JP2004226593A - Photomask blank, its manufacturing method, and photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a photomask blank and a photomask having little warpage, high chemical resistance against acid or alkali, and high quality. <P>SOLUTION: The photomask blank has at least one layer of film formed on a transparent substrate, with the warpage of the substrate due to the film being ≤0.5 μm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photomask blank and a photomask used for fine processing of a semiconductor integrated circuit, a color filter for a CCD (charge coupled device), an LCD (liquid crystal display device), a magnetic head, and the like.
[0002]
[Prior art]
Photomasks used for a wide range of applications, including the manufacture of semiconductor integrated circuits such as ICs and LSIs, are basically formed by forming a light-shielding film such as chromium on a light-transmitting substrate in a predetermined pattern. is there. In recent years, pattern miniaturization has rapidly progressed in response to market requirements such as higher integration of semiconductor integrated circuits, and this has been dealt with by shortening the exposure wavelength.
[0003]
However, while shortening the exposure wavelength improves resolution, it also causes a decrease in the depth of focus, resulting in a decrease in process stability and a negative effect on product yield.
[0004]
One effective pattern transfer method for such a problem is a phase shift method, and a phase shift mask is used as a mask for transferring a fine pattern. The phase shift mask changes the phase of light depending on the portion to be transmitted, and forms a fine pattern using interference of light having different phases.
[0005]
The phase shift mask is formed by patterning a phase shift film 2 on a substrate 1 as shown in FIGS. FIG. 6B shows the phase difference between light passing through the first light transmitting portion 1a and the phase shifter portion (second light transmitting portion) 2a forming the pattern portion on the mask. By setting the angle to 180 °, the light intensity at the interference portion becomes zero due to the light interference at the pattern boundary portion, and the contrast of the transferred image can be improved. Also, by using the phase shift method, it is possible to increase the depth of focus when obtaining the required resolution, compared to the case where a normal mask having a general exposure pattern made of a chrome film or the like is used. It is possible to improve the resolution and the margin of the exposure process.
[0006]
The above-mentioned phase shift masks can be practically classified into a complete transmission type phase shift mask and a halftone type phase shift mask according to the light transmission characteristics of the phase shifter. The complete transmission type phase shift mask is a mask which has the same light transmittance of the phase shifter portion as the substrate and is transparent to the exposure wavelength. On the other hand, in a halftone phase shift mask, the light transmittance of the phase shifter is about several percent to several tens of percent of the exposed part of the substrate.
[0007]
FIG. 1 shows a basic structure of a halftone type phase shift mask blank, and FIG. 2 shows a basic structure of a halftone type phase shift mask. The halftone type phase shift mask blank shown in FIG. 1 has a halftone type phase shift film 2 formed on a substrate 1 transparent to exposure light. The halftone type phase shift mask shown in FIG. 2 has a halftone type phase shifter portion 2a for patterning the shift film 2 to form a pattern portion on the mask, and a substrate exposed portion having no phase shift film. 1a.
[0008]
Here, the phase of the exposure light transmitted through the phase shifter 2a is shifted with respect to the exposure light transmitted through the substrate exposed portion 1a (see FIGS. 6A and 6B). The transmittance of the phase shifter 2a is set so that the exposure light transmitted through the phase shifter 2a has a light intensity that does not expose the resist on the transfer target substrate. Therefore, the phase shifter 2a has a function of substantially blocking the exposure light.
[0009]
As the halftone phase shift mask, a single-layer halftone phase shift mask having a simple structure has been proposed. As such a single-layer halftone phase shift mask, molybdenum silicide oxide ( A device having a phase shift film made of MoSiO) or molybdenum silicide oxynitride (MoSiON) has been proposed (Patent Document 1: JP-A-7-140635).
