JP2003173018A - Method of manufacturing mask blank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a mask blank which is free of build-ups of a resist film in the peripheral part of a substrate. <P>SOLUTION: The method of manufacturing the mask blank has a step of preparing the substrate formed with a thin film for forming transfer patterns, a step of forming the resist film on the main surface of the substrate, a step of rotating the substrate at a prescribed number f1 of revolutions while covering at least the main surface of the substrate on the side formed with the resist film with a cover member, supplying a solvent from above this cover member and dissolving the unnecessary resist film through a solvent flow passage and a step of stopping the supplying of the solvent, rotating the substrate at a prescribed number f2 of revolutions greater in the number of revolutions than the number f1 of revolutions to remove the dissolved unnecessary resist film and drying the region where the resist film is removed. The deceleration speed before the substrate stops rotating after the number f2 of revolutions is confined to 1,000 rpm/sec in the above method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask blank manufacturing method in which a resist film on a peripheral portion of a rectangular substrate of a mask blank is removed.

[0002]

2. Description of the Related Art In a manufacturing process of a mask blank, in particular, a photomask blank which is an original plate of a photomask in which a thin film pattern which is a pattern of an electronic circuit is formed on a transparent substrate, a resist is formed on the substrate surface. After that, the substrate is held by the transport mechanism or inserted into or removed from the substrate storage case while undergoing various processing steps. At this time, when the peripheral part of the substrate contacts the chuck part of the transfer mechanism or the storage groove in the storage case, the resist film on the peripheral part of the substrate peels off and becomes a dust source. Defects caused by the adhesion to the main surface of the are problematic.

Therefore, after a resist is spin-coated to form a resist film, a treatment for removing the resist film in the peripheral portion of the substrate is performed in advance. In this treatment, while the substrate is horizontally rotated around a predetermined rotation center, a treatment liquid for dissolving the resist is supplied to the resist in the peripheral portion of the substrate to dissolve and remove the coating film in the peripheral portion of the substrate.

For example, in the method disclosed in Patent Document 1, a hollow pyramid-shaped cover is arranged on the surface of a substrate, and a solvent is supplied from above the apex of the pyramid to supply the solvent to the peripheral portion. It is a thing.

[Patent Document 1] Japanese Patent Publication No. Sho 58-19350 (No. 1-
(Page 4, Figure 6)

[0005]

However, it has been found that in the case of such a conventional example, as shown in FIG. 10, swelling occurs in the peripheral portion of the resist film remaining after removing the resist in the peripheral portion of the substrate. It was found that this was observed when the resist on the peripheral portion of the substrate was removed with the cover member covering the surface of the substrate on which the resist film was formed. When there is a swell as shown in FIG. 10, when the resist film is peeled off and becomes a dust source when the substrate is inserted into and removed from the substrate storage case as described above, or when the swell region is formed widely in the center of the substrate. This is a cause of pattern collapse when patterning the vicinity of the substrate such as alignment marks, which is a problem. Further, when the height of the swell is large, the pattern (eg, alignment mark or quality assurance pattern) near the periphery of the substrate becomes a pattern defect, and the resist film is exposed a plurality of times to prevent the pattern defect. This is a problem because the patterning process becomes complicated.

Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a method of manufacturing a mask blank in which swelling after the removal of the resist film in the peripheral portion of the substrate is suppressed. To do.

[0007]

In order to solve the above-mentioned problems, the first means is to prepare a substrate on which a thin film to be a transfer pattern is formed so as to be transferred to an object to be transferred, and the substrate. A step of forming a resist film on the main surface of the substrate, and rotating the substrate at a predetermined rotation speed f1 with at least the main surface of the substrate on the side where the resist film is formed being covered with a cover member. A step of dissolving the unnecessary resist film with the solvent by supplying the solvent from the solvent through the solvent flow path, and stopping the supply of the solvent, and rotating at a predetermined rotation speed f2 larger than the rotation speed f1. A removal / drying step of removing the unnecessary film that has been dissolved and drying the removed area, and the deceleration speed from the rotation speed f2 until the rotation of the substrate is stopped is 1000 rpm /
It is a method of manufacturing a mask blank, which is characterized in that the time is not more than sec.

According to a second means, a peripheral flat portion is formed on the outer peripheral portion of the cover member, and the size of the gap formed by the inner wall of the peripheral flat portion and the surface of the substrate is set to the solvent. The mask blank manufacturing method according to the first means is characterized in that the solvent is set to a size that allows the solvent to pass through the gap and spread only in the gap when being supplied.

A third means is such that the cover member has the gap formed in the removal region of the main surface of the substrate and a space larger than the gap in the non-removal region of the main surface of the substrate. 2. The method of manufacturing a mask blank according to the first means or the second means, characterized in that the main surface of the substrate is covered with.

A fourth means is any one of the first to third means, wherein the solvent flow path is a solvent supply hole provided at a predetermined portion of the cover member. It is a method of manufacturing a photomask blank.

