JP2004018997A - Molecular beam source cell for thin film deposition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To deposit a thin film with a uniform film thickness on the face to be film-deposited of a substrate 1, and to prevent the flying of molecules made into a cluster by a spitting phenomenon even when the face to be film-deposited of the substrate 1 is made close to a molecule outlet 4. <P>SOLUTION: The molecular beam source cell for thin film deposition has a crucible 5 housing a film deposition material (a), a heating means for heating the film deposition material (a) in the crucible 5, and sublimating or evaporating the same, a buffer chamber 9 as a small space making the molecules of the film deposition material (a) formed from the crucible 5 pass through, a reserve chamber 10 leading to the buffer chamber 9 via a molecule passage 13, and having a space with a volume sufficiently larger than that of the buffer chamber 9, and a molecule outlet 4 opening to the wall of the reserve chamber 10, and ejecting the molecules therein toward the film deposition face on the solid surface. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, by heating a film-forming material, the film-forming material is sublimated or melted and evaporated to generate molecules of the film-forming material, and the molecules of the film-forming material are emitted toward a solid surface. The present invention relates to a thin film deposition molecular beam source cell used for growing a film by depositing molecules on a solid surface, and a thin film deposition method using the same.
[0002]
[Prior art]
A thin film deposition apparatus called a molecular beam epitaxy apparatus installs a substrate in a vacuum chamber capable of reducing the pressure to a high vacuum, heats the substrate to a required temperature, and moves a molecule such as a Knudsen cell toward a thin film growth surface of the substrate. A source cell is installed. The film-forming material stored in the crucible of the molecular beam source cell is heated by a heater to sublimate or melt and evaporate, and the generated molecules are incident on the thin film growth surface of the substrate, and the thin film is epitaxially grown on the surface. Then, a film of a film forming material is formed.
[0003]
The molecular beam source cell used in such a thin film deposition apparatus stores a film forming material in a crucible made of, for example, PBN (pyrrolytic boron nitride) having high thermal and chemical stability. Then, the film-forming material is heated by an electric heater provided outside the crucible, thereby sublimating or melting and evaporating the film-forming material to generate film-forming molecules.
[0004]
2. Description of the Related Art In recent years, research and development of organic electroluminescent elements (organic EL elements) have been promoted in fields such as displays and optical communications. This organic EL element is an element in which a light emitting layer is formed of an organic low molecular weight or organic high molecular weight material having EL light emitting ability, and its characteristics are attracting attention as a self light emitting type element. For example, the basic structure is such that a film of a hole transporting material such as triphenyldiamine (TPD) is formed on a hole injecting electrode, and a fluorescent substance such as an aluminum quinolinol complex (Alq ₃ ) is laminated thereon as a light emitting layer. Further, a metal electrode having a small work function, such as Mg, Li, or Ca, is formed as an electron injection electrode.
[0005]
[Problems to be solved by the invention]
Recently, large screens have become a requirement of the times. Therefore, even in the display using the organic EL as described above, it is required to form an organic EL film on a large-sized substrate. In particular, in a display using an organic EL, it is required to form a uniform organic EL film on a substrate.
[0006]
However, in a conventional vacuum deposition apparatus used for forming an organic EL film, a film forming material is sublimated or evaporated from one crucible to fire molecules on the surface of a substrate, and the film forming material is deposited to form a film. Because of the growth method, it is difficult to form a uniform thin film on a large-area substrate.
[0007]
Such an organic EL material is used in the form of a powder as a material serving as an evaporation source, and sublimates the powdered evaporation source material to generate molecules thereof. However, at this time, a so-called spitting phenomenon, in which molecules of the film forming material are aggregated with each other, clustered and scattered, is likely to occur. Then, the clustered molecules are scattered toward and adhere to the solid film formation surface to be formed. The clusters adhering to the film formation surface cause nonuniformity and discontinuity of the film, and cause a defect of the film. Therefore, it is necessary to form a film by separating the film forming surface to such a distance that the cluster does not fly, and there is a problem that the film forming efficiency is extremely poor.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in a vacuum deposition apparatus using a conventional thickness gauge, and a first object of the present invention is to enable a thin film having a uniform thickness to be formed on a solid deposition surface. It is in. A second object of the present invention is to prevent so-called spitting phenomena from causing molecules clustered by the so-called spitting phenomenon to fly to the film-forming surface even when the film-forming surface of the solid is brought close to the molecule discharge port.
