The present invention relates to a method for manufacturing an organic EL element. EL represents an electroluminescence. The manufacturing method includes a step of forming a transparent electrode on a transparent substrate, a step of aligning shadow mask with the transparent substrate after the electrode forming step, and a step of laminating an organic EL layer on the transparent electrode by deposition after the aligning step.
Recently, attention has been focused on an organic electroluminescence element which is a light-emitting element of a self light emitting type. A basic method for manufacturing an organic EL element includes a step of preparing a glass substrate where an anode which is a transparent electrode is patterned and a step of laminating the organic EL layer and a cathode on the glass substrate. The organic EL layer has a laminated structure including a hole transport layer, a light-emitting layer, and an electron transport layer. A hole injection layer may be provided between the anode and the hole transport layer, and an electron injection layer may be provided between the cathode and the electron transport layer. A light-emitting layer emitting white light may be formed by only one layer or may be formed by laminating a red light-emitting layer, a green light-emitting layer and a blue light-emitting layer.
When each layer of the organic EL element is formed on the substrate, the substrate is arranged in a vacuum chamber and the substrate is covered with a mask with close contact. The mask has a plurality of openings which are formed to have a predetermined minute pattern. An organic raw material is evaporated in the vacuum chamber and passes through the openings of the mask. Accordingly, the organic raw material is deposited on the substrate. As a result, the organic EL element is manufactured. Since development of the organic EL element has been headed for color images having high resolution recently, the openings of the mask are formed to be quite minute. Therefore, at each deposition step, the mask having many minute openings needs to be positioned precisely on the substrate where the deposition has been carried out at the previous step.
For positioning the mask with respect to the glass substrate, a substrate mark may be formed on the glass substrate as an alignment mark after the transparent electrode is patterned on the glass substrate. A mask mark is formed on the mask as another alignment mark. The mask is positioned with respect to the glass substrate by using the substrate mark and the mask mark. Generally, the substrate mark is formed by a metal film so as to be visible by irradiation of the white light to the substrate mark at the alignment step.
Conventionally, an exposure device used for manufacturing a semiconductor device has an alignment measurement device. The alignment measurement device positions the mask with respect to a semiconductor wafer prior to the exposure. In the alignment measurement device disclosed in Japanese Laid-Open Patent Publication No. 5-226220, image data having good contrast between the substrate mark and portions except for the substrate mark is obtained. An object of the alignment measurement device is to obtain good contrast even if a surface reflection ratio of a semiconductor wafer, which is a sample that is to be aligned, a height of the substrate mark, a thickness of a resist coated on the semiconductor wafer and other conditions vary.
The alignment measurement device disclosed in the above publication has an irradiation light source for irradiating the substrate mark, a plurality of optical filters, and a wavelength selection device. The irradiation light source has a continuous and flat emission spectrum. Each of the optical filters has a narrow transmission wavelength range. A central wavelength of the transmission wavelength of each of the optical filters is different from each other. The wavelength selection device arranges one of the optical filters on a light path of the irradiation light. The alignment measurement device previously changes the optical filter at the various process steps to measure the substrate mark, and stores the optical filter with which maximum contrast is obtained. When actually measuring the alignment, the alignment measurement device controls the wavelength selection device such that the stored optical filter is positioned on the light path of the irradiation light.
However, when the substrate mark is formed of a metal film, a dedicated step of forming the substrate mark on the glass substrate is required. This increases the manufacturing steps.
The above publication discloses that the contrast of the substrate mark is improved by the irradiation of light via the optical filter. However, there is no description of the manufacturing of the organic EL element in the above publication.
It is an objective of the present invention to provide a method for manufacturing an organic EL element that has no dedicated step of forming an alignment mark on a transparent substrate and aligns a shadow mask with the transparent substrate by irradiating light to the alignment mark, the light having an appropriate wavelength corresponding to a thickness of a transparent electrode.
