JP5921955B2 - Method for producing crucible for vapor deposition - Google Patents

Description

  One embodiment of the present invention relates to a method for manufacturing a crucible for vapor deposition.

  A light-emitting element having a layer containing a light-emitting organic compound (hereinafter also referred to as an EL layer) is called an organic electroluminescence element (organic EL element), and the EL layer is formed using a resistance heating vapor deposition apparatus. Can be formed. Generally, a resistance heating vapor deposition apparatus is an apparatus that heats a solid vapor deposition material contained in a container such as a crucible or a boat by resistance heat, and forms a vapor deposited vapor deposition material on an object to be formed. It is widely used as an apparatus for forming a layer containing a light-emitting organic compound constituting a light-emitting element.

  A crucible which is one container for depositing a vapor deposition material can be manufactured using various materials such as metal, ceramics, graphite, silicon nitride, or boron nitride. There is also a technique for covering the outer wall or inner wall of the crucible with a material different from the material constituting the crucible in order to improve the heat resistance and thermal conductivity of the crucible.

  For example, Prior Art Document 1 discloses a technique for diamond coating on the inner wall of a crucible made of boron nitride. Prior art document 2 discloses a technique for coating glassy carbon on the surface of a long container containing a vapor deposition material.

JP-A-8-225926 JP 2003-293120 A

  Prior art document 1 describes using a CVD method including a plasma CVD (Chemical Vapor Deposition) method as a diamond coating method. Further, Prior Art Document 2 has a description of using a CVD method or an immersion method as a method for coating glassy carbon.

  For example, in the case where an inorganic oxide (such as lithium oxide) is formed using a crucible composed of PBN (thermally decomposable boron nitride), when the temperature of the crucible becomes high (for example, 800 ° C. or higher), the inorganic oxide The PBN constituting the crucible may be decomposed by reacting with oxygen in the material, and the crucible may be damaged. Therefore, it is considered that the breakage can be suppressed by using the technique disclosed in Prior Art Document 1.

  In addition, the film formed by diamond coating or glassy carbon coating has excellent thermal conductivity, and there is a merit that the deposition material can be heated uniformly by covering the crucible with the film. In order to suppress uneven film formation of the material, it is useful to cover the crucible with the film.

  However, in order to perform diamond coating or glassy carbon coating using the CVD method or the immersion method, a device such as a CVD device is required in addition to a device for forming a deposition material, and a source gas or the like is also required. Therefore, it is not easy and the manufacturing cost is high. Furthermore, in the plasma CVD method or the like, the crucible body may be damaged by the plasma.

  In addition, examples of the crucible material include metals such as titanium, tantalum, molybdenum, and tungsten, and ceramics such as aluminum oxide, aluminum nitride, and aluminum oxynitride. However, in a crucible made of metal, a deposition material is formed. At this time, there is a possibility that the metal is mixed as an impurity in the formed film (also referred to as a vapor deposition film), or there is a possibility that the vapor deposition material and the metal react to decompose the vapor deposition material. Therefore, in the case where a light-emitting element (organic EL element) is formed by stacking vapor deposition films, the performance and reliability of the element may be deteriorated due to mixed impurities. In addition, when a crucible made of ceramic is heated to a high temperature, a degassing component such as oxygen is generated from the crucible, and the vapor deposition material is oxidized by the degassing component or mixed into the vapor deposition film. Performance and reliability may be reduced.

  Thus, an object of one embodiment of the present invention is to provide a method for easily manufacturing a crucible coated with a film containing carbon.

  In solving the above problems, a film containing carbon (hereinafter also referred to as a carbon film) covering the inner wall surface of the crucible by using a phenomenon called carbonization in which an organic compound is thermally decomposed in an environment having a low oxygen concentration. Can be formed.

  Thus, one embodiment of the present invention is to heat a vapor deposition crucible under reduced pressure, to react an organic compound on the inner wall surface of the heated vapor deposition crucible, and to generate carbon on the inner wall surface of the vapor deposition crucible by the reaction. Thus, a vapor deposition crucible manufacturing method is characterized in that a film containing carbon is formed on the inner wall surface of the vapor deposition crucible.

  Another embodiment of the present invention includes a step of heating an organic compound by lowering a temperature at which vaporization is performed by reducing a pressure in a treatment chamber of a vacuum apparatus. For example, the temperature at which the organic compound sublimes (also referred to as a sublimation point) can be changed by the pressure applied to the organic compound.

  Organic compounds tend to vaporize at a higher temperature than the temperature at which they thermally decompose (also referred to as decomposition point) as the molecular weight increases. Thermal decomposition of an organic compound is a kind of chemical reaction, and depends largely on the bonding force between elements constituting the organic compound. Therefore, it can be said that the decomposition point of the organic compound does not change even under reduced pressure conditions.

  A carbon film can be formed on the inner wall surface of the crucible by making the inside of the treatment chamber carbonized while the organic compound is sublimated. This can be performed by controlling (reducing pressure) the processing chamber to a pressure at which the temperature at which the organic compound sublimes and the temperature at which the organic compound is thermally decomposed coexist.

  As a vacuum apparatus for forming a carbon film on the inner wall surface of the crucible, it is preferable to use a vapor deposition apparatus for forming a vapor deposition film constituting a desired light emitting element. By using the same apparatus, it is not necessary to provide a separate apparatus only for forming the carbon film, and the carbon film can be easily formed. For example, although depending on the type and molecular weight of the vapor deposition material, it is preferable to use a resistance heating vapor deposition apparatus with a relatively simple apparatus configuration.

  As a method of providing an organic compound in the crucible, a method of simply providing an organic compound at the bottom of the crucible may be used, or an organic compound may be provided by adhering to the entire inner wall surface of the crucible. Furthermore, the organic compound may be provided by wetting the entire inner wall surface of the crucible with a solvent in which the organic compound is dispersed or a solution in which the organic compound is dissolved. The solvent may be removed after the entire inner wall surface of the crucible is wetted. Thus, by providing the organic compound over the entire inner wall surface of the crucible, the entire inner wall surface of the crucible can be uniformly coated with the carbon film.

  When an organic compound is provided at the bottom of the crucible, a carbon film can be uniformly formed on the entire inner wall surface of the crucible by carbonizing the organic compound while sublimating. On the other hand, when the organic compound is generally provided on the inner wall surface of the crucible, the carbon film can be uniformly formed on the inner wall surface without reducing the pressure in the processing chamber as the organic compound is provided at the bottom of the crucible.

  By reducing the pressure in the processing chamber (depressurized state), the effect of suppressing the impurities contained in the crucible and the impurities contained in the organic compound from being mixed into the formed carbon film is also exhibited. In one embodiment of the present invention, pressure control in the processing chamber is preferably performed as appropriate. For example, one embodiment of the present invention can be preferably used for a crucible having an oxygen concentration of 0.1% by weight or more.

  As the organic compound provided in the crucible, various organic compounds can be used as long as they are solid organic compounds at normal temperature and normal pressure or liquid compounds at normal temperature and normal pressure. It is preferably 1500 or less and an organic compound having an aromatic ring is preferably used. For example, an organic compound used for manufacturing a desired light-emitting element can be used. A gaseous organic compound can also be used at normal temperature and pressure. Moreover, in this specification, normal temperature shall be 5 degreeC or more and 35 degrees C or less, and normal pressure shall be 1 atmosphere.

  In the above method, the carbon film is preferably an amorphous film that can be easily formed.

