JP2005060789A - Sputtering target for forming oxide film and manufacturing method of oxide film using the same - Google Patents

Abstract

When a metal oxide film suitable for an optical thin film is formed by sputtering, it is possible to increase the production efficiency of the metal oxide film, and thus the optical thin film, by suppressing a decrease in the deposition rate of the metal oxide film. A sputtering target for forming an oxide film is provided.
A sputtering target for forming an oxide film of at least one element selected from Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg, and Ca. Such a sputtering target for forming an oxide film is substantially composed of the above-described elements and carbon in the range of 1 to 50% by mass.
[Selection figure] None

Description

  The present invention relates to a sputtering target for forming an oxide film suitably used for forming an optical thin film such as an antireflection film, and a method for producing an oxide film using the sputtering target.

  As a display device, a device using a cathode ray tube (CRT) has been widely used. However, since a CRT requires a certain installation space, a liquid crystal display device is rapidly spread as a lightweight and thin display device. doing. Liquid crystal display devices are used in various home appliances such as display units such as mobile phones and PDAs, monitors for personal computers, and home televisions. As a self-luminous display device, a plasma display panel (PDP) has been put into practical use. Furthermore, a display device using an electron-emitting device such as a field emission cold cathode, that is, a so-called field emission display device (FED) has been put into practical use.

  Naturally, various display devices as described above are required to be easy to see. For this reason, it is necessary to suppress the surface reflection of the screen in order to prevent the reflection of the background, which causes a decrease in contrast. Therefore, the surface of the display device is generally subjected to antireflection treatment. The anti-reflection film is formed by alternately laminating thin films with different refractive indexes, depending on the optical design, to interfere with the reflected light and attenuate the reflectance. As a method for forming such an antireflection film, a vapor deposition method or a sol-gel method has been mainly employed. Recently, however, a sputtering method has begun to be employed from the viewpoint of productivity and film thickness controllability.

As a constituent material of the antireflection film, an oxide film such as Ta, Nb, Ti, Zr, and Hf is mainly used as a high refractive index film, and an Si oxide film is mainly used as a low refractive index film (for example, Patent Documents). 1 and Patent Document 2). As a method of forming these metal oxide films, (1) a method of forming an oxide film by reactive sputtering in a mixed gas atmosphere of Ar and O ₂ using a metal target (Nb target, Si target, etc.) (2) A method of forming an oxide film by sputtering in an Ar atmosphere or a mixed gas atmosphere of Ar and O ₂ using a metal oxide target (NbO ₂ target, SiO ₂ target, etc.) is known. It has been.

  However, in the film forming method using any of the above-mentioned (1) metal target and (2) metal oxide target, the problem is that oxidation of the target surface during the sputter film forming process reduces the film forming speed. ing. The decrease in the film formation rate due to the oxidation of the target surface is a factor in decreasing the production efficiency of the metal oxide film and, in turn, the antireflection film. In particular, a metal target can reduce film formation costs (reduction of equipment cost and improvement of film formation efficiency, etc.) and can be applied to DC sputtering which is advantageous for film formation over a large area. There is a problem that the film formation rate is significantly reduced due to oxidation of the target surface during film formation.

Japanese Patent Laid-Open No. 11-171596 JP 2002-338354 A

  As described above, in an oxide film forming process using a conventional metal target (Ta target, Nb target, Si target, etc.), the film forming rate is significantly reduced due to oxidation of the target surface. This has been a factor in reducing production efficiency. The metal oxide film is used as an optical thin film having, for example, an antireflection function, a wavelength demultiplexing function, a wavelength synthesizing function, and the like, and particularly in the field of display devices to which the antireflection film is applied, mass production is required. There is a strong demand to increase the productivity of metal oxide films.

  The present invention has been made in order to cope with such problems. In sputter deposition of a metal oxide film suitable for an optical thin film having an antireflection function, a wavelength demultiplexing function, a wavelength synthesis function, and the like, a metal oxide film is formed. The present invention provides a sputtering target for forming an oxide film, which can increase the production efficiency of a metal oxide film, and thus an optical thin film, and a method for producing an oxide film using the same, by suppressing a decrease in the film formation rate of It is aimed.

