JP2007033857A - Method for manufacturing glass substrate for mask blanks, glass substrate for mask blanks, method for manufacturing mask blanks, and mask blanks - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems associated with "roughened surface generated in the surface of a recessed part formed by laser light irradiation" as shown in the figure. <P>SOLUTION: The method for manufacturing a glass substrate for mask blanks includes a marking step for forming the recessed part used as a marker for identifying the glass substrate for mask blanks, by irradiating with laser light the substrate surface in a region having no effect on the transference in the surface of the glass substrate for mask blanks and by melting or subliming it. The method further includes a step for making the part where the marking is performed by irradiation with the laser light and the surrounding surface of the substrate into the surface state in which the source material causing and the "roughened surface generated in the surface of the recessed part formed by laser light irradiation" (with reference to the figure) is eliminated and for performing the marking by the irradiation with the laser beam in this state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a glass substrate for mask blanks, a glass substrate for mask blanks, a method for manufacturing mask blanks, and mask blanks.

2. Description of the Related Art Conventionally, there has been known a mask blank in which an optical reading type area code is provided on a metal film formed on an end surface or a back surface of a glass substrate (for example, see Patent Document 1).
Moreover, the mask blanks by which the predetermined symbol was marked in the frosted part of the glass substrate side surface (end surface) are known (for example, refer patent document 2).

  In recent years, the wavelength of an exposure light source has been shortened to, for example, 200 nm or less, and the quality (size and number of allowable defects) required for a mask blank glass substrate and mask blanks has become increasingly severe. Depending on how the area code or the like is formed, dust may be generated in a later process, which may make it difficult to satisfy the required quality. Further, in the recent glass substrate for mask blanks, the end surface may be mirror-polished, and there is a possibility that sufficient reading accuracy cannot be obtained with a glossy symbol or the like.

Therefore, the present inventors have developed and filed an application for a marking technique suitable for a glass substrate for mask blanks under the above background (Patent Document 3).
Such a technique identifies the mask blank glass substrate by irradiating a laser beam onto a mirror-like surface and melting or sublimating it in a region that does not affect transfer on the mask blank glass substrate surface. And a marking step for forming a recess (hereinafter referred to as a marker recess) used as a marker. In such a technique, a concave portion for a marker is formed by melting or sublimating a mirror-like surface by laser irradiation, and therefore, in various aspects of the manufacturing process of a mask blank glass substrate, a large amount of information about the substrate is recorded on the marker. Suitable for In addition, the marker formed in this way has sufficient reading accuracy and is less likely to generate dust in a later process as compared with other forming methods.
JP 2002-116533 A JP 59-15938 A Japanese Patent Application No. 2005-096976

The invention relating to the marking technology suitable for the glass substrate for mask blanks described in Patent Document 3 has an excellent feature based on forming the concave portion for the marker by melting or sublimating the glass surface by laser irradiation. However, in order to further improve the characteristics, it is necessary to find a problem based on (1) forming a concave portion for a marker by melting or sublimating the glass surface by laser irradiation, and to take countermeasures (2 The invention described in Patent Document 3 intends to record a lot of information on a marker and is a method suitable for it. However, in order to adapt to the large amount of information, each point such as a two-dimensional code is necessarily constructed. It is necessary to form a large number of concave portions for the marker with respect to one marker, and to find out a problem that occurs based on that and to take measures against it.
That is, an object of the present invention is to find a problem and devise a countermeasure for further improvement of characteristics in relation to the marking technology of the glass substrate for mask blanks described in Patent Document 3 above. .

