Metal grating and preparation method thereof

Abstract

The invention provides a metal grating and a preparation method thereof, and relates to the technical field of optical elements. The metal grating comprises a substrate layer and grating bars periodically arranged on the first surface of the substrate layer in the first direction. Grooves are periodically formed in the first surface in the first direction, the grooves extend in the second direction, the first direction and the second direction are perpendicular to each other and are parallel to the first surface, and the included angle between the side wall of each groove and the first surface is an acute angle, so that the groove opening width of each groove in the first direction is larger than the groove bottom width. According to the metal grating, the grooves with the inclined side walls are formed in the intervals of the grating bars of each period on the substrate layer, in the equivalent refractive index theory, the inclined side walls can be regarded as continuous refractive index transition, and the p light transmittance can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of optical elements, and in particular to a metal grating and a method for preparing the same. Background Art

[0002] Metal grating is a high-performance polarization beam splitter that allows most of the p-light in the incident light to pass through and most of the s-light to reflect, thereby separating the two different polarization lights. Compared with traditional polarization devices, metal gratings have the advantages of small size, thin film, compact structure, easy integration, and good polarization. Therefore, they have been widely used in optical fiber communication, liquid crystal display, optical projection, photoelectric detection and other fields.

[0003] The existing metal grating includes a base layer and a grating layer arranged on the base layer, wherein the surface of the base layer for arranging the grating layer is flat and has no obvious concave structure. Although the metal grating of this structure can allow most of the p light in the incident light to pass through, its p light transmittance still has room for improvement. Summary of the invention

[0004] The purpose of the present application is to provide a metal grating and a method for preparing the same, which can improve the p-light transmittance, in view of the deficiencies in the above-mentioned prior art.

[0005] To achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows:

[0006] In one aspect of an embodiment of the present application, a metal grating is provided, comprising: a base layer and grating bars periodically arranged along a first direction on a first surface of the base layer; grooves are periodically arranged along the first direction on the first surface, the grooves extend along a second direction, the first direction and the second direction are perpendicular to each other and respectively parallel to the first surface, and the angle between the side wall of the groove and the first surface is an acute angle, so that the groove width in the first direction is greater than the groove bottom width.

[0007] Optionally, the angle between the side wall of the groove and the first surface is 45° to 80°.

[0008] Optionally, a longitudinal section of the groove perpendicular to the second direction is trapezoidal or triangular.

[0009] Optionally, the depth of the groove is 5 nm to 150 nm.

[0010] Optionally, a circular chamfer is provided at a corner of the groove, and the radius of the circular chamfer is less than or equal to 10 nm.

[0011] Optionally, the period of the grating strips is 50 nm to 200 nm, the width of the grating strips is 30 nm to 100 nm, and the height of the grating strips is 50 nm to 300 nm.

[0012] Optionally, a surface of the grating strips away from the substrate layer is provided with a protection strip, and the protection strip completely covers the surface of the grating strips away from the substrate layer.

[0013] On the other hand, an embodiment of the present application provides a method for preparing a metal grating, comprising: providing a base layer and forming a metal layer on a first surface of the base layer; etching the metal layer and the base layer in sequence to divide the metal layer into grating strips that are periodically arranged along a first direction and extend along a second direction, and forming periodically arranged grooves along the first direction on the first surface, wherein the first direction and the second direction are perpendicular to each other and are respectively parallel to the first surface, and the angle between the side wall of the groove and the first surface is an acute angle, so that the groove width in the first direction is greater than the groove bottom width.

[0014] Optionally, etching the metal layer and the base layer in sequence includes: over-etching the metal layer using a metal etcher, and stopping the etching in the base layer.

[0015] Optionally, a method for preparing a metal grating includes: providing a base layer, and forming a metal layer and a protective layer in sequence on a first surface of the base layer along a third direction, wherein the third direction is perpendicular to the first surface; etching the protective layer to divide the protective layer into protective strips that are periodically arranged along a first direction and extend along a second direction, wherein the first direction and the second direction are perpendicular to each other and are respectively parallel to the first surface; etching the metal layer and the base layer exposed by the protective strips in sequence to divide the metal layer into grating strips that are periodically arranged along the first direction and extend along the second direction, and forming periodically arranged grooves on the first surface along the first direction, wherein a surface of the grating strips away from the base layer is completely covered by the protective strips, and an angle between the side wall of the groove and the first surface is an acute angle, so that the groove width in the first direction is greater than the groove bottom width.

