KR20210001948A - Mask blank, transfer mask, transfer mask manufacturing method, and semiconductor device manufacturing method - Google Patents

Abstract

Provided is a mask blank capable of resolving a pattern with a line width smaller than a wavelength of a laser beam of a laser drawing device onto a resist film. The mask blank includes a light-shielding film on a substrate. The light-shielding film includes a material containing a metal element. The light-shielding film is a composition gradient film in which a content of the metal element changes in a thickness direction. When the light-shielding film is divided into a light-shielding part and an anti-reflection part sequentially from a location closer to the substrate, a refractive index n_A of the anti-reflection part to light of a wavelength region of 350-520 nm is 2.1 or less. A phase difference generated in the light of the wavelength region is 28 degrees or more when the light of the wavelength region passes through the anti-reflection part.

Description

Mask blank, transfer mask, transfer mask manufacturing method, and semiconductor device manufacturing method {MASK BLANK, TRANSFER MASK, TRANSFER MASK MANUFACTURING METHOD, AND SEMICONDUCTOR DEVICE MANUFACTURING METHOD}

The present invention relates to a mask blank, a transfer mask, a transfer mask manufacturing method, and a semiconductor device manufacturing method.

Generally, in the manufacturing process of a semiconductor device, formation of a fine pattern is performed using a photolithography method. In addition, several transfer masks are usually used for formation of this fine pattern. In general, this transfer mask is formed by providing a light-shielding fine pattern including a metal thin film on a translucent glass substrate, and a photolithography method is also used in manufacturing this transfer mask.

In the production of a transfer mask by a photolithography method, a mask blank having a light-shielding film on a light-transmitting substrate such as a glass substrate is used. In the manufacture of a transfer mask using this mask blank, an exposure step of performing a desired pattern exposure on a resist film formed on the mask blank, a developing step of developing the resist film according to the desired pattern exposure to form a resist pattern, and , An etching step of etching the light shielding film along the resist pattern, and a step of peeling and removing the remaining resist pattern are performed. In the above developing step, after a desired pattern exposure is performed on the resist film formed on the mask blank, a developer is supplied, and a portion of the resist film soluble in the developer is dissolved to form a resist pattern. Further, in the above etching step, the resist pattern is used as a mask, by dry etching, the exposed portion of the light-shielding film on which the resist pattern is not formed is dissolved, thereby forming a desired mask pattern on the light-transmitting substrate. In this way, the transfer mask is completed.

For example, in Patent Document 1, a mask blank provided with a light-shielding film made of a chromium-based material is disclosed. In addition, in Patent Document 2, a step of forming an i-line resist film on a light-shielding film of a chromium-based material, a step of exposing a pattern in a laser exposure apparatus, a step of forming a resist pattern by performing a development treatment, etc., and a resist pattern as a mask. A step of forming a pattern on a light-shielding film by performing etching is disclosed.

Japanese Patent No. 3276954 Japanese Patent Publication No. 2004-077800

In order to expose (sensitize) a fine pattern on the resist film, exposure drawing with an electron beam is suitable. However, the conventional electron beam drawing apparatus has a problem that it takes a lot of time to draw a pattern on a resist film by exposure. The main reason is that the electron beam irradiator (electron gun) is a principle of exposing patterns without interruption, and that only one electron beam irradiator is mounted in an ordinary electron beam drawing apparatus.

On the other hand, the laser drawing apparatus is provided with a mechanism capable of irradiating a plurality of laser beams onto a resist film from one laser light source. For this reason, there is an advantage that the speed of exposure drawing with a laser beam is significantly faster than that of exposure drawing with an electron beam. In addition, although the line width of exposure drawing with an electron beam is significantly smaller than that of a laser beam, it is not always required to create a transfer pattern with the line width of an electron beam, and exposure drawing with an electron beam is sometimes not essential. When the number of cases in which an electron beam exposure drawing apparatus is not required for drawing exposure of a mask blank onto a resist film increases, effective use of resources is achieved. In addition, the throughput of exposing the pattern to the resist film of the mask blank is also greatly improved.

However, the wavelength of the laser light used in the laser drawing apparatus is about 350 nm even if it is as short as possible. On the other hand, as the line width of the transfer pattern, a smaller size of about 300 nm is sometimes required. Conventionally, in exposure drawing by a laser drawing device, even if a pattern with a line width narrower than the wavelength of the laser beam used therein is exposed to a resist film of a mask blank, a pattern drawn by exposure when developing a resist film after exposure drawing is applied to the resist film It was difficult to dismiss.

The present invention has been made in order to solve the above conventional problems, and a mask blank capable of resolving a pattern of a line width narrower than the wavelength of the laser light of a laser drawing apparatus on a resist film, a transfer mask, a method of manufacturing a transfer mask, and a semiconductor device It is an object of the present invention to provide a method of manufacturing.

In order to achieve the above object, the present invention has the following configuration.

(Configuration 1)

It is a mask blank provided with a light shielding film on the substrate,

The light shielding film contains a material containing a metal element,

The light shielding film is a composition gradient film whose content of the metal element changes in the thickness direction,

When the light-shielding film is sequentially divided into a light-shielding portion and an anti-reflection portion from a side closer to the substrate,

The refractive index n _A of the antireflection unit for light in a wavelength region of 350 nm or more and 520 nm or less is 2.1 or less,

The phase difference generated in the light in the wavelength region when the light in the wavelength region passes through the antireflection unit is 28 degrees or more.

Mask blank, characterized in that

(Configuration 2)

The mask blank according to Configuration 1, wherein the phase difference is 42 degrees or less.

(Configuration 3)

The mask blank according to the configuration 1 or 2, wherein the refractive index n _A of the antireflection portion is 1.9 or more.

(Configuration 4)

The mask blank according to any one of Configurations 1 to 3, wherein the refractive index n _S of the light shielding portion is 1.9 or more.

(Configuration 5)

The mask blank according to any one of Configurations 1 to 4, wherein the refractive index n _S of the light-shielding portion is 2.8 or less.

(Configuration 6)

The mask blank according to any one of Configurations 1 to 5, wherein an extinction coefficient k _S of the light-shielding portion for light in the wavelength region is 2.8 or more.

