Reflective phase difference structure and method for manufacturing same

Abstract

Provided is a reflective phase difference structure having uniform characteristics over a wide band. The reflective phase difference structure (200) has a laminated structure of a metal reflective layer (210), a dielectric spacer layer (220), and an anisotropic structure layer (230). The anisotropic structure layer (230) includes a plurality of metal constituent elements (232) made of an aluminum-based metal.

Description

Technical Field

[0001] The present disclosure relates to a reflective phase difference structure. Background Art

[0002] In the field of optics, light phase control is an important technology. As optical components for controlling the phase of light, wavelength plates such as a quarter wavelength plate and a half wavelength plate are widely used.

[0003] By forming an anisotropic structure on the surface of an object by microfabrication, the function of a phase difference plate can be realized.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-210479 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Conventionally, since the wavelength characteristics of the reflective phase difference structure are determined by the material used, there is a problem that it is difficult to obtain uniform characteristics over a wide frequency band.

[0009] The present disclosure has been made in view of the above-mentioned problems, and one of the exemplary purposes of one aspect thereof is to provide a reflective phase difference structure having uniform characteristics over a wide frequency band.

[0010] Means for solving problems

[0011] One aspect of the present disclosure relates to a reflective phase difference structure including a metal reflective layer, an anisotropic structure layer including a plurality of metal components made of aluminum-based metal, and a dielectric spacer layer sandwiched between the metal reflective layer and the anisotropic structure layer.

[0012] Another scheme disclosed herein comprises: a process of forming a metal reflective layer; a process of forming a dielectric spacer layer on the metal reflective layer; a process of forming an anisotropic structural layer including a plurality of metal constituent elements made of aluminum-based metals on the spacer layer; and a process of forming a dielectric protective layer on the upper layer of the anisotropic structural layer by atomic layer deposition.

[0013] It should be noted that arbitrarily combining the above-mentioned constituent elements and mutually replacing constituent elements or expressions of the present disclosure in the form of methods, apparatuses, systems, etc. may also be additional aspects of the present disclosure.

[0014] Effects of the Invention

[0015] According to one aspect of the present disclosure, it is possible to provide a reflective phase difference structure having uniform characteristics over a wide frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a perspective view of a reflective phase difference structure according to an embodiment.

[0017] Figure 2 yes Figure 1 Cross-sectional view of a reflective phase difference structure.

[0018] Figure 3 Yes means Figure 1 A diagram showing the reflectivity and phase difference characteristics (simulation results) of the reflective phase difference structure.

[0019] Figure 4 It is a graph showing the reflectivity and phase difference characteristics (simulation results) of the reflection type phase difference structure of Comparative Example 1.

[0020] Figure 5 It is a graph showing the reflectivity of various metal materials.

[0021] Figure 6 It is a cross-sectional view of the reflective phase difference structure of Modification Example 1.

[0022] Figure 7 Yes means Figure 6 A diagram showing the reflectivity and phase difference characteristics (simulation results) of the reflective phase difference structure.

[0023] Figure 8 It is a graph showing the reflectivity and phase difference characteristics (simulation results) of the reflection type phase difference structure of Comparative Example 2.

[0024] Fig. 9 It is a cross-sectional view of the reflective phase difference structure of Modification Example 2.

[0025] Fig.10 Yes means Fig. 9 A diagram showing the reflectivity and phase difference characteristics (simulation results) of the reflective phase difference structure.

[0026] Fig.11 It is a graph showing the reflectivity and phase difference characteristics (simulation results) of the reflection type phase difference structure of Comparative Example 3.

[0027] Fig.12 is the reflectivity R of the TE wave of the reflection type phase difference structure TE , TM wave reflectivity R TM And a graph of the dependence of the phase difference characteristics on the thickness of the dielectric spacer layer.

[0028] Fig.13is the reflectivity R of the TE wave of the reflection type phase difference structure TE , TM wave reflectivity R TM And phase difference characteristics.

[0029] Fig.14 This is a stereoscopic view of a reflective phase difference structure according to Modification 3.

[0030] Fig.15 It is a plan view for explaining the design parameters of the anisotropic structural layer of Modification Example 3.

