KR102067290B1 - Manufacturing method of mask blank, manufacturing method of transfer mask, and manufacturing method of semiconductor device - Google Patents

Abstract

The manufacturing method of the mask blank which suppressed the deterioration of flatness, and the manufacturing method of a transfer mask are provided. A step of preparing a glass substrate subjected to mirror polishing on a main surface, a step of performing a light heating treatment of irradiating light including a wavelength of an infrared region to the prepared glass substrate, and the glass substrate after the light heating treatment. It is a manufacturing method of the mask blank characterized by including the process of forming the thin film which consists of a material which contains tantalum on a main surface and does not contain hydrogen substantially.

Description

MANUFACTURING METHOD OF MASK BLANK, MANUFACTURING METHOD OF TRANSFER MASK, AND MANUFACTURING METHOD OF SEMICONDUCTOR DEVICE}

This invention relates to the manufacturing method of the mask blank provided with the low stress thin film, and the manufacturing method of the transfer mask. In particular, it is related with the manufacturing method of the mask blank which reduced the time-dependent change of the stress of a thin film, and the manufacturing method of the transfer mask. Moreover, it is related with the manufacturing method of the semiconductor device using this transfer mask.

Generally, in the manufacturing process of a semiconductor device, fine pattern formation is performed using the photolithographic method. In addition, the board | substrate called a transfer mask of several purchases is used for formation of this fine pattern. This transfer mask generally forms a fine pattern made of a metal thin film or the like on a light-transmissive glass substrate, and the photolithography method is also used in the production of the transfer mask.

In the manufacture of the transfer mask by the photolithography method, a mask blank having a thin film (for example, a light shielding film) for forming a transfer pattern (mask pattern) on a light transmissive substrate such as a glass substrate is used. The manufacture of the transfer mask using the mask blank includes an exposure step of performing a desired pattern drawing on a resist film formed on the mask blank, and a developing step of developing the resist film by forming the resist pattern in accordance with a desired pattern drawing; And an etching step of etching the thin film in accordance with the resist pattern, and a step of peeling and removing the remaining resist pattern. In the above development step, after the desired pattern drawing (exposure) is performed on the resist film formed on the mask blank, a developer is supplied to dissolve a portion of the resist film available in the developer to form a resist pattern. In the above etching step, the resist pattern is used as a mask, and a portion where the resist pattern is not formed by dry etching or wet etching is dissolved, thereby forming a desired mask pattern on the light-transmissive substrate. do. In this way, the transfer mask is completed.

In miniaturizing the pattern of the semiconductor device, in addition to miniaturization of the mask pattern formed on the transfer mask, shortening of the wavelength of the exposure light source used in photolithography is required. As an exposure light source at the time of semiconductor device manufacture, shortening of the wavelength from a KrF excimer laser (wavelength 248 nm) to an ArF excimer laser (wavelength 193 nm) is progressing in recent years.

As a transfer mask, the binary mask which has the light shielding film pattern which consists of chromium system materials on a translucent board | substrate is known from the past.

In recent years, a binary mask for an ArF excimer laser using a material (MoSi-based material) containing a molybdenum silicide compound as a light shielding film has also appeared (Patent Document 1). Moreover, the binary mask etc. for ArF excimer laser which used the material (tantalum-type material) containing a tantalum compound as a light shielding film are also emerging (patent document 2). In patent document 3, when a light mask which washes with acid wash and hydrogen plasma is performed with respect to the photomask which consists of a tantalum, niobium, vanadium, or a metal containing at least two of tantalum, niobium, and vanadium, the light shielding film is hydrogen-embedded. It is disclosed that the light shielding film may be deformed and deformed. Moreover, as a solution means, after forming a pattern in a light shielding film, forming a hydrogen-blocking film which air-tightly covers the upper surface and the side surface of a light shielding film is disclosed.

On the other hand, in patent document 4, the manufacturing method of the mask board | substrate for vacuum ultraviolet rays which consists of synthetic quartz glass is disclosed. Here, the necessity of reducing the OH group in the synthetic quartz glass is disclosed in order to improve the transmittance of light in the vacuum ultraviolet region of the synthetic quartz glass. As one of the solutions, it is disclosed to reduce the Si-H content and the H ₂ content in the synthetic quartz glass to a predetermined value or less.

In addition, Patent Literature 5 discloses an optical heating device that heats an object by irradiating the object with light emitted from a plurality of incandescent lamps as an optical heating device.

Japanese Patent Application Publication No. 2006-78807 Japanese Patent Application Publication No. 2009-230112 Japanese Patent Application Laid-open No. 2010-192503 Japanese Patent Application Laid-open No. 2004-26586 Japanese Patent Application Laid-Open No. 2001-210604

In recent years, the required level of pattern position precision for the transfer mask has become particularly strict. One element for achieving high pattern position accuracy is to improve the flatness of the mask blank serving as the original plate for producing the transfer mask. In order to improve the flatness of the mask blank, first, it is necessary to improve the flatness of the main surface of the side on which the thin film of the glass substrate is formed. The glass substrate for manufacturing a mask blank starts with manufacturing the glass ingot as described in patent document 4, and cutting out to the shape of a glass substrate. In the glass substrate immediately after cutting out, the flatness of the main surface is bad, and the surface state is also rough. For this reason, a several stage grinding process and a grinding | polishing process are performed with respect to a glass substrate, and it finishes with high flatness and favorable surface roughness (mirror surface). In addition, after the grinding | polishing process using abrasive abrasive grains, washing | cleaning with the washing | cleaning liquid containing a hydrofluoric acid solution and / or a silicic acid solution is performed. Moreover, the washing | cleaning by the washing | cleaning liquid containing an alkaline solution may be performed before the process of forming a thin film.

However, in order to manufacture a mask blank of high flatness, it alone is insufficient. If the film stress of the thin film for forming the pattern formed on the main surface of the glass substrate is high, the glass substrate is deformed, resulting in deterioration of flatness. For this reason, in order to reduce the film stress of the thin film for forming a pattern, various measures have been taken at the time of film-forming or after film-forming. Until now, even if the mask blank adjusted to such a high degree of countermeasure is taken and stored for a long time (for example, about half a year) after manufacture, it was thought that even if it is enclosed and stored in a case, flatness will not change significantly. . However, in the case of the mask blank in which the material containing tantalum was used for the thin film for pattern formation, even if it is airtightly stored in the case, as time passes from manufacture, it was confirmed that the flatness of the main surface deteriorates. Specifically, with the passage of time, the flatness of the main surface of the side on which the thin film was formed deteriorated in the direction in which the convex tendency became stronger.

This means that, when the glass substrate is not the cause, the tendency of the compressive stress gradually increases in the film stress of the thin film. In the case of a mask blank having a thin film using a material containing a chromium-based material and / or a molybdenum silicide compound, such a remarkable phenomenon does not occur. From this, this phenomenon occurring in the mask blank using the material containing tantalum in the thin film for pattern formation is estimated that the glass substrate itself is not deformed, but the compressive stress of the thin film increases with time. do. On the other hand, when a transfer mask is manufactured using such a mask blank of a thin film having a high compressive stress, there is a problem that a large positional displacement of the pattern occurs in the region of the thin film opened from the film stress by the formation of the pattern. . In addition, even in the case where a transfer mask is produced in a short period of time after the mask blank is manufactured, there is a problem that the positional shift of the pattern occurs with the passage of time after the production.

 This invention is made | formed under such a situation, The objective is the mask blank which used the material containing tantalum in the thin film for pattern formation WHEREIN: The film stress of a thin film has a tendency of a compressive stress with passage of time. The problem of becoming strong is solved, and the manufacturing method of the mask blank which suppressed the deterioration of flatness, and the manufacturing method of the transfer mask are provided. Moreover, it aims at providing the manufacturing method of the semiconductor device using this transfer mask.

MEANS TO SOLVE THE PROBLEM In order to achieve the said subject, the manufacturing method of the mask blank of this invention irradiates the light including the wavelength of an infrared region with respect to the process of preparing the glass substrate which mirror-polished with respect to the main surface, and the prepared said glass substrate. And a step of forming a thin film made of a material containing tantalum and substantially free of hydrogen on the main surface of the glass substrate after the light heating treatment. have. According to the method for producing a mask blank of the present invention, the problem that the film stress of a thin film becomes stronger as time goes by and the compressive stress tends to be solved, thereby providing a method for producing a mask blank in which flatness is suppressed. Can be.

