JP2005302995A - Non-linear element and manufacturing method thereof, electro-optical device and electronic instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-linear element reduced in an element capacitance, excellent in the easiness of manufacturing, and capable of being optimally employed for a highly precise electro-optical device or the like. <P>SOLUTION: A TFD element 13 is equipped with a lower electrode 14 laminated on a substrate 10, an insulating film 18, and an upper electrode 19. The insulating film 18 comprises a first insulating film 181 formed on the side surface 14b of the lower electrode 14, and a second insulating film 182 having a film thickness larger than that of the first insulating film 181 and formed on the upper surface 14a of the lower electrode. The insulating film 18 is an oxide film obtained by oxidizing a Ta film containing nitrogen. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a nonlinear element, a method for manufacturing the same, an electro-optical device, and an electronic apparatus.

As an active matrix type electro-optical device, there is known a liquid crystal display device that employs a two-terminal type non-linear element having a laminated structure (MIM structure) of a first conductive film / insulating film / second conductive film as a pixel switching element. ing. The non-linear element having the above structure is effective in reducing the cost of the liquid crystal display device because a high manufacturing yield can be obtained and it can be manufactured at low cost. In addition, technological developments to improve the display quality are being promoted. For example, Patent Document 1 below discloses a nonlinear element 200 having a planar structure and a cross-sectional structure in FIGS. 6A and 6B, respectively. The nonlinear element 200 includes a first conductive film 203 formed on a substrate 201 via a base insulating film 202, an insulating film 204 formed so as to cover the first conductive film 203, and a second conductive film 205. The first conductive film 203 is formed integrally with the data line, and is connected to the pixel electrode 206 through the second conductive film 205. This document discloses that the use of a Ta film containing nitrogen for the first conductive film 203 can realize a reduction in resistance of the nonlinear element and can improve contrast.
Japanese Patent No. 2841571

By the way, in recent liquid crystal display devices and the like, the display definition is remarkably increased, and as the pixel definition is increased, the capacitance of the liquid crystal is reduced accordingly. Therefore, in order to obtain a high contrast display, the capacitance of the nonlinear element is also increased. It is necessary to reduce the capacity ratio and ensure the capacity ratio. According to the study of the present inventor, the nonlinear element described in Patent Document 1 does not cause a problem related to the capacitance ratio when used in a liquid crystal display device having a definition of 200 ppi or less, but has a definition of about 250 ppi or more. When manufacturing a liquid crystal display device, it turned out that the following problems arise.
In other words, miniaturization of the element size is effective for reducing the capacity of the nonlinear element, but there are cases where the electrode cannot be sufficiently miniaturized due to limitations due to the capability of the manufacturing apparatus. If an attempt is made to reduce the element capacitance by increasing the insulating film thickness constituting the element, there arises a problem that the element characteristics deteriorate due to the deterioration of nonlinearity or the increase of element resistance.

  The present invention has been made in view of the above-described problems of the prior art, has a reduced element capacity, is excellent in manufacturability, and can be suitably used for a high-definition electro-optical device or the like. It aims at providing a nonlinear element and its manufacturing method. Another object of the present invention is to provide an electro-optical device that can provide high-quality display and can be manufactured at low cost.

In order to solve the above-described problems, the present invention provides a nonlinear element including a first conductive film, an insulating film, and a second conductive film laminated on a base material, wherein the insulating film includes the first conductive film. A first insulating film formed on a side surface of the first conductive film; and a second insulating film formed on the upper surface of the first conductive film and having a thickness larger than that of the first insulating film. The non-linear element is characterized in that the insulating film is an oxide film formed by oxidizing a Ta film containing nitrogen.
The nonlinear element having the above-described configuration is a nonlinear element having a so-called lateral structure in which a portion that substantially functions as an element is formed on the side surface of the first conductive film that functions as a lower electrode. Further, by using an oxide film obtained by oxidizing a Ta film containing nitrogen as the insulating film, the relative dielectric constant of the insulating film itself is reduced, thereby realizing a reduction in element capacitance.

In the nonlinear element of the present invention, the insulating film is preferably an oxide film formed by oxidizing a metal film containing Ta ₂ N. According to the oxide film obtained by oxidizing Ta ₂ N, an insulating film having a uniform and low relative dielectric constant can be obtained, so that the thickness of the first insulating film and the second insulating film can be reduced. . Further, by reducing the thickness of the first insulating film, a low-resistance element can be obtained, so that a non-linear element that can be driven at a low voltage is obtained, and the thickness of the second insulating film is reduced. Thus, patterning at the time of manufacture is facilitated, and the step coverage of the second conductive film formed on the second insulating film can be improved. Thereby, a low-capacity non-linear element that can be driven at a low voltage and can be manufactured with a high yield can be provided.

In the nonlinear element of the present invention, the insulating film may be an oxide film formed by oxidizing a metal film containing a mixed phase of α-Ta and Ta ₂ N. This configuration can also provide a low-capacity non-linear element that can be driven at a low voltage and can be manufactured with a high yield.

In the nonlinear element of the present invention, the insulating film may be an oxide film formed by oxidizing a Ta metal film containing an additive element other than nitrogen, and the insulating film is (Ta _x M _{1 −x} ) ₂ N (where 0 <x <1, M is one or more elements selected from Nb, V, W, Mo, Cr and Si), and oxidizes a metal film containing a compound represented by the composition formula It can be set as the structure which is an oxide film formed.
According to this configuration, it is possible to obtain a non-linear element capable of obtaining a good display with no display afterimage since the change with time of the current-voltage characteristic is sufficiently small.

