JP2007073404A - Sputtering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering device in which damage is reduced in film-forming a barrier film of an organic EL element, and in which erosion is less likely to occur in a target when forming the barrier film. <P>SOLUTION: On the sputtering device forming a protective film on an organic electroluminescent element formed on a substrate, the shape of the target is cylindrical, and sputtering is carried out in the inside of the cylindrical form. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetron sputtering apparatus for forming a protective film on an organic electroluminescence (EL) element.

  In recent years, organic EL elements have attracted attention as time light emitting elements. An organic EL device is a device in which a light-emitting layer of a thin organic compound is sandwiched between electrodes on a substrate such as glass, and emits light when a current is supplied between the electrodes.

  Organic EL elements are easily deteriorated by oxygen and moisture, and these shorten the product life. Therefore, immediately after forming an organic EL element from the viewpoint of reliability, the organic EL element is covered with a stable barrier film to completely shut off the outside air. It is desirable to do. Examples of the barrier film include a metal nitride film and an oxide film. In the case of a so-called top emission configuration in which light emitted from the organic EL element is extracted in the direction of transmitting from the barrier film, a barrier film with high transparency is required.

On the other hand, the barrier film is formed by a thin film forming method such as an electron beam method, a sputtering method, a plasma CVD method, or an ion plating method. Here, the sputtering method can form a film relatively easily even with a high melting point material or compound, and can be easily deposited on a large area depending on the shape of the cathode. Used for formation. For example, Patent Document 1 discloses a technique of a facing target type sputtering apparatus.
JP 2002-332567 A

  In the conventional sputtering apparatus, by making the target face the box shape, high-energy ionized electrons, ionized sputtered particles, etc. stay inside the box shape, and the organic EL on the substrate placed outside the box shape. The rate of incidence on the element is small. For this reason, there is an advantage that physical destruction of the organic EL element is reduced. However, since the target is arranged in a box shape, erosion (erosion) occurs in the target due to variations in the generated plasma distribution. For this reason, the use period is shortened due to non-uniform consumption of the target, and this has been a cause of cost increase particularly in the production process.

  The present invention has been made in view of the above points, and an object of the present invention is to reduce sputtering during the formation of a barrier film while forming a barrier film while preventing the formation of erosion on a target. To provide an apparatus.

  The above object of the present invention is achieved by the following means.

  1. A sputtering apparatus for forming a protective film on an organic electroluminescence element formed on a substrate, wherein the target has a cylindrical shape, and sputtering is performed inside the cylindrical shape.

  2. 2. The sputtering apparatus according to 1 above, wherein a cross-sectional shape of the cylindrical target is inclined so that an opening on the substrate side becomes large.

  3. 3. The sputtering apparatus according to 1 or 2, wherein a diameter of the cylindrical target is less than a length of a diagonal line of the substrate.

  4). 4. The magnet according to any one of 1 to 3, wherein the magnet of the sputtering apparatus is disposed on the side opposite to the sputtering surface of the target and the magnetic pole is disposed in a direction in which the magnetic flux lines are closed. Sputtering equipment.

  5. The organic electroluminescent element is formed by laminating a reflective electrode, an organic layer, and a transparent electrode in order from a substrate, and before forming the protective film, the transparent electrode is formed by a sputtering apparatus. The sputtering apparatus according to claim 1.

  According to the present invention, there has been provided a sputtering apparatus in which damage to an organic EL element when a barrier film is formed is reduced and erosion is unlikely to occur on a target.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The sputtering apparatus is an apparatus that forms a thin film on a substrate in the following process.

First, a sputtering gas such as Ar, He, N ₂ , Xe, or Kr is introduced into the apparatus, a voltage of several hundred V to several kV is applied to the target, glow discharge is performed, and plasma by the sputtering gas is generated. Electrons, ions, and neutral particles having high energy in the plasma collide with the target surface, and the atoms and molecules forming the target surface are released to the outside by exchanging momentum. This phenomenon is called sputtering, and surface atoms and molecules of the target material released by sputtering are deposited on the substrate to form a thin film.

  For example, surface atoms and molecules emitted from the target material are deposited on the substrate on which the organic EL element is formed, and a thin film and a barrier film are formed on the organic EL element to block them from the outside air.

  Sputtering is not a thermal process as in the vapor deposition method, so it is not necessary to dissolve the material to be formed in the thin film, and even a high melting point material having a high gas barrier property such as a metal nitride or oxide can be used as the target material. Sputtering can be easily performed.

