Glass substrate for thin film device, and film deposition method therefor

The present invention relates to a glass substrate for a thin film device, a film forming method thereof, and a mask blank for extreme ultraviolet light reflection type lithography manufactured by using the glass substrate. In particular, the present invention relates to a glass substrate for a mask blank for extreme ultraviolet light reflection type lithography and a method for forming a film thereof.

In recent years, irregularities and foreign substances in the film are required for thin film devices such as mask blanks for semiconductor lithography, magnetic recording disks, magnetic recording heads, thin film devices for optical communication, liquid crystal display devices, and organic EL display devices. Alternatively, specifications such as the size and number of defects such as pinholes have become extremely strict as thin film devices have become finer and more integrated. Further, in accordance with the demand, specifications such as the size and number of defects of the glass substrate for forming a thin film as such a thin film device are also becoming strict. Especially in the mask blank used for extreme ultraviolet light reflection type lithography, the wavelength of the light used for lithography is very short, about 13.5 nm, so the fine pattern of the semiconductor produced by using it is very short, 45 nm or less. It is small, and as a result, it is required to eliminate those with a size of 25 nm or more as a specification of defects.

On the other hand, such thin film devices are often manufactured by forming a film using a sputtering method such as magnetron sputtering or ion beam sputtering, or a CVD method such as thermal CVD or plasma CVD. In general, film formation is performed in a vacuum chamber, so in consideration of shortening the time required for the film formation process, a vacuum chamber equipped with a load lock, which is an opening / closing mechanism for loading and unloading a substrate, and a film formation chamber for film formation. It is necessary to put the substrate in and out of the film forming chamber while maintaining the vacuum of the film forming chamber.

As such a load lock function, the glass substrate used for film formation is set in the substrate holder in the load lock chamber opened to the atmosphere, the load lock chamber is evacuated to a predetermined degree of vacuum, and then the substrate is loaded. Transferred from the lock chamber to the film forming chamber while holding the vacuum, film formation was performed in the film forming chamber, then transferred again to the load lock chamber while holding the vacuum, and the load lock chamber was opened to the atmosphere again. The filmed glass substrate is taken out. In the load lock of the film forming apparatus provided with such a vacuum chamber, particles are generated in the load lock chamber when the vacuum is exhausted, the particles adhere to the glass substrate, and the film is formed on the glass substrate to which the particles adhere. There was a problem that defects were generated in the film when the above was performed.

One of the causes of such particles generated during vacuum exhaust is that water vapor in the atmosphere in the load lock chamber when opened to the atmosphere condenses due to temperature drop due to adiabatic expansion during vacuum exhaust of the load lock chamber. However, it can be a particle.

In some cases, the particles generated in this way become larger by combining with the surrounding particles, or by taking in an ionic substance that exists in the vacuum chamber and affects the film formation. Adhesion on a glass substrate causes defects in the film to be formed.

Therefore, conventionally, as a countermeasure against particles generated during vacuum exhaust in the load lock chamber of a film forming apparatus equipped with such a vacuum chamber, dry nitrogen gas is used to open the load lock chamber to the atmosphere, or the atmosphere of the load lock chamber is used. The opening speed is very slow, the water vapor in the load lock chamber is removed by a cold trap, and the substrate is heated at the time of exhaust. Such prior art is disclosed in the following patent documents.

However, it is difficult to completely prevent the particles generated in the load lock chamber by such a conventional technique, and in order to reduce the particles consisting of condensed water adhering to the surface of the glass substrate, the exhaust speed of the load lock chamber is increased. Although measures are taken to slow it down, there is a problem that the shortening of the process time of the film forming process is reduced.

On the other hand, the surface of a glass substrate used for thin film devices such as mask blanks for semiconductor lithography, magnetic recording disks, magnetic recording heads, thin film devices for optical communication, liquid crystal display devices, organic EL display devices, etc. is very large. It is required to be clean. When the glass substrate is clean, the contact angle of water with respect to the glass surface is very small, and when water adheres, it spreads widely. The surface of the glass substrate in this state is said to be hydrophilic, and as a result, particles composed of condensed water adhering to the surface of the glass substrate spread widely on the surface of the glass substrate, and defects are less likely to occur in the film to be formed. .. Specifically, this is taken in by the particles made of water containing the above-mentioned ionic substances, but since the particles made of water spread widely on the surface of the glass substrate, the ionic substances do not collect in one place but spread widely. The defects of the film to be formed can be less likely to occur.

