was 1.2 to 1.35.

[Example 2]
In Example 2, not only the side surface (T surface) of the glass substrate but also the chamfered surface (C surface) and the ridge portion of the glass substrate were polished. Since the other points are the same as those in the first embodiment, description thereof will be omitted.

In Example 2, by using the above-mentioned substrate finishing device (manufactured by QED Technologies), the side surface (T surface) and the chamfered surface (C surface) of the glass substrate were processed by the magnetic viscoelastic fluid polishing (Magneto Rheological Finishing: MRF) processing method. ), and the ridge portion were polished.

FIG. 15 is a schematic diagram showing an aspect in which a chamfered surface (C surface) and a ridge line portion of a glass substrate are polished by a substrate finishing apparatus. As shown in FIG. 15, by bringing the chamfered surface (C surface) of the glass substrate into contact with the apex portion of the rotating wheel 206, polishing can proceed in the contact region. This makes it possible to polish not only the chamfered surface (C surface) of the glass substrate, but also the ridge line portion located at the boundary between the chamfered surface and the main surface. When the chamfered surface (C surface) of the glass substrate was polished, the longitudinal direction of the chamfered surface was set to the same direction as the rotation axis of the wheel 206.

In the same manner as in Example 1, the flatness of the front surface and the back surface of the obtained mask blank substrate 10 was measured 10 times each. As a result, the flatness of the front surface was 18 nm±2 nm, and the flatness of the back surface was 21 nm±1 nm, showing small variations.

Further, with respect to the obtained mask blank substrate 10, an area of 1 μm×1 μm at an arbitrary position of the transfer pattern forming area (132 mm×132 mm) was measured by an atomic force microscope. As a result, the root mean square roughness (Rq) of the surface of the mask blank substrate 10 was 0.13 nm. Similarly, an area of 10 μm×10 μm was measured with an atomic force microscope at a resolution of 512×512 pixels. As a result, the four side surfaces (T surface) of the mask blank substrate 10 have Rq _{A in} the longitudinal direction of 0.49 to 0.48 nm, Rq _{B in} the vertical direction of 0.35 to 0.37 nm, and Rq _A >. It was Rq _B. Rq _A / Rq _B was 1.2 to 1.3. In addition, Rq _{A in} the longitudinal direction of the eight chamfered surfaces (C surfaces) was 0.5 to 0.6 nm, Rq _{B in} the vertical direction was 0.4 to 0.47 nm, and Rq _A >Rq _B. Rq _A /Rq _B was 1.1 to 1.35. The Rq _{A in} the longitudinal direction of the four ridges was 0.24 to 0.3 nm, the Rq _{B in} the vertical direction was 0.2 to 0.25 nm, and Rq _A >Rq _B. Rq _A /Rq _B was 1.1 to 1.3.

[Comparative example]
In the comparative example, the end surfaces (side surface (T surface), chamfered surface (C surface), and ridge portion) of the glass substrate were not polished. Since the other points are the same as those in the first embodiment, the description thereof will be omitted.

A mask blank substrate was obtained by the same steps as in Example 1 except that the end surface of the glass substrate was not polished. The flatness of the front surface and the back surface of the obtained mask blank substrate was measured 10 times each. As a result, the flatness of the front surface was 22 nm±4 nm, and the flatness of the back surface was 24 nm±5 nm, which was more varied than in Examples 1 and 2.

Further, with respect to the obtained mask blank substrate 10, an area of 1 μm×1 μm at an arbitrary position of the transfer pattern forming area (132 mm×132 mm) was measured by an atomic force microscope. As a result, the root mean square roughness (Rq) of the surface of the mask blank substrate 10 was 0.13 nm. Similarly, an area of 10 μm×10 μm was measured with an atomic force microscope at a resolution of 512×512 pixels. As a result, longitudinal Rq _A is 0.45～0.5Nm four sides of the mask blank substrate 10 (T plane), vertical Rq _B is 0.45～0.5Nm, and Rq _A There was no difference from Rq _B, and Rq _A /Rq _B was 1. Rq _{A in} the longitudinal direction of the chamfered surface (C surface) is 0.52 to 0.53 nm, Rq _{B in} the vertical direction is 0.52 to 0.53 nm, and there is no difference between Rq _A and Rq _B, and Rq _A /Rq _B was 1. Rq _{A in} the longitudinal direction of the ridge portion is 0.19 to 0.21 nm, Rq _{B in} the vertical direction is 0.19 to 0.21 nm, there is no difference between Rq _A and Rq _B, and Rq _A /Rq _B is It was 1.