  The sputtering target for forming an oxide film of the present invention is a sputtering target for forming an oxide film of at least one element selected from Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg and Ca, It is characterized by substantially consisting of an element and carbon in the range of 1 to 50% by mass.

  The method for producing an oxide film according to the present invention includes the above-described method for forming an oxide film of at least one element selected from Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg, and Ca. Using the sputtering target for forming an oxide film of the invention, the method includes a step of performing a sputter film formation in an atmosphere containing oxygen.

  In the present invention, an oxide film of at least one metal element selected from Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg and Ca (herein referred to as a metal element including Si) is formed. In the sputtering target used when performing, carbon of 1-50 mass% is contained. By including carbon in the sputtering target composed of the above metal element, carbon preferentially reacts with oxygen during sputtering film formation in an atmosphere containing oxygen. For this reason, since the production | generation of the metal oxide in the target surface is suppressed, it becomes possible to raise the film-forming speed | rate of an oxide film.

  According to the sputtering target for forming an oxide film of the present invention, the deposition rate of the metal oxide film can be increased based on the carbon contained in the target. According to the oxide film manufacturing method using such a sputtering target, it is possible to increase the production efficiency of a metal oxide film suitable for an optical thin film or a constituent film thereof.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, modes for carrying out the present invention will be described.
The sputtering target for forming an oxide film according to an embodiment of the present invention includes at least one metal element selected from Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg, and Ca (here, including Si). A target used when forming an oxide film of a metal element), which is substantially composed of the element (the metal element described above) mainly constituting the target and carbon in the range of 1 to 50% by mass. ing.

  Such a sputtering target is used, for example, for forming an optical thin film having an antireflection function, a wavelength demultiplexing function, a wavelength synthesizing function, or the like or a metal oxide film suitable as a constituent film thereof. Examples of the optical thin film having an antireflection function include a multilayer film in which high refractive index films and low refractive index films are alternately laminated based on the optical design. In the constituent films of such an antireflection film, oxide films of Ta, Nb, Ti, Zr, and Hf are used as high refractive index films, and oxide films of Si, Al, Y, Mg, and Ca are low refractive. Used as a rate film.

  In consideration of the use as an optical thin film or the like, for example, a metal material having a purity of 99% or more, that is, Ta, Nb, Ti, Zr, Hf, Al is used as the metal material that is the main constituent material of the oxide film forming sputtering target. It is preferable to use at least one metal material selected from Y, Si, Mg and Ca. The purity mentioned here refers to subtracting the total content (mass%) of impurity elements other than metal elements as main constituent elements, for example, elements such as Fe, Ni, Cr, Cu, Na, and K, from 100%. Value.

  The purity as a sputtering target, that is, the purity based on a value obtained by subtracting the content of a metal element as a main constituent element and an impurity element other than carbon from 100% is also preferably 99% or more. Practically, it is preferable to use a sputtering target having an impurity element amount in the range of 0.01 to 1% by mass (the purity of the metal element and carbon as main constituent elements is 99 to 99.99%). It should be noted that Fe, Ni, Cr, Cu, Na, and K are cited as impurities because these elements are inevitably included in the raw material powder and the manufacturing process, or elements that have an adverse effect when included in the optical thin film. Because. In other words, impurities other than these elements are unavoidably contained in raw materials and processes, and thus can be ignored practically.

A metal oxide film suitable for an optical thin film, a constituent film thereof, or the like can be obtained by performing reactive sputtering, for example, in a mixed gas atmosphere of Ar and O ₂ using the sputtering target as described above. At this time, by using a sputtering target containing a predetermined amount of carbon, the deposition rate can be improved as compared with a sputtering target composed of a conventional simple metal element. When reactive sputtering is performed using a conventional sputtering target composed of a single metal element, oxygen contained in the sputtering atmosphere oxidizes the target surface, and the generation of this oxide reduces the deposition rate. It is.