On the other hand, the glass substrate used for such an application is usually handled in a clean room in order to prevent particles suspended in the atmosphere from adhering to the surface. However, it is said that many so-called volatile organic compounds are present in the atmosphere in a clean room, and when they adhere to or deposit on the surface of the glass substrate, the surface of the glass substrate loses its hydrophilicity and the contact angle with water is increased. It is known to do. As a result, the water adhering to the surface of the glass substrate cannot spread, causing defects in the film formed on the glass substrate. Specifically, when the particles made of water containing the above-mentioned ionic substances are taken in, the particles made of water cannot spread widely on the surface of the glass substrate, and the ionic substances are gathered in one place. , It remains as a large foreign substance on the substrate and causes defects in the film to be formed.

In addition, the deposition of this volatile organic compound on the surface of the glass substrate also affects the growth process of the film deposited on the surface of the glass substrate (shape when the film grows). In many cases, the deposition of volatile organic compounds promotes island-like film growth, and the film surface after film formation becomes uneven. For this reason, island-like film growth is generally unfavorable for applications that require a film with a smoother surface and a steeper interface, such as thin film device applications. In particular, a mask blank for extreme ultraviolet light reflection type lithography is not particularly preferable for the following reasons. The mask blank for extreme ultraviolet light reflection type lithography is roughly divided into a reflection layer that reflects light having a wavelength of about 13.5 nm and an absorption layer that absorbs light having a wavelength of about 13.5 nm. The reflective layer is composed of alternating layers of high-refractive index material and low-refractive index material, and the smoothness of the layers and the steepness of the interface between the layers are required to obtain high reflectance. .. On the other hand, in the absorption layer, light is scattered in the portion where the smoothness of the outermost surface is poor, that is, the uneven portion, but the scattered light called flare interferes with the light reflected by the reflection layer and has an adverse effect. Therefore, the smoothness of the film is also required.

In addition, particles of organic compounds that are separated from the human body of the worker and are suspended in the surrounding atmosphere adhere to the surface of the glass substrate and form a film on the glass substrate, which causes defects in the film. These drawbacks can be mitigated by working in a clean room with reduced particles in the atmosphere, but cannot be completely eliminated. In particular, it is not easy to eliminate particles of an organic compound having a size of about 25 to 100 nm, which is a problem in a mask blank for extreme ultraviolet light reflection type lithography, in a clean room.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 5-190497</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 2005-76089</text></patcit><patcit num="3"><text>Japanese Patent Application Laid-Open No. 2005-116851</text></patcit>

<p> The present invention not only prevents the defects of the film formed on the surface of the glass substrate due to the particles composed of condensed water generated during the vacuum exhaust of the load lock chamber, but also the volatileity adhering to or deposited on the surface of the glass substrate. Provided are a glass substrate for a thin film device capable of preventing the influence of an organic compound on the film growth process, and a method for forming a film thereof. At the same time, the present invention provides a glass substrate for a thin film device and a method for forming the film, which can prevent defects of a film formed on the surface of the glass substrate due to particles of an organic compound adhering to the surface of the glass substrate. .. Further, the present invention is for extreme ultraviolet light reflection type lithography which can prevent defects having a size of 30 nm or more by being used for film formation of a mask blank for extreme ultraviolet light reflection type lithography which requires specifications of extremely strict defects. A glass substrate for a mask blank, a film forming method thereof, and a mask blank for extreme ultraviolet light reflection type lithography produced by using them are provided.</p>

<p> In order to achieve the above object, the first invention of the present invention provides a glass substrate for a thin film device, characterized in that a surface on which a film is formed has photocatalytic properties.</p><p> Here, the photocatalytic property is TiO.₂It refers to a phenomenon in which high hydrophilicity and strong oxidizing action appear on the surface of a semiconductor material represented by the above when it is irradiated with ultraviolet light or visible light. Due to this high hydrophilicity, it is possible to prevent particles composed of condensed water adhering to the surface of the glass substrate from being widely spread on the surface of the glass substrate and causing defects in the film. Further, due to this strong oxidizing action, it is possible to deposit volatile organic compounds on the surface of the glass substrate and decompose particles of the organic compounds.</p><p> Further, in the second invention of the present invention, a TiO having a thickness of 20 to 3000 nm having photocatalytic properties on the surface on which the film is formed is formed.₂The glass substrate for a thin film device according to claim 1, further comprising a layer containing the above.</p><p> Further, the third invention of the present invention provides the glass substrate for a thin film device according to the first or second invention, which is used as a substrate for a mask blank for extreme ultraviolet light reflection type lithography. Further, in the fourth invention of the present invention, before the film is formed on the glass substrate for the thin film device according to the first to third inventions, the surface to be formed is irradiated with ultraviolet light or visible light. Provided is a method for forming a thin film device, which is a feature.</p><p> Further, the fifth invention of the present invention provides a mask blank for extreme ultraviolet light reflection type lithography formed on the substrate glass for a thin film device according to the third invention.</p><p> Further, the sixth invention of the present invention provides a mask blank for extreme ultraviolet light reflection type lithography formed by the film forming method of the thin film device according to the fourth invention.</p>