[0031] Fig.16 Yes Description Figure 2 A diagram of the manufacturing process of the reflective phase difference structure.

[0032] Fig.17 This is a SEM image of a cross section of a reflective phase difference structure formed by the ALD method.

[0033] Fig.18 It means Fig.17 Graph of the phase characteristics corresponding to the reflective phase difference structure. DETAILED DESCRIPTION

[0034] (Overview of Embodiments)

[0035] An overview of several exemplary embodiments of the present disclosure is described. This overview serves as a preface to the detailed description that will be described later. It is intended to provide a basic understanding of the embodiments and simplifies and describes several concepts of one or more embodiments. It does not limit the breadth of the invention or disclosure. In addition, this overview is not a comprehensive overview of all embodiments considered and does not limit the indispensable components of the embodiments. For convenience, "one embodiment" is sometimes used as a statement referring to one embodiment (an embodiment or a variation) or multiple embodiments (an embodiment or a variation) disclosed in this specification.

[0036] A reflective phase difference structure according to one embodiment includes a metal reflective layer, an anisotropic structural layer including a plurality of metal components made of aluminum-based metal, and a dielectric spacer layer interposed between the metal reflective layer and the anisotropic structural layer.

[0037] In the case of a structure in which the anisotropic structure layer is formed in contact with the metal reflective layer, i.e., a structure without a dielectric spacer layer, it is difficult to obtain uniform characteristics over the entire wide wavelength range. In contrast, by inserting a dielectric spacer layer between the metal reflective layer and the anisotropic structure layer and optimizing its material and thickness, the characteristics can be uniformed over the entire wide frequency band.

[0038] Furthermore, by using aluminum-based metals as materials for constituent elements of the anisotropic structural layer instead of Au and Ag, which are common metasurface materials, uniform characteristics can be obtained over a wide band in the entire visible light region.

[0039] It should be noted that the phase difference structure can be evaluated by the phase difference characteristics and the reflectance characteristics. Ideally, uniform phase difference characteristics and uniform reflectance characteristics are preferred. However, depending on the application, there are cases where the uniformity of either one is prioritized.

[0040] In one embodiment, the anisotropic structural layer may further include a dielectric filling member for filling gaps between the plurality of metal components. By adding the dielectric filling member, the dispersion of the phase difference can be reduced.

[0041] In one embodiment, the dielectric spacer layer and the dielectric filling member may be made of the same material.

[0042] In one embodiment, the reflective phase difference structure may further include a dielectric protection layer formed on the anisotropic structure layer. By adding the dielectric protection layer and optimizing its thickness, the dispersion of the phase difference can be adjusted to obtain more uniform characteristics.

[0043] In one embodiment, the dielectric filling member and the dielectric protection layer may be made of the same material.

[0044] (Implementation Method)

[0045] Hereinafter, preferred embodiments are described with reference to the accompanying drawings. The same or equivalent components, members, and processes shown in the respective drawings are marked with the same reference numerals, and repeated descriptions are appropriately omitted. In addition, the embodiments do not limit the disclosure or invention, but are exemplified, and all features and combinations thereof described in the embodiments are not necessarily limited to the essential contents of the disclosure or invention.

[0046] In addition, the dimensions (thickness, length, width, etc.) of each component recorded in the drawings are sometimes appropriately enlarged or reduced for easy understanding. Furthermore, the dimensions of multiple components are not necessarily limited to representing their size relationship. In the drawings, even if a certain component A is depicted thicker than another component B, it is possible that component A is thinner than component B.

[0047] Figure 1 2 is a perspective view of a reflective phase difference structure 200 according to the embodiment. The reflective phase difference structure 200 has a stacked structure including a metal reflective layer 210 , a dielectric spacer layer 220 , an anisotropic structure layer 230 , and a dielectric protective layer 240 .

[0048] As the material of the metal reflective layer 210, Ag, Al, etc. are suitable in the visible light region. In the case of designing assuming near infrared, Au, Cu, etc. can be used. In the case where high reflectivity is not required, Cr, Ni, Fe, etc. can also be used. The metal reflective layer 210 is formed on the surface of a substrate not shown in the figure, or on the surface of another component that is intended to function as a phase difference plate.

