JP2009258357A - Substrate for photomask, photomask, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gradation photomask substrate on which a fine pattern can be formed with high precision by wet etching of high productivity while an etching solution and manufacturing steps such as a film forming step and a photoprocess are reduced as much as possible, the gradation photomask, and a method of manufacturing the same. <P>SOLUTION: The gradation photomask substrate comprises a transparent substrate 10, a semi-transmissive layer 20 which is formed on the transparent substrate 10 and has transmissivity to irradiation light controlled, and a light shield layer 43 which substantially blocks the irradiation light, wherein substances forming the light shield layer 43 and semi-transmissive layer 20 are made of the same metal or compound thereof, and a stopper layer 30 formed of a substance differing in etching resistance from the light shield layer 43 and semi-transmissive layer 20 is provided between the light shield layer 43 and semi-transmissive layer 20, and the stopper layer 30 is laminated on the semi-transmissive layer 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photomask substrate, a photomask, and a method for manufacturing the same, and in particular, display elements such as LCD, PDP, EL, etc., display elements for flat panel displays such as wiring patterns, black matrices, color filters, etc. Substrate for photomask for pattern formation and photomask used for surface modification such as antireflection plate using fine scattering unevenness, diffuse reflection plate with or without fine particles, microlens array, and other array-like unevenness formation, and the like It relates to a manufacturing method.

  With the expansion of demand for flat panel display elements such as liquid crystal display elements, plasma display elements, organic EL display elements, and other display elements, many types of photomasks are used. For example, in the formation of liquid crystal display elements, pattern edge improvement when forming display electrode patterns and wiring routing patterns (for example, taper formation, etc.), and forming a black matrix pattern that requires a semi-transmissive portion on the opposite color filter side, color Photomasks corresponding to respective uses and functions are used for forming color filters that require a degree of adjustment, for forming gap materials having different heights, and for forming irregularities such as partition walls in plasma display elements.

  As the number of masks to be used increases due to demands for various applications and functions, as a method of reducing the number of exposures and photomasks, it is possible to form patterns with two or more functions with a single exposure or to expose different patterns to the same photo. A method using a gradation photomask that can be performed using a mask is known.

There are multiple types of gradation photomasks, and it is possible to change the irradiation light stepwise by changing the surface shape of the photomask or forming a semi-transparent layer with intermediate transmittance Has been.
For example, as a gradation photomask in which the surface shape of a photomask is adjusted, the technique described in Patent Document 1 adjusts the surface shape, thereby adjusting the characteristics and level of the thermosetting photosensitive resin and the photosensitive resin. By combining the exposure, the surface unevenness due to unevenness formation and etching of the substrate is changed (a layer having an antireflection effect or a scattering effect is arbitrarily formed).
Further, in the technique described in Patent Document 2, the resist is decomposed stepwise or inclined to an arbitrary depth to form stepped or tapered edges.
In the techniques described in Patent Documents 3 and 4, a method of modifying the surface of the photosensitive resin or thin film to the vicinity or a certain depth, or processing the photosensitive resin itself in the same manner to add a new function. A method is disclosed.

On the other hand, as a gradation photomask having a semi-transmissive layer having an intermediate transmittance, a light-shielding region that substantially shields the irradiation light on the transparent substrate, a semi-transmission region that controls the transmittance for the irradiation light, There are known ones having three types of layers having different optical characteristics from a region of only a transparent substrate that transmits irradiation light.
The semi-transmission region of the gradation photomask is a region where the amount of exposure to be irradiated can be controlled as appropriate, and the resist can be cured or decomposed and developed according to the amount of exposure to develop an afterimage. For this reason, a resist region different from the light shielding region and the total transmission region can be secured.

Further, a gradation photomask (for example, see Patent Documents 5, 6, 7, and 10) in which the transflective layer and the light shielding layer are made of the same material, and a gradation photomask (for example, Patent Document 8) that is made of a different material. In any case, the number and order of layer formation are not particularly limited depending on the number, pattern shape, and etching method of the semi-transmissive layer and the light shielding layer.
For example, according to the technique described in Patent Document 10, a photomask substrate on which a semi-transmissive layer or a light-shielding layer is formed is prepared as a case where the semi-transmissive layer and the light-shielding layer are made of a similar material. After patterning either the transmissive layer or the light shielding layer, the resist is removed and washed. A method of forming a light-shielding layer or a semi-transmissive layer on a layer patterned again using a vacuum apparatus or the like, and then patterning the later formed layer again in a photolithography process is shown.

On the other hand, as a case where the transflective layer and the light shielding layer are made of different materials, for example, according to the technique described in Patent Documents 8, 9, and 11, a photomask in which the transflective layer and the light shielding layer are continuously formed. There is a method in which a substrate is prepared and a pattern of each layer is formed by dry etching or chemical etching.
In the techniques described in Patent Documents 6 and 9, the light-shielding layer, the semi-transmissive layer, and the antireflection layer are made of the same metal or a compound thereof, and after the light-shielding pattern is formed, the semi-transmissive layer is laminated again. A method of forming a light-shielding pattern and a semi-transmissive pattern by collectively etching a portion where a pattern of only a transmissive layer, a light-shielding layer, and a semi-transmissive layer are laminated is disclosed. In this case, since patterning is possible with one kind of etching, the patterning process can be simplified.

  Furthermore, in the techniques described in Patent Documents 8 and 12, for substrates on which a semi-transmissive layer and a light-shielding layer made of materials that are resistant to each other are sequentially formed, an etching solution corresponding to each layer is used properly. Discloses a method of manufacturing a gradation photomask.

Japanese Patent Laid-Open No. 2004-240411 JP 2003-043331 A JP 2004-252396 A JP 2000-066011 A JP 2007-171651 A JP 2007-183591 A JP 2007-114759 A JP 2007-249198 A JP 2007-264516 A Japanese Patent Application Laid-Open No. 07-049410 JP 2001-147516 A Japanese Patent No. 4005622

  However, in the case where the layer structure is composed of the same type of material, it is impossible to clearly separate and etch each other in the patterning process, and either the light shielding layer or the semi-transmissive layer is formed. Since the resist is removed by patterning the substrate once, it is necessary to perform the second patterning again after forming either the light-shielding layer or the semi-transmissive layer, which is disadvantageous in terms of cost. .

  In addition, when the layer structure is composed of different layers, it is possible to form the film once by configuring the light shielding layer and the semi-transmissive layer with a material resistant to each other's etching solution. In the etching process, it is necessary to prepare a plurality of etching solutions and etching gases, and since acid, alkali, oxygen gas, etc. are used in the substrate cleaning and resist removal processes, the selective etching property of the light shielding layer and the semi-transmissive layer is not to mention. At the same time, it is necessary to ensure sufficient resistance to these chemicals.

  In both dry etching and wet etching, there are few combinations of substances that can be selectively etched with different materials, and there are subtle mask effects and patterns due to adhesion at the interface where each layer contacts and generation of residues near the interface. There are inconveniences that it is difficult to ensure sufficient accuracy in the patterning process because the edge is unclear, damage due to the etching solution or etching gas, or increase in transmittance due to film thickness reduction due to over-etching occurs. .

  In view of the above-described problems, the present invention provides a method for manufacturing a photomask substrate, a photomask, and a method for manufacturing a photomask using the substrate for producing a gradation mask in wet etching with high productivity. It is in.

According to the photomask substrate of the first aspect, the problem is that the transparent substrate, the first layer formed on the upper side of the transparent substrate and semi-transmissive to the irradiation light, and the first layer are provided. A third layer formed thereon for substantially shielding the irradiation light; and a second layer formed between the first layer and the third layer and semi-transparent to the irradiation light; A gradation photomask substrate comprising:
The first layer and the third layer are insoluble or hardly soluble in the second etching solution and more easily soluble in the first etching solution than the second layer,
The second layer is more soluble in the second etchant and insoluble or less soluble in the first etchant than the first layer and the third layer,
Each of the first layer and the third layer is a layer mainly composed of one or more components selected from the group consisting of chromium, chromium oxide, chromium nitride, and chromium oxynitride,
The second layer is a layer mainly composed of one or more components selected from the group consisting of titanium, titanium oxide, titanium nitride, and titanium oxynitride.
The first etching solution is a mixed solution of cerium ammonium nitrate, perchloric acid and water,
The second etching solution is solved by being a mixed solution of potassium hydroxide, hydrogen peroxide and water.

With the above structure, the semi-transparent first layer and the third light-shielding layer are made of the same metal or a compound thereof, and are formed between the third layer and the first layer, and with respect to the irradiation light. The second layer having semi-permeability is composed of different physical properties, and the first layer and the third layer are insoluble or sparingly soluble in the second etching solution than the second layer. Since it is easily soluble in the first etchant, the first layer and the third layer can be selectively etched using the second etchant. The second layer is more soluble in the second etching solution than the first and third layers and is insoluble or hardly soluble in the first etching solution. The second layer can be selectively etched using one etchant.
In particular, titanium, titanium oxide, titanium nitride, and titanium oxynitride are insoluble or sparingly soluble in a mixed solution of cerium ammonium nitrate, perchloric acid, and water, which are the first etching solution. It is easily soluble in a liquid mixture of potassium hydroxide, hydrogen peroxide and water. On the other hand, chromium, chromium oxide, chromium nitride, and chromium oxynitride are readily soluble in a mixed solution of cerium ammonium nitrate, perchloric acid, and water, which is the first etching solution. It is insoluble or hardly soluble in a mixture of potassium hydroxide, hydrogen peroxide and water.
For this reason, the first layer and the third layer are mainly composed of one or more components selected from the group consisting of chromium, chromium oxide, chromium nitride, and chromic oxynitride, respectively. As the main layer, the main component is one or more components selected from the group consisting of titanium, titanium oxide, titanium nitride, and titanium oxynitride, thereby improving the selectivity to each etching solution. It is possible to form a more accurate and fine pattern.
As described above, the second layer, the first layer, and the third layer have resistance to different etching solutions, and the first layer and the third layer are used by utilizing the difference in resistance. The second layer is hardly modified or damaged by the first etching solution that solubilizes the first layer, and conversely, the first layer and the second layer are not affected by the second etching solution that solubilizes the second layer. The layer 3 is hardly modified or damaged. Therefore, it is possible to manufacture a photomask on which a fine pattern is formed with high accuracy by a photolithography process in which layers formed by a single thin film formation process are continuously performed. Further, by changing the composition ratio of the second layer, it is possible to finely adjust the optical characteristics and the etching rate as the semi-transmissive layer, and it is possible to secure higher etching properties.
Further, the second layer is made of a different material from the first and second layers, and has a semi-transparent property. Therefore, the first layer and the second layer are laminated by an etching process. By forming the pattern, it is possible to form a semi-transmissive layer having a transmittance different from that of the first layer.
In addition, titanium compounds are highly resistant to chemicals such as acids and alkalis, and therefore are not easily damaged by chemicals used in etching processes such as resist removal solutions. Therefore, selective etching can be performed smoothly, and a highly accurate and fine pattern can be formed.
In this manner, since etching with high accuracy is possible even by wet etching, productivity of a particularly large photomask is improved, and a multi-tone photomask can be manufactured at a low price.

