Plasma treatment apparatus and surface treatment apparatus of substrate

Abstract

A plasma treatment apparatus of the present invention comprises: a plasma generation chamber 34 for activating gas supplied thereto so as to generate plasma; a depressurization chamber 50 which is connected to the plasma generation chamber 34 and which accommodates a member 52 to be plasma-treated; and a diffuser 58 which is provided at a joint part of the plasma generation chamber 34 and the depressurization chamber 50, which guides the plasma in a direction inclined to a gas flow path of the plasma generation chamber 34, and which introduces the plasma into the depressurization chamber 50 while diffusing the plasma in the depressurization chamber 50.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plasma treatment apparatus capable of uniformly treating a surface of a substrate having a larger area than a cross sectional area of a plasma introductory part, and a surface treatment apparatus for treating a surface of a substrate by a gas plasma.

2. Description of Related Art

According to a semiconductor apparatus and an OLED (organic light emitting diode) display in which a conductive thin film formed on a substrate, a surface of the conductive thin film is plasma-treated so as to improve or stabilize properties thereof.

In the OLED display, a thin film containing a fluorescent or phosphorescent organic chemical compound is sandwiched between an anode electrode and a cathode electrode. In the OLED display, positive holes and electrons are injected into the thin film from the anode electrode's side and the cathode electrode's side, respectively, so as to recombine them. Due to energy that is discharged by this recombination, the fluorescent or phosphorescent organic chemical compound is excited to emit light. Accordingly, it is preferable to deposit a plurality of chemical compounds so that ionized potential (Ip) is made smaller from the anode electrode's side toward the cathode electrode's side.

In addition, in order to enhance a work function of the anode electrode and improve injection of the positive hole, it has been known that a surface of the anode electrode is treated by UV-O₃, O₂ plasma, the like (see patent document 1, for example).

FIG. 5 is a perspective view of a substantial part of a structure of an OLED display during manufacture, and FIG. 6 is sectional view of a substantial part of the OLED display taken on a line of A-A of FIG. 5. In the drawings, a reference numeral 10 denotes an insulating substrate such as glass, and reference numerals 12a and 12b denote a pair of thin film transistors formed on the insulating substrate 10. Although not shown in the drawings, many thin film transistors are formed in the form of a matrix. A reference numeral 14 denotes a layer that is connected to an electrode through which a main electric current of the thin film transistor 12a passes, for example, a drain electrode wiring layer that is connected to a drain electrode. On the insulating substrate 10, except for the thin film transistor 12a, a source electrode wiring layer through which the main electric current passes, a power source wire, a grounding wire, and a gate electrode wire of the thin film transistor 12b are formed, however, they are omitted in the drawings.

A reference numeral 16 denotes a resin insulating layer which coats the surface of the insulating substrate 10 so as to smooth out the irregularities of the surface of the insulating substrate 10 which are caused by the thin film transistor 12 or the like. The resin insulating layer 16 is formed from an acrylic transparent resin, for example. A reference numeral 18 denotes a through hole that is formed in a portion of the resin insulating layer 16. A diameter of the through hole 18 is made smaller from an opening top toward a bottom, and the drain electrode wiring layer 14 is exposed at its bottom. Reference numerals 20a and 20b denote electrode wiring layers formed on the resin insulating layer 16, respectively. The electrode wiring layer 20a is connected to a power source (not shown), while the other electrode wiring layer 20b is electrically connected to the drain electrode wiring layer 14 at the bottom of the through hole 18. Therefore, the electrode wiring layer 20b and the thin film transistor 12a are electrically connected through the drain electrode wiring layer 14. A reference numeral 22 denotes an edge insulating layer which coats the surface of the resin insulating layer 16. In the edge insulating layer 22, a portion of the electrode wiring layer 20a is exposed through a window 22a to form an anode electrode 24 and to form a window 22b at the through hole 18. A reference numeral 26 denotes resin deposited layers that are placed opposite to each other and that sandwich an area including the anode electrode 24 and the through hole 18, and their opposed walls are inversely tapered.

