JP2004054261A - Light emission display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the secular degradation of a thin film transistor in a current light emitting element which is driven by thin film transistors. <P>SOLUTION: In the light emission display device, at least one of transistors constituting a pixel circuit is defined as a p-channel type transistor. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light emitting device including a light emitting element such as an organic electroluminescence (hereinafter, referred to as EL) element and a method for manufacturing the same.
[0002]
[Prior art]
The inventors of the present invention have scrutinized a thin film transistor driven organic EL display element. As a result, the following was found.
[0003]
(1) In a thin film transistor driven organic EL display element, since the organic EL display element is a direct current element, a direct current also flows through a thin film transistor inserted in series to control the same.
[0004]
(2) Thin film transistors are classified into an n-channel type and a p-channel type. The n-channel type and the p-channel type have very different aspects of deterioration over time.
[0005]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to suppress the deterioration over time of a thin film transistor in a current light emitting element driven by the thin film transistor.
[0006]
[Means for Solving the Problems]
A first light-emitting display device of the present invention is a light-emitting display device including a scanning line, a data line, and a pixel, wherein the pixel has a first conductive state controlled by a potential of the scanning line. A transistor, a storage capacitor that holds an image signal supplied from the data line via the first transistor, and a second transistor that controls conduction between a pixel electrode and a common electrode by a potential of the storage capacitor. A light-emitting element between the pixel electrode and the counter electrode, wherein at least one of the first transistor and the second transistor is a p-channel transistor.
[0007]
A second light-emitting display device according to the present invention is a light-emitting display device including a scan line, a data line, and a pixel, wherein the pixel has a first conductive state controlled by a potential of the scan line. A transistor, a storage capacitor that holds an image signal supplied from the data line via the first transistor, and a second transistor that controls conduction between a pixel electrode and a common electrode by a potential of the storage capacitor. A light-emitting element between the pixel electrode and the counter electrode, wherein the second transistor is a p-channel transistor.
[0008]
A third light-emitting display device according to the present invention is a light-emitting display device including a scanning line, a data line, and a pixel, wherein the pixel is controlled to be conductive by a potential of the scanning line. A transistor, a light-emitting element between a pixel electrode and a counter electrode, a storage capacitor for holding an image signal supplied from the data line through the first transistor, and a light-emitting element between the pixel electrode and a common line. And a second transistor inserted in series with the second transistor, wherein at least one of the first transistor and the second transistor is a p-channel transistor.
[0009]
A fourth light-emitting display device of the present invention is a light-emitting display device including a scanning line, a data line, and a pixel, wherein the pixel is controlled to be conductive by a potential of the scanning line. A transistor, a light-emitting element between a pixel electrode and a counter electrode, a storage capacitor for holding an image signal supplied from the data line through the first transistor, and a light-emitting element between the pixel electrode and a common line. And a second transistor inserted in series with the second transistor, wherein the second transistor is a p-channel transistor.
[0010]
A fifth display device of the present invention is a light-emitting display device including a scanning line, a data line, and a pixel, wherein the pixel has a first transistor whose conduction is controlled by a potential of the scanning line. A storage capacitor for storing an image signal supplied from the data line via the first transistor; a second transistor for controlling conduction between a pixel electrode and a common electrode by a potential of the storage capacitor; A light-emitting element between a pixel electrode and a counter electrode, wherein the first transistor and the second transistor are an n-channel transistor and a p-type transistor, respectively.
[0011]
A sixth light emitting display device according to the present invention includes a substrate, a plurality of scanning lines provided on the substrate, a plurality of data lines provided on the substrate, the plurality of scanning lines, and the plurality of data. A plurality of pixels provided in a matrix by intersecting lines, and a scan line driving circuit provided on the substrate, for outputting a scan signal to the plurality of scan lines; and Each includes a first transistor whose conduction is controlled by the scanning signal, a storage capacitor for holding an image signal supplied from the data line via the first transistor, and a pixel which is driven by a potential of the storage capacitor. A second transistor that controls conduction between an electrode and a common electrode; and a light-emitting element between the pixel electrode and a counter electrode. At least one of the first transistor and the second transistor includes p It is Yaneru type transistors, and wherein.
[0012]
In the above light emitting display device, it is preferable that the scanning side driving circuit includes a transistor, and the transistor is a thin film transistor together with the first transistor and the second transistor.
[0013]
In the above light-emitting display device, it is preferable that at least one of the first transistor and the second transistor and a thin film transistor included in the scan driver circuit are formed in the same step.
