JP2009042529A - Light control device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light control device in which the resistance value of an electrode is stable and can be manufactured with high reliability, and a manufacturing method thereof.
An optical characteristic, particularly a refractive index, of incident light is changed, and a non-linear electro-optical film 4 that emits light having the changed optical characteristic, and an electric field is applied to the non-linear electro-optical film 4 in order to change the optical characteristic. A diffusion prevention film 5 is provided between the nonlinear electro-optic film 4 and the lower electrode 3, and its components diffuse into the lower electrode 3 when the electro-optic film 4 is baked. A light control device 6 that prevents the resistance value of the electrode 3 from increasing.
[Selection] Figure 1

Description

  The present invention relates to a light control device suitable for, for example, a display device and a manufacturing method thereof.

  Conventionally, with respect to display devices such as television receivers and information terminal devices, a cathode ray tube (CRT) type that has limitations in weight and thickness in order to meet demands for thinning, lightening, large screens, and high-definition display. There is a lot of development to move from display devices to flat panel display devices.

  In particular, as a flat panel display device as an information terminal device, for example, a liquid crystal display is widely used, and research and development have recently been conducted on increasing the brightness and size of the liquid crystal display.

  However, while the liquid crystal display has various advantages, there are technical problems caused by the display principle such as a slow response speed, a narrow viewing angle, a low contrast ratio, and a large power consumption.

  Regarding these problems, lowering the viscosity of the liquid crystal material, reducing the thickness of the liquid crystal layer, a device to overshoot the display drive waveform (overdrive), inserting a black display between display frames according to the display drive waveform, and backlight Measures such as flickering are taken. However, although the response speed is slightly improved, the fundamental characteristics have not been improved.

  On the other hand, a new light control device has also been proposed, and a high-speed light control device using a photonic crystal having a so-called opal 3D structure has been proposed. However, this structure requires that a 3D structure be formed on the substrate, and the process is very complex.

  On the other hand, there has been proposed a light control device in which a layer capable of controlling the light transmittance (light absorption) of a specific wavelength is provided on a substrate. For example, by applying a voltage to a photonic crystal, the refractive index of its constituent elements By changing the photonic band wavelength, the light transmittance (light absorption) of a specific wavelength is controlled.

  An external optical modulator using such a nonlinear optical material is an element indispensable for optical communication because of its high speed. Bulk type external optical modulators such as KDP (potassium dihydrogen phosphate) have already been used, but thin film type optical modulators are desired as elements to be mounted on optical circuits.

  The light modulator having a thin film configuration can be applied to an optical shutter or an optical switch that changes the amount of light at high speed by utilizing its action.

  For example, a vertical optical modulator that can change the dielectric constant by applying an electric field in the direction perpendicular to the surface of the electro-optic thin film, and obtain the phase change of the light by making light incident in the direction perpendicular to the surface of the electro-optic thin film. When it is going to consist of a thin film, it is necessary to form an electro-optic thin film between at least two transparent thin film electrodes.

  This electro-optic effect can be obtained by various materials regardless of whether it is an organic material or an inorganic material. However, an inorganic material crystallized by firing has a great electro-optic effect.

Examples of this type of material include PLZT (PbLaZrTiO ₃ ) and PZT (PbZrO ₃ —PbTiO ₃ ). As for the respective compositions, for example, PLZT is Pb _0.92 La _0.08 Zr _0.65 Ti _0.35 O _x , and PZT is Pb _1.00 Zr _0.65 Ti _0.35 O _x .

  These materials are usually formed by sputtering, CVD (chemical vapor deposition), vapor deposition, sol-gel, or the like, and then fired in an air atmosphere at about 700 ° C. to be crystallized.

  There are various materials for the transparent electrode. For example, an ITO (indium-tin-oxide) film that is indium tin oxide is widely used.

  FIG. 5 shows a configuration example of such a conventional light control device (vertical optical modulator) 56 (see Non-Patent Document 1 described later).

  As shown in FIGS. 5A and 5B, for example, a lower electrode (ITO thin film) 53 having a thickness of 200 nm is formed in a stripe shape on a quartz substrate 51, and a thickness of 100 nm is formed thereon. The non-linear electro-optic film 54 is formed by a usual sputtering method and baked in an air atmosphere at 700 ° C.

  Further, an upper electrode (ITO thin film) 52 is formed on the nonlinear electro-optic film 54 with a thickness of 200 nm, so that the nonlinear electro-optic film 54 is sandwiched between the two electrodes 52 and 53. A control device (vertical optical modulator) 56 is manufactured.