<p> According to the glass substrate for a thin film device of the first invention of the present invention, since the substrate has high hydrophilicity due to photocatalytic properties, it is unlikely to be a defect even if water particles are generated, so that the vacuum exhaust rate can be increased. it can. That is, it is possible to manufacture a thin film device in which the defect caused by the condensation of water vapor is not present in the film without reducing the time reduction of the film forming process. Further, according to the glass substrate for a thin film device of the first invention, the volatile organic compound deposited on the surface on which the film is formed can be decomposed by the photocatalytic property to reduce the adverse effect on the growth of the film during the film formation. it can. Further, according to the glass substrate for a thin film device of the first invention, particles of an organic compound adhering to the surface of the glass substrate can be decomposed and defects in the film can be reduced. Further, according to the substrate glass for thin film devices of the first invention, since the surface of the glass substrate has high hydrophilicity, particles adhering to the surface of the glass substrate can be easily cleaned as compared with the conventional glass substrate for thin film devices. Can be removed.</p><p> According to the glass substrate for a thin film device of the second invention of the present invention, TiO having excellent photocatalytic properties.₂By using the above, the effect of the glass substrate for the thin film device of the first invention can be obtained more effectively. Further, according to the glass substrate for a thin film device of the second invention of the present invention, TiO is compared with the usual quartz-based substrate alone.₂Since the reflectance of visible light or ultraviolet light is high on the substrate having the layer containing the above, it is possible to improve the accuracy of the inspection when performing the defect inspection using the visible light laser or the ultraviolet light laser.</p><p> According to the glass substrate for a thin film device of the third invention of the present invention, as a mask blank for extreme ultraviolet light reflection type lithography, defects having a size of 25 nm or more in the film can be reduced as much as possible, and the extreme with few defects. A mask blank for EUV light reflection type lithography can be easily produced. Further, according to the glass substrate for a thin film device of the third invention, the smoothness of the film can be improved and the interface of the layer can be sharpened as a mask blank for extreme ultraviolet light reflection type lithography. As a result, it is possible to produce a mask blank for extreme ultraviolet light reflection type lithography, which is preferable in that the reflectance of the reflective layer is high and at the same time, the flare of the absorbing layer is small.</p><p> According to the film forming method of the thin film device of the fourth invention of the present invention, in order to irradiate the surface to be filmed with ultraviolet light or visible light before the film is formed, the time required for the film forming process is further increased. It is possible to provide a film formation process that can be shortened and has no defects due to particles due to condensation of water vapor on the surface of the glass substrate. Further, according to the film forming method of the thin film device of the fourth invention, the volatile organic compound deposited on the surface of the glass substrate is irradiated with ultraviolet light or visible light on the surface to be formed before the film is formed. It is possible to increase the decomposition rate and reduce the adverse effect of volatile organic compounds on the growth of the film during film formation. Further, according to the film forming method of the thin film device of the fourth invention, the surface to be filmed is irradiated with ultraviolet light or visible light before the film is formed, and the particles of the organic compound adhering to the surface of the glass substrate are decomposed. It can increase the speed and reduce the defects in the film.</p><p> According to the mask blank for extreme ultraviolet light reflection type lithography according to the fifth aspect of the present invention, it is possible to provide a mask blank for extreme ultraviolet light reflection type lithography having a feature that there are few defects in the film. Further, according to the mask blank for extreme ultraviolet light reflection type lithography of the fifth invention, the extreme ultraviolet light reflection type lithography is characterized in that the light reflectance of the reflection layer is high at around 13.5 nm and at the same time, the flare of the absorption layer is small. Mask blanks can be provided.</p><p> According to the mask blank for extreme ultraviolet light reflection type lithography according to the sixth aspect of the present invention, it is possible to provide a mask blank for extreme ultraviolet light reflection type lithography which is preferable in that there are few defects in the film. Further, according to the mask blank for extreme ultraviolet light reflection type lithography of the sixth invention, extreme ultraviolet light reflection type lithography is preferable in that the light reflectance of the reflective layer around 13.5 nm is high and at the same time, the flare of the absorbing layer is small. Mask blanks can be provided.</p>