In FIG. 6, a reference numeral 28 denotes an OLED layer formed on the anode electrode 24 and the OLED layer 28 is formed through a metallic mask (not illustrated). In addition, an opening of the resin deposited layer 26 is used as a portion of the mask and an end of the OLED layer 28 is spaced apart from a base portion of the resin deposited layer 26. A reference numeral 30 denotes a cathode electrode wiring layer formed through a metallic mask (not shown) on the OLED layer 28 and the resin insulating layer 16 except for an anode electrode wiring layer 20. Further, the cathode electrode wiring layer 30 is formed using the opening of the resin deposited layer 26 as a portion of the mask, and a portion of the cathode electrode wiring layer 30 which overlaps the OLED layer 28 is formed as a cathode electrode 32. This cathode electrode wiring layer 30 is connected to the drain electrode wiring layer 14 formed on the insulating substrate 10 through the through hole 18 formed in the edge insulating layer 22.

Further, the OLED display shown in FIG. 6 is hermetically sealed by putting the transparent glass substrate thereon. The OLED display is used as a light emitting apparatus or a display unit by releasing the light emitted from the OLED layer 28 from the transparent glass through the cathode electrode wiring layer 30. Such OLED display is called a top-emission OLED display. In the top-emission OLED display, the light emitted from the OLED layer 28 to the anode electrode 24 is reflected on the surface of the anode electrode 24 so as to enhance the brightness.

In this display unit, the anode electrode 24 functions as a source for injecting positive holes into the OLED layer 28 and is associated with efficiency of light emission of the OLED layer 28. Accordingly, as a material of an electrode, a material having a large work function is desired.

In order to effectively release the light emitted from the OLED layer 28, a material with high reflectivity is selected for the anode electrode wiring layer 20 and the anode electrode 24. For example, AlNd or the like is used.

Thus, it is preferable to form the anode electrode 24 from an electrode material satisfying different properties of the working function and the reflectivity. However, there is no material that satisfies the both properties at the same time and that can be easily handled. Furthermore, in even a proper electrode material, effects of the material may vary depending on its surface condition. ITO and Nickel inherently have large work functions, so that positive holes can be injected therein very well only by cleaning their surfaces through a cleaning processing and then oxidizing the surfaces. However, a drawback to the ITO and Nickel is low reflectivity. In the meanwhile, aluminum and aluminum base alloy have high reflectivity and can be easily handled. However, their working functions are small, so that it is necessary to form a functional organic film after the cleaning processing in order to enhance their working functions.

For this reason, in the structure during manufacture shown in FIG. 5, the surface of the anode electrode 24 is cleaned before forming the OLED layer 28. Such cleaning enhances the working function and the reflectivity of the anode electrode 24. Further, in order to increase the working function, an functional organic film is formed on the cleaned surface of the electrode. For example, cleaning process is carried out by ozone UV-O₃ which is generated by applying ultraviolet rays to a substrate to be surface-treated in oxygen atmosphere. In the cleaning using ozone UV-O₃, there are few damages in the resin structures 16, 22, and 26 located at the edge of the anode electrode 24. However, since the functional organic film cannot be formed on the surface of the electrode in succession from the cleaning operation, an additional equipment is needed.

On the contrary, a plasma treatment apparatus does not require any additional equipment. In the plasma treatment apparatus, the surface of the electrode can be cleaned by oxygen plasma and a functional organic film can be formed on the cleaned surface of the electrode by using a different material gas. In a typical parallel flat plate type plasma treatment apparatus, two parallel electrodes are placed opposite to each other in a depressurization chamber and a substrate is provided between the parallel electrodes. When high-frequency power is applied between the parallel electrodes, gas in the depressurization chamber is reacted and thus plasma is generated. As far as the structure of the apparatus is simple and the substrate can be provided between the parallel plate electrodes, even a large substrate can be uniformly treated.

In an ECR plasma treatment apparatus, high-density plasma is generated by adding a micro wave and a magnetic filed from an electromagnet in a plasma generation chamber connected to the depressurization chamber and setting intensity of the magnetic field in such a manner that an electron cyclotron resonance condition is satisfied. In the ECR plasma treatment apparatus, a large substrate can also be treated.