The fifth means is, before the unnecessary film dissolving step,
The method for producing a photomask blank according to any one of the first to fourth means, wherein the substrate with a resist film is vacuum dried.

As in the above-mentioned first means, the rotation speed of the substrate in the unnecessary film dissolving step of dissolving the resist film formed on the peripheral portion of the substrate with the solvent is f1, the dissolved unnecessary film is removed, and the removed region is obtained. The substrate rotation speed in the removal / drying process
2, the rotation speed f2 is made larger than the rotation speed f1,
Since the deceleration speed from the rotation speed f2 to the stop of the rotation of the substrate is 1000 rpm / sec or less, the swelling can be suppressed. I'm not sure why,
It is assumed that this is due to the following.

When the substrate surface is covered with the cover member and rotated at a high speed, the atmospheric pressure between the cover member and the substrate surface decreases. Therefore, when the rotation of the substrate is stopped immediately after the resist film is dissolved and removed, the atmospheric pressure between the cover member and the substrate surface tends to be restored, and the resist film in the peripheral portion is changed due to the change in the atmospheric pressure. Flow toward the center of the substrate to form a bulge.

In order to suppress the flow of the resist film due to the change of the atmospheric pressure, the deceleration speed from the rotation speed f2 of the substrate in the removing / drying process to the stop of the rotation of the substrate as in the first means described above. Is 1000 rpm / sec or less. That is, the height of the convex portion formed by the resist film flowing in the center direction (rotation center direction) of the substrate due to the change in atmospheric pressure between the cover member and the main surface of the substrate is equal to or less than a predetermined value (for example, The bulge (projection) becomes a dust source and adheres to the surface of the photomask blank and becomes defective, and the relationship between the defect rate and the height of the projection is grasped to keep the defect rate below a certain level. Since the height of the protrusions is set to a predetermined value, etc.), the change in atmospheric pressure between the cover member and the surface of the substrate can be moderated, and the resist film in the peripheral portion is directed toward the center of the substrate. To prevent it from flowing,
It can suppress the excitement.

Here, the rotation speed f2 is made larger than the rotation speed f1 because if the rotation speed f2 is small, it will lose the force of the expanded resist to gather. Further, the substrate rotation speed f1 in the unnecessary film dissolving step is 200
~ 750 rpm, the substrate rotation speed f2 in the drying step is
It is appropriately set in the range of 350 to 2500 rpm depending on the material of the unnecessary film (resist film). Here, the deceleration speed of the substrate immediately before the removal / drying process is completed is 100.
0 rpm / sec or less, preferably 700 r
pm / sec or less, more preferably 500 rpm /
sec or less, more preferably 250 rpm / sec or less is desirable. As the deceleration speed decreases, the height of the convex portion decreases, but the production efficiency decreases. Considering the height of the convex portion and production efficiency, the deceleration speed is over 250 rpm / sec 700
It is preferably rpm / sec or less.

When the resist film formed on the peripheral portion of the substrate is removed by dissolution with a solvent by the method for manufacturing a mask blank according to the above-mentioned first means, and the resist film surface before the removal is used as a reference plane. The mask blank having a height (rise) of 1 μm or less (0 μm or more and 1 μm or less) from the reference surface around the resist film, and further, the resist film formed on the substrate peripheral part is removed by dissolution by a solvent and removed. When the resist film surface near the center of the substrate excluding the peripheral portion of the resist film facing the exposed area is used as the reference surface, the height (protrusion) of the peripheral portion of the resist film is 1 μm or less (0 μm or more and 1 μm or less) from the reference surface. A mask blank of is obtained.

Therefore, it is possible to prevent the resist film from peeling off and becoming a dust source when the substrate is inserted into and removed from the substrate storage case, and it is possible to prevent a pattern (for example, an alignment mark) near the periphery of the substrate from being defective. Above all, when the resist film surface near the center of the substrate excluding the resist film peripheral portion facing the removed region is used as the reference surface, the height (protrusion) of the resist film peripheral portion is 1 μm or less (0 μm or more from the reference surface. In order to reduce the thickness to 1 μm or less), it is preferable that the resist film thickness is formed evenly until the peripheral portion of the resist film is removed. The height (protrusion) of the peripheral portion of the resist film is preferably 0.75 μm or less (0 μm or more and 0.75 μm or less), and more preferably 0.5 μm or less (0 μm or more and 0.5 μm or less).

The mask blank referred to in the present invention refers to both a transmissive mask blank and a reflective mask blank, and these structures have a thin film to be a transfer pattern on a substrate to be transferred to an object to be transferred and a resist. And a film. The transmissive mask blank uses a translucent substrate as the substrate, and the thin film that becomes the transfer pattern is a thin film that causes an optical change with respect to the exposure light used when it is transferred to the transfer target (for example, it has a light-shielding function. Is a photomask blank using a thin film). Here, the thin film that causes an optical change with respect to the exposure light refers to a light-shielding film that blocks the exposure light, a phase shift film that changes the phase difference of the exposure light, and the like. Further, the “thin film having a light shielding function” includes a so-called halftone film having a light shielding function and a phase shift function, and a light shielding film having a light shielding function.

