JP5818861B2 - Mask blank, method of manufacturing the same, and mask - Google Patents

Description

  The present invention relates to a mask used for manufacturing an electronic device, a mask blank serving as an original plate, and a method for manufacturing the mask blank.

  With recent rapid development of IT technology, further miniaturization is required for recent electronic devices, particularly color filters or TFT elements for semiconductor elements and liquid crystal monitors. One of the technologies that support such a fine processing technology is a lithography technology using a photomask called a transfer mask. In this lithography technique, a fine pattern is formed on a silicon wafer by exposing an electromagnetic wave or light wave of an exposure light source to a silicon wafer with a resist film through a photomask. This photomask is usually manufactured by forming a thin film pattern to be a transfer pattern by patterning the thin film using a lithography technique on a mask blank in which a thin film such as a light-shielding film is formed on a translucent substrate.

  By the way, in order to achieve pattern miniaturization, it is also extremely important to improve the quality of a mask blank that is an original for manufacturing a photomask. Conventionally, the main surface of the glass substrate for mask blank is mirror-polished, and the end surface formed on the periphery of the main surface of the glass substrate is also polished so as to have a predetermined mirror surface. For example, in Patent Document 1, in order to suppress the occurrence of defects such as pinholes due to the irregularities of the end face generated during the cutting process of the glass substrate and the abrasive particles captured in the fine fissures, Describes a mask substrate for an electronic device that has been subjected to mirror polishing.

Japanese Patent Publication No.61-34669

  By improving the smoothness by mirror polishing the substrate end surface, it is possible to suppress the occurrence of defects caused by fine particles generated from the end surface of the glass substrate as described in Patent Document 1 described above. However, according to the study of the present inventor, it has been found that the following problems have not been solved.

1. When miniaturizing a pattern of an electronic device, in addition to miniaturization of a mask pattern formed on a photomask, it is necessary to shorten the wavelength of an exposure light source used in photolithography. For example, as an exposure light source in manufacturing a semiconductor device, in recent years, the wavelength has been shortened from a KrF excimer laser (wavelength 248 nm) to an ArF excimer laser (wavelength 193 nm) and further to an F2 excimer laser (wavelength 157 nm). With such miniaturization of patterns and shortening of the exposure light source wavelength, the CD accuracy of patterns required for photomasks has become very strict. The pattern CD accuracy has various factors such as the in-plane film thickness uniformity of the mask blank in the mask blank and the mask manufacturing process. It has become. Conventionally, as described above, the smoothness of the end face of the glass substrate has been studied to some extent, but the flatness of the end face of the glass substrate has not been considered at all. Although smoothness of the end surface of the glass substrate can be obtained to some extent by polishing the end surface of the glass substrate, the flatness at the end surface of the glass substrate is not necessarily good. Therefore, when the resist is applied and formed by spin coating, the resist is liable to stay and the resist is not liable to stay when the resist is applied by spin coating due to the “flatness” due to poor flatness on the end face of the glass substrate, particularly the chamfered surface. As a result, there is a problem that the film thickness variation of the resist film near the outer periphery of the main surface of the substrate occurs, and the in-plane film thickness uniformity of the resist film is not improved. In particular, this problem is considered to become more prominent because the resist film tends to be thinned from the viewpoint of miniaturizing the mask pattern formed on the photomask. Furthermore, since the effective area of the photomask pattern tends to expand in recent years, it is considered that the influence of variations in the in-plane film thickness of the resist film during photomask manufacturing is increased.

2. Furthermore, due to waviness caused by poor flatness on the end surface of the glass substrate, especially the chamfered surface, the resist swells near the outer periphery of the main surface of the substrate, causing variations in dust generation and resist swell. Even when the portion is removed, there is a problem that the residue of the resist due to the variation and the cross section of the boundary portion where the resist film is removed become jagged so that dust is generated from the portion.

3. When a resist film for electron beam drawing is formed as a resist film, a light-shielding film made of a conductive material (for example, chromium (Cr)) is used to prevent charge-up in a mask pattern drawing process during mask manufacturing. The chamfered surface of the glass substrate may be formed. In this case, a light-shielding film is formed on the chamfered surface by oblique incidence, so that the film adhesion is weak and the film is not attached to the chamfered surface due to undulation due to poor flatness on the chamfered surface. There was a problem that variation in adhesion force occurred, and dust generation occurred during taking in and out of the storage case and transporting the mask blank.

  The present invention has been made to solve the above-mentioned problems. The object of the present invention is, firstly, a photomask blank substrate capable of improving the in-plane film thickness uniformity of the resist film and obtaining high mask pattern accuracy, and It is to provide a photomask blank, and secondly, to provide a photomask in which a fine pattern is formed with high pattern accuracy using such a photomask blank.

