JP7526157B2 - Evaporation source and deposition device - Google Patents

Description

The present invention relates to a deposition source and a deposition device.

Metal electrode wiring for display panels and solar cells, organic electroluminescence (EL) layers, semiconductor layers, and other organic and inorganic thin films may be formed by deposition such as vacuum deposition. A deposition apparatus for performing such deposition is usually composed of a deposition source (also called an evaporation source, etc.) that heats a solid deposition material at room temperature and sprays the vaporized deposition material toward the substrate surface, and a substrate holder that holds the substrate. The deposition source includes a crucible that contains the deposition material, and a heating means that directly or indirectly heats and vaporizes the deposition material. It is known that induction heating is used as a heating means for the deposition source (see Patent Documents 1 and 2). The induction heating method is said to have advantages such as better heating efficiency and superior thermal response compared to the resistance heating method.

JP 2011-52301 A JP 2020-176298 A

Conventionally, coils used for induction heating have a shape in which electric wire is wound in a spiral shape at equal intervals. Therefore, in induction heating methods using coils, the magnetic field is strongest in the center of the coil, and this center is most easily heated. When a coil is arranged to cover the periphery of a crucible and the crucible is heated by induction heating, the magnetic field is relatively weak at the opening of the crucible and its surroundings, and the temperature is lower than that of the center because it is open. Therefore, when the deposition material contained in the crucible is vaporized by heating and diffuses outside the crucible, part of the deposition material is likely to precipitate at the opening of the crucible and its surroundings. The deposition material precipitated at the opening of the crucible and its surroundings can hinder the diffusion of the deposition material and may cause blockage.

The present invention was made based on the above circumstances, and its purpose is to provide a deposition source that can prevent deposition of the deposition material on the opening of the crucible and its surroundings and can stably diffuse the deposition material, and a deposition device equipped with such a deposition source.

The present invention, which has been made to solve the above problems, is an induction heating type vapor deposition source that includes a crucible with an opening and a coil arranged to cover the periphery of the crucible, the coil being made of spirally wound electric wire, and the spacing between the electric wires that cover the periphery of the opening side of the crucible in the coil is narrower than the spacing between the electric wires that cover the periphery of the other parts of the crucible.

It is preferable that the opening side portion of the crucible has a narrowed portion.

Another aspect of the present invention, which has been made to solve the above problems, is a deposition device equipped with the deposition source.

The present invention provides a deposition source that can prevent deposition of the deposition material on the opening of the crucible and its surroundings and can stably diffuse the deposition material, and a deposition device equipped with such a deposition source.

FIG. 1 is a schematic side view showing a deposition source according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing a deposition apparatus according to one embodiment of the present invention.

The deposition source and deposition device according to one embodiment of the present invention will be described in detail below with reference to the drawings as appropriate.

<Vapor deposition source>
1 includes a crucible 11, a coil 12 arranged so as to surround the crucible 11, and a power supply device 19 connected to the coil 12. The evaporation source 10 is an induction heating type evaporation source.

The crucible 11 is a container that holds the deposition material to be vaporized. The crucible 11 is heated by induction heating. The crucible 11 has a generally cylindrical shape with a bottom. In the crucible 11 of FIG. 1, the bottom is on the bottom and the top is open. That is, the crucible 11 has an opening 13 at the top end. In addition, a constricted portion 14 is formed near the opening 13 of the crucible 11.

Here, in the crucible 11, the opening 13 side is defined as the opening side portion 15 (the portion above the imaginary plane B in FIG. 1) with the boundary being the imaginary plane B perpendicular to the central axis A (the symmetry axis of the crucible 11 in FIG. 1). On the other hand, the portion of the crucible 11 other than the opening side portion 15 is defined as the other portion 16 (the portion below the imaginary plane B in FIG. 1). The opening side portion 15 can be, for example, a portion from the opening 13 (the upper end in FIG. 1) to 10% to 50% of the height of the crucible 11. The opening side portion 15 of the crucible 11 has a constricted portion 14. The other portion 16 is the portion on the bottom side. The other portion 16 may be the portion in which the deposition material is mainly contained. However, the deposition material may be contained up to the opening side portion 15.

The crucible 11 is made of the same material as the crucible of the deposition source of the conventionally known induction heating method. Examples of materials for forming the crucible 11 include metals such as iron, titanium, tantalum, tungsten, and stainless steel, and non-metals such as carbon. The material for forming the crucible 11 is preferably a metal. In addition, the material for forming the crucible 11 is preferably a ferromagnetic material, and more preferably a ferromagnetic metal.