(Configuration 7)

The mask blank according to any one of Configurations 1 to 6, wherein an extinction coefficient k _A of the antireflection unit for light in the wavelength region is 1.0 or less.

(Configuration 8)

The mask blank according to any one of Configurations 1 to 7, wherein the light-shielding film is formed of a material containing chromium.

(Configuration 9)

The mask blank according to any one of Configurations 1 to 8, wherein the light-shielding film has an optical density of 3 or more with respect to exposure light.

(Configuration 10)

The mask blank according to any one of Configurations 1 to 9, wherein a resist film is formed in contact with the surface of the light shielding film.

(Composition 11)

The mask blank according to Configuration 10, wherein the refractive index n _R of the resist film with respect to the light in the wavelength region is 1.50 or more.

(Composition 12)

The mask blank according to Configuration 10 or 11, wherein the resist film is formed of a material that is photosensitive by exposure light in a wavelength range of 350 nm or more and 520 nm or less.

(Configuration 13)

It is a transfer mask provided with a light shielding film having a transfer pattern on the substrate,

The light shielding film contains a material containing a metal element,

The light shielding film is a composition gradient film whose content of the metal element changes in the thickness direction,

When the light-shielding film is sequentially divided into a light-shielding portion and an anti-reflection portion from a side closer to the substrate,

The refractive index n _A of the antireflection unit for light in a wavelength region of 350 nm or more and 520 nm or less is 2.1 or less,

The phase difference generated in the light in the wavelength region when the light in the wavelength region passes through the antireflection unit is 28 degrees or more.

Transfer mask, characterized in that.

(Configuration 14)

The transfer mask according to Configuration 13, wherein the phase difference is 42 degrees or less.

(Configuration 15)

The transfer mask according to the configuration 13 or 14, wherein the refractive index n _A of the antireflection portion is 1.9 or more.

(Configuration 16)

The transfer mask according to any one of Configurations 13 to 15, wherein the refractive index n _S of the light-shielding portion is 1.9 or more.

(Configuration 17)

The transfer mask according to any one of Configurations 13 to 16, wherein the refractive index n _S of the light-shielding portion is 2.8 or less.

(Configuration 18)

The transfer mask according to any one of Configurations 13 to 17, wherein an extinction coefficient k _S of the light-shielding portion with respect to the light in the wavelength region is 2.8 or more.

(Configuration 19)

The transfer mask according to any one of Configurations 13 to 18, wherein an extinction coefficient k _A of the antireflection unit for light in the wavelength region is 1.0 or less.

(Configuration 20)

The transfer mask according to any one of configurations 13 to 19, wherein the light shielding film is formed of a material containing chromium.

(Configuration 21)

The transfer mask according to any one of Configurations 13 to 20, wherein the light shielding film has an optical density of 3 or more with respect to exposure light.

(Configuration 22)

It is a manufacturing method of a transfer mask using the mask blank according to any of configurations 10 to 12,

After exposing the transfer pattern to the resist film with exposure light in a wavelength region of 350 nm or more and 520 nm or less, development treatment is performed to form a resist film having the transfer pattern;

Step of forming a transfer pattern on the light-shielding film by etching using the resist film having the transfer pattern as a mask

A method of manufacturing a transfer mask, characterized in that it has a.

(Configuration 23)

In the step of forming a transfer pattern on the light-shielding film, the transfer pattern is formed on the light-shielding film by dry etching using a gas containing chlorine.

(Configuration 24)

A method for manufacturing a semiconductor device, comprising: a step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the transfer mask according to any one of configurations 13 to 21.

(Configuration 25)

A method for manufacturing a semiconductor device, comprising: a step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using a transfer mask manufactured by the method for producing a transfer mask according to configuration 22 or 23.

According to the mask blank according to the present invention, a pattern having a narrower line width than the wavelength of the laser light of the laser drawing device can be resolved in the resist film. Thereby, it is possible to increase the number of cases in which the electron beam exposure drawing apparatus is not required for drawing exposure to the resist film of the mask blank, and effective use of resources can be achieved.

1 is a schematic diagram showing a configuration of a mask blank in an embodiment of the present invention.
2 is a schematic diagram showing a manufacturing process of a transfer mask in the embodiment of the present invention.
3 is a graph showing the relationship between the phase difference and the surface reflectance in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention, and a curve calculated based on these relationships.

First, a description will be given of how the invention has been reached.

The present inventors have conducted extensive research on the configuration of a mask blank for resolving a pattern with a line width narrower than the wavelength of the laser light of the laser drawing device on the resist film. A mask blank for manufacturing a transfer mask includes a light shielding film on a substrate, and a resist film is formed on the light shielding film. In addition, as the exposure wavelength of the laser light (that is, exposure light) used in the laser drawing apparatus, a wavelength range of 350 nm or more and 520 nm or less is usually used. The present inventors produced a plurality of mask blanks by changing the film formation conditions of the light shielding film without changing the film formation conditions of the resist film. As the exposure light used for laser drawing, a plurality of laser lights having different wavelengths from the range of the wavelength range were selected. Then, on the resist films of each of the mask blanks, laser drawing was performed using each of the selected laser beams. Further, development treatment was performed on the resist film of each mask blank after drawing, and the resolution accuracy of the pattern (resist pattern) formed on the resist film of each mask blank was compared. As a result, it was found that even for a resist film of the same material and thickness, there is a large difference in the resolution accuracy of the resist pattern depending on the characteristics of the light shielding film.

The inventor of the present invention further studied the factors affecting the resolution accuracy of the resist pattern. In order to increase the photosensitive accuracy of the resist over a wavelength region of 350 nm or more and 520 nm or less, it is required that the reflectance of the light-shielding film is not more than a certain level. However, when the light-shielding film is a single-layer or multi-layered structure having a uniform composition in the thickness direction, the reflectance at a specific wavelength can be suppressed, but it is not more than a certain range over a relatively wide wavelength range of 350 nm to 520 nm. It was found that it was difficult to do.