  The sputtering apparatus of the present invention is an apparatus in which a magnet is disposed in the above-described sputtering apparatus and a magnetic field is applied in the vicinity of sputtering to increase collision of ions and neutral particles on the target surface, thereby increasing the film forming speed. It is.

  Embodiments of a sputtering apparatus according to the present invention will be described below with reference to the drawings.

  First, the organic EL element will be described.

FIG. 1 is a schematic diagram of an organic EL element.
In the figure, an organic EL element 10 is an element in which an anode 12, an organic layer 13, and a cathode 14 are laminated on a substrate 11.

  The anode 12 is a transparent electrode made of a conductive material having a work function of 4 eV or more and a transmittance of 40% or more, such as indium tin oxide (ITO), indium zinc oxide (IZO), gold, tin oxide, and zinc oxide.

  The organic layer 13 is a single layer or a plurality of layers of an organic compound or complex having a thickness of several nm to several μm including a light emitting layer that emits light, for example, a hole transport layer in contact with the anode, a light emitting layer provided with a light emitting material, and an electron in contact with the cathode. In a device having a structure such as three transport layers, a lithium fluoride layer, an inorganic metal salt layer, or a layer containing them may be arranged at an arbitrary position.

  The cathode 14 is a reflective electrode made of a metal material having a work function of less than 4 eV and a reflectance of 60% or more, such as aluminum, sodium, lithium, magnesium, silver, and calcium.

  The substrate 11 may be a substrate for a solid substrate such as glass or quartz, or polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone. , Polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), cellulose acetate propionate (CAP) and the like.

  The organic EL element 10 according to the present invention emits light using the excitation energy generated by the combination of electrons and holes in the organic layer 13 by an electric current supplied from the outside through the anode 12 and the cathode 14. In the device, light from the organic layer 13 is extracted through the anode 12. Examples of the light emission that uses excitation energy include fluorescence that uses singlet energy for light emission, or phosphorescence that uses triplet energy for light emission. In particular, phosphorescence is desirable light emission as a light source because triplet excitons contribute to light emission, and high luminous efficiency is obtained compared to fluorescence.

  Light emitted from the light emitting layer of the organic EL element 10 is transmitted through the anode 12 and the substrate 11 (bottom emission), but is a substantially transparent cathode in which a thin film cathode material and a highly transmissive anode material are laminated. A top emission configuration in which light is emitted from the projector may be used.

  Next, an embodiment of the sputtering apparatus of the present invention for forming a barrier film on the organic EL element will be described below.

  FIG. 2 is a schematic view of a sputtering apparatus showing the first embodiment of the present invention.

  The sputtering apparatus 100 includes a vacuum chamber 20, an exhaust port 21, a target 30, a cathode 31, a magnet 32, a substrate 11, a power source 50, a matching unit 51, and the like.

  The matching unit is usually used as a set when using a high frequency power source for plasma in an RF magnetron sputtering apparatus, so that the high frequency power output from the high frequency power source for plasma is efficiently sent to the chamber where the plasma is generated. Equipment.

  The vacuum tank 20 is a tank that provides a decompression space that is blocked from outside air, and the inside of the tank is decompressed by a vacuum pump (not shown) connected to the exhaust port 21.

  The target 30 is a target material having a cylindrical shape and is the same material as the constituent material of the barrier film formed on the organic EL element or the same material as the constituent material by reaction with the sputtering gas.

  The barrier film is a film containing at least one kind of metal oxide film, nitride film, metal thin film, diamond-like carbon film having a high barrier property against water, oxygen and other gases, and has a thickness of 50 nm or more and 50 μm or less. It is a thin film.

  The target 30 is connected to the cathode 31, and when a voltage is applied from the power source 50 via the cathode 31 and a sputtering gas is introduced from the gas supply port 33, the target 30 has a predetermined gas pressure. Plasma is generated in the cylindrical inner space, and sputtering is performed.

  Unlike the conventional counter target type sputtering apparatus in which the target is disposed so as to face the target in a box shape, the sputtering apparatus of the present invention has a cylindrical shape of the target 30. Is generated in a plane. For this reason, even if the target is sputtered, there is little generation of so-called erosion that decreases nonuniformly.

