JP2008108804A - Method for manufacturing nonlinear element and method for manufacturing electro-optical device - Google Patents

Abstract

When a tantalum oxide film containing hydrogen and nitrogen is used as an insulating layer, a method of manufacturing a non-linear element capable of distributing nitrogen throughout the thickness direction of the tantalum oxide film, and an electric power using this method A method for manufacturing an optical device is provided.
In manufacturing a non-linear element 10x, a lower electrode 13x is formed of a tantalum film containing tungsten and nitrogen, and then the surface of the lower electrode 13x is oxidized to form an insulating layer 14x made of a tantalum oxide film. Next, after introducing hydrogen into the insulating layer 14x, the upper electrode 15x is formed. When forming the insulating layer 14x, a tantalum oxide film having a film thickness necessary for forming the insulating layer 14x is formed by vapor phase oxidation, and then anodic oxidation is performed.
[Selection] Figure 1

Description

  The present invention relates to a method of manufacturing a nonlinear element including a lower electrode, an insulating layer, and an upper electrode, and a method of manufacturing an electro-optical device including the nonlinear element as a pixel switching element.

  As a non-linear element used as a pixel switching element in an active matrix type electro-optical device, for example, a TFD having a MIM (Metal-Insulator-Metal) structure including a lower electrode, an insulating layer, and an upper electrode is used. (Thin Film Diode). In such a non-linear element, generally, the lower electrode is made of a tantalum film, the insulating layer is made of a tantalum oxide film, and the upper electrode is made of a chromium film.

For such a nonlinear element, the surface of the lower electrode made of a nitrogen-containing tantalum film is anodized for the purpose of improving the contrast of the image displayed by the electro-optical device, so that the nitrogen-containing tantalum oxide is used as an insulating layer. It has been proposed to improve the nonlinearity of a nonlinear element by forming a film (for example, Patent Document 1).
JP-A-9-166792

  As a result of repeated experiments, the inventor of the present application obtains the knowledge that nonlinearity is improved when hydrogen is added to the insulating layer, and proposes to improve the nonlinearity based on this knowledge. However, when hydrogen is added to the insulating layer, an irreversible shift phenomenon of current-voltage characteristics occurs, and there is a problem that burn-in occurs in the displayed image. That is, when hydrogen is added to the insulating layer, hydrogen is desorbed from the insulating layer when a voltage is applied, and the nonlinearity is irreversibly lowered. As a result, in the pixels that have been energized to display the image, the linearity of the nonlinear element is reduced, and even when the image is switched, the trace of the image that has been displayed remains. The seizure phenomenon will occur.

  Therefore, the present inventor proposes to prevent hydrogen desorption by introducing nitrogen together with hydrogen into the insulating layer to enhance the hydrogen holding power of the insulating layer.

  However, when an insulating layer is formed on the surface of the lower electrode made of a nitrogen-containing tantalum film by anodic oxidation, tantalum moves in the film thickness direction as ions during anodic oxidation, but nitrogen does not move. When mass analysis is performed, the distribution of nitrogen atoms in the insulating layer in the film thickness direction is indicated by dots L31 in FIG. 4, and the distribution of oxygen atoms in the film thickness direction as a comparison is indicated by dots L32. While the content is large, there are no nitrogen atoms in the surface layer portion. For this reason, since the surface layer portion of the insulating layer has a low hydrogen holding power, if the hydrogen in the surface layer portion moves toward the interface with the upper electrode and desorbs, the element resistance decreases, while the hydrogen in the surface layer portion decreases. If it moves toward the interface with the lower electrode and is trapped by oxygen vacancies in a region where the nitrogen content is high, the charge carriers derived from oxygen vacancies decrease, so that the device resistance increases. As a result, there is a problem that image sticking or afterimage occurs.

  In view of the above problems, an object of the present invention is to provide a non-linear element capable of distributing nitrogen throughout the thickness direction of a tantalum oxide film when using a tantalum oxide film containing hydrogen and nitrogen as an insulating layer. And a method of manufacturing an electro-optical device using the method.

  In order to solve the above problems, in the present invention, in a method for manufacturing a non-linear element including a lower electrode, an insulating layer covering the surface side of the lower electrode, and an upper electrode facing the lower electrode through the insulating layer Forming a lower electrode with a nitrogen-containing tantalum film; forming a nitrogen-containing tantalum oxide film by oxidizing the surface of the lower electrode by a vapor-phase oxidation method; and And a hydrogen introduction step of introducing hydrogen into the tantalum oxide film.

  In the present invention, since hydrogen is contained in the insulating layer by the hydrogen introduction step, the nonlinearity is high and the occurrence of the element drift phenomenon that causes the afterimage phenomenon can be prevented. Moreover, the addition of nitrogen to the insulating layer also has an effect of improving nonlinearity. Here, the single addition of nitrogen to the insulating layer has a problem of increasing the element drift phenomenon. However, in the present invention, since the insulating layer contains both hydrogen and nitrogen, even if nitrogen is added. Occurrence of the element drift phenomenon can be suppressed. Further, since nitrogen exhibits a function of preventing the desorption of hydrogen when a voltage is applied, it is possible to prevent occurrence of an irreversible shift phenomenon of nonlinear characteristics that causes image sticking. Furthermore, the insulating layer includes a nitrogen-containing tantalum oxide film formed by a vapor phase oxidation process. Unlike the anodic oxide film, the nitrogen-containing tantalum oxide film has a surface layer portion of the insulating layer and a deep portion thereof. Similarly, it contains a large amount of nitrogen and has sufficient hydrogen retention. Therefore, the hydrogen in the surface layer portion does not move toward the interface with the upper electrode and desorb, so that the device resistance does not decrease. In addition, since hydrogen in the surface layer moves toward the interface with the lower electrode and is not trapped by oxygen defects in a region where the nitrogen content is high, the charge carriers derived from oxygen defects are not reduced, and the element resistance Does not increase. Therefore, according to the present invention, it is possible to prevent image sticking and afterimages from occurring.