Thus, the present inventors have considered making the light-shielding film a compositional gradient film in which the content of the metal element changes in the thickness direction. By setting it as a composition gradient film, it becomes possible to suppress the reflectance over a wide wavelength range. However, in the case of the compositional gradient film, it is advantageous in that it suppresses the variation of the reflectance in the wavelength region, but it is very difficult to directly calculate the optical properties to be satisfied. In order to solve this problem, the present inventors examined pseudo-modeling a light-shielding film, which is a composition gradient film, into a two-layer structure. Specifically, with respect to the light shielding film on the substrate, the transmittance, the surface reflectance, and the back surface reflectance were measured with a spectroscopic ellipsometer, respectively, in the wavelength region. And, a plurality of wavelengths (at least 2 or more, more preferably 3 or more) are selected from the range of the above-described wavelength range, and at each wavelength, the upper and lower films have a refractive index or extinction coefficient that matches the measured value. The thickness, refractive index, and extinction coefficient were calculated|required by simulation. In addition, the lower part obtained by this simulation mainly functions as a light-shielding part, and the upper part mainly functions as an antireflection part.

Then, the present inventor studied the optical properties to be satisfied when the light-shielding film, which is a composition gradient film, is divided into a light-shielding portion and an antireflection portion. As a result, if the refractive index n _A of the anti-reflection unit for light in the wavelength region of 350 nm or more and 520 nm or less is 2.1 or less, and the phase difference generated in the light in the wavelength region when the light in the wavelength region passes through the anti-reflection unit is 28 degrees or more, , It was found that the reflectance of the light-shielding film can be suppressed to 15% or less over the above-described wavelength region, and the resolution accuracy of the resist pattern can be improved.

That is, the mask blank of the present invention is a mask blank provided with a light-shielding film on a substrate, the light-shielding film contains a material containing a metal element, and the light-shielding film has a change in the content of the metal element in the thickness direction. A composition gradient film, wherein the light-shielding film is divided into a light-shielding part and an anti-reflection part in order from a side closer to the substrate, and the refractive index n _A of the anti-reflection part for light in a wavelength region of 350 nm or more and 520 nm or less is 2.1 or less. , When the light in the wavelength region passes through the antireflection unit, a phase difference generated in the light in the wavelength region is 28 degrees or more. In addition, unless otherwise specified, the optical properties (reflectance, refractive index, extinction coefficient, retardation, etc.) mentioned below are for light in the above-described wavelength range of 350 nm or more and 520 nm or less.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 is a schematic diagram showing a configuration of a mask blank in an embodiment of the present invention. The mask blank 10 of FIG. 1 has a structure in which a light shielding film 2 is stacked on a light-transmitting substrate 1 in this order. Here, as the translucent substrate 1, a glass substrate is generally used. Since the glass substrate is excellent in flatness and smoothness, when performing pattern transfer onto a semiconductor substrate using a transfer mask, high-precision pattern transfer can be performed without causing deformation of the transfer pattern or the like.

The mask blank 10 in this embodiment is provided with the light shielding film 2. The light shielding film 2 contains a material containing a metal element. As a metal element, it is preferable that it is formed from a material containing chromium. As a material containing chromium, chromium alone may be sufficient, and chromium and an additional element may be included. As such an additive element, oxygen and/or nitrogen are preferable from the viewpoint that the dry etching rate can be accelerated. Further, the light shielding film 2 may contain other elements such as carbon, hydrogen, boron, indium, tin, and molybdenum. Further, the light-shielding film 2 may be made of a material other than a chromium-based material as long as it satisfies the optical properties described in the present specification. For example, a silicon-based material, a transition metal silicide-based material, a tantalum-based material, or the like may be applied to the material for forming the light-shielding film 2 within a range that satisfies the required optical properties.

The light-shielding film 2 has a surface reflectance of 15 for light having a laser drawing wavelength (laser light having a wavelength within the wavelength range) in a state in which the resist film is not stacked (i.e., a state in which the upper surface of the light-shielding film 2 is exposed). It is preferable that it is a film controlled so that it may become% or less, and further 13% or less. Moreover, it is preferable that the light-shielding film 2 is a film controlled so that the transmittance|permeability with respect to the light of a laser drawing wavelength (laser light of a wavelength in the said wavelength range) becomes 0.1% or less, and further 0.05% or less.

The method for forming the light shielding film 2 is not particularly limited, but a film forming method using an in-line sputtering device is preferably mentioned. By forming a film by an in-line sputtering device, it becomes easy to manufacture a composition gradient film in which optical properties (reflectance, etc.) are strictly controlled.

The thickness of the light-shielding film 2 is preferably 150 nm or less, and more preferably 120 nm or less. By reducing the film thickness to some extent, it is possible to reduce the aspect ratio of the pattern (the ratio of the pattern depth to the pattern width), and it is possible to reduce the line width error due to the global loading phenomenon and the microloading phenomenon. The light shielding film 2 in the present invention can obtain a desired optical density (usually 3.0 or more) even if the film thickness is a thin film of 150 nm or less for exposure light of 350 nm or more and 520 nm or less. About the lower limit of the film thickness of the light-shielding film 2, it can be made thin as long as a desired optical density is obtained.

In addition, when the light-shielding film 2 satisfies the above-described film thickness and is divided into a light-shielding portion and an anti-reflection portion as described above, the film thickness of the anti-reflection portion is preferably greater than 20 nm, and more preferably 30 nm or more. Do. When the film thickness of the antireflection portion is thick enough, it is possible to reduce the variation width of the surface reflectance of the light-shielding film with respect to the light in the wavelength band of the laser drawing wavelength. Moreover, it is preferable that it is 60 nm or less, and, as for the film thickness of a reflection prevention part, it is more preferable that it is 50 nm or less. When the film thickness of the antireflection portion is large, the total film thickness of the light-shielding film 2 becomes large. On the other hand, if the entire film thickness of the light-shielding film 2 is not made thick, it is necessary to significantly reduce the thickness of the light-shielding portion. In that case, there is a possibility that the optical density of the light shielding film 2 with respect to exposure light may be insufficient. As can be understood from the description of the film thickness of the light-shielding film 2 and the film thickness of the anti-reflection portion, the film thickness of the light-shielding portion is preferably 30 nm or more, and more preferably 40 nm or more. Moreover, it is preferable that it is 90 nm or less, and, as for the film thickness of a light-shielding part, it is more preferable that it is 80 nm or less.