[0010]
As a method of manufacturing such a phase shift mask, a method of forming a pattern on a phase shift mask blank by a lithography method is used. In this lithography method, a resist is applied on a phase shift mask blank, a desired portion of the resist is exposed to light by an electron beam or ultraviolet light, developed, and the desired portion of the phase shift film is etched using the patterned resist film as a mask. Then, the substrate is exposed, and then the resist film is peeled off to obtain a phase shift mask.
[0011]
However, in the above-mentioned phase shift mask blank, a film such as a phase shift film is usually formed by sputtering. However, stress is generated in this film and the substrate is distorted by this. Is warped. When a photomask is manufactured by patterning this photomask blank, the stress is released after patterning into a film, so that the warpage of the substrate returns to a state before film formation to some extent, and the flatness of the substrate changes. Due to this change, the dimension of the pattern changes between the design at the time of pattern exposure and the actually completed mask, and the dimensional change has a greater effect as the mask pattern becomes finer. In addition, the focus position may be shifted.
[0012]
Further, in the process of manufacturing a photomask from a photomask blank, an acid such as sulfuric acid or an aqueous solution of ammonia, or an alkaline solution such as a mixed solution of ammonia and hydrogen peroxide is used to clean surface dirt and foreign matter. In addition, films used for photomask blanks and photomasks often have insufficient chemical resistance to acids, alkalis, and the like, and in particular, phase shift films have a problem that the phase difference is changed by alkali treatment. .
[0013]
[Patent Document 1]
JP-A-7-140635
[Problems to be solved by the invention]
The present invention has been made in order to solve the above problems, and has an object to provide a high-quality photomask blank having a small warpage and high chemical resistance to acids and alkalis, a method for manufacturing the same, and a photomask. I do.
[0015]
Means for Solving the Problems and Embodiments of the Invention
The present inventor has conducted intensive studies in order to solve the above problems, and as a result, a photomask blank in which the warpage of the substrate due to the film of the photomask blank in which at least one layer is provided on a transparent substrate is 0.5 μm or less, In particular, when the film is a phase shift film, the film is immersed in an alkaline solution in which 29% ammonia water, 31% hydrogen peroxide solution and water are mixed at a volume ratio of 1: 1: 20 at 30 ° C. for 10 minutes. A photomask blank having a phase change of 2 ° or less is a photomask blank that provides a high-precision and high-quality photomask that can respond to pattern miniaturization, and such a photomask blank is formed on a transparent substrate. When manufacturing a photomask blank provided with at least one layer of film, the present invention has been found to be obtained by irradiating light containing ultraviolet rays after film formation, and the present invention has been made. Reached.
[0016]
That is, the present invention provides the following photomask blank and photomask.
Claim 1:
What is claimed is: 1. A photomask blank comprising a transparent substrate provided with at least one layer of a film, wherein a warpage of the substrate due to the film is 0.5 μm or less.
Claim 2:
What is claimed is: 1. A photomask blank comprising at least one film provided on a transparent substrate, wherein said film is a phase shift film, and 29% ammonia water, 31% hydrogen peroxide solution and water are mixed at a volume ratio of 1: A photomask blank, wherein a phase change amount when immersed in an alkaline solution mixed at 1:20 at 30 ° C. for 10 minutes is within 2 °.
Claim 3:
3. The photomask blank according to claim 2, wherein the amount of phase change is within 1 [deg.].
Claim 4:
The photomask blank according to any one of claims 1 to 3, wherein the film is formed by sputtering.
Claim 5:
The photomask blank according to any one of claims 2 to 4, wherein the phase shift film contains silicon and at least one metal other than silicon, and further contains at least one of oxygen, carbon, and nitrogen. .
Claim 6:
What is claimed is: 1. A method for manufacturing a photomask blank comprising a transparent substrate and at least one layer provided thereon, wherein the method includes irradiating light including ultraviolet rays after film formation.
Claim 7:
7. The method for manufacturing a photomask blank according to claim 6, wherein the absorptance of the irradiated light to the film is larger than the absorptance to the substrate.