  In the present invention, after the vapor phase oxidation step, an anodization step is performed in which anodization is performed with the lower electrode as an anode, between the vapor phase oxidation step and the anodization step, and after the anodization step. It is preferable to perform the hydrogen introduction step in at least one of them. In the nitrogen-containing tantalum oxide film formed by the vapor phase oxidation process, defects such as surface irregularities and pinholes are likely to occur, but in the present invention, such defects are eliminated by the anodization process, so the reliability of the nonlinear element is improved. Can be improved.

  In the present invention, in the vapor phase oxidation step, a nitrogen-containing tantalum oxide film having substantially the same thickness as the insulating layer is formed, and in the anodization step, a voltage corresponding to the thickness of the nitrogen-containing tantalum oxide film is applied. It is preferable to apply to the lower electrode. With this configuration, even when defects such as surface irregularities and pinholes have occurred in the nitrogen-containing tantalum oxide film formed in the gas phase oxidation process, such defects can be eliminated in the anodization process, Since there is no film growth during the anodic oxidation process, the insulating layer can maintain a state in which nitrogen is uniformly distributed throughout the thickness direction.

  The method of manufacturing a nonlinear element according to the present invention can be used in a method of manufacturing an electro-optical device such as a liquid crystal device. In this case, the nonlinear element is formed as a pixel switching element in each of a plurality of pixel regions on the element substrate. To do. The electro-optical device according to the present invention is used in electronic devices such as a mobile phone and a mobile computer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing referred to in the following description, the scale may be different for each layer or each member in order to make the size recognizable on the drawing.

(Configuration of nonlinear element)
1A to 1D are cross-sectional views showing a nonlinear element to which the present invention is applied and a method for manufacturing the same. As shown in FIG. 1D, the nonlinear element 10x of this embodiment includes a lower electrode 13x made of a tantalum film, an insulating layer 14x made of a tantalum oxide film covering the surface side of the lower electrode 13x, and the insulating layer 14x. A TFD (Thin Film Diode) element including an upper electrode 15x opposed to the lower electrode 13x. A base insulating layer 201x made of a tantalum oxide film or the like is formed on the surface of the substrate 20x, and the nonlinear element 10x is formed on the surface of the base insulating layer 201x.

  In manufacturing the nonlinear element 10x, as will be described in detail later, a lower electrode formation forming step of forming the lower electrode 13x with a tantalum film, and an insulating layer 14x made of a tantalum oxide film by oxidizing the surface of the lower electrode 13x. An oxidation step for forming the upper electrode, a hydrogen introduction step for introducing hydrogen into the insulating layer 14x, and an upper electrode forming step for forming the upper electrode 15x on the insulating layer 14x are performed.

(Layer structure of nonlinear element)
2A to 2E are explanatory views showing the relationship between the material and electric characteristics of each layer constituting the nonlinear element. 2A is an explanatory diagram of the influence of tungsten, hydrogen, and nitrogen contained in the insulating layer in the nonlinear element on the nonlinear element, and FIG. 2B is a tantalum that forms the lower electrode of the nonlinear element. It is a graph showing the relationship between the nitrogen content of the film, the non-linearity of the non-linear element using the tantalum oxide film formed by anodizing the lower electrode as an insulating layer (β value), and the specific resistance of the tantalum film, FIG. 2C shows the relationship between the amount of hydrogen introduced and the element drift value when a nitrogen-containing tantalum film is used as the insulating layer of the nonlinear element and when a tantalum oxide film not containing nitrogen is used. FIG. 2D is a graph showing the relationship between the tungsten content in the insulating layer (tantalum oxide film) used in the nonlinear element and the element drift amount, and FIG. element And the tungsten content in the insulating layer (tantalum oxide film) was used, a graph showing the relationship between the irreversible shift amount of nonlinearity.

  In the nonlinear element 10x, there is the following relationship described with reference to FIG. 2 between the material constituting each layer and the electrical characteristics. In this embodiment, the lower electrode 13x is formed by a tantalum film containing tungsten and nitrogen. By forming the electrode 13x, the insulating layer 14x formed by oxidizing the surface of the lower electrode 13x is used as a tantalum oxide film containing tungsten and nitrogen. Further, hydrogen is introduced into the insulating layer 14x.

  As shown in FIG. 2A, in the insulating layer 14x, tungsten does not affect the nonlinearity, but reduces the element drift phenomenon while increasing the shift phenomenon. Hydrogen improves non-linearity and reduces the element drift phenomenon. Nitrogen improves the nonlinearity while increasing the element drift phenomenon. Nitrogen also reduces the shift phenomenon by preventing the desorption of hydrogen.

  The element drift phenomenon is a phenomenon in which when the current-voltage characteristic is measured for the first time and then the current-voltage characteristic is measured for the second time, a difference occurs in the measurement result, and the insulation is high in the second measurement. It is. In such an element drift phenomenon, when the current-voltage characteristic is measured again after, for example, one hour has passed since the second measurement, the result equivalent to the first measurement result is obtained. -When the voltage characteristic is measured, a result showing high insulation is obtained as in the second measurement result. Such an element drift phenomenon is considered to occur due to ionic oxygen depletion in the insulating layer 14x being drawn to one of the lower electrode 13x / insulating layer 14x interface or the insulating layer 14x / upper electrode 15x interface, When the ionic oxygen depletion in the insulating layer 14x is gradually returned to the low resistance state where the oxygen depletion is uniformly distributed from the high resistance state where the ionic oxygen depletion is attracted to one interface, a reverse current is generated due to the movement of the oxygen depletion. As a result, the afterimage phenomenon occurs as a result of the response of the liquid crystal.

