Method for manufacturing waveguide grating with continuous gradually-changing groove depth

Abstract

The invention relates to a waveguide grating, in particular to a method for manufacturing a waveguide grating with continuous gradually-changing groove depth, which comprises the following steps of: accurately measuring and calibrating ion beam current density distribution of a used ion beam in a working plane; establishing a cooperative control model associated with a target groove depth curve, ion beam current density distribution and scanning speed, associating the etching depth with the ion beam total dose, and accurately controlling the ion beam total dose received by each point on the waveguide grating by dynamically regulating and controlling the scanning speed of the substrate relative to the ion beam, so as to realize accurate control of the etching depth. The accurate control on the groove depth distribution is realized; based on the cooperative control model, the scanning speed corresponding to the target groove depth curve is solved by combining the set target groove depth curve and the calibrated ion beam current density distribution; and performing ion beam etching based on the solved scanning speed, and finally forming a continuous gradual change groove depth accurately corresponding to the target groove depth curve on the waveguide grating. The method can effectively overcome the defect that the high-precision waveguide grating with the continuous gradually-changing groove depth is difficult to manufacture.

Description

TECHNICAL FIELD

[0001] The present application relates to waveguide grating, in particular to a waveguide grating manufacturing method with continuous and gradually changing groove depth. BACKGROUND

[0002] Waveguide grating is a key optical element that realizes light regulation through periodic modulation of surface structure, and its application has deeply penetrated into optical communication, sensing, spectral analysis, and the rapidly developing augmented reality (AR) field in recent years. AR grating optical waveguide mainly relies on two core mechanisms of total reflection transmission and grating diffraction to transmit micro-display images to glasses and be observed by the human eye. However, as the transmission distance increases, energy is continuously coupled out, and light intensity gradually decays, causing differences in display uniformity.

[0003] In order to solve the above problems, it is necessary to optimize the grating diffraction efficiency at different positions of the coupling-out area, thereby improving the light efficiency uniformity of the coupling-out area, that is, by modulating the grating parameters to design the coupling-out area in sections. The sectional grating produced by the conventional etching scheme has obvious boundary lines and may have abrupt loss, resulting in an undesirable imaging effect and poor user experience. Continuous and gradually changing groove depth is an effective way to solve these problems, but due to the difficulty in processing, there has been no good manufacturing method. SUMMARY

[0004] (I) Technical problems solved In view of the above-mentioned shortcomings of the prior art, the present application provides a waveguide grating manufacturing method with continuous and gradually changing groove depth, which can effectively overcome the defect that it is difficult to manufacture a waveguide grating with high-precision continuous and gradually changing groove depth.

[0005] (II) Technical solutions In order to achieve the above-mentioned purposes, the present application is realized by the following technical solutions: A waveguide grating manufacturing method with continuous and gradually changing groove depth, comprising the following steps: S1, setting a target groove depth curve; S2, accurately measuring and calibrating the ion beam flux density distribution of the used ion beam in the working plane; S3, establishing a cooperative control model associated with the target groove depth curve, the ion beam flux density distribution and the scanning speed, correlating the etching depth with the total ion beam dose, and accurately controlling the total ion beam dose received by each point on the waveguide grating by dynamically regulating the scanning speed of the substrate relative to the ion beam, to realize accurate control of the groove depth distribution; S4, based on the cooperative control model, combining the set target groove depth curve and the calibrated ion beam flux density distribution, solving the scanning speed corresponding to the target groove depth curve; S5. Perform ion beam etching based on the solved scanning speed, and finally form a continuous gradient groove depth on the waveguide grating that accurately corresponds to the target groove depth curve.

[0006] Preferably, setting the target groove depth curve in S1 includes: According to the specific application requirements, set the target groove depth curve d(x) with respect to the waveguide grating length x; The target groove depth curve d(x) is a smooth curve described by an arbitrary mathematical function.

