JP3708916B2 - Light emitting device - Google Patents

Description

【０２４２】
なお、本発明における無機導電層は、元素周期律の第２族に属する元素を含む窒化物、硫化物、ホウ化物、または珪化物といった無機化合物からなる導電膜である。そのため陰極材料として仕事関数の小さいアルカリ金属を含む合金を用いる場合に比べて、ＴＦＴの特性に影響を与えるといわれているアルカリ金属の拡散を防ぐことができる。さらに、本発明において、導電層は導電性を有する材料により形成されるため、従来の絶縁材料からなる陰極バッファー層を用いた場合に生じる薄膜化の問題を素子特性に影響を与えることなく解決することができる。すなわち、本発明において発光素子に無機導電層を用いることにより、従来の陰極材料および陰極バッファー層を用いた場合と同等の特性を維持しつつ、上述した効果を得ることができる。
【０２４３】
（実施例８）
実施例１〜実施例５において示した発光素子における有機化合物層は、低分子系もしくは高分子系の有機化合物を用いて形成される場合について示しているが、本発明は、そのような構成に限られることはなく、有機化合物層の一部に無機材料（具体的には、ＳｉおよびＧｅの酸化物の他、アルカリ金属元素、アルカリ土類金属元素、およびランタノイド系元素のいずれかの酸化物とＺｎ、Ｓｎ、Ｖ、Ｒｕ、Ｓｍ、およびＩｒのいずれかとの組み合わせた材料等）を用いることも可能である。また、これらの有機化合物層が積層構造を有する場合において、各積層界面に各層を形成する材料からなる混合層を共蒸着法等により形成することも可能である。
【０２４４】
【発明の効果】
本発明では、陰極と有機化合物層との界面に陰極材料よりも仕事関数が小さく、かつ導電性を有する無機化合物からなる無機導電層を形成する。これにより、膜厚を極端に薄くする必要が無くなるので、膜厚の制御が容易になり、素子間のバラツキの問題を解決することができる。
【０２４５】
さらに、本発明では、元素周期律の２族に属する元素を含む導電性の無機化合物を用いて無機導電層を形成するため、これまでのように元素周期律の２族に属する元素を単体で用いた場合に比べて素子内部への拡散の問題を低減させることができると共に、単体よりも酸素との反応性も低いことから酸素による劣化に強い発光素子の形成が可能となる。
【図面の簡単な説明】
【図１】 本発明の発光装置の素子構造を説明する図。
【図２】 本発明の発光装置の素子構造を説明する図。
【図３】 本発明の発光装置の素子構造を説明する図。
【図４】 本発明の発光装置の素子構造を説明する図。
【図５】 本発明の発光装置の作製工程を説明する図。
【図６】 本発明の発光装置の作製工程を説明する図。
【図７】 本発明の発光装置の作製工程を説明する図。
【図８】 本発明の発光装置の作製工程を説明する図。
【図９】 本発明の発光装置の素子構造を説明する図。
【図１０】 発光装置の画素部の上面図。
【図１１】 本発明の発光装置の素子構造を説明する図。
【図１２】 逆スタガ型ＴＦＴの構造を説明する図。
【図１３】 パッシブマトリクス型の発光装置を説明する図。
【図１４】 電気器具の一例を示す図。
【図１５】 従来の発光素子の素子特性について測定した結果。
【図１６】 従来の発光素子の素子特性について測定した結果。
【図１７】 本発明の発光素子の素子特性について測定した結果。
【図１８】 本発明の発光素子の素子特性について測定した結果。
【図１９】 本発明の発光素子の素子特性について測定した結果。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light-emitting device using a light-emitting element in which fluorescence or phosphorescence is obtained by applying an electric field to an element in which a film containing an organic compound (hereinafter referred to as an “organic compound layer”) is provided between a pair of electrodes. . Note that the light-emitting device in this specification refers to an image display device, a light-emitting device, or a light source. Also, modules with light-emitting elements such as connectors such as FPC (Flexible printed circuit) or TAB (Tape Automated Bonding) tape or TCP (Tape Carrier Package), modules with a printed wiring board at the end of TAB tape or TCP In addition, a module in which an IC (integrated circuit) is directly mounted on a light emitting element by a COG (Chip On Glass) method is also included in the light emitting device.
[0002]
[Prior art]
The light emitting element as used in the field of this invention is an element light-emitted by applying an electric field. The light emission mechanism is such that when a voltage is applied with an organic compound layer sandwiched between electrodes, electrons injected from the cathode and holes injected from the anode recombine in the organic compound layer, and excited molecules (Hereinafter referred to as “molecular excitons”), and when the molecular excitons return to the ground state, they are said to emit energy and emit light.
[0003]
In addition, as a kind of molecular exciton which an organic compound forms, it is thought that a singlet excited state and a triplet excited state are possible, However, In this specification, the case where either excited state contributes to light emission is also included. I will do it.
[0004]
In such a light emitting device, the organic compound layer is usually formed as a thin film having a thickness of less than 1 μm. Further, since the light emitting element is a self-luminous element in which the organic compound layer itself emits light, a backlight as used in a conventional liquid crystal display is not necessary. Therefore, it is a great advantage that the light-emitting element can be manufactured to be extremely thin and light.
[0005]
For example, in an organic compound layer of about 100 to 200 nm, the time from carrier injection to recombination is about several tens of nanoseconds considering the carrier mobility of the organic compound layer. Even if the process from light emission to light emission is included, light emission occurs in the order of microseconds or less. Therefore, one of the features is that the response speed is very fast.
[0006]
Further, since the light-emitting element is a carrier injection type light-emitting element, it can be driven with a DC voltage, and noise is hardly generated. Regarding the driving voltage, the thickness of the organic compound layer is first made to be a uniform ultrathin film of about 100 nm, and electrode materials are selected so as to reduce the carrier injection barrier with respect to the organic compound layer. Furthermore, the heterostructure (two-layer structure) is selected. 100 cd / m at 5.5V ² (Reference 1: CW Tang and SA Van Slyke, “Organic electroluminescent diodes”, Applied Physics Letters, vol. 51, No. 12, 913-915 (1987)).
[0007]
Due to these characteristics such as thin and light weight, high-speed response, and direct current low voltage drive, the light emitting element is attracting attention as a next-generation flat panel display element. Further, since it is a self-luminous type and has a wide viewing angle, the visibility is relatively good, and it is considered effective as an element used for a display screen of a portable device.
[0008]
In addition, a driving method such as passive matrix driving (simple matrix type) and active matrix driving (active matrix type) can be used for a light-emitting device formed by arranging such light-emitting elements in a matrix. However, when the pixel density increases, the active matrix type in which a switch is provided for each pixel (or one dot) is considered to be advantageous because it can be driven at a lower voltage.
[0009]
By the way, in such a light emitting device, a metal material having a low work function is used as the cathode in order to facilitate electron injection. So far, magnesium alloys such as Mg: Ag and aluminum alloys such as Al: Li have been studied as materials satisfying practical characteristics. Any material system is easily oxidized by moisture in the atmosphere, causing dark spots, which are light-emitting defects of the device, and increasing the voltage. Therefore, some form of protective film and sealing structure are required as the final element form.
[0010]
Development of a more stable cathode was desired against the background of the above alloy electrode. Recently, a cathode buffer layer such as lithium fluoride (LiF) is interposed as an insulating layer (0.5 nm) of an ultrathin film. As a result, it has been reported that even an aluminum cathode can obtain emission characteristics equivalent to or better than those of a cathode formed using an alloy such as Mg: Ag (Reference 2: LSHung, CWTang and MGMason: Appl. Phys. Lett., 70 (2), 13 January (1997).
[0011]
The characteristic improvement mechanism by providing the cathode buffer layer is that AlF in which the LiF forming the cathode buffer layer forms the electron transport layer of the organic compound layer. _Three Alq when formed in contact with _Three This is considered to be because the electron injection barrier is lowered by bending the energy band.
[0012]
As described above, in a light-emitting element composed of an anode, a cathode, and an organic compound layer, a device for improving the carrier injectability from the electrode due to the improvement of the element characteristics of the light-emitting element has been devised.
[0013]
[Problems to be solved by the invention]
Conventionally, a cathode buffer layer is formed at the interface between the cathode and the organic compound layer by using, as a material having a small work function, a single element belonging to Group 1 or Group 2 of the element periodic rule or a compound containing the element. It was.
[0014]
However, when an alkali metal or alkaline earth metal belonging to Group 1 or Group 2 of the element periodic rule is used alone as the cathode buffer layer, it diffuses and adversely affects the characteristics of the TFT connected to the light emitting element. Problems arise.
[0015]
On the other hand, when a compound containing an element belonging to Group 1 or Group 2 of the element periodic table is used as the cathode buffer layer, generally, the element periodic group 16 having a large electronegativity in order to make the work function smaller, or Compounds with oxygen and fluorine belonging to Group 17 are used. However, since these compounds are insulative, the electron injection property is improved, while the cathode buffer layer needs to be formed as thin as 1 nm or less in order not to deteriorate the device characteristics. Therefore, the film thickness is likely to vary from pixel to pixel, resulting in difficulty in controlling the film thickness.
[0016]
Therefore, in the present invention, in order to solve the problem that occurs when the cathode buffer layer is formed as in the past in the production of the light-emitting element, a new alternative layer is formed, and the electron injectability from the cathode is increased. It is an object of the present invention to provide means for improving and solving manufacturing problems.
[0017]
[Means for Solving the Problems]
In the present invention, an inorganic conductive layer is formed at the interface between the cathode and the organic compound layer using an inorganic compound that is composed of a combination of a metal element and a non-metal element instead of the conventional cathode buffer layer and has conductivity. Furthermore, the inorganic compound is characterized by having a work function smaller than that of the cathode material.
[0018]
Note that the inorganic conductive layer formed in the present invention is formed using a conductive inorganic compound containing an element belonging to Group 2 of the element periodic rule having a work function smaller than that of the cathode material. Thereby, the energy barrier at the interface between the cathode and the organic compound layer can be relaxed, so that the electron injectability from the cathode can be improved.
[0019]
Further, by forming an inorganic conductive layer made of an inorganic compound having conductivity, it is mainly formed from a covalent bond as compared with the case of forming a cathode buffer layer made of a single element belonging to Group 1 or Group 2 of the element periodic rule. Therefore, the problem of diffusion that occurs when a single element is used can be prevented. Furthermore, compared with the case where a cathode buffer layer made of an insulating inorganic compound is formed, light emission from the light-emitting element can be sufficiently obtained even if the film thickness is increased, so that the film thickness can be easily controlled and manufactured. Cost reduction and yield improvement can be realized.
[0020]
The structure of the invention disclosed in the present invention is a light-emitting device having a light-emitting element including an anode, a cathode, and an organic compound layer, and the organic compound layer formed in contact with the anode, and between the organic compound layer and the cathode. And a conductive film that has a work function smaller than that of the cathode and has a conductivity of 1 × 10 ^-Ten A light-emitting device comprising a material of S / m or more.
[0021]
Note that an inorganic compound used as a cathode buffer layer that is usually formed at the interface between the cathode and the organic compound layer has a low electrical conductivity, so that if it is not formed with a film thickness of 1 nm or less, light emission from the light emitting element is sufficient. In the present invention, the conductive film is 1 × 10 ^-Ten By using an inorganic compound having a conductivity of S / m or higher, the film thickness can be controlled, and sufficient light emission can be obtained from the light-emitting element formed thereby. .
[0022]
In another light emitting device having a light emitting element comprising an anode, a cathode, and an organic compound layer, the organic compound layer formed in contact with the anode is formed between the organic compound layer and the cathode. And a conductive film having a work function of 3.5 eV or less and a conductivity of 1 × 10 6. ^-Ten A light-emitting device comprising a material of S / m or more.
[0023]
Note that an organic compound forming an organic compound layer has an electron affinity smaller than that of a metal or the like, and therefore, an electrode having a small work function is required as an electrode material for improving electron injectability. For example, an Mg: Ag alloy that has been studied as a cathode material that satisfies practical properties so far has a work function of 3.7 eV (Reference 3: MA Baldo, S. Lamansky, PE Burrows, ME Thompson, S. R. Forrest; Very high-efficiency green organic light-emitting devices based on electrophosphorescence ;, Applied Physics Letters, vol. 75, No. 1, 4-6 (1999)).