  In addition, the plasma generated in the cylindrical inner space 40 is densified by sputtering ions and neutral particles reciprocating in the space between the targets 30, so that the sputtering gas pressure can be reduced. It is possible to maintain a high degree of vacuum and to reduce the damage of the organic EL element due to oxygen and moisture.

  Further, the gas supply port 33 for the sputtering gas is provided directly under the cylindrical target 30 where sputtering is performed, so that the introduced sputtering gas can be efficiently used for sputtering. Of course, as in the conventional facing target type sputtering, ionized electrons, ionized sputtered particles, and the like do not jump out from the side surface of the cylindrical target 30 to the substrate 11 side. Damage is also reduced.

  Although the size of the target 30 is not particularly limited, the barrier film formed on the substrate has a small deviation in film composition with respect to the incident angle of the sputtering material and has a wide application range. It may be less than the length of the diagonal line. That is, even if the light emitting area of the organic EL element is increased and the substrate is enlarged, the cathode and the target material can be made smaller than the substrate size, and the device cost is reduced.

  The magnet 32 is, for example, a permanent magnet such as Fe-Nd-B, Sm-Co rare earth sintered magnet, Ba based or Sr based sintered ferrite magnet, ferrite based bonded magnet, alnico based cast magnet, or the like. Magnetic field generating means for generating a predetermined magnetic field, such as a magnet or an electromagnet.

  The magnet 32 may be disposed at a position where a predetermined magnetic field is generated in the plasma generation space. However, as illustrated, the configuration in which the magnet 32 is disposed on the side opposite to the inner surface of the target material 30 on which the sputtering is performed has a magnetic field strength. From the viewpoint of storage efficiency in the vacuum chamber 20, this is a preferable configuration. The direction of the magnetic pole of the magnet will be described later.

  Further, a cooling means (not shown) may be provided so as to be in contact with the magnet 32 to reduce the magnet 32 from being heated to a high temperature due to sputtering.

  The substrate 11 is a substrate on which the target 30 is sputtered to form a barrier film, and is the substrate of the organic EL element 10 described above. In order to improve the uniformity of the film thickness distribution of the barrier film, it is preferable to rotate the substrate 11 during sputtering by the rotation support member 42. However, the substrate 11 is not limited to substrate rotation, and the substrate 11 is fixedly supported without rotating. May be.

  The power source 50 is a power source for applying a voltage to the target 30 and generates a direct current, an alternating current, or an alternating current to which a direct current bias is applied depending on the conductivity of the material. When an AC voltage is applied, the matching unit 51 performs impedance matching with the target 30.

  Next, the magnet 32 will be described.

  3A is a cross-sectional view showing the arrangement of magnets in the first embodiment, and FIG.

  A plurality of magnets 32 are arranged on the surface of the target 30 opposite to the surface (inner side) on which sputtering is performed, that is, on the opposite side of the inner space 40 of the cylindrical target. In the figure, the magnets 32 are evenly arranged over the back surface of the target 30 to make the magnetic flux uniform, but the present invention is not limited to this. The direction of the magnetic poles of the magnet 32 is such that, for example, the magnets facing each other have an N pole on the target 30 side, the other has an S pole, and conversely, the target 30 side has an S pole and the other has an N pole. It has become.

FIG. 4 is a top view showing the arrangement of magnets in the second embodiment of the present invention.
In the second embodiment, since the other configuration is the same except for the magnet 32 of the first embodiment, the description of the other configuration is omitted.

  Since the magnetic poles on the target 30 side of the magnet 32 in the first embodiment are opposite to the magnetic poles of the magnets facing each other across the target 30, the magnetic flux lines generated between them are closed. However, the magnetic flux lines of the magnetic poles on the side opposite to the target 30 cannot be closed, and magnetic flux leakage occurs. For this reason, in order to reduce the leakage magnetic flux and increase the effective magnetic flux, it is necessary to install an iron yoke or the like having a predetermined thickness, and the vacuum chamber 20 is enlarged, so that the capacity of the exhaust pump is also increased. Need arises.

  Therefore, in the second embodiment, the magnets 32 installed on the back side of the target 30 are arranged so that adjacent magnets have opposite magnetic poles. Therefore, since the magnetic flux lines are closed on both the target 30 side of the magnet 32 and the opposite magnetic pole, the leakage magnetic flux is greatly reduced, and even if an iron yoke is installed, compared to the first embodiment. Miniaturization is possible.

  FIG. 5 is a cross-sectional view of a target showing a third embodiment of the present invention.