  According to one embodiment of the present invention, a crucible coated with a carbon film can be easily manufactured. Further, with the use of the crucible according to one embodiment of the present invention, impurities can be prevented from being mixed into a deposited film to be formed; thus, a light-emitting element with improved performance and reliability can be manufactured.

Cross-sectional schematic diagram of a crucible. The upper surface schematic diagram of a vapor deposition apparatus. FIG. 6 illustrates a structure of a light-emitting element. FIG. 6 illustrates a structure of a display panel. FIG. 6 illustrates a structure of a display panel. FIG. 6 illustrates a structure of a display panel.

  Embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below. Note that in structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description thereof is not repeated.

  Note that in each drawing described in this specification, the size, the layer thickness, or the region of each component is exaggerated for simplicity in some cases. Therefore, it is not necessarily limited to the scale.

(Embodiment 1)
In this embodiment, an evaporation crucible according to one embodiment of the present invention will be described with reference to drawings. FIG. 1 is a schematic cross-sectional view of a vapor deposition crucible according to one embodiment of the present invention.

  A crucible 100 according to one embodiment of the present invention includes a vapor deposition material container 101 and an upper lid 105 provided with a discharge port 103 through which vaporized vapor deposition material is discharged, and an inner wall surface and an upper lid of the vapor deposition material container 101. A carbon film 107 is provided on the inner wall surface of 105. In this specification, the inner wall surface of the vapor deposition crucible means at least the inner wall surface of the vapor deposition material container 101 and may include the inner wall surface of the upper lid 105. In addition, the crucible 100 may be configured to have not only the upper lid 105 but also an inner lid inside the crucible 100. When the inner lid is provided, the carbon film 107 is also formed on the inner lid.

  The vapor deposition material container 101 and the upper lid 105 are made of a material applicable to a known vapor deposition crucible. Examples thereof include metals such as titanium, tantalum, molybdenum, and tungsten, ceramics such as aluminum oxide, aluminum nitride, and aluminum oxynitride, graphite, silicon nitride, and boron nitride. For example, in this embodiment, it is assumed that the vapor deposition material container 101 and the upper lid 105 are made of pyrolytic boron nitride (PBN).

  Moreover, the vapor deposition material accommodating part 101 and the upper cover 105 can be produced by a known method. For example, it can be produced by molding pyrolytic boron nitride using the mold of the vapor deposition material accommodating portion 101 and the upper lid 105, and the pyrolytic boron nitride is directly grown on the mold of the vapor deposition material accommodating portion 101 and the upper lid 105. It can also be made.

  The carbon film 107 may be an amorphous carbon film or a carbon film having crystallinity. Further, it may be a carbon film having both an amorphous part and a crystalline part. Since the carbon film having crystallinity takes a long time to form, it is more convenient and preferable to use an amorphous carbon film.

  The thickness of the carbon film 107 is preferably about 0.03 μm to 1 μm. When the thickness is less than 0.03 μm, the following effects cannot be obtained sufficiently, and when the thickness is 1 μm or more, the time or cost for forming the carbon film increases, so the above range is preferable.

  In this embodiment, since the carbon film 107 is provided on the inner wall surface of the crucible 100, when an inorganic oxide (such as lithium oxide) is formed using the crucible 100, the inorganic oxide is the inner wall of the crucible 100. Therefore, even if the temperature of the crucible becomes high (for example, 800 ° C. or higher), oxygen in the inorganic oxide does not react with the crucible 100, and the crucible 100 is prevented from being damaged. Can do.

  In addition, the carbon film 107 has excellent thermal conductivity, and the carbon film 107 is provided on the crucible 100, whereby the vapor deposition material can be uniformly heated, and uneven deposition of the vapor deposition material can be suppressed. it can.

  Since the crucible 100 is provided with the carbon film 107, even when the crucible 100 is heated to a high temperature, it is possible to suppress release of degassing components such as oxygen from the vapor deposition material accommodating portion 101 and the upper lid 105. Further, even when the material constituting the vapor deposition material container 101 and the upper lid 105 is a metal, the carbon film 107 is provided, so that when the vapor deposition material is formed, the metal is removed from the vapor deposition material container 101 and the upper lid 105. Can be prevented from being released. Therefore, since a degassing component such as oxygen or a metal is mixed in the vapor deposition film, or decomposition of the vapor deposition material that can easily react with the material constituting the crucible 100 can be suppressed, the crucible 100 is used. A light-emitting element with improved performance and reliability can be manufactured. For example, in a crucible in which the oxygen concentration contained in the vapor deposition material container 101 and the upper lid 105 is 0.1% by weight or more, the inner wall surface of the crucible is covered with the carbon film 107, thereby degassing the vapor deposition film such as oxygen. It can suppress that a component or a metal mixes.

  The carbon film 107 can be formed by thermally decomposing (carbonizing) an organic compound in an environment having a low oxygen concentration. As the organic compound, various organic compounds can be used. For example, an organic compound that is solid at normal temperature and pressure, an organic compound that is liquid at normal temperature and pressure, or an organic compound that is gas at normal temperature and pressure can be used. However, when an organic compound that is a gas at room temperature and normal pressure is used, a control system that controls the organic compound gas is required. Therefore, an organic compound that is solid at room temperature and normal pressure, and an organic compound that is liquid at room temperature and normal pressure Is preferably used.

  Furthermore, in one embodiment of the present invention, an organic compound that is solid at normal temperature and pressure is preferable because it is easier to handle than an organic compound that is liquid at normal temperature and pressure. For example, when an organic compound is provided on the entire inner wall surface of the crucible, even if the entire inner wall surface of the crucible is wetted with a liquid organic compound, it accumulates at the bottom of the crucible, and the organic compound is provided on the entire inner wall surface of the crucible. There are cases where it is not possible. On the other hand, if it is a solid organic compound, the organic compound is removed by wetting the entire inner wall surface of the crucible with a dispersion liquid dispersed in a low boiling point solvent or a solution dissolved in a low boiling point solvent, and then removing the solvent. Only on the entire inner wall surface of the crucible. In addition, since an organic compound having an aromatic ring exists more as a solid at normal temperature and pressure than an aliphatic organic compound, an organic compound having an aromatic ring is used in one embodiment of the present invention. preferable.

  In general, as the molecular weight of an organic compound increases, the vaporization temperature tends to be higher than the decomposition point. Therefore, in one embodiment of the present invention, it is preferable to use an organic compound having a molecular weight of 200 to 1500.

  As a vacuum apparatus for forming the carbon film 107, it is preferable to use a vapor deposition apparatus that forms a vapor deposition film constituting a desired light emitting element. By using a vapor deposition apparatus, it is not necessary to separately provide a vacuum apparatus such as a CVD apparatus just for forming the carbon film 107, and the carbon film 107 can be easily formed. Further, although depending on the type and molecular weight of the vapor deposition material, it is preferable to use a resistance heating vapor deposition apparatus with a relatively simple apparatus configuration.

  The organic compound for forming the carbon film 107 may be provided at the bottom of the crucible to be coated, or may be provided by attaching the organic compound to the entire inner wall surface of the crucible.

  Furthermore, the organic compound may be provided by wetting the entire inner wall surface of the crucible with a solvent in which the organic compound is dispersed or a solution in which the organic compound is dissolved. Examples of the solvent include alcohols such as methanol and ethanol, and aliphatic hydrocarbons such as hexane.

  When an organic compound is provided at the bottom of the crucible, the carbon film 107 can be uniformly formed on the entire inner wall surface of the crucible by carbonizing while sublimating. On the other hand, when the organic compound is generally provided on the inner wall surface of the crucible, the carbon film 107 can be uniformly formed on the inner wall surface without reducing the pressure in the processing chamber as in the case where the organic compound is provided at the bottom of the crucible. .

