JP2007298858A - Method for producing substrate for mask blank, method for producing mask blank and method for producing mask for exposure, and mask blank and mask for exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a substrate for mask blank including steps suitable for imparting a higher cleanliness factor to only a target portion with no need of evenly cleaning the whole substrate. <P>SOLUTION: The method for producing a substrate for mask blank includes: a step of covering a foreign body 3 present on a surface of a substrate 2 for mask blank with a liquid 1; a step of solidifying the liquid 1 covering the foreign body 3; and a step of removing the foreign body 3 from the substrate 2 surface together with a solidified body 1' formed by solidifying the liquid 1 covering the foreign body 3 by removing the solidified body 1' from the substrate 2 surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mask blank substrate manufacturing method, a mask blank manufacturing method, an exposure mask manufacturing method, and a mask blank and an exposure mask manufactured by using these manufacturing methods.

In manufacturing a semiconductor LSI, a liquid crystal panel, or the like, a fine pattern is transferred to an exposure object (transfer object) using an exposure mask. Cleaning of the mask blank substrate in this exposure mask is generally performed by dipping (dipping) cleaning, spin cleaning, or the like (Patent Document 1).
In dip (immersion) cleaning, cleaning may be performed while applying ultrasonic waves. Also, spin cleaning may involve cleaning by ejecting pure water or chemical from a nozzle at high speed (Patent Document 2).
JP-A-6-69178 JP 2002-131889 A

However, the above-described mask blank substrate cleaning method has the following problems.
When cleaning the deposit on the mask blank substrate, the mechanism of the cleaning is analyzed in detail. (1) Move the deposit, (2) Enclose the deposit, (3) Move the deposit to the target location, It consists of three processes.
(1) In the movement of deposits, the chemical movement pressure action of chemicals, the physical movement pressure action of brushes and sponges, the cavitation effect by ultrasonic waves and megahertz ultrasonic waves (megasonic), the fluid ejected from the nozzle And movement on the substrate by the impact pressure action of the droplets.
(2) In the enclosure of deposits, chemical enclosure with a surfactant or a chelating agent is performed.
(3) In many cases, the movement of the deposit to the target location is driven out of the substrate by a laminar flow of the liquid.
Such a wet process is suitable for cleaning the entire substrate on average, but is not suitable for making the targeted portion higher in cleanliness. The main reasons are as follows: (1) In the process of moving the deposit, it is necessary to use different chemicals depending on the type of foreign matter (organic, inorganic, metal), and it is difficult to select a chemical that can move all types of foreign matter. It is. Further, there is an occurrence of deposits caused by the scrub body due to contamination of the scrub body itself such as a brush or a sponge. Also, cleaning using ultrasonic waves or megahertz ultrasonic waves (megasonic), or cleaning using a fluid ejected from a nozzle (for example, mixing liquid such as pure water or chemical liquid with gas such as air or N ₂₎ There is also a strongly adhered foreign substance that cannot be moved only by the physical action of two-fluid jet cleaning that ejects the two fluids from the nozzle at high speed.
(2) In the enclosure process of deposits, the deposits are reattached to another place due to insufficient enclosure. Further, if the rinsing process is insufficient, a surfactant or chelating agent remains.
In the incomplete deposit expelling step (3), the enclosed deposit always moves on the substrate due to the surface tension of the liquid, so that the deposit moves to the outside of the substrate (that is, the target location). When drying is completed halfway, there is reattachment of the deposit to another place. Centrifugal drying by spin, which is observed in spin cleaning, greatly affects the effect depending on the distance from the spin center, and the drying on the outside of the substrate is faster, making it more likely that the deposits cannot move out of the substrate. ing. Usually, the ultrapure water used for the final rinse has a low flow velocity at the interface with the substrate due to its viscosity, and it is difficult to drive out sufficient foreign matter.
Due to the above causes (1) to (3), the adhering foreign matter remains on the substrate surface and the adhering foreign matter is reattached to another location.
If there is such an adhering foreign matter, a film is formed on the adhering foreign matter, resulting in a film defect of the mask blank (a defect in the optical characteristics of the film or a convex defect in the film), or an exposure mask. When producing the film, the adhered foreign material is peeled off together with the film on the film, or the adhered foreign material remains in a place where the film is to be removed, resulting in a film defect. As a result, a transfer pattern defect occurs in the transfer target.

