JP2023094541A - Mask blank, manufacturing method of transfer mask, and manufacturing method of semiconductor device - Google Patents

Abstract

To provide a mask blank capable of forming a fine space pattern on a pattern-forming thin film.SOLUTION: A mask blank having a structure in which a pattern-forming thin film, a first hard mask film, and a second hard mask film are laminated in this order on a main surface of a substrate. The pattern-forming thin film contains at least one or more elements selected from silicon and transition metals. The first hard mask film contains chromium. The second hard mask film contains tantalum, and the tantalum of the second hard mask film contains tantalum unsaturated to oxygen. The film thickness of the thin film for pattern formation is 20 nm or more, the film thickness of the first hard mask film is 15 nm or less, and the film thickness of the second hard mask film is 10 nm or less.SELECTED DRAWING: Figure 1

Description

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

As for a mask blank used for manufacturing a transfer mask, a technique is known in which a hard mask film is provided for the purpose of miniaturizing a pattern to be formed on the transfer mask. For example, Patent Document 1 below describes "a photomask blank in which a light-shielding film and an etching mask film (hard mask film) are sequentially formed on a translucent substrate, wherein the light-shielding film comprises at least a transition metal silicide and a surface antireflection layer formed on the light shielding layer and mainly composed of a tantalum compound containing at least one of oxygen and nitrogen, wherein the etching mask film contains of chromium compounds containing at least one” are described. In addition, according to this, "when patterning an etching mask film made of a chromium compound, the tantalum compound forming the surface antireflection layer transitions to a chlorine-based gas containing oxygen, which is an etching gas for dry etching the etching mask film. It has a higher resistance than metal silicide.Therefore, it is possible to perform over-etching so that the side wall of the processed cross-section of the etching mask film rises almost vertically."

Japanese Patent No. 5606028

However, the chromium compound forming the hard mask film (etching mask film) is isotropically etched by a chlorine-based gas containing oxygen. For this reason, in etching using a resist film as a mask, when patterning a hard mask film (etching mask film) made of a chromium compound, the etching side wall (processed cross-sectional side wall) recedes, and the pattern formed in the hard mask film recedes. It is unavoidable that the opening width (opening dimension) of the This can be a factor that hinders miniaturization of the pattern formed on the pattern-forming thin film by etching using the patterned hard mask film as a mask. Furthermore, it can be a factor that hinders high integration of semiconductor devices manufactured using a transfer mask provided with this pattern-forming thin film.

Accordingly, the present invention provides a method for manufacturing a mask blank and a transfer mask that can form a fine pattern on a pattern-forming thin film, and a transfer mask manufactured by this method for manufacturing a transfer mask. It aims at providing the manufacturing method of the semiconductor device which used.

The present invention has the following configurations as means for solving the above-described problems.

(Configuration 1)
A mask blank having a structure in which a pattern-forming thin film, a first hard mask film, and a second hard mask film are laminated in this order on a main surface of a substrate,
The pattern-forming thin film contains at least one element selected from silicon and transition metals,
the first hard mask film contains chromium,
the second hard mask film contains tantalum,
the tantalum of the second hard mask film includes tantalum unsaturated with respect to oxygen;
The film thickness of the thin film for pattern formation is 20 nm or more,
the film thickness of the first hard mask film is 15 nm or less;
A mask blank, wherein the film thickness of the second hard mask film is 10 nm or less.

(Configuration 2)
A mask blank having a structure in which a pattern-forming thin film, a first hard mask film, and a second hard mask film are laminated in this order on a main surface of a substrate,
The pattern-forming thin film contains at least one element selected from silicon and transition metals,
the first hard mask film contains chromium,
The second hard mask film contains tantalum and swells in an oxygen-containing gas atmosphere,
The film thickness of the thin film for pattern formation is 20 nm or more,
the film thickness of the first hard mask film is 15 nm or less;
A mask blank, wherein the film thickness of the second hard mask film is 10 nm or less.

(Composition 3)
3. The mask blank according to Structure 1 or 2, wherein the ratio of the oxygen content to the tantalum content of the second hard mask film is 1.5 or less.

(Composition 4)
4. The mask blank according to any one of Structures 1 to 3, wherein the second hard mask film contains the most tantalum among metal elements and silicon.

(Composition 5)
The mask blank according to any one of Structures 1 to 4, wherein the film thickness of the second hard mask film is 1 nm or more.

(Composition 6)
6. The mask blank according to any one of Structures 1 to 5, wherein the first hard mask film contains chromium and at least one of oxygen and nitrogen.

(Composition 7)
7. The mask blank according to any one of Structures 1 to 6, wherein the film thickness of the first hard mask film is thicker than the film thickness of the second hard mask film.

(Composition 8)
The thin film for pattern formation is a light absorbing film containing tantalum,
8. The mask blank according to any one of Structures 1 to 7, wherein a multilayer reflective film is provided between the substrate and the pattern-forming thin film.

(Composition 9)
The mask blank according to any one of Structures 1 to 8, wherein the pattern-forming thin film is a light-shielding film containing silicon.

(Configuration 10)
A method for manufacturing a transfer mask using the mask blank according to any one of Structures 1 to 9,
forming a second hard mask pattern on the second hard mask film by dry etching using a patterned resist film formed on the second hard mask film as a mask;
Using the second hard mask pattern as a mask, etching sidewalls of the second hard mask pattern are swelled by oxidation by dry etching using a gas containing oxygen, and the first hard mask pattern is formed on the first hard mask film. forming;
and forming a thin film pattern on the pattern forming thin film by dry etching using the first hard mask pattern as a mask.

(Composition 11)
An exposure step of pattern-transferring the thin film pattern of the transfer mask to a resist film on a semiconductor device substrate by a lithography method using the transfer mask manufactured by the transfer mask manufacturing method according to Structure 10. A method of manufacturing a semiconductor device, comprising:

According to the present invention, a method for manufacturing a mask blank and a transfer mask capable of forming a fine pattern on a pattern forming thin film, and a transfer mask manufactured by this method for manufacturing a transfer mask are provided. can provide a method of manufacturing a semiconductor device using

1 is a cross-sectional view showing the configuration of a mask blank according to a first embodiment of the invention; FIG. FIG. 2 is a manufacturing process diagram (part 1) showing a method of manufacturing a transfer mask using the mask blank of the first embodiment of the present invention; FIG. 2 is a manufacturing process diagram (part 2) showing a method of manufacturing a transfer mask using the mask blank of the first embodiment of the present invention; FIG. 5 is a cross-sectional view showing the configuration of a mask blank according to a second embodiment of the present invention; FIG. 10 is a manufacturing process diagram (part 1) showing a method of manufacturing a transfer mask using the mask blank of the second embodiment of the present invention; FIG. 10 is a manufacturing process diagram (Part 2) showing a method of manufacturing a transfer mask using the mask blank of the second embodiment of the present invention; It is a figure explaining an example and a comparative example. It is a manufacturing-process figure which shows the manufacturing method of the transfer mask of a comparative example.

Hereinafter, each embodiment to which the present invention is applied will be described based on the drawings. In addition, the same code|symbol is attached|subjected and demonstrated to the same component in each figure.

<<First Embodiment>>
First, the configuration of the mask blank 1 of the first embodiment will be described with reference to FIG. 1, and then a method of manufacturing a transfer mask and a method of manufacturing a semiconductor device using this mask blank 1 will be described.
<Mask blank 1>
FIG. 1 is a cross-sectional view showing the configuration of a mask blank 1 according to the first embodiment of the invention. A mask blank 1 shown in this figure is used for manufacturing a transmissive transfer mask. This mask blank 1 has a pattern forming thin film 11, a first hard mask film 12, and a second hard mask film formed on one main surface S of a translucent substrate 10 in this order from the translucent substrate 10 side. It has a structure in which 13 are laminated. Moreover, the mask blank 1 may have a structure in which a resist film 14 is laminated on the second hard mask film 13 as necessary. The details of the main components of the mask blank 1 will be described below.