[Document 1] Japanese Unexamined Patent Publication No. (Patent Kokai No.) 08-167479 (1996) (See paragraph [0013]) However, since a portion of coating resin such as the resin insulating layer 16 and the edge insulating layer 22 is exposed when the anode electrode 24 is cleaned, the surface of the coating resin is exposed to plasma. The surface of the coating resin is ruined if the high-density plasma is allowed to directly contact the surface. Particularly, if the surface of the coating resin near the anode electrode 24 is ruined, a portion of the resin that is scraped thereby adheres to the surface of the anode, and brightness of this portion may be lowered or this portion may not emit light (thus, a dark spot is formed). This dark spot portion is enlarged with time. Such enlargement of the dark spot area is accelerated by blinking, and at last, the all the pixels do not emit light. Thus, this exerts adverse effects on a display quality and reliability.

In the meanwhile, if cleaning of the surfaces of the electrodes formed on the substrate and forming the functional organic film on the electrode surfaces are sequentially carried out using a single apparatus, foreign matter is generated by reaction with plasma gas and deposited in a chamber. Thus-deposited functional organic film material is decomposed during the cleaning process and then adheres to the anode electrode again. Therefore, it is necessary that such deposit is periodically removed from depressurization chamber.

For such a reason, while the structure of the parallel flat plate type plasma treatment apparatus is simple, there are many problems in both carrying out the cleaning of the surfaces of the electrodes and forming the functional organic film on the electrode surface using the same apparatus.

On the contrary, in the ECR plasma treatment apparatus, high-density plasma generated at a plasma generation source is diffused in the depressurization chamber in which the substrate is provided so as to expose the substrate to such plasma. Therefore, the ECR plasma treatment apparatus can prevent the damage of the coating resin. However, since the plasma introductory part of the depressurization chamber is away from the substrate, if the opening diameter of the plasma introductory part is small, the plasma introduced in the depressurization chamber is scattered in all directions. Therefore, the electrodes on the flat substrate cannot be uniformly treated in the ECR plasma treatment apparatus and the unevenness of the treatment is severe in the large substrate.

Therefore, plasma to be introduced in the depressurization chamber is diffused by a diffuser (a diffusion plate) to realize a uniform treatment. Many diffusers have been manufactured by way of trial under various conditions by changing a hole diameter and a space between the holes, for example, and the treatment states have been observed. However, such conventional diffusers cannot solve a big difference in a cleaning level of the electrodes between a center portion and a marginal area of a large substrate. In addition, the ECR plasma treatment apparatus requires an electromagnet and advanced control apparatus, so that the apparatus has a complicated structure and is expensive.

As a plasma treatment apparatus in which a plasma generation source is connected to a depressurization chamber, there is an apparatus using an inductive coupled plasma (ICP) for generating plasma by a high-frequency electric field. This apparatus is cheaper than the ECR plasma treatment apparatus. However, this apparatus has the same problem as the ECR plasma treatment apparatus because the plasma introductory part of the depressurization chamber is away from the substrate.

Further, it is also conceivable that a plurality of plasma generation sources are provided in one depressurization chamber and plasma is diffused on one substrate from each plasma generation source. However, it is difficult to control a plurality of plasma generation sources under the same condition. Moreover, maintenance of the apparatus is complicated and the cost of equipment is high.

SUMMARY OF THE INVENTION

In order to solve the above problems, we have eventually found the present invention. Accordingly, an object of the present invention is to provide a plasma treatment apparatus which comprises: a plasma generation chamber for activating gas supplied thereto so as to generate plasma; a depressurization chamber which is connected to the plasma generation chamber and which accommodates a member to be plasma-treated; and a diffuser which is provided at a joint part of the plasma generation chamber and the depressurization chamber, which guides the plasma in a direction inclined to a gas flow path of the plasma generation chamber, and which introduces the plasma into the depressurization chamber while diffusing the plasma in the depressurization chamber.

Further, the present invention provides a surface treatment apparatus which comprises: a plasma generation chamber for activating gas supplied thereto so as to generate plasma; a depressurization chamber which is connected to the plasma generation chamber and which accommodates a substrate with a conductive thin film and an organic thin film formed on a main surface thereof; and a diffuser which is provided at a joint part of the plasma generation chamber and the depressurization chamber, which guides the plasma in a direction inclined to a gas flow path of the plasma generation chamber, and which introduces the plasma into the depressurization chamber while diffusing the plasma in the depressurization chamber, wherein a surface of the conductive thin film formed on the substrate is treated using different gas plasma by successively feeding different material gases to the plasma generation chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view of a substantial part of a plasma treatment system of the present invention.

FIG. 2 is a graph for comparing thicknesses of organic films between a conventional system and a system of the present invention.

