JP7220980B2 - Method for manufacturing mask blank substrate for manufacturing display device, method for manufacturing mask blank, and method for manufacturing mask - Google Patents

Description

The present invention relates to a mask blank substrate for manufacturing a display device, a mask blank and a mask using this mask blank substrate, and manufacturing methods thereof.

The sizes of glass substrates for manufacturing masks for display devices (smartphones, tablets, TVs, etc.) range from G1-G2 size with a short side of 330 mm to G10 size with a short side of over 1600 mm. Large compared to some 6 inches by 6 inches (6025).
Partly due to the price reduction of display devices, masks for manufacturing display devices are used for a longer period of time than masks for manufacturing semiconductors. With repeated use, it may become unusable due to stains or scratches. The glass substrates of used masks are recycled from the viewpoint of effective utilization of resources and from the viewpoint of reducing manufacturing costs since large-sized glass substrates are expensive.
In recent years, with the demand for higher definition of display devices, the flatness and parallelism of both main surfaces required for the glass substrate of the mask for manufacturing display devices have become stricter. The defect quality required for the surface is also becoming stricter. For example, as a high-precision glass substrate for a high-definition panel, the flatness of the main surface on the side where the thin film is formed is 10 μm or less and the parallelism is 15 μm or less, and the flatness of the main surface is 7 μm or less and the parallelism is 10 μm. It is required that: The defect quality of the main surface on which the thin film is formed is required to be free of defects of 2 μm or more, and further free of defects of 1.5 μm or more.
In order to specify the main surface of the side where the thin film to be the transfer pattern is formed, the glass substrate of the display device manufacturing mask and the semiconductor manufacturing mask is usually provided with four corners (that is, corners) on one side of the glass substrate. part) is provided with a notch mark formed by cutting in an oblique cross-section. This notch mark has a size of 1.0 to 2.0 mm in the cut off portion. A glass substrate having notch marks formed on the corners of the front and back surfaces has also been proposed (Patent Document 1).

Korean Patent Publication No. 2012-0056905

Glass substrates of conventional masks are provided with notch marks formed by cutting corners on one or both of the main surfaces. Since the notch mark has a size of 1.0 to 2.0 mm, it is difficult to remove the notch mark when the glass substrate of the used mask is recycled in the same size.
The glass substrate of the mask must meet strict requirements for the flatness of the main surface on which the thin film serving as the transfer pattern is formed, and strict requirements for defect quality of the main surface on which the thin film serving as the transfer pattern is formed. Due to these requirements, when recycling glass substrates, the glass surface on the same side as the original cannot be used as the film formation surface, and the glass surface on the opposite side (generally, notch marks are formed). The glass surface on the side where the film is formed may be desirable as the film formation surface.
However, depending on the transfer pattern formed on the mask, it may not be possible to form the transfer pattern on the main surface where the notch marks are formed. For this reason, there have been cases where a mask having a predetermined transfer pattern cannot be formed using a recycled glass substrate. As a result, there has been a problem that the production yield may be lowered when manufacturing mask blank substrates by recycling glass substrates from used masks.

In addition, when using a mask blank substrate manufactured by recycling a glass substrate from a used mask, the mask is In the blank manufacturing process, there is a risk that a thin film that will become a transfer pattern will be formed on the main surface on the same side as the initial one, and the film formation process will be wasted. As a result, there is a problem that the manufacturing yield in manufacturing mask blanks may be lowered.

Further, when the above notch marks are formed on a glass substrate, edge sag occurs on the main surface near the corner where the notch mark is formed, and on the opposite main surface corresponding to the vicinity of the corner, It has been reported that bumps occur (WO2012/157629).
Therefore, the glass substrate on which the notch marks are formed may not be able to satisfy the flatness required for the main surface on which the thin film to be the transfer pattern is formed. As a result, there has been a problem that the manufacturing yield may decrease when manufacturing a mask blank substrate suitable for manufacturing a mask for forming a high-definition pattern.

Therefore, the present invention has been made in view of the above-described problems, and provides a mask blank substrate for manufacturing a mask blank and a mask blank substrate for manufacturing a display device with a high production yield when manufacturing the mask blank, and a mask blank for the mask blank. An object of the present invention is to obtain a mask blank and a mask using a substrate, and a method for manufacturing them.

In order to achieve the above-mentioned object, the present inventors have made extensive studies and found that a mark specifying the first main surface on which a thin film, which is to be a transfer pattern of a translucent substrate, is formed is formed during the manufacturing process of a mask blank substrate. The present inventors have found that it is effective to solve the above-described problems if it can be removed during the manufacturing process of the mask blank.

The present invention has been made based on this finding, and has the following configurations.

(Configuration 1)
In a mask blank substrate for manufacturing display devices,
A first main surface on which a thin film to be a transfer pattern is formed, a second main surface provided opposite to the first main surface, and the first main surface and the second main surface a translucent substrate having an end face perpendicular to the
The translucent substrate has a mark specifying the first main surface,
the mark is provided on at least one of the first main surface, the second main surface and the end surface;
The marks can be removed by at least one of mirror polishing of the first main surface and the second main surface, roughening treatment and mirror polishing of the end face, and cleaning of the translucent substrate. A mask blank substrate characterized by:

(Configuration 2)
The mark includes a rough surface portion provided in an outer peripheral region of the first main surface or the second main surface,
The rough surface portion has a roughness that can be identified visually or by the difference in optical characteristics between the mark and the other area, and the first main surface on which the mark is formed or the second main surface. The mask blank substrate according to Structure 1, wherein the main surface has a roughness that can be removed by mirror polishing.

(Composition 3)
The mask blank substrate according to Structure 2, wherein the mark is provided at a corner of the first main surface or the second main surface.

(Composition 4)
The mark includes a mirror surface portion provided on the end face,
The mirror surface portion has roughness that can be identified visually or by a difference in optical characteristics between the mark and other areas, and can be removed by roughening the end face. A mask blank substrate according to any one of Structures 1 to 3.

(Composition 5)
The mark includes a rough surface portion provided on the end face,
The rough surface portion has roughness that can be identified visually or by the difference in optical characteristics between the mark and other regions, and has roughness that can be removed by mirror polishing the end surface. The mask blank substrate according to any one of Structures 1 to 3.

(Composition 6)
The mark includes a marker portion containing a water-based dye or water-based pigment provided on the outer peripheral region of the second main surface or on the end face,
6. The mask blank substrate according to any one of Structures 1 to 5, wherein the marker portion can be removed by cleaning the translucent substrate.

(Composition 7)
7. The mask blank substrate according to any one of configurations 1 to 6, wherein the translucent substrate is a recycled product obtained by removing a thin film having a transfer pattern formed thereon from a used mask.

(Composition 8)
In a method for manufacturing a mask blank substrate for manufacturing a display device,
A first main surface on which a thin film to be a transfer pattern is formed, a second main surface provided opposite to the first main surface, and the first main surface and the second main surface providing a translucent substrate having an end face perpendicular to the
mirror-polishing the first main surface and the second main surface of the translucent substrate;
forming a mark specifying the first main surface on at least one of the first main surface, the second main surface, and the end surface after the mirror polishing,
The marks can be removed by at least one of mirror polishing of the first main surface and the second main surface, roughening treatment and mirror polishing of the end face, and cleaning of the translucent substrate. A method for manufacturing a mask blank substrate, characterized by:

(Composition 9)
The method of manufacturing a mask blank substrate according to Structure 8, further comprising: roughening the end face before forming the mark.

(Configuration 10)
The method of manufacturing a mask blank substrate according to Structure 8, further comprising mirror-polishing the end face before forming the mark.

(Composition 11)
Acquiring at least one surface information of flatness, surface roughness, and defect information of the first main surface and the second main surface after the mirror polishing,
11. The method of manufacturing a mask blank substrate according to any one of Structures 8 to 10, wherein the marks are formed according to the surface information.

(Composition 12)
The mask blank substrate according to any one of configurations 8 to 11, wherein the translucent substrate is a recycled product obtained by removing a thin film having a transfer pattern formed thereon from a used mask. Production method.

(Composition 13)
In mask blanks for manufacturing display devices,
A first main surface on which a thin film to be a transfer pattern is formed, a second main surface provided opposite to the first main surface, and the first main surface and the second main surface a mask blank substrate including a translucent substrate having an end face perpendicular to the mask blank;
a thin film forming a transfer pattern formed on the first main surface of the translucent substrate,
The translucent substrate has a mark specifying the first main surface,
the mark is provided on at least one of the first main surface, the second main surface and the end surface;
The mask blank, wherein the marks are removable by at least one of mirror polishing of the first main surface and the second main surface, and roughening and mirror polishing of the end faces.

(Composition 14)
In a method for manufacturing a mask blank for manufacturing a display device,
A first main surface on which a thin film to be a transfer pattern is formed, a second main surface provided opposite to the first main surface, and the first main surface and the second main surface preparing a mask blank substrate including a translucent substrate having an end face perpendicular to the mask blank substrate;
a step of cleaning the mask blank substrate;
forming a thin film that will be a transfer pattern on the first main surface of the translucent substrate after cleaning,
The translucent substrate has a mark specifying the first main surface,
the mark is provided on at least one of the first main surface, the second main surface and the end surface;
The marks can be removed by at least one of mirror polishing of the first main surface and the second main surface, roughening treatment and mirror polishing of the end face, and cleaning of the translucent substrate. A mask blank manufacturing method characterized by:

(Composition 15)
In masks for manufacturing display devices,
A first main surface on which a thin film to be a transfer pattern is formed, a second main surface provided opposite to the first main surface, and the first main surface and the second main surface a mask blank substrate including a translucent substrate having an end face perpendicular to the mask blank;
a thin film having a transfer pattern formed on the first main surface of the translucent substrate,
The translucent substrate has a mark specifying the first main surface,
the mark is provided on at least one of the first main surface, the second main surface and the end surface;
The mask, wherein the marks are removable by at least one of mirror polishing of the first main surface and the second main surface, and roughening and mirror polishing of the end faces.

