Method for preparing grating with continuous gradient depth

Abstract

The invention provides a method for preparing a depth continuous gradual change grating, which comprises the following steps of: determining the etching moving speed of each sub-region in different grating sub-regions in the same functional grating region of a substrate, controlling the different grating sub-regions to be exposed at the emergent position of an ion beam, and controlling the deflection angle and position of the substrate relative to the incident direction of the ion beam. Completing the etching of the grating with continuous gradual change depth in different sub-regions through one-time patterning and one-time etching processes; during etching, the etching step comprises two steps: step 1, etching a target structure according to a certain percentage; 2, etching according to a certain percentage; on one hand, the morphology of the etched grating can be ensured, and the roughness of the surface and the side wall of the grating and the vertical or inclined angle of the grating structure are trimmed; the method also can guarantee the gradual change continuity of the grating depth, optimizes the visualization of boundary lines between different grating sub-regions, reduces the visibility of the boundary lines, and reduces the influence of the boundary lines with different grating depth changes on the appearance of the diffraction optical waveguide.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, and in particular to a method for preparing a depth-continuously-varying grating. BACKGROUND

[0002] As one of the important optical devices in the field of augmented reality display technology, diffractive optical waveguide has become the focus of industry technology research and development. In the preparation of diffractive optical waveguide, in order to achieve the uniformity and high efficiency of waveguide optical imaging display, it is often necessary to limit the diffractive gratings in different coupling-out regions of the waveguide to have different diffraction efficiencies.

[0003] The prior art has given a scheme for modulating the coupling-out diffraction efficiency of different coupling-out regions, such as coating different refractive index metal films on different regions of the grating surface, or limiting the depths of the diffractive gratings in different coupling-out regions to be different. The second scheme is easier to control and implement. However, when making gratings with different depths in different coupling-out regions, on the one hand, the existing process is relatively complex, with many procedures, and needs to be masked and etched multiple times, which is tedious and prone to errors. On the other hand, the different depth grating structures prepared based on the existing process are prone to form a relatively obvious partition phenomenon in appearance, and the depth change of the gratings at different positions is particularly obvious and prominent at the boundary position, which will have a great visual impact on the appearance of the diffractive optical waveguide, which is not desirable for those skilled in the art. Therefore, how to improve the existing grating preparation process, reduce the process flow and preparation steps, while ensuring the diffraction efficiency of different coupling-out regions and minimizing the boundary line of different grating depth changes affecting the appearance of the diffractive optical waveguide, and optimizing the appearance of the waveguide, is a technical problem faced by those skilled in the art.

[0004] Therefore, the present application proposes a method for preparing a depth-continuously-varying grating to solve the above technical problems. SUMMARY

[0005] The present application provides a method for preparing a depth-continuously-varying grating to reduce the preparation process steps of the existing preparation of a gradually-varying grating and improve the process precision of the depth-continuously-varying grating.

[0006] A method for preparing a depth-continuously-varying grating, comprising the following steps:

[0007] (1) providing a substrate and forming a hard mask layer on any surface of the substrate;

[0008] (2) forming a photoresist layer on the side surface of the hard mask layer away from the substrate; and performing a patterning process;

[0009] (3) determining the energy of the ion beam emitted by the ion source;

[0010] (4) etching the hard mask layer in step (2) to obtain a patterned hard mask layer, and removing the photoresist layer;

[0011] (5) determining the volume etching depth of each sub-region of the different sub-regions of the depth-continuously-varying grating based on the preset etching environment requirement;

[0012] (6) determining the etching moving speed of each sub-region of the different sub-regions of the substrate based on the energy of the ion beam determined in step (3) and the volume etching depth of each sub-region of the different sub-regions of the grating determined in step (5), to obtain the etching moving speed of the different sub-regions of the grating;

[0013] (7) controlling the exposure of the different sub-regions of the substrate to the exit position of the ion beam, and based on the etching moving speed of the different sub-regions of the grating obtained in step (6), controlling the deflection angle and position of the substrate relative to the incident direction of the ion beam, to etch the substrate structure in step (4) to obtain the depth-continuously-varying grating.