[0009]
[Means for Solving the Problems]
In the present invention, in order to achieve the above object, molecules generated by evaporation or sublimation from the crucible 5 are not immediately released to the solid film-forming surface, but are first temporarily held in the buffer chamber 9, Molecules are stored in a reserve chamber 10 having a sufficiently large volume, and the molecules are released from a molecule discharge port 4 toward a film forming surface of a solid surface.
[0010]
That is, the molecular beam source cell for depositing a thin film according to the present invention comprises a crucible 5 for accommodating a film forming material a, a heating means for heating the film forming material a in the crucible 5 to sublime or evaporate, A buffer chamber 9 which is a small space through which molecules of the film forming material a generated from the crucible 5 pass, and a reserve chamber 10 which communicates with the buffer chamber 9 through a molecular passage 13 and has a space which is sufficiently larger than the buffer chamber 9. And a molecule release port 4 which is opened on the wall of the reserve chamber 10 and releases molecules therein toward the film-forming surface of the solid surface.
[0011]
In such a thin-film deposition molecular beam source cell, molecules generated by evaporation or sublimation from the crucible 5 are temporarily held in the buffer chamber 9 and further stored in a larger reserve chamber 10, and then the molecule emission port 4 is formed. Released from Therefore, particles of the cluster-like film-forming material generated by a so-called stippling phenomenon are trapped in the buffer chamber 9 and the reserve chamber 10 and are not released to the film-forming surface side.
[0012]
Further, the molecules of the film-forming material a generated in the crucible 5 are stored in the buffer chamber 9 and then stored in the reserve chamber 10 having a still larger volume, and then released from the molecule discharge port 4 to thereby form the crucible. The amount of molecules generated by evaporation or sublimation from 5 or abrupt increase or decrease or wave-like repeated increase and decrease is buffered, and almost constant molecules can be stably released from the molecule discharge port 4 per unit time. As a result, a uniform thin film having a uniform thickness without unevenness can be formed even when the film formation surface is close to the molecular emission port 4.
[0013]
It is preferable that the reserve chamber 10 be heated to a higher temperature than the buffer chamber 9 side by a heating means different from the heating means for heating the film forming material a. By doing so, it is possible to prevent the generated molecules from being re-coagulated in the reserve chamber 10 and to evaporate or sublimate the cluster-like film-forming material, thereby reliably preventing the cluster-like film-forming material from scattering. I can do it.
[0014]
The reserve chamber 10 is provided separately from the buffer chamber 9, the reserve chamber 10 is rotatably connected to the buffer chamber 9, and the direction of the molecule discharge port 4 can be changed by the rotation. By doing so, molecules can be released from the molecule release port 4 of the reserve chamber 10 in any direction to form a film.
[0015]
In this case, if the monitoring molecule release port 16 is provided on the rotation axis of the reserve chamber 10, the monitoring molecule release port 16 does not move even if the reserve chamber 10 rotates. By arranging the film thickness meter 11 opposite the outlet 16, the absolute amount of the molecules flowing into the reserve chamber 10 can be monitored by one film thickness meter 11 irrespective of the direction of the molecule discharge port 4. Becomes possible.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described specifically and in detail with reference to the drawings.
FIG. 1 is a vertical sectional side view showing one embodiment of a molecular beam source cell for depositing a thin film according to the present invention. The molecular beam source cell includes a molecule generating section 2 as a generator, and a reservoir 6 for temporarily storing generated molecules and then releasing the generated molecules.
[0017]
In the molecule generator 2, the crucible 5 containing the film forming material a is attached by a crucible setter 8. The opening side of the crucible 5 in which the crucible setter 8 is set communicates with the buffer chamber 9 as a small room through the molecule passage hole 7. On the wall surface of the buffer chamber 9, the film-forming material a housed in the crucible 5 is heated and sublimated or evaporated to generate molecules of the film-forming material a, and the inside of the buffer chamber 9 is heated. A heating unit 3 is provided as heating means for keeping the film-forming material inside in a molecular state. A cartridge heater 14 is detachably attached to the heating unit 3.