On the other hand, since the sputtering target of the present invention contains carbon in the range of 1 to 50% by mass, carbon in the target reacts preferentially with oxygen in the sputtering atmosphere. Oxygen that has reacted with carbon is volatilized into the atmosphere, for example, as CO or CO ₂ . Alternatively, the oxide on the target surface can be removed as CO or CO ₂ to remove the oxide on the target surface. Furthermore, a non-erosion region usually exists on the target surface, and sputtered particles (oxide particles) are reattached there, and this reattached matter is also removed or reduced by reacting with carbon in the target. be able to.

  Thus, by preferentially reacting the carbon in the target with oxygen, a non-oxidized portion appears on the target surface when viewed microscopically. When Ar ions collide with the non-oxidized portion (metal surface), sputter evaporation in a metal state occurs. By realizing sputtering in such a metal state, it is possible to improve the deposition rate as compared with a sputtering target composed of a conventional simple metal element. Of course, since the sputtered metal atoms or atomic groups are oxidized in the process of reaching the substrate, a desired metal oxide (Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg and Ca are selected. A film of at least one metal oxide) can be obtained.

  In addition, the reattachment deposited in the non-erosion region of the sputtering target may be mixed as particles in the sputtered film or cause abnormal discharge. By suppressing this, it is possible to reduce the rate of occurrence of defects due to particle mixing, abnormal discharge, or the like. As described above, by using the sputtering target for forming an oxide film containing carbon, it is possible to increase the deposition rate of the metal oxide film, and further reduce the incidence of film defects.

  As described above, carbon contained in the sputtering target for forming an oxide film is formed by reactive sputtering of at least one oxide film selected from Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg, and Ca. This contributes to the improvement of the film forming speed when forming the film. In order to obtain such an effect of improving the film formation rate, the sputtering target shall contain carbon in the range of 1% by mass or more. When the carbon content is less than 1% by mass, it is not possible to stably obtain the effect of suppressing the formation and removal of oxides on the target surface by carbon. In order to obtain the effect of improving the deposition rate more effectively, the carbon content of the sputtering target is preferably 10% by mass or more.

  On the other hand, when there is too much carbon content in the sputtering target for forming an oxide film, the amount of carbon contained in the formed oxide film increases, and the characteristics as an optical thin film such as an antireflection film deteriorate. For example, in both the high-refractive index film and the low-refractive index film of the antireflection film, the refractive index decreases when the amount of carbon in the metal oxide film becomes excessive. For this reason, the sputtering target is assumed to contain carbon in a range of 50% by mass or less. In order to further improve the properties of the metal oxide film as an optical thin film, the carbon content of the sputtering target is preferably 40% by mass or less.

  Carbon also has an effect on improving the conductivity (decrease in resistivity) of the sputtering target, thereby improving the suitability for DC sputtering. For example, considering the case of a Si target, the resistivity of a sputtering target made of a single Si element is too high, and the discharge becomes unstable when DC sputtering is applied. Can't get. By including carbon in the range of 1 to 50% by mass in such a Si target, the conductivity is improved and DC sputtering can be applied. Also for metal targets other than Si, suitability for DC sputtering by improving conductivity, film formation efficiency during DC sputtering, and the like can be increased.

  As a material (target material) constituting the oxide film forming sputtering target, it is preferable to apply a sintered material of a mixture of the above-described metal element and carbon. In addition to the sintered material, a melting material is also known as the target material. However, the sintered target has an advantage that it has excellent controllability of the carbon content in addition to its low manufacturing cost. Furthermore, since the target surface having a non-oriented state or a state close to it can be obtained for the sintered target, there is also a decrease in deposition rate over time and variations in film thickness due to the target surface with a specific crystal plane oriented. It becomes possible to suppress.

  From such points, it is preferable to apply a sintered target to the sputtering target. In particular, when a refractory metal such as Ta or Nb is applied, it is preferable to use a sintered material that is easy to obtain an inexpensive and high-performance target. Furthermore, although a single crystal material is generally used for the Si target, the film forming rate can be improved by using a sintered material for the Si target. In addition, the Si target containing a predetermined amount of carbon can be applied with DC sputtering, and from this point, the film formation cost can be reduced.