In order to solve the above-mentioned problems, the present invention has the following configuration.
(Configuration 1) A photomask blank substrate having a thin film for forming a transfer pattern on a translucent substrate, wherein the substrate has a main surface and an end surface formed on the periphery of the main surface. The end surface includes a side surface of the substrate and a chamfered surface interposed between the side surface and the main surface, and the end surface is a chamfered surface continuous with at least the main surface on which the thin film is formed. A photomask blank substrate having a flatness of 50 μm or less.
(Configuration 2) The configuration 1 is characterized in that, of the chamfered surfaces, at least the chamfered surface continuous with the main surface on which the thin film is formed has an arithmetic average surface roughness (Ra) of 2 nm or less. It is a photomask blank substrate as described.

(Structure 3) A photomask blank characterized in that a thin film for forming a transfer pattern is formed on the main surface of the photomask blank substrate according to Structure 1 or 2.
(Structure 4) The photomask blank according to Structure 3, wherein a conductive thin film is formed on the chamfered surface of the substrate.
(Structure 5) A photomask blank according to Structure 3 or 4, wherein a resist film is provided on the thin film.

(Structure 6) A photomask, wherein a transfer pattern is formed on a thin film of the photomask blank according to any one of structures 3 to 5.

(Structure 7) A method for manufacturing a substrate for a photomask blank having a thin film for forming a transfer pattern on a translucent substrate, wherein the substrate is an end surface formed on a main surface and a peripheral edge of the main surface And the end surface includes a side surface of the substrate and a chamfered surface interposed between the side surface and the main surface, and is continuous with at least the main surface of the chamfered surface on which the thin film is formed. An end face of the substrate is polished so that the flatness of the chamfered surface is 50 μm or less.
(Configuration 8) While supplying a polishing liquid containing polishing abrasive grains, polishing the end surface of the substrate by relatively moving the polishing brush provided with polishing brush bristles and the substrate. It is a manufacturing method of the substrate for photomask blanks according to Structure 7 which is characterized.

  As in Configuration 1, the present invention is a substrate for a photomask blank having a thin film for forming a transfer pattern on a translucent substrate, and the substrate is disposed on a main surface and a periphery of the main surface. An end face formed, and the end face includes a side surface of the substrate and a chamfered surface interposed between the side surface and the main surface, and at least the main film on which the thin film is formed among the chamfered surfaces. The flatness of the chamfered surface continuous with the surface is 50 μm or less. By setting the flatness of at least the main surface on which the thin film is formed among the chamfered surfaces to 50 μm or less, a resist film in the vicinity of the outer periphery of the substrate main surface when the resist is applied by spin coating. The film thickness variation of the resist film is small, and the in-plane film thickness uniformity of the resist film can be improved. Therefore, when a photomask is manufactured using such a photomask blank substrate, high mask pattern accuracy can be obtained. In particular, this effect is remarkable when the resist film is thinned from the viewpoint of miniaturizing the mask pattern formed on the photomask.

Further, even if the resist swells near the outer periphery of the main surface of the substrate, the variation is small, and even when the resist swelled part is removed, dust generation from the removed part can be suppressed.
Further, when forming a resist film for electron beam drawing as a resist film, a light-shielding film made of a conductive material is formed up to the chamfered surface of the substrate in order to prevent charge-up in the mask pattern drawing process during mask manufacturing. Even in this case, the flatness of the chamfered surface is good, so the dispersion of the film adhesion of the light-shielding film on the chamfered surface is small, and dust generation due to film peeling is suppressed when taking it in and out of the storage case or transporting the mask blank. can do.

  Further, as in Configuration 2, the surface roughness of the chamfered surface continuous with at least the main surface on which the thin film is formed among the chamfered surfaces is 2 nm or less in terms of arithmetic average surface roughness (Ra), When the smoothness of the end face of the substrate is low, it is possible to suppress the occurrence of defects caused by fine particles that are easily trapped on the end face.

Further, as in Configuration 3, according to the photomask blank in which a thin film for forming a transfer pattern is formed on the main surface of the photomask blank substrate, a resist film is formed on the photomask blank. In this case, since the in-plane film thickness uniformity of the resist film is good, a fine pattern can be formed with high pattern accuracy using such a photomask blank.
Further, in the photomask blank in which the conductive thin film is formed on the chamfered surface of the substrate as in the configuration 4, since the flatness on the chamfered surface is good, the light-shielding film on the chamfered surface is good. The present invention is suitable because variations in the film adhesion force are small and dust generation can be suppressed during taking in and out of the storage case and transporting the mask blank.

  In addition, in the photomask blank having the resist film on the thin film as in the configuration 5, when the resist film is applied and formed by spin coating, the film thickness variation of the resist film near the outer periphery of the main surface of the substrate is reduced. In-plane film thickness uniformity of the resist film is small, and when a photomask is manufactured using such a photomask blank, high mask pattern accuracy can be obtained. In particular, it is suitable for a photomask blank in which a resist film is thinned from the viewpoint of miniaturizing a mask pattern formed on the photomask. Further, when the resist film is formed, even if the resist swells near the outer periphery of the main surface of the substrate, the variation is small, and even when the resist swelled part is removed, dust generation from the removed part can be suppressed. .