Specifically, as in claim 2, it is preferable that the first layer is directly formed on the transparent substrate.
With the above configuration, it becomes easy to maintain the transmittance with respect to the irradiation light at a target value.

More specifically, as in claim 3, it is preferable that the second layer has a transmittance with respect to irradiation light of 5% or more and 70% or less.
Further, as in claim 4, it is more preferable that the second layer has a thickness of 10 nm to 70 nm.
With the above structure, the second layer has a function of completely protecting the first layer in the step of etching the third layer, and has an appropriate transmittance in the region laminated with the first layer. A semi-transmissive layer can be formed.

  More specifically, as in claims 5 and 6, the photomask substrate is formed by sequentially laminating the first layer, the second layer, and the third layer on the transparent substrate, The third layer is composed of a light shielding layer that substantially shields the irradiation light and an antireflection layer that is formed on the surface side of the light shielding layer, and the antireflection layer is made of chromium oxide or chromium nitride. And one or more components selected from the group consisting of chromic oxynitrides are preferred.

With the above configuration, the antireflection effect can be obtained by providing the antireflection layer in the third layer, and the occurrence of moire and halation caused by irregular reflection of irradiation light during exposure of the photomask is prevented. Thus, the pattern accuracy can be improved.
Moreover, since the antireflection layer is formed of a layer having one or two or more components selected from the group consisting of chromium oxide, chromium nitride and chromic oxynitride having a low reflectance, it is high. The antireflection effect can be obtained, and the pattern accuracy can be improved by preventing the occurrence of moire and halation caused by irregular reflection of irradiation light during exposure of the photomask.
At this time, when the antireflection layer is made of the same material as the light shielding layer, it is possible to perform etching simultaneously with the light shielding layer with the same etching solution.

  According to a seventh aspect of the present invention, it is preferable that the first layer, the second layer, and the third layer are formed by a sputtering method, an ion plating method, or an evaporation method.

  As described above, the first layer, the second layer, and the third layer are formed by a vacuum film formation method such as a sputtering method, an ion plating method, or an evaporation method, so that the film thickness and the like are appropriately adjusted. Thus, a photomask substrate having desired optical characteristics can be obtained. In addition, by manufacturing with a thin film forming technique such as sputtering, it is possible to appropriately adjust physical characteristics such as chemical resistance and robustness of the photomask substrate.

  According to the photomask of claim 8, the above problem is solved by a photomask manufactured by the photomask substrate according to any one of claims 1 to 7.

  Thus, according to the photomask of the present invention, a photomask having the features of claims 1 to 7 can be obtained.

  The subject is a photomask manufacturing method using the photomask substrate according to any one of claims 1 to 6, wherein the photomask manufacturing method according to claim 9 is provided on the surface of the third layer. A first resist coating step for coating a resist; a first exposure step for exposing the resist coated in the first resist coating step through a mask on which a first mask pattern is formed; A first resist removing step of removing an exposed portion or a non-exposed portion of the resist after the first exposure step; and the third layer exposed in the region where the resist is removed. A first etching step of forming a light-shielding pattern by etching with the etching solution, and the second layer exposed in the region where the third layer is removed by the first etching step. A second etching step for forming a light-shielding pattern by etching with an etchant; a first resist stripping step for stripping the resist remaining in the first resist removal step; and a second resist coating on the surface again. A resist coating step, a second exposure step of exposing the resist coated in the second resist coating step through a mask on which a second mask pattern is formed, and the second exposure step after the second exposure step. A second resist removing step for removing an exposed portion or a non-exposed portion of the resist, and the third layer and the first layer exposed in the region where the resist is removed. Etching with an etching solution left in the third etching step for exposing the second layer and the transparent substrate and the second resist removing step, respectively. A second resist peeling step of peeling off the serial resist is solved by performing.

Thus, according to the method for manufacturing a photomask according to claim 9, by utilizing the difference in resistance to the etchant between the first layer, the third layer, and the second layer, Because it is hardly modified or damaged by the etchant used to etch the layer,
A light-shielding region with the third layer exposed on the surface, a first semi-transmissive region with the second layer exposed on the surface by the first etching step, and the first layer surface by the second etching step It is possible to obtain a high-accuracy four-tone photomask including the second transflective region exposed to the surface and the total transmissive region where the transparent substrate is exposed on the surface by the third etching step.

  According to a method of manufacturing a photomask according to claim 10, the subject is a method of manufacturing a photomask using the photomask substrate according to claims 1 to 6, wherein the photomask substrate is formed on the surface of the third layer. A first resist coating step for coating a resist; a first exposure step for exposing the resist coated in the first resist coating step through a mask on which a first mask pattern is formed; A first resist removing step of removing an exposed portion or a non-exposed portion of the resist after the first exposure step; and the third layer exposed in the region where the resist is removed. A first etching step for forming a light-shielding pattern by etching with an etching solution, a first resist stripping step for stripping the resist remaining in the first resist removal step, and a resist A second resist coating step for coating the surface with the second resist coating step, and a second exposure step for exposing the resist coated in the second resist coating step through a mask on which a second mask pattern is formed; A second resist removal step of removing an exposed portion or a non-exposed portion of the resist after the second exposure step, and the second layer exposed in the region where the resist is removed. Etching with a second etchant to expose the first layer, the third layer exposed in the region where the resist has been removed, and the second etching step to A third etching step for exposing the transparent substrate by etching the first layer exposed in the region from which the second layer has been removed with the first etching solution and the second resist removal. A second resist separation step of separating the resist remaining in step, is solved by performing.

  Thus, according to the method for manufacturing a photomask according to claim 10, by utilizing the difference in resistance to the etchant between the first layer, the third layer, and the second layer, Since the etching solution used for etching the layer hardly undergoes modification or damage, the light shielding region where the third layer is exposed on the surface and the second layer where the second layer is exposed on the surface by the first etching step. It is possible to form a highly accurate three-tone photomask including one transflective region and a total transmissive region where the transparent substrate is exposed on the surface by the second etching step and the third etching step.

According to the photomask substrate according to claim 1, the second layer, the first layer, and the third layer have resistance to different etching solutions, and use the difference in resistance. Thus, the second layer is hardly damaged or modified by the first etching solution that solubilizes the first layer and the third layer, and conversely the second layer that solubilizes the second layer. The first layer and the third layer are hardly modified or damaged by the etching solution. Therefore, it is possible to manufacture a photomask on which a fine pattern is formed with high accuracy by a photolithography process in which layers formed by a single thin film formation process are continuously performed. Further, by changing the composition ratio of the second layer, it is possible to finely adjust the optical characteristics and the etching rate as the semi-transmissive layer, and it is possible to ensure higher etching properties. The first layer and the third layer are made of a different material and have semi-transparency, so that a pattern in which the first layer and the second layer are stacked is formed by an etching process. Makes it possible to form a semi-transmissive layer having a transmittance different from that of the first layer, and also enables high-accuracy etching even by wet etching. Thus, a photomask substrate capable of manufacturing a multi-tone mask at an inexpensive price with improved performance can be provided.
According to the photomask substrate of the second aspect, it is possible to provide a photomask substrate that can easily maintain the transmittance with respect to the irradiation light at a target value.
According to the photomask substrate of claims 3 and 4, the second layer has a function of completely protecting the first layer in the step of etching the third layer, A photomask substrate can be provided in which a semi-transmissive layer having an appropriate transmittance can be formed in the stacked region.
According to the photomask substrate according to claims 5 and 6, the antireflection layer has one or more components selected from the group consisting of chromium oxide, chromium nitride, and chrome oxynitride having a low reflectance. Since it is formed of the main component layer, a high antireflection effect can be obtained, and the pattern accuracy can be improved by preventing the occurrence of moire and halation caused by the irregular reflection of the irradiated light during exposure of the photomask. A photomask substrate can be provided.
According to the photomask substrate of claim 7, the first layer, the second layer, and the third layer are formed by a vacuum film formation method such as a sputtering method, an ion plating method, or an evaporation method. Thus, a substrate for a photomask having desired optical characteristics can be obtained by appropriately adjusting the film thickness and the like. Further, a photomask substrate capable of appropriately adjusting physical properties such as chemical resistance and fastness of the photomask substrate can be provided by manufacturing the thin film formation technique such as sputtering.
According to the photomask of the eighth aspect, it is possible to provide a photomask having the features of the first to seventh aspects.
According to the method for manufacturing a photomask according to claims 9 and 10, etching of other layers is performed by utilizing the difference in resistance to the etching solution between the first layer, the third layer, and the second layer. Therefore, it is possible to provide a gradation photomask that can form a highly accurate and fine pattern with almost no modification or damage by the etching solution used in the above process.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be noted that the members, structures, configurations, procedures, and the like described below do not limit the present invention, and various modifications can be made according to the spirit of the present invention.

1 is a longitudinal sectional view of a gradation photomask substrate according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a gradation photomask according to an embodiment of the present invention, and FIGS. FIG. 6 to FIG. 8 are explanatory diagrams showing the process of patterning a three-tone photomask, and FIG. 9 is an electron microscope (SEM) photograph of the test pattern taken from above. is there.
1 to 8 schematically illustrate a gradation photomask substrate, a gradation photomask, and a method of manufacturing a gradation photomask by describing the thickness of each layer to be larger than the actual thickness for the sake of explanation. Is shown.
Table 1 shows various test results of Examples and Comparative Examples.

FIG. 1 is a cross-sectional view of a gradation photomask substrate 1 according to the present invention, in which a transparent substrate 10, a semi-transmissive layer 20 formed on the transparent substrate 10, a composite layer 40, and etching formed therebetween. It is constituted by a stopper layer (stopper layer 30).
The stopper layer 30 corresponds to the second layer of the present invention, and the semi-transmissive layer 20 and the composite layer 40 correspond to the first layer and the third layer, respectively.
The composite layer 40 is formed by a light shielding layer 43 that substantially shields the irradiation light and an antireflection layer 45 laminated on the surface thereof.