  Here, the method for manufacturing the crucible according to one embodiment of the present invention includes providing the organic compound in the crucible using any of the methods described above, and the temperature at which the organic compound sublimates in the treatment chamber in the vapor deposition apparatus. Heating is performed by controlling the pressure so that the temperature at which the organic compound thermally decomposes coexists. Since the pressure and the temperature at which the crucible is heated vary depending on the organic compound to be used, it can be selected using a phase diagram or the like.

  For example, when N, N-bis (naphthalen-1-yl) -N, N-bisphenyl-benzidine is used as the organic compound and provided at the bottom of the crucible, the pressure in the processing chamber of the vapor deposition apparatus is set to 100 Pa. The entire inner wall surface of the crucible can be covered with the carbon film 107 by heating under a reduced pressure below and in a temperature range lower than the temperature at which the crucible is damaged by heat from 500 ° C. or higher.

  When heating a crucible provided with an organic compound, the crucible may be heated by gradually (slowly or stepwise) raising the temperature from room temperature to a temperature at which the organic compound carbonizes while sublimating. Thus, the carbon film 107 may be formed. Note that when the temperature is rapidly increased, the organic compound is more easily carbonized than sublimation. Therefore, when the organic compound is provided on the entire inner wall surface of the crucible, the uniform carbon film 107 can be easily formed by rapidly raising the temperature of the crucible. Further, when the temperature is gradually raised, the rate of sublimation is higher than when the temperature is rapidly raised. Therefore, when the organic compound is provided at the bottom of the crucible, the uniform carbon film 107 can be easily formed by gradually raising the temperature of the crucible.

  Next, the crucible manufactured according to one embodiment of the present invention can be applied to a known vapor deposition apparatus as shown in FIG. FIG. 2 is a schematic top view of a vapor deposition apparatus 200 to which the crucible manufactured according to one embodiment of the present invention can be applied. The vapor deposition apparatus 200 includes a load lock chamber 201 that holds a substrate, a transfer chamber 203 in which a transfer mechanism 211 is provided, and a processing chamber 205 for forming a film on the substrate. An openable / closable gate 207 is provided between the load lock chamber 201 and the transfer chamber 203, and the load lock chamber 201 and the transfer chamber 203 are connected by the gate 207. A gate 209 that can be opened and closed is provided between the transfer chamber 203 and the processing chamber 205, and the transfer chamber 203 and the processing chamber 205 are connected by a gate 209.

  The load lock chamber 201 includes an opening / closing door for loading or unloading a substrate, a cassette for holding the substrate, and the like (not shown). Further, the load lock chamber 201 is provided with an exhaust means (P) for depressurizing the interior of the chamber, and a gas supply means (G) for returning the interior of the chamber from the reduced pressure to the atmospheric pressure when the substrate is loaded or unloaded. ) Is provided. Note that when the substrate is inserted or taken out, it is preferable that the interior of the chamber be set to a positive pressure rather than the outside. In this way, it is possible to prevent particles from entering the chamber from the outside.

  The transfer chamber 203 is provided with the transfer mechanism 211 as described above, and further includes an opening / closing door that is used when cleaning the transfer chamber 203 or repairing or maintaining the transfer mechanism 211, although not illustrated. Yes. The transport mechanism 211 can transport the substrate loaded into the load lock chamber 201 to the processing chamber 205 while supporting the end portion of the substrate. Further, the film formation method of the vapor deposition apparatus 200 may be a face-down method or a face-up method. Therefore, it is preferable that the transport mechanism 211 is provided with a rotation mechanism. Further, the transfer chamber 203 is provided with an exhaust means (P) for reducing the pressure inside the chamber, and both the load lock chamber 201 and the transfer chamber 203 can transfer the substrate under reduced pressure. By transporting the substrate in this manner, particles and the like can be prevented from adhering to the substrate during transport, and as a result, the occurrence of defects during film formation can be reduced. Gas supply means (G) for returning the reduced pressure state of the transfer chamber 203 to atmospheric pressure is also provided.

  The processing chamber 205 includes an opening / closing door 213 used when supplying a deposition material and repairing or maintaining the processing chamber 205, an exhaust means (P) for evacuating the processing chamber 205, particularly a vacuum, and a processing chamber Gas supply means (G) for returning the pressure from vacuum to atmospheric pressure, a pedestal (not shown) on which the crucible can be installed through the open / close door 213, and heat treatment means (not shown) for heating the crucible. ) And at least. In addition, a deposition preventing plate 215 may be provided to prevent the film forming material from adhering to the inner wall of the processing chamber 205.

  An example of a method for forming a deposited film using the method for manufacturing a crucible according to one embodiment of the present invention is described below.

  First, an organic compound is provided in the crucible, the crucible is installed on a pedestal provided in the processing chamber 205 through the open / close door 213, the processing chamber 205 is controlled under reduced pressure by the exhaust processing means (P), and the heat processing means. By heating the crucible, the organic compound can be carbonized while being sublimated to form the carbon film 107. In addition, the above can be referred to for the decompression conditions or the temperature at which the crucible is heated.

  After that, the crucible 100 is taken out through the opening / closing door 213, the vapor deposition material of the vapor deposition film constituting the desired light emitting element is provided in the crucible 100, and again placed on the pedestal in the processing chamber 205. Next, after the substrate previously set in the load lock chamber 201 is transferred to the processing chamber 205 by the transfer mechanism 211, the processing chamber 205 is controlled under reduced pressure, and the crucible 100 is heated by the heat processing means to form the substrate. A vapor deposition film can be formed. By vapor-depositing in this manner, a vapor deposition film in which the materials constituting the vapor deposition material accommodating portion 101 and the upper lid 105 and the impurities that are degassing components such as oxygen are suppressed can be produced.

  From the above, a crucible coated with a carbon film can be easily produced. In addition, by using the crucible manufactured according to one embodiment of the present invention, impurities contained in the crucible can be prevented from being mixed into a deposited film to be formed, and a light-emitting element with improved performance and reliability can be manufactured. .

(Embodiment 2)
In this embodiment, an example of a structure of a light-emitting element that can be manufactured by vapor deposition using a crucible manufactured according to one embodiment of the present invention will be described with reference to FIGS.

  For example, when the crucible and the evaporation apparatus described in Embodiment 1 are used, a light-emitting element described below as an example can be manufactured.

  The light-emitting element exemplified in this embodiment includes a layer containing at least a light-emitting organic compound (EL layer) between the first electrode and the second electrode. Either the first electrode or the second electrode functions as an anode, and the other functions as a cathode. The EL layer is provided between the first electrode and the second electrode, and the structure of the EL layer may be selected as appropriate in accordance with the materials of the first electrode and the second electrode. Although an example of a structure of a light emitting element is illustrated below, the structure of a light emitting element is not limited to these.

<Structure Example 1 of Light Emitting Element>
An example of a structure of the light-emitting element is illustrated in FIG. In the light-emitting element illustrated in FIG. 3A, an EL layer is sandwiched between an anode 301 and a cathode 302.

  When a voltage higher than the threshold voltage of the light-emitting element is applied between the anode 301 and the cathode 302, holes are injected from the anode 301 side and electrons are injected from the cathode 302 side into the EL layer. The injected electrons and holes are recombined in the EL layer, and the light-emitting substance contained in the EL layer emits light.