The height of the crucible 11 may be, for example, in the range of 36 mm to 190 mm. The diameter (inner diameter) of the crucible 11 may be, for example, in the range of 9 mm to 45 mm. This diameter (inner diameter) of the crucible 11 may be the diameter (inner diameter) at the other part 16 or the bottom. The ratio of the diameter (inner diameter) of the necked portion 14 to the diameter (inner diameter) of the crucible 11 may be, for example, in the range of 0.1 to 0.9, or in the range of 0.2 to 0.7. The average thickness of the sidewall of the crucible 11 may be, for example, in the range of 0.3 mm to 1 mm.

When performing deposition using the crucible 11, a deposition material is placed in the crucible 11. The deposition material is not particularly limited, and examples include organic materials for forming an organic EL layer, etc., and inorganic materials for forming a semiconductor layer, metal wiring, etc. In this way, the deposition source 10 is suitable for use in both organic deposition and inorganic deposition.

In consideration of vaporization efficiency, the crucible 11 may contain a granular heat transfer medium that is thermally and chemically stable and has a higher thermal conductivity than the deposition material together with the deposition material. Alternatively, the crucible 11 may contain a composite material composed of a granular heat transfer medium and a deposition material that covers the heat transfer medium. The crucible 11 may also contain a heating medium that is heated by induction heating together with the deposition material.

The coil 12 is arranged so as to surround the crucible 11. The coil 12 has a cylindrical shape and is made of electric wire wound in a spiral shape. The coil 12 is arranged so that the central axis A of the crucible 11 and the central axis A of the coil 12 coincide with each other.

In the coil 12, the spacing of the electric wire 17 that wraps around the opening side portion 15 of the crucible 11 is narrower than the spacing of the electric wire 18 that wraps around the other portion 16 of the crucible 11. That is, in the deposition source 10 of FIG. 1, the coil 12 is not wound with the electric wire at equal intervals, but the electric wire (electric wire 17) is tightly wound in the range above the imaginary plane B, and the electric wire (electric wire 18) is loosely wound in the range below the imaginary plane B.

In the deposition source 10, the electric wires of the coil 12 are densely arranged around the opening side portion 15 of the crucible 11, so that when a current is passed through the coil 12, the magnetic field in the opening side portion 15 becomes stronger than in the other portion 16. In other words, the magnetic flux density in the opening side portion 15 becomes higher than in the other portion 16. Therefore, when a current is passed through the coil 12 to perform induction heating, the opening side portion 15 of the crucible 11 is more likely to become hotter than the other portion 16, suppressing deposition of the vaporized deposition material in the opening 13 and its surroundings, and allowing the deposition material to be diffused stably. The opening 13 and its surroundings may be a part or all of the opening side portion 15.

For example, the spacing (the distance between the centers of adjacent wires) of the electric wires 17 that surround the opening side portion 15 is preferably 1/4 to 3/4 of the spacing (the distance between the centers of adjacent wires) of the electric wires 18 that surround the other portion 16, and more preferably 1/3 to 2/3.

As described above, the opening side portion 15 of the crucible 11 has a narrowed portion 14. That is, the opening side portion 15 has a portion with a narrow diameter. According to the knowledge of the inventors, by providing the narrowed portion 14 on the opening side portion 15 of the crucible 11, advantages such as uniform diffusion of the deposition material are obtained regardless of the amount of deposition material or the degree of heating. On the other hand, in a conventional crucible having such a narrowed portion on the opening side portion, the deposition material is particularly likely to precipitate at this narrowed portion, which is likely to cause clogging. Therefore, when the present invention is applied to a deposition source using a crucible having a narrowed portion, the advantage of being able to suppress deposition of the deposition material on the opening of the crucible and its surroundings (such as the narrowed portion) can be particularly notably obtained.

The power supply device 19 is connected to the coil 12 and typically supplies alternating current to the coil 12. The power supply device 19 is connected to a commercial power source or the like and typically generates alternating current at a predetermined frequency. The frequency of the current supplied from the power supply device 19 to the coil 12 is not particularly limited and can be set according to the material forming the crucible 11, and can be in the range of several tens to several hundreds of kHz, for example, or may be in the range of 100 to 600 kHz, or may be in the range of 300 to 500 kHz.

The deposition source may have, for example, a deposition material storage chamber and a diffusion chamber. In this case, a crucible containing the deposition material is placed in the deposition material storage chamber with its periphery covered with a coil. A spray nozzle for spraying the deposition material may be connected to the diffusion chamber. In such a deposition source, the deposition material in the crucible that has been vaporized by heating moves from the deposition material storage chamber to the diffusion chamber. The gaseous deposition material that has moved to the diffusion chamber is sprayed from the spray nozzle. The spray nozzle may be placed, for example, on the upper surface of the diffusion chamber. The deposition material storage chamber and the diffusion chamber may be integrated or may be separate. The deposition source may be configured to be able to control the amount of deposition material released by a power supply device, a valve provided in the flow path of the deposition material, or the like.