[0007] Preferably, in S2, the ion beam current density distribution of the ion beam used in the working plane is accurately measured and calibrated, including: Before ion beam etching, the ion beam current density distribution J(x',y') of the ion beam used in the working plane is accurately measured and calibrated by a beam profile analyzer; Where x' and y' are the horizontal and vertical coordinates in the working plane. The ion beam current density distribution J(x', y') has the highest density in the center and gradually decays toward the edge, which is approximately a Gaussian distribution.

[0008] Preferably, before the ion beam etching is performed, the ion beam current density distribution J(x', y') of the ion beam used in the working plane is accurately measured and calibrated by a beam profile analyzer, including: A two-dimensional Faraday cup array is placed in the working plane. The distribution of the ion beam current density J(x', y') in the working plane is measured and plotted. Through data fitting, the ion beam current density distribution J(x', y') is approximated to a two-dimensional Gaussian function: ; Where J0 is the central peak density, is the beam spot radius.

[0009] Preferably, a coordinated control model is established in S3 that associates the target groove depth curve, ion beam current density distribution, and scanning speed. The etching depth is associated with the total ion beam dose. By dynamically adjusting the scanning speed of the substrate relative to the ion beam, the total ion beam dose received by each point on the waveguide grating is precisely controlled to achieve precise control of the groove depth distribution, including: For the target groove depth curve d(x) and the ion beam current density distribution J(x',y'), the etching depth d at any point on the waveguide grating is proportional to the total ion beam dose received at that point: ; Where, dose(x) is the total dose of the ion beam received at the waveguide grating length x, R m is the etching depth per unit ion beam dose, determined experimentally; For the ion beam current density distribution J(x',y') and the scanning speed v(x), when the workbench drives the waveguide grating to scan along its length at the scanning speed v(x), the total ion beam dose received by any point on the waveguide grating is the time integral of the ion beam current density when the ion beam scans through the point. This integral is inversely proportional to the scanning speed v(x). When the workbench drives the waveguide grating to scan along its length at the scanning speed v(x), the ion beam bombardment time experienced by any point on the waveguide grating is related to 1 / v(x); Taking into account the relationship between the target groove depth curve d(x) and the ion beam current density distribution J(x', y'), and the ion beam current density distribution J(x', y') and the scanning speed v(x), for any point x0 on the center line y=0 of the waveguide grating, its etching depth d(x0) can be expressed as an integral equation: ; in, It represents the effective intensity of the ion beam current density at other positions (x', y') relative to the etching depth d(x0) at the current calculation point (x0, y0) during the scanning process. For the center line of the waveguide grating, y0=0, and L is the total length of the waveguide grating.

[0010] Preferably, the etching depth R under the unit ion beam dose is m Determined through experiments, including: A SiO2 sample is uniformly ion-beam etched for a fixed time, and the etching depth is measured by a step profiler or atomic force microscope AFM. The etching depth R of the SiO2 sample under unit ion beam dose is calculated. m .

[0011] Preferably, in S4, based on the collaborative control model, the scanning speed corresponding to the target slot depth curve is solved in combination with the set target slot depth curve and the calibrated ion beam current density distribution, including: For solving the inverse problem of the collaborative control model, a numerical iterative algorithm is used to transform the target groove depth curve d(x) and the known ion beam current density distribution J(x', y'), the etching depth R under unit ion beam dose, and the target groove depth curve d(x) into the target groove depth curve d(x). m Substitute into the collaborative control model and reversely solve the scanning speed v(x) corresponding to the target groove depth curve d(x); Among them, the scanning speed v(x) is approximately inversely proportional to the target groove depth curve d(x): That is, for locations with deeper etching depths, the scanning speed should be slowed down; for locations with shallower etching depths, the scanning speed should be accelerated.