FIG. 3 is a sectional side view for showing a shape of an opening end of a diffuser.

FIG. 4 is a enlarged sectional side view of a substantial part of a variation of the diffuser.

FIG. 5 is a sectional side view of a substantial part of an OLED display.

FIG. 6 is a perspective view of a substantial part of a structure of the OLED display during manufacture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below with reference to FIG. 1. In FIG. 1, a reference numeral 34 denotes a plasma generation chamber for generating plasma by activating gas supplied thereto. In the plasma generation chamber 34, a plurality of gas cylinders 36, 38, 40 which is opened and closed by valves 36a, 38a, and 40a are connected through a flow rate controller 42 to a gas inlet 34a which is provided at a lower end of the chamber 34. A reference numeral 44 denotes an induction coil that is wound around the plasma generation chamber 34. The induction coil 44 is connected to a high frequency oscillator 48 through a matching circuit 46. When a high frequency current flows through the induction coil 44, the gas supplied in the plasma generation chamber 34 is excited into plasma. A reference numeral 50 denotes a depressurization chamber. In the depressurization chamber 50, a gate (not shown) is disposed at a peripheral surface thereof. The plasma generation chamber 34 is connected to a bottom 50a of the chamber 50, and the plasma gas is supplied from a plasma inlet (plasma introductory part) 34b. A reference numeral 52 denotes a substrate (a member to be plasma-treated) whose surface is coated with resin and in which conductive thin film is provided on a substantial part of the resin coating. The surface of the conductive thin film is cleaned by contacting it with the plasma gas (a detailed explanation is herein omitted). A reference numeral 54 denotes a substrate supporting means for supporting the substrate 52 with the conductive thin film formation surface down. To the substrate supporting means 54, a moving mechanism 56 for moving the substrate 52 in a horizontal direction, a swinging mechanism for swinging a main surface of the substrate 52 with respect to a horizontal plane, a rotation mechanism for rotating the substrate around a rotational axis perpendicular to the horizontal plane, and heating means for heating the substrate (not shown) or the like are provided when necessary.

A reference numeral 58 denotes a diffuser that is a characteristic of the present invention. The diffuser 58 is provided at a joint part of the plasma generation chamber 34 and the depressurization chamber 50 and diffuses the plasma introduced in the depressurization chamber 50 over the whole surface of the substrate 52. According to the illustrated example, two tubular bodies 60a and 60b inclined relative to the surface of the substrate 52 guide the plasma in an inclined direction. One end side of the tubular body 60a and one end side of the tubular body 60b are in intimate contact with each other and are connected to the plasma inlet 34b of the plasma generation chamber 34, while the other end sides of the tubular bodies 60a and 60b are separated from each other. Respective axes a and b shown by a dashed line in the drawing are extended to the ends of the substrate 52 so that extensions of the axes a and b intersect with the ends of the substrate 52. Respective axes a and b are inclined at 45 degrees relative to the horizontal plane, and opening ends c and d of the tubular bodies 60a and 60b substantially perpendicularly intersect these axes a and b. Thus, the substrate 52 and the opening ends c and d are not arranged parallel to each other. The illustrated tubular bodies 60a and 60b are circular in cross section.

A reference numeral 62 denotes a pressure controller for controlling a pressure within the depressurization chamber 50, and a reference numeral 64 denotes a turbo-molecular pump that is connected to the pressure controller 62. A reference numeral 66 denotes a dry pump. The pressure controller 62 and the turbo-molecular pump 64 are connected to the dry pump 66 through a valve 68 and a valve 70, respectively, so as to depressurize the depressurization chamber 50.

The operation of the above-described plasma treatment apparatus will be described below. First, a substrate (a member to be plasma-treated) 52 is prepared. As is the case with the structure of the OLED display during manufacture shown in FIG. 6, in the substrate 52, a conductive pattern formed on an insulating substrate is covered with a coating resin and a portion of the conductive pattern is exposed through a window formed in a substantial part of this coating resin so as to form a conductive thin film (anode electrode). In the substrate 52, in order to enhance the working function of the surface of the anode electrode and increase the efficiency of positive hole injection, the surface of the conductive thin film is cleaned and then oxidized, and then a coating made of organic material is formed on the conductive thin film.

