Patent Application
20070287209
An embodiment mode of the present invention is described with reference to
Although the present invention is fully described by way of an embodiment mode and embodiments with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the spirit and scope of the present invention, they should be construed as being included therein. Note that in each structure of the present invention described below, reference numerals are used in common through the drawings.
First, a first electrode 102 is formed over a substrate 101 (see
For the first electrode 102 and a second electrode 105 which is formed in a later step, a metal, an alloy, a conductive compound, a mixture thereof, or the like can be used. Specifically, indium oxide-tin oxide (Indium Tin Oxide which is also called ITO), indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide (Indium Zinc Oxide which is also called IZO), tungsten oxide-indium oxide containing tungsten oxide and zinc oxide, and the like can be given as examples. Such a conductive metal oxide film is usually formed by sputtering. For example, indium oxide-zinc oxide (IZO) can be formed by sputtering using a target in which zinc oxide is added at 1 to 20 wt % with respect to indium oxide. Tungsten oxide-indium oxide containing zinc oxide can be formed by sputtering using a target in which tungsten oxide is added at 0.5 to 5 wt % and zinc oxide is added at 0.1 to 1 wt % with respect to indium oxide.
Alternatively, for the first electrode 102 and the second electrode 105, aluminum (Al), silver (Ag), gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), nitride of a metal material (e.g., titanium nitride: TiN), or the like can be used.
Note that in the case where at least one of the first electrode 102 and the second electrode 105 is formed as a light-transmitting electrode, even a material of which has low transmittance of visible light can be used for the light-transmitting electrode by forming a film thereof with a thickness of approximately 1 to 50 nm, preferably approximately 5 to 20 nm. Note that each electrode can also be formed by using vacuum evaporation, CVD, or a sol-gel method as well as sputtering.
Note that since light emission is taken outside through the first electrode 102 or the second electrode 105, it is necessary that at least one of the first electrode 102 and the second electrode 105 is formed of a light-transmitting material. In addition, it is preferable that each material be selected such that a work function of the first electrode 102 becomes larger than that of the second electrode 105. Further, each of the first electrode 102 and the second electrode 105 is not necessarily one layer; two or more layers may also be used.
Next, a resin material 107 is formed over the substrate 101 and the first electrode 102 (see
Next, the formed resin material 107 is shaped into a predetermined shape to form a partition wall 103 (see
Next, the substrate 101 is disposed into a hot plate or an oven to perform a step of heating the partition wall 103. As shown in
Then, the substrate 101 is held at the temperature of T2 for a time period of ΔHa. In this embodiment mode, ΔHa is set at 0.5 hour.
Next, the temperature is raised again from T2 to T3, and the substrate 101 is held at the temperature of T3 which is higher than the curing temperature for a time period of ΔHb. In this embodiment mode, T3 is set at 300 to 350° C. and ΔHb is set at 0.5 hour.
Next, the substrate 101 is cooled to room temperature (r.t.), and is taken out from the hot plate or the oven. Alternatively, the substrate 101 may be taken out from the hot plate or the oven when the temperature is 100 to 200° C., e.g., 150° C., and disposed at room temperature to be cooled gradually.
As described above, by baking at a temperature which is higher than the usual curing temperature, such as T3 and by holding at the temperature of T2 which is lower than the usual curing temperature for a time period of ΔHa, a solvent contained in the resin material 107 forming the partition wall 103 can be removed and moisture generation from the resin material 107 forming the partition wall 103 can also be suppressed. Consequently, a partition wall with a reduced degassing yield and reduced moisture evaporation can be obtained. Accordingly, an advantage such that lives of an EL element and a light-emitting device including the EL element can be prolonged can be obtained.
Next, a light-emitting layer 104 is formed over the partition wall 103 and the first electrode 102. In this embodiment mode, an organic compound is used for the light-emitting layer 104.
As the organic compound of the light-emitting layer 104, the following material can be used. For example, as a light-emitting material which emits red light, Alq3:DCM, Alq3:rubrene:BisDCJTM, or the like is used. As a light-emitting material which emits green light, Alq3:DMQD (N,N′-dimethylquinacridone), Alq3:coumarin 6, or the like is used. As a light-emitting material which emits blue light, α-NPD, tBu-DNA, or the like is used.
Further, the present invention can also be applied to the case where an inorganic compound is used for the light-emitting layer 104. Since moisture generation from the partition wall 103 is suppressed by the present invention, a long-life inorganic EL element can be obtained.
An inorganic EL element using an inorganic compound as a light-emitting material is classified into a dispersion type inorganic EL element and a thin-film type inorganic EL element, depending on its element structure. The former and the latter are different in that the former has an electroluminescence layer where particles of the light-emitting material are dispersed in a binder whereas the latter has an electroluminescence layer formed of a thin film of the light-emitting material. However, the former and the latter have in common that electrons accelerated by a high electric field are necessary. Note that, as a mechanism of light emission that is obtained, there are donor-acceptor recombination type light emission that utilizes a donor level and an acceptor level, and localized type light emission that utilizes inner-shell electron transition of a metal ion. In usual, in many cases, a dispersion type inorganic EL element exhibits donor-acceptor recombination type light emission, and a thin-film type inorganic EL element exhibits localized type light emission.
The light-emitting material which can be used in the present invention includes a host material and an impurity element to be a light-emission center. By changing the impurity element that is contained, light emission of various colors can be obtained. As a manufacturing method of the light-emitting material, various methods such as a solid phase method and a liquid phase method (a coprecipitation method) can be used. Further, an evaporative decomposition method, a double decomposition method, a method by heat decomposition reaction of a precursor, a reversed micelle method, a method in which such a method is combined with high temperature baking, a liquid phase method such as a lyophilization method, or the like can also be used.
The solid phase method is a method in which a host material, and an impurity element or a compound containing an impurity element are weighed, mixed in a mortar, heated and baked in an electric furnace to be reacted, thereby containing the impurity element in the host material. The baking temperature is preferably 700 to 1500° C. This is because the solid reaction does not progress when the temperature is too low, whereas the host material is decomposed when the temperature is too high. Note that although baking may be performed in a powder state, it is preferable to perform baking in a pellet state. Although baking is necessarily performed at a comparatively high temperature, the solid phase method is easy; thus, the solid phase method is suitable for mass production because of high productivity.
The liquid phase method (a coprecipitation method) is a method in which a host material or a compound containing a host material is reacted with an impurity element or a compound containing an impurity element in a solution, dried, and then baked. Particles of the light-emitting material are distributed uniformly, and the reaction can progress even when the grain size is small and the baking temperature is low.
As the host material used for the light-emitting material, sulfide, oxide, or nitride can be used. As sulfide, for example, zinc sulfide (ZnS), cadmium sulfide (CdS), calcium sulfide (CaS), yttrium sulfide (Y2S3), gallium sulfide (Ga2S3), strontium sulfide (SrS), barium sulfide (BaS), or the like can be used. As oxide, for example, zinc oxide (ZnO), yttrium oxide (Y2O3), or the like can be used. As nitride, for example, aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), or the like can be used. Further, zinc selenide (ZnSe), zinc telluride (ZnTe), or the like can also be used. Alternatively, a ternary mixed crystal such as calcium sulfide-gallium (CaGa2S4), strontium sulfide-gallium (SrGa2S4), or barium sulfide-gallium (BaGa2S4) may also be used.
As the light-emission center of localized type light emission, manganese (Mn), copper (Cu), samarium (Sm), terbium (Tb), erbium (Er), thulium (Tm), europium (Eu), cerium (Ce), praseodymium (Pr), or the like can be used. Note that a halogen element such as fluorine (F) or chlorine (Cl) may be added as charge compensation.
On the other hand, as the light-emission center of donor-acceptor recombination type light emission, a light-emitting material containing a first impurity element which forms a donor level and a second impurity element which forms an acceptor level can be used. As the first impurity element, for example, fluorine (F), chlorine (Cl), aluminum (Al), or the like can be used. As the second impurity element, for example, copper (Cu), silver (Ag), or the like can be used.