[0016] The beneficial effects of this application include:

[0017] The present application provides a metal grating, comprising: a substrate layer and grating bars periodically arranged on a first surface of the substrate layer along a first direction; grooves are periodically arranged on the first surface along the first direction, the grooves extend along a second direction, the first direction and the second direction are perpendicular to each other and parallel to the first surface respectively, and the angle between the sidewall of the groove and the first surface is an acute angle, so that the groove width in the first direction is greater than the groove bottom width. The metal grating is provided with grooves with inclined sidewalls within the interval of the grating bars of each period on the substrate layer, and in the equivalent refractive index theory, the inclined sidewalls of the grooves can be regarded as a continuous refractive index transition, and therefore, it has a certain anti-transmission effect on p-light and can improve the p-light transmittance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 One of the structural schematic diagrams of the metal grating provided in the embodiment of the present application;

[0020] Figure 2 for Figure 1 Spectral measurement diagram of the metal grating;

[0021] Figure 3 The second structural schematic diagram of the metal grating provided in the embodiment of the present application;

[0022] Figure 4 The third structural schematic diagram of the metal grating provided in the embodiment of the present application;

[0023] Figure 5 The fourth structural schematic diagram of the metal grating provided in the embodiment of the present application;

[0024] Figure 6 One of the flow charts of the method for preparing the metal grating provided in the embodiment of the present application;

[0025] Figure 7 The second flowchart of the method for preparing the metal grating provided in the embodiment of the present application.

[0026] Icon: 10-metal grating; 11-base layer; 111-first surface; 112-groove; 1121-slot; 1122-groove bottom; 1123-arc chamfer; 12-grating bars; 13-protective strips; X-first direction; Y-second direction; Z-third direction; B1-width of grating bars; B2-width of slot; B3-width of groove bottom; H1-depth of groove; H2-height of grating bars; H3-height of protective strips; θ1-angle between the side wall of the groove and the first surface; θ2-angle between the side wall of the grating bars and the first surface of the base layer. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. It should be noted that, in the absence of conflict, the various features in the embodiments of the present application can be combined with each other, and the combined embodiments are still within the scope of protection of the present application.

[0029] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0030] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0031] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] In one aspect of the embodiment of the present application, please refer to Figure 1 , a metal grating 10 is provided, comprising: a base layer 11 and grating bars 12 periodically arranged on a first surface 111 of the base layer 11 along a first direction X, and the grating bars 12 extend along a second direction Y. The base layer 11 is mainly made of glass wafer, and the grating bars 12 can be made of metal materials such as gold, silver, aluminum, chromium, tungsten, molybdenum, and titanium.

[0033] The first surface 111 is provided with grooves 112 periodically along the first direction X, and the grooves 112 extend along the second direction Y, and the grooves 112 are recessed from the first surface 111 of the substrate layer 11 to the inside of the substrate layer 11. The first direction X and the second direction Y are perpendicular to each other, and the first direction X and the second direction Y are parallel to the first surface 111, respectively. The groove 112 has a notch 1121 close to the grating strips 12 and a groove bottom 1122 away from the grating strips 12, and the angle θ1 between the side wall of the groove and the first surface is an acute angle, so that the notch width B2 of the groove 112 is greater than the groove bottom width B3.

[0034] It can be understood that the groove 112 is located on the side of the grating strip 12 , and the outer edge of the orthographic projection of the groove 112 on the first surface 111 coincides with the outer edge of the orthographic projection of the grating strip 12 located on the side of the groove 112 on the first surface 111 .

[0035] The metal grating 10 sets the sidewall of the groove 112 as an inclined slope, so that the groove width B2 of the groove 112 is greater than the groove bottom width B3. In the equivalent refractive index theory, the inclined sidewall of the groove 112 can be regarded as a continuous refractive index transition, so it has a certain anti-reflection effect on p-light and can improve the p-light transmittance.

[0036] Optionally, an angle θ1 between the side wall of the groove and the first surface is 45° to 80°.

[0037] The angle θ1 between the sidewall of the groove and the first surface is within the above range, which can further improve the p-light transmittance and facilitate the processing of the groove 112. It should be noted that the angle θ1 between the sidewall of the groove and the first surface can be 45° or 80°.

[0038] Optionally, the depth H1 of the groove is 5 nm to 150 nm.

[0039] It should be noted that the depth H1 of the groove refers to the dimension of the groove 112 in a direction perpendicular to the first surface 111 of the base layer 11 .

[0040] Please refer to Figure 2 , Figure 2 for Figure 1 The measured spectrum of the metal grating 10, Figure 2 The horizontal axis λ is the wavelength, the vertical axis Tp is the p-light transmittance, the blue curve represents the p-light transmittance of the metal grating 10 at different wavelengths when the depth of the groove 112 is hnm, and the red curve represents the p-light transmittance of the metal grating 10 at different wavelengths when the depth of the groove 112 is (h+5)nm. Figure 2 It can be seen that, under the premise that other parameters of the metal grating 10 remain unchanged, the p-light transmittance of the metal grating 10 will indeed increase as the depth of the groove 112 increases.