  The present invention has been made in view of the above-mentioned problems, and a first object thereof is to provide a mask blank substrate, a mask blank, and a method for manufacturing the same, in which there are no deposits on the main surface of the mask blank substrate. There is. A second object is to provide an exposure mask that does not cause transfer pattern defects and a method of manufacturing the same.

The method of the present invention has the following configuration.
(Configuration 1) A step of covering the foreign matter existing on the surface of the mask blank substrate with a liquid;
Solidifying the liquid covering the foreign matter;
Removing the foreign matter from the substrate surface together with the solidified body by removing the solidified body obtained by solidifying the liquid covering the foreign matter from the substrate surface;
A method for manufacturing a mask blank substrate, comprising:
(Configuration 2) Reduce the adhesion of foreign matter adhering to the surface by bringing the solidified body obtained by solidifying the liquid into contact with the foreign matter existing on the surface of the mask blank substrate and adhering to the surface. The manufacturing method of the mask blank board | substrate of the structure 1 characterized by including the process to make.
(Configuration 3) After the main surface of the mask blank substrate is precisely polished, the defect inspection of the main surface is performed to identify the defect based on the foreign matter existing on the main surface, and against the defect based on the specified foreign matter A method for manufacturing a mask blank substrate, comprising applying the process according to Configuration 1 or 2.
(Structure 4) The manufacturing method of the mask blank substrate according to any one of Structures 1 to 3, wherein pure water is used as the liquid covering the foreign matter.
(Structure 5) The mask blank substrate according to any one of Structures 1 to 3, wherein a liquid in which a low melting point metal or an alloy made of a low melting point metal is used is used as the liquid covering the foreign matter. Method.
(Structure 6) A mask manufactured by forming a thin film to be a mask pattern on the main surface of a mask blank substrate obtained by the method for manufacturing a mask blank substrate according to any one of structures 1 to 5. blank.
(Structure 7) An exposure mask manufactured by forming a mask pattern on the main surface of a mask blank substrate using the mask blank obtained by the method for manufacturing a mask blank according to Structure 6.
(Configuration 8) A step of preparing a mask blank in which a thin film to be a mask pattern is formed on the main surface of the mask blank substrate;
Covering the foreign matter present on the surface of the mask blank with a liquid;
Solidifying the liquid covering the foreign matter;
Removing a solidified body obtained by solidifying a liquid covering the foreign matter from the surface of the mask blank by removing the solidified body together with the solidified body from the surface of the mask blank. Method.
(Configuration 9) A step of preparing an exposure mask having a mask pattern formed on the main surface of a mask blank substrate;
Covering the foreign matter present on the surface of the exposure mask with a liquid;
Solidifying the liquid covering the foreign matter;
Removing the foreign matter from the exposure mask surface together with the solidified body by removing the solidified body obtained by solidifying the liquid covering the foreign matter from the exposure mask surface. Mask manufacturing method.

According to the present invention, it is possible to perform local cleaning only on a portion where a foreign substance exists on the surface of a substrate, a mask blank, or an exposure mask by utilizing liquid solidification (freezing, etc.). Therefore, it is suitable for making the target portion higher in cleanliness.
In addition, it is not necessary to wash the entire substrate, mask blank or exposure mask on average, and a place without a foreign substance (clean place) on the surface of the substrate, mask blank or exposure mask can be maintained without cleaning, Due to the above causes (1) to (3), the adhering foreign matter remains on the surface of the substrate, the mask blank or the exposure mask, and the adhering foreign matter does not reattach to another place.

