JP2005066781A - Manufacturing method for glass substrate for electronic device, manufacturing method for mask blank, and manufacturing method for transfer mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide manufacturing methods for a glass substrate for an electronic device and a mask blank with which no fine uneven surface defect occurs on a substrate surface or a failure rate is low, and a manufacturing method for a transfer mask free from a phase defect or a pattern defect caused by the fine uneven surface defect on the substrate surface. <P>SOLUTION: The glass substrate for an electronic device is manufactured by pushing polishing surface plates 5 and 6 with a polishing pad 7 glued against the glass substrate and relatively moving the plates 5 and 6 and the glass substrate while feeding a polishing fluid containing colloidal silica abrasive grains thereby precision-polishing the substrate surface. The polishing pad 7 used in precision-polishing has a base material and a nap layer having a fine aperture on the surface with a thickness of 700 μm or more. Hardness of the pad (Asker-C) is 65 or less. A mask blank and a transfer mask are manufactured by using the glass substrate thus manufactured. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a glass substrate for electronic devices having no minute surface defects on the substrate surface, a method for producing mask blanks using the substrate, and a method for producing a transfer mask.

Due to the recent increase in density and accuracy of VLSI devices, the demands for flatness and surface defects of glass substrates for electronic devices such as glass substrates for mask blanks are becoming stricter year by year. Here, as a precision polishing method for reducing the surface roughness of a conventional glass substrate for mask blanks, for example, there is one described in Patent Document 1 (Japanese Patent Laid-Open No. 64-40267). In this precision polishing method, polishing is performed using an abrasive mainly composed of cerium oxide, and then finish polishing is performed using colloidal silica.
According to the above publication, as the polishing pad to be used, a nonwoven fabric as a base fabric impregnated with polyurethane resin and foamed can be used, and in the examples, an example using a suede type polishing pad is used. Is described.
In addition, as a suede type polishing pad, as disclosed in the following Patent Document 2 (Japanese Patent Laid-Open No. 2002-59356), a nap layer is used to suppress the occurrence of minute scratches and latent scratches when mirror polishing a semiconductor wafer. A polishing pad having a thickness of 520 μm and 570 μm is disclosed.
JP-A 64-40267 JP 2002-59356 A

According to the study of the present inventor, it has been found that even if the technique described in the above-mentioned prior art document is used, it does not satisfy a high level condition for a surface defect that has been required in recent years. That is, on the surface of the glass substrate obtained by the polishing method listed in the prior art, a convex protrusion having a height of about 2 nm to 7 nm and a size of about several tens of nm to 2000 nm, and a depth of several nm to 200 nm. It was found that a concave defect having a size of about several tens of nm to 500 nm was formed. This is a small-sized convex protrusion or concave defect that cannot be confirmed by conventional visual inspection, and was developed to confirm the above-mentioned demand for surface defect-free high level that has recently been required. It was confirmed for the first time by the inspection device.
For example, when a thin film is formed on this convex protrusion and a mask blank and a transfer mask are produced, the size of the convex protrusion is enlarged, so that 0.3 μm required as a next-generation substrate is required. Even if it is satisfied that there is no defect of the above, further that there is no defect of 0.1 μm or more, and that there is no defect of 0.05 μm or more, and mask blanks produced using this substrate, and transfer When a defect inspection of a mask is performed, there may be a problem.

In addition, when a phase shift mask blank and a phase shift mask are produced using a glass substrate on which convex protrusions having a height of about several nanometers are formed, as the wavelength of the exposure light becomes shorter, the convex shape The change in phase difference due to the projection becomes large (when the height of the convex projection is 5 nm, when the exposure light is ArF excimer laser (exposure wavelength: 193 nm), the phase angle change is 4.6 degrees, and the F2 excimer laser (exposure wavelength: exposure wavelength: At 157 nm), the phase angle change is 5.7 degrees), which is a problem that cannot be ignored.
In addition, when a reflective mask blank and a reflective mask are produced using a glass substrate on which convex projections of about several nm are formed, if convex projections exist in the vicinity of the mask surface pattern, Changes in phase due to the convex protrusions. This change in phase causes the positional accuracy and contrast of the transferred pattern to deteriorate. In particular, when short-wavelength light such as extreme ultraviolet (Extreme Ultra Violet, EUV) light having a wavelength of about 0.2 to 100 nm is used as exposure light, the phase change is very large with respect to fine irregularities on the mask surface. Since it becomes sensitive, the influence on the transferred image is increased. For example, when the height of the convex protrusion is 5 nm, the exposure wavelength is 13.5 nm and the phase change exceeds 20 degrees. As a result, the CD error is poor and cannot be ignored.
Similarly, a concave defect causes a phase defect or a pattern defect in a phase shift mask or a reflective mask.