In the case of synthesizing the light-emitting material of donor-acceptor recombination type light emission by the solid phase method, the host material, the first impurity element or a compound containing the first impurity element, and the second impurity element or a compound containing the second impurity element are each measured, mixed in a mortar, heated and baked in an electric furnace. As the host material, any of the above described host materials can be used. As the first impurity element or the compound containing the first impurity element, for example, fluorine (F), chlorine (Cl), aluminum sulfate (Al2S3), or the like can be used. As the second impurity element or the compound containing the second impurity element, for example, copper (Cu), silver (Ag), copper sulfide (Cu2S), silver sulfide (Ag2S), or the like can be used. The baking temperature is preferably 700 to 1500° C. This is because the solid reaction does not progress when the temperature is too low, whereas the host material is decomposed when the temperature is too high. Note that although baking may be performed in a powder state, it is preferable to perform baking in a pellet state.
As the impurity element in the case of utilizing solid reaction, a compound containing the first impurity element and the second impurity element may be combined. In this case, since the impurity element is easily diffused and solid reaction progresses easily, a uniform light-emitting material can be obtained. Further, since an unnecessary impurity element does not enter, a light-emitting material having high purity can be obtained. As the compound containing the first impurity element and the second impurity element, for example, copper chloride (CuCl), silver chloride (AgCl), or the like can be used.
Note that the concentration of these impurity elements may be 0.01 to 10 atomic % with respect to the host material, and is preferably in the range of 0.05 to 5 atomic %.
In the case of a thin-film type inorganic EL element, a light-emitting layer is a layer containing the above light-emitting material, which can be formed by a vacuum evaporation method such as a resistance heating evaporation method or an electron beam evaporation (EB evaporation) method, a physical vapor deposition method (PVD) such as sputtering, a chemical vapor deposition method (CVD) such as an organic metal CVD method or a hydride transport low-pressure CVD method, an atomic layer epitaxy method (ALE), or the like.
Next, the second electrode 105 is formed over the light-emitting layer 104 (see
In this manner, a light-emitting device is manufactured. In the light-emitting device of this embodiment, the light-emitting layer 104 is less affected because the degassing yield from the partition wall 103 is small. Consequently, a long-life light-emitting device can be obtained.
Note that this embodiment can be combined with any description of embodiments, if necessary.
In this embodiment, changes in properties of polyimide depending on a baking condition were observed.
Polyimide (hereinafter abbreviated to PI) which is a resin having heat-resisting properties and insulation properties has been widely used with photosensitivity provided in a semiconductor field; in many cases, it is used as a partition wall for partitioning pixels in a light-emitting device including an EL element.
In this embodiment, heat-resisting properties and optical properties were evaluated in order to examine how much properties of PI depend on a baking condition.
As for the heat-resisting properties, a mass spectrum was measured by Thermal Desorption Spectroscopy (hereinafter called TDS) so that kinds and amounts of generated gases were weighed up.
Description is made below on the TDS measurement.
First, PI samples for the TDS measurement were manufactured in conditions shown in Table 1. Note that in this embodiment, a baking temperature corresponds to the temperature of T3 in
A schematic diagram of a sample stage of measurement equipment of TDS is
In the measurement equipment in
A TDS spectrum was measured in conditions shown in Table 2 with the measurement equipment shown in
Results of Scan measurement are shown in
From comparison among the TDS spectra of
Estimation of constituents corresponding to the spectrum peaks and characteristics in change of degassing yield depending on the baking temperature are written up in Table 3.
Note that when a mass spectrum of any molecule, it is detected almost always with a plurality of constituenTDSecomposed. For example, in the case of benzene, decomposed constituents (fragments) other than a constituent with a mass number of 78 corresponding to C6H6 are always detected, and an intensity ratio of them is fixed. Unless the detected intensity ratio of these fragment constituents completely agrees with a value listed in a literature, the constituents cannot be identified. Therefore, chemical species shown in Table 3 are just estimation and are not confirmed.
Note that, although as shown in Table 3, as for HF, CO, and CO2, each degassing yield tends to be small in the low-temperature baked sample, which is considered important, just qualitative evaluation can be performed as for the baking temperature dependency only by reviewing spectrum data obtained from the above-described Scan measurement.
Therefore, MID (Multi-ion Detection) measurement which has a higher quantitativity was also performed in the same conditions. Described below are results of the MID measurement.
In the MID measurement, the measurement is performed to the constituents with the mass numbers of which degassing was confirmed in the TDS spectra of
As shown in
Further, if the film density is increased as the baking temperature is increased, it results in that the amount of moisture absorbed in the film is decreased as the baking temperature of the sample is increased. At any rate, from the aspect of moisture generation, it is preferable that the baking temperature be high.
As shown in
It can be considered that in the process of thermal decomposition, single fluorine (F) is not generated but is combined with peripheral hydrogen (H) to become HF which is more stable.
As shown in
As shown in
As shown in
Further,
From
In summary, it can be concluded that properties such as the heat-resisting properties or the moisture-resisting properties can be improved as the baking temperature is increased in the range of 260° C. to 320° C.
In this embodiment, changes in properties of polybenzoxazole (also called benzoxazole which is hereinafter abbreviated to PBO) depending on a baking condition were observed.
Polybenzoxazole is known to have higher heat-resisting properties, higher mechanical properties, lower hygroscopic properties, and a lower dielectric constant than polyimide (PI). Therefore, its application as a surface protective film or an interlayer insulating film instead of PI has been widened.
In this embodiment, heat-resisting properties were evaluated in order to examine how much properties of polybenzoxazole depend on a baking condition.
For evaluating the heat-resisting properties, Thermal Desorption Spectroscopy (TDS) was adopted. Mass spectra of gasses generated at vacuum heating were measured by this method so that kinds and amounts thereof were weighed up.
Samples for the TDS measurement were manufactured in conditions shown in Table 4. Note that in this embodiment, a baking temperature corresponds to the temperature of T3 in
In addition, the sample stage of TDS equipment shown in
Measurement conditions of this embodiment are shown in Table 5.
Results of Scan measurement are shown in
From comparison among the spectra of
Estimation of constituents corresponding to the spectrum peaks and characteristics in change of degassing yield depending on the baking temperature in
Next, MID measurement which has a higher quantitativity was performed in the same conditions. Results of the MID measurement are shown in
Dependency on the baking temperature of the constituent with the mass number of 18 shown in
On the other hand, from
Thus, in this embodiment mode, TDS measurement was performed by baking polybenzoxazole at four conditions of temperature in the range of 280° C. to 340° C. Consequently, it was understood that the degassing yield tended to be smaller as the baking temperature of polybenzoxazole was higher.
Further,
From
In this embodiment, organic EL properties in the cases where polyimide (PI) and polybenzoxazole (PBO) are used respectively for partition walls were examined.
Each of polyimide (PI) and polybenzoxazole (PBO) is an insulating material having good heat-resisting properties. In Embodiments 1 and 2, the TDS measurement of the single-layer samples were performed as tests for the heat-resisting properties of polyimide (PI) and polybenzoxazole (PBO) respectively, and the results were compared.
However, which heat-resisting properties are superior could not be judged only from the results of the TDS measurement.
Further, the plurality of samples of each of polyimide and polybenzoxazole were manufactured with the baking condition (the baking temperature) changed, and TDS measurement thereof were performed. Consequently, it could be confirmed that the degassing yield detected was smaller as the baking temperature of the sample was higher in either case of polyimide or polybenzoxazole.
Thus in this embodiment, in order to verify whether the above-described tendency affects initial properties or reliability of light emission of an organic EL element or not, an organic EL material was evaporated to each of substrates where PI and PBO which were baked at higher temperatures than in the standard condition were formed as partition walls, and properties thereof were evaluated.
First, a silicon oxide film was formed as a base film over a substrate at a thickness of 200 nm. After that, a first electrode was formed by using a stacked-layer film of aluminum (Al) and titanium (Ti).
A second electrode was formed using indium oxide-tin oxide (Indium Tin Oxide which is also called ITO).
Next, polyimide or polybenzoxazole which was a material of a partition wall was formed over the substrate and shaped into a desired shape. Then, development treatment was performed and baking at a temperature shown in Table 7 was performed. Note that in this embodiment, the baking temperature corresponds to the temperature of T3 in
A light-emitting layer was formed using an organic material which emits green light. In this manner, organic EL elements of this embodiment were formed.