[0024]
In the present invention, by forming an inorganic conductive film having a work function of 3.5 eV or less between the cathode and the organic compound layer, the cathode and the organic compound can be used even when the work function of the cathode itself is not so small. Since the energy barrier between the layers can be relaxed, the electron injectability from the cathode can be improved.
[0025]
Furthermore, in another light emitting device having a light emitting device comprising an anode, a cathode, and an organic compound layer, the structure is formed between the organic compound layer formed in contact with the anode, and the organic compound layer and the cathode. The cathode and the conductive film both have a film thickness of 20 nm or less, the conductive film has a work function smaller than that of the cathode, and the conductivity is 1 × 10 6. ^-Ten A light-emitting device comprising a material of S / m or more.
[0026]
Furthermore, in another light emitting device having a light emitting device comprising an anode, a cathode, and an organic compound layer, the structure is formed between the organic compound layer formed in contact with the anode, and the organic compound layer and the cathode. The cathode and the conductive film have a transmittance of 70% or more, the conductive film has a work function smaller than that of the cathode, and the conductivity is 1 × 10 6. ^-Ten The light-emitting device is formed with a thickness of 1 to 20 nm using a material of S / m or more. The transmittance refers to that having a visible light transmittance of 70 to 100%.
[0027]
Furthermore, in another light emitting device having a light emitting device comprising an anode, a cathode, and an organic compound layer, the structure is formed between the organic compound layer formed in contact with the anode, and the organic compound layer and the cathode. The cathode and the conductive film both have a film thickness of 20 nm or less, the conductive film has a work function of 3.5 eV or less, and the conductivity is 1 ×. 10 ^-Ten The light emitting device is formed of a material having S / m or more.
[0028]
Furthermore, in another light emitting device having a light emitting device comprising an anode, a cathode, and an organic compound layer, the structure is formed between the organic compound layer formed in contact with the anode, and the organic compound layer and the cathode. The cathode and the conductive film have a transmittance of 70% or more, the conductive film has a work function of 3.5 eV or less, and the conductivity is 1 × 10 6. ^-Ten The light-emitting device is formed with a thickness of 1 to 20 nm using a material of S / m or more.
[0029]
Note that in the above structure, the conductive film includes one or a plurality of elements selected from elements belonging to Group 2 of the element periodic rule.
[0030]
In the above structure, the conductive film includes one or more selected from nitrides, sulfides, borides, and silicides containing an element belonging to Group 2 of the periodic table.
[0031]
Further, in the above structure, the conductive film is one or more selected from calcium nitride, magnesium nitride, calcium sulfide, magnesium sulfide, strontium sulfide, barium sulfide, magnesium boride, magnesium silicide, calcium silicide, strontium silicide, and barium silicide. Including seeds.
[0032]
In the above structure, the conductive film includes one or more selected from borides containing rare earth elements.
[0033]
Further, in the above structure, one or more kinds selected from yttrium boride, lanthanum boride, and cerium boride are included.
[0034]
Further, in the above structure, the inorganic conductive layer is mainly formed by a vapor deposition method, but in the case of a substance having a high melting point such as a rare earth boride, a sputtering method may be used. In the case where the inorganic conductive layer is formed after the organic compound layer is formed using the sputtering method, it is desirable to provide a barrier layer for preventing damage to the organic compound layer during sputtering. As a material for forming the barrier layer, specifically, copper phthalocyanine (hereinafter referred to as Cu-Pc) or the like can be used.
[0035]
Conventionally, when a cathode buffer layer made of an insulating material was formed, the film thickness could not be increased. However, by adopting the configuration of the present invention, the thickness of the inorganic conductive layer can be reduced. Since it can be formed thicker than the layer, it is possible to easily control the film thickness between the pixels, so that problems in the manufacturing process can be improved.
[0036]
Note that the light-emitting device of the present invention includes both an active matrix light-emitting device and a passive matrix light-emitting device each having a light-emitting element electrically connected to a TFT.
[0037]
Note that light emission obtained from the light-emitting device of the present invention includes light emission in one or both of the singlet excited state and the triplet excited state.
[0038]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS. The light-emitting device of the present invention includes a light-emitting element having an element structure illustrated in FIG.
[0039]
As shown in FIG. 1A, a cathode 102 is formed over a substrate 101, and an inorganic conductive layer 103 is formed in contact with the cathode 102.
[0040]
Note that the inorganic conductive layer 103 is a material having a work function smaller than that of the cathode material, and is preferably formed of a material having a work function of 3.5 eV or less. The inorganic conductive layer 103 has a conductivity of 1 × 10. ^-Ten It is formed of a material of S / m or higher. Note that the inorganic conductive layer 103 in the present invention can be increased in thickness because it has conductivity. However, in consideration of improvement in light extraction efficiency, the thickness is preferably set to about 1 to 30 nm. .
[0041]
Further, an organic compound layer 104 is formed in contact with the inorganic conductive layer 103. Note that the organic compound layer 104 may be formed of a single layer structure including only a light emitting layer, but a hole injection layer, a hole transport layer, a hole blocking layer, an electron transport layer, and an electron injection layer other than the light emitting layer. A plurality of layers having different functions with respect to the carrier can be formed.
[0042]
Next, the anode 105 is formed in contact with the organic compound layer 104.
[0043]
FIG. 1B shows an energy band diagram of the light-emitting element having the element structure shown in FIG. Here, the organic compound layer 104 formed between the cathode 102 and the anode 105 includes an electron transport layer 106, a light-emitting layer 107, a hole transport layer 108, and a hole injection layer 109. FIG. It has a work function magnitude relationship as shown in B).
[0044]
Note that the inorganic conductive layer 103 of the present invention is formed using a material having an energy level between the electron transport layer 106 and the cathode 102 which form part of the organic compound layer 104, so that electrons can be emitted from the cathode 102. The energy barrier 110 when implanted can be relaxed. Thereby, the electron injectability in the light emitting element can be improved.
[0045]
Note that although FIG. 1A illustrates an element structure in which the cathode 102 is formed in contact with the substrate 101, the present invention is not limited to this, and the anode is formed in contact with the substrate 101. A configuration is also possible. In this case, an element structure is formed in which an anode is formed in contact with the substrate 101, an organic compound layer is formed in contact with the anode, and an inorganic conductive layer is formed between the organic compound layer and the cathode.
[0046]
Next, Embodiments 1 to 3 in the active matrix light-emitting device having the above element structure will be described below with reference to FIGS.
[0047]
(Embodiment 1)
As Embodiment Mode 1 of the present invention, a cross-sectional structure of a pixel portion of a light-emitting device will be described with reference to FIG.
[0048]
In FIG. 2A, a semiconductor element is formed over a substrate 201. Note that as the substrate 201, a glass substrate is used as a light-transmitting substrate, but a quartz substrate may be used. A TFT is used as a semiconductor element, and an active layer of each TFT includes at least a channel formation region 202, a source region 203, and a drain region 204.
[0049]
The active layer of each TFT is covered with a gate insulating film 205, and a gate electrode 206 is formed so as to overlap the channel formation region 202 with the gate insulating film 205 interposed therebetween. An interlayer insulating film 207 that covers the gate electrode 206 is provided, and an electrode that is electrically connected to the source region or drain region of each TFT is provided on the interlayer insulating film 207. The electrode reaching the drain region 204 of the current control TFT 222 which is an n-channel TFT is a cathode 208 of the light emitting element. In addition, an insulating layer 209 having an opening is provided so as to cover an end portion of the cathode 208 and have a tapered edge. In addition, an inorganic conductive layer 210 is formed over the cathode 208, an organic compound layer 211 is provided thereon, and an anode 212 is provided over the organic compound layer 211 to form a light-emitting element. Note that the light-emitting element is sealed with the sealing substrate 214 while the space 213 remains.
[0050]
In this embodiment mode, the inorganic conductive layer 210 is formed in contact with the cathode 208 electrically connected to the TFT, and the organic compound layer 211 is formed in contact therewith.
[0051]
Furthermore, since the inorganic conductive layer 210 has conductivity, it can be formed with a film thickness of 1 to 30 nm, and the film thickness can be easily controlled.
[0052]
In Embodiment 1, by using a transparent conductive film for the anode 212, light generated by carrier recombination in the organic compound layer 211 can be emitted from the anode 212 side.
[0053]
In the first embodiment, the inorganic conductive layer 210 includes an element belonging to Group 2 of the element periodic rule, or includes these nitrides, sulfides, borides, or silicides. Alternatively, a rare earth element boride may be included.
[0054]
More specifically, it can be formed using materials such as calcium nitride, magnesium nitride, calcium sulfide, magnesium sulfide, strontium sulfide, barium sulfide, magnesium boride, magnesium silicide, calcium silicide, strontium silicide, and barium silicide. . Other borides including rare earth elements (Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), particularly preferably boride It can be formed using materials such as lanthanum, yttrium boride, and cerium boride. In addition, by using a stable compound mainly composed of a covalent bond in this way, impurity ions (typically alkali metal ions and alkaline earths) that become a problem when using elemental elements such as alkali metals and alkaline earth metals are used. The diffusion of the metal ions) can be prevented, and the electron injectability from the cathode 208 can be improved.
[0055]
As a material for forming the organic compound layer 211, a known high molecular organic compound can be used, and a low molecular known organic compound can also be used.
[0056]
In Embodiment 1, since the anode 212 made of a transparent conductive film is formed by a sputtering method after the organic compound layer 211 is formed, it is possible to prevent damage to the organic compound layer 211 during film formation. A barrier layer (not shown) is preferably provided. Note that by providing a hole injection layer that forms the organic compound layer 211, the function of a barrier layer can be provided, and thus a hole injection layer may be provided. Cu-Pc can be used as the hole injection layer.
[0057]
Although the top gate type TFT has been described as an example here, the present invention is not particularly limited, and can be applied to a bottom gate type TFT, a forward stagger type TFT, and other TFT structures instead of the top gate type TFT. It is.
[0058]
(Embodiment 2)
As Embodiment Mode 2 of the present invention, a cross-sectional structure of a pixel portion of a light-emitting device will be described with reference to FIG. Note that the configuration until the interlayer insulating film 207 is formed is the same as that in Embodiment 1 except that the current control TFT is formed in a p-channel type, and thus detailed description thereof is omitted.
[0059]
An electrode that is electrically connected to the source region or drain region of each TFT is provided on the interlayer insulating film 207. An electrode reaching the drain region 204 of the current control TFT 222 which is a p-channel TFT is electrically connected to the anode 231 of the light emitting element. In addition, an insulating layer 232 having an opening is provided so as to cover an end portion of the anode 231 and have a tapered edge.
[0060]
An organic compound layer 233 is formed over the anode 231, an inorganic conductive layer 234 is provided over the organic compound layer 233, and a cathode 235 is provided over the inorganic conductive layer 234 to form a light-emitting element. Note that the light-emitting element is sealed with the sealing substrate 214 while the space 213 is left in the same manner as described in Embodiment Mode 1.
[0061]
In this embodiment mode, the organic compound layer 233 is formed in contact with the anode 231 electrically connected to the TFT, and the inorganic conductive layer 234 is formed in contact with the organic compound layer 233 and the cathode 235, respectively. It has a configuration.
[0062]
In Embodiment 2, by using a transparent conductive film for the anode 231, light generated by carrier recombination in the organic compound layer 233 can be emitted from the anode 231 side. In the second embodiment, the light transmitted from the anode 231 side is also transmitted through the substrate 201 and emitted to the outside. Therefore, it is necessary to use a light-transmitting material as the material used for the substrate 201. Specifically, a material such as glass, quartz, or plastic is used.
[0063]
In Embodiment 2, since the inorganic conductive layer 234 is formed by a sputtering method after the organic compound layer 233 is formed, a barrier layer (for preventing damage to the organic compound layer 233 during film formation) (Not shown) may be provided. Note that Cu—Pc or the like can be used as the barrier layer.