  Further, as described in Structure 6, according to the photomask in which the transfer pattern is formed on the thin film of the photomask blank, since the in-plane film thickness uniformity of the resist film formed on the photomask blank is good, it is high. A photomask having a fine pattern formed with pattern accuracy is obtained.

  The present invention also provides a method for producing a substrate for a photomask blank having a thin film for forming a transfer pattern on a light-transmitting substrate as in Configuration 7, wherein the substrate comprises a main surface and the substrate. An end face formed on a peripheral edge of the main surface, the end face including a side surface of the substrate and a chamfered surface interposed between the side surface and the main surface, and at least the thin film among the chamfered surfaces. This is a method for manufacturing a photomask blank substrate in which the end face of the substrate is polished so that the flatness of the chamfered surface continuous with the main surface on which the film is formed is 50 μm or less. When the resist is applied and formed by spin coating, the substrate end surface is polished so that the flatness of the chamfered surface continuous with at least the main surface on which the thin film is deposited is 50 μm or less. The resist film thickness variation in the vicinity of the outer periphery of the surface is small, and the in-plane film thickness uniformity of the resist film can be improved. When a photomask is manufactured using such a photomask blank substrate, high mask pattern accuracy can be obtained. In particular, this effect is remarkably obtained when the resist film is thinned from the viewpoint of miniaturizing the mask pattern formed on the photomask. Further, even if the resist swells near the outer periphery of the main surface of the substrate, the variation is small, and even when the resist swelled part is removed, dust generation from the removed part can be suppressed.

  Further, when forming a resist film for electron beam drawing as a resist film, a light-shielding film made of a conductive material is formed up to the chamfered surface of the substrate in order to prevent charge-up in the mask pattern drawing process during mask manufacturing. Even in this case, since the flatness of the chamfered surface is good, the variation in the film adhesion of the light-shielding film on the chamfered surface is small, and dust generation can be suppressed during taking in and out of the storage case and transporting the mask blank.

  Further, as described in Structure 8, in the method for producing a photomask blank substrate according to Structure 7, a polishing brush having polishing brush hairs protruding while supplying a polishing liquid containing polishing abrasive grains By polishing the end surface of the substrate by relatively moving the substrate and the substrate, the flatness of the chamfered surface continuous with at least the main surface on which the thin film is formed out of the chamfered surfaces is 50 μm or less. It can be preferably polished.

According to the present invention, it is possible to provide a photomask blank substrate and a photomask blank that can improve the in-plane film thickness uniformity of a resist film and obtain high mask pattern accuracy.
Moreover, according to this invention, the photomask in which the fine pattern was formed with high pattern precision using the photomask blank which concerns on this invention can be provided.

It is sectional drawing of the board | substrate for photomask blanks of this invention. It is sectional drawing of the photomask blank of this invention which formed the electroconductive light-shielding film | membrane on the chamfering surface. It is sectional drawing of one Embodiment of the photomask blank of this invention. It is sectional drawing which shows the manufacturing process of the photomask using the photomask blank of this invention. It is a partial perspective view of the board | substrate for demonstrating the measurement point at the time of measuring the flatness in a chamfering surface.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of the vicinity of the outer periphery of a photomask blank substrate according to the present invention.
A translucent substrate (hereinafter simply referred to as “substrate”) 1 is a substrate for a photomask blank, and has main surfaces 11a and 11b on both sides and end surfaces 12 formed on the peripheral edges of the main surfaces 11a and 11b. The end surface 12 includes a side surface 12c of the substrate 1 and chamfered surfaces 12a and 12b interposed between the side surface 12c and the main surfaces 11a and 11b. In the present invention, the flatness of the chamfered surface (for example, 12a) continuous with at least the main surface (for example, 11a) on which a thin film for forming a transfer pattern is formed is 50 μm or less. .

  By setting the flatness of at least the main surface on which the thin film is formed among the chamfered surfaces to 50 μm or less, a resist film in the vicinity of the outer periphery of the substrate main surface when the resist is applied by spin coating. The film thickness variation of the resist film is small, and the in-plane film thickness uniformity of the resist film can be improved. Therefore, when a photomask is manufactured using the photomask blank substrate 1, high mask pattern accuracy can be obtained. In particular, since the resist film tends to be thinned from the viewpoint of miniaturizing the mask pattern formed on the photomask, the effect of improving the in-plane film thickness uniformity of the resist film is prominent in that case. Further, even if the resist swells near the outer periphery of the main surface of the substrate, the variation is small, and even when the resist swelled part is removed, dust generation from the removed part can be suppressed.