Hereinafter, the present invention will be described in detail.
The manufacturing method of the mask blank substrate of the present invention is as follows.
A step of covering the foreign matter present on the surface of the mask blank substrate with a liquid;
Solidifying the liquid covering the foreign matter;
Removing the foreign matter from the substrate surface together with the solidified body by removing the solidified body obtained by solidifying the liquid covering the foreign matter from the substrate surface;
(Structure 1).
Here, in the step of covering the foreign matter existing on the substrate surface with the liquid, at least the foreign matter existing on the substrate surface and the periphery thereof are covered with the liquid. At that time, as shown in FIG. 1 (1) as an example, it is desirable that only the foreign material 3 existing on the surface of the substrate 2 and the periphery thereof are covered with the liquid 1 (enclosed locally). To cover only the foreign matter and its surroundings with a liquid is usually performed by dropping the foreign matter and / or the liquid around the foreign matter, or liquefying the foreign matter and / or the solidified body therearound.

In the step of solidifying the liquid covering the foreign matter, the means for solidifying the liquid covering the foreign matter differs depending on the liquid.
When the liquid covering the foreign matter is ultrapure water or the like (Configuration 4), the ultrapure water or the like is frozen to be solidified.
At this time, it is preferable to freeze the ultrapure water etc. which covers a foreign material by making the frozen body obtained by freezing ultrapure water etc. contact the ultrapure water etc. which cover a foreign material. For example, as shown in FIG. 2, ultrapure water or the like that covers foreign matter is brought into contact with ultrapure water or the like 1 that covers foreign matter 3 by contacting frozen body 100 obtained by freezing ultrapure water or the like. It is preferable to freeze. The reason for this is that local cooling of the ultrapure water 1 covering the foreign matter 3 with the frozen body 100 is possible, and the phase from the contact surface between the frozen body 100 and the ultrapure water 1 etc. to the ice of the ultrapure water 1 etc. This is because the change proceeds and the frozen body 100 and the frozen body 1 ′ such as ultrapure water are firmly joined. The frozen body 100 is also used as a jig for peeling a frozen body 1 ′ such as ultrapure water, which will be described later. The form of the frozen body 100 can be an elliptical column shape, a cylindrical shape, or a prismatic shape, and can be a substantially spherical shape as shown in FIG. The frozen body 100 uses a cooling-resistant mold (for example, a mold made of polypropylene), poured pure water or the like into this mold, and inserted into a local cooling spot 14 ′ such as a Peltier module to be frozen. Alternatively, it can be obtained by allowing it to stand for about 15 hours in a refrigerator at about −20 ° C. and freeze (freeze) it.
Instead of the frozen body 100 obtained by freezing ultrapure water or the like, it is also possible to freeze the liquid by bringing the cooling body cooled to a minus temperature into contact with the ultrapure water 1 or the like covering the foreign material 3. is there.
The means for solidifying the liquid covering the foreign matter is solidified (solidified) by natural cooling or the like when the liquid is a liquid in which a low melting point metal or an alloy made of a low melting point metal is dissolved (melted). .
In the step of solidifying the liquid covering the foreign matter, the deposit is strongly enclosed by the solidified body obtained by solidifying the liquid. In addition, at the gap or interface between the substrate and the foreign matter, an action of reducing the adhesion force between the substrate and the foreign matter works due to the liquid penetration action and the volume expansion action of the liquid.

The present invention includes a step of removing the foreign matter from the substrate surface together with the solidified body by removing the solidified body obtained by solidifying the liquid covering the foreign matter from the substrate surface.
In this step, as shown in FIG. 1 (2), as an example, the solidified body 1 ′ obtained by solidifying the liquid covering the foreign body 3 is removed from the surface of the substrate 2, thereby the foreign body 3 together with the solidified body 1 ′. Is removed from the surface of the substrate 2. At this time, the foreign material 3 is strongly enclosed and held by the solidified body 1 ′. By this step, the foreign matter 3 is reliably moved to a place (target place) where there is no possibility of reattachment to the substrate.
Here, examples of means for removing the solidified body obtained by solidifying the liquid covering the foreign matter from the substrate surface include means using a peeling jig joined to the solidified body.
Specifically, for example, in the step of solidifying the liquid covering the foreign matter, a peeling jig is brought into contact with or inserted into the liquid covering the foreign matter, and then the liquid is solidified and the solidified. The body and the peeling jig are joined (fixed) to each other, and the solidified body in which the liquid covering the foreign matter is solidified is removed (stripped) from the substrate surface by the peeling jig. The frozen body 100 described above is an example of a jig for peeling the frozen body 1 ′ such as ultrapure water, and is also used as a local cooling jig for the ultrapure water 1 or the like covering the foreign material 3. Other examples of the peeling jig include a rod-shaped body and a wire, and the form of the joint with the liquid covering the foreign matter in these peeling jigs solidifies the liquid covering the foreign matter. The solidified body and the peeling jig can be in a form suitable for joining (adhering) to each other.
As another means for removing the solidified body obtained by solidifying the liquid covering the foreign matter from the substrate surface (including removal, removal, peeling, peeling, etc.), solidification including foreign matter such as a frozen body Examples include contact with a body, suction of a solidified body containing foreign matter by a suction means, adsorption of a solidified body containing foreign matter by an adsorption means, and a combination means thereof.