  Next, the method for manufacturing a nonlinear element according to the present invention includes a first conductive film laminated on a base material, an insulating film, and a second conductive film, and the insulating film is the first conductive film. A method for manufacturing a non-linear element, comprising: a first insulating film formed on a side surface portion of the first insulating film; and a second insulating film having a larger film thickness than the first insulating film and formed on an upper surface portion of the first conductive film. A step of forming a first conductive film made of Ta containing nitrogen on a substrate, a surface of the first conductive film is oxidized to form a second insulating film, and the first conductive film and the first conductive film Forming a laminated film comprising two insulating films, patterning the laminated film into a predetermined shape, and oxidizing the side surfaces of the first conductive film to cover the first conductive film and the side surfaces thereof. A step of forming a first insulating film, and a step of forming the second conductive film covering the patterned laminated film When, characterized in that a step of patterning the second conductive film into a predetermined shape.

The non-linear element manufactured by this manufacturing method is a non-linear element having a lateral structure in which an effective element portion is formed on the side surface portion of the first conductive film. In this manufacturing method, since the insulating film formed on the conductive film is an oxide film formed by oxidizing a Ta film containing nitrogen, the relative dielectric constant is smaller than that of a conventional tantalum oxide film. . Thereby, since the film thickness of the insulating film formed on the conductive film can be reduced, patterning can be performed efficiently and with high accuracy when the laminated film is patterned in a subsequent process. Furthermore, since the amount of etching gas used is reduced, it contributes to a reduction in manufacturing cost.
Also, since the first insulating film formed on the side surface of the first conductive film is also made of a Ta oxide containing nitrogen, a low capacitance element is formed with a small relative dielectric constant and a thin film thickness. As a result, a non-linear element having a low element resistance can be formed.
Therefore, according to this manufacturing method, low voltage driving is possible, and a small-capacity nonlinear element can be manufactured easily and efficiently.

In the manufacturing method, the step of forming the first conductive film made of Ta containing nitrogen on the base material is a step of forming the first conductive film containing Ta ₂ N on the base material. Also good.
The step of forming the first conductive film made of Ta containing nitrogen on the base material includes the step of forming the first conductive film containing a mixed phase of α-Ta and Ta ₂ N on the base material. It may be.
Furthermore, the step of forming the first conductive film made of Ta containing nitrogen on the base material is a step of forming the first conductive film made of Ta containing an additive element other than nitrogen on the base material. May be.
Alternatively, the step of forming a first conductive film made of Ta containing nitrogen onto the substrate, on the substrate _{(Ta x M 1-x)} 2 N ( where, 0 <x <1, M is Nb , V, W, Mo, Cr, Si) may be a step of forming the first conductive film including a compound represented by a composition formula.
According to these manufacturing methods, since an insulating film having a uniform film quality and a low relative dielectric constant can be obtained, a nonlinear element having excellent reliability can be obtained.

  Next, an electro-optical device according to the present invention includes the above-described nonlinear element according to the present invention as a pixel switching element. According to this configuration, it is possible to provide an electro-optical device that can provide a high-contrast, high-definition display.

  Next, an electronic apparatus according to the present invention includes the electro-optical device according to the present invention described above. According to such a configuration, an electronic device including a display unit capable of high-contrast, high-quality, high-definition display is provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in each drawing referred to below, the relationship between dimensions and sizes is appropriately changed for easy understanding of the drawing.

(Liquid crystal display device)
FIG. 1 is a block diagram showing an electrical configuration of a liquid crystal display device which is an example of an electro-optical device according to the present invention. The liquid crystal display device shown in FIG. 1 has a TFD (Thin Film Diode) element (two-element switching element) as a switching element. This is an active matrix liquid crystal display device using a terminal-type nonlinear element. The liquid crystal display device includes a plurality of scanning lines 25 extending in the X direction, a plurality of data lines 11 extending in the Y direction, and subpixels 50 provided at each intersection of the scanning lines 25 and the data lines 11. And have. Further, among the plurality of scanning lines 25, the odd-numbered scanning lines 25 counted from the top in FIG. 1 (hereinafter simply referred to as “odd-numbered scanning lines”) are connected to the first Y driver IC 401, The even-numbered scanning lines 25 (hereinafter simply referred to as “even-numbered scanning lines”) counted from the top in FIG. 1 are connected to the second Y driver IC 402. The scanning signal generated by these Y driver ICs is supplied to each scanning line 25.

  Hereinafter, the first Y driver IC 401 and the second Y driver IC 402 are simply referred to as “Y driver IC 40” when it is not necessary to distinguish between them. Each data line 11 is connected to an X driver IC 41, and a data signal generated by the X driver IC 41 is supplied. On the other hand, each of the plurality of sub-pixels 50 arranged in a matrix corresponds to one of R (red), G (green), and B (blue). Each sub-pixel 50 has a configuration in which a liquid crystal display element 51 and a TFD element 13 are connected in series.

Next, FIG. 2 is a perspective view showing a configuration when the liquid crystal display device according to the present embodiment is viewed from the back side (that is, the side opposite to the side where the observer should be positioned). As shown in FIG. 2, the negative direction of the X axis is defined as “A side” and the positive direction is defined as “B side”.
As shown in FIG. 2, the liquid crystal display device includes an element substrate (support substrate) 10 and a counter substrate (other substrate) 20 facing each other, which are bonded together by a sealing material 30. A liquid crystal (not shown in FIG. 2) that is an electro-optical material is sealed in the enclosed region. The sealing material 30 is formed in a substantially rectangular frame shape along the edge of the counter substrate 20, but has a shape in which a part is opened to enclose the liquid crystal. For this reason, the opening is sealed with the sealing material 31 after the liquid crystal is sealed.

  The sealing material 30 has a large number of conductive particles dispersed therein. The conductive particles are, for example, plastic particles plated with metal or conductive resin particles. The conductive particles are electrically connected to each other on the element substrate 10 and the counter substrate 20. It also functions as a spacer that keeps the gap (cell gap) between the substrates constant. Actually, a polarizing plate for polarizing incident light, a retardation plate for compensating for interference colors, and the like are appropriately attached to the outer surfaces of the element substrate 10 and the counter substrate 20.