Here, a glass substrate is suitable as the substrate 1. Since the glass substrate is excellent in smoothness and flatness of the main surface, when performing pattern transfer onto a semiconductor substrate using a photomask, high-precision pattern transfer can be performed without causing distortion of the transfer pattern. The Further, the flatness of the chamfered surface can be reduced to 50 μm or less by polishing the end surface of the glass substrate.
In the present invention, the flatness is the difference between the maximum height and the minimum height of the surface shape in the chamfered surface from the reference surface arbitrarily provided on the surface side of the chamfered surface of the substrate (calculated from the measurement surface by the method of least squares). Difference between the maximum value and the minimum value of the measurement surface relative to the virtual absolute plane (focal plane).

The flatness measurement on the chamfered surface (for example, 12a) of the substrate 1 can be performed using, for example, a flatness measuring device using light interference, a substrate shape inspection device, or the like. Specifically, using these devices, height information from a reference plane (focal plane calculated by the method of least squares) at a plurality of measurement points in the chamfered surface is acquired, and the maximum information is obtained from this height information. The value and the minimum value are obtained, and the difference between the maximum value and the minimum value, that is, the flatness is calculated.
The measurement point in this case can be arbitrarily set as long as it is within the chamfered surface. For example, referring to FIG. 5, when measuring the flatness of the chamfered surface 12 a, for example, a plurality of measurement points are set along the longitudinal direction (see arrow 13 in the figure) about the approximate center of the measurement region. Height information from the reference plane at the measurement point is measured. In addition, measurement points are set along a plurality of dividing lines 14 (14a, 14b, 14c,... 14n,...) That cut (round cut) the measurement region in a direction substantially orthogonal to the longitudinal direction. You may make it measure the height information from the said reference plane in a measurement point. Further, in order to measure the flatness with high accuracy, it is desirable to increase as many measurement points as possible to obtain height information. However, if there are too many measurement points, it will take time for measurement, so it may be set as appropriate in view of this.
Furthermore, the height information may be acquired from data obtained by measuring the surface shape of the measurement region three-dimensionally.

  In order to measure the flatness with high accuracy, it is desirable that the measurement area for acquiring the height information is as much as possible on the entire chamfered surface. However, the corner portion of the substrate 1 has a rounded corner portion 16 and a rounded corner portion 15 chamfered with the width of the chamfered surface (see FIG. 5), and a chamfered surface 12a. It may be difficult to measure the height information with high accuracy in the vicinity of the boundary between the edge portion and the chamfered portion 15 at both ends thereof. In consideration of this point, a measurement area for obtaining the height information is a region obtained by removing a predetermined width from both ends in the longitudinal direction of the chamfered surface (a region obtained by removing a predetermined width from both ends in the longitudinal direction from the entire surface of the chamfered surface). It is preferable to do. How much the predetermined width in this case is set differs somewhat depending on the size of the substrate 1 and the polishing state of the corners of the end face of the substrate 1 and cannot be generally stated. For example, the size of the substrate 1 is 152 mm × 152 mm. In this case, a region obtained by removing a width of 5 mm from both ends in the longitudinal direction of the chamfered surface (a region obtained by removing a width of 5 mm from both ends in the longitudinal direction from the entire surface of the chamfered surface) is set as a measurement region for acquiring the height information. It is preferable.

In the present invention, the flatness of the chamfered surface is 50 μm or less, preferably 20 μm or less, more preferably 10 μm or less.
Further, in the present invention, the surface shape of the chamfered surface is not particularly limited and is arbitrary, but from the viewpoint of effectively removing the polishing agent residue used for polishing from the substrate surface in the cleaning after polishing the substrate. It is preferably flat or a convex shape in which the height of the chamfered surface gradually decreases from the central region of the chamfered surface toward the peripheral edge.

  In the present invention, the flatness of the chamfered surface (for example, 12a) continuous with at least the main surface (for example, 11a) on the film forming side of the chamfered surface is 50 μm or less. It is desirable that the chamfered surface (for example, 12b) continuous with the main surface (for example, 11b) also has good flatness, for example, 50 μm or less.

  Further, in addition to the flatness of the chamfered surface (for example, 12a) continuous with at least the main surface (for example, 11a) on which the thin film is formed among the chamfered surfaces, the surface roughness is an arithmetic average. The surface roughness (Ra) is preferably 2 nm or less. In addition to good flatness, it also has good smoothness, which can cause defects caused by fine particles (such as abrasive fine particles) that are easily trapped on the end face when the smoothness of the end face of the substrate is low. Can be suppressed.

The photomask blank substrate of the present invention can be obtained by polishing the end face of the substrate so that the flatness of the chamfered surface continuous with at least the main surface on which the thin film is formed is 50 μm or less. it can.
As a polishing method in this case, for example, while supplying a polishing liquid containing polishing abrasive grains, the polishing brush with protruding polishing bristles and the substrate are relatively moved to move the end surface of the substrate. A method of polishing is mentioned. According to such a polishing method, the substrate end surface can be preferably polished so that the flatness of the chamfered surface is 50 μm or less.