"Vertical light modulator using electro-optic effect and inverse piezoelectric effect" Seikei University Engineering Research Report, J. Fac. Eng., Seikei Univ. Vol.41, No.1 (2004), pp21-27

  However, when the non-linear electro-optic film 54 crystallized by firing such as PLZT or PZT is formed on the lower electrode 53, the resistance value of the lower electrode 53 in contact with the electro-optic film 54 is very large after firing. There is a problem of becoming.

  As a result, for example, it has been found that even when a voltage is applied between the two electrodes 52-53, no voltage is applied to the electro-optic film 54, and the device does not operate as an optical modulator.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a light control device in which the resistance value of an electrode is stable and can be manufactured with high reliability, and a method for manufacturing the same.

  That is, the present invention changes an optical characteristic of incident light, emits light having the changed optical characteristic (for example, a nonlinear electro-optic film: the same applies hereinafter), and the optical characteristic layer to change the optical characteristic. A counter electrode (for example, a pair of ITO thin film electrodes: hereinafter the same) that applies an electric field to the optical function layer, and a diffusion prevention layer is provided between the optical function layer and one of the counter electrodes. It relates to the light control device.

  A step of forming a first electrode on the substrate; a step of forming a diffusion prevention layer on the first electrode; a step of forming an optical functional layer on the diffusion prevention layer by a baking treatment; And a step of forming a second electrode on the layer.

  According to the light control device and the method for manufacturing the same according to the present invention, since the diffusion preventing layer is provided between the one electrode and the optical function layer, the optical function layer is formed by firing. The component of the functional layer can be prevented from entering into the one electrode to prevent an increase in the resistance value of the one electrode, a light control device with a stable resistance value of the electrode can be provided, and A light control device having a fine structure with a thin film capable of sufficiently firing the optical functional layer can be manufactured with high reliability.

  In the present invention, in order to prevent the component of the optical functional layer from entering the one electrode and increasing the resistance value of the one electrode, the diffusion is performed in a region where the one electrode and the optical functional layer overlap. A prevention layer is preferably provided.

  In order to sufficiently prevent the components of the optical functional layer from entering the one electrode, it is desirable that the thickness of the diffusion preventing layer is 10 nm or more.

  SiO or SiN can be used as the material of the diffusion preventing layer.

  The diffusion preventing layer functions as a buffer layer for preventing the components of the optical functional layer from entering the one electrode.

  In addition, it is desirable to have a vertical structure in which the optical functional layer and the counter electrode are laminated.

  In this case, the first electrode, the diffusion preventing layer, the optical functional layer, and the second electrode can be stacked on the substrate.

The optical functional layer is preferably made of a nonlinear optical material crystallized by firing PLZT (PbLaZrTiO ₃ ) or PZT (PbZrO ₃ —PbTiO ₃ ).

  Next, a preferred embodiment of the present invention will be described with reference to the drawings.

Embodiment FIG. 1 shows the structure of a light control device 6 according to this embodiment.

  As shown in FIGS. 1A and 1B, for example, on a quartz substrate 1, a stripe-like lower electrode (one electrode or first electrode) 3 made of ITO and a stripe-like electrode made of PLZT. A non-linear electro-optical film (optical functional layer) 4 is laminated, and in these overlapping regions, a diffusion preventive film (diffusion preventive layer or buffer layer) made of SiO between and in contact with the lower electrode 3 and the electro-optical film 4 ) 5 is formed. Further, an upper electrode (second electrode) 2 made of, for example, ITO is formed on the electro-optic film 4, and a power source V is connected between both electrodes 3-2 to produce the light control device 6.

  According to the present embodiment, by providing the diffusion prevention film 5, the components of the nonlinear electro-optic film 4 are applied to the lower electrode 3 in the overlapping region between the lower electrode 3 and the nonlinear electro-optic film 4 during firing described later. An increase in the resistance value of the lower electrode 3 due to intrusion can be prevented, and the light control device 6 in which the resistance value of the lower electrode 3 is stable can be obtained.

  The light control device 6 can be manufactured as a vertical optical modulator having a thin film structure in which a nonlinear thin film crystallized by firing is sandwiched between oxide-based transparent electrodes. That is, the refractive index of the nonlinear electro-optic film 4 can be changed by applying a voltage from the power supply V, and incident light incident on the film surface can be phase-converted and emitted.