Moreover, the manufacturing method of the mask blank of this invention performs the process of preparing the glass substrate which mirror-polished with respect to the main surface, and the light heating process which irradiates the light including the wavelength of an infrared region with respect to the prepared said glass substrate. The glass substrate after a process and a photo-heating process are installed in a film-forming chamber, the target containing tantalum is used, the sputtering gas which does not contain hydrogen is introduce | transduced into a film-forming chamber, and sputtering method is carried out on the main surface of the said glass substrate. It is characterized by including the process of forming a thin film. In the method for producing a mask blank of the present invention, by using a predetermined sputtering gas, the problem that the film stress of the thin film becomes stronger with the passage of time becomes stronger, and the flatness is suppressed from deteriorating. It is possible to provide a method for producing a mask blank.

In the manufacturing method of each said mask blank, it is preferable that the light irradiated to a glass substrate in the said optical heat processing contains the wavelength of 1.3 micrometers or more. A glass substrate made of synthetic quartz has a band in which transmittance decreases in a wavelength range of 1.3 µm or more. Since the light absorbed in the glass substrate is converted into heat, the glass substrate can be sufficiently heated, and hydrogen can be sufficiently removed out of the glass substrate.

In the above-mentioned mask blank manufacturing method, it is preferable that the light irradiated to the glass substrate in the light heating treatment includes at least one of wavelengths of 1.38 µm, 2.22 µm, and 2.72 µm. . The glass substrate which consists of synthetic quartz containing an OH group and / or water has the absorption band in which a transmittance | permeability falls at each said wavelength. For this reason, the light absorbed in the glass substrate is converted into heat with high efficiency by irradiating the glass substrate with light including at least one of the wavelengths described above. Thereby, a glass substrate can be heated enough and hydrogen can be fully excluded outside a glass substrate.

In the manufacturing method of each said mask blank, it is preferable that the said light-heating process is a process which irradiates the said glass substrate with the light emitted from a halogen heater. The wavelength spectrum of light emitted from the halogen heater is particularly high in intensity of light in the infrared region compared with the intensity of light in other wavelength regions. For this reason, a glass substrate can be heated efficiently and hydrogen can fully be taken out of a glass substrate.

It is preferable that the said thin film is formed in contact with the main surface of the said glass substrate in the said manufacturing method of each mask blank. In the case where the thin film made of a material containing tantalum is formed in contact with the main surface of the glass substrate after the heat treatment, hydrogen or the like present in the glass substrate is directly introduced into the thin film. In the case of such a structure, the effect by having excluded OH group, hydrogen, water, etc. from a glass substrate by heat processing can be acquired more remarkably.

In the above-mentioned manufacturing method of each mask blank, it is preferable that the said thin film consists of a material which contains tantalum and nitrogen and does not contain hydrogen substantially. By containing nitrogen in tantalum, the oxidation of tantalum can be suppressed.

In the manufacturing method of each said mask blank, the said thin film has the structure which a lower layer and an upper layer are laminated | stacked from the said glass substrate side, The said lower layer contains a material which contains tantalum and nitrogen, and does not contain hydrogen substantially. It is preferable that the upper layer is made of a material containing tantalum and oxygen. By setting it as such a structure, it can function as a film (antireflection film) which has a function which controls the surface reflectance with respect to the exposure light of a thin film in an upper layer.

The manufacturing method of the transfer mask of this invention forms a transfer pattern in the said thin film of the said mask blank using the mask blank manufactured by said manufacturing method of each said mask blank. Since the flatness of the mask blank of the present invention is maintained at the required high level, the transfer mask produced by using the mask blank having such characteristics can also have the required high flatness.

The manufacturing method of the semiconductor device of this invention is characterized by exposing and transferring the said transfer pattern to the resist film on a semiconductor substrate using the transfer mask manufactured by said manufacturing method of a transfer mask. By exposing and transferring a transfer pattern to the resist film on a semiconductor substrate using the transfer mask of this invention, the semiconductor device which has a high precision pattern can be manufactured.

According to the method for producing a mask blank of the present invention, even in a mask blank in which a material containing tantalum is used in the thin film for pattern formation, the tendency of the compressive stress does not increase with the passage of time. Thereby, after manufacturing a mask blank, it can suppress that flatness deteriorates with progress of time. In addition, since the mask blank manufactured by the manufacturing method of the mask blank of this invention can suppress that the film stress of the thin film for pattern formation increases with time, the film stress of a thin film is the level at the time of manufacture. Can be maintained. Thereby, large position shift of the pattern which arises when the transfer mask is produced from the mask blank which has a thin film with high film stress can be suppressed. In addition, when a transfer mask is produced from the mask blank manufactured by the manufacturing method of the mask blank of this invention, it can also suppress that position shift of a pattern generate | occur | produces with passage of time after preparation. Further, the transfer pattern can be transferred to the resist film on the semiconductor substrate by using a transfer mask in which the deterioration of the flatness of the main surface due to the film stress of the thin film is suppressed and the positional shift of the pattern formed in the thin film is also suppressed. From this, it is possible to manufacture a semiconductor device having a fine and high precision circuit pattern on the semiconductor substrate.

1 is a cross-sectional view showing a configuration of a mask blank according to an embodiment of the present invention.
2 is a cross-sectional view showing a configuration of a transfer mask according to an embodiment of the present invention.
3 is a cross-sectional view showing a process from a mask blank according to an embodiment of the present invention to producing a transfer mask.
4 shows the results by HFS / RBS analysis of mask blanks in the examples.
Fig. 5 shows the results by HFS / RBS analysis of mask blanks in Comparative Example.
It is a figure which shows the structure of the optical heating apparatus which optically heat-processes the glass substrate which concerns on embodiment of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described.

MEANS TO SOLVE THE PROBLEM This inventor earnestly researched the cause by which the thin film containing tantalum immediately after film-forming on a glass substrate increases compressive stress with time. First of all, in order to confirm that there is no cause for storing the mask blank after film formation, various storage cases and storage methods were verified, but in any case, the flatness of the main surface of the mask blank deteriorated, and no clear correlation was obtained. Did. Next, heat treatment was performed using a hot plate for the mask blank whose main surface flatness deteriorated in the convex direction. The conditions of heat processing were made into about 5 minutes at 200 degreeC. When this heat treatment was performed, the convex shape of the main surface temporarily changed in a somewhat favorable direction. However, it has been found that when time passes after the heat treatment, the flatness of the main surface of the mask blank deteriorates again, which does not lead to a fundamental solution.

Next, the present inventor examined the possibility that the material containing tantalum has a characteristic which is easy to introduce hydrogen. That is, the hypothesis that hydrogen is gradually introduced into the thin film containing tantalum with time and the compressive stress is increased. However, in this mask blank, in which the phenomenon that the compressive stress increases with the passage of time has occurred, the factor of introducing hydrogen was not found in the conventional knowledge. The glass substrate used for this mask blank is formed with the synthetic quartz glass, and the process which suppressed hydrogen containing was used at the time of manufacture of a synthetic quartz ingot. Moreover, the thin film containing tantalum also had a structure which laminated | stacked the lower layer which consists of a material containing tantalum and nitrogen, and the upper layer which consists of a material containing oxygen to the tantalum formed on the lower layer on the main surface side of a glass substrate. Since a film made of a material containing oxygen in tantalum has an effect of suppressing the ingress of hydrogen from outside air, it was considered that hydrogen in the outside air is difficult to invade the thin film containing tantalum.

In order to confirm whether hydrogen was introduce | transduced in the thin film containing tantalum by the time progress from the completion | finish of film-forming, the following verification was done. Specifically, a mask blank comprising a thin film made of a material containing tantalum, which is housed in a case after film formation, does not elapse much for about two weeks, and thus the mask blank in which the flatness of the thin film is not deteriorated, 4 months after the film was formed into the case, the compressive stress of the thin film was increased and the flatness was deteriorated (coordinate TIR in a square inner region where one side was 142 mm based on the center of the main surface of the glass substrate). In the flatness, the film composition was analyzed for each of the mask blanks having a variation in the flatness of about 300 nm). Membrane analysis was used HFS / RBS analysis (hydrogen forward scattering analysis / Rutherford backscattering analysis). As a result, in the thin film of about two weeks after film-forming, the thin film which passed four months after film-forming contained about 6 at% of hydrogen, while the hydrogen content was below the lower limit of detection.

From these results, it was confirmed that film stress was changed by introducing hydrogen into the thin film containing tantalum after film formation. Next, the inventor doubted the glass substrate as a source of hydrogen. After the polishing is performed until the flatness and the surface roughness of the main surface become higher than or equal to those required for the glass substrate for mask blanks, a glass substrate subjected to light heat treatment for irradiating light including the wavelength of the infrared region is prepared. Then, a thin film made of a material containing tantalum was formed to perform the same verification as above. As a result, in the case of the mask blank using the glass substrate which performed the photoheating process, even if it passed four months after film-forming, the degree of deterioration of flatness was small and the hydrogen content in a film was also suppressed.