The gradation photomask substrate 1 is a substrate for manufacturing the gradation photomask 2, and the transflective layer 20, the light shielding layer 43, and the stopper are used by using different etching solutions in an etching process and a photolithography process to be described later. The gradation photomask 2 can be manufactured by sequentially etching and patterning the gradation photomask substrate 1 on which the layer 30 is formed.
The semi-transmissive layer 20 is a layer formed on the gradation photomask substrate 1 and is semi-transmissive to irradiation light. It is a layer in which the transmittance at wavelengths of 300 nm to 450 nm including i-ray (wavelength 365 nm) and g-ray (wavelength 436 nm) as irradiation light can be adjusted by changing the film thickness. A semi-transparent layer consisting only of the semi-transmissive layer 20 is defined as a first semi-transmissive layer (region).

The stopper layer 30 is a layer that is formed on the semi-transmissive layer 20 and has a protective function of the semi-transmissive layer 20 together with a stopper function that regulates a range to be etched when the composite layer 40 is etched. In addition, since the layer is semi-transparent to the irradiation light, the second semi-transparent layer (region) can be formed by maintaining the lamination with the semi-transparent layer 20 in the photolithography process described later. is there. Therefore, the second semi-transmissive layer (region) can have a transmittance different from that of the first semi-transmissive layer (region) including only the semi-transmissive layer 20.
The composite layer 40 including the light shielding layer 43 and the antireflection layer 45 is a layer that functions as a light shielding layer that substantially blocks the irradiation light of the present invention.

FIG. 2 is a transverse cross-sectional view of the gradation photomask 2 of the present invention. The transparent substrate 10, the first semi-transmissive pattern 20 a formed on the transparent substrate 10, and the first semi-transmissive pattern 20 a are illustrated. The stopper pattern 30a is formed on the stopper pattern 30a, the light-shielding pattern 43a is formed on the stopper pattern 30a, and the anti-reflection pattern 45a is formed on the surface of the light-shielding pattern 43a.
The transflective pattern 20a is a pattern formed by etching the transflective layer 20 of the gradation photomask substrate 1 of the present invention, and the stopper pattern 30a is a pattern formed by etching the stopper layer 30, and a light shielding pattern. 43a is a pattern formed by etching the light shielding layer 43, and an antireflection pattern 45a is a pattern formed by etching the antireflection layer 45. A light shielding layer pattern 40a is formed by the light shielding pattern 43a and the antireflection pattern 45a.
The gradation photomask 2 includes a light shielding region 1a (light shielding region 1a) in which a part of the antireflection pattern 45a (that is, the light shielding pattern 40a) is exposed on the surface and a part of the stopper pattern 30a when viewed from above. A region 1b (second semi-transmissive region 1b) exposed on the surface, a region 1c (first semi-transmissive region 1c) in which a part of the semi-transmissive pattern 20a is exposed on the surface, and a region 1d (totally transparent substrate only) A transmission amount region 1d).

Below, each member which comprises the board | substrate 1 for gradation photomasks is demonstrated.
(Transparent substrate 10)
The transparent substrate 10 is a transparent substrate serving as a base when forming a gradation photomask substrate. The transparent substrate 10 may be made of a glass substrate such as natural quartz glass, synthetic quartz glass, borosilicate glass, or soda glass, or a material such as a low expansion transparent resin. The term “transparent” as used herein specifically means that the transmittance (air reference) for exposure light of i-line (wavelength 365 nm) and g-line (wavelength 436 nm) in the photolithography process is in the range of 80 to 95%. Shall be.

(Semi-transmissive layer 20)
The semi-transmissive layer 20 (first semi-transmissive layer) is formed on the surface of the transparent substrate 10. The transflective layer 20 of this embodiment has a transmittance of 5 to 70% for exposure light of i-line (wavelength 365 nm) or g-line (wavelength 436 nm) in the photolithography process, and is made of chromium (Cr) and nitrogen (N ₂ ) And oxygen (O ₂ ). The transmittance is determined by changing the film thickness depending on the application.

The semi-transmissive layer 20 is designed to intentionally increase the difference in transmittance for each wavelength used in accordance with the exposure wavelength used and the characteristics of the resist, and to make the transmittance flat in a plurality of wavelength ranges used. Is made. The transmittance can be adjusted by forming a compound of chromium (Cr), oxygen (O ₂ ), nitrogen (N ₂ ), or a combination of these gases. For example, the ratio of oxygen in the film is increased (the ratios of chromium, oxygen, and nitrogen in the film are 34.5 to 38.5 atm%, 43.5 to 50.5 atm%, and 15.0 to 19.5 atm%, respectively. : Quantitative analysis value by ESCA X-ray photoelectron spectroscopy manufactured by JEOL: hereinafter referred to as ESCA quantitative analysis value), the transmittance difference between i-line and g-line is 8.5% to 9.0%, and the film The ratio of chromium, oxygen and nitrogen in the film is 44.0 to 50.5 atm%, 25.0 to 29.0 atm%, and 25.5 to 28.0 atm%, respectively. ESCA quantification Analysis value), it is possible to make the transmittance difference between the i-line and the g-line 0.9 to 1.6%.
In selecting the etchant, considering the etching resistance of the stopper layer 30 in contact with the semi-transmissive layer 20 and the etching rate of the composite layer 40, a combination of a metal and one or more compounds of oxygen, nitrogen, and carbon is used. A thin film is formed. In this embodiment, since the base metal is chromium (Cr), a mixed solution ((NH ₄ ) ₂ Ce (NO ₃ ) of perchloric acid, cerium ammonium nitrate, and water is used as the etching solution (first etching solution). ₆ : HClO ₄ : H ₂ O = 15: 3: 82 normal temperature).

(Stopper layer 30)
A stopper layer 30 is formed on the semi-transmissive layer 20. The stopper layer 30 is a layer having a function of reliably completing the etching and a function of preventing the semi-transmissive layer 20 from being etched when the composite layer 40 on the stopper layer 30 is etched. It is a layer having resistance to liquid.
In addition, when the semi-transmissive layer 20 is etched, the stopper layer 30 also functions as a mask. Therefore, it is necessary to form with a substance having high chemical resistance and good etching characteristics.
The stopper layer 30 in this embodiment includes titanium (Ti) and a compound of titanium, oxygen, and nitrogen (ratio of titanium, oxygen, and nitrogen in the film is 26.5 to 36.5 atm%, 32.0 to 39, respectively. .5 atm%, 29.5 to 41.0 atm%: ESCA quantitative analysis value).
Further, as an etching solution (second etching solution) for the stopper layer 30, a mixed solution of hydrogen peroxide, potassium hydroxide, and water ((H ₂ O ₂ (35%): KOH (30%): H ₂ ). O = 1: 16: 32 (volume ratio) normal temperature) is used.

  In the present invention, the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are composed of chromic oxynitride (compound of chromium, oxygen, and nitrogen), chrome, and chromic oxynitride, and are etched with the same etching solution. As long as the material has etching selectivity with respect to the stopper layer 30, the light shielding layer 43, the antireflection layer 45, and the transflective layer 20 are made of different materials and different etching solutions. There is no particular limitation.

Further, since the stopper layer 30 is a semi-transmissive material, it can have a second gradation function (second semi-transmissive region 1b) by being laminated with the semi-transmissive layer 20.
For example, a stopper layer (thickness≈200 mm) of a compound of titanium, oxygen, and nitrogen is formed on the semi-transmissive layer 20 having a film thickness of chromium / oxygen / nitrogen compound≈100 mm and a transmittance of 54.11%. In this case, the transmittance of the second semi-transmissive region 1b at the g-line is 26.08%.
The stopper layer 30 preferably has a thickness of 10 to 70 nm (100 to 700 mm).

(Composite layer 40)
The composite layer 40 in this embodiment is formed on a layer in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and is composed of two layers, a light shielding layer 43 and an antireflection layer 45 on the surface side. The light shielding layer 43 is made of chromium metal having high absorption, and the antireflection layer 45 is a compound of chromium, oxygen, and nitrogen that absorbs less than the light shielding layer 43 (ratio of chromium metal, oxygen and nitrogen in the film is 37, respectively). .5-44.5 atm%, 39.5-46.0 atm%, 13.5-17.0 atm%: ESCA quantitative analysis value). That is, an antireflection effect due to multiple interference of light occurs between the light shielding layer 43 and the antireflection layer 45 formed thereon. In the present embodiment, by utilizing this principle, an optical film thickness (nd = λ / 4: n is a refractive index and d is a substantial film thickness) that matches the exposure wavelength to be used is formed. Therefore, by changing the etching solution, the light shielding layer 43 and the antireflection layer 45 can be composed of nickel, molybdenum, aluminum, copper, a compound of an alloy thereof, or the like.
In addition, the composite layer 40 that substantially blocks exposure light that is irradiation light has an optical density of 3.0 (transmittance of 0.1% or less) or more, and is laminated on the stopper layer 30 in this embodiment. Since it is formed, it can surely exert a light shielding effect, and the reflectance of the film surface can be reduced to 10% or less in the range of 350 nm to 450 nm, and the reflectance on the glass surface side can be reduced to 15% or less. Unnecessary reflection and scattering during exposure can be prevented.

Next, the manufacturing method of the gradation photomask of this invention is demonstrated.
The gradation photomask 2 of the present invention uses a photomask substrate 1 in which a transflective layer 20, a stopper layer 30, a light shielding layer 43, and an antireflection layer 45 are sequentially stacked on the surface of a transparent substrate 10, Each layer is manufactured by forming a predetermined pattern by wet etching. Examples of the film forming method include physical vapor deposition (PVD) using vacuum such as sputtering, ion plating, and vapor deposition, and vapor deposition (CVD) such as plasma CVD and thermal CVD. In addition, when forming into a film by sputtering, reactive sputtering can also be utilized other than normal sputtering.
In this embodiment, the film was formed by reactive sputtering.