  In addition, since it has a thin film configuration, a fine structure can be constructed and used as a functional element of an optical circuit. Furthermore, a thin optical shutter can be configured, and for example, it can be applied to a thin film electronic shutter of a display and an imaging device.

  Next, the change in the resistance value of the lower electrode will be described along the manufacturing process of the light control device.

  First, for comparison, in the process of manufacturing the conventional light control device (vertical light modulator) shown in FIG. 5, on the substrate 1 made of quartz, for example, as shown in FIG. A stripe-shaped lower electrode (ITO film) 3 having a width of 5 mm, a length of 30 mm, and a thickness of 200 nm was formed by a conventional sputtering method. When the resistance value of both end faces of the lower electrode 3 was measured, it was 1 kΩ or less.

  Next, as shown in FIG. 3B, without providing the diffusion prevention film 5 on the lower electrode 3, for example, in a direction perpendicular to the lower electrode 3, the width is 5 mm, the length is 30 mm, and the thickness is 100 nm. A nonlinear electro-optical film 4 made of PLZT was formed by a conventional sputtering method, and then fired at 700 ° C. in an air atmosphere to be crystallized. After this firing, the resistance value of both end faces of the lower electrode 3 was measured and found to be 3 megaΩ or more.

  As described above, when the nonlinear electro-optical film 4 is directly formed on the lower electrode 3 and baked, the lower electrode 3 and the nonlinear electro-optical film 4 are investigated in order to investigate the cause of the increase in resistance at both ends of the lower electrode 3. Secondary ion mass spectrometry was performed on the portion where and overlap. As a result, it was found that Pb and Ti which are components of the nonlinear electro-optic film 4 are diffused in the lower electrode 3 portion in contact with the nonlinear electro-optic film 4.

  From this, the reason why the resistance value of the lower electrode 3 increases after firing is that Pb and Ti, which are components of the nonlinear electro-optical film 4, diffuse into the lower electrode 3 and the composition of the lower electrode 3 changes. I found out.

  A conventional vertical light having a structure in which an ITO thin film having a thickness of 200 nm is formed on the electro-optic film 4 and the electro-optic film is sandwiched between two ITO thin-film electrodes as shown in FIG. A modulator was fabricated.

  In this conventional vertical optical modulator 56, as shown in FIG. 5B, He-Ne laser light (measurement light) having two orthogonal polarization planes is irradiated from a direction of 45 degrees with respect to the substrate. Then, the phase difference between the two polarization planes was measured. At this time, a voltage of 30 V was applied between the upper and lower ITO electrodes. As a result, the phase difference between the two polarization planes was almost zero, and the operation as an optical modulator could not be confirmed.

  From this, the reason why the phase difference of the conventional light control device 56 shown in FIG. 5 is zero is the portion where the lower electrode 3 (or 53) and the nonlinear electro-optic film 4 (or 54) overlap. It has been found that the resistance value of the lower electrode is caused by the fact that no voltage is applied to the nonlinear electro-optic film 4 (or 54).

  On the other hand, according to the present embodiment, first, as shown in FIG. 2A, a lower part having a thickness of 200 nm is formed on a quartz substrate 1 in a stripe shape having a width of 5 mm and a length of 30 mm, for example. An electrode (ITO film) 3 was formed by a conventional sputtering method. When the resistance values of both end faces of the striped lower electrode 3 were measured, it was 1 kΩ or less as in FIG.

  Then, as shown in FIG. 2 (B), a diffusion prevention film 5 made of rectangular SiO is formed on the stripe-shaped lower electrode 3, and the same as described in FIG. 3 (B). Then, after the striped nonlinear electro-optical film 4 orthogonal to the lower electrode 3 was provided, the resistance value of the lower electrode 3 was measured, and the resistance value of the lower electrode 3 was equivalent to that of ITO.

  From this result, since the diffusion of Pb and Ti to the lower electrode 3 can be prevented by the presence of the diffusion preventing film 5, even if the electro-optic film 4 is formed by baking the nonlinear optical material, the resistance value of the lower electrode 3 is obtained. Does not rise and functions sufficiently as a light control device. This will be described in detail below.

  In the manufacturing process of the light control device 6 according to the present embodiment, the resistance value between both ends of the lower electrode 3 was measured by changing the thickness of the diffusion prevention film 5 after the electro-optic film was baked.