(Composition 16)
In a method for manufacturing a mask for manufacturing a display device,
A first main surface on which a thin film to be a transfer pattern is formed, a second main surface provided opposite to the first main surface, and the first main surface and the second main surface preparing a mask blank including a mask blank substrate including a light-transmitting substrate having an end surface perpendicular to the first main surface of the light-transmitting substrate, and a thin film serving as a transfer pattern formed on the first main surface of the light-transmitting substrate; process and
forming a transfer pattern on the thin film,
The translucent substrate has a mark specifying the first main surface,
the mark is provided on at least one of the first main surface, the second main surface and the end surface;
The method of manufacturing a mask, wherein the marks can be removed by at least one of mirror polishing of the first main surface and the second main surface, and roughening and mirror polishing of the end face. .

As described above, a mask blank substrate for manufacturing a display device according to the present invention includes a light-transmitting substrate, the light-transmitting substrate has a mark for specifying a first main surface, and the mark is the first main surface. The marks are provided on at least one of the first main surface, the second main surface and the end face, and the marks are formed by mirror polishing the first main surface and the second main surface, roughening treatment and mirror polishing of the end face, and transparency. It is removable by at least one process of cleaning the optical substrate. Therefore, when manufacturing a mask blank using this mask blank substrate, or when manufacturing a mask blank substrate by recycling a translucent substrate from a mask manufactured using this mask blank substrate, The above marks are removed by at least one of mirror polishing of the first main surface and second main surface, roughening treatment and mirror polishing of the end face of the light-transmitting substrate, and cleaning of the light-transmitting substrate. can do. As a result, the production yield of mask blank substrates and mask blanks does not decrease due to the notch marks formed by cutting the corners of the main surface of the translucent substrate, and the mask blank substrates and mask blanks are manufactured. It is possible to obtain a mask blank substrate for manufacturing a display device with a high manufacturing yield. The use of such a mask blank substrate increases the manufacturing yield of mask blanks and masks.

FIG. 2 is a diagram showing a first example of marks provided on a mask blank substrate; FIG. 10 is a diagram showing a second example of marks provided on the mask blank substrate; FIG. 10 is a diagram showing a third example of marks provided on the mask blank substrate; FIG. 10 is a diagram showing a fourth example of marks provided on the mask blank substrate; FIG. 10 is a diagram showing a fifth example of marks provided on the mask blank substrate; FIG. 10 is a diagram showing a sixth example of marks provided on the mask blank substrate; FIG. 12 is a diagram showing a seventh example of marks provided on the mask blank substrate;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following embodiment is one form for embodying the present invention, and does not limit the scope of the present invention. In addition, in the drawings, the same or equivalent parts may be denoted by the same reference numerals, and the description thereof may be simplified or omitted.

Embodiment 1.
In Embodiment 1, a mask blank substrate for manufacturing a display device and a manufacturing method thereof will be described.

<Mask blank substrate>
The mask blank substrate according to the first embodiment has a first main surface on which a thin film to be a transfer pattern is formed, a second main surface provided opposite to the first main surface, and a first main surface. It includes a translucent substrate having a surface and an end surface perpendicular to the second major surface. The translucent substrate has marks identifying the first major surface. The mark is provided on at least one of the first main surface, the second main surface and the end surface. The marks can be removed by at least one of mirror polishing of the first and second main surfaces, roughening and mirror polishing of the end faces, and cleaning of the translucent substrate.

The light-transmitting substrate may be one obtained by cutting an ingot or the like into a substrate shape and applying processing such as polishing to the substrate, or one obtained by removing a thin film having a transfer pattern formed thereon from a used mask. It may be a recycled product formed by performing processing such as polishing.
The first main surface and the second main surface of the translucent substrate are rectangular with a side length of 330 mm or more. For example, length x width is preferably 330 mm x 450 mm to 1220 mm x 1400 mm.
The translucent substrate is made of a material containing silicon and oxygen, and is made of a glass material such as synthetic quartz glass, quartz glass, aluminosilicate glass, soda lime glass, low thermal expansion glass (SiO ₂ —TiO ₂ glass, etc.). be able to.
The first main surface and the second main surface of the translucent substrate are mirror-polished. The flatness of the first main surface is preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 5 μm or less. The flatness of the second main surface is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. Also, the parallelism of the translucent substrate is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. The first main surface preferably has no defects of 5 μm or more, more preferably no defects of 2 μm or more. The second main surface preferably has no defects of 20 μm or more, more preferably no defects of 10 μm or more.
The end face of the translucent substrate may be roughened or mirror-polished. When the end surface of the light-transmitting substrate is roughened, it is possible to reduce the risk of the light-transmitting substrate slipping down when the light-transmitting substrate is gripped and transported. In this case, the end surface of the translucent substrate preferably has an arithmetic mean roughness (hereinafter referred to as Ra) of 0.05 μm or more, more preferably 0.1 μm or more. When the end faces of the translucent substrate are mirror-polished, it is possible to suppress the generation of particles and the like from the end faces that cause defects in the first main surface and the second main surface. In this case, the end face of the translucent substrate preferably has an Ra of 0.03 μm or less, more preferably 0.02 μm or less.

A mark specifying the first main surface is provided on at least one of the first main surface, the second main surface and the end face, and the first main surface and the second main surface are mirror-polished and the end face is roughened. It can be removed by at least one of planarization treatment, mirror polishing, and cleaning of the translucent substrate.

Examples of marks are described below.
1. Rough Surface Formed on the Peripheral Region of the Main Surface As an example of the mark, one comprising a rough surface portion provided on the outer peripheral region of the mirror-polished first main surface or the mirror-polished second main surface. mentioned. In the case of this mark, in the configuration in which the mark is provided on the first main surface, the side on which the rough surface portion is provided can be specified as the first main surface, and in the configuration in which the mark is provided on the second main surface, The side opposite to the side on which the rough surface portion is provided can be specified as the first main surface. In a configuration in which marks are provided on the first main surface, this rough surface portion can be used as a reference position for a defect map or an optical characteristic data map on the first main surface of the translucent substrate. The rough surface portion has roughness that can be identified visually or by the difference in optical characteristics between the mark and the other area, and the first main surface or the second main surface on which the mark is formed is mirror-polished. It has a roughness that can be removed by Reflectance and transmittance are examples of optical characteristics that distinguish marks from other areas.
The outer peripheral region where the rough surface portion is provided is preferably within 10 mm, more preferably within 2 mm, from the outer peripheral edge of the first main surface or the second main surface of the translucent substrate. preferable. If the rough surface portion is provided in an area exceeding 10 mm, it may overlap with the film forming area of the first main surface of the translucent substrate.
The position of the rough surface portion is not particularly limited as long as it is in the outer peripheral region, but it is preferable if it is the corner portion (that is, the corner portion) because it is at the same position as the conventional notch mark.
The first main surface and the second main surface are mirror-polished with a slurry containing abrasive grains such as cerium oxide and colloidal silica so that the surface roughness Ra is 0.5 nm or less. . The surface roughness Ra of the mirror-polished first and second main surfaces is preferably 0.3 nm or less, more preferably 0.2 nm or less.
On the other hand, the roughness of the rough surface portion is preferably 0.05 μm or more in terms of Ra. When Ra is 0.05 μm or more, the rough surface portion can be identified visually or by the difference in optical characteristics between the mark and the other regions. The roughness of the rough surface portion is preferably 0.2 μm or less in terms of Ra. When Ra is 0.2 μm or less, the rough surface portion can be removed by mirror-polishing the first main surface or the second main surface on which the mark is formed. The roughness of the rough surface portion is preferably 0.05 μm or more and 0.2 μm or less in Ra, and more preferably 0.05 μm or more and 0.15 μm or less in Ra.
The shape and size of the rough surface portion are not particularly limited as long as the shape and size are identifiable visually or by the difference in optical characteristics between the mark and the other regions.
The rough surface portion can be formed by etching or sandblasting using a roughening agent. Examples of surface roughening agents include fluorine-based etchants such as hydrofluoric acid aqueous solutions.
When forming the roughened portion by etching using a roughening agent, for example, the roughening agent is applied to the outer peripheral region of the first main surface or the second main surface and left for a predetermined time. When the surface roughening agent is applied to a predetermined roughness, the translucent substrate is washed to remove the roughening agent. When forming the rough surface portion by sandblasting, for example, abrasive grains of #600 to #3000 are blown with air.
The rough surface portion provided in the outer peripheral region of the first main surface or the second main surface is used in the process of manufacturing a mask blank substrate from a used mask, which will be described later (that is, in the process of manufacturing a mask blank substrate from a used mask). In the recycling process), the first main surface and the second main surface can be removed by mirror-polishing.

