KR20200052207A - Optical modulating device - Google Patents

Abstract

According to the present invention, provided is an optical modulation element which includes a reflective layer, a dielectric layer formed on the reflective layer, a first electrode and a second electrode formed on the dielectric layer, and an optical modulation layer formed between the first electrode and the second electrode. The thickness of the optical modulation layer is 20 nm to 100 nm. The optical modulation element can improve the durability during repeated operations by suppressing the formation of voids inside the optical modulation layer.

Description

Optical modulating device

The present invention relates to an optical modulation device, and more particularly, to an optical modulation device including a phase change material having a thickness of 20 nm to 100 nm and an operation method thereof.

Recently, a holographic 3D image display has been researched to display a more natural stereoscopic image. Light can be thought of as a wave having intensity information and phase information, and holography technology displays an image through control of light phase and light intensity. Therefore, a holographic 3D image display device needs an element capable of controlling the amplitude (intensity) or phase of light. To this end, an optical modulating device including a phase change material (PCM) and a transparent electrode is used. As a phase change material, a germanium-antimony-tellurium alloy (GST) is used.

An object of the present invention is to provide an optical modulation element capable of improving the durability of repeated operation.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention includes a reflective layer, a dielectric layer formed on the reflective layer, a first electrode and a second electrode formed on the dielectric layer, and an optical modulation layer formed between the first electrode and the second electrode, wherein the optical modulation layer It provides an optical modulation device having a thickness of about 20 nm to 100 nm.

The optical modulation device according to the present invention suppresses the formation of a cavity inside the optical modulation layer during the operation process, thereby improving the durability of repeated operations, thereby enabling stable three-dimensional hologram implementation.

1 is a cross-sectional view of an optical modulation device according to an embodiment of the present invention.
2A to 2C are cross-sectional views illustrating a method of operating an optical modulation device according to an embodiment of the present invention.
2D is a graph for comparatively comparing the magnitude and duration of the first voltage and the second voltage in the method of operating the optical modulation device according to an embodiment of the present invention.
2E to 2H are graphs showing measurement of reflectance or diffraction efficiency according to the wavelength of incident light in some steps of an operation method of a light modulation device according to an embodiment of the present invention.
3A and 3B are cross-sectional views illustrating a method of operating an optical modulation device according to another embodiment of the present invention.

In order to fully understand the configuration and effects of the present invention, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various modifications and changes can be made. However, the present invention is provided through the description of the present embodiment, and is provided to completely inform the scope of the invention to those skilled in the art to which the present invention pertains. In the accompanying drawings, the components are enlarged in size than actual ones for convenience of description, and the proportion of each component may be exaggerated or reduced.

The terminology used herein is for describing the embodiments and is not intended to limit the present invention. In addition, the terms used in this specification may be interpreted as meanings commonly known to those of ordinary skill in the art unless otherwise defined.

In the present specification, the singular form also includes the plural form unless otherwise specified in the phrase. As used herein, 'comprises' and / or 'comprising' refers to the components, steps, operations and / or elements mentioned above, the presence of one or more other components, steps, operations and / or elements. Or do not exclude additions.

In the present specification, when a layer is referred to as being “on” another layer, it may be formed directly on the other layer or a third layer may be interposed between them.

Although terms such as first and second are used herein to describe various areas, layers, and the like, these areas and layers should not be limited by these terms. These terms are only used to distinguish one region or layer from another. Accordingly, a part referred to as a first part in one embodiment may be referred to as a second part in another embodiment. The embodiments described and illustrated herein also include its complementary embodiments. Parts indicated by the same reference numerals throughout the specification indicate the same components.

Hereinafter, embodiments of the light modulation device according to the present invention will be described in detail with reference to FIGS. 1 to 3B.

1 is a cross-sectional view of an optical modulation device according to an embodiment of the present invention. 2A is a cross-sectional view of the optical modulation device after the first set step. 2B is a cross-sectional view of the optical modulation element after the first reset step. 2C is a cross-sectional view of an optical modulator at the beginning of the second set stage. 2D is a graph for comparatively comparing the magnitude and duration of the first voltage and the second voltage in the method of operating the optical modulation device according to an embodiment of the present invention. 2E to 2H are graphs showing measurement of reflectance or diffraction efficiency at some stages of an operation method of a light modulation device according to an embodiment of the present invention.

Referring to FIG. 1, a light modulating element 10 according to an embodiment of the present invention includes a reflective layer 101, a dielectric layer 102, a first electrode 103, a second electrode 104, and a light modulating layer 105. ).

The reflective layer 101 may be formed of metal. For example, the reflective layer 101 may be formed of Ta, TiW, TaN, Al, Ti, Pt, Mo, Cr, W, Co or Ni. For example, the reflective layer 101 may be formed to a thickness of about 100nm.