Initial properties of the manufactured organic EL elements are shown in
From
In the current efficiency in
From
In summary of the above-described results and consideration, the material or the baking condition of the partition wall does not remarkably affect initial properties of each element.
Attenuation curves of a reliability test of the organic EL elements of this embodiment are shown in
In this embodiment, the reliability test was performed with an initial luminance of M2 each organic EL element which emits green light, of 3000 cd/m2. Based on
As for reliability of the elements with the partition materials baked at higher temperatures which are higher than 300° C., which are evaporated to the substrates, five elements out of six elements show results greater than a result of the element baked at 250° C. Accordingly, it can be said that reliability tends to be improved as the baking temperature is increased.
As a reason why it can be considered that increase in baking temperature of the partition material contributes to increase in reliability of the EL element, decrease in degassing yield from the partition material can be considered as shown in the results of the TDS measurement.
It is known that PI is imidized at 200° C. or higher and an imidizing rate (a curing rate) thereof is 100% at 250° C. or higher. Therefore, it should be sufficient for the partition material to be baked at 250° C.
However, even in a temperature range which is equal to or higher than 250° C., it is considered that the film quality depends on the baking temperature because of the rate of content of a low-molecular-weight constituent such as a photosensitive agent, the average molecular weight, the film density, or the like, and difference in degassing yield is generated as is seen from the results of the TDS measurement.
Since the amount of gas detected by the TDS measurement is small and an actual EL element is not heated at the time of light emission, it is difficult to intuitively consider that an amount of gas by which deterioration occurs is generated from the partition material.
However, as for an EL element incorporated into a light-emitting device, since it is used continuously for hundreds or thousands of hours, it can also be considered that a certain constituent such as moisture may gradually deteriorate the EL element even if the degassing yield is very small. Therefore, as a requirement for a partition material of an EL element, it is preferable that the degassing yield be small as much as possible.
An example of using a method for manufacturing a semiconductor device using the present invention is described with reference to
First, as shown in
The base film 502 is provided in order to prevent an alkali metal or an alkali-earth metal such as Na contained in the substrate 501 from diffusing into a semiconductor film to adversely affect characteristics of a semiconductor element.
Silicon oxide, silicon nitride, silicon oxide containing nitrogen, silicon nitride containing oxygen, or the like can be used for the base film 502, and the base film 502 may be a single layer or have a stacked-layer structure of two layers, three layers, or the like. In addition, it is effective to provide the base film to prevent impurity diffusion in the case of using a substrate containing an alkali metal or an alkali-earth metal, such as a glass substrate, a stainless steel substrate, or a plastic substrate. However, when impurity diffusion is not matter as in the case of using a quartz substrate or the like, the base film is not necessarily provided.
In this embodiment, a silicon nitride film containing oxygen is formed as a lower-layer base film 502a at a thickness of 50 nm with SiH4, NH3, N2O, N2 and H2 as reaction gases over the substrate, and a silicon oxide film containing nitrogen is formed as an upper-layer base film 502b at a thickness of 100 nm with SiH4 and N2O as reaction gases thereover. Note that, the thickness of the silicon nitride film containing oxygen may also be 140 nm and the thickness of the stacked silicon oxide film containing nitrogen may also be 100 nm.
Next, a semiconductor film 503 is formed over the base film 502. The thickness of the semiconductor film 503 is set to 25 to 100 nm (preferably 30 to 60 nm). It is to be noted that not only silicon (Si) but also silicon-germanium (SiGe) can be used as the semiconductor. In the case of using silicon germanium, the germanium concentration is preferably approximately 0.01 to 4.5 atomic %.
For the semiconductor film 503, an amorphous semiconductor that is manufactured by vapor deposition or sputtering using a semiconductor material gas such as silane or germane, a semi-amorphous semiconductor (also called a microcrystal, and hereinafter also referred to as an “SAS”), or the like can be used.
The semi-amorphous semiconductor (SAS) is a semiconductor that has an intermediate structure between amorphous and crystalline (including a single crystal and a polycrystal) structures and has a third state that is stable in terms of free energy, and includes a crystalline region that has a short-range order with lattice distortion. In at least one region of the film, a crystal region of 0.5 to 20 nm can be observed. In the case of including silicon as a main component, Raman spectrum is shifted toward a low wavenumber side which is lower than 520 cm−1.
Diffraction peaks of (111) and (220), which are considered to be derived from a silicon crystal lattice, are observed in X-ray diffraction. In order to terminate dangling bonds, hydrogen or halogen is included at least at 1 atomic % or more.
The SAS is formed by glow discharge decomposition (plasma CVD) of a gas containing silicon. As the gas containing silicon, SiH4, Si2H6, SiH2Cl2, SiHCl3, SiCl4, SiF4 or the like can be used, which may be further mixed with F2 or GeF4. The gas containing silicon may be diluted with H2 or with H2 and at least one kind of rare gas elements selected from He, Ar, Kr and Ne.
The dilution ratio is in the range of 2 to 1000 times, the pressure is in the range of 0.1 to 133 Pa, and the power supply frequency is 1 to 120 MHz, preferably 13 to 60 MHz. The substrate heating temperature is preferably 300° C. or less, and the SAS can also be formed at a substrate heating temperature of 100 to 200° C.
Here, as for impurity elements taken mainly during the film formation, it is preferable that the concentration of impurities derived from atmospheric components such as oxygen, nitrogen and carbon be 1×1020 cm−3 or less, and in particular, the oxygen concentration be 5×1019 cm−3 or less, more preferably 1×1019 cm−3 or less.
In addition, by adding a rare gas element such as helium, argon, krypton, or neon to further promote the lattice distortion, a favorable SAS with stability improved can be obtained. Alternatively, as the semiconductor film, an SAS layer which is formed by using a hydrogen-based gas may be stacked on an SAS layer which is formed by using a fluorine-based gas.
The amorphous semiconductor is typified by hydrogenated amorphous silicon or the like. Further, as described above, a semi-amorphous semiconductor or a semiconductor including a crystalline phase as a part of its semiconductor film can also be used.
In this embodiment, as the semiconductor film 503, an amorphous silicon film is formed by plasma CVD at a thickness of 54 nm.
Next, a metal element which promotes crystallization of a semiconductor is introduced into the semiconductor film 503. The method for introducing the metal element into the semiconductor film 503 is not particularly limited as long as the metal element can be existed in a surface of or inside the semiconductor film 503, and for example, sputtering, CVD, plasma treatment (including plasma CVD), an absorption method, or a method of adding a solution of a metal salt can be used.
Among them, the method of using a solution is simple and is useful in that the concentration of the metal element is easily controlled. In addition, at this time, it is preferable to form an oxide film by UV light irradiation in an oxygen atmosphere, thermal oxidation, a treatment with ozone water including a hydroxyl radical or hydrogen peroxide, or the like in order to improve surface wettability of the semiconductor film 503 and spread the solution over the entire surface of the amorphous semiconductor film.
As the metal element which promotes crystallization of a semiconductor, one or more elements selected from nickel (Ni), germanium (Ge), iron (Fe), palladium (Pd), tin (Sn), lead (Pb), cobalt (Co), platinum (Pt), copper (Cu), and gold (Au) can be used. In this embodiment, nickel (Ni) is used as the metal element, and a liquid-phase nickel acetate solution is applied as a solution 504 containing the metal element to the surface of the semiconductor film 503 by spin coating (see
Next, hydrogen in the semiconductor film 503 is released by keeping at a temperature of 450 to 500° C. for one hour in a nitrogen atmosphere. This is for reducing the threshold energy in the following crystallization by purposely forming dangling bonds in the semiconductor film 503.
Then, by performing a heat treatment at a temperature of 550 to 600° C. for 4 to 8 hours in a nitrogen atmosphere, the semiconductor film 503 is crystallized to form a crystalline semiconductor film 505. This metal element allows the crystallization temperature of the semiconductor film 503 to be a relatively low temperature of 550 to 600° C.
