JP2001337436A - Halftone phase shift photomask and blanks for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a halftone phase shift photomask with a structure using a tantalum silicide-base halftone phase shift film material and having an enhanced etching selectivity ratio to a quartz substrate while retaining superior workability and chemical stability after working peculiar to the tantalum silicide-base material and to provide blanks for a halftone phase shift photomask capable of manufacturing such halftone phase shift photomasks. SOLUTION: A halftone phase shift layer on a transparent substrate comprises a multilayer film including at least a layer consisting essentially of tantalum, silicon and oxygen and a layer based on chromium or a chromium-tantalum alloy. The latter layer is first formed on the transparent substrate and the former layer is formed on the latter layer.

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 a phase shift photomask The present invention relates to a blank for a halftone phase shift photomask for manufacturing a mask.

[0002]

2. Description of the Related Art Semiconductor integrated circuits such as ICs, LSIs, and VLSIs are manufactured by repeating a lithography process using a photomask. The use of a phase shift photomask as disclosed in Japanese Patent Publication No. 62-59296 and Japanese Patent Publication No. 62-59296 has been studied. Various types of phase shift photomasks have been proposed. Among them, for example, a halftone phase shifter disclosed in Japanese Patent Application Laid-Open No. 4-136854 and US Pat. No. 4,890,309 has been proposed. Photomasks are attracting attention from the viewpoint of early practical use. And Japanese Patent Laid-Open No. 5-22
As described in JP-A-59-59, JP-A-5-127361, and the like, several proposals have been made for structures and materials capable of improving the yield and reducing the cost by reducing the number of manufacturing steps.

Here, a halftone phase shift method and 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. The amplitude of the light on the wafer, FIGS. 6 (d) and 7 (d) show the light intensity on the wafer, respectively.
911 and 921 are substrates, 922 is a 100% light shielding film, 9
12 shifts the phase of the incident light by substantially 180 degrees, and
Halftone phase shift films 913 and 923 whose transmittance is in the range of 1% to 50% are incident light. In the conventional method, as shown in FIG. 7A, a 100% light shielding film 92 made of chrome or the like is formed on a substrate 921 made of quartz glass or the like.
2 and a light transmitting portion of a desired pattern is merely formed. The light intensity distribution on the wafer is shown in FIG.
As shown in the figure, the skirt spreads, and the resolution is inferior.
On the other hand, in the halftone phase shift shift method, the phase of the light transmitted through the halftone phase shift film 912 and the phase of the light transmitted through the opening thereof are substantially inverted.
As shown in (d), the light intensity at the pattern boundary on the wafer becomes 0, the spread of the skirt can be suppressed, and the resolution can be improved.

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, regarding the phase inversion function, the halftone phase shift film 912 is used.
It suffices that the phase is substantially inverted between the exposure light transmitting through the opening and the exposure light transmitting through the opening. Here, a halftone phase shift film (also referred to as a halftone phase shift layer) 912 is formed of, for example, M.P. Bor
n, E. Wolf, "Principles of Op
tics ”, pages 628-632, multiple interference can be neglected, and the phase change φ of vertically transmitted light is calculated by the following equation, where φ is nπ ± π / 3 (n is an odd number). , The above-described phase shift effect is obtained.

[0005]

[Equation 3] Here, φ is a phase change received by light vertically transmitted through a photomask in which the (m−2) halftone phase shift layer is formed on the transparent substrate, and x (k, k +
1) is a phase change occurring at the interface between the k-th layer and the (k + 1) -th layer, u (k) and d (k) are the refractive index and the film thickness of the material constituting the k-th layer, and λ is This 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.

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 size, area, arrangement, shape, etc. of the transfer pattern, and differs depending on the pattern. In effect,
In order to obtain the above effect, the exposure light transmittance of the halftone phase shift film 912 must be within the range of several percent of the optimum transmittance centered on the optimum transmittance determined by the pattern. 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. Actually, the phase inversion function and the transmittance adjustment function are the complex refractive index (refractive index and extinction coefficient) of the material constituting the halftone phase shift film (in the case of a multilayer, each material constituting each layer). It is determined by the film thickness. In other words, the thickness of the halftone phase shift film is adjusted, and a material in which the phase difference φ determined by the above equation 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 tone 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 Japanese Patent Application No. -281414, attempts to apply to a halftone phase shift film by oxidizing or nitriding tantalum have been actively studied. In addition, as the exposure wavelength has been shortened due to the miniaturization of LSI patterns,
For example, research using a tantalum silicide-based material compatible with shorter wavelength exposure, as disclosed in JP-A-6-83027, has been advanced.

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

[0009]

As described above, as the exposure wavelength becomes shorter as the LSI pattern becomes finer, a tantalum silicide-based material corresponding to shorter wavelength exposure is transferred to a halftone phase shift film. Attempts have been made to apply it, but the tantalum silicide-based halftone phase shift film material itself exhibits excellent processing characteristics and chemical stability after processing, but also takes into account high-precision control of the phase difference. If it is included, there is a problem that high-precision patterning becomes difficult, and this measure has been demanded. The present invention responds to this problem by using a tantalum silicide-based halftone phase shift film material, and maintaining excellent processing characteristics of the tantalum silicide-based material, chemical stability after processing, and the like. An object of the present invention is to provide a halftone phase shift photomask having a structure in which an etching selectivity with a substrate is improved. At the same time, an object of the present invention is to provide a blank for a halftone phase shift photomask which enables the production of such a halftone phase shift photomask.