2. Mirror Surface Portions Formed on End Faces Another example of the mark is a mark composed of a mirror surface portion provided on the end faces. This mark can be applied to a roughened end face. In the case of this mark, by making the mirror surface part into a predetermined shape (for example, an asymmetrical shape in the thickness direction), or by providing the mirror surface part at a position shifted from the central position of the translucent substrate in the thickness direction , the first major surface can be identified. The mirror portion has roughness that can be identified visually or by the difference in optical characteristics between the mark and the other regions, and can be removed by roughening the end face. Reflectance and transmittance are examples of optical characteristics that distinguish marks from other areas.
As described above, the surface roughness Ra of the roughened end face is preferably 0.05 μm or more.
On the other hand, the roughness Ra of the mirror surface portion is preferably 0.03 μm or less. When Ra is 0.03 μm or less, the mirror portion can be identified visually or by the difference in optical characteristics between the mark and the other regions.
The size of the mirror surface portion is not particularly limited as long as it is identifiable visually or by the difference in optical characteristics between the mark and the other regions.
The mirror surface portion can be formed by partial mirror polishing using a rotary processing tool to which a polishing pad is attached.
When forming the mirror surface portion, for example, a polishing pad is attached to a cylindrical rotary processing tool having a diameter smaller than the thickness of the mask blank substrate, and a slurry containing abrasive grains such as cerium oxide or colloidal silica is applied. While supplying between the polishing pad and the translucent substrate, the polishing pad and the translucent substrate are brought into contact with each other through relative motion.
The mirror surface portion provided on the end face is used for the end face of the translucent substrate in the process of manufacturing a mask blank substrate from a used mask (that is, the process of recycling a mask blank substrate from a used mask), which will be described later. It can be removed during roughening treatment.

3. Rough Surface Portions Formed on End Faces Another example of a mark is a mark composed of a rough surface portion provided on an end face. This mark can be applied to an end face that is mirror finished. In the case of this mark, by making the rough surface portion into a predetermined shape (for example, an asymmetrical shape in the thickness direction), or by providing the rough surface portion at a position shifted from the central position of the translucent substrate in the thickness direction. , the first major surface can be identified. The rough surface portion has roughness that can be identified visually or by the difference in optical characteristics between the mark and the other region, and has roughness that can be removed by mirror-polishing the end face. Reflectance and transmittance are examples of optical characteristics that distinguish marks from other areas.
As described above, the mirror-polished end surface preferably has a surface roughness Ra of 0.03 μm or less.
The roughness of the rough surface portion is preferably 0.05 μm or more in terms of Ra. When Ra is 0.05 μm or more, the mirror portion can be identified visually or by the difference in optical characteristics between the mark and the other regions. The roughness of the rough surface portion is preferably 0.2 μm or less in terms of Ra. When the Ra is 0.2 μm or less, the rough surface portion can be removed by mirror-polishing the end face. The roughness of the rough surface portion is preferably 0.05 μm or more and 0.2 μm or less in Ra, and more preferably 0.05 μm or more and 0.15 μm or less in Ra.
The size of the rough surface portion is not particularly limited as long as it is identifiable visually or by the difference in optical characteristics between the mark and the other regions.
The rough surface portion can be formed by etching or sandblasting using a roughening agent. Examples of surface roughening agents include fluorine-based etchants such as hydrofluoric acid aqueous solutions, as described above.
In the case of forming the rough surface portion by etching using a surface roughening agent, for example, the surface roughening agent is applied to the end surface and left for a predetermined period of time. When the surface roughening agent is applied to a predetermined roughness, the translucent substrate is washed to remove the roughening agent. When forming the rough surface portion by sandblasting, for example, abrasive grains of #600 to #3000 are blown with air.
The rough surface portion provided on the end surface of the light-transmitting substrate is used in the process of manufacturing the mask blank substrate from the used mask (that is, the process of recycling the mask blank substrate from the used mask), which will be described later. It can be removed during mirror polishing.

4. Marker portion formed on the outer peripheral region or end face of the second main surface Another example of the mark is composed of a marker portion containing a water-based dye or water-based pigment attached to the outer peripheral region or end face of the second main surface. What is done is mentioned. In the case of this mark, in the configuration where the mark is attached to the second main surface, the side opposite to the side on which the marker portion is attached can be identified as the first main surface. In addition, in the configuration in which the mark is attached to the end surface, the mark portion is formed in a predetermined shape (for example, an asymmetrical shape in the thickness direction), or the mark portion is shifted from the center position in the thickness direction of the translucent substrate. By positioning, the first major surface can be identified. The marker portion can be removed by washing the translucent substrate.
In the configuration where the mark is attached to the second main surface, the outer peripheral area where the marker is attached and the position of the marker are determined from the rough surface provided on the outer peripheral area of the first main surface or the second main surface. It is the same as if it is configured.
As described above, the second main surface is mirror-polished with a slurry containing abrasive grains such as cerium oxide or colloidal silica so that the surface roughness Ra is 0.5 nm or less. The surface roughness Ra of the mirror-polished second main surface is preferably 0.3 nm or less, more preferably 0.2 nm or less. Also, the end faces may be either roughened or mirror-polished. As described above, the surface roughness of the roughened end face is preferably 0.05 μm or more in Ra, and the surface roughness of the mirror-polished end face is, as described above, 0.03 μm in Ra. It is preferable that it is below.
The shape and size of the marker portion are not particularly limited as long as the shape and size are visually identifiable.
The marker part can be formed by a writing implement using water-based dye or water-based pigment as ink, such as felt-tip pen or highlighter pen.
When forming the marker portion, for example, an arbitrary shape is written on the outer peripheral region or the end surface of the second main surface with a writing instrument such as a felt-tip pen.
The marker portion attached to the outer peripheral region or the end face of the second main surface can be removed when cleaning the translucent substrate in the process of manufacturing the mask blank, which will be described later.

5. Another example of the recess mark formed in the outer peripheral region or end face of the main surface is a recess formed in the outer peripheral region or end face of the first or second main surface. In the case of this mark, in the configuration in which the mark is provided on the first main surface, the side on which the recess is provided can be specified as the first main surface, and in the configuration in which the mark is provided on the second main surface, the side on which the recess is provided can be specified as the first main surface. can be specified as the first main surface. In a configuration in which marks are provided on the first main surface, this recess can be used as a reference position for a defect map or an optical property data map on the first main surface of the translucent substrate. In addition, in the configuration in which a mark is provided on the end face, the plurality of recesses are formed so as to be recognizable as an asymmetric shape, or one or more recesses are shifted from the center position in the thickness direction of the translucent substrate. A first major surface can be specified by forming at a position. The concave portion has a depth that can be identified visually or by the difference in optical properties between the mark and the other region, and the first main surface or the second main surface on which the mark is formed is mirror-polished; Alternatively, it has a depth that can be removed by mirror-polishing or roughening the end face. Reflectance and transmittance are examples of optical characteristics that distinguish marks from other areas.
In the configuration where the mark is provided on the first main surface or the second main surface, the mark is provided on the outer peripheral region of the first main surface or the second main surface with respect to the outer peripheral region where the recess is provided and the position of the recess. It is the same as the case where it is composed of a rough surface portion.
As described above, the first main surface and the second main surface are mirror-finished with a slurry containing abrasive grains such as cerium oxide and colloidal silica so that the surface roughness Ra is 0.5 nm or less. polished. The surface roughness Ra of the mirror-polished first and second main surfaces is preferably 0.3 nm or less, more preferably 0.2 nm or less. In addition, the end face may be either roughened or mirror-polished. However, the difference in optical characteristics between the mark and the other regions makes it easier to distinguish visually. In addition, it is preferably mirror-polished. The surface roughness of the roughened end face is preferably 0.05 μm or more in terms of Ra and not more than a degree of surface roughness that can be distinguished from the depth of the recess, and the surface roughness of the mirror-polished end face is preferably 0.03 μm or less in terms of Ra, as described above.
On the other hand, the depth of the recess is preferably 1 μm or more. When the thickness is 1 μm or more, the concave portion can be identified visually or by the difference in optical characteristics between the mark and the other regions. The depth of the recess is preferably 5 μm or less. If it is 5 μm or less, the recesses can be removed by mirror-polishing the first main surface or the second main surface on which the recesses are formed, or by mirror-polishing or roughening the end faces on which the recesses are formed. can be done.
The shape and size of the concave portion are not particularly limited as long as the shape and size are identifiable visually or by the difference in optical characteristics between the mark and the other regions.
The recess can be formed by a diamond stylus or a microindenter.
When forming recesses, for example, a diamond stylus is scanned on the glass substrate to form processing marks, or a micro indenter is pressed into the glass substrate (indentation).
The concave portion provided in the outer peripheral region of the first main surface or the second main surface is used in the process of manufacturing a mask blank substrate from a used mask described later (that is, by recycling a mask blank substrate from a used mask). process), the first main surface and the second main surface can be removed by mirror polishing. In addition, the concave portion provided in the end surface is formed in the end surface of the light-transmitting substrate in the process of manufacturing the mask blank substrate from the used mask (that is, the process of recycling the mask blank substrate from the used mask), which will be described later. can be removed during mirror polishing or roughening treatment.