The inventors have continued development in accordance with the above-mentioned purpose. And the following became clear.
In the method for manufacturing a mask blank glass substrate described in Patent Document 3, for example, after a series of mask blank glass substrate manufacturing processes such as grinding and polishing (precise polishing of the main surface and end face, ultra-precise polishing and cleaning) is completed. In the case where a concave portion for a marker is formed by performing a substrate inspection and then melting or sublimating a mirror-like substrate surface (for example, a mirror-like end surface) using a laser such as a CO ₂ laser, as shown in FIG. It has been found that the raised portion 21 may occur at the peripheral edge of the marker recess 20. The bulging portion 21 at the peripheral edge was black, dirty, and looked burned when observed with a microscope. Analysis of the raised portion 21 at the peripheral edge revealed that it was composed of a mixture of SiO ₂ and organic contaminants (such as carbon black). However, the raised portion 21 at the peripheral edge can be almost removed by performing strong and sufficient cleaning (specifically, cleaning with hydrofluoric acid) after laser marking. It wasn't.
However, the present inventor found that the raised portion 21 generated at the peripheral edge portion was contaminated because the surface (interface) itself of the portion to be marked before laser marking was contaminated from the state of the microscopic observation and the analysis result. It is presumed that it was formed by some action between the laser beam to be contaminated and the contamination of the surface (interface), and after the substrate inspection process and before the laser marking process (when a marker is formed on the end face) Laser marking was performed using the substrate that had been introduced with the end face cleaning step). As a result, it has been elucidated that the problem that the raised portion 21 that looks black and dirty and looks burned on the peripheral portion of the marker recess 20 can be solved.
However, even when laser marking is performed using a substrate that has been implemented by introducing a cleaning step between the substrate inspection step and the laser marking step as described above, a two-dimensional code as shown in FIG. 1 is formed. As a result of producing a large number of substrates on which the marker 18 composed of the many marker recesses 20 is formed and examining each of the many marker recesses in detail and carefully, as shown in FIG. It has been found that there is a marker concave portion in which a locally roughened portion (surface roughening) 22 is present on the surface of. FIG. 9 shows a state in which a part including a part having a rough surface is observed with a scanning electron microscope (SEM).
This surface roughness is also considered to be surface roughness caused by laser irradiation of a CO ₂ laser or the like, but there are no regularities in the occurrence locations of the surface roughness in the marker recesses, and some of the marker recesses among the many marker recesses Only occurred (about 50%).
Then, when this inventor conducted the Raman analysis of said local surface roughening site | part, the Raman analysis result of the surface roughening generation | occurrence | production site | part with respect to the Raman analysis result (lower signal of FIG. 10) of a site | part without surface roughening. A different peak appears in (the upper signal in FIG. 10), and it has been found that the glass surface is not simply roughened by laser irradiation of a CO ₂ laser or the like. Furthermore, it was clarified from the peak position that the surface was rough based on an organic substance or the like.
As a result of further investigation, it is not sufficient to simply perform laser marking using a substrate that has been implemented by introducing a cleaning process between the substrate inspection process and the laser marking process, and laser marking by laser irradiation of a CO ₂ laser or the like. It was clarified that the interface of the time needs to be an interface state that excludes the causative substances that cause the surface roughness as described above. In other words, it is clarified that it is necessary to set the interface of the place where laser marking is to be performed to the surface (interface) state excluding the causative substances causing the surface roughness as described above, and to carry out the marking in this state. Invented.

The present invention has the following configuration.
(Configuration 1) The mask blank glass substrate is used as a marker for identifying the mask blank glass substrate by irradiating the substrate surface in a region that does not affect the transfer on the mask blank glass substrate surface with melting and sublimation. A method for producing a mask blank glass substrate comprising a marking step for forming a recess,
The surface where the marking is performed by laser light irradiation and the surrounding substrate surface are made into a surface state in which the causative substances that cause surface roughness generated on the surface of the concave portion due to the formation of the concave portion by laser light irradiation are excluded, and this state The manufacturing method of the glass substrate for mask blanks characterized by including the process of marking by laser beam irradiation.
(Configuration 2)
The means for “removing a causative substance that causes surface roughness generated on the surface of the concave portion by the formation of the concave portion by laser light irradiation” means UV cleaning, ozone cleaning, UV / ozone cleaning, hydrofluoric acid type The method for producing a glass substrate for a mask blank according to Configuration 1, wherein the method is one or more cleaning means selected from cleaning using a cleaning agent and cleaning using an alkaline cleaning agent having an etching action.
(Configuration 3)
The means for “making a surface state excluding a causative substance that causes surface roughness generated on the surface of the concave portion by the formation of the concave portion by laser light irradiation and performing marking by laser light irradiation in this state” is described in Configuration 2. The method for producing a glass substrate for a mask blank according to Configuration 2, which is a means for carrying out marking immediately after performing the cleaning.
(Configuration 4)
The means for “making a surface state excluding a causative substance that causes surface roughness generated on the surface of the concave portion by the formation of the concave portion by laser light irradiation and performing marking by laser light irradiation in this state” is described in Configuration 2. The method of manufacturing a glass substrate for a mask blank according to Configuration 2, wherein the substrate is stored and transferred in a state where the causative substance does not adhere to the substrate, and marking is performed. .
(Configuration 5)
A mask blank glass substrate produced by the method for producing a mask blank glass substrate according to any one of Structures 1 to 4.
(Configuration 6)
A glass substrate for mask blanks according to Configuration 5,
A mask blank, comprising: a mask pattern thin film to be a mask pattern formed on the mask blank glass substrate.
(Configuration 7)
A method for producing a mask blank, comprising a step of forming a mask pattern thin film to be a mask pattern on the glass substrate for a mask blank according to Configuration 5.