  The shift phenomenon is a phenomenon that occurs due to the desorption of hydrogen from the insulating layer 14x. When the hydrogen added to improve the nonlinearity is desorbed, the linearity of the nonlinear element 10x is irreversibly lowered. However, in the pixel in which the nonlinear element 10x is energized in order to display an image, even when the image is switched, the trace of the image displayed so far always remains, and a burn-in phenomenon occurs.

  First, as indicated by a solid line L1 in FIG. 2B, when nitrogen is contained in the tantalum film constituting the lower electrode 13x, the insulating layer 14x becomes a nitrogen-containing tantalum oxide film, resulting in nonlinearity of the nonlinear element 10. (Β value) is improved. Moreover, since the nitrogen content in the insulating layer 14x increases as the nitrogen content of the tantalum film constituting the lower electrode 13x increases, the nonlinearity of the nonlinear element 10 improves. On the other hand, the relationship between the nitrogen content in the tantalum film and the specific resistance is as follows. As shown by the dotted line L2 in FIG. As the tantalum is formed, the specific resistance is high. However, when the nitrogen content in the tantalum film is changed from 0.25 at% to 0.7 at% or 0.8 at%, the cubic tantalum and the tetragonal structure are in the meantime. Since the crystalline tantalum is mixed, the specific resistance decreases. Then, when the nitrogen content in the tantalum film is 0.7 to 0.8 at%, it becomes a cubic single-phase tantalum, so that the specific resistance shows a minimum value. When the nitrogen content in the tantalum film increases from 0.8 at% to 2 at%, it becomes pseudo cubic single-phase tantalum and the specific resistance increases. Further, when the nitrogen content in the tantalum film increases, a mixed phase of pseudo cubic tantalum and tantalum nitride is formed, and the specific resistance further increases. Therefore, when the lower electrode 13x is formed simultaneously with the wiring, the nitrogen amount of the lower electrode 13x is controlled to an optimum range from the relationship between nonlinearity and specific resistance.

With reference to FIG.2 (c), the relationship between nitrogen and hydrogen and an element drift phenomenon is demonstrated. In the graph shown in FIG. 2 (c), the results plotted with a square and solid line L6 are the results when a nitrogen-containing tantalum film is used, and the results plotted with a circle and dotted line L7 are tantalum films not containing nitrogen. It is a result at the time of using. The drift value on the vertical axis is the difference between the voltage values indicating the current value of 1 × 10 ⁻⁸ A in the first measurement and the second measurement immediately thereafter in the current-voltage characteristics of the nonlinear element 10. Yes, it can be said that the larger the value, the more likely the afterimage phenomenon occurs. Note that the values shown in FIG. 2C are the results obtained with the nonlinear element 10x in which the opposing area of the lower electrode 13x and the upper electrode 15x is 2.5 μm × 3.0 μm and the thickness of the insulating layer 14x is 50 nm. It is. In obtaining the data shown in FIG. 2C, nitrogen is introduced into the tantalum oxide film constituting the insulating layer 14x by forming the lower electrode 13x with the nitrogen-containing tantalum film and then anodizing the surface. This was realized by forming the insulating layer 14x. On the other hand, when the lower electrode is formed with a tantalum film containing no nitrogen and then the surface is anodized to form an insulating layer, nitrogen is not introduced into the tantalum oxide film constituting the insulating layer. It will be. Further, the introduction of hydrogen into the tantalum oxide film constituting the insulating layer 14x was performed by performing an annealing process in an atmosphere containing hydrogen after the insulating layer 14x was formed. Accordingly, the higher the annealing temperature, the larger the amount of hydrogen introduced into the tantalum oxide film.

  As shown in FIG. 2C, when the annealing temperature for introducing hydrogen is 0 ° C., that is, when the annealing process for introducing hydrogen is not performed, a non-linear element using a nitrogen-containing tantalum oxide film as the insulating layer 14x 10x has a significantly higher drift value than the nonlinear element 10x using a tantalum oxide film containing no nitrogen as the insulating layer 14x. In addition, when hydrogen is introduced into a tantalum oxide film that does not contain nitrogen, the drift value increases as the amount of hydrogen introduced increases. In contrast, when hydrogen is introduced into the nitrogen-containing tantalum oxide film, the drift value decreases as the amount of hydrogen introduced increases. When the annealing temperature is 250 ° C. or higher, the drift value can be reduced to a sufficient level. When the annealing temperature is increased to 320 ° C., the afterimage phenomenon can be reliably prevented.

Next, with reference to FIGS. 2D and 2E, the effect of tungsten, hydrogen, and nitrogen is explained. In the graphs shown in FIGS. 2D and 2E, the circle and the solid line L11 are plotted. These are the results of a tantalum oxide film not containing nitrogen that was subjected to a hydrogenation annealing step at 320 ° C., and plotted with a square and a dotted line L12 are the nitrogen-containing tantalum oxide films that were subjected to a hydrogenation annealing step at 260 ° C. Is the result of 2D and 2E, the results of the tantalum oxide film containing nitrogen (content 1.5 at%) obtained by performing the hydrogenation annealing process at 260 ° C. are also plotted with triangles. The results of the tantalum oxide film containing nitrogen (content 2.0 at%) performed at 260 ° C. are also plotted with x marks. In the graph shown in FIG. 2 (e), the shift value on the vertical axis means that a positive and negative rectangular pulse that causes a current of 1 × 10 ⁻⁷ A to flow through the nonlinear element 10 is alternately applied every second. In the case of continuing, it is a value representing the change rate of the current value after the elapse of 100 seconds from the start of application in percentage, and it can be said that the larger the value, the easier the burn-in occurs.