In the present invention, a solidified body obtained by solidifying a liquid is brought into contact with a foreign substance that exists on the surface of the mask blank substrate and adheres to the surface, thereby increasing the adhesion of the foreign substance attached to the surface. It is possible to have a step of reducing (Configuration 2).
The process according to Configuration 2 is particularly normal when the foreign matter present on the surface of the mask blank substrate is present on the surface of the mask blank substrate and is attached to the surface (attached foreign matter). This is useful when the foreign matter is strongly attached to the substrate surface to the extent that it cannot be removed.
The process according to the configuration 2 is performed simultaneously with the “step of covering the surface of the mask blank substrate with the liquid with the liquid” in the process according to the configuration 1, or before the process or after the process. It is preferable to carry out until the liquid to be covered is solidified.
In the process according to Configuration 2, the force (physical movement pressure action) for bringing the solidified body into contact with the foreign matter (attached foreign matter) adhering to the substrate surface is larger than the adhesion force of the foreign matter to the substrate surface. It is preferable to act on the foreign matter, thereby reducing the adhesion force of the foreign matter adhering to the surface, and preferably moving the foreign matter from the attachment location or scraping (scraping off) the foreign matter from the surface. desirable.
In the process according to Configuration 2, as shown in FIG. 3, the contact of the solidified body with the adhering foreign matter causes the solidified body to vibrate in a direction parallel to the normal substrate surface (in a plane parallel to the substrate surface). (Including the case of circular movement of the tip plane).
When the solidified body is a frozen body such as ultrapure water, there is no risk of the glass surface being damaged by contact with the glass surface. As shown to a), it can carry out, making the frozen body 200 contact the substrate surface.
As shown in FIG. 3B, the solidified body can be brought into contact with the adhering foreign matter without bringing the frozen body or solidified body 200 into contact with the substrate surface. In this case, if the solidified body is a frozen body such as ultrapure water, there is no risk of scratching the glass surface even if the frozen body contacts the glass surface.
The form of the frozen body or solidified body 200 can be an elliptic cylinder shape, a cylindrical shape, or a prismatic shape, and can be a substantially spherical shape as shown in FIG.

The environment (atmosphere) for performing each step in the present invention, particularly the step according to Configuration 2, is an atmosphere in which clean air is circulated, specifically, in a clean room, and is affected by dust and dirt in the atmosphere. For example, generation of ultra-fine concave defects (such as scratches) due to the presence of dust or dirt between the frozen or solidified body 200 and the substrate shown in FIG. 3 is preferable. The clean room class is preferably 1000 or less.
Moreover, when using a frozen body, it is preferable that the temperature which performs each process in this invention shall be 10 to 25 degreeC from a viewpoint of the intensity | strength and durability of a frozen body.

The present invention is particularly suitable as a local cleaning method after the final inspection process in the mask blank substrate manufacturing process (Configuration 3). This is because it is usually necessary to clean the entire substrate by an average cleaning in the previous process. However, it is useful to apply the present invention to strong local cleaning of local foreign matters that cannot be removed by normal cleaning in the previous process.
In addition, the present invention is particularly suitable as a local cleaning method for mask blanks and masks (Configuration 8 and Configuration 9).
Furthermore, the present invention provides a mask blank manufactured by forming a thin film to be a mask pattern on the main surface of a mask blank substrate, a mask blank with a resist film in which a resist film is formed on the thin film, and a mask blank substrate. It can also be applied as a local cleaning method for a mask having a mask pattern formed on its main surface.