The present invention will be described in detail below.
The present invention provides a marker for identifying the glass substrate for mask blanks by irradiating the substrate surface in a region (part) having no influence on transfer on the glass substrate surface for mask blanks with melting or sublimation. A method for producing a glass substrate for a mask blank comprising a marking step for forming a recess used as
A portion where marking is to be performed by laser light irradiation and the surrounding glass substrate surface are made into a surface state in which a causative substance that causes surface roughness generated on the surface of the concave portion by the formation of the concave portion by laser light irradiation is excluded, and this The method includes a step of performing marking by laser light irradiation in a state (Configuration 1).
The present invention is a causative substance that generates “surface roughness as described above” caused by interaction with laser irradiation light, that is, “surface roughness generated on the surface of the recess due to formation of the recess by laser light irradiation”. "Surface roughness generated on the surface of the concave portion due to the formation of the concave portion by the laser light irradiation" caused by the interaction with the laser irradiation light by performing the marking by the laser light irradiation in this state. It is the invention which made it not produce substantially.
In the present invention, “a surface state in which a causative substance that causes surface roughness generated on the surface of the concave portion due to the formation of the concave portion by laser beam irradiation” is marked on a considerable number of substrates (for example, 100 sheets). Thus, the level where the surface roughness as described above is not found and is zero.
In the present invention, “a surface state in which a causative substance that causes surface roughness generated on the surface of the concave portion due to the formation of the concave portion by laser light irradiation” is excluded, for example, when the total amount of organic substances on the surface is 10 ng / cm ² or less. A surface state. The total amount of organic substances is measured by GC-MS (gas chromatograph mass spectrometer).
In the present invention, the total amount of organic substances (measured by GC-MS) on the surface of the glass substrate surface (substrate main surface or end face) where marking is to be performed by laser light irradiation and the surrounding area is preferably 5 ng / cm ² or less. Preferably it is 1 ng / cm ² or less. This is because by reducing the total amount of organic matter, it is possible to prevent the surface roughness as described above from occurring even when the output of the laser marker is increased.
According to the present invention, (1) the problem that it is necessary to inspect and inspect the surface roughness of each of the many marker recesses to be formed, and (2) such a large number is formed. It is difficult to inspect and manage the surface roughness of each of the marker recesses, and these operations are extremely complicated, and the implementation of these operations is not practical and practical in terms of cost and work. The above-mentioned problems (1) and (2) occur because measures to prevent the surface roughness from occurring are taken in advance to substantially eliminate the substrate having the surface roughness at the mass production level. The above problems (1) and (2) can be cleared (solved) fundamentally and in advance.

  In the present invention, as a specific means for obtaining “a surface state that eliminates a causative substance that causes surface roughness generated on the surface of the concave part by the formation of the concave part by laser light irradiation”, (1) Removal of the causative substance Effective in UV cleaning by ultraviolet irradiation, ozone cleaning using ozone water or gaseous ozone, UV / ozone cleaning combining UV cleaning and ozone cleaning, and (2) effective in removing the causative substances (etching) Cleaning with a hydrofluoric acid-based cleaning agent or an alkaline cleaning agent having a relatively strong etching action is effective (Configuration 2). The cleaning treatments listed in the above (1) and (2) can be implemented by selecting a plurality of them from each of them and combining them (1) and (2).