This substrate 52 is placed in the depressurization chamber 50 and then the chamber 50 is hermetically sealed. The substrate 52 placed in the depressurization chamber 50 is set at an earth potential or a proper bias potential.

Next, the valve 68 is opened to operate the dry pump 66 and to depressurize the depressurization chamber 50. Then, the valve 70 is opened to operate the turbo-molecular pump 64, and the valve 68 is closed to depressurize the depressurization chamber 50 sufficiently. When the depressurization chamber 50 is sufficiently depressurized, the gas cylinders 36 to 40 are opened or closed selectively by controlling the opening and closing of the valves 36a to 40a, predetermined gas is fed into the plasma generating chamber 34, and the pressure in the depressurization chamber 50 is maintained at a predetermined value by the flow rate controller 42. Under such condition, when a high frequency current flows through the induction coil 44 and an induction magnet field is generated in the plasma generation chamber 34, the material gas is oscillated at a high frequency and thus plasma is generated.

When an oxygen gas is supplied as the material gas, O₂ plasma is fed into the depressurization chamber 50 through the diffuser 58. This oxygen decomposes and removes contamination adhering to the surface of the electrode formed on the surface of the substrate 52, and further, it oxidizes the cleaned surface of the electrode.

When the aforementioned operation is completed, a functional organic layer is formed on the cleaned surface of the conductive thin film. Therefore, the supply of the oxygen gas is stopped, the current flow to the induction coil 44 is temporarily stopped, and the oxygen gas remaining in the depressurization chamber 50 is discharged. After checking that the pressure is sufficiently decreased and the oxygen gas is sufficiently discharged, a gas to be used as a material for forming an organic film is supplied to the plasma generation chamber 34.

If C_xH_yF_z (x>1, y≧0, z≧2) is used as the gas to be used as a material for forming an organic film, a functional organic film that is mainly composed of CF_x can be formed on the substrate 52 having the conductive thin film. The gas to be used as a material for forming an organic film is supplied to the plasma generation chamber 34. When a current flows through the induction coil 44 again, plasma gas is fed into the depressurization chamber 50 through the diffuser 58. On the surface of the substrate 52 having the conductive thin film on which an organic layer is formed, the functional organic film is formed.

Thus, by successively treating the substrate 52 using various material gases, it is possible to perform cleaning of the surface of the conductive thin film and forming the coating resin in one depressurization chamber without changing the substrate.

When such successive operations are completed, the current flow to the induction coil 44 is stopped, and the supply of the gas to be used as a material for forming an organic film is stopped. After a nitrogen gas is supplied into the depressurization chamber 50 to bring back the depressurization chamber 50 to the atmosphere pressure, the substrate 52 is taken out from the depressurized chamber 50. Then, the depressurization chamber 50 is hermetically sealed and sufficiently depressurized, and the gas made by mixing the oxygen gas as a main gas with an argon gas or the like is fed to the plasma generation chamber 34. The depressurization chamber 50 is maintained at a constant pressure, a current is passed through the induction coil 44 so as to generate plasma, and the generated plasma is supplied to the depressurization chamber 50 through the diffuser 58.

By conducting such operation, organic films deposited on an inner wall of the plasma generation chamber 34, inner walls of the tubular bodies 60a and 60b of the diffuser 58, and an inner wall of the depressurization chamber 50 are decomposed by O₂-plasma gas, and this decomposition gas is discharged from the depressurization chamber 50 to the outside.

After removing the functional organic film in this way, the current flow to the induction coil 44 is stopped, the supply of the oxygen gas or the like is stopped, the depressurization chamber 50 is brought back to the atmosphere pressure by supplying nitrogen gas thereto, and the depressurization chamber 50 is opened. After that, a new substrate 52 is put into the depressurization chamber 50 and is subjected to the above-described operations.

In the plasma treatment apparatus according to the present invention, the cleaning of the substrate 52 in the depressurization chamber 50 by O₂-plasma and the depositing of the organic film on the substrate 52 can be successively conducted. The organic film adhering to the inner wall or the like of the diffuser during the depositing process can be decompounded by O₂-plasma and removed from the depressurization chamber 50 prior to cleaning a new substrate. Therefore, the operations can be repeated without posing any problem to the cleaning operation of the new substrate.