The dielectric layer 102 may be formed on the reflective layer 101. For example, the dielectric layer 102 may be formed of TiO ₂ , SiO ₂ , Al ₂ O ₃ , AlN, HfO ₂ , SiC or MgO. For example, the dielectric layer 102 may be formed to a thickness of about 300 nm or less. The dielectric layer 102 can increase the light modulation efficiency of the light modulation element 10. According to another embodiment, unlike shown, the dielectric layer 102 may be omitted.

The first electrode 103 and the second electrode 104 may be formed on the dielectric layer 102. The first electrode 103 and the second electrode 104 may be formed of a transparent electrode material. The first electrode 103 and the second electrode 104 may be formed of a transparent conductive oxide (TCO). For example, the first electrode 103 and the second electrode 104 may be formed of Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), or Aluminum-doped Zinc Oxide (AZO). However, this is exemplary, and any material that is conductive and transparent to incident light may be applied. The thickness of each of the first electrode 103 and the second electrode 104 may be determined in consideration of the refractive index of the material constituting it. For example, the first electrode 103 and the second electrode 104 may be formed to a thickness of about 10 nm to 100 nm. For example, the thickness of the first electrode 103 and the thickness of the second electrode 104 may be substantially the same. As another example, the thickness of the second electrode 104 may be greater than the thickness of the first electrode 103. At least one of the first electrode 103 and the second electrode 104 may be connected to the voltage application device. According to another embodiment, as illustrated, one of the first electrode 103 and the second electrode 104 may not be provided.

The light modulation layer 105 may be formed between the first electrode 103 and the second electrode 104. The light modulation layer 105 may be formed of a phase change material (PCM). The light modulation layer 105 may be formed of a germanium-antimony-tellurium alloy, which is one of chalcogenide compounds. For example, the light modulation layer 105 may be formed of Ge ₂ Sb ₂ Te ₅ (GST). For example, the thickness L1 of the light modulation layer 105 may be about 20 nm to 100 nm, and more specifically about 40 nm to 100 nm. When the light modulating layer 105 is formed of GST, the phase of the light modulating layer 105 may be changed from amorphous to crystalline or from crystalline to amorphous. The phase of the light modulation layer 105 may be reversibly changed according to the magnitude and duration of the applied voltage. The crystalline structure of the light modulation layer 105 may be an FCC structure (Face Centered Cubic structure). The optical properties of the light modulating layer 105 may be changed according to the phase change of the GST. In addition, the optical characteristics of the light modulating layer 105 may be changed only by a partial phase change of the GST. In the visible light region, GST may have a high refractive index when it is amorphous, and GST may have a low refractive index when it is crystalline. That is, the refractive index of the light modulating layer 105 may vary according to the phase change of the GST. As the refractive index of the light modulation layer 105 is changed, reflectance and transmittance of the light modulation layer 105 may be changed. In the optical modulation element 10 before the first set step, the optical modulation layer 105 may be an amorphous optical modulation layer 105A.

1 to 2C, an operation method of the optical modulation element 10 according to an embodiment of the present invention may include a set (SET) step and a reset (RESET) step.

Referring to FIG. 2A, in the first set step, the light modulating element 11 may be heated to a temperature of about 120 degrees to 250 degrees for several hours, for example. In the light modulating element 11 after the first set step, the light modulating layer 105 may be a crystalline light modulating layer 105C.

2B and 2D, in the first reset step, the first voltage V1 may be applied to the second electrode 104 of the optical modulation element 12 for the first duration T1. For example, the magnitude of the first voltage V1 may be about 15 V or less. For example, the first duration T1 may be less than several μs. By the first voltage V1, a part of the light modulating layer 105 of the light modulating element 12 may be melt-quenched to change the phase from crystalline to amorphous. In the optical modulation element 12 after the first reset step, the optical modulation layer 105 includes a crystalline light modulation layer 105C adjacent to the first electrode 103 and an amorphous light modulation layer adjacent to the second electrode 104 ( 105A). For example, the thickness L2 of the amorphous light modulating layer 105A adjacent to the second electrode 104 may be about 5 nm to 40 nm. The thickness L2 of the amorphous light modulating layer 105A adjacent to the second electrode 104 may be determined by the size of the first voltage V1 and the first duration T1.