The following possibility is considered as a factor which exists in the glass substrate of the mask blank manufactured using the glass ingot produced by the manufacturing method which is hard to mix OH group and hydrogen as a factor which OH group, hydrogen, and water which generate hydrogen generate | occur | produce. do.

Usually, the conditions of the flatness and surface roughness of the main surface required for the glass substrate used for the mask blank are strict. Therefore, it is difficult to satisfy the condition as a glass substrate for mask blanks as it is, cut out in the shape of a glass substrate from a glass ingot. It is necessary to perform a grinding | polishing process and a grinding | polishing process in several steps with respect to the glass substrate of the cut-out state, and to finish a main surface with high flatness and surface roughness. The polishing liquid used in the polishing step contains colloidal silica abrasive grains as the abrasive. Since colloidal silica abrasive grains tend to adhere to the glass substrate surface, it is also common to clean with a cleaning liquid containing hydrofluoric acid and / or silicic acid which has an action of etching the glass substrate surface during and / or after a plurality of polishing processes. It is done.

In a grinding process and a grinding | polishing process, a process alteration layer is easy to form in the surface layer of a glass substrate, and there exists a possibility that OH group and hydrogen are introduce | transduced into the process alteration layer. In addition, there exists a possibility that OH group and hydrogen are introduce | transduced from the processing altered layer and inside the glass substrate at this time. At the time of washing | cleaning between polishing processes, OH group and hydrogen may also be introduce | transduced even when micro-etching the glass substrate surface. In addition, a hydration layer may be formed on the surface of the glass substrate.

The present invention has been made in consideration of the above. That is, the manufacturing method of the mask blank of this invention performs the process of preparing the glass substrate which mirror-polished with respect to the main surface, and the light heating process which irradiates the light including the wavelength of an infrared region with respect to the prepared said glass substrate. And a step of forming a thin film made of a material containing tantalum and substantially free of hydrogen on the main surface of the glass substrate after the light heating treatment.

Moreover, the manufacturing method of the mask blank of this invention performs the process of preparing the glass substrate which mirror-polished with respect to the main surface, and the light heating process which irradiates the light including the wavelength of an infrared region with respect to the prepared said glass substrate. The glass substrate after a process and a photo-heating process are installed in a film-forming chamber, the target containing tantalum is used, the sputtering gas which does not contain hydrogen is introduce | transduced into a film-forming chamber, and sputtering method is carried out on the main surface of the said glass substrate. It is characterized by including the process of forming a thin film.

After mirror polishing is performed in the polishing step, heat treatment is performed on the glass substrate at the stage that satisfies the conditions for the mask blank substrate, thereby forcibly removing OH groups, hydrogen, and water introduced into the surface layer or inside of the glass substrate. Can be discharged. Then, by depositing a thin film containing tantalum on the glass substrate after performing a light heating treatment for irradiating light including a wavelength in the infrared region, it is possible to suppress the introduction of hydrogen into the thin film containing tantalum, The increase in compressive stress can be suppressed.

The step of preparing a glass substrate subjected to mirror polishing on the main surface includes a square inner region (hereinafter referred to as 142 mm x 142 mm region) in which one side is 142 mm based on the center of the main surface of the glass substrate after this step. It is preferable that the surface roughness in the square inner region having a flatness of 0.5 µm or less and one side of 1 µm is Rq (hereinafter simply referred to as surface roughness Rq) of 0.2 nm or less. Moreover, as for the flatness in 132 mm x 132 mm area | region of the main surface of a glass substrate, it is more preferable that it is 0.3 micrometer or less. In the glass substrate cut out from the glass ingot, such high flatness and surface roughness cannot be satisfied. In order to satisfy the conditions of high flatness and surface roughness, it is essential to perform mirror polishing on at least the main surface of the glass substrate. In this mirror polishing, it is preferable to simultaneously polish both main surfaces of the glass substrate by double-side polishing using a polishing liquid containing abrasive grains of colloidal silica. Moreover, it is preferable to finish with the main surface which satisfy | fills the conditions of the required flatness and surface roughness by performing a grinding process and a grinding | polishing process in several steps with respect to the glass substrate of the cut-out state. In this case, at least in the final stage of the polishing process, a polishing liquid containing abrasive grains of colloidal silica is used.

It is preferable that the light heating process performed with respect to the prepared glass substrate uses the light which has a wavelength of 1.3 micrometers or more as an infrared region. In the case of light having only a wavelength shorter than 1.3 mu m, the transmittance of the glass substrate is high, and the photothermal conversion efficiency inside the glass substrate is low, so that the prepared glass substrate may not be sufficiently heated. Moreover, the glass substrate containing OH group, water, etc. has a remarkable absorption band in wavelength 1.38 micrometers, 2.22 micrometers, and 2.72 micrometers. For this reason, it is preferable that a light heat processing is a process which irradiates the prepared glass substrate with the light containing at least any one of said wavelength. Moreover, since the fall of the transmittance of the wavelength of 2.72 micrometers is especially remarkable for the glass substrate containing OH group, water, etc., it is more preferable to irradiate the glass substrate with the light containing this wavelength.

Moreover, the glass substrate which consists of synthetic quartz has the remarkably low transmittance | permeability with respect to the light of wavelength 3.5micrometer or more, and the photothermal conversion efficiency in a glass substrate is high. For this reason, it is preferable that light heat processing irradiates the prepared glass substrate with the light of 3.5 micrometers or more. It is preferable to perform light heat processing with respect to the prepared glass substrate using the light of an infrared region, and it is more preferable to carry out light heat processing with the light which does not contain the wavelength exceeding 6.0 micrometers exceeding an infrared region.

It is preferable that the optical heat processing performed with respect to the prepared glass substrate is processed on irradiation conditions as much as heating a glass substrate to 300 degreeC or more. In heat processing below 300 degreeC, since temperature is inadequate, there exists a possibility that the effect which discharge | releases hydrogen in a glass substrate to the outside of a glass substrate may not fully be acquired. In the case of irradiation conditions to heat at 400 degreeC or more, light heat processing can obtain the above-mentioned better effect. If light heating treatment is the irradiation condition which heats more than 500 degreeC, even if the irradiation time of light is shortened, the sufficient effect of removing hydrogen out of a glass substrate can be acquired. On the other hand, it is necessary for light heat processing to be irradiation conditions heated below 1600 degreeC. This is because the softening point of the synthetic quartz is generally 1600 ° C, and when the heating temperature is 1600 ° C or higher, the glass substrate is softened and deformed. It is preferable if it is irradiation conditions heated at 1000 degrees C or less, and, as for light heat processing, it is more preferable that it is irradiation conditions heated at 800 degrees C or less. In addition, although the processing time of the optical heat processing performed with respect to a glass substrate is based also on heating temperature, it is preferable that it is at least 5 minutes or more. Moreover, it is more preferable that it is 15 minutes or more, and, as for the processing time of the optical heat processing performed with respect to a glass substrate, it is more preferable that it is 20 minutes or more.

It is preferable to perform light heat processing in the state in which the gas in which hydrogen was remove | excluded as much as possible around a glass substrate exists. Although the amount of hydrogen itself is small in air, there is much water vapor. The humidity in the clean room is controlled, but there is a relatively large amount of water vapor. By performing the heat treatment on the glass substrate in dry air, the penetration of hydrogen into the glass substrate due to water vapor can be suppressed. Moreover, it is more preferable to heat-process a glass substrate in the gas (inert gas, such as nitrogen, and rare gas, etc.) which does not contain hydrogen and water vapor. The light heat treatment can be performed in a gas at atmospheric pressure or in a vacuum. In order to reliably reduce the OH group, hydrogen, water, and the like introduced into the surface layer and the inside of the glass substrate, it is preferable to set the circumference of the glass substrate to be subjected to the light heat treatment to a certain degree of vacuum. As for the vacuum degree, it is more preferable that it is medium vacuum (0.1 kPa-100 kPa).

It is preferable that a light heating process is a process which irradiates the glass substrate with the light emitted from a halogen heater. The wavelength spectrum of light emitted from the halogen heater is particularly high in intensity of light in the infrared region compared with the intensity of light in other wavelength regions. For this reason, by the light emitted from a halogen heater, a glass substrate can be heated efficiently, and hydrogen can fully be taken out of a glass substrate. Light emitted from the halogen heater is multicolored light containing a plurality of wavelengths. As mentioned above, the glass substrate containing OH group, water, etc. has a remarkable absorption band in wavelength 1.38 micrometers, 2.22 micrometers, and 2.72 micrometers. Therefore, the light emitted from the halogen heater is preferably sufficiently strong in the wavelengths of 1.38 µm, 2.22 µm and 2.72 µm. In consideration of this condition, the halogen heater used for the light heating treatment preferably has a color temperature of 2200K or more, and preferably 3400K or less.