In the present invention, a specific example for "a surface state in which a causative substance that causes surface roughness generated on the surface of the concave portion by the formation of the concave portion by laser light irradiation is eliminated and marking by laser light irradiation is performed in this state" As typical means, means shown in the following (1) and (2) are exemplified.
(1) Marking is performed immediately after performing the cleaning exemplified above (Configuration 3). Here, “immediately after performing the cleaning” means that marking is performed within 12 hours (about half a day) after the cleaning is performed at the latest, and it is preferable to perform the marking as soon as possible after the cleaning is performed. . It should be noted that the causative substance is not attached when the substrate is stored and transferred after the cleaning is performed until the marking is performed.
(2) The cleaning exemplified above is performed, and the substrate is stored and transferred in a state where the causative substance does not adhere thereto, and then marking is performed (Configuration 4). However, even in this case, it is not preferable that the storage days become long, and it is preferable to perform marking within about one day after the cleaning exemplified above is performed. The storage environment is preferably stored in an environment in which a causative substance is filtered by a chemical filter.

In the present invention, the marker formation by the marking process is performed on the substrate surface in a region (part) which does not affect the transfer on the mask blank glass substrate surface.
For example, the region will be described with reference to FIG. 4. The side surface 1a of the glass substrate that does not affect the transfer, the chamfered surface 1b provided between the main surface 2 and the side surface 2a, and the notch mark of the glass substrate. And other parts (not shown). The side surface 1a and the chamfered surface 1b of the glass substrate are collectively referred to as an end surface 1d of the glass substrate.
Another example of such a region is a main surface of the glass substrate main surface 2 on the side where the mask pattern thin film is not formed, and a region such as a peripheral region that does not affect the transfer.

In the present invention, examples of the material of the glass substrate include synthetic quartz glass and SiO ₂ —TiO ₂ multicomponent glass.
Depending on the material of the glass substrate, the wavelength of the laser beam for forming a recess by melting or sublimating by laser beam irradiation is selected. If the wavelength of the laser beam appropriate for the material of the glass substrate is not selected, for example, a scratch-like marker will be formed in the portion irradiated with the laser beam. In this case, scratch-like markers cause dust generation, which is not preferable.
In the case of the glass substrate material as described above, in the marking process, for example, a marker can be formed by a laser marker using a carbon dioxide (CO ₂ ) gas laser.
By appropriately adjusting the energy of the laser beam, a part of the surface of the glass substrate can be appropriately melted or sublimated, and the recess formed by melting or sublimating can be read with high accuracy. And generation | occurrence | production of the crack by aged deterioration can also be suppressed.
Moreover, a marking process can also form a several recessed part by irradiating a laser beam in multiple times to the position which should become each recessed part. In this way, variation in the shape of the plurality of recesses can be reduced. Therefore, the marker reading accuracy can be improved.
Each of the plurality of concave portions may constitute, for example, each point of a two-dimensional code such as a data matrix or a QR code, may constitute each bar of the barcode, or a third party may provide the marker. It is good also as a hidden code or a random number code so that information of this may not be known.