[0010]

According to a blank for a halftone phase shift photomask of the present invention, a halftone phase shift layer on a transparent substrate is composed of one layer mainly composed of tantalum, silicon, and oxygen, and one layer of chromium or silicon. It is characterized by being constituted by a multilayer film containing at least one layer mainly composed of a chromium tantalum alloy. In the above, a layer mainly containing chromium or a chromium-tantalum alloy is first formed on the transparent substrate, and a layer mainly containing tantalum, silicon, and oxygen is formed thereon. It is assumed that. Further, in the above, one layer containing chromium or a chromium tantalum alloy as a main component contains silicon. Further, in the above, one layer containing chromium or a chromium tantalum alloy as a main component contains oxygen, fluorine, or nitrogen.
Further, in the above, the halftone phase shift layer has a phase difference φ obtained by the following equation on a transparent substrate, which is nπ ±
It is characterized in that it is formed to be in the range of π / 3 radian (n is an odd number).

(Equation 4) Here, φ is a phase change received by light vertically transmitted through a photomask in which the (m−2) halftone phase shift layer is formed on the transparent substrate, and x (k, k +
1) is a phase change occurring at the interface between the k-th layer and the (k + 1) -th layer, u (k) and d (k) are the refractive index and the film thickness of the material constituting the k-th layer, and λ is This 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. In the above, the transmittance of the halftone phase shift layer for exposure light is 1 to 5 when the transmittance of the transparent substrate for the exposure light is 100%.
It is characterized in that it is formed on the transparent substrate with a film thickness of 0%. Also, in the above,
The absolute reflectance of the surface on which the halftone phase shift layer is formed with respect to exposure light is 0 to 30%. In the above, a light-shielding film containing chromium as a main component is continuously formed on the halftone phase shift layer. Further, in the above, a pattern of a light-shielding film containing chromium as a main component is formed below the halftone phase shift layer.

According to the halftone phase shift photomask of the present invention, the halftone phase shift layer on the transparent substrate is mainly composed of tantalum, silicon and oxygen, and chromium or a chromium-tantalum alloy. And a multilayer film containing at least the following. In the above, a layer mainly containing chromium or a chromium-tantalum alloy is first formed on the transparent substrate, and a layer mainly containing tantalum, silicon, and oxygen is formed thereon. It is assumed that. Further, in the above, one layer containing chromium or a chromium tantalum alloy as a main component contains silicon. Further, in the above, one layer containing chromium or a chromium tantalum alloy as a main component contains oxygen, fluorine, or nitrogen. Further, in the above description, the halftone phase shift layer is formed on the transparent substrate such that the phase difference φ determined by the following equation is in the range of nπ ± π / 3 radians (n is an odd number). It is a feature.

(Equation 5) Here, φ is a phase change received by light vertically transmitted through a photomask in which the (m−2) halftone phase shift layer is formed on the transparent substrate, and x (k, k +
1) is a phase change occurring at the interface between the k-th layer and the (k + 1) -th layer, u (k) and d (k) are the refractive index and the film thickness of the material constituting the k-th layer, and λ is This 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. In the above, the transmittance of the halftone phase shift layer to the exposure light is 100% of the transmittance of the opening of the halftone phase shift layer to the exposure light.
%, It is characterized by being 1 to 50%. Further, in the above, the absolute reflectance for the exposure light of the surface formed with the halftone phase shift layer or,
0 to 30%. Also,
In the above, a pattern of a light-shielding film containing chromium as a main component is formed on the pattern of the halftone phase shift shift layer. Further, in the above, a pattern of a light-shielding film containing chromium as a main component is formed below the pattern of the halftone phase shift layer.

[0012]

According to the blank for a halftone phase shift photomask of the present invention having such a structure, a tantalum silicide-based halftone phase shift film material is used, and the tantalum silicide-based material has excellent processing characteristics. It is possible to provide blanks for halftone phase shift photomasks that can produce halftone phase shift photomasks with a structure that improves the etching selectivity with quartz substrates while maintaining chemical stability after processing. And High-precision patterning with sufficient etching selectivity with transparent substrates such as synthetic quartz while maintaining the chemical stability and processing characteristics unique to tantalum-based materials and the short wavelength applicability unique to silicide-based materials Is possible,
In addition, it is possible to provide a blank for a halftone phase shift photomask having excellent stability after mask processing. The halftone phase shift film is composed of a multilayer film, one of which (chromium or chromium-tantalum alloy as a main component) is composed of a transparent substrate and a material that can provide a sufficiently large etching selectivity. Processing is possible. Specifically, the halftone phase shift layer on the transparent substrate is composed of a multilayer film containing at least a layer mainly containing tantalum, silicon, and oxygen and a layer mainly containing chromium or a chromium-tantalum alloy. More specifically, more specifically, a layer mainly composed of chromium or chromium-tantalum alloy is first formed on a transparent substrate, and a layer mainly composed of tantalum, silicon, and oxygen is further formed thereon. This is achieved by being formed.

That is, as a halftone phase shift layer,
Tantalum, silicon, and a blank for a halftone phase shift photomask including a layer mainly composed of oxygen,
By providing a layer mainly composed of chromium, high-precision patterning is enabled. The film mainly composed of chromium or chromium tantalum alloy is made of Cl ₂ , CH ₂ C
Etching can be performed using a chlorine-based etching gas such as l ₂ or a gas obtained by adding O ₂ thereto. However, with these chlorine-based gases, a transparent substrate such as synthetic quartz is not substantially etched. Here, the film mainly composed of chromium or a chromium-tantalum alloy is desirably formed as a first layer directly on a transparent substrate because of its role. For example, first, a film mainly composed of chromium or a chromium-tantalum alloy is formed on synthetic quartz, and a film mainly composed of tantalum, silicon, and oxygen is formed thereon. In the case of a shift film, in patterning, first, a film mainly composed of tantalum, silicon, and oxygen is etched with a fluorine-based dry etching gas, and then sufficient etching with the substrate is performed using a chlorine-based dry etching gas. By performing patterning while maintaining the dry etching selectivity, highly accurate phase difference control becomes possible.