  In this specification, a layer or a stack including one region where electrons and holes injected from both ends are recombined is referred to as a light-emitting unit. Therefore, it can be said that Structural Example 1 of the light-emitting element includes one light-emitting unit.

  The light-emitting unit 303 only needs to include one or more light-emitting layers containing at least a light-emitting substance, and may have a structure in which layers other than the light-emitting layer are stacked. Examples of the layer other than the light emitting layer include, for example, a material having a high hole-injecting property, a material having a high hole-transporting property, a material having a poor hole-transporting property (blocking), a material having a high electron-transporting property, and a material having a high electron-injecting property And a layer containing a substance having a bipolar property (a high electron and hole transport property) and the like.

  An example of a specific structure of the light-emitting unit 303 is illustrated in FIG. In the light-emitting unit 303 illustrated in FIG. 3B, a hole injection layer 313, a hole transport layer 314, a light-emitting layer 315, an electron transport layer 316, and an electron injection layer 317 are stacked in this order from the anode 301 side.

<Configuration Example 2 of Light-Emitting Element>
FIG. 3C illustrates another example of the structure of the light-emitting element. In the light-emitting element illustrated in FIG. 3C, an EL layer including a light-emitting unit 303 is sandwiched between an anode 301 and a cathode 302. Further, an intermediate layer 304 is provided between the cathode 302 and the light emitting unit 303. The light emitting unit 303 of the light emitting element configuration example 2 can be applied with the same configuration as that of the light emitting unit included in the light emitting element configuration example 1 described above. Can be considered.

  The intermediate layer 304 only needs to be formed to include at least the charge generation region, and may have a structure in which layers other than the charge generation region are stacked. For example, a structure in which the first charge generation region 304c, the electron relay layer 304b, and the electron injection buffer 304a are sequentially stacked from the cathode 302 side can be used.

  The behavior of electrons and holes in the intermediate layer 304 will be described. When a voltage higher than the threshold voltage of the light-emitting element is applied between the anode 301 and the cathode 302, holes and electrons are generated in the first charge generation region 304c, and the holes move to the cathode 302, and electrons Moves to the electronic relay layer 304b. The electron relay layer 304b has a high electron transporting property, and quickly transfers the electrons generated in the first charge generation region 304c to the electron injection buffer 304a. The electron injection buffer 304 a relaxes the barrier for injecting electrons into the light emitting unit 303 and increases the efficiency of electron injection into the light emitting unit 303. Accordingly, electrons generated in the first charge generation region 304c are injected into the LUMO level of the light emitting unit 303 through the electron relay layer 304b and the electron injection buffer 304a.

  In addition, the electron relay layer 304b prevents an interaction such as a substance constituting the first charge generation region 304c and a substance constituting the electron injection buffer 304a from reacting at the interface, and the mutual functions being impaired. it can.

  The material that can be used for the cathode of Structural Example 2 of the light-emitting element only needs to receive holes generated by the intermediate layer, and a material with a relatively large work function can be used. Therefore, the selection range of the material that can be used for the cathode of the configuration example 2 of the light-emitting element is wider than the selection range of the material that can be used for the cathode of the configuration example 1.

<Configuration Example 3 of Light-Emitting Element>
FIG. 3D illustrates another example of the structure of the light-emitting element. A light-emitting element illustrated in FIG. 3D includes an EL layer in which two light-emitting units are provided between an anode 301 and a cathode 302. Further, an intermediate layer 304 is provided between the first light emitting unit 303a and the second light emitting unit 303b.

  Note that the number of light emitting units provided between the anode and the cathode is not limited to two. A light-emitting element illustrated in FIG. 3E has a structure in which a plurality of light-emitting units 303 are stacked, that is, a so-called tandem light-emitting element. However, in the case where, for example, an n (n is a natural number of 2 or more) layer light emitting unit 303 is provided between the anode 301 and the cathode 302, the m (m is a natural number of 1 or more and (n-1) or less) light emission. An intermediate layer 304 is provided between each unit and the (m + 1) th light emitting unit.

  The light emitting unit 303 of the light emitting element configuration example 3 can be applied to the same structure as that of the light emitting element configuration example 1 described above, and the intermediate layer 304 of the light emitting element configuration example 3 can be applied. The same configuration as that of Configuration Example 2 of the light-emitting element described above can be applied. Therefore, for details, the description of Structure Example 1 of the light-emitting element or Structure Example 2 of the light-emitting element can be referred to.

  The behavior of electrons and holes in the intermediate layer 304 provided between the light emitting units will be described. When a voltage higher than the threshold voltage of the light emitting element is applied between the anode 301 and the cathode 302, holes and electrons are generated in the intermediate layer 304, and the holes move to the light emitting unit 303b provided on the cathode 302 side. Then, the electrons move to the light emitting unit 303a provided on the anode side. The holes injected into the light emitting unit 303b provided on the cathode side recombine with the electrons injected from the cathode side, and the light emitting substance contained in the light emitting unit 303b emits light. In addition, electrons injected into the light emitting unit 303a provided on the anode side recombine with holes injected from the anode side, and a light emitting substance contained in the light emitting unit 303a emits light. Therefore, holes and electrons generated in the intermediate layer 304 are emitted in different light emitting units.

  In addition, when the same structure as an intermediate | middle layer is formed between both by providing light emitting units in contact, light emitting units can be provided in contact. Specifically, when a charge generation region is formed on one surface of the light emitting unit, the charge generation region functions as the first charge generation region of the intermediate layer. it can.

  Structure Examples 1 to 3 of the light-emitting element can be used in combination with each other. For example, an intermediate layer may be provided between the cathode 302 and the light emitting unit 303b in the configuration example 3 of the light emitting element.

  In addition, by using a plurality of light-emitting substances having different emission colors, the emission spectrum can be widened to obtain, for example, white light emission. In order to obtain white light emission, for example, a configuration including at least two EL layers may be used, and each layer may be configured to emit light exhibiting a complementary color. Specific complementary color relationships include, for example, blue and yellow or blue green and red.

  Furthermore, when obtaining white light emission with good color rendering properties, it is preferable that the emission spectrum extends over the entire visible light region, for example, a single light emitting element emits blue light, a green light layer, What is necessary is just to set it as the structure provided with the layer which emits the light which exhibits red.

  Note that this embodiment can be combined with any of the other embodiments described in this specification as appropriate.

(Embodiment 3)
In this embodiment, an example of a structure of a display panel to which a light-emitting element that can be manufactured by vapor deposition using a crucible manufactured according to one embodiment of the present invention will be described.

<Configuration of display panel>
The structure of the display panel exemplified in this embodiment is illustrated in FIG. 4A is a top view of the structure of the display panel exemplified in this embodiment, and FIG. 4B is a cross-sectional view taken along cutting lines AB and CD in FIG. FIG. 4C is a cross-sectional view taken along a cutting line EF in FIG.

  A display panel 400 described as an example in this embodiment includes a display portion 401 over a first substrate 410, and a plurality of pixels 402 are provided there. In addition, a plurality of (for example, three) sub-pixels are provided in the pixel 402 (see FIG. 4A). A source side driver circuit portion 403 s and a gate side driver circuit portion 403 g for driving the display portion 401 are provided together with the display portion 401 on the first substrate 410. Note that the driver circuit portion can be formed not on the first substrate 410 but outside.

  The display panel 400 includes an external input terminal and receives a video signal, a clock signal, a start signal, a reset signal, and the like via an FPC (flexible printed circuit) 409. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The display panel in this specification includes not only the display panel body but also a state in which an FPC or PWB is attached thereto.