[0064]
(Embodiment 3)
As Embodiment Mode 3 of the present invention, a cross-sectional structure of a pixel portion of a light-emitting device will be described with reference to FIG. Note that the configuration until the interlayer insulating film 207 is formed is the same as that in Embodiment 1 except that the current control TFT is formed in a p-channel type, and thus detailed description thereof is omitted.
[0065]
In Embodiment Mode 3, the first electrode 241 electrically connected to the TFT is formed as described in Embodiment Mode 1. Note that as a material for forming the first electrode 241, a light-shielding and highly reflective conductive material, for example, one or a plurality of stacked layers of aluminum, titanium, tungsten, or the like is used. preferable.
[0066]
Further, a second electrode 242 made of a material having a high work function is formed over the first electrode 241. Note that as a material for forming the second electrode 242, a material having a low work function such as ITO is preferably used. In addition, an insulating layer 243 having an opening is provided so as to cover an end portion of the second electrode 242 and have a tapered edge. Note that in Embodiment Mode 3, the first electrode having a light-blocking property or reflectivity and the second electrode having a small work function are stacked to function as the anode 244 of one light-emitting element.
[0067]
In addition, an organic compound layer 245 is formed over the anode 244, an inorganic conductive layer 246 is provided over the organic compound layer 245, and a cathode 247 is provided over the inorganic conductive layer 246 to form a light-emitting element. Note that the light-emitting element is sealed with the sealing substrate 214 while having the space 213 as in Embodiment Modes 1 and 2.
[0068]
In Embodiment 3, the anode 244 is formed by stacking the first electrode 241 and the second electrode 242 electrically connected to the TFT, and the organic compound layer 245 is formed in contact with the anode 244. An inorganic conductive layer 246 is formed between and in contact with the organic compound layer 245 and the cathode 247.
[0069]
With such a structure, the organic compound layer 245 can emit light emitted from the recombination of carriers efficiently from the cathode 247 side without being emitted from the anode 242 side.
[0070]
In Embodiment 3, since the inorganic conductive layer 246 is formed by a sputtering method after the organic compound layer 245 is formed, a barrier layer (for preventing damage to the organic compound layer 245 during film formation) (Not shown) may be provided. Note that a material such as Cu—Pc can be used for the barrier layer.
[0071]
Furthermore, in Embodiment 3, in order to emit light emitted from the organic compound layer 245 from the cathode 247 side, the thickness of the inorganic conductive layer 246 is preferably 1 to 20 nm. The cathode 247 is also preferably formed with a thickness of 1 to 20 nm in order to transmit light.
[0072]
The present invention having the above-described configuration will be described in more detail with the following examples.
[0073]
【Example】
Examples of the present invention will be described below.
[0074]
(Example 1)
In this example, a light-emitting device having the element structure described in Embodiment Mode 1, Embodiment Mode 2, and Embodiment Mode 3 will be described in detail.
[0075]
FIG. 3A illustrates the structure of the light-emitting element described in Embodiment 1. That is, the inorganic conductive layer 302 is formed over the cathode 301, the organic compound layer 303 is formed over the inorganic conductive layer 302, and the anode 307 is formed over the organic compound layer 303. The light having the upward emission type element structure is transmitted through the anode 307 and emitted to the outside. In addition, in the case of this element structure, ITO, which is a transparent conductive film, is formed on the organic compound layer 303 by a sputtering method, so that it is formed by a vapor deposition method to prevent damage to the organic compound layer 303 during sputtering. It is desirable to provide a barrier layer 306 to be formed.
[0076]
The cathode 301 is an electrode electrically connected to the current control TFT 222 as shown in FIG. 2A. In this embodiment, the cathode 301 is formed of Al with a thickness of 120 nm.
[0077]
The inorganic conductive layer 302 formed on the cathode 301 is formed with a film thickness of 30 nm by vapor deposition using CaN.
[0078]
In this embodiment, the organic compound layer 303 formed on the inorganic conductive layer 302 has a stacked structure of a light emitting layer 304 and a hole transport layer 305. Note that the case where the organic compound layer 303 in this embodiment is formed using a high molecular weight organic compound is described; however, a low molecular weight organic compound may be formed as a single layer or a stacked layer. .
[0079]
For the light-emitting layer 304, a polyparaphenylene vinylene-based, polyparaphenylene-based, polythiophene-based, or polyfluorene-based material can be used.
[0080]
Examples of the polyparaphenylene vinylene-based material include poly (p-phenylene vinylene) (hereinafter referred to as PPV) and poly (2- (2′-ethyl-hexoxy)) that can emit orange light. -5-methoxy-1,4-phenylene vinylene) (poly [2- (2'-ethylhexoxy) -5-methoxy-1,4-phenylene vinylene]) (hereinafter referred to as MEH-PPV), green light emission The resulting poly (2- (dialkoxyphenyl) -1,4-phenylene vinylene) (poly [2- (dialkoxyphenyl) -1,4-phenylene vinylene]) (hereinafter referred to as ROPh-PPV) or the like can be used. it can.
[0081]
As a polyparaphenylene-based material, poly (2,5-dialkoxy-1,4-phenylene) (hereinafter referred to as RO— Poly (2,5-dihexoxy-1,4-phenylene)) or the like can be used.
[0082]
Examples of polythiophene-based materials include poly (3-alkylthiophene) (hereinafter referred to as PAT), poly (3-hexylthiophene) (poly (3-hexylthiophene) (poly (3-hexylthiophene)). )) (Hereinafter referred to as PHT), poly (3-cyclohexylthiophene) (hereinafter referred to as PCHT), poly (3-cyclohexyl-4-methylthiophene) (poly (3-cyclohexyl) -4-methylthiophene)) (hereinafter referred to as PCHMT), poly (3,4-dicyclohexylthiophene) (hereinafter referred to as PDCHT), poly [3- (4-octylphenyl) ) -Thiophene] (poly [3- (4octylphenyl) -thiophene]) (hereinafter referred to as POPT), poly [3- (4-octylphenyl) -2,2-bithiophene] (poly [3- (4-octylphenyl)) -2,2-bithiophene]) (hereinafter PTOP) And the like can be used.
[0083]
Furthermore, poly (9,9-dialkylfluorene) (hereinafter referred to as PDAF), poly (9,9-dioctylfluorene), which can obtain blue light emission, is a polyfluorene-based material. (poly (9,9-dioctylfluorene) (hereinafter referred to as PDOF) or the like can be used.
[0084]
Note that these materials for forming the light emitting layer are formed by applying a solution dissolved in an organic solvent by a coating method. In addition, as an organic solvent used here, toluene, benzene, chlorobenzene, dichlorobenzene, chloroform, tetralin, xylene, dichloromethane, cyclohexane, NMP (N-methyl-2-pyrrolidone), dimethyl sulfoxide, cyclohexanone, dioxane, THF (tetrahydrofuran) ) Etc.
[0085]
In addition, the hole transport layer 305 is formed using both PEDOT (poly (3,4-ethylene dioxythiophene)) and polystyrene sulfonic acid (hereinafter referred to as PSS) which is an acceptor material. (Shown as PANI) and acceptor material camphor sulfonic acid (hereinafter referred to as CSA). Since these materials are water-soluble, an aqueous solution is applied by a coating method to form a film.
[0086]
In this embodiment, a film made of PPV is formed as the light emitting layer 304 with a thickness of 80 nm, and a film made of PEDOT and PSS is formed as the hole transport layer 305 with a thickness of 30 nm.
[0087]
A barrier layer 306 is formed on the organic compound layer 303. Note that as a material for forming the barrier layer 306, in addition to a material having a high work function such as gold or silver, Cu-Pc or the like can be used. In this embodiment, Au is used to form a film with a thickness of 20 nm by vapor deposition.
[0088]
Next, an anode 307 is formed. Note that the anode 307 is formed using a light-transmitting material such as ITO (indium tin oxide) or IZO (indium zinc oxide). In this embodiment, ITO is used and formed with a film thickness of 110 nm by a sputtering method.
[0089]
Through the above steps, the upward emission light-emitting element described in Embodiment Mode 1 can be obtained.
[0090]
Next, the structure of the light-emitting element described in Embodiment 2 is illustrated in FIG. That is, the organic compound layer 312 is formed on the anode 311, the inorganic conductive layer 316 is formed on the organic compound layer 312, and the cathode 317 is formed thereon, and the light generated in the organic compound layer 312 is This is a downward emission type element structure that passes through the anode 311 and is emitted to the outside.
[0091]
The anode 311 is a light-transmitting electrode electrically connected to the current control TFT 222 as shown in FIG. 2B, and is formed of ITO with a film thickness of 110 nm in this embodiment.
[0092]
The organic compound layer 312 formed over the anode 311 is formed by stacking a hole transport layer 313 and a light emitting layer 314 in the same manner as shown in FIG. Note that the above-described materials can be used for forming the hole-transporting layer 313 and the light-emitting layer 314, but the film thickness of PEDOT and PSS is also used here as in FIG. 3A. A hole transport layer 313 having a thickness of 30 nm and a light-emitting layer 314 having a thickness of 80 nm made of PPV are formed.
[0093]
The inorganic conductive layer 316 formed over the organic compound layer 312 is formed with a film thickness of 30 nm by vacuum evaporation using CaN as in FIG.
[0094]
A cathode 317 is formed on the inorganic conductive layer 316. Here, Al is used as the cathode material and is formed with a thickness of 120 nm.
[0095]
Thus, the bottom emission type light-emitting element described in Embodiment Mode 2 can be obtained.
[0096]
Next, FIG. 4 illustrates the structure of the light-emitting element described in Embodiment 3. That is, the organic compound layer 402 is formed on the anode 401, the inorganic conductive layer 406 is formed on the organic compound layer 402, and the cathode 407 is formed thereon. The light generated in the organic compound layer 402 is This is an upward emission type element structure that passes through the inorganic conductive layer 406 and the cathode 407 and is emitted to the outside.
[0097]
The anode 401 is formed by stacking a first electrode 241 and a second electrode 242 electrically connected to the current control TFT 222 as shown in FIG. In this embodiment, the anode 401 is formed by stacking Al having a thickness of 100 nm for forming the first electrode 241 and ITO having a thickness of 50 nm for forming the second electrode 242. .
[0098]
The organic compound layer 402 formed over the anode 401 is formed by stacking a hole transport layer 403 and a light emitting layer 404 in the same manner as shown in FIG. Note that the material for forming the hole-transporting layer 403 and the light-emitting layer 404 can be selected from the above-described materials, but again from PEDOT and PSS, as shown in FIG. A hole transport layer 403 having a thickness of 30 nm and a light emitting layer 404 having a thickness of 80 nm made of PPV are formed.
[0099]
The inorganic conductive layer 406 formed over the organic compound layer 402 is formed by vacuum evaporation using CaN as in FIG. However, here, the light-emitting layer is formed with a thickness of 10 nm so that light generated in the organic compound layer 402 can pass through the inorganic conductive layer 406.
[0100]
A cathode 407 is formed over the inorganic conductive layer 406. Here, Al is used as the cathode material and is formed with a thickness of 20 nm in consideration of light transmittance.
[0101]
Through the above steps, the upward emission light-emitting element described in Embodiment Mode 3 can be obtained.
[0102]
(Example 2)
In this embodiment, a pixel portion and TFTs (n-channel TFT and p-channel TFT) of a driver circuit provided around the pixel portion are formed on the same substrate at the same time, and the TFT is electrically connected to the TFT in the pixel portion. A method for forming an element substrate by forming connected light-emitting elements will be described with reference to FIGS. Note that in this example, a light-emitting element having the element structure described in Embodiment Mode 1 is formed.
[0103]
First, in this embodiment, a substrate 600 made of glass such as barium borosilicate glass represented by Corning # 7059 glass or # 1737 glass or aluminoborosilicate glass is used. Note that the substrate 600 is not limited as long as it is a light-transmitting substrate, and a quartz substrate may be used. Further, a plastic substrate having heat resistance that can withstand the processing temperature of this embodiment may be used.