  First, as shown in FIG. 2D, the element drift value decreases as the tungsten content increases in the tantalum oxide film constituting the insulating layer 14x. However, as shown in FIG. 2 (e), in the tantalum oxide film constituting the insulating layer 14x, the greater the tungsten content, the greater the irreversible shift amount of the nonlinearity, and the displayed image is burned. Tend to. That is, when tungsten is added to the insulating layer 14x, the specific resistance of the insulating layer 14x increases, so that the driving voltage required when a current of the same level is applied to the liquid crystal is compared with the case where tungsten is not added. As a result, the hydrogen added to the insulating layer 14x is desorbed, and the nonlinearity is irreversibly lowered. As a result, the non-linearity of the non-linear element 10x is reduced in the pixels that are energized to the non-linear element 10x to display an image, and even when the image is switched, the trace of the image that has been displayed is always left. Will occur (burn-in phenomenon). However, in this embodiment, since the insulating layer 14x of the nonlinear element 10x contains nitrogen and nitrogen has an effect of suppressing desorption of hydrogen, tungsten and hydrogen are added to the insulating layer 14x to add nonlinearity. Even in the case where both improvement of the device and prevention of the element drift phenomenon are achieved, however, if the tantalum oxide film constituting the insulating layer 14x contains nitrogen, the irreversible shift amount of the nonlinearity can be kept low.

(Nonlinear device manufacturing method)
When the nonlinear element 10x is manufactured, if the insulating layer 14x is formed by anodizing the surface of the lower electrode 13x made of a nitrogen-containing tantalum film, the tantalum is ionized during the anodic oxidation as described with reference to FIG. However, since nitrogen does not move, the nitrogen content is large in the deep portion of the insulating layer 14x, whereas the surface layer portion hardly contains nitrogen, and the surface layer of the insulating layer 14x contains hydrogen. Holding power becomes low. Therefore, in the present invention, the manufacturing method described below is adopted to improve the presence of sufficient nitrogen even in the shallow portion of the insulating layer 14x.

  First, in the base film forming step ST101 shown in FIG. 3, as shown in FIG. 1A, an insulating layer such as tantalum oxide is formed to a uniform thickness over the entire surface of the substrate 20x, and the base layer 201x. Form.

Next, a lower electrode formation step ST110 shown in FIG. 3 is performed. In this lower electrode forming step ST110, first, in the nitrogen-containing tantalum film forming step ST111, a tungsten-containing tantalum film 13 containing tungsten and nitrogen is used while introducing a nitrogen gas and an argon gas into the sputtering chamber. Form. Next, in the tantalum film patterning step ST112, with the resist mask formed on the tantalum film 13, a dry etching is performed on the tantalum film 13 using an etching gas containing CF _4, SF _6, or the like. After patterning 13, the resist mask is removed. As a result, the lower electrode 13b is formed as shown in FIG. At that time, a power supply line (not shown) used for anodization described later is formed.

Next, in the vapor phase oxidation step ST121 shown in FIG. 3, vapor phase oxidation is performed on the surface of the lower electrode 13x, and as shown in FIG. 1C, tantalum containing tungsten and nitrogen is formed on the surface of the lower electrode 13x. An insulating layer 14x made of an oxide film is formed. More specifically, a gas containing oxygen (O ₂ , O ₃ , H ₂ O) is introduced into the processing chamber while the processing chamber containing the substrate 20x is set to a temperature condition of 350 ° C., and thermal oxidation is performed. The insulating layer 14x is formed by a gas phase oxidation method such as a vapor oxidation method or an ozone oxidation method. At that time, for the purpose of efficiently supplying active atomic oxygen to the surface of the element substrate 20, the surface of the lower electrode 13x may be used in combination with Kr plasma irradiation, ultraviolet irradiation, and laser irradiation. In this embodiment, in the gas phase oxidation step ST121, the gas pressure, temperature, and processing time are adjusted to form a tantalum oxide film having a film thickness necessary for forming the insulating layer 14x.

  Next, in an anodic oxidation step ST122 shown in FIG. 3, anodic oxidation is performed in the organic acid or inorganic acid aqueous solution with the lower electrode 13x as the anode. At this time, since a tantalum oxide film having a thickness necessary for forming the insulating layer 14x has already been formed in the vapor phase oxidation step ST121, the tantalum oxidation formed in the vapor phase oxidation step ST121 is performed in the anodic oxidation step ST122. A voltage corresponding to the thickness of the film is applied to the lower electrode 13x. Therefore, in the anodic oxidation step ST122, defects in the tantalum oxide film formed in the vapor phase oxidation step ST121 are repaired, but no film growth occurs.

  Next, in the hydrogen addition annealing step ST130 (hydrogen introduction step) shown in FIG. 3, the substrate 20x is heated in an atmosphere containing hydrogen. As a result, the insulating layer 14x becomes a tantalum oxide film containing tungsten, nitrogen, and hydrogen. Specifically, the processing chamber containing the substrate 20x is set to a temperature of about 320 ° C., and in this state, a gas containing water vapor, for example, the atmosphere, is introduced into the processing chamber. In the hydrogen addition annealing step ST130, pressurized water vapor may be supplied in a state where the substrate 20x is heated to a predetermined temperature. Moreover, as a hydrogen introduction | transduction process, it may replace with hydrogen addition annealing and may irradiate with hydrogen plasma.

  Next, in the bridge portion removing step ST140 shown in FIG. 3, after removing the bridge portion (not shown) connecting the lower electrode 13x and the power supply line, the upper electrode forming step ST150 shown in FIG. 3 is performed. For this purpose, first, a chromium film is formed with a uniform thickness by sputtering or the like in the chromium film forming step ST151, and then, in the chromium film patterning step ST152, the chromium film is patterned using a photolithographic technique. The upper electrode 15x shown in (d) is formed. As described above, the nonlinear element 10x is formed on the substrate 20x. Note that the bridge portion removal step ST140 shown in FIG. 3 may be performed after the upper electrode formation step ST150.