  The element substrate 10 and the counter substrate 20 are light-transmitting plate-like base materials such as glass, quartz, and plastic. Among these, the plurality of data lines 11 described above are formed on the inner surface (opposite substrate 20 side) surface of the element substrate 10 located on the observation side, while the inner side (element substrate 10 side) of the counter substrate 20 located on the back side. A plurality of scanning lines 25 are formed on the surface. In addition, the element substrate 10 has an area outside the sealing material 30 (that is, an area that does not face the sealing material 30 and the liquid crystal; hereinafter, referred to as an “edge area”) 10 a. The X driver IC 41 is located near the center of the edge region 10a in the X direction, and the first Y driver IC 401 and the second Y driver IC 402 are located on both sides of the X driver IC 41, respectively. (Chip on Glass) technology. That is, these driver ICs are mounted on the element substrate 10 via an anisotropic conductive film (ACF) in which conductive particles are dispersed in an adhesive. Further, a plurality of terminals 17 are formed in the vicinity of the edge portion of the element substrate 10 in the edge region 10a, and one end of a flexible substrate (not shown) is joined in the vicinity of the portion where the terminals 17 are formed. Is done. An external device such as a circuit board is joined to the other end of the flexible board.

  Under such a configuration, the X driver IC 41 generates a data signal according to a signal input from an external device via the flexible substrate and the pad 17, and outputs the data signal to the data line 11. On the other hand, the Y driver ICs 401 and 402 generate and output a scanning signal in accordance with a signal input from an external device via the flexible substrate and the pad 17. This scanning signal is transmitted from the routing wiring 16 formed on the element substrate 10 to the counter substrate 20 side through the conductive particles in the sealing material 30, and is applied to each scanning line 25 on the upper substrate 20.

  Next, a configuration in a region (hereinafter referred to as “display region”) surrounded by the inner peripheral edge of the sealing material 30 in the liquid crystal display device will be described. FIG. 3 is a diagram showing a portion in the display area of the cross section taken along line C-C ′ in FIG. 2. 4A is a plan configuration diagram showing one sub-pixel region of the liquid crystal display device according to the present embodiment, and FIG. 4B is an enlarged view of the TFD element 13 shown in FIG. 4A. 4 (c) is a cross-sectional configuration diagram taken along the line DD 'shown in FIG. 4 (b).

  As shown in FIG. 3, the liquid crystal display device of this embodiment is sealed in a region sandwiched between the element substrate 10 and the counter substrate 20 that are disposed to face each other and the substrates 10 and 20. The liquid crystal 35 is provided. A plurality of pixel electrodes 12 arranged in a matrix and a plurality of pixel electrodes 12 extending in the Y direction on the inner surface (on the liquid crystal 35 side) surface of the element substrate 10 in the display region shown in FIG. Data lines 11 are formed. Each pixel electrode 12 is a substantially rectangular electrode in plan view formed of a transparent conductive material such as ITO (Indium Tin Oxide). Each pixel electrode 12 and the data line 11 adjacent to the pixel electrode 12 on one side are connected via a TFD element (not shown) (see FIG. 4A). Further, as shown in FIG. 3, the surface of the element substrate 10 on which the data lines 11, the pixel electrodes 12, and the TFD elements are formed is covered with an alignment film 151. The alignment film 151 is an organic thin film made of polyimide or the like, and is subjected to a rubbing process for defining the alignment direction of the liquid crystal 35 when no voltage is applied.

  Here, as shown in FIG. 4A, when the region corresponding to one subpixel 50 among the elements on the element substrate 10 is viewed from the counter substrate 20 side, the length of the pixel electrode 12 having a substantially rectangular shape in plan view. A data line 11 extends along the side direction. As shown in the enlarged plan view of FIG. 4B, the TFD element 13 includes a lower electrode (first conductive film) 14 having a rectangular shape in plan view and extending substantially parallel to the data line 11, and the lower electrode 14 The first upper electrode (second conductive film) 11a and the second upper electrode (second conductive film) 19 formed on the insulating film 18 apart from each other. It consists of and. As shown in FIG. 4A, the first upper electrode 11a is formed by extending a part of the data line 11 toward the pixel electrode 12, and the second upper electrode 19 is formed by the lower electrode. The TFD element 13 and the pixel electrode 12 are electrically connected so as to partially overlap the pixel electrode 12 at the end opposite to the pixel 14.

  The TFD element 13 includes a first TFD element 131 and a second TFD element 132, and faces the first upper electrode 11 a through the first insulating film 181 in the surface region of the lower electrode 14. A first TFD element 131 is formed in the region, and a second TFD element 132 is formed in a region facing the second upper electrode 19 with the first insulating film 181 interposed therebetween.

The second TFD element 132 will be described in more detail. As shown in FIG. 4C, the TFD element 132 includes a lower electrode (first conductive film) 14 formed on the element substrate 10 and a lower electrode. 14 and the second upper electrode 19 formed so as to partially ride on the insulating film 18. The insulating film 18 includes a first insulating film 181 that covers the side surface 14b of the lower electrode 14, and a second insulating film 182 that is continuous therewith. And, as a result of adopting a metal / insulator / metal sandwich structure in a region where the second upper electrode 19 and the lower electrode 14 face each other through the insulating film 18, it has a positive and negative bidirectional diode switching characteristic. A TFD element 132 is configured.
In the present embodiment, the first insulating film 181 is thinly formed by the second insulating film 182, and with this configuration, the region where the lower electrode 14 and the upper electrode 19 face each other through the first insulating film 181 (lower This is a so-called lateral structure TFD element in which the side portion of the electrode 14 substantially operates as an element.
Although not shown, the first TFD element 131 has a configuration in which the first upper electrode 11a is arranged in place of the upper electrode 19 in the cross-sectional structure shown in FIG.

The film thickness of the second insulating film 182 that covers the upper surface 14a of the lower electrode 14 is preferably more than twice the film thickness of the first insulating film 181 that covers the side surface 14b of the lower electrode 14. For example, the film thickness of the first insulating film 181 is about 10 to 20 nm, and the film thickness of the second insulating film 182 is about 30 to 100 nm.
The film thickness of the first insulating film 181 forming the element capacitance of the TFD element 13 is set according to the element characteristics of the TFD element 13, and the second insulating film 182 forms a predetermined element capacitance of the TFD element. It is formed to an appropriate thickness.

