Patent Application
20100187516
This invention is related to an organic semiconductor device and a method for manufacturing the organic semiconductor device.
With respect to the semiconductor device, it has been generally known that heat which is applied to the device during the manufacturing processes thereof, or hydrogen, hydrogen ion, oxygen and water which were happened to generate due to certain external perturbations exert influences upon the long-term reliability of the semiconductor device. In addition, it has been also known that, even after the manufacturing of the device, hydrogen, hydrogen ion, oxygen and water which were happened to generate due to other certain external perturbations exert influences upon the long-term reliability of the semiconductor device.
Particularly, since the hydrogen is the light weight atom, it can easy reach the interior of the semiconductor device (for instance, a first electrode, an organic functional layer, and a second electrode), and thus it brings an adverse influence to the long-term reliability of the semiconductor device. For instance, on the organic EL element, problems such as the degression in the element's properties and the shortening of the element's lifetime, are caused by the influence of the hydrogen or hydrogen atom. In addition, owing to the growth of the dark spot(s) caused by the influence of the hydrogen or hydrogen atom, the problem that quantity of light which is emitted by the organic EL element becomes lower along the time course, i.e., the progress of non-luminescence, arises.
Furthermore, with respect to the active organic EL, a problem that the invasion of hydrogen brings adverse influences such as fluctuations of VTH in TFT also arises.
Under such a situation, in Patent Literature 1, a technique for preventing the invasion of oxygen and water is disclosed, wherein a protective layer is provided, the protective layer being made of a glass which comprises a glass forming material and glass modifiers of oxide and sulfide which are doped into the glass forming material, and which has a dense structure as compared with that of the glass which includes only the glass forming material.
In Patent Literature 2, a technique that a silicon resistance layer in a silicon device is covered with a Ti (titanium) type barrier metal film so as to absorb hydrogen existing in the silicon resistance layer is disclosed.
Patent Literature 1: JP Hei 11-097169 A
Patent Literature 2: JP 2001-168287 A
However, the protective layer disclosed in Patent Literature 1 is provided by forming a glass which has a dense structure as compared with that of the glass which includes only the glass forming material, and prohibits the invasion of oxygen and water into the device. Although the protective layer can prohibit the invasion of oxygen and water into the device, but it can not prohibit the invasion of hydrogen or hydrogen atom.
In Patent Literature 2, since the Ti type barrier metal film can absorb hydrogen, it protects the device from the invasion of hydrogen temporary. However, because the bond energy between hydrogen and Ti is weak, the barrier metal film tends to cut off the once absorbed hydrogen and release it again. Therefore, the again released hydrogen can invade into the device. Thus, the perfect prohibition of the hydrogen invasion can not be attained.
The present invention is contrived by concerning the above mentioned situations, and it's a main subject is to provide an organic semiconductor device which can protect the respective layers which constitute the device from the invasion of hydrogen or hydrogen ion, and thus which has a long-term reliability, and a method for manufacturing such an organic semiconductor device.
The organic semiconductor device claimed in claim 1 comprises at least a substrate, a first electrode, an organic functional component, and a second layer, which are layered in this order, and which further comprises a hydrogen absorbing layer which is provided onto or above the second layer, wherein the hydrogen absorbing layer comprises one member selected from the group consisting of alkaline metals, alkaline earth metals, metals having a high affinity for hydrogen, and metal compounds including any one of these metals as metal component thereof.
First, the organic semiconductor device according to the present invention will be described concretely with reference to the drawings.
As shown in
Now, the respective layers which constitute the organic semiconductor device 100 will be described sequentially.
As shown in
As material of the substrate 10, there is no particular limitation as far as it can function as the basis, and it can be selected arbitrarily in accordance with the use of the organic semiconductor device intended. Concretely, for instance, glass, silicon oxide, various resins, and so on, can be enumerated.
In addition, the substrate 10 is not necessarily constituted by a single layer (in
Further, with respect to the method for preparing the substrate 10 which is used in the organic semiconductor device according to the present invention, there is no particular limitation and it is able to utilize appropriately any one of known procedures for preparing the substrate.
As shown in
As material of the first electrode 11, there is no particular limitation, and it can be selected arbitrarily from various materials as far as it can function as mentioned above. Concretely, for instance, various metals (including alloys thereof) can be enumerated, and more concretely, Ag (silver), Al (Aluminum), ITO (indium tin oxide), and other various low resistance materials can be enumerated.