[0104]
Next, a base film 601 formed of an insulating film such as a silicon oxide film, a silicon nitride film, or a silicon oxynitride film is formed over the substrate 600. Although a two-layer structure is used as the base film 601 in this embodiment, a single-layer film of the insulating film or a structure in which two or more layers are stacked may be used. As the first layer of the base film 601, a plasma CVD method is used, and SiH _Four , NH _Three And N ₂ A silicon oxynitride film 601a formed using O as a reactive gas is formed to a thickness of 10 to 200 nm (preferably 50 to 100 nm). In this embodiment, a silicon oxynitride film 601a (composition ratio Si = 32%, O = 27%, N = 24%, H = 17%) having a thickness of 50 nm is formed.
[0105]
Next, as the second layer of the base film 601, a plasma CVD method is used, and SiH _Four And N ₂ A silicon oxynitride film 601b formed using O as a reaction gas is stacked to a thickness of 50 to 200 nm (preferably 100 to 150 nm). In this embodiment, a silicon oxynitride film 601b (composition ratio Si = 32%, O = 59%, N = 7%, H = 2%) having a thickness of 100 nm is formed.
[0106]
Next, semiconductor layers 602 to 605 are formed over the base film 601. The semiconductor layers 602 to 605 are formed by forming a semiconductor film having an amorphous structure by a known means (a sputtering method, an LPCVD method, a plasma CVD method, or the like), and then a known crystallization treatment (laser crystallization method, heat A crystalline semiconductor film obtained by performing a crystallization method or a thermal crystallization method using a catalyst such as nickel) is formed by patterning into a desired shape. The semiconductor layers 602 to 605 are formed with a thickness of 25 to 80 nm (preferably 30 to 60 nm). The material of the crystalline semiconductor film is not limited, but is preferably silicon (silicon) or silicon germanium (Si _1-X Ge _X (X = 0.0001 to 0.02)) or the like.
[0107]
In this embodiment, a plasma CVD method is used to form a 55 nm amorphous silicon film, and then a solution containing nickel is held on the amorphous silicon film. This amorphous silicon film is dehydrogenated (500 ° C., 1 hour), then thermally crystallized (550 ° C., 4 hours), and further laser annealed to improve crystallization. To form a crystalline silicon film. Then, semiconductor layers 602 to 605 are formed by patterning the crystalline silicon film by photolithography.
[0108]
Further, a small amount of impurity element (boron or phosphorus) may be doped before or after the semiconductor layers 602 to 605 are formed in order to control the threshold value of the TFT.
[0109]
In the case of manufacturing a crystalline semiconductor film by a laser crystallization method, a pulse oscillation type or continuous emission type gas laser or solid laser can be used. Examples of gas lasers include excimer lasers, Ar lasers, Kr lasers, and solid lasers include YAG lasers and YVO lasers. _Four Laser, YLF laser, YAlO _Three A laser, a glass laser, a ruby laser, an alexandride laser, a Ti: sapphire laser, or the like can be used.
[0110]
Note that in the case of using these lasers, it is preferable to use a method in which laser light emitted from a laser oscillator is linearly collected by an optical system and irradiated onto a semiconductor film. Crystallization conditions are appropriately selected by the practitioner. When an excimer laser is used, the pulse oscillation frequency is 300 Hz and the laser energy density is 100 to 400 mJ / cm. ² (Typically 200-300mJ / cm ² ). When a YAG laser is used, the second harmonic is used and the pulse oscillation frequency is set to 30 to 300 Hz, and the laser energy density is set to 300 to 600 mJ / cm. ² (Typically 350-500mJ / cm ² ) Then, when the laser beam condensed linearly with a width of 100 to 1000 μm, for example, 400 μm is irradiated over the entire surface of the substrate, the superposition ratio (overlap ratio) of the linear laser light at this time is 50 to 90%. Good.
[0111]
Next, a gate insulating film 607 covering the semiconductor layers 602 to 605 is formed. The gate insulating film 607 is formed of an insulating film containing silicon with a thickness of 40 to 150 nm by a plasma CVD method or a sputtering method. In this embodiment, a silicon oxynitride film (composition ratio Si = 32%, O = 59%, N = 7%, H = 2%) is formed to a thickness of 110 nm by plasma CVD. Needless to say, the gate insulating film 607 is not limited to a silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure.
[0112]
When a silicon oxide film is used, TEOS (Tetraethyl Orthosilicate) and O ₂ The reaction pressure is 40 Pa, the substrate temperature is 300 to 400 ° C., and the high frequency (13.56 MHz) power density is 0.5 to 0.8 W / cm. ² And can be formed by discharging. The silicon oxide film thus manufactured can obtain good characteristics as a gate insulating film by thermal annealing at 400 to 500 ° C. thereafter.
[0113]
Next, as illustrated in FIG. 5A, a first conductive film 608 with a thickness of 20 to 100 nm and a second conductive film 609 with a thickness of 100 to 400 nm are stacked over the gate insulating film 607. In this embodiment, a first conductive film 608 made of a TaN film with a thickness of 30 nm and a second conductive film 609 made of a W film with a thickness of 370 nm are stacked. The TaN film is formed by sputtering using a Ta target in an atmosphere containing nitrogen. The W film is formed by sputtering using a W target. In addition, tungsten hexafluoride (WF ₆ It can also be formed by a thermal CVD method using
[0114]
In any case, in order to use as a gate electrode, it is necessary to reduce the resistance, and the resistivity of the W film is desirably 20 μΩcm or less. The resistivity of the W film can be reduced by increasing the crystal grains. However, when there are many impurity elements such as oxygen in the W film, the crystallization is hindered and the resistance is increased. Therefore, in this embodiment, a sputtering method using a target of high purity W (purity 99.9999%) is used, and the W film is formed with sufficient consideration so that impurities are not mixed in from the gas phase during film formation. By forming, a resistivity of 9 to 20 μΩcm can be realized.
[0115]
In this embodiment, the first conductive film 608 is TaN and the second conductive film 609 is W. However, there is no particular limitation, and all of them are Ta, W, Ti, Mo, Al, Cu, Cr, Nd. You may form with the element selected from these, or the alloy material or compound material which has the said element as a main component. Alternatively, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. Moreover, you may use the alloy which consists of Ag, Pd, and Cu.
[0116]
In addition, the first conductive film 608 is formed using a tantalum (Ta) film, the second conductive film 609 is formed using a W film, the first conductive film 608 is formed using a titanium nitride (TiN) film, and the second The conductive film 609 is a combination of W films, the first conductive film 608 is a tantalum nitride (TaN) film, the second conductive film 609 is an Al film, and the first conductive film 608 is a tantalum nitride film. (TaN) film is formed, the second conductive film 609 is a combination of Cu films, the first conductive film 608 is formed of W, Mo, or a film made of W and Mo, and the second conductive film 609 is formed. A film made of Al and Si, Al and Ti, Al and Sc, or Al and Nd is formed, and a third conductive film (not shown) is formed of Ti, TiN, or a film made of Ti and TiN. It is good also as a combination.
[0117]
Next, as shown in FIG. 5B, resist masks 610 to 613 are formed by photolithography, and a first etching process for forming electrodes and wirings is performed. The first etching process is performed under the first and second etching conditions. In this embodiment, an ICP (Inductively Coupled Plasma) etching method is used as the first etching condition, and CF is used as an etching gas. _Four And Cl ₂ And O ₂ Each gas flow rate ratio is 25/25/10 (sccm), and 500 W RF (13.56 MHz) power is applied to the coil-type electrode at a pressure of 1 Pa to generate plasma and perform etching. . Here, a dry etching apparatus (Model E645- □ ICP) using ICP manufactured by Matsushita Electric Industrial Co., Ltd. is used. 150 W RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied.
[0118]
The W film is etched under this first etching condition so that the end portion of the first conductive layer is tapered. Under the first etching conditions, the etching rate with respect to W is 200.39 nm / min, the etching rate with respect to TaN is 80.32 nm / min, and the selection ratio of W with respect to TaN is about 2.5. Further, the taper angle of W is about 26 ° under this first etching condition.
[0119]
After that, as shown in FIG. 5B, the resist masks 610 to 613 are not removed and the second etching condition is changed, and the etching gas is changed to CF. _Four And Cl ₂ The gas flow ratio is 30/30 (sccm), and 500 W of RF (13.56 MHz) power is applied to the coil-type electrode at a pressure of 1 Pa to generate plasma for about 15 seconds. Etching is performed. 20 W RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. CF _Four And Cl ₂ Under the second etching condition in which is mixed, the W film and the TaN film are etched to the same extent.
[0120]
The etching rate for W under the second etching conditions is 58.97 nm / min, and the etching rate for TaN is 66.43 nm / min. Note that in order to perform etching without leaving a residue on the gate insulating film, it is preferable to increase the etching time at a rate of about 10 to 20%.
[0121]
In the first etching process, the shape of the mask made of resist is made suitable, and the end portions of the first conductive layer and the second conductive layer are tapered due to the effect of the bias voltage applied to the substrate side. It becomes. The angle of the tapered portion may be 15 to 45 °. Thus, the first shape conductive layers 615 to 618 (first conductive layers 615 a to 618 a and second conductive layers 615 b to 618 b) composed of the first conductive layer and the second conductive layer by the first etching treatment. Form. Reference numeral 620 denotes a gate insulating film, and a region that is not covered with the first shape conductive layers 615 to 618 is etched and thinned by about 20 to 50 nm.
[0122]
Then, a first doping process is performed without removing the resist mask, and an impurity element imparting n-type conductivity is added to the semiconductor layer (FIG. 5B). The doping process may be performed by ion doping or ion implantation. The condition of the ion doping method is a dose of 1 × 10 ¹³ ~ 5x10 ¹⁵ atoms / cm ² The acceleration voltage is set to 60 to 100 keV. In this embodiment, the dose is 1.5 × 10 ¹⁵ atoms / cm ² And the acceleration voltage is 80 keV.
[0123]
As an impurity element imparting n-type, an element belonging to Group 15, typically phosphorus (P) or arsenic (As), is used here, but phosphorus (P) is used. In this case, the conductive layers 615 to 618 serve as a mask for the impurity element imparting n-type, and the high concentration impurity regions 621 to 624 are formed in a self-aligning manner. The high concentration impurity regions 621 to 624 have 1 × 10 ²⁰ ~ 1x10 ^{twenty one} atoms / cm ^Three An impurity element imparting n-type is added in a concentration range of.
[0124]
Next, as shown in FIG. 5C, a second etching process is performed without removing the resist mask. The second etching process is performed under the third and fourth etching conditions. Here, as the third etching condition, CF as an etching gas is used. _Four And Cl ₂ The gas flow ratio is 30/30 (sccm), and 500 W of RF (13.56 MHz) power is applied to the coil-type electrode at a pressure of 1 Pa to generate plasma for about 60 seconds. Etching is performed. 20 W RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied. CF _Four And Cl ₂ Under the third etching condition in which is mixed, the W film and the TaN film are etched to the same extent.
[0125]
The etching rate for W under the third etching condition is 58.97 nm / min, and the etching rate for TaN is 66.43 nm / min. Note that in order to perform etching without leaving a residue on the gate insulating film, it is preferable to increase the etching time at a rate of about 10 to 20%.
[0126]
After that, as shown in FIG. 5C, the resist masks 610 to 613 are not removed and the fourth etching condition is changed, and the etching gas is changed to CF. _Four And Cl ₂ And O ₂ The gas flow rate ratio is 20/20/20 (sccm), and 500 W RF (13.56 MHz) power is applied to the coil-type electrode at a pressure of 1 Pa to generate plasma, and about 20 Etch for about 2 seconds. 20 W RF (13.56 MHz) power is also applied to the substrate side (sample stage), and a substantially negative self-bias voltage is applied.
[0127]
The etching rate for TaN in the fourth etching process is 14.83 nm / min. Therefore, the W film is selectively etched. By this fourth etching process, second conductive layers 626 to 629 (first conductive layers 626a to 629a and second conductive layers 626b to 629b) are formed.
[0128]
Next, a second doping process is performed as shown in FIG. Doping is performed such that the first conductive layers 626a to 629a and the second conductive layers 626b to 629b are used as masks against the impurity element, and the impurity element is added to the semiconductor layer below the tapered portion of the first conductive layer. To do. In this embodiment, P (phosphorus) is used as the impurity element, and the dose amount is 1.5 × 10. ¹⁴ Plasma doping is performed at a current density of 0.5 μA and an acceleration voltage of 90 keV.