Claim 8:
A resist pattern is formed on the film of the photomask blank according to any one of claims 1 to 5 by a photolithography method, and then the resist-uncoated portion of the film is removed by an etching method, and then the resist is removed. A photomask characterized by being obtained by:
[0017]
According to the present invention, the warpage of the photomask blank can be reduced, and the chemical resistance of the photomask blank and the film of the photomask to acid and alkali can be improved. The change in the phase difference can be suppressed.
[0018]
Hereinafter, the present invention will be described in more detail.
The photomask blank of the present invention is a photomask blank in which at least one film is provided on a transparent substrate, and has a substrate warpage of 0.5 μm or less, preferably 0.3 μm or less. The warp means a difference between the maximum value and the minimum value of the surface height using the least square plane calculated as the reference surface, which is calculated from all the measurement data of the surface height without suction.
[0019]
Further, the photomask blank of the present invention is a photomask blank in which at least one layer is provided on a transparent substrate, wherein the layer is a phase shift film, and is immersed in an alkaline aqueous solution containing ammonia and hydrogen peroxide. In particular, the phase change when immersed at 30 ° C. for 10 minutes in an alkaline solution obtained by mixing 29% ammonia water, 31% hydrogen peroxide solution and water at a volume ratio of 1: 1: 20 is 2 °. Less than 1 °.
[0020]
Such a photomask blank can be obtained by forming a film such as a light-shielding film and a phase shift film on a substrate through which exposure light such as quartz or CaF ₂ is transmitted, and then irradiating the film with ultraviolet light. it can. In this case, it is particularly preferable to use light whose absorptance of the irradiated light to the film is higher than that of the substrate.
[0021]
By irradiating light including ultraviolet rays after forming the light shielding film, the phase shift film, and the like, the film quality is improved. The reasons for the improvement of the film quality are not limited thereto, but include changes due to absorption of ultraviolet rays, rapid changes in the temperature of the film, or a combination thereof, the bonding state of atoms in the film, the amount of defects, and the surface composition. (Eg, the degree of oxidation or the degree of nitridation) is considered to be due to a change.
[0022]
Examples of the type of lamp that emits light for irradiation include an ultraviolet lamp and an ultraviolet laser, and an ultraviolet lamp is particularly preferably used.
[0023]
The atmosphere for light irradiation is not particularly limited, such as in an inert gas such as argon, in nitrogen, in oxygen, in a mixed gas of two or more of these gases, in a vacuum, or in the atmosphere. When it is desired to do so, light irradiation may be performed in an atmosphere containing oxygen or nitrogen, or in an inert gas or vacuum if the oxidation or nitridation of the film is not desired.
[0024]
In the present invention, when the film is irradiated with light, the light may be irradiated so as to complete the irradiation in one time or may be irradiated in a plurality of times. When the film has a multilayer structure, irradiation can be performed each time a film is formed, or irradiation can be performed collectively after forming a plurality of films. In particular, when manufacturing a phase shift mask blank in which a phase shift film is formed on a substrate and further a light shielding film or an antireflection film, for example, a metal film such as a Cr film is formed, light is irradiated after forming the phase shift film. After that, it is preferable to form a metal film.
[0025]
On the other hand, a known method can be used for forming a phase shift film, a light-shielding film, an anti-reflection film, and the like on a substrate, but in the present invention, warpage of a film formed by a sputtering method is obtained. It is preferable because the effect of reducing the chemical resistance and improving the chemical resistance is great. As a method of sputtering, when a light element such as oxygen, nitrogen, or carbon is contained in the film, a reactive sputtering method is preferable, and a target having a predetermined composition is used, and under a sputtering gas atmosphere containing the required light element. A film can be formed by sputtering.