Next, the crystalline semiconductor film 505 is irradiated with a linear laser beam 500 to improve crystallinity furthermore (see
In the case of performing laser crystallization, a heat treatment at 500° C. for 1 hour may also be performed to the crystalline semiconductor film 505 before the laser crystallization in order to enhance resistance of the crystalline semiconductor film 505 to the laser.
For the laser crystallization, a continuous wave laser, or a pulsed oscillation laser at a repetition rate of 10 MHz or more, preferably 80 MHz or more, as a pseudo CW laser can be used.
Specifically, as continuous wave lasers, there are an Ar laser, a Kr laser, a CO2 laser, a YAG laser, a YVO4 laser, a YLF laser, a YAlO3 laser, a GdVO4 laser, a Y2O3 laser, a ruby laser, an alexandrite laser, a Ti:sapphire laser, a helium cadmium laser, and the like.
In addition, as pseudo CW lasers, pulsed oscillation lasers such as an Ar laser, a Kr laser, an excimer laser, a CO2 laser, a YAG laser, a Y2O3 laser, a YVO4 laser, a YLF laser, a YAlO3 laser, a GdVO4 laser, a glass laser, a ruby laser, an alexandrite laser, a Ti:sapphire laser, a copper vapor laser, and a gold vapor laser can be used as long as pulsed oscillation can be performed at a repetition rate of 10 MHz or more, preferably 80 MHz or more.
These pulsed oscillation lasers eventually exhibit an effect equivalent to the continuous wave laser as a result of increasing the repetition rate.
For example, in the case of using a solid laser that is capable of continuous wave oscillation, a crystal of large grain size can be obtained by irradiation with laser light of any of the second to fourth harmonics. Typically, it is preferable to use the second harmonic (532 nm) or the third harmonic (355 nm) of a YAG laser (fundamental wave: 1064 nm). For example, laser light emitted from a continuous wave YAG laser is converted into a harmonic by a non-linear optical element, and is used to irradiate the semiconductor film 505. The energy density may be set at approximately 0.01 to 100 MW/cm2 (preferably 0.1 to 10 MW/cm2).
Note that the laser light irradiation may be performed in an atmosphere containing an inert gas such as a rare gas or nitrogen. This makes it possible to suppress roughness of the semiconductor surface due to laser light irradiation and suppress variations in threshold voltage caused by variations in interface state density.
A crystalline semiconductor film 506 with crystallinity more improved is formed by irradiating the semiconductor film 505 with the laser beam 500 described above (see
Next, as shown in
Next, an impurity for controlling the threshold value is introduced into the island-shaped semiconductor films 507 to 510. In this embodiment, boron (B) is introduced into the island-shaped semiconductor films 507 to 510 by doping with diborane (B2H6).
Next, an insulating film 511 is formed so as to cover the island-shaped semiconductor films 507 to 510. For the insulating film 511, for example, silicon oxide, silicon nitride, silicon oxide containing nitrogen, or the like can be used. In addition, plasma CVD, sputtering, or the like can be used as a film formation method thereof.
Next, after forming a conductive film over the insulating film 511, a first conductive film 512 and a second conductive film 513 are formed, and by using them, gate electrodes 515 to 519 are formed.
The gate electrodes 515 to 519 are formed by using a single layer of a conductive film or a stacked-layer structure of two or more layers of conductive films. In the case where two or more conductive films are stacked, the gate electrodes 515 to 519 may be formed by stacking an element selected from tantalum (Ta), tungsten (W), titanium (Ti), molybdenum (Mo), and aluminum (Al), an alloy material containing the element as a main component, or a compound material. Alternatively, each gate electrode may be formed by using a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorous (P).
In this embodiment, as the first conductive film 512, for example, a tantalum nitride (TaN) film is formed at a thickness of 10 to 50 nm, e.g., at 30 nm, first. Then, as the second conductive film 513, for example, a tungsten (W) film is formed over the first conductive film 512 at a thickness of 200 to 400 nm, e.g., at 370 nm, thereby forming a stacked-layer film of the first conductive film 512 and the second conductive film 513 (see
Next, by performing anisotropic etching continuously to the second conductive film and the first conductive film and then by performing isotropic etching to the second conductive film, upper-layer gate electrodes 515b to 519b and lower-layer gate electrodes 515a to 519a are formed. In this manner, the gate electrodes 515 to 519 are formed (see
Each of the gate electrodes 515 to 519 may be formed as a part of a gate wiring, or a gate wiring may be separately formed to be connected to the gate electrodes 515 to 519.
In addition, a part of the insulating film 511 is also etched at the time of forming the gate electrodes 515 to 519, to form a gate insulating film 514.
Then, by using each of the gate electrodes 515 to 519 or a resist as a mask, each of the island-shaped semiconductor films 507 to 510 is doped with an impurity which imparts one conductivity (n-type or p-type conductivity) to form source regions, drain regions, and further low-concentration impurity regions, and the like.
First, phosphorous (P) is introduced into the island-shaped semiconductor films by using phosphine (PH3) at an accelerating voltage of 60 to 120 keV and at a dosage of 1×1013 to 1×1015 cm−2. By this introduction of the impurity, a channel formation region 525 for an n-channel TFT 542, and channel formation regions 528 and 531 for an n-channel TFT 543 are formed.
In addition, in order to manufacture p-channel TFTs 541 and 544, boron (B) is introduced into the island-shaped semiconductor films by using diborane (B2H6) at an applied voltage is 60 to 100 keV, e.g., 80 keV, and at a dosage is 1×1013 to 5×1015 cm−2, e.g., 3×1015 cm−2. Consequently, source or drain regions 521 and 533 for p-channel TFTs 541 and 544 respectively are formed, and channel formation regions 522 and 534 for the p-channel TFTs 541 and 544 respectively are formed by this introduction of the impurity.
Further, phosphorous (P) is introduced into the island-shaped semiconductor films 508 and 509 for the n-channel TFTs 542 and 543 by using phosphine (PH3) at an applied voltage of 40 to 80 keV, e.g., at 50 keV, and at a dosage of 1.0×1015 to 2.5×1016 cm−2, e.g., at 3.0×1015 cm−2. Consequently, a low-concentration impurity region 524 and a source or drain region 523 for the n-channel TFT 542, and low-concentration impurity regions 527 and 530 and source or drain regions 526, 529, and 532 for the n-channel TFT 543 are formed (see
In this embodiment, phosphorous (P) is contained at a concentration of 1×1019 to 5×1021 cm−3 in each of the source or drain region 523 for the n-channel TFT 542, and the source or drain regions 526, 529, and 532 for the n-channel TFT 543.
In addition, phosphorous (P) is contained at a concentration of 1×1018 to 5×1019 cm−3 in each of the low-concentration impurity region 524 for the n-channel TFT 542, and the low-concentration impurity regions 527 and 530 for the n-channel TFT 543.
Further, boron (B) is contained at a concentration of 1×1019 to 5×1021 cm−3 in each of the source or drain region 521 for the p-channel TFT 541, and the source or drain region 533 for the p-channel TFT 544.
Next, a first interlayer insulating film 551 is formed so as to cover the island-shaped semiconductor films 507 to 510, the gate insulating film 514, and the gate electrodes 515 to 519.
As the first interlayer insulating film 551, an insulating film containing silicon, e.g., a silicon oxide film, a silicon nitride film, a silicon oxide film containing nitrogen, or a stacked-layer film thereof is formed by plasma CVD or sputtering. It is needless to say that the first interlayer insulating film 551 is not limited to the silicon oxide film containing nitrogen, the silicon nitride film, or the stacked-layer film thereof, and another insulating film containing silicon may also be used as a single layer or in a stacked-layer structure.
In this embodiment, after introducing the impurities, a silicon oxide film containing nitrogen is formed by plasma CVD at a thickness of 50 nm, and the impurities are activated by a laser irradiation method or heating at 550° C. in a nitrogen atmosphere for 4 hours after the silicon oxide film containing nitrogen is formed.
Next, a silicon nitride film is formed by plasma CVD at a thickness of 50 nm, and a silicon oxide film containing nitrogen is further formed at a thickness of 600 nm. This stacked-layer film of the silicon oxide film containing nitrogen, the silicon nitride film, and the silicon oxide film containing nitrogen is the first interlayer insulating film 551.