The first electrode 11 can be colored or can be a non-colored transparent one depending upon the usage of the organic semiconductor device 100. The thickness of the first electrode 11 is preferably in the range of 10 nm-1000 nm.
Further, with respect to the method for preparing such first electrode 11, there is no particular limitation and it is able to utilize appropriately any one of known procedures for preparing the electrode. Concretely, for instance, the photolithographic patterning method may be mentioned.
As shown in
Generally, the organic functional component 12 may be formed by stacking various kinds of thin layers, and thus, the organic functional component 12 is not necessarily constituted by a single layer (in
As material of the organic functional layer(s) which constitutes the organic functional component 12, there is no particular limitation, and it can be selected arbitrarily from various materials as far as it can function as mentioned above.
Further, with respect to the method for preparing the organic functional layer(s) which constitutes the organic functional component 12, there is no particular limitation and it is able to utilize appropriately any one of known procedures for preparing the organic functional layer(s). Concretely, for instance, when a high molecular organic functional layer is formed, wet coating methods such as spin coating, spin coating, splaying, ink-jet printing, etc., may be utilized. When a low molecular organic layer is formed, vacuum deposition method or the like may be utilized. Alternatively, when the high polymer organic functional layer, the electron hole transporting layer, the organic luminescent layer, the electron injection layer, and the like are stacked in this order, for instance, ohmic-resistance heating deposition method or the like may be adaptable.
As shown in
As material of the second electrode 13, there is no particular limitation, and it can be selected arbitrarily from various materials as far as it can function as mentioned above. Concretely, for instance, various metals (including alloys thereof) which are similar with those described above as for the first electrode 11, and other various low resistance materials can be enumerated.
The second electrode 13 can be colored or can be a non-colored transparent one depending upon the usage of the organic semiconductor device 100. The thickness of the second electrode 13 is preferably in the range of 10 nm-1000 nm.
Further, with respect to the method for preparing such second electrode 13, there is no particular limitation and it is able to utilize appropriately any one of known procedures for preparing the electrode. Concretely, for instance, when aluminum is used for the second electrode, ohmic-resistance heating deposition method for aluminum, or the like, may be adaptable.
As shown in
With respect to the formation of the hydrogen absorbing layer which should perform the functions as mentioned above, we, the inventors have made selection of the material of the hydrogen absorbing layer in consideration of the following points.
Namely, the material of the hydrogen absorbing layer is selected from (1) materials which can absorb hydrogen and hydrogen ion and can not release the absorbed hydrogen or hydrogen ion and (2) materials which have a high absorbing capability against hydrogen and hydrogen ion, and, even when which may release the once absorbed hydrogen or hydrogen ion, which are able to re-absorb them immediately after releasing.
When the hydrogen absorbing layer is formed with any one of the above mentioned materials (1) and (2), it becomes possible to retain the hydrogen or hydrogen ion within the hydrogen absorbing layer as a whole, and thus, the adverse effect of the hydrogen or hydrogen ion against the individual layers which constitutes the organic semiconductor device can be excluded.
First, the materials (1) which can absorb hydrogen and hydrogen ion and can not release the absorbed hydrogen or hydrogen ion as the material of the hydrogen absorbing layer 14 will be described as follows.
In general, when the hydrogen absorbing layer 14 absorbs hydrogen or hydrogen ion, hydride is produced by reacting the material which constitute the hydrogen absorbing layer 14 with the hydrogen or hydrogen ion.
Herein, the hydride which is produced from the material which constitute the hydrogen absorbing layer 14 with the hydrogen or hydrogen ion reduces its tendency to release the hydrogen or hydrogen atom absorbed in the hydrogen absorbing layer 14 as the binding energy of the hydride becomes higher. Therefore, it is preferable that the hydrogen absorbing layer 14 of the organic semiconductor device according to the present invention is that of contributing a high binding energy of the hydride which is formed when the hydrogen or hydrogen ion is absorbed into the hydrogen absorbing layer 14. Concretely, it is preferable that the hydrogen absorbing layer 14 is made of a material which contributes a high binding energy of the hydride.
As the material of the hydrogen absorbing layer 14 which can contribute such a function, metals or metal compounds are desirable. Further, metals or metal compounds which can produce the hydride via ionic bond(s) with the hydrogen(s) or hydrogen ion(s), wherein the hydride thus produced becomes an ionic hydride, are more desirable.