Further, the halftone phase shift film includes:
It has excellent chemical stability and processability, which are the characteristics of tantalum-based thin films, and uses a silicide film, so that krypton fluoride excimer laser lithography (exposure wavelength: 248 nm) and argon fluoride excimer laser lithography (exposure) (Wavelength: 193 nm), so that it can be used as a halftone phase shift film.

In general, in halftone phase shift lithography, a layer formed by a light-shielding film is often provided in addition to the halftone phase shift layer in order to prevent exposure of the resist due to overlapping of adjacent shots. In addition to the above-mentioned purpose, the light-shielding film may be used for adjusting transfer characteristics of a pattern to be transferred. A chromium-based film is used for this light-shielding film because of its excellent plate making characteristics and durability. After forming a halftone phase shift film pattern, the plate is made of a cerium nitrate wet etchant. In some cases. However, in the blank for a halftone phase shift mask of the present invention, since the halftone phase shift film contains a film containing chromium or a chromium-tantalum alloy as a main component, the film is attacked by a cerium nitrate-based wet etchant ( FIG. 5 (d) of a process described later.
), There is a concern that a defect may occur in the pattern. However, the film containing chromium or a chromium tantalum alloy as a main component in the present invention contains oxygen, fluorine, nitrogen, or the like. By using an alloy with another metal such as tantalum, corrosion resistance can be improved. In general, the film mainly composed of chromium or chromium-tantalum alloy has a small thickness, and thus is unlikely to be attacked as shown in FIG. Alternatively, it is expected to be at a level that does not substantially cause a problem in transfer characteristics even if it is invaded.

The halftone phase shift photomask according to the present invention, having such a configuration, enables highly accurate patterning, has excellent stability after mask processing, and has a krypton fluoride excimer laser ( wavelength:
248 nm) and a halftone phase shift photomask that can be applied to short-wavelength exposure such as an argon fluoride excimer laser (wavelength: 193 nm).

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a cross-sectional view of a first example of an embodiment of a blank for a halftone phase shift photomask of the present invention, and FIG. 1B is an implementation of a blank for a halftone phase shift photomask of the present invention. FIG. 2A is a sectional view of a first example of the embodiment of the halftone phase shift photomask of the present invention, and FIG. 2B is a sectional view of the second example of the present invention. FIG. 3 is a cross-sectional view of a second example of the embodiment of the halftone phase shift photomask, FIG. 3 is a cross-sectional view of a manufacturing process of the halftone phase shift photomask shown in FIG. 2A, and FIG. FIG. 5 is a cross-sectional view for explaining a method of manufacturing the halftone phase shift photomask of the second example and explaining an etching shape. In FIG. 1, 110 is a transparent substrate, 120 is a halftone phase shift layer, 121 is a layer mainly containing chromium (hereinafter also referred to as a first layer), and 122 is mainly tantalum, silicon, and oxygen. Layer (hereinafter also referred to as a second layer); 125, a halftone pattern region (shift layer pattern region); 130, a light-shielding layer (also referred to as a substantial light-shielding film); 140, a resist layer; The resist layer 145A is an opening.

First, a first embodiment of a blank for a halftone phase shift photomask according to the present invention will be described with reference to FIG. The blanks for the halftone phase shift photomask of this example are tantalum,
Second layer 122 mainly containing silicon and oxygen
And a multi-layered film composed of the first layer 121 mainly composed of chromium as the halftone phase shift layer 120. The first substrate mainly composed of chromium is sequentially formed on the transparent substrate 110 composed of synthetic quartz. A layer 121 and a second layer 122 containing tantalum, silicon, and oxygen as main components are formed. In addition, when the first layer 121 mainly containing chromium is etched with a chlorine-based gas at the time of manufacturing a photomask, it has a chemical stability and processing characteristics unique to a tantalum-based material. A sufficient etching selectivity with the transparent substrate 110 made of quartz can be obtained. Thereby, high-precision patterning is possible at the time of manufacturing a photomask.
The halftone phase shift layer 120 of the blank for a halftone phase shift photomask of this example has a second layer 12 mainly containing tantalum, silicon, and oxygen.
2 is provided, and the photomask manufactured from this is
Krypton fluoride excimer laser (wavelength: 248n
m), argon fluoride excimer laser (wavelength: 193)
nm) and the like.

In the present embodiment, the halftone phase shift layer 120 is formed so that a phase shift effect can be obtained when a halftone phase shift photomask is manufactured.
The transparent substrate 110 is formed on the transparent substrate 110 such that m = 4 in the following equation, and the obtained phase difference φ is in the range of nπ ± π / 3 radians (n is an odd number).

(Equation 6) Here, φ is a phase change received by light vertically transmitting through a photomask in which two halftone phase shift layers 120 are formed on the transparent substrate 110, and x (k, k +
1) is a phase change occurring at the interface between the k-th layer and the (k + 1) -th layer, and u (k) and d (k) are the materials (the tantalum layer 121 and the metal silicide oxide film) constituting the k-th layer, respectively. 122) is the refractive index, the film thickness, and λ is the wavelength of the exposure light. However, the layer where k = 1 is the transparent substrate 110, and the layer where k = 4 is air.

