JP4619811B2 - Sputtering target, high refractive index film and manufacturing method thereof, and antireflection film and display device using the same - Google Patents

Description

The present invention relates to a method and a sputtering target used to form the high refractive index film which an anti-reflection film for the high-refractive-index film using a manufacturing reflection preventing film, and was applied to such high-refractive-index film reflective The present invention relates to a prevention film and a display device.

  As a display device, a device using a cathode ray tube (CRT) has been widely used. However, since the CRT requires a certain installation space, a liquid crystal display device (LCD) is used as a lightweight and thin display device. It is rapidly spreading. LCDs are used in various home appliances such as display units such as mobile phones and PDAs, personal computer monitors, 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.

  The various display devices described above are naturally 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.

The constituent materials of the antireflection film include a Ti oxide film (see, for example, Patent Document 1), an Nb oxide film (see, for example, Patent Documents 2 and 3), a Ta oxide film, and the like as a high refractive index film. As the rate film, an oxide film of Si is mainly used. As a method for forming a metal oxide film (oxide film of Ti, Nb, Ta, etc.) applied to the high refractive index film, (1) reactive sputtering in a mixed gas atmosphere of Ar and O ₂ using a metal target And (2) a method of plasma oxidizing a metal film formed using a metal target, and (3) a method of forming a sputter film using a metal oxide target.
JP 2004-002202 A JP 2002-338354 A JP 2003-306766 A

  By the way, the refractive index is particularly important for a thin film for an antireflection film. For example, the high refractive index film constituting the antireflection film is required to further increase the refractive index in order to improve the antireflection function that affects the visibility of the display device. However, the conventional high refractive index film made of an oxide film such as Ti, Nb, or Ta has a limit in improving the refractive index. For these reasons, there is a need for a metal oxide film having a higher refractive index and a sputtering target that can obtain such a metal oxide film with good reproducibility.

  The present invention has been made to cope with such a problem. For example, a sputtering target capable of obtaining a metal oxide film having a higher refractive index as a high-refractive index film of an antireflection film and a sputtering target used therefor are used. An object of the present invention is to provide a high-refractive index film and a method for manufacturing the same, and an antireflection film and a display device to which the high-refractive index film is applied.

The first sputtering target in the present invention is a sputtering target for forming a high refractive index film in an antireflection film,
General formula: (M _1-a Fe _a ) _100-x O _x
(Wherein M represents at least one element selected from Ti, Nb and Ta, and a and x are numbers satisfying 0.1 ≦ a ≦ 0.5 and 50 ≦ x ≦ 80 atomic%)
It has the composition represented by these.

The second sputtering target in the present invention is a sputtering target for forming a high refractive index film in an antireflection film,
General formula: M _100-z Fe _z
(Wherein M represents at least one element selected from Ti, Nb and Ta, and z is a number satisfying 10 ≦ z ≦ 50 atomic%)
It has the composition represented by these.

The high refractive index film for antireflection film of the present invention is
General formula: (M _1-a Fe _a ) _100-x O _x
(Wherein M represents at least one element selected from Ti, Nb and Ta, and a and x are numbers satisfying 0.1 ≦ a ≦ 0.5 and 50 ≦ x ≦ 80 atomic%)
It has the composition represented by these.

The manufacturing method of the 1st high refractive index film | membrane for anti-reflective films in this invention uses said 1st sputtering target of this invention, and said M element in the inert gas atmosphere or the inert gas atmosphere containing oxygen And a step of sputtering a composite oxide film of Fe and Fe. The second method for producing a high refractive index film for an antireflection film according to the present invention comprises using the above-described second sputtering target of the present invention to combine the M element and Fe in an inert gas atmosphere containing oxygen. It is characterized by comprising a step of forming a film by sputtering.

  The antireflection film of the present invention comprises the above-described high refractive index film of the present invention and a low refractive index film laminated with the high refractive index film. The display device of the present invention is characterized by comprising a display device body having a display screen and the antireflection film of the present invention formed on the display screen.