In this light heating treatment, an optical heating device as shown in FIG. 6 can be used. This optical heating apparatus has a main structure provided with the mounting base 14 which mounts the light source unit 12 and the glass substrate 1 in the process chamber 11. The light source unit 12 can have a structure in which the cylindrical flame heater 16 is arranged in the unit frame 15 in two upper and lower stages in parallel. Each of the upper and lower halogen heaters 16 can be arranged in a lattice shape when viewed from above. By such a configuration of the light source unit 12, light of the infrared region can be irradiated almost uniformly to the main surface of the glass substrate 1. Moreover, as an optical heating apparatus, the apparatus of the structure which uses a halogen heater instead of an incandescent lamp can be used in the optical heating apparatus described in patent document 5, for example.

The reflecting plate 17 can be provided in the surface of the unit frame 15 on the upper side of the halogen heater 16 of the upper end. Thereby, the light of the infrared region radiated | emitted upward from the halogen heater 16 is reflected by the reflecting plate 17, and can irradiate the main surface of the glass substrate 1 to it. The mounting base 14 can be made into the shape which has an opening so that it may become a shape which keeps the outer periphery of the glass substrate 1. The reflecting plate 18 can also be provided below the opening. In this case, since the light transmitted through the glass substrate is reflected by the reflecting plate 18, the reflected light can be irradiated to the main surface of the rear side of the glass substrate 1.

In addition, when performing the optical heating process of the glass substrate 1 in an optical heating apparatus in vacuum, the process chamber 11 can be made into the structure which can perform a vacuum process. In this case, the halogen heater 16 or the like can be arranged in a vacuum atmosphere inside the processing chamber 11. In addition, the structure in which the halogen heater 16 or the like is disposed at an open position at atmospheric pressure, and the light from the halogen heater 16 is transmitted through the transparent window capable of vacuum sealing, and is made to enter the processing chamber 11 under vacuum. You can do It is preferable that the transparent window used for this structure has a high transmittance with respect to the light of the predetermined wavelength mentioned above.

After the light heating treatment, a thin film made of a material containing tantalum and substantially free of hydrogen is formed on the main surface of the glass substrate for the manufacture of the mask blank. For forming the thin film, a film forming apparatus using a vacuum such as a sputtering apparatus is usually used. In the case where the optical heating treatment is performed in a vacuum, in order to avoid absorption of hydrogen by the glass substrate, contamination of the surface of the glass substrate, and the like, the optical heating apparatus and the film deposition apparatus are connected to be capable of transporting the glass substrate while maintaining the degree of vacuum. It is preferable. In addition, when it is necessary to expose the glass substrate after a photoheating process to atmospheric pressure by the structure of an apparatus, it is preferable to make time until a thin film is formed by a film forming apparatus after a photoheating process as short as possible. Do.

It is preferable that the glass substrate which performs light heat processing performs a predetermined washing process. When the optical heat treatment is performed in the state where the abrasive grains used in the polishing step are attached, the abrasive grains adhere to the surface of the glass substrate, and may not be removed even if a normal cleaning step is performed after the optical heat treatment. In particular, in the case of a material similar to a glass substrate such as colloidal silica, there is a possibility that it may be firmly adhered to the surface of the glass substrate. Thus, with a cleaning liquid containing hydrofluoric acid and / or silicic acid, which has an action of etching against the surface of the glass substrate. It is preferable to wash.

Examples of the glass substrate on the mask blank of the material, there may be mentioned in addition to the synthetic quartz glass, quartz glass, aluminosilicate glass, soda lime glass, such as a low thermal expansion glass (SiO ₂ -TiO ₂ glass or the like). In particular, since the synthetic quartz glass has a high transmittance with respect to ArF excimer laser light (wavelength 193 nm), it is preferable to use synthetic quartz glass as the material of the glass substrate. The exposure light applied to the mask blank and the transfer mask of the present invention is not particularly limited, and examples thereof include ArF excimer laser light, KrF excimer laser light, and i-ray light. The mask blank and transfer mask which apply an ArF excimer laser to exposure light have very high required levels, such as the flatness of a main surface and the positional precision of the transfer pattern formed from a thin film. Therefore, it is especially effective to use the manufacturing method of this invention for manufacture of the mask blank and transfer mask which apply an ArF excimer laser to exposure light.

The optical heat treatment to the glass substrate after mirror polishing is especially effective when forming the thin film which consists of a material containing tantalum. This is because the material containing tantalum has a property of easily introducing hydrogen. Since tantalum has brittleness characteristics when hydrogen is introduced, it is desired to suppress the hydrogen content even in a state immediately after forming a thin film. For this reason, in this invention, the thin film formed on the main surface of the glass substrate of heat processing selects the material which contains tantalum and does not contain hydrogen substantially. The term "contains substantially no hydrogen" means that the hydrogen content in the thin film is at least 5 at% or less. It is preferable that it is 3 at% or less, and, as for the preferable range of hydrogen content in a thin film, it is more preferable that it is below a detection lower limit. For the same reason, in the present invention, in the present invention, the step of forming a thin film is provided with a glass substrate after an optical heating treatment in a film formation chamber, a target containing tantalum, and a sputtering gas containing no hydrogen in the film formation chamber. It can also be performed by introducing and forming a thin film by the sputtering method on the main surface of a glass substrate.

As a material containing tantalum and substantially free of hydrogen for forming a thin film formed on a glass substrate, for example, tantalum metal and at least one element selected from nitrogen, oxygen, boron and carbon in tantalum And a material that does not substantially contain hydrogen. For example, as a material which contains tantalum and does not contain hydrogen substantially, Ta, TaN, TaON, TaBN, TaBON, TaCN, TaCON, TaBCN, TaBOCN, etc. are mentioned. About said material, you may contain metal other than tantalum in the range by which the effect of this invention is acquired.

In the material for forming the thin film, examples of metals other than tantalum include hafnium, zirconium, germanium, platinum, and gold. However, when it contains said metal, it is necessary to make the content rate of tantalum when the content of all the metals in a thin film be 1 is made larger than 0.5, It is preferable to set it as 0.6 or more, and to set it as 0.7 or more. It is more preferable.

Moreover, although there exists a metal which has a property which is easy to introduce hydrogen other than tantalum, when the tantalum in the material of the said thin film is replaced by the metal which has a property which is easy to introduce another hydrogen, the effect similar to this invention is acquired. Examples of the metal having the property of easily introducing other hydrogen include niobium, vanadium, titanium, magnesium, lanthanum, zirconium, scandium, yttrium, lithium and praseodymium. In addition, the same effect is acquired also about the alloy which consists of tantalum and two or more metals chosen from the metal group which has the property to introduce hydrogen easily. Even when a thin film made of a material containing these metals or alloys is formed on the glass substrate, the light heating treatment on the glass substrate is effective.

When the thin film made of a material containing tantalum has an oxygen content of 50 at% or more, the effect of preventing hydrogen from being introduced into the material is obtained to some extent. For this reason, if the material of the thin film on the glass substrate main surface side is a material containing tantalum having an oxygen content of less than 50 at%, the effect of light-heating the glass substrate before film formation is more preferable.

In the case where the thin film made of a material containing tantalum is formed in contact with the main surface of the glass substrate, hydrogen or the like present in the glass substrate is directly introduced into the thin film. In such a structure, the effect by removing OH group, hydrogen, water, etc. from a glass substrate by a light heating process can be acquired more remarkably.

It is preferable that the thin film of the said mask blank is formed from the material which contains tantalum and nitrogen, and does not contain hydrogen substantially. Tantalum is a natural oxidizable material. As oxidation progresses, tantalum lowers the light shielding performance (optical density) with respect to the exposure light. In addition, from the viewpoint of forming a thin film pattern, the material in a state where oxidation of tantalum is not advanced includes an etching gas containing fluorine (fluorine based etching gas) and an etching gas containing chlorine and not containing oxygen (oxygen ratio). It can be said that dry etching is possible with any of chlorine-containing etching gas). However, tantalum which has undergone oxidation is a material which is difficult to dry etch with an oxygen-free chlorine etching gas from the viewpoint of forming a thin film pattern, and it can be said that only fluorine etching gas can be dry etched. By containing nitrogen in tantalum, oxidation of tantalum can be suppressed. Moreover, when the thin film which consists of a material containing tantalum is formed in contact with the main surface of a glass substrate, it is preferable to contain nitrogen. This is because by including nitrogen in the material containing tantalum, it is possible to suppress the decrease in the optical density as compared with the case of containing oxygen while reducing the back reflectance of the exposure light. It is preferable that nitrogen content in a thin film is 30 at% or less from a viewpoint of an optical density, It is more preferable that it is 25 at% or less, It is further more preferable that it is 20 at% or less. In addition, when the nitrogen content in a thin film needs to make the back surface reflectance less than 40%, it is desired that it is 7 at% or more.