[0014]
A seventh light emitting display device according to the present invention includes a substrate, a plurality of scanning lines provided on the substrate, a plurality of data lines provided on the substrate, the plurality of scanning lines and the plurality of data. A plurality of pixels provided in a matrix by intersection of lines, and a scan-side drive circuit provided on the substrate, which outputs a scan signal to the plurality of scan lines, and a plurality of data lines A data-side driving circuit provided on the substrate, wherein each of the plurality of pixels has a first transistor whose conduction is controlled by the scanning signal; and A storage capacitor that holds an image signal supplied from the data line via a transistor, a second transistor that controls conduction between a pixel electrode and a common electrode by a potential of the storage capacitor, and a pixel electrode and a counter electrode. Between Wherein the optical element, the at least one of the first transistor and the second transistor being a p-channel transistor, and wherein.
[0015]
In the above light emitting display device, it is preferable that the data side driving circuit and the scanning side driving circuit include a transistor, and the transistor is a thin film transistor together with the first transistor and the second transistor.
[0016]
In the above light-emitting display device, a thin film transistor included in the scan side driver circuit and the data side driver circuit and at least one of the first transistor and the second transistor are formed in the same step. Is preferred.
[0017]
An eighth light emitting display device according to the present invention includes a substrate, a plurality of scanning lines provided on the substrate, a plurality of data lines provided on the substrate, the plurality of scanning lines, and the plurality of data. A plurality of pixels provided in a matrix by crossing lines, and a driver circuit provided on the substrate, for outputting a signal to the plurality of scanning lines or the plurality of data lines; Each of the pixels has a first transistor of which conduction is controlled by the scanning signal, a storage capacitor for holding an image signal supplied from the data line via the first transistor, and a potential of the storage capacitor. A second transistor that controls conduction between the pixel electrode and the common electrode, and a light-emitting element between the pixel electrode and the counter electrode, wherein a small number of the first transistor and the second transistor are provided. Both it One is a p-channel transistor, and wherein.
[0018]
In the above light-emitting display device, at least one of the first transistor and the second transistor is a p-channel thin film transistor; the driving circuit includes a thin film transistor; the thin film transistor includes the p-channel thin film transistor; It is preferable that they are formed by the same process.
[0019]
In the above light-emitting display device, the driving circuit includes a complementary thin film transistor, and the first transistor and the second transistor are an N-channel thin film transistor and a P-channel thin film transistor, respectively. And
[0020]
In the above method for manufacturing a light emitting display device, an N-channel thin film transistor of the complementary thin film transistor is formed by the same process as that of the first transistor, and a P-channel thin film transistor of the complementary thin film transistor is formed with the second transistor. It is characterized by being formed by the same process. According to this, it is possible to provide a high-performance light-emitting display device with little deterioration over time without increasing the number of manufacturing steps.
[0021]
(1) The present invention further provides a current-driven light-emitting display device in which a plurality of scanning lines and a plurality of data lines are formed, and a thin film transistor and a current light-emitting element are formed at each intersection of the scanning lines and the data lines. Wherein at least one of the thin film transistors is a p-channel thin film transistor.
[0022]
According to the above invention, it is possible to suppress deterioration of the thin film transistor over time.
[0023]
(2) Further, according to the present invention, a plurality of scanning lines, a plurality of data lines, a common electrode, and a counter electrode are formed, and a first thin film transistor, a second thin film transistor, and a holding device are provided corresponding to each intersection of the scanning line and the data line. A capacitor, a pixel electrode, and a current light emitting element are formed, the first thin film transistor controls conduction between a data line and a storage capacitor according to a potential of a scanning line, and the second thin film transistor controls a common electrode according to a potential of the storage capacitor. In the current-driven light-emitting display device that controls the current flowing through the current light-emitting element between the pixel electrode and the counter electrode by controlling conduction between the pixel electrode and the counter electrode, the second thin film transistor is a p-channel thin film transistor. Features.
[0024]
(3) Further, in the above invention, a drive circuit for driving the light emitting element is formed on the substrate together with the plurality of scanning lines, the plurality of data lines, the thin film transistor, and the current light emitting element. That is, it is preferable that the p-channel thin film transistor is formed by the same process as the thin film transistor in the drive circuit.
[0025]
In the above invention, it is preferable that the thin film transistor is a polysilicon thin film transistor.
[0026]
Further, in the above invention, the driving circuit is formed of a complementary thin film transistor, the first thin film transistor and the N-channel thin film transistor in the driving circuit are formed in the same process, and the second thin film transistor and the driving circuit are formed in the same manner. It is preferable that the p-channel thin film transistor is formed by the same process.