In accordance with one aspect of the present invention, a method for manufacturing an organic EL element is provided. The manufacturing method includes a step of forming transparent electrodes on a transparent substrate and a step of forming a substrate mark on the transparent substrate as an alignment mark. The substrate mark is formed at the same time as the transparent electrodes are formed on the transparent substrate. The substrate mark is formed of the same material as the transparent electrodes. The substrate mark has a thickness. The transparent substrate is arranged above a shadow mask so as to align the shadow mask with the transparent substrate. A white light source and a plurality of optical filters are prepared. A center wavelength of a transmission wavelength of each of the optical filters is different from each other. The optical filter that corresponds to the thickness of the substrate mark is selected from the optical filters. Light is irradiated from the white light source to the substrate mark via the selected optical filter. Accordingly, the shadow mask is aligned with the transparent substrate using the substrate mark. An organic EL layer is laminated on the transparent electrodes by deposition via the shadow mask.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
A method for manufacturing an organic EL element according to a first embodiment of the present invention will be explained with reference to
The organic EL element has a first electrode, an organic EL layer (not shown), and a second electrode (not shown) which are laminated on a transparent substrate in this order. The first electrode is a transparent electrode 12, and the organic EL layer includes a plurality of thin film layers. The method for manufacturing the organic EL element includes a step of forming the transparent electrode 12 on the transparent substrate 11, a step of forming the organic EL layer on the transparent electrode 12, and a step of forming a second electrode on the organic EL layer, in this order.
The thin film layers of the organic EL layer are formed by laminating through deposition using a shadow mask 14. The thin film layers are formed on the transparent substrate 11 with high precision so as to have a predetermined pattern. Therefore, the shadow mask 14 having a plurality of minute openings 14a for forming the thin films needs to be positioned with respect to the transparent substrate 11.
In the first embodiment, a glass substrate is used for the transparent substrate 11. The transparent electrodes 12 are made of ITO (indium-tin-oxide) which is used for the transparent electrode of known organic EL elements.
As shown in
The substrate marks 13 are formed on the predetermined positions at the same time as the transparent electrodes 12 are formed on the transparent substrate 11 in the step of forming the transparent electrodes 12. The step of forming the transparent electrodes 12 is one of the steps in the method for manufacturing an organic EL element.
Specifically, the transparent electrodes 12 are formed in the following steps. An ITO film is formed on the transparent substrate 11 made of glass with a known thin film forming method. A resist pattern is formed on the ITO film through photolithography. Thereafter, the transparent electrodes 12 are patterned by etching.
In the first embodiment, when patterning the transparent electrodes 12, a pattern corresponding to the substrate marks 13 are also formed on the resist pattern. As a result, the substrate marks 13 are formed on the transparent substrate 11 at the same time as the transparent electrodes 12 are formed. The thickness of the substrate marks 13 is the same as that of the transparent electrodes 12.
As shown in
An alignment method of the shadow mask 14 with respect to the transparent substrate 11 will be explained with reference to
As shown in
As shown in
Specifically, “selecting an optical filter 17 corresponding to the thickness of the substrate mark 13” means the following. Since the substrate mark 13 is formed of the same material as the transparent electrodes 12, the wavelength of light which makes the transparent substrate mark 13 visible varies in accordance with the thickness of the substrate mark 13. Therefore, “selecting an optical filter 17 corresponding to the thickness of the substrate mark 13” means that one optical filter is selected from a plurality of optical filters 17 so as to allow the light having the wavelength that makes the substrate mark 13 visible to pass through the substrate 11.
As shown in
The control device 23 controls the XY stage 21 and the e stage 22 based on image data received from the CCD camera 19. As a result, the control device 23 aligns the shadow mask 14 with the transparent substrate 11. The control device 23 adjusts the position of the shadow mask 14 such that the mask marks 15 are aligned with the substrate marks 13 as shown in
Therefore, corresponding to the thickness of the substrate marks 13 or the thickness of the transparent electrodes 12, the light having a wavelength of the transmittance of 85% or less needs to be irradiated to the transparent substrate 11. When the film thickness of the ITO is 100 nm as shown by the first curved line t1 in
Since the white light source is used as the irradiation light source 16, the emission spectrum of the irradiation light from the irradiation light source 16 is continuous over a large wavelength zone and flat. One appropriate optical filter 17 is selected from a plurality of optical filters 17 each of which has different center wavelength of the transmission wavelength, and the appropriate optical filter 17 is attached to the irradiation light source 16. The appropriate optical filter 17 has an appropriate center wavelength of the transmission wavelength corresponding to the thickness of the transparent electrodes 12. As a result, the irradiation light having an appropriate wavelength is irradiated to the transparent substrate 11 and the substrate marks 13 is recognized.