<Vapor deposition equipment>
2 includes an evaporation source 10, a substrate holder 21, and a vacuum chamber 22. At least the crucible 11 and the coil 12 of the evaporation source 10, and the substrate holder 21 are disposed in the vacuum chamber 22. The power supply device 19 may be disposed outside the vacuum chamber 22.

The deposition source 10 (crucible 11 surrounded by coil 12) is placed at the bottom inside the vacuum chamber 22. The crucible 11 contains solid deposition material X.

The substrate holder 21 is disposed at the top of the vacuum chamber 22. The substrate Y on which deposition is to be performed is disposed facing downwards on the substrate holder 21. The material constituting the substrate Y is not particularly limited and may be a resin, metal, oxide, etc.

The vacuum chamber 22 allows the space in which deposition takes place to be maintained at an appropriate degree of vacuum. In other words, the deposition apparatus 20 may be a vacuum deposition apparatus. The vacuum chamber 22 may be equipped with a vacuum pump that exhausts gas from the vacuum chamber 22 to reduce the pressure therein, and a venting means that injects a certain amount of gas into the vacuum chamber 22 to increase the pressure therein.

The deposition device 20 can be used in the same manner as a conventional deposition device (e.g., a conventional vacuum deposition device). The deposition device 20 can suppress deposition of the deposition material X at the opening of the crucible 11 and its surroundings during deposition. Therefore, the deposition device 20 can perform deposition stably over a long period of time.

<Other embodiments>
The present invention is not limited to the above-mentioned embodiment, and the configuration can be changed without departing from the gist of the present invention. For example, the shape of the crucible is not particularly limited, and may be a shape other than a cylindrical shape. In addition, the crucible may have a shape without a constriction at the opening side.

The coil used in the deposition source may have wire spacing that varies in three or more steps. Even in such a case, it is sufficient that the spacing of the wires surrounding the opening side of the crucible is narrower than the spacing of the wires surrounding the other parts of the crucible.

The present invention will be described in more detail below with reference to examples. Note that the present invention is not limited to the following examples.

Example 1
A titanium crucible having a capacity of 2 ^cm3 and a generally cylindrical shape with a constricted portion at the opening side was prepared. A coil was fabricated so that the spacing between the electric wires covering the periphery of the opening side of the crucible was half the spacing between the electric wires covering the periphery of the other parts of the crucible. The deposition source of Example 1 was assembled using the crucible and the coil.

Example 2
A crucible similar to that used in Example 1 was prepared, except that the capacity was ⁵ cm3. An evaporation source of Example 2 was assembled in the same manner as in Example 1, except that this crucible was used.

<Comparative Example 1>
An evaporation source of Comparative Example 1 was assembled in the same manner as in Example 1, except that a coil with uniform wire spacing was used.

<Comparative Example 2>
An evaporation source of Comparative Example 2 was assembled in the same manner as in Example 2, except that a coil with uniform wire spacing was used.

[evaluation]
For each of the deposition sources of Examples 1 and 2 and Comparative Examples 1 and 2, a deposition material was placed in a crucible and vaporized by induction heating. Alq3 (tris(8-quinolinolato)aluminum) was used as the deposition material, and induction heating was performed by passing an AC current with a frequency of 350 kHz through a coil. For each of the deposition sources of Comparative Examples 1 and 2, the deposition material gradually precipitated around the opening, eventually causing blockage, whereas for each of the deposition sources of Examples 1 and 2, deposition of the deposition material did not occur around the opening.

The deposition source and deposition apparatus of the present invention can be suitably used for forming metal electrode wiring, semiconductor layers, organic EL layers, and other organic and inorganic material thin films for display panels and solar cells, etc.

REFERENCE SIGNS LIST 10 evaporation source 11 crucible 12 coil 13 opening 14 constricted portion 15 opening side portion 16 other portion 17 electric wire covering the periphery of the opening side portion of the crucible 18 electric wire covering the periphery of the other portion of the crucible 19 power supply device 20 evaporation device 21 substrate holder 22 vacuum chamber A central axis B imaginary plane perpendicular to central axis A X evaporation material Y substrate

Claims (2)

A crucible having an opening and made of metal or carbon;
a coil formed by winding an electric wire in a spiral shape and arranged to cover the periphery of the crucible,
In the one coil, the spacing of the electric wires covering the periphery of the opening side portion of the crucible is narrower than the spacing of the electric wires covering the periphery of the other portion of the crucible,
The deposition source has a narrowed portion at an opening side of the crucible . An evaporation device comprising the evaporation source according to claim 1 .

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