Therefore, the photomask blank according to the present invention includes a normal photomask blank in which a light shielding film is formed as a thin film having a light shielding function, and a phase shift mask blank in which a halftone film is formed as a thin film having a light shielding function. (Halftone type phase shift mask blank),
It includes a phase shift mask blank on which a phase shift film is formed. The thin film having a light shielding function may be a laminate of the above halftone film and the light shielding film. Further, it includes a phase shift mask blank in which a layer having a phase shift function is formed in addition to a thin film having a light shielding function. The layer with the phase shift function is
When the phase shift function is formed by engraving the transparent substrate, the transparent substrate serves as a layer having the phase shift function. Further, a phase shift layer may be formed.

Further, the reflective mask blank uses a low thermal expansion substrate as a substrate, and a light reflection multilayer film is formed on the substrate.
It is a mask blank having a light absorber film to be a transfer pattern. In addition to the above-mentioned films, the mask blank includes a resist underlayer antireflection film (BARC: Bottom).
Anti-Reflective Coatin
g), a resist upper layer antireflection film (TARL: Top A)
A film such as an anti-reflective layer, a resist upper protective film, and a conductive film may be formed.

Here, the solvent means a liquid capable of removing the resist film. For example, it means an organic solvent for dissolution and removal, a developing solution for developing and removing after exposing the resist film.

The solvent flow path may be a solvent flow path provided with a solvent supply hole for supplying a solvent to a position corresponding to an unnecessary resist film portion in the cover member, or the solvent flow path may be provided outside the cover member. A guide member may be provided, and the cover member and the solvent guide member may be used as the solvent flow path.

As in the above-mentioned second means, the specific resist film removing method of the present invention uses the cover member as
A peripheral flat portion is formed on the outer peripheral portion of the cover member, and the size of the gap formed by the inner wall of the peripheral flat portion and the surface of the substrate is determined so that the solvent fills the gap when the solvent is supplied to the gap. The size is set so that it can be spread only in the gap. In this way, in the gap formed between the substrate surface and the cover member, the solvent is filled in the gap due to the meniscus due to the surface tension of the solvent, but the solvent is not supplied to the other regions. By removing the resist film in the peripheral portion of the substrate using the above-described principle, the removed region can be controlled accurately.

Further, like the above-mentioned third means, in the cover member, the gap is formed in the removed region of the main surface of the substrate, and is larger than the gap in the non-removed region of the main surface of the substrate. By covering the main surface of the substrate so that a space is formed, the removal region of the resist film on the main surface of the substrate can be accurately controlled.
The cover member covers at least the main surface of the substrate on which the resist film is formed, and may cover the chamfered portion of the substrate and the side surface of the substrate.

Further, as in the above-mentioned fourth means, the solvent flow path for supplying the solvent to the peripheral portion of the substrate is provided with the solvent at a predetermined portion of the cover member (a position corresponding to an unnecessary resist film portion). It is used as a solvent supply hole for supplying.

As in the fifth means described above, by performing vacuum drying (vacuum drying) of the substrate with the resist film before the unnecessary film dissolving step, the swelling area can be narrowed and the height of the peripheral portion of the resist film ( This is preferable because the swelling can be further reduced and the cross section becomes good. As a vacuum drying method, for example,
There is a vacuum pump or the like, and the vacuum drying conditions are appropriately set according to the resist type. The range of specific conditions is, for example, a vacuuming time of 5 to 600 seconds.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a photomask blank according to an embodiment of the present invention. FIG. 2 is an enlarged view of an end portion of the substrate before the unnecessary film dissolving step according to the embodiment. Figure 3
FIG. 3 is a side sectional view showing the structure of the unnecessary film removing device according to the example. 4 and 5 are partially enlarged sectional views of FIG. FIG. 6 is an exploded perspective view of the unnecessary film removing device according to the embodiment. FIG. 7 is a graph showing the change over time in the rotation speed of the turntable according to the example. FIG. 8 is a graph showing the change over time in the rotation speed of the turntable according to the example. FIG. 9 is a graph showing the change over time in the number of revolutions after the removal / drying process according to the example until the substrate rotation is stopped.

In the following description, first, a photomask blank on which an unnecessary film is formed will be described, then, a structure of an unnecessary film removing device for removing the unnecessary film by dissolving with a solvent will be described, and finally, a peripheral part of the peripheral portion will be described. A method of manufacturing a photomask blank for removing an unnecessary film (resist film) and a photomask blank obtained by the manufacturing method will be described.

3 to 6, a substrate 10 is a transparent substrate (6 inches × 6 inches ×) made of synthetic quartz glass.
A light-shielding film 12 made of chromium is formed on the surface of 0.25 inch (1 inch = 25.4 mm) 11, and further, a resist film in an unbaked state having a thickness of 4000 angstrom is formed on the light-shielding film 12 (for example, , Chisso Corporation, trade name: PBSC) 13 is a photomask blank formed by a spin coating method or the like.