[0014] Further, the depth-continuously-varying grating refers to a same functional grating region including at least two sub-regions of different depths, and the grating depths of the at least two sub-regions of different depths increase in turn in a direction away from the minimum grating depth.

[0015] Further, the depth-varying range of the grating is 0-300 nm.

[0016] Further, the grating depths in each of the sub-regions of the grating can be the same or different.

[0017] In some other embodiments, in the step (3), the energy of the ion beam emitted by the ion source is determined based on the different target depths of the grating, specifically, the energy of the ion beam during etching is limited based on the maximum and minimum values of the target depths of the grating in the different sub-regions of the grating.

[0018] In some other embodiments, in the step (5), the volume etching depth of each sub-region of the different sub-regions of the depth-continuously-varying grating is determined based on the preset etching environment requirement, specifically, the volume etching depth of each sub-region at different positions is determined by the following formula (1):

[0019] H (x,y) = K × C (x,y) × [(M (x,y) × V) / (L × N)] (1)

[0020] In formula (1), H (x,y)represents the volume etching depth of the grating at coordinates (x, y); K represents a coefficient factor, with a value range of [0, 1]; C (x,y) represents the duty cycle of the grating at coordinates (x, y); M (x,y) represents the etching amount (nm) of the substrate material at coordinates (x, y); V represents the etching scanning rate (cm / s); L represents the number of ion beam scanning lines per centimeter; N represents the scanning times of the ion beam in one period.

[0021] In some other embodiments, in the step (6), based on the energy of the ion beam determined in the step (3) and the volume etching depth of each of the different grating sub-regions determined in the step (5), the etching moving speed of each of the different grating sub-regions of the substrate is determined, to obtain the etching moving speed of the different grating sub-regions, specifically, based on the energy of the ion beam determined in the step (3) and the volume etching depth of each of the different grating sub-regions determined in the step (5), the etching moving speed of each of the different grating sub-regions is calculated in combination with the etching selection ratio and the etching gas type of the substrate.

[0022] In some other embodiments, in the step (7), the exposure of the different grating sub-regions of the substrate to the exit position of the ion beam is controlled, the deflection angle and position of the different grating sub-regions of the substrate relative to the incident direction of the ion beam are controlled based on the etching moving speed determined in the step (6), and the etching moving speed of the exposure of the different grating sub-regions of the substrate to the position of the ion beam is controlled, to etch the substrate structure in the step (4), to obtain a depth-continuously-graduated grating; the deflection angle is 0-180°.

[0023] In some other embodiments, the etching step includes two steps: in the first step, fluorine-based gas is used as the etching gas to form electrically neutral ion gas clusters to etch the target structure by a certain percentage; in the second step, Ar electrically neutral ion gas clusters are used to etch by a certain percentage; finally, the target gradual depth is achieved by the sum of the etching depths of the two parts, and the depth continuity is ensured.

[0024] In some other embodiments, in the etching step, the depth etching depth range of the fluorine-based ion gas clusters in the first step is (20%-90%) of the target depth; the depth etching depth range of the Ar ion gas clusters in the second step is (10%-80%) of the target depth.

[0025] In some other embodiments, in the first step, the flow rate of the fluorine-based gas ranges from 10 to 125 sccm; in the second step, the flow rate of Ar ranges from 10 to 500 sccm.

[0026] This invention provides a method for fabricating depth-gradient gratings. Compared to existing technologies, this method involves multiple grating sub-regions within the same functional grating region. By determining the etching speed of each sub-region, the method controls the exposure position of different grating sub-regions of the substrate to the ion beam emission, and controls the deflection angle and position of the substrate relative to the ion beam incident direction. This invention completes the etching of depth-gradient gratings in different sub-regions through a single patterning and etching process. The etching process includes two steps: First, a fluorine-based gas is used as the etching gas to form electrically neutral ion gas clusters, which are applied to the target structure according to a certain percentage... The etching process is performed in two steps: first, etching is carried out in two stages; second, Ar neutral ion gas clusters are used for etching in a certain percentage; finally, the target gradient depth is achieved by summing the two etching depths while ensuring depth continuity. This process ensures the morphology of the etched grating, corrects the roughness of the grating surface and sidewalls, and adjusts the vertical or tilt angle of the grating structure. On the other hand, it also ensures the continuity of the grating depth gradient, making the gradient between different etching depths less obvious, optimizing the visualization of the boundary lines between different grating sub-regions, reducing the visibility of the boundary lines, minimizing the impact of the boundary lines of different grating depths on the appearance of the diffracted waveguide, and improving the aesthetics of the waveguide display. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of a cross-section of a depth-continuously gradient grating structure provided by the present invention;