In the present invention, pure water, ultrapure water, or the like is used as the pure water used as the liquid covering the foreign matter (Configuration 4). When high cleanliness is required, it is preferable to use ultrapure water.
In the present invention, a liquid that covers a foreign substance, or a frozen body 100 or 200 shown in FIGS. 2 or 3 or the like, which is obtained by adding a substance that lowers the freezing point (for example, gelatin) to pure water or ultrapure water, is used. can do. As a result, the liquid covering the foreign matter is easily frozen at about room temperature, and the frozen bodies 100 and 200 shown in FIGS. 2 and 3 are hardly melted at about room temperature.

  In the present invention, examples of the low melting point metal or an alloy made of a low melting point metal used as a liquid for covering foreign matter include tin, indium, and alloys thereof (Configuration 5).

The present invention is applicable when the foreign matter existing on the surface of the mask blank substrate is present on the surface of the mask blank substrate and is attached to the surface.
The present invention can also be applied to the case where the foreign matter present on the surface of the mask blank substrate is present on the surface of the mask blank substrate and is not attached to the surface.
The present invention can be applied not only to the local cleaning of the adhered foreign matter existing on the main surface of the mask blank substrate, but also to the local cleaning of the adhered foreign matter existing on the end face (side surface, chamfered surface) of the mask blank substrate.

  In the present invention, the material of the substrate is not particularly limited. Glass materials such as synthetic quartz glass, alkali-free glass, soda lime glass, aluminosilicate glass, ultra-low expansion glass, glass ceramics, ceramics, and calcium fluoride may be used.

The mask blank of the present invention is manufactured by forming a thin film to be a mask pattern on the main surface of the mask blank substrate obtained by the above-described mask blank substrate manufacturing method according to the present invention. (Configuration 6).
For example, a photomask blank is manufactured by forming a light-shielding film as a thin film on the main surface of the mask blank substrate obtained by the method for manufacturing a mask blank substrate according to the present invention described above, or a half as a thin film A halftone phase shift mask blank is manufactured by forming a tone film, or a halftone film and a light shielding film are sequentially formed as a thin film to manufacture a halftone phase shift mask blank. These photomask blanks and halftone phase shift mask blanks are transmissive mask blanks. In addition, a reflective mask blank is formed by forming a multilayer reflective film and an absorber film as a thin film on the main surface of the mask blank substrate obtained by the above-described mask blank substrate manufacturing method according to the present invention. To manufacture. Furthermore, a mask film with a resist film may be manufactured by forming a resist film on a thin film of a transmission type or reflection type mask blank.

The exposure mask of the present invention is manufactured by forming a mask pattern on the main surface of a mask blank substrate using the mask blank obtained by the above-described mask blank manufacturing method according to the present invention. (Configuration 7).
For example, a transmissive mask blank, a reflective mask blank, or a mask blank with a resist film manufactured as described above is exposed and developed to form a resist pattern. Next, the thin film is etched using the resist pattern as a mask, and a mask pattern is formed on the main surface of the mask blank substrate to manufacture an exposure mask.

The present invention is particularly suitable for cleaning a large mask blank substrate, a large mask blank, and a large mask.
For dip cleaning of large glass substrates and ultrasonic / megasonic cleaning, a series of cleaning such as loading / unloading time to substrate cleaning tank, substrate immersion time, substrate lifting time, substrate drying time, etc. In each individual operation, since it takes time compared to a small substrate (6 inches or the like), the total cleaning time becomes longer. Similarly, in spin cleaning and brush cleaning of large glass substrates, the time required for loading and unloading the substrate to the spin chuck takes longer than that of small substrates, and the rotation of the substrate is slower than that of small substrates. Since the cleaning time takes longer than that of a small substrate, the total cleaning time becomes longer. For these reasons, normal cleaning of large glass substrates and the like takes time and cost, but by applying the present invention in place of normal cleaning, cleaning time and cost can be reduced. .
In the present invention, a large mask blank substrate, a large mask blank, and a large mask include a large mask blank substrate for manufacturing FPD devices such as LCD (liquid crystal display), plasma display, and organic EL (electroluminescence) display, A mask blank and a mask are mentioned.