In addition, when the light-shielding film 2 is divided into a light-shielding portion and an anti-reflection portion as described above, a distance equal to the thickness of the anti-reflection portion is generated in the light of the wavelength region when light of the laser drawing wavelength passes through the anti-reflection portion. It is required that the phase difference φ between the light that has passed through the air is 28 degrees or more. On the other hand, the phase difference of the antireflection unit is preferably 42 degrees or less, and more preferably 40 degrees or less. In addition, the phase difference φ [degrees] is φ = 360 × d _A × (n _A ) when the refractive index of the anti-reflection unit is n _A , the film thickness of the anti-reflection unit is d _A [nm], and the wavelength of light is λ [nm]. It is calculated as -1)/λ. As shown by the following equation, in order to increase the phase difference φ of the antireflection portion, it is necessary to increase the film thickness d _A or the refractive index n _A. In general, however, a large refractive index n _A material, a change width of the refractive index n _A of the change in the wavelength of the light there is a large tendency is not preferable. Further, as described above, it is also not preferable to increase the film thickness d _A.

The refractive index n _A of the antireflection portion is preferably 1.9 or more, and more preferably 1.92 or more from the viewpoint of increasing the retardation φ in the film thickness of the thinner antireflection portion. In addition, the refractive index n _A of the antireflection unit is preferably 2.1 or less from the viewpoint of reducing the width of change of the refractive index n _A with respect to the change of the wavelength of light.

The extinction coefficient k _A of the antireflection portion is preferably 0.7 or more, and more preferably 0.8 or more from the viewpoint of thinning the light-shielding film 2. In addition, the extinction coefficient k _A of the antireflection portion is preferably 1.0 or less from the viewpoint of reducing the surface reflectance of the light shielding film 2.

The refractive index n _S of the light-shielding portion is preferably 1.9 or more. In addition, the refractive index n _S of the light-shielding portion is preferably 2.8 or less.

The extinction coefficient k _S of the light-shielding portion is preferably 2.8 or more, and more preferably 2.9 or more, from the viewpoint of thinning the light-shielding film 2. In addition, the extinction coefficient k _S of the light-shielding portion is preferably 3.5 or less, and more preferably 3.4 or less from the viewpoint of reducing the reflectance of the back surface of the light-shielding film 2.

In addition, the mask blank 10 may be in a form in which the resist film 3 is formed in contact with the surface of the light-shielding film 2 as shown in Fig. 2A to be described later. In order to obtain high resolution, it is preferable that the material of the resist film 3 be made of a material that is photosensitive by exposure light in the wavelength range. The resist material is not particularly limited, but may be a positive resist material, a negative resist material, a non-chemically amplified resist, or a chemically amplified resist. The resist film 3 preferably has a refractive index n _R of 1.90 or less for light in a wavelength region of 350 nm or more and 520 nm or less, and more preferably 1.80 or less. In addition, the resist film 3 preferably has a refractive index n _R of 1.50 or more, more preferably 1.60 or more, and even more preferably 1.67 or more. On the other hand, the resist film 3 preferably has an extinction coefficient k _R for light in the wavelength range of 0.01 or more, and more preferably 0.02 or more. In addition, the resist film 3 preferably has an extinction coefficient k _R for light in the wavelength range of 0.06 or less, and more preferably 0.05 or less.

The reflectance of the resist film 3 with respect to the laser drawn light is preferably 5% or less, and more preferably 4% or less. This is because the photosensitive efficiency of the resist film 3 can be increased by reducing the reflectance. Further, another layer may be interposed between the light shielding film 2 and the resist film 3 as long as it satisfies the reflectance of the laser writing light. The other layer may be, for example, a layer having a function of improving the adhesion between the light shielding film 2 and the resist film 3.

Further, in the mask blank 10, a phase shift film may be provided between the light-transmitting substrate 1 and the light shielding film 2. The transfer mask (phase shift mask) manufactured from the mask blank in this case is provided with a transfer pattern in the phase shift film, but the light shielding film 2 is limited to relatively small patterns such as a light shielding band. However, even in the case of the mask blank in this case, when the transfer pattern to be formed on the phase shift film is exposed and drawn on the resist film with laser light, the light shielding film 2 is present immediately under the resist film. For this reason, in order to resolve a transfer pattern of a line width narrower than the wavelength of the laser light to the resist film, it is required that the light shielding film 2 has the above optical properties.

Next, the manufacturing method of the transfer mask 20 using the mask blank 10 shown in FIG. 1 is demonstrated. In the manufacturing method of the transfer mask 20 using this mask blank 10, after exposing the transfer pattern to the resist film 3 with exposure light in a wavelength region of 350 nm or more and 520 nm or less, development treatment is performed, A step of forming a resist film having a transfer pattern (resist pattern 3a) and a step of forming a transfer pattern on the light-shielding film 2 by etching using the resist pattern 3a as a mask are provided.

FIG. 2 is a schematic diagram sequentially showing a manufacturing process of the transfer mask 20 using the mask blank 10.

FIG. 2A shows a state in which the resist film 3 is formed on the light shielding film 2 of the mask blank 10 of FIG. 1.

Next, FIG. 2B shows an exposure step of performing a desired pattern exposure on the resist film 3 formed on the mask blank 10. Pattern exposure is performed using a laser drawing device or the like. As the above-described resist material, one having photosensitivity corresponding to laser exposure light is used.

Next, FIG. 2C shows a developing process of forming the resist pattern 3a by developing the resist film 3 according to the desired pattern exposure. In the developing process, after performing a desired pattern exposure to the resist film 3 formed on the mask blank 10, a developer is supplied to dissolve a portion of the resist film soluble in the developer to form a resist pattern 3a. do.

Next, Fig. 2D shows an etching process of etching the light shielding film 2 along the resist pattern 3a. In the present invention, it is suitable to use dry etching. In the etching process, by using the resist pattern 3a as a mask, dry etching is performed to dissolve the exposed portion of the light-shielding film 2 on which the resist pattern 3a is not formed, thereby having a desired transfer pattern. A light-shielding film 2 (light-shielding pattern 2a) is formed on the light-transmitting substrate 1.