Moreover, it is preferable that the high oxide layer containing 60at% or more of oxygen is formed in the surface layer (surface layer of the thin film on the opposite side to a glass substrate main surface) of the said thin film of the mask blank. As described above, hydrogen draws not only from the glass substrate, but also hydrogen in the gas surrounding the mask blank from inside the thin film surface. The high oxide film of the thin film material has a high binding energy and has a property of preventing the penetration of hydrogen into the thin film. In addition, the high oxide layer (tantalum high oxide layer) of the material containing tantalum also has excellent chemical resistance, hot water resistance, and light resistance to ArF exposure light.

It is desired that the thin film in the mask blank and the transfer mask has a crystal structure of microcrystalline, preferably amorphous. When the crystal structure of the thin film is microcrystalline or amorphous, the crystal structure in the thin film is less likely to be a single structure, and the crystal structure is likely to be in a mixed state. That is, in the case of the tantalum high oxide layer, TaO bonds, Ta ₂ O ₃ bonds, TaO ₂ bonds, and Ta ₂ O ₅ bonds tend to be mixed. As the ratio of the presence of Ta ₂ O ₅ bonds to a predetermined surface layer in the light shielding film increases, all of the characteristics of preventing hydrogen invasion, chemical resistance, hot water resistance, and ArF light resistance become high, and these characteristics increase as the presence ratio of TaO bond increases. This tends to be lowered.

In the tantalum high oxide layer, when the oxygen content in the layer is 60at% or more and less than 66.7at%, it is considered that the tantalum and oxygen bonding state in the layer tends to be mainly composed of Ta ₂ O ₃ bonds. In the case of oxygen content in this layer, it is thought that TaO bond which is the most unstable bond becomes very small compared with the case where the oxygen content in a layer is less than 60at%. In the tantalum high oxide layer, when the oxygen content in the layer is 66.7 at% or more, the combined state of tantalum and oxygen in the layer is considered to be a high tendency for the TaO ₂ bond to be mainly. In the case of the oxygen content in this layer, it is considered that both TaO bond which is the most unstable bond and Ta ₂ O ₃ which is the next unstable bond are very small.

When the tantalum high oxide layer has an oxygen content of 68 at% or more in the layer, not only the TaO ₂ bond is the main component but also the ratio of the bonded state of Ta ₂ O ₅ is considered to be high. After this the same oxygen content, "Ta ₂ O _3", and the bonding state of "TaO _2" are so rarely present, combination state advances are not be present in the "TaO". If the oxygen content in the layer of the tantalum high oxide layer is 71.4 at%, it is considered that it is substantially formed only in the bonded state of Ta ₂ O ₅ . When the oxygen content in the layer of the tantalum high oxide layer is 60 at% or more, not only "Ta ₂ O ₅ " which is the most stable bonding state but also the bonding states of "Ta ₂ O ₃ " and "TaO ₂ " are included. In addition, when the oxygen content in the layer is 60 at% or more, the TaO bond, which is at least the most unstable bond, becomes a very small amount such that it does not affect the ability to inhibit hydrogen penetration, the resistance, and the ArF light resistance. Therefore, the lower limit of the oxygen content in the layer is considered to be 60 at%.

The ratio of Ta ₂ O ₅ and the combination of a tantalum oxide layer, is higher than the ratio of Ta ₂ O ₅ combined in the thin film other than the oxide layer and is preferable. Ta ₂ O ₅ bond is a bonded state having a very high stability, by increasing the abundance ratio of Ta ₂ O ₅ bond in the high oxide layer, mask cleaning resistance such as properties that prevent hydrogen intrusion, chemical resistance and hot water resistance, and ArF Light resistance greatly increases. In particular, the tantalum high oxide layer is most preferably formed only in a bonded state of Ta ₂ O ₅ . In addition, it is preferable that content of nitrogen and other elements of a tantalum high oxide layer is a range which does not affect the effect, such as the property which inhibits hydrogen intrusion, and it is preferable that it is not contained substantially.

It is preferable that the thickness of the said tantalum high oxide layer is 1.5 nm or more and 4 nm or less. If it is less than 1.5 nm, the effect of preventing hydrogen penetration is too small, and if it exceeds 4 nm, the influence on the surface reflectivity becomes large, and a predetermined surface reflectance (reflectance for exposure light or reflectance spectrum for light of each wavelength) The control to get is difficult. In addition, since the optical density of the tantalum high oxide layer is very low with respect to the ArF exposure light, the optical density that can be ensured in the surface antireflection layer is lowered, and it acts negatively from the viewpoint of thinning the film thickness of the thin film. In consideration of the balance between the viewpoint of securing the optical density of the entire thin film and the viewpoint of preventing hydrogen intrusion, improving the chemical resistance and ArF light resistance, the thickness of the high oxide layer is more preferably 1.5 nm or more and 3 nm or less. desirable.

The method for forming the tantalum high oxide layer may include hot water treatment, ozone-containing water treatment, heat treatment in a gas containing oxygen, ultraviolet irradiation treatment in a gas containing oxygen, and / or a mask blank after a thin film is formed. Or O ₂ plasma treatment. In addition, a high oxide layer is not limited to the high oxide film of the metal which forms a thin film. As long as there is a property of preventing hydrogen intrusion, a high oxide film of any metal may be used, or a structure in which the high oxide film is laminated on the surface of the thin film may be used. Moreover, as long as it is a material which has a characteristic which prevents the penetration of hydrogen into a thin film, it may not be a high oxide and it can also be set as the structure which laminated | stacked the material film on the surface of a thin film.

The thin film of the mask blank has a structure in which a lower layer and an upper layer are laminated from the glass substrate side, and the lower layer is made of a material containing tantalum and nitrogen and substantially free of hydrogen, and the upper layer is It is preferable to consist of a material containing tantalum and oxygen. By having such a structure, it can function as a film (antireflection film) which has a function which controls the surface reflectance with respect to the exposure light of a thin film in the upper layer.

Moreover, it is preferable to form the high oxide layer containing 60at% or more of oxygen in the upper surface layer (surface layer on the opposite side to lower layer side). The form and action effects of the high oxide layer and the high oxide layer of the material containing tantalum are the same as above. In consideration of the ease of control of surface reflectance characteristics (reflectance to ArF exposure light or reflectance spectrum to light of each wavelength), the upper layer preferably has an oxygen content of less than 60 at% except for the surface layer portion.

The upper layer is formed of a material containing oxygen in tantalum. From the viewpoint of forming a thin film pattern, dry etching of the upper layer (a material containing oxygen in tantalum) is difficult with an oxygen-free chlorine etching gas, and dry etching is possible only with a fluorine etching gas. In contrast, the lower layer is formed of a material containing tantalum and nitrogen. From the viewpoint of forming a thin film pattern, the dry etching of the lower layer (tantalum and nitrogen-containing material) may be either a fluorine-based etching gas or an oxygen-free chlorine-based etching gas. For this reason, when dry-etching a thin film by using a resist pattern (resist film in which the transfer pattern was formed) as a mask, when forming a pattern by dry-etching, a pattern is formed by performing dry etching with a fluorine-type etching gas to an upper layer, and masking an upper pattern As a result, a process of forming a pattern by performing dry etching with an chlorine-based etching gas containing no oxygen in the lower layer can be used. By applying such an etching process, it is possible to reduce the thickness of the resist film.

In order to make the dry etching of the upper layer by the oxygen-free chlorine etching gas more difficult, what is necessary is just to increase the abundance amount of the bonding of tantalum and oxygen with a comparatively high bond energy in an upper layer. In order to make dry etching of an upper layer more difficult, it is preferable that the ratio of oxygen content with respect to tantalum content of an upper layer is 1 or more. When the upper layer is formed only of tantalum and oxygen, the oxygen content in the upper layer is preferably 50 at% or more.

About the material which forms the lower layer of the said thin film, it is the same as what was listed to the material which contains said tantalum and does not contain hydrogen substantially. Moreover, as for the material which forms an upper layer, the material containing tantalum and oxygen, and also containing nitrogen, boron, carbon, etc. is preferable. As a material which forms an upper layer, TaO, TaON, TaBO, TaBON, TaCO, TaCON, TaBCO, TaBOCN, etc. are mentioned, for example.