[0041] Optionally, see Figure 1 and Figure 3 The longitudinal section of the groove 112 perpendicular to the second direction Y is a trapezoid or a triangle.

[0042] The side wall of the groove 112 with a trapezoidal or triangular longitudinal section is inclined and easy to process. Furthermore, the longitudinal section of the groove 112 perpendicular to the second direction Y is an isosceles trapezoid or an isosceles triangle.

[0043] Optionally, the longitudinal section of the grating strips 12 perpendicular to the second direction Y is rectangular or trapezoidal. If the longitudinal section of the grating strips 12 is trapezoidal, the angle θ2 between the sidewalls of the grating strips and the first surface of the substrate layer is 85° to 90°.

[0044] Optionally, see Figure 4 A circular chamfer 1123 is provided at the corner of the groove 112, and the radius of the circular chamfer 1123 is less than or equal to 10 nm.

[0045] The arc chamfer 1123 is a naturally formed arc angle in the actual processing process and has no effect on improving the p-light transmittance, but allowing the existence of the arc chamfer 1123 can reduce the processing difficulty.

[0046] Optionally, see Figure 1 The period of the grating strips 12 is 50nm-200nm, the width B1 of the grating strips is 30nm-100nm, and the height H2 of the grating strips is 50nm-300nm. Such an arrangement can ensure that the metal grating 10 realizes the polarization extinction function and reduces the generation of stray light.

[0047] Optionally, see Figure 5 A protective strip 13 is provided on the surface of the grating bars 12 away from the base layer 11 , and the protective strip 13 completely covers the surface of the grating bars 12 away from the base layer 11 to protect the top of the grating bars 12 and improve the reliability of the metal grating 10 .

[0048] Optionally, the height H3 of the protection strip is 0 nm to 30 nm, and the height H3 of the protection strip is positively correlated with the depth H1 of the groove.

[0049] Optionally, the material of the protection strip 13 is silicon dioxide, and the surface of the protection strip 13 away from the grating strips 12 is an arc surface, so as to further improve the reliability of the metal grating 10 .

[0050] Please refer to Figure 6 This embodiment also provides a method for preparing a metal grating, comprising:

[0051] S100: providing a base layer, and forming a metal layer on a first surface of the base layer.

[0052] S200: The metal layer and the base layer are sequentially etched to divide the metal layer into grating strips that are periodically arranged along a first direction and extend along a second direction, and grooves that are periodically arranged along the first direction are formed on the first surface, wherein the first direction and the second direction are perpendicular to each other and are respectively parallel to the first surface, and an angle between a side wall of the groove and the first surface is an acute angle, so that a groove width in the first direction is greater than a groove bottom width.

[0053] Please refer to Figure 1 , a complete metal layer is formed on the first surface 111 of the base layer 11, and the metal layer can be formed by material deposition. The metal layer is etched to divide the metal layer into grating strips 12 periodically distributed along the first direction X, and the grating strips 12 extend along the second direction Y. After the metal layer is etched, the base layer 11 at the bottom is partially exposed, and then the exposed base layer 11 is etched to form grooves 112 periodically distributed along the first direction X in the base layer 11, and the grooves 112 also extend along the second direction Y. The groove 112 is located in the middle of two adjacent grating strips 12. The sidewalls of the groove 112 formed by etching are inclined, so that the groove width B2 of the groove 112 is greater than the groove bottom width B3.

[0054] The metal grating 10 prepared by the above-mentioned method for preparing the metal grating has a certain anti-transmission effect on p-light and can improve the p-light transmittance.

[0055] Optionally, etching the metal layer and the base layer in sequence includes:

[0056] The metal layer is over-etched using a metal etcher, and the etching stops within the base layer.

[0057] In this way, the grating strips 12 and the grooves 112 can be formed by etching once, making the process simpler. The depth H1 of the groove and the inclination angle of the side wall of the groove 112 can be adjusted by adjusting the etching gas parameters (such as the values ​​of x and y in the CxFy fluorocarbon etching gas) and the etching time.

[0058] Optionally, see Figure 7 , a method for preparing a metal grating, comprising:

[0059] S300: providing a base layer, and sequentially forming a metal layer and a protective layer on a first surface of the base layer along a third direction, wherein the third direction is perpendicular to the first surface.

[0060] Please refer to Figure 5 The metal layer is formed on the first surface 111 of the base layer 11, and the protective layer is formed on the surface of the metal layer away from the base layer 11. The base layer 11, the metal layer and the protective layer are sequentially distributed along the third direction Z. Both the metal layer and the protective layer are complete film layers and can be formed by material deposition.

[0061] S400: etching the protection layer to divide the protection layer into protection strips that are periodically arranged along a first direction and extend along a second direction, wherein the first direction and the second direction are perpendicular to each other and are parallel to the first surface respectively.