Next, hydrogenation is performed by heating the whole at 410° C. for 1 hour to release hydrogen from the silicon nitride film.
Next, a second interlayer insulating film 552 which functions as a planarization film is formed so as to cover the first interlayer insulating film 551 (see
For the second interlayer insulating film 552, a photosensitive or non-photosensitive organic material (polyimide, acrylic, polyamide, polyimideamide, resist, or benzocyclobutene), siloxane, or a stacked-layer structure thereof can be used. As the organic material, a positive photosensitive organic resin or a negative photosensitive organic resin can be used.
Siloxane has a skeleton structure formed by bonding silicon (Si) and (O), where an organic group containing at least hydrogen (e.g., an alkyl group or aromatic hydrocarbon) is used as a substituent. A fluoro group may also be used as a substituent. Alternatively, an organic group containing at least hydrogen and a fluoro group may be used as substituents.
In this embodiment, siloxane is formed by spin coating for the second interlayer insulating film 552.
Further, a third interlayer insulating film may be formed over the second interlayer insulating film 552. As the third interlayer insulating film, a film through which moisture, oxygen, or the like is hardly transmitted as compared with other insulating films is used. Typically, a silicon nitride film, a silicon oxide film, a silicon nitride film containing oxygen (composition ratio: N>O), or a silicon oxide film containing nitrogen (composition ratio: N<O) that is obtained by sputtering or CVD, a thin film containing carbon as a main component (e.g., a diamond-like carbon film (a DLC film) or a carbon nitride film (a CN film)), or the like can be used.
Next, a transparent conductive film 553 is formed over the second interlayer insulating film 552 (see
As well as the indium tin oxide containing Si, a transparent conductive film such as a conductive film formed by using a target in which zinc oxide (ZnO), tin oxide (SnO2), indium oxide, or indium oxide is mixed with zinc oxide (ZnO) at 2 to 20 wt % may also be used. In this embodiment, for the transparent conductive film 553, an indium tin oxide containing Si is stacked by sputtering at a thickness of 110 nm.
Next, a pixel electrode 554 is formed of the transparent conductive film 553 (see
The first interlayer insulating film 551 and the second interlayer insulating film 552 are etched to form contact holes reaching to the island-shaped semiconductor films 507 to 510 in the first interlayer insulating film 551 and the second interlayer insulating film 552 (see
A third conductive film 555 and a fourth conductive film 556 are formed over the second interlayer insulating film 552 through the contact holes (see
For this embodiment, a film made of molybdenum (Mo), tungsten (W), tantalum (Ta), or chromium (Cr), or an alloy film using any element thereof is preferably used as the third conductive film 555. In this embodiment, molybdenum (Mo) is stacked by sputtering at a thickness of 100 nm.
In addition, a film containing aluminum as a main component is formed by sputtering as the fourth conductive film 556. As the film containing aluminum as a main component, an aluminum film, an aluminum alloy film containing at least one kind of element of nickel, cobalt, and iron, or an aluminum alloy film containing carbon and at least one kind of element of nickel, cobalt, and iron can be used. In this embodiment, an aluminum film is formed by sputtering at a thickness of 700 nm.
Next, the fourth conductive film 556 is etched to form electrodes 561b, 562b, 563b, 564b, 565b, 566b, and 567b (see
For etching of the fourth conductive film 556, dry etching is performed by using a mixed gas of BCl3 and Cl2. In this embodiment, dry etching is performed by supplying BCl3 and Cl2 at flow rates of 60 sccm and 20 sccm respectively.
At this time, the third conductive film 555 functions as an etching stopper, so that the pixel electrode 554 is not in contact with the mixed gas of BCl3 and Cl2. Therefore, particles can be prevented from being generated.
Next, the third conductive film 555 is etched to form electrodes 561a, 562a, 563a, 564a, 565a, 566a, and 567a. In this embodiment, dry etching of the third conductive film 555 is performed by supplying CF4 and O2 at flow rates of 30 to 60 sccm and 40 to 70 sccm respectively.
At this time, since the pixel electrode 554 does not react with CF4 or O2, fine particles are not formed. In addition, the pixel electrode 554 functions as an etching stopper for etching the third conductive film 555 to form the electrode 567a.
In this manner, electrodes 561 to 567 are formed. For each of the electrodes 561 to 567, an electrode and a wiring may be formed of the same material in the same process, or an electrode and a wiring may be formed separately and connected to each other.
Through the series of steps described above, the n-channel TFTs 542 and 543 and the p-channel TFTs 541 and 544 are formed. The n-channel TFT 542 and the p-channel TFT 541 are connected by the electrode 562 to form a CMOS circuit 571 (see
In this manner, a TFT substrate of a dual-emission type display device is formed. In
In the pixel portion 596, the p-channel TFT 544 which functions as a pixel TFT and the n-channel TFT 543 which drives the pixel TFT are formed. In this embodiment, the pixel electrode 554 functions as an anode of a light-emitting element.
After forming the electrodes 561 to 567, an insulator 581 (called a partition wall, a barrier, or the like) covering an end portion of the pixel electrode 554 is formed. For the insulator 581, polyimide or polybenzoxazole is used.
A baking method of the insulator 581 may be the same as that described in the embodiment mode. A solvent can be removed by heating at a temperature which is lower than the curing temperature, e.g., at 150 to 200° C. Then, baking at a temperature which is higher than the curing temperature, e.g., at 300 to 350° C. is performed, thereby an insulator (a partition wall) with less degassing yield can be obtained.
After forming the insulator 581, an organic compound layer 582 is formed. Then, a second electrode 583, i.e., a cathode of the light-emitting element is formed at a thickness of 10 to 800 nm (see
The organic compound layer 582 includes a hole injecting layer 601, a hole transporting layer 602, a light-emitting layer 603, an electron transporting layer 604, and an electron injecting layer 605 which are formed by an evaporation method or a coating method. Note that, in order to improve reliability of the light-emitting element, it is preferable to perform vacuum heating for degassing before the organic compound layer 582 is formed. For example, before evaporation of an organic compound material is performed, it is preferable to perform a heat treatment at 200 to 300° C. in a reduced-pressure atmosphere or an inert atmosphere in order to remove gas contained in the substrate.
Next, molybdenum oxide (MoOx), 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (α-NPD), and rubrene are co-evaporated selectively over the pixel electrode 554 by using an evaporation mask to form the hole injecting layer 601.
Further, as well as MoOx, a material having high hole-injecting properties such as copper phthalocyanine (CuPc), vanadium oxide (VOx), ruthenium oxide (RuOx), and tungsten oxide (WOx) can be used. Further alternatively, a polymer material having high hole injecting properties such as a polyethylene dioxythiophene solution (PEDOT) or a polystyrene sulphonate solution (PSS) may be stacked by a coating method, for the hole injecting layer 601.
Then, α-NPD is selectively evaporated by using an evaporation mask to form the hole transporting layer 602 over the hole injecting layer 601. Note that as well as α-NPD, a material having high hole transporting properties typified by an aromatic amine compound such as 4,4′-bis[N-(3-methylphenyl)-N-phenyl-amino]-biphenyl (abbreviation: TPD), 4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine (abbreviation: TDATA), and 4,4′,4″-tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenylamine (abbreviation: MTDATA) can be used.
Next, the light-emitting layer 603 is selectively formed. For forming a full-color display device, an evaporation mask is aligned for each light emission color (each of R, G, and B) and evaporation is performed selectively.
Then, Alq3 (tris(8-quinolinolato)aluminum) is selectively evaporated by using an evaporation mask to form the electron transporting layer 604 over the light-emitting layer 603. Note that as well as Alq3, a material having high electron transporting properties typified by a metal complex having a quinoline skeleton or a benzoquinoline skeleton, such as tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq3), bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviation: BeBq2), and bis(2-methyl-8-quinolinolato)-4-phenylphenolato-aluminum (abbreviation: BAlq), and the like can be used.