[0027]
According to this, it is possible to provide a high-performance current-driven light-emitting display device that does not deteriorate with time without increasing the number of manufacturing steps.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
(Overall structure of organic EL display element)
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a central portion on the substrate 1 is a display unit. A data-side driving circuit 3 that outputs an image signal to the data line 112 is formed on the upper side of the outer peripheral portion of the transparent substrate 1 as viewed in the drawing, and a scanning line 111 is formed on the left side as viewed in the drawing. A scanning side driving circuit 4 that outputs a scanning signal is configured. In these driving circuits 3 and 4, an N-type thin film transistor and a P-type thin film transistor constitute a complementary TFT, and the complementary thin film transistor constitutes a shift register circuit, a level shifter circuit, an analog switch circuit and the like.
[0029]
A plurality of scanning lines 111 and a plurality of data lines 112 extending in a direction intersecting with the extending direction of the scanning lines 111 are formed on the transparent substrate 1. The pixels 7 are configured in a matrix by the intersection with.
[0030]
Each of the pixels 7 includes a first thin film transistor (hereinafter, referred to as a switching thin film transistor) 121 to which a scanning signal is supplied to a gate electrode 21 (first gate electrode) via a scanning line 111. One of the source / drain regions of the switching thin film transistor 121 is electrically connected to the data line 112, and the other source / drain region is electrically connected to the potential holding 113. Further, a common line 114 is arranged in parallel with the scanning line 111, and a storage capacitor 123 is formed between the common line 114 and the potential holding electrode 113. The common line is kept at a constant potential. Therefore, when the switching thin film transistor 121 is turned on by being selected by the scanning signal, an image signal is written from the data line 112 to the storage capacitor 123 via the switching thin film transistor.
[0031]
A gate electrode of a second thin film transistor (hereinafter, referred to as a current thin film transistor) 122 is electrically connected to the potential holding electrode 113, and one of a source / drain region of the current thin film transistor 122 is electrically connected to a common line 114. On the other hand, the other source / drain region is electrically connected to one electrode 115 of the light emitting element 131. When the current thin film transistor 122 is turned on, the current of the common line 114 flows through the current thin film transistor 122 to the light emitting element 131 such as an organic EL display element, and the light emitting element 131 emits light. In this configuration, one electrode of the storage capacitor is connected to the common line 114. However, the storage capacitor may be connected to the common line 114 without being connected to the common line 114. Good. Further, one electrode of the storage capacitor may be connected to an adjacent gate line.
(Example 1)
FIG. 1 is an equivalent circuit diagram of an organic EL display device including the thin film transistor according to the first embodiment of the present invention. FIG. 2 is a driving voltage diagram of the organic EL display device including the thin film transistor according to the first embodiment of the present invention. FIG. 3 is a current-voltage characteristic diagram of the current thin film transistor according to the first embodiment of the present invention, and FIG. 4 is a current-voltage characteristic diagram of the organic EL display element according to the first embodiment of the present invention.
[0032]
In FIG. 1, 111 is a scanning line, 112 is a data line, 113 is a holding electrode, 114 is a common line, 115 is a pixel electrode made of Al, 116 is a counter electrode made of ITO, 121 is a switching thin film transistor, 122 Is an n-channel type current thin film transistor, 123 is a storage capacitor, 131 is an organic EL display element that emits light by current flowing from the power supply line 116 toward the pixel electrode 115 (hereinafter, referred to as a positive organic EL display element) 13, 141. This is the direction of the current of the organic EL display element.
[0033]
2, reference numeral 211 denotes a scanning potential, 212 denotes a signal potential, 213 denotes a holding potential, 214 denotes a common potential, 215 denotes a pixel potential, and 216 denotes a counter potential. Note that FIG. 2 shows only a part of each potential in order to explain the relationship between the potentials. The potential of the scanning line 111 is the scanning potential 211, the potential of the data line 112 is the signal potential 212, the potential of the holding electrode 113 is the holding potential 213, the potential of the common line 114 is the common potential 214, and the potential of the pixel electrode 115 formed of Al. Corresponds to the pixel potential 215, and the potential of the counter electrode 116 formed of ITO (Indium Tin Oxide) corresponds to the counter potential 216. FIG. 2 schematically and partially shows each signal potential.
[0034]
Reference numeral 221 denotes a period in which the pixel is in a display state, and a current flows through the organic EL display element 131 to emit light. Reference numeral 222 denotes a period in which the pixel is in a non-display state, in which a current flows through the organic EL display element 131. Does not flow and does not emit light.
[0035]
4, reference numeral 31 denotes a current-voltage characteristic of the n-channel current thin film transistor 122 when the drain voltage is 4 V, and 32 denotes a current-voltage characteristic of the n-channel current thin film transistor 122 when the drain voltage is 8 V. At either drain voltage, when the gate voltage is low, the n-channel current thin film transistor 122 is turned off, a small drain current flows, the source-drain resistance becomes high, and when the gate voltage is high, n It can be seen that the channel type current thin film transistor 122 is turned on, a large drain current flows, and the resistance between the source and the drain becomes low.