[0062] The protective layer is etched to divide the protective layer into protective strips 13 periodically distributed along the first direction X, and the protective strips 13 extend along the second direction Y.

[0063] S500: The metal layer and the base layer exposed by the protective strip are sequentially etched to divide the metal layer into grating strips that are periodically arranged along a first direction and extend along a second direction, and periodically arranged grooves are formed on the first surface along the first direction, wherein the surface of the grating strip away from the base layer is completely covered by the protective strip, and the angle between the side wall of the groove and the first surface is an acute angle, so that the groove width in the first direction is greater than the groove bottom width.

[0064] After the protective layer is etched, the metal layer at the bottom thereof is partially exposed, and the exposed metal layer is etched to divide the complete metal layer into grating bars 12 periodically distributed along the first direction X. After the metal layer is etched, the base layer 11 at the bottom thereof is partially exposed, and then the exposed base layer 11 is etched to form grooves 112 periodically distributed along the first direction X on the base layer 11. Here, a metal etcher can be used to over-etch the metal layer, so that the etching stops in the base layer 11, thereby forming periodically distributed grating bars 12 and grooves 112 through one etching.

[0065] For example, etching the protective layer includes: coating a photoresist on the surface of the protective layer, exposing and developing the photoresist, curing the photoresist and converting it into a photoresist layer with etched through holes; etching the protective layer by etching through holes to transfer the pattern of the etched through holes to the protective layer, thereby forming the periodic protection strips 13. Etching can be performed by dry etching using a dielectric etcher, or by etching using an electron beam.

[0066] The etching of the metal layer and the base layer 11 is similar to the etching of the protective layer, and will not be described in detail in this embodiment.

[0067] It should be understood that, although the various steps in the aforementioned flow chart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless there is a clear description in this article, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flow chart may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0068] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A metal grating, characterized in that: include: A base layer and grating strips periodically arranged on a first surface of the base layer along a first direction, grooves are periodically arranged on the first surface along the first direction, the grooves extend along a second direction, the first direction and the second direction are perpendicular to each other and parallel to the first surface respectively, and the angle between the side wall of the groove and the first surface is an acute angle, so that the groove width in the first direction is greater than the groove bottom width.

2. The metal grating according to claim 1, characterized in that: The angle between the side wall of the groove and the first surface is 45° to 80°.

3. The metal grating according to claim 1, characterized in that: The longitudinal section of the groove perpendicular to the second direction is trapezoidal or triangular.

4. The metal grating according to claim 1, characterized in that: The depth of the groove is 5nm to 150nm.

5. The metal grating according to claim 1, characterized in that: A circular chamfer is provided at a corner of the groove, and the radius of the circular chamfer is less than or equal to 10 nm.

6. The metal grating according to any one of claims 1 to 5, characterized in that: The period of the grating strips is 50nm-200nm, the width of the grating strips is 30nm-100nm, and the height of the grating strips is 50nm-300nm.

7. The metal grating according to any one of claims 1 to 5, characterized in that: A protective strip is disposed on a surface of the grating strips away from the base layer, and the protective strip completely covers the surface of the grating strips away from the base layer.

8. A method for preparing a metal grating, characterized in that: include: Providing a base layer, and forming a metal layer on a first surface of the base layer; The metal layer and the base layer are etched in sequence to divide the metal layer into grating strips that are periodically arranged along a first direction and extend along a second direction, and periodically arranged grooves are formed on the first surface along the first direction, wherein the first direction and the second direction are perpendicular to each other and are respectively parallel to the first surface, and the angle between the side wall of the groove and the first surface is an acute angle, so that the groove width in the first direction is greater than the groove bottom width.

9. The method for preparing a metal grating according to claim 8, characterized in that: Sequentially etching the metal layer and the base layer comprises: The metal layer is over-etched by using a metal etcher, and the etching stops within the base layer.

10. The method for preparing a metal grating according to claim 8, characterized in that: include: Providing a base layer, and sequentially forming a metal layer and a protective layer on a first surface of the base layer along a third direction, wherein the third direction is perpendicular to the first surface; Etching the protective layer to divide the protective layer into protective strips that are periodically arranged along a first direction and extend along a second direction, wherein the first direction and the second direction are perpendicular to each other and parallel to the first surface respectively; The metal layer and the base layer exposed by the protective strip are sequentially etched to divide the metal layer into grating strips periodically arranged along the first direction and extending along the second direction, and periodically arranged grooves are formed on the first surface along the first direction, wherein the surface of the grating strip away from the base layer is completely covered by the protective strip, and the angle between the side wall of the groove and the first surface is an acute angle, so that the groove width in the first direction is greater than the groove bottom width.

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