FIG. 2 is an enlarged view of an end portion of the substrate 10 which is a photomask blank on which an unnecessary film is formed. Originally, the resist film 13 should be formed only on the main part of the surface of the transparent substrate 11. However, as shown in the unnecessary film portion 13a, it is formed even on the peripheral portion of the surface of the transparent substrate 11 that is not originally formed, the side surface portion of the substrate, and in some cases, the rear surface portion of the substrate. The transparent substrate 11 in this embodiment is chamfered.

A specific unnecessary film removing device for removing the unnecessary film portion 13a on the peripheral portion of the front surface of the substrate 10, the side surface portion of the substrate 10, and the rear surface portion of the substrate 10 will be described below.

FIG. 3 shows an unnecessary film removing device of this embodiment.
The upper surface side of the substrate 10 mounted and held on the rotary table 20 is covered with a cover member 30, and MCA (methyl cellosolve acetate) is supplied from above the cover member 30 through a nozzle 40.
The solvent 50 such as the above is ejected and supplied to the unnecessary film portion 13a through the solvent supply hole 31 of the cover member 30 to dissolve and remove it.

The cover member 30 covers the substrate 10 so as to cover it from above, and most of the central portion to the periphery is a flat portion 32. An inclined portion 33 is formed from the flat portion 32 toward the outer peripheral portion, a peripheral flat portion 34 is formed from the inclined portion 33 toward the outer peripheral portion, and an outer peripheral end of the peripheral flat portion 34 is formed at a substantially right angle downward. The side surface portion 35 is formed by being bent.

A large number of through holes, which are solvent supply holes 31, are formed in the peripheral flat portion 34. This solvent supply hole 31
An appropriate shape, size, and formation interval are selected according to the viscosity of the solvent 50 and the like. That is, the hole shape may be square, rectangular, circular, elliptical, or any other shape. The size of the holes is set so that the solvent is uniformly supplied to the unnecessary film portion 13a at a constant supply rate. Further, the interval between the holes is set to an interval at which the solvent supplied from the solvent supply hole 31 can be spread over the entire unnecessary film portion 13a without any space.

In this embodiment, the pore diameter is 10.0 mm or less, and the solvent is allowed to pass through by a quantity more than the quantity that can dissolve the unnecessary film portion 13a near the pores. The distance from the outside) was set to 10.0 mm or less. If the pore diameter is too small, unnecessary film portion 1 near the pore
This is because if 3a cannot be dissolved and the thickness is 10 mm or more, the boundary between the removed portion and the other portion tends to be jagged, and it becomes difficult to maintain the mechanical strength of the cover member 30. Further, if the distance between the holes is too small, it becomes difficult to maintain the mechanical strength of the cover member 30, and depending on the hole diameter, stable supply of the solvent may not be possible. Conversely, the distance between holes is 10.0 mm
This is because the boundary between the removed portion and another portion becomes jagged and it becomes difficult to remove the portion to be removed accurately and completely.

The region of the substrate surface facing the inner wall of the flat portion 32, which is the majority from the center to the periphery of the cover member 30, is the required region of the resist film 13 (the unnecessary film portion 13).
area other than a), and in this area, the inner wall of the cover member 30 and the substrate 10 are larger than d1 described later so that the meniscus due to the surface tension of the solvent does not work between the substrate surface and the cover member. Is larger than a predetermined value so that the temperature distribution of the resist film 13 is not affected by the heat transfer from the inner wall surface of the cover member 30, and the convection of gas occurs in the gap. The value d3 is set to a value smaller than a predetermined value so that the temperature distribution does not occur in the resist film 13 on the main surface of the substrate.

In this embodiment, d3 is 0.05 mm to 2
It is 0.0 mm. If the thickness is 0.05 mm or less, heat transfer from the cover member is likely to occur. For example, when the heat of vaporization of the solvent acts irregularly on the surface of the cover member to generate a large temperature distribution, the temperature distribution is directly reflected. There is a high possibility that the temperature distribution is given to the resist film 13. On the other hand, 2
If it is 0.0 mm or more, natural convection is generated in the gap, and there is a high possibility that a temperature distribution is generated in the resist film 13.

As shown in FIG. 4, solvent-resistant (for example, resin-based) yarns 60 are passed through appropriate points (for example, four points) in the solvent supply hole 31, and the inner wall of the cover member 30 is passed through. The size of these gaps is set by being interposed between the substrate and the surface of the substrate 10. That is, the thread 60 passes through the solvent supply hole 31, between the inner wall of the peripheral flat portion 34 and the surface of the substrate 10, and between the inner wall of the side surface portion 35 and the side surface of the substrate 10, and further the cover member 30. It passes through the outside of the side surface portion 35 and is formed in a loop shape.

