JP2001174973A - Halftone phase shift photomask and blanks for same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a halftone phase shift photomask and blanks for the photomask having an enhanced etching selectivity ratio of a tantalum silicide- base material to a quartz substrate while retaining superior working characteristics of the tantalum silicide-base material and superior chemical stability after working. SOLUTION: The blanks 104 and the halftone phase shift photomask have a halftone phase shift layer on a transparent substrate 101 and the phase shift layer comprises a multilayer film including at least a layer 103 consisting essentially of tantalum, silicon and oxygen and a layer 102, based on tantalum and not substantially containing silicon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LSI,
Photomask used for manufacturing high-density integrated circuits and the like, and a photomask blank for manufacturing the photomask, in particular, a halftone phase shift photomask capable of obtaining a projection image of fine dimensions, and the phase shift photomask The present invention relates to a blank for a halftone phase shift photomask for manufacturing the same.

[0002]

2. Description of the Related Art Semiconductor integrated circuits such as ICs, LSIs, and VLSIs are manufactured by repeating a so-called lithography process using a photomask. Use of a phase shift photomask as disclosed in Japanese Patent Publication No. 173744, Japanese Patent Publication No. 62-59296, and the like has been studied. Various types of phase shift photomasks have been proposed.
A so-called halftone phase shift photomask as disclosed in Japanese Patent Application Laid-Open No. 854-854 and US Pat. No. 4,890,309 has attracted attention from the viewpoint of early commercialization.
Some proposals have been made with respect to structures and materials capable of improving the yield and reducing the cost by reducing the number of manufacturing steps, such as Japanese Patent Application Laid-Open No. 2259 and Japanese Patent Application Laid-Open No. 5-127361.

Here, a halftone phase shift photomask will be briefly described with reference to the drawings. FIG. 6 shows the principle of the halftone phase shift method, and FIG. 7 shows the conventional method. FIGS. 6A and 7A are cross-sectional views of the photomask, FIGS. 6B and 7B are the amplitudes of light on the photomask, and FIGS. 6C and 7C are FIGS. 6 (d) and 7 (d) show the light intensity on the wafer, respectively, and 911 and 921 the substrate and 922, respectively.
Denotes a 100% light shielding film, and 912 denotes a phase of incident light substantially equal to 1.
Halftone phase shift films 913 and 923 shifted by 80 ° and having a transmittance of 1 to 50% are incident light. In the conventional method, as shown in FIG. 7A, a substrate 921 made of quartz glass or the like
Only a 0% light-shielding film 922 is formed to form a light transmitting portion of a desired pattern, and the light intensity distribution on the wafer spreads as shown in FIG. 7D, resulting in poor resolution. I will. On the other hand, in the halftone phase shift method,
Since the phases of the light transmitted through the halftone phase shift film 912 and the light transmitted through the opening thereof are substantially inverted,
As shown in FIG. 6D, the light intensity at the pattern boundary on the wafer becomes 0, and the spread of the skirt can be suppressed, and therefore, the resolution can be improved.

It should be noted that in phase shift lithography of a type other than halftone, since the light shielding film and the phase shifter film are made of different materials and patterns, at least two plate making steps are required. On the other hand, halftone phase shift lithography has only one pattern, so that the plate making process is essentially required only once, which is a great advantage of halftone phase shift lithography.

Incidentally, the halftone phase shift film 912 of the halftone phase shift photomask is required to have two functions of phase inversion and transmittance adjustment. Among them, the phase inversion function may be such that the phase is substantially inverted between the exposure light transmitted through the halftone phase shift film 912 and the exposure light transmitted through the opening. Here, the halftone phase shift film 912
For example, Born, E .; Wolf "Prin
chips optics ”, pages 628 to 632, multiple interference can be ignored, and the phase change φ of vertically transmitted light is When φ is in the range of nπ ± π / 3 (n is an odd number), the above-described phase shift effect is obtained. In equation (1), φ is a phase change received by light that vertically transmits through a photomask having a (m−2) multilayer film formed on a substrate, and χ ^{k, k + 1} is k Layer and (k + 1)
The phase change occurring at the interface with the k-th layer, u _k and d _k are the refractive index and the film thickness of the material constituting the k-th layer, respectively, and λ is the wavelength of the exposure light. Here, the layer where k = 1 is the transparent substrate, and the layer where k = m is air.