The present invention performs a substrate inspection after a series of mask blank glass substrate manufacturing processes such as grinding and polishing (main surface and end surface precision polishing, ultra-precision polishing and cleaning), and then uses a laser such as a CO ₂ laser. It is preferable to apply the method when the marker recess is formed by melting or sublimating the substrate surface.
The reason for this is that, as described above, in the above process, it is not sufficient to simply perform laser marking using a substrate that has been implemented by introducing a cleaning process between the substrate inspection process and the laser marking process. In addition, the mirror surface finished in a mirror-like shape by precision polishing and ultraprecision polishing of the main surface and the end surface is obtained by removing surface foreign matters in these polishing steps.
The present invention is (1) during each stage of grinding and polishing, for example, after grinding of a glass substrate, after precision polishing or ultraprecision polishing of the end surface of the glass substrate, or precision polishing or ultraprecision polishing of the main surface of the glass substrate. After mirror polishing, etc., between precision polishing and ultra-precision polishing of the main surface or end surface of the glass substrate, or (2) before grinding and polishing of the glass substrate such as when receiving the glass substrate, (3) mask blanks It can be applied to the case where the marking step is performed during the manufacturing process (before and after each step such as thin film formation, inspection, resist coating, and inspection). In these cases, after the normal cleaning process performed after each process, for example, the cleaning means listed above as a specific means for obtaining the “interface state excluding the causative substance causing the surface roughness” is sufficiently strong. It is preferable to carry out the marking step after a sufficient time.
In the present invention, precision polishing is polishing performed using, for example, a polishing liquid containing cerium oxide and water, and a polishing brush or polishing pad.
The ultra-precision polishing is polishing performed using, for example, a polishing liquid containing colloidal silica and water, and a polishing brush or a polishing pad.

In the present invention, the marker can be used as, for example, identification information (identification code) unique to each glass blank glass substrate to be manufactured. In this way, single wafer management of individual glass substrates for mask blanks, which has not been possible in the past, becomes possible.
Further, this identification information can be associated with, for example, information (surface information such as defect information, surface roughness, flatness, etc.) acquired during the manufacturing process for each mask blank glass substrate. In this way, it is possible to reliably associate the acquired information with individual mask blank glass substrates via the identification information.
In the marking process, a marker that directly indicates information acquired during the manufacturing process may be formed instead of the marker indicating identification information or in addition to the marker indicating identification information. Examples of information acquired during the manufacturing process include substrate inspection data information and process history information.

When the marking process is performed after the substrate inspection, for example, a marker indicating inspection data information of the glass substrate is formed. If it does in this way, inspection data information on a glass substrate and a glass substrate can be made to correspond directly, and a one-to-one correspondence can be performed reliably (a correspondence relationship is not mistaken).
Here, as the inspection data information, for example, inspection data information of various surface roughnesses of the main surface and / or end surface of the glass substrate can be mentioned, and for the shape of the main surface of the glass substrate, for example, thickness, surface shape, etc. Inspection data information such as warpage shape of the main surface, unevenness of the entire main surface, waviness, etc., flatness, parallelism, and the like.
Other inspection data information includes, for example, inspection data information on defects on the main surface and / or end surface of the glass substrate (for example, the position and type of defects (convex defects (foreign matter adhesion, etc.)), and concave defects (scratches, pinholes). Etc.), others), and the size of defects, etc.). If such defect data is known, the substrate can be used while avoiding defects, for example.
When the marking process is performed after the substrate inspection, the substrate can be classified according to the use / grade of the blank according to the inspection result of the substrate inspection process, and the substrate identification information ( Markers indicating application information and management information) can be formed together.
A plurality of grades (grades) having different qualities exist depending on the exposure wavelength and application (formation pattern). Depending on the grade, the allowable defect size, number, etc. vary. In addition, there are a plurality of types of mask pattern thin films (phase shift films, light shielding films, etc.) and resist films that are formed when the mask blanks are manufactured. Therefore, it is not easy to manage the grade and the types of thin films and resist films to be formed at the time of manufacturing mask blanks. However, when the information for management is marked, mask blanks can be managed. Therefore, when manufacturing mask blanks, it is possible to appropriately manage the grades and types of thin films and resist films to be formed.
Further, since the mask blanks can be reliably managed, for example, when information on the mask blanks is supplied to the mask manufacturer together with the mask blanks, this information can be reliably associated with the mask blanks. . Information on the mask blank includes information such as the optical characteristics of the mask pattern thin film, the surface shape of the thin film, the inspection result of the thin film inspection process for inspecting at least one of the defects, and the inspection result of the resist inspection process.
In addition, when a marking process is performed before board | substrate inspection, the marker which shows the identification information of a glass substrate is formed, for example.