[Translucent substrate 10]
The light-transmissive substrate 10 as the substrate in the first embodiment is made of a material having good transparency to the exposure light used in the exposure process in lithography. If an ArF excimer laser beam (wavelength: 193 nm) is used as the exposure light, it may be composed of a material having transparency to this. Synthetic quartz glass is used as such a material, but in addition to this, aluminosilicate glass, soda lime glass, low thermal expansion glass (SiO ₂ —TiO ₂ glass, etc.), and various other glass substrates can be used. can. In particular, the quartz substrate has high transparency in the region of ArF excimer laser light or shorter wavelengths, so it can be particularly suitably used for the mask blank of the present invention.

The exposure process in lithography referred to here is an exposure process in lithography using a transmissive transfer mask produced using this mask blank 1, and hereinafter, exposure light is used in this exposure process. It is assumed that the exposure light is As the exposure light, any of ArF excimer laser light (wavelength: 193 nm), KrF excimer laser light (wavelength: 248 nm), and i-line light (wavelength: 365 nm) can be applied. From this point of view, it is desirable to apply ArF excimer laser light to the exposure light. Therefore, an embodiment in which an ArF excimer laser beam is applied to the exposure light will be described below.

[Thin film for pattern formation 11]
The pattern forming thin film 11 is a light shielding film against exposure light. Such a pattern-forming thin film 11 can contain at least one element selected from silicon and transition metals. Here, as an example, the pattern forming thin film 11 is made of a material containing silicon (Si). The pattern forming thin film 11 is preferably made of a material containing nitrogen (N) in addition to silicon. Such a pattern-forming thin film 11 can be patterned by dry etching using a fluorine-based gas. Patterning with sufficient etch selectivity is possible.

The pattern-forming thin film 11 may further contain one or more elements selected from metalloid elements, non-metal elements, and metal elements as long as patterning is possible by dry etching using a fluorine-based gas. .

Among these, the metalloid element may be any metalloid element in addition to silicon, and examples thereof include boron (B), germanium (Ge), antimony (Sb), and tellurium (Te). The non-metallic element can be any non-metallic element (including halogens and noble gases) in addition to nitrogen (N), such as oxygen (O), carbon (C), hydrogen (H), phosphorus ( P), sulfur (S), selenium (Se), fluorine (F), helium (He), argon (Ar), krypton (Kr), and xenon (Xe). Metal elements include molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), zirconium (Zr), hafnium (Hf), niobium (Nb), vanadium (V), cobalt (Co), and chromium. (Cr), nickel (Ni), ruthenium (Ru), and tin (Sn) are exemplified.

The thickness of the pattern-forming thin film 11 is not particularly limited, but may be, for example, 20 nm or more in order to obtain sufficient light shielding properties against exposure light. Thereby, when etching the pattern forming thin film 11, the second hard mask pattern 13P (described later) can be efficiently removed while ensuring the light shielding property of the pattern forming thin film 11. FIG. In order to form fine patterns with high accuracy, the film thickness of the pattern-forming thin film 11 is preferably 70 nm or less, more preferably 60 nm or less, and even more preferably 50 nm or less.

[First hard mask film 12]
The first hard mask film 12 is preferably made of a material having sufficient etching resistance in dry etching of the pattern forming thin film 11 using a fluorine-based gas. Such a first hard mask film 12 can be made of, for example, a material containing chromium (Cr). The first hard mask film 12 made of a material containing chromium (Cr) can be patterned by dry etching using a gas containing oxygen. Materials containing chromium forming the first hard mask film 12 include chromium metal and materials containing chromium and at least one of oxygen, nitrogen, and carbon. In particular, it preferably contains chromium and at least one of oxygen and nitrogen. For example, it can be configured to contain chromium and nitrogen. As a result, the etching rate can be increased when the first hard mask film 12 is etched using a gas containing oxygen as an etchant.

In addition, the first hard mask film 12 has a sufficient etching selectivity with respect to the pattern forming thin film 11 formed of a material containing silicon (Si), and the pattern forming thin film 11 has almost the same etching selectivity. Alternatively, it is possible to etch away the first hard mask film 12 without causing any damage.

Furthermore, the first hard mask film 12 has sufficient etching selectivity with respect to the second hard mask film 13 made of a material containing tantalum (Ta), which will be described below. The first hard mask film 12 can be patterned using the hard mask film 13 as a mask.

The first hard mask film 12 as described above can have a film thickness of 15 nm or less, for example, in order to form a fine pattern. Also, the film thickness of the first hard mask film 12 is preferably thicker than the film thickness of the second hard mask film 13 described below.

[Second hard mask film 13]
The second hard mask film 13 is preferably made of a material that has sufficient etching resistance and swells in dry etching of the first hard mask film 12 using an oxygen-containing gas. Such a second hard mask film 13 can be made of a material containing tantalum (Ta). That is, the material of the second hard mask film 13 may contain tantalum (Ta) and swell under an oxygen-containing gas atmosphere. The material containing tantalum (Ta) contained in the second hard mask film 13 contains tantalum (Ta) unsaturated with oxygen. It can be said that the material forming the second hard mask film 13 contains tantalum (Ta) that is incompletely oxidized. When tantalum (Ta) is completely oxidized, it becomes stable tantalum pentoxide (Ta ₂ O ₅ ). Therefore, incompletely oxidized tantalum means tantalum in a bonding state other than a Ta ₂ O ₅ bond. I can say

As a result, tantalum (Ta) contained in the second hard mask film 13 is oxidized and the second hard mask film 13 swells during dry etching of the first hard mask film 12 using a gas containing oxygen. The ratio of the oxygen content to the tantalum (Ta) content of the second hard mask film 13 is preferably 1.5 or less. Thereby, the amount of swelling due to oxidation of tantalum (Ta) can be made a sufficient value. Also, this swelling amount can be controlled by appropriately adjusting the ratio of the oxygen content to the tantalum (Ta) content of the second hard mask film 13 . More specifically, when the second hard mask film 13 is formed, the film formation conditions (composition ratio of atoms forming the sputtering target, type of sputtering gas, gas flow rate ratio, etc.) are controlled to achieve the second hard mask film. 2 The ratio of the oxygen content to the tantalum (Ta) content of the hard mask film 13 may be adjusted to a desired value. It should be noted that each film forming apparatus has its own characteristics, so the above film forming conditions need to be adjusted in accordance with each film forming apparatus to be used. Also, the contents of tantalum (Ta) and oxygen (O) can be measured by XPS (X-ray photoelectron spectroscopy).

The second hard mask film 13 may contain at least one of metal elements other than tantalum (Ta) and silicon. Even when the second hard mask film 13 contains at least one of metal elements other than tantalum (Ta) and silicon, the second hard mask film 13 contains tantalum (Ta), other metal elements, and Among silicon, it is preferable to contain the most tantalum (Ta). It can also be said that the second hard mask 13 preferably contains the most tantalum, excluding oxygen. Thereby, the amount of swelling due to oxidation of tantalum (Ta) can be made a sufficient value.

Moreover, the film thickness of the second hard mask film 13 is preferably thinner than the film thickness of the first hard mask film 12 . The film thickness of such a second hard mask film 13 is, for example, 10 nm or less.
By setting the film thickness of the second hard mask film 13 to be thin, the film thickness of the resist film 14 serving as an etching mask for the second hard mask film 13 can be reduced, and the pattern formed in the pattern forming thin film 11 can be made finer. . Furthermore, by making the second hard mask film 13 thinner than the first hard mask film 12, the pattern forming thin film 11 is etched using the first hard mask film 12 as a mask, as will be described later. In this case, the second hard mask film 13 can be removed while the first hard mask film 12 remains. The film thickness of the second hard mask film 13 is 1 nm or more. As a result, when the first hard mask film 12 is dry-etched using the oxygen-containing gas, the etched side wall of the already patterned second hard mask film 13 (second hard mask pattern 13P) is sufficiently large. The effect of swelling can be obtained. The etching side wall of the second hard mask pattern 13P means the side wall of the second hard mask pattern when the mask blank 1 with the second hard mask film 13 patterned is viewed in cross section. In the cross-sectional view, the angle formed by the side wall and the main surface of the substrate is a right angle or a substantially right angle.