  The sputtering target of the present invention contains an appropriate amount of Fe in a Ti, Nb, Ta oxide target or a Ti, Nb, Ta metal target, so that the metal oxidation has a high refractive index and suppressed light absorption. A membrane can be obtained. According to the high refractive index film made of such a metal oxide film, it is possible to improve the antireflection function and the like. Furthermore, by applying an antireflection film having such a high refractive index film to a display device, characteristics such as visibility can be further enhanced.

Hereinafter, modes for carrying out the present invention will be described. A sputtering target according to the first embodiment of the present invention comprises:
General formula: (M _1-a Fe _a ) _100-x O _x (1)
(Wherein M represents at least one element selected from Ti, Nb and Ta, and a and x are numbers satisfying 0.1 ≦ a ≦ 0.5 and 50 ≦ x ≦ 80 atomic%)
The oxide target having a composition substantially represented by the formula (1) is used for forming a metal oxide film suitable for a high refractive index film in an antireflection film or the like.

A sputtering target according to the second embodiment of the present invention is
General formula: M _100-z Fe _z (2)
(Wherein M represents at least one element selected from Ti, Nb and Ta, and z is a number satisfying 10 ≦ z ≦ 50 atomic%)
As in the first embodiment, the metal target is used for forming a metal oxide film suitable for a high refractive index film such as an antireflection film.

In the sputtering target according to the first and second embodiments described above, the M element is at least one element selected from Ti, Nb, and Ta. The M element may be any one of Ti, Nb and Ta, Ti and Nb, Ti and Ta, Nb and Ta, two elements, Ti, Nb and Ta. These M elements are known to form oxides in the form of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O _5, etc., and become metal oxide films having a high refractive index. Thus, although the M element oxide film has a high refractive index, as described above, there is a limit to the improvement of the refractive index with only the M element oxide film.

Therefore, as a result of adding an additive to a Ti, Nb, Ta oxide target or a Ti, Nb, Ta metal target and examining the refractive index of the metal oxide film formed using them, the above-described oxide target or It has been found that adding Fe to a metal target is effective. Here, Fe is easy to form an oxide in the form of Fe ₂ O _{3 and the} like, and it is known that the refractive index of the Fe oxide film is high, but the Fe oxide film has a large absorption of light. In particular, it is not applied to a high refractive index film as an antireflection film. Thus, although the Fe oxide film alone is not suitable as an antireflection film, a high refractive index metal oxide film (a composite oxide film of M element and Fe) can be obtained by containing an appropriate amount of Fe in the M element oxide film. ) Can be obtained.

  The sputtering target according to the first and second embodiments is a metal oxide film that suppresses light absorption while improving the refractive index by adding an appropriate amount of Fe to M element or an oxide of M element. (Mixed oxide film of M element and Fe) can be obtained. In order to obtain a metal oxide film having such characteristics, it is important to control the composition ratio of Fe to M element. That is, in the oxide-based sputtering target according to the first embodiment, the value of a in the above equation (1) is set in the range of 0.1 to 0.5. Further, in the metal sputtering target according to the second embodiment, the value of z in the above equation (2) is set in the range of 10 to 50 atomic%.

  In the oxide-based sputtering target according to the first embodiment, if the value of a exceeds 0.5, the resulting sputtered film (metal oxide film) absorbs too much light. That is, the extinction coefficient of the sputtered film becomes large, and when applied to uses such as an antireflection film, the performance is degraded. In order to reduce light absorption of the resulting sputtered film, the value of a is more preferably 0.45 or less. On the other hand, when the value of a is less than 0.1, the effect of improving the refractive index by adding Fe cannot be sufficiently obtained. In order to increase the refractive index of the obtained sputtered film, the value of a is more preferably 0.15 or more.

  The same applies to the metal-based sputtering target according to the second embodiment, and if z exceeds 50 atomic%, the resulting sputtered film (metal oxide film) absorbs too much light. That is, the extinction coefficient of the sputtered film becomes large, and when applied to uses such as an antireflection film, the performance is degraded. In order to reduce light absorption of the resulting sputtered film, z is more preferably set to 45 atomic% or less. On the other hand, when z is less than 10 atomic%, the effect of improving the refractive index by adding Fe cannot be sufficiently obtained. In order to increase the refractive index of the obtained sputtered film, z is more preferably 15 atomic% or more.