Further alternatively, a metal complex having an oxazole-based or thiazole-based ligand, such as bis[2-(2-hydroxyphenyl)-benzoxazolato]zinc (abbreviation: Zn(BOX)2) and bis[2-(2-hydroxyphenyl)-benzothiazolato]zinc (abbreviation: Zn(BTZ)2), or the like can be used.
Further alternatively, as well as the metal complex, the following can also be used for the electron transporting layer 604 because the electron transporting properties are high: 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD); 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviation: OXD-7); 3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: TAZ); 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ); bathophenanthroline (abbreviation: BPhen); bathocuproine (abbreviation: BCP); and the like.
Then, 4,4-bis(5-methylbenzoxazole-2-yl)stilbene (abbreviation: BzOs) and lithium (Li) are co-evaporated to form the electron injecting layer 605 over the entire surface covering the electron transporting layer 604 and insulator 581. Damage due to sputtering at the time of forming the second electrode 583 which is performed in a subsequent process is suppressed by using benzoxazole derivative (BzOs).
Further, as well as BzOs:Li, a material having high electron injecting properties such as a compound of an alkali metal or an alkali-earth metal, e.g., CaF2, lithium fluoride (LiF), cesium fluoride (CsF), or the like, can be used. Further alternatively, a mixture of Alq3 and magnesium (Mg) can be used.
Next, the second electrode 583, i.e., the cathode of the organic light-emitting element is formed over the electron injecting layer 605 at a thickness of 10 to 800 nm. For the second electrode 583, as well as an indium tin oxide (ITO), for example, an indium tin oxide containing Si or a conductive film formed using a target in which indium oxide is mixed with zinc oxide (ZnO) at 2 to 20 wt % can be used.
Note that although a light-transmitting electrode is used as the second electrode 583 because the case of manufacturing the dual-emission type display device is described in this embodiment, a reflective conductive material may be used to form the second electrode 583 in the case of manufacturing a one-side emission type display device. It is preferable to use a metal, an alloy, an electrically conducting compound, a mixture thereof, or the like which is low in work function (a work function of 3.8 eV or less) as such a conductive material.
Note also that specific examples of the material for the second electrode 583 include elements that belong to Group 1 or 2 of the periodic table of the elements, i.e., alkali metals such as Li and Cs and alkali-earth metals such as Mg, Ca, and Sr, and alloys (Mg:Ag and Al:Li) and compounds (LiF, CsF, and CaF2) containing any of these elements, and transition metals containing rare-earth metals. Further, the second electrode 583 can also be formed of a stacked-layer structure of the above-described material and a metal (including an alloy) such as Al or Ag.
In this manner, a light-emitting element 584 is manufactured. Respective materials for the anode 554, the organic compound layer 582, and the cathode 583 forming the light-emitting element 584 are appropriately selected, and each film thickness is also adjusted. It is preferable that the same material be used for the anode and the cathode and the anode and the cathode have the similar thicknesses, more preferably be as thin as 100 nm.
Further, if necessary, a transparent protective layer 585 which prevents moisture penetration is formed so as to cover the light-emitting element 584 as shown in
In a pixel for green (G), a pixel TFT 544G is connected to a pixel electrode 554G and a hole injecting layer 601G, a hole transporting layer 602G, a light-emitting layer 603G, an electron transporting layer 604G, an electron injecting layer 605G; the cathode 583, and the transparent protective film 585 are formed.
In a pixel for blue (B), a pixel TFT 544B is connected to a pixel electrode 554B, and a hole injecting layer 601B, a hole transporting layer 602B, a light-emitting layer 603B, an electron transporting layer 604B, an electron injecting layer 605B, the cathode 583, and the transparent protective film 585 are formed.
For the light-emitting layer 603R which emits red light, a material such as Alq3:DCM or Alq3:rubrene:BisDCJTM is used. For the light-emitting layer 603G which emits green light, a material such as Alq3:DMQD (N,N′-dimethylquinacridone) or Alq3:coumarin 6 is used. For the light-emitting layer 603B which emits blue light, a material such as α-NPD or tBu-DNA is used.
Next, a sealing material 593 containing a gap material for ensuring substrate spacing is provided over the driver circuit portion 595 including the CMOS circuit 571, and a second substrate 591 is attached to the substrate 501. Also as the second substrate 591, a light-transmitting glass substrate or quartz substrate may be used.
It is to be noted that a drying agent may be disposed as an air gap (an inert gas) in a region 592 of the space between the substrates 501 and 591, below which the pixel portion 596 is provided, or the region 592 may be filled with a transparent sealing material (e.g., an ultraviolet-curing or thermosetting epoxy resin).
Since the pixel electrode 554 and the second electrode 583 of the light-emitting element are formed of light-transmitting materials, light can be extracted from two directions, that is, from both sides of one light-emitting element.
With the panel structure described above, light emission from the top surface can be made substantially equal to light emission from the bottom surface.
Further, optical films (polarizing plates or circularly polarizing plates) 597 and 598 are preferably provided for the substrates 501 and 591 respectively to improve the contrast (see
Note that although the TFTs are top-gate TFTs in this embodiment, the structures thereof are not limited to the structures; a bottom-gate (inversely staggered) TFT or a staggered TFT can also be used as appropriate. In addition, the TFTs are not limited to single-gate TFTs; a multi-gate TFT that has a plurality of channel formation regions, for example, a double-gate TFT may also be employed.
In the light-emitting device in accordance with this embodiment, generation of moisture, gas, or the like from the insulator 581 can be suppressed, thereby a favorable display device with high reliability and long life can be manufactured.
This embodiment can be combined freely with any description of the embodiment mode and Embodiments 1 to 3, if necessary.
In this embodiment, examples of applying the present invention to an inorganic EL element are described with reference to
A light-emitting element utilizing electroluminescence is distinguished by whether a light-emitting material is an organic compound or an inorganic compound; in usual, the former is called an organic EL element and the latter is called an inorganic EL element. Described in Embodiment 4 is the example of using an organic EL element in the present invention.
An inorganic EL element is classified into a dispersion type inorganic EL element and a thin-film type inorganic EL element, depending on its element structure. The former and the latter are different in that the former has an electroluminescence layer where particles of the light-emitting material are dispersed in a binder whereas the latter has an electroluminescence layer formed of a thin film of the light-emitting material. However, the former and the latter have in common that electrons accelerated by a high electric field are necessary.
Note that, as a mechanism of light emission that is obtained, there are donor-acceptor recombination type light emission that utilizes a donor level and an acceptor level, and localized type light emission that utilizes inner-shell electron transition of a metal ion. In usual, in many cases, a dispersion type inorganic EL element exhibits donor-acceptor recombination type light emission, and a thin-film type inorganic EL element exhibits localized type light emission.
The light-emitting material which can be used in the present invention includes a host material and an impurity element to be a light-emission center. By changing the impurity element that is contained, light emission of various colors can be obtained. As a manufacturing method of the light-emitting material, various methods such as a solid phase method and a liquid phase method (a coprecipitation method) can be used. Further, an evaporative decomposition method, a double decomposition method, a method by heat decomposition reaction of a precursor, a reversed micelle method, a method in which such a method is combined with high temperature baking, a liquid phase method such as a lyophilization method, or the like can also be used.
The solid phase method is a method in which a host material, and an impurity element or a compound containing an impurity element are weighed, mixed in a mortar, heated and baked in an electric furnace to be reacted, thereby containing the impurity element in the host material. The baking temperature is preferably 700 to 1500° C. This is because the solid reaction does not progress when the temperature is too low, whereas the host material is decomposed when the temperature is too high. Note that although baking may be performed in a powder state, it is preferable to perform baking in a pellet state. Although baking is necessarily performed at a comparatively high temperature, the solid phase method is easy; thus, the solid phase method is suitable for mass production because of high productivity.
The liquid phase method (a coprecipitation method) is a method in which a host material or a compound containing a host material is reacted with an impurity element or a compound containing an impurity element in a solution, dried, and then baked. Particles of the light-emitting material are distributed uniformly, and the reaction can progress even when the grain size is small and the baking temperature is low.