Further, when a halftone phase shift photomask is manufactured, the transmittance of the halftone phase shift layer 120 to the exposure light is substantially reduced because the phase shift effect is obtained. The film is formed on the transparent substrate 110 so as to have a thickness in the range of 1% to 50% when the transmittance of 110 is 100%.

Examples of the first layer 121 containing chromium as a main component include a chromium layer, a chromium oxide layer, a chromium nitride layer, and a chromium oxynitride layer which can be etched with a chlorine-based gas. The first layer 121 containing chromium as a main component can also be easily formed by a sputtering method conventionally used for forming a thin film for a photomask. When chromium metal is used as a target and oxygen and nitrogen are mixed with argon gas as a sputtering gas, a chromium oxide film and a chromium nitride film can be obtained. Adjustment of the refractive index can be controlled not only by the gas mixture ratio but also by the sputter pressure, the sputter current and the like. The chromium-based film can be formed by a film forming technique such as a vacuum evaporation method, a CVD method, an ion plating method, or an ion beam sputtering method, in addition to the sputtering method. The second layer 122 mainly containing tantalum, silicon, and oxygen can be easily formed by a sputtering method conventionally used for forming a thin film for a photomask. For example, a tantalum silicide oxide film is obtained by using tantalum silicide as a target and mixing oxygen with argon gas as a sputtering gas. The adjustment of the refractive index of the tantalum silicide oxide film 122 can be controlled not only by the gas mixing ratio but also by the sputtering pressure, the sputtering current, and the like. still,
Second containing tantalum, silicon, and oxygen as main components
Layer 122 is formed by vacuum evaporation,
Film formation can also be performed using a film formation technique such as a CVD method, an ion plating method, or an ion beam sputtering method. Synthetic quartz as the transparent substrate 110 is also transparent to short-wavelength exposure light such as krypton fluoride excimer laser (wavelength: 248 nm) and argon fluoride excimer laser (wavelength: 193 nm). When the first layer 121 as a main component is etched with a chlorine-based gas, a sufficient etching selectivity between the first layer 121 and the transparent substrate 110 can be obtained.

Next, a second example of the embodiment of the blank for a halftone phase shift photomask of the present invention will be described.
This will be described with reference to FIG. The blank for a halftone phase shift photomask of the second example has a light-shielding layer 130 provided on the phase shift layer 120 of the first example. The light-shielding layer 130 is provided around a halftone pattern area (shift layer pattern area) 125 to prevent exposure by multiple exposure of adjacent shots in wafer exposure, to form alignment marks, and the like. It is a substantially light-shielding film. As the light-shielding layer 130, a chromium-based metal layer such as a single layer of chromium, chromium oxide, chromium nitride, and chromium oxynitride is generally used, but is not limited thereto. These chromium-based films can be formed by a film forming technique such as a vacuum evaporation method, a CVD method, an ion plating method, or an ion beam sputtering method, in addition to the sputtering method.

When a halftone phase shift photomask is manufactured, a cerium nitrate-based wet etchant is used, and a blank in the case where the light-shielding layer 130 is wet-etched is made of a first material mainly composed of chromium.
Preferably, the layer 121 contains oxygen, fluorine, nitrogen, or the like, or is made of an alloy with another metal such as silicon, tantalum, or the like to improve corrosion resistance.

As a modification of the blank for a halftone phase shift photomask of the first example and the blank for a halftone phase shift photomask of the second example, the first layer 121 may be etched with a chlorine-based gas. A film made of a chromium tantalum alloy as a main component may also be used. A film containing a chromium-tantalum alloy as a main component can also be formed using a film formation technique such as a vacuum evaporation method, a CVD method, an ion plating method, or an ion beam sputtering method, in addition to the sputtering method.

Next, a first embodiment of a halftone phase shift photomask according to the present invention will be described with reference to FIG. This example is manufactured using the halftone phase shift photomask blank of the first example shown in FIG. 1A, and the phase shift layer 120 is patterned in a predetermined shape. The material and optical characteristics of each layer are not described here instead of the description of the halftone phase shift photomask blank of the first example shown in FIG.

Next, a second embodiment of the halftone phase shift photomask according to the present invention will be described with reference to FIG. This example is manufactured by using the halftone phase shift photomask blank of the second example shown in FIG. 1B, in which the phase shift layer 120 is patterned into a predetermined shape and the phase shift effect is obtained. A halftone pattern region (shift layer pattern region) 125 for obtaining
A light-shielding pattern region 135 for obtaining a substantial light-shielding effect is provided. For the material and optical characteristics of each layer, see FIG.
Instead of the description of the halftone phase shift photomask blank of the second example shown in FIG.

As a modified example of the halftone phase shift photomask of the first example and the halftone phase shift photomask of the second example, a chromium tantalum alloy in which the first layer 121 can be etched with a chlorine-based gas is used. As a photomask using the blanks of the above-described modified example in which the film is mainly composed of, a photomask having the same form as that shown in FIGS. 2A and 2B is exemplified.