[0049] The anisotropic structural layer 230 has different structures in the first direction (x direction) and the second direction (y direction) perpendicular to each other in the plane (xy) of the reflective phase difference structure 200. The anisotropic structural layer 230 includes a plurality of metal components 232. In this embodiment, the anisotropic structural layer 230 has a wire grid structure (wire and spacer structure), and the plurality of metal components 232 are a plurality of wire grids extending along the y direction and adjacent to each other in the x direction.

[0050] The metal component 232 of the anisotropic structural layer 230 is made of aluminum (Al) metal. The so-called aluminum metal refers to a metal containing at least aluminum, and includes pure aluminum, aluminum mixed with impurities, or aluminum alloys with aluminum as the main component. In short, the aluminum metal has aluminum as the main component and can contain other materials within the range that the optical properties of pure aluminum are not damaged or the optical properties equivalent to those of pure aluminum can be obtained.

[0051] The anisotropic structural layer 230 further includes a dielectric filling member 234 that fills the gaps between the plurality of metal components 232 .

[0052] The dielectric spacer layer 220 is sandwiched between the metal reflective layer 210 and the anisotropic structure layer 230. A dielectric protection layer 240 is formed on the upper layer of the anisotropic structure layer 230. That is, the reflective phase difference structure 200 has a stacked structure in which the metal reflective layer 210, the dielectric spacer layer 220, the anisotropic structure layer 230, and the dielectric protection layer 240 are stacked in sequence.

[0053] The dielectric spacer layer 220, the dielectric filling member 234, and the dielectric protection layer 240 may be made of the same material or different materials. As the material of the dielectric spacer layer 220, the dielectric filling member 234, and the dielectric protection layer 240, SiO2, TiO2, MgF2, Al2O3, MgO, Y2O3, HfO2, ZrO2, Ta2O5, etc. may be used.

[0054] Figure 2 yes Figure 12 is a cross-sectional view of a reflective phase difference structure 200. The reflective phase difference structure 200 can be designed with optical properties using the thickness d1 and material of the dielectric spacer layer 220, the structure or size (height d2 and line width W1, spacing width Ws) of the metal component 232 of the anisotropic structure layer 230, the material of the dielectric filling member 234, and the thickness d3 or material of the dielectric protection layer 240 as parameters.

[0055] Figure 3 Yes means Figure 1 Graph of the reflectivity and phase difference characteristics (simulation results) of the reflective phase difference structure 200. The simulation is performed relative to light with an incident angle of 0°, and the polarized light component along the gate is set to S polarized light, and the polarized light perpendicular to it is set to P polarized light. The thickness of the metal reflective layer 210 is set to 100nm, the thickness d1 of the dielectric spacer layer 220 is set to 50nm, the height d2 of the anisotropic structure layer 230 is set to 30nm, and the thickness d3 of the dielectric protective layer 240 is set to 60nm. In addition, the line width of the anisotropic structure layer 230 is set to 20nm, and the interval width is set to 70nm. The material of the dielectric spacer layer 220 is set to SiO2, the material of the dielectric filling member 234 is set to SiO2, the material of the dielectric protective layer 240 is set to SiO2, and the material of the metal reflective layer 210 is set to Al.

[0056] Figure 4 : is a graph showing the reflectivity and phase difference characteristics (simulation results) of the reflective phase difference structure of Comparative Example 1. The reflective phase difference structure of Comparative Example 1 has the same structure as that of the embodiment, but Ag, which is generally used as a metasurface material in the visible light region, is used as the metal component 232 of the anisotropic structure layer 230.

[0057] like Figure 4 As shown in , it is found that when the metal component 232 is set to Ag, the reflectivity decreases on the short wavelength side and the phase difference characteristics deteriorate. In contrast, if the reflective phase difference structure 200 of the embodiment is used, as shown in Figure 3 As shown in , uniform phase difference characteristics are obtained in the entire visible light region.

[0058] Figure 5It is a graph showing the reflectivity of various metal materials. As a metasurface material generally used in the visible light region, Au and Ag are mostly used as materials for the constituent elements from the viewpoints of conductivity, reflection characteristics, stability, etc. Regarding Al, although there are occasional examples of its application in color filters, etc., it is not easy to become a candidate material when high functions are required because it has inferior reflection characteristics compared to Au in the near infrared and Ag in the visible light region. Considering that the use of the reflective phase difference structure in the visible light region includes its structure and Al is most suitable, the invention of this application can be said to be ingenious.