On the other hand, the exposure light transmittance of the halftone phase shift film 912 for obtaining the halftone phase shift effect is determined by the dimensions, area, arrangement, shape, etc. of the transfer pattern, and differs depending on the pattern. In order to substantially obtain the above-described effects, the exposure light transmittance of the halftone phase shift film must be within the range of the optimum transmittance ± several% around the optimum transmittance determined by the pattern. No. Normally, the optimum transmittance greatly varies within a wide range of 1 to 50% depending on the transfer pattern when the opening is 100%. That is, a halftone phase shift photomask having various transmittances is required to correspond to all patterns.

[0007] Actually, the phase inversion function and the transmittance adjusting function correspond to the complex refractive index (refractive index and extinction) of the material constituting the halftone phase shift film (in the case of a multilayer, each material constituting each layer). Coefficient) and the film thickness. That is,
A material in which the thickness of the halftone phase shift film is adjusted and the phase difference φ obtained by the above equation (1) is included in the range of nπ ± π / 3 (n is an odd number) is used for the halftone phase shift photomask. Can be used as a halftone phase shift layer.

By the way, generally, as a thin film material for a photomask pattern, for example, Japanese Patent Application Laid-Open No. 57-64739
JP, JP-B-62-51460, JP-B-62-51460
A tantalum-based material as disclosed in Japanese Patent Application Laid-Open No. 51461 is known, and its processing characteristics, chemical stability after processing, and the like are extremely excellent.
No. 96, JP-A-7-134396, JP-A-7-134396
As described in JP-A-281414, attempts to apply tantalum to a halftone phase shift film by oxidizing or nitriding tantalum have been actively studied. Further, as the exposure wavelength becomes shorter with the miniaturization of LSI patterns, a tantalum silicide-based material corresponding to shorter wavelength exposure, for example, as disclosed in JP-A-6-83027, is used. Research has also proceeded.

[0009]

However, in general, tantalum silicide is composed of CF ₄ , CHF ₃ , SF ₆ ,
Dry etching is performed using a fluorine-based etching gas such as C ₂ F ₆ , NF ₃ , CF ₄ + H ₂ , or CBrF _3. At this time, a transparent substrate such as synthetic quartz as a substrate material is also etched. Accurate dry etching is not possible,
There was a problem. Generally, in the manufacture of a halftone phase shift photomask, high precision control of the phase angle is indispensable. However, as described above, when the quartz substrate is also etched during the etching of the halftone phase shift film. However, an error occurs in the phase difference by the amount of the excavation. Also, since the etching of the halftone phase shift film plays an important role in controlling the pattern dimensions, it is desirable to set conditions so as to obtain the best possible uniformity and reproducibility of the pattern dimensions. There is also a problem that the addition of a new parameter called an etching selectivity causes the margin for setting conditions to be narrowed. This is a problem that arises because the optimum etching process for dimensional control does not always match the optimum etching process for emphasizing the phase difference control. In other words, the tantalum silicide-based halftone phase shift film material itself exhibits excellent processing characteristics and chemical stability after processing, but when high-precision control of the phase difference is also taken into account, high-precision patterning is possible. The problem is that it becomes difficult.

The present invention has been made in view of such circumstances of the prior art, and has as its object to maintain excellent processing characteristics of tantalum silicide-based materials, chemical stability after processing, etc. An object of the present invention is to provide a halftone phase shift photomask and a blank for the halftone phase shift photomask, which have an improved etching selectivity with respect to a substrate.

[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a halftone phase shift film composed of a multilayer film, wherein one of the layers is formed of a material having a sufficiently large etching selectivity with a transparent substrate. The research has been completed to develop a halftone phase shift photomask and a blank for the halftone phase shift photomask capable of high precision processing.