(Thin film formation process)
In the thin film formation (film formation) in the present embodiment, the transflective layer 20 is sputtered on the transparent substrate 10 using a chromium target. Argon gas (Ar) and nitrogen gas (N ₂ ) and / or oxygen gas (O ₂ ) were introduced into a thin film forming apparatus evacuated to about 1 × 10 ⁻⁴ Pa (Pascal), and 2 to 3 × A compound thin film made of chromium, nitrogen, and oxygen is formed by sputtering in a reactive gas atmosphere of about 10 ⁻¹ Pa.
The transparent substrate 10 is set in the apparatus so as to face the target. By applying a negative voltage to the target, the chromium sputtered from the target is accelerated by the plasma in a nitrogen gas and oxygen gas atmosphere to reach the substrate, thereby forming a thin film.
When the proportion of nitrogen in the thin film is small, the etching rate is increased, and overetching tends to occur when the light shielding layer is etched at the same time. Therefore, the amount of nitrogen gas introduced at the time of sputtering is controlled appropriately.
Of course, when the transmittance is flattened at a plurality of exposure wavelengths to be used (350 nm to 500 nm) or a certain difference in transmittance is required, not only the above-described nitrogen and oxygen, but also oxygen or carbon dioxide (CO ₂ ) And hydrocarbons (CH ₄ ) and the like can also be used in combination.

Next, the stopper layer 30 is sputtered on the semi-transmissive layer 20 using a titanium target. As in the case of the semi-transmissive layer 20, the thin film is formed by introducing oxygen gas (O ₂ ) and nitrogen gas (N ₂ ) into a thin film forming apparatus that is evacuated to about 1 × 10 ⁻⁴ Pa, and 2 to 3 ×. A titanium oxynitride thin film is formed by sputtering in a reactive gas atmosphere of about 10 ⁻¹ Pa. The transparent substrate 10 on which the semi-transmissive layer 20 is formed is set facing. By applying a negative voltage to the target, titanium sputtered from the target is accelerated by the plasma in an atmosphere of oxygen gas and nitrogen gas to reach the substrate, thereby forming a thin film.
At this time, the ratio of titanium, oxygen and nitrogen in the thin film is 26.5 to 36.5 atm%, 32.0 to 39.5 atm%, and 29. A range of 5 to 41.0 atm% (ESCA quantitative analysis value) is preferable.
When the ratio of nitrogen taken in during the film formation of the stopper layer 30 increases, the stopper function tends to decrease and the etching rate becomes slower. On the other hand, when the nitrogen ratio is low and the oxygen ratio is increased, the pattern breakage becomes worse and the alkaline solution resistance tends to deteriorate.
Moreover, a titanium (Ti) thin film can be formed by introducing only argon gas (Ar) into a thin film forming apparatus and performing sputtering in an inert gas atmosphere of about 1 × 10 ⁻¹ Pa. By applying a negative voltage to the target, titanium is sputtered from the target and reaches the substrate, thereby forming the stopper layer 30.

Next, the light shielding layer 43 is sputtered on the stopper layer 30 formed as described above using a chromium target. Similarly to the above, chromium is obtained by introducing only argon gas (Ar) into a thin film forming apparatus evacuated to about 1 × 10 ⁻⁴ Pa and sputtering in an inert gas atmosphere of about 1 × 10 ⁻¹ Pa. A thin film is formed. At this time, the transparent substrate 10 on which the semi-transmissive layer 20 is formed is set in the apparatus so as to face the target. By applying a negative voltage to the target, chromium sputtered from the target reaches the substrate to form the light shielding layer 43.

  Further, an antireflection layer 45 is formed on the light shielding layer 43. This antireflection layer 45 can also be formed into a thin film by sputtering. The antireflection layer 45 uses a reactive gas such as oxygen or nitrogen because it is necessary to form a thin film that absorbs less irradiation light than the light shielding layer 43 in order to produce an antireflection effect. Furthermore, the etching rate and the pattern edge shape can be finely controlled by utilizing the reaction with any of carbon dioxide, hydrocarbon gas, or mixed gas.

  A process for forming a pattern on the gradation photomask substrate 1 formed as described above will be described below with reference to FIGS. 3 to 5 and FIGS.

First, the pattern forming process shown in FIGS. 3A to 5L will be described.
As shown in FIG. 3A, a gradation photomask substrate 1 in which a thin film is formed (film formation) by sputtering is prepared.
FIG. 3B shows a first resist coating process.
A resist 50 is coated on the surface of the gradation photomask substrate 1 by spin coating or roll coating. The coated resist 50 is cured (prebaked) by an oven or the like.

FIG. 3C shows the first exposure process.
A mask pattern is drawn on the resist 50 using the first mask original plate 60. A desired pattern is prepared in advance on the mask original, and this pattern can be transferred to the resist 50. Exposure is performed by irradiating the resist 50 with ultraviolet rays through the mask original. Thus, the resist 50 is exposed.

FIG. 3D shows a first resist removal step.
The resist 50 that has been exposed is immersed in a developing solution, and the resist in the region exposed to the ultraviolet rays of the resist 50 is dissolved and removed to expose the surface of the antireflection layer 45 along the resist pattern. After removing a part of the resist 50, the remaining resist pattern 50 is heated by an oven or the like to be fully cured (post-baked). The same pattern as the mask pattern 1 is formed by the resist 50.

FIG. 4E shows the first etching process.
The antireflection layer 45 and the light shielding layer 43 are etched using a first etching solution (mixed solution of ceric ammonium nitrate, perchloric acid, and water). Etching includes a method of immersing the substrate in the above-described state in a constant temperature bath filled with an etching solution and a constant temperature, and a method of applying an etching solution by a shower of etching solution controlled to a constant temperature, etc. A method may be used. The antireflection layer 45 and the light shielding layer 43 are formed of a material having physical properties that can be collectively etched in the thin film forming process. By the first etching process, an antireflection pattern 45 a and a light shielding pattern 43 a are formed on the antireflection layer 45 and the light shielding layer 43 in accordance with the mask pattern 1.
At this time, since the stopper layer 30 has sufficient resistance to the first etching solution (mixed solution of cerium ammonium nitrate, perchloric acid and water), the semi-transmissive layer 20 can be surely affected without any damage. In addition, the composite layer 40 can be etched.

FIG. 4F shows the second etching process.
After the etching solution used in the first etching step is washed away, the etching solution is changed as it is, and the stopper layer 30 is etched. Etching is performed in the same manner as in etching step 1 by filling the second etching solution (mixed solution of hydrogen peroxide, potassium hydroxide and water) and immersing the substrate in a constant temperature bath controlled at a constant temperature, There is a method of applying an etching solution by a temperature-controlled etching solution shower or the like, and any method may be used.
In this way, the stopper layer 30 is etched to form the stopper pattern 30a. At this time, the transflective layer 20, the antireflection pattern 45a, and the light shielding pattern 43a are sufficiently resistant to the etching solution of the stopper 30, and therefore, damage due to etching does not occur. Depending on the configuration of the etching line, even if the resist pattern is removed and then etched, there is no problem because the light shielding pattern 43a and the antireflection pattern 45a are sufficiently resistant to the second etching solution.

FIG. 4G shows the first resist stripping process.
The resist remaining on the surface is removed by dissolving with a resist stripping solution, and the surface is further washed. Thus, the same pattern as the first mask pattern can be formed on the transparent substrate 10.

FIG. 4H shows a second resist coating process.
On the substrate surface where the pattern in which the semi-transmissive layer 20 and the stopper layer 30 (stopper pattern 30a), the light shielding layer 43 (light shielding pattern 43a), and the antireflection layer 45 (antireflection pattern 45a) are laminated is exposed on the surface, spin coating or The resist 50 is coated by roll coating or the like. Further, the coated resist 50 is cured (prebaked) by an oven or the like.

FIG. 5I shows a second exposure process.
A mask pattern is drawn on the resist 50 using the second mask original plate 70. A desired pattern is prepared in advance on the mask original, and this pattern can be transferred to the resist 50. The resist 50 is exposed to ultraviolet rays through the second mask original plate 70 to be exposed. Thus, the resist 50 is exposed.

FIG. 5J shows the second resist removal step.
The resist 50 that has been exposed is immersed in a developing solution, and the resist in the region exposed to ultraviolet rays of the resist 50 is dissolved and removed, so that the surfaces of the antireflection layer 45 and the semi-transmissive layer 20 are exposed along the resist pattern. After removing a part of the resist 50, the remaining resist pattern 50 is heated by an oven or the like to be fully cured (post-baked). Thus, the same pattern as the mask pattern 2 is created by the resist 50.

FIG. 5K shows a third etching step.
The antireflection pattern 45a, the light shielding pattern 43a, and the semi-transmissive layer 20 are etched using a first etching solution (mixed solution of ceric ammonium nitrate, perchloric acid, and water). Etching is performed by the same method as in the first etching step.
The antireflection pattern 45a and the light shielding pattern 43a are formed of a material having physical properties that can be collectively etched in the thin film forming process. At this time, the semi-transmissive layer 20 is also etched together with a mixed solution of cerium ammonium nitrate, perchloric acid, and water to form a semi-transmissive pattern 20a. The stopper pattern 30a is sufficiently resistant to the first etching solution (mixed solution of cerium ammonium nitrate, perchloric acid, and water), so that the stopper pattern 30a can be reliably etched without causing any damage or the like.

FIG. 5L shows the second resist stripping step.
The resist remaining on the surface is removed by dissolving with a resist stripping solution, and the surface is further washed. Thus, the same pattern as the second mask pattern can be formed on the transparent substrate 10.

  In this way, a pattern in which the first mask pattern and the second mask pattern are combined is completed. As a result, a four-tone pattern (four-tone photomask) having a cross-sectional view shown in FIG. 2 can be manufactured.

Next, the pattern forming process shown in FIGS. 6A to 8L will be described.
First, as shown in FIG. 6A, the above-described gradation photomask substrate 1 formed by sputtering is prepared.
FIG. 6B shows a first resist coating process.
A resist 50 is coated on the surface of the gradation photomask substrate by spin coating or roll coating. Further, the coated resist 50 is cured (prebaked) by an oven or the like.

FIG. 6C shows the first exposure process.
A mask pattern is drawn on the resist 50 using the first mask original plate 60. A desired pattern is prepared in advance on the mask original, and this pattern can be transferred to the resist 50. Exposure is performed by irradiating the resist 50 with ultraviolet rays through the mask original. Thus, the resist 50 is exposed.

FIG. 6D shows the first resist removal step.
The resist 50 that has been exposed is immersed in a developing solution, and the resist in the region exposed to the ultraviolet rays of the resist 50 is dissolved and removed to expose the surface of the antireflection layer 45 along the resist pattern. After removing a part of the resist 50, the remaining resist pattern 50 is heated by an oven or the like to be fully cured (post-baked). Thus, the same pattern as the mask pattern 1 is created by the resist 50.