The thin film of the above mask blank is not limited to only the above laminated structure. It may be set as a three-layer laminated structure, it may be set as the composition gradient film of a single | mono layer, and it may be set as the film structure in which the composition was inclined between upper layer and lower layer. Although the thin film of said mask blank is used as a light shielding film which functions as a light shielding pattern when the transfer mask is produced, it is not limited to this. The thin film of the mask blank can be applied as an etching stopper film or an etching mask film (hard mask film), and can also be applied to a halftone phase shift film or a light semitransmissive film as long as it is within the constraints required for the thin film. It is possible. In addition, since the said mask blank can suppress the time-dependent change of the compressive stress of a thin film, the double patterning technique (conventional double patterning technique (DP technique), double exposure which requires high positional precision for the pattern formed from a thin film) In the case of producing a transfer mask set to which a technique (DE technique) or the like is applied, it can be particularly preferably used.

In the thin film of the mask blank, a material having etching selectivity between the glass substrate and the thin film, both the glass substrate and the thin film (materials containing Cr, for example, Cr, CrN, CrC, CrO, CrON, CrC, etc.) You may form the etching stopper film or the etching mask film which consist of these. Further, a halftone phase shift film having a predetermined phase shift effect and transmittance or a light semitransmissive film having only a predetermined transmittance may be formed between the glass substrate and the thin film (in this case, the thin film may be a light shielding band and // Or as a light shielding film for forming a light shielding patch or the like). However, these films in contact with the thin film are basically materials that do not contain hydrogen (they are not actively contained and the treatment performed until the thin film is formed is a means for preventing the introduction of hydrogen as much as possible). It is necessary to form.

It is preferable that the transfer mask manufactured by the manufacturing method of this invention is produced by forming a transfer pattern in the thin film of said mask blank using the mask blank manufactured by said manufacturing method. Since the increase of the compressive stress of the thin film with time lapse is suppressed in the mask blank which passed more than a fixed period after manufacture, the flatness of the mask blank is maintained at the high level requested | required. By using a mask blank having such characteristics, the completed transfer mask can be made to the required high flatness. Moreover, since the compressive stress of a thin film is suppressed, the amount of position shift on the main surface which each pattern of the thin film released | released from the surrounding compressive stress after the etching process which manufactures a transfer mask can also be suppressed.

On the other hand, when a transfer mask is produced using a mask blank that has not elapsed since manufacture, the transfer mask (conventional transfer mask) immediately after production by a conventional manufacturing method is required to have high flatness. There is a road. However, since the transfer mask of the conventional transfer mask is stored in a mask case without being used or stored in the mask case or used continuously in the exposure apparatus, the compressive stress of the thin film is increased, thereby deteriorating flatness. There exists a possibility that each pattern of a thin film may largely shift position. When the transfer mask of the present invention produced by using the mask blank manufactured by the manufacturing method of the present invention can be used to suppress the increase in compressive stress of the thin film over time, the mask case is not used after production. Even if it is stored and stored in the case, or when it is set and used continuously by the exposure apparatus, the required high flatness can be maintained continuously, and the position shift of each pattern of a thin film can also be suppressed.

Moreover, it is preferable that the high oxide layer containing 60at% or more of oxygen is formed in the surface layer of the transfer pattern formed from the thin film of this transfer mask. The form and working effects of the high oxide layer and the high oxide layer of the material containing tantalum are the same as above.

The transfer mask can be used as a binary mask, and is particularly preferable when ArF excimer laser light is applied to the exposure light. In addition, the transfer mask is also applicable to a wave entering Levenson type phase shift mask, a halftone type phase shift mask, an enhancer type phase shift mask, a chromeless phase shift mask (CPL mask), and the like. In addition, since the transfer mask is excellent in pattern position accuracy, the transfer mask can be particularly preferably used for a transfer mask set to which a double patterning technique (DP technique, DE technique, etc.) is applied.

As the etching performed on the mask blank when producing the transfer mask, dry etching effective for forming a fine pattern is suitably used. For dry etching of the thin film by the above-mentioned fluorine-containing etching gas, for example, fluorine-based etching gas such as SF ₆ , CF ₄ , C ₂ F ₆ and CHF ₃ can be used. Further, dry etching of the thin film by the etching gas containing chlorine and oxygen does not include at least one of chlorine-based gas such as Cl ₂ and CH ₂ Cl ₂ or these chlorine-based gases, He, H _2, N _2, may be used to mix gases such as Ar and / or C ₂ H _4.

By exposing and transferring said transfer pattern to a resist film on a semiconductor substrate using the transfer mask manufactured by the above manufacturing method, a semiconductor device having a high precision pattern can be manufactured. This is because the transfer mask has high flatness and pattern position precision required at the time of manufacture. In addition, the transfer mask is stored in a mask case without use after fabrication, stored in a mask case for a period of time, and then placed in an exposure apparatus and started to be used for exposure transfer or after exposure to the exposure apparatus without time. This is because, even when set and used for exposure transfer, the required high flatness can be maintained continuously, and the positional shift of each pattern of the thin film can be suppressed.

As shown in Fig. 1, in the mask blank according to the present embodiment, an underlayer (light shielding layer) 2 having a main component of tantalum and nitrogen having a thickness of 42.5 nm is formed on a glass substrate 1 made of synthetic quartz. The upper layer (reflective prevention layer) 3 which has a thickness of 5.5 nm thick and oxygen as a main component is formed on this lower layer 2, and the tantalum high-oxidation layer 4 is formed in the surface layer of this upper layer 3. . Furthermore, the light shielding film 30 is comprised from the lower layer 2 and the upper layer 3 containing the tantalum high oxide layer 4.

In addition, in the transfer mask according to the present embodiment, as shown in FIG. 2, the light shielding film 30 of the mask blank shown in FIG. 1 is patterned so that the light shielding film 30 remains on the glass substrate 1. A fine pattern composed of the light shielding portion 30a and the removed light transmitting portion 30b is formed. Tantalum high oxide layer 4a is formed in the surface layer of light shielding film pattern (thin film pattern) 30a. Moreover, tantalum high oxide layer 4b is formed in the surface layer of the side wall of the pattern 3a of the upper layer 3, and tantalum is formed in the surface layer of the side wall of the pattern 2a of the lower layer 2 in the side wall of the light shielding film pattern 30a. The high oxide layer 4c is formed. The method of forming the tantalum high oxide layers 4b and 4c on the sidewalls of the patterns 2a and 3a of the lower layer 2 and the upper layer 3 is similar to the method of forming the tantalum high oxide layer in the mask blank. to be.

EXAMPLE

Next, the example which manufactured the mask blank and transfer mask which concern on this embodiment is demonstrated as an Example, referring FIG.

(Example 1)

[Production of Mask Blanks]

The synthetic quartz ingot manufactured by the manufacturing method (suit method) conventionally used was heat-processed at 1000 degreeC or more for 2 hours or more. Next, from the synthetic quartz ingot after heat processing, the glass substrate which consists of synthetic quartz of about 152 mm x 152 mm and a thickness of about 152 mm x 152 mm and thickness was cut out, and the chamfering surface was formed suitably.

About the cut glass substrate, grinding was performed about the main surface and the cross section. The rough polishing process and the precision polishing process were performed in order with respect to the main surface of the glass substrate after grinding. Specifically, the glass substrate supported by the carrier is sandwiched between the upper and lower plates of the double-side polishing apparatus provided with polishing pads (hard polishers) on the upper and lower surface plates, and the abrasive grains of cerium oxide (grain rough polishing process: 2 to 2). The glass substrate was planetary geared while the polishing liquid containing 3 µm and a precision polishing step: 1 µm) was introduced into the surface surface. The glass substrate after each process was immersed in a washing tank (ultrasound application), and the washing | cleaning which removes the abrasive grain to which adhered was performed.

An ultrafine polishing process and a final polishing process were performed on the main surface of the glass substrate after washing. Specifically, the glass substrate supported by the carrier is sandwiched between the upper and lower plates of the double-side polishing apparatus having a polishing pad (super soft polisher) on each of the upper and lower surfaces, and the abrasive grains of colloidal silica (particle size ultra-precision polishing process: The glass substrate was subjected to planetary gear movement while a polishing liquid containing 30 to 200 nm and a final polishing step: average 80 nm) was introduced into the surface surface. The glass substrate after the ultra-precise polishing process was immersed in a cleaning tank containing hydrofluoric acid and silicic acid (ultrasound applied) to remove the abrasive grains.