That is, the present invention relates to a halftone phase shift photomask including a layer mainly composed of tantalum, silicon, and oxygen as a halftone phase shift layer, and a blank for the halftone phase shift photomask. By providing one layer substantially free of silicon as a component, the above-described high-precision patterning is achieved. Here, a film substantially free of silicon as a main component tantalum, can also be etched with a chlorine-based etching gas, such as Cl _2, CH ₂ Cl _2, in these chlorine-based gases, synthetic quartz Is not substantially etched.

Here, it is desirable that the film mainly containing tantalum and containing substantially no silicon is formed as the first layer immediately above the transparent substrate because of its role. For example, first, on a synthetic quartz, a film mainly containing tantalum and containing substantially no silicon is formed, and then tantalum, silicon,
In the case where a film mainly composed of oxygen is formed and a halftone phase shift film is formed by these two layers, first, in the patterning, a film mainly composed of tantalum, silicon, and oxygen is etched with a fluorine-based dry etching gas. By performing etching and then patterning with a chlorine-based dry etching gas while maintaining a sufficient dry etching selectivity with respect to the substrate, highly accurate phase difference control becomes possible. Further, this halftone phase shift film has excellent chemical stability and workability, which are characteristics of a tantalum-based thin film, and uses a silicide film, so that krypton fluoride excimer laser lithography (exposure wavelength: 2
48 nm) and also has sufficient translucency for argon fluoride excimer laser lithography (exposure wavelength: 193 nm), so that it can be used as a halftone phase shift film.

FIG. 4 shows a typical optical characteristic spectrum of the blank for a halftone phase shift photomask thus obtained. In general, it is considered that this optical characteristic spectrum is sufficient for practical use. However, it is expected that the reflectivity of the film surface may be slightly high. That is, in general, the film surface reflectance of exposure light is 30
% Or less, preferably 20% or less. In such a case, it is possible to provide a third film between this film and the transparent substrate in order to change the reflectance spectrum. In this case, if this film is sufficiently thin, even if the etching selectivity between the film and the transparent substrate is low, it is considered that substantially no large error is caused in the phase difference. For example, tantalum, silicon, tantalum, silicon,
It is also possible to form a film mainly composed of oxygen by several tens to 100 degrees. In this case, it is possible to freely change the reflectance spectrum by changing the thickness of the thin film within the above range, and since the thickness is small, the influence on the mask phase difference is small even if the selectivity is poor. .

The reflectance spectrum can also be controlled by adding a small amount of oxygen or nitrogen to a film mainly containing tantalum and containing substantially no silicon.

As described above, according to the blank for a halftone phase shift photomask of the present invention, the halftone phase shift layer on the transparent substrate is made of tantalum, silicon, and silicon.
It is characterized by comprising a multilayer film including at least one layer mainly containing oxygen and one layer mainly containing tantalum and substantially not containing silicon.

In this case, one layer mainly containing tantalum and containing substantially no silicon is first formed on the transparent substrate, and one layer mainly containing tantalum, silicon and oxygen is formed thereon. Can be

Further, one layer containing tantalum as a main component and containing substantially no silicon may contain oxygen or nitrogen.

The halftone phase shift layer has a phase difference φ obtained by the following equation on a transparent substrate: nπ ± π / 3
It is desirable to form the radian (n is an odd number).

[0020] Here, φ is a phase change received by light vertically transmitting through a photomask blank in which a (m−2) -layer multilayer film is formed on a transparent substrate, and χ ^{k, k + 1} is a k-th phase change. Phase change occurring at the interface between the layer and the (k + 1) th layer, u _k ,
d _k is the refractive index and film thickness of the material forming the k-th layer, and λ is the wavelength of the exposure light. However, the layer where k = 1 is a transparent substrate, and the layer where k = m is air.

Further, the transmittance of the halftone phase shift layer to the exposure light is 1 to 50% when the transmittance of the transparent substrate to the exposure light is 100%. Preferably, it is formed.