  In the TFD element 13 according to the present embodiment, the first TFD element 131 and the second TFD element 132 are formed on the lower electrode 14 so as to be separated from each other. Has opposite diode switching characteristics. Thus, since the TFD element 13 has a configuration in which two diodes are connected in series in opposite directions, the current-voltage nonlinear characteristic is bi-directional with positive and negative in comparison with the case where one diode is used. Symmetrized over. However, in order to ensure the symmetry of such nonlinear characteristics, the thickness of the first insulating film 181 constituting the first TFD element 131 and the thickness of the first insulating film 181 constituting the second TFD element 132 And the areas of the upper electrodes 11a and 19 in a region facing the lower electrode 14 through the first insulating film 181 must be equal to each other. In this embodiment, if the upper electrodes 11a and 19 are formed to have the same width, the positive / negative symmetry of the current-voltage characteristics of the TFD element 13 can be easily obtained.

In the case of this embodiment, the lower electrode 14 is formed of a metal film made of Ta ₂ N, and the insulating film 18 covering the lower electrode 14 is formed by anodizing the Ta ₂ N film. It is an oxide film.
The insulating film 18 having such a configuration has a relative dielectric constant of about 13, which is significantly smaller than the relative dielectric constant (22 to 28) of a conventionally used Ta oxide film. By providing such an insulating film 18 and adopting a lateral structure, the TFD element 13 according to the present embodiment realizes a significant narrowing of the effective element area, and the element capacitance is remarkable. It has been reduced to.
Thus, according to the TFD element 13 in which the element capacity is greatly reduced, even when the liquid crystal capacity is reduced due to the high definition of pixels, a sufficient capacity ratio with respect to the liquid crystal capacity can be obtained, and a high contrast display can be obtained. Can be obtained.

In addition, since the relative dielectric constant of the first insulating film 18 that constitutes an effective element portion is small, the film thickness can be reduced and the element resistance can be reduced. Accordingly, the driving voltage of the element can be reduced, and the power consumption of the liquid crystal display device can be reduced.
Further, in the TFD element 13, since the capacity of the second insulating film 182 covering the upper surface 14a of the lower electrode 14 can be reduced, the film thickness can be reduced. Thereby, since the total film thickness of the lower electrode 14 and the second insulating film 182 is also reduced, the step coverage of the upper electrodes 11a and 19 formed so as to partially run on the second insulating film 182 is improved. This contributes to improving the reliability and manufacturing yield of the TFD element 13.

  Further, the lateral-structure TFD element 13 is formed by forming an oxide film to be the second insulating film 182 on the upper surface of the metal film, and then patterning the stacked structure of the metal film and the oxide film into a predetermined planar shape. However, since the oxide film is difficult to be processed as compared to a metal film, if the oxide film is thick, the processing efficiency and processing accuracy are reduced. Processing itself may not be possible due to damage to the resist. On the other hand, in the TFD element 13 according to the present invention, since the second insulating film 182 can be thinned, the processing efficiency and processing accuracy in the patterning process can be improved.

Furthermore, when the metal film (Ta ₂ N film) for forming the lower electrode 14 has the same thickness as the Ta film used conventionally, the film thickness of the second insulating film 182 formed by anodic oxidation is conventionally increased. Since the thickness of the lower electrode 14 which is the remaining portion can be reduced, the thickness of the lower electrode 14 becomes thicker than before. For this reason, the variation (deviation) in film thickness of the plurality of lower electrodes 14 formed on the substrate is reduced, thereby effectively suppressing variations in brightness and contrast and obtaining a high-quality display. .

In the present embodiment, the lower electrode 14 can have a mixed phase structure of Ta (α-Ta) having an α structure (bcc crystal system) and Ta ₂ N, and the insulating film 18 covering the lower electrode 14 is a metal having the mixed phase structure. An oxide film formed by oxidizing the film can be obtained. Even in such a configuration, since the dielectric constant of the insulating film 18 is small, the device capacitance and the device resistance can be reduced, and a high-definition and high-contrast display can be obtained.

The lower electrode 14 _is shown _{(Ta x M 1-x)} 2 N ( where, 0 <x <1, M is Nb, V, W, Mo, Cr, and elements selected from Si) in the composition formula comprising A metal film containing a compound can be used, and the insulating film 18 can be an oxide film formed by oxidizing the metal film. As described above, by using the lower electrode 14 containing the above-mentioned elements, the change with time of the current-voltage characteristics is sufficiently reduced, whereby a good display without a display afterimage can be obtained. Of the additive elements M listed above, if the structure contains tungsten (W) in particular, the above-described effects can be further improved.

  The data line 11 (including the first upper electrode 11a) and the second upper electrode 19 are formed of the same layer made of various conductive materials such as chrome (Cr) and aluminum (Al), for example. In addition to materials, tantalum or molybdenum (Mo) can also be used.

On the other hand, as shown in FIG. 3, a reflective layer 21, a color filter 22, a light shielding layer 23, an overcoat layer 24, a plurality of scanning lines 25 and an alignment film 26 are formed on the surface of the counter substrate 20.
The reflective layer 21 is a thin film formed of a metal having light reflectivity such as aluminum or silver. Light incident on the liquid crystal display device from the observation side is reflected on the surface of the reflective layer 21 and emitted to the observation side, thereby realizing a so-called reflection type display. Here, as shown in FIG. 3, the region covered with the reflective layer 21 on the inner surface of the counter substrate 20 is a rough surface on which a large number of fine irregularities are formed. Therefore, fine irregularities (that is, scattering structures) reflecting the rough surface are formed on the surface of the reflective layer 21 formed in a thin film so as to cover the rough surface. As a result, incident light from the observation side is reflected in a state of being appropriately scattered on the surface of the reflective layer 21, and a specular reflection on the surface of the reflective layer 21 is avoided to realize a wide viewing angle.