The step of forming the light shielding pattern 2a on the light shielding film 2 is preferably performed by dry etching using a gas containing chlorine. By performing dry etching using the dry etching gas, the dry etching rate can be increased, the dry etching time can be shortened, and the light shielding pattern 2a having a good cross-sectional shape can be formed. Examples of the chlorine-based gas used for the dry etching gas include Cl ₂ , SiCl ₄ , HCl, CCl ₄ , and CHCl ₃ . Further, for dry etching, in addition to the chlorine-based gas, a dry etching gas containing a mixed gas containing oxygen gas or the like may be used.

Fig. 2(e) shows a transfer mask 20 obtained by peeling and removing the remaining resist pattern 3a. In this way, a transfer mask in which the light shielding pattern 2a having a good cross-sectional shape is formed with high precision is completed.

In addition, the present invention is not limited to the embodiments described above. That is, it is not limited to a so-called binary mask mask blank in which a light-shielding film is formed on a light-transmitting substrate, and may be, for example, a mask blank for use in manufacturing a halftone phase shift mask or a Levenson phase shift mask. In this case, the light-shielding film is formed on the halftone phase shift film on the light-transmitting substrate, and the desired optical density (preferably 3.0 or more) can be obtained by combining the halftone phase shift film and the light-shielding film. May be set to a value less than 3.0, for example.

On the other hand, the transfer mask of the present invention has the same characteristics as the mask blank of the present invention. That is, the transfer mask of the present invention includes a light-shielding film 2 (light-shielding pattern 2a) having a transfer pattern on the substrate 1, and the light-shielding film 2 contains a material containing a metal element. And, the light-shielding film 2 is a composition gradient film in which the content of the metal element changes in the thickness direction, and the light-shielding film has a wavelength of 350 nm or more and 520 nm or less when divided into a light-shielding portion and an anti-reflection portion in order from the side closer to the substrate. The refractive index n _A of the anti-reflection unit with respect to the light in the region is 2.1 or less, and a phase difference generated in the light in the wavelength region when the light in the wavelength region passes through the anti-reflection unit is 28 degrees or more. Other matters (substrate, light shielding film, etc.) relating to the transfer mask of the present invention are the same as those of the mask blank of the present invention.

In the mask blank or transfer mask of the present invention, it is preferable that the light-shielding film 2 (or the light-shielding pattern 2a) is provided on the substrate 1 so as to contact the main surface of the substrate 1. It is not limited to this, and may be provided on the substrate 1 with another film interposed therebetween. For example, even in the case of a mask blank in which a phase shift film and a light-shielding film are stacked in this order on a light-transmitting substrate, it functions effectively even if the light-shielding film of the present invention is applied to the light-shielding film. In the phase shift mask (transfer mask) manufactured from this mask blank, a transfer pattern is basically provided on the phase shift film, and no transfer pattern is provided on the light shielding film. However, in the process of manufacturing a phase shift mask from a mask blank, a resist film is provided on the light shielding film. By using the light-shielding film of the present invention, when a pattern (transfer pattern) to be formed on the phase shift film is exposed to the resist film in a laser drawing apparatus, the resolution of the resist pattern is greatly improved. As a result, it is possible to form a transfer pattern on the phase shift film with high precision.

That is, the phase shift mask (transfer mask) in this case includes a phase shift film (phase shift pattern) having a transfer pattern and a light shielding film (light shielding pattern) having a pattern including a light shielding band on the substrate 1 It has a laminated structure, the light-shielding film contains a material containing a metal element, the light-shielding film 2 is a composition gradient film in which the content of the metal element changes in the thickness direction, and the light-shielding film is from the side closer to the substrate. When sequentially divided into a light-shielding part and an anti-reflection part, the refractive index n _A of the anti-reflection part for light in a wavelength range of 350 nm to 520 nm is 2.1 or less, and when light in the wavelength range passes through the anti-reflection part, the wavelength It is characterized in that the phase difference generated in the light of the region is 28 degrees or more.

The method of manufacturing a semiconductor device of the present invention includes a step of exposing a transfer pattern to a resist film on a semiconductor substrate by using the transfer mask 20 manufactured by the method of manufacturing the transfer mask 20 It is characterized by that. In addition, the method for manufacturing a semiconductor device of the present invention is characterized by including a step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the transfer mask 20. For this reason, this transfer mask 20 is set in an exposure apparatus, and a KrF excimer laser or i-ray is irradiated from the side of the translucent substrate 1 of the transfer mask 20 to a transfer object (a resist film on a semiconductor wafer, etc.). ), the desired pattern can be transferred to the transfer object with high precision.

<Example>

Hereinafter, embodiments of the present invention will be described more specifically by way of examples.

(Example 1)

[Production of mask blank]

A translucent substrate 1 including synthetic quartz glass having a main surface dimension of about 152 mm x about 152 mm and a thickness of about 6.35 mm was prepared. In this light-transmitting substrate 1, the end surface and the main surface were polished to a predetermined surface roughness, and thereafter, a predetermined cleaning treatment and drying treatment were performed.

On this light-transmitting substrate 1, a light-shielding film 2 having a composition inclined structure was formed by using an in-line sputtering device. The light shielding film 2 is formed by arranging each Cr target in each space (sputtering chamber) continuously arranged in the in-line sputtering device with respect to the substrate transport direction, and performing reactive sputtering while transporting the translucent substrate 1 in each space. I did. Specifically, first, an Ar gas and N ₂ gas were used as sputtering gases, and a lower region of the light-shielding film 2 containing CrN as a main component was formed to a thickness of 16 nm. Next, Ar gas and CH ₄ gas were used as sputtering gases, and a central region containing CrC as a main component was formed to a thickness of 63 nm. In addition, an upper region containing Ar gas and NO gas as sputtering gas and CrON as a main component was formed to a thickness of 24 nm. By the above process, the light shielding film 2 was formed on the light-transmitting substrate 1 to a thickness of 103 nm.

The central region of the light-shielding film 2 contains N (nitrogen) by the N ₂ gas or NO gas used in the formation of the lower region or the upper region, and Cr and N in all of the lower region, the middle region, and the upper region. Was included. The chromium content in the three regions of the light-shielding film 2 was increased in the order of the upper region, the lower region, and the middle region. In addition, the average content of the lower region of the light shielding film 2 was about 60 atomic% of chromium, about 34 atomic% of nitrogen, and about 6 atomic% of carbon. The average content of the central region of the light-shielding film 2 was about 70 atomic% of chromium, about 10 atomic% of carbon, and about 20 atomic% of nitrogen. The average content of the upper region of the light-shielding film 2 was about 36 atomic% of chromium, about 40 atomic% of oxygen, about 22 atomic% of nitrogen, and about 2 atomic% of carbon.