FIG. 7E shows the first etching step.
The antireflection layer 45 and the light shielding layer 43 are etched using a first etching solution (mixed solution of ceric ammonium nitrate, perchloric acid, and water). Etching includes a method of immersing the substrate in the above-described state in a constant temperature bath filled with an etching solution and a constant temperature, and a method of applying an etching solution by a shower of etching solution controlled to a constant temperature, etc. A method may be used. The antireflection layer 45 and the light shielding layer 43 are formed of a material having physical properties that can be collectively etched in the thin film forming process.
At this time, since the stopper layer 30 has sufficient resistance to the first etching solution (mixed solution of cerium ammonium nitrate, perchloric acid and water), the semi-transmissive layer 20 can be surely affected without any damage. In addition, the composite layer 40 can be etched.

FIG. 7F shows a first resist stripping process.
The resist remaining on the surface is removed by dissolving with a resist stripping solution, and the surface is further washed. Thus, the same pattern as the first mask pattern is formed by laminating the first semi-transmissive layer 20 and the stopper layer 30 on the transparent substrate 10, and further, the pattern 40a in which the light shielding layer 43a and the antireflection layer 45a are laminated thereon. Form.

FIG. 7G shows the second resist coating step.
A resist 50 is coated by spin coating, roll coating, or the like on the substrate surface where the pattern in which the stopper layer 30, light shielding layer 43, and antireflection layer 45 are laminated is exposed on the surface. Further, the coated resist 50 is cured (prebaked) by an oven or the like.

FIG. 7H shows the second exposure process.
A mask pattern is drawn on the resist 50 using the second mask original plate 70. A desired pattern is prepared in advance on the mask original, and this pattern can be transferred to the resist 50. Exposure is performed by irradiating the resist 50 with ultraviolet rays through the mask original. Thus, the resist 50 is exposed.

FIG. 8I shows a second resist removal step.
The resist 50 that has been exposed is immersed in a developing solution, and the resist in the region exposed to ultraviolet rays of the resist 50 is dissolved and removed to expose the surfaces of the antireflection layer 45 and the stopper layer 30 along the resist pattern. After removing a part of the resist 50, the remaining resist pattern 50 is heated by an oven or the like to be fully cured (post-baked). Thus, the same pattern as the mask pattern 2 is formed by the resist 50.

FIG. 8J shows the second etching process.
The stopper layer 30 is etched using a second etching solution (mixed solution of hydrogen peroxide, potassium hydroxide and water). Etching consists of a method of immersing the substrate in a constant temperature bath filled with a second etching solution (mixed solution of hydrogen peroxide, potassium hydroxide and water) and controlled at a constant temperature, and etching controlled at a constant temperature. There is a method of applying an etching solution by a liquid shower or the like, and any method may be used. Since the antireflection layer 45, the light shielding layer 43, and the semi-transmissive layer 20 are sufficiently resistant to the second etching solution (mixed solution of hydrogen peroxide, potassium hydroxide, and water), there is no influence such as damage. Therefore, the stopper layer 30 can be etched without fail.

FIG. 8K shows a third etching step.
After the second etching solution is washed away, the etching solution is changed as it is, and the light shielding layer 43, the antireflection layer 45, and the semi-transmissive layer 20 are etched. Etching can be performed by a method of immersing the substrate in a constant temperature bath filled with the first etching solution and controlled at a constant temperature, and a shower of etching solution controlled at a constant temperature, as in the etching step 1. . In this way, the light shielding layer 43, the antireflection layer 45, and the semi-transmissive layer 20 can be etched. At this time, the stopper 30 is sufficiently resistant to the etching solution (first etching solution) for the semi-transmissive layer 20, the antireflection layer 45, and the light shielding layer 43.

FIG. 8L shows a second resist stripping step.
The resist remaining on the surface is removed by dissolving with a resist stripping solution, and the surface is further washed. Thus, the same pattern as the second mask pattern can be formed on the transparent substrate 10.

  In this way, a pattern in which the first mask pattern and the second mask pattern are combined is completed. As a result, a three-tone pattern (three-tone photomask) without the first semi-transmissive layer 1c in the cross-sectional view shown in FIG. 2 can be manufactured.

According to the manufacturing method of the gradation photomask of the present invention, only the transparent substrate 10 is obtained by one thin film forming step and two photolithography steps by the manufacturing method shown in FIGS. 3 (a) to 5 (l). 4th floor where there is a transparent region 1d, a first semi-transmissive region 1c, a second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are stacked, and a light-shielding region 1a having a low reflective layer A toned photomask (see FIG. 2) can be manufactured.
Further, according to the manufacturing method shown in FIGS. 6A to 8L, the entire transmission region 1d, the semi-transmission layer 20 and the stopper only in the transparent substrate 10 are obtained by one thin film forming process and two photolithography processes. A three-tone photomask in which the second semi-transmissive region 1b formed by stacking the layers 30 and the light-shielding region 1a having a low reflection layer are present can be manufactured.

Specific examples of the present invention will be described below.
(Example 1)
The formation method of each layer of the present invention is a manufacturing method using vacuum technology, and basically controls the substrate temperature, film formation pressure, film formation rate, and reaction gas in the sputtering method, ion plating method, vapor deposition method, etc. By doing so, a desired thin film can be obtained.
In Example 1, a chromium, nitrogen and oxygen compound thin film as the semi-transmissive layer 20, a titanium, nitrogen and oxygen compound thin film as the stopper layer 30, a chromium thin film as the light shielding layer 43, This is an example in which a compound thin film of chromium, oxygen, and nitrogen as the antireflection layer 45 is formed. In Example 1, the semi-transmissive layer 20, the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are stacked by sputtering.

In Example 1, first, a quartz substrate (transparent substrate 10) that has been flattened by polishing and sufficiently cleaned is set in a holder in a sputtering apparatus, and a commercially available metal chromium target (purity: 99.99% up) is used. Then, reactive sputtering was performed. Sputtering is a vacuum apparatus in which, after evacuating to 1 × 10 ⁻⁴ Pa, argon gas, oxygen gas and nitrogen gas are introduced at a ratio of 35:15:50 and maintained at 2.5 × 10 ⁻¹ Pa. Sputtering while reacting with chromium at an inner atmosphere and a substrate temperature of 150 ° C., the compound of chromium as the semi-transmissive layer 20 (ratio of chromium, oxygen and nitrogen in the film is 34.5 to 38.5 atm%, respectively) 43.5 to 50.5 atm%, 15.0 to 19.5 atm%: ESCA quantitative analysis value).
At this time, the semi-transmissive layer 20 was directly formed on the substrate so that the transmittance at i-line (wavelength 365 nm) was 50%.
The target for forming the semi-transmissive layer 20 may be a target obtained by bonding a mixed sintered body of chromium oxide and chromium metal in addition to the metal chromium target.

The metal chromium target was switched to the metal titanium target, and the stopper layer 30 was formed on the surface of the semi-transmissive layer 20 so as to have a film thickness of 100 mm (10 nm). Sputtering is performed in an atmosphere in a vacuum apparatus in which nitrogen gas and oxygen gas are introduced at a ratio of 98: 2 and maintained at 1 × 10 ⁻¹ Pa, at a substrate temperature of 150 ° C., with titanium compound 30 (titanium, oxygen in the film, The ratio of nitrogen formed 26.5-36.5 atm%, 32.0-39.5 atm%, 29.5-41.0 atm%: ESCA quantitative analysis value, respectively.
The target at this time may be a sintered body of titanium nitride powder other than the metal titanium target. Further, as with the semi-transmissive layer 20, since the degree of reaction varies depending on the apparatus, the film forming conditions are adjusted in combination as appropriate.

Next, switching to another metal chromium target, a chromium film as the light shielding layer 43 was formed to a thickness of 700 mm (70 nm). Sputtering at this time was formed in a vacuum apparatus atmosphere maintained at 1 × 10 ⁻¹ Pa only by introducing argon gas and at a substrate temperature of 150 ° C. The chromium film thickness of 700 mm formed here has an optical density of about 3.1, and has a function of sufficiently shielding the exposure light (365 nm, 436 nm).
Further, the reflectance of the light-shielding layer chromium film at this time is usually around 55%, and this reflectance has an adverse effect upon exposure. It is therefore necessary to make this reflection as low as possible.

Then, a chromium target is switched to the metallic chromium target used for film formation of the semi-transmissive layer 20, while introducing argon gas and oxygen gas and nitrogen gas at a ratio of 30:10:60 2.5 × 10 ^- Sputtering while reacting with chromium at an atmosphere in a vacuum apparatus maintained at ¹ Pa and a substrate temperature of 150 ° C., the compound of chromium as the antireflection layer 45 (the ratio of chromium metal to oxygen and nitrogen in the film is 37 respectively) .5-44.5 atm%, 39.5-46.0 atm%, 13.5-17.0 atm%: ESCA quantitative analysis value).
At this time, the antireflection layer 45 is a thin film that absorbs less irradiation light than the chromium of the light shielding layer 43 and has a thickness of about 300 mm. As a result, an antireflection effect due to multiple interference of light (reflectance at 365 nm to 436 nm is 15% or less) occurs between the light shielding layer 43 and the antireflection layer 45 formed thereon. Light reflection and scattering were reduced.

  The formed photomask substrate 1 is subjected to ultrasonic cleaning with a plurality of alkaline detergents, neutral detergents, and pure water, and then a resist (manufactured by AZ Electronic Materials Co., Ltd.) is formed on the surface. AZRFP-230K2) was applied over the entire surface and temporarily cured. In this resist coating process, the surface of the photomask substrate 1 is not surface-treated with chemicals, plasma, ultraviolet rays, or the like. Hereinafter, the same applies to similar processing.

After curing the resist, exposure of the first test pattern (Oak Manufacturing Jet Printer: light source CHM-2000, exposure for 20 seconds with an ultra-high pressure mercury lamp), development (Tokyo Ohka Co., Ltd. PMER: developer: temperature 30 ° C., 1 Minute) and main curing (DX402 dry oven manufactured by Yamato Scientific: 120 ° C., 10 minutes). Subsequently, a mixed solution of perchloric acid, cerium ammonium nitrate and water as the first etching liquid (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) As a result, a part of the stopper layer 30 was exposed and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
The first etching solution was washed with pure water and dried as it was, and then the substrate (photomask substrate 1 subjected to processing) was taken out and the surface was observed. The effect of the stopper layer 30 as a stopper layer was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 85 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, the pattern (semi-transmissive pattern 20a) surface of the semi-transmissive layer 20 is damaged to the semi-transmissive layer 20 in the same manner as when etching is completed. In addition, no damage was observed on the surface of the antireflection layer 45 as well.