Further, if an opening region in which the reflective layer 21 is not partially formed is provided in the planar region of the pixel electrode 12 shown in FIG. 4A, transmissive display through the opening region becomes possible, and transflective reflection occurs. Type liquid crystal display device can be constructed.
Note that FIG. 3 illustrates a case where the uneven shape is directly formed on the surface of the substrate 20, but the structure for imparting the scattering function to the reflective layer 21 is not limited to the example given in this embodiment. For example, a resin film is formed on the substrate 20 and irregularities are formed on the surface thereof, or an optical element having light scattering properties on the reflective layer 21 (a resin film obtained by kneading and curing materials having different refractive indexes) Of course, it is also possible to apply the one provided with.

The color filter 22 is a resin layer formed on the surface of the reflective layer 21 corresponding to each sub-pixel 50, and any of R (red), G (green), and B (blue) depending on the dye or pigment. It is colored crab. A pixel (dot) of the display image is configured by the three sub-pixels 50 corresponding to different colors. The light shielding layer 23 is formed in a lattice shape corresponding to the gaps between the pixel electrodes 12 arranged in a matrix on the element substrate 10, and plays a role of shielding the gaps between the pixel electrodes 12.
As shown in FIG. 3, the light shielding layer 23 in the present embodiment has a configuration in which color filters 22 for three colors of R, G, and B are laminated. The overcoat layer 24 is a layer for flattening the unevenness formed by the color filter 22 and the light shielding layer 23, and is formed of, for example, an epoxy or acrylic resin material.

The scanning line 25 is a belt-like electrode formed on the surface of the overcoat layer 24 by a transparent conductive material such as ITO. Each scanning line 25 is formed to extend in the X direction in the figure so as to face the plurality of pixel electrodes 12 that are arranged in the X direction on the element substrate 10. Then, the liquid crystal display element 51 shown in FIG. 1 is configured by the pixel electrode 12, the scanning line 25 opposed to the pixel electrode 12, and the liquid crystal 35 sandwiched therebetween.
That is, when a voltage higher than the threshold is applied to the TFD element 13 by supplying a scanning signal to the scanning line 25 and supplying a data signal to the data line 11, the TFD element 13 is turned on. As a result, charges are accumulated in the liquid crystal display element 51 connected to the TFD element 13, and the alignment direction of the liquid crystal 35 changes. Thus, the desired display is performed by changing the orientation direction of the liquid crystal 35 for each sub-pixel 50. On the other hand, even if the TFD element 13 is turned off after the charge is accumulated, the charge accumulation in the liquid crystal display element 51 is maintained. Further, the surface of the overcoat layer 24 on which the plurality of scanning lines 25 are formed is covered with an alignment film 26 similar to the alignment film 151 on the element substrate 10.

In the liquid crystal display device of the present embodiment having the above configuration, as shown in FIG. 4, in the TFD element 13, the first insulating film 181 and the second insulating film 182 are formed so as to cover the lower electrode 14, and The first insulating film 181 covering the side surface 14b of the electrode 14 is formed thinner than the second insulating film 182 covering the upper surface 14a of the lower electrode 14. With this configuration, the element capacitance of the TFD elements 131 and 132 is formed on the side surface portion of the lower electrode 14. By adopting a lateral structure in which is formed, the effective element area of the TFD elements 131 and 132 can be reduced, and the lower electrode 14 is made of Ta ₂ N, and the insulating film 18 Is a Ta ₂ N oxide film, the relative dielectric constant of the first insulating film 181 constituting the TFD elements 131 and 132 is reduced, and the element capacitance can be reduced. Therefore, according to the liquid crystal display device of the present embodiment, the element capacity of the TFD elements 131 and 132 can be remarkably reduced by narrowing the effective element area and lowering the relative dielectric constant of the insulating film. Even when the liquid crystal capacity becomes smaller due to higher definition, the ratio between the element capacity and the liquid crystal capacity (capacity ratio) can be made sufficiently large, and high-definition and high-quality display can be obtained. Yes.
As described above, according to the present invention, the TFD element provided in each pixel of the electro-optical device including the liquid crystal display device can obtain high reliability with high in-plane uniformity, and low consumption of the electro-optical device. It contributes to electric power.

(Nonlinear device manufacturing method)
Next, a method for manufacturing a nonlinear element according to the present invention will be described with reference to the drawings.
According to the manufacturing method of the present invention, it is possible to accurately form the TFD element 13 according to the above-described embodiment, and to provide an element substrate suitable for use in a high-definition electro-optical device without causing variations in element characteristics. Can be manufactured. Hereinafter, a method for manufacturing an element substrate including a nonlinear element according to the present invention and a method for manufacturing the liquid crystal display device according to the previous embodiment including the element substrate will be described with reference to FIG.

FIG. 5 is a cross-sectional process diagram illustrating a manufacturing process of the element substrate according to the present embodiment.
First, as shown to Fig.5 (a), the support substrate (base material) 10 which has translucency, such as glass and a plastics, is prepared. The support substrate 10 constitutes the element substrate 10 shown in FIGS. 2 to 4 through the respective steps according to the present embodiment. Then, on the supporting substrate 10, a metal film 114 made of Ta ₂ N, and an insulating film 180 formed by anodizing the Ta ₂ N, to form a multilayer film 130 by laminating in this order by sputtering or the like . Alternatively, the insulating film 180 may be formed by partially oxidizing the upper surface of the metal film 114 made of Ta ₂ N by anodic oxidation. The metal film 114 can be made of Ta ₂ N by using a mixed gas obtained by adding a predetermined amount of nitrogen gas to argon in a sputtering method using a Ta target. The metal film 114 forms the lower electrode 14 shown in FIG. 4 through a subsequent process, and the insulating film 180 forms the second insulating film 182 through a subsequent process.