2C and 2D, in the second set step, the second voltage V2 may be applied to the second electrode 104 of the optical modulation element 13 for the second duration T2. The size of the second voltage V2 may be smaller than the size of the first voltage V1. For example, the size of the second voltage V2 may be about 10 V or less. The second duration T2 may be longer than the first duration T1. For example, the second duration T2 may be less than tens of microseconds. Due to the second voltage V2, a part of the light modulating layer 105 of the light modulating element 13 may change its phase from amorphous to crystalline. In the optical modulation element 13 at the beginning of the second set step, the optical modulation layer 105 is a crystalline optical modulation layer 105C adjacent to the first electrode 103 and an amorphous optical modulation adjacent to the second electrode 104 Layer 105A may be included. In the amorphous light modulating layer 105A of the light modulating element 13 at the beginning of the second set step, the portion adjacent to the crystalline light modulating layer 105C is first at a lower energy than the portion adjacent to the second electrode 104 Crystallization may occur. That is, in the optical modulation element 13 at the beginning of the second set step, a part of the optical modulation layer 105 whose phase is changed may be a part of the amorphous optical modulation layer 105A adjacent to the crystalline optical modulation layer 105C. . In the light modulation element 13 at the beginning of the second set step process, the thickness L2 'of the amorphous light modulation layer 105A adjacent to the second electrode 104 is after the first reset step shown in FIG. 2B. It may be smaller than the thickness L2.

The operation method of the optical modulation element 10 according to an embodiment of the present invention may include a first set step, a first reset step and a second set step. In the light modulation element 10 including the light modulation layer 105 having a thickness of about 20 nm to 100 nm, the first reset step may change only a part of the light modulation layer 105 to amorphous. In the optical modulation element 10 including the light modulation layer 105 having a thickness of about 20 nm to 100 nm, the second set step may cause crystallization from a portion adjacent to the crystalline light modulation layer 105C. In the first reset step, only a part of the light modulating layer 105 is changed to amorphous, and in the second set step, crystallization occurs from a portion adjacent to the crystalline light modulating layer 105C, thereby suppressing the occurrence of lattice mismatch. Can be. Accordingly, void formation inside the light modulation layer 105 caused by lattice mismatch can be suppressed. That is, according to an operation method of the optical modulation element 10 according to an embodiment of the present invention, the formation of a cavity inside the optical modulation layer 105 is suppressed, so that the repeating endurance of the optical modulation element 10 Can be improved.

In addition, when the light modulating layer 105 is crystallized, the density may be changed by about 7%. The stress due to the density change may create a cavity in the light modulating layer 105. The thicker the light modulating layer 105, the less stress due to a change in density during crystallization. Accordingly, cavity formation in the light modulation layer 105 can be suppressed.

In the graphs of FIGS. 2E to 2H, when the dielectric layer 102 is omitted and the thickness L1 of the entire light modulation layer 105 is about 100 nm, the light modulation elements 11 and 12 according to the wavelength of incident light Graphs showing reflectance or diffraction efficiency.

2E and 2F compare and show the reflectivity 111 of the light modulation element 11 after the first set step and the reflectances 121a and 121b of the light modulation element 12 after the first reset step. In this case, FIG. 2E shows the reflectivity 121a of the light modulation element 12 according to the wavelength of the incident light when the thickness L2 of the amorphous light modulation layer 105A adjacent to the second electrode 104 is about 20 nm. do. In addition, FIG. 2F shows the reflectivity 121b of the light modulation element 12 according to the wavelength of the incident light when the thickness L2 of the amorphous light modulation layer 105A adjacent to the second electrode 104 is about 30 nm. do. The graphs show that the change in reflectance can be confirmed even if only a part of the light modulating layer 105 is changed to amorphous in the light modulating element 12 after the first reset step.

2G and 2H show diffraction efficiency according to the wavelength of incident light when the light modulating element 11 after the first set step and the light modulating element 12 after the first reset step are two-dimensionally arranged. . In this case, FIG. 2G shows light modulation in which the thickness (L2) of the optical modulation element 11 after the first set step and the amorphous light modulation layer 105A adjacent to the second electrode 104 after the first reset step is about 20 nm. Shows the diffraction efficiency according to the wavelength of incident light when the elements 12 are two-dimensionally arranged. In addition, FIG. 2F shows light modulation in which the thickness L2 of the optical modulation element 11 after the first set step and the amorphous light modulation layer 105A adjacent to the second electrode 104 after the first reset step is about 30 nm. Shows the diffraction efficiency according to the wavelength of the incident light when the elements 12 are two-dimensionally arranged. The graphs show that when the light modulating element 12 after the first reset step in which only a part of the light modulating element 11 and the light modulating layer 105 after the first set step is changed to amorphous is two-dimensionally arranged, the hologram is implemented. It indicates that a diffraction efficiency of a possible level can be obtained.