  In the oxide sputtering target according to the first embodiment, the composition ratio of oxygen (the value of b in the formula (2)) is set in the range of 50 to 80 atomic%. When the composition ratio of oxygen is less than 50 atomic%, abnormal discharge tends to occur when sputtering is performed in an inert gas atmosphere or the like, and the amount of dust mixed in the sputtered film increases. This is a cause of deterioration in the quality and characteristics of the sputtered film. On the other hand, when the oxygen composition ratio of the oxide-based sputtering target exceeds 80 atomic%, the film forming rate is extremely lowered, and the characteristics of the film formed by sputtering as a high refractive index film are deteriorated. The composition ratio of oxygen depends on the M element to be applied, but is more preferably in the range of 55 to 75 atomic%.

  The sputtering target according to the first and second embodiments is preferably made of a material having a purity of 99% or more, for example, in consideration of the intended use as an antireflection film (high refractive index film) or the like. The purity of the constituent material here refers to the total value of M element, Fe, and oxygen (excluding oxygen in the case of a metal-based sputtering target). Further, since impurities are mainly Ni, Cr, Al, Cu, Na, K, and C (which are often contained in the raw materials of M element and Fe), each content of these impurity elements (mass) %)) May be used by subtracting the total amount from 100%. The purity of the target constituent material is more preferably in the range of 99-99.9%.

  Among the above impurity elements, carbon (C) in particular causes abnormal discharge during sputtering, so the content of C in the oxide-based sputtering target and the metal-based sputtering target should be 500 ppm or less by mass ratio. Is preferred. That is, the amount of dust generated due to abnormal discharge or the like can be reduced by setting the C content of the oxide-based and metal-based sputtering targets to 500 ppm or less. The C content of the sputtering target is preferably 400 ppm or less.

  Note that the purity and the amount of impurity elements of the above-described constituent materials can be measured using high frequency inductively coupled plasma emission-mass spectrometry (ICP analysis). Specifically, samples are cut out from five or more locations of the sputtering target. Select samples so that there is no bias and cut out from more than 5 locations for evaluation. Quantitative analysis of each sample is performed by ICP analysis, and an average value of these measured values is obtained. When evaluating the sputtering target before use, a target larger than the target dimension may be produced, and the sample may be cut out and evaluated so as not to be biased from the outer peripheral portion.

  The sputtering target by embodiment mentioned above can be produced as follows, for example. In producing the oxide-based sputtering target according to the first embodiment, first, an oxide powder of M element and an oxide powder of Fe are prepared so as to have a predetermined composition ratio, and thereafter, using a ball mill or the like. Mix evenly. Either a dry method or a wet method may be applied. Among these, it is preferable to use dry mixing with a simple process. The container material of the mixing apparatus to be used and the material of the media such as balls are not particularly limited as long as the sputtering target to be produced has a desired purity.

  Moreover, the raw material powder used for producing the sputtering target (sintered body) is not particularly limited, and a commercially available metal oxide powder can be used, but a more uniform and high-density sintered body is obtained. Therefore, the purity of the raw material powder is preferably 99% or more. The purity of the raw material powder is more preferably 99.9% or more. The average particle size of the raw material powder is preferably 75 μm or less, more preferably 50 μm or less. Furthermore, in order to adjust the oxygen content and the like of the sputtering target, a metal powder (a simple M element powder, an alloy powder, an Fe powder, or the like) can be used in combination as a raw material powder.

  Next, a mixed powder of the M element oxide powder and the Fe oxide powder is temporarily formed with a press or the like, and then sintered in, for example, an atmospheric sintering furnace. The atmosphere during normal pressure sintering is not particularly limited, and may be an ordinary atmospheric atmosphere. When producing a large-sized sputtering target, it is preferable to perform temporary molding by CIP. Further, in order to increase the sintered density, the obtained mixed powder may be filled into a carbon mold or the like and subjected to pressure sintering using a hot press machine. Moreover, you may produce a sintered compact by HIP.