Next, an example of a method of manufacturing the halftone phase shift photomask of the first example will be described with reference to FIG. First, a halftone phase shift photomask blank of the first example shown in FIG. 1A is prepared (FIG. 3).
(A)), a resist layer 140 is applied on the halftone phase shift layer 120 and dried (FIG. 3 (b), and only a predetermined area of the resist layer 140 is exposed to light using an electron beam lithography apparatus or the like and developed. Half-tone phase shift layer 1 to be produced
A resist layer 140 is formed according to the pattern shape of No. 20. (FIG. 3C) As the resist for forming the resist layer 140, a resist having good processability, a predetermined resolution, and good dry etching resistance is preferable, but is not limited. Next, using the resist layer 140 as an etching-resistant mask, a second layer mainly containing tantalum, silicon, and oxygen of the halftone phase shift layer 120 using a fluorine-based gas and a chlorine-based gas in that order. The second layer 122 and the first layer 121 mainly containing chromium are successively etched (FIG. 3D), and the resist layer 140 is peeled off to obtain a halftone phase shift layer pattern. (FIG. 3 (e))

Next, an example of a method of manufacturing the halftone phase shift photomask of the second example will be described with reference to FIG. Here, the light-blocking layer 130 is a chromium-based light-blocking layer. First, a halftone phase shift photomask blank of the second example shown in FIG. 1B is prepared, and a resist layer is formed in the same manner as in the method of manufacturing the halftone phase shift photomask of the first example shown in FIG. The light-shielding layer 130 is formed in a predetermined shape on the light-shielding layer 130, and the resist layer is used as an etching-resistant mask, and the light-shielding layer 130 is formed using a chlorine-based gas. The second layer 122 mainly containing chromium is etched successively using the chlorine-based gas to the first layer 121 mainly containing chromium. Next, the resist layer is peeled off, and a new resist layer 145 having an opening 145A of a predetermined shape is similarly formed on the light-shielding layer 130 (FIG. 5A). Then, wet etching is performed using a cerium nitrate-based wet etchant (FIG. 5B), the resist layer 145 is peeled off, and the halftone phase shift photomask of the second example shown in FIG. 2B is used. obtain.

At the time of wet etching, the first layer 121 containing chromium as a main component shown in FIG. 5A is etched, and when enlarged, the first layer 121 becomes as shown in FIG. 5D. However, as described above, in general, the chromium-based film 121 is generally used.
Has a low possibility of being attacked as shown in FIG. Alternatively, it is expected to be at a level that does not substantially cause a problem in transfer characteristics even if it is affected. FIGS. 5C and 5D are enlarged views of the D1 portion in FIG. 5A and the D2 portion in FIG. 5B, respectively.
It is. The film 121 containing chromium as a main component contains oxygen, fluorine, nitrogen, or the like.
By using an alloy with another metal such as tantalum, corrosion resistance can be improved. That is, W0 shown in FIG. 5D can be made extremely small, so that no problem occurs in the transfer characteristics.

The halftone phase shift photomask of the modified example can be manufactured basically in the same manner by the manufacturing method of the first example or the manufacturing method of the second example.

[0032]

EXAMPLE 1 In Example 1, the halftone phase shift photomask blank of the first example shown in FIG. 1A was used, and the manufacturing method shown in FIG. It is an example in which the halftone phase shift photomask of the first example shown is formed. Hereinafter, a description will be given based on FIGS. 1, 2, and 3. First, the transparent substrate 11 is made as follows.
0, a first layer 121 mainly composed of chromium,
Second containing tantalum, silicon, and oxygen as main components
A blank for a halftone phase shift photomask in which a halftone phase shift film 120 made of the layer 122 was formed. The blanks for a halftone phase shift photomask manufactured are for manufacturing a halftone phase shift photomask for KrF exposure.
A transparent substrate 110 is a high-purity synthetic quartz substrate having an inch square and a thickness of 0.25 inch. First, a first layer 121 of chromium as a main component of the halftone phase shift layer 120 was formed to a thickness of about 10 nm on one surface of a transparent substrate 110 that had been optically polished and washed well under the following conditions. <Sputtering conditions of first layer 121> Film forming apparatus: planar DC magnetron sputter apparatus Target: metallic chromium gas and flow rate: argon gas 70 sccm sputter pressure: 0.35 pascal sputter current: 5.0 amps The halftone phase shift layer 120 is placed on the lever.
The second layer 122 containing tantalum, silicon, and oxygen as main components was formed under the following conditions. Here, the film thickness was about 140 nm. <Sputtering conditions for second layer 122> Film forming apparatus: planar DC magnetron sputter apparatus Target: tantalum: silicon = 1: 3 (atomic ratio) Gas and flow rate: 50 sccm of argon gas + 5 of oxygen gas
0 sccm Sputter pressure: 0.3 Pascal Sputter current: 3.5 amps This results in a blank for a halftone phase shift photomask for KrF excimer laser exposure (transmittance 6%) of the first example shown in FIG. I got

A sample (a test piece shown in FIG. 4) was formed by forming a film on a synthetic quartz substrate masked with a tape under the same conditions, and forming a step by a lift-off method of peeling off the masking after the film formation. The phase difference and transmittance with respect to 248 nm light were measured with a commercially available phase difference measuring device (MPM248 manufactured by Lasertec Co., Ltd.) and found to be 179.22 degrees and 5.88%, respectively.