Next, after thoroughly cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, a resist (AZRFP-230K2 manufactured by AZ Electronic Materials Co., Ltd.) is applied to the entire surface of the substrate. Application and temporary curing were performed. After curing the resist, exposure of the second test pattern (Oak Manufacturing Jet Printer: light source CHM-2000, exposure for 20 seconds with an ultra-high pressure mercury lamp), development (Tokyo Ohka Co., Ltd. PMER: developer: temperature 30 ° C., 1 Minute) and main curing (DX402 dry oven manufactured by Yamato Scientific: 120 ° C., 10 minutes). Subsequently, a mixed solution of perchloric acid, cerium ammonium nitrate and water (perchloric acid: cerium ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds, which is the first etching solution. ) To etch part of the laminated pattern of the light shielding layer 43 and the antireflection layer 45 and part of the semi-transmissive layer 20.
The resist is removed by a predetermined resist stripping solution, the light shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the first of the semi-transmissive layer 20 only. A four-tone photomask having a semi-transmission region 1c and a total transmission region 1d of only the transparent substrate 10 was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Example 2)
Example 2 is a design example in which the thickness of the stopper layer 30 is changed. In Example 2, the film thickness of the stopper layer 30 is set to 200 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film formation conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in the first embodiment.

As in Example 1, a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: cerium ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching) Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage was observed on the semi-transmissive layer 20, and the effect of the stopper layer 30 was ensured. It was appearing.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 170 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, the resist was removed with a predetermined resist stripping solution, and the pattern surface was confirmed. As a result, the pattern surface of the semi-transmissive layer 30 was not damaged similarly to the time when the etching was completed. Was in very good condition.

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Example 1, perchloric acid and cerium ammonium nitrate as the first etching solution are used. A pattern in which the light-shielding layer 43 and the antireflection layer 45 are laminated by immersion in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Example 3)
Example 3 is a design example in which the thickness of the stopper layer 30 is changed. In Example 3, the film thickness of the stopper layer 30 is set to 300 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film formation conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in the first embodiment.

As in Example 1, a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: cerium ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching) Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage was observed on the semi-transmissive layer 20, and the stopper layer 30 was used as an etching stopper layer. The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 260 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, no damage was observed on the pattern surface of the semi-transmissive layer 20, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Example 1, perchloric acid and cerium ammonium nitrate as the first etching solution are used. A pattern in which the light-shielding layer 43 and the antireflection layer 45 are laminated by immersion in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

Example 4
Example 4 is a design example in which the thickness of the stopper layer 30 is changed. In Example 4, the film thickness of the stopper layer is set to 400 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film formation conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in the first embodiment.

As in Example 1, a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: cerium ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching) Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage was observed on the semi-transmissive layer 20, and the stopper layer 30 was used as an etching stopper layer. The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 340 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, no damage was observed on the pattern surface of the semi-transmissive layer 20, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Example 1, perchloric acid and cerium ammonium nitrate as the first etching solution are used. A pattern in which the light-shielding layer 43 and the antireflection layer 45 are laminated by immersion in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Example 5)
Example 5 is a design example in which the thickness of the stopper layer 30 is changed. In Example 5, the film thickness of the stopper layer 30 is set to 500 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film formation conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in the first embodiment.

As in Example 1, a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: cerium ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching) Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage was observed on the semi-transmissive layer 20, and the stopper layer 30 was used as an etching stopper layer. The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 420 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, no damage was observed on the pattern surface of the semi-transmissive layer 20, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Example 1, perchloric acid and cerium ammonium nitrate as the first etching solution are used. A pattern in which the light-shielding layer 43 and the antireflection layer 45 are laminated by immersion in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed with a predetermined resist stripping solution, the light-shielding region 1a having the antireflection layer, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the first of the semi-transmissive layer only. The four-tone photomask having the semi-transmissive region 1c and the total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Example 6)
In the sixth embodiment, unlike the first to fifth embodiments, the chemical component of the stopper layer 30 is replaced with a titanium thin film from a titanium compound thin film (a compound of titanium, nitrogen, and oxygen). The semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in Examples 1 to 5.

In Example 6, first, a quartz substrate (transparent substrate 10) that was flattened by polishing and sufficiently cleaned was set in a holder in a sputtering apparatus, and a commercially available metal chromium target (99.99% up) was used. Reactive sputtering was performed. Sputtering is performed by evacuating to 1 × 10 ⁻⁴ Pa once, and then the atmosphere in the vacuum apparatus is maintained at 2.5 × 10 ⁻¹ Pa while introducing argon gas, nitrogen gas, and oxygen gas at a ratio of 35:15:50. Sputtering was performed while reacting with chromium at a substrate temperature of 150 ° C., thereby forming a chromium compound as the semi-transmissive layer 20. At this time, the semi-transmissive layer 20 was directly formed on the substrate so that the transmittance of i-line (wavelength 365 nm) was 50% as in Example 1.

Next, the metal chromium target was switched to the metal titanium target, and the stopper layer 30 was formed on the surface of the semi-transmissive layer 20 so as to have a film thickness of 100 mm (10 nm). In this sputtering, a titanium thin film was formed in an atmosphere in a vacuum apparatus maintained at 1 × 10 ⁻¹ Pa while introducing only argon gas.

Subsequently, switching to another metal chromium target was performed, and a chromium film as the light shielding layer 43 was formed to a film thickness of 700 mm (70 nm). Sputtering at this time was formed in an atmosphere in a vacuum apparatus maintained at about 1 × 10 ⁻¹ Pa only by introducing argon gas. The chromium film thickness of 700 mm formed here has an optical density of about 3.1, and has a function of shielding the exposure light (365 nm, 436 nm).

Then, a chromium target is switched to the metallic chromium target used for film formation of the semi-transmissive layer 20, introducing argon gas and oxygen gas and nitrogen gas at a ratio of 30:10:60, 2.5 × 10 ^- Sputtering was performed while reacting with chromium in a vacuum apparatus atmosphere maintained at ¹ Pa to form a chromium compound as the antireflection layer 45.

  The substrate on which the film was formed was subjected to ultrasonic cleaning with each of a plurality of alkaline detergents, neutral detergents, and pure waters, and then a resist (AZ Electronic Materials Co., Ltd.) was formed on the surface of the photomask substrate 1. ) AZRFP-230K2) was applied over the entire surface and temporarily cured.

After curing the resist, exposure of the first test pattern (Oak Manufacturing Jet Printer: light source CHM-2000, exposure for 20 seconds with an ultra-high pressure mercury lamp), development (Tokyo Ohka Co., Ltd. PMER: developer: temperature 30 ° C., 1 Minute) and main curing (DX402 dry oven manufactured by Yamato Scientific: 120 ° C., 10 minutes). Subsequently, a mixed solution of perchloric acid, cerium ammonium nitrate and water as the first etching liquid (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) As a result, a part of the stopper layer 30 was exposed and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage was observed on the semi-transmissive layer 20, and the stopper layer 30 was used as an etching stopper layer. The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 65 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, the resist was removed with a predetermined resist stripping solution and the pattern surface was confirmed. As a result, no damage was observed on the pattern surface of the semi-transmissive layer 20, and the effect of the stopper layer 30 appeared. The surface of the antireflection layer 45 had no problem at all.

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, a resist (AZRFP-230K2 manufactured by AZ Electronic Materials Co., Ltd.) is formed on the surface of the substrate. Was applied to the entire surface and temporarily cured. After curing the resist, exposure of the second test pattern (Oak Manufacturing Jet Printer: light source CHM-2000, exposure for 20 seconds with an ultra-high pressure mercury lamp), development (Tokyo Ohka Co., Ltd. PMER: developer: temperature 30 ° C., 1 Minute) and main curing (DX402 dry oven manufactured by Yamato Scientific: 120 ° C., 10 minutes). Subsequently, a mixed solution of perchloric acid, cerium ammonium nitrate and water as the first etching solution (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) Then, a part of the laminated pattern of the light shielding layer 43 and the antireflection layer 45 and a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Example 7)
Example 7 is a design example in which the thickness of the stopper layer 30 of Example 6 is changed. In Example 7, the film thickness of the stopper layer 30 is set to 200 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film formation conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in the first embodiment.

As in Example 6, a mixed solution of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: cerium ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching as in Example 6) Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage was observed on the semi-transmissive layer 20, and the stopper layer 30 was used as an etching stopper layer. The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 130 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, no damage was observed on the pattern surface of the semi-transmissive layer 20, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, the same as in Example 6, perchloric acid and cerium ammonium nitrate as the first etching solution A pattern in which the light-shielding layer 43 and the antireflection layer 45 are laminated by immersion in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed with a predetermined resist stripping solution, and only the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer 20 only. A four-tone photomask having the first transflective region 1c and the total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Example 8)
Example 8 is a design example in which the thickness of the stopper layer 30 of Example 6 is changed. In Example 8, the film thickness of the stopper layer 30 is set to 300 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film formation conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in the first embodiment.

As in Example 6, a mixed solution of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: cerium ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching as in Example 6) Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. The effect was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 200 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, the pattern surface of the semi-transmissive layer 20 is not damaged as in the first etching completion, and the antireflection layer The 45 surface had no problem at all.

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, the same as in Example 6, perchloric acid and cerium ammonium nitrate as the first etching solution A pattern in which the light-shielding layer 43 and the antireflection layer 45 are laminated by immersion in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

  Furthermore, the chromium compound thin film of the semi-transmissive layer 20 is in a state in which the nitrogen ratio is higher than those in Examples 1 to 5 and Examples 6 to 8 (the ratios of chromium, oxygen, and nitrogen in the film are 44.0 to 50.5 atm, respectively). %, 25.0-29.0 atm%, 25.5-28.0 atm%: ESCA quantitative analysis value), the same results as in Examples 1-5 and Examples 6-8 were obtained.

In Examples 1 to 8 described above, the semi-transmissive layer 20 is formed of a compound of chromium, nitrogen, and oxygen.
In the following Comparative Examples 1 to 8, examples where the transflective layer 20 is replaced with chromium metal will be described.
The stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are the same as in Examples 1-8.