The thickness of the thread 60 is the size d1 of the gap between the inner wall of the peripheral flat portion 34 and the surface of the substrate 10. When the solvent is supplied to this gap, the solvent is dispersed in the gap by the meniscus due to the surface tension of the solvent. It is set to a size that allows it to be extended into the gap by tying. In this embodiment, d1 is 0.0
It is set to 5 mm to 3 mm. If the thickness is 0.05 mm or less and 3 mm or more, it becomes difficult for the solvent to pass through the gap and spread in the gap, and there may be a part that cannot be removed, or the boundary between the removed part and other parts may be jagged. Because.

The size d2 of the gap between the inner wall of the side surface portion 35 and the side face of the substrate 10 may be any size that allows the solvent to pass through the gap while contacting the film.

As shown in FIG. 5, a nozzle 40 a for solvent supply is also provided below the substrate 10, and the nozzle 40
The solvent 50a is supplied from a to ensure removal of the unnecessary film portion 13a.

The manner in which the substrate 10 is held on the turntable 20 will be described with reference to FIG. The rotary table 20 has four support arms 22 attached to a rotary shaft 21 and extending in a radial direction in the horizontal direction, and a pair of holding pedestals 23 provided at the tip ends of the respective support arms 22. The four corners of the substrate 10 are arranged and held on the holding pedestal 23. Rotating shaft 21
Is coupled to a rotary drive device (not shown) and is rotated at a desired rotation speed. The substrate 10 covered with the cover member 30 is held by the turntable 20 and processed while being rotated.

An embodiment of the unnecessary film removing method using the above apparatus will be described below with reference to FIG.

(Embodiment 1) First, the substrate 10 is placed on the turntable 20.
And the cover member 30 is covered, the solvent 50 is supplied from the nozzle 40 while adjusting the supply amount. at the same time,
5 to 300 for the turntable 20 at a rotation speed of 200 to 500 rpm
Spin for seconds. As a result, the solvent 50 becomes the solvent supply hole 3
1 penetrates the unnecessary film portion 13a, and the unnecessary film portion 13a
a is dissolved. (Unnecessary film dissolving step P1)

Next, the supply of the solvent 50 from the nozzle 40 is stopped, and the rotary table 20 is rotated at a rotation speed of 650 to 2000 rpm for 5 to 300 seconds. As a result, the dissolved unnecessary film portion 13a is removed, and then the unnecessary film portion 13a is removed.
The area removed is dried. (Removal / drying process P
2)

Next, the change in the number of rotations from the number of rotations in the removing / drying process to the stop of the rotation of the substrate is changed by the change in atmospheric pressure between the cover member 30 and the main surface of the substrate 10 so that the resist film 13 is formed on the substrate 10. The rotation table 20 is monotonically and continuously decelerated (deceleration speed 300 to 500 rpm / sec) so as to prevent the rotation table 20 from flowing in the central direction, and the rotation table is rotated for 3 to 6 seconds from the number of rotations in the removal / drying process. Stopped.

After the removing / drying process, a baking process or the like is performed to obtain a photomask blank with a resist film in which the resist film 13 is formed in a substantially square shape in the central portion of the substrate. The removal width of the resist film on the main surface of the substrate on which the light-shielding film is formed is 1.5 mm ± from the side surface of the substrate so that the removal area of the resist film does not cover the pattern near the peripheral portion of the substrate.
0.3 mm, the average film thickness of the resist film is 4000
It was a little less than Angstrom.

FIG. 1 shows the photomask blank thus obtained. The state of the resist film 13 was visually observed. As a result, no ring-shaped color unevenness due to the temperature distribution applied to the resist film 13 during the treatment is observed,
Further, it was found that the boundary line between the resist film 13 and the removed portion was almost linear, and the removal width was almost constant, and the removal was accurate. Furthermore, when the resist film 13 was observed with a microscope, no pinholes due to solvent splashes were observed. Further, when the swelling (height of the convex portion) of the peripheral portion of the removed resist film 13 was measured by a stylus type film thickness measuring device (Taly Step manufactured by Taylor Hobson Co.), the resist film facing the removed region was measured. The height h from the reference surface was 0.25 μm when the surface of the resist film 13 near the central portion of the substrate excluding the peripheral portion of 13 was used as the reference surface (and up to the point where the peripheral portion of the resist film 13 was removed). Since the resist film 13 was formed to have a uniform thickness, the height before the removal of the unnecessary film portion 13a was used as a reference surface was 0.25 μm.)

The thus obtained photomask blank was stored in a substrate storage case, and then a photomask was produced. As a result, the pattern defect due to the swelling of the resist film 13 and the defect defect due to dust generation did not occur.

Example 2 A photomask blank was obtained in the same manner as in Example 1 except that the resist film-coated substrate was vacuum dried before the unnecessary film dissolving step. As a result, a photomask blank with a resist film was obtained in which the resist film 13 was formed in a substantially square shape in the central portion of the substrate 10.