  In the photomask blank of the present invention, a thin film for forming a transfer pattern is formed on the main surface of the photomask blank substrate 1. According to the photomask blank of the present invention, when a resist film is formed on the photomask blank, the film thickness of the resist film is also near the outer periphery of the main surface of the substrate due to good flatness on the chamfered surface of the substrate end surface. Since the variation is small and the in-plane film thickness uniformity of the resist film is good, a fine pattern can be formed with high pattern accuracy using such a photomask blank.

  The photomask blank of the present invention can be obtained by forming a predetermined thin film on the main surface of the substrate 1 by using a film forming method such as sputtering or CVD. For example, a photomask blank is a light-shielding film made of a material such as chromium on a substrate, or a thin film made of chromium oxide or the like (an antireflection film) on a thin film made of a material such as chromium in order to reduce the reflectance with respect to exposure light. ) Are stacked. Further, in a mask blank for a phase shift mask, for example, a metal such as molybdenum, tungsten, tantalum, or hafnium, silicon, oxygen, or the like that has a predetermined light shielding property and reverses the phase of incident exposure light on the substrate. And / or a phase shifter film made of a material mainly composed of nitrogen is formed. Further, a light-shielding film made of a material such as chromium or a light-shielding film in which a thin film (antireflection film) such as chromium oxide is laminated may be formed on the phase shifter film. Further, in a mask blank for a reflective mask that uses extreme ultraviolet light, which is light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, as exposure light, for example, molybdenum that reflects the exposure light on the substrate. And a multilayer reflective film made of alternating layers of silicon and silicon, and an absorber film made of, for example, a tantalum material that absorbs exposure light.

  The photomask blank of the present invention may have a form in which a resist film is formed on the thin film. In the photomask blank having the resist film according to the present invention, the flatness on the chamfered surface of the substrate end surface is good, so that when the resist film is applied and formed by spin coating, in the vicinity of the outer periphery of the main surface of the substrate. Since the film thickness variation of the resist film is small and the in-plane film thickness uniformity of the resist film can be improved, high mask pattern accuracy can be obtained when a photomask is manufactured using such a photomask blank. In particular, from the viewpoint of miniaturizing the mask pattern formed on the photomask, the resist film is suitable for a photomask blank in which the resist film is thinned (for example, from about 4500 mm to about 3000 mm or 2500 mm). Further, when the resist film is formed, even if the resist swells near the outer periphery of the main surface of the substrate, the variation is small, and even when the resist swelled part is removed, dust generation from the removed part can be suppressed. .

  When a resist film for electron beam drawing is formed as the resist film, a conductive material (for example, chromium) is used to prevent charge-up in the mask pattern drawing process during mask manufacturing, for example, as shown in FIG. In some cases, the light-shielding film 2 is formed up to a chamfered surface 12 a continuous with the main surface 11 a of the substrate 1. Even in this case, since the flatness of the chamfered surface 12a is good, the variation in the film adhesion force of the light-shielding film 2 on the chamfered surface is reduced. As a result, the film is taken in and out of the storage case and transported the mask blank. Dust generation due to peeling or the like can be suppressed, and the present invention is suitable.

The photomask of the present invention forms a transfer pattern by patterning the thin film of the photomask blank. According to the photomask of the present invention, since the in-plane film thickness uniformity of the resist film formed on the photomask blank is good, a photomask in which a fine pattern is formed with high pattern accuracy can be obtained.
Here, as an example, a photomask manufacturing method using the photomask blank 10 shown in FIG. 3 will be described. The photomask blank 10 shown in FIG. 3 has a light-shielding film 2 on the substrate 1.

FIG. 4 is a cross-sectional view sequentially illustrating a photomask manufacturing process using the photomask blank 10.
FIG. 4A shows a state in which a resist film 3 is formed on the light-shielding film 2 of the photomask blank 10 of FIG. As described above, in the photomask blank 10 of the present invention, since the flatness of the chamfered surface of the end face of the substrate 1 is 50 μm or less, when the resist film is applied and formed by spin coating, the substrate 1 main Variations in the film thickness of the resist film in the vicinity of the outer periphery of the surface are small, and the in-plane film thickness uniformity of the resist film is good. As the resist material, either a positive resist material or a negative resist material can be used.

Next, FIG. 4B shows a step of performing desired pattern exposure (pattern drawing) on the resist film 3 formed on the photomask blank 10. Pattern exposure is performed using an electron beam drawing apparatus or the like.
Next, FIG. 4C shows a process of developing the resist film 3 according to desired pattern exposure to form a resist pattern 3a. In this step, the resist film 3 formed on the photomask blank 10 is subjected to a desired pattern exposure, and then a developing solution is supplied to dissolve a portion of the resist film that is soluble in the developing solution. Form.