6. Another example of the laser marking mark formed on the outer peripheral region or the end face of the main surface is a laser marking provided on the outer peripheral region or the end face of the first main surface or the second main surface. . In the case of this mark, in the configuration in which the mark is provided on the first main surface, the side on which the laser marking is provided can be specified as the first main surface, and in the configuration in which the mark is provided on the second main surface, The side opposite to the side on which the laser marking is provided can be identified as the first major surface. In a configuration in which marks are provided on the first main surface, this laser marking can be used as a reference position for a defect map or an optical property data map on the first main surface of the translucent substrate. In addition, in the configuration where marks are provided on the end face, by forming a plurality of laser markings so that they can be recognized as an asymmetric shape, or by forming a single or a plurality of laser markings from the center position in the thickness direction of the translucent substrate The first main surface can be specified by forming it at a shifted position. Laser marking can be identified visually or by the difference in optical properties between the mark and the other area, and mirror polishing of the first main surface or second main surface on which the mark is formed, or the end surface It is formed in a depth range that can be removed by mirror polishing or roughening treatment. Reflectance and transmittance are examples of optical characteristics that distinguish marks from other areas.
In the configuration in which the mark is provided on the first main surface or the second main surface, the mark is provided on the outer peripheral region of the first main surface or the second main surface with respect to the outer peripheral region where the laser marking is provided and the position of the laser marking. It is the same as the case where it is composed of the provided rough surface portion.
As described above, the first main surface and the second main surface are mirror-finished with a slurry containing abrasive grains such as cerium oxide and colloidal silica so that the surface roughness Ra is 0.5 nm or less. polished. The surface roughness Ra of the mirror-polished first and second main surfaces is preferably 0.3 nm or less, more preferably 0.2 nm or less. In addition, the end face may be either roughened or mirror-polished. However, the difference in optical characteristics between the mark and the other regions makes it easier to distinguish visually. In addition, it is preferably mirror-polished. As described above, the surface roughness of the roughened end face is preferably 0.05 μm or more in Ra, and the surface roughness of the mirror-polished end face is, as described above, 0.03 μm in Ra. It is preferable that it is below.
On the other hand, the depth at which the laser marking is formed is preferably 5 μm or less from the first main surface, second main surface, or end face where the laser marking is formed. When it is 5 μm or less, the laser marking is performed by mirror polishing the first main surface or the second main surface on which the laser marking is formed, or by mirror polishing or roughening treatment of the end surface on which the laser marking is formed. can be removed.
The shape and size of the laser marking are not particularly limited as long as the shape and size are identifiable visually or by the difference in optical properties between the mark and other areas.
Laser marking can be formed by a YAG laser, a carbon dioxide laser, or the like.
The laser marking provided on the outer peripheral region of the first main surface or the second main surface is used in the process of manufacturing a mask blank substrate from a used mask, which will be described later (that is, the process of manufacturing a mask blank substrate from a used mask). In the recycling process), the first main surface and the second main surface can be removed by mirror-polishing. In addition, the laser marking provided on the end face is used in the process of manufacturing a mask blank substrate from a used mask, which will be described later (that is, in the process of recycling the mask blank substrate from a used mask). It can be removed when the end face is mirror-polished or roughened.

According to the mask blank substrate of Embodiment 1, the mark for specifying the first main surface provided on the translucent substrate is obtained by mirror-polishing the first main surface and the second main surface, It can be removed by at least one of surface roughening treatment, mirror polishing, and cleaning of the translucent substrate. Therefore, when manufacturing a mask blank using this mask blank substrate, or when manufacturing a mask blank substrate by recycling a translucent substrate from a mask manufactured using this mask blank substrate, The above marks are removed by at least one of mirror polishing of the first main surface and second main surface, roughening treatment and mirror polishing of the end face of the light-transmitting substrate, and cleaning of the light-transmitting substrate. can do. As a result, the production yield of mask blank substrates and mask blanks does not decrease due to the notch marks formed by cutting the corners of the main surface of the translucent substrate, and the mask blank substrates and mask blanks are manufactured. It is possible to obtain a mask blank substrate for manufacturing a display device with a high manufacturing yield. The use of such a mask blank substrate increases the manufacturing yield of mask blanks and masks.

<Method for manufacturing mask blank substrate>
The method for manufacturing a mask blank substrate according to the first embodiment includes steps of preparing a light-transmitting substrate, mirror-polishing a first main surface and a second main surface of the light-transmitting substrate, and forming a mark identifying the first main surface on at least one of the first main surface, the second main surface and the end surface of the. The marks can be removed by at least one of mirror polishing of the first and second main surfaces, roughening and mirror polishing of the end faces, and cleaning of the translucent substrate.
When the end face is roughened, the end face is roughened before the mark is formed, and when the end face is mirror-polished, the end face is mirror-polished before the mark is formed. have
Acquiring at least one surface information of flatness, surface roughness, and defect information of the first main surface and the second main surface after mirror polishing, wherein the mark is formed according to the surface information is preferred.
The translucent substrate to be prepared may be one obtained by cutting an ingot or the like into a substrate shape, or may be a recycled product obtained by removing a thin film having a transfer pattern formed thereon from a used mask.
The details of the translucent substrate and the marks are as described above.
A method for manufacturing a mask blank substrate according to Embodiment 1 will be described in detail below.

(Translucent substrate preparation step)
First, an ingot or the like is cut into a substrate shape, and both main surfaces, one main surface and the other main surface, are subjected to surface grinding to obtain a translucent substrate.
When the translucent substrate is a recycled product, the thin film having the transfer pattern formed thereon is removed from the used mask to obtain the translucent substrate. In order not to damage the light-transmitting substrate, it is desirable to remove this thin film using a wet etchant capable of obtaining a sufficient etching rate difference with respect to the light-transmitting substrate. Specifically, when a chromium-based material is used for the thin film, it is preferable to use a chromium etchant containing ceric ammonium nitrate and perchloric acid. When the thin film is made of a MoSi-based material, it is preferable to use an etchant containing ammonium hydrogen fluoride and hydrogen peroxide.

(Substrate thickness inspection process)
Next, the thickness of the substrate is measured using a substrate thickness measuring machine (for example, a flatness tester (manufactured by Kuroda Seiko Co., Ltd.)) or the like to check whether or not the substrate has a sufficient polishing allowance. As a standard for the determination, the plate thickness obtained by adding 100 μm to the specification of the lower limit of plate thickness is a guideline. For example, if the lower limit specification of the plate thickness of a translucent substrate having a size of 800 mm×920 mm×10 mm is 9.8 mm, it is inspected whether the plate thickness is 9.9 mm or more.
If there is sufficient polishing allowance for the plate thickness, proceed to the scratch/defect inspection on the translucent substrate surface.

(Scratches and defects inspection process)
In the scratch/defect inspection, the scratch/defect of the translucent substrate is inspected by visual inspection or the like. This flaw/defect inspection is performed on both main surfaces. If there is no damage (if no damage is found), proceed to the flatness calculation step.
The scratch/defect inspection process may be performed before the board thickness inspection process or after the flatness calculation process.

(Flatness calculation process)
In the flatness calculation step, first, the shapes of both main surfaces of the translucent substrate are measured by a surface morphology information measuring device, and then the flatness is calculated based on the measurement data. Here, depending on a measuring device such as a flatness tester manufactured by Kuroda Seiko Co., Ltd., substrate thickness and flatness can be obtained together as surface morphology information.

(Local wet etching process)
In the local wet etching step, local etching is performed by bringing a wet etchant into contact with at least a relatively convex region exceeding the allowable value on at least one of the two main surfaces. .
Since the local wet etching is chemical etching, damage to the surface of the translucent substrate is small, and as a result, the machining allowance can be reduced.
A chemical solution (wet etchant) for local wet etching includes a hydrofluoric acid aqueous solution, an alkaline aqueous solution such as KOH and NaOH, and phosphoric acid.
After performing the local wet etching process, the process proceeds to the mirror polishing process.

(Mirror polishing process)
In the mirror polishing step, both main surfaces of the translucent substrate are polished to further increase flatness and parallelism, and to improve surface smoothness. Here, for this polishing, for example, both surfaces are polished one surface at a time using a single-sided polishing apparatus. For this polishing, both surfaces may be polished simultaneously using a double-sided polishing machine instead of polishing one side at a time using a single-sided polishing machine.
The mirror polishing process is selected from one-step polishing to multi-step polishing according to the required values of flatness and parallelism. In multi-stage polishing, it is preferable that the final polishing be used for smoothing the surface of the translucent substrate, and the previous polishing be used to increase flatness and parallelism. In order to improve flatness and parallelism, it is preferable to acquire surface morphology information in the middle and feed back the information to the polishing conditions.
When the translucent substrate is a recycled product, a mark composed of a rough surface provided on the outer peripheral region of the first main surface or the second main surface, which is applied before recycling in the mark forming step described later; Constructed from a mark made up of recesses provided in the outer peripheral region of the first main surface or the second main surface, and laser markings provided in the outer peripheral region of the first main surface or the second main surface Marks that are to be removed are removed in this step.

(Surface information acquisition step)
After mirror polishing, at least one surface information of flatness, surface roughness, and defect information is obtained for both the first main surface and the second main surface of the translucent substrate.
The flatness is calculated and acquired in the same manner as the flatness calculation step described above. Defect information is acquired using a defect inspection device or the like. The surface roughness is obtained using a surface roughness measuring instrument (eg SJ-210 manufactured by Mitutoyo).