The absolute reflectance of the surface on which the halftone phase shift layer is formed with respect to the exposure light is 0 to 30%.
It is desirable that

The blank for a halftone phase shift photomask according to the present invention includes a halftone phase shift layer on which a light-shielding film mainly composed of chromium is continuously formed, or a halftone phase shift photomask. A pattern of a light-shielding film containing chromium as a main component may be formed below the layer.

According to the halftone phase shift photomask of the present invention, the halftone phase shift layer on the transparent substrate comprises one layer mainly composed of tantalum, silicon and oxygen;
It is characterized by comprising a multilayer film containing at least one layer containing tantalum as a main component and substantially not containing silicon.

In this case, one layer mainly containing tantalum and containing substantially no silicon is first formed on the transparent substrate, and one layer mainly containing tantalum, silicon and oxygen is formed thereon. Can be

One layer containing tantalum as a main component and containing substantially no silicon may contain oxygen or nitrogen.

Further, the halftone phase shift layer has a phase difference φ obtained by the following equation on the transparent substrate, which is nπ ± π / 3.
It is desirable to form the radian (n is an odd number).

[0028] Here, φ is a phase change received by light vertically transmitted through a photomask in which a (m−2) -layer multilayer film is formed on a transparent substrate, and χ ^{k, k + 1} are the k-th layer and the The phase change occurring at the interface with the (k + 1) -th layer, u _k and d _k are the refractive index and the film thickness of the material forming the k-th layer, respectively, and λ is the wavelength of the exposure light. However, the layer where k = 1 is a transparent substrate, and k = m
Layer shall be air.

The transmittance of the halftone phase shift layer for exposure light is 1% when the transmittance of the opening of the halftone phase shift layer for the exposure light is 100%.
It is desirable to be 50% to 50%.

The absolute reflectance of the surface on which the halftone phase shift layer is formed with respect to the exposure light is 0 to 30%.
It is desirable that

The halftone phase shift photomask of the present invention has a pattern of a light-shielding film mainly composed of chromium formed on a pattern of a halftone phase shift layer, or a halftone phase shift photomask. Under the pattern of the layer, a pattern of a light-shielding film containing chromium as a main component may be formed.

In the halftone phase shift photomask and the blank for a halftone phase shift photomask of the present invention, the halftone phase shift layer on the transparent substrate is composed of one layer mainly composed of tantalum, silicon and oxygen. Since it is composed of a multilayer film containing at least one layer containing tantalum as a main component and substantially not containing silicon, in addition to the chemical stability and processing characteristics specific to tantalum-based materials, short films specific to silicide-based materials are obtained. While maintaining wavelength applicability, a sufficient etching selectivity with a transparent substrate such as synthetic quartz can be obtained, enabling highly accurate patterning, and
An ideal mask member having excellent stability after mask processing can be realized.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a halftone phase shift photomask and a blank for a halftone phase shift photomask according to the present invention will be described.

[Embodiment 1] An embodiment of a blank for a KrF exposure halftone phase shift photomask according to the present invention will be described with reference to FIGS. In this embodiment, the halftone phase shift film is composed of two layers.

As shown in FIG. 1A, optical polishing is performed.
A first layer 102 of a halftone phase shift film is formed on a 6-inch square, 0.25-inch thick high-purity synthetic quartz substrate 101 that has been well cleaned under the following conditions. Here, the thickness of the first layer 102 is about 25 nm.

Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Metal tantalum Gas and flow rate: Argon gas 50 sccm Sputter pressure: 0.3 Pascal Sputter current: 3.0 amps Next, a halftone phase shift is continuously performed on this. The second of the membrane
The layer 103 is formed under the following conditions. Here, the second layer 1
03 has a thickness of about 140 nm.

Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Tantalum: Silicon = 1: 3 (atomic ratio) Gas and flow rate: Argon gas 50 sccm + Oxygen gas 50 sccm Sputter pressure: 0.3 Pascal Sputter current: 3.5 amps As a result, a blank 104 for a halftone phase shift photomask having a transmittance of 6% for KrF excimer laser exposure according to the present invention is obtained. FIG. 4 shows the optical characteristic spectrum of this blank.