The glass substrate for a thin film device according to the present invention, which has photocatalytic properties on the surface on which the film is formed, may have photocatalytic properties on the material itself of the glass substrate, and the photocatalyst on the surface on which the film is formed. It may have a layer having characteristics. Further, a thin glass plate or a film having photocatalytic properties may be attached to the surface side of the glass substrate on which the film is formed. Further, the surface on which the film is formed by surface modification such as ion implantation may have photocatalytic properties. The film forming method of the film having photocatalytic properties may be any film forming method such as magnetron sputtering, ion beam sputtering, thermal CVD, plasma CVD, binder method, sol-gel method, vacuum deposition method and the like. The photocatalytic property may be activated by either ultraviolet light or visible light. TiO as a photocatalytic material₂, Ta₂O₅, ZnO, WO₃, SiC and Fe₂O₃, Or a mixture of these, or a mixture of these, which is doped with nitrogen, carbon, transition metals, etc., or a part of these materials lacking oxygen or an excessive amount of oxygen added. The glass substrate for a thin film device of the first invention may have photocatalytic properties depending on any material.

TiO having photocatalytic properties on the surface on which the film is formed₂If you have a layer containing₂From the viewpoint of photocatalytic properties, the thickness of the layer containing the above is preferably thick in order to improve the decomposition performance and hydrophilicity of organic substances. On the other hand, if the thickness of the layer is increased, the deformation of the substrate due to the film stress is increased, so that the flatness of the substrate is deteriorated, and at the same time, the smoothness of the surface of the glass substrate is also deteriorated. It is desirable that the thickness is thin. For thin film devices, it is necessary to consider from both viewpoints, and it is preferably 20 to 3000 nm. Further, it is more preferably 100 to 1000 nm. Within the above range, the photocatalytic characteristics are sufficient, and the flatness and smoothness of the substrate are good.

Also, TiO₂There are three types of crystal structure, anatase type, rutile type, and brookite type. In an environment with a large amount of ultraviolet light irradiation, TiO has an anatase type crystal structure.₂Is preferable, and TiO having a rutile-type crystal structure is used in an environment where the amount of visible light is large.₂Is preferable. TiO₂May be used by doping nitrogen, carbon, a transition metal, or the like to change the wavelength of activation, or may partially lack oxygen or add excessive oxygen. Also, TiO₂Ta for layers containing₂O₅, ZnO, WO₃, SiC and Fe₂O₃Other materials with photocatalytic properties, such as, may be added. Furthermore, TiO₂A material having no photocatalytic property may be added in order to improve the film stress, the smoothness of the glass substrate surface, and the like as long as the photocatalytic property of the above is not impaired. Also, TiO₂One or more layers may be added above or below the layer containing. For example, TiO₂On the layer containing₂It is also possible to further improve the hydrophilicity of the surface by adding a layer containing. Also, TiO₂Layer containing TiO₂Of the surface of the glass substrate, TiO in order to cancel the film stress of₂The flatness of the substrate may be ensured by forming a layer or more on the surface on the side where the layer containing the above is not formed.

When the glass substrate for a thin film device of the present invention is used as a substrate for a mask blank for extreme ultraviolet light reflection type lithography having photocatalytic properties on the surface on which the film is formed, the glass substrate for the thin film device is extremely ultraviolet. A reflective layer that reflects light with a wavelength of around 13.5 nm used for photoreflective lithography, a protective layer above the reflective layer, a buffer layer above the protective layer, an absorption layer that absorbs light with a wavelength of around 13.5 nm, etc. Are formed in order.