[0029] Figure 2 This is a schematic diagram of a method for preparing a depth-gradient grating provided by the present invention;

[0030] Figure 3 A schematic diagram of a diffractive waveguide gradient grating layout provided by the present invention;

[0031] Figure 4 This is a schematic diagram of the substrate etched by an ion beam in a method for fabricating a depth-gradient grating provided by the present invention;

[0032] Figure 5 This is a schematic diagram of a fabrication method for a depth-gradient oblique tooth grating structure provided by the present invention;

[0033] Figure 6 This is a schematic diagram of a process for fabricating a depth-gradient grating provided by the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] Based on the technical problems pointed out in the background section, this invention proposes to solve the complexity of the process in fabricating diffraction grating structures and the problem of gradual changes in different depth regions of diffraction waveguides in the prior art, and proposes a method for fabricating depth-gradient gratings.

[0037] A method for fabricating a depth-gradient grating includes the following steps:

[0038] (1) Provide a substrate, and form a hard mask layer on any surface of the substrate;

[0039] (2) A photoresist layer is formed on the surface of the hard mask layer away from the substrate; and patterning is performed.

[0040] (3) Determine the energy of the ion beam emitted by the ion source;

[0041] (4) Etch the hard mask layer in step (2) to obtain a patterned hard mask layer and remove the photoresist layer;

[0042] (5) Based on the preset etching environment requirements, determine the volume etching depth of each sub-region of the depth-gradient grating in different grating sub-regions;

[0043] (6) Based on the energy of the ion beam determined in step (3) and the volume etching depth of each sub-region in different grating sub-regions determined in step (5), the etching moving speed of each sub-region in different grating sub-regions on the substrate is determined, and the etching moving speed of the grating in different sub-regions is obtained.

[0044] (7) Control the exposure of different grating sub-regions of the substrate to the ion beam exit position, and based on the etching moving speed of the different grating sub-regions obtained in step (6), control the deflection angle and position of the substrate relative to the incident direction of the ion beam, and etch the substrate structure in step (4) to obtain the depth-gradient grating.

[0045] The fabrication method provided by this invention, compared with the traditional gradient etching for multi-sub-region grating depth, requires multiple photolithography patterns and grating depths to be patterned in the target grating pattern and grating depth if conventional photolithography and plasma etching are used, which involves more processes and higher costs. In this method, the etching of continuously gradient gratings with different sub-region depths is completed in one patterning and one etching, which involves fewer processes and a lower error rate.

[0046] Figure 6 This invention provides a schematic flowchart for fabricating a depth-gradient grating. The diagram illustrates the steps of the method for fabricating a depth-gradient grating. Figure 6 The order of the process steps is not limited, and those skilled in the art can make random adjustments to the process steps according to the etching situation, all of which are within the scope of protection of this application.

[0047] Furthermore, before step (1), step (0) is included to determine the etching process parameters of each sub-region of the depth-continuous gradient grating based on preset grating parameters.

[0048] In detail, in step (0), based on the requirements of the design ID, the preset grating parameters of each diffractive waveguide under different ID conditions are determined, and based on the etching process requirements, the etching process parameters of the depth-gradient grating in different sub-regions are determined based on the preset grating parameters, such as the grating parameters including depth, duty cycle, period, etc., so as to realize the device import of the preset grating parameters.