The result is shown in FIG. 4. For example, when the thickness of the diffusion prevention film 5 is 10 nm or more, the resistance value of the lower electrode 3 is the case without the diffusion prevention film 5 (resistance value is about 10 ³ kΩ). It can be seen that it decreases rapidly compared to. Further, when the thickness of the diffusion preventing film 5 is 100 nm, the lower electrode 3 has the same resistance value as that of the ITO film alone.

  As described above, in the present embodiment, by sandwiching the diffusion preventing film 5 in the overlapping region between the lower electrode 3 and the nonlinear electro-optical film 4, a part of the nonlinear optical material (Pb or Ti) is formed in the lower part during firing. Intrusion into the electrode 3 can be prevented, and an increase in the resistance value of the lower electrode 3 that occurs after firing the nonlinear optical material can be suppressed. For this reason, the nonlinear optical material can be sufficiently baked and crystallized, and the performance can be exhibited well.

  With respect to the light control device 6 according to the present embodiment, as shown in FIG. 1B, a He—Ne laser beam (measurement light) having two orthogonal polarization planes from a direction of 45 degrees with respect to the substrate 1. The phase difference between the two polarization planes was measured. At this time, a voltage of 30 V was applied between the upper and lower electrodes. As a result, the phase difference between the two polarization planes was 8 nm or more.

  Therefore, by disposing the diffusion prevention film 5 between the lower electrode 3 and the nonlinear electro-optical film 4 as in the present embodiment, the resistance value of the electrode is low and stable, and the thin film configuration can operate normally. A vertical optical modulator can be obtained with good reliability.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to the example at all, and can be suitably changed in the range which does not deviate from the main point of invention.

  For example, PLZT is used as the material of the electro-optical film, the ITO film is used as the material of the transparent thin film electrode, and the SiO film is used as the material of the buffer layer. However, the material is not limited to these materials. That is, PZT can be used as the material of the nonlinear electro-optical film 4, and a film having a diffusion preventing effect such as SiN can be used as the material of the diffusion preventing film 5. Further, the pattern shape, size, thickness, etc. of each film may be changed.

  Further, the light control device 6 according to the above-described embodiment can be applied to a display device or the like as a one-dot display pixel, or can be applied to a simple display device in which each film is solid. .

  In addition, a plurality of structures according to the above-described embodiment may be stacked in the vertical direction, but this can further expand the range of light modulation.

  The light control device of the present invention can be applied to, for example, an optical shutter and an optical switch that change the amount of light at high speed.

It is the top view (A) and X-X 'sectional view (B) of the light control apparatus by embodiment of this invention. It is a top view (A) and (B) at the time of resistance measurement of a lower electrode equally. It is a top view (A) and (B) at the time of resistance measurement of the lower electrode in the light control device for comparison. It is a graph which shows the relationship between the resistance value of the lower electrode of the light control apparatus by embodiment of this invention, and the film thickness of a diffusion prevention film. It is the top view (A) of the light control apparatus by a prior art example, and its Y-Y 'sectional view (B).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Upper electrode, 3 ... Lower electrode, 4 ... Non-linear electro-optic film, 5 ... Diffusion prevention film,
6. Light control device

Claims (9)

  An optical functional layer that changes an optical characteristic of incident light and emits light having the changed optical characteristic; and a counter electrode that applies an electric field to the optical functional layer to change the optical characteristic. A light control device, wherein a diffusion prevention layer is provided between the functional layer and one electrode of the counter electrode.   The light control device according to claim 1, wherein the diffusion prevention layer is provided in a region where the one electrode and the optical functional layer overlap.   The light control device according to claim 1, wherein the diffusion prevention layer has a thickness of 10 nm or more.   The light control apparatus according to claim 1, wherein SiO or SiN is used as a material of the diffusion prevention layer.   The light control device according to claim 1, wherein the diffusion preventing layer functions as a buffer layer for preventing a component of the optical functional layer from entering the one electrode.   The light control device according to claim 1, wherein the optical functional layer and the counter electrode are laminated.   The light control device according to claim 6, wherein the first electrode, the diffusion preventing layer, the optical functional layer, and the second electrode are laminated on a substrate. The light control device according to claim 6, wherein the optical functional layer is made of a nonlinear optical material crystallized by firing PLZT (PbLaZrTiO ₃ ) or PZT (PbZrO ₃ —PbTiO ₃ ).   Forming a first electrode on the substrate; forming a diffusion prevention layer on the first electrode; forming an optical functional layer on the diffusion prevention layer by baking; and on the optical functional layer And a step of forming a second electrode.

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