  The sintering temperature of the mixed powder is preferably 800 ° C. or higher. When the sintering temperature is less than 800 ° C., the relative density becomes, for example, 60% or less, and a high-density sputtering target cannot be obtained. The sintering temperature is more preferably 900 ° C. or higher, and further preferably 1000 ° C. or higher. Since the sintering of the above mixed powder needs to be performed at a temperature not higher than the melting point of each raw material (M element oxide, Fe oxide, etc.), the sintering temperature is preferably 1500 ° C. or lower. The holding time depending on the sintering temperature is preferably 1 hour or longer, more preferably 2 hours or longer. In addition, if the cooling rate after sintering is too fast, defects such as cracks and cracks are likely to occur in the sintered body, so the cooling rate is preferably 600 ° C./hour or less. The cooling rate is more preferably 300 ° C./hour or less.

  In preparing the metal-based sputtering target according to the second embodiment, first, the M element and Fe are prepared so as to have a predetermined composition ratio, and then a melting ingot is applied by applying high frequency melting, EB melting, arc melting, or the like. Is made. Of these, it is preferable to apply EB dissolution, in which an ingot can be produced in a relatively short time and a high-purity product is easily obtained. Since the melted ingot has a coarse crystal grain size, it is preferable to perform a hot working or a cold working or the like to further refine the crystal grain size, and further perform a recrystallization heat treatment.

  Specifically, in order to refine the average particle size of the molten ingot (for example, 200 μm or less), after performing forging (rolling) processing at a processing rate of 50% or more, 1000 to 1500 ° C. for recrystallization. It is preferable to perform a heat treatment at a temperature of 1 hour or longer. When heat treatment is performed at a temperature of 1500 ° C. or higher, crystal grains grow and become coarse. The heat treatment temperature is more preferably 1200 ° C. or lower. Since the number of times of processing described above affects the variation in crystal grain size and the like, it is preferable to perform the above operation twice or more. Thus, a sputtering target having a fine and uniform crystal grain size can be produced.

  The raw material used for producing the metal-based sputtering target is not particularly limited, and a commercially available raw material can be used. The purity is preferably 99% or more, and more preferably 99.9% or more. Further, in order to produce a sputtering target with little variation in composition, it is preferable to produce a sintered body once and carry out EB melting or the like using this sintered body as a melting raw material. Note that a sintering process similar to that for the oxide sputtering target can be applied to the metal sputtering target manufacturing process.

  The above-described sintered body and melted material are processed into desired dimensions by dry or wet machining, and further bonded to a backing plate for cooling the heat during sputtering, if necessary. In this way, the sputtering target according to the first and second embodiments of the present invention is obtained. The material of the backing plate is generally Al or Cu. Further, general diffusion bonding, solder bonding, or the like 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. The diffusion bonding temperature is preferably 600 ° C. or lower. The shape of the sputtering target can be appropriately selected depending on the sputtering apparatus to be used.

  Next, embodiments of the high refractive index film and the method for producing the same of the present invention will be described. The high refractive index film according to one embodiment of the present invention uses the oxide-based sputtering target according to the first embodiment described above or the metal-based sputtering target according to the second embodiment, and in an inert gas atmosphere or oxygen. It can be obtained by performing sputter deposition in an inert gas atmosphere. That is, when an oxide-based sputtering target is used, a complex oxide film of M element and Fe is formed by sputtering in an inert gas atmosphere or an inert gas atmosphere containing oxygen. When a metal sputtering target is used, a complex oxide film of M element and Fe is formed by sputtering in an inert gas atmosphere containing oxygen.

  In general, when an oxide-based sputtering target is applied, film formation is performed using a high-frequency sputtering apparatus. The film forming atmosphere may be only an inert gas such as Ar. However, when oxygen vacancies occur, it is preferable to assist oxygen and form the film in a mixed atmosphere of Ar and oxygen. The substrate temperature is not particularly limited, but is usually set to room temperature to about 300 ° C. When a metal sputtering target is applied, film formation is performed using a direct current sputtering apparatus. The film forming atmosphere is a mixed atmosphere of oxygen and an inert gas such as Ar. By performing reactive sputtering in an inert gas atmosphere containing oxygen, a metal oxide film can be obtained using a metal-based sputtering target. The substrate temperature is not particularly limited, but is usually set to room temperature to about 300 ° C.