Hereinafter, the present invention will be described in more detail based on examples.
(Example 1)
(Manufacture and inspection of glass substrates for mask blanks)
End surface processing and chamfering of synthetic quartz glass substrate, and the surface of the glass substrate that has been ground by a double-sided lapping device is set in a double-sided polishing device, and has high smoothness through a rough polishing process, a precision polishing process, and a cleaning process A glass substrate for mask blank was obtained.
The main surface of the obtained glass substrate for mask blank was inspected by a defect inspection apparatus for a convex defect or a concave defect. The defect information obtained by the defect inspection apparatus stores the defect type (convex defect, concave defect), defect size, defect position information, and the like.
As a result of the defect inspection, a convex defect based on a minute adhered foreign substance having a height of about 40 nm and a size of about 6 μm was discovered. It was confirmed that the convex defect based on the minute adhered foreign matter was not removed even when the mask blank glass substrate was washed again, and was a foreign matter that adhered relatively firmly to the glass substrate surface. Such a convex defect based on a minute adhered foreign substance on the glass substrate for mask blank is caused by a film defect on the mask blank (defect in optical characteristics of the film or film Convex defect), or when the exposure mask is produced, the adhered foreign matter is peeled off together with the film on it, or the adhered foreign matter remains in the place where the film is to be removed. In any case, it becomes a defect of a mask blank or a mask, and eventually a transfer pattern defect in the transfer target.

(Preparation of frozen body)
Next, a frozen body was prepared as follows.
As shown in FIG. 4, a frozen body manufacturing unit 10 using a Peltier module 11 and a power source (not shown) for cooling control were prepared. The frozen body manufacturing unit 10 is provided with a local cooling spot 14 (diameter: 3 mm, length: 50 mm, cylindrical body (aluminum)) made of aluminum mounted on a cooling surface (aluminum) 12 of the Peltier module 11. And the heat insulating material 13 made of urethane foam is attached so as to cover the local cooling spot 14. An exhaust fan 16 is attached to the surface of the Peltier module 11 opposite to the cooling surface 12 via a heat sink 15, and exhaust heat is released from the exhaust fan 16.
As shown in FIGS. 5 (1) to (3), the tip of the local cooling spot 14 is grooved on the portion 14c excluding the circumferential portion 14a and the cross body portion 14b in order to increase the adhesion of the frozen body. is there.
5 ml of ultrapure water was prepared, and the temperature of this ultrapure water was set to 21 ° C., the same as the environmental temperature. The local cooling spot was set to −20 ° C. by passing an electric current through the Peltier module.
As shown in FIG. 6, 0.03 ml of ultrapure water is dropped on the tip of the local cooling spot 14 and left for several seconds to cause a phase change to ice, and then 0.03 ml of ultrapure water is dropped again. The process was repeated several times to obtain a hemispherical (substantially spherical) frozen body 20 (diameter of about 6 mmφ) with a rounded tip. The temperature of the hemispherical frozen body 20 is −20 ° C., which is the same as the local cooling spot.