[0018]
As described above, the small chamber-shaped buffer chamber 9 is provided adjacent to and adjacent to the crucible setter 8 in which the crucible 5 is installed, and the crucible 5 side and the buffer chamber 9 are provided on a plurality of partition walls provided therebetween. It communicates through the molecule passage hole 7.
One end of a cylindrical support shaft 12 is horizontally mounted on the side surface of the buffer chamber 9. The inside of the support shaft 12 is hollow and forms a molecular passage 13 that is continuous with the buffer chamber 9.
[0019]
A reservoir 6 is attached to the other end of the support shaft 12 so as to be rotatable around the center axis of the support shaft 13 as a rotation center. The reservoir 6 is box-shaped, and its inside is hollow, forming a reserve chamber 10. The reserve chamber 10 is connected to the buffer chamber 9 via a molecule passage 13 in the support shaft 12. Further, the volume of the reserve chamber 10 is sufficiently larger than that of the buffer chamber 10, and is several times to several tens times the volume. A heating unit 15 as heating means for heating the reserve chamber 10 is attached to a pair of opposite side surfaces of the reservoir 6. The heating unit 15 is similar to the above-described heating unit 3, but generates a larger amount of heat.
[0020]
In FIG. 1, a plurality of molecule release ports 4 are opened on the upper wall surface of the reserve chamber 10. FIG. 1 shows two molecule emission ports 4, but in the illustrated example, a total of four molecule emission ports 4 are opened side by side two by two. The molecule emission port 4 is open toward the film formation surface of the substrate 1 for forming a thin film.
[0021]
Further, a molecule discharge port 16 for monitoring is provided on a side wall of the reserve chamber 10 at a position on an extension of the center axis of the support shaft 13. The film thickness meter 11 is attached to the side of the reservoir 6 so as to face the molecule discharge port 16 for monitoring. This film thickness meter 11 has a quartz oscillator, and measures the thickness of the thin film to be formed by changing the natural frequency of the quartz oscillator when a thin film is deposited on the surface of the quartz oscillator. Is what you do.
[0022]
In such a molecular beam source cell for depositing a thin film, a part of molecules generated from the crucible 5 by being heated and evaporated or sublimated by the heating unit 3 is first passed through the molecular passage holes 7 to form a buffer chamber as a small room. Enter 9 Further, these molecules enter the reserve chamber 10 from the buffer chamber 9 through the above-mentioned molecule passage 13, and after being stagnated to some extent, are released from the molecule release port 4 and deposited on the film forming surface of the substrate 1. . At this time, the buffer chamber 9 and the reserve chamber 10 trap the particles of the cluster-like film-forming material generated by the so-called stippling phenomenon. Is not emitted to the film forming surface side of the film. Thereby, occurrence of a defect in the film can be prevented.
[0023]
Further, molecules stored in the reserve chamber 10 having a sufficiently larger volume than the buffer chamber 9 are released from the molecule discharge port 4, so that the increase or decrease in the amount of molecules generated by evaporation or sublimation from the crucible 5 is buffered. From the molecule discharge port 4, certain molecules can be stably released per unit time. As a result, a uniform thin film having a uniform thickness without unevenness can be formed even when the film formation surface is close to the molecular emission port 4.
[0024]
In such a film forming process, the reserve chamber 10 is preferably heated to a higher temperature than the buffer chamber 9 by the heating unit 15. By doing so, it is possible to prevent the generated molecules from being re-coagulated in the reserve chamber 10 and to evaporate or sublimate the cluster-like film-forming material, thereby reliably preventing the cluster-like film-forming material from scattering. I can do it.
[0025]
At this time, some molecules in the reserve chamber 10 are released from the monitoring molecule release port 16 and are deposited on the quartz oscillator of the film thickness gauge 11. As a result, the natural frequency of the crystal resonator changes, and the film thickness is measured based on the change in the natural frequency.