Next, using the blank for a halftone phase shift photomask obtained as described above,
The halftone phase shift photomask of the first example shown in FIG. 2A was manufactured as follows. First, the obtained blank for a halftone phase shift mask (FIG. 3)
On the halftone phase shift layer 120 of (a)), a resist mainly composed of an organic material, ZEP7000 (manufactured by Zeon Corporation) 140 is applied and dried (FIG. 3).
(B)) Only a predetermined region of the resist was exposed and developed by an electron beam lithography apparatus to obtain a resist layer 140 having a desired shape. (FIG. 3C) Next, a commercially available dry mask for photomask (PTI)
The halftone phase shift layer 120 exposed from the resist layer 140 was selectively dry-etched by exposing the resist layer 140 to high-density plasma to obtain a desired halftone phase shift layer 120 pattern. (FIG. 3D) Here, the second layer 1 of the halftone phase shift layer 120 mainly containing tantalum, silicon, and oxygen is used.
22 and the first layer 121 containing chromium as a main component were successively etched. The dry etcher used had two etching processing chambers, and the following etching conditions 1 and 2 were performed in separate processing chambers. <Etching 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 <Etching condition 2> Etching gas Cl ₂ + O ₂ gas (2: 3) Pressure 100 mTorr ICP power (generation of high-density plasma) 500 W bias power (drawing power) 25 W time 200 seconds Next, the remaining resist layer 140 is peeled off by a conventional method, and the transmittance of the halftone phase shift layer for 248 nm light is 6 or less.
% Was obtained.
(FIG. 3 (e))

It should be noted that in the etching under the etching condition 2, the synthetic quartz as the transparent substrate 110 is hardly etched, and the phase difference can be controlled with extremely high precision. The obtained halftone phase shift photomask can be put to practical use in all of the dimensional accuracy, cross-sectional shape, film thickness distribution, transmittance distribution, adhesion of the film to the substrate, etc. of the removed portion. Was.

(Example 2) In Example 2, the halftone phase shift photomask blank of the second example shown in FIG. 1B was used, and the manufacturing method shown in FIGS.
This is an example in which the halftone phase shift photomask of the second example shown in FIG. 2B is formed. Hereinafter, description will be made based on FIGS. 1, 2, 3, and 5. FIG. First, a halftone including a first layer 121 mainly containing chromium, a second layer 122 mainly containing tantalum, silicon, and oxygen is sequentially formed on the transparent substrate 110 as follows. A blank for a halftone phase shift photomask, in which the phase shift film 120 and the light-shielding layer 130 made of chromium were formed, was produced. Here, of the two layers constituting the halftone phase shift film, a film mainly containing chromium (first film)
By mixing tantalum into the layer 121), an improvement in corrosion resistance is realized. That is, the light-shielding layer 1 made of chromium when producing a halftone phase shift photomask
The sample No. 30 was made of a cerium nitrate-based wet etchant to improve the corrosion resistance to the wet etchant during wet etching. In the case of Example 2,
The blank for a halftone phase shift photomask manufactured is for manufacturing a halftone phase shift photomask for KrF exposure, and is 6 inches square, 0.25 mm.
An inch-thick high-purity synthetic quartz substrate is used as the transparent substrate 110.

First, on one surface of a transparent substrate 110 that has been optically polished and cleaned well, the first layer 12 mainly composed of ROM of the halftone phase shift layer 120 is formed under the following conditions.
1 was formed to a film thickness of about 10 nm. <Sputtering conditions for the first layer 121> Film forming apparatus: planar DC magnetron sputter apparatus Target: metal tantalum: chromium = 1: 9 alloy Gas and flow rate: argon gas 70 sccm sputter pressure: 0.35 pascal sputter current: 5 Next, the halftone phase shift layer 120
Second containing tantalum, silicon, and oxygen as main components
Was formed under the following conditions. Here, the film thickness was about 90 nm. <Sputtering conditions for second layer 122> Film forming apparatus: planar DC magnetron sputter apparatus Target: tantalum: silicon = 1: 3 (atomic ratio) Gas and flow rate: 50 sccm of argon gas + 5 of oxygen gas
0 sccm Sputter pressure: 0.3 Pascal Sputter current: 3.5 amps Next, the light-shielding layer 130 is formed on the halftone phase shift layer 120 on the second layer 122 containing tantalum, silicon, and oxygen as main components. Under the conditions, sputtering was performed to a thickness of 1000 °. <Sputtering conditions for light-shielding layer layer 130> Film forming apparatus: Planar type DC magnetron sputter apparatus Target: Metal chromium Gas and flow rate: Argon gas 50 sccm Sputter pressure: 0.3 Pascal Sputter current: 3.5 amps By this, KrF is obtained. For excimer laser exposure; transmittance 6
% Of a halftone phase shift photomask blank was obtained.

A sample (a test piece shown in FIG. 4) was formed by forming a film on a synthetic quartz substrate masked with a tape under the same conditions and forming a step by a lift-off method in which the masking was removed after the film was formed. The phase difference and the transmittance for 248 nm light were measured with a commercially available phase difference measuring device (MPM248 manufactured by Lasertec Co., Ltd.) and found to be 180.12 degrees and 6.33%, respectively. This film was coated on a commercially available chrome etchant (MR-E manufactured by Inktec Co., Ltd.).
A sample immersed in S) at room temperature for 240 seconds was prepared, and the pattern cross section was observed by SEM. As a result, no erosion as shown in FIG. 5D was observed. For comparison, the sample prepared in Example 1 was similarly immersed in a commercially available chrome etchant (MR-ES manufactured by Inktec Co., Ltd.) at room temperature for 180 seconds and for 240 seconds, and the pattern cross section was observed by SEM. However, erosion as shown in FIG. 5D was not observed in the cross-sectional shape of the sample at 180 seconds, but slight erosion was observed at the cross-section at 240 seconds.
From this, the first layer having the composition of Example 2 is better than that of Example 1
It can be seen that the corrosion resistance to the chromium etchant is higher than that of the first layer having the composition of