[0129]
In this manner, low concentration impurity regions 631a to 634a that overlap with the first conductive layer and low concentration impurity regions 631b to 634b that do not overlap with the first conductive layer are formed in a self-aligned manner. The concentration of phosphorus (P) added to the low concentration impurity regions 631 to 634 is 1 × 10 6. ¹⁷ ~ 5x10 ¹⁸ atoms / cm ^Three It is. Further, an impurity element is also added to the high concentration impurity regions 621 to 624 to form high concentration impurity regions 635 to 638.
[0130]
Next, as shown in FIG. 6B, a mask made of resist (639, 640) is formed, and a third doping process is performed. By this third doping treatment, an impurity region 641 in which an impurity element imparting a conductivity type (p-type) opposite to the one conductivity type (n-type) is added to the semiconductor layer that becomes the active layer of the p-channel TFT. , 642. The first conductive layer 627a and the second conductive layer 627b are used as masks for the impurity element, and an impurity element imparting p-type conductivity is added to form an impurity region in a self-aligning manner.
[0131]
In this embodiment, the impurity regions 641 and 642 are diborane (B ₂ H ₆ ) Using an ion doping method. By the first doping process and the second doping process, phosphorus is added to the impurity regions 641 and 642 at different concentrations, respectively, and the concentration of the impurity element imparting p-type in each region is 2 ×. 10 ²⁰ ~ 2x10 ^{twenty one} atoms / cm ^Three By performing the doping treatment so as to become, no problem arises because it functions as the source region and drain region of the p-channel TFT.
[0132]
Next, the resist masks 639 and 640 are removed, and a first interlayer insulating film 643 is formed as shown in FIG. 6C. In this embodiment, a stacked film of a first insulating film 643 a containing silicon and nitrogen and a second insulating film 643 b containing silicon and oxygen is formed as the first interlayer insulating film 643.
[0133]
First, the first insulating film 643a containing silicon is formed using an insulating film containing silicon with a thickness of 100 to 200 nm by using a plasma CVD method or a sputtering method. In this embodiment, a silicon oxynitride film with a thickness of 100 nm is formed by a plasma CVD method. Needless to say, the first insulating film 643a is not limited to the above-described film, and another insulating film containing silicon may be used as a single layer or a stacked structure.
[0134]
Next, a step of activating the impurity element added to each semiconductor layer is performed. This activation process is performed by a thermal annealing method using a furnace annealing furnace. As the thermal annealing method, it may be performed at 400 to 700 ° C., typically 500 to 550 ° C. in a nitrogen atmosphere having an oxygen concentration of 1 ppm or less, preferably 0.1 ppm or less. The activation treatment was performed by heat treatment. In addition to the thermal annealing method, a laser annealing method or a rapid thermal annealing method (RTA method) can be applied.
[0135]
In this embodiment, at the same time as the activation treatment, nickel used as a catalyst during crystallization is gettered to impurity regions (635, 636, 637, 638) containing high-concentration phosphorus, and mainly the channel. The nickel concentration in the semiconductor layer that becomes the formation region is reduced. A TFT having a channel formation region manufactured in this manner has a low off-current value and good crystallinity, so that high field-effect mobility can be obtained and good characteristics can be achieved.
[0136]
In addition, an activation process may be performed before forming the first interlayer insulating film. However, when the wiring material used is weak against heat, after forming an interlayer insulating film (insulating film containing silicon as a main component, for example, a silicon nitride film) to protect the wiring and the like as in this embodiment. It is preferable to perform an activation treatment.
[0137]
In addition, the first interlayer insulating film may be formed by performing a doping process after the activation process.
[0138]
Furthermore, a heat treatment is performed at 300 to 550 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% hydrogen to perform a step of hydrogenating the semiconductor layer. In this embodiment, heat treatment was performed at 410 ° C. for 1 hour in an atmosphere containing about 100% hydrogen. This step is a step of terminating dangling bonds in the semiconductor layer with hydrogen contained in the first interlayer insulating film. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed.
[0139]
In the case where a laser annealing method is used as the activation treatment, it is desirable to irradiate a laser beam such as an excimer laser or a YAG laser after performing the hydrogenation.
[0140]
Next, a second insulating film 643b is formed over the first insulating film 643a by an insulating film containing silicon with a thickness of 1 to 2 μm by a plasma CVD method or a sputtering method. In this embodiment, a silicon oxide film having a thickness of 1.2 μm is formed by plasma CVD. Needless to say, the second insulating film 643b is not limited to the above-described film, and another insulating film containing silicon may be used as a single layer or a stacked structure.
[0141]
As described above, the first interlayer insulating film 643 including the first insulating film 643a and the second insulating film 643b can be formed.
[0142]
Next, patterning is performed to form contact holes that reach the impurity regions 635, 636, 637, and 638.
[0143]
Note that each of the first insulating film 643a and the second insulating film 643b is an insulating film containing silicon formed by a plasma CVD method. Therefore, a dry etching method or a wet etching method is used for forming the contact hole. In this embodiment, etching is performed by using a wet etching method for the first insulating film and using a dry etching method for the second insulating film.
[0144]
First, the second insulating film 643b is etched. Here, ammonium hydrogen fluoride (NH _Four HF ₂ ) 7.13% and ammonium fluoride (NH _Four Wet etching is performed at 20 ° C. using a mixed solution (product name: LAL500, manufactured by Stella Chemifa Co.) containing 15.4% of F) as an etchant.
[0145]
Next, the first insulating film 643a is etched. At this time, CHF for etching gas _Three , The gas flow ratio is set to 35 (sccm), and 800 W RF power is applied to the electrode at a pressure of 7.3 Pa to perform dry etching.
[0146]
Then, wirings 645 to 651 and a cathode 652 that are electrically connected to the respective high concentration impurity regions 635, 636, 637, and 638 are formed. In this embodiment, Al is used to form a film having a thickness of 500 nm and then patterned, but in addition to a single layer film made of Ti, TiN, Al: Si, etc., Ti, TiN, Al: A laminated film formed by sequentially laminating Si and Ti can also be used.
[0147]
In this embodiment, the cathode 652 is formed at the same time as the formation of the wiring, and is also formed as a wiring with the high concentration impurity region 638.
[0148]
Next, an insulating film is formed to a thickness of 1 μm. In this embodiment, a film made of silicon oxide is used as a material for forming the insulating film. However, in some cases, in addition to an insulating film containing silicon such as silicon nitride and silicon oxynitride, polyimide, polyamide, acrylic Organic resin films such as (including photosensitive acrylic) and BCB (benzocyclobutene) can also be used.
[0149]
An opening is formed at a position corresponding to the cathode 652 of this insulating film to form an insulating layer 653 (FIG. 7B).
[0150]
Specifically, an insulating film having a thickness of 1 μm is formed using photosensitive acrylic, and after patterning by a photolithography method, an insulating layer 653 is formed by performing an etching process.
[0151]
Next, an inorganic conductive layer 654 is formed by evaporation on the cathode 652 exposed in the opening of the insulating layer 653. In this embodiment, as a material for forming the inorganic conductive layer 654, conductive nitrides, oxides, carbides, borides, and silicides composed of elements belonging to Group 2 of the periodic table can be used. Here, the inorganic conductive layer 654 is formed using calcium nitride (CaN).
[0152]
In this embodiment, the inorganic conductive layer 654 is formed using a vacuum evaporation method so that the film thickness is 1 to 50 nm, preferably 10 to 20 nm. Note that in this embodiment, the inorganic conductive layer 654 is formed to a thickness of 30 nm.
[0153]
Next, as illustrated in FIG. 8B, an organic compound layer 655 is formed over the inorganic conductive layer 654 by an evaporation method. Here, in this embodiment, one of the organic compound layers formed by the organic compounds exhibiting three types of light emission of red, green, and blue is shown, but three types of organic compound layers are formed. The combination of organic compounds to be described will be described with reference to FIG.
[0154]
Note that the light-emitting element illustrated in FIG. 9A includes a cathode 901, an inorganic conductive layer 902, an organic compound layer 903, a barrier layer 908, and an anode 909. The organic compound layer 903 includes an electron-transport layer 904 and a blocking layer 905. , A light emitting layer 906 and a hole transport layer 907. Note that the material and thickness of the light-emitting element that emits red light is shown in FIG. 9B, the material and thickness of the light-emitting element that emits green light is shown in FIG. 9C, and blue light is emitted. FIG. 9D illustrates materials and thicknesses included in the light-emitting element.
[0155]
First, an organic compound layer that emits red light is formed. Specifically, the electron-transport layer 904 includes tris (8-quinolinolato) aluminum (hereinafter referred to as Alq) which is an electron-transport organic compound. _Three Is formed to a thickness of 40 nm, the blocking layer 905 is formed of a blocking organic compound, bathocuproine (hereinafter referred to as BCP), to a thickness of 10 nm, and the light-emitting layer 906 emits light. Organic compound (hereinafter referred to as host material) which is a host of 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphyrin-platinum (hereinafter referred to as PtOEP) And 4,4′-dicarbazole-biphenyl (hereinafter referred to as CBP) to form a film having a thickness of 30 nm, and the hole transport layer 907 is an organic compound having a hole transport property. 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl (hereinafter referred to as α-NPD) having a thickness of 40 nm is formed into an organic compound that emits red light. A physical layer is formed.
[0156]
Here, the case where the organic compound layer for red light emission is formed using five kinds of organic compounds having different functions has been described. However, the present invention is not limited to this, and the organic compound layer for emitting red light is used. Known materials can be used.
[0157]
Next, an organic compound layer that emits green light is formed. Specifically, the electron-transport layer 904 is an Alq which is an electron-transporting organic compound. _Three The blocking layer 905 forms a blocking organic compound BCP with a thickness of 10 nm, and the light emitting layer 906 uses CBP as a hole transporting host material. Tris (2-phenylpyridine) iridium (Ir (ppy)), a luminescent organic compound _Three ) And co-evaporated to form a film with a thickness of 30 nm, and the hole transport layer 907 emits green light by forming a film of α-NPD, which is a hole transporting organic compound, with a thickness of 40 nm. Organic compounds can be formed.
[0158]
Here, the case where the organic compound layer that emits green light is formed using four types of organic compounds having different functions has been described, but the present invention is not limited to this, and is known as an organic compound that emits green light. These materials can be used.
[0159]
Next, an organic compound layer that emits blue light is formed. Specifically, the electron-transport layer 904 is an Alq which is an electron-transporting organic compound. _Three Is formed with a film thickness of 40 nm, the blocking layer 905 is a blocking organic compound, BCP is formed with a film thickness of 10 nm, and the light emitting layer 906 is a light emitting and hole transporting organic compound. A certain blue-emitting organic compound layer can be formed by forming α-NPD with a thickness of 40 nm.
[0160]
Here, the case where the organic compound layer for blue light emission is formed using three types of organic compounds having different functions has been described, but the present invention is not limited to this, and is known as an organic compound exhibiting blue light emission. These materials can be used.
[0161]
By forming the organic compound described above on the cathode, an organic compound layer that exhibits red light emission, green light emission, and blue light emission can be formed in the pixel portion.
[0162]
Note that in the structure of the light-emitting element in this embodiment, after the organic compound layer 903 is formed, an anode 909 made of a transparent conductive film is formed by a sputtering method. Therefore, some damage is given to the surface of the organic compound layer 903 when the anode 909 is formed. Therefore, in this embodiment, the barrier layer 908 is provided on the organic compound layer 903 to prevent damage to the organic compound layer 903.
[0163]
Note that as a material for forming the barrier layer 908, a material having a high work function such as gold or silver, Cu-Pc having hole injection property, or the like can be used. In this embodiment, the barrier film 908 is formed by forming gold with a thickness of 10 nm (FIG. 9A).
[0164]
Next, as shown in FIG. 8B, an anode 656 made of a transparent conductive film is formed so as to cover the organic compound layer 655 and the insulating layer 653. In this embodiment, as a material for forming the anode 656, an indium tin oxide (ITO) film or a transparent conductive film in which 2 to 20% zinc oxide (ZnO) is mixed with indium oxide has a thickness of 80 to 120 nm. The film is used after forming. Note that the anode 656 can be formed using another known material as long as it is a transparent conductive film having a high work function.