Since the ionic hydride which is produced by ionic bond possesses a high binding energy and thus it becomes stable, it become possible to retain the hydrogen even at a high temperature region. Thus, the hydrogen or hydrogen ion once absorbed in the hydrogen absorbing layer 14 is never released.
As such a metal or metal compound which bonds to hydrogen(s) or hydrogen(s) ion via ionic bond(s) and thereby forms an ionic hydride, alkaline metals and alkaline earth metals, as well as metal compounds which include one of such metals as one component are enumerated concretely. These metals form ionic bond(s) with hydrogen(s), and produce ionic hydride.
2MI+H2→2MIH MI=alkaline metal
MII+H2→MIIH2 MII=alkaline earth metal
As the alkaline metal, for instance, Li (lithium), Na (Sodium), K (potassium), Rb (rubidium), Cs (cesium), etc., are enumerated, and as the alkaline earth metal, for instance, Be (beryllium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium), etc., are enumerated. Further, as the metal compound which includes one of such metals, for instance, LiF (lithium fluoride), Li2O (lithium oxide), CaO (calcium oxide), BaO (barium oxide), BaF2 (barium fluoride), CaF2 (calcium fluoride), etc., are enumerated.
Further, the binding energy of the hydride is dominated by the heat of formation (standard enthalpy of formation), ΔH, of the hydride, and the binding energy of the hydride becomes higher as the ΔH value becomes lower.
Thus, it is preferable that the hydrogen absorbing layer 14 is made of a material which provides a lower value of heat of formation (standard enthalpy of formation), ΔH, of the hydride which is formed when the hydrogen absorbing layer 14 absorbs hydrogen or hydrogen ion. More concretely, it is preferable that the hydrogen absorbing layer 14 is made of a material which provides a value of heat of formation (standard enthalpy of formation), ΔH, of the hydride being not more than −90 kJ/mol.
As the material which constitutes the hydrogen absorbing layer 14 with providing such a heat of formation (standard enthalpy of formation), ΔH, value, for instance, Li (lithium), Ba (barium), Ca (calcium), etc., are enumerated. As the metal compound which includes one of such metals, for instance, LiF (lithium fluoride), Li2O (lithium oxide), Cao (calcium oxide), BaO (barium oxide), BaF2 (barium fluoride), CaF2 (calcium fluoride), etc., are enumerated.
When such a material which constitutes the hydrogen absorbing layer and hydrogen or hydrogen ion are bonded mutually, the hydride which has a value of heat of formation (standard enthalpy of formation), ΔH, being not more than −90 kJ/mol, such as LiH (lithium hydride), BaH2 (barium hydride), CaH2 (calcium hydride), etc., is formed.
Next, the materials (2) which have a high absorbing capability against hydrogen and hydrogen ion, and, even when which may release the once absorbed hydrogen or hydrogen ion, which are able to re-absorb them immediately after releasing, will be described as follows.
As the material of the hydrogen absorbing layer 14 which can contribute such a function, metals or metal compounds are desirable. Further, metals or metal compounds which has a high affinity for hydrogen are more desirable. As such a metal having a high affinity for hydrogen, for instance, Pd (palladium), Fe (iron), Mn (manganese), La (lanthanum), Zr (zirconium), Sc (scandium), Y (yttrium), etc., are enumerated, and as the metal compound which includes one of such metals, for instance, MnO2 (manganese dioxide), Fe2O3 (iron oxide), La2O3 (lanthanum oxide), etc., are enumerated. Since such metals and metal compound has a high affinity for hydrogen or hydrogen ion, they absorb hydrogen or hydrogen ion with ease, and produce metal hydrides by forming bond(s) between the metal and such absorbed hydrogen or hydrogen ion. Therefore, when adapting a metal or metal compound which has a high affinity for hydrogen or hydrogen ion as the material of the hydrogen absorbing layer 14, it becomes possible to retain the hydrogen or hydrogen ion within the hydrogen absorbing layer, even when which may release the once absorbed hydrogen or hydrogen ion, which are able to re-absorb them immediately after releasing.
In either case of using the above mentioned material (1) or material (2), there is no particular limitation for the shape or configuration of the hydrogen absorbing layer 14, and the hydrogen absorbing layer 14 may be provided at any position as far as the hydrogen or hydrogen ion can be absorbed efficiently at the position.