The high refractive index film made of the composite oxide film of M element and Fe thus obtained reflects the target composition,
General formula: (M _1-a Fe _a ) _100-x O _x
(Wherein M represents at least one element selected from Ti, Nb and Ta, and a and x are numbers satisfying 0.1 ≦ a ≦ 0.5 and 50 ≦ x ≦ 80 atomic%)
The composition is substantially represented by: In addition, when using a metal type sputtering target, the high refractive index film | membrane of a target composition can be obtained by adjusting the amount of oxygen to assist. As described above, the high refractive index film having such a composition has a higher refractive index than the oxide film of Ti, Nb, and Ta and suppresses light absorption. Is used. The high refractive index film can also be applied to optical thin films other than the antireflection film, such as a wavelength demultiplexing film or a wavelength synthesis film.

  Examples of the antireflection film using the above-described high refractive index film include those having a structure in which a low refractive index film and a high refractive index film made of an Si oxide film or the like are alternately stacked based on an optical design. The antireflection film having such a laminated structure is used by being formed on a display screen of a display device. That is, the display device according to this embodiment includes a display device body having a display screen, such as a CRT, LCD, PDP, FED, and the like, and an antireflection film formed on the display screen. According to such a display device, it is possible to further improve the characteristics such as visibility, based on the characteristics of the high refractive index film constituting the antireflection film.

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

Examples 1-7
First, TiO powder having a purity of 99.9% and an average particle diameter of 2 μm, TiO ₂ powder, Nb ₂ O ₅ powder and Ta ₂ O ₅ powder, and Fe ₂ O ₃ powder having a purity of 99.9% and an average particle diameter of 1 μm were prepared. Further, Ti, Nb, Ta, and Fe metal powders having a purity of 99.9% and an average particle diameter of 10 μm were prepared. These powders were prepared so as to satisfy the compositional ratios shown in Table 1, and then put into a resin ball mill container together with alumina balls and mixed for 24 hours.

  Next, each mixed powder was filled in a rubber, and temporary molding was performed at a pressure of 100 MPa using an isostatic press (CIP). Further, these compacts were sintered under atmospheric pressure in the atmosphere at a sintering temperature of 1200 ° C. and a holding time of 4 hours. The heating rate was 300 ° C./hour, and the cooling rate was 300 ° C./hour. Each obtained sintered body was machined into a disk shape (diameter 127 mm × thickness 5 mm), and then joined to an oxygen-free copper backing plate by applying a solder joining method. In this way, sputtering targets having the target composition were prepared. Each of these sputtering targets was subjected to the characteristic evaluation described later.

Comparative Examples 1-5, Reference Example 1
In Example 1 described above, a sputtering target was produced in the same manner as in Example 1 except that the preparation composition and purity of each raw material powder were changed. Each of these sputtering targets was also subjected to the characteristic evaluation described later.

Examples 8-10
As raw metal powders, Ti, Nb, Ta, and Fe powders having a purity of 99.9% and an average particle diameter of 10 μm were prepared. These powders were prepared so as to satisfy the compositional ratios shown in Table 2, and then put into a resin ball mill container together with alumina balls and mixed for 24 hours. Next, each mixed powder was filled in a rubber, and temporary molding was performed at a pressure of 100 MPa using an isostatic press (CIP). Further, these compacts were sintered under normal pressure in a vacuum atmosphere under conditions of a sintering temperature of 1500 ° C. and a holding time of 5 hours.