  The sealant 405 is formed by bonding the first substrate 410 and the second substrate 440, and the display portion 401 is sealed in a space 431 formed therebetween (see FIG. 4B).

  A structure including a cross section of the display panel 400 will be described with reference to FIG. The display panel 400 includes a source-side driver circuit portion 403 s, a sub-pixel 402 G included in the pixel 402, and a lead wiring 408. Note that the display portion 401 of the display panel 400 exemplified in this embodiment emits light in a direction of an arrow illustrated in the drawing to display an image.

  The source side driver circuit portion 403s includes a CMOS circuit in which an n-channel transistor 413 and a p-channel transistor 414 are combined. Note that the driving circuit is not limited to this configuration, and may be configured by various CMOS circuits, PMOS circuits, or NMOS circuits.

  The lead wiring 408 transmits a signal input from the external input terminal to the source side driver circuit portion 403s and the gate side driver circuit portion 403g.

  The sub-pixel 402G includes a switching transistor 411, a current control transistor 412 and a light emitting module 450G. Note that an insulating layer 416 and a partition 418 are formed over the transistor 411 and the like. The light emitting module 450G includes a reflective film, a semi-transmissive / semi-reflective film, and a light-emitting element 420G between the reflective film and the semi-transmissive / semi-reflective film, and the side of the semi-reflective film that emits light emitted from the light-emitting element 420G. Is provided with a color filter 441G. In the light-emitting module 450G illustrated in this embodiment, the first electrode 421G of the light-emitting element 420G serves as a reflective film, and the second electrode 422 serves as a semi-transmissive / semi-reflective film. Note that the direction in which the display unit 401 displays an image is determined by the direction in which light emitted from the light emitting element 420G is extracted. Note that the light-emitting element 420G of the display panel 400 illustrated in FIGS. 4B and 4C can be a top-emission (also referred to as top emission) light-emitting element.

  In addition, a light shielding film 442 is formed so as to surround the color filter 441G. The light shielding film 442 is a film that prevents the display panel 400 from reflecting external light, and has an effect of increasing the contrast of an image displayed on the display unit 401. Note that the color filter 441G and the light-shielding film 442 are formed over the second substrate 440.

  The insulating layer 416 is an insulating layer for flattening a step generated due to the structure of the transistor 411 or the like, or suppressing diffusion of impurities into the transistor 411 or the like, and is a single layer. Alternatively, a laminate of a plurality of layers may be used. The partition 418 is an insulating layer having an opening, and the light-emitting element 420G is formed in the opening of the partition 418.

  The light-emitting element 420G includes a first electrode 421G, a second electrode 422, and a layer 423 containing a light-emitting organic compound.

<Pixel configuration>
A structure of the pixel 402 provided in the display portion 401 is described with reference to FIG.

  A pixel 402 exemplified in this embodiment includes a sub-pixel 402G. The sub-pixel 402G includes a first electrode 421G that also functions as a reflective film, a second electrode 422 that also functions as a semi-transmissive / semi-reflective film, and a light-emitting organic compound. A light-emitting element 420G including a layer 423a including a layer 423b, a layer 423b including a light-emitting organic compound, and an intermediate layer 424. In addition, a color filter 441G is provided on the second electrode 422 side so as to overlap with the light-emitting element 420G.

  The pixel 402 includes a sub-pixel 402B that emits light B that exhibits blue, a sub-pixel 402G that emits light G that exhibits green, and a sub-pixel 402R that emits light R that exhibits red. Each subpixel includes a driving transistor and a light emitting module. Each of the light emitting modules includes a reflective film, a semi-transmissive / semi-reflective film, and a light-emitting element between the reflective film and the semi-transmissive / semi-reflective film.

  If a microresonator is configured by overlapping a reflective film and a semi-transmissive / semi-reflective film and a light emitting element is provided between them, light of a specific wavelength can be efficiently extracted from the semi-transmissive / semi-reflective film. Specifically, if the optical distance of the microresonator is set so that it is n / 2 times the wavelength of the light to be extracted (n is a natural number), the light extraction efficiency can be increased. The wavelength of the extracted light depends on the distance between the reflective film and the semi-transmissive / semi-reflective film, and the distance can be adjusted by forming an optical adjustment layer therebetween.

  As a material that can be used for the optical adjustment layer, a layer containing a light-emitting organic compound can be used in addition to a conductive film that transmits visible light. For example, the thickness may be adjusted using a charge generation region. Alternatively, it is preferable to use a region including a substance having a high hole-transport property and an acceptor substance for the optical adjustment layer because an increase in driving voltage can be suppressed even when the optical adjustment layer is thick.

  As a structure of the light-emitting element, a layer 423a containing a light-emitting organic compound and a light-emitting organic compound are provided between the first electrode 421G that also functions as a reflective film and the second electrode 422 that also functions as a semi-transmissive / semi-reflective film. A light-emitting element 420G including the layer 423b including the intermediate layer 424 is provided.

  Note that the structure described in Embodiment 2 can be applied to a structure example of the light-emitting element.

  In the light-emitting module exemplified in this embodiment, the second electrode 422 of the light-emitting element provided in each light-emitting module serves as a semi-transmissive and semi-reflective film. Specifically, the second electrode 422 provided in common to the light emitting element 420B, the light emitting element 420G, and the light emitting element 420R serves as a transflective / semireflective film of the light emitting module 450B, the light emitting module 450G, and the light emitting module 450R. I also serve.

  In addition, the first electrode of the light emitting element provided electrically independently in each light emitting module also serves as a reflective film. Specifically, the first electrode 421B provided on the light emitting element 420B is a reflective film of the light emitting module 450B, the first electrode 421G provided on the light emitting element 420G is a reflective film of the light emitting module 450G, and the light emitting element 420R. The first electrode 421 </ b> R provided in the light-emitting device also serves as a reflective film of the light emitting module 450 </ b> R.

  The first electrode also serving as a reflective film of the light emitting module has a configuration in which an optical adjustment layer is laminated on the reflective film. The optical adjustment layer is formed of a conductive film having a property of transmitting visible light, and the reflective film is preferably a metal film having high reflectivity for visible light and having conductivity.

  The thickness of the optical adjustment layer is adjusted according to the wavelength length of light extracted from the light emitting module.

  For example, the first light emitting module 450B serves as a color filter 441B that transmits blue light and a reflective film whose optical distance is adjusted to i / 2 times (i is a natural number) that is 400 nm or more and less than 500 nm. The electrode 421 </ b> B and the second electrode 422 serving as a semi-transmissive / semi-reflective film are provided.

  In addition, the second light emitting module 450G includes a color filter that transmits green light, a reflective film whose optical distance is adjusted to j / 2 times (j is a natural number) of 500 nm or more and less than 600 nm, and semi-transmission / semi-reflection. It is set as the structure provided with a film | membrane.

  In addition, the third light emitting module 450R includes a color filter that transmits red light, a reflective film whose optical distance is adjusted to k / 2 times (k is a natural number) of 600 nm or more and less than 800 nm, and semi-transmission / semi-reflection. It is set as the structure provided with a film | membrane.

  In the light emitting module having such a configuration, light emitted from the light emitting element interferes between the reflective film and the semi-transmissive / semi-reflective film, and specific light among light having a wavelength of 400 nm or more and less than 800 nm is strengthened, Color filters absorb unwanted light.

  Note that each of the first light-emitting module 450B, the second light-emitting module 450G, and the third light-emitting module 450R includes a layer 423a containing a light-emitting organic compound, a layer 423b containing a light-emitting organic compound, and an intermediate layer 424. Including. One of the pair of electrodes of the light emitting element also serves as a reflective film, and the other serves as a semi-transmissive / semi-reflective film.