[0059] Next, a modification example of the reflective phase difference structure 200 will be described.

[0060] (Variant 1)

[0061] Figure 6 2 is a cross-sectional view of a reflective phase difference structure 200A according to Modification 1. Figure 2 The difference between the reflective phase difference structure 200 and the reflective phase difference structure 200 is that the dielectric protection layer 240 is omitted.

[0062] Figure 7 Yes means Figure 6 Graph showing the reflectivity and phase difference characteristics (simulation results) of the reflective phase difference structure 200A. The simulation parameters are the same as those in the embodiment.

[0063] Figure 8 : is a graph showing the reflectivity and phase difference characteristics (simulation results) of the reflection type phase difference structure of Comparative Example 2. Comparative Example 2 has the same structure as Modified Example 1, and the material of the metal component 232 is changed to Ag.

[0064] If the variation 1 ( Figure 7 ) and Comparative Example 2 ( Figure 8 ), when the metal component 232 is Ag, the reflectivity is reduced on the short wavelength side, and the phase difference characteristics are deteriorated. On the other hand, when the metal component 232 is Al, the reflectivity characteristics and phase difference characteristics on the short wavelength side can be improved.

[0065] In addition, if the implementation method ( Figure 3 ) and Modification 1( Figure 7 ) is compared, it is known that the embodiment further suppresses the dispersion of the phase difference characteristics. That is, the dispersion of the phase difference characteristics can be controlled by the dielectric protection layer 240.

[0066] (Variant 2)

[0067] Fig. 92 is a cross-sectional view of a reflective phase difference structure 200B according to Modification 2. Figure 2 The difference between the reflective phase difference structure 200 and the dielectric protection layer 240 is that the dielectric filling member 234 of the anisotropic structure layer 230 is omitted.

[0068] Fig.10 Yes means Fig. 9 Graph showing the reflectivity and phase difference characteristics (simulation results) of the reflective phase difference structure 200B. The simulation parameters are the same as those in the embodiment.

[0069] Fig.11 : is a graph showing the reflectivity and phase difference characteristics (simulation results) of the reflection type phase difference structure of Comparative Example 3. Comparative Example 3 has the same structure as Modified Example 2, and the material of the metal component 232 is changed to Ag.

[0070] If the variation 2 ( Fig.10 ) and Comparative Example 3 ( Fig.11 ) are compared, it is found that when the metal component 232 is Ag, the reflectivity is reduced on the short wavelength side, and the phase difference characteristics are deteriorated. On the other hand, when the metal component 232 is Al, the reflectivity characteristics and phase difference characteristics on the short wavelength side can be improved.

[0071] In addition, if the modification example 1 ( Figure 7 ) and Modification 2( Fig.10 ) is compared with the above, it is found that the dispersion of the phase difference characteristics is further suppressed in the modification example 1. That is, it is found that the dielectric filling member 234 of the anisotropic structure layer 230 has the function of suppressing the dispersion of the phase difference characteristics.

[0072] Next, the contribution of the dielectric spacer layer 220 to the optical characteristics of the reflective retardation structure 200 will be described. In order to examine the contribution of the dielectric spacer layer 220, in the reflective retardation structure 200B of Modification 2, the thickness d1 of the dielectric spacer layer 220 was changed.

[0073] Fig.12 is the reflectivity R of the TE wave of the reflection type phase difference structure 200B. TE , TM wave reflectivity R TM The dependence of the phase difference characteristics on the thickness d1 of the dielectric spacer layer 220 is shown in the figure. In the figure, the arrow indicates the visible light region. The vertical axis indicates the thickness d1 of the dielectric spacer layer 220, and the horizontal axis indicates the wavelength. d1=0 indicates that there is no dielectric spacer layer 220. If d1 is small (d1<30nm), the reflectivity R of the TM wave TE In addition, the dispersion of phase difference also increases.

[0074] It is found that if the thickness d1 of the dielectric spacer layer 220 is gradually increased, the reflectivity R TE In this example, it is found that uniform reflectance and phase difference characteristics can be obtained in the entire visible light region around d1 = 60 nm.