[0049] The depth-continuous gradient grating defined in this invention refers to a functional grating region, such as a transition grating region or a coupling grating region, where each functional grating region includes multiple different grating sub-regions. For example, a transition grating region includes multiple different grating sub-regions, and a coupling grating region includes multiple different grating sub-regions. The grating depth differs between different grating sub-regions within the same functional grating region, and the grating depth continuously changes between adjacent grating sub-regions, such as continuously increasing or continuously decreasing depth, with the depth difference ranging from 2% to 5%. The grating depth within the same grating sub-region can be consistent, meaning the grating depth is the same within the same grating sub-region. Alternatively, it can be inconsistent based on design considerations, meaning the grating depth within the same grating sub-region can also differ, such as gradually increasing depth within a range of 2% to 5%. In other words, the grating depth within each grating sub-region can be the same or different. Furthermore, the depth-continuous gradient grating is defined as including at least two grating sub-regions with different depths. The grating depth of at least two grating sub-regions of different depths increases sequentially in the direction away from the minimum grating depth. For example... Figure 1 As shown, the depth-gradient grating comprises multiple grating sub-regions of different depths, such as... Figure 1 The diagram, shown by multiple rectangular frames, illustrates four raster sub-regions with different depths. Each dashed frame represents a single raster sub-region, where the raster depth is the same. Different raster sub-regions have different raster depths. As shown, each raster sub-region includes a region with a minimum raster depth. Figure 1 As shown on the far left, other grating sub-regions gradually increase in size along the grating sub-regions that are farthest from the minimum grating depth, in order to achieve continuous depth gradient modulation.

[0050] Of course, as another embodiment of the present invention, it may also be limited to, for example... Figure 1 The grating depth in each grating sub-region shown in the solid box can also be different to achieve different modulations with continuous gradients. This is feasible for those skilled in the art and falls within the protection scope of this invention. The depth illustration in the dashed box is merely an example and does not represent a specific limitation on the depth of the continuously gradient grating.

[0051] In step (1), the substrate (10) is a silicon substrate, glass substrate, germanium substrate, gallium arsenide, SiC, TiO2, or other metal substrate; a hard mask layer is formed on one side surface of the substrate, such as... Figure 2 As shown, a hard mask layer (20) is formed on one surface of the substrate (10), for example, a material with a high refractive index, such as TiO2, SiC, lithium niobate, etc.; the thickness of the hard mask layer (20) ranges from 10 to 150 nm.

[0052] In step (2), a photoresist layer (30) is formed on the surface of the hard mask layer (20) away from the substrate (10). The thickness of the spin-coated photoresist layer (30) ranges from 200 to 1000 nm. The thickness of the spin-coated photoresist layer is selected according to different etching selectivity ratios or based on different etching requirements. The photoresist layer (30) is then patterned.

[0053] In step (3), based on the different target depths of the grating, specifically based on the different target depths of the depth-continuous gradient grating, the etching energy parameters of the ion source emitting the ion beam are determined; specifically, based on the maximum and minimum values ​​of the target depths of the gradient grating in different grating sub-regions, and based on considerations of etching efficiency and etching substrate material, the energy of the ion source emitting the ion beam during etching is limited; the different target depths of the depth-continuous gradient grating vary from 0 to 300 nm, and the determined ion beam energy is from 50 to 200 μA.

[0054] Combination Figure 2 In step (4), the hard mask layer (20) in step (2) is etched to obtain a patterned hard mask layer (20), and the photoresist layer is removed; in detail, this includes determining the patterned etching selection ratio between the hard mask layer and the photoresist layer, and performing exposure and development; the hard mask layer is used as the mask for etching the target structure.

[0055] In step (5), based on preset etching environment requirements, the volumetric etching depth of each sub-region of the depth-gradient grating in different grating sub-regions is determined; specifically, the preset etching environment includes requirements for etching parameters such as different etching gases and different bias voltages. In this invention, based on different etching environment requirements, the volumetric etching depth of the depth-gradient grating at different positions is limited by the following formula:

[0056] H (x,y) =K×C (x,y) ×[(M (x,y) [×V) / (L×N)] (1)

[0057] In equation (1), H (x,y) The volumetric etching depth of the grating at coordinates (x, y) is represented by K; K represents the coefficient factor, with a value range of [0, 1]; C (x,y) M represents the duty cycle of the grating at coordinates (x, y); (x,y) V represents the amount of substrate material etched at coordinate (x, y) in nm; V represents the etching scan rate (cm / s); L represents the number of ion beam scan lines per centimeter; and N represents the number of ion beam scans per cycle.