  Also in the third embodiment, since the configuration other than the target 30 is the same as that in the first embodiment, description of other configurations is omitted.

  The cross section of the target 30 in the third embodiment is inclined so that the opening 41 on the substrate side is larger than the other opening. For this reason, the inner diameter d of the target 30 is larger than that of the first embodiment, and the barrier film can be formed on a larger substrate size.

  The inner diameter of the cylindrical target in claim 3 refers to the diameter of the opening.

  Although the degree of inclination is arbitrary, it is preferably 45 ° or less, preferably 30 ° or less with respect to the normal line of the cathode (θ in FIG. 5) in order to obtain the effect due to the cylindrical shape. . The inclination does not necessarily have to be linearly inclined when viewed in cross section.

  Hereinafter, the present invention will be described more specifically, but the present invention is not limited thereto.

  As an example of a method for producing an organic EL element, production of an organic EL element composed of an anode / hole transport layer / light emitting layer / cathode will be described.

(Production of bottom emission organic EL elements)
The cleaned glass 100 mm square substrate is placed in a vapor deposition vacuum chamber in a vacuum environment at a vacuum degree of 10 ⁻⁵ Pa. In an evaporation vacuum chamber, an anode was prepared by forming ITO, which is a material for an anode, with an electron beam so as to have a thickness of 1000 mm.

Next, α-NPD, which is an organic EL element material, was vapor-deposited at a rate of 2 liters / second as a hole transporting layer to a thickness of 500 liters. Next, Alq ₃ was deposited as a light emitting layer at a rate of 2 liters / second to form a thickness of 600 liters. After the formation of these layers, a cathode material was deposited thereon by depositing Al, which is a cathode material, at a rate of 3 liters / second so as to have a film thickness of 2000 liters.

(Production of top emission organic EL elements)
The cleaned glass 100 mm square substrate is placed in a vapor deposition vacuum chamber in a vacuum environment at a vacuum degree of 10 ⁻⁵ Pa. In the vapor deposition vacuum chamber, an anode was produced by forming gold as a reflective electrode by an electron beam method so as to have a thickness of 1000 mm.

Next, α-NPD, which is an organic EL element material, was vapor-deposited at a rate of 2 liters / second as a hole transporting layer to a thickness of 500 liters. Next, Alq ₃ was deposited as a light emitting layer at a rate of 2 liters / second to form a thickness of 600 liters. After these layers were formed, the cathode material AL was deposited thereon at a rate of 3 liters / second so as to have a film thickness in the range of 50 liters.

Example 1
The substrate of the produced bottom emission organic EL element was transferred to the sputtering apparatus shown in the first embodiment of the present invention for performing sputtering while maintaining the vacuum environment.

Silicon nitride (Si ₃ N ₄ ) was used as a target material, and the distance between the upper end of the cylindrical target (opening diameter 100 mm, thickness 20 mm) and the substrate of the organic EL element was set to 7 cm. The gas pressure was 1.33 × 10 ⁻² Pa using argon containing 2% by volume of oxygen as the sputtering gas. When the film forming rate was monitored with a crystal resonator when the input power was 100 W with an AC power supply with a frequency of 13.56 MHz, the power supply was 1 振動 子 / sec.

  A sample 1 was prepared by forming a barrier film having a thickness of 5000 mm on the organic EL element under these conditions.

(Example 2)
The substrate of the produced bottom emission organic EL element was transferred to the sputtering apparatus shown in the second embodiment of the present invention for performing sputtering while maintaining the vacuum environment.

  The configuration other than the magnet was 1.5 の / sec when the film forming rate when the input power of the AC power source was 100 W under the same conditions as in the first embodiment was monitored by a crystal resonator. A sample 2 was prepared by forming a barrier film having a thickness of 5000 mm on the organic EL element under these conditions.

(Example 3)
The substrate of the produced top emission organic EL element was transferred to the sputtering apparatus shown in the third embodiment of the present invention for performing sputtering while maintaining the vacuum environment.

Using indium tin oxide (ITO) as a target material, a cylindrical target (target opening diameter 100 mm, tilt angle (θ with respect to the cathode normal) 30 degrees, thickness 20 mm), an organic EL element substrate, The distance was 7 cm. The gas pressure was set to 1 × 10 ⁻⁴ Torr using argon containing 5% by volume of oxygen as the sputtering gas. The power source was 1 Å / sec when the film forming rate when the input power was 100 W with an AC power source was monitored by a crystal resonator. Under this condition, an ITO film having a thickness of 1000 mm was formed on the organic EL element to form a substantially transparent cathode.