[0165]
Thus, as shown in FIG. 8B, a cathode 652 electrically connected to the current control TFT 704 and a gap between the cathode 652 and the first electrode (not shown) of the adjacent pixel are formed. The insulating layer 653 includes an inorganic conductive layer 654 formed over the cathode 652, an organic compound layer 655 formed over the inorganic conductive layer 654, and an anode 656 formed over the organic compound layer 655 and the insulating layer 653. An element substrate including the light-emitting element 657 can be formed.
[0166]
Note that in the manufacturing process of the light-emitting device in this embodiment, the source signal line is formed using the material forming the gate electrode and the source and drain electrodes are formed because of the circuit configuration and the process. Although the gate signal line is formed using the wiring material, it is possible to use different materials.
[0167]
In addition, a driver circuit 705 including an n-channel TFT 701 and a p-channel TFT 702, a pixel portion 706 including a switching TFT 703 and a current control TFT 704 can be formed over the same substrate.
[0168]
The n-channel TFT 701 in the driver circuit 705 has a channel formation region 501, a low concentration impurity region 631 (GOLD region) overlapping with the first conductive layer 626a which forms part of the gate electrode, and a high concentration functioning as a source region or a drain region. An impurity region 635 is provided. The p-channel TFT 702 includes a channel formation region 502 and impurity regions 641 and 642 functioning as a source region or a drain region.
[0169]
The switching TFT 703 of the pixel portion 706 includes a channel formation region 503, a low concentration impurity region 633a (LDD region) overlapping with the first conductive layer 628a forming the gate electrode, and a low concentration impurity region not overlapping with the first conductive layer 628a. 633b (LDD region) and a high concentration impurity region 637 which functions as a source region or a drain region.
[0170]
The current control TFT 704 of the pixel portion 706 includes a channel formation region 504, a low concentration impurity region 634a (LDD region) overlapping with the first conductive layer 629a forming the gate electrode, and a low concentration impurity not overlapping with the first conductive layer 628a. A region 634b (LDD region) and a high concentration impurity region 638 functioning as a source region or a drain region are provided.
[0171]
In this embodiment, the driving voltage of the TFT is 1.2 to 10V, preferably 2.5 to 5.5V.
[0172]
Further, when the display of the pixel portion is in operation (in the case of moving image display), the background is displayed by the pixel emitting light, and the character display is performed by the pixel where the light emitting element does not emit light. However, when the video display of the pixel portion is stationary for a certain period or longer (referred to as standby in this specification), the display method is switched (reversed) to save power. It is good to leave. Specifically, a character is displayed by a pixel from which the light emitting element emits light (also referred to as character display), and a background is displayed by a pixel from which the light emitting element does not emit light (also referred to as background display).
[0173]
Here, FIG. 10A shows a detailed top structure of the pixel portion of the light-emitting device described in this embodiment, and FIG. 10B shows a circuit diagram. Since FIGS. 10A and 10B use common reference numerals, they may be referred to each other.
[0174]
In FIG. 10, the switching TFT 1000 provided on the substrate is formed using the switching (n-channel type) TFT 703 in FIG. Accordingly, the description of the switching (n-channel type) TFT 703 may be referred to for the description of the structure. A wiring denoted by 1002 is a gate wiring that electrically connects the gate electrodes 1001 (1001a and 1001b) of the switching TFT 1000.
[0175]
Note that although a double gate structure in which two channel formation regions are formed is used in this embodiment, a single gate structure in which one channel formation region is formed or a triple gate structure in which three channel formation regions are formed may be used.
[0176]
The source of the switching TFT 1000 is connected to the source wiring 1003 and the drain is connected to the drain wiring 1004. The drain wiring 1004 is electrically connected to the gate electrode 1006 of the current control TFT 1005. Note that the current control TFT 1005 is formed using the current control (n-channel type) TFT 704 in FIG. Therefore, the description of the structure may be referred to the description of the current control (n-channel type) TFT 704. In this embodiment, a single gate structure is used, but a double gate structure or a triple gate structure may be used.
[0177]
The source of the current control TFT 1005 is electrically connected to the current supply line 1007 and the drain is electrically connected to the drain wiring 1008. Further, the drain wiring 1008 is electrically connected to a cathode 1009 indicated by a dotted line.
[0178]
A wiring indicated by 1010 is a gate wiring electrically connected to the gate electrode 1012 of the erasing TFT 1011. Note that the source of the erasing TFT 1011 is electrically connected to the current supply line 1007, and the drain is electrically connected to the drain wiring 1004.
[0179]
Note that the erasing TFT 1011 is formed in the same manner as the current control (n-channel type) TFT 704 in FIG. Therefore, the description of the structure may be referred to the description of the current control (n-channel type) TFT 704. In this embodiment, a single gate structure is used, but a double gate structure or a triple gate structure may be used.
[0180]
In addition, a storage capacitor (capacitor) is formed in a region indicated by 1013. The capacitor 1013 is formed between the semiconductor film 1014 electrically connected to the current supply line 1007, an insulating film (not shown) in the same layer as the gate insulating film, and the gate electrode 1006. A capacitor formed by the gate electrode 1006, the same layer (not shown) as the first interlayer insulating film, and the current supply line 1007 can also be used as the storage capacitor.
[0181]
Note that a light-emitting element 1015 illustrated in the circuit diagram of FIG. 10B includes a cathode 1009, an organic compound layer (not illustrated) formed over the cathode 1009, and an anode (not illustrated) formed over the organic compound layer. ). In the present invention, the cathode 1009 is connected to the source region or drain region of the current control TFT 1005.
[0182]
A counter potential is applied to the anode of the light emitting element 1015. A power supply potential is applied to the current supply line 1007. The potential difference between the counter potential and the power supply potential is always kept at such a potential difference that the light emitting element emits light when the power supply potential is applied to the cathode. The power source potential and the counter potential are supplied to the light emitting device of the present invention by a power source provided by an external IC or the like. Note that a power source for applying a counter potential is particularly referred to as a counter power source 1016 in this specification.
[0183]
(Example 3)
In this embodiment, an external view of an active matrix light-emitting device of the present invention will be described with reference to FIG. 11A is a top view illustrating the light-emitting device, and FIG. 11B is a cross-sectional view taken along line AA ′ in FIG. 11A. Reference numeral 1101 indicated by a dotted line denotes a source side driver circuit, 1102 denotes a pixel portion, and 1103 denotes a gate side driver circuit. Reference numeral 1104 denotes a sealing substrate, 1105 denotes a sealant, and the inside surrounded by the sealant 1105 is a space.
[0184]
Reference numeral 1108 denotes a wiring for transmitting signals input to the source signal line driver circuit 1101 and the gate signal line driver circuit 1103. A video signal and a clock signal are received from an FPC (flexible printed circuit) 1109 serving as an external input terminal. receive. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The light-emitting device in this specification includes not only a light-emitting device body but also a state in which an FPC or a PWB is attached thereto.
[0185]
Next, a cross-sectional structure is described with reference to FIG. A driver circuit and a pixel portion are formed over the substrate 1110. Here, a source side driver circuit 1101 and a pixel portion 1102 are shown as the driver circuits.
[0186]
Note that the source side driver circuit 1101 is formed with a CMOS circuit in which an n-channel TFT 1113 and a p-channel TFT 1114 are combined. The TFT forming the driving circuit may be formed by a known CMOS circuit, PMOS circuit or NMOS circuit. Further, in this embodiment, a driver integrated type in which a drive circuit is formed on a substrate is shown, but this is not always necessary, and it can be formed outside the substrate.
[0187]
The pixel portion 1102 is formed of a plurality of pixels including a current control TFT 1111 and an anode 1112 electrically connected to the drain thereof.
[0188]
An insulating layer 1113 is formed on both ends of the anode 1112, and an organic compound layer 1114 is formed on the anode 1112. Further, an inorganic conductive layer 1116 is formed over the organic compound layer 1114, and a cathode 1117 is formed over the inorganic conductive layer 1116. Thus, a light emitting element 1118 including the anode 1112, the organic compound layer 1114, and the cathode 1117 is formed.
[0189]
The cathode 1117 also functions as a wiring common to all pixels, and is electrically connected to the FPC 1109 via the connection wiring 1108.
[0190]
In addition, the sealing substrate 1104 is attached to the light emitting element 1118 formed over the substrate 1110 with a sealant 1105. Note that a spacer made of a resin film may be provided in order to secure a space between the sealing substrate 1104 and the light-emitting element 1018. The space 1107 inside the sealing agent 1105 is filled with an inert gas such as nitrogen. Note that an epoxy resin is preferably used as the sealant 1105. The sealing agent 1105 is preferably a material that does not transmit moisture and oxygen as much as possible. Further, the space 1107 may contain a substance having a hygroscopic effect or a substance having an effect of preventing oxidation.
[0191]
Further, in this embodiment, a plastic substrate made of FRP (Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), Mylar, polyester, acrylic, or the like is used as a material constituting the sealing substrate 1104 in addition to a glass substrate or a quartz substrate. be able to. Further, after the sealing substrate 1104 is bonded using the sealing agent 1105, the sealing substrate 1104 can be further sealed with a sealing agent so as to cover the side surface (exposed surface).
[0192]
By enclosing the light emitting element in the space 1107 as described above, the light emitting element can be completely blocked from the outside, and a substance that promotes deterioration of the organic compound layer such as moisture and oxygen can be prevented from entering from the outside. Can do. Therefore, a highly reliable light-emitting device can be obtained.
[0193]
The configuration of the present embodiment can be implemented by freely combining with the configuration of either Embodiment 1 or Embodiment 2.
[0194]
(Example 4)
In Embodiments 1 to 3, the active matrix light-emitting device having a top gate TFT has been described. However, the present invention is not limited to the TFT structure, and therefore, a bottom gate TFT as shown in FIG. (Typically, an inverted staggered TFT) may be used. The inverted stagger type TFT may be formed by any method.
[0195]
Note that FIG. 12A is a top view of a light-emitting device using a bottom-gate TFT. However, sealing with a sealing substrate has not been performed yet. A source side driver circuit 1201, a gate side driver circuit 1202, and a pixel portion 1203 are formed. FIG. 12B is a cross-sectional view of the region a1204 in the pixel portion 1203 when the light-emitting device is turned off at xx ′ in FIG.
[0196]
12B, only the current control TFT among TFTs formed in the pixel portion 1203 will be described. Reference numeral 1211 denotes a substrate, and reference numeral 1212 denotes an insulating film serving as a base (hereinafter referred to as base film). As the substrate 1211, a light-transmitting substrate, typically a glass substrate, a quartz substrate, a glass ceramic substrate, or a crystallized glass substrate can be used. However, it must withstand the maximum processing temperature during the fabrication process.
[0197]
In addition, the base film 1212 is particularly effective when a substrate containing mobile ions or a conductive substrate is used, but the base film 1212 may not be provided on the quartz substrate. As the base film 1212, an insulating film containing silicon may be used. Note that in this specification, an “insulating film containing silicon” specifically refers to silicon such as a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film (SiOxNy: x and y are each represented by an arbitrary integer). On the other hand, it refers to an insulating film containing oxygen or nitrogen at a predetermined ratio.
[0198]
Reference numeral 1213 denotes a current control TFT, which is formed of an n-channel TFT. In this embodiment, the cathode 1223 of the light emitting element 1229 is preferably formed of a p-channel TFT because it is connected to the current control TFT 1213. However, the present invention is not limited to this and is formed of an n-channel TFT. You may do it.
[0199]
The current control TFT 1213 includes an active layer including a source region 1214, a drain region 1215, and a channel formation region 1216, a gate insulating film 1217, a gate electrode 1218, an interlayer insulating film 1219, a source wiring 1220, and a drain wiring 1221. Formed. In this embodiment, the current control TFT 1213 is a p-channel TFT.