[0026]
The amount of molecules emitted from the crucible 5 and emitted from the molecule release port 4 of the reserve chamber 10 toward the film-forming surface of the substrate 1 passes through the molecule release port 16 for monitoring, and flies to the thickness gauge 11 side. There is a certain correlation with the amount of the molecule, which is usually proportional. Therefore, the amount of molecules radiated from the molecular emission port 4 toward the film formation surface of the substrate 1 can be easily estimated from the film thickness measured by the film thickness meter 11.
[0027]
By monitoring the amount of released molecules, the amount of released molecules is grasped, processed by the measuring device 17 to output a control signal, and the heating controller 18 controls the heating temperatures of the heating units 3 and 15. Do. The amount of evaporation or sublimation of molecules from the crucible 5 is controlled mainly by controlling the heating unit 3 on the molecule generation source side.
[0028]
As described above, the reservoir 6 is provided so as to be rotatable around the central axis of the support shaft 12. For this reason, it is possible to change the direction of the molecule discharge port 4. For example, FIGS. 1 and 2 show a state in which the molecule discharge port 5 is directed upward. FIG. 3 shows a state where the molecule discharge port 5 is turned sideways. As described above, since the direction of the molecular emission port 4 can be changed, the arrangement of the substrate 1 can be arbitrarily selected.
On the other hand, since the molecular emission port 16 for monitoring is on an extension of the central axis of the support shaft 13, the position of the molecular emission port 16 does not change at all even if the direction of the reservoir 6 changes. Therefore, the amount of released molecules can be monitored regardless of the orientation of the reservoir 6 simply by arranging the film thickness gauge at one location.
[0029]
【The invention's effect】
As described above, in the molecular beam source cell for depositing a thin film according to the present invention, particles of a cluster-like film-forming material generated by a so-called stippling phenomenon are trapped in the buffer chamber 9 or the reserve chamber 10 and released to the film-forming surface side. Not done. Also, the increase or decrease in the amount of molecules generated by evaporation or sublimation from the crucible 5 is buffered, and a substantially constant molecule can be stably released from the molecule discharge port 4 per unit time. As a result, a uniform thin film having a uniform thickness without unevenness or defects can be formed even when the film formation surface is close to the molecular emission port 4, so that the film formation efficiency can be improved.
[Brief description of the drawings]
FIG. 1 is a vertical sectional side view showing a thin film deposition molecular beam source cell according to an embodiment of the present invention.
FIG. 2 is a perspective view of the molecular beam source cell for depositing a thin film according to the same embodiment, showing a state in which a molecular emission port of a reservoir faces upward.
FIG. 3 is a perspective view showing the molecular beam source cell for depositing a thin film according to the embodiment, with the molecular emission port of the reservoir directed sideways;
[Explanation of symbols]

Claims (4)

By heating the film-forming material (a), the film-forming material (a) is sublimated or evaporated to generate molecules for growing a thin film on a solid surface. A crucible (5) for accommodating the material (a), heating means for heating and sublimating or evaporating the film-forming material (a) in the crucible (5), and a component generated from the crucible (5). A buffer chamber (9), which is a small space through which molecules of the membrane material (a) pass, and a space having a volume sufficiently larger than that of the buffer chamber (9) communicating with the buffer chamber (9) through a molecular passage (13). Characterized by having a reserve chamber (10) having therein, and a molecule discharge port (4) which is open to the wall of the reserve chamber (10) and releases molecules therein toward the film-forming surface of the solid surface. Molecular beam source cell for thin film deposition. 2. The storage chamber (10) is heated to a higher temperature from the buffer chamber (9) side by a heating means different from a heating means for heating the film forming material (a). Source cell for thin film deposition. 3. The thin film deposition according to claim 1, wherein the reserve chamber (10) is rotatably connected to the buffer chamber (9), and the direction of the molecular emission port (4) is variable by the rotation. Molecular beam source cell. A molecular emission port (16) for monitoring is provided on the rotation axis of the reserve chamber (10), and the film thickness meter (11) is arranged to face the molecular emission port (16) for monitoring. The molecular beam source cell for depositing a thin film according to claim 3.

Images