The present invention has been made in view of the above-mentioned problems, and manufacturing of glass blanks for electronic devices and mask blanks, in which minute convex or concave surface defects do not occur on the glass substrate surface or the incidence is low. The primary purpose is to provide a method.
A second object of the present invention is to provide a method for producing a transfer mask free from phase defects and pattern defects caused by minute convex and concave surface defects on the glass substrate surface.

The present inventor has examined why convex or concave surface defects are formed when polishing is performed using a polishing liquid and a polishing pad containing conventional polishing abrasive grains. As a result of many experiments and considerations, convex surface defects have a processing condition (polishing rate) on the substrate immediately before the completion of precision polishing, and concave surface defects have a processing pressure on the glass substrate in precision polishing. It was found that this was largely due to the occurrence of surface defects.
In order to solve the above-described problems, the present inventor has conducted further studies based on the obtained knowledge, and as a result, has completed the invention having the following configuration.

(Configuration 1) A glass substrate for an electronic device is pressed against a polishing surface plate to which a polishing pad is adhered, and the polishing surface plate and the glass substrate are relatively moved while supplying a polishing liquid containing polishing abrasive grains. A method of manufacturing a glass substrate for an electronic device comprising a step of precisely polishing the surface of the substrate, wherein the polishing pad has a nap layer having a fine opening on the surface, and the thickness of the nap layer is 700 μm. It is the above, The manufacturing method of the glass substrate for electronic devices characterized by the above-mentioned.
(Structure 2) The glass substrate for electronic devices is pressed on the polishing surface plate to which the polishing pad is adhered, and the polishing surface plate and the glass substrate are relatively moved while supplying the polishing liquid containing the abrasive grains. A method for producing a glass substrate for an electronic device, comprising the step of precisely polishing the surface of the substrate, wherein the polishing pad has a nap layer having a fine opening on the surface, and the hardness of the polishing pad (Asker− C) is 65 or less, The manufacturing method of the glass substrate for electronic devices characterized by the above-mentioned.

(Structure 3) The method for producing a glass substrate for an electronic device according to Structure 1 or 2, wherein an opening diameter of the nap layer surface of the polishing pad is 10 to 70 μm.
(Structure 4) Structure 1 is characterized in that the carbon content contained in the nap layer is adjusted so that the fine pad surface defect and / or the fine concave surface defect does not occur in the polishing pad. The manufacturing method of the glass substrate for electronic devices in any one of thru | or 3.
(Structure 5) The method for producing a glass substrate for an electronic device according to any one of Structures 1 to 4, wherein the substrate is a glass substrate for mask blanks.

(Structure 6) On the main surface of the glass substrate for electronic devices obtained by the method for manufacturing a glass substrate for electronic devices according to any one of Structures 1 to 5, a thin film that causes an optical change with respect to exposure light is formed. A method for manufacturing a mask blank, characterized in that:
(Structure 7) A method for producing a transfer mask, wherein the thin film in the mask blank obtained by the method for producing a mask blank described in Structure 6 is patterned to form a thin film pattern on the main surface of the glass substrate. .

According to the present invention, by setting the thickness of the nap layer of the polishing pad used for precision polishing of the glass substrate surface to 700 μm or more, the polishing rate for the substrate immediately before the completion of precision polishing can be reduced, and the processing pressure in precision polishing can be reduced. Since the size can be reduced, the occurrence of minute convex and concave surface defects on the surface of the glass substrate can be suppressed.
Further, according to the present invention, by setting the hardness (Asker-C) of the polishing pad used for precision polishing of the glass substrate surface to 65 or less, the polishing rate for the substrate immediately before the completion of precision polishing can be reduced, and in precision polishing. Since the processing pressure can be reduced, the occurrence of minute convex and concave surface defects on the glass substrate surface can be suppressed.
In addition, by setting the opening diameter of the nap layer surface to 10 to 70 μm, the abrasive grains at the time of precision polishing flow uniformly on the polishing pad surface, and further improve the uniformity of the processing pressure on the glass substrate. It is effective in suppressing the occurrence of minute convex and concave surface defects on the glass substrate surface.
In addition, the polishing pad has a thickness of the nap layer by adjusting a carbon content contained in the nap layer so as not to generate a minute convex surface defect and / or a minute concave surface defect. (700 μm or more) and the hardness of the polishing pad (65 (Asker-C) or less) can be satisfied, and the effect of suppressing the occurrence of minute convex and concave surface defects on the glass substrate is tremendous. is there.