(Mark formation process)
A mark specifying the first main surface is formed on at least one of the mirror-polished first and second main surfaces and the end face. The mark is preferably formed according to the surface information obtained in the surface information acquisition step. For example, if the surface information obtained in the surface information acquisition step is the flatness of both surfaces, the surface that satisfies the specifications of the mask blank substrate is set as the first main surface, and a mark specifying that surface is formed.
When the mark is composed of a rough surface portion provided in the outer peripheral region of the first main surface or the second main surface, it is formed by etching using a roughening agent, sandblasting, or the like. .
When the mark is composed of a mirror surface portion provided on the end face, it is formed by partial mirror polishing using a rotary processing tool to which a polishing pad is attached. In this case, the step of roughening the end faces is preferably performed before the surface information acquisition step. The roughening treatment of the end face is performed by etching using a roughening agent, sandblasting, or the like.
When the mark is composed of a roughened portion provided on the end face, it is formed by etching using a roughening agent, sandblasting, or the like. In this case, it is preferable to perform the step of mirror-polishing the end face before the surface information acquisition step. In the mirror polishing of the end faces, a slurry containing polishing abrasive grains such as cerium oxide or colloidal silica is supplied between the polishing pad or brush and the translucent substrate, and the polishing pad or brush and the translucent substrate are separated. are brought into contact with each other while moving relative to each other.
When the mark is composed of a marker portion containing an aqueous dye or aqueous pigment attached to the outer peripheral region or end face of the second main surface, a water-based dye or water-based It is formed by a writing instrument that uses pigment as ink.
When the mark is composed of a concave portion provided on the outer peripheral region or end face of the first main surface or the second main surface, pressurization marks obtained by scanning a diamond stylus, indentation by a microindenter and so on.
When the mark is composed of laser marking provided on the outer peripheral region or end face of the first main surface or the second main surface, it is formed by a YAG laser, a carbon dioxide gas laser, or the like.

A mask blank substrate is manufactured by carrying out the mark forming process.

When the light-transmitting substrate is a recycled product, a mark formed of a mirror surface portion provided on the end surface, a mark formed of a rough surface portion provided on the end surface, a mark formed on the end surface, and a mark provided on the end surface before recycling Marks composed of recessed portions and marks composed of laser markings provided on the end face are removed by performing a step of roughening the end face or a step of mirror-polishing the end face before the surface information acquisition step. .

Embodiment 2.
In Embodiment 2, a mask blank for manufacturing a display device and a manufacturing method thereof will be described.

<Mask blank>
A mask blank according to the second embodiment includes a mask blank substrate including a translucent substrate, and a thin film, which is to be a transfer pattern, formed on the first main surface of the mask blank substrate. The translucent substrate has marks identifying the first major surface. The mark is provided on at least one of the first main surface, the second main surface and the end surface. The marks can be removed by at least one of mirror polishing of the first main surface and the second main surface, and roughening and mirror polishing of the end faces.
The details of the translucent substrate and the marks are as described above.

<Manufacturing method of mask blank>
A mask blank manufacturing method according to a second embodiment includes steps of preparing a mask blank substrate including a light-transmitting substrate, cleaning the mask blank substrate, and cleaning the light-transmitting substrate after cleaning. and forming a thin film on the surface to be a transfer pattern. The translucent substrate has marks identifying the first major surface. The mark is provided on at least one of the first main surface, the second main surface and the end surface. The marks can be removed by at least one of mirror polishing of the first and second main surfaces, roughening and mirror polishing of the end faces, and cleaning of the translucent substrate.
The details of the translucent substrate and the marks are as described above.
The method of manufacturing the mask blank according to the second embodiment will be described in detail below.

(Substrate preparation process for mask blank)
First, the mask blank substrate manufactured in Embodiment 1 is prepared.

(Mask blank substrate cleaning process)
Next, the mask blank substrate manufactured in Embodiment 1 is washed.
In this step, the mark made up of the marker portion is removed.

(Thin film formation process)
Next, a thin film to be a transfer pattern is formed on the mask blank substrate manufactured in the first embodiment.
As this thin film, a film suitable for each type of mask, ie, a binary mask (a normal photomask having a light-shielding film pattern formed on a mask blank substrate), a halftone type phase shift mask, or the like is used. A sputtering method is preferably used as a method for forming a thin film, but the method is not limited to the sputtering method.
For example, in a mask blank used for a binary mask, materials mainly containing Cr such as Cr, CrO, CrN, CrC, CrON, CrOC, CrCN, and CrCON can preferably be used as the thin film. The film thickness of the thin film is set to a film thickness that blocks the exposure light and provides an optical density OD of 2.0 or more, preferably 2.5 or more, more preferably 3.0 or more.
In the case of a mask blank (phase shift mask blank) used for a halftone type phase shift mask, the thin film is a phase shift film for obtaining a predetermined transmittance and phase difference with respect to exposure light. This phase shift film is a film having a function of generating a phase difference of approximately 180° (for example, 180°±20°) with respect to the exposure light and a function of transmitting part of the exposure light. The transmittance of the exposure light is set to a predetermined value of 1% or more and 80% or less, usually 3% or more and 40% or less, depending on the pattern transfer application. Materials for the phase shift film include chromium compound materials such as chromium oxycarbide (CrOC), chromium oxynitride (CrON), chromium oxycarbide nitride (CrOCN), and chromium nitride (CrN), or molybdenum such as MoSi. Materials such as molybdenum silicide oxide (MoSiO), molybdenum silicide oxynitride (MoSiON), and molybdenum silicide nitride (MoSiN) containing oxygen, nitrogen, etc. in molybdenum silicide containing a compound of silicon and silicon as a main component are preferably used. be able to.
In the case of a mask blank (phase shift mask blank) used for a halftone type phase shift mask, a light shielding film may be formed in addition to the phase shift film.

A mask blank is manufactured by carrying out up to the thin film forming process.

According to the mask blank of the second embodiment, a thin film to be a transfer pattern is formed on the first main surface of the mask blank substrate of the first embodiment. As a result, the mask blank of the second embodiment has a high production yield.

Embodiment 3.
In Embodiment 3, a mask for manufacturing a display device and a manufacturing method thereof will be described.

<Mask>
The mask of the third embodiment includes a mask blank substrate including a translucent substrate, and a thin film having a transfer pattern formed on the first main surface of the translucent substrate. The translucent substrate has marks identifying the first major surface. The mark is provided on at least one of the first main surface, the second main surface and the end surface. The marks can be removed by at least one of mirror polishing of the first main surface and the second main surface, and roughening and mirror polishing of the end faces.
The details of the translucent substrate and the marks are as described above.

<Mask manufacturing method>
A method of manufacturing a mask according to the third embodiment prepares a mask blank including a mask blank substrate including a translucent substrate and a thin film forming a transfer pattern formed on a first main surface of the translucent substrate. and forming a transfer pattern on the thin film. The translucent substrate has marks identifying the first major surface. The mark is provided on at least one of the first main surface, the second main surface and the end surface. The marks can be removed by at least one of mirror polishing of the first main surface and the second main surface, and roughening and mirror polishing of the end faces.
The details of the translucent substrate and the marks are as described above.
Details of the mask manufacturing method of the third embodiment will be described below.

(Mask blank preparation process)
First, the mask blank manufactured in Embodiment 2 is prepared. At this time, if a resist film is not formed on the mask blank, a resist film is formed on the mask blank. Here, the resist film is composed of a positive photoresist material or a negative photoresist material, and is formed using, for example, a slit coater or a spin coater.

(Transfer pattern forming step)
Subsequently, a resist film pattern is formed by drawing and exposing a desired pattern on the resist film using a laser drawing machine or the like, and developing the resist film by a technique such as a spray method.
Then, using the formed resist film pattern as a mask, the thin film is etched to form a transfer pattern. For etching of the thin film, for example, when the thin film is made of a Cr-based material, an etchant for chromium containing cerium di-ammonium nitrate and perchloric acid is used. When the thin film is made of MoSi-based material, an etchant containing ammonium hydrogen fluoride and hydrogen peroxide is used.
After that, the resist film pattern is removed using a remover or the like. The upper surface of the manufactured transfer pattern is preferably covered with a pellicle.

A mask is manufactured by carrying out up to the transfer pattern forming process.

According to the mask of the third embodiment, a transfer pattern is formed on the first main surface of the mask blank substrate of the first embodiment. As a result, the manufacturing yield of the mask of the third embodiment is high.

Hereinafter, the present invention will be described more specifically based on examples and comparative examples. The following examples are examples of the present invention and do not limit the present invention.

Examples 1 to 5 and Comparative Example 1 describe the case where the light-transmitting substrate is a glass substrate made of synthetic quartz glass, and the thin film formed on the light-transmitting substrate is a phase shift film made of a chromium-based material. do. The present invention can be similarly applied to other combinations of translucent substrates and thin films.

Example 1.
A mask blank substrate for manufacturing a display device of Example 1 was manufactured by the following method. The specifications of the mask blank substrate for manufacturing the display device of Example 1 are such that the flatness of the side (first main surface) on which the thin film is formed is 7 μm or less, the parallelism is 10 μm or less, and the thin film is formed. The defect quality of the side (first main surface) was defined as the absence of defects of 2 μm or more.

<<Glass substrate preparation process>>
First, one main surface and the other main surface of a substrate obtained by cutting an ingot of synthetic quartz glass into a substrate shape were subjected to surface grinding and chamfering using #1200 diamond abrasive grains. A glass substrate made of synthetic quartz glass of 8092 size of 920 mm×10 mm was obtained. The obtained glass substrate had no notch marks formed on both main surfaces.