The state of the resist film 13 of the photomask blank thus obtained was visually observed. As a result, no ring-shaped color unevenness due to the temperature distribution applied to the resist film 13 during the treatment is observed, and the boundary line between the resist film 13 and the removed portion is almost linear, and the removal width is Was found to be almost constant and removed accurately. Furthermore, when the resist film 13 was observed with a microscope, no pinholes due to the droplets of the solvent 50 were observed.
Further, when the swelling (height of the convex portion) of the peripheral portion of the resist film 13 was measured by a stylus type film thickness measuring device (Tally Step manufactured by Taylor Hobson Co.), the peripheral portion of the resist film 13 facing the removed region was measured. The height from the reference surface was 0.1 μm when the surface of the resist film 13 in the vicinity of the central portion of the substrate except for was the reference surface (and the unnecessary film portion 13a
Since the resist film 13 was formed to have a uniform thickness up to the point where the film was removed, the height before the removal of the unnecessary film portion 13a was the reference plane was 0.1 μm. ).

The thus obtained photomask blank was stored in a substrate storage case, and then a photomask was produced. As a result, the pattern defect due to the swelling of the resist film 13 and the defect defect due to dust generation did not occur.

By performing vacuum drying as in this embodiment, the swelling (height of the convex portion) in the peripheral portion of the removed resist film is further reduced as compared with the case of the first embodiment.
The cross section became good.

(Examples 3 to 5) Next, in Example 1 described above, the resist film 13 is prevented from flowing toward the center of the substrate 10 due to a change in atmospheric pressure between the cover member 30 and the main surface of the substrate 10. As described above, the rotary base 20 is monotonically and continuously decelerated, and the deceleration speed is over 100 rpm / sec.
0 rpm / sec or less (Example 3), deceleration speed of 500
rpm / sec> 750 rpm / sec (Example 4), deceleration speed> 750 rpm / sec> 1000 rp
A photomask blank was produced in the same manner as in Example 1 except that the rotation of the turntable was stopped at m / sec or less (Example 5).

The swelling (height of the convex portion) of the peripheral portion of the resist film 13 was measured by a stylus type film thickness measuring device (Tally Step manufactured by Taylor Hobson Co.), and the periphery of the resist film 13 facing the removed region was measured. When the surface of the resist film 13 in the vicinity of the central portion of the substrate excluding the portions is used as a reference surface, the height h from the reference surface is 0.25 μm in Example 3, 0.25 to 0.3 μm in Example 4, respectively. Example 5 is 0.5-1
was μm.

From the above results, it is understood that the deceleration speed should be 1000 rpm / sec or less in order to reduce the height of the convex portion to 1 μm or less. Deceleration speed is 500 rpm / s
If the height is less than ec, no change in the height of the protrusion can be confirmed.
/ Sec or more and 700 rpm / sec or less is preferable. The obtained photomask blank was stored in a substrate storage case, and then a photomask was produced. As a result, the pattern defect due to the swelling of the resist film 13 and the defect defect due to dust generation did not occur.

(Example 6) Next, the same procedure as in Example 1 was carried out except that the resist was changed to a polymer type resist (ZEP manufactured by Nippon Zeon Co., Ltd.) and the solvent was made soluble. A photomask blank was prepared in the same manner as in Example 1.

In the same manner as in Example 1, when the swelling (height of the convex portion) of the peripheral portion of the removed resist film 13 was measured by a stylus type film thickness measuring device (Tally Step manufactured by Taylor Hobson Co.), the removal was found. When the surface of the resist film 13 in the vicinity of the central portion of the substrate excluding the peripheral portion of the resist film 13 facing the exposed area is used as the reference surface, the height h from the reference surface is 0.0
5 μm (Also, since the thickness of the resist film 13 was formed to the point where the peripheral portion of the resist film 13 was removed, the height before the removal of the unnecessary film portion 13a was used as a reference plane was 0. It was 05 μm.).

After the photomask blank thus obtained was stored in a substrate storage case, a photomask was produced. As a result, the pattern defect due to the swelling of the resist film 13 and the defect defect due to dust generation did not occur.

(Comparative Example 1) In the above-mentioned Example 1, the rotation speed f2 of the rotary table in the removing / drying step was 150 to 500 rp.
A photomask blank was produced in the same manner as in Example 1 except that the photomask blank was rotated at m for 10 to 120 seconds.

The swelling (height of the convex portion) in the peripheral portion of the resist film 13 was measured by a stylus type film thickness measuring device (Taly Step manufactured by Taylor Hobson Co.), and the periphery of the resist film 13 facing the removed region was measured. When the surface of the resist film 13 in the vicinity of the central portion of the substrate excluding the area is used as the reference surface, the height from the reference surface is 3.5 μm, and when the surface before removal of the unnecessary film portion 13a is used as the reference surface, The height was 2.5 μm.

The photomask blank thus obtained was housed in a substrate housing case, and then a photomask was produced. As a result, dust generation due to the swelling of the resist film 13 and pattern defects due to dust generation were confirmed. Further, a pattern defect was found near the periphery of the substrate due to the swelling of the resist film 13.