Further, the present invention is suitable for manufacturing a mask blank glass substrate, and particularly suitable for manufacturing a phase shift mask blank glass substrate or a reflective mask blank glass substrate. A change in phase difference caused by a defect can be suppressed, and a phase defect on the surface of the multilayer reflective film formed thereon can be suppressed by a minute surface defect.
Moreover, according to the manufacturing method of the mask blank of this invention, on the glass substrate by forming the thin film which brings an optical change with respect to exposure light on the main surface of the glass substrate for electronic devices manufactured by this invention. Mask blank defects (subfilm defects) due to the formed fine convex and concave surface defects can be prevented.
Moreover, according to the manufacturing method of the transfer mask of the present invention, the thin film in the mask blank obtained by the present invention is patterned to form a thin film pattern on the main surface of the glass substrate for electronic devices, thereby forming a microscopic surface on the substrate surface. As a result, a transfer mask free from pattern defects of a thin film pattern caused by uneven surface and concave surface defects can be obtained.

Hereinafter, the manufacturing method of the glass substrate for electronic devices, the manufacturing method of mask blanks, and the manufacturing method of a transfer mask concerning the best embodiment for implementing this invention are demonstrated in detail.
In the following description, a minute convex surface defect refers to a convex protrusion whose main component includes Si and O, the height is about 2 nm to 7 nm, and the size is several tens of nm. It is about ˜2000 nm. A minute concave surface defect has a depth of about several nm to 200 nm and a size of about several tens of nm to 500 nm.
The manufacturing method of the glass substrate for electronic devices according to the embodiment of the present invention is characterized in that the thickness of the nap layer of the polishing pad used in the precision polishing step is set to 700 μm or more, as in Configuration 1. Further, as described in Structure 2, the hardness (Asker-C) of the polishing pad used in the precision polishing step is set to 65 or less.
According to the inventor's investigation, convex surface defects are caused by processing conditions (polishing rate) on the substrate immediately before the completion of precision polishing, and concave surface defects are caused by processing pressure on the glass substrate in precision polishing. It turned out to be largely attributed to.

According to the inventor's consideration, the following may be considered as a mechanism for forming convex surface defects.
During the precision polishing process, the polishing abrasive grains contained in the polishing liquid form a single abrasive body or agglomerates and roll on the surface of the glass substrate to perform the polishing process. When the aggregate of abrasive grains remains on the surface of the glass substrate immediately before the relative movement of the substrate is stopped, the residue prevents the polishing of only that portion, resulting in a minute convex surface defect. . If the polishing rate immediately before the end of precision polishing is high, the height of the convex surface defects increases. Therefore, the occurrence of convex surface defects can be suppressed when the polishing rate immediately before the end of precision polishing is low (slow). In general, when the processing pressure is constant, the polishing rate decreases as the thickness of the nap layer of the polishing pad increases (it can be said that the length increases) and as the hardness of the nap layer decreases.

Further, the mechanism for forming the concave surface defects is considered as follows.
Precise polishing of aggregates of abrasive grains contained in the polishing liquid, falling off of the polishing pad or carrier coming into contact with the gear of the polishing apparatus, and falling off of abrasive abrasive grains due to deposits on the polishing apparatus It is thought that it becomes a minute concave surface defect. Therefore, generation of concave surface defects can be suppressed when the processing pressure on the substrate in precision polishing is smaller. In general, when the load from the polishing body is constant, the processing pressure on the substrate decreases as the thickness of the nap layer of the polishing pad increases (it can be said that the length increases) and as the hardness of the nap layer decreases. Become.