(Main effects of this form)
FIG. 4 shows the analysis result of the insulating layer by dynamic secondary ion mass spectrometry. In this embodiment, since hydrogen is contained in the insulating layer 14x by the hydrogen addition annealing step ST130 (hydrogen introduction step), the nonlinearity is high and the occurrence of the element drift phenomenon that causes the afterimage phenomenon can be prevented. it can. Moreover, the addition of nitrogen to the insulating layer 14x also has an effect of improving the nonlinearity. Here, the single addition of nitrogen to the insulating layer 14x has a problem of increasing the element drift phenomenon. However, in the present invention, since the insulating layer 14x contains both hydrogen and nitrogen, nitrogen is added. However, the occurrence of the element drift phenomenon can be suppressed. Furthermore, the insulating layer 14x contains nitrogen, and the nitrogen exhibits a function of preventing the desorption of hydrogen when a voltage is applied at room temperature. Therefore, the irreversible shift phenomenon of the non-linear characteristic that causes seizure is caused. Occurrence can be prevented.

  Furthermore, the insulating layer 14x includes a nitrogen-containing tantalum oxide film formed in the gas phase oxidation step ST121. Unlike the anodic oxide film, the nitrogen-containing tantalum oxide film is analyzed by secondary ion mass spectrometry. The dot L41 indicates the distribution of the nitrogen atoms in the thickness direction of the insulating layer, and the distribution of the oxygen atoms in the thickness direction as a comparison is indicated by the dots L42, so that the surface layer portion of the insulating layer 14x is the same as the deep portion thereof. Contains enough nitrogen. For this reason, according to this embodiment, the insulating layer 14x also has a sufficient hydrogen holding power in the surface layer portion. Accordingly, since the hydrogen in the surface layer portion of the insulating layer 14x does not move toward the interface with the upper electrode 15x and desorb, the element resistance does not decrease. Further, since hydrogen in the surface layer portion moves toward the interface with the lower electrode 13x and is not trapped by oxygen defects in a region where the nitrogen content is large, charge carriers derived from oxygen defects are not reduced, and the device Resistance does not increase. Therefore, according to this embodiment, it is possible to prevent the occurrence of image sticking or afterimage.

  Further, in this embodiment, since the anodic oxidation step ST122 is performed after the vapor phase oxidation step ST121, even when defects such as irregularities and pinholes occur in the nitrogen-containing tantalum oxide film formed in the vapor phase oxidation step ST121 Defects can be eliminated in the anodization step ST122, and the reliability of the nonlinear element 10x can be improved.

  In this embodiment, in the vapor phase oxidation step ST121, a nitrogen-containing tantalum oxide film having substantially the same thickness as the insulating layer 14x is formed. In the anodic oxidation step ST122, a voltage corresponding to the thickness of the nitrogen-containing tantalum oxide film is formed. Is applied to the lower electrode 13x. Therefore, even when defects such as irregularities and pinholes are eliminated in the anodic oxidation step ST122 in the nitrogen-containing tantalum oxide film formed in the vapor phase oxidation step ST121, there is no film growth during the anodic oxidation step, so the insulating layer 14x The state in which nitrogen is uniformly distributed throughout the thickness direction can be maintained.

[Other manufacturing methods]
In the above embodiment, as shown in FIG. 3, the lower electrode formation step ST110, the vapor phase oxidation step ST121, the anodization step ST122, and the hydrogenation annealing step ST130 are performed in this order. As shown in FIG. The lower electrode formation step ST110, the gas phase oxidation step ST121, the hydrogen addition annealing step ST130, and the anodic oxidation step ST122 may be performed in this order. Further, as shown in FIG. 6, lower electrode formation step ST110, vapor phase oxidation step ST121, first hydrogen addition annealing step ST131 (first hydrogen introduction step) anodization step ST122, and second hydrogen addition annealing step ST132 (second hydrogen introduction step) may be performed in this order.

Further, when the hydrogenation annealing step is performed after the gas phase oxidation step ST121, these steps may be performed continuously in the same processing chamber. That is, in a state in which the processing chamber containing the substrate 20x is set to a temperature condition of 350 ° C., oxygen-containing gas (O ₂ , O ₃ , H ₂ O, N ₂ O) is introduced into the processing chamber, and thermal oxidation is performed. After the insulating layer 14x is formed by the gas phase oxidation method such as the steam oxidation method, the steam oxidation method, or the ozone oxidation method, the temperature of the processing chamber is reduced to, for example, 320 ° C. while the temperature of the processing chamber is lowered. The hydrogen addition annealing step may be performed by releasing the atmosphere and introducing an atmosphere containing moisture (H ₂ O) into the treatment chamber and setting the treatment chamber as a hydrogen-containing atmosphere.

  Furthermore, when sufficient film quality is obtained with the tantalum oxide film formed in the vapor phase oxidation step ST121, the insulating layer 14x may be formed only in the vapor phase oxidation step ST121, and the anodic oxidation step may be omitted.

[Example of application to electro-optical devices]
(overall structure)
FIG. 7 is a block diagram showing an electrical configuration of an active matrix electro-optical device (liquid crystal device) to which the present invention is applied. FIG. 8 is a cross-sectional view schematically showing a configuration of an electro-optical device to which the present invention is applied.

  As shown in FIG. 7, in the electro-optical device 100, a plurality of scanning lines 51 are formed extending in the row (X) direction, and a plurality of data lines 52 are extended in the column (Y) direction. Is formed. Further, pixels 53 are formed at positions corresponding to the intersections of the scanning lines 51 and the data lines 52, and these pixels 53 are arranged in a matrix. In each pixel 53, the liquid crystal layer 54 and the nonlinear element 10 made of TFD are connected in series. In the example shown in FIG. 7, the liquid crystal layer 54 is on the scanning line 51 side, and the nonlinear element 10 is on the data line 52. Connected to each side. The liquid crystal layer 54 may be connected to the data line 52 side, and the nonlinear element 10 may be connected to the scanning line 51 side. Here, each scanning line 51 is driven by a scanning line driving circuit 57, while each data line 52 is driven by a data line driving circuit 58.