[0058] Furthermore, within the same functional area, such as referring to the folding grating area and the coupling grating area respectively.Figure 3 As shown, the diffractive waveguide includes a coupling-in grating region (IN), a coupling-out grating region (OUT), and may also include multiple functional regions such as a transition grating region (EPE); different grating structures or different depths of grating structures can be defined in different functional regions, as determined by this invention. Figure 3 The etching depth requirements of each functional region at different coordinate positions (x, y) are determined based on formula (1) to determine the volume etching depth at a certain position (x, y) within multiple different functional regions or different positions within the same functional region.

[0059] Furthermore, in step (6), based on the ion beam energy determined in step (3) and the volume etching depth of each sub-region in different grating sub-regions determined in step (5), the etching moving speed of each sub-region in different grating sub-regions of the substrate is determined, thus obtaining the etching moving speed of the grating in different sub-regions; specifically, under high vacuum, after the etching gas is ionized, it forms charged ion gas clusters, which are accelerated under the action of accelerating voltage, and then neutralized by Ar ionization, so that the entire ion group is electrically neutral. After the electrically neutral ion gas clusters reach the substrate surface, chemical and physical reactions occur on the surface to achieve etching. In order to obtain a grating with continuously varying depth to achieve precise control of the volume etching depth of each different sub-region, the etching moving speed of the entire substrate in different sub-regions is calculated based on the ion beam energy and the volume etching depth determined in step (5), thereby determining the speed at which the entire substrate moves and travels during each stroke in the etching process. Furthermore, an etching depth cloud map can be generated based on the etching movement speed of the gratings in different sub-regions of the platform, and etching control of each sub-region can be achieved based on this map. Alternatively, in some other embodiments, the etching movement dwell time of the gratings in different sub-regions can be limited to control the etching time of each grating sub-region.

[0060] In some embodiments, in step (7), different grating sub-regions of the substrate are exposed to the ion beam exit position, and based on the etching moving speed determined in step (6), the deflection angle and position of different grating sub-regions of the substrate relative to the ion beam incident direction are controlled, as well as the etching moving speed of different grating sub-regions of the substrate exposed to the ion beam position is controlled, to etch the substrate structure in step (4) to obtain a depth-gradient grating; the deflection angle is between 0 and 180°. Figure 4As shown, the ion beam acts on the substrate at a certain angle α relative to the substrate at the etch position determined by the substrate. The substrate moves along the X-axis and Y-axis under the action of the stage (the stage adsorbs the substrate and controls the movement of the substrate at different positions on the X and Y axes), thereby adjusting different etch positions. Based on the etch moving speed of the entire substrate in different sub-regions of the grating determined in step (6), different etch amounts in different sub-regions are achieved, thereby realizing the fabrication of a depth-continuously gradient grating.

[0061] Furthermore, in step (7), the angle α between the ion beam and the substrate surface is as follows: Figure 4 The angle shown is 90°, meaning the ion beam is incident perpendicularly to the substrate surface. By moving the substrate stage to different directional positions, the following can be achieved: Figure 1 The fabrication of the depth-gradient straight-tooth grating shown.

[0062] In some other embodiments, when the stage plane is deflected relative to the ion beam, such as Figure 4 As shown, when the X-axis rotates at a certain angle relative to the Z-axis, the substrate can be deflected at a certain angle relative to the direction of ion beam incidence (i.e., the Z-axis). By calculating parameters such as etching position and etching depth, the distance the stage moves in three different directions can be controlled, and different etching depths at different positions of the substrate can be determined. This allows for the fabrication of depth-continuously gradient helical gratings. By controlling the etching angle, different tilt angles of the grating can be controlled, such as... Figure 5 The structure shown enables the fabrication of angled gratings with continuously varying depths. It is understood that the tilt angle of the angled grating can be controlled by varying the deflection angle of the substrate relative to the incident ion beam direction, thereby enabling the fabrication of angled gratings with different tilt angles, such as... Figure 4 The etching of the depth-gradient grating is shown. Those skilled in the art can limit the angle of grating fabrication based on design requirements, such as uniformity, efficiency, and process complexity. However, this invention does not limit the specific grating tooth shape or grating tilt angle, as both are within the scope of the fabrication process claimed in this invention.