  Moreover, it is preferable that the relative density of the sintered material (sintering target) which comprises the sputtering target for oxide film formation is 50% or more. If the relative density of the sputtering target is too low, it will oxidize into the relatively increasing vacancies at the time of sputtering film formation, and even if it is a carbon-containing target, it will fully exhibit the oxide generation suppression effect and removal effect As a result, the film formation rate is reduced. The relative density of the sintered target is more preferably 70% or more, and further preferably 80% or more. However, since the film formation rate may decrease even if the relative density is too high, the relative density of the sputtering target is preferably 95% or less, and more preferably 90% or less.

  The above-described sputtering target for forming an oxide film is preferably produced by applying a sintering method as described below. First, a metal powder (at least one metal powder selected from Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg, and Ca) having a purity as described above and a carbon powder at a desired ratio To adjust the raw material powder. The raw material powder may be a mixture of a metal powder and its carbide powder, or a mixture of a metal powder and an organic resin that generates carbon by firing. When preparing the raw material powder, it is preferable to sufficiently mix the starting materials so that a uniform mixed state of the metal element and carbon can be obtained.

  Next, the above-mentioned raw material powder (mixed powder) is sintered by a known sintering method such as a hot press method, an HIP method, or an atmospheric pressure sintering method to produce a target material. Specifically, the raw material powder is filled into a mold (for example, a carbon mold) according to a desired target shape. The raw material powder filled in the mold is heated to the sintering temperature of the metal powder used, and is pressure sintered by, for example, hot pressing. The pressure-sintered body thus obtained may be subjected to HIP treatment as necessary. Various sintering methods such as a combination of normal pressure molding and HIP, a combination of CIP and atmospheric pressure sintering, and the like can be applied.

The sintering temperature at the time of hot pressing is preferably a temperature that is 1/2 or more of the melting point of the applied metal element, and more preferably 2/3 or more of the melting point. Further, the sintering time is preferably 3 hours or more, and more preferably 5 hours or more. Furthermore, the pressure during sintering is preferably 20 MPa or more. If the sintering conditions deviate from these conditions, the progress of the sintering may be insufficient, and a target material having a desired density may not be obtained. The atmosphere during sintering is preferably a vacuum atmosphere or an inert atmosphere such as Ar. When a vacuum atmosphere is applied, the pressure is preferably 1 × 10 ⁻³ Pa or less. By carrying out sintering in such a vacuum, impurities such as Na and K can be sufficiently removed.

  A target material (sintered material) produced by applying the sintering process as described above is machined into a predetermined shape, and then joined to a backing plate made of, for example, Al or Cu, thereby forming a target sputtering target. (Carbon-containing sputtering target) is obtained. General diffusion bonding or solder bonding can be applied to the bonding with the backing plate. When applying solder joint, it joins with a backing plate via the well-known In type or Sn type joining material.

As described above, the sputtering target for forming an oxide film of the present invention is an optical thin film having an antireflection function, a wavelength demultiplexing function, a wavelength synthesizing function, or the like, or a metal oxide film suitable as a constituent film thereof, such as a TaO _x film or NbO _x. Film, TiO _x film, ZrO _x film, HfO _x film, AlO _x film, YO _x film, SiO _x film, MgO _x film, CaO _x film (x is basically a value based on the stoichiometric composition ratio. However, it may be a value that deviates from these), or is preferably used for forming these composite oxide films.

Such a metal oxide film can be obtained by performing reactive sputtering in an oxygen-containing atmosphere such as a mixed gas of Ar and O ₂ using a carbon-containing sputtering target for forming an oxide film. Although the obtained metal oxide film preferably does not contain much carbon, it may contain carbon as long as it does not affect the properties of the target optical thin film or the like. In addition, the metal oxide film can be formed by applying DC sputtering, thereby reducing the film formation cost and improving the film formation efficiency. However, application of RF sputtering is not excluded.

  Next, specific examples of the present invention and evaluation results thereof will be described.

Example 1 and Comparative Example 1
First, Ta powder having a purity of 3N and carbon powder were prepared, and these were mixed so that the carbon content in the target was the value shown in Table 1. The mixing of the Ta powder and the carbon powder was carried out for 6 hours or more using a ball mill. Next, these mixed powders were filled in a carbon mold, set in a hot press apparatus, and pressure sintered at the sintering temperature and sintering time shown in Table 1, respectively. The pressure during sintering was 20 MPa, and the sintering atmosphere was a vacuum atmosphere of 1 × 10 ⁻³ Pa or less.