  Specifically, such an electro-optical device 100 is configured as shown in FIG. 8, for example. In FIG. 8, one of the pair of substrates arranged to face each other is the element substrate 20 on which the nonlinear element 10 and the pixel electrode are formed, and the other substrate is the opposite substrate 30. Among these substrates, on the inner surface of the element substrate 20, a plurality of data lines 52, a plurality of nonlinear elements 10 connected to the data lines 52, and a one-to-one connection with the nonlinear elements 10 are connected. The pixel electrode 23 to be formed is formed. The data lines 52 are formed so as to extend in the direction perpendicular to the paper surface in FIG. 8, while the nonlinear elements 10 and the pixel electrodes 23 are arranged in a dot matrix. An alignment film 24 subjected to uniaxial alignment processing, for example, rubbing processing, is formed on the surface of the pixel electrode 23 and the like.

  A color filter 38 is formed on the inner surface of the counter substrate 30 and constitutes a colored layer of three colors “R”, “G”, and “B”. Note that a black matrix 39 is formed in the gap between the colored layers of these three colors to block incident light from the gap between the colored layers. A planarizing film 37 is formed on the surfaces of the color filter 38 and the black matrix 39, and a counter electrode 31 functioning as a scanning line 51 is formed on the surface in a direction perpendicular to the data lines 52. The planarizing film 37 is provided for the purpose of improving the smoothness of the color filter 38 and the black matrix 39 and preventing the counter electrode 31 from being disconnected. Further, an alignment film 34 subjected to a rubbing process is formed on the surface of the counter electrode 31, and the alignment films 24 and 34 are generally formed of polyimide or the like.

  The element substrate 20 and the counter substrate 30 are bonded to each other with a predetermined gap by a sealing material 104 including a spacer (not shown), and the liquid crystal 105 is sealed in the gap. A polarizing plate 217 having an optical axis corresponding to the rubbing direction to the alignment film 24 is attached to the outer surface of the element substrate 20, and the outer surface of the counter substrate 30 corresponds to the rubbing direction to the alignment film 34. A polarizing plate 317 having an optical axis is attached. Note that the electro-optical device 100 according to this embodiment employs a COG (Chip On Glass) technique, and the liquid crystal driving IC chip 260 is mounted directly on the surface of the element substrate 20.

(Configuration of pixel 53)
9 is a plan view showing a layout for several pixels including the TFD in the electro-optical device to which the present invention is applied, and FIG. 10 is an explanatory diagram of the TFD formed in each pixel shown in FIG. .

  As shown in FIGS. 9 and 10, the nonlinear element 10 of the present embodiment has a Back-to-Back structure including a first TFD 10a and a second TFD 10b. That is, the non-linear element 10 is formed on the lower layer 13b formed on the surface of the element substrate 20 and the insulating layer 14b formed on the surface of the lower electrode 13b. The upper electrode 15a and 15b which were spaced apart are provided, and the upper surface and side surface of the lower electrode 13b and the upper electrode 15a and 15b are opposed to each other through the insulating layer 14b. The upper electrode 15 a is formed integrally with the metal layer 15 c that becomes the data line 52 as it is, while the upper electrode 15 b is connected to the pixel electrode 23. The data line 52 includes a tantalum wiring 13a formed simultaneously with the lower electrode 13b, and an insulating layer 14a formed simultaneously with the insulating layer 14b is formed on the surface of the tantalum wiring 13a. The underlayer 201 is formed of an insulating layer such as a tantalum oxide film having a thickness of about 50 to 200 nm, for example, and may be omitted depending on the configuration of the lower electrode 13b.

  In the nonlinear element 10 of this embodiment, the lower electrode 13b and the tantalum wiring 13a are formed of a tantalum film having a thickness of about 50 to 150 nm, for example, and the tantalum film contains tungsten and nitrogen. As will be described later, the insulating layers 14a and 14b have a thickness of 20 formed by oxidizing the surfaces of the metal layer 13a and the lower electrode 13b by the vapor phase oxidation method alone or by the vapor phase oxidation method and the anodic oxidation method. The tantalum oxide film has a thickness of about ˜40 nm, and the tantalum oxide film contains tungsten, nitrogen, and hydrogen. The upper electrodes 15a and 15b are formed to a thickness of about 100 to 500 nm by a metal film such as chromium (Cr).

  When viewed from the data line 52 side, the first TFD 10a is, in order, an upper electrode 15a / insulating layer 14b / lower electrode 13b to form a sandwich structure of metal (conductor) / insulator / metal (conductor). Therefore, it has diode switching characteristics. On the other hand, when viewed from the data line 52 side, the second TFD 10b becomes the lower electrode 13b / insulating layer 14b / upper electrode 15b in order, and has a diode switching characteristic opposite to that of the first TFD 10a. Become. Therefore, since the nonlinear element 10 has a configuration in which two diodes are connected in series in opposite directions, the current-voltage nonlinear characteristics are symmetric in both positive and negative directions compared to the case where one diode is used. Will be. If it is not necessary to strictly symmetrize the nonlinear characteristics as described above, only one nonlinear element may be used.

  The pixel electrode 23 is formed of a conductive transparent film such as ITO (Indium Tin Oxide) when used as a transmissive type, while having a reflectivity such as aluminum or silver when used as a reflective type. It may be formed from a large reflective metal film. Note that the pixel electrode 23 may be formed of a transparent metal such as ITO even if it is a reflective type. In this case, after the reflective metal as the reflective layer is formed, the transparent pixel electrode 23 is formed through the insulating layer. On the other hand, when it is used as a transflective type, the reflective layer is formed thin to form a transflective film, or a slit is provided. As the element substrate 20 itself, for example, an insulating substrate such as quartz or glass is used. When used as a transmission type, the element substrate 20 is also required to be transparent, but when used as a reflection type, it is not necessary to be transparent. The reason why the base layer 201 is provided on the surface of the element substrate 20 is to prevent the lower electrode 13b and the like from being peeled from the base by heat treatment, and to prevent impurities from diffusing into the lower electrode 13b. Therefore, if this does not cause a problem, the base layer 201 can be omitted.