In consideration of the above points, when used as a glass substrate for electronic devices, in order to prevent the occurrence of convex surface defects that become phase defects and concave surface defects that become phase defects or pattern defects, The thickness of the nap layer of the pad is 700 μm or more and / or the hardness (Asker-C) of the polishing pad is 65 or less.
The thickness of the nap layer of the polishing pad is particularly preferably in the range of 700 μm to 1000 μm. When the thickness of the nap layer exceeds 1000 μm, the polishing rate decreases and the processing time increases, the sinking of the polishing pad increases at the outer peripheral portion of the glass substrate, and the edge of the glass substrate increases and the edge sag increases. Since the shape of the part deteriorates, it is not preferable.
Further, the hardness (Asker-C) of the nap layer of the polishing pad is preferably 60 or less, particularly preferably in the range of 40-60. When the hardness of the polishing pad is less than 40, it is difficult to manufacture a polishing pad of such hardness itself, the polishing speed is reduced and the processing time is increased, and the polishing pad sinks in the outer peripheral portion of the glass substrate. This is not preferable because the shape of the edge of the glass substrate deteriorates. In the present invention, the hardness of the polishing pad (Asker-C) is defined in SRIS0101 (Japan Rubber Association Standard), and a polishing pad (one piece) is used as a sample, and the polishing pad is an Asker-C hardness meter (load). 1 kg).

A polishing pad having a substrate and a nap layer having a fine opening on the surface is generally produced by a wet coagulation method using a urethane resin composition. In this wet coagulation method, after preparing a urethane resin composition, this urethane resin composition is applied to a substrate, and then a dispersion stabilizer such as a surfactant and a wet coagulation aid are added to water and dimethylformamide. A wet coagulation treatment is performed in the added mixed solution to form a foamed layer on the base material, followed by drying and buffing the outermost surface.
The polishing pad having the predetermined nap layer thickness and / or the polishing pad having the predetermined hardness can be obtained by adjusting the urethane resin composition, additives, wet coagulation treatment conditions, and the like.
Further, the opening diameter on the surface of the nap layer is preferably smaller from the viewpoint of uniformly flowing abrasive grains on the surface of the polishing pad during precision polishing and further improving the uniformity of processing pressure on the glass substrate. Therefore, as in the configuration 3, the opening diameter on the surface of the nap layer is preferably 10 to 70 μm. When the opening diameter exceeds 70 μm, the polishing rate increases, and it becomes difficult to control the processing pressure immediately before the end of precision polishing, which causes the generation of minute convex surface defects. When the opening diameter is less than 10 μm, clogging occurs. In any case, the polishing rate is remarkably lowered, which is not preferable. A preferable opening diameter on the surface of the nap layer is 10 to 50 μm. The opening diameter on the surface of the nap layer can be adjusted by the buff processing conditions in the manufacturing process of the polishing pad described above.

Further, in order to prevent the occurrence of convex surface defects in the surface defects described above, the processing pressure on the substrate in precision polishing is divided into, for example, a plurality of stages, and precision polishing is completed (polishing surface plate and glass substrate). It is preferable that the processing pressure on the substrate immediately before is 100 g / cm ² or less. Further, by reducing the processing pressure on the substrate immediately before the end of precision polishing, there is an advantage that edge sagging due to sinking of the polishing pad in the outer peripheral portion of the glass substrate is reduced and flatness is improved. In the embodiment of the present invention, it is preferably 50 g / cm ² or less, particularly preferably 25 g / cm ² or less, and further preferably 10 g / cm ² or less.
The polishing time at the above processing pressure is preferably 90 seconds or more, particularly preferably 120 seconds or more, and further preferably 180 seconds or more. However, in consideration of productivity, it is desirable that it is 360 seconds or less.

Moreover, the abrasive grains in the present invention are preferably colloidal silica from the viewpoint of obtaining good smoothness and flatness of the glass substrate. However, the polishing liquid containing colloidal silica abrasive grains is usually made into an alkaline polishing liquid by adding an inorganic alkali such as NaOH or KOH or an organic alkali such as amine from the viewpoint of stability. Therefore, the viscosity of the polishing liquid is higher than that of the polishing liquid to which no alkali is added, so the probability that colloidal silica agglomerates will adhere to certain locations on the glass substrate during precision polishing is increased, resulting in convex surface defects. There is a risk that the occurrence rate will increase. Therefore, in order to suppress the occurrence of convex surface defects from such a viewpoint, it is preferable to use a polishing liquid having a low viscosity. As a method for producing a low-viscosity polishing liquid containing colloidal silica abrasive grains, for example, colloidal silica that can be used in a neutral region not containing alkali is preferable. Colloidal silica in the neutral range is obtained by hydrolyzing an organosilicon compound that can be purified by distillation, and it is possible to obtain high-purity colloidal silica in the neutral range and with few alkali metals such as Na and K. is there.
In the above embodiment, the material of the glass substrate is not particularly limited. Examples of the material of the glass substrate include synthetic quartz glass, borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, soda lime glass, alkali-free glass, and crystallized glass.
Further, the precision polishing in the above embodiments may be either double-side polishing or single-side polishing.