[Resist film 14]
The resist film 14 is preferably formed in contact with the surface of the second hard mask film 13 in the mask blank 1 . The resist film 14 is, for example, a chemically amplified positive resist, but is not limited to this as long as a fine pattern can be formed. The thickness of the resist film 14 is more preferably 80 nm or less from the viewpoint of forming a fine pattern by lithography processing of the resist film 14 and from the viewpoint of preventing pattern collapse of the formed resist pattern.

<Method for manufacturing transfer mask>
FIG. 2 is a manufacturing process diagram (part 1) showing a manufacturing method of a transfer mask using the mask blank 1 of the first embodiment of the present invention. FIG. 3 is a manufacturing process diagram (part 2) showing a manufacturing method of a transfer mask using the mask blank 1 of the first embodiment of the present invention. A method of manufacturing a transmissive transfer mask will be described below with reference to these drawings.

First, a mask blank 1 having the configuration described with reference to FIG. 1 is prepared. If the mask blank 1 does not have the resist film 14 , the resist film 14 is formed on the second hard mask film 13 . Note that the mask blank 1 may have a resist film 14 as shown in FIG.

[Step (1)]
In the step (1) shown in FIG. 2, a pattern to be formed on the pattern forming thin film 11 is written on the resist film 14 of the mask blank 1 by exposure. An electron beam can be used for this exposure drawing. After that, if necessary, the resist film 14 is subjected to a predetermined treatment such as a PEB (Post Exposure Bake) treatment, a development treatment, a post-bake treatment, etc., and the resist film 14 is patterned. The patterned resist film 14 has a space pattern 14a, and the opening width [W14] of this space pattern 14a is, for example, the minimum space width. The space pattern in this embodiment refers to a pattern formed by partially removing a film, and includes a linear pattern and a hole-shaped pattern (hole pattern). A space pattern can also be called a blank pattern. When the space pattern is hole-shaped, the opening width [W14] is the diameter of the hole. The same applies to the following description.

[Step (2)]
In step (2) shown in FIG. 2, the second hard mask film 13 is etched using the patterned resist film 14 as a mask. At this time, the second hard mask film 13 made of a material containing tantalum (Ta) is patterned by dry etching using a fluorine-based gas as an etchant. Transfer to membrane 13 . Thus, a second hard mask pattern 13P is formed on the second hard mask film 13. Next, as shown in FIG.

Here, dry etching of a material containing tantalum (Ta) using a fluorine-based gas as an etchant is highly anisotropic. Therefore, in the second hard mask pattern 13P, a space pattern 13a having an opening width [W13] substantially equal to the space pattern 14a having an opening width [W14] formed in the resist film 14 is formed. In this step, the resist film 14 may remain on the second hard mask pattern 13P. The remaining resist film 14 may be removed by ashing (ashing) using oxygen gas or ozone gas, or may be removed when the first hard mask film 12 is etched as described later.

[Step (3)]
In step (3) shown in FIG. 2, the first hard mask film 12 is etched using the second hard mask pattern 13P as a mask. At this time, the oxygen-containing gas is used as an etchant to swell the second hard mask pattern 13P. By this dry etching, the first hard mask film 12 is patterned to form a first hard mask pattern 12P. When the first hard mask film 12 is made of a material containing chromium (Cr), the etchant gas preferably contains chlorine gas in addition to oxygen. The resist film 14 left on the second hard mask pattern 13P may be removed by ashing with an etchant containing oxygen.

This dry etching uses a gas containing oxygen and chlorine as an etchant, and etching of the first hard mask film 12 made of a material containing chromium (Cr) is slightly isotropic, though not as strong as wet etching. proceed as intended.

Here, in this dry etching, the second hard mask pattern 13P is exposed to an oxygen-containing gas, and tantalum (Ta) contained in the second hard mask pattern 13P is oxidized. This oxidation spreads isotropically from the exposed surface of the second hard mask pattern 13P, and the exposed surface of the second hard mask pattern 13P becomes the oxidized portion 13b. Due to such swelling due to oxidation, the opening width [W13] of the space pattern 13a formed in the second hard mask pattern 13P becomes a reduced opening width [W13'] due to the swelling of the second hard mask pattern 13P. . As described above, when the remaining resist film 14 is removed by ashing (ashing) using oxygen gas or ozone gas, the tantalum contained in the second hard mask pattern 13P is removed even in this ashing step. (Ta) is oxidized and the second hard mask pattern 13P swells. The same applies to the second embodiment.

Therefore, a second hard mask pattern 13P having an opening width [W13′] smaller than the opening width [W14] of the space pattern 14a formed in the resist film 14 in step (1) is used as a mask to form the first hard mask film. 12 isotropic dry etching proceeds. As a result, the first hard mask pattern 12 has a space pattern 12a with a fine opening width [W12] in which side etching is suppressed by an amount corresponding to the swelling amount of the second hard mask pattern 13P. 12P is formed.

[Step (4)]
In step (4) shown in FIG. 3, the pattern-forming thin film 11 is etched using the first hard mask pattern 12P as a mask. At this time, the pattern forming thin film 11 made of a material containing silicon (Si) is patterned by dry etching using a fluorine-based gas as an etchant, and the first hard mask pattern 12P is transferred to the pattern forming thin film 11. Then, a thin film pattern 11P is formed. During the etching of the pattern-forming thin film 11, the second hard mask pattern 13P remaining on the first hard mask pattern 12P, including the oxidized portion 13b, is removed by etching with a fluorine-based gas etchant. is preferred.

Dry etching of a material containing silicon (Si) using a fluorine-based gas as an etchant is highly anisotropic. Therefore, in the thin film pattern 11P made of a material containing silicon (Si), the space pattern 12a having the opening width [W12] formed in the first hard mask pattern 12P has an opening width that is almost as fine as that of the space pattern 12a. A space pattern 11a having [W11] is formed.

[Step (5)]
In step (5) shown in FIG. 3, the first hard mask pattern 12P on the thin film pattern 11P is removed by etching. At this time, the first hard mask pattern 12P made of a material containing chromium (Cr) is etched by dry etching using a chlorine-containing gas as an etchant. This chlorine-containing gas may further contain oxygen.

As a result, a transmissive transfer mask 100 is obtained in which the thin film pattern 11P formed by patterning the pattern forming thin film 11 is provided on the translucent substrate 10 as a light shielding pattern. The thin film pattern 11P formed on the transfer mask 100 has a space pattern 11a with a fine opening width [W11] in which side etching is suppressed by an amount corresponding to the swelling amount of the second hard mask pattern 13P.

As described above, the transfer mask 100 having the thin film pattern 11P in which the finer space pattern 11a is formed is obtained.

<Method for manufacturing a semiconductor device>
In the semiconductor device manufacturing method, the transmission type transfer mask 100 manufactured by the transfer mask manufacturing method described above is used to expose and transfer the thin film pattern 11P onto the resist film on the semiconductor device substrate. It is characterized by A method for manufacturing such a semiconductor device is performed as follows.

First, a substrate for forming a semiconductor device is prepared. This substrate may be, for example, a semiconductor substrate, a substrate having a semiconductor thin film, or a substrate having a microfabricated film formed thereon. A resist film is formed on the prepared substrate, pattern exposure is performed on the resist film using the transfer mask 100, and the thin film pattern 11P formed on the transfer mask 100 is pattern-transferred to the resist film. do. At this time, as the exposure light, as described above, for example, ArF excimer laser light (wavelength: 193 nm), KrF excimer laser light (wavelength: 248 nm), or i-line light (wavelength: 365 nm) can be applied. However, from the viewpoint of pattern miniaturization, it is desirable to apply ArF excimer laser light to the exposure light.