  The target material (mixed sintered body of Ta and carbon) thus obtained was machined into a shape of 500 mm in diameter and 5 mm in thickness, and then brazed and joined to a Cu backing plate. A sputtering target for forming an oxide film was obtained. The sputtering target according to Comparative Example 1 in Table 1 was produced in the same manner except that the carbon content was outside the scope of the present invention. The density of each sputtering target (measured by the Archimedes method) was as shown in Table 1.

Next, using each sputtering target (sputtering target made of a mixture of Ta and carbon) according to Example 1 and Comparative Example 1 described above, sputtering method: magnetron sputtering, DC output: 2 kW, Ar: 50 sccm, O ₂ : A Ta oxide film (TaO _x film) was formed on the glass substrate (BK-7) under the conditions of 10 sccm, sputtering pressure: 5 Pa, and sputtering time: 300 sec. The film thickness of the obtained oxide film was measured, and this was divided by the film formation time to obtain the film formation rate (nm / sec). Further, the refractive index of each Ta oxide film was measured. These measurement and evaluation results are also shown in Table 1.

  As is clear from Table 1, it can be seen that the Ta target containing a predetermined amount of carbon has an improved deposition rate compared to the Ta target alone. However, even if it is a Ta target containing a predetermined amount of carbon, if the relative density is too low, the film formation rate will decrease, so the relative density of the target is preferably 50% or more. On the other hand, if the Ta target has too much carbon content (carbon content> 50% by mass), the refractive index of the resulting Ta oxide film decreases, and the characteristics as an optical thin film (for example, a high refractive index film of an antireflection film). Will deteriorate.

Example 2 and Comparative Example 2
First, Ta powder having a purity of 3N and TaC powder were prepared, and these were mixed so that the carbon content in the target was a value shown in Table 2. The mixing of the Ta powder and the TaC powder was carried out for 6 hours or more using a ball mill. Next, these mixed powders were filled in a carbon mold, set in a hot press apparatus, and pressure sintered at the sintering temperature and sintering time shown in Table 2, respectively. The pressure during sintering was 20 MPa, and the sintering atmosphere was a vacuum atmosphere of 1 × 10 ⁻³ Pa or less.

  The target material (mixed sintered body of Ta and carbon) thus obtained was machined into a shape of 500 mm in diameter and 5 mm in thickness, and then brazed and joined to a Cu backing plate. A sputtering target for forming an oxide film was obtained. The sputtering target according to Comparative Example 2 in Table 2 was produced in the same manner except that the carbon content was outside the scope of the present invention. The density of each sputtering target (measured by Archimedes method) was as shown in Table 2.

Next, using each sputtering target (sputtering target made of a mixture of Ta and carbon) according to Example 2 and Comparative Example 2 described above, sputtering method: magnetron sputtering, DC output: 2 kW, Ar: 50 sccm, O ₂ : A Ta oxide film (TaO _x film) was formed on the glass substrate (BK-7) under the conditions of 10 sccm, sputtering pressure: 5 Pa, and sputtering time: 300 sec. The film thickness of the obtained oxide film was measured, and this was divided by the film formation time to obtain the film formation rate (nm / sec). Further, the refractive index of each Ta oxide film was measured. These measurement and evaluation results are also shown in Table 2.

Example 3 and Comparative Example 3
First, Nba powder and carbon powder having a purity of 3N were prepared, and these were mixed so that the carbon content in the target was the value shown in Table 3. The mixing of the Nb powder and the carbon powder was performed for 6 hours or more using a ball mill. Next, these mixed powders were filled in a carbon mold, set in a hot press apparatus, and subjected to pressure sintering at the sintering temperature and sintering time shown in Table 3, respectively. The pressure during sintering was 20 MPa, and the sintering atmosphere was a vacuum atmosphere of 1 × 10 ⁻³ Pa or less.