Further, as in Configuration 5, the glass substrate for electronic devices is, for example, a glass substrate for mask blanks. In this case, photomask blanks, phase shift mask blanks, reflective mask blanks and the like are listed as mask blanks. LSI (semiconductor integrated circuit) mask blanks, LCD (liquid crystal display) mask blanks and the like are used as mask blanks. Can be mentioned.
Further, the substrate according to Configuration 5 is preferably a glass substrate for phase shift mask blanks or a glass substrate for reflection mask blanks. As described above, the method for manufacturing a glass substrate for an electronic device according to an embodiment of the present invention can suppress a change in phase difference caused by a minute convex or concave surface defect, a minute convex or concave shape. Since the surface defects can suppress phase defects and the like on the surface of the multilayer reflective film formed thereon, the glass substrate for phase shift mask blanks and the glass substrate for reflective mask blanks are particularly effective.

Further, as in Configuration 6, a thin film that causes an optical change with respect to exposure light is formed on the main surface of the glass substrate for electronic devices manufactured by the method for manufacturing a glass substrate for electronic devices according to Configurations 1 to 5. By the mask blank manufacturing method characterized by this, it is possible to prevent a mask blank defect (subfilm defect) due to minute convex and concave surface defects formed on the glass substrate.
Here, the thin film that optically changes the exposure light means a phase shift film (including a multilayer) that changes the phase of the exposure light, a light shielding film (including a multilayer) that blocks the exposure light, or A film in which a phase shift film and a light shielding film are laminated, a halftone film having a phase shift function and a light shielding function (including a case of multilayers), a reflective film that reflects exposure light, an absorber film that absorbs exposure light, etc. Point to. Therefore, the mask blank referred to in the present invention is used in a broad sense, in addition to a photomask blank in which only a light-shielding film is formed, a phase shift mask blank in which a phase shift film, a halftone film, etc. are formed, and a reflection film. A reflective mask blank on which an absorber film or the like is formed is included.
In the mask blank referred to in the present invention, a resist film or the like may be formed on the thin film in addition to the above-described thin film.

  Further, as in Configuration 7, the thin film pattern in the mask blank obtained by the mask blank manufacturing method according to Configuration 6 is patterned to form a thin film pattern on the main surface of the glass substrate for electronic devices. According to the transfer mask manufacturing method, a transfer mask free from pattern defects or phase defects of a thin film pattern caused by minute convex and concave surface defects on the substrate surface can be obtained. The thin film pattern can be formed by preparing a mask blank with a resist film, forming a resist pattern by a photolithography process, and etching the thin film using the resist pattern as a mask.

Hereinafter, based on an Example, this invention is demonstrated more concretely. In the following examples, a glass substrate for phase shift mask blanks and a glass substrate for EUV reflective mask blanks (hereinafter simply referred to as glass substrates) will be described as examples of glass substrates for electronic devices.
First, a planetary gear type double-side polishing apparatus used for precision polishing in the following embodiments will be described with reference to FIG.
The planetary gear type double-side polishing apparatus is engaged with the sun gear 2, the internal gear 3 arranged concentrically on the outer side, the sun gear 2 and the internal gear 3, and the sun gear 2 and the internal gear 3. The carrier 4 that revolves and rotates according to the rotation, the upper surface plate 5 and the lower surface plate 6 that can hold the workpiece 1 held by the carrier 4 to which the polishing pad 7 is attached, and the upper surface plate 5. And a lower surface plate 6 are provided with a polishing liquid supply unit (not shown) for supplying a polishing liquid.
At the time of precision polishing, the workpiece 1 held by the carrier 4 is sandwiched between the upper surface plate 5 and the lower surface plate 6, and between the polishing pad 7 of the upper and lower surface plates 5, 6 and the workpiece 1 to be polished. While supplying the polishing liquid, the upper and lower surfaces of the workpiece 1 are precisely polished while the carrier 4 revolves and rotates according to the rotation of the sun gear 2 and the internal gear 3.