Thereafter, the resist film onto which the thin film pattern 11P has been exposed and transferred is developed to form a resist pattern. Using this resist pattern as a mask, the surface layer of the substrate is subjected to an etching process or a process of introducing impurities. . After the processing is finished, the resist pattern is removed.

The above-described lithography process is repeatedly performed on the substrate while exchanging the transfer mask 100, and further necessary processing is performed to complete the semiconductor device.

In manufacturing a semiconductor device as described above, a highly integrated semiconductor device can be obtained by using a transfer mask 100 having a fine space pattern 11a manufactured by the transfer mask manufacturing method described above. can be done.

<<Second embodiment>>
First, the structure of the mask blank 2 of the second embodiment will be described with reference to FIG. 4, and then a method of manufacturing a transfer mask and a method of manufacturing a semiconductor device using this mask blank 2 will be described.

<Mask blank 2>
FIG. 4 is a cross-sectional view showing the structure of a mask blank 2 according to a second embodiment of the invention. The mask blank 2 shown in this figure is a master of a reflective transfer mask (hereinafter referred to as a reflective mask) for EUV lithography using extreme ultraviolet (EUV: Extreme Ultra Violet, hereinafter referred to as EUV light) as exposure light. is. The mask blank 2 is formed on one main surface S of the substrate 20 in this order from the substrate 20 side: a multilayer reflective film 21, a protective film 22, a pattern forming thin film 11', a first hard mask film 12, and a second film. 2 hard mask films 13 are laminated. Moreover, the mask blank 2 may have a structure in which a resist film 14 is laminated on the second hard mask film 13 as necessary. The details of the main components of the mask blank 2 will be described below.

[Substrate 20]
Low-expansion glass is preferably used for the substrate 20 in order to prevent the transfer pattern from being distorted due to heat generated during exposure (EUV exposure) using a reflective mask formed by processing the mask blank 2 . As the low-expansion glass, for example, SiO ₂ —TiO ₂ -based glass, multi-component glass-ceramics, or the like can be used. The transfer pattern is a pattern formed by processing the pattern forming thin film 11', which will be described later.

[Multilayer reflective film 21]
The multilayer reflective film 21 is a film arranged between the substrate 20 and the pattern forming thin film 11' on the main surface S of the substrate 20, and reflects the EUV light, which is the exposure light, with high reflectance. The multilayer reflective film 21 provides the function of reflecting EUV light to the reflective transfer mask formed using the mask blank 2, and each layer mainly composed of elements with different refractive indices is periodically formed. It is a multi-layered film that is laminated systematically.

In general, a thin film of a light element or its compound that is a high refractive index material (high refractive index layer) and a thin film of a heavy element that is a low refractive index material or its compound (low refractive index layer) are alternately formed 40 times. A multilayer film is used as the multilayer reflective film 21, which is laminated for about 60 cycles. For example, as the multilayer reflective film 21 for EUV light with a wavelength of 13 nm to 14 nm, a Mo/Si periodic laminated film in which Mo films and Si films are alternately laminated for about 40 to 60 cycles is preferably used. The high refractive index layer, which is the uppermost layer of the multilayer reflective film 21, may be formed of silicon (Si).

[Protective film 22]
The protective film 22 is a film provided to protect the multilayer reflective film 21 from etching and cleaning when the mask blank 2 is processed to manufacture a reflective mask for EUV lithography. The protective film 22 is provided on the multilayer reflective film 21 in contact with the multilayer reflective film 21 or via another film, and may have a single-layer structure or a laminated structure.

Such protective film 22 preferably contains ruthenium (Ru). The material of the protective film 22 may be Ru metal alone, or ruthenium (Ru), titanium (Ti), niobium (Nb), molybdenum (Mo), zirconium (Zr), yttrium (Y), rhodium (Rh), and boron. It may be a Ru alloy containing at least one metal selected from (B), lanthanum (La), cobalt (Co), rhenium (Re), and the like, and may contain nitrogen. On the other hand, the protective film 22 is made of silicon (Si), a material containing silicon (Si) and oxygen (O), a material containing silicon (Si) and nitrogen (N), silicon (Si), oxygen (O) and nitrogen ( Materials selected from silicon-based materials such as those containing N) can also be used.

[Thin film for pattern formation 11']
The pattern forming thin film 11' is a light absorbing film for exposure light. Such a pattern-forming thin film 11' can be made of a material containing tantalum (Ta). The pattern-forming thin film 11' may have a single-layer structure, or may have a laminated structure as shown. In this case, a laminated structure of a first thin film 11-1 and a second thin film 11-2 is exemplified in order from the substrate 20 side. Although the material of the pattern forming thin film 11' is not particularly limited, the materials of the first thin film 11-1 and the second thin film 11-2 can be, for example, as follows.

The first thin film 11-1 is made of a material that has good light absorption with respect to the exposure light and that can be etched with a high selectivity with respect to the protective film 22. As shown in FIG. Such a first thin film 11-1 is made of a material containing at least tantalum (Ta) and nitrogen (N), for example. In the mask blank for the reflective transfer mask, the crystalline state of the light absorbing film is preferably amorphous or microcrystalline in terms of smoothness and flatness. By adding boron (B), silicon (Si) and/or germanium (Ge) to tantalum (Ta), an amorphous structure can be easily obtained and smoothness can be improved. Furthermore, if nitrogen (N) and/or oxygen (O) are added to Ta, resistance to oxidation is improved, and stability over time can be improved. For these reasons, the first thin film 11-1 can be TaN, TaON, TaBN, TaBON, TaCN, TaCON, TaBCN, or TaBOCN, for example.

In addition, the second thin film 11-2 is preferably made of a material that has good light absorption with respect to the exposure light and that can be etched with high selectivity with respect to the first hard mask film 12. . Such a second thin film 11-2 can be made of a material containing at least tantalum (Ta) and oxygen (O). can. This enables patterning with sufficient etching selectivity to the first hard mask film 12 made of a material containing chromium (Cr), which will be described below.

The first thin film 11-1 can be dry-etched using a fluorine-based gas or a chlorine-based gas that does not substantially contain oxygen. The second thin film 11-2 can be dry-etched using a fluorine-based gas or a chlorine-based gas that does not substantially contain oxygen, but is preferably etched with a fluorine-based gas having a higher etching rate.

Also, the pattern-forming thin film 11' has a film thickness of, for example, 20 nm or more in order to obtain sufficient absorption of exposure light (EUV light). In order to reduce the shadowing effect, the film thickness of the pattern forming thin film 11' is preferably 70 nm or less, more preferably 60 nm or less, and even more preferably 50 nm or less.

[First hard mask film 12]
The first hard mask film 12 is the same as the first hard mask film 12 of the mask blank 1 described with reference to FIG. 1 in the first embodiment. That is, the first hard mask film 12 is preferably made of a material having sufficient etching resistance in dry etching of the pattern forming thin film 11' using a fluorine-based gas. Such a first hard mask film 12 can be made of a material containing chromium (Cr), for example, chromium containing at least one of oxygen, nitrogen, and carbon. . A more detailed description of the configuration of the first hard mask film 12 will be omitted.

[Second hard mask film 13]
The second hard mask film 13 is the same as the second hard mask film 13 of the mask blank 1 described with reference to FIG. 1 in the first embodiment. That is, the second hard mask film 13 is made of a material that has sufficient etching resistance and swells in the dry etching of the first hard mask film 12 using an oxygen-containing gas. Such a second hard mask film 13 is preferably made of a material containing tantalum (Ta). A more detailed description of the configuration of the second hard mask film 13 will be omitted.

[Resist film 14]
The resist film 14 is the same as the resist film 14 of the mask blank 1 described with reference to FIG. 1 in the first embodiment, and redundant description of the detailed configuration will be omitted here.