In addition, with respect to light in a wavelength range of 350 nm or more and 520 nm or less, the transmittance, surface reflectance R, and back surface reflectance of the light-shielding film 2 were measured with a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam). And, from the wavelength region, a plurality of wavelengths WL (355 nm, 403 nm, 413 nm, 442 nm, 488 nm, 500 nm, 514 nm) are selected, and at each wavelength, a light-shielding portion that becomes a refractive index or extinction coefficient consistent with an actual measured value, and The film thickness, refractive index, and extinction coefficient of the antireflection portion were obtained by simulation. As a result, the thickness d _A of the antireflection portion became 40 nm, and the thickness d _S of the light-shielding portion became 63 nm. In addition, for the plurality of wavelengths described above, the refractive index n _A , the extinction coefficient k _A , and the phase difference [degrees] in the antireflection unit are calculated, and the refractive index n _S and the extinction coefficient k _S in the light shielding unit are calculated. I did. The results are shown in Table 1. In addition, the phase difference φ [degree] was calculated by the relational expression of φ = 360 × d _A × (n _A -1)/λ.

As shown in Table 1, in any of the plurality of wavelengths described above, the phase difference of the antireflection portion exceeded 28 degrees. And the surface reflectance of the antireflection part was less than 15%.

Then, by spin coating, a resist film 3 containing a positive resist (THMR-iP3500, manufactured by Tokyo Oka Kogyo Co., Ltd.) was formed in contact with the surface of the light-shielding film 2, targeting a film thickness of 290 nm The mask blank 10 of Example 1 was produced.

[Manufacture of mask for transcription]

Next, the mask blank 10 of Example 1 was separately manufactured by the same procedure, and using it, the transfer mask 20 of Example 1 was manufactured by the following procedure. In addition, in the separately manufactured mask blank 10, the reflectance of this resist film 3 in exposure light having a wavelength of 413 nm was 2.814%.

First, with respect to the resist film 3, a transfer pattern to be formed on the light-shielding film 2 was laser drawn with exposure light having a wavelength of 413 nm. This laser-drawn transfer pattern contained a line-and-space pattern with a line width of 300 nm. Then, the resist film 3 of the mask blank 10 after laser drawing was subjected to a predetermined development treatment to form a resist pattern 3a. When the formed resist pattern 3a was observed with a CD-SEM (Critical Dimension-Scanning Electron Microscope), a pattern 3a including a line width narrower than the wavelength of the laser light of the laser drawing device was resolved on the resist film 3 It was possible. Then, dry etching was performed on the light shielding film 2 using the resist pattern 3a formed on the mask blank 10 as a mask. As the dry etching gas, a mixed gas of Cl ₂ and O ₂ (Cl ₂ :O ₂ =4:1) was used. After forming the pattern 2a of the light-shielding film 2 on the substrate 1 by dry etching, the remaining resist pattern 3a was peeled off using thermally concentrated sulfuric acid, and the transfer mask of Example 1 ( 20) was obtained.

When the pattern 2a of the light-shielding film in the transfer mask 20 of Example 1 was observed with a CD-SEM, the amount of positional displacement from the design pattern was all within the allowable range within the plane. Next, with respect to the transfer mask 20 of the first embodiment, the KrF excimer laser was set on a mask stage of an exposure apparatus using exposure light, and KrF exposure light from the translucent substrate 1 side of the transfer mask 20 Was irradiated, and the pattern was transferred by exposure to the resist film on the semiconductor device. Then, the resist film after exposure transfer was subjected to a predetermined treatment to form a resist pattern, and the resist pattern was observed with a CD-SEM. As a result, the amount of positional deviation from the design pattern was all within the allowable range within the plane. From this result, it can be said that a circuit pattern can be formed on a semiconductor device with high precision using this resist pattern as a mask.

(Comparative Example 1)

[Production of mask blank]

The mask blank of this Comparative Example 1 was manufactured by the same procedure as in Example 1 except for the light shielding film. The light-shielding film of Comparative Example 1 was also formed using the same in-line sputtering device as used in Example 1, and had a compositional gradient structure. Specifically, first, an Ar gas and N ₂ gas were used as sputtering gases, and a lower region of the light shielding film containing CrN as a main component was formed to a thickness of 41 nm. Next, Ar gas and CH ₄ gas were used as sputtering gas, and a central region containing CrC as a main component was formed to a thickness of 18 nm. Further, an upper region containing Ar gas and NO gas as sputtering gas and CrON as a main component was formed to a thickness of 11 nm. By the above process, a light-shielding film was formed on the light-transmitting substrate to a thickness of 70 nm to prepare a mask blank of Comparative Example 1. The central region of the light-shielding film contains N (nitrogen) by the N ₂ gas or NO gas used for the formation of the lower region or the upper region, and Cr and N are contained in all of the lower region, the middle region, and the upper region. there was. The chromium content in the three regions of the light-shielding film was increased in the order of the upper region, the lower region, and the middle region.

In addition, the average content of the lower region of the light-shielding film of Comparative Example 1 was about 50 atomic% of chromium, about 45 atomic% of nitrogen, and about 5 atomic% of carbon. The average content of the central region of the light-shielding film was about 42 atomic% of chromium, about 20 atomic% of oxygen, about 27 atomic% of nitrogen, and about 11 atomic% of carbon. The average content of the upper region of the light-shielding film was about 34 atomic% of chromium, about 44 atomic% of oxygen, about 19 atomic% of nitrogen, and about 3 atomic% of carbon.