Further, as described above, the lower electrode 14 can have a mixed phase structure of Ta ₂ N and α-Ta, and can also include elements other than Ta and nitrogen. In the case of a mixed phase structure of α-Ta and Ta ₂ N, when the metal film 114 is formed by the sputtering method, the mixed phase structure is easily formed by adjusting the nitrogen gas concentration in the film forming gas. be able to. Also the lower electrode _{14 (Ta x M 1-x} ) 2 N ( where, 0 <x <1, M is Nb, V, W, Mo, Cr, chosen element from Si) from represented by a composition formula compounds To achieve this, a target containing Ta and the element M (M = Nb, V, W, Mo, Cr, Si) at a predetermined composition ratio is used as a target used for forming the metal film 114. It can be formed by performing sputtering in a film forming gas atmosphere containing nitrogen.

Next, as shown in FIG. 5B, by using a known photolithography technique, the laminated film 130 is patterned into a predetermined shape, and the laminated film 130a in which the metal film 114a and the second insulating film 182 are laminated is formed. obtain. In the step of forming the laminated film 130, the thickness of the insulating film 180 is set to a thickness corresponding to the thickness of the second insulating film 182 shown in FIG. 4, but in the TFD element 13 according to the present invention, Since the second insulating film 182 can be made thin as described in (1), the patterning process shown in FIG. 5B can be performed easily and with high accuracy. For example, if the insulating film 180 is a Ta oxide film that has been used in the past, its relative dielectric constant is as large as about 22 to 28. Therefore, a Ta ₂ N oxide film was used as in the present invention. In order to realize an element capacity equivalent to the case, it is necessary to increase the thickness of the insulating film to about 2 to 3 times. Thus, when the insulating film thickness is increased, the selective removal becomes extremely difficult. In other words, if the etching energy is increased in order to remove the thick insulating film, the photoresist serving as the mask material is damaged, and it becomes difficult to remove the photoresist or patterning itself cannot be performed accurately. On the other hand, in the present invention, as described above, since the film thickness of the second insulating film 182 (insulating film 180) made of the Ta ₂ N oxide film can be reduced, the above-described problem does not occur. Improvement in machining efficiency and machining accuracy can be realized.

In addition, when the insulating film 180 is formed by anodic oxidation, the film thickness is thinner than when a conventional tantalum oxide film is used. If so, the thickness of the metal film 114 after the anodic oxidation becomes thicker than before. Therefore, even if the initial film thickness of the metal film 114 varies within the substrate surface, the variation in the film thickness becomes relatively small, and the TFD within the substrate surface due to the film thickness variation of the lower electrode 14 is reduced. The characteristic variation of the element 13 can be reduced.
Furthermore, since the amount of etching gas used for the patterning can be reduced, the manufacturing cost can be reduced.

  Thereafter, as shown in FIG. 5C, the first insulating film 181 is formed by oxidizing the side surface of the metal film 114a. Through this oxidation process, the portion of the metal film 114 a that remains unoxidized becomes the lower electrode 14. The oxidation treatment of the metal film 114a can be performed by anodic oxidation, thermal oxidation, high-pressure steam oxidation, plasma oxidation, ozone oxidation, UV oxidation, or the like.

In the present embodiment, since the metal film 114 is made of Ta ₂ N, the first insulating film 181 is a Ta ₂ N oxide film. As shown in FIG. 4C, the first insulating film 181 forms an effective element portion between the upper electrodes 11a and 19 and the lower electrode 14 in the TFD element 13. . Therefore, the film thickness is set according to the element characteristics of the TFD element 13 to be manufactured. However, in the manufacturing method of this embodiment, the first insulating film 181 also has a small relative dielectric constant, so the film thickness is reduced. Therefore, it is possible to realize a reduction in element resistance as well as a reduction in element capacitance, and a small-capacity nonlinear element that can be driven at a low voltage.

Subsequently, as shown in FIG. 5D, the upper electrode 19 made of chromium is patterned so as to partially cover the first insulating film 181 and the second insulating film 182, so that the TFD of the above embodiment is used. Element 132 is obtained. The cross-sectional structure shown in FIG. 5 (d) corresponds to the cross-sectional structure along the line DD 'shown in FIG. 4 (b). In practice, the data line 11 is also formed when the pattern of the upper electrode 19 is formed. A pattern is formed at the same time.
Also in the step of forming the upper electrode 19, a useful effect can be obtained by forming the second insulating film 182 thin. That is, the total thickness of the lower electrode 14 and the second insulating film 182 can be reduced by the second insulating film 182 that can significantly reduce the film thickness as compared with the conventional case. The step height with respect to the upper surface of the second insulating film 182 is reduced, and as a result, the step coverage of the upper electrode 19 formed on the second insulating film 182 from the surface of the support substrate 10 is improved, so that the TFD element is obtained. 13 reliability can be improved.

  Furthermore, the effect of increasing the step coverage is particularly great when the thickness of the lower electrode 14 is reduced to the same level as in the prior art. That is, if the initial film thickness of the metal film 114 before the insulating film 180 is formed by anodic oxidation is thinned in advance, the laminated film 130 after the insulating film 180 having a film thickness capable of obtaining a predetermined element capacity is formed. Since the film thickness is also reduced, the step coverage of the upper electrode 19 becomes better.

  Next, as shown in FIG. 4A, the pixel electrode 12 made of a transparent conductive material such as ITO is formed so as to partially ride on one end side (the side opposite to the lower electrode 14) of the second upper electrode 19. If the alignment film 151 covering these constituent members is formed, the element substrate 10 shown in FIG. 2 is obtained. In forming the upper electrodes 19 and 11a and the data line 11, a method of patterning using a photolithography technique by forming a metal film by a film forming method such as a sputtering method can be applied.

  Then, the element substrate 10 obtained through the manufacturing process according to the manufacturing method of the present embodiment is bonded to the counter substrate 20 separately manufactured by a known manufacturing method and the sealing material 30 as shown in FIG. In addition, the liquid crystal display device of the previous embodiment is obtained by sealing the liquid crystal in a space between the sealing material 30 and the two substrates 10 and 20.