  The light emitting module having such a structure can be formed in the same process as the layer containing a light emitting organic compound. Alternatively, the pair of electrodes serves as the reflective film and the semi-transmissive / semi-reflective film.

<Partition structure>
A partition 418 is formed so as to cover end portions of the first electrode 421B, the first electrode 421G, and the first electrode 421R.

  A curved surface having a curvature is formed at the lower end of the partition wall 418. As a material of the partition wall 418, a positive type or a negative type photosensitive resin can be used.

  Note that application of a material that absorbs visible light to the partition wall has an effect of suppressing a phenomenon in which light leaks from one of the adjacent light-emitting elements to the other (also referred to as a crosstalk phenomenon).

  In addition, in a configuration in which a semi-transmissive / semi-reflective film is provided on the first substrate 410 side and light emitted from the light emitting module is extracted to the first substrate 410 side to display an image, the partition wall absorbs visible light. When the material is applied, the partition can absorb external light reflected by the reflective film provided on the first substrate 410 and suppress the reflection.

<Sealing structure>
A display panel 400 exemplified in this embodiment includes a structure in which a light-emitting element is sealed in a space 431 surrounded by a first substrate 410, a second substrate 440, and a sealant 405.

  The space 431 may be filled with resin in addition to filling with an inert gas (such as nitrogen or argon). Further, an adsorbent (for example, a desiccant) of impurities (typically, one or both of water and oxygen) may be provided.

  The sealant 405 and the second substrate 440 are preferably made of a material that does not transmit impurities (typically water and / or oxygen) in the atmosphere as much as possible. As the sealant 405, an epoxy resin, glass frit, or the like can be used.

  Examples of materials that can be used for the second substrate 440 include glass substrates, quartz substrates, plastic substrates made of PVF (polyvinyl fluoride), polyester, acrylic, and the like, FRP (Fiberglass-Reinforced Plastics), and the like. Can be listed.

<Modification>
A modification of the present embodiment is shown in FIG. 5A is a cross-sectional view taken along cutting lines AB and CD in FIG. 4A, and FIG. 5B is a cross-sectional view taken along cutting line EF in FIG.

  The display panel illustrated in FIG. 5 is a modification of the display panel illustrated in FIG. 4, and has a pixel configuration different from that of the display panel illustrated in FIG. 5. Specifically, the difference is that no color filter is provided, and that subpixels having different emission colors are provided with layers containing different luminescent organic compounds. A modification example of the structure of the pixel 402 provided in the display portion 401 is described with reference to FIG.

  The pixel 402 exemplified in the modification of this embodiment includes a sub-pixel 402B that emits light B that exhibits blue, a sub-pixel 402G that emits light G that exhibits green, and a sub-pixel 402R that emits light R that exhibits red. Have. Each subpixel includes a driving transistor and a light emitting module. Each of the light emitting modules includes a reflective film, a semi-transmissive / semi-reflective film, and a light-emitting element between the reflective film and the semi-transmissive / semi-reflective film.

  The sub-pixel 402B includes a first electrode 421B also serving as a reflective film, a second electrode 422 also serving as a semi-transmissive / semi-reflective film, a layer 423B including a light-emitting organic compound that emits light including blue light, And the optical distance of the microresonator is adjusted so as to emit blue light with a half-width of the spectrum of 60 nm or less.

  The sub-pixel 402G includes a first electrode 421G also serving as a reflective film, a second electrode 422 also serving as a semi-transmissive / semi-reflective film, a layer 423G including a light-emitting organic compound that emits light including green light, And the optical distance of the microresonator is adjusted so as to emit green light having a half-width of the spectrum of 60 nm or less.

  The sub-pixel 402R includes a first electrode 421R that also serves as a reflective film, a second electrode 422 that also serves as a semi-transmissive / semi-reflective film, a layer 423R that includes a light-emitting organic compound that emits light including red light, and And the optical distance of the microresonator is adjusted so as to emit green light having a half-width of the spectrum of 60 nm or less.

  Note that the structure described in Embodiment 2 can be applied to a material that can be used for each layer containing a light-emitting organic compound.

  Note that this embodiment can be combined with any of the other embodiments described in this specification as appropriate.

(Embodiment 4)
In this embodiment, an example of a structure of a display panel to which a light-emitting element that can be manufactured by vapor deposition using a crucible manufactured according to one embodiment of the present invention will be described.

  6A and 6B are cross-sectional views taken along section lines AB and CD in FIG. 4A.

  The display panel illustrated in FIG. 6A or FIG. 6B has the same top surface structure as that of the display panel illustrated in Embodiment 3, but has a cross-sectional structure illustrated in Embodiment 3. Different from that of the display panel. Note that the same reference numerals are applied to portions having the same configurations as those described in Embodiment 3, and the description of Embodiment 3 is incorporated.

<Configuration Example 1 of Display Panel>
In the display panel illustrated in FIG. 6A, a display portion including the sub-pixel 402G and a driver circuit portion 403s on the source side are provided over the first substrate 410. The sub-pixel 402G is provided with a transistor 471, and the source-side driver circuit portion 403s is provided with a transistor 472, both of which are bottom-gate transistors.

  Note that a second gate electrode (also referred to as a back gate) may be provided over the semiconductor in a region where a channel of the transistor is formed. The characteristics (eg, threshold voltage) of the transistor provided with the second gate electrode can be controlled by a potential applied to the second gate electrode.

  In addition, a pair of spacers 445 is provided over the partition wall 418, and the distance between the first substrate 410 and the second substrate 440 is controlled. A pattern (also referred to as a Newton ring) derived from an optical interference phenomenon that occurs between the first substrate 410 and the second substrate 440 is observed, and a defect in which the appearance is impaired can be prevented. Further, the optical crosstalk phenomenon can be suppressed by providing light leakage from adjacent subpixels.

  An example of a semiconductor that can be favorably used for a region where a channel of a transistor described as an example in this embodiment is formed is described below.

<Configuration Example 2 of Display Panel>
A bottom-gate transistor is applied to the display panel illustrated in FIG. In addition, the light-emitting module provided in the pixel of the display portion is configured to emit light toward the first substrate 410 side.

  Specifically, the first electrode 421G of the light emitting element 420G included in the light emitting module 450G serves as a semi-transmissive / semi-reflective film, and the second electrode 422 serves as a reflective film. As a result, light emitted from the light-emitting element 420G is extracted from the first substrate 410 through the color filter 428G provided between the first electrode 421G and the first substrate 410. In other words, the light-emitting element 420G of the light-emitting module 450G can be a bottom emission (also referred to as bottom emission) light-emitting element.

  The color filter 428G is formed over the first substrate 410 over which the transistor 481 is provided. Note that the light shielding film 442 is formed so as to surround the color filter 428G.

(Embodiment 5)
In this embodiment, a transistor applied to the display panel described in Embodiments 3 and 4 will be described.

  In the display panel 400, transistors with various structures can be used for the driver circuit portion 403s on the source side, the driver circuit portion 403g on the gate side, and the subpixel.

  A top gate transistor is applied to the display panel 400 illustrated in FIGS. 4B and 4C and FIGS. 5A and 5B. In addition, a bottom-gate transistor is applied to the display panel 400 illustrated in FIGS. 6A and 6B.

  In addition, various semiconductors can be used for a region (semiconductor layer) where a channel of these transistors is formed. Specifically, an amorphous semiconductor, polysilicon, single crystal silicon, an oxide semiconductor, or the like can be used.