[0200]
The drain region of the switching TFT is connected to the gate electrode 1218 of the current control TFT 1213. Although not shown, specifically, the gate electrode 1218 of the current control TFT 1213 is electrically connected to the drain region (not shown) of the switching TFT via the drain wiring (not shown). Note that the gate electrode 1218 has a single gate structure, but may have a multi-gate structure. The source wiring 1220 of the current control TFT 1213 is connected to a current supply line (not shown).
[0201]
The current control TFT 1213 is an element for controlling the amount of current injected into the light emitting element, and a relatively large amount of current flows. Therefore, it is preferable to design the channel width (W) to be larger than the channel width of the switching TFT. Further, it is preferable that the channel length (L) is designed to be long so that excessive current does not flow through the current control TFT 1213. Desirably, it is set to 0.5 to 2 μA (preferably 1 to 1.5 μA) per pixel.
[0202]
Further, the deterioration of the TFT may be suppressed by increasing the thickness of the active layer (particularly the channel formation region) of the current control TFT 1213 (preferably 50 to 100 nm, more preferably 60 to 80 nm).
[0203]
After the current control TFT 1213 is formed, an interlayer insulating film 1219 is formed, and a cathode 1223 electrically connected to the current control TFT 1213 is formed. In this embodiment, the wiring for electrically connecting the current control TFT 1213 and the cathode 1223 and the cathode 1223 are simultaneously formed of the same material. As a material for forming the cathode 1223, a conductive material having a low work function is preferably used. In this embodiment, the cathode 1223 is formed using Al.
[0204]
After the cathode 1223 is formed, the insulating layer 1224 is formed. Note that the insulating layer 1224 is also referred to as a bank.
[0205]
Next, an inorganic conductive layer 1225 is formed. Note that the light-emitting element in this example has the same structure as that described in Embodiment 1. That is, an organic compound layer 1226 is formed over the inorganic conductive layer 1225, and a barrier layer 1227 is formed thereover. Note that as the material for forming the inorganic conductive layer 1225, the organic compound layer 1226, and the barrier layer 1227, the materials described in Embodiment 1 may be used.
[0206]
Next, an anode 1228 is formed on the barrier layer 1227. As a material for the anode 1228, a light-transmitting conductive film is used. In this embodiment, the anode 1228 is formed by forming ITO with a thickness of 110 nm.
[0207]
Through the above, a light-emitting device having an inverted staggered TFT can be formed. Note that the light-emitting device manufactured according to this example can emit light in the direction of the arrow (upper surface) in FIG.
[0208]
Since the inverted stagger type TFT has a structure in which the number of steps is easily reduced as compared with the top gate type TFT, it is very advantageous for reducing the manufacturing cost which is the subject of the present invention.
[0209]
Note that the structure of this embodiment shows a light emitting device having an element structure in which an inversely staggered TFT is provided and light is emitted from the cathode side of the light emitting element. It is also possible to combine light-emitting elements having various structures shown in FIG. Further, in addition to the manufacturing method and materials shown in Embodiment 2, the sealing structure shown in Embodiment 3 can be freely combined with this embodiment.
[0210]
(Example 5)
In this embodiment, a case where a passive (simple matrix) light-emitting device having the element structure of the present invention is manufactured will be described. FIG. 13 is used for the description. In FIG. 13, 1301 is a glass substrate, 1302 is an anode made of a transparent conductive film. In this embodiment, a compound of indium oxide and zinc oxide is formed as a transparent conductive film by a vapor deposition method. Although not shown in FIG. 13, a plurality of anodes 1302 are arranged in stripes parallel to the paper surface.
[0211]
A bank 1303 made of an insulating material is formed so as to cross the anodes 1302 arranged in a stripe shape. The bank 1303 is in contact with the anode 1302 and formed in a direction perpendicular to the paper surface.
[0212]
Next, an organic compound layer 1304 is formed. As a material for forming the organic compound layer 1304, in addition to the materials shown in Embodiments 1 and 2, a known material that can emit light can be used.
[0213]
For example, by forming an organic compound layer that emits red light, an organic compound layer that emits green light, and an organic compound layer that emits blue light, a light-emitting device having three types of light emission can be formed. Since these organic compound layers 1304 are formed along the grooves formed by the banks 1303, they are arranged in stripes in a direction perpendicular to the paper surface.
[0214]
Note that in the structure of the light-emitting element in this embodiment, after the organic compound layer 1304 is formed, the inorganic conductive layer 1306 is formed by a vacuum evaporation method.
[0215]
Next, the cathode 1307 is formed. Note that the cathode 1307 is formed over the inorganic conductive layer 1306 by a vapor deposition method using a metal mask.
[0216]
In this embodiment, since the lower electrode (anode 1302) is formed of a light-transmitting anode, light generated in the organic compound layer is emitted to the lower side (substrate 1301 side).
[0217]
Next, a ceramic substrate is prepared as the sealing substrate 1309. In the structure of this embodiment, a ceramic substrate is used because light shielding is sufficient, but a substrate made of plastic or glass can also be used.
[0218]
The sealing substrate 1309 thus prepared is bonded with a sealing agent 1310 made of an ultraviolet curable resin. Note that an inner side 1308 of the sealing agent 1310 is a sealed space and is filled with an inert gas such as nitrogen or argon. It is also effective to provide a moisture absorbing material typified by barium oxide in the sealed space 1308. Finally, an anisotropic conductive film (FPC) 1311 is attached to complete a passive light emitting device. In this embodiment, the organic compound layer can be formed by freely combining the materials shown in Embodiment 1 or Embodiment 2, or the sealing structure shown in Embodiment 3 can be combined. It is.
[0219]
(Example 6)
Since a light-emitting device using a light-emitting element is a self-luminous type, it is superior in visibility in a bright place and has a wide viewing angle as compared with a liquid crystal display device. Therefore, it can be used for display portions of various electric appliances.
[0220]
As an electric appliance using a light emitting device manufactured according to the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, a sound reproduction device (car audio, audio component, etc.), a notebook personal computer, a game A device, a portable information terminal (mobile computer, mobile phone, portable game machine, electronic book, etc.), an image playback device equipped with a recording medium (specifically, a recording medium such as a digital video disc (DVD)) And a device provided with a display device capable of displaying an image). In particular, a portable information terminal that frequently sees a screen from an oblique direction emphasizes the wide viewing angle, and thus a light emitting device having a light emitting element is preferably used. Specific examples of these electric appliances are shown in FIG.
[0221]
FIG. 14A illustrates a display device, which includes a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. The light-emitting device manufactured according to the present invention can be used for the display portion 2003. Since a light-emitting device having a light-emitting element is a self-luminous type, a backlight is not necessary and a display portion thinner than a liquid crystal display device can be obtained. The display devices include all information display devices for personal computers, for receiving TV broadcasts, for displaying advertisements, and the like.
[0222]
FIG. 14B shows a digital still camera, which includes a main body 2101, a display portion 2102, an image receiving portion 2103, operation keys 2104, an external connection port 2105, a shutter 2106, and the like. The light-emitting device manufactured according to the present invention can be used for the display portion 2102.
[0223]
FIG. 14C illustrates a laptop personal computer, which includes a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing mouse 2206, and the like. The light-emitting device manufactured according to the present invention can be used for the display portion 2203.
[0224]
FIG. 14D illustrates a mobile computer, which includes a main body 2301, a display portion 2302, a switch 2303, operation keys 2304, an infrared port 2305, and the like. The light-emitting device manufactured according to the present invention can be used for the display portion 2302.
[0225]
FIG. 14E shows a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 2401, a housing 2402, a display portion A2403, a display portion B2404, and a recording medium (DVD or the like). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. Although the display portion A 2403 mainly displays image information and the display portion B 2404 mainly displays character information, the light-emitting device manufactured according to the present invention can be used for the display portions A, B 2403, and 2404. Note that an image reproducing device provided with a recording medium includes a home game machine and the like.
[0226]
FIG. 14F illustrates a goggle type display (head mounted display), which includes a main body 2501, a display portion 2502, and an arm portion 2503. The light emitting device manufactured according to the present invention can be used for the display portion 2502.
[0227]
FIG. 14G illustrates a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control reception portion 2605, an image receiving portion 2606, a battery 2607, an audio input portion 2608, operation keys 2609, and an eyepiece. Part 2610 and the like. The light-emitting device manufactured according to the present invention can be used for the display portion 2602.
[0228]
Here, FIG. 14H shows a mobile phone, which includes a main body 2701, a housing 2702, a display portion 2703, an audio input portion 2704, an audio output portion 2705, operation keys 2706, an external connection port 2707, an antenna 2708, and the like. The light-emitting device manufactured according to the present invention can be used for the display portion 2703. Note that the display portion 2703 can reduce power consumption of the mobile phone by displaying white characters on a black background.
[0229]
If the emission luminance of the organic material is increased in the future, the light including the output image information can be enlarged and projected by a lens or the like and used for a front type or rear type projector.
[0230]
In addition, the electric appliances often display information distributed through electronic communication lines such as the Internet or CATV (cable television), and in particular, opportunities to display moving image information are increasing. Since the response speed of the organic material is very high, the light-emitting device is preferable for displaying moving images.
[0231]
In addition, since the light emitting portion of the light emitting device consumes power, it is preferable to display information so that the light emitting portion is minimized. Therefore, when a light emitting device is used for a display unit mainly including character information, such as a portable information terminal, particularly a mobile phone or a sound reproduction device, it is driven so that character information is formed by the light emitting part with the non-light emitting part as the background. It is preferable to do.
[0232]
As described above, the applicable range of the light-emitting device manufactured using the manufacturing method of the present invention is so wide that the light-emitting device can be used for electric appliances in various fields. Moreover, the electric appliance of a present Example can use the light-emitting device produced by implementing Example 1- Example 5 for the display part.
[0233]
(Example 7)
In this example, as a configuration of a conventional light emitting device, (1) when an alloy containing an alkali metal having a low work function is used for the cathode, (2) a conventional cathode buffer layer (insulation) is formed at the interface between the cathode and the organic compound layer. The results of measurement of element characteristics in the case of forming the element using the inorganic conductive layer as a part of the light emitting element as the structure of the light emitting element of the present invention are shown.
[0234]
First, (1) element characteristics of a light-emitting element when an alloy containing an alkali metal having a small work function is used for the cathode. Here, an alloy of aluminum and lithium (Al: Li) is used for the cathode of the light-emitting element. FIG. 15A and FIG. 15B show current and voltage characteristics when the element is manufactured. Note that the structure of the manufactured light-emitting element was Al: Li (100 nm) (cathode) / Alq. _Three (50 nm) / α-NPD (30 nm) / Cu—Pc (20 nm) / ITO (anode).
[0235]
As current characteristics, 20 (mA / cm ² ) 1000 (cd / m) ² ) Is obtained. The voltage characteristic is 1000 (cd / m at 7V). ² ) Is obtained.
[0236]
Next, (2) element characteristics of the light emitting element when a conventional cathode buffer layer (insulator) is provided at the interface between the cathode and the organic compound layer. Here, the characteristics of the cathode of the light emitting element and the organic compound layer are shown. 16A and 16B show current and voltage characteristics in the case where an element is manufactured by providing a cathode buffer layer (LiF) between them, respectively. Note that the structure of the manufactured light-emitting element was Al (100 nm) (cathode) / LiF (1 nm) (cathode buffer) / Alq. _Three (50 nm) / α-NPD (30 nm) / Cu—Pc (20 nm) / ITO (anode).
[0237]
The current characteristics are almost the same as when an Al: Li alloy is used for the cathode, and 25 (mA / cm ² ) 1000 (cd / m) ² ) Is obtained. Similarly, the voltage characteristic is 1000 (cd / m at 7V). ² ) Is obtained.
[0238]
Next, (3) with respect to element characteristics of the light-emitting element when an element is formed using the inorganic conductive layer as a part of the light-emitting element, a conductive film made of an inorganic compound between the cathode of the light-emitting element and the organic compound layer ( Ca _Three N ₂ , Mg ₂ N _Three , MgB ₂ 17 to 19 show current and voltage characteristics of the light-emitting element having the structure of the present invention, each of which is provided. Note that the structure of the manufactured light-emitting element is Al (100 nm) (cathode) / conductive film (Ca _Three N ₂ , Mg ₂ N _Three Or MgB ₂ ) (100 nm) / Alq _Three (50 nm) / α-NPD (30 nm) / Cu—Pc (20 nm) / ITO (anode).