Next, FIG. 4D shows a step of etching the light-shielding film 2 along the resist pattern 3a. In the etching step, the resist pattern 3a is used as a mask to remove a portion where the light-shielding film 2 where the resist pattern 3a is not formed is exposed, and thereby a desired light-shielding film pattern 2a (mask pattern) is formed on the substrate 1. To form.
FIG. 4E shows a photomask 20 obtained by peeling and removing the remaining resist pattern 3a. Thus, according to the present invention, a photomask having a fine pattern formed with high pattern accuracy is completed.

Hereinafter, embodiments of the present invention will be described more specifically with reference to examples. In addition, a comparative example for the embodiment will also be described.
Example 1
The synthetic quartz glass substrate (approx. 152mm x approx. 152mm x approx. 6.5mm) is chamfered and ground, and the glass substrate that has been subjected to rough polishing is set in a double-side polishing machine, and the main surface of the substrate is precisely polished. Went. Further, the end surface of the substrate was also precisely polished as follows.
While supplying the polishing liquid containing the abrasive grains, the polishing brush provided with polishing brush bristles and the substrate were moved relatively to polish the end face of the substrate. Specifically, the polishing apparatus described in Japanese Patent No. 2585727 was used to polish the end face of the substrate so that the brush hairs were in uniform contact with the end face of the glass substrate and pressure was applied. In order to manage the amount of the brush pushed into the end face of the substrate, a servo motor was attached to the polishing brush and the pressure was automatically adjusted.

  The surface roughness of the main surface of the glass substrate thus obtained was 0.2 nm in terms of arithmetic average surface roughness (Ra), the flatness was 0.5 μm, and the shape of the main surface was finished to a convex shape. Moreover, the surface roughness of the chamfered surfaces (the above-mentioned 12a and 12b) of the glass substrate is 2 nm in terms of arithmetic average surface roughness (Ra), the flatness is 50 μm, and the shape of the chamfered surface is a convex shape. It was finished. In addition, the flatness of the main surface was measured with a flatness measuring machine (manufactured by Tropel) in a rectangular area of 142 mm × 142 mm. Further, the flatness of the chamfered surface is a region excluding 5 mm width at both ends in the longitudinal direction using a substrate shape inspection apparatus (manufactured by OG Corporation: Smart Scope Zip250S), and the height of the approximate center along the longitudinal direction. Information was measured and calculated based on the height information.

  Next, on the glass substrate (152 mm × 152 mm × 6.5 mm) whose main surface and end surface are finished by precision polishing as described above, an inline sputtering apparatus is used, a chromium target is used as a sputtering target, and argon gas is used. A chromium light-shielding layer was formed by performing reactive sputtering in an atmosphere. Subsequently, an antireflection layer was formed by performing reactive sputtering in a mixed gas atmosphere of argon and nitric oxide (Ar: 90% by volume, NO: 10% by volume). In this manner, a light-shielding film composed of a light-shielding layer having a total thickness of 70 nm and an antireflection layer was formed on the substrate to obtain a photomask blank. The light-shielding film composed of the light-shielding layer and the antireflection layer was formed so as to cover the main surface of the substrate and the chamfered surface continuous with the main surface.

  Next, an electron beam resist film (CAR-FEP171 manufactured by Fuji Film Electronics Materials), which is a chemically amplified resist, was formed on the photomask blank. The resist film was formed by spin coating using a spinner (rotary coating apparatus). Note that after the resist film was applied, a pre-bake treatment at 130 ° C. was performed. And the film thickness of the resist film was measured using a spectral reflection type film thickness meter (manufactured by Nanometrics Japan Co., Ltd .: AFT6100M) at a plurality of points evenly arranged over the entire area of 145 mm × 145 mm square in the center of the substrate. Overall, the film thickness variation “(maximum value of film thickness) − (minimum value of film thickness)” was as small as 50 mm or less, and the film thickness variation of the resist film in the vicinity of the outer periphery of the main surface of the substrate was also small.

The photomask blank with a resist film manufactured in this way was stored in a storage case made of polymethylmethacrylate in a clean room.
Next, a vibration test of a storage case storing the photomask blank with a resist film was performed. The vibration test in this case was conducted in accordance with MIL-STD-810F of the US military standard MIL (Military Specifications and Military Standards) and assuming a moving environment in a clean room.
After the vibration test, the storage case was opened in a clean room, and the number of defects due to adhering foreign matter on the main surface was measured using a defect inspection apparatus M3320 (manufactured by Lasertec Corporation) for the taken out photomask blank. The evaluation was performed by measuring the number of defects before the vibration test in advance and increasing the number of defects after the vibration test, but no increase was observed. Further, the number of particles in the storage case before the vibration test was measured, and the number of particles in the storage case after the vibration test was measured, but no particular increase was observed.

Next, using the photomask blank, a photomask was produced according to the process shown in FIG. First, a desired pattern was drawn on the resist film formed on the photomask blank using an electron beam drawing apparatus, and then developed with a predetermined developer to form a resist pattern (FIG. 4C). )reference).
Next, along the resist pattern, the light-shielding film composed of the light-shielding layer and the antireflection layer was dry-etched to form a light-shielding film pattern (see FIG. 4D). Here, a mixed gas of Cl ₂ and O ₂ (Cl ₂ : O ₂ = 4: 1) was used as the dry etching gas.
Next, the remaining resist pattern was peeled off to obtain a photomask (see FIG. 5E).