As the host material used for the light-emitting material, sulfide, oxide, or nitride can be used. As sulfide, for example, zinc sulfide (ZnS), cadmium sulfide (CdS), calcium sulfide (CaS), yttrium sulfide (Y2S3), gallium sulfide (Ga2S3), strontium sulfide (SrS), barium sulfide (BaS), or the like can be used. As oxide, for example, zinc oxide (ZnO), yttrium oxide (Y2O3), or the like can be used. As nitride, for example, aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), or the like can be used.
Further, as the host material used for the light-emitting material, zinc selenide (ZnSe), zinc telluride (ZnTe), or the like can also be used, or alternatively a ternary mixed crystal such as calcium sulfide-gallium (CaGa2S4), strontium sulfide-gallium (SrGa2S4), or barium sulfide-gallium (BaGa2S4) may also be used.
As the light-emission center of localized type light emission, manganese (Mn), copper (Cu), samarium (Sm), terbium (Tb), erbium (Er), thulium (Tm), europium (Eu), cerium (Ce), praseodymium (Pr), or the like can be used. Note that a halogen element such as fluorine (F) or chlorine (Cl) may be added as charge compensation.
On the other hand, as the light-emission center of donor-acceptor recombination type light emission, a light-emitting material containing a first impurity element which forms a donor level and a second impurity element which forms an acceptor level can be used. As the first impurity element, for example, fluorine (F), chlorine (Cl), aluminum (Al), or the like can be used. As the second impurity element, for example, copper (Cu), silver (Ag), or the like can be used.
In the case of synthesizing the light-emitting material of donor-acceptor recombination type light emission by the solid phase method, the host material, the first impurity element or a compound containing the first impurity element, and the second impurity element or a compound containing the second impurity element are each measured, mixed in a mortar, heated and baked in an electric furnace.
As the host material, any of the above described host materials can be used. As the first impurity element or the compound containing the first impurity element, for example, fluorine (F), chlorine (Cl), aluminum sulfate (Al2S3), or the like can be used. As the second impurity element or the compound containing the second impurity element, for example, copper (Cu), silver (Ag), copper sulfide (Cu2S), silver sulfide (Ag2S), or the like can be used.
The baking temperature is preferably 700 to 1500° C. This is because the solid reaction does not progress when the temperature is too low, whereas the host material is decomposed when the temperature is too high. Note that although baking may be performed in a powder state, it is preferable to perform baking in a pellet state.
As the impurity element in the case of utilizing solid reaction, a compound containing the first impurity element and the second impurity element may be combined. In this case, since the impurity element is easily diffused and solid reaction progresses easily, a uniform light-emitting material can be obtained. Further, since an unnecessary impurity element does not enter, a light-emitting material having high purity can be obtained. As the compound containing the first impurity element and the second impurity element, for example, copper chloride (CuCl), silver chloride (AgCl), or the like can be used.
Note that the concentration of these impurity elements may be 0.01 to 10 atomic % with respect to the host material, and is preferably in the range of 0.05 to 5 atomic %.
In the case of a thin-film type inorganic EL element, a light-emitting layer is a layer containing the above light-emitting material, which can be formed by a vacuum evaporation method such as a resistance heating evaporation method or an electron beam evaporation (EB evaporation) method, a physical vapor deposition method (PVD) such as sputtering, a chemical vapor deposition method (CVD) such as an organic metal CVD method or a hydride transport low-pressure CVD method, an atomic layer epitaxy method (ALE), or the like.
For manufacturing light-emitting devices using the light-emitting elements of
Each of the light-emitting elements shown in
Further, although the insulating layer 254 is provided so as to be in contact with the first electrode layer 250 in
In the case of a dispersion type inorganic EL element, particles of a light-emitting material are dispersed in a binder to form an electroluminescent layer film. In the case where particles each having a desired size cannot be sufficiently obtained depending on a manufacturing method of the light-emitting material, processing into particles may be performed by crushing with a mortar or the like. A binder is a substance for fixing the particles of the light-emitting material in the dispersed state, and holding with a form as an electroluminescent layer. The light-emitting material is uniformly dispersed and fixed in the electroluminescent layer by the binder.
In the case of a dispersion type inorganic EL element, the electroluminescent layer can be formed by a droplet discharge method by which an electroluminescent layer can be selectively formed, a printing method (e.g., screen printing or offset printing), a coating method such as spin coating, a dipping method, a dispenser method, or the like. The thickness thereof is not particularly limited; however, it is preferably in a range of 10 to 1000 nm. In addition, in the electroluminescent layer containing the light-emitting material and the binder, the ratio of the light-emitting material is preferably more than or equal to 50 wt % and less than or equal to 80 wt %.
For manufacturing light-emitting devices using the light-emitting elements of
As the binder which can be used in this embodiment, an organic material or an inorganic material can be used, or a mixed material of an organic material and an inorganic material may also be used. As the organic material, a resin such as a polymer having a comparatively high dielectric constant like a cyanoethyl cellulose-based resin, polyethylene, polypropylene, a polystyrene-based resin, a silicone resin, an epoxy resin, or vinylidene fluoride can be used. Further, a heat-resistant high molecule such as aromatic polyamide or polybenzimidazole, or a siloxane resin may also be used.
A siloxane resin corresponds to a resin containing a Si—O—Si bond. Siloxane is composed of a skeleton structure formed by the bond of silicon (Si) and oxygen (O). As a substituent thereof, an organic group containing at least hydrogen (e.g., an alkyl group or aromatic hydrocarbon) is used. Further, a fluoro group may also be used as a substituent. Further, an organic group containing at least hydrogen and a fluoro group may also be used as substituents.
Further, a vinyl resin such as polyvinyl alcohol or polyvinyl butyral, or a resin material such as a phenol resin, a novolac resin, an acrylic resin, a melamine resin, a urethane resin, or an oxazole resin (polybenzoxazole) may also be used. A dielectric constant can also be controlled by mixing the above-described resin with microparticles having a high dielectric constant such as barium titanate (BaTiO3) or strontium titanate (SrTiO3) as appropriate.
As the inorganic material contained in the binder, a material selected from the following can be used: silicon oxide (SiOx), silicon nitride (SiNx), silicon containing oxygen and nitrogen, aluminum nitride (AlN), aluminum containing oxygen and nitrogen or aluminum oxide (Al2O3), titanium oxide (TiO2), BaTiO3, SrTiO3, lead titanate (PbTiO3), potassium niobate (KNbO3), lead niobate (PbNbO3), tantalum oxide (Ta2O5), barium tantalate (BaTa2O6), lithium tantalate (LiTaO3), yttrium oxide (Y2O3), zirconium oxide (ZrO2), zinc sulfide (ZnS), and other substances containing an inorganic material. By mixing the organic material with an inorganic material having a high dielectric constant (by adding or the like), a dielectric constant of the electroluminescent layer containing the light-emitting material and the binder can be further controlled and increased.
In a manufacturing process, the light-emitting material is dispersed in a solution containing a bindel However, as a solvent of the solution containing the binder which can be used in this embodiment, it is preferable to select such a solvent that dissolves a binder material and can make a solution with the viscosity which is suitable for a method for forming the electroluminescent layer (various wet processes) and a desired film thickness. An organic solvent or the like can be used and, for example, in the case where a siloxane resin is used as the binder, propylene glycolmonomethyl ether, propylene glycolmonomethyl ether acetate (also called PGMEA), 3-methoxy-3-methyl-1-butanol (also called MMB), or the like can be used.
Each of the light-emitting elements shown in
Further, although the insulating layer 264 is provided so as to be in contact with the first electrode layer 260 in
Although the insulating layers 254 and 254a and 254b in
For example, silicon oxide (SiO2), yttrium oxide (Y2O3), titanium oxide (TiO2), aluminum oxide (Al2O3), hafnium oxide (HfO2), tantalum oxide (Ta2O5), barium titanate (BaTiO3), strontium titanate (SrTiO3), lead titanate (PbTiO3), silicon nitride (Si3N4), zirconium oxide (ZrO2), or the like, or a mixed film or a staked-layer film of two or more kinds thereof can be used.
Such an insulating film can be formed by sputtering, evaporation, CVD, or the like. Further, the insulating layer may also be formed by dispersing particles of such an insulating material in a binder. The binder material may be formed of the same material and by the same method as the binder contained in the electroluminescent layer. A film thickness of the insulating layer is not particularly limited, and is preferably in the range of 10 to 1000 nm.