  As described above, according to the manufacturing method of the present embodiment, an element substrate including a small-capacity lateral TFD element having uniform element characteristics and excellent reliability can be easily and highly accurately and at low cost. Therefore, it is possible to manufacture a liquid crystal display device excellent in display uniformity and reliability.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, the technical scope of this invention is not limited to an Example.

(Example 1)
In this example, as the working samples 1 and 2, the liquid crystal display device according to the previous embodiment is manufactured by the above-described manufacturing method, and the constituent materials of the lower electrode (first conductive film) are different as the comparative samples 1 and 2. A liquid crystal display device provided with a nonlinear element was manufactured, and as the comparative samples 3 and 4, the liquid crystal display device described in the above-mentioned Patent Document 1 was manufactured, and the characteristics were compared.

<Example 1>
As an implementation sample 1, an active matrix liquid crystal display device having a definition of 200 ppi was manufactured. The manufacturing procedure of this sample follows the process shown in FIG.
First, a glass substrate was prepared as the support substrate 10, and a metal film 114 made of Ta ₂ N was formed on the surface thereof. Film formation was performed by sputtering using a Ta target and a mixed gas of Ar—at 15% N ₂ (meaning a partial pressure of N ₂ gas in Ar gas + N ₂ gas of 15%). Thereafter, the surface of the obtained Ta ₂ N film was anodized to form an insulating film 180 made of Ta ₂ N oxide on the metal film 114.

Next, the laminated film 130 of the metal film and the insulating film obtained by the anodizing process is patterned into a predetermined shape to form a laminated film 130a, and then insulated on the side surfaces by the anodizing process using the metal film 114a as an electrode. By forming the film 181, insulating films 181 and 182 were formed so as to cover the lower electrode 14.
Next, the upper electrodes 19 and 11a are formed by patterning a Cr film at a position facing the lower electrode 14 through the insulating film 181, and the TFD element 13 having the same configuration as that shown in FIG. Obtained.
In the obtained TFD element 13, the thickness of the lower electrode 14 is 100 nm, the thickness of the first insulating film 181 is 20 nm, and the thickness of the second insulating film 182 is 50 nm.

  Next, a pixel electrode 12 is formed by patterning an ITO film so as to be conductively connected to the upper electrode 19, the obtained element substrate 10 and a separately prepared counter substrate 20 are bonded together, and a liquid crystal is bonded between both substrates. Was sealed to obtain a liquid crystal display device.

<Example 2>
Next, as an implementation sample 2, an active matrix liquid crystal display device having a definition of 250 ppi was manufactured. In this liquid crystal display device, the above implementation sample 1 is provided except that the TFD element 13 having a thickness of the lower electrode 14 of 100 nm, a thickness of the first insulating film 181 of 20 nm, and a thickness of the second insulating film 182 of 100 nm is provided. It was set as the same structure.

<Comparative sample 1>
Next, an active matrix liquid crystal display device having a definition of 200 ppi was manufactured as a comparative sample 1. The liquid crystal display device has the same configuration as that of the above-described sample 1 except that a Ta film is used as the metal film 114. In this sample, since the metal film 114 is a Ta film, the insulating films 181 and 182 formed so as to cover the lower electrode 14 are tantalum oxide films. The thickness of the lower electrode 14 is 100 nm, the thickness of the first insulating film 181 is 20 nm, and the thickness of the second insulating film 182 is 100 nm.

<Comparative sample 2>
Next, an active matrix liquid crystal display device having a definition of 250 ppi was manufactured as a comparative sample 2. In this liquid crystal display device, the comparative sample 1 is provided except that the TFD element 13 is provided in which the thickness of the lower electrode 14 is 100 nm, the thickness of the first insulating film 181 is 200 nm, and the thickness of the second insulating film 182 is 250 nm. It was set as the same structure.

<Comparative sample 3>
Next, an active matrix liquid crystal display device having a definition of 200 ppi was manufactured as a comparative sample 3. This sample is a liquid crystal display device provided with the TFD element 200 having the conventional structure shown in FIG. 6, and the manufacturing procedure conforms to the manufacturing method described in Patent Document 1 above. In the TFD element 200, the first conductive film 203 has a mixed phase structure of α-Ta and Ta ₂ N, and the film thickness is 80 nm. In addition, the insulating film 204 covering the first conductive film 203 was formed by anodic oxidation treatment, and the film thickness was 20 nm.

<Comparative sample 4>
Next, an active matrix liquid crystal display device having a definition of 250 ppi was manufactured as a comparative sample 4. In this liquid crystal display device, the configuration of the TFD element 200 was the same as that of the comparative sample 3, and only the pixel definition was improved (the planar dimension of the pixel electrode 206 was reduced).

<Characteristic evaluation>
Table 1 shows the results of measuring the capacitance ratio between the TFD element and the liquid crystal for the liquid crystal display devices of Examples 1 and 2 and Comparative Samples 1 to 4.

As shown in Table 1, the working sample 1 and the working sample 2 having the requirements of the present invention have good capacity ratios. In contrast, in Comparative Samples 1 and 2 in which the insulating film covering the lower electrode is made of tantalum oxide, it can be seen that the capacitance ratio can be secured to some extent by increasing the thickness of the second insulating film, but the comparative sample of 250 ppi In No. 2, the thickness of the second insulating film reached 250 nm, and in the patterning process, it was confirmed that the photoresist as the mask material was damaged by dry etching, and the patterning accuracy was lowered.
Further, in the comparative samples 3 and 4 having the TFD element 200 having the conventional structure shown in FIG. 6, the capacitance ratio of 3.5 is obtained in the comparative sample 3 of 200 ppi. This capacitance ratio is a practical contrast. This is close to the lower limit value that can ensure the image quality, and the capacity ratio of the comparative sample 4 of 250 ppi is clearly insufficient, suggesting that it is extremely difficult to obtain a practical image quality.

(Example 2)
Next, the following implementation samples 3 and 4 and comparative samples 5 and 6 were prepared, and the element resistance was evaluated.

<Examples 3 and 4>
As working samples 3 and 4, a liquid crystal display device having the same configuration as in the working sample 2 except that the thickness of the first insulating film was changed to 15 nm and 10 nm, respectively, was produced.