This example is a specific example of the method for manufacturing the glass substrate for electronic devices according to the embodiment.
A synthetic quartz glass substrate (152 mm × 152 mm) end face is chamfered and ground, and further, the glass substrate that has been subjected to rough polishing with a polishing liquid containing cerium oxide abrasive grains is set on the carrier of the above-described double-side polishing apparatus, Precision polishing was performed under the following polishing conditions.
Polishing pad: Suede type (manufactured by wet coagulation method using urethane resin composition, nap layer thickness: 760 μm, polishing pad hardness (Asker-C): 56, nap layer surface opening diameter: 10 ~ 50μm)
Polishing liquid: Alkaline aqueous solution containing colloidal silica abrasive grains (average particle diameter 100 nm) Processing pressure: 50 to 100 g / cm ²
Processing time: 60 min
At the start of precision polishing, the processing pressure was set to 100 g / cm ^2, and this was reduced stepwise, and was set to 50 g / cm ² for 300 seconds before the end.
After the precision polishing was completed, in order to remove the abrasive grains adhering to the glass substrate, the glass substrate was immersed in a cleaning tank containing a cleaning solution containing a dilute hydrofluoric acid solution (applied with ultrasonic waves) for cleaning.
A plurality of batches of the above-described precision polishing were performed to prepare 100 glass substrates (glass substrates for phase shift mask blanks) subjected to the precision polishing.

The surface roughness of the main surface of the obtained glass substrate was as good as 0.15 nm or less in terms of root mean square roughness (RMS).
Further, the main surface of the obtained glass substrate is formed with a minute convex surface defect having a height of about several nm (about 2 nm to 7 nm) and a depth of about 10 using a defect inspection apparatus using a laser interference confocal optical system. When a minute concave surface defect of ˜50 nm was examined, it was confirmed on one glass substrate out of 100. That is, the incidence of minute surface defects was 1%.

In Example 1 described above, Example 1 and Example 1 were used except that the polishing liquid used for precision polishing was an aqueous solution containing neutral (pH: 7 to 7.6) colloidal silica (average particle size 30 to 200 nm). Similarly, 100 glass substrates (glass substrates for phase shift mask blanks) were produced.
The surface roughness of the main surface of the obtained glass substrate was as good as 0.15 nm or less in terms of root mean square roughness (RMS).
Further, the main surface of the obtained glass substrate is formed with a minute convex surface defect having a height of about several nm (about 2 nm to 7 nm) and a depth of about 10 using a defect inspection apparatus using a laser interference confocal optical system. When a minute concave surface defect of ˜50 nm was examined, it was not confirmed from any of the 100 glass substrates. That is, the incidence of minute surface defects was 0%.

In Example 1 described above, the urethane resin composition of the polishing pad was changed, and the nap layer thickness was 700 μm, the polishing pad hardness (Asker-C) was 60, and the nap layer surface opening diameter was 10 to 50 μm. 100 glass substrates (glass substrates for phase shift mask blanks) were produced in the same manner as in Example 1 except that the pads were used.
The surface roughness of the main surface of the obtained glass substrate was as good as 0.15 nm or less in terms of root mean square roughness (RMS).
Further, the main surface of the obtained glass substrate is formed with a minute convex surface defect having a height of about several nm (about 2 nm to 7 nm) and a depth of about 10 using a defect inspection apparatus using a laser interference confocal optical system. As a result of examining minute concave surface defects of ˜50 nm, it was confirmed on 5 out of 100 glass substrates. That is, the incidence of minute surface defects was 5%.

In Example 1 described above, the urethane resin composition of the polishing pad was changed, and the nap layer thickness was 680 μm, the polishing pad hardness (Asker-C) was 58, and the nap layer surface opening diameter was 10 to 50 μm. 100 glass substrates (glass substrates for phase shift mask blanks) were produced in the same manner as in Example 1 except that the pads were used.
The surface roughness of the main surface of the obtained glass substrate was as good as 0.15 nm or less in terms of root mean square roughness (RMS).
Further, the main surface of the obtained glass substrate is formed with a minute convex surface defect having a height of about several nm (about 2 nm to 7 nm) and a depth of about 10 using a defect inspection apparatus using a laser interference confocal optical system. When a minute concave surface defect of ˜50 nm was examined, it was confirmed on 3 out of 100 glass substrates. That is, the incidence of minute surface defects was 3%. Compared with Example 1, the occurrence of convex surface defects was slightly increased.