The transparent substrate 11 is transported in a transfer chamber for laminating the organic EL layer on the transparent substrate 11. The transfer chamber has a plurality of deposition chambers which are connected to each other. In the deposition chambers, each layer comprising the organic EL layer, such as a hole transport layer, a light emitting layer and an electron transport layer, is deposited. A melting pot in which an organic raw material evaporates is provided in each deposition chamber. A transfer robot transports the transparent substrate 11 to the deposition chamber in a state that the transparent electrodes 12 face down. In each deposition chamber, the shadow mask 14 is aligned with the transparent substrate 11 as described above and maintained with a close contact with the transparent substrate 11. The organic raw material which evaporates in each deposition chamber passes through the openings 14a of the shadow mask 14 and is directly deposited on the transparent substrate 11. As a result, each layer comprising the organic EL layer is formed.
The first embodiment has following advantages.
(1) In the step of forming the transparent electrodes 12, the substrate marks 13 are formed at the same time as the transparent electrodes 12 are formed on the transparent substrate 11. The substrate marks 13 are formed of the same material as the transparent electrodes 12. Each of the substrate marks 13 is formed in a predetermined position on the transparent substrate 11. The substrate mark 13 functions as an alignment mark used for adjusting the position of the shadow mask 14 with respect to the transparent substrate 11. Therefore, a dedicated step of forming the substrate marks 13 is not necessary. This reduces the number of steps.
(2) In the step of aligning the shadow mask 14 with the transparent substrate 11, the transparent substrate 11 is arranged above the shadow mask 14. The irradiation light source 16 as the white light source and a plurality of optical filters 17 are prepared. Each of the optical filters 17 has a different center wavelength of a transmission wavelength. One optical filter 17 having a transmission wavelength corresponding to the thickness of the substrate marks 13 is selected from a plurality of optical filters 17. White light is irradiated from the irradiation light source 16 to the substrate marks 13 via the selected optical filter 17. Accordingly, the transparent substrate marks 13 are recognized and the shadow mask 14 is aligned with the transparent substrate 11. The organic EL layer is laminated on the transparent electrodes 12 by deposition via the shadow mask 14.
The substrate marks 13 are formed at the same time as the transparent electrodes 12 are formed in the step of patterning the transparent electrodes 12. The thickness of the substrate marks 13 is the same as that of the transparent electrodes 12. That is, the appropriate wavelength of the irradiation light for allowing the substrate marks 13 to be recognized varies in accordance with thickness of the transparent electrodes 12.
Generally, when the substrate marks 13 formed of a transparent material are irradiated by a general white light source for alignment, it is difficult to visually recognize the substrate marks 13. When the transparent substrate marks 13 are irradiated by a single color light from a LED (light emitting diode) light source, the substrate marks 13 may be hardly visible depending on the film thickness of the substrate marks 13.
However, in the first embodiment, an appropriate optical filter 17 is selected from a plurality of optical filters 17. Light is irradiated to the substrate marks 13 via the selected optical filter. In the first embodiment, a wavelength of light irradiated to the substrate marks 13 during the alignment operation can be changed corresponding to the thickness of the transparent electrodes 12. Therefore, light of a wavelength having low transmittance corresponding to the thickness of the transparent electrodes 12 is irradiated from the irradiation light source 16 to the substrate marks 13 such that the transparent substrate marks 13 are visible. Therefore, in the first embodiment, it is not necessary to adjust the thickness of the substrate marks 13 such that the thickness corresponds to the irradiation light source 16 that is used for aligning the shadow mask 14 with the transparent substrate 11. In other words, it is not necessary to consider the thickness of the transparent electrodes 12.
The visibility of the transparent substrate marks 13 is improved in the first embodiment compared to the following case. For example, the visibility of the substrate marks 13 is improved in the first embodiment compared to a case in which it is required to use a lighting device emitting light of a wavelength close to an appropriate wavelength since an LED emitting light having an appropriate wavelength corresponding to the thickness of the transparent electrodes 12 cannot be prepared.
(3) The shadow mask 14 is aligned with the transparent substrate 11 by making the substrate marks 13 visible by a reflection method. Accordingly, the cost of the alignment device is reduced in the first embodiment compared to a method for making the substrate marks recognizable by a transmission method as shown in
(4) The optical filter 17 is detachably attached to the irradiation light source 16. One optical filter which transmits light having an appropriate wavelength corresponding to the thickness of the transparent electrodes 12 is selected from a plurality of optical filters 17. Therefore, the structure is simple and compact in the first embodiment compared to the following case. For example, a plurality of optical filters each of which has a different transmission wavelength are provided integrally with a filter member with a predetermined distance therebetween. The filter member is moved by a moving device so as to arrange an appropriate optical filter in a light path of irradiation light from the irradiation light source 16. Compared to this structure, the first embodiment has a compact structure.