Herein, in the organic functional device 100, when it has a layered structure wherein, for example, the first electrode 11, the organic functional component 12, and the second electrode are stacked in this order as shown in
When the hydrogen absorbing layer is provided not only to cover the surface of the second electrode 13 but also to have an area larger than the second electrode 13, i.e., to cover also the flank sides of the layered structure, it becomes possible to repress efficiently the influence of hydrogen or hydrogen ion which is generated when plasma etching or the like is employed in the manufacturing process of the organic semiconductor device and which goes around the flank sides of the layered structure.
In addition, the hydrogen absorbing layer 14 made of the above mentioned material can also be allowed to function as a mask on the plasma etching treatment. It is because the hydrogen absorbing layer 14 made of a metal or metal compound as described above has a predominant resistance to the plasma as compared to the other thin layers (e.g., organic functional component 12) in the organic semiconductor device 100. When the hydrogen absorbing layer 14 is intended to function also as the mask on the case of performing the plasma etching, the hydrogen absorbing layer 14 should be formed on and at a part other than the part to be removed by the plasma etching treatment (i.e., the part to be remained after the plasma etching).
The thickness of the hydrogen absorbing layer 14 may be set appropriately within a range that does not disturb the function of being able to absorb the hydrogen or hydrogen ion and not to release the absorbed hydrogen or hydrogen ion, regardless whether the adopted is the material (1) or (2).
Meanwhile, when the hydrogen absorbing layer 14 is also intended to function as the mask for the plasma etching treatment, the hydrogen absorbing layer should be designed so as to have a thickness which can not be consumed down to a dysfunctional thickness as the mask until the plasma etching is completed, and the thickness remained after the etching is laid within a range that does not disturb the function of being able to absorb the hydrogen or hydrogen ion and not to release the absorbed hydrogen or hydrogen ion.
In either case of using the above mentioned material (1) or material (2), there is no particular limitation for the method of forming the hydrogen absorbing layer, and any one of known procedures for preparing such a layer can be utilized. Concretely, for instance, the plasma etching method, the sputtering method, the vacuum deposition method and so on can be exemplified.
As shown in
As material of the protective layer 15, there is no particular limitation, and it can be selected arbitrarily from various materials as far as it can function as mentioned above. Concretely, for instance, various insulation films can be mentioned. More concretely, SiN (silicon nitride) film, SiON (silicon oxynitride), glass, SiO2 (silicon oxide), and so on, are enumerated.
With respect to the shape or configuration of the protective layer 15 in the organic semiconductor device according to the present invention, there is also no particular limitation, and the protective layer 15 may be formed so as to cover the whole of the organic semiconductor device 100, as shown in
With respect to the thickness of the protective layer 15, there is no particular limitation for the present invention, and thus it can be set arbitrarily as far as it can function as mentioned above. For instance, a thickness of 100 nm-10 μm is usually adopted for the protective layer 15.
As a typical method for forming such a protective layer 15, the plasma CVD method can be mentioned. The plasma CVD method has been generally used for the preparation of protective film for various electrical devices. In order to prevent the hydrogen invasion into the device, wherein the hydrogen will be generated during the plasma film formation, a process capable of decreasing the hydrogen quantity in the film to be formed, particularly, under a low temperature (not more than 200° C.) condition, has been sought for. However, in the plasma CVD process using monosilane and ammonium, and, in the plasma CVD process using monosilane and nitrogen, hydrogen is compelled to generate because of the ion elimination under thermal or plasma film forming condition, as shown in the following expressions (3) and (4), respectively. The generated hydrogen tends to invade easily into the interior of the device.
3SiH4+4NH3→Si3N4+12H2 (3)
3SiH4+2N2→Si3N4+6H2 (4)
Even when such hydrogen generates during the protective film forming process by the plasma CVD method, the hydrogen absorbing layer 14 according to the present invention can play a role of absorbing the hydrogen thus generated and not releasing once trapped hydrogen, and therefore, the hydrogen thus generated does not invade into the interior of the device. Furthermore, the hydrogen absorbing layer 14 also plays a role of a buffer layer (stress relaxation layer) on the formation of above mentioned protective layer 15.