[0036]
In FIG. 5, reference numeral 4 denotes a current-voltage characteristic of the organic EL display element 131. Here, the voltage represents a counter potential 216 with respect to the pixel potential 215, and the current represents a current flowing from the counter electrode 116 to the pixel electrode 115. When the threshold voltage is equal to or lower than a certain threshold voltage, the positive organic EL display element 131 is turned off, has high resistance, does not flow current, and does not emit light. When the voltage is equal to or higher than the threshold voltage, the transistor is turned on, a current flows with low resistance, and light is emitted. Here, the threshold voltage is approximately 2V.
[0037]
The operation of the organic EL display device including the thin film transistor of the present embodiment will be described with reference to FIGS. 2, 3, 4, and 5.
[0038]
The switching thin film transistor 121 controls conduction between the data line 112 and the holding electrode 113 in accordance with the potential of the scanning line 111. That is, conduction between the signal potential 212 and the holding potential 213 is controlled by the scanning potential 211. Here, the switching thin film transistor 121 is an n-channel thin film transistor, but may be a p-channel thin film transistor.
[0039]
In the period 221 in which the pixel is in the display state, the signal potential 212 is at a high potential, and the high potential is held in the holding potential 213. During the period 222 in which the pixel is in the non-display state, the signal potential 212 becomes low, and the low potential is held in the holding potential 213.
[0040]
The n-channel current thin film transistor 122 has the characteristics shown in FIG. 3, and controls the conduction between the common line 114 and the pixel electrode 115 by the potential of the holding electrode 113. That is, conduction between the common potential 214 and the pixel potential 222 is controlled by the holding potential 213. The holding potential 213 is at a high potential during the period 221 in which the pixel is in the display state, so that the common line 114 and the pixel electrode 115 are conducted, and the holding potential 213 is in the period 222 in which the pixel is in the non-display state. Since 213 has a low potential, the common line 114 and the pixel electrode 115 are disconnected.
[0041]
The organic EL display element 131 has the characteristics shown in FIG. 5, and a current flows between the pixel electrode 115 and the counter electrode 116 during a period 221 when the pixel is in a display state, and the organic EL display element 131 emits light. During a period 222 in which the pixel is in a non-display state, no current flows and no light is emitted.
[0042]
FIG. 6A is a cross-sectional view of a thin film transistor organic EL display element (pixel) according to an embodiment of the present invention, and FIG. 6B is a cross-sectional view of a thin film transistor organic EL display element (one pixel) according to an embodiment of the present invention. It is a top view. The cross section AA ′ in FIG. 6A corresponds to the cross section AA ′ in FIG.
[0043]
In FIG. 5, 132 is a hole injection layer, 133 is an organic EL layer, and 151 is a resist.
[0044]
Here, regarding the switching thin film transistor 121 and the n-channel type current thin film transistor 122, the structure and process of the low-temperature polysilicon thin film transistor used in the thin film transistor liquid crystal display element, that is, the top gate structure and the process at the maximum temperature of 600 ° C. or less Although used, other structures and processes may be used.
[0045]
A positive organic EL display element 131 is formed by the pixel electrode 115 formed of Al, the counter electrode 116 formed of ITO, the hole injection layer 132, and the organic EL layer 133. In the normal organic EL display element 131, the current direction 141 of the organic EL display element can be set to the direction from the counter electrode 116 formed of ITO to the pixel electrode 115 formed of Al. Note that the organic EL display element is not limited to the structure used here, but may have another structure as long as the current direction 141 of the organic EL display element can be directed from the counter electrode to the pixel electrode. I don't care.
[0046]
Here, the hole injection layer 132 and the organic EL layer 133 are formed by an inkjet printing method using a resist 151 as a separation structure between pixels, and the counter electrode 116 formed of ITO is formed by a sputtering method. It is formed, but other methods may be used.
[0047]
In this embodiment, the common potential 214 is lower than the counter potential 216. The current thin film transistor is the n-channel type current thin film transistor 122.
[0048]
In a period 221 in which a pixel is in a display state, the n-channel current thin film transistor 122 is in an on state. The current flowing through the positive organic EL display element 131, that is, the on-current of the n-channel current thin film transistor 122 depends on the gate voltage as shown in FIG. Here, the gate voltage is a potential difference between the holding potential 213 and the lower one of the common potential 214 and the pixel potential 215. According to the present embodiment, since the common potential 214 is lower than the pixel potential 215, the gate voltage is the potential difference between the holding potential 213 and the common potential 214. Since this potential difference can be made sufficiently large, a sufficiently large ON current can be obtained. Note that the on-state current of the n-channel current thin film transistor 122 also depends on the drain voltage, but the conclusion here does not change.