In the same manner as in Example 1, the transmittance, surface reflectance R, and back surface reflectance of the light-shielding film 2 were measured with a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam) for light in a wavelength range of 350 nm or more and 520 nm or less. Next, a plurality of wavelengths WL (355 nm, 403 nm, 413 nm, 442 nm, 488 nm, 500 nm, 514 nm) are selected from the wavelength range of 350 nm or more and 520 nm or less, and at each wavelength, the refractive index or extinction coefficient corresponding to the measured value is obtained, The film thickness, refractive index, and extinction coefficient of the light-shielding portion and the anti-reflection portion were determined by simulation. As a result, the thickness d _A of the antireflection portion became 20 nm, and the thickness d _S of the light shielding portion was 50 nm. In addition, for the plurality of wavelengths described above, the refractive index n _A , the extinction coefficient k _A , and the phase difference [degrees] in the antireflection unit are calculated, and the refractive index n _S and the extinction coefficient k _S in the light shielding unit are calculated. I did. The results are shown in Table 2.

As shown in Table 2, in any of the plurality of wavelengths described above, the phase difference of the antireflection portion was less than 28 degrees. And the surface reflectance of the antireflection part was more than 15%.

Next, in the same manner as in Example 1, a resist film including a positive type resist was formed by contacting the surface of the light-shielding film by a spin coating method, targeting a film thickness of 290 nm, and a mask blank of Comparative Example 1 was prepared.

[Manufacture of mask for transcription]

Next, using the mask blank of Comparative Example 1, a transfer mask of Comparative Example 1 was manufactured in the same procedure as in Example 1. When the formed resist pattern was inspected by a CD-SEM, it was impossible to resolve a pattern with a line width narrower than the wavelength of the laser light of the laser drawing apparatus on the resist film. For this reason, as in Example 1, even if dry etching using the formed resist pattern as a mask was performed on the light shielding film, it was impossible to form a desired light shielding pattern. Thus, using the mask blank of Comparative Example 1, it was not possible to fabricate a transfer mask provided with a light-shielding pattern having a narrower line width than the wavelength of the laser light of the laser drawing apparatus, and thus it was impossible to form a circuit pattern on a semiconductor device.

(Comparative Example 2)

[Production of mask blank]

The mask blank of this comparative example 2 was also manufactured by the same procedure as in Example 1 except for the light shielding film. The light-shielding film of Comparative Example 2 was also formed using the same in-line sputtering device as used in Example 1, and had a compositional inclined structure. Specifically, first, Ar gas and N ₂ gas were used as sputtering gases, and a lower region of the light shielding film containing CrN as a main component was formed to a thickness of 20 nm. Next, Ar gas and CH ₄ gas were used as sputtering gases, and a central region containing CrC as a main component was formed to a thickness of 38 nm. Further, an upper region containing Ar gas and NO gas as sputtering gas and CrON as a main component was formed to a thickness of 15 nm. By the above process, a light-shielding film was formed on the light-transmitting substrate to a thickness of 73 nm to prepare a mask blank of Comparative Example 2. The central region of the light-shielding film contains N (nitrogen) by the N ₂ gas or NO gas used for the formation of the lower region or the upper region, and Cr and N are contained in all of the lower region, the middle region, and the upper region. there was. The chromium content in the three regions of the light-shielding film was increased in the order of the upper region, the lower region, and the middle region.

In addition, the average content of the lower region of the light-shielding film of Comparative Example 2 was about 61 atomic% in chromium, about 32 atomic% in nitrogen, and about 7 atomic% in carbon. The average content of the central region of the light-shielding film was about 71 atomic% of chromium, about 11 atomic% of carbon, and about 18 atomic% of nitrogen. The average content of the upper region of the light-shielding film was about 37 atomic% of chromium, about 41 atomic% of oxygen, about 21 atomic% of nitrogen, and about 1 atomic% of carbon.

In the same manner as in Example 1, the transmittance, surface reflectance R, and back surface reflectance of the light-shielding film 2 were measured with a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam) for light in a wavelength range of 350 nm or more and 520 nm or less. Next, a plurality of wavelengths (355 nm, 403 nm, 413 nm, 442 nm, 488 nm, 500 nm, 514 nm) are selected from the wavelength range of 350 nm or more and 520 nm or less, and at each wavelength, the difference between the refractive index and extinction coefficient corresponding to the measured value The film thickness, refractive index, and extinction coefficient of the light portion and the anti-reflection portion were determined by simulation. As a result, the thickness d _A of the antireflection portion became 18 nm, and the thickness d _S of the light-shielding portion was 55 nm. In addition, for the plurality of wavelengths described above, the refractive index n _A , the extinction coefficient k _A , and the phase difference [degrees] in the antireflection unit are calculated, and the refractive index n _S and the extinction coefficient k _S in the light shielding unit are calculated. I did. The results are shown in Table 3.

As shown in Table 3, in any of the plurality of wavelengths described above, the phase difference of the antireflection portion was less than 28 degrees. And the surface reflectance of the antireflection part was more than 15%.

Next, in the same manner as in Example 1, a resist film including a positive type resist was formed by contacting the surface of the light-shielding film by a spin coating method, targeting a film thickness of 290 nm, and a mask blank of Comparative Example 2 was prepared. In the same procedure as in Example 1, a reflectance meter was used to measure the reflectance in the transfer pattern formation region of the resist film in exposure light having a wavelength of 413 nm. The measured reflectance was 1.494%.

[Manufacture of mask for transcription]

Next, using the mask blank of Comparative Example 2, a transfer mask of Comparative Example 2 was manufactured in the same procedure as in Example 1. When the formed resist pattern was inspected by a CD-SEM, it was impossible to resolve a pattern with a line width narrower than the wavelength of the laser light of the laser drawing apparatus on the resist film. For this reason, as in Example 1, even if dry etching using the formed resist pattern as a mask was performed on the light shielding film, a desired light shielding pattern could not be formed. In this way, using the mask blank of Comparative Example 2, a transfer mask having a light-shielding pattern having a narrower line width than the wavelength of the laser light of the laser drawing apparatus could not be produced, and a circuit pattern could not be formed on the semiconductor device.

3 is a graph showing the relationship between the phase difference and the surface reflectance in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention, and a curve calculated based on these relationships. As shown in FIG. 3, in the wavelength region of 350 nm or more and 520 nm or less, if the phase difference of the anti-reflection unit is 28 degrees or more, it can be seen that the surface reflectance of the anti-reflection unit can be suppressed to 15% or less.