  According to the present invention, various problems associated with “surface roughness generated on the surface of the recess due to the formation of the recess by laser light irradiation” can be solved.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
FIG. 5 is a side view showing an example of the configuration of the mask blank 10 according to an embodiment of the present invention. In this example, the mask blank 10 is a mask blank for an exposure light source having a wavelength of 200 nm or less, such as an ArF excimer laser (wavelength 193 nm) or an F ₂ excimer laser (wavelength 157 nm). 14 and a resist film 16.

The glass substrate 12 is a glass substrate for mask blanks, and the substrate material is made of, for example, synthetic quartz glass. The main surface and end surface (side surface, chamfered surface) of the glass substrate 12 are polished to a predetermined surface roughness so as to be a mirror surface (for example, 1 nm or less in arithmetic average surface roughness Ra). Moreover, in this example, the glass substrate 12 has the marker 18 for identifying the glass substrate 12 in a part of side surface. By using the marker 18, the glass substrate 12 and the mask blanks 10 are managed as a single wafer.

The mask pattern thin film 14 is a thin film such as a light shielding film or a phase shift film. The mask pattern thin film 14 is patterned in the mask manufacturing process to form a mask pattern. The resist film 16 is formed on the mask pattern thin film 14.

FIG. 1 shows an example of the configuration of the marker 18. In this example, the marker 18 is a two-dimensional code, and has a plurality of recesses 20 that constitute each point of the two-dimensional code. Each recess 20 is formed by melting or sublimating a part of the end surface of the glass substrate 12 by irradiation with laser light.
In this example, the marker 18 indicates identification information unique to the glass substrate 12, substrate inspection data information, and the like.

FIG. 2 shows an example of a detailed form of the recess 20. In this example, the recess 20 is formed of carbonic acid (CO
₂ ) A hole formed by a laser marker using a gas laser. The plan view shape of the opening of the recess 20 is substantially circular. Moreover, the cross-sectional shape of the recess 20 has a gentle cross-sectional curve. It is preferably a gentle cross-sectional curve having L / D of 3 or more. By setting the cross-sectional shape of the recess 20 to such a form, the reading accuracy of the marker 18 (see FIG. 1) can be improved.
The opening width L of the recess 20 is, for example, about 100 to 500 μm, more preferably about 150 to 300 μm. The depth D of the recessed part 20 is 3-20 micrometers, for example, More preferably, it is about 5-15 micrometers. As described above, L / D is preferably 3 or more.
The surface roughness of the recesses is, for example, preferably in the range of 0.1 to 5 nm, more preferably 0.1 to 2 nm in terms of arithmetic average surface roughness Ra. Arithmetic mean surface roughness Ra is in accordance with Japanese Industrial Standard (JIS) B0601. Specifically, the surface roughness of the recess is the surface roughness of the entire recess (shoulder, side, bottom).
The shape of the opening of the recess 20 in plan view may be a circle, a substantially circle, a vertically long barcode, a polygon such as a quadrangle, or a shape with rounded corners of the polygon.

FIG. 6 is a flowchart illustrating an example of a method for manufacturing the mask blank 10.
(Manufacture of glass substrates for mask blanks)
In this example, first, grinding is performed by a double-sided lapping device for the glass substrate 12 whose end face is chamfered (grinding step S102).
Next, the end surface and the main surface of the glass substrate 12 are polished by the double-side polishing apparatus (polishing step S10).
4) and cleaning after polishing is performed (cleaning step S106). In the polishing step S104, for example, rough polishing, precision polishing, and ultra-precision polishing are performed on the end surface and the main surface of the glass substrate 12 to finish a mirror surface having a root mean square roughness RMS of 0.2 nm or less.

Next, substrate inspection is performed to obtain information on the surface shape, flatness, and defects of the glass substrate 12 (substrate inspection step S108). The substrate inspection step S108 is performed by, for example, the glass substrate 12
For example, the thickness, flatness, warpage shape of the main surface (unevenness of the entire main surface), etc. are inspected. Moreover, about the defect of the glass substrate 12, the position of a defect, a kind, size, etc. are test | inspected, for example. In this case, the defect size is, for example, 0.2 μm or less, 0.
Whether it is 2 to 0.5 μm, 0.5 to 1 μm, 1 μm or more is identified. If identified in this way, the grade of the glass substrate 12 can be appropriately classified.