(Method of manufacturing electro-optical device 100)
FIG. 11 is a process diagram illustrating a manufacturing process of a nonlinear element in the manufacturing method of the electro-optical device 100 according to the present embodiment, in which a cross-sectional view is shown on the left side and a plan view is shown on the right side.

  In this embodiment, when the electro-optical device 100 is manufactured, the element substrate forming process including the nonlinear element forming process to the sealing material printing process and the counter substrate forming process including the color filter forming process to the rubbing process are performed separately. Is called. In addition, these steps are performed in a state of a large original substrate that can take a large number of the element substrate 20 and the counter substrate 30, but in the following description, the single substrate size and the large original substrate are not distinguished, and the element substrate 20 Also referred to as counter substrate 30.

  In this embodiment, by performing a nonlinear element formation process on the large element substrate 20, the data lines 52 and the nonlinear elements 10 for a plurality of electro-optical devices are formed. In this nonlinear element forming step, the manufacturing method described with reference to FIGS. 1, 3, 5 and 6 is performed. In the following description, an example in which the process sequence described with reference to FIGS. 1 and 3 is employed will be described.

  First, in the base film forming step ST101 shown in FIG. 3, an insulating layer such as tantalum oxide having a thickness of about 50 to 200 nm is uniformly formed on the entire surface of the substrate 20, as shown in FIG. Then, the base layer 201 is formed by forming a film.

Next, a lower electrode formation step ST110 shown in FIG. 3 is performed. In this lower electrode forming step ST110, first, in the nitrogen-containing tantalum film forming step ST111, a tungsten-containing tantalum film 13 containing tungsten and nitrogen is used while introducing a nitrogen gas and an argon gas into the sputtering chamber. Is formed to a thickness of 50 to 150 nm. Next, in the tantalum film patterning step ST112, with the resist mask formed on the tantalum film 13, a dry etching is performed on the tantalum film 13 using an etching gas containing CF _4, SF _6, or the like. After patterning 13, the resist mask is removed, and a lower electrode 13 b is formed as shown in FIG. At this time, the tantalum wiring 13a of the data line 52 is simultaneously formed. In this state, the tantalum wiring 13a and the lower electrode 13b are connected by the bridge portion 13c.

  Next, in the vapor phase oxidation step ST121 shown in FIG. 3, vapor phase oxidation is performed on the surface of the lower electrode 13b. As shown in FIG. 11C, tantalum containing tungsten and nitrogen is formed on the surface of the lower electrode 13b. An insulating layer 14b made of an oxide film is formed. An insulating layer 14a made of a tantalum oxide film containing tungsten and nitrogen is formed on the surface of the tantalum wiring 13a. In this embodiment, in the vapor phase oxidation step ST121, a tantalum oxide film having a thickness necessary for forming the insulating layer 14b, for example, a tantalum oxide film having a thickness of about 20 to 40 nm is formed.

  Next, in the anodic oxidation step ST122 shown in FIG. 3, anodic oxidation is performed using the lower electrode 13b as an anode in an organic acid-based or inorganic acid-based aqueous solution. At this time, since a tantalum oxide film having a thickness necessary for forming the insulating layer 14b is formed in the vapor phase oxidation step ST121, in the anodization step ST122, the tantalum oxide film formed in the vapor phase oxidation step ST121. Is applied to the lower electrode 13b. Therefore, in the anodic oxidation step ST122, defects in the tantalum oxide film formed in the vapor phase oxidation step ST121 are repaired, but no film growth occurs.

  Next, in the hydrogen addition annealing step ST130 (hydrogen introduction step) shown in FIG. 3, the element substrate 20 is heated in an atmosphere containing hydrogen. As a result, the insulating layer 14b becomes a tantalum oxide film containing tungsten, nitrogen, and hydrogen.

  Next, in the bridge portion removing step ST140 shown in FIG. 3, the bridge portion 13c is removed from the large element substrate 20 by dry etching, for example, as shown in FIG. As a result, the lower electrode 13b and the insulating layer 14b are separated from the data line 52 in an island shape. In this step, in addition to the bridge portion, unnecessary portions of the power supply pattern that remain on the element substrate 20 when the large element substrate 20 is cut are also removed. Further, the base layer 201 in the region corresponding to the pixel electrode 23 is removed as necessary.

  Next, an upper electrode formation step ST150 shown in FIG. 3 is performed. First, in the chromium film forming step ST151, Cr having a thickness of about 100 to 500 nm is formed with a uniform thickness by sputtering or the like, and then in the chromium film patterning step ST152, a photolithography technique is used. Then, the chromium film is patterned to form the metal layer 15c as the uppermost layer of the data line 52, the upper electrode 15a of the first TFD 10a, and the upper electrode 15b of the second TFD 10b as shown in FIG. . As described above, the necessary number of nonlinear elements 10 (TFDs 10 a and 10 b) are formed on the surface of the element substrate 20. Note that the bridge portion removal step ST140 shown in FIG. 3 may be performed after the upper electrode formation step ST150.

  Although illustration of subsequent manufacturing steps is omitted, after forming ITO with a uniform thickness by sputtering or the like to form the pixel electrode 23, the ITO film is patterned, and a part of the pixel electrode 23 is formed. It is formed so as to overlap the upper electrode 15b. Through the series of steps, the nonlinear element 10 and the pixel electrode 23 shown in FIGS. 9 and 10 are formed. After that, in the alignment film process P3, after forming the alignment film 24 by forming polyimide, polyvinyl alcohol, etc. in a uniform thickness on the surface of the element substrate 20 (see FIG. 8), in the rubbing process process, A rubbing process or other alignment process is performed on the alignment film 24. Next, in the sealing material printing step, the sealing material 104 (see FIG. 8) is annularly applied by a dispenser, screen printing, or the like. Note that a liquid crystal injection port is formed in part of the sealing material 104.