  Next, each sintered body described above was used as a melting raw material and melted in an EB melting furnace to produce an ingot. Each obtained ingot was subjected to cold forging at a processing rate of 50% and recrystallization heat treatment under conditions of 1200 ° C. × 5 hours alternately. Further, after cold rolling at a processing rate of 50%, recrystallization heat treatment was performed at 1200 ° C. for 5 hours to form a plate. Each obtained plate-like body was processed into a disk shape (diameter 127 mm × thickness 5 mm) by machining, and then joined to an oxygen-free copper backing plate by applying a solder joining method. In this way, sputtering targets having the target composition were prepared. Each of these sputtering targets was subjected to the characteristic evaluation described later.

  Next, using the sputtering targets according to Examples 1 to 10, Comparative Examples 1 to 5, and Reference Example 1 described above, sputtering film formation was performed as follows. For the oxide-based sputtering targets (Examples 1 to 7, Comparative Examples 1 to 5 and Reference Example 1), glass was used under the conditions of a substrate temperature of 25 ° C. and an argon atmosphere (0.5 MPa) using a high-frequency sputtering apparatus. A metal oxide film having a thickness of 200 ± 20 nm was formed on the substrate. For metal sputtering targets (Examples 8 to 10), using a direct current sputtering apparatus, on a glass substrate under the conditions of a substrate temperature of 25 ° C. and a mixed atmosphere (0.5 MPa) in a ratio of argon: oxygen = 8: 2. A metal oxide film having a thickness of 200 ± 20 nm was formed. The film thickness was measured using a tactile film thickness measuring instrument (α step).

  The characteristics and dust generation rate of each metal oxide film thus formed by sputtering were measured and evaluated. The characteristics of the metal oxide film were evaluated by measuring the refractive index and extinction coefficient of the single layer film formed on the glass substrate using a spectroscope. Further, the dust generation rate was evaluated by measuring the average number of dust particles having a size of 1 μm or more by performing film formation 5 times using the same substrate as described above. These results are shown in Table 3.

  As is apparent from Table 3, the metal oxide film formed using each oxide-based sputtering target of Examples 1 to 7 and the metal oxide film formed using each metal-based sputtering target of Examples 8 to 10 It can be seen that the film has a higher refractive index and a good extinction coefficient than the films formed using the sputtering targets of Comparative Examples 1 to 4. Further, when the oxide-based sputtering target having a small x value of the target composition according to Comparative Example 5 or the sputtering target having a C content exceeding 500 ppm according to Reference Example 1, the refractive index of the sputtered film is high, but abnormal. It can be seen that dust due to discharge increases.

Claims (8)

A sputtering target for forming a high refractive index film in an antireflection film,
General formula: (M _1-a Fe _a ) _100-x O _x
(Wherein M represents at least one element selected from Ti, Nb and Ta, and a and x are numbers satisfying 0.1 ≦ a ≦ 0.5 and 50 ≦ x ≦ 80 atomic%)
The sputtering target characterized by having the composition represented by these. A sputtering target for forming a high refractive index film in an antireflection film,
General formula: M _100-z Fe _z
(Wherein M represents at least one element selected from Ti, Nb and Ta, and z is a number satisfying 10 ≦ z ≦ 50 atomic%)
The sputtering target characterized by having the composition represented by these. In the sputtering target according to claim 1 or 2,
A sputtering target having a carbon content of 500 ppm or less. General formula: (M _1-a Fe _a ) _100-x O _x
(Wherein M represents at least one element selected from Ti, Nb and Ta, and a and x are numbers satisfying 0.1 ≦ a ≦ 0.5 and 50 ≦ x ≦ 80 atomic%)
A high refractive index film for an antireflective film , characterized by having a composition represented by: An antireflection method comprising the step of sputtering the composite oxide film of the M element and Fe in an inert gas atmosphere or an inert gas atmosphere containing oxygen using the sputtering target according to claim 1. Manufacturing method of high refractive index film for film. A high refractive index for an antireflection film , comprising the step of sputtering the composite oxide film of the M element and Fe in an inert gas atmosphere containing oxygen using the sputtering target according to claim 2. A method for producing a membrane. An antireflection film comprising the high refractive index film according to claim 4 and a low refractive index film laminated with the high refractive index film. A display device body having a display screen;
A display device comprising: the antireflection film according to claim 7 formed on the display screen.