Each light-emitting element described in this embodiment, which can emit light when a voltage is applied between the pair of the electrode layers interposing the electroluminescent layer, can be operated either by DC drive or AC drive.
By applying the present invention to an inorganic EL element, generation of gas or moisture from a partition wall (an insulator) can be suppressed. In particular, by preventing moisture which adversely affects an inorganic EL element from being generated, lives of an inorganic EL element and a light-emitting device using the inorganic EL element can be made longer than usual ones.
This embodiment can be combined freely with any description of the embodiment mode and the other embodiments, if necessary.
Electronic equipment to which the present invention is applied includes a camera such as a video camera or a digital camera, a goggle-type display, a navigation system, a sound reproduction device (e.g., a car audio system), a computer, a game machine, a portable information terminal (e.g., a mobile computer, a cellular phone, a portable game machine, or an electronic book), an image reproduction device provided with a recording medium (specifically, a device provided with a display that can reproduce a recording medium such as a Digital Versatile Disc (DVD) and display the image), and the like.
Specific examples of the electronic equipment are shown in
This display panel 301 includes a pixel portion 302 including a plurality of pixels, a scan line driver circuit 303, and a signal line driver circuit 304 which supplies a video signal to a selected pixel. The display panel 301 of the EL module may be manufactured by using the method for manufacturing the display device, which is described in Embodiment 4 or 5.
A television receiver can be completed by the EL module shown in
The audio signal of the signals received by the tuner 321 is transmitted to an audio signal amplifier circuit 325, and output thereof is supplied to a speaker 327 through an audio signal processing circuit 326. A control circuit 328 receives control information of a receiving station (a received frequency) and volume from an input portion 329, and transmits signals to the tuner 321 and the audio signal processing circuit 326.
As shown in
In addition, the device shown in
By using the present invention for each television receiver shown in
It is needless to say that the present invention can be applied not only to the television receiver but also to various uses such as a monitor of a personal computer, an information display panel at a train station, an airport, or the like, and an advertising display panel on a street, particularly as a large-area display medium.
The printed wiring board 352 includes a controller 357, a central processing unit (CPU) 358, a memory 359, a power supply circuit 360, an audio processing circuit 361, a transmitting-receiving circuit 362, and the like. The printed wiring board 352 and the display panel 351 are connected by a flexible printed circuit (FPC) 363. The printed wiring board 352 may also be provided with a capacitor, a buffer circuit, or the like so that noise on a power supply voltage or a signal or delay in signal rising is prevented. Further, the controller 357, the audio processing circuit 361, the memory 359, the CPU 358, the power supply circuit 360, or the like can be mounted on the display panel 351 by using a COG (Chip On Glass) method. The COG method allows the size of the printed wiring board 352 to be reduced.
Various control signals are inputted and outputted through an interface 364 provided for the printed wiring board 352. In addition, an antenna port 365 for transmitting and receiving signals to and from an antenna is provided for the printed wiring board 352.
The power supply circuit 360 supplies power for operating the display panel 351, the controller 357, the CPU 358, the audio processing circuit 361, the memory 359, and the transmitting-receiving circuit 362. In addition, depending on the panel specifications, the power supply circuit 360 may be provided with a current source.
The CPU 358 includes a control signal generating circuit 370, a decoder 371, a register 372, an operational circuit 373, a RAM 374, an interface 379 for the CPU 358, and the like. Various signals inputted to the CPU 358 through the interface 379 are once held in the register 372, and then inputted into the operational circuit 373, the decoder 371, or the like. In the operational circuit 373, operation is performed based on the inputted signals, and locations to which various instructions are transmitted are specified. On the other hand, the signal inputted into the decoder 371 is decoded and inputted into the control signal generating circuit 370. Based on the inputted signal, the control signal generating circuit 370 generates signals including various instructions, and transmits to the locations specified by the operational circuit 373, specifically, the memory 359, the transmitting-receiving circuit 362, the audio processing circuit 361, the controller 357, or the like.
Each of the memory 359, the transmitting-receiving circuit 362, the audio processing circuit 361, and the controller 357 operates in accordance with the received instruction. The operations are briefly described below.
A signal inputted from an input means 375 is transmitted through the interface 364 to the CPU 358 mounted on the printed wiring board 352. The control signal generating circuit 370 coverts image data stored in the VRAM 366 into a predetermined format in accordance with the signal transmitted from the input means 375 such as a pointing device or a keyboard, and transmits to the controller 357.
The controller 357 performs data processing to the signal including the image data transmitted from the CPU 358 in accordance with the panel specifications, and supplies to the display panel 351. In addition, based on a power supply voltage inputted from the power supply circuit 360 and various signals inputted from the CPU 358, the controller 357 generates a Hsync signal, a Vsync signal, a clock signal CLK, an alternating voltage (AC Cont), and a switching signal L/R, and supplies to the display panel 351.
In the transmitting-receiving circuit 362, signals that are as radio waves transmitted and received at an antenna 378 are processed, and specifically, high-frequency circuits such as an isolator, a band pass filter, a VCO (Voltage Controlled Oscillator), an LPF (Low Pass Filter), a coupler, and a balun are included. In the transmitting-receiving circuit 362, a signal including audio information among signals that are transmitted and received is transmitted to the audio processing circuit 361 in accordance with an instruction from the CPU 358.
The signal including the audio information, which has been transmitted in accordance with the instruction of the CPU 358, is demodulated into an audio signal in the audio processing circuit 361, and transmitted to a speaker 377. In addition, an audio signal transmitted from a microphone 376 is modulated in the audio processing circuit 361, and transmitted to the transmitting-receiving circuit 362 in accordance with an instruction from the CPU 358.
The controller 357, the CPU 358, the power supply circuit 360, the audio processing circuit 361, and the memory 359 can be mounted as a package of this embodiment. This embodiment can be applied to any circuit other than high-frequency circuits such as an isolator, a band pass filter, a VCO (Voltage Controlled Oscillator), an LPF (Low. Pass Filter), a coupler, and a balun.
The display panel 351 is connected to the printed board 381 via the FPC 363. Over the printed board 381, a speaker 382, a microphone 383, a transmitting-receiving circuit 384, and a signal processing circuit 385 including a CPU, a controller, and the like are formed. This module is combined with an input means 386, a battery 387, and an antenna 390, and is put in a housing 389. The pixel portion of the display panel 351 is arranged so as to be seen from a window formed in the housing 389.
The cellular phone in accordance with this embodiment can be changed in various modes depending on the function or use thereof. For example, even when the cellular phone is provided with a plurality of panels or the housing is divided into a plurality of parts as appropriate and can be opened and closed with a hinge, the advantageous effect described above can be obtained.
By using the present invention for the cellular phone shown in
By using the present invention, a favorable display with long life and high reliability can be obtained.
By using the present invention, a favorable computer with long life and high reliability can be obtained.
By using the present invention, a favorable computer with long life and high reliability can be obtained.
By using the present invention, a favorable game machine with long life and high reliability can be obtained.
The first display portion 443 mainly displays image information, while the second display portion 444 mainly displays character information. The present invention is applicable to the first display portion 443 and the second display portion 444 with the use of the structures of the EL module shown in
By using the present invention, a favorable image reproduction device with long life and high reliability can be obtained.
For each display device used for the electronic equipment, a heat-resisting plastic substrate can also be used as well as a glass substrate depending on the size, strength, or the intended use, whereby further reduction in weight can be achieved.
Note that the examples shown in this embodiment are just examples, and the present invention it is not limited to these applications.
In addition, this embodiment can be implemented freely in combination with any description of the embodiment mode and the other embodiments.
The present invention can be used for a light-emitting device and a semiconductor device each using an EL element. Generation of gas or moisture is suppressed in a partition wall of the present invention, thereby an adverse effect on a light-emitting layer of an EL element can be prevented. Accordingly, a light-emitting device and a semiconductor device with long life and high reliability can be obtained.
This application is based on Japanese Patent Application Serial No. 2006-127012 filed in Japan Patent Office on 28, Apr. 2006, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-127012 | Apr 2006 | JP | national |