As shown in FIG. 1B, a sample was formed on a synthetic quartz substrate which had been previously masked with a tape or the like under the same conditions, and a step was formed by a lift-off method in which the masking was removed after the film formation. 105 is produced and used,
When the phase difference and the transmittance with respect to the light having a wavelength of 248 nm were measured by a commercially available phase difference measuring device (MPM248 manufactured by Lasertec), they were 182.62 ° and 5.37%, respectively.

Next, the results of examining the resistance of the sample 105 to chemicals such as a cleaning solution and an etching solution used in the photomask manufacturing process are shown below.

Chemical solution (a) Sulfuric acid: nitric acid = 10: 1 (volume ratio), temperature: 80 ° C. Chemical solution (b) 10% aqueous ammonia, room temperature Chemical solution (c) Commercially available chromium etchant (MR-ES manufactured by Inktec), room temperature

[Embodiment 2] An embodiment of a halftone phase shift photomask of the present invention will be described with reference to the manufacturing process diagram of FIG.

As shown in FIG. 2A, a desired resist pattern containing an organic substance as a main component is formed on the blanks 201 (104) obtained in Example 1 by a conventional electron beam lithography method or photolithography method. 202 was obtained.

Next, as shown in FIG. 2B, a commercially available dry etcher for a photomask (VLR7 manufactured by PTI) is used.
00), the halftone phase shift film (102 + 103) exposed from the resist pattern 202 was selectively dry-etched by exposing it to high-density plasma to obtain a desired halftone phase shift film pattern 203. The dry etcher used in this experiment had two etching processing chambers, and the following conditions 1 and 2 were performed in separate processing chambers.

Condition 1 Etching gas CF ₄ gas pressure 10 mTorr ICP power (generation of high-density plasma) 950 W bias power (drawing power) 50 W time 360 seconds Condition 2 Etching gas Cl ₂ gas pressure 3 mTorr ICP power (generation of high-density plasma) 500 W bias Power (pull-out power) 25 W time 200 seconds Next, the remaining resist 204 is peeled off by a conventional method, and FIG.
As shown in (c), a halftone phase shift photomask 205 having a transmittance of 6% for the wavelength 248 nm light of the halftone phase shift portion was obtained. What should be noted here is
In the etching under the condition 2, the synthetic quartz as the substrate is hardly etched, and extremely high-precision phase difference control is possible.

The halftone phase shift photomask 205 can be put to practical use in terms of dimensional accuracy, cross-sectional shape, film thickness distribution, transmittance distribution, adhesion of the film to the substrate, etc. of the removed portion. Things.

[Embodiment 3] With respect to the blank for a halftone phase shift photomask for KrF exposure of the present invention, an embodiment of a blank having a lower film surface reflectance at a wavelength of 248 nm than the blank of the embodiment 1 is shown in FIG. The manufacturing process will be described with reference to the drawings. Here, a low reflection is realized by adding a small amount of oxygen to a tantalum-based film substantially containing no silicon among the two layers constituting the halftone phase shift film.

As shown in FIG. 3A, optical polishing is performed.
A first layer 302 of a halftone phase shift film is formed on a well-washed 6-inch square, 0.25-inch thick high-purity synthetic quartz substrate 301 under the following conditions. Here, the thickness of the first layer 302 is about 40 nm.

Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Metal tantalum gas and flow rate: Argon gas 40 sccm + Oxygen gas 5 sccm Sputter pressure: 0.3 Pascal Sputter current: 2.0 amps Second of the tone phase shift film
The layer 303 is formed under the following conditions. Here, the second layer 3
03 has a thickness of about 90 nm.

Film forming apparatus: Planar type DC magnetron sputtering apparatus Target: Tantalum: Silicon = 1: 3 (atomic ratio) Gas and flow rate: Argon gas 50 sccm + Oxygen gas 50 sccm Sputter pressure: 0.3 Pascal Sputter current: 3.5 amperes As a result, a blank 304 for a halftone phase shift photomask having a transmittance of 6% for KrF excimer laser exposure according to the present invention is obtained. FIG. 5 shows the optical characteristic spectrum of this blank.