[0239]
Note that a light-emitting element using the inorganic conductive film having the above structure as a part thereof is 25 (mA / cm) regardless of which material is used. ² ) 1000 (cd / m) ² ) Is obtained. The voltage characteristic is 1000 (cd / m at 6.5 V). ² ) Is obtained. This is because a conventional light emitting device ((1) when an alloy containing an alkali metal having a low work function is used for the cathode (2) when a conventional cathode buffer layer (insulator) is provided at the interface between the cathode and the organic compound layer This indicates that the inorganic conductive layer of the present invention is not affected in terms of device characteristics as compared with the conventional device structure.
[0240]
Further, resistivity and work function were measured for three types of materials: calcium nitride, magnesium nitride, and magnesium boride. Regarding the measurement of resistivity, aluminum electrodes are formed at intervals of 1.9 cm, and the above three kinds of materials are formed so as to have a width of 3 cm between the electrodes. _Three N ₂ : 70 nm, Mg _Three N ₂ : 30 nm, MgB ₂ : 40 nm), and the resistivity was obtained by measuring the resistance value with a tester.
The work function was measured using a contact potential measurement method (measuring device: Fermi level measuring device FAC-1 (manufactured by Riken Keiki)). The results are shown in Table 1 below.
[0241]
[Table 1]

[0242]
The inorganic conductive layer in the present invention is a conductive film made of an inorganic compound such as a nitride, sulfide, boride, or silicide containing an element belonging to Group 2 of the element periodic rule. Therefore, compared with the case where an alloy containing an alkali metal having a small work function is used as the cathode material, diffusion of alkali metal, which is said to affect the TFT characteristics, can be prevented. Furthermore, in the present invention, since the conductive layer is formed of a conductive material, the problem of thinning that occurs when a cathode buffer layer made of a conventional insulating material is used is solved without affecting the device characteristics. be able to. That is, by using an inorganic conductive layer for the light emitting element in the present invention, the above-described effects can be obtained while maintaining the same characteristics as when using a conventional cathode material and cathode buffer layer.
[0243]
(Example 8)
Although the organic compound layer in the light-emitting elements shown in Examples 1 to 5 is formed using a low-molecular or high-molecular organic compound, the present invention has such a structure. There is no limitation, and an inorganic material (specifically, an oxide of any one of an alkali metal element, an alkaline earth metal element, and a lanthanoid element in addition to an oxide of Si and Ge) is included in a part of the organic compound layer And any combination of Zn, Sn, V, Ru, Sm, and Ir can be used. Moreover, when these organic compound layers have a laminated structure, it is also possible to form a mixed layer made of a material for forming each layer at each laminated interface by a co-evaporation method or the like.
[0244]
【The invention's effect】
In the present invention, an inorganic conductive layer made of an inorganic compound having a work function smaller than that of the cathode material and having conductivity is formed at the interface between the cathode and the organic compound layer. This eliminates the need to make the film thickness extremely thin, thereby facilitating control of the film thickness and solving the problem of variation between elements.
[0245]
Furthermore, in the present invention, an inorganic conductive layer is formed using a conductive inorganic compound containing an element belonging to Group 2 of the element periodic rule. The problem of diffusion into the element can be reduced as compared with the case of using it, and the reactivity with oxygen is lower than that of a single element, so that it is possible to form a light emitting element that is resistant to deterioration by oxygen.
[Brief description of the drawings]
1A and 1B illustrate an element structure of a light-emitting device of the present invention.
FIG. 2 illustrates an element structure of a light-emitting device of the present invention.
FIG. 3 illustrates an element structure of a light-emitting device of the present invention.
4A and 4B illustrate an element structure of a light-emitting device of the present invention.
FIGS. 5A and 5B illustrate a manufacturing process of a light-emitting device of the present invention. FIGS.
6A and 6B illustrate a manufacturing process of a light-emitting device of the present invention.
7A and 7B illustrate a manufacturing process of a light-emitting device of the present invention.
8A and 8B illustrate a manufacturing process of a light-emitting device of the present invention.
FIG 9 illustrates an element structure of a light-emitting device of the present invention.
FIG. 10 is a top view of a pixel portion of a light emitting device.
FIG. 11 illustrates an element structure of a light-emitting device of the present invention.
FIG. 12 illustrates a structure of an inverted staggered TFT.
FIG. 13 illustrates a passive matrix light-emitting device.
FIG. 14 illustrates an example of an electric appliance.
FIG. 15 shows measurement results of element characteristics of a conventional light emitting element.
FIG. 16 shows measurement results of element characteristics of a conventional light emitting element.
FIG. 17 shows measurement results of element characteristics of the light-emitting element of the present invention.
FIG. 18 shows measurement results of element characteristics of the light-emitting element of the present invention.
FIG. 19 shows measurement results of element characteristics of the light-emitting element of the present invention.

Claims (17)

A light emitting device having an anode, a cathode, and an organic compound layer,
The organic compound layer formed in contact with the anode, and a conductive film made of an inorganic compound formed between the organic compound layer and the cathode,
The conductive film has a work function smaller than that of the cathode, has a conductivity of 1 × 10 ⁻¹⁰ S / m or more, and is made of silicide containing an element belonging to Group 2 of the element periodic rule. Light emitting device. A light emitting device having an anode, a cathode, and an organic compound layer,
The organic compound layer formed in contact with the anode, and a conductive film made of an inorganic compound formed between the organic compound layer and the cathode,
The conductive film has a work function smaller than that of the cathode, has a conductivity of 1 × 10 ⁻¹⁰ S / m or more, and is made of a boride containing an element belonging to Group 2 of the element periodic rule. Light emitting device. A light emitting device having an anode, a cathode, and an organic compound layer,
The organic compound layer formed in contact with the anode, and a conductive film made of an inorganic compound formed between the organic compound layer and the cathode,
The light-emitting device, wherein the conductive film is made of one or a plurality of inorganic compounds selected from magnesium silicide, strontium silicide, calcium silicide, barium silicide, and magnesium boride . A light emitting device having an anode, a cathode, and an organic compound layer,
The organic compound layer formed in contact with the anode, and a conductive film made of an inorganic compound formed between the organic compound layer and the cathode,
The light-emitting device, wherein the conductive film is made of one or two inorganic compounds selected from yttrium boride and cerium boride . A light emitting device having an anode, a cathode, and an organic compound layer,
The organic compound layer formed in contact with the anode, and a conductive film made of an inorganic compound formed between the organic compound layer and the cathode,
The cathode and the conductive film have a transmittance of 70% or more,
The conductive film has a work function smaller than that of the cathode, has a conductivity of 1 × 10 ⁻¹⁰ S / m or more, and is made of a silicide containing an element belonging to the second group of the element periodic rule. A light-emitting device having a thickness . A light emitting device having an anode, a cathode, and an organic compound layer,
The organic compound layer formed in contact with the anode, and a conductive film made of an inorganic compound formed between the organic compound layer and the cathode,
The cathode and the conductive film have a transmittance of 70% or more,
The conductive film has a work function smaller than that of the cathode, has a conductivity of 1 × 10 ⁻¹⁰ S / m or more, is a boride containing an element belonging to the second group of the element periodic rule, and has a thickness of 1 to 20 nm. A light-emitting device having a thickness . A light emitting device having an anode, a cathode, and an organic compound layer,
The organic compound layer formed in contact with the anode, and a conductive film made of an inorganic compound formed between the organic compound layer and the cathode,
The cathode and the conductive film have a transmittance of 70% or more,
The light-emitting device, wherein the conductive film is made of one or a plurality of inorganic compounds selected from magnesium silicide, strontium silicide, calcium silicide, barium silicide, and magnesium boride and has a thickness of 1 to 20 nm. A light emitting device having an anode, a cathode, and an organic compound layer,
The organic compound layer formed in contact with the anode, and a conductive film made of an inorganic compound formed between the organic compound layer and the cathode,
The cathode and the conductive film have a transmittance of 70% or more,
The light-emitting device, wherein the conductive film is made of one or two inorganic compounds selected from yttrium boride and cerium boride and has a thickness of 1 to 20 nm. In a light emitting device having a TFT provided on an insulating surface of a substrate and a light emitting element electrically connected to the TFT,
The light-emitting element is formed by sequentially stacking an anode, an organic compound layer, a conductive film made of an inorganic compound, and a cathode.
The conductive film has a work function smaller than that of the cathode, has a conductivity of 1 × 10 ⁻¹⁰ S / m or more, and is made of silicide containing an element belonging to Group 2 of the element periodic rule. Light emitting device. In a light emitting device having a TFT provided on an insulating surface of a substrate and a light emitting element electrically connected to the TFT,
The light-emitting element is formed by sequentially stacking an anode, an organic compound layer, a conductive film made of an inorganic compound, and a cathode.
The conductive film has a work function smaller than that of the cathode, has a conductivity of 1 × 10 ⁻¹⁰ S / m or more, and is made of a boride containing an element belonging to Group 2 of the element periodic rule. Light emitting device. In a light emitting device having a TFT provided on an insulating surface of a substrate and a light emitting element electrically connected to the TFT,
The light-emitting element is formed by sequentially stacking an anode, an organic compound layer, a conductive film made of an inorganic compound, and a cathode.
The light-emitting device, wherein the conductive film is made of one or a plurality of inorganic compounds selected from magnesium silicide, strontium silicide, calcium silicide, barium silicide, and magnesium boride . In a light emitting device having a TFT provided on an insulating surface of a substrate and a light emitting element electrically connected to the TFT,
The light-emitting element is formed by sequentially stacking an anode, an organic compound layer, a conductive film made of an inorganic compound, and a cathode.
The light-emitting device, wherein the conductive film is made of one or two inorganic compounds selected from yttrium boride and cerium boride . In a light emitting device having a TFT provided on an insulating surface of a substrate and a light emitting element electrically connected to the TFT,
The light-emitting element is formed by sequentially stacking an anode, an organic compound layer, a conductive film made of an inorganic compound, and a cathode.
The cathode and the conductive film have a transmittance of 70% or more,
The conductive film has a work function smaller than that of the cathode, has a conductivity of 1 × 10 ⁻¹⁰ S / m or more, and is made of a silicide containing an element belonging to the second group of the element periodic rule. A light-emitting device having a thickness . In a light emitting device having a TFT provided on an insulating surface of a substrate and a light emitting element electrically connected to the TFT,
The light-emitting element is formed by sequentially stacking an anode, an organic compound layer, a conductive film made of an inorganic compound, and a cathode .
The cathode and the conductive film have a transmittance of 70% or more,
The conductive film has a work function smaller than that of the cathode, has a conductivity of 1 × 10 ⁻¹⁰ S / m or more, is a boride containing an element belonging to the second group of the element periodic rule, and has a thickness of 1 to 20 nm. A light-emitting device having a thickness . In a light emitting device having a TFT provided on an insulating surface of a substrate and a light emitting element electrically connected to the TFT,
The light-emitting element is formed by sequentially stacking an anode, an organic compound layer, a conductive film made of an inorganic compound, and a cathode.
The cathode and the conductive film have a transmittance of 70% or more,
The light-emitting device, wherein the conductive film is made of one or a plurality of inorganic compounds selected from magnesium silicide, strontium silicide, calcium silicide, barium silicide, and magnesium boride and has a thickness of 1 to 20 nm. In a light emitting device having a TFT provided on an insulating surface of a substrate and a light emitting element electrically connected to the TFT,
The light-emitting element is formed by sequentially stacking an anode, an organic compound layer, a conductive film made of an inorganic compound, and a cathode.
The cathode and the conductive film have a transmittance of 70% or more,
The light-emitting device, wherein the conductive film is made of one or two inorganic compounds selected from yttrium boride and cerium boride and has a thickness of 1 to 20 nm. A light emitting device according to any one of claims 1 to 16 is used for a display unit, and a display device, a digital still camera, a personal computer, a mobile computer, a portable image reproducing device including a recording medium, An electric appliance characterized by being a kind selected from a goggle type display, a video camera, and a mobile phone.

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