[0012] Preferably, in S5, ion beam etching is performed based on the solved scanning speed, and finally a continuous gradient groove depth accurately corresponding to the target groove depth curve is formed on the waveguide grating, including: S51, fixing the photoresist grating mask produced by holographic interference lithography on a workbench in the vacuum chamber of the ion beam etching system; S52, program the scanning speed v(x) corresponding to the target groove depth curve d(x) into the high-precision motion control system of the workbench, set the process parameters, turn on the ion beam source and keep the process parameters constant during the scanning process to ensure that the etching depth R under unit ion beam dose is m stability; S53, the motion control system drives the workbench to scan the waveguide grating along its length direction at a scanning speed v(x), and the ion beam continuously etches the waveguide grating. Due to the continuous change of the scanning speed v(x), a continuously gradient groove depth that accurately corresponds to the target groove depth curve d(x) is eventually formed on the waveguide grating; Among them, process parameters include ion energy, beam current, beam pressure, reaction gas composition and flow rate.

[0013] (3) Beneficial effects Compared with the prior art, the method for fabricating a waveguide grating with a continuously gradient groove depth provided by the present invention has the following beneficial effects: 1) Extremely high precision and controllability: By establishing a precise mathematical model, the complex problem of continuously varying groove depth control is transformed into a relatively simple problem of scanning speed control. The high-precision motion control system also offers extremely high speed control accuracy. Combined with precise ion beam density distribution calibration, it can accurately reproduce sub-nanometer groove depth profiles, resulting in a grating structure with extremely high fidelity. 2) Excellent design flexibility: The system can produce continuously gradient groove depth curves described by any mathematical function, whether it is a simple linear gradient or a complex Gaussian, sinusoidal, or other non-periodic groove depth profile. New grating structures can be generated by simply changing the target groove depth curve, greatly enhancing the freedom of device design and R&D efficiency. 3) Simplified process flow and improved processing efficiency: This method is a "digitally controlled" mask-free processing technology that uses a continuous scanning method. For the production of one-dimensional gratings with continuously gradient groove depth, the processing efficiency is significantly improved. The entire production process is highly automated and repeatable, which helps reduce production costs and shorten the R&D cycle. 4) Improved grating device performance: The ability to precisely manufacture an ideal, continuously gradient groove depth profile effectively optimizes the optical performance of the grating. 5) Strong universality: This method is applicable to a variety of waveguide grating materials, including but not limited to silicon dioxide (SiO2), silicon nitride (Si3N2), tantalum pentoxide (Ta2O5), hafnium dioxide (HfO2), etc. By adjusting process parameters including ion energy and reaction gas composition (reactive ion beam etching), it can adapt to the etching requirements of different materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0015] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 A schematic diagram of ion beam etching in the present invention; Figure 3 Schematic diagram of the target groove depth curve in the present invention; Figure 4 Schematic diagram of the ion beam etching rate at different positions on the workbench in the present invention. DETAILED DESCRIPTION

[0016] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0017] The following describes the specific process of the method for manufacturing a waveguide grating with a continuously gradient groove depth provided by the present invention with reference to specific examples (eg Figure 1 shown) and technical effects.

[0018] 1. Set the target groove depth curve.

[0019] According to the specific application requirements, set the target groove depth curve d(x) with respect to the waveguide grating length x; The target groove depth curve d(x) is a smooth curve described by any mathematical function, and can be a linear, exponential, Gaussian, sinusoidal or other smooth curve described by any mathematical function.

[0020] For a 12-inch waveguide grating, a photoresist grating mask with a period of 350nm was produced by holographic interference lithography. The mask pattern needs to be transferred to the substrate by ion beam etching. The total length of the waveguide grating is L = 100mm. The target groove depth curve d(x) varies linearly along the length of the waveguide grating. That is, as the waveguide grating length x ranges from 0 to L, the corresponding target groove depth curve d(x) changes linearly from 50nm to 200nm, as shown in Figure 2. Figure 3 As shown. At this time, the expression of the target groove depth curve d(x) is: (Unit: nm).

[0021] 2. Accurately measure and calibrate the ion beam current density distribution of the ion beam used in the working plane.

[0022] Before ion beam etching, the ion beam current density distribution J(x',y') of the ion beam used in the working plane is accurately measured and calibrated by a beam profile analyzer; Where x' and y' are the horizontal and vertical coordinates in the working plane. The ion beam current density distribution J(x', y') has the highest density in the center and gradually decays toward the edge, which is approximately a Gaussian distribution.