  The target material (mixed sintered body of Nb and carbon) thus obtained was machined into a shape of 500 mm in diameter and 5 mm in thickness, and then brazed and joined to a Cu backing plate. A sputtering target for forming an oxide film was obtained. The sputtering target according to Comparative Example 3 in Table 3 was prepared in the same manner except that the carbon content was outside the scope of the present invention. The density of each sputtering target (measured by Archimedes method) was as shown in Table 3.

Next, using each sputtering target (sputtering target made of a mixture of Nb and carbon) according to Example 3 and Comparative Example 3 described above, sputtering method: magnetron sputtering, DC output: 2 kW, Ar: 50 sccm, O ₂ : An Nb oxide film (NbO _x film) was formed on the glass substrate (BK-7) under the conditions of 10 sccm, sputtering pressure: 5 Pa, and sputtering time: 300 sec. The film thickness of the obtained oxide film was measured, and this was divided by the film formation time to obtain the film formation rate (nm / sec). Further, the refractive index of each Nb oxide film was measured. These measurement / evaluation results are also shown in Table 3.

  As is clear from Table 3, it can be seen that the Nb target containing a predetermined amount of carbon has an improved film forming rate as compared with the Nb target alone. However, even in the case of an Nb target containing a predetermined amount of carbon, if the relative density is too low, the film formation rate is lowered. Therefore, the relative density of the target is preferably 50% or more. On the other hand, if the Nb target has too much carbon content (carbon content> 50% by mass), the refractive index of the obtained Nb oxide film decreases, and the characteristics as an optical thin film (for example, a high refractive index film of an antireflection film). Will deteriorate.

Example 4 and Comparative Example 4
First, Nb powder and NbC powder having a purity of 3N were prepared, and these were mixed so that the carbon content in the target was a value shown in Table 2. The mixing of the Nb powder and the NbC powder was carried out for 6 hours or more using a ball mill. Next, these mixed powders were filled into a carbon mold, set in a hot press apparatus, and pressure sintered at the sintering temperature and sintering time shown in Table 4, respectively. The pressure during sintering was 20 MPa, and the sintering atmosphere was a vacuum atmosphere of 1 × 10 ⁻³ Pa or less.

  The target material (mixed sintered body of Ta and carbon) thus obtained was machined into a shape of 500 mm in diameter and 5 mm in thickness, and then brazed and joined to a Cu backing plate. A sputtering target for forming an oxide film was obtained. The sputtering target according to Comparative Example 4 in Table 4 was produced in the same manner except that the carbon content was outside the scope of the present invention. In addition, the density (measured by Archimedes method) of each sputtering target was as shown in Table 4.

Next, using each sputtering target (sputtering target made of a mixture of Nb and carbon) according to Example 4 and Comparative Example 4 described above, sputtering method: magnetron sputtering, DC output: 2 kW, Ar: 50 sccm, O ₂ : An Nb oxide film (NbO _x film) was formed on the glass substrate (BK-7) under the conditions of 10 sccm, sputtering pressure: 5 Pa, and sputtering time: 300 sec. The film thickness of the obtained oxide film was measured, and this was divided by the film formation time to obtain the film formation rate (nm / sec). Further, the refractive index of each Nb oxide film was measured. These measurement / evaluation results are also shown in Table 4.

Example 5, Comparative Example 5
First, Si powder having a purity of 3N and carbon powder were prepared, and these were mixed so that the carbon content in the target was a value shown in Table 5. Mixing of the Si powder and the carbon powder was performed for 6 hours or more using a ball mill. Next, these mixed powders were filled in a carbon mold, set in a hot press apparatus, and sintered under pressure at the sintering temperature and sintering time shown in Table 5, respectively. The pressure during sintering was 20 MPa, and the sintering atmosphere was a vacuum atmosphere of 1 × 10 ⁻³ Pa or less.

  The target material (mixed sintered body of Si and carbon) thus obtained was machined into a shape of 500 mm in diameter and 5 mm in thickness, and then brazed and joined to a Cu backing plate. A sputtering target for forming an oxide film was obtained. The sputtering target according to Comparative Example 5 in Table 5 was produced in the same manner except that the carbon content was outside the scope of the present invention. In addition, the density (measured by Archimedes method) of each sputtering target was as shown in Table 5.