The glass substrate after the final polishing process has a flatness of 0.3 µm or less in a thickness of 6.35 mm and a 142 mm square inner region (hereinafter referred to as 142 mm x 142 mm region) based on the center of the main surface. Roughness Rq was 0.2 nm or less, and it was a level sufficient as the glass substrate used for the mask blank of a 22 nm node.

Next, this glass substrate was set in the mounting base 14 of the optical heating apparatus shown in FIG. 6, and the optical heating process with respect to the glass substrate 1 was performed. The circumference | surroundings of the glass substrate 1 in the process chamber 11 were made into the vacuum of 20 kPa, and the halogen heater 16 to be used used the thing of the color temperature 2500K. The photoheating process was performed on the conditions which the state in which the temperature of the glass substrate heated to 500 degreeC continues for 20 minutes. In addition, the glass substrate 1 after the heat treatment is cleaned with a detergent and rinsed with pure water, and further irradiated with an Xe excimer lamp in the air, by ultraviolet rays and O ₃ generated by the ultraviolet rays. The main surface was washed.

Next, the glass substrate after washing | cleaning was introduce | transduced into the DC magnetron sputter apparatus. A mixed gas of Xe and N ₂ was introduced into the sputtering apparatus, and a TaN layer (lower layer) 2 having a film thickness of 42.5 nm was formed in contact with the main surface of the glass substrate 1 by the sputtering method using a tantalum target ( (A) of FIG. 3). Further, the gas in the sputtering device was replaced with a mixed gas of Ar and O ₂ , and a TaO layer (upper layer) 3 having a thickness of 5.5 nm was formed by sputtering using a tantalum target in the same manner (FIG. 3 ( a). In the step immediately after the film formation, the flatness of the mask blank including the light shielding film 30 on the surface of the light shielding film 30 on the main surface of the glass substrate was measured by a flatness measuring device UltraFLAT 200M (manufactured by Corning TOROPEL). Moreover, as a result of performing HFS / RBS analysis about the mask blank manufactured on the same conditions, the hydrogen content in TaN film was below a detection lower limit.

Next, the glass substrate in which the light shielding film 30 of the laminated structure of the TaN layer (lower layer) 2 and the TaO layer (upper layer) 3 was formed is provided in a heating furnace, the gas in a furnace is replaced with nitrogen, and a heating temperature is carried out. The heat treatment for 1 hour was performed at 300 degreeC, and the accelerated test which forcibly introduces hydrogen in a glass substrate to the light shielding film was done. About the mask blank provided with the light shielding film 30 after an acceleration test, the flatness in the surface of the light shielding film 30 on the glass substrate main surface was measured with the flatness measuring device Ultra FLAT 200M (made by Corning TOROPEL). The difference between the flatness measured after the acceleration test and the flatness measured before the acceleration test was 29 nm (the surface shape changed in the convex direction after the acceleration test) due to the flatness difference in the region within 142 mm x 142 mm. The numerical value of this flatness difference exists in the range of a measurement error, and the change in flatness was hardly seen before and after heat processing. Moreover, the result of having performed HFS / RBS analysis about the mask blank provided with the light shielding film 30 after an acceleration test is shown in FIG. From the result of FIG. 4, it can be said that about 2at% (atomic%) of hydrogen is contained in a TaN layer. From this result, since a heating furnace is nitrogen atmosphere, the source of hydrogen introduced into a TaN layer can be called a glass substrate. In addition, it can be seen from the flatness difference before and after the acceleration test that the degree of introduction of hydrogen into the TaN layer by about 2 at% hardly affects the flatness of the main surface.

Next, the mask blank which formed the light shielding film 30 of the laminated structure of TaN layer 2 and TaO layer 3 in contact with the main surface of the glass substrate 1 was manufactured on the same conditions as the above. This mask blank was installed in a hot plate, and the heat processing at 300 degreeC was performed in air | atmosphere, and the high oxide layer 4 of tantalum was formed in the surface layer in TaO layer 3 (refer FIG.3 (b)). HFS / RBS analysis was performed on the mask blank after the high oxide layer 4 was formed, and it was confirmed that the high oxide layer 4 having a high oxygen content was formed from the surface of the TaO layer 3 to a depth of 2 nm. It became. Also showed a high peak at the position of the XPS analysis (X-ray photoelectron spectroscopy), carried out the bar, the light-shielding film 30 to the narrow spectrum of the outermost surface layer, Ta ₂ O ₅ bound energy (25.4eV) of the. Further, in the narrow spectrum in the layer having a depth of 1 nm from the surface of the light shielding film 30, it is between the peak at the position of the binding energy (25.4 eV) of Ta ₂ O _{5 and} the binding energy (21.0 eV) of Ta. A peak was observed near Ta ₂ O ₅ . These results can be said that from the high oxide layer 4 having a Ta ₂ O ₅ bonded to the surface of the TaO layer 3 is formed. As described above, the light shielding film 30 having the laminated structure of the TaN layer 2 and the TaO layer 3 including the tantalum high oxide layer 4 is provided on the main surface of the glass substrate 1. The mask blank of Example 1 was obtained.

The reflectance (surface reflectance) at the film surface of the light shielding film 30 manufactured as described above was 30.5% with ArF exposure light (wavelength 193 nm). The reflectance (rear reflectance) of the surface on which the light shielding film of the glass substrate 1 was not formed was 38.8% with ArF exposure light. In addition, the optical density in ArF exposure light was 3.02.

[Creation of Warrior Mask]

Next, using the obtained mask blank, the transfer mask of Example 1 was produced with the following procedure.

First, a chemically amplified resist 5 for electron beam drawing with a film thickness of 100 nm is applied by spin coating (see FIG. 3C), and electron beam drawing and development are performed to form a resist pattern 5a. (See FIG. 3 (d)). In addition, the pattern which carried out the electron beam drawing used either the thing which divided | segmented the fine pattern of 22 nm node into two comparatively coarse transcription patterns using the double patterning technique.

Next, dry etching using a fluorine-based (CF ₄ ) gas was performed to prepare a pattern 3a of the TaO layer (upper layer) 3 including the high oxide layer 4 (see FIG. 3E). Subsequently, dry etching using a chlorine-based (Cl ₂ ) gas was performed to produce a pattern 2a of the TaN layer (lower layer) 2, and a light shielding film pattern 30a was produced on the glass substrate 1 (FIG. 3). (F)). Subsequently, the resist on the light shielding film pattern 30a was removed to obtain a light shielding film pattern 30a having a function as a transfer mask (see FIG. 3G). The transfer mask (binary mask) was obtained by the above.

Next, with respect to the transfer mask produced, deionized water at 90 ° C. was stored before natural oxidation proceeded (for example, within 1 hour after film formation) or in an environment where natural oxidation did not proceed after film formation. DI water) was immersed for 120 minutes, and hot water treatment (surface treatment) was performed. This obtained the transfer mask of Example 1.

In the transfer mask of this Example 1, formation of the tantalum high oxide layers 4a, 4b, and 4c as schematically shown in FIG. 2 was observed on the surface layer of the light shielding film pattern 30a. Specifically, the cross-sectional observation by a scanning transmission electron microscope (STEM) confirmed the high oxide layers 4a, 4b, and 4c having a thickness of 3 nm. In addition, HFS / RBS analysis was performed on the part with the light shielding film of the light shielding film pattern 30a. According to the analysis result of the depth direction profile of the light shielding film, it was confirmed that the tantalum high oxide layer 4a of the surface layer of the TaO layer 3 has 71.4 to 67 at% of oxygen content. On the other hand, it is difficult to confirm oxygen content by HFS / RBS analysis about the pattern side wall parts 4b and 4c. For this reason, compared with the result of HFS / RBS analysis of the high-oxidation layer 4a of the surface layer of the light-shielding film pattern 30a analyzed previously using EDX (energy-dispersive X-ray spectroscopy) analysis at the time of observation by STEM, It was confirmed that the oxygen content was the same in the high oxide layer 4a and the high oxide layers 4b and 4c.

The accelerated test was performed on the transfer mask of Example 1 produced under the same conditions as that performed on the mask blank (substituting gas in the furnace with nitrogen and heating at 300 ° C. for 1 hour). In addition, before and after the acceleration test, the pattern width and the space width at the in-plane predetermined portions of the transfer mask were respectively measured. Before and after the acceleration test, the variation widths of the pattern width and the space width were all within the allowable range. By the same procedure, using the mask blank of Example 1, and using a double patterning technique, the transfer pattern having the other transfer pattern among the fine patterns of 22 nm nodes divided into two relatively coarse transfer patterns. A mask was produced. By the above procedure, the transfer mask set which can transfer the fine pattern of a 22 nm node to a transfer object was obtained by exposing and transferring by double patterning technique using two transfer masks.