[0023] Specifically, before ion beam etching, the ion beam current density distribution J(x',y') of the ion beam used in the working plane is accurately measured and calibrated by a beam profile analyzer, including: A two-dimensional Faraday cup array is placed in the working plane. The distribution of the ion beam current density J(x', y') in the working plane is measured and plotted. Through data fitting, the ion beam current density distribution J(x', y') is approximated to a two-dimensional Gaussian function: ; Where J0 is the central peak density, is the beam spot radius.

[0024] 3. Establish a collaborative control model that associates the target groove depth curve, ion beam density distribution and scanning speed, associates the etching depth with the total ion beam dose, and accurately controls the total ion beam dose received at each point on the waveguide grating by dynamically adjusting the scanning speed of the substrate relative to the ion beam, thereby achieving precise control of the groove depth distribution.

[0025] 1) For the target groove depth curve d(x) and the ion beam current density distribution J(x',y'), the etching depth d at any point on the waveguide grating is proportional to the total ion beam dose received at that point: ; Where, dose(x) is the total dose of the ion beam received at the waveguide grating length x, Rm is the etching depth per unit ion beam dose, i.e., the ion beam etching rate, which is determined experimentally; 2) For the ion beam current density distribution J(x',y') and the scanning speed v(x), when the worktable drives the waveguide grating to scan along its length at the scanning speed v(x), the total ion beam dose received by any point on the waveguide grating is the time integral of the ion beam current density when the ion beam scans through that point. This integral is inversely proportional to the scanning speed v(x). When the worktable drives the waveguide grating to scan along its length at the scanning speed v(x), the ion beam bombardment time experienced by any point on the waveguide grating is related to 1 / v(x); 3) Considering the relationship between the target groove depth curve d(x) and the ion beam current density distribution J(x', y'), and the ion beam current density distribution J(x', y') and the scanning speed v(x), for any point x0 on the center line y=0 of the waveguide grating, its etching depth d(x0) can be expressed as an integral equation: ; in, It represents the effective intensity of the ion beam current density at other positions (x', y') relative to the etching depth d(x0) at the current calculation point (x0, y0) during the scanning process. For the center line of the waveguide grating, y0=0, and L is the total length of the waveguide grating.

[0026] Specifically, the etching depth R under unit ion beam dose is m Determined through experiments, including: A SiO2 sample is uniformly ion-beam etched for a fixed time, and the etching depth is measured by a step profiler or atomic force microscope AFM. The etching depth R of the SiO2 sample under unit ion beam dose is calculated. m .

[0027] Figure 4 This is a schematic diagram of the ion beam etching rate at different positions on the workbench. It is calibrated through experiments. The method is to arrange 20 lines of coarse photoresist grating mask at different positions, etch for 10 minutes under the static state of the workbench, and use a step meter to perform depth detection on the coarse grating companion plate, which reflects the relationship between the ion beam etching rate and the ion beam current density.

[0028] 4. Based on the collaborative control model, combined with the set target slot depth curve and the calibrated ion beam density distribution, the scanning speed corresponding to the target slot depth curve is solved.

[0029] For solving the inverse problem of the collaborative control model, a numerical iterative algorithm is used to transform the target groove depth curve d(x) and the known ion beam current density distribution J(x', y'), the etching depth R under unit ion beam dose, and the target groove depth curve d(x) into the target groove depth curve d(x). mSubstitute into the collaborative control model and reversely solve the scanning speed v(x) corresponding to the target groove depth curve d(x); Among them, the scanning speed v(x) is approximately inversely proportional to the target groove depth curve d(x): That is, for locations with deeper etching depths, the scanning speed should be slowed down; for locations with shallower etching depths, the scanning speed should be accelerated.

[0030] 5. Perform ion beam etching based on the obtained scanning speed, such as Figure 2 As shown, a continuous gradient groove depth that accurately corresponds to the target groove depth curve is finally formed on the waveguide grating.