<< Board thickness inspection process >>
One main surface and the other main surface of the washed glass substrate were measured with a flatness tester manufactured by Kuroda Seiko Co., Ltd. to acquire surface morphology information.
This surface morphology information is information indicating the unevenness of both main surfaces, and is height information of each measurement point on both main surfaces with respect to a virtual absolute plane, which is measured at intervals of 10 mm in areas excluding the outer circumference of 5 mm on both main surfaces. .
Based on the obtained surface morphology information, the plate thickness of the glass substrate was calculated including variations in the plate thickness.
The thickness specification of the 8092 size photomask substrate is 10 mm±0.2 mm. In consideration of the lower limit (9.8 mm) of the thickness specification and the polishing allowance in the subsequent polishing process, it was inspected whether the minimum thickness of the glass substrate was 9.9 mm or more.
As a result of the inspection, it was confirmed that the minimum plate thickness exceeded 9.9 mm and that the required polishing allowance was provided to obtain the required surface roughness.

<< Scratches and defects inspection process >>
After that, the presence or absence of scratches on both main surfaces of the glass substrate was visually inspected. Empirically, scratches with a depth of 20 μm or more can be detected (confirmed) by visual inspection. When the obtained glass substrate was inspected, no scratches that could be detected by visual inspection could be confirmed on both main surfaces.

<<Flatness calculation process>>
The flatness of both main surfaces was calculated based on the obtained surface morphology information.
As a result of calculating the flatness of both main surfaces, one main surface was 22.5 μm and the other main surface was 8.5 μm.

<<Local wet etching process>>
Next, based on the previously acquired surface morphology information (position information and height information with respect to the reference surface) of both main surfaces, at least the areas that are relatively convex exceeding the allowable value are filtered. Local wet etching with an acid aqueous solution was performed.

As a result, the flatness of one main surface was 5.4 μm.
No surface roughness due to local wet etching was confirmed.
Local wet etching can reduce the load of the subsequent polishing process while suppressing the removal amount.

<<mirror polishing process>>
The mirror polishing process here includes a first polishing process, a post-polishing surface morphology information acquiring process, a post-polishing flatness calculating process, a second polishing process, and a third polishing process.

<<<first polishing step>>>
In the first polishing step, both the first main surface and the second main surface of the glass substrate were polished using a double-sided polishing apparatus for the purpose of removing minute scratches that are difficult to visually confirm. Here, the polishing conditions were as follows.
Polishing conditions:
Polishing liquid: cerium oxide (average particle size: 1 μm), loose abrasive grains obtained by adding water to abrasive grains Polishing cloth: hard polisher Rotation speed of upper surface plate: 1 to 30 rpm (rotates clockwise when viewed from the top of the double-sided polishing device)
Lower surface plate rotation speed: 1 to 30 rpm (counterclockwise rotation when viewed from the top of the double-sided polishing machine)
Pressure: 80-100g/ ^cm2
After completion of the first polishing step, the glass substrate was chemically cleaned using a low-concentration alkaline aqueous solution, and then the glass substrate was cleaned with pure water.

<<<Post-polishing surface morphology information acquisition step>>>
In the post-polishing surface morphology information acquisition step, surface morphology information was acquired for both main surfaces of the glass substrate that had undergone chemical cleaning and pure water cleaning after the first polishing step.
This surface morphology information is information indicating the unevenness of both main surfaces, and specifically, height information of each measurement point on a virtual absolute plane, which is measured at intervals of 10 mm in areas excluding the outer circumference of 5 mm on both main surfaces. is.
A flatness tester manufactured by Kuroda Seiko Co., Ltd. was used as a measuring instrument for acquiring surface morphology information.

<<<Post-polishing Flatness Calculation Process>>>
In the post-polishing flatness calculation step, a computer is used to calculate the flatness of both main surfaces from the surface morphology information of both main surfaces obtained in the post-polishing surface morphology information acquisition step, and the parallelism of the glass substrate is also calculated. Calculated.
As a result, the flatness of one main surface was 6.1 μm, the flatness of the other main surface was 9.4 μm, and the parallelism of the glass substrate was 10.8 μm.

<<<second polishing step>>>
In the second polishing step, the processing conditions of the single-sided polishing apparatus with different processing amounts within the plane of the other main surface so that the flatness of the other main surface is 7 μm or less and the parallelism of the glass substrate is 10 μm or less. was determined, and single-side polishing was performed on the other main surface.
The conditions for this polishing are as follows.
Polishing conditions:
Polishing liquid: cerium oxide (average particle diameter: 1 μm) free abrasive grains obtained by adding water to abrasive grains Polishing cloth: soft polisher Number of revolutions of substrate holding plate: 3 to 20 rpm (counterclockwise when viewed from the top surface of substrate holding plate) rotate)
Polishing surface plate rotation speed: 3 to 20 rpm (clockwise rotation when viewed from the top surface of the substrate holding plate)
After the second polishing step was completed, the glass substrate was chemically cleaned using a low-concentration alkaline aqueous solution, and then the glass substrate was cleaned with pure water.

<<<Third polishing step>>>
In the third polishing step (precision polishing step), both surfaces of the glass substrate were polished using a double-sided polishing apparatus for the purpose of increasing the smoothness of both main surfaces. The polishing conditions are as follows.
Polishing conditions:
Polishing liquid: Colloidal silica (average particle size: 50 to 80 nm), free abrasive grains obtained by adding water to abrasive grains Polishing cloth: Soft polisher Rotational speed of upper surface plate: 1 to 30 rpm (rotates clockwise when viewed from the top of the double-sided polishing machine) )
Lower surface plate rotation speed: 1 to 30 rpm (counterclockwise rotation when viewed from the top of the double-sided polishing machine)
Pressure: 80-100g/ ^cm2
After completion of the third polishing step, the glass substrate was chemically washed using a low-concentration alkaline aqueous solution, and then washed with pure water.

<<Surface Flatness/Parallelism, Surface Roughness, Defect Inspection>>
After the third polishing step, surface morphology information of both main surfaces of the glass substrate was obtained after chemical cleaning and pure water cleaning. Then, from the obtained surface morphology information, the flatness and the parallelism of both main surfaces were calculated.
As a result, the flatness of one main surface was 6.1 μm, the flatness of the other main surface was 8.8 μm, and the parallelism was 7.7 μm. Further, when defects on both main surfaces of the glass substrate were inspected by a defect inspection apparatus, no defect of 2 μm or more was detected. Moreover, when the surface roughness of both main surfaces of the glass substrate was measured by a surface roughness measuring instrument, the surface roughness of both main surfaces was 0.2 nm in terms of Ra. Based on the results of this inspection, the above-described one main surface of the glass substrate was defined as the first main surface on which the thin film forming the transfer pattern was formed, and the other main surface was defined as the second main surface.
The obtained glass substrate has a flatness of 7 μm or less on the first main surface, a parallelism of 10 μm or less, and no defects of 2 μm or more on the first main surface, so that a high-definition pattern can be formed. It met the specifications of a mask blank substrate suitable for manufacturing masks for

<<Mark formation process>>
Any of the marks shown in FIGS. 1 to 7 for specifying the first main surfaces of the glass substrates were formed on the seven glass substrates obtained by the same procedure as above.
FIG. 1 shows a first example of marks. This mark is composed of a rough surface portion 11 provided at the corner portion of the outer peripheral region of the second main surface 10 of the glass substrate. This mark was formed by applying an aqueous solution of hydrofluoric acid to the corners of the second peripheral region of the glass substrate, leaving it for a predetermined time, and then washing the glass substrate to remove the etchant. The surface roughness Ra of the rough surface portion 11 was 0.07 μm. The roughened portion can also be formed on the first main surface.
FIG. 2 shows a second example of marks. This mark is composed of a mirror surface portion 21 provided on the end surface 20 of the glass substrate. The end face 20 of the glass substrate that forms this mark is subjected to #1200 diamond abrasive grains after the local wet etching process and before the mirror polishing process of the first and second main surfaces of the glass substrate. Roughening treatment was applied by chamfering using . The surface roughness Ra of the roughened portion 22 other than the mirror surface portion 21 was 0.11 μm. The mark composed of the mirror surface portion 21 was formed by partial mirror polishing using a cylindrical rotary processing tool to which a polishing pad was attached and a slurry of cerium oxide. The surface roughness Ra of the mirror surface portion 21 was 0.01 μm. In the example of FIG. 2, the mirror surface portion 21 has a trapezoidal shape that is wider on the second main surface 10 side and narrower on the first main surface 30 side, but it may be vice versa.
FIG. 3 shows a third example of marks. This mark is composed of a rough surface portion 23 provided on the end surface 20 of the glass substrate. The end surface 20 of the glass substrate that forms this mark is etched using a slurry of cerium oxide after the local wet etching process and before the mirror polishing process of the first and second main surfaces of the glass substrate. Mirror polishing was applied by brush polishing. The surface roughness Ra of the mirror-polished portion 24 other than the rough surface portion 23 was 0.01 μm. The mark composed of the rough surface portion 23 was formed by sandblasting. The surface roughness Ra of the rough surface portion 23 was 0.012 μm. In the example of FIG. 3, the rough surface portion 23 has a trapezoidal shape that is wider on the second main surface 10 side and narrower on the first main surface 30 side, but it may be vice versa.
FIG. 4 shows a fourth example of marks. This mark consists of a marker portion 12 containing a water-based dye or water-based pigment, attached to the corner of the peripheral region of the second main surface 10 of the glass substrate. This marker portion 12 was formed by a felt-tip pen. The marker portion can also be formed on the end face.
FIG. 5 shows a fifth example of marks. This mark consists of recesses 13 provided at the corners of the outer peripheral region of the second main surface 10 of the glass substrate. This mark was formed by a pressure mark made by scanning a diamond stylus. The depth of the recess 13 was 2.2 μm. This recess can also be formed in the first main surface or the end face.
FIG. 6 shows a sixth example of marks. This mark consists of a laser marking 14 provided at the corner of the peripheral region of the second main surface 10 of the glass substrate. This mark was formed using the fourth harmonic of a YAG laser (wavelength: 266 μm). This mark was formed by forming eight cross-shaped laser markings 14 having a circular shape with a diameter of 10 μm and a depth of 3.3 μm. This laser marking can also be formed on the first major surface.
FIG. 7 shows a seventh example of marks. This mark consists of a laser marking 25 provided on the end face 20 of the glass substrate. This mark was formed using the fourth harmonic of a YAG laser (wavelength: 266 μm). This mark was formed by forming eight trapezoidal laser markings 25 having a circular shape with a diameter of 10 μm and a depth of 3.3 μm at positions shifted from the central position in the thickness direction of the end surface. In the example of FIG. 7, the surface closer to the side on which the laser marking 25 is formed is the second main surface 10, but it may be the other way around.