[0075] Next, the contribution of the dielectric filling member 234 and the dielectric protection layer 240 to the optical characteristics of the reflective phase difference structure 200 will be described.

[0076] Fig.13 is the reflectivity R of the TE wave of the reflection type phase difference structure 200. TE , TM wave reflectivity R TM In the figure, the arrow indicates the visible light region. The vertical axis h indicates the height from the surface of the dielectric spacer layer 220 to the surface of the dielectric filling member 234 or the dielectric protection layer 240. The height d2 of the metal component 232 is 30 nm.

[0077] h=0nm corresponds to Modification 2 ( Fig. 9 ) status.

[0078] The range of h<30 nm corresponds to a state where the dielectric protection layer 240 does not exist and only the dielectric filling member 234 is filled halfway into the anisotropic structural layer 230 .

[0079] h=30nm corresponds to the variation 1 ( Figure 6 ) as shown in FIG. 2 . The anisotropic structure layer 230 is filled with the dielectric filling member 234.

[0080] h>30nm corresponds to the embodiment ( Figure 2 ) The dielectric protection layer 240 is in a state where the dielectric protection layer 240 exists. The thickness d3 of the dielectric protection layer 240 is d3 = h-30 nm.

[0081] If Fig.13 As can be seen, in the range of h>30 nm, the dispersion characteristics of the phase difference are controlled according to the height h. In particular, when h=80 nm, that is, d3=50 nm, it is found that a flat phase difference characteristic is obtained in the entire visible light region.

[0082] Next, a modification example of the anisotropic structural layer 230 will be described.

[0083] In the embodiment, the cross section of the metal component 232 of the anisotropic structural layer 230 is a rectangle, but the invention is not limited thereto. The cross section of the metal component 232 may be a triangle or a trapezoid.

[0084] In addition, the anisotropic structural layer 230 may have a double patterning structure in which a pair of two wire grids close to each other in the x direction are repeatedly formed in the x direction.

[0085] Furthermore, the anisotropic structural layer 230 is not limited to a collection of wire grids.

[0086] Fig.14 3 is a perspective view of a reflective phase difference structure 200F of modification 3. In this modification, the plurality of metal components 232F are a collection of a plurality of blocks adjacent in the x direction and the y direction. The anisotropic structure layer 230F may also include a dielectric filling member 234, and a dielectric protective layer 240 may also be formed on the anisotropic structure layer 230F.

[0087] Fig.15 2 is a plan view for explaining design parameters of the anisotropic structural layer 230F of Modification 3. The anisotropic structural layer 230F can be formed by the length Δx in the x direction, the length Δy in the y direction, and the interval d in the x direction of the metal component 232F. x , the interval d in the y direction y In order to make the anisotropic structure layer 230F an anisotropic structure, as long as Δx≠Δy and d x ≠d y At least one of the following will suffice.

[0088] (Manufacturing method)

[0089] exist Figure 2 , Figure 6 In the reflective phase difference structure 200, 200A, a dielectric filling member 234 and a dielectric protection layer 240 are formed on a metal component 232 as a microstructure. Hereinafter, the dielectric filling member 234 and the dielectric protection layer 240 are collectively referred to as a dielectric film.

[0090] Fig.16 Yes Description Figure 2 FIG. 1 is a diagram showing a manufacturing process of a reflective phase difference structure 200. In step S100, a dielectric spacer layer 220 is formed on a metal reflective layer 210. The metal reflective layer 210 can be formed on a substrate (not shown) by, for example, vapor deposition.

[0091] In step S110, an anisotropic structure layer 230 is formed on the dielectric spacer layer 220, in which the metal components 232 are arranged. For example, a metal layer is formed on the entire surface of the dielectric spacer layer 220, and a patterned mask structure is formed thereon by an exposure process. Then, the metal layer is patterned by dry etching using the mask structure, thereby forming the metal components 232.

[0092] In the next step S120 , a dielectric film is formed on the anisotropic structural layer 230 , and the dielectric filling member 234 is filled in the gaps between the metal components 232 .