3A and 3B are cross-sectional views illustrating a method of operating an optical modulation device according to another embodiment of the present invention. 3A is a cross-sectional view of the optical modulation element after the first reset step. 3B is a cross-sectional view of an optical modulator at the beginning of the second set stage. 3A and 3B, the same reference numerals may be used for components that are substantially the same or similar to the light modulating element described with reference to FIGS. 1 to 2D, and duplicate descriptions are omitted.

1, 2A, 3A, and 3B, an operation method of the optical modulation elements 22 and 23 according to another embodiment of the present invention may include a SET step and a RESET step. Can be. The operation method before the first reset step may be substantially the same as described above with reference to FIGS. 1 and 2A. The magnitudes of the first voltage V1 and the second voltage V2 and the first duration T1 and the second duration T2 applied to the first electrode 103 in the first reset step and the second set step. May be substantially the same as shown in FIG. 2D.

Referring to FIGS. 2D and 3A, in the first reset step, the first voltage V1 is applied to the first electrode 103 and the second electrode 104 of the light modulating element 22 with a first duration T1. Can be applied for a while. For example, the magnitude of the first voltage V1 may be about 15 V or less. For example, the first duration T1 may be less than several μs. By the first voltage V1, a part of the light modulating layer 105 of the light modulating element 22 may be melt-quenched to change the phase from crystalline to amorphous. In the light modulating element 22 after the first reset step, the light modulating layer 105 includes an amorphous light modulating layer 105A1 adjacent to the first electrode 103 and an amorphous light modulating layer adjacent to the second electrode 104 ( 105A2) and the crystalline light modulation layer 105C between the amorphous light modulation layers 105A1 and 105A2. For example, the thickness L3 of the amorphous light modulation layer 105A1 adjacent to the first electrode 103 and the thickness L4 of the amorphous light modulation layer 105A2 adjacent to the second electrode 104 are about 5 nm to 40 nm. Can be However, the sum of the thicknesses L3 and L4 of the amorphous light modulation layers 105A1 and 105A2 may be smaller than the thickness L1 of the entire light modulation layer 105. The thicknesses L3 and L4 of the amorphous light modulation layers 105A1 and 105A2 may be determined by the magnitude of the first voltage V1 and the first duration T1. For example, the thickness L3 of the amorphous light modulation layer 105A1 adjacent to the first electrode 103 and the thickness L4 of the amorphous light modulation layer 105A2 adjacent to the second electrode 104 may be substantially the same. have.

2D and 3B, in the second set step, the second voltage V2 is the second duration T2 of the first electrode 103 and the second electrode 104 of the optical modulation element 23. Can be applied for a while. The size of the second voltage V2 may be smaller than the size of the first voltage V1. For example, the size of the second voltage V2 may be about 10 V or less. The second duration T2 may be longer than the first duration T1. For example, the second duration T2 may be less than tens of microseconds. Due to the second voltage V2, a part of the light modulating layer 105 of the light modulating element 23 may change its phase from amorphous to crystalline. In the optical modulation element 23 at the beginning of the second set step, the optical modulation layer 105 is an amorphous optical modulation layer 105A1 adjacent to the first electrode 103 and an amorphous optical modulation adjacent to the second electrode 104 And a crystalline light modulation layer 105C between layers 105A2 and amorphous light modulation layers 105A1 and 105A2. In the amorphous light modulating layers 105A1 and 105A2 of the light modulating element 23 at the beginning of the second set step process, portions adjacent to the crystalline light modulating layer 105C are the first electrode 103 and the second electrode 104 ), Crystallization may occur first at a lower energy than those adjacent to. That is, in the optical modulation element 23 at the beginning of the second set step, a part of the optical modulation layer 105 whose phase is changed is formed of the amorphous optical modulation layers 105A1 and 105A2 adjacent to the crystalline optical modulation layer 105C. It can be a part. In the light modulating element 23 at the beginning of the second set step process, the thickness L3 'of the amorphous light modulating layer 105A1 adjacent to the first electrode 103 and the amorphous light modulating layer adjacent to the second electrode 104 The thickness L4 'of 105A2 may be smaller than the thicknesses L3 and L4 after the first reset step illustrated in FIG. 3A.

The embodiments of the present invention have been described above with reference to the accompanying drawings, but those of ordinary skill in the art to which the present invention pertains can implement the present invention in other specific forms without changing its technical spirit or essential features. You will understand that there is. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

10, 11, 12, 13, 22, 23: optical modulation element
101: reflective layer
102: dielectric layer
103: first electrode
104: second electrode
105: light modulation layer

Claims (1)

Reflective layer;
A dielectric layer formed on the reflective layer;
A first electrode and a second electrode formed on the dielectric layer; And
A light modulation layer formed between the first electrode and the second electrode;
The light modulation layer has a thickness of 20nm to 100nm light modulation device.

Images