<Method for manufacturing transfer mask>
FIG. 5 is a manufacturing process diagram (No. 1) showing a manufacturing method of a transfer mask using the mask blank 2 of the second embodiment of the present invention. FIG. 6 is a manufacturing process diagram (No. 2) showing a manufacturing method of a transfer mask using the mask blank 2 of the second embodiment of the present invention. The procedure of the manufacturing method shown in these figures is basically the same as the procedure of the manufacturing method described with reference to FIGS. 2 and 3 in the first embodiment. A method of manufacturing a reflective transfer mask will be described below with reference to these drawings.

First, the mask blank 2 having the configuration described with reference to FIG. 4 is prepared. If the mask blank 2 does not have the resist film 14 , the resist film 14 is formed on the second hard mask film 13 . The mask blank 2 may have a resist film 14 as shown in FIG. 4, and in this case, the procedure for forming the resist film 14 is unnecessary.

[Steps (1) to (3)]
Next, the steps (1) to (3) shown in FIG. 5 are performed in the same procedure as the steps (1) to (3) shown in FIG. 2 in the first embodiment. detailed description is omitted.

In step (3) in particular, the first hard mask film 12 containing chromium (Cr) is patterned by isotropic dry etching using an oxygen-containing gas using the second hard mask pattern 13P as a mask. do. For dry etching here, it is preferable to use a gas containing chlorine in addition to oxygen.

In this dry etching, the second hard mask pattern 13P is exposed to an oxygen-containing gas, and tantalum (Ta) contained in the second hard mask pattern 13P is oxidized. This oxidation spreads isotropically from the exposed surface of the second hard mask pattern 13P, and the exposed surface of the second hard mask pattern 13P becomes the oxidized portion 13b. Due to such swelling due to oxidation, the opening width [W13] of the space pattern 13a formed in the second hard mask pattern 13P becomes a reduced opening width [W13'] due to the swelling of the second hard mask pattern 13P. .

Therefore, a second hard mask pattern 13P having an opening width [W13′] smaller than the opening width [W14] of the space pattern 14a formed in the resist film 14 in step (1) of FIG. Isotropic dry etching of the hard mask film 12 proceeds. As a result, the first hard mask pattern 12 has a space pattern 12a with a fine opening width [W12] in which side etching is suppressed by an amount corresponding to the swelling amount of the second hard mask pattern 13P. 12P is formed.

[Step (4)]
In step (4) shown in FIG. 6, the second thin film 11-2 in the pattern forming thin film 11' is etched using the first hard mask pattern 12P as a mask. At this time, the second thin film 11-2 made of a material containing at least tantalum (Ta) and oxygen (O) is patterned by dry etching using a fluorine-based gas as an etchant to form the first hard mask pattern 12P. The formed pattern is transferred to the second thin film 11-2. During the etching of the second thin film 11-2, the second hard mask pattern 13P remaining on the first hard mask pattern 12P, including the oxidized portion 13b, is removed by etching with a fluorine-based gas etchant. is preferred.

Dry etching of a material containing tantalum (Ta) using a fluorine-based gas as an etchant is highly anisotropic. Therefore, in the second thin film 11-2 made of a material containing at least tantalum (Ta) and oxygen (O), the space pattern 12a with the opening width [W12] formed in the first hard mask pattern 12P and , a space pattern 11a' having an opening width [W11'] that is approximately the same as fine is formed.

[Step (5)]
In step (5) shown in FIG. 6, the first thin film 11-1 in the pattern forming thin film 11' is further etched using the first hard mask pattern 12P as a mask. At this time, the first thin film 11-1 made of a material containing at least tantalum (Ta) and nitrogen (N) is patterned by dry etching using chlorine gas as an etchant to form a first hard mask pattern 12P. The resulting pattern is transferred to the first thin film 11-1. During the etching of the first thin film 11-1, the first hard mask pattern 12P left on the second thin film 11-2 is preferably removed by etching with a chlorine-based gas etchant.

Dry etching of a material containing tantalum (Ta) using a chlorine-based gas as an etchant is highly anisotropic. Therefore, in the first thin film 11-1 made of a material containing at least tantalum (Ta) and nitrogen (N), the space pattern 12a with the opening width [W12] formed in the first hard mask pattern 12P and the , a space pattern 11a' having an opening width [W11'] that is approximately the same as fine is formed.

In dry etching using a chlorine-based gas as an etchant, the protective film 22 containing ruthenium (Ru) acts as an etching stopper to protect the multilayer reflective film 21 .

As a result, a reflective transfer mask 200 is obtained in which a thin film pattern 11P' serving as a light absorption pattern is provided on the substrate 20 via the multilayer reflective film 21 and the protective film 22. FIG. The thin film pattern 11P' formed on the transfer mask 200 is a space pattern 11a' having a fine opening width [W11'] in which side etching is suppressed by an amount corresponding to the swelling amount of the second hard mask pattern 13P. have.

As described above, the reflective transfer mask 200 having the thin film pattern 11P' formed with the finer space pattern 11a' is obtained.

<Method for manufacturing a semiconductor device>
In the semiconductor device manufacturing method, the reflective transfer mask 200 manufactured by the transfer mask manufacturing method described above is used to expose and transfer the thin film pattern 11P' onto the resist film on the semiconductor device substrate. It is characterized by A method for manufacturing such a semiconductor device is performed as follows.

First, a substrate for forming a semiconductor device is prepared. This substrate may be, for example, a semiconductor substrate, a substrate having a semiconductor thin film, or a substrate having a microfabricated film formed thereon. A resist film is formed on the prepared substrate, pattern exposure is performed on the resist film using a transfer mask 200, and the thin film pattern 11P' formed on the transfer mask 200 is exposed and transferred to the resist film. . At this time, EUV light is used as the exposure light, and the resist film is irradiated with the exposure light (EUV light) reflected by the transfer mask 200 .

Thereafter, the resist film onto which the thin film pattern 11P' has been exposed and transferred is developed to form a resist pattern. Using this resist pattern as a mask, the surface layer of the substrate is etched or impurities are introduced. conduct. After the processing is finished, the resist pattern is removed.

The lithography process as described above is repeatedly performed on the substrate while exchanging the transfer mask 200, and further necessary processing is performed to complete the semiconductor device.

In manufacturing the semiconductor device as described above, by using the transfer mask 200 having the fine space pattern 11a' manufactured by the transfer mask manufacturing method described above, a highly integrated semiconductor device can be obtained. be able to.

Next, Examples 1 to 3 to which the present invention is applied, and Comparative Examples 1 and 2 will be described. The results shown in these examples and comparative examples were obtained by simulation based on the previously known etching rate of each film for each etching gas and the swelling rate of the tantalum-containing film (second hard mask film) in an oxygen gas atmosphere. It is obtained by FIG. 7 is a diagram for explaining examples and comparative examples. FIG. 7 shows the configurations of mask blanks in Examples and Comparative Examples, and the opening widths of the space patterns formed on each film of these mask blanks. Hereinafter, a comparative example and an example will be described with reference to FIGS. 1 to 6 and other figures together with FIG.

<Comparative Example 1>
[Preparation of mask blank]
As a mask blank of Comparative Example 1, a mask blank used for manufacturing a transmissive transfer mask was produced as follows.

First, silicon nitride (SiNx) was sputtered to a thickness of 62 nm as a thin film 11 for pattern formation on a translucent substrate 10 made of synthetic quartz glass and having a thickness of about 6.35 mm. A first hard mask film 12 of chromium nitride (CrNx) was sputtered to a thickness of 5 nm on the pattern forming thin film 11 . A mask blank of Comparative Example 1 was obtained by depositing a chemically amplified positive resist with a thickness of 60 nm as a resist film 14 without forming the second hard mask film 13 on the first hard mask film 12. .