Although the plasma CVD method has been mentioned as a typical method for forming the protective layer in the above description, the method for forming the protective layer is not limited to this method. Other CVD methods such as thermal CVD, Cat-CVD (Catalytic CVD), LPCVD (Low Pressure CVD), photo CVD, APCVD (Atmospheric Pressure CVD), laser CVD, RTPCVD (Rapid Thermal Pressure CVD) may be adaptable. Further, the protective layer of the sealing can type may be prepared. When the sealing can type protective layer is formed, the protective layer can play a role of absorbing hydrogen or hydrogen ion existing in the interior of the sealing can after the formation of the protective layer.
Since the respective layers which constitute the organic semiconductor device 200 in this embodiment shown in
As shown in
The organic semiconductor device according to the present invention can be also used for various usages in addition to such a panel with division wall 16. Concretely, for instance, organic EL, organic EL display, organic solar cell, organic transistor, semiconductor laser, etc., are enumerated.
When the organic semiconductor device according to the present invention is constructed as a top emission type (i.e., the configuration of taking light out in an upward direction) organic EL, it is preferable that the visible light transmittance through the hydrogen absorbing layer is high. Concretely, the visible light transmittance of the hydrogen absorbing layer is preferably to be not less than 80%.
Next, the method for manufacturing the organic semiconductor device according to the present invention will be explained specifically with reference to the drawings.
As illustrated in
Now, the respective steps will be described in detail.
Herein, because the respective layers which constitute the organic semiconductor device in the respective steps are the same as mentioned above, the explanations thereof are omitted.
As shown in
As shown in
As shown in
As shown in
Concretely, this step S4 is the etching step where the unnecessary part of the organic functional component 32 in the organic semiconductor device is etched out. More specifically, for instance, at the part corresponding to the lead-out part for the electrode, or the like, the organic functional component 32, and optionally, other layers is etched out.
As described above, the hydrogen absorbing layer 34 plays a role of absorbing hydrogen or hydrogen ion and not releasing the absorbed hydrogen or hydrogen ion. Further, the hydrogen absorbing layer 34 made of a metal or metal compound also plays a role of a protective mask which is used when the organic functional component 32 is processed to a prescribed shape, in addition to the former role. It is because the hydrogen absorbing layer 34 made of the metal or metal compound has a predominant resistance to the plasma as compared to the organic functional component 32.
During this step, the organic functional component 32 located at a part on which the hydrogen absorbing layer 34 has not been formed is selectively and gradually etched and removed out. Finally, the organic functional component 32 can be patterned into the prescribed shape.
As the etching method utilized in this method according to the present invention, there is no particular limitation as far as it can etch predominantly the organic functional component over the hydrogen absorbing layer. Thus, various procedures known in the art may be adaptable. A concrete example of such an etching method, for instance, a method, wherein a mixture gas in which a rare gas (e.g., Ar or Kr) is added to oxygen is used, oxygen plasma is created by RF discharge, and thus formed plasma is used for etching, can be exemplified. Although a mixture gas of oxygen and a rare gas (e.g., Ar or Kr) is used in the above example, a sole oxygen gas is also usable, and a sole rare gas is usable, too. The plasma discharge may be formed by using a capacitive coupling type, anode coupling or cathode coupling. In such cases, there is no particular limitation with respect to the gas species and the plasma discharge mode, and any one of various methods known in the art may be adaptable.
Herein, the hydrogen absorbing layer 34 must retain the functions of absorbing hydrogen or hydrogen ion, of not releasing the absorbed hydrogen or hydrogen ion, even after the etching. Therefore, it is necessary that the hydrogen absorbing layer 34 remains as the mask until the etching of the organic functional component 32 is completed, and leaves a thickness within a range that does not disturb the function of being able to absorb the hydrogen or hydrogen ion and not to release the absorbed hydrogen or hydrogen even after the etching process. Therefore, the thickness of the hydrogen absorbing layer 34 can be varied arbitrarily depending on the kind and thickness of the organic functional component 32 as the target of etching, or other factors.
This step is the step S5 at which the protective layer 35 is provided so as to cover the organic semiconductor device after the above mentioned fourth step S4. In the case of providing the protective layer 35, the hydrogen absorbing layer used in the fourth step can play a role of absorbing hydrogen or hydrogen ion and not releasing the absorbed hydrogen or hydrogen ion, as well as a role of a buffer layer (stress relaxation layer, plasma damage protecting layer) on the formation of the protective layer.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/063146 | 6/29/2007 | WO | 00 | 12/28/2009 |