(Comparative Example 1)
In Comparative Example 1, first, a quartz substrate 10 that has been flattened by polishing and sufficiently cleaned is set in a holder in a sputtering apparatus, and a commercially available metal chromium target (99.99% up) is used to perform reactive sputtering. Went. Sputtering is performed by evacuating the metal chromium to 1 × 10 ⁻⁴ Pa and then sputtering metal chromium in an atmosphere in a vacuum apparatus maintained at 1 × 10 ⁻¹ Pa while introducing argon gas. A certain chromium thin film was formed. At this time, the semi-transmissive layer 20 was directly formed on the substrate so that the transmittance of i-line (wavelength 365 nm) was 50%.

Next, the metal chromium target was switched to the metal titanium target, and the stopper layer 30 was formed on the surface of the semi-transmissive layer 20 so as to have a film thickness of 100 mm (10 nm). Sputtering at this time was performed in an atmosphere in a vacuum apparatus maintained at 1 × 10 ⁻¹ Pa while introducing nitrogen gas and oxygen gas, and the titanium compound 30 (the ratios of titanium, oxygen, and nitrogen in the film were 26. 5-36.5 atm%, 32.0-39.5 atm%, 29.5-41.0 atm%: ESCA quantitative analysis value). Sputtering at this time formed a titanium compound in an atmosphere in a vacuum apparatus maintained at 1 × 10 ⁻¹ Pa while introducing nitrogen gas and oxygen gas at a ratio of 98: 2.

Subsequently, switching to another metal chromium target was performed, and a chromium film as the light shielding layer 43 was formed to a film thickness of 700 mm (70 nm). Sputtering at this time was formed in an atmosphere in a vacuum apparatus maintained at 1 × 10 ⁻¹ Pa only by introducing argon gas. The chromium film thickness of 700 mm formed here has an optical density of about 3.1, and has a function of shielding the exposure light (365 nm, 436 nm).

Subsequently, the chromium target is switched to the metal chromium target used for forming the semi-transmissive layer 20, and 1 × 10 ⁻¹ Pa while introducing argon gas, oxygen gas, and nitrogen gas at a ratio of 30:10:60. The oxynitride thin film, which is a compound of chromium as the antireflection layer 45, was formed to a thickness of 300 mm by sputtering while reacting with chromium in an atmosphere in a vacuum apparatus held in the above.

  The substrate on which the film was formed was subjected to ultrasonic cleaning with a plurality of alkaline detergents, neutral detergents, and pure water, and then a resist (AZ Electronic Materials Co., Ltd.) was formed on the surface of the photomask substrate 1. ) AZRFP-230K2) was applied over the entire surface and temporarily cured. In this resist coating process, the surface of the photomask substrate 1 is not surface-treated with chemicals, plasma, ultraviolet rays, or the like. Hereinafter, the same applies to similar processing.

After curing the resist, exposure of the first test pattern (Oak Manufacturing Jet Printer: light source CHM-2000, exposure for 20 seconds with an ultra-high pressure mercury lamp), development (Tokyo Ohka Co., Ltd. PMER: developer: temperature 30 ° C., 1 Minute) and main curing (DX402 dry oven manufactured by Yamato Scientific: 120 ° C., 10 minutes). Subsequently, a mixed solution of perchloric acid, cerium ammonium nitrate and water as the first etching liquid (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) As a result, a part of the stopper layer 30 was exposed and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage to the chromium thin film as the semi-transmissive layer 20 was observed, and the stopper layer 30 The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, the reaction temperature was 30 ° C., the etching time was 85 seconds), and the stopper layer 30 was etched.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, no damage was observed on the pattern surface of the semi-transmissive layer 20, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the pattern substrate on which the semi-transmissive layer 20 (semi-transmissive pattern 20a), the stopper layer 30 (stopper pattern 30a), and the composite layer 40 (composite pattern 40a) are stacked, the surface of the surface of the substrate A resist (AZRFP-230K2 manufactured by AZ Electronic Materials Co., Ltd.) was applied onto the entire surface of the resist and temporarily cured. After curing the resist, exposure of the second test pattern (Oak Manufacturing Jet Printer: light source CHM-2000, exposure for 20 seconds with an ultra-high pressure mercury lamp), development (Tokyo Ohka Co., Ltd. PMER: developer: temperature 30 ° C., 1 Minute) and main curing (DX402 dry oven manufactured by Yamato Scientific: 120 ° C., 10 minutes). Subsequently, a mixed solution of perchloric acid, cerium ammonium nitrate and water as the first etching solution (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) Then, a part of the laminated pattern of the light shielding layer 43 and the antireflection layer 45 and a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed with a predetermined resist stripping solution, the light-shielding region 1a having the antireflection layer, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the first of the semi-transmissive layer only. The four-tone photomask having the semi-transmissive region 1c and the total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, taper shape and appearance defect in each layer were not confirmed, and the film was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Comparative Example 2)
Comparative Example 2 is a design example in which the thickness of the stopper layer 30 of Comparative Example 1 is changed. In Comparative Example 2, the film thickness of the stopper layer 30 is set to 200 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film forming conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in Comparative Example 1.

As in Comparative Example 1, the first etchant was a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage to the chromium thin film as the semi-transmissive layer 20 was observed, and the stopper layer 30 The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 170 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, the pattern surface of the semi-transmissive layer 20 was not damaged, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Comparative Example 1, the first etching solution is perchloric acid or cerium ammonium nitrate. A pattern in which the light-shielding layer 43 and the antireflection layer 45 are laminated by immersion in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Comparative Example 3)
Comparative Example 3 is a design example in which the thickness of the stopper layer 30 is changed. In Comparative Example 3, the film thickness of the stopper layer 30 is set to 300 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film forming conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in Comparative Example 1.

As in Comparative Example 1, the first etchant was a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage to the chromium thin film as the semi-transmissive layer 20 was observed, and the stopper layer 30 The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 260 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, the pattern surface of the semi-transmissive layer 20 was not damaged, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Comparative Example 1, the first etching solution is perchloric acid or cerium ammonium nitrate. And a mixed solution of water (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) and a pattern in which the light shielding layer 43 and the antireflection layer 45 are laminated. A part and a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Comparative Example 4)
Comparative Example 4 is a design example in which the thickness of the stopper layer 30 is changed. In Comparative Example 4, the film thickness of the stopper layer 30 is set to 400 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film forming conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in Comparative Example 1.

As in Comparative Example 1, the first etchant was a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etchant was washed with pure water and dried, and then the substrate was taken out and the surface was observed. The effect was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 340 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, the pattern surface of the semi-transmissive layer 20 was not damaged, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Comparative Example 1, the first etching solution is perchloric acid or cerium ammonium nitrate. A pattern in which the light-shielding layer 43 and the antireflection layer 45 are laminated by immersion in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Comparative Example 5)
Comparative Example 5 is a design example in which the film thickness of the stopper layer 30 is changed. In Comparative Example 5, the thickness of the stopper layer is set to 500 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film forming conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in Comparative Example 1.

As in Comparative Example 1, the first etchant was a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. No damage was observed on the semi-transmissive layer 20, and the effect of the stopper layer 30 was recognized. It was.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 420 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, no damage was observed on the pattern surface of the semi-transmissive layer 20, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Comparative Example 1, the first etching solution is perchloric acid or cerium ammonium nitrate. A pattern in which the light-shielding layer 43 and the antireflection layer 45 are laminated by immersion in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed with a predetermined resist stripping solution, the light-shielding region 1a having the antireflection layer, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the first of the semi-transmissive layer only. The four-tone photomask having the semi-transmissive region 1c and the total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Comparative Example 6)
Unlike Comparative Examples 1 to 5, Comparative Example 6 is an example in which the chemical component of the stopper layer 30 is replaced with a titanium (Ti) thin film from a titanium compound thin film (a compound of titanium, nitrogen, and oxygen). . The transflective layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in Comparative Examples 1-5.

In Comparative Example 6, first, a quartz substrate (transparent substrate 10) flattened by polishing and sufficiently cleaned is set in a holder in a sputtering apparatus, and a commercially available metal chromium target (99.99% up) is used. Sputtering was performed. Sputtering is performed in the semi-transparent layer 20 by evacuating to 1 × 10 ⁻⁴ Pa once and then sputtering chromium in an atmosphere in a vacuum apparatus maintained at 1 × 10 ⁻¹ Pa while introducing only argon gas. A certain chromium thin film was formed. At this time, the semi-transmissive layer 20 was directly formed on the substrate so that the transmittance of i-line (wavelength 365 nm) was 50%.

Next, the metal chromium target was switched to the metal titanium target, and the stopper layer 30 was formed on the surface of the semi-transmissive layer 20 so as to have a film thickness of 100 mm (10 nm). In this sputtering, a titanium thin film was formed in an atmosphere in a vacuum apparatus maintained at 1 × 10 ⁻¹ Pa while introducing only argon gas.

Subsequently, switching to another metal chromium target was performed, and a chromium film as the light shielding layer 43 was formed to a film thickness of 700 mm (70 nm). Sputtering at this time was formed in an atmosphere in a vacuum apparatus maintained at 1 × 10 ⁻¹ Pa only by introducing argon gas. The chromium film thickness of 700 mm formed here has an optical density of about 3.1, and has a function of shielding the exposure light (365 nm, 436 nm).

Subsequently, the chromium target was switched to the metal chromium target used for forming the semi-transmissive layer 20, and the atmosphere in the vacuum apparatus was maintained at 1 × 10 ⁻¹ Pa while introducing argon gas, oxygen gas, and nitrogen gas. Sputtering while reacting with chromium formed a chromium compound as the antireflection layer 45.

  The substrate on which the film was formed was subjected to ultrasonic cleaning with each of a plurality of alkaline detergents, neutral detergents, and pure waters, and then a resist (AZ Electronic Materials Co., Ltd.) was formed on the surface of the photomask substrate 1. ) AZRFP-230K2) was applied over the entire surface and temporarily cured.

After curing the resist, exposure of the first test pattern (Oak Manufacturing Jet Printer: light source CHM-2000, exposure for 20 seconds with an ultra-high pressure mercury lamp), development (Tokyo Ohka Co., Ltd. PMER: developer: temperature 30 ° C., 1 Minute) and main curing (DX402 dry oven manufactured by Yamato Scientific: 120 ° C., 10 minutes). Subsequently, a mixed solution of perchloric acid, cerium ammonium nitrate and water as the first etching liquid (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) As a result, a part of the stopper layer 30 was exposed and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage to the chromium thin film as the semi-transmissive layer 20 was observed, and the stopper layer 30 The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 65 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, the pattern surface of the semi-transmissive layer 20 was not damaged, and the surface of the antireflection layer 45 had no problem at all. .