  The obtained photomask had small in-plane variation of the resist film formed on the photomask blank due to good flatness of the chamfered surface of the substrate end surface (the in-plane film thickness uniformity was good) Therefore, the CD loss (CD error) (deviation of the measured line width with respect to the design line width) of the formed light-shielding film pattern was as small as 20 nm, and the pattern accuracy of the light-shielding film pattern was good.

(Example 2)
In precision polishing of the end face of the glass substrate in Example 1, the amount of oscillation of the polishing brush relative to the substrate and the number of rotations of the rotary table for rotating the substrate were optimized, and a glass substrate was produced in the same manner as in Example 1.
The surface roughness of the main surface of the obtained glass substrate was 0.2 nm in terms of arithmetic average surface roughness (Ra), the flatness was 0.5 μm, and the shape of the main surface was finished in a convex shape. Further, the surface roughness of the chamfered surfaces (the above-mentioned 12a and 12b) of the glass substrate end surface is 0.2 nm in arithmetic average surface roughness (Ra), the flatness is 30 μm, and the shape of the chamfered surface is convex. It was finished in shape. These measurements were performed in the same manner as in Example 1.

Next, a light-shielding film composed of the same light-shielding layer and antireflection layer as in Example 1 was formed on the glass substrate to produce a photomask blank.
Next, the same resist film as in Example 1 was formed on this photomask blank by a spin coat method. Then, the film thickness variation of the resist film was measured, but the film thickness variation was small overall, and the film thickness variation of the resist film in the vicinity of the outer periphery of the main surface of the substrate was also small.

The photomask blank with a resist film manufactured as described above was stored in a storage case in the same manner as in Example 1, and a vibration test was performed. After the vibration test, the storage case was opened in a clean room, and the taken out photomask blank was measured for the number of defects due to adhering foreign matter on the main surface using a defect inspection apparatus M3320 (manufactured by Lasertec Corporation). No increase in the number of defects after the vibration test with respect to the number of defects was observed. Further, the number of particles in the storage case after the vibration test with respect to the number of particles in the storage case before the vibration test was not particularly increased.

Next, using the photomask blank, a photomask was produced according to the above-described process of FIG.
The obtained photomask had small in-plane variation of the resist film formed on the photomask blank due to good flatness of the chamfered surface of the substrate end surface (the in-plane film thickness uniformity was good) Therefore, the CD loss (CD error) (deviation of the measured line width with respect to the design line width) of the formed light-shielding film pattern was as small as 20 nm, and the pattern accuracy of the light-shielding film pattern was good.

(Comparative example)
In the precision polishing of the end face of the glass substrate in the first embodiment, the setting of the swing amount of the polishing brush with respect to the substrate and the rotation number of the rotary table for rotating the substrate is changed. Otherwise, the glass substrate is the same as in the first embodiment. Was made.
The surface roughness of the main surface of the obtained glass substrate was 0.2 nm in terms of arithmetic average surface roughness (Ra), the flatness was 0.5 μm, and the shape of the main surface was finished in a convex shape. Further, the surface roughness of the chamfered surfaces (the above-mentioned 12a and 12b) of the glass substrate end surface is 2 nm in terms of arithmetic average surface roughness (Ra), the flatness is 70 μm, and the shape of the chamfered surface is a convex shape. It was finished. These measurements were performed in the same manner as in Example 1.

Next, a light-shielding film composed of the same light-shielding layer and antireflection layer as in Example 1 was formed on the glass substrate to produce a photomask blank.
Next, the same resist film as in Example 1 was formed on this photomask blank by a spin coat method. The film thickness variation of the resist film was measured, and the film thickness variation of the resist film was particularly large near the outer periphery of the main surface of the substrate.

  The photomask blank with a resist film manufactured as described above was stored in a storage case in the same manner as in Example 1, and a vibration test was performed. After the vibration test, the storage case was opened in a clean room, and the taken out photomask blank was measured for the number of defects due to adhering foreign matter on the main surface using a defect inspection apparatus M3320 (manufactured by Lasertec Corporation). An increase in the number of defects after the vibration test with respect to the number of defects was observed. An increase was also observed in the number of particles in the storage case after the vibration test relative to the number of particles in the storage case before the vibration test. These are due to the generation of dust due to variations in the film thickness of the resist film and variations in the film adhesion of the light-shielding film on the chamfered surface, which are caused by the large flatness value of the chamfered surface of the substrate. Considered due to dust.