On the other hand, a plurality of translucent substrates different from those in Example 1 were prepared, a light shielding film was formed under the same film formation conditions as in Example 1, and a plurality of mask blanks were formed by changing only the film thickness of the resist film. Similarly, a plurality of translucent substrates different from Comparative Example 1 and Comparative Example 2 were prepared, respectively, a light shielding film was formed under the same film forming conditions as Comparative Examples 1 and 2, and a plurality of mask blanks were formed by changing only the film thickness of the resist film. I did. Then, a plurality of mask blanks each corresponding to Example 1, Comparative Example 1, and Comparative Example 2 were laser drawn at a predetermined exposure wavelength (413 nm) to prepare a transfer mask. As a result, at any film thickness, in the mask blank corresponding to Example 1, a desired light-shielding pattern could be formed, but in the mask blank corresponding to Comparative Examples 1 and 2, forming a desired light-shielding pattern It was impossible. Similarly, a plurality of transparent substrates different from Comparative Example 1 and Comparative Example 2 were prepared, respectively, a light shielding film was formed under the same film forming conditions as Comparative Examples 1 and 2, and the plurality of mask blanks were changed only by changing the film thickness of the resist film. Was formed into a film, and laser drawing was performed by changing the exposure wavelength to prepare a transfer mask. As a result, at any exposure wavelength, it was possible to form a desired light-shielding pattern in the mask blank corresponding to Example 1, but in the mask blanks corresponding to Comparative Examples 1 and 2, a desired light-shielding pattern was formed. It was impossible. From these points as well, in the mask blank 10 of Example 1, even if the film thickness or the exposure wavelength of the resist film 3 is changed, a pattern having a narrower line width than the wavelength of the laser light of the laser drawing device is resolved on the resist film. It is expected to be able to make it. On the other hand, in the mask blank of Comparative Example 1, even if the film thickness or exposure wavelength of the resist film is changed, it is expected that it is impossible to resolve a pattern with a line width narrower than the wavelength of the laser light of the laser drawing apparatus on the resist film.

In the above, the present invention has been described with reference to a preferred embodiment, but the present invention is not limited to the above embodiment.

1: light-transmitting substrate
2: shading screen
2a: shading pattern (transfer pattern)
3: resist film
3a: resist pattern
10: mask blank
20: transcription mask

Claims (25)

It is a mask blank provided with a light shielding film on the substrate,
The light shielding film contains a material containing a metal element,
The light shielding film is a composition gradient film whose content of the metal element changes in the thickness direction,
When the light-shielding film is sequentially divided into a light-shielding portion and an anti-reflection portion from a side closer to the substrate,
The refractive index n _A of the antireflection unit for light in a wavelength region of 350 nm or more and 520 nm or less is 2.1 or less,
The phase difference generated in the light in the wavelength region when the light in the wavelength region passes through the antireflection unit is 28 degrees or more.
Mask blank, characterized in that. The method of claim 1,
The phase difference is a mask blank, characterized in that 42 degrees or less. The method of claim 1,
The mask blank, wherein the refractive index n _A of the antireflection portion is 1.9 or more. The method of claim 1,
The mask blank, wherein the refractive index n _S of the light blocking portion is 1.9 or more. The method of claim 1,
The mask blank, wherein the refractive index n _S of the light blocking portion is 2.8 or less. The method of claim 1,
The mask blank, wherein an extinction coefficient k _S of the light-shielding portion for light in the wavelength region is 2.8 or more. The method of claim 1,
The mask blank, wherein an extinction coefficient k _A of the anti-reflection unit for light in the wavelength region is 1.0 or less. The method of claim 1,
The mask blank, wherein the light-shielding film is formed of a material containing chromium. The method of claim 1,
The mask blank, wherein the light shielding film has an optical density of 3 or more with respect to exposure light. The method of claim 1,
A mask blank, wherein a resist film is formed in contact with the surface of the light shielding film. The method of claim 10,
The mask blank, wherein the refractive index n _R of the resist film with respect to the light in the wavelength region is 1.50 or more. The method of claim 10,
The mask blank, wherein the resist film is formed of a material that is photosensitive by exposure light in a wavelength range of 350 nm to 520 nm. It is a transfer mask provided with a light shielding film having a transfer pattern on the substrate,
The light shielding film contains a material containing a metal element,
The light shielding film is a composition gradient film whose content of the metal element changes in the thickness direction,
When the light-shielding film is sequentially divided into a light-shielding portion and an anti-reflection portion from a side closer to the substrate,
The refractive index n _A of the antireflection unit for light in a wavelength region of 350 nm or more and 520 nm or less is 2.1 or less,
The phase difference generated in the light in the wavelength region when the light in the wavelength region passes through the antireflection unit is 28 degrees or more.
Transfer mask, characterized in that. The method of claim 13,
The phase difference is 42 degrees or less. The method of claim 13,
The refractive index n _A of the antireflection unit is 1.9 or more. The method of claim 13,
The mask for transfer, characterized in that the refractive index n _S of the light-shielding portion is 1.9 or more. The method of claim 13,
The refractive index n _S of the light shielding portion is 2.8 or less. The method of claim 13,
An extinction coefficient k _S of the light-shielding portion for light in the wavelength region is 2.8 or more. The method of claim 13,
An extinction coefficient k _A of the anti-reflection unit for light in the wavelength region is 1.0 or less. The method of claim 13,
The light shielding film is a transfer mask, wherein the light-shielding film is made of a material containing chromium. The method of claim 13,
The light-shielding film is a transfer mask, characterized in that the optical density with respect to exposure light is 3 or more. It is a method of manufacturing a transfer mask using the mask blank according to claim 10,
After exposing the transfer pattern to the resist film with exposure light in a wavelength region of 350 nm or more and 520 nm or less, development treatment is performed to form a resist film having the transfer pattern;
Step of forming a transfer pattern on the light-shielding film by etching using the resist film having the transfer pattern as a mask
A method of manufacturing a transfer mask, characterized in that it has a. The method of claim 22,
In the step of forming a transfer pattern on the light-shielding film, a transfer pattern is formed on the light-shielding film by dry etching using a gas containing chlorine. A method for manufacturing a semiconductor device comprising a step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using the transfer mask according to any one of claims 13 to 21. Manufacture of a semiconductor device, comprising a step of exposing and transferring a transfer pattern to a resist film on a semiconductor substrate using a transfer mask manufactured by the method for producing a transfer mask according to claim 22 or 23. Way.

Images