Next, using the blank for a halftone phase shift photomask obtained as described above,
The halftone phase shift photomask of the second example shown in FIG. 2B was manufactured as follows. First, the obtained blank for a halftone phase shift mask (FIG. 1)
On the light-shielding layer 130 of (b)), a resist mainly composed of an organic substance, ZEP7000 (manufactured by Zeon Corporation) is applied and dried, and in the same manner as in Example 1, an electron beam lithography apparatus is used. , Exposure and development of only a predetermined area of the resist,
After obtaining a resist layer 140 having a desired shape, the halftone phase shift layer 120 exposed from the resist layer is selectively exposed to a high-density plasma using a commercially available dry etcher for a photomask (VLR700 manufactured by PTI). Then, a desired pattern of the halftone phase shift layer 120 was obtained. Here, the light shielding layer 13
0, the second layer 122 mainly composed of tantalum, silicon, and oxygen of the halftone phase shift layer 120, and the first layer 121 mainly composed of chromium. The etching was performed under the conditions of etching condition 2 and etching condition 3. The dry etcher used had two etching processing chambers, and the following etching conditions 1, 2 and 3 were used in different processing chambers. <Etching condition 1> Etching gas Cl ₂ + O ₂ gas (2: 3) pressure 100 mTorr ICP power (generation of high-density plasma) 500 W bias power (drawing power) 25 W time 200 seconds <etching condition 2> etching gas CF4 gas pressure 10 mTorr ICP Power (generation of high-density plasma) 950 W Bias power (drawing power) 50 W time 360 seconds <Etching condition 3> Etching gas Cl ₂ + O ₂ gas (2: 3) Pressure 100 mTorr ICP power (generation of high-density plasma) 500 W Bias power (drawing) Power) 25W time 200 seconds

Next, a resist, IP3
500 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), and a photolithography method was used to obtain a resist layer 145 in which only the region where the halftone film was to be exposed was opened (FIG. 5).
(A)) Then, wet etching is performed under the following conditions, and the light-shielding layer 13 in a region exposed from the resist layer 145 is formed.
0 was selectively removed. (FIG. 5B) Next, the remaining resist layer 145 is peeled off by a conventional method, and the transmittance of the halftone phase shift layer for 248 nm light is 6%.
% Was obtained.
(FIG. 2B) Regarding the halftone phase shift photomask obtained in this way, the erosion of the first layer 121 containing chromium as a main component as shown in FIG. Was not seen.

In Example 2, as in Example 1, in the etching under the etching condition 3, the synthetic quartz as the transparent substrate 110 was hardly etched, and extremely high-precision phase difference control was possible. The obtained halftone phase shift photomask can be put to practical use in all of the dimensional accuracy, cross-sectional shape, film thickness distribution, transmittance distribution, adhesion of the film to the substrate, etc. of the removed portion. Was.

(Embodiment 3) In Embodiment 3, as in Embodiment 2, the halftone phase shift photomask blanks of the second embodiment shown in FIG. 1B are used, and the manufacturing method shown in FIGS. 2B, the half-tone phase shift photomask of the second example shown in FIG. 2B was formed. In Example 2, the film forming conditions for the first layer and the etching conditions for the first layer (Example 2 (Corresponding to Condition 3) is as follows. Other than that is the same as the second embodiment, and the description is omitted. <Sputtering conditions for first layer 121> Film forming apparatus: planar DC magnetron sputter apparatus Target: metal tantalum: chromium = 97: 3 alloy Gas and flow rate: 95 sccm argon gas sputter pressure: 1.0 Pascal sputter current: 1 Ampere <Etching conditions for first layer> Etching gas Cl ₂ pressure 3 mTorr ICP power (high-density plasma generation) 250 W bias power (drawing power) 25 W time 250 seconds The optical characteristic spectrum of this blank is shown in FIG.

[0043]

According to the present invention, as described above, the tantalum silicide-based halftone phase shift film material is used, and the excellent processing characteristics of the tantalum silicide-based material and the chemical stability after the processing are maintained. In addition, it has become possible to provide a halftone phase shift photomask having a structure in which the etching selectivity with respect to a quartz substrate is improved. At the same time, it has become possible to provide a blank for a halftone phase shift photomask which enables the production of such a halftone phase shift photomask. In particular, in addition to the chemical stability and processing characteristics unique to tantalum-based materials, while maintaining the short-wavelength applicability unique to silicide-based materials, the etching selectivity with a transparent substrate such as synthetic quartz can be sufficiently obtained. Precise patterning is possible and excellent in stability after mask processing,
An ideal mask member 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. 1A is a cross-sectional view of a first embodiment of a blank for a halftone phase shift photomask of the present invention, and FIG. 1B is a halftone phase shift photomask of the present invention. It is sectional drawing of the 2nd example of embodiment of the blank for use.

FIG. 2A is a cross-sectional view of a first example of an embodiment of a halftone phase shift photomask according to the present invention.
(B) is a sectional view of a second example of the embodiment of the halftone phase shift photomask of the present invention.

FIG. 3 is a cross-sectional view showing a manufacturing process of the halftone phase shift photomask shown in FIG.

FIG. 4 is a sectional view of a test piece.

FIG. 5 is a cross-sectional view for explaining a method for manufacturing a halftone phase shift photomask of a second example and explaining an etching shape.

FIG. 6 is a diagram for explaining a halftone phase shift method;

FIG. 7 is a transfer method using a conventional mask (projection exposure method).
Diagram for explaining

FIG. 8 is a diagram of an optical characteristic spectrum of a blank for a halftone phase shift photomask of Example 3.