In the above Examples and Comparative Examples, an example in which the root mean square roughness Rq of the surface and the end surface of the glass substrate is measured by measuring an area of 10 μm×10 μm with a resolution of 512×512 pixels using an atomic force microscope. However, the present invention is not limited to such an aspect. When obtaining the root mean square roughness Rq of the surface and the end face of the glass substrate, the region to be measured by using the atomic force microscope can be appropriately selected. For example, the area measured using an atomic force microscope may be 1 μm×1 μm or 5 μm×5 μm.

In the above-mentioned Examples and Comparative Examples, the example of performing the local surface processing of the glass substrate by the magnetic viscoelastic fluid polishing method was shown, but the present invention is not limited to such an aspect. The local surface processing may be, for example, a processing method using gas cluster ion beams (GCIB) or local plasma.

In the above Examples and Comparative Examples, an example in which the end surface (side surface (T surface), chamfered surface (C surface), and ridge line portion) of the glass substrate is polished by local surface processing using a magnetic viscoelastic fluid polishing method or the like. However, the present invention is not limited to such an embodiment. For example, the end surface (side surface (T surface), chamfered surface (C surface), and ridge portion) of the glass substrate may be polished by a polishing device.

10 Mask Blank Substrates 12, 12a, 12b Main Surfaces 14, 14a to 14d End Faces 16 Sides 18a, 18b Chamfered Surfaces 20a, 20b Ridges 30 Multilayer Reflective Film Substrate 40 Reflective Mask Blanks 50 Reflective Masks 60 Transparent Mask Blanks 70 transmissive mask 100 flatness measuring device 102 stages 104a to 104c holder

Claims (12)

A pair of main surfaces facing each other, a mask blank substrate having an end face adjacent to the outer edge of the pair of main surfaces,
The value of the root mean square surface roughness measured along the longitudinal direction of the end surface in at least a part of the end face is Rq _A , and the value of the root mean square surface roughness measured along the direction perpendicular to the longitudinal direction. the when the Rq _B, satisfy the relationship of Rq a> Rq _B, a substrate for a mask blank. The end surface includes a side surface and a chamfered surface formed between the side surface and the main surface,
The mask blank substrate according to claim 1, wherein the relationship of Rq _A >Rq _B is satisfied in at least one of the side surface and the chamfered surface. The chamfered surface includes a ridge portion adjacent to the main surface,
The mask blank substrate according to claim 2, wherein a relationship of Rq _A >Rq _B is satisfied in the ridge portion. The mask blank substrate according to claim 1, wherein Rq _A is 0.1 nm or more on at least a part of the end face. The substrate for mask blank according to claim 1, wherein Rq _A /Rq _B is 1.1 or more on at least a part of the end face. The substrate for mask blanks according to any one of claims 1 to 5, a multilayer reflective film that reflects EUV light formed on the one main surface of the substrate for mask blanks, and the multilayer reflective film. A substrate with a multilayer reflective film, comprising a protective film formed on the substrate. A reflective mask blank comprising the substrate with a multilayer reflective film according to claim 6 and an absorber film which is formed on a protective film of the substrate with a multilayer reflective film and serves as a transfer pattern. A reflective mask comprising: the substrate with a multilayer reflective film according to claim 6; and an absorber film pattern formed on a protective film of the substrate with a multilayer reflective film. A transmissive mask comprising: the mask blank substrate according to any one of claims 1 to 5; and a light-shielding film serving as a transfer pattern formed on the one main surface of the mask blank substrate. blank. A transmissive mask comprising: the mask blank substrate according to claim 1; and a light-shielding film pattern formed on the one main surface of the mask blank substrate. A method of manufacturing a semiconductor device, comprising the step of performing a lithography process using an exposure apparatus using the reflective mask according to claim 8 to form a transfer pattern on a transfer target. A method of manufacturing a semiconductor device, comprising the step of performing a lithography process using an exposure apparatus, using the transmissive mask according to claim 10, to form a transfer pattern on a transfer target.