[0026]
In this case, as a sputtering gas for forming the film, a film containing a gas containing oxygen, nitrogen, various kinds of nitrogen oxide, various kinds of carbon oxides, etc., oxygen, nitrogen, carbon, or the like in an inert gas such as argon. Can be appropriately added so as to have a desired composition.
[0027]
Further, as a sputtering method, a method using a direct current (DC) power supply or a method using a high frequency (RF) power supply may be used, and a magnetron sputtering method or a conventional method may be used. Note that the film forming apparatus may be a passing type or a single wafer type.
[0028]
In the present invention, the film irradiated with light including ultraviolet light is not particularly limited as long as it is a film formed on a substrate as a photomask blank, and examples thereof include a phase shift film, a light shielding film, and an antireflection film. In particular, a film having a higher absorptance to the exposure light than the substrate, particularly a halftone type phase shift film, dislikes a slight change in the film due to the treatment with a chemical solution, and therefore has a large effect of light irradiation, and is therefore preferable.
[0029]
As the phase shift film, for example, those containing silicon and at least one or more metals other than silicon, and those containing any one or more of oxygen, nitrogen and carbon are preferable. Examples of the metal other than silicon include W, Mo, Ti, Ta, Zr, Hf, Nb, V, Co, Cr, and Ni, and those based on Mo reduce warpage and improve chemical resistance. The effect of improvement is great, especially molybdenum silicide oxide (MoSiO), molybdenum silicide nitride (MoSiN), molybdenum silicide carbide (MoSiC), molybdenum silicide oxynitride (MoSiON), molybdenum silicide oxycarbide (MoSiOC) or molybdenum silicide oxide It is preferable to be made of nitrided carbide (MoSiONC). Such a molybdenum silicide-based phase shift film can be formed by a reactive sputtering method using MoSi or the like as a target.
[0030]
The thickness of the phase shift film varies depending on the exposure wavelength when the phase shift mask is used, the transmittance of the phase shift layer, the amount of phase shift, and the like, but is usually preferably 50 to 200 nm, particularly preferably 50 to 130 nm.
[0031]
As shown in FIGS. 3 and 4, a light shielding film 3 is provided on the phase shift film 2, and an antireflection film 4 for reducing reflection from the light shielding film 3 is formed on the light shielding film 3. You can also.
[0032]
In this case, a chromium-based film such as chromium oxycarbide (CrOC) or chromium oxynitride carbide (CrONC) or a laminate of these can be used as the light-shielding film or the antireflection film.
[0033]
Such a Cr-based light-shielding film or Cr-based antireflection film uses, as a target, for example, chromium alone or a chromium compound obtained by adding any one of oxygen, nitrogen, and carbon to chromium, and uses a chromium compound such as argon or krypton. A film can be formed by reactive sputtering using a sputtering gas in which a carbon gas such as carbon monoxide gas, carbon dioxide gas, or methane is added as a carbon source to an active gas.
[0034]
The photomask of the present invention is obtained by patterning the film of the photomask blank. For example, when the film is a phase shift film, as shown in FIG. 2, the space between the patterned phase shifter portions is the first light transmission portion 1a (substrate exposed portion), and the patterned phase shifter portion is the second light shift portion. It becomes the light transmitting portion 2a.
[0035]
When manufacturing the phase shift mask, specifically, as shown in FIG. 5, a resist film 5 is further formed on the phase shift mask blank in which the phase shift film 2 is formed on the substrate 1 as described above, A method of patterning the resist film 5 by a lithography method, further etching the phase shift film 2, and then removing the resist film 5 can be adopted. In this case, application, patterning (exposure and development), etching, and removal of the resist film can be performed by a known method.
[0036]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.
[0037]
[Example 1]
A phase shift film made of MoSiON is formed on a 6 ″ square quartz substrate using MoSi as a target and N ₂ and O ₂ as a sputtering gas by a reactive DC sputtering method so that the phase difference becomes 180 °. The phase shift film had a film thickness of 1,030 ° and a transmittance of 6.3% for light of 248 nm. A phase shift mask blank was obtained by irradiating the entire film with a lamp that emits light having a peak wavelength of 400 to 500 nm in an Ar atmosphere.