Next, using each sputtering target (sputtering target made of a mixture of Si and carbon) according to Example 5 and Comparative Example 5 described above, sputtering method: magnetron sputtering, DC output: 2 kW, Ar: 50 sccm, O ₂ : A Si oxide film (SiO _x film) was formed on the glass substrate (BK-7) under the conditions of 10 sccm, sputtering pressure: 5 Pa, and sputtering time: 300 sec. The film thickness of the obtained oxide film was measured, and this was divided by the film formation time to obtain the film formation rate (nm / sec). Moreover, the refractive index of each Si oxide film was measured. These measurement and evaluation results are also shown in Table 5.

  As is apparent from Table 5, it can be seen that the Si target containing a predetermined amount of carbon can be applied with DC sputtering well, and the film formation rate is improved as compared with the target of Si alone. However, even if it is a Si target containing a predetermined amount of carbon, if the relative density is too low, the film formation rate is lowered, so the relative density of the target is preferably 50% or more. On the other hand, when the carbon content of the Si target is too high (carbon content> 50 mass%), the refractive index of the Si oxide film decreases and the characteristics as an optical thin film (for example, a low refractive index film of an antireflection film) decrease. Resulting in.

Example 6 and Comparative Example 6
First, Si powder and SiC powder with a purity of 3N were prepared, and these were mixed so that the carbon content in the target would be the value shown in Table 6. The mixing of the Si powder and the SiC powder was performed for 6 hours or more using a ball mill. Next, these mixed powders were filled into a carbon mold, set in a hot press apparatus, and pressure-sintered at the sintering temperature and sintering time shown in Table 6, respectively. The pressure during sintering was 20 MPa, and the sintering atmosphere was a vacuum atmosphere of 1 × 10 ⁻³ Pa or less.

  The target material (mixed sintered body of Si and carbon) thus obtained was machined into a shape of 500 mm in diameter and 5 mm in thickness, and then brazed and joined to a Cu backing plate. A sputtering target for forming an oxide film was obtained. The sputtering target according to Comparative Example 6 in Table 6 was produced in the same manner except that the carbon content was outside the scope of the present invention. In addition, the density (measured by Archimedes method) of each sputtering target was as shown in Table 6.

Next, using the sputtering targets (sputtering targets made of a mixture of Si and carbon) according to Example 6 and Comparative Example 6 described above, sputtering method: magnetron sputtering, DC output: 2 kW, Ar: 50 sccm, O ₂ : A Si oxide film (SiO _x film) was formed on the glass substrate (BK-7) under the conditions of 10 sccm, sputtering pressure: 5 Pa, and sputtering time: 300 sec. The film thickness of the obtained oxide film was measured, and this was divided by the film formation time to obtain the film formation rate (nm / sec). Moreover, the refractive index of each Si oxide film was measured. These measurement and evaluation results are also shown in Table 6.

Claims (7)

A sputtering target for forming an oxide film of at least one element selected from Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg and Ca,
A sputtering target for forming an oxide film, characterized by substantially consisting of the element and carbon in the range of 1 to 50% by mass. The sputtering target according to claim 1, wherein
The said target contains the said carbon in 10-40 mass%, The sputtering target for oxide film formation characterized by the above-mentioned. In the sputtering target for forming an oxide film according to claim 1 or 2,
A sputtering target for forming an oxide film, comprising a sintered material having a relative density of 50% or more. In the sputtering target according to any one of claims 1 to 3,
A sputtering target for forming an oxide film, which is used as a target for forming an optical thin film. In forming an oxide film of at least one element selected from Ta, Nb, Ti, Zr, Hf, Al, Y, Si, Mg and Ca,
A method for producing an oxide film, comprising the step of performing sputtering film formation in an atmosphere containing oxygen using the oxide film-forming sputtering target according to any one of claims 1 to 3. In the manufacturing method of the oxide film according to claim 5,
The method of manufacturing an oxide film, wherein the oxide film is an optical thin film. In the manufacturing method of the oxide film according to claim 5,
The method of manufacturing an oxide film, wherein the oxide film is a constituent film of an antireflection film.