[Production of transfer mask (see FIGS. 7 and 8)]
Using the mask blank of Comparative Example 1, a transmissive transfer mask was produced. 8A to 8D are manufacturing process diagrams showing a manufacturing method of the transfer mask of Comparative Example 1. FIG. A procedure for manufacturing a transfer mask using the mask blank of Comparative Example 1 will be described below with reference to FIG.

First, as shown in step (1) of FIG. 8, a space pattern 14a having an opening width [W14]=34 nm was formed in the resist film 14 by lithography. This opening width [W14] is the minimum space width by lithographic processing for manufacturing a transmissive transfer mask at present.

Next, as shown in step (2) of FIG. 8, the patterned resist film 14 was used as a mask to etch the first hard mask film 12 . At this time, the first hard mask film 12 made of chromium nitride (CrNx) is patterned by dry etching using an oxygen-containing chlorine gas (Cl ₂ +O ₂ ) as an etchant to form a first hard mask pattern 12P having a space pattern 12a. formed. In this etching, the first hard mask film 12 made of chromium nitride (CrNx) was isotropically etched. Therefore, the opening width [W12] of the space pattern 12a formed in the first hard mask pattern 12P is larger than the opening width [W14] of the resist film 14, and the opening width [W12]=38 nm. Resist film 14 left on first hard mask pattern 12P was removed by ashing with an etchant containing oxygen.

Next, as shown in step (3) of FIG. 8, the pattern-forming thin film 11 was etched using the first hard mask pattern 12P as a mask. At this time, the pattern forming thin film 11 made of silicon nitride (SiNx) was patterned by dry etching using a fluorine-based gas (SF ₆ +He) as an etchant to form a thin film pattern 11P having a space pattern 11a. In this etching, the pattern forming thin film 11 made of silicon nitride (SiNx) was etched with good anisotropy. Therefore, the opening width [W11] of the space pattern 11a formed in the thin film pattern 11P is approximately the same as the opening width [W12] of the first hard mask film 12, and the opening width [W11]=40 nm. rice field.

After that, as shown in step (4) of FIG. 8, the first hard mask pattern 12P remaining on the thin film pattern 11P was removed by dry etching using oxygen-containing chlorine gas (Cl ₂ +O ₂ ) as an etchant. As a result, a transfer mask of Comparative Example 1 was obtained in which the thin film pattern 11P made of silicon nitride (SiNx) was used as the light shielding pattern on the translucent substrate 10 .

<Comparative Example 2>
[Preparation of mask blank (see FIGS. 1 and 7)]
As the mask blank 1 of Comparative Example 2, a mask blank used for manufacturing a transmissive transfer mask was produced. Here, in the mask blank manufacturing procedure of Comparative Example 1, after forming the first hard mask film 12 and before forming the resist film 14, a tantalum (Ta) target was used, and argon (Ar) and oxygen Reactive sputtering was performed in a mixed gas atmosphere of (O ₂ ), and as the second hard mask film 13, tantalum oxide (TaOx) was sputtered to a thickness of 3 nm. Thus, a mask blank 1 of Comparative Example 2 having the configuration described with reference to FIG. 1 was produced. The ratio O/Ta of the content of oxygen (O) to the content of tantalum (Ta) in the second hard mask film 13 was 2.5. That is, tantalum (Ta) of the second hard mask film 13 was saturated with oxygen. It can also be said that the second hard mask film 13 was substantially made of tantalum pentoxide (Ta ₂ O ₅ ).

[Production of transfer mask]
A method of manufacturing a transmissive transfer mask using the mask blank 1 of Comparative Example 2 will be described. 2 and 3 except that the second hard mask film 13 does not swell, the flow of the transfer mask manufacturing method in Comparative Example 2 will be described with reference to FIGS. .

First, a space pattern 14a having an opening width [W14]=34 nm was formed in the resist film 14 by lithography. This opening width [W14] is the minimum space width by lithographic processing for manufacturing a transmissive transfer mask at present.

Next, using the patterned resist film 14 as a mask, the second hard mask film 13 was etched. At this time, the second hard mask film 13 made of tantalum oxide (TaOx) is patterned by dry etching using a fluorine-based gas (SF ₆ +He) as an etchant to form a second hard mask pattern 13P having a space pattern 13a. bottom. In this etching, the second hard mask film 13 made of tantalum oxide (TaOx) was etched with good anisotropy. Therefore, the opening width [W13] of the space pattern 13a formed in the second hard mask pattern 13P is approximately the same as the opening width [W14] of the resist film 14, and the opening width [W13]=34 nm. rice field.

After that, the first hard mask film 12 was etched using the second hard mask pattern 13P as a mask. At this time, the first hard mask film 12 made of chromium nitride (CrNx) is patterned by dry etching using an oxygen-containing chlorine gas (Cl ₂ +O ₂ ) as an etchant to form a first hard mask pattern 12P having a space pattern 12a. formed.

In this etching, even if the second hard mask pattern 13P is exposed to oxygen-containing chlorine gas (Cl ₂ +O ₂ ), the tantalum (Ta) contained in the second hard mask pattern 13P is not oxidized and the second hard mask pattern 13P is not oxidized. Mask pattern 13P did not swell. Therefore, after etching the first hard mask film 12, the opening width [W13] of the space pattern 13a of the second hard mask pattern 13P remained at 34 nm.

In this etching, the first hard mask film 12 made of chromium nitride (CrNx) was isotropically etched. Therefore, the opening width [W12] of the space pattern 12a formed in the first hard mask pattern 12P is larger than the opening width [W13] of the space pattern 13a, and the opening width [W12]=38 nm. Resist film 14 left on second hard mask pattern 13P was removed by ashing with an etchant containing oxygen.

Then, using the first hard mask pattern 12P as a mask, the pattern-forming thin film 11 was etched. At this time, the pattern forming thin film 11 made of silicon nitride (SiNx) was patterned by dry etching using a fluorine-based gas (SF ₆ +He) as an etchant to form a thin film pattern 11P having a space pattern 11a. In this etching, the pattern forming thin film 11 made of silicon nitride (SiNx) was etched with good anisotropy. Therefore, the opening width [W11] of the space pattern 11a formed in the thin film pattern 11P is approximately the same as the opening width [W12] of the space pattern 12a in the first hard mask pattern 12P. = 40 nm.

After that, the first hard mask pattern 12P remaining on the thin film pattern 11P was removed by dry etching using oxygen-containing chlorine gas (Cl ₂ +O ₂ ) as an etchant. As a result, a transfer mask 100 of Comparative Example 2 was obtained in which a thin film pattern 11P made of silicon nitride (SiNx) was provided as a light shielding pattern on the translucent substrate 10 .

<Example 1>
[Preparation of mask blank (see FIGS. 1 and 7)]
As the mask blank 1 of Example 1, a mask blank used for manufacturing a transmissive transfer mask was produced. Here, in the mask blank manufacturing procedure of Comparative Example 1, after forming the first hard mask film 12 and before forming the resist film 14, a tantalum (Ta) target was used, and argon (Ar) and oxygen Reactive sputtering was performed in a mixed gas atmosphere of (O ₂ ), and as the second hard mask film 13, tantalum oxide (TaOx) was sputtered to a thickness of 3 nm. Thus, the mask blank 1 of Example 1 having the configuration described with reference to FIG. 1 was produced. The ratio O/Ta of the content of oxygen (O) to the content of tantalum (Ta) in the second hard mask film 13 is 1.3. was unsaturated.

[Preparation of transfer mask (see FIGS. 2 and 3)]
A method of manufacturing a transmissive transfer mask using the mask blank 1 of Example 1 will be described with reference to FIGS. 2 and 3. FIG.

First, as shown in step (1) of FIG. 2, a space pattern 14a having an opening width [W14]=34 nm was formed in the resist film 14 by lithography. This opening width [W14] is the minimum space width by lithographic processing for manufacturing a transmissive transfer mask at present.