  For example, by using an oxide semiconductor for a semiconductor layer of a transistor included in the display panel 400, the following advantages can be obtained. An oxide semiconductor has a large energy gap of 3.0 eV or more, a transistor to which an oxide semiconductor layer obtained by processing the oxide semiconductor under appropriate conditions and sufficiently reducing the carrier density is applied. Since the leakage current (off-state current) between the source and drain in the off state can be made extremely lower than that of a conventional transistor using silicon, power consumption of the display panel 400 can be reduced. .

  An applicable oxide semiconductor preferably contains at least indium (In) or zinc (Zn). In particular, In and Zn are preferably included. In addition, it is preferable that gallium (Ga) be included in addition to the stabilizer for reducing variation in electrical characteristics of the transistor including the oxide semiconductor. Moreover, it is preferable to have tin (Sn) as a stabilizer. Further, the stabilizer is selected from hafnium (Hf), zirconium (Zr), titanium (Ti), scandium (Sc), yttrium (Y), lanthanoid (eg, cerium (Ce), neodymium (Nd), gadolinium (Gd)). It is preferable that one kind or a plurality of kinds are included.

  For example, as an oxide semiconductor, indium oxide, tin oxide, zinc oxide, binary metal oxides such as In—Zn oxide, Sn—Zn oxide, Al—Zn oxide, Zn—Mg oxide Oxides, Sn—Mg oxides, In—Mg oxides, In—Ga oxides, In—Ga—Zn oxides (also referred to as IGZO) which are oxides of ternary metals, In— Al-Zn oxide, In-Sn-Zn oxide, Sn-Ga-Zn oxide, Al-Ga-Zn oxide, Sn-Al-Zn oxide, In-Hf-Zn oxide In-Zr-Zn-based oxide, In-Ti-Zn-based oxide, In-Sc-Zn-based oxide, In-Y-Zn-based oxide, In-La-Zn-based oxide, In-Ce -Zn-based oxide, In-Pr-Zn-based oxide, In-Nd-Zn-based oxide, I -Sm-Zn oxide, In-Eu-Zn oxide, In-Gd-Zn oxide, In-Tb-Zn oxide, In-Dy-Zn oxide, In-Ho-Zn oxide Oxides, In-Er-Zn-based oxides, In-Tm-Zn-based oxides, In-Yb-Zn-based oxides, In-Lu-Zn-based oxides, and quaternary metal oxides In- Sn-Ga-Zn-based oxide, In-Hf-Ga-Zn-based oxide, In-Al-Ga-Zn-based oxide, In-Sn-Al-Zn-based oxide, In-Sn-Hf-Zn-based An oxide or an In—Hf—Al—Zn-based oxide can be used.

  Here, the In—Ga—Zn-based oxide means an oxide containing In, Ga, and Zn as main components, and there is no limitation on the ratio of In, Ga, and Zn. Moreover, metal elements other than In, Ga, and Zn may be contained.

Alternatively, a material represented by InMO ₃ (ZnO) _m (m> 0 is satisfied, and m is not an integer) may be used as the oxide semiconductor. Note that M represents one metal element or a plurality of metal elements selected from Ga, Fe, Mn, and Co, or the above-described element as a stabilizer. Alternatively, a material represented by In ₂ SnO ₅ (ZnO) _n (n> 0 is satisfied, and n is an integer) may be used as the oxide semiconductor.

  For example, In: Ga: Zn = 1: 1: 1, In: Ga: Zn = 3: 1: 2, or In: Ga: Zn = 2: 1: 3 atomic ratio In: Ga: Zn-based oxidation An oxide in the vicinity of the product or its composition may be used.

  The oxide semiconductor layer may be single crystal or non-single crystal. In the latter case, it may be amorphous or polycrystalline. Moreover, the structure which contains the part which has crystallinity in an amorphous may be sufficient, and a non-amorphous may be sufficient.

  Preferably, the oxide semiconductor film is a CAAC-OS (C Axis Crystallized Oxide Semiconductor) film.

  Hereinafter, the CAAC-OS film is described.

  The CAAC-OS film is not completely single crystal nor completely amorphous. The CAAC-OS film is an oxide semiconductor film with a crystal-amorphous mixed phase structure where crystal parts are included in an amorphous phase. Note that the crystal part is often large enough to fit in a cube whose one side is less than 100 nm. Further, in the observation image obtained by a transmission electron microscope (TEM), the boundary between the amorphous part and the crystal part included in the CAAC-OS film is not clear. Further, a grain boundary (also referred to as a grain boundary) cannot be confirmed in the CAAC-OS film by TEM. Therefore, in the CAAC-OS film, reduction in electron mobility due to grain boundaries is suppressed.

  The crystal part included in the CAAC-OS film is triangular when viewed from the direction perpendicular to the ab plane and the c-axis is aligned in a direction parallel to the normal vector of the formation surface of the CAAC-OS film or the normal vector of the surface. It has a shape or hexagonal atomic arrangement, and metal atoms are arranged in layers or metal atoms and oxygen atoms are arranged in layers as viewed from the direction perpendicular to the c-axis. Note that the directions of the a-axis and the b-axis may be different between different crystal parts. In this specification, a simple term “perpendicular” includes a range from 85 ° to 95 °. In addition, a simple term “parallel” includes a range from −5 ° to 5 °.

  Note that the distribution of crystal parts in the CAAC-OS film is not necessarily uniform. For example, in the formation process of the CAAC-OS film, when crystal growth is performed from the surface side of the oxide semiconductor film, the ratio of crystal parts in the vicinity of the surface of the oxide semiconductor film is higher in the vicinity of the surface. In addition, when an impurity is added to the CAAC-OS film, the crystal part in a region to which the impurity is added becomes amorphous in some cases.

  Since the c-axis of the crystal part included in the CAAC-OS film is aligned in a direction parallel to the normal vector of the formation surface of the CAAC-OS film or the normal vector of the surface, the shape of the CAAC-OS film (formation surface) Depending on the cross-sectional shape or the cross-sectional shape of the surface). Note that the c-axis direction of the crystal part is parallel to the normal vector of the surface where the CAAC-OS film is formed or the normal vector of the surface. The crystal part is formed by film formation or by performing crystallization treatment such as heat treatment after film formation.

  In the case where a CAAC-OS film is used as the oxide semiconductor film, there are three methods for forming the CAAC-OS film.

  First, the oxide semiconductor film is formed at a deposition temperature of 200 ° C. to 450 ° C. so that the c-axis of the crystal part included in the oxide semiconductor film is a normal vector of the surface to be formed or the surface This is a method for forming crystal parts aligned in a direction parallel to the normal vector.

  Second, after the oxide semiconductor film is formed with a small thickness, heat treatment is performed at 200 ° C. to 700 ° C. so that the c-axis of the crystal part included in the oxide semiconductor film is a method of forming a surface. This is a method of forming crystal parts aligned in a direction parallel to a line vector or a surface normal vector.

  Third, after forming a thin oxide semiconductor film of the first layer, heat treatment at 200 ° C. to 700 ° C. is performed, and further, a second oxide semiconductor film is formed. In which the c-axis of the crystal part is aligned in a direction parallel to the normal vector of the surface to be formed or the normal vector of the surface.

  A transistor including a CAAC-OS film can reduce variation in electrical characteristics due to irradiation with visible light or ultraviolet light. Therefore, the transistor has high reliability.

  The above is the description of the CAAC-OS film.