[0063] Furthermore, in the etching process, SF6 is conventionally used as the core etching gas, and C4F8, CHF3, etc. are used as auxiliary etching gases to form a high-density plasma for etching. However, in step (7) of this method, the present invention uses fluorine-based gas and Ar as etching gases to form electrically neutral ion gas clusters for etching, resulting in higher etching efficiency. More specifically, the etching process of the present invention is divided into two steps: the first step is to use fluorine-based gas as the etching gas to form electrically neutral ion gas clusters and etch the target structure according to a certain percentage; the second step is to use Ar electrically neutral ion gas clusters to etch according to a certain percentage; finally, the target gradient depth is achieved by summing the two etching depths.

[0064] More specifically, in order to achieve tunable depth with continuous gradient, in step (7), the flow rate range of the etching gas fluorine-based gas is defined as 10 to 125 sccm; the flow rate range of Ar is 10 to 500 sccm; the acceleration voltage range is 10 to 60 kV; and the ion bias current range is 10 to 200 mA.

[0065] In the two-step etching process in step (7), the first step involves etching 20% ​​to 90% of the fluorine-based gas ion cluster depth, meaning that the first step etches 20% to 90% of the target depth; the fluorine-based gas flow rate ranges from 10 to 125 sccm. Then, the process switches to the second step, where the second step involves etching 10% to 80% of the Ar ion gas cluster depth, meaning that the remaining 10% to 80% of the target depth is etched; the Ar flow rate ranges from 10 to 500 sccm.

[0066] The etching process in step (7) involves the etching gas being ionized under high vacuum to form charged ion gas clusters. These clusters are then accelerated by an accelerating voltage and neutralized by Ar ionization, making the entire ion group electrically neutral. Once the electrically neutral ion gas clusters reach the substrate surface, chemical and physical reactions occur on the surface, achieving the purpose of etching.

[0067] This invention defines a two-step etching process. In the first step, a pre-etching depth of a certain proportion of the target depth is obtained, such as 20% to 90% of the target depth. Then, the gas is switched to perform the second step etching, which etches the remaining 10% to 80% of the target depth to reach the target depth. Through these two etching processes, on the one hand, the morphology of the grating is modified using different process routes, such as the surface roughness of the sidewall edges and bottom, and the angle of the grating edges is modified, such as the perpendicularity of the edge contour or other preset tilt angles of the oblique tooth grating, such as straight teeth or oblique teeth, to achieve the preset angle and realize high-precision etching. On the other hand, step-by-step etching can ensure the continuity of depth between different grating sub-regions as much as possible, especially the boundary line problem between different grating depths, and blur or optimize the visualization problem of the boundary line between different sub-regions as much as possible, reducing the visibility of the boundary line and reducing the impact of the boundary line of different grating depth variations on the appearance of the diffraction waveguide, thereby improving the appearance of the diffraction waveguide. Overall, while ensuring and improving the diffraction efficiency and display uniformity of the diffraction waveguide, the aesthetics of the waveguide are improved, making wearable devices more acceptable to a wider range of consumers.

[0068] Compared to existing technologies, this invention controls the exposure position of different grating sub-regions of the substrate to the ion beam emission by determining the etching movement speed of each sub-region in different grating sub-regions of the substrate, and controls the deflection angle and position of the substrate relative to the incident direction of the ion beam. This invention completes the etching of continuously gradient gratings of different sub-regions through a single patterning and etching process. In the etching process, the etching steps include two steps: the first step uses fluorine-based gas as the etching gas to form electrically neutral ion gas clusters, which etch the target structure according to a certain percentage; the second step uses Ar electrically neutral ion gas clusters to etch according to a certain percentage; finally, the target gradient depth is achieved by summing the etching depths of the two parts, ensuring the continuity of the depth.

[0069] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method of making a deep continuously-graded grating, characterized by, The method comprises the following steps: (1) providing a substrate, and forming a hard mask layer on any surface of the substrate; (2) forming a photoresist layer on a side surface of the hard mask layer away from the substrate, and performing a patterning process; (3) determining the energy of an ion beam emitted by an ion source; (4) etching the hard mask layer in step (2) to obtain a patterned hard mask layer, and removing the photoresist layer; (5) determining the volume etching depth of each sub-region of the depth-continuously-graduated grating in different grating sub-regions based on preset etching environment requirements; (6) determining the etching moving speed of each sub-region of the substrate in different grating sub-regions based on the energy of the ion beam determined in step (3) and the volume etching depth of each sub-region of the different grating sub-regions determined in step (5), to obtain the etching moving speed of the different grating sub-regions; (7) controlling the exposure of the different grating sub-regions of the substrate to the exit position of the ion beam, and controlling the deflection angle and position of the substrate relative to the incident direction of the ion beam based on the etching moving speed of the different grating sub-regions obtained in step (6), to etch the substrate structure in step (4) and obtain the depth-continuously-graduated grating.