Next, as shown in step (2) of FIG. 2, the patterned resist film 14 was used as a mask to etch the second hard mask film 13 . At this time, the second hard mask film 13 made of tantalum oxide (TaOx) is patterned by dry etching using a fluorine-based gas (SF ₆ +He) as an etchant to form a second hard mask pattern 13P having a space pattern 13a. bottom. In this etching, the second hard mask film 13 made of tantalum oxide (TaOx) was etched with good anisotropy. Therefore, the opening width [W13] of the space pattern 13a formed in the second hard mask pattern 13P is approximately the same as the opening width [W14] of the resist film 14, and the opening width [W13]=34 nm. rice field.

Thereafter, as shown in step (3) of FIG. 2, the first hard mask film 12 was etched using the second hard mask pattern 13P as a mask. At this time, the first hard mask film 12 made of chromium nitride (CrNx) is patterned by dry etching using an oxygen-containing chlorine gas (Cl ₂ +O ₂ ) as an etchant to form a first hard mask pattern 12P having a space pattern 12a. formed.

In this etching, the second hard mask pattern 13P is exposed to an oxygen-containing chlorine gas (Cl ₂ +O ₂ ), and the tantalum (Ta) contained in the second hard mask pattern 13P is oxidized so that the second hard mask pattern 13P is swollen. That is, the second hard mask film 13 in Example 1 contained tantalum unsaturated with respect to oxygen. Due to this oxidation of tantalum, the opening width [W13] of the space pattern 13a of the second hard mask pattern 13P was reduced to 30 nm due to the swelling of the second hard mask pattern 13P [W13'].

In this etching, the first hard mask film 12 made of chromium nitride (CrNx) was isotropically etched. Therefore, the opening width [W12] of the space pattern 12a formed in the first hard mask pattern 12P is larger than the opening width [W13'] of the reduced space pattern 13a, and the opening width [W12]=34 nm. rice field. Resist film 14 left on second hard mask pattern 13P was removed by ashing with an etchant containing oxygen.

Next, as shown in step (4) of FIG. 3, the pattern-forming thin film 11 was etched using the first hard mask pattern 12P as a mask. At this time, the pattern forming thin film 11 made of silicon nitride (SiNx) was patterned by dry etching using a fluorine-based gas (SF ₆ +He) as an etchant to form a thin film pattern 11P having a space pattern 11a. In this etching, the pattern forming thin film 11 made of silicon nitride (SiNx) was etched with good anisotropy. Therefore, the opening width [W11] of the space pattern 11a formed in the thin film pattern 11P is approximately the same as the opening width [W12] of the space pattern 12a in the first hard mask pattern 12P. = 36 nm.

After that, as shown in step (5) of FIG. 3, the first hard mask pattern 12P remaining on the thin film pattern 11P was removed by dry etching using oxygen-containing chlorine gas (Cl ₂ +O ₂ ) as an etchant. As a result, the transfer mask 100 of Example 1 was obtained, in which the thin film pattern 11P made of silicon nitride (SiNx) was provided as a light shielding pattern on the translucent substrate 10 .

<Example 2>
[Preparation of mask blank (see FIGS. 1 and 7)]
As the mask blank 1 of Example 2, a mask blank used for manufacturing a transmissive transfer mask was produced. Here, in the mask blank manufacturing procedure of Comparative Example 1, after forming the first hard mask film 12 and before forming the resist film 14, a tantalum (Ta) target was used, and argon (Ar) and nitrogen gas were used. Reactive sputtering was performed in a mixed gas atmosphere of (N ₂ ), and as the second hard mask film 13, tantalum nitride (TaNx) was sputtered to a thickness of 3 nm. Thus, the mask blank 1 of Example 2 having the configuration described with reference to FIG. 1 was produced. The ratio O/Ta of the content of oxygen (O) to the content of tantalum (Ta) in the second hard mask film 13 is 0, and the tantalum (Ta) in the second hard mask film 13 is impervious to oxygen. It was saturated.

[Preparation of transfer mask (see FIGS. 2 and 3)]
Using the mask blank 1 of Example 2, a transmissive transfer mask was produced. Here, a procedure similar to that of the production of the transfer mask in Example 1 is performed, and a thin film pattern 11P is formed by patterning a pattern forming thin film 11 made of silicon nitride (SiNx) on a translucent substrate 10. A transfer mask 100 of Example 1 was obtained. The opening width of the space pattern formed in each step is also shown in FIG. In Example 2 as well, when the first hard mask film 12 is etched using the second hard mask pattern 13P as a mask, tantalum (Ta) contained in the second hard mask pattern 13P is oxidized. 2 The hard mask pattern 13P was swollen. That is, the second hard mask film 13 contained tantalum unsaturated with respect to oxygen.

<Example 3>
[Preparation of mask blank (see FIGS. 4 and 7)]
As a mask blank of Example 3, a mask blank 2 used for manufacturing a reflective transfer mask was produced as follows.

First, a multilayer reflective film 21 was formed on a substrate 20 made of low-expansion glass having a thickness of about 6.35 mm, and a protective film 22 made of a ruthenium-niobium alloy (RuNb) was formed on the multilayer reflective film 21 . The multilayer reflective film 21 and protective film 22 were used as a base film. The total film thickness of the underlying film was set to 289 nm.

On the base film, a first thin film 11-1 of the pattern forming thin film 11' was formed of tantalum nitride (TaNx) by sputtering, and then a second thin film 11-2 of tantalum oxide (TaOx) was formed by sputtering. The total film thickness of the pattern forming thin film 11' was set to 62 nm.

A first hard mask film 12 of chromium oxide carbonitride (CrOCN) was sputtered to a thickness of 6 nm on the pattern forming thin film 11'. Furthermore, using a tantalum (Ta) target, reactive sputtering is performed in a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) to form a second film made of tantalum nitride (TaNx) on the first hard mask film 12 . A hard mask film 13 was formed by sputtering to a film thickness of 3 nm. A mask blank 2 of Example 3 was obtained by forming a chemically amplified positive resist with a thickness of 40 nm as a resist film 14 on the second hard mask film 13 . The ratio O/Ta of the content of oxygen (O) to the content of tantalum (Ta) in the second hard mask film 13 is 0, and the tantalum (Ta) in the second hard mask film 13 is was unsaturated.

[Preparation of transfer mask (see FIGS. 5 and 6)]
A method of manufacturing a reflective transfer mask using the mask blank 2 of Example 3 will be described with reference to FIGS. 5 and 6. FIG.

First, as shown in step (1) of FIG. 5, a space pattern 14a having an opening width [W14]=26 nm was formed in the resist film 14 by lithography. This aperture width [W14] is the minimum space width by lithography processing for manufacturing a reflective transfer mask at present.

Next, as shown in step (2) of FIG. 5, the patterned resist film 14 was used as a mask to etch the second hard mask film 13 . At this time, the second hard mask film 13 made of tantalum nitride (TaNx) is patterned by dry etching using a fluorine-based gas (SF ₆ +He) as an etchant to form a second hard mask pattern 13P having a space pattern 13a. bottom. In this etching, the second hard mask film 13 made of tantalum nitride (TaNx) was etched with good anisotropy.
Therefore, the opening width [W13] of the space pattern 13a formed in the second hard mask pattern 13P is approximately the same as the opening width [W14] of the space pattern 14a formed in the resist film 14, and the opening width [W13]=26 nm.

Thereafter, as shown in step (3) of FIG. 5, the first hard mask film 12 was etched using the second hard mask pattern 13P as a mask. At this time, by dry etching using oxygen-containing chlorine gas (Cl ₂ +O ₂ ) as an etchant, the first hard mask film 12 made of chromium oxide carbonitride (CrOCN) is patterned to form a first hard mask having a space pattern 12a. A pattern 12P was formed.