[0049]
Conversely, in order to obtain a necessary on-current, the holding potential 213 can be made lower, so that the amplitude of the signal potential 212 and, consequently, the amplitude of the scanning potential 211 can be reduced. That is, in the switching thin film transistor 121 and the n-channel current thin film transistor 122, the drive voltage can be reduced without deteriorating image quality, abnormal operation, or lowering the operable frequency.
Further, in this embodiment, the signal potential 212 for the pixel to be displayed is lower than the counter potential 216.
[0050]
As described above, in the period 221 when the pixel is in the display state, the on-state current of the n-channel current thin film transistor 122 depends on the potential difference between the holding potential 213 and the common potential 214, and the potential difference between the holding potential 213 and the opposite potential 216. Does not depend directly on Therefore, the holding potential 213, that is, the signal potential 212 for the pixel to be in the display state can be made lower than the opposite potential 216 while securing a sufficiently large on-state current in the n-channel type current thin film transistor 122. Thus, the amplitude of the signal potential 212 and the amplitude of the scanning potential 211 can be reduced. That is, in the switching thin film transistor 121 and the n-channel current thin film transistor 122, the drive voltage can be reduced without deteriorating image quality, abnormal operation, or lowering the operable frequency.
[0051]
Further, in this embodiment, the signal potential 212 for the pixel to be in the non-display state is higher than the common potential 214. When the signal potential 212 is slightly higher than the common potential 214 in the period 222 in which the pixel is in the non-display state, the n-channel current thin film transistor 122 is not completely turned off. However, the resistance between the source and the drain of the n-channel type current thin film transistor 122 becomes considerably high as shown in FIG. For this reason, the pixel potential 215 is determined by dividing the common potential 214 and the counter potential 216 by the resistance of the n-channel type current thin film transistor 122 and the resistance of the positive organic EL display element 131. Potential.
[0052]
The voltage applied to the positive organic EL display element 131 is a potential difference between the pixel potential 215 and the counter potential 216. As shown in FIG. Does not emit light. That is, the signal potential 212 is slightly higher than the common potential 214 and the n-channel current thin film transistor 122 is completely turned off by using the threshold voltage of the EL display element 131 which is placed right. It is possible to prevent the positive value organic EL display element 131 from emitting light even if it does not enter the state.
[0053]
Here, by setting the signal potential 212 for a pixel to be in a non-display state to be higher than the common potential 214, the amplitude of the signal potential 212 and thus the amplitude of the scanning potential 211 can be reduced. . That is, in the switching thin film transistor 121 and the n-channel current thin film transistor 122, the drive voltage can be reduced without deteriorating image quality, abnormal operation, or lowering the operable frequency.
[0054]
The operation of the organic EL display device including the thin film transistor of the present embodiment is not simple as described above, but operates under a more complicated relationship between voltage and current, but approximately and qualitatively as described above. Holds.
(Example 2)
FIG. 7 is an equivalent circuit diagram of an organic EL display device including the thin film transistor according to the second embodiment of the present invention. FIG. 7 is a driving voltage diagram of the organic EL display device including the thin film transistor according to the second embodiment of the present invention. FIG. 8 is a current-voltage characteristic diagram of the current thin film transistor according to the second embodiment of the present invention, and FIG. 9 is a current-voltage characteristic diagram of the organic EL display element according to the second embodiment of the present invention.
[0055]
In FIG. 7, reference numeral 615 denotes a pixel electrode formed of ITO, 616 denotes a counter electrode formed of Al, 622 denotes a p-channel current thin film transistor, and 631 denotes an organic EL which emits light by a current flowing from the pixel electrode 615 to the power supply line 616. A display element (hereinafter, referred to as an inverted organic EL display element) 641 indicates the direction of the current of the organic EL display element, but the direction is opposite to that of FIG. 1 and FIG.
[0056]
8, the level of each potential is different from that in FIG. Otherwise, it is the same as FIG.
[0057]
9, reference numeral 81 denotes a current-voltage characteristic of the p-channel current thin film transistor 622 when the drain voltage is 4 V, and reference numeral 82 denotes a current-voltage characteristic of the p-channel current thin film transistor 622 when the drain voltage is 8 V.
[0058]
In FIG. 10, reference numeral 9 denotes a current-voltage characteristic of the inverted organic EL display element 631. The operation of the organic EL display device including the thin film transistor of this embodiment is the same as that of the first embodiment except that the current thin film transistor is a p-channel thin film transistor 622, so that the potential relation related to the current thin film transistor is inverted. It is.