(Comparative Example 2) In the above-mentioned Example 1, the rotation in the removal / drying process was not monotonically and continuously reduced without changing the rotation speed in the removal / drying process until the rotation of the substrate was stopped. A photomask blank was prepared in the same manner as in Example 1 except that the rotation of the turntable was suddenly stopped. (The deceleration speed at this time is 1000 rpm / sec.
It was a condition that exceeded. )

The swelling (height of the convex portion) of the peripheral portion of the resist film 13 was measured by a stylus type film thickness measuring device (Tally Step manufactured by Taylor Hobson Co.), and the periphery of the resist film 13 facing the removed region was measured. The height from the reference surface is 3 μm when the surface of the resist film 13 near the central portion of the substrate except the area is the reference surface, and when the surface before removing the unnecessary film portion 13a is the reference surface, the height is It was 2 μm.

The obtained photomask blank was stored in a substrate storage case, and then a photomask was produced. As a result, a pattern defect near the periphery of the substrate due to the rise of the resist film 13 and a pattern defect due to dust generation were confirmed.

It should be noted that the above-mentioned upper limit of d3 is 20.0.
mm is not necessarily regulated. For example, it is possible to prevent the temperature distribution from being generated by natural convection by forcibly stirring the gas in the gap uniformly. However, increasing the gap inevitably increases the height of the flat portion 32 of the cover member 30. If the height of the flat portion 32 becomes too high, the distance that the solvent supplied from the nozzle 40 reaches the peripheral flat portion 34 becomes long, the amount of vaporization in the middle increases, and the cover member and the substrate are rotated. In the case of treatment, there is a high possibility that the solvent will scatter around. In addition, the device becomes large in size, which is not desirable.

The size of d2 described above is preferably the same as that of d1, but it may be different from d1. When differentiating, d1 <d2 and d
There are cases where 1> d2.

Although not shown, when d1 <d2,
For example, a hole may be separately formed in the side surface portion 35 and a yarn thicker than the yarn 60 may be used to regulate the size of the gap. When d1> d2, a hole through which the thread 60 is passed is formed separately on the peripheral flat portion 34 on the side surface portion 35 side of the solvent supply hole 31, and the thread 60 is passed through the hole and the solvent supply hole 31. A hole is separately formed in the side surface portion 35 to allow a thread thinner than the thread 60 to pass therethrough. That is, this thread passes through the hole formed in the side surface portion 35, between the side surface portion 35 and the substrate 10, and outside the side surface portion 35 of the cover member 30.

It should be noted that the dropping of the solvent 50 is preferably started after the rotational speed of the rotary table 20 becomes constant in the unnecessary film dissolving step P1, but it may be started when the rotary table 20 starts rotating.

As shown in FIG. 8, the unnecessary film solvent step P1,
By repeating the removal / drying step P2 a plurality of times, the swelling (height of the convex portion) of the peripheral portion of the resist film 13 is further reduced, and the cross-sectional shape of the boundary portion after removing the unnecessary film portion 13a is improved. .

FIG. 9 is a graph showing the change over time in the number of rotations from the number of rotations in the removing / drying process to when the rotation of the substrate is stopped according to the embodiment. As shown in FIG.
There is no particular limitation on the deceleration method from the rotation speed of the drying process P2 to the stop of the rotation of the substrate. For example, stepwise deceleration, continuous deceleration, and stepwise deceleration and continuous deceleration can be combined. Specifically, selections such as 91 to 94 in FIG. 9 can be made. 91 is the rotation speed f of the substrate
This is the case where 2 is monotonically and continuously decelerated. The reference numeral 92 indicates that the resist film immediately after the peripheral resist film was removed was in contact with the solvent. Therefore, the viscosity of the resist is small, so the speed of the resist film is gradually reduced until it becomes a dry state to a certain extent, and the dry state is made to a certain extent. This is the case when the rate of deceleration is increased. 93 is a case where continuous deceleration and stepwise deceleration are combined. 94 is a case where the deceleration is gradually performed.

In the above embodiment, MCA (methyl cellosolve acetate) was used as the solvent for dissolving the resist film 13, but the solvent is not limited to this, and any solvent capable of dissolving and removing the resist film 13 can be used. It can be anything. A developing solution can be used when an unnecessary portion of the resist is exposed and removed by development. Further, although the resin-based thread 60 is used as the gap setting member in the above-mentioned embodiment, any other material may be used as long as it has flexibility and resistance to the solvent. Further, the gap setting member is not limited to the filamentous member, and may be any member as long as the gap can be set, for example, a convex member provided on the inner wall of the cover member.

As a material forming the cover member 30,
Any material may be used as long as it is difficult to transfer heat, has resistance to a solvent, and has a predetermined mechanical strength. For example, a resin material, a glass material, a ceramic material, a composite material thereof, or the like can be given. Of these, a resin material is preferable because it is relatively hard to transfer heat, is easy to process, and is easy to reduce the weight. In addition, it is preferable that at least a portion of the cover member 30 that covers a region other than the unnecessary film portion 13a on the surface of the substrate 10 is made of the above material.