Next, using the photomask blank, a photomask was produced according to the above-described process of FIG.
The obtained photomask had a large in-plane variation of the resist film formed on the photomask blank because the flatness of the chamfered surface of the substrate end face was not as good as 70 μm (good in-plane film thickness uniformity) Therefore, the CD loss (CD error) of the formed light-shielding film pattern (deviation of the measured line width with respect to the design line width) is as large as 50 nm, and the pattern accuracy of the light-shielding film pattern is higher than that of the example. It was bad.

DESCRIPTION OF SYMBOLS 1 Translucent substrate 2 Light-shielding film 3 Resist film 10 Photomask blank 11a, 11b Main surface 12 End surface 12a, 12b Chamfered surface 12c Side surface 13, 14 Measurement point 20 Photomask

Claims (16)

A mask blank having a thin film for forming a transfer pattern on a substrate,
The substrate has a main surface and an end surface formed at a peripheral edge of the main surface, and the end surface includes a side surface of the substrate and a chamfered surface interposed between the side surface and the main surface,
The chamfered surface has a convex shape in which the height of the chamfered surface gradually decreases from the central region toward the peripheral edge in the region of the chamfered surface excluding the chamfered portion of the rounded corner of the substrate,
The flatness of the chamfered surface continuous with at least the main surface on which the thin film is formed among the chamfered surfaces is 50 μm or less,
The flatness is a difference between the maximum height and the minimum height of the surface shape in the chamfered surface from the reference surface arbitrarily provided on the surface side of the chamfered surface of the substrate,
The flatness measurement region is a region excluding a width of 5 mm from both ends in the longitudinal direction of the chamfered surface,
A mask blank, wherein a thin film is formed on a chamfered surface continuous with a main surface on which the thin film is formed. The thin film is an absorber film that absorbs exposure light;
The mask blank according to claim 1, wherein the mask blank is for a reflective mask.   The surface roughness of the chamfered surface continuous with at least the main surface on which the thin film is formed among the chamfered surfaces is 2 nm or less in terms of arithmetic average surface roughness (Ra). Mask blank. The mask blank according to any one of claims 1 to 3 , wherein the main surface has a convex shape. The flatness is obtained by setting a plurality of measurement points along the longitudinal direction at the approximate center of the measurement region and measuring height information from the reference plane at each measurement point. The mask blank according to any one of claims 1 to 4 , characterized in that: The flatness is obtained by setting measurement points along a plurality of dividing lines that are cut in a direction substantially perpendicular to the longitudinal direction of the measurement region, and measuring height information from the reference plane at each measurement point. mask blank according to any one of claims 1 to 4, characterized in that the obtained those. Mask blank according to any one of claims 1 to 6, wherein a resist film on the thin film. Mask, characterized in that by forming a transfer pattern on the thin film of the mask blank according to any one of claims 1 to 7. A method of manufacturing a mask blank having a thin film for forming a transfer pattern on a substrate,
The substrate has a main surface and an end surface formed at a peripheral edge of the main surface, and the end surface includes a side surface of the substrate and a chamfered surface interposed between the side surface and the main surface,
The chamfered surface has a convex shape in which the height of the chamfered surface gradually decreases from the central region toward the peripheral edge in the region of the chamfered surface excluding the chamfered portion of the rounded corner of the substrate,
The flatness of the chamfered surface continuous with at least the main surface on which the thin film is formed among the chamfered surfaces is 50 μm or less,
The flatness is a difference between the maximum height and the minimum height of the surface shape in the chamfered surface from the reference surface arbitrarily provided on the surface side of the chamfered surface of the substrate,
The flatness measurement region is a region excluding a width of 5 mm from both ends in the longitudinal direction of the chamfered surface,
A method of manufacturing a mask blank, comprising forming a thin film on a chamfered surface continuous with a main surface on which the thin film is formed. The thin film is an absorber film that absorbs exposure light;
The mask blank manufacturing method according to claim 9 , wherein the mask blank is for a reflective mask. Surface roughness of the chamfered surface continuous with the major surface for forming at least the thin film of the chamfered surface, according to claim 9 or 10, characterized in that it is 2nm or less in terms of arithmetic average surface roughness (Ra) Mask blank manufacturing method. The main shape of the surface, a manufacturing method of a mask blank according to any one of claims 9 to 11, characterized in that the convex shape. The flatness of the approximate center of the measurement area along the longitudinal direction to set a plurality of measurement points, according to claim 9 to 12, characterized in that to measure the height information from the reference surface at each measurement point The manufacturing method of the mask blank as described in any one of these. The flatness is obtained by setting measurement points along a plurality of dividing lines cut in a direction substantially orthogonal to the longitudinal direction of the measurement region and measuring height information from the reference plane at each measurement point. A method for manufacturing a mask blank according to any one of claims 9 to 12 . The substrate is polished by supplying a polishing liquid containing abrasive grains while relatively moving the polishing brush provided with polishing bristles and the substrate, and polishing the end surface of the substrate. Item 15. A method for producing a mask blank according to any one of Items 9 to 14 . Method for producing a mask blank according to any one of claims 9 to 15, wherein a resist film on the thin film.

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