[0059]
FIG. 11A is a cross-sectional view of an organic EL display element (one pixel) including a thin film transistor according to an embodiment of the present invention, and FIG. 11B is a thin film transistor organic EL display element according to Embodiment 2 of the present invention. It is a top view of (one pixel). The cross section AA ′ in FIG. 11A corresponds to the cross section AA ′ in FIG.
[0060]
In FIG. 10, 632 is a hole injection layer, and 633 is an organic EL layer. Otherwise, it is the same as FIG. An inverted organic EL display element 631 is formed by the pixel electrode 615 formed of ITO, the counter electrode 616 formed of Al, the hole injection layer 632, and the organic EL layer 633. In the inverted organic EL display element 631, the current direction 641 of the organic EL display element can be set to the direction from the pixel electrode 615 formed of ITO to the counter electrode 616 formed of Al.
[0061]
In this embodiment, the common potential 714 is higher than the counter potential 716. The current thin film transistor is a p-channel type current thin film transistor 622.
[0062]
Further, in this embodiment, the signal potential 712 for the pixel to be in the display state is higher than the counter potential 716.
Further, in this embodiment, the signal potential 712 for the pixel to be in the non-display state is lower than the common potential 714.
[0063]
All the effects of the thin film transistor organic EL display element of this embodiment are also the same as those of the potential related to the current thin film transistor except that the potential relationship related to the current thin film transistor is inverted because the current thin film transistor is the p-channel thin film transistor 622. It is the same as the first embodiment except that the relationship is reversed.
[0064]
In this embodiment, the current thin film transistor 122 is a p-channel thin film transistor. With this configuration, the deterioration with time of the current thin film transistor 122 can be significantly reduced. Further, by using a p-channel type polysilicon thin film transistor, it is possible to further reduce the deterioration with time of the current thin film transistor 122.
[0065]
FIG. 14 is a manufacturing process diagram of a current-driven light-emitting display device including the thin film transistor according to the embodiment of the present invention. First, as shown in FIG. 14A, an amorphous silicon layer of 200 to 600 Å is formed on the entire surface of a substrate 1, and the amorphous silicon is polycrystallized by annealing with a laser or the like. Form a layer. Thereafter, the polycrystalline silicon layer is patterned to become a silicon thin film 421 serving as a source / drain / channel region of the switching thin film transistor 121, a first electrode 423 of the storage capacitor 123, and a source / drain / channel region of the current thin film transistor 122. A silicon thin film 422 is formed.
[0066]
Next, an insulating film 424 serving as a gate insulating film is formed over the silicon thin films 421 and 422 and the first electrode 423. Next, phosphorus (P) ions are selectively implanted into the first electrode 423 to reduce the resistance. Next, as shown in FIG. 14B, gate electrodes 111 and 111 'made of a TaN layer are formed on the silicon thin films 421 and 422 via a gate insulating film.
[0067]
Next, a resist mask 42 is formed on the silicon layer 422 to be a current thin film transistor, and phosphorus (P) is ion-implanted by self-alignment using the gate electrode as a mask to form n-type source / drain regions in the silicon layer 421. Form. Next, as shown in FIG. 14 (c), a resist mask 412 'is formed on the first silicon layer 421 and the first electrode, and the silicon (422) is self-aligned with boron ( B) is ion-implanted to form p-type source / drain regions in the silicon layer 422. As described above, the switching thin film transistor 121 is formed by the n-channel impurity doping 411. At this time, the current thin film transistor 122 is protected by the resist mask 42 and the n-channel impurity doping 411 is not performed. Next, the current thin film transistor 122 is formed by the p-channel type impurity doping 412.
[0068]
Although not shown, a thin film transistor that forms a shift register, a sample and hold circuit, and the like of a driver circuit portion for driving the switching transistor 121 can be formed simultaneously on the same substrate by the same process as the above process. is there. Note that the second electrode 425 of the storage capacitor may be formed of the same material at the same time as the gate electrodes 111 and 111 ′, or may be formed of another material. Next, as shown in FIG. 14D, after forming an interlayer insulating film 43, forming a contact hole, electrode layers 426, 427, 428 and 429 made of aluminum or ITO are formed.
[0069]
Next, after the interlayer insulating film 44 is formed and planarized, a contact hole is formed, and ITO 45 is formed at 1000 to 2000 Å, preferably about 1600 Å so as to be connected to one electrode of the current thin film transistor. Next, bank layers 46 and 47 each having a size of 2.0 μm or more are formed for each pixel region. Next, an organic EL layer 48 is formed in a region surrounded by the bank layers 46 and 47 by an inkjet method or the like. After forming the organic EL 48, aluminum lithium of 6000 to 8000 Å is formed as a counter electrode 49 on the organic EL layer 48. A hole injection layer may be provided between the organic EL 48 and the counter electrode 49 as shown in FIG.