In this etching, the second hard mask pattern 13P is exposed to an oxygen-containing chlorine gas (Cl ₂ +O ₂ ), and the tantalum (Ta) contained in the second hard mask pattern 13P is oxidized so that the second hard mask pattern 13P is swollen. That is, the second hard mask film 13 in Example 3 contained tantalum unsaturated with respect to oxygen. Due to this oxidation of tantalum, the opening width [W13] of the space pattern 13a of the second hard mask pattern 13P was reduced to 20 nm due to the swelling of the second hard mask pattern 13P [W13'].

In this etching, the first hard mask film 12 made of chromium oxide carbonitride (CrOCN) was isotropically etched. Therefore, the opening width [W12] of the space pattern 12a formed in the first hard mask pattern 12P is larger than the opening width [W13'] of the reduced space pattern 13a, and the opening width [W12]=24 nm. rice field. Resist film 14 left on second hard mask pattern 13P was removed by ashing with an etchant containing oxygen.

Next, as shown in step (4) of FIG. 6, the second thin film 11-2 of the pattern forming thin film 11' was etched using the first hard mask pattern 12P as a mask. At this time, the second thin film 11-2 of the pattern forming thin film 11' made of tantalum oxide (TaOx) was patterned by dry etching using a fluorine-based gas (SF ₆ +He) as an etchant. In this etching, the second thin film 11-2 made of tantalum oxide (TaOx) was anisotropically etched well. Further, when etching the second thin film 11-2, the second hard mask pattern 13P including the oxidized portion 13b was removed.

Subsequently, as shown in step (5) of FIG. 6, using the first hard mask pattern 12P as a mask, the first thin film 11-1 of the pattern forming thin film 11' was etched. At this time, the first thin film 11-1 of the pattern forming thin film 11' made of tantalum nitride (TaNx) was patterned by dry etching using chlorine gas ( _Cl.sub.2 ) as an etchant. In this etching, the first thin film 11-1 made of tantalum nitride (TaNx) was etched with good anisotropy.

Thus, a thin film pattern 11P' was formed by patterning the first thin film 11-1 and the second thin film 11-2 of the pattern forming thin film 11'. The opening width [W11'] of the space pattern 11a' formed in the thin film pattern 11P' is approximately the same as the opening width [W12] of the first hard mask film 12, and the opening width [W11']=26 nm. became. Note that this etching removed the first hard mask pattern 12P.

As described above, the thin film pattern 11P′ formed by patterning the pattern forming thin film 11′ having a laminated structure of tantalum nitride (TaNx) and tantalum oxide (TaOx) on the substrate 20 is provided as a light absorption pattern according to the third embodiment. A reflective transfer mask 200 was obtained.

<Evaluation Results of Examples and Comparative Examples>
As shown in FIG. 7, in the production of the transfer mask using the mask blanks of Examples 1 to 3, the opening width [W11] of each space pattern 11a, 11a' formed in the pattern forming thin films 11, 11' , [W11'] were about the same as the opening width [W14] of the space pattern 14a formed in the resist film 14. FIG. Specifically, the rate of increase in the width dimension from the opening width [W14] of the space pattern 14a formed in the resist film 14 is 6% in Example 1 and 0% in Examples 2 and 3, which is low. value was suppressed. Note that the increase rate of the width dimension described above is the value obtained by subtracting the opening width [W14] from the opening width [W11] or the opening width [W11′] and dividing the value by [W14] (([ W11]-[W14])/[W14] or ([W11']-[W14])/[W14]). On the other hand, in the production of the transfer mask using the mask blank of Comparative Example 1, the opening width [W11] of the space pattern 11a formed in the pattern forming thin film 11 was equal to that of the space pattern 14a formed in the resist film 14. It was 6 nm larger than the aperture width [W14]. That is, the rate of increase in the width dimension in Comparative Example 1 was a large value of 18%. Similarly, in Comparative Example 2, the opening width [W11] of the space pattern 11a formed in the pattern forming thin film 11 is 6 nm larger than the opening width [W14] of the space pattern 14a formed in the resist film 14. , the increase rate of the width dimension was 18%.

From this, it was confirmed that the mask blank to which the present invention is applied can form a fine space pattern on the pattern-forming thin film.

Further, by comparing Example 1 and Example 2, the smaller the amount of oxidation of tantalum (Ta) contained in the second hard mask film 13, the larger the amount of swelling of the second hard mask pattern 13P and the shrinkage due to the swelling. It was confirmed that the opening width [W13'] was made smaller. It was also confirmed that the amount of swelling of the second hard mask pattern 13P can be controlled by the amount of oxidation of tantalum (Ta) contained in the second hard mask film 13. FIG.

Moreover, by using the mask blank to which the present invention is applied, it is possible to manufacture a transfer mask having a fine pattern, and a semiconductor device manufactured using the transfer mask thus manufactured can be highly integrated. It was confirmed that it is possible to achieve

DESCRIPTION OF SYMBOLS 1, 2... Mask blank 10... Translucent substrate 11, 11'... Thin film for pattern formation 11P, 11P'... Thin film pattern 12... First hard mask film 12P... First hard mask pattern 13... Second hard mask film 13P ... second hard mask pattern 20 ... substrate 100, 200 ... transfer mask

Claims (11)

A mask blank having a structure in which a pattern-forming thin film, a first hard mask film, and a second hard mask film are laminated in this order on a main surface of a substrate,
The pattern-forming thin film contains at least one element selected from silicon and transition metals,
the first hard mask film contains chromium,
the second hard mask film contains tantalum,
the tantalum of the second hard mask film includes tantalum unsaturated with respect to oxygen;
The film thickness of the thin film for pattern formation is 20 nm or more,
the film thickness of the first hard mask film is 15 nm or less;
A mask blank, wherein the film thickness of the second hard mask film is 10 nm or less. A mask blank having a structure in which a pattern-forming thin film, a first hard mask film, and a second hard mask film are laminated in this order on a main surface of a substrate,
The pattern-forming thin film contains at least one element selected from silicon and transition metals,
the first hard mask film contains chromium,
The second hard mask film contains tantalum and swells in an oxygen-containing gas atmosphere,
The film thickness of the thin film for pattern formation is 20 nm or more,
the film thickness of the first hard mask film is 15 nm or less;
A mask blank, wherein the film thickness of the second hard mask film is 10 nm or less. 3. The mask blank according to claim 1, wherein the ratio of the oxygen content to the tantalum content of the second hard mask film is 1.5 or less. 4. The mask blank according to any one of claims 1 to 3, wherein the second hard mask film contains the most tantalum among metal elements and silicon. The mask blank according to any one of claims 1 to 4, wherein the film thickness of the second hard mask film is 1 nm or more. 6. The mask blank according to any one of claims 1 to 5, wherein the first hard mask film contains chromium and at least one of oxygen and nitrogen. The mask blank according to any one of claims 1 to 6, wherein the thickness of the first hard mask film is thicker than the thickness of the second hard mask film. The thin film for pattern formation is a light absorbing film containing tantalum,
8. The mask blank according to any one of claims 1 to 7, further comprising a multilayer reflective film between the substrate and the pattern-forming thin film. The mask blank according to any one of claims 1 to 8, wherein the pattern-forming thin film is a light-shielding film containing silicon. A method for manufacturing a transfer mask using the mask blank according to any one of claims 1 to 9,
using a resist film formed on the second hard mask film and having a pattern as a mask;
forming a second hard mask pattern on the second hard mask film by dry etching;
Using the second hard mask pattern as a mask, etching sidewalls of the second hard mask pattern are swelled by oxidation by dry etching using a gas containing oxygen, and the first hard mask pattern is formed on the first hard mask film. forming;
and forming a thin film pattern on the pattern forming thin film by dry etching using the first hard mask pattern as a mask. Using a transfer mask manufactured by the method for manufacturing a transfer mask according to claim 10,
A method of manufacturing a semiconductor device, comprising an exposure step of pattern-transferring the thin film pattern of the transfer mask onto a resist film on a semiconductor device substrate by a lithography method.

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