Next, after sufficiently cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, a resist (AZRFP-230K2 manufactured by AZ Electronic Materials Co., Ltd.) is formed on the surface of the substrate. Was applied to the entire surface and temporarily cured. After curing the resist, exposure of the second test pattern (Oak Manufacturing Jet Printer: light source CHM-2000, exposure for 20 seconds with an ultra-high pressure mercury lamp), development (Tokyo Ohka Co., Ltd. PMER: developer: temperature 30 ° C., 1 Minute) and main curing (DX402 dry oven manufactured by Yamato Scientific: 120 ° C., 10 minutes). Subsequently, a mixed solution of perchloric acid, cerium ammonium nitrate and water as the first etching solution (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) Then, a part of the laminated pattern of the light shielding layer 43 and the antireflection layer 45 and a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Comparative Example 7)
Comparative Example 7 is a design example in which the thickness of the stopper layer 30 is changed. In Comparative Example 7, the film thickness of the stopper layer 30 is set to 200 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film forming conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in Comparative Example 1.

As in Comparative Example 1, the first etchant was a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage to the chromium thin film as the semi-transmissive layer 20 was observed, and the stopper layer 30 The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 130 seconds) and etching the stopper layer 30 to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, the pattern surface of the semi-transmissive layer 20 was not damaged, and the surface of the antireflection layer 45 had no problem at all. .

Next, after thoroughly cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Comparative Example 6, the first etching solution is perchloric acid, cerium ammonium nitrate. A pattern in which the light shielding layer 43 and the antireflection layer 45 are laminated by immersing in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

(Comparative Example 8)
Comparative Example 8 is a design example in which the thickness of the stopper layer 30 is changed. In Comparative Example 8, the film thickness of the stopper layer 30 is set to 300 mm by simply adjusting the sputtering time of the stopper layer 30. The film thickness and film forming conditions of the semi-transmissive layer 20, the light shielding layer 43, and the antireflection layer 45 are the same as those in Comparative Example 1.

As in Comparative Example 1, the first etchant was a mixture of perchloric acid, cerium ammonium nitrate, and water (perchloric acid: ammonium cerium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching Time: 60 seconds), a part of the stopper layer 30 was exposed by etching, and a pattern in which the light shielding layer 43 and the antireflection layer 45 were laminated was formed.
In this state, the first etching solution was washed with pure water and dried, and then the substrate was taken out and the surface was observed. As a result, no damage to the chromium thin film as the semi-transmissive layer 20 was observed, and the stopper layer 30 The effect of was recognized.

Next, this substrate is mixed with hydrogen peroxide, potassium hydroxide, and water as a second etching solution (hydrogen peroxide (35%) aqueous solution: potassium hydroxide aqueous solution (30%): water = 16: 1: 32, reaction temperature 30 ° C., etching time: 200 seconds) and etching the stopper layer to form a pattern in which the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 are laminated.
Subsequently, as a result of removing the resist with a predetermined resist stripping solution and confirming the pattern surface, no damage was observed on the pattern surface of the semi-transmissive layer 20, and the surface of the antireflection layer 45 had no problem at all. .

Next, after thoroughly cleaning the substrate on which the pattern composed of the stopper layer 30, the light shielding layer 43, and the antireflection layer 45 is formed, as in Comparative Example 6, the first etching solution is perchloric acid, cerium ammonium nitrate. A pattern in which the light shielding layer 43 and the antireflection layer 45 are laminated by immersing in a mixed solution of water (perchloric acid: ceric ammonium nitrate: water = 3: 15: 82, reaction temperature: 30 ° C., etching time: 60 seconds) And a part of the semi-transmissive layer 20 were etched.
Subsequently, the resist is removed by a predetermined resist stripping solution, and the light-shielding region 1a having the antireflection layer 45, the second semi-transmissive region 1b in which the stopper layer 30 and the semi-transmissive layer 20 are laminated, and the semi-transmissive layer only. A four-tone photomask having one semi-transmissive region 1c and a total transmissive region 1d was formed.

As a result of confirming the pattern edge of the formed photomask, the pattern edge shape, the taper shape and the appearance defect in each layer were not confirmed, and it was in a very good state.
Using a part of the test pattern, the transmittance of the first semi-transmissive region 1c, the transmittance of the second semi-transmissive region 1b in which the semi-transmissive layer 20 and the stopper layer 30 are laminated, and the light shielding region 1a Optical density and film thickness, surface observation result after final pattern formation, surface observation result when photomask substrate is immersed in Cr etching solution (5 min, 10 min, 20 min), and after composite layer 40 etching Table 1 shows the results of surface observation after immersion in an alkaline solution with the stopper layer 30 exposed.

  In the present invention, by forming the stopper layer 30 having semi-transmissivity with titanium or a compound containing titanium as a main component, etching can be performed with an etchant different from the composite layer 40 and the semi-transmissive layer 20, so that wet etching is performed. Therefore, the pattern can be formed with high accuracy without causing etching damage to each other. Further, since the thin film formation of the photomask substrate can be completed by a single film formation, a photomask substrate can be produced at a low cost, and a gradation photomask can be easily manufactured using the substrate.

: A longitudinal sectional view of a gradation photomask substrate according to an embodiment of the present invention. : It is a longitudinal cross-sectional view of the gradation photomask which concerns on one implementation of this invention. : It is explanatory drawing (1) which shows the process of patterning a 4-tone photomask. : It is explanatory drawing (2) which shows the process of patterning a 4-tone photomask. : It is explanatory drawing (3) which shows the process of patterning a 4-tone photomask. : It is explanatory drawing (1) which shows the process of patterning a three-tone photomask. : It is explanatory drawing (2) which shows the process of patterning a 3 gradation photomask. : It is explanatory drawing (3) which shows the process of patterning a three-tone photomask. : An electron microscope (SEM) photograph of a test pattern taken from above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photomask substrate 2 Photomask 1a Light-shielding region 1b Second transflective region 1c First transflective region 1d Totally transmissive region 10 Transparent substrate 20 Translucent layer 20a Transflective pattern 30 Stopper layer 30a Stopper pattern 40 Composite layer 40a Composite pattern 43 Light shielding layer 43a Light shielding pattern 45 Antireflection layer 45a Antireflection pattern 50 Photoresist 60, 70 Photomask

Claims (10)

A transparent substrate; a first layer formed on the transparent substrate and semi-transparent to the irradiation light; and a third layer formed on the first layer and substantially blocking the irradiation light. A photomask substrate comprising: a second layer formed between the first layer and the third layer and having a semi-transmissivity to irradiation light,
The first layer and the third layer are insoluble or hardly soluble in the second etching solution and more easily soluble in the first etching solution than the second layer,
The second layer is more soluble in the second etchant and insoluble or less soluble in the first etchant than the first layer and the third layer,
Each of the first layer and the third layer is a layer mainly composed of one or more components selected from the group consisting of chromium, chromium oxide, chromium nitride, and chromium oxynitride,
The second layer is a layer mainly composed of one or more components selected from the group consisting of titanium, titanium oxide, titanium nitride, and titanium oxynitride.
The first etching solution is a mixed solution of cerium ammonium nitrate, perchloric acid and water,
The photomask substrate, wherein the second etching solution is a mixed solution of potassium hydroxide, hydrogen peroxide and water.   The photomask substrate according to claim 1, wherein the first layer is formed directly on the transparent substrate.   3. The photomask substrate according to claim 1, wherein the second layer has a transmittance with respect to irradiation light of 5% to 70%.   4. The photomask substrate according to claim 1, wherein the second layer has a thickness of 10 nm to 70 nm. 5. The photomask substrate is formed by sequentially laminating the first layer, the second layer, and the third layer on the transparent substrate,
The third layer according to any one of claims 1 to 4, wherein the third layer includes a light shielding layer that substantially shields the irradiation light and an antireflection layer that is formed on a surface side of the light shielding layer. 2. The photomask substrate according to item 1.   6. The photomask according to claim 5, wherein the antireflection layer contains, as a main component, one or more components selected from the group consisting of chromium oxide, chromium nitride, and chromium oxynitride. substrate.   The first layer, the second layer, and the third layer are formed by a sputtering method, an ion plating method, or a vapor deposition method, according to any one of claims 1 to 6. The substrate for photomasks as described.   A photomask manufactured by the photomask substrate according to claim 1. A method of manufacturing a photomask using the photomask substrate according to claim 1,
A first resist coating step of coating a resist on the surface of the third layer;
A first exposure step of exposing the resist coated in the first resist coating step through a mask on which a first mask pattern is formed;
A first resist removing step of removing an exposed portion or non-exposed portion of the resist after the first exposure step;
A first etching step of etching the third layer exposed in the region from which the resist has been removed with the first etching solution to form a light shielding pattern;
A second etching step of forming a light-shielding pattern by etching the second layer exposed in the region where the third layer has been removed by the first etching step with the second etching solution;
A first resist stripping step of stripping off the resist remaining in the first resist removal step;
A second resist coating step for coating the surface with the resist again;
A second exposure step of exposing the resist coated in the second resist coating step through a mask on which a second mask pattern is formed;
A second resist removing step of removing an exposed portion or non-exposed portion of the resist after the second exposure step;
Etching the third layer and the first layer exposed in the region where the resist has been removed with the first etchant to expose the second layer and the transparent substrate, respectively. Process,
And a second resist stripping step of stripping the resist remaining in the second resist removal step. A method of manufacturing a photomask using the photomask substrate according to claim 1,
A first resist coating step of coating a resist on the surface of the third layer;
A first exposure step of exposing the resist coated in the first resist coating step through a mask on which a first mask pattern is formed;
A first resist removing step of removing an exposed portion or non-exposed portion of the resist after the first exposure step;
A first etching step of etching the third layer exposed in the region from which the resist has been removed with the first etching solution to form a light shielding pattern;
A first resist stripping step of stripping off the resist remaining in the first resist removal step;
A second resist coating step for coating the surface with the resist again;
A second exposure step of exposing the resist coated in the second resist coating step through a mask on which a second mask pattern is formed;
A second resist removing step of removing an exposed portion or non-exposed portion of the resist after the second exposure step;
Etching the second layer exposed in the region where the resist has been removed with the second etchant to expose the first layer; and
The third layer exposed in the region from which the resist has been removed and the first layer exposed in the region from which the second layer has been removed by the second etching step are formed with the first etching solution. A photomask manufacturing method comprising: performing a third etching step for etching to expose the transparent substrate; and a second resist stripping step for stripping the resist remaining in the second resist removal step. .

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