In Example 1 described above, the urethane resin composition of the polishing pad was changed, the nap layer thickness was 560 μm, the polishing pad hardness (Asker-C) was 62, and the nap layer surface opening diameter was 30 to 60 μm. 100 glass substrates (glass substrates for phase shift mask blanks) were produced in the same manner as in Example 1 except that the pads were used.
The surface roughness of the main surface of the obtained glass substrate was as good as 0.15 nm or less in terms of root mean square roughness (RMS).
Further, the main surface of the obtained glass substrate is formed with a minute convex surface defect having a height of about several nm (about 2 nm to 7 nm) and a depth of about 10 using a defect inspection apparatus using a laser interference confocal optical system. As a result of examining minute concave surface defects of ˜50 nm, it was confirmed on 8 out of 100 glass substrates. That is, the incidence of minute surface defects was 8%. Compared with Example 1, the occurrence of convex surface defects was slightly increased.

(Comparative Example 1)
In Example 1 described above, the urethane resin composition of the polishing pad was changed, and the nap layer thickness was 560 μm, the polishing pad hardness (Asker-C) was 67, and the nap layer surface opening diameter was 30 to 100 μm. 100 glass substrates (glass substrates for phase shift mask blanks) were produced in the same manner as in Example 1 except that the pads were used.
The surface roughness of the main surface of the obtained glass substrate was all good in terms of root mean square roughness (RMS) of 0.15 nm or less, but it was high using a defect inspection apparatus using a laser interference confocal optical system. When a minute convex surface defect having a thickness of about several nm (about 2 nm to 7 nm) and a minute concave surface defect having a depth of about 10 to 50 nm were examined, it was confirmed on 17 out of 100 glass substrates. . That is, the incidence of minute surface defects was as high as 17%.

A glass substrate (glass for EUV reflective mask blanks) was prepared in the same manner as in Example 1 except that the material of the glass substrate in Example 1 was changed to a SiO ₂ —TiO ₂ -based low thermal expansion glass substrate (152 mm × 152 mm). Substrate) 100 sheets were produced.
The surface roughness of the main surface of the obtained glass substrate was as good as 0.15 nm or less in terms of root mean square roughness (RMS).
Further, the main surface of the obtained glass substrate is formed with a minute convex surface defect having a height of about several nm (about 2 nm to 7 nm) and a depth of about 10 using a defect inspection apparatus using a laser interference confocal optical system. When a minute concave surface defect of ˜50 nm was examined, it was confirmed on 3 out of 100 glass substrates. That is, the incidence of minute surface defects was 3%.

(Comparative Example 2)
In Example 6 described above, the same polishing pad as in Comparative Example 1 described above was used, with a nap layer thickness of 560 μm, a polishing pad hardness (Asker-C) of 67, and a nap layer surface opening diameter of 30 to 100 μm. Except for this, 100 glass substrates (glass substrates for EUV reflective mask blanks) were produced in the same manner as in Example 1.
The surface roughness of the main surface of the obtained glass substrate was all good in terms of root mean square roughness (RMS) of 0.15 nm or less, but it was high using a defect inspection apparatus using a laser interference confocal optical system. When a minute convex surface defect having a thickness of about several nm (about 2 nm to 7 nm) and a minute concave surface defect having a depth of about 10 to 50 nm were examined, it was confirmed on 22 out of 100 glass substrates. . In other words, the incidence of minute surface defects was very high at 22%.
In addition, when component analysis was performed on the minute convex surface defects confirmed in Examples 1 to 6 and Comparative Examples 1 and 2 using EPMA (ElectronProbe (X-ray) Micro Analyzer), the main component was Si. , O was confirmed.

From a molybdenum silicide nitride film on one main surface of a glass substrate for phase shift mask blanks having no fine convex and concave surface defects produced by the method for producing a glass substrate for electronic devices according to Examples 1 to 5 described above. A halftone film to be formed was formed by a sputtering method, and then a resist film was formed to produce a phase shift mask blank.
Further, the resist film was patterned by predetermined drawing and development to form a resist pattern, and then using this resist pattern as a mask, the molybdenum silicide nitride film was etched away by dry etching, and the resist pattern was removed to prepare a phase shift mask.
(Comparative Example 3)
A phase shift mask was formed in the same manner as in Example 5 on one main surface of a glass substrate for phase shift mask blanks having fine convex and concave surface defects manufactured by the manufacturing method of Comparative Example 1 described above. Blanks were produced, and a phase shift mask was produced from the mask blanks.