The reflective layer is formed by alternately laminating a layer of a high refractive index material and a layer of a low refractive index material. Examples of the combination of the high refractive index material and the low refractive index material include Mo / Si, Mo / Be, and Mo compound / Si compound in terms of (high refractive index material / low refractive index material). To explain the formation of the reflective layer using Mo / Si as an example, a Si target is used as the target and Ar gas (gas pressure 1.3 × 10) is used as the sputtering gas.^-2Pa ~ 2.7 × 10^-2Using Pa), a Si film is formed on the photocatalytic surface of the glass substrate so that the ion acceleration voltage is 300 to 1500 V, the film formation speed is 0.03 to 0.30 nm / sec, and the thickness is 4.5 ± 0.1 nm. Next, a Mo target is used as the target, and Ar gas (gas pressure 1.3 × 10) is used as the sputter gas.^-2Pa ~ 2.7 × 10^-2It is preferable to use Pa) to form a Mo film so that the ion acceleration voltage is 300 to 1500 V, the film formation rate is 0.03 to 0.30 nm / sec, and the thickness is 2.3 ± 0.1 nm. A reflective layer is formed by alternately laminating 40 to 60 cycles with this as one cycle.

A protective layer is formed on the reflective layer. The protective layer is effective in preventing the surface of the reflective layer from being oxidized. Examples of the material constituting the protective layer include a Si layer and a Ru layer. When Ru is used as a protective layer, it has an effect as a buffer layer as well as an effect as a protective layer. When the material constituting the protective layer is the same as the material constituting the reflective layer, the film may be formed so that the uppermost layer becomes a film of the material constituting the protective layer in the above-mentioned procedure for forming the reflective layer. .. Specifically, in the case of a Mo / Si reflective layer, a protective layer of the Si layer can be formed by forming a film so that the uppermost layer is the Si layer. When the material constituting the protective layer is different from the material constituting the reflective layer, the reflective layer is formed by the procedure described above, and then a film is formed using a target material corresponding to the film composition of the protective layer. Here, with respect to the film and the layer, a film in which several layers are laminated is called a film.

A buffer layer and an absorption layer are formed on the protective layer in order. Materials constituting the buffer layer that functions as an etching stopper include Cr, Al, Ru, Ta, nitrides thereof, and SiO.₂, Si₃N₄, Al₂O₃And so on. The thickness of the buffer layer is preferably 10 to 60 nm. Examples of the material constituting the absorption layer include Cr. The thickness of the absorption layer is preferably 50 to 150 nm. The buffer layer can be omitted if the protective layer above the reflective layer has an effect as an etching stopper.

Glass substrate for thin film device in the present invention When the surface to be filmed on the glass substrate is irradiated with ultraviolet light or visible light before the thin film device is formed, the substrate is irradiated with ultraviolet light or visible light. The time until charging into the load lock can be lengthened accordingly as long as the photocatalytic properties can be maintained, but it is preferably as short as possible, specifically within 1 hour. Furthermore, it is preferably within 10 minutes. In addition, ultraviolet light is preferable to visible light in terms of photocatalytic characteristics, and the light intensity on the surface on which the film is formed is 1 mW / cm.²It is preferable to irradiate the above light for 10 minutes or more. More preferably, the light intensity on the surface on which the film is formed is 10 mW / cm.²It is recommended to irradiate the above ultraviolet light for 30 minutes or more. When only visible light is used, the photocatalytic property of the surface on which the glass substrate is formed needs to be activated by visible light.

The mask blank for extreme ultraviolet light reflection type lithography of the present invention is characterized in that it is formed by forming a reflective layer, a protective layer, a buffer layer, an absorption layer, etc., which constitute the mask blank for extreme ultraviolet light reflection type lithography. And. One or more layers between the reflective layer, the protective layer, the buffer layer, and the absorbing layer, or on the substrate side of the reflective layer or on the side opposite to the substrate of the absorbing layer, which constitute the mask blank for extreme ultraviolet light reflection type lithography. May be added. For example, it is possible to improve the smoothness of the reflective layer by adding a base layer under the reflective layer. In addition, by adding a low-reflection layer on the absorption layer, the reflectance of the absorption layer to vacuum ultraviolet light and deep ultraviolet light is reduced, and the surface shape inspection of the mask for extreme ultraviolet light reflection type lithography using these lights is performed. Can be facilitated.

Since it prevents defects of the film due to particles generated when the vacuum film forming apparatus is exhausted, it can be applied when a thin film device is formed on a glass substrate by the vacuum forming apparatus.

<figref num="1">It is a figure which showed the glass substrate for the thin film device of this invention.</figref>

Code description

1: Glass substrate 2: Layer with photocatalytic properties