(Local cleaning)
As shown in FIG. 7, the hemispherical frozen body 20 prepared as described above is used, and the hemispherical frozen body 20 is brought close to the minute adhered foreign matter 50 on the glass substrate 40 (FIG. 4 (1)).
Thereafter, immediately before contact between the hemispherical frozen body 20 and the glass substrate 40, 0.03 ml of ultrapure water is dropped on the surface of the hemispherical frozen body 20, and the ultrapure water is transferred to the surface of the hemispherical frozen body 20. Then, the ultrapure water 30 is brought into contact with the glass substrate 40 including the minute adhered foreign matter 50. During the phase change of the ultrapure water 30 to ice (before the ultrapure water 30 is frozen), a hemispherical frozen body is subjected to a load of 0.5 g per square centimeter applied to the tip of the hemispherical frozen body 20. The tip of 20 is brought into contact with the surface of the glass substrate 40 (FIG. 4 (2)).
Thereafter, during the phase change of the ultrapure water 30 to ice (before the ultrapure water 30 is frozen), a load of 0.5 g per square centimeter is applied to the tip of the hemispherical frozen body 20, The tip of the hemispherical frozen body 20 and the surface of the glass substrate 40 are moved relative to each other in the direction A in FIG. The adhering foreign matter 50 is moved (the state of adhesion to the substrate surface is released) (FIG. 4 (3)).
Thereafter, the ultrapure water 30 (around the convex defect) was cooled and frozen for 3 minutes to obtain a frozen body in which the hemispherical frozen body 20 and the frozen body of the ultrapure water 30 were integrally frozen (FIG. 4 ( 4)). Thereafter, the frozen body obtained by integrally freezing the hemispherical frozen body 20 and the frozen body of the ultrapure water 30 is pulled away in the normal direction of the substrate surface (direction B in the drawing) and separated from the substrate (FIG. 4 (5)). )). Thereby, the foreign material 50 in the frozen body of the ultrapure water 30 was separated from the substrate.
Finally, the entire substrate surface was left in a clean clean room and dried to obtain a glass substrate for mask blank.
The hemispherical frozen body forming process, the local cleaning process using the frozen body, and the drying process described above were performed in a Class 1000 clean room in an environment where both the ambient temperature and the substrate temperature were 21 ° C.
Again, defects on the surface of the glass substrate were inspected by the above-described defect inspection apparatus, but neither a convex defect nor a concave defect was confirmed. Moreover, when the surface was observed with the atomic force microscope (AFM) about the area | region where the above-mentioned convex defect was formed, and its peripheral area | region, it was favorable without the damage by the contact of a frozen body.
In addition, the preferable substrate temperature in Example 1 and the temperature of atmosphere are 10 to 25 degreeC.

(Example 2)
In the “local cleaning” step of the first embodiment, instead of the step of “contacting the surface of the hemispherical frozen body 20 with 0.03 ml of ultrapure water”, the tip of the hemispherical frozen body 20 and the surface of the glass substrate 40 And the ultrapure water 30 covering the minute adhered foreign matter 50 was obtained by melting only the tip of the hemispherical frozen body 20 (see FIG. 4 (2)). The other steps were the same as in Example 1.
Although defects on the glass substrate surface were inspected by the above-described defect inspection apparatus, neither convex defects nor concave defects were confirmed. Moreover, when the surface was observed with the atomic force microscope (AFM) about the area | region where the above-mentioned convex defect was formed, and its peripheral area | region, it was favorable without the damage by the contact of a frozen body.
In the case of performing local cleaning by melting the tip of the frozen body in contact with the substrate as in the second embodiment, the substrate temperature and atmosphere are such that only the tip of the frozen body in contact with the substrate can be melted and locally cleaned. It is preferable to set the temperature in terms of the strength of the frozen body and the control of the local cleaning position. A preferable substrate temperature and ambient temperature are 10 ° C. to 25 ° C.

  A mask blank is formed by laminating a light-shielding film containing chromium and an antireflection film containing chromium and oxygen on the main surface of the glass substrate 40 obtained in Examples 1 and 2 to form a light-shielding film serving as a mask pattern. Obtained. By forming a resist film on the light-shielding film of the obtained mask blank, drawing on the resist film, applying a development process to form a resist pattern, and then etching the light-shielding film using the resist pattern as a mask An exposure mask was prepared. When the obtained exposure mask was inspected for defects, it was satisfactory with no mask pattern defects.

Example 3
A mask blank glass substrate having a high smoothness with a precisely polished main surface is prepared, and a mask is formed by laminating a light shielding film containing chromium and an antireflection film containing chromium and oxygen on the main surface of the glass substrate. A mask blank was obtained by forming a light-shielding film to be a pattern.
The main surface of the obtained mask blank was inspected for a convex defect or a concave defect by a defect inspection apparatus. The defect information obtained by the defect inspection apparatus stores the defect type (convex defect, concave defect), defect size, defect position information, and the like.
As a result of the defect inspection, a convex defect based on a minute adhered foreign substance having a height of about 45 nm and a size of about 7 μm was discovered.
The frozen defect was removed from the mask blank surface by bringing the frozen body into contact with the raised defect by the same method as in Example 1.
Again, the defect on the mask blank surface was inspected by the above-described defect inspection apparatus, but neither a convex defect nor a concave defect was confirmed. Moreover, when the surface was observed with the atomic force microscope (AFM) about the area | region where the above-mentioned convex defect was formed, and its peripheral area | region, it was favorable without the damage by the contact of a frozen body.
By forming a resist film on the light-shielding film of the mask blank obtained above, forming a resist pattern by drawing and developing on the resist film, and then etching the light-shielding film using the resist pattern as a mask An exposure mask was prepared. When the obtained exposure mask was inspected for defects, it was satisfactory with no mask pattern defects.