The diffuser 58 is composed of the tubular bodies 60a and 60b. The axes of the respective tubular bodies 60a and 60b are inclined relative to the axis of the plasma generation chamber 34. The cross sectional areas of the openings of the respective tubular bodies 60a and 60b are smaller than the cross sectional area of the plasma inlet 34b.

Gas is supplied into the plasma generation chamber 34 and the depressurization chamber 50 is depressurized by the pumps 64 and 66. For this reason, there is a pressure gradient in a gas flow path between the diffuser 58, the depressurization chamber 50, and the pump 66. Therefore, the gas supplied to the plasma generation chamber 34 is drawn into the depressurization chamber 50 from the opening end of the diffuser 58 and then diffused in the depressurization chamber 50.

In this time, the gas in the depressurization chamber behaves as an elastic body. Since molecules of the gas repeatedly collide against each other or against the wall of the chamber, their moving direction is changed. Accordingly, the gas in the tubular diffuser 58 flows in a direction synthesized from the moving direction controlled by the pressure gradient and the moving direction changed by the collision.

Therefore, the plasma gas generated in the plasma generation chamber 34 enters into the tubular bodies 60a and 60b from various directions relative to their axes. Then, the plasma gas is guided through the tubular bodies 60a and 60b towards the depressurization chamber 50 while reflecting and swirling inside the tubular bodies 60a and 60b, and then it is discharged from the tubular bodies 60a and 60b into the depressurization chamber 50.

The plasma gas enters into the tubular bodies 60a and 60b from various directions and reflects on the inner walls of the respective tubular bodies 60a and 60b in various directions. Therefore, the gas moves in various directions at the opening ends of respective tubular bodies 60a and 60b. However, the gas discharged from the opening ends is released from the guide of the tubular body 60, so that the gas moves substantially straight ahead in the same direction as is discharged.

Some of the plasma gas discharged from the opening ends of the respective tubular bodies 60a and 60b may move in substantially parallel with the surface of the opening end of each tubular body.

Therefore, a diameter and a length of the diffuser 58 are set in such a manner that the extensions of the respective axis of the respective tubular bodies 60a and 60b intersect with the ends of the substrate 52 and the extensions of the surfaces of the opening ends of the respective tubular bodies intersect the center part of the substrate 52. It is preferable that the diameter and the length of the diffuser 58 are set in such a manner that the areas which are exposed to the plasma gas discharged from the respective tubular bodies 60a and 60b overlap at the center part. Thus, even if the axes of the tubular bodies 60a and 60b and the opening ends substantially perpendicularly intersect each other, the whole area of the substrate 52 can be exposed to the plasma gas.

In order to check an advantage of the apparatus of the present invention, various disc diffusers with a diameter of 150 mm, in which many holes are formed concentrically, were prepared. It was found out that the plasma current is 0.07 mA or less when the hole diameter is 3 mm or less, and the plasma current is about 1.2 mA when the hole diameter is 5 mm or 10 mm. Therefore, a diffuser with holes of 10 mm in diameter is used for making comparison with the diffuser to be used in the apparatus of the present invention. In the diffuser 58 to be used in the apparatus of the present invention, two tubular bodies 60a and 60b of 50 mm in diameter are used, one end side of the tubular body 60 is in intimate contact with one end side of the tubular body 60b, the respective axes of the tubular bodies 60a and 60b perpendicularly intersect each other, and axial lengths from this intersecting point to other end sides of the tubular bodies 60a and 60b are defined as 200 mm.

The plasma generation chamber 34 is 80 mm in outer diameter, a tubular body with a diameter of 150 mm and with a height of 40 mm is connected onto the plasma inlet 34b within the depressurization chamber 50, and each diffuser is connected to the upper end of the tubular body. The substrate 52 is attached horizontally to the bottom surface of the depressurization chamber 50 in such a manner that the height of the substrate 52 is adjustable. For example, the substrate 52 having a size of 325×465 mm is placed at a height of 400 mm.

FIG. 2 shows a film thickness of the functional organic film (in a range from the center toward the edges of the substrate 52) that is formed on the substrate 52 under the above-described conditions. The thickness of the film that is formed by using the disc diffuser (which is a diffuser for comparison with the diffuser to be used in the present invention) is changed from 1,330 nm to 780 nm from the center toward the respective edges of the substrate. Thus, the difference in thickness between the center and the respective edges is 550 nm. In this case, the distance from the center toward the respective edges of the substrate is 215 mm. Thus, the film is the thickest at its center and gradually becomes thinner toward the edges. The thickness of the film is dramatically decreased at a position about 170 nm or more apart from the center. The thickness uniformity of the film over the entire substrate is about 45% and thus the thickness of the film varies widely.