  After the oxide semiconductor film is formed, dehydration treatment (dehydrogenation treatment) is performed to remove hydrogen or moisture from the oxide semiconductor film so that impurities are contained as little as possible, and dehydration treatment ( It is preferable to add oxygen that has been simultaneously reduced by dehydrogenation treatment to the oxide semiconductor, or supply excess oxygen to fill oxygen vacancies in the oxide semiconductor film. In this specification and the like, the case where oxygen is supplied to the oxide semiconductor film may be referred to as oxygenation treatment or peroxygenation treatment.

In this manner, the oxide semiconductor film is made i-type (intrinsic) or i-type by removing hydrogen or moisture by dehydration treatment (dehydrogenation treatment) and filling oxygen vacancies by oxygenation treatment. The oxide semiconductor film can be almost as close as possible. In such an oxide semiconductor film, the number of carriers derived from donors is extremely small (near zero), and the carrier concentration is less than 1 × 10 ¹⁴ / cm ³ , preferably less than 1 × 10 ¹² / cm ³ , and more preferably Is less than 1 × 10 ¹¹ / cm ³ , more preferably less than 1.45 × 10 ¹⁰ / cm ³ .

In this manner, a transistor including an oxide semiconductor layer in which the hydrogen concentration is sufficiently reduced to be highly purified and the defect level in the energy gap due to oxygen deficiency is reduced by supplying sufficient oxygen is extremely high. Excellent off-current characteristics can be realized. For example, the off current at room temperature (25 ° C.) (here, the value per unit channel width (1 μm)) is 100 zA / μm (1 zA (zeptoampere) is 1 × 10 ⁻²¹ A) or less, preferably 10 zA / Μm or less. Further, at 85 ° C., it is 100 zA / μm (1 × 10 ⁻¹⁹ A / μm) or less, preferably 10 zA / μm (1 × 10 ⁻²⁰ A / μm) or less. In this manner, a transistor having extremely excellent off-state current characteristics can be obtained by using an i-type (intrinsic) or substantially i-type oxide semiconductor layer.

  Further, when a single crystal semiconductor is used for a channel formation region in a region (semiconductor layer) where a channel of a transistor included in the display panel 400 is formed, the transistor size can be reduced; Can be further refined.

  As the single crystal semiconductor constituting the semiconductor layer, typically, a single crystal semiconductor substrate made of a group 14 element, such as a single crystal silicon substrate, a single crystal germanium substrate, or a single crystal silicon germanium substrate, a compound semiconductor substrate (SiC substrate) A semiconductor substrate such as a GaN substrate can be used. Preferably, an SOI (Silicon On Insulator) substrate having a single crystal semiconductor layer over an insulating surface can be used.

  As a method for manufacturing an SOI substrate, oxygen ions are implanted into a mirror-polished wafer and then heated at a high temperature to form an oxide layer at a certain depth from the surface and to eliminate defects generated in the surface layer. A method, a method of cleaving a semiconductor substrate using growth by heat treatment of microvoids formed by hydrogen ion irradiation, a method of forming a single crystal semiconductor layer by crystal growth on an insulating surface, or the like can be used.

  In this embodiment mode, ions are added from one surface of the single crystal semiconductor substrate to form a weakened layer at a certain depth from one surface of the single crystal semiconductor substrate. An insulating layer is formed on either the top or the first substrate 410. In a state where the single crystal semiconductor substrate and the first substrate 410 are overlapped with each other with the insulating layer interposed therebetween, a crack is generated in the weakened layer, and heat treatment is performed to separate the single crystal semiconductor substrate with the weakened layer. A single crystal semiconductor layer is formed over the first substrate 410 as a semiconductor layer from the substrate. Note that a glass substrate can be used as the first substrate 410.

  Alternatively, an insulating isolation region may be formed in the semiconductor substrate, and the switching transistor and the current control transistor may be formed using the isolated semiconductor region.

  By using a single crystal semiconductor as a channel formation region, variation in electrical characteristics such as a threshold voltage of a transistor due to bonding defects in a grain boundary can be reduced. The light emitting element can be normally operated without arranging a threshold voltage compensation circuit in each pixel. Therefore, circuit elements in one pixel can be reduced, and the degree of freedom in layout is improved. Therefore, high definition of the display panel can be achieved. For example, the pixel includes a plurality of pixels arranged in a matrix of 300 or more per inch (the horizontal resolution is 300 ppi (pixels per inch) or more), more preferably 400 or more (the horizontal resolution is 400 ppi or more). It can be configured.

  Further, a transistor using a single crystal semiconductor as a channel formation region can be miniaturized while maintaining high current driving capability. Since the area of the circuit portion that does not contribute to display can be reduced by using the minute transistor, the display area can be increased and the display panel can be narrowed in the display portion.

  Note that this embodiment can be combined with any of the other embodiments described in this specification as appropriate.

100 crucible 101 vapor deposition material container 103 discharge port 105 upper lid 107 carbon film 200 vapor deposition apparatus 201 load lock chamber 203 transfer chamber 205 processing chamber 207 gate 209 gate 211 transfer mechanism 213 opening / closing door 301 anode 302 cathode 303 light emitting unit 303a light emitting unit 303b light emission Unit 304 Intermediate layer 304a Electron injection buffer 304b Electron relay layer 304c Charge generation region 313 Hole injection layer 314 Hole transport layer 315 Light emitting layer 316 Electron transport layer 317 Electron injection layer 400 Display panel 401 Display unit 402 Pixel 402B Sub pixel 402G Sub Pixel 402R Subpixel 403g Drive circuit portion 403s Drive circuit portion 405 Seal material 408 Wiring 410 First substrate 411 Transistor 412 Transistor 413 n-channel transistor 414 p-th N-channel transistor 416 Insulating layer 418 Partition 420B Light-emitting element 420G Light-emitting element 420R Light-emitting element 421B First electrode 421G First electrode 421R First electrode 422 Second electrode 423 Layer 423a containing a light-emitting organic compound Layer 423b containing an organic compound 423B layer containing a luminescent organic compound 423G Layer containing a luminescent organic compound 423G Layer 423R containing a luminescent organic compound 424 Layer containing a luminescent organic compound 424 Intermediate layer 428G Color filter 431 Space 440 Second substrate 441B Color filter 441G Color filter 442 Light shielding film 445 Spacer 450B Light emitting module 450G Light emitting module 450R Light emitting module 471 Transistor 472 Transistor 481 Transistor

Claims (4)

After attaching the organic compound to the entire inner wall surface of the vapor deposition crucible, heating the vapor deposition crucible under a pressure at which the temperature at which the organic compound sublimes and the temperature at which the organic compound is thermally decomposed coexist . A method for producing a vapor deposition crucible, comprising forming a film containing carbon on an inner wall surface of the vapor deposition crucible. A pressure at which the temperature at which the organic compound sublimes and the temperature at which the organic compound thermally decomposes coexist after wetting the entire inner wall surface of the evaporation crucible with a solvent in which the organic compound is dispersed or a solution in which the organic compound is dissolved. A method for producing a vapor deposition crucible, comprising: forming a film containing carbon on the inner wall surface of the vapor deposition crucible by heating the vapor deposition crucible below . In claim 1 or claim 2 ,
A method for producing a crucible for vapor deposition, wherein a crucible having an oxygen concentration of 0.1% by weight or more is used as the vapor deposition crucible. In any one of Claims 1 thru | or 3 ,
A method for producing a crucible for vapor deposition, wherein an organic compound having an molecular weight of 200 to 1500 and having an aromatic ring is used as the organic compound.

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