In addition, a Mo film and Si are formed on one main surface of a glass substrate for EUV reflective mask blanks having no fine convex or concave surface defects manufactured by the method for manufacturing a glass substrate for electronic devices according to Example 6 described above. A multilayer reflective film is formed by forming alternating laminated films over 40 cycles, an absorber film made of a TaBN film is formed on the multilayer reflective film, and a resist film is formed to produce an EUV reflective mask blank. did.
Further, the resist film was patterned by predetermined drawing and development to form a resist pattern. Then, using this resist pattern as a mask, the TaBN film was etched away by dry etching, and the resist pattern was removed to produce an EUV reflective mask.
(Comparative Example 4)
Film formation was performed in the same manner as in Example 6 on one main surface of a glass substrate for EUV reflective mask blanks having minute convex and concave surface defects manufactured by the manufacturing method of Comparative Example 2 described above, and EUV reflection was performed. A mold mask blank was produced, and an EUV reflective mask was produced from the mask blank.

(Evaluation results)
When the defect inspection of the phase shift mask blanks, phase shift masks, EUV reflective mask blanks, and EUV reflective masks thus manufactured was performed, the phase shift mask manufactured using the glass substrate for electronic devices according to Examples 1-6. Convex and concave surface defects were not observed in the blanks, the phase shift mask, and the EUV reflective mask blanks and the EUV reflective mask. In contrast, phase shift mask blanks, phase shift masks, and EUV reflective mask blanks manufactured using the glass substrates for electronic devices according to Comparative Examples 1 and 2 in which minute convex and concave surface defects were confirmed. In the reflective mask, convex and concave surface defects were confirmed on the glass substrate surface, the boundary of the halftone film pattern, the surface of the multilayer reflective film, and the boundary of the absorber film pattern. These surface defects also affect the pattern accuracy of the transferred image when pattern transfer is performed using a mask.

It is sectional drawing which shows schematic structure of the double-side polish apparatus of the planetary gear system used in a precision grinding | polishing process.

Explanation of symbols

1 Workpiece 2 Sun gear 3 Internal gear 4 Carrier 5 Upper surface plate 6 Lower surface plate 7 Polishing pad

Claims (7)

A glass substrate for an electronic device is pressed against a polishing platen to which a polishing pad is attached, and the polishing platen and the glass substrate are moved relatively while supplying a polishing liquid containing polishing abrasive grains. A method for producing a glass substrate for an electronic device having a step of precisely polishing a surface,
The method for producing a glass substrate for an electronic device, wherein the polishing pad has a nap layer having a fine opening on a surface, and the thickness of the nap layer is 700 μm or more. A glass substrate for an electronic device is pressed against a polishing platen to which a polishing pad is attached, and the polishing platen and the glass substrate are moved relatively while supplying a polishing liquid containing polishing abrasive grains. A method for producing a glass substrate for an electronic device having a step of precisely polishing a surface,
The method for producing a glass substrate for an electronic device, wherein the polishing pad has a nap layer having a fine opening on the surface, and the hardness (Asker-C) of the polishing pad is 65 or less. The method for producing a glass substrate for an electronic device according to claim 1 or 2, wherein an opening diameter of a surface of the nap layer of the polishing pad is 10 to 70 µm. The said polishing pad adjusts the carbon content contained in the said nap layer so that a micro convex surface defect and / or a micro concave surface defect may not generate | occur | produce. The manufacturing method of the glass substrate for electronic devices in any one. The method for producing a glass substrate for an electronic device according to any one of claims 1 to 4, wherein the substrate is a glass substrate for mask blanks. A thin film that causes an optical change with respect to exposure light is formed on the main surface of the glass substrate for an electronic device obtained by the method for producing a glass substrate for an electronic device according to any one of claims 1 to 5. A method for manufacturing mask blanks. A method for producing a transfer mask, comprising patterning the thin film in a mask blank obtained by the method for producing a mask blank according to claim 6 to form a thin film pattern on a main surface of the glass substrate.

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