As shown in
As shown in
A first line L1 and a second line L2 are recognized and an angle α is measured. The first line L1 passes through the center of the first substrate mark 13a and the center of the mask mark 15. The second line L2 passes through the center of the second substrate mark 13b and the center of the mask mark 15. The angle α is formed by the first line L1 and the second line L2.
Further, a deviation X in an X-axis direction and a deviation Y in a Y-axis direction with respect to a desired positional relationship between the mask mark 15 and the second substrate mark 13b are measured respectively.
Alignment accuracy is determined based on the measured angle α, the deviation X, and the deviation Y. When the angle a is a preset value and each of the deviation X and the deviation Y is zero, the shadow mask 14 is positioned with respect to the transparent substrate 11 with high accuracy.
The above embodiments may be modified as follows.
The material of the transparent electrodes 12 is not limited to ITO but may be IZO (indium zinc oxide), ZnO (zinc oxide), SnO2 (stannic oxide) or others. However, the relationship between the film thickness of the transparent electrodes 12 and the transmittance of each wavelength of light varies according to the material. Therefore, by previously checking the relationship between the film thickness of the transparent electrodes 12 and the transmittance of an appropriate wavelength by experiments, an appropriate optical filter 17 can be selected at the time of alignment of the shadow mask 14.
The shape of the substrate mark 13 is not limited to a cross. For example, the substrate mark 13 may be formed in a shape of which the center is easily recognized such as a polygon including a right triangle or a rectangle, a circle, a star or other shapes.
The shape of the substrate mark 13 may be the same as that of the mask mark 15. In this case, the positional relationship between the shadow mask 14 and the transparent substrate 11 can be recognized based on the overlapping degree of the substrate mark 13 and the mask mark 15. The shape of the substrate mark 13 and the mask mark 15 may not be a shape of which the center is easily recognized.
The two substrate marks 13 are not necessarily arranged on a diagonal of the transparent substrate 11. The two substrate marks 13 may be arranged on two positions on one side of the transparent substrate 11 respectively. Each of the two substrate marks 13 may be arranged on any two sides of the transparent substrate 11. The position of the mask marks 15 also may be changed on the shadow mask 14.
The number of the substrate marks 13 and mask marks 15 is not necessarily two but may be one or three or more. If one substrate mark 13 and one mask mark 15 are arranged, the shape of the substrate mark 13 and the mask mark 15 preferably has a right angled portion. This is because the position is easily adjusted by the right angled portion.
A white light emitting organic EL element may be used as a white light source comprising the irradiation light source 16.
The optical filter 17 is not necessarily detachably attached to the irradiation light source 16 by being replaced one by one. The filter member having a plurality of optical filters 17 integrally with each other may be moved by a moving device such that an appropriate optical filter 17 is selected. Specifically, the filter member has a plurality of optical filters 17 having different transmission wavelengths with a predetermined distance therebetween. The moving device moves the filter member such that an appropriate optical filter 17 is arranged on a light path of the irradiation light from the irradiation light source 16.
The half mirror 18 does not need to be arranged between the irradiation light source 16 and the transparent substrate 11. For example, light may be irradiated slantly to the transparent substrate 11 such that light that passes through the transparent substrate 11 and is reflected by the shadow mask 14 advances in a direction deviated from the irradiation light source 16.
The substrate marks 13, the first substrate marks 13a, the second substrate marks 13b, and the mask marks 15 are recognized for adjusting the alignment of the shadow mask 14 with respect to the transparent substrate 11. The marks are not necessarily recognized by the reflection method but may be recognized by a transmission method shown in
As shown in
The shadow mask 14 may be aligned with the transparent substrate 11 by allowing only the substrate marks 13 to be recognized with the transmission method.
An XYZ stage or an XYZθ stage may be used for moving the shadow mask 14 for the alignment adjustment.
Quarts glass, optical glass, Pyrex (registered mark) glass, a silicon substrate, silicon, wafer substrate, a resin substrate, a plastic substrate, a film substrate, and various transparent substrates may be used as the transparent substrate 11.
Number | Date | Country | Kind |
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2007-138208 | May 2007 | JP | national |