While the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above embodiments.
The present invention is also useful as a method for locally removing foreign substances adhered to the surface of a substrate, mask blank or exposure mask with such a strength that it cannot be removed by air blow or the like.

It is a mimetic diagram for explaining one mode of a manufacturing method of a mask blank substrate concerning the present invention. It is a mimetic diagram for explaining one mode of one process of a manufacturing method of a substrate for mask blanks concerning the present invention. It is a schematic diagram for demonstrating one aspect | mode of the other process of the manufacturing method of the mask blank substrate which concerns on this invention. It is a schematic diagram for demonstrating the frozen body manufacturing unit using a Peltier module. It is a schematic diagram for demonstrating one form of the front-end | tip of a local cooling spot, FIG.2 (1) is a top view, FIG.2 (2) is the elements on larger scale of FIG.2 (1), FIG.2 (3) is a side surface. FIG. It is a schematic diagram for demonstrating one form of the frozen body formed in the front-end | tip of a local cooling spot. It is a schematic diagram for demonstrating the manufacturing method of the mask blank substrate which concerns on an Example.

Explanation of symbols

1 Liquid 2 Substrate 3 Foreign matter

Claims (9)

A step of covering the foreign matter present on the surface of the mask blank substrate with a liquid;
Solidifying the liquid covering the foreign matter;
Removing the foreign matter from the substrate surface together with the solidified body by removing the solidified body obtained by solidifying the liquid covering the foreign matter from the substrate surface;
A method for manufacturing a mask blank substrate, comprising:   It has the process of reducing the adhesion of the foreign substance adhering to the surface by bringing the solidified body obtained by solidifying the liquid into contact with the foreign substance existing on the surface of the mask blank substrate and adhering to the surface. The method for producing a mask blank substrate according to claim 1. After the main surface of the mask blank substrate is precisely polished, the defect inspection of the main surface is performed to identify a defect based on the foreign matter existing on the main surface, and the defect based on the specified foreign matter is claimed. Or a process for producing a mask blank substrate, wherein the process according to 2 is applied. The method for manufacturing a mask blank substrate according to any one of claims 1 to 3, wherein pure water is used as the liquid covering the foreign matter. The method for producing a mask blank substrate according to any one of claims 1 to 3, wherein a liquid in which a low melting point metal or an alloy made of a low melting point metal is dissolved is used as the liquid covering the foreign matter. A mask blank produced by forming a thin film to be a mask pattern on the main surface of the mask blank substrate obtained by the method for producing a mask blank substrate according to claim 1. An exposure mask manufactured by forming a mask pattern on the main surface of a mask blank substrate using the mask blank obtained by the mask blank manufacturing method of claim 6. Preparing a mask blank in which a thin film to be a mask pattern is formed on the main surface of the mask blank substrate;
Covering the foreign matter present on the surface of the mask blank with a liquid;
Solidifying the liquid covering the foreign matter;
Removing a solidified body obtained by solidifying a liquid covering the foreign matter from the surface of the mask blank by removing the solidified body together with the solidified body from the surface of the mask blank. Method. Preparing an exposure mask having a mask pattern formed on the main surface of the mask blank substrate;
Covering the foreign matter present on the surface of the exposure mask with a liquid;
Solidifying the liquid covering the foreign matter;
Removing the foreign matter from the exposure mask surface together with the solidified body by removing the solidified body obtained by solidifying the liquid covering the foreign matter from the exposure mask surface. Mask manufacturing method.

Images