Further, in the above-mentioned embodiment, an example in which the resist film 13 is formed on the light-shielding film 12 has been described. However, in this embodiment, the SOG film is formed on the transparent substrate 11, and the SOG film is formed on the SOG film. It can also be applied to the case where the light shielding film 12 is formed. In that case, a film such as a transparent conductive film and an etching stopper film may be provided outside the light shielding film 12.

Further, for example, a protective film of a magnetic disk medium is applied, an unnecessary film formed at the time of applying a protective film of a color filter is removed, or insulation is formed on an electrode portion of a wiring on a display substrate. It can also be applied when removing the film. Further, for example, when the unnecessary film is a resist, a liquid in which the resist is soluble, such as a ketone, an ester, an aromatic hydrocarbon, a halogenated hydrocarbon, or an ether, can be used as a solvent.

Further, when the unnecessary film is SOG, the coating film is hard to melt after baking, so that the coating film on the back surface, the side surface and the peripheral portion of the surface of the substrate before the baking as in the first embodiment described above. Is preferably dissolved and removed, but when the coating film is a resist, it may be dissolved even after baking depending on the type of the resist. Further, the position where the solvent supply hole 31 is provided is not limited to the above-mentioned embodiment.

In the above embodiment, the substrate 10 and the cover member 30 are integrally rotated, but this is not always necessary. However, rotation is preferable because the solvent can be spread relatively quickly and uniformly into the gap. Further, in the above-described embodiment as the cover member 30, an example in which the peripheral portion of the coating film formed on the square substrate is removed to leave the square coating film, the shape of the substrate and the remaining coating film The shape is not limited to a square, but may be a circle, a triangle, a polygon, or any other shape. In that case, the shape of the solvent supplying surface and the non-supplying surface of the cover member may be formed as such.

[0078]

According to the method of manufacturing a mask blank of the present invention, the rotation speed of the substrate in the unnecessary film dissolving step is f1, the dissolved unnecessary film is removed, and the removed region is dried. When the rotation speed is f2, f2> f1
Further, since the deceleration speed from the rotation speed f2 until the rotation of the substrate is stopped is 1000 rpm / sec or less, it is possible to obtain a photomask blank in which swelling of the resist film after removal of the resist film periphery is suppressed. Therefore, the mask blank manufactured by this manufacturing method can eliminate a dust source and prevent pattern defects near the periphery of the substrate.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a photomask blank according to an example.

FIG. 2 is an enlarged view of an end portion of the substrate before the unnecessary film dissolving step according to the example.

FIG. 3 is a side sectional view showing a configuration of an unnecessary film removing device according to an embodiment.

FIG. 4 is a partially enlarged sectional view of FIG.

5 is a partially enlarged sectional view of FIG.

FIG. 6 is an exploded perspective view of the unnecessary film removing device according to the embodiment.

FIG. 7 is a graph showing a change over time in the number of rotations of the turntable according to the example.

FIG. 8 is a graph showing the change over time in the number of rotations of the turntable according to the example.

FIG. 9 is a graph showing a change with time in the number of rotations from the number of rotations in the removing / drying process to stopping the rotation of the substrate according to the example.

FIG. 10 is an enlarged view of an end portion of a photomask blank obtained when an unnecessary film is removed by a conventional technique.

[Explanation of symbols]

10 ... Substrate, 11 ... Transparent substrate, 12 ... Shading film (thin film having a shading function), 13 ... Resist film.

Claims (5)

[Claims] 1. A step of preparing a substrate on which a thin film to be a transfer pattern is formed so as to be transferred to a transfer target, a step of forming a resist film on the main surface of the substrate, and a side on which the resist film is formed. While the substrate surface is covered with a cover member, the substrate is rotated at a predetermined rotation speed f1, and a solvent is supplied from above the cover member to dissolve the solvent in an unnecessary resist film through the solvent flow path. And the step of dissolving the unnecessary film, stopping the supply of the solvent, and rotating at a predetermined rotation speed f2, which is higher than the rotation speed f1, to remove the dissolved unnecessary film and dry the removed area. And a deceleration speed from the rotation speed f2 until the rotation of the substrate is stopped is 1000 rpm / sec or less. 2. A peripheral flat portion is formed on an outer peripheral portion of the cover member, and a size of a gap formed by an inner wall of the peripheral flat portion and a surface of the substrate is determined by supplying the solvent to the gap. The method of manufacturing a mask blank according to claim 1, wherein the solvent is set to have a size that allows the solvent to pass through the gap and spread only in the gap. 3. The cover member is configured such that the gap is formed in a removed region of the substrate main surface and a space larger than the gap is formed in a non-removed region of the substrate main surface. The method for manufacturing a mask blank according to claim 1 or 2, wherein the surface is covered. 4. The method of manufacturing a mask blank according to claim 1, wherein the solvent flow path is a solvent supply hole provided at a predetermined portion of the cover member. 5. The method of manufacturing a mask blank according to claim 1, wherein the substrate with the resist film is vacuum-dried before the unnecessary film dissolving step.