On the contrary, in the apparatus of the present invention, the thickness of the film is kept between 680 nm±10 from the center part toward the edges of the substrate. The thickness of the film is decreased from 670 nm to 550 nm in a range of 30 mm around the peripheral surface of the substrate. Thus, the difference in thickness is 130 nm. The thickness uniformity of the film over the entire substrate is bout 4.6%, and therefore, variations in thickness can be minimized.

In the plasma treatment apparatus according to the present invention, the plasma gas can be substantially uniformly applied to a large substrate from its center to its edges. Therefore, it is possible to form an organic film of substantially uniform thickness from its center toward its edges.

Therefore, in the plasma treatment apparatus of the present invention, where the anode electrodes formed on the substrates are cleaned and then the functional organic film is formed on the cleaned anode electrodes, cleaning of the surfaces of the electrodes formed on the substrate and forming the functional organic film on the electrode surfaces are sequentially carried out using a single apparatus, and thus operating efficiency can be improved.

Further, although the conductive thin films which function as the electrodes on the substrate are formed on portions of the coating resin and therefore O₂-plasma gas for cleaning the electrodes is exposed not only to the surfaces of the electrodes but also to the surface of the coating resin, the plasma gas generated in the plasma generation chamber 34 passes through the diffuser 58 and is diffused in the depressurization chamber 50. In this way, the surfaces of the electrodes can be cleaned without damaging the coating resin. Moreover, since the smoothness of the coating resin is maintained, a display unit having no dark spots, an excellent display quality, and a high reliability can be realized.

Further, according to the apparatus of the present invention, even if the substrate 52 is upsized so as to use it for a large display unit or the like, the entire surface of the substrate can be uniformly treated, and there is no difference in display quality between the center and the edges of the substrate. Therefore, the present invention can minimize variations in quality and can realize a serious cost reduction.

In the diffuser 58 according to the above-described embodiment, the angles of inclination of the tubular bodies 60a and 60b are set at 45 degrees. When the height of the substrate 52 is kept constant and the angles of the inclination of the tubular bodies are set at 45 degrees or less, a larger substrate can be treated as the inclination angles are smaller. However, the center part of the substrate is likely to be insufficiently cleaned and the film cannot be formed sufficiently. Thus, the substrate may not be treated uniformly. Alternatively, when the angles of inclination of the tubular bodies are set at 45 degrees or more, a larger substrate cannot be treated as the inclination angles are larger. In addition, since the opening ends of the two tubular bodies are close to each other, the center part of the substrate is double-treated by the two tubular bodies and thus treated too much. Therefore, it is preferable that the angles of the inclination of the tubular bodies 60a and 60b are set at 20 to 70 degrees. The diameter and the length of each tubular body may be set in accordance with the inclination angle.

In the aforementioned embodiment, an angle between the axis and the opening end of each tubular body is set at 90 degrees (or 45 degrees relative to the substrate 52) when the inclination angle of each tubular body is 45 degrees. However, this angle may also vary in accordance with the inclination angle of each tubular body. As shown in FIG. 3, in an area 52a which ranges from the center part of the substrate 52 to the outside ends thereof, assume that an opposite area from the tubular body 60a is an area 52b and a surface which intersects the area 52b is a virtual surface P. A surface of the tubular body 60a which is intersected by the virtual surface P can be defined as the opening end of the tubular body 60a. When the inclination angle of the tubular body 60a is 45 degrees, the opening end of the tubular body is inclined at about 45 degrees relative to the substrate 52. However, when the inclination angle of the tubular body 60a is less than 45 degrees, the opening end of the tubular body 60a is inclined at less than 45 degrees to the substrate 52. Thus, as the inclination angle is smaller, the opening end becomes closer to horizontal to the substrate 52. When the inclination angle of the tubular body 60a is more than 45 degrees, the opening end of the tubular body 60a is inclined at more than 45 degrees to the substrate 52. Therefore, as the inclination angle is larger, the opening end becomes closer to vertical to the substrate. The opening end of the tubular body 60a may be formed not only in a manner that the entire surface of the opening end contacts the virtual surface P but also in a manner that a portion of the opening end contacts the virtual surface P.