[0038]
When the warpage of the substrate due to the film of the phase shift mask blank was measured, the warpage was 0.42 μm due to the tensile stress. Further, this phase shift mask blank was immersed in an alkaline solution in which 29% ammonia water, 31% hydrogen peroxide solution and pure water were mixed at a volume ratio of 1: 1: 20 at 30 ° C. for 10 minutes. When the phase difference was measured, the amount of change in the phase difference before and after immersion was 1.1 ° or less. The warpage was measured using Nidek FT-900 (the same applies hereinafter).
[0039]
[Comparative Example 1]
In Example 1, after forming the phase shift film, a phase shift mask blank was obtained without irradiating a lamp, and the warpage was measured. As a result, the warp was 0.9 μm due to compressive stress. The phase shift mask blank was immersed in an alkaline solution in the same manner as in Example 1, and the phase difference was measured. The change in the phase difference before and after immersion was 4.9 °.
[0040]
【The invention's effect】
As described above, according to the present invention, a high-quality photomask blank and a photomask having small warpage and high chemical resistance to acids and alkalis can be obtained.
[Brief description of the drawings]
FIG. 1 is a sectional view of a phase shift mask blank according to one embodiment of the present invention.
FIG. 2 is a sectional view of a phase shift mask according to one embodiment of the present invention.
FIG. 3 is a cross-sectional view of a phase shift mask blank provided with a light shielding film according to one embodiment of the present invention.
FIG. 4 is a cross-sectional view of a phase shift mask blank provided with a light shielding film and an anti-reflection film according to one embodiment of the present invention.
5A and 5B are explanatory diagrams showing a method of manufacturing a phase shift mask, wherein FIG. 5A shows a state in which a resist film is formed, FIG. 5B shows a state in which the resist film is patterned, and FIG. (D) is a schematic cross-sectional view of a state where the resist film is removed.
6A and 6B are diagrams for explaining the principle of a halftone type phase shift mask, and FIG. 6B is a partially enlarged view of FIG.
[Explanation of symbols]
1 Substrate 1a Substrate exposed part (first light transmitting part)
2 Phase shift film 2a Phase shifter section (second light transmitting section)
3 light shielding film 4 antireflection film 5 resist film

Claims (8)

What is claimed is: 1. A photomask blank comprising a transparent substrate provided with at least one layer of a film, wherein a warpage of the substrate due to the film is 0.5 μm or less. What is claimed is: 1. A photomask blank comprising at least one film provided on a transparent substrate, wherein the film is a phase shift film, and 29% ammonia water, 31% hydrogen peroxide solution and water are mixed at a volume ratio of 1: A photomask blank, wherein a phase change amount when immersed in an alkaline solution mixed at 1:20 at 30 ° C. for 10 minutes is within 2 °. 3. The photomask blank according to claim 2, wherein the amount of phase change is within 1 [deg.]. The photomask blank according to any one of claims 1 to 3, wherein the film is formed by sputtering. The photomask blank according to any one of claims 2 to 4, wherein the phase shift film contains silicon and at least one kind of metal other than silicon, and further contains at least one kind of oxygen, carbon or nitrogen. . What is claimed is: 1. A method for manufacturing a photomask blank, comprising providing at least one layer of a film on a transparent substrate, wherein the method includes irradiating light including ultraviolet rays after film formation. 7. The method for manufacturing a photomask blank according to claim 6, wherein the absorptance of the irradiated light to the film is larger than the absorptance to the substrate. A resist pattern is formed on the film of the photomask blank according to any one of claims 1 to 5 by a photolithography method, and then the uncoated portion of the film is removed by an etching method, and then the resist is removed. A photomask characterized by being obtained by:

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