[0093] Furthermore, in step S130, a dielectric protection layer 240 is formed on the anisotropic structural layer 230. When the anisotropic structural layer 230 and the dielectric protection layer 240 are made of the same material, steps S120 and S130 may be performed continuously.

[0094] Generally, as a method for forming a dielectric film, sputtering, chemical vapor deposition (CVD), evaporation, and atomic layer deposition (ALD) can be used. The same is true for the dielectric filling member 234 and the dielectric protection layer 240 in this embodiment. In steps S120 and S130, any of these methods can be used.

[0095] Metallic Al may be oxidized by oxygen plasma generated during the film formation process of the dielectric filling member 234 and the dielectric protection layer 240 as oxide films. In this case, the phase difference providing function of the anisotropic structure layer 230 is impaired, and the function as a phase difference structure body cannot be obtained.

[0096] In addition, if the gap portion of the metal component 232 is not filled and a void is generated, the refractive index changes sharply in the void portion, and there is a problem of deterioration of the phase characteristic. Specifically, it is possible that the phase difference that can be given becomes smaller, and the broadband characteristic is impaired. These problems may be caused, for example, when sputtering is used as a film forming method for the dielectric film.

[0097] It should be noted that this description does not deny or exclude the film formation of dielectric films using the sputtering method. Even if the sputtering method is used in general, there are cases where good characteristics can be obtained depending on the device used and the film formation conditions. In addition, the reflective phase difference structure 200 formed by the sputtering method of the dielectric film is fully practical according to the required specifications.

[0098] Fig.17 This is a SEM image of a cross section of a reflective phase difference structure 200 formed by the ALD method. Fig.17 , the cross-sectional structure of the reflective phase difference structure 200 formed at three different locations D to F on the wafer is shown.

[0099] Fig.18 It means Fig.17Graph of phase characteristics corresponding to the reflective phase difference structure 200. By using the ALD method, oxidation of Al caused by oxygen plasma can be prevented. In addition, in the ALD method, since the dielectric filling member 234 is densely filled between the metal components 232, it is not easy to generate gaps. As a result, the rapid change of the refractive index caused by the gap is also suppressed.

[0100] If you observe Fig.18 , it is found that regarding the phase characteristic, a value close to the designed value of 180° can be obtained in a wide band.

[0101] Explanation of symbols

[0102] 200 Reflective phase difference structure

[0103] 210 Metal reflective layer

[0104] 220 dielectric spacer layer

[0105] 230 Anisotropic structural layer

[0106] 232 Metal components

[0107] 234 Dielectric filling member

[0108] 240 Dielectric protective layer

Claims

1. A reflective phase difference structure, characterized in that: It has: Metal reflective layer, The invention discloses an anisotropic structural layer including a plurality of metal components made of aluminum-based metal, and a dielectric spacer layer sandwiched between the metal reflective layer and the anisotropic structural layer.

2. The reflective phase difference structure according to claim 1, characterized in that: The anisotropic structural layer further includes a dielectric filling member that fills gaps between the plurality of metal components.

3. The reflective phase difference structure according to claim 2, characterized in that: The dielectric spacer layer and the dielectric filling member are made of the same material.

4. The reflective phase difference structure according to claim 2 or 3, characterized in that: The invention further comprises a dielectric protection layer formed on the anisotropic structural layer.

5. The reflective phase difference structure according to claim 4, characterized in that: The dielectric filling member and the dielectric protection layer are made of the same material.

6. A manufacturing method, characterized in that: The method for manufacturing a reflective phase difference structure according to claim 2, The method comprises the step of forming the dielectric filling member by atomic layer deposition.

7. A method for manufacturing a reflective phase difference structure, characterized in that: It has: A process for forming a metal reflective layer; forming a dielectric spacer layer on the metal reflective layer; forming an anisotropic structural layer including a plurality of metal components made of aluminum-based metal on the spacer layer; A step of forming a dielectric protection layer on the anisotropic structural layer by atomic layer deposition.

8. The method for manufacturing a reflective phase difference structure according to claim 7, characterized in that: The process of forming the anisotropic structural layer comprises: forming a metal layer on the dielectric spacer layer; forming a mask structure for dry etching on the upper side of the metal layer by an exposure process; and A process of patterning the metal layer by dry etching using the mask structure.

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