In the aforementioned embodiment, two tubular bodies 60a and 60b whose both ends are the same in diameter are used as the diffuser 58. However, as the tubular bodies 60a and 60b, a tubular whose both ends are different in diameter can also be used. In this case, if the opening end with a larger diameter is located at the plasma inlet 34b's side and the opening end with a smaller diameter is located at the depressurization chamber 50's side, the plasma gas can be more complicatedly moved in the diffuser 58, and therefore, preferable diffusion of the plasma gas can be obtained in the depressurization chamber 50. Alternatively, if the opening end with a smaller diameter is located at the plasma inlet 34b's side and the opening end with a larger diameter is located at the depressurization chamber 50's side, the adhesion of the organic film material to the inner walls of the tubular body 60a and 60b can be reduced.

In the aforementioned embodiment, two tubular bodies 60a and 60b are arranged in a substantial V shape or a substantial Y shape. However, the number of the tubular body may be two or more. Alternatively, for example, as shown in FIG. 4, two conical plates 72 and 74 may be arranged parallel to each other. In this case, a space between the conical plates 72 and 74 are used as a path of plasma gas. A vertex of the conical plate 72 is cut off so as to connect the plate 72 to the plasma inlet 34b. The distance between the conical plates 72 and 74 is kept constant by a support post 76. By using a thin rod as the support post 76, the plasma gas can be fed to the depressurization chamber 50 in all directions. Alternatively, by using a quadrant rod as the support post 76, an opening area of the plasma inlet and the direction that the opening of the plasma inlet faces can be restricted. The tubular bodies 60a and 60b may be not only a cylindrical body but also a polygonal tubular body.

In the aforementioned embodiment, the cleaning of the member to be plasma-treated and the forming of the organic film are successively carried out by changing material gas for plasma. However, the apparatus of the present invention can also be applied to only one of the operations: cleaning of the member to be plasma-treated or forming of the organic film. Further, the member to be plasma-treated is not limited to an in-process substrate to be used for an OLED display, but it can be a any member which requires the cleaning operation or the organic film forming operation.

While the embodiments of the present invention have thus been described with reference to the drawings, it should be understood that the present invention is not limited to the aforementioned embodiments. Various changes, modifications, and improvements can be made to the embodiments on the basis of knowledge of those skilled in the art without departing from the scope of the present invention. This application claims priority from Japanese Patent Application No. 2003-302815, which is incorporated herein by reference.

Claims

1. A plasma treatment apparatus comprising:

a plasma generation chamber for activating gas supplied thereto so as to generate plasma;

a depressurization chamber connected to the plasma generation chamber and accommodating a member to be plasma-treated; and

a diffuser for guiding the plasma in a direction inclined to a gas flow path of the plasma generation chamber and for introducing the plasma into the depressurization chamber while diffusing the plasma in the depressurization chamber, said diffuser provided at a joint part of the plasma generation chamber and the depressurization chamber.

2. The plasma treatment apparatus according to claim 1, wherein said diffuser is composed of a plurality of tubular bodies, and one end side of each tubular body is in intimate contact with one end side of another tubular body and is connected to the plasma generation chamber, while the other end sides of the respective tubular bodies are separated from each other.

3. The plasma treatment apparatus according to claim 1, wherein an angle between an opening end which is opened in the depressurization chamber and an axis of each tubular body is determined in accordance with an angle of inclination of each tubular body.

4. The plasma treatment apparatus according to claim 1, wherein said tubular body is cylindrically shaped.

5. A surface treatment apparatus, comprising:

a plasma generation chamber for activating gas supplied thereto so as to generate plasma;

a depressurization chamber connected to the plasma generation chamber and accommodating a substrate with a conductive thin film and an organic thin film formed on a main surface thereof; and

a diffuser for guiding the plasma in a direction inclined to a gas flow path of the plasma generation chamber and for introducing the plasma into the depressurization chamber while diffusing the plasma in the depressurization chamber, said diffuser provided at a joint part of the plasma generation chamber and the depressurization chamber,

wherein a surface of the conductive thin film formed on the substrate is treated using different gas plasma by successively feeding different material gases to the plasma generation chamber.