After forming the marks shown in FIGS. 1 to 7, the flatness and parallelism of the seven glass substrates were calculated in the same manner as above. The glass substrates on which the marks shown in FIGS. 1 to 7 were formed maintained the flatness and parallelism before formation, and the production yield by forming the marks shown in FIGS. 1 to 7 was 100%.

Example 2.
A mask blank substrate for manufacturing a display device of Example 2 was manufactured by the following method.
In Example 2, a case of manufacturing a mask blank substrate by recycling a glass substrate from a used mask (for example, the mask of Example 4) manufactured using the mask blank substrate of Example 1 will be described. . The specifications of the mask blank substrate for manufacturing the display device of Example 2 are such that the flatness of the side (first main surface) on which the thin film is formed is 7 μm or less, the parallelism is 10 μm or less, and the thin film is formed. It was assumed that there were no defects with a defect quality of 2 μm or more on the side (first main surface).

First, 70 mask blank substrates of Example 1 on which the marks of FIGS. A used mask on which a phase shift film pattern made of material was formed was prepared.
Next, the phase shift film pattern was removed with a chromium etchant containing ceric ammonium nitrate, perchloric acid, and pure water to obtain a glass substrate. At this stage, the glass substrate obtained by recycling the mask manufactured using the glass substrate on which the marks shown in FIGS. The mark shown in is formed. Since the marks shown in FIG. 4 are removed when the glass substrate is washed in the manufacturing process of the mask blank, the glass obtained by recycling the mask manufactured using the glass substrate on which the marks shown in FIG. 4 are formed No marks shown in FIG. 4 are formed on the substrate.

After removing the phase shift film pattern with an etchant for chromium, a mask blank substrate was manufactured in the same manner as in Example 1 on the cleaned glass substrate.

The marks shown in FIGS. 1, 5 and 6 formed on the glass substrate obtained by recycling the mask manufactured using the glass substrate on which the marks shown in FIGS. removed by
The mark shown in FIG. 2 formed on the glass substrate obtained by recycling the mask manufactured using the glass substrate on which the mark shown in FIG. It was removed by rough polishing or sandblasting.
The mark shown in FIG. 3 formed on the glass substrate obtained by recycling the mask manufactured using the glass substrate on which the marks shown in FIGS. The formed portion was removed by partial mirror polishing using a rotary machining tool.

In the same manner as in Example 1, the surface morphology information of both main surfaces was obtained for 70 glass substrates after the chemical cleaning and the pure water cleaning after the third polishing step, and the obtained surface morphology information. While calculating the flatness of both main surfaces, the parallelism was calculated.
As a result, the flatness of one main surface was in the range of 5 μm to 20 μm, the flatness of the other main surface was in the range of 5 μm to 12 μm, and the parallelism was in the range of 7 μm to 18 μm. Further, when defects on both main surfaces of the glass substrate were inspected by a defect inspection apparatus, no defects of 2 μm or more were detected on the first and second main surfaces having good flatness. Further, when the surface roughness of both main surfaces of the glass substrate was measured by a surface roughness measuring instrument, the surface roughness of both the first main surface and the second main surface was 0.3 nm or less in terms of Ra. . In Example 2, the first main surface was the surface on which the thin film serving as the transfer pattern was formed even before recycling, and the second main surface was the back surface even before recycling.

Since the glass substrates obtained by recycling the masks manufactured using the glass substrates on which the marks shown in FIGS. Any of the marks shown in FIGS. 1 to 7 were formed on the glass substrate in the mark forming step, specifying the surface with good flatness as the first main surface. The manufacturing yield of mask blank substrates satisfying the specifications of flatness of 7 μm or less and parallelism of 10 μm or less on the side (first main surface) on which the thin film is formed was 97%.

After forming any of the marks shown in FIGS. 1 to 7 again, the flatness and parallelism of the glass substrate were calculated in the same manner as above. The glass substrates on which the marks shown in FIGS. 1 to 7 were formed maintained the flatness and parallelism before formation, and the production yield by forming the marks shown in FIGS. 1 to 7 was 100%.

Example 3.
In Example 3, the mask blank substrate obtained in Example 2 was used to manufacture a phase shift mask blank, which is a photomask blank, by the following method.

First, the mask blank substrate obtained in Example 2 was chemically washed with a low-concentration alkaline aqueous solution, and then washed with pure water. The marks shown in FIG. 4 were removed by this cleaning.
Next, the first main surface of the mask blank substrate was set so as to face the surface of the sputtering target installed in the sputtering apparatus. Then, a phase shift film was formed on the first main surface of the mask blank substrate by a sputtering method.

Specifically, first, a mixed gas consisting of Ar gas, _N2 gas and _CO2 gas was introduced into the sputtering chamber of a sputtering apparatus in which a chromium target was arranged, and a film thickness of 89 nm made of CrOCN was formed by reactive sputtering. was deposited as a phase shift layer. Here, the flow rate of each component constituting this mixed gas is 35 sccm for Ar, 35 sccm for _N2 , and 14.5 sccm for _CO2 .
Next, a mixed gas of Ar gas and CH ₄ gas was introduced into the sputtering chamber in which the chromium target was placed, and a metal layer made of CrC and having a thickness of 10 nm was formed by reactive sputtering. Here, this mixed gas is a mixed gas containing 8% _CH4 gas in Ar gas.

Finally, a mixed gas consisting of Ar gas, _N2 gas and _CO2 gas is introduced into the sputtering chamber where the chromium target is placed, and a 30 nm-thick reflection reduction layer made of CrOCN is formed by reactive sputtering. bottom. Here, the flow rate of each component constituting this mixed gas is 35 sccm for Ar, 35 sccm for _N2 , and 18.2 sccm for _CO2 .
As a result, a phase shift film including a phase shift layer made of CrOCN with a thickness of 89 nm, a metal layer made of CrC with a thickness of 10 nm, and a reflection reduction layer made of CrOCN with a thickness of 30 nm is formed on the substrate. A shift mask blank was obtained.

The phase shift film formed as described above has a transmittance of 5.98% for light of 365 nm and a phase difference of 178.66° due to the three-layer structure of the phase shift layer, the metal layer, and the reflection reduction layer. Was. Here, the transmittance and phase difference were measured using MPM-100 (trade name) manufactured by Lasertec Corporation.
Further, the flatness of the main surface of the obtained phase shift mask blank on the side where the thin film is formed depends on the flatness of the first main surface of the mask blank substrate obtained in Example 2. The value was 10 μm or less.
The parallelism of the obtained phase shift mask blank also depended on the parallelism of the mask blank substrate obtained in Example 2, and the value was 12 μm or less.

The phase shift mask blank manufactured by the above process has a flatness of 10 μm or less on the main surface on which the thin film is formed, and a parallelism of 12 μm or less. Suitable for
In particular, phase shift masks in which a line and space pattern of 2.0 μm or less (eg, 1.2 μm to 2.0 μm) or a hole pattern of 2.0 μm or less (eg, 1.5 to 2.0 μm) are formed. suitable for manufacturing.
This phase shift mask is applied to the manufacture of high-resolution display panels (liquid crystal panels and organic EL panels) with a resolution exceeding 500 ppi (for example, 600 ppi or more).

Example 4.
In Example 4, the phase shift mask blank produced in Example 3 was used to produce a photomask (phase shift mask) by the following method.
First, on the phase shift film of the phase shift mask blank manufactured in Example 3, a resist film made of a novolac positive photoresist was formed. After that, a predetermined pattern was drawn on the resist film using a laser beam with a wavelength of 413 nm using a laser drawing machine. After that, the resist film was developed with a predetermined developer to form a resist film pattern on the phase shift film.
Thereafter, the phase shift film pattern was formed by etching the phase shift film using the resist film pattern as a mask.

Each of the phase shift layer, the metal layer, and the reflection reduction layer that constitute the phase shift film is made of a chromium-based material containing chromium (Cr). Therefore, the phase shift layer, the metal layer, and the reflection reduction layer can be etched with the same etchant.
Here, an etchant for chromium containing ceric ammonium nitrate and perchloric acid was used as an etchant for etching the phase shift film.
After that, a mask for exposure was obtained by stripping the resist film pattern using a resist stripping solution.