As shown in FIG. 3 (b), a sample was formed on a synthetic quartz substrate previously masked with a tape or the like under the same conditions, and a step was formed by a lift-off method in which the masking was peeled off after the film formation. 305 is manufactured and used,
The phase difference and transmittance with respect to the light having a wavelength of 248 nm were measured with a commercially available phase difference measuring device (MPM248 manufactured by Lasertec Co., Ltd.), and were 186.59 ° and 6.07%, respectively.

FIG. 5 shows the film surface reflection spectrum of this blank. Wavelength 24 of blanks of Example 1 shown in FIG.
While the film surface reflectance at 8 nm is about 43%, in the case of this embodiment, it can be reduced to about 2%, and a low reflectance can be realized.

[0052]

As is apparent from the above description, according to the halftone phase shift photomask and the blank for the halftone phase shift photomask of the present invention, the halftone phase shift layer on the transparent substrate is made of tantalum, silicon, And a multilayer film including at least one layer containing oxygen as a main component and one layer containing tantalum as a main component and containing substantially no silicon, so that the chemical stability unique to the tantalum-based material is achieved. In addition to processing characteristics, while maintaining the short wavelength applicability unique to silicide, a sufficient etching selectivity with a transparent substrate such as synthetic quartz can be obtained, enabling high-precision patterning, and after mask processing. An ideal mask member having excellent stability can be realized.
As a result, a high-precision halftone phase shift photomask can be realized with good yield and at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a manufacturing process of a blank for a halftone phase shift photomask according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a manufacturing process of a halftone phase shift photomask according to a second embodiment of the present invention.

FIG. 3 is a diagram for explaining a manufacturing process of a blank for a halftone phase shift photomask according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a transmittance and a reflectance spectrum of a blank for a halftone phase shift photomask of Example 1 of the present invention.

FIG. 5 is a diagram showing a transmittance and a reflectance spectrum of a blank for a halftone phase shift photomask of Example 3 of the present invention.

FIG. 6 is a diagram illustrating the principle of halftone phase shift lithography.

FIG. 7 is a diagram showing the principle of a conventional method.

[Explanation of symbols]

101: High-purity synthetic quartz substrate 102: First layer of a halftone phase shift film (a film containing tantalum as a main component and substantially containing no silicon) 103: Second layer of a halftone phase shift film (tantalum, silicon, and , A film mainly composed of oxygen) 104: blanks for a halftone phase shift photomask 105: samples for measuring phase difference and transmittance 201: blanks for a halftone phase shift photomask (104) 202: resist pattern 203: halftone phase Shift film pattern 204: Resist pattern remaining after dry etching 205: Halftone phase shift photomask 301: High-purity synthetic quartz substrate 302: First layer of halftone phase shift film (substantially containing tantalum as a main component and a small amount of oxygen Film that does not contain silicon) 303 A second layer of a halftone phase shift film (tantalum, silicon, and film oxygen mainly) 304 ... halftone phase shift photomask blank 305 ... phase difference, a sample for transmittance measurement

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Takashi Okamura, Inventor 1-1-1, Ichigaya-Kagacho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. (72) Yoshinori Kinase 1-chome, Ichigaya-cho, Shinjuku-ku, Tokyo No. 1-1 Inside Dai Nippon Printing Co., Ltd. (72) Hiroshi Mohri 1-1-1, Ichigaya Kagacho, Shinjuku-ku, Tokyo Inside Dainippon Printing Co., Ltd. (72) Junji Fujikawa, Ichigaya-cho, Shinjuku-ku, Tokyo 1-1-1 Dai Nippon Printing Co., Ltd. F term (reference) 2H095 BB02 BB03 BC11

Claims (16)