[0070]
Through the above steps, a high-performance thin film transistor driven organic EL display element can be formed. In addition, polysilicon has much higher carrier mobility than amorphous silicon, so that high-speed operation is possible. In particular, in this embodiment, when forming the p-type current thin film transistor 122 and the n-type switching thin film transistor 121, the p-type and n-type thin film transistors of the complementary type thin film transistors constituting the shift register of the driving circuit, the sample-and-hold circuit, etc. Can be simultaneously formed using the above-described embodiment. According to this configuration, it is possible to obtain a configuration that reduces the deterioration with time of the current thin film transistor 122 without increasing the number of manufacturing processes.
[0071]
As described above, in the first embodiment, the n-channel current thin film transistor is used, and in the second embodiment, the p-channel current thin film transistor is described. Here, the deterioration with time of the p-channel and n-channel thin film transistors will be discussed. I do.
[0072]
FIG. 12 and FIG. 13 are diagrams showing the deterioration over time of n-channel and p-channel thin film transistors, particularly polysilicon thin film transistors, under the same voltage application conditions. Reference numerals 511 and 512 in FIG. 12 indicate transfer characteristics of the n-channel thin film transistor at Vd = 4 V and Vd = 8 V before voltage application. Reference numerals 521 and 522 denote transfer characteristics of the n-channel thin film transistor at Vd = 0 V, Vd = 15 V, and Vd = 4 V and Vd = 8 V after application of a voltage of about 1000 seconds.
[0073]
Reference numerals 811 and 812 in FIG. 13 show transfer characteristics of the p-channel thin film transistor at Vd = 4 V and Vd = 8 V before voltage application. Reference numerals 821 and 822 denote transfer characteristics of the p-channel thin film transistor when Vg = 0 V, Vd = 15 V, and Vd = 4 V and Vd = 8 V after application of a voltage of about 1000 seconds. Obviously, the p-channel thin film transistor has a smaller decrease in on-current and a smaller increase in off-current.
[0074]
In consideration of the difference in the aging characteristics of the p-type and n-type thin film transistors shown in FIGS. 12 and 13, at least one of the switching thin film transistor and the current thin film transistor is formed of a p-channel thin film transistor, particularly a p-type polysilicon thin film transistor. Thereby, deterioration with time can be suppressed. Further, by forming not only the current thin film transistor but also the switching thin film transistor with a p-type thin film transistor, it is possible to further maintain the characteristics of the display element.
[0075]
Although the above-described embodiment has been described using an organic EL display element as a light emitting element, it is needless to say that the present invention is not limited to an organic EL display element, but can be applied to an inorganic EL element or another current-driven light emitting element. .
[0076]
(Industrial applications)
The display device according to the present invention can be used as a display device including various current-driven light-emitting elements such as an organic EL display element and an inorganic EL element, and a switching element such as a thin film transistor that drives the light-emitting element.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of a display device to which the present invention is applied.
FIG. 2 is an equivalent circuit diagram of a display element including the thin film transistor according to the first embodiment of the present invention.
FIG. 3 is a driving voltage diagram of a display device including the thin film transistor according to the first embodiment of the present invention.
FIG. 4 is a current-voltage characteristic diagram of the current thin film transistor according to the first embodiment of the present invention.
FIG. 5 is a current-voltage characteristic diagram of the organic EL display element according to Example 1 of the present invention.
6A is a cross-sectional view of an organic EL display device including a thin film transistor according to the first embodiment of the present invention, and FIG. 6B is a plan view of the organic EL display device including the thin film transistor according to the first embodiment of the present invention. FIG.
FIG. 7 is an equivalent circuit diagram of an organic EL display device including a thin film transistor according to Embodiment 2 of the present invention.
FIG. 8 is a driving voltage diagram of the organic EL display device including the thin film transistor according to the second embodiment of the present invention.
FIG. 9 is a current-voltage characteristic diagram of a current thin film transistor according to Example 2 of the present invention.
FIG. 10 is a current-voltage characteristic diagram of an organic EL display element according to Example 2 of the present invention.
11A is a cross-sectional view of an organic EL display device including a thin film transistor according to Example 2 of the present invention, and FIG. 11B is a plan view of the organic EL display device including the thin film transistor according to Example 2 of the present invention. FIG.
FIG. 12 is a diagram illustrating deterioration over time of an n-channel thin film transistor.
FIG. 13 is a diagram showing the degradation of a p-channel thin film transistor.
FIG. 14 is a manufacturing process diagram of a thin film transistor driven organic EL display element according to the present invention.