[Manufacture of Semiconductor Device]

Using the produced transfer mask set, an exposure apparatus using an ArF excimer laser as exposure light, a double patterning technique was applied to expose and transfer a 22 nm node fine pattern to a resist film on a semiconductor device. The predetermined development process was performed to the resist film on the semiconductor device after exposure, the resist pattern was formed, the underlayer film was dry-etched using the resist pattern as a mask, and the circuit pattern was formed. When the circuit pattern formed in the semiconductor device was confirmed, there was no wiring short circuit and disconnection of the circuit pattern due to lack of overlapping accuracy.

(Comparative Example 1)

[Production of Mask Blanks]

By the same procedure as in Example 1, a glass substrate after the final polishing step was prepared. The glass substrate was not subjected to the same heat treatment as in Example 1, but washed with a detergent and rinsed with pure water, and irradiated with an Xe excimer lamp in the air, and generated by ultraviolet rays and the ultraviolet rays. The main surface was washed with O ₃ . The light shielding film 30 was formed into a film on the glass substrate after washing | cleaning on the film forming conditions similar to Example 1. FIG. In the step immediately after the film formation, the flatness of the mask blank including the light shielding film 30 on the surface of the light shielding film 30 on the main surface of the glass substrate was measured by the flatness measuring device UltraFLAT 200M (manufactured by Corning TOROPEL). Moreover, as a result of performing HFS / RBS analysis about the mask blank manufactured on the same conditions, the hydrogen content in TaN film was below a detection lower limit.

Next, the glass substrate which formed the light shielding film 30 of the laminated structure of TaN layer (lower layer) 2 and TaO layer (upper layer) 3 is provided in a heating furnace, the gas in a furnace is replaced with nitrogen, and heating is carried out. The heat treatment for 1 hour was performed at the temperature of 300 degreeC, and the acceleration test which forcibly introduces hydrogen in a glass substrate into the light shielding film was done. About the mask blank provided with the light shielding film 30 after an acceleration test, the flatness in the surface of the light shielding film 30 on the glass substrate main surface was measured with the flatness measuring device UltraFLAT 200M (made by Corning TOROPEL). The difference between the flatness measured after the acceleration test and the flatness measured before the acceleration test is 219 nm (the surface shape changes in the convex direction after the acceleration test) due to the flatness difference in the region within 142 mm x 142 mm, and the flatness greatly changes. It was. This flatness difference was unacceptable in the mask blank for at least 22 nm node. In addition, the result of having performed HFS / RBS analysis about the mask blank provided with the light shielding film 30 after an acceleration test is shown in FIG. From the result of FIG. 5, the TaN layer contains about 6.5 at% of hydrogen. From this result, since a heating furnace is nitrogen atmosphere, the source of hydrogen introduced into a TaN layer can be called a glass substrate. From the flatness difference before and after the acceleration test, it was found that when the hydrogen was introduced into the TaN layer by about 6.5 at%, the flatness of the main surface was greatly deteriorated.

Next, the mask blank which formed the light shielding film 30 of the laminated structure of TaN layer 2 and TaO layer 3 in contact with the main surface of the glass substrate 1 was manufactured on the same conditions as the above. This mask blank was installed in a hot plate similarly to Example 1, and it heat-processed at 300 degreeC in air | atmosphere, and formed the high oxide layer 4 of tantalum in the surface layer in TaO layer 3 (FIG.3 (b). ) Reference). As described above, the light shielding film 30 having the laminated structure of the TaN layer 2 and the TaO layer 3 including the tantalum high oxide layer 4 is provided on the main surface of the glass substrate 1. The mask blank of Comparative Example 1 was obtained.

[Creation of Warrior Mask]

Next, using the obtained mask blank, the transfer mask of the comparative example 1 was produced by the procedure similar to Example 1. With respect to the transfer mask of Comparative Example 1 produced, an accelerated test was performed under the same conditions as that performed on the mask blank (substituting gas in the furnace with nitrogen and heating at 300 ° C. for 1 hour). In addition, before and after the acceleration test, the pattern width and the space width at the in-plane predetermined portions of the transfer mask were respectively measured. Before and after the acceleration test, the variation widths of the pattern width and the space width were both large and were clearly outside the permissible range in the transfer mask to which the double patterning technique for at least the 22 nm node was applied. For this reason, according to the same procedure, a transfer mask set having a transfer pattern having the other transfer pattern among the fine patterns of 22 nm nodes divided into two relatively coarse transfer patterns using a double patterning technique is produced. Even if it was produced, the superposition accuracy was low and it could not be used as a transfer mask set for double patterning.

Moreover, the transfer mask of the comparative example 1 was produced by the procedure similar to Example 1 using the mask blank after performing said acceleration test. As a result, since the flatness was already greatly deteriorated in the state of the mask blank, the movement on the main surface of the pattern was remarkable when chucked to the mask stage of the exposure apparatus, so that a double patterning technique for at least 22 nm node was applied. In the transfer mask, it was clearly outside the permissible range. Moreover, since the compressive stress of the light shielding film was remarkably large, the pattern of the light shielding film after dry etching had large deviation from the electron beam drawing pattern.

1: glass substrate
2: lower layer (TaN layer)
2a: Underlayer Pattern
3: upper layer (TaO layer)
3a: upper layer pattern
4, 4a, 4b, 4c: tantalum high oxide layer
5: resist film
11: processing chamber
12: light source unit
14: wit
15: unit frame
16: halogen heater
17, 18: reflector
30: light shielding film
30a: shading part
30b: floodlight

Claims (16)

A glass substrate subjected to mirror polishing on a main surface thereof, the step of preparing a glass substrate having an absorption band with a wavelength of 2.72 µm,
A step of performing a light heating treatment for irradiating light having a wavelength of 2.72 μm to the prepared glass substrate,
And a step of forming a thin film made of a material containing tantalum and substantially free of hydrogen on the main surface of the glass substrate after the light heating treatment. delete delete The method of claim 1,
The said photo heat processing is a process of irradiating the said glass substrate with the light emitted from a halogen heater, The manufacturing method of the mask blank characterized by the above-mentioned. The method of claim 1,
The said thin film is formed in contact with the main surface of the said glass substrate, The manufacturing method of the mask blank characterized by the above-mentioned. The method of claim 1,
The said thin film is a manufacturing method of the mask blank characterized by the above-mentioned material which consists of a material which contains tantalum and nitrogen and does not contain hydrogen substantially. The method of claim 1,
The thin film has a structure in which a lower layer and an upper layer are laminated from the glass substrate side, and the lower layer is made of a material containing tantalum and nitrogen and substantially no hydrogen, and the upper layer is tantalum and oxygen. The manufacturing method of the mask blank characterized by the above-mentioned material. A glass substrate subjected to mirror polishing on a main surface thereof, the step of preparing a glass substrate having an absorption band with a wavelength of 2.72 µm,
A step of performing a light heating treatment for irradiating light having a wavelength of 2.72 μm to the prepared glass substrate,
The glass substrate after the optical heating treatment is provided in a film formation chamber, a target containing tantalum is used, a sputtering gas containing no hydrogen is introduced into the film formation chamber, and sputtering is performed on the main surface of the glass substrate. A process for producing a mask blank, comprising the step of forming a thin film. delete delete The method of claim 8,
The said photo heat processing is a process of irradiating the said glass substrate with the light emitted from a halogen heater, The manufacturing method of the mask blank characterized by the above-mentioned. The method of claim 8,
The said thin film is formed in contact with the main surface of the said glass substrate, The manufacturing method of the mask blank characterized by the above-mentioned. The method of claim 8,
The said thin film is a manufacturing method of the mask blank characterized by the above-mentioned material which consists of a material which contains tantalum and nitrogen and does not contain hydrogen substantially. The method of claim 8,
The thin film has a structure in which a lower layer and an upper layer are laminated from the glass substrate side, and the lower layer is made of a material containing tantalum and nitrogen and substantially no hydrogen, and the upper layer is tantalum and oxygen. The manufacturing method of the mask blank characterized by the above-mentioned material. A transfer pattern is formed on the thin film of the mask blank by using the mask blank produced by the method of manufacturing the mask blank according to any one of claims 1, 4 to 8, and 11 to 14. The manufacturing method of the transfer mask characterized by the above-mentioned. The method of manufacturing a semiconductor device, wherein the transfer pattern is exposed and transferred to a resist film on a semiconductor substrate using the transfer mask manufactured by the method for manufacturing a transfer mask according to claim 15.

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