Next, for example, by using a laser marker of a carbon dioxide laser, a part of the end surface of the glass substrate 12 is melted or sublimated by laser light irradiation, thereby forming each recess 20 of the marker 18 (marking step S112).
In the present invention, prior to the marking step (S112), the surface to be marked by laser light irradiation and the surrounding glass substrate surface are roughened due to the formation of the concave portions by laser light irradiation. In this state, marking is performed by irradiating with laser light.
The marker 18 indicates, for example, identification information unique to the glass substrate 12 and substrate inspection data information.

(Mask blank manufacturing process)
Next, the marker 18 is read, and a mask blank type suitable for using the glass substrate 12 is selected based on the read marker 18.
Next, according to the type of mask blank selected above, the mask pattern thin film 14 is formed on the main surface of the glass substrate 12 with a film thickness that provides desired optical characteristics (film formation step S114). Further, a resist film 16 is applied (formed) on the mask pattern thin film 14 (resist film forming step S116), and the mask blank 10 is completed.

Example 1
In Example 1, 100 glass substrates for mask blanks for ArF excimer laser exposure were manufactured in steps S102 to S106 in the above embodiment, and these glass substrates were inspected in the substrate inspection step (step S108).
Next, as a causative substance exclusion step S110, UV cleaning and subsequent cleaning by immersion in a hydrofluoric acid solution are performed. Immediately thereafter (within 3 hours), carbonic acid (CO2) is formed on the end surface (side surface) of the glass substrate. ₂ ) A two-dimensional code marker similar to that shown in FIG. 1 was formed by a laser marker using a gas laser. The size of the entire marker 18 was 3.25 mm × 3.5 mm.
In addition, when the total organic matter amount on the glass substrate surface (substrate main surface, end face) before laser marking after the above-described cleaning was measured by GC-MS, the total organic matter amount was 0.242 ng / cm ² (DOP conversion). It was.
The output of the laser marker was 24 mW / shot, and each recess was formed by one shot. The diameter of each recess was about 250 μm. The cross-sectional form of each recess is shown in FIG.
When the surface of all the concave portions for the marker was observed with a scanning electron microscope (SEM), no surface roughness as shown in FIG. 9 was found and was zero. Moreover, the surface roughness of the whole recessed part (shoulder part, side part, bottom part) was 0.1-1 nm in arithmetic mean surface roughness Ra, respectively.

(Comparative Example 1)
In Example 1, it was the same as Example 1 except that the marking was performed without interposing the cleaning process between the substrate inspection process and the marking process.
In addition, when the total organic matter amount of the glass substrate surface (substrate main surface, end face) before the laser marking was measured by GC-MS, the total organic matter amount was 30.549 ng / cm ² (DOP conversion).
As a result, as shown in FIG. 7, a large number of phenomena in which the swelled portion 21 occurs at the peripheral edge of the marker recess 20 were observed.

(Example 2)
In Example 2, the output of the laser marker was 12 mW / shot, and each recess was formed by one shot. The diameter of each recess was about 200 μm. FIG. 3B shows a cross-sectional form of each recess. Others were the same as in Example 1.
When the surface of all the concave portions for the marker was observed with a scanning electron microscope (SEM), no surface roughness as shown in FIG. 9 was found and was zero. Moreover, the surface roughness of the whole recessed part (shoulder part, side part, bottom part) was 0.1-1 nm in arithmetic mean surface roughness Ra, respectively.

(Example 3)
In Examples 1 and 2, a cleaning process by UV cleaning was interposed between the substrate inspection process and the marking process. Immediately after this cleaning (within 3 hours), the substrate was laser-marked. Others were the same as in Example 1 or 2.
In addition, when the total amount of organic substances on the glass substrate surface (substrate main surface, end face) before laser marking was measured by GC-MS after the above cleaning, the total amount of organic substances was 3.777 ng / cm ² (DOP conversion). It was.
As a result, when the output of the laser marker was high, surface roughness as shown in FIG. 9 occurred (occurrence of about 10%) in some of the marker recesses among the many marker recesses.