2. The method of claim 1, wherein the depth-continuous grating is prepared by the steps of: The depth-continuously-graduated grating refers to a functional grating region that includes at least two grating sub-regions with different depths, and the grating depths of the at least two grating sub-regions with different depths increase in turn in a direction away from the minimum grating depth.

3. A method of making a deep continuously-graded grating as claimed in claim 2, wherein, The depth-graduated range of the grating is 0-300 nm, and the grating depths in each grating sub-region can be the same or different.

4. The method of claim 1-2, wherein, In step (3), the energy of the ion beam emitted by the ion source is determined based on the different target depths of the grating, specifically, the energy of the ion beam during etching is limited based on the maximum and minimum values of the target depths of the grating in different grating sub-regions.

5. A method of making a deep continuously-graded grating as claimed in claim 4, wherein, In step (5), the volume etching depth of each sub-region of the depth-continuously-graduated grating in different grating sub-regions is determined based on preset etching environment requirements, specifically, the volume etching depth of each sub-region at different positions is determined by formula (1) as follows: H (x,y) = K x C (x,y) x [(M (x,y) x V) / (L x N)] (1) In formula (1), H (x,y) represents the volume etching depth of the grating at coordinates (x, y); K represents a coefficient factor, and the value range is [0, 1]; C (x,y) represents the duty cycle of the grating at coordinates (x, y); M (x,y) represents the etching amount (nm) of the substrate material at coordinates (x, y); V represents the etching scanning rate (cm / s); L represents the number of ion beam scanning lines per centimeter; and N represents the scanning times of the ion beam in one period.

6. A method of making a deep continuously-graded grating as claimed in claim 4 or 5, wherein, In step (6), the etching moving speed of each sub-region of the substrate in different grating sub-regions is determined based on the energy of the ion beam determined in step (3) and the volume etching depth of each sub-region of the different grating sub-regions determined in step (5), to obtain the etching moving speed of the different grating sub-regions, specifically, the etching moving speed of each sub-region in different grating sub-regions is calculated based on the energy of the ion beam determined in step (3), the volume etching depth of each sub-region of the different grating sub-regions determined in step (5), the etching selectivity of the substrate, and the etching gas type.

7. A method of making a deep continuously-graded grating as claimed in claim 4 or 5, wherein, In the step (7), the different grating sub-regions of the substrate are exposed to the exit position of the ion beam, the deflection angle and position of the different grating sub-regions of the substrate relative to the incident direction of the ion beam are controlled based on the etching moving speed determined in the step (6), and the etching moving speed of the different grating sub-regions of the substrate exposed to the ion beam position is controlled, so as to etch the substrate structure in the step (4) to obtain a depth-continuous gradient grating. The deflection angle is 0-180°.

8. The method of claim 2 or 5, wherein the depth-continuous grating is prepared by the steps of: The etching step includes two steps: in the first step, fluorine-based gas is used as etching gas to form electrically neutral ion gas clusters, and the target structure is etched by a certain percentage; in the second step, Ar electrically neutral ion gas clusters are used to etch by a certain percentage; finally, the sum of the etching depths of the two parts reaches the target gradient depth and ensures the depth continuity.

9. The method of claim 5, wherein the depth-continuous grating is prepared by the steps of: In the etching step, the first step of fluorine-based ion gas cluster depth etching depth range is target depth*(20%-90%); the second step of Ar ion gas cluster depth etching depth range is target depth*(10%-80%).

10. The method of claim 5, wherein the method is used to fabricate a deep continuous-gradation grating. In the first step, the flow rate of fluorine-based gas is 10-125sccm; in the second step, the flow rate of Ar is 10-500sccm.

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