  Separately from the above element substrate forming process, an opposing substrate forming process (color filter forming process to rubbing process) is performed. First, as shown in FIG. 8, after preparing a large counter substrate 30 formed of a translucent material such as a glass substrate, black color is formed on the surface of the large counter substrate 30 in the color filter forming step. A matrix 39 and a color filter 38 are formed. Here, when color display is not necessary, the color filter 38 need not be formed. Next, in the flattening layer forming step, the flattening film 37 is formed to a uniform thickness on the color filter 38 to flatten the surface. Next, in the counter electrode forming step, the stripe-shaped counter electrode 31, that is, the scanning line 51 is formed using an ITO film or the like. Next, after an alignment film 34 having a uniform thickness is formed on the scanning line 51 or the like with polyimide or the like in the alignment film formation process, an alignment process such as a rubbing process is performed on the alignment film 34 in the rubbing process process. Apply.

  Thereafter, the large element substrate 20 and the large counter substrate 30 are aligned, and the sealing material 104 is sandwiched therebetween (bonding step), and the sealing material 104 is cured by ultraviolet curing or other methods ( Sealing material curing step). As a result, an empty panel structure including a plurality of liquid crystal devices is formed. Thereafter, the empty panel structure is cut into strip-shaped panel structures (primary cutting step 3). At the cut portion of the strip-shaped panel structure, the liquid crystal injection port consisting of the cut off portion of the sealing material 104 is opened to the outside. Therefore, after the liquid crystal is injected from the exposed liquid crystal injection port to the inside of the panel structure under reduced pressure. (Liquid crystal injection step) A sealing material such as resin is applied to each liquid crystal injection port to seal each liquid crystal injection port (injection port sealing step). In addition, since a liquid crystal adheres to a panel structure body by this process, the panel structure body which finished injecting the liquid crystal is cleaned (cleaning process). Thereafter, the panel structure is further cut to cut out a plurality of electro-optical devices 100 (secondary cutting step). Thereafter, the liquid crystal driving IC chip 260 and the like are mounted on the electro-optical device 100 to complete the electro-optical device 100 (mounting process).

[Other application examples to electro-optical devices]
In the above embodiment, since the TN mode or VAN mode liquid crystal device (electro-optical device) has been described as an example, the counter electrode is formed on the counter substrate. However, the pixel electrode and the counter electrode (common electrode) are formed on the element substrate. The present invention may be applied to a liquid crystal device (electro-optical device) in IPS (In-Plane Switching) mode or FFS (Fringe Field Switching) mode in which both of the above are formed.

[Example of mounting on electronic devices]
The electro-optical device to which the present invention is applied includes a personal computer (PC), an engineering work station (EWS), a pager, a word processor, a television, a viewfinder type or a monitor in addition to a mobile phone or a mobile personal computer. In addition to being applicable to electronic devices such as direct-view video tape recorders, electronic notebooks, electronic desk calculators, car navigation devices, POS terminals, touch panels, etc., they are used to construct electronic devices with large screens exceeding 30 inches. You can also.

(A)-(d) is sectional drawing which shows the nonlinear element to which this invention is applied, and its manufacturing method. It is explanatory drawing which shows the relationship between the material of each layer which comprises a nonlinear element, and an electrical property. It is process drawing which shows the manufacturing method of the nonlinear element to which this invention is applied. It is an analysis result of the insulating layer by dynamic secondary ion mass spectrometry. It is process drawing which shows the manufacturing method of another nonlinear element to which this invention is applied. It is process drawing which shows the manufacturing method of another nonlinear element to which this invention is applied. 1 is a block diagram showing an electrical configuration of an electro-optical device (liquid crystal device) to which the present invention is applied. 1 is a cross-sectional view schematically showing a configuration of an electro-optical device to which the present invention is applied. FIG. 8 is a plan view showing a layout for several pixels including nonlinear elements in the electro-optical device shown in FIG. 7. FIG. 8 is an explanatory diagram of nonlinear elements formed in each pixel in the electro-optical device illustrated in FIG. 7. FIG. 8 is a process diagram showing a part of an element substrate forming process in the manufacturing process of the electro-optical device shown in FIG.

Explanation of symbols

10, 10x ··· Non-linear element (TFD), 13 ·· Tantalum film, 13b, 13x ·· Lower electrode, 14b, 14x · · Insulating layer, 15b, 15x · · Upper electrode, 20 · · Device substrate, 100 · · · Electro-optic device

Claims (4)

In a method for manufacturing a nonlinear element comprising a lower electrode, an insulating layer covering the surface side of the lower electrode, and an upper electrode facing the lower electrode through the insulating layer,
A lower electrode forming step of forming the lower electrode with a nitrogen-containing tantalum film;
A gas phase oxidation step of oxidizing the surface of the lower electrode by a gas phase oxidation method to form a nitrogen-containing tantalum oxide film;
A hydrogen introduction step of introducing hydrogen into the nitrogen-containing tantalum oxide film;
A method for manufacturing a non-linear element, comprising: After the vapor phase oxidation step, an anodic oxidation step of performing anodization using the lower electrode as an anode,
2. The method of manufacturing a nonlinear element according to claim 1, wherein the hydrogen introduction step is performed between at least one of the gas phase oxidation step and the anodization step and after the anodization step.   In the vapor phase oxidation step, a nitrogen-containing tantalum oxide film having the same thickness as the insulating layer is formed, and in the anodic oxidation step, a voltage corresponding to the thickness of the nitrogen-containing tantalum oxide film is applied to the lower electrode. The method of manufacturing a nonlinear element according to claim 2. An electro-optical device manufacturing method using the nonlinear element manufacturing method according to claim 1,
A method of manufacturing an electro-optical device, wherein the nonlinear element is formed as a pixel switching element in each of a plurality of pixel regions on an element substrate.

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