Thereafter, on the organic EL element in the same manner as in Example 2, using Si ₃ N ₄ formed in the same cylindrical shape (target opening diameter 100 mm, tilt angle (θ with respect to the cathode normal) 30 degrees, thickness 20 mm). A sample 3 was prepared by forming a barrier film having a thickness of 5000 mm.

(Comparative example)
The substrate of the produced bottom emission organic EL element is covered with a glass material sealing material 15 as shown in FIG. 6 so that the organic EL material is shielded from the outside air in an atmosphere of dry nitrogen, and a UV-curing adhesive. Sample 4 was prepared by adhering the sealing material to the substrate by 16.
As the adhesive, UV-curable resin Nagase Chemtech 5516XNR was used.

(Evaluation results)
In Table 1, each of the organic EL element samples prepared immediately after production in Examples was driven at a constant current of ^2.5 mA / cm ^{2 in} a dry nitrogen gas atmosphere at 23 ° C. to emit light. Luminescence was measured using a spectral radiance meter CS-1000 (manufactured by Konica Minolta), and the external extraction efficiency (%) was calculated and compared for each sample. In addition, the driving voltage of each element at that time was compared.

  Samples 1, 2, and 3 immediately after fabrication have the same external extraction efficiency and drive voltage, indicating that there is little damage to the organic EL element when the barrier film is formed. Furthermore, Sample 3 shows that there is little damage due to ITO film formation.

  Under each condition from Example 1 to Example 3, when the difference in average surface roughness from the initial stage of the target when 100 barrier films were continuously formed on the organic EL element substrate, the difference was found under all conditions. The increase amount was 0.9 mm or less. Since this value is 5% or less with respect to the initial thickness of the target of 20 mm, erosion is at a level that causes no problem in practice.

  The average surface roughness is the centerline average roughness Ra defined by JIS-B-0601. The inside of the target was measured using a RSTPLUS non-contact three-dimensional micro surface shape measurement system manufactured by WYKO. It is.

Furthermore, Sample 1, Sample 2, Sample 3, and Sample 4 were stored at 60 ° C. and 90% RH at a high temperature and high humidity for 500 hours, and after storage, they were driven at a constant current of ^2.5 mA / cm ² , Similarly, the external extraction efficiency and drive voltage, and the number of non-light emitting points (dark spots) that can be visually confirmed in a 2 mm × 2 mm square range were compared between the samples. Sample 1, Sample 2, Sample 3 Even when compared with Sample 4 (organic EL element sealed with glass), the same storage characteristics were confirmed for the external extraction efficiency, drive voltage, and dark spot.

It is a schematic diagram of an organic EL element. It is a schematic diagram of the sputtering device which shows the 1st Embodiment of this invention. It is sectional drawing and upper surface arrangement drawing which show arrangement | positioning of the magnet in 1st Embodiment. It is a top view which shows arrangement | positioning of the magnet in the 2nd Embodiment of this invention. It is sectional drawing of the target which shows the 3rd Embodiment of this invention. It is the schematic which shows the cross section of the organic EL element sealed with the sealing material of the glass material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Organic EL element 11 Substrate 12 Anode 13 Organic layer 14 Cathode 20 Vacuum chamber 21 Exhaust port 30 Target 31 Cathode 32 Magnet 50 Power supply 51 Matching unit 100 Sputtering device

Claims (5)

A sputtering apparatus for forming a protective film on an organic electroluminescence element formed on a substrate, wherein the target has a cylindrical shape, and sputtering is performed inside the cylindrical shape. 2. The sputtering apparatus according to claim 1, wherein a cross-sectional shape of the cylindrical target is inclined so that an opening on a substrate side becomes large. The sputtering apparatus according to claim 1, wherein a diameter of the cylindrical target is less than a length of a diagonal line of the substrate. 4. The magnet according to claim 1, wherein the magnet of the sputtering device is opposite to the sputtering surface of the target, and the magnetic pole is disposed in a direction in which the magnetic flux lines are closed. The sputtering apparatus described. The organic electroluminescence element is formed by laminating a reflective electrode, an organic layer, and a transparent electrode in order from a substrate, and before forming the protective film, the transparent electrode is formed by a sputtering apparatus. The sputtering apparatus according to any one of claims.

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