Since the pattern was drawn on a highly flat substrate, the CD (Critical Dimension) variation of the phase shift film pattern was as good as 70 nm. Here, the CD variation is the width of deviation from the target line-and-space pattern (width of line pattern: 2.0 μm, width of space pattern: 2.0 μm). The CD variation of the phase shift film pattern was measured using SIR8000 manufactured by Seiko Instruments Nanotechnology.
The phase shift mask described above has flatness and parallelism that satisfy the required standards, and has excellent pattern cross-sectional shape and excellent CD uniformity. It can be said that a high-definition display device (organic EL panel) can be manufactured.

Example 5.
In Example 5, as in Example 2, a case will be described in which a mask blank substrate is manufactured by recycling a glass substrate from a used mask manufactured using a mask blank substrate.
A mask blank substrate for manufacturing a display device of Example 5 was manufactured by the following method.

First, a used mask was prepared in which a phase shift film pattern made of a chromium-based material was formed on a mask blank substrate. These glass substrates had notch marks of 1.0 to 2.0 mm at two diagonal corners on the back surface before recycling.
As described above, notch marks cause edge sag and bumps. Therefore, when manufacturing a mask for forming a high-definition pattern, a mask blank substrate without notch marks should be used. is preferred. However, there is a need to use substrates already formed with notch marks as recycled products. The required accuracy is relaxed as compared with the above-mentioned high definition.
Considering these points, the first specification of the mask blank substrate for manufacturing the display device of Example 5 (specification suitable for manufacturing a high-definition phase shift mask, etc.) is the same as in Example 2. There should be no defects with flatness of 7 μm or less, parallelism of 10 μm or less on the side where is formed (first main surface), and defect quality of 2 μm or more on the side where the thin film is formed (first main surface). and The second specification (specification for middle layer and rough layer) is that the flatness of the first main surface is 10 μm or less, the parallelism is 20 μm or less, and the defect quality of the first main surface is 5 μm or more. It was assumed that there were no defects in
Next, the phase shift film pattern was removed with a chromium etchant containing ceric ammonium nitrate, perchloric acid, and pure water to obtain a glass substrate.
After removing the phase shift film pattern with an etchant for chromium, the cleaned glass substrate was subjected to <substrate thickness inspection step>, <flaw inspection step> and <flatness calculation step> in the same manner as in Example 1. rice field.

As a result, it was confirmed that the minimum plate thickness exceeded 9.9 mm and that the required polishing allowance was provided to obtain the required surface roughness.
As for the presence or absence of scratches on both main surfaces of the glass substrate, it was confirmed that scratches detectable by visual inspection were formed on the front and back surfaces.
The flatness of both main surfaces was 10 μm for one main surface and 12 μm for the other main surface.
Next, a notch mark having the same size was formed at a position on one main surface facing the notch mark formed on the other main surface of the glass substrate. In the fifth embodiment, notch marks corresponding to notch marks already formed on the other main surface are formed on one main surface, thereby suppressing the occurrence of bumps, which has been a problem in the prior art. Then, in the same manner as in Example 1, the <second polishing step> and <third polishing step> out of the <local wet etching step> and the <mirror polishing step> were performed. The substrate was chemically cleaned using a low-concentration alkaline aqueous solution and then cleaned with pure water.

Surface morphology information on both main surfaces of the obtained glass substrate was obtained. Then, from the obtained surface morphology information, the flatness and the parallelism of both main surfaces were calculated.
As a result, the flatness of the one main surface was 9.8 μm, the flatness of the other main surface was 6.9 μm, and the parallelism was 9.9 μm. Further, when defects on both main surfaces of the glass substrate were inspected by a defect inspection apparatus, no defect of 2 μm or more was detected. Moreover, when the surface roughness of both main surfaces of the glass substrate was measured by a surface roughness measuring instrument, the surface roughnesses of the one main surface and the other main surface were both Ra of 0.2 nm.

Based on these inspection results, in this glass substrate, the other main surface used as the back surface before recycling is set to the first main surface on which the thin film that becomes the transfer pattern is formed, and the front surface before recycling One of the main surfaces used as a was set as the second main surface. The obtained glass substrate has a flatness of 7 μm or less on the other main surface, a parallelism of 10 μm or less, and no defects of 2 μm or more on the second main surface, so that a high-definition pattern can be formed. It met the specifications of a mask blank substrate suitable for manufacturing masks for
Next, a mark as shown in FIG. 3 for specifying the first main surface was formed to obtain a mask blank substrate.

Next, as in Example 3, a phase shift mask blank was produced. The obtained phase shift mask blank had a main surface on which the thin film was formed had a flatness of 10 μm or less and a parallelism of 12 μm or less.
Furthermore, in the same manner as in Example 4, a phase shift mask was produced. The CD variation of the obtained phase shift film pattern was as good as 76 nm. The phase shift mask of Example 5 has flatness and parallelism that meet the required standards, and has excellent CD uniformity. It can be said that
For 70 glass substrates manufactured by the manufacturing method described above, surface morphology information on both main surfaces was obtained, and the flatness and parallelism of both main surfaces were calculated from the obtained surface morphology information. As a result, the flatness of one main surface was in the range of 5 μm to 30 μm, the flatness of the other main surface was in the range of 5 μm to 20 μm, and the parallelism was in the range of 7 μm to 30 μm. The manufacturing yield of mask blank substrates suitable for manufacturing masks and the like for forming high-definition patterns, which satisfies the first specification described above, was 87%. rice field. Moreover, the manufacturing yield of the mask blank substrates for the middle layer and the rough layer, which satisfies the above-described second specification, was 94%, which was a further favorable value.

In the fifth embodiment, the case where notch marks are formed on both the first main surface and the second main surface has been described, but the present invention is not limited to this. When it is judged that local processing is not necessary or middle Depending on the situation, such as being used for layers, the marks of this embodiment for specifying the surface that satisfies the specifications for flatness and defect quality may be formed on a glass substrate having notch marks formed only on one side. good too.

Comparative example 1.
Comparative Example 1 is an example of manufacturing a mask blank substrate by forming conventional notch marks on a glass substrate in place of the mark forming process of Example 1. FIG. Notch marks having a size of 1.0 to 2.0 mm were formed at two ends of the second main surface of the glass substrate. Then, the first specification and the second specification of Comparative Example 1 were set in the same manner as in Example 5.
70 mask blank substrates were manufactured in the same manner as in Example 1 until <<surface flatness/parallelism, surface roughness, defect inspection>> after the third polishing step (precision polishing step).

After forming the notch marks, the flatness and parallelism of the glass substrate were calculated in the same manner as above. As a result, the first main surface on which no notch marks are formed has a flatness of 7 μm or less, a parallelism of 10 μm or less, and no defects having a defect quality of 2 μm or more on the first main surface. The manufacturing yield of mask blank substrates suitable for manufacturing masks for forming high-definition patterns satisfying the specifications of was 20%. The production yield of the mask blank substrates for the middle layer and rough layer satisfying the second specification was 37%.

10 second main surface 11 rough surface portion 12 marker portion 13 concave portion 14 laser marking 20 end surface 21 mirror surface portion 22 roughening treatment portion 23 rough surface portion 24 mirror polishing portion 25 laser marking 30 a first major surface;

Claims (7)

In a method for manufacturing a mask blank substrate for manufacturing a display device,
The mask blank substrate has a first main surface on which a thin film to be a transfer pattern is formed, a second main surface provided opposite to the first main surface, the first main surface and and an end surface perpendicular to the second main surface,
preparing a translucent substrate having one main surface, the other main surface facing the one main surface, and an end surface perpendicular to the one main surface and the other main surface and
mirror-polishing the one main surface and the other main surface of the translucent substrate;
a surface information acquisition step of acquiring surface information including at least each flatness of the one main surface and the other main surface after the mirror polishing;
Of the one main surface and the other main surface, the main surface having a better flatness obtained in the surface information acquisition step is defined as a first main surface, and only the second main surface is provided with the forming a mark identifying the first major surface;
The mark can be removed by at least one of mirror polishing of the one main surface and the other main surface, roughening treatment and mirror polishing of the end face, and cleaning of the translucent substrate,
The translucent substrate is a recycled product obtained by removing a thin film having a transfer pattern formed thereon from a used mask,
A method of manufacturing a mask blank substrate, wherein the translucent substrate does not have a notch mark. 2. The method of manufacturing a mask blank substrate according to claim 1, further comprising the step of roughening the end face before forming the mark. 3. The method of manufacturing a mask blank substrate according to claim 2, further comprising the step of mirror-polishing the end face before forming the mark. measuring the thickness of the recycled light-transmitting substrate, wherein the one main surface of the light-transmitting substrate having the measured minimum thickness of the light-transmitting substrate equal to or greater than a reference value is measured; 4. The method of manufacturing a mask blank substrate according to claim 1, wherein said other main surface is mirror-polished. 5. The step of preparing the translucent substrate includes a step of removing the thin film having the transfer pattern from the used mask to obtain the recycled translucent substrate. 3. A method for manufacturing a mask blank substrate according to any one of . and forming a thin film to be a transfer pattern on the first main surface of the mask blank substrate manufactured by the mask blank substrate manufacturing method according to any one of claims 1 to 5 . A method for manufacturing a mask blank to 7. A method of manufacturing a mask, comprising the step of forming a transfer pattern on the thin film of a mask blank manufactured by the method of manufacturing a mask blank according to claim 6 .

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