[Explanation of symbols]
111 scanning line 112 data line 113 common line 114 holding electrode 115 pixel electrode 116 formed of Al counter electrode 121 formed of ITO switching thin film transistor 122 n-channel type current thin film transistor 123 storage capacitor 131 fixed organic EL display element 132 hole Injection layer 133 Organic EL layer 141 Current direction of current emitting element 151 Resist 211 Scanning potential 212 Signal potential 213 Holding potential 214 Common potential 215 Pixel potential 216 Opposing potential 221 Period 222 in which pixel is in display state 222 Pixel is in non-display state Period 31 Current-voltage characteristics of n-channel type current thin film transistor when drain voltage is 4 V 32 Current-voltage characteristics of n-channel type current thin film transistor when drain voltage is 8 V 4 Current-voltage characteristics 6 of normal organic EL display element 11 scanning line 612 data line 613 common line 614 holding electrode 615 pixel electrode 616 formed of ITO counter electrode 621 formed of Al switching thin film transistor 622 p-channel current thin film transistor 623 storage capacitor 631 inverted organic EL display element 632 hole Injection layer 633 Organic EL layer 641 Current direction 651 of current light emitting element Resist 711 Scanning potential 712 Signal potential 713 Holding potential 714 Common potential 715 Pixel potential 716 Opposing potential 721 Period during which pixel is in display state 722 Pixel is in non-display state Period 81 Current-voltage characteristics of p-channel type current thin film transistor when drain voltage is 4 V 82 Current-voltage characteristics of p-channel type current thin film transistor when drain voltage is 8 V 9 Current-voltage characteristics 51 of inverted organic EL display element 1 Transfer characteristics of n-channel thin film transistor at Vd = 4 V before voltage application 512 Transfer characteristics of n-channel thin film transistor at Vd = 8 V before voltage application Transfer characteristics 522 of n-channel thin film transistor at Vd = 4 V after voltage application Transfer characteristics of n-channel thin film transistor at Vd = 8 V after application 811 Transfer characteristics of p-channel thin film transistor at Vd = 4 V before voltage application 812 Transfer characteristics of p-channel thin film transistor at Vd = 8 V before voltage application After voltage application Transfer Characteristics of P-Channel Thin Film Transistor at Vd = 4V at 822 V Transfer Characteristics of p-Channel Thin Film Transistor at Vd = 8 V after Applying Voltage

Claims (5)

A light-emitting display device including a scanning line, a data line, and a pixel,
The pixel is
A first transistor whose conduction is controlled by the potential of the scanning line;
A storage capacitor for holding an image signal supplied from the data line via the first transistor;
A second transistor that controls conduction between a pixel electrode and a common electrode by the potential of the storage capacitor;
A light-emitting element between the pixel electrode and the counter electrode,
At least one of the first transistor and the second transistor is a p-channel transistor;
A light emitting display device characterized by the above-mentioned. A light-emitting display device including a scanning line, a data line, and a pixel,
The pixel is
A first transistor whose conduction is controlled by the potential of the scanning line;
A storage capacitor for holding an image signal supplied from the data line via the first transistor;
A second transistor that controls conduction between a pixel electrode and a common electrode by the potential of the storage capacitor;
A light-emitting element between the pixel electrode and the counter electrode,
The second transistor is a p-channel transistor;
A light emitting display device characterized by the above-mentioned. A light-emitting display device including a scanning line, a data line, and a pixel,
The pixel is
A first transistor whose conduction is controlled by the potential of the scanning line;
A light emitting element between the pixel electrode and the counter electrode,
A storage capacitor for holding an image signal supplied from the data line via the first transistor;
A second transistor inserted in series between the pixel electrode and a common line,
At least one of the first transistor and the second transistor is a p-channel transistor;
A light emitting display device characterized by the above-mentioned. A light-emitting display device including a scanning line, a data line, and a pixel,
The pixel is
A first transistor whose conduction is controlled by the potential of the scanning line;
A light emitting element between the pixel electrode and the counter electrode,
A storage capacitor for holding an image signal supplied from the data line via the first transistor;
A second transistor inserted in series between the pixel electrode and a common line,
The second transistor is a p-channel transistor;
A light emitting display device characterized by the above-mentioned. A light-emitting display device including a scanning line, a data line, and a pixel,
The pixel is
A first transistor whose conduction is controlled by the potential of the scanning line;
A storage capacitor for holding an image signal supplied from the data line via the first transistor;
A second transistor that controls conduction between a pixel electrode and a common electrode by the potential of the storage capacitor;
A light-emitting element between the pixel electrode and the counter electrode,
The first transistor and the second transistor are an n-channel transistor and a p-type transistor, respectively;
A light emitting display device characterized by the above-mentioned.

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