[Claims] 1. A halftone phase shift layer on a transparent substrate, wherein the halftone phase shift layer mainly comprises tantalum, silicon, and oxygen.
A blank for a halftone phase shift photomask, comprising: a multilayer film including at least a layer and one layer containing tantalum as a main component and substantially not containing silicon. 2. A layer according to claim 1, wherein a layer containing tantalum as a main component and containing substantially no silicon is first formed on the transparent substrate, and a layer containing tantalum, silicon and oxygen as main components is formed thereon. A blank for a halftone phase shift photomask, characterized in that a blank is formed. 3. The blank for a halftone phase shift photomask according to claim 1, wherein one layer containing tantalum as a main component and substantially not containing silicon contains oxygen or nitrogen. 4. In any one of claims 1 to 3,
A halftone phase shift layer formed on a transparent substrate such that a phase difference φ determined by the following equation is in a range of nπ ± π / 3 radians (n is an odd number). Blanks for photomasks. Here, φ is a phase change received by light vertically transmitting through a photomask blank in which a (m−2) -layer multilayer film is formed on the transparent substrate, and χ ^{k, k + 1} is a k-th phase change. Phase change occurring at the interface between the (k + 1) th layer and the
u _k and d _k are the refractive index and the thickness of the material constituting the k-th layer, respectively, and λ is the wavelength of the exposure light. However, the layer where k = 1 is the transparent substrate, and the layer where k = m is air. 5. The method according to claim 1, wherein:
The transmittance of the halftone phase shift layer for exposure light is
A half-tone phase shift photomask formed on the transparent substrate to have a thickness of 1 to 50% when the transmittance of the transparent substrate to the exposure light is 100%. Blanks. 6. In any one of claims 1 to 5,
A blank for a halftone phase shift photomask, wherein the absolute reflectance of the surface on which the halftone phase shift layer is formed with respect to exposure light is 0 to 30%. 7. The method according to claim 1, wherein:
A blank for a halftone phase shift photomask, characterized in that a light shielding film containing chromium as a main component is continuously formed on the halftone phase shift layer. 8. The method according to claim 1, wherein:
A blank for a halftone phase shift photomask, wherein a pattern of a light shielding film containing chromium as a main component is formed under the halftone phase shift layer. 9. A halftone phase shift layer on a transparent substrate, wherein the halftone phase shift layer mainly contains tantalum, silicon, and oxygen.
A halftone phase shift photomask comprising a multilayer film including at least a layer and one layer containing tantalum as a main component and substantially not containing silicon. 10. A layer according to claim 9, wherein one layer mainly containing tantalum and substantially containing no silicon is formed on the transparent substrate, and one layer mainly containing tantalum, silicon and oxygen is formed thereon. A halftone phase shift photomask, wherein 11. The halftone phase shift photomask according to claim 9, wherein one layer containing tantalum as a main component and containing substantially no silicon contains oxygen or nitrogen. 12. The halftone phase shift layer according to claim 9, wherein a phase difference φ on the transparent substrate is nπ ± π / 3 radians (n is an odd number) obtained by the following equation. A halftone phase shift photomask, characterized in that it is formed so that Here, φ is a phase change received by light vertically transmitted through a photomask having a multilayer film of (m−2) layers on the transparent substrate, and χ ^{k, k + 1} is a k-th layer. And (k + 1)
The phase change occurring at the interface with the k-th layer, u _k and d _k are the refractive index and the film thickness of the material constituting the k-th layer, respectively, and λ is the wavelength of the exposure light. However, the layer where k = 1 is the transparent substrate, and the layer where k = m is air. 13. The halftone phase shift layer according to claim 9, wherein a transmittance of the halftone phase shift layer to exposure light is 100%, and a transmittance of the opening of the halftone phase shift layer to the exposure light is 100%. Sometimes 1 to 50%
A halftone phase shift photomask, characterized in that: 14. The halftone phase according to claim 9, wherein an absolute reflectance of the surface on which the halftone phase shift layer is formed with respect to exposure light is 0 to 30%. Shift photomask. 15. The halftone according to claim 9, wherein a pattern of a light-shielding film containing chromium as a main component is formed on the pattern of the halftone phase shift layer. Phase shift photomask. 16. The halftone according to claim 9, wherein a pattern of a light-shielding film containing chromium as a main component is formed under the pattern of the halftone phase shift layer. Phase shift photomask.