<Comparative samples 5 and 6>
As working samples 5 and 6, a liquid crystal display device having the same configuration as in the comparative sample 1 except that the thickness of the first insulating film was changed to 15 nm and 10 nm, respectively, was produced.

<Element resistance evaluation>
Next, Table 2 below shows the measurement results of the element resistances of the TFD elements of the working samples 3 and 4 and the comparative samples 5 and 6 obtained above together with the TFD elements of the working sample 1 and the comparative sample 2. Show. In addition, the measured element resistance is a value when an applied voltage is 10V.
As shown in Table 2, the TFD elements according to Samples 1, 3, and 4 in which the first insulating film constituting the effective element portion is composed of a Ta ₂ N oxide film has the first insulating film The element resistance is lower than that of the TFD elements according to Comparative Samples 2, 5 and 6 made of the tantalum oxide film, and the TFD element having the structure according to the present invention is driven at a lower voltage than the conventional case. It can be seen that this can contribute to lower power consumption of the liquid crystal display device.

(Electronics)
FIG. 7 is a perspective configuration diagram illustrating an example in which the electro-optical device according to the invention is applied to a display unit of a mobile phone. As shown in the figure, a cellular phone 1300 includes the liquid crystal display device (electro-optical device) of the above embodiment as a small-size display unit 1301, and includes a plurality of operation buttons 1302, a reception mouth 1303, and a mouthpiece 1304. It is prepared for.
The liquid crystal display device of the above embodiment is not limited to the mobile phone, but is an electronic book, a personal computer, a digital still camera, a liquid crystal television, a viewfinder type or a monitor direct view type video tape recorder, a car navigation device, a pager, and an electronic notebook. It can be suitably used as an image display means for devices such as calculators, word processors, workstations, videophones, POS terminals, touch panels, etc., and to provide high-definition, high-contrast display in any electronic device Can do.

FIG. 1 is a circuit block diagram of a liquid crystal display device according to an embodiment. FIG. 2 is a perspective configuration diagram showing the external appearance. FIG. 3 is a cross-sectional configuration diagram taken along line C-C ′ of FIG. 2. 4A is a plan view of the pixel region of the liquid crystal display device, FIG. 4B is an enlarged plan view of the TFD element, and FIG. 4C is a cross-sectional view taken along the line D-D ′ of FIG. FIG. 5 is a sectional process diagram of the manufacturing method according to the embodiment. FIG. 6 is a plan view (a) and a cross-sectional view (b) of a conventional nonlinear element. FIG. 7 is a perspective configuration diagram illustrating an example of an electronic apparatus according to the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Element board | substrate, 11 ... Data line, 11a ... 1st upper electrode (2nd electrically conductive film), 12 ... Pixel electrode, 13 ... TFD element (two terminal type nonlinear element), 14 ... Lower electrode (1st electrically conductive film) , 19 ... Second upper electrode (second conductive film), 20 ... Counter substrate, 114 ... First metal film, 181 ... First insulating film, 182 ... Second insulating film

Claims (12)

A non-linear element comprising a first conductive film, an insulating film, and a second conductive film laminated on a substrate,
A first insulating film formed on a side surface of the first conductive film; and a second insulating film formed on the upper surface of the first conductive film having a thickness greater than the first insulating film. An insulating film,
The non-linear element, wherein the insulating film is an oxide film formed by oxidizing a Ta film containing nitrogen. The nonlinear element according to claim 1, wherein the insulating film is an oxide film formed by oxidizing a metal film containing Ta ₂ N. The nonlinear element according to claim 1, wherein the insulating film is an oxide film formed by oxidizing a metal film containing a mixed phase of α-Ta and Ta ₂ N.   4. The nonlinear element according to claim 1, wherein the insulating film is an oxide film formed by oxidizing a Ta metal film containing an additive element other than nitrogen. 5. The insulating film is a compound represented by a composition formula of (Ta _x M _1-x ) ₂ N (where 0 <x <1, M is an element selected from Nb, V, W, Mo, Cr, Si). The nonlinear element according to claim 4, wherein the nonlinear element is an oxide film formed by oxidizing a metal film. A first conductive film laminated on a substrate; an insulating film; and a second conductive film, wherein the insulating film is formed on a side surface of the first conductive film; A non-linear element manufacturing method including a second insulating film having a thickness larger than that of the first insulating film and formed on the upper surface of the first conductive film,
Forming a first conductive film made of Ta containing nitrogen on a substrate;
Oxidizing the surface of the first conductive film to form a second insulating film, and forming a laminated film composed of the first conductive film and the second insulating film;
Patterning the laminated film into a predetermined shape;
Forming the first insulating film by oxidizing a side surface of the first conductive film;
Forming the second conductive film covering the patterned laminated film;
Patterning the second conductive film into a predetermined shape;
A method for manufacturing a non-linear element, comprising: The step of forming the first conductive film made of Ta containing nitrogen on the base material,
The method for manufacturing a nonlinear element according to claim 6, wherein the first conductive film containing Ta ₂ N is formed on the base material. The step of forming the first conductive film made of Ta containing nitrogen on the base material,
The method of manufacturing a nonlinear element according to claim 6, wherein the first conductive film including a mixed phase of α-Ta and Ta ₂ N is formed on the base material. The step of forming the first conductive film made of Ta containing nitrogen on the base material,
The method for manufacturing a nonlinear element according to claim 6, wherein the first conductive film made of Ta containing an additive element other than nitrogen is formed on the base material. The step of forming the first conductive film made of Ta containing nitrogen on the base material,
A compound represented by a composition formula (Ta _x M _1-x ) ₂ N (where 0 <x <1, M is an element selected from Nb, V, W, Mo, Cr, Si) on the base material. The method of manufacturing a nonlinear element according to claim 6, wherein the first conductive film is formed.   An electro-optical device comprising the nonlinear element according to claim 1 as a pixel switching element.   An electronic apparatus comprising the electro-optical device according to claim 7.

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