A mask pattern thin film for ArF excimer laser exposure is formed on the glass substrate for mask blanks subjected to laser marking in the above examples and comparative examples to obtain mask blanks, and then the mask pattern thin film is patterned to form a mask. Produced.
As a result, the mask pattern defect was zero in the mask according to the embodiment, whereas the mask pattern defect was present in the mask according to the comparative example. Presumed to be the cause.

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.
For example, in the present invention, even when the output of the laser marker is set high, the surface roughness does not occur, so that the margin of the laser marker output or the like can be widened. Although the present invention has such characteristics, in the present invention, by setting the output of the laser marker low, the surface of the laser marker output surface is less likely to be roughened. The concave portion can be formed by irradiating the laser beam one or more times.

It is a top view which shows an example of a structure of the marker which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the cross-sectional shape of a recessed part. It is a figure which shows a mode that the cross-sectional form of the recessed part formed in the Example was observed with the scanning electron microscope (SEM). It is a typical fragmentary sectional view for demonstrating the area | region which does not affect transcription | transfer. It is a side view showing an example of composition of a mask blank concerning one embodiment of the present invention. It is a flowchart which shows an example of the manufacturing method of a mask blank. It is typical sectional drawing for demonstrating the phenomenon which a rising part produces in the peripheral part of a recessed part by formation of the recessed part by laser beam irradiation. It is typical sectional drawing for demonstrating the surface roughness which generate | occur | produces on the surface of this recessed part by formation of the recessed part by laser beam irradiation. It is a figure which shows a mode that the surface roughness which generate | occur | produces on the surface of this recessed part by formation of the recessed part by laser beam irradiation was observed with the scanning electron microscope (SEM). It is a figure which shows the result of having analyzed the site | part with a rough surface in a recessed part, and the site | part without a rough surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Mask blanks, 12 ... Glass substrate, 14 ... Thin film for mask patterns, 16 ... Resist film, 18 ... Marker, 20 ... Recessed part

Claims (7)

By irradiating the substrate surface in a region that does not affect the transfer on the mask blank glass substrate surface with laser light to melt or sublimate, a concave portion used as a marker for identifying the mask blank glass substrate is formed. A method for manufacturing a mask blank glass substrate comprising a marking step,
The surface where the marking is performed by laser light irradiation and the surrounding substrate surface are made into a surface state in which the causative substances that cause surface roughness generated on the surface of the concave portion due to the formation of the concave portion by laser light irradiation are excluded, and this state The manufacturing method of the glass substrate for mask blanks characterized by including the process of marking by laser beam irradiation.   The means for “removing a causative substance that causes surface roughness generated on the surface of the concave portion by the formation of the concave portion by laser light irradiation” means UV cleaning, ozone cleaning, UV / ozone cleaning, hydrofluoric acid type 2. The method for producing a glass substrate for a mask blank according to claim 1, wherein the method is one or more cleaning means selected from cleaning using a cleaning agent and cleaning using an alkaline cleaning agent having an etching action. .   The means for “making the surface state excluding causative substances that cause surface roughness generated on the surface of the concave portion by the formation of the concave portion by laser light irradiation and performing marking by laser light irradiation in this state” is provided. 3. The method for producing a glass substrate for a mask blank according to claim 2, wherein the marking is performed immediately after the cleaning described above.   The means for “making the surface state excluding causative substances that cause surface roughness generated on the surface of the concave portion by the formation of the concave portion by laser light irradiation and performing marking by laser light irradiation in this state” is provided. The glass substrate for mask blank according to claim 2, wherein the cleaning is performed as described above, and the substrate is stored and transported in a state where the causative substance does not adhere thereto, and then marking is performed. Production method.   A glass substrate for a mask blank produced by the method for producing a glass substrate for a mask blank according to claim 1. A glass substrate for mask blanks according to claim 5,
A mask blank, comprising: a mask pattern thin film to be a mask pattern formed on the mask blank glass substrate.   A method for producing a mask blank, comprising a step of forming a mask pattern thin film to be a mask pattern on the glass substrate for a mask blank according to claim 5.

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