[Explanation of symbols]

Reference Signs List 110 Transparent substrate 120 Halftone phase shift layer 121 Layer mainly containing chromium (hereinafter also referred to as first layer) 122 Layer mainly containing tantalum, silicon, and oxygen (hereinafter also referred to as second layer) 125 Halftone pattern region (shift layer pattern region) 130 Light-shielding layer (also referred to as substantial light-shielding film) 140 Resist layer 140A opening 145 Resist layer 145A opening

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Hiroo Nakagawa 1-1-1, Ichigaya-Kaga-cho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd. No. 1 Dai Nippon Printing Co., Ltd. (72) Inventor Satoshi Yusa 1-1-1, Ichigaya Kagacho, Shinjuku-ku, Tokyo Dainippon Printing Co., Ltd. (72) Inventor Yoshinori Kinase 1-1-1, Dai Nippon Printing Co., Ltd. (72) Inventor Junji Fujikawa 1-1-1, Ichigaya Kagacho, Shinjuku-ku, Tokyo (72) Inventor Masaji Otsuki Ichigaya, Shinjuku-ku, Tokyo 1-1-1 Kagacho Dai Nippon Printing Co., Ltd. F-term (reference) 2H095 BB03

Claims (18)

[Claims] 1. A halftone phase shift layer on a transparent substrate is composed of a multilayer film containing at least a layer mainly containing tantalum, silicon, and oxygen and a layer mainly containing chromium or a chromium-tantalum alloy. A blank for a halftone phase shift photomask, characterized in that: 2. A layer according to claim 1, wherein a layer mainly composed of chromium or a chromium-tantalum alloy is first formed on the transparent substrate, and a layer mainly composed of tantalum, silicon and oxygen is formed thereon. A blank for a halftone phase shift photomask. 3. The blank for a halftone phase shift photomask according to claim 1, wherein one layer mainly composed of chromium or a chromium tantalum alloy contains silicon. 4. A blank for a halftone phase shift photomask according to claim 1, wherein a layer mainly composed of chromium or a chromium tantalum alloy contains oxygen, fluorine or nitrogen. 5. The method according to claim 1, wherein the halftone phase shift layer has a phase difference φ determined by the following equation on a transparent substrate within a range of nπ ± π / 3 radians (n is an odd number). Blanks for a halftone phase shift photomask, wherein the blanks are formed on a substrate. [Formula 1] Here, φ is a phase change received by light vertically transmitted through a photomask in which the (m−2) halftone phase shift layer is formed on the transparent substrate, and x (k, k +
1) is a phase change occurring at the interface between the k-th layer and the (k + 1) -th layer, u (k) and d (k) are the refractive index and the film thickness of the material constituting the k-th layer, and λ is This 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. 6. The halftone phase shift layer according to claim 1, wherein a transmittance of the halftone phase shift layer to exposure light is 1 to 50% when a transmittance of the transparent substrate to the exposure light is 100%. A blank for a halftone phase shift photomask, wherein the blank is formed on the transparent substrate with a suitable thickness. 7. The blank for a halftone phase shift photomask according to claim 1, 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%. . 8. The blank for a halftone phase shift photomask according to claim 1, wherein a light shielding film containing chromium as a main component is continuously formed on the halftone phase shift layer. 9. The blank for a halftone phase shift photomask according to claim 1, wherein a pattern of a light-shielding film containing chromium as a main component is formed under the halftone phase shift layer. 10. A halftone phase shift layer on a transparent substrate is composed of a multilayer film containing at least a layer mainly containing tantalum, silicon and oxygen, and a layer mainly containing chromium or a chromium-tantalum alloy. A halftone phase shift photomask, characterized in that: 11. A layer according to claim 10, wherein a layer mainly composed of chromium or a chromium-tantalum alloy is first formed on the transparent substrate, and a layer mainly composed of tantalum, silicon and oxygen is formed thereon. A halftone phase shift photomask, characterized in that: 12. The halftone phase shift photomask according to claim 10, wherein one layer mainly composed of chromium or a chromium tantalum alloy contains silicon. 13. A halftone phase-shift photomask according to claim 10, wherein one layer containing chromium or a chromium tantalum alloy as a main component contains oxygen, fluorine, or nitrogen. 14. The halftone phase shift layer according to claim 10, wherein a phase difference φ determined by the following equation on a transparent substrate is in a range of nπ ± π / 3 radians (n is an odd number). A halftone phase shift photomask formed on a substrate. [Formula 2] Here, φ is a phase change received by light vertically transmitted through a photomask in which the (m−2) halftone phase shift layer is formed on the transparent substrate, and x (k, k +
1) is a phase change occurring at the interface between the k-th layer and the (k + 1) -th layer, u (k) and d (k) are the refractive index and the film thickness of the material constituting the k-th layer, and λ is This 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. 15. The halftone phase shift layer according to claim 10, wherein the transmittance of the halftone phase shift layer to exposure light is 1 to 100% when the transmittance of the opening of the halftone phase shift layer to the exposure light is 100%. A halftone phase shift photomask characterized by 50%. 16. The halftone phase shift photomask according to claim 10, wherein an absolute reflectance of exposure light on the surface on which the halftone phase shift layer is formed is 0 to 30%. 17. A halftone phase shift photomask according to claim 10, wherein a pattern of a light-shielding film containing chromium as a main component is formed on the pattern of the halftone phase shift shift layer. . 18. The halftone phase shift photomask according to claim 10, 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.