[0031] 1) Fix the photoresist grating mask produced by holographic interference lithography on the workbench in the vacuum chamber of the ion beam etching system; 2) Program the scanning speed v(x) corresponding to the target groove depth curve d(x) and load it into the high-precision motion control system of the workbench, set the process parameters, turn on the ion beam source and keep the process parameters constant during the scanning process to ensure the etching depth R under unit ion beam dose. m stability; 3) The motion control system drives the workbench to scan the waveguide grating along its length at a scanning speed v(x). The ion beam continuously etches the waveguide grating. Due to the continuous change of the scanning speed v(x), a continuously gradient groove depth that accurately corresponds to the target groove depth curve d(x) is eventually formed on the waveguide grating. Among them, the process parameters include ion energy, beam current, beam pressure, reaction gas composition and flow rate.

[0032] After ion beam etching, the fabricated waveguide grating was characterized using an atomic force microscope (AFM). The AFM measurements showed that the grating groove depth exhibited a linear gradient along the length of the waveguide grating, consistent with the target groove depth curve, with a groove depth profile error of less than 5%.

[0033] This example fully demonstrates the feasibility and superiority of this method. By precisely controlling the single variable of scanning speed, combined with a deep understanding of the physical properties of ion beams and mathematical modeling, it successfully achieved precise and efficient manufacturing of gratings with complex groove depth structures, providing strong technical support for the development of high-performance integrated photonic devices.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for fabricating a waveguide grating with a continuously gradient groove depth, characterized in that: The following steps are involved: S1. Set the target groove depth curve; S2. Accurately measure and calibrate the ion beam current density distribution of the ion beam used in the working plane; S3. Establish a collaborative control model that associates the target groove depth curve, ion beam current density distribution, and scanning speed. This model relates the etching depth to the total ion beam dose. By dynamically adjusting the substrate scanning speed relative to the ion beam, the total ion beam dose received at each point on the waveguide grating is precisely controlled, achieving precise control of the groove depth distribution. S4. Based on the collaborative control model, the scanning speed corresponding to the target slot depth curve is solved in combination with the set target slot depth curve and the calibrated ion beam current density distribution; S5. Perform ion beam etching based on the solved scanning speed, and finally form a continuous gradient groove depth on the waveguide grating that accurately corresponds to the target groove depth curve.

2. The method for fabricating a waveguide grating with a continuously gradient groove depth according to claim 1, wherein: The target groove depth curve is set in S1, including: According to the specific application requirements, set the target groove depth curve d(x) with respect to the waveguide grating length x; The target groove depth curve d(x) is a smooth curve described by an arbitrary mathematical function.

3. The method for fabricating a waveguide grating with a continuously gradient groove depth according to claim 2, wherein: S2 accurately measures and calibrates the ion beam current density distribution within the working plane, including: Before ion beam etching, the ion beam current density distribution J(x',y') of the ion beam used in the working plane is accurately measured and calibrated by a beam profile analyzer; Where x' and y' are the horizontal and vertical coordinates in the working plane. The ion beam current density distribution J(x', y') has the highest density in the center and gradually decays toward the edge, which is approximately a Gaussian distribution.

4. The method for fabricating a waveguide grating with a continuously gradient groove depth according to claim 3, wherein: Before the ion beam etching is performed, the ion beam current density distribution J(x', y') of the ion beam used in the working plane is accurately measured and calibrated by a beam profile analyzer, including: A two-dimensional Faraday cup array is placed in the working plane. The distribution of the ion beam current density J(x', y') in the working plane is measured and plotted. Through data fitting, the ion beam current density distribution J(x', y') is approximated to a two-dimensional Gaussian function: ； Where J0 is the central peak density, is the beam spot radius.

5. The method for fabricating a waveguide grating with a continuously gradient groove depth according to claim 4, wherein: In S3, a collaborative control model is established that associates the target groove depth curve, ion beam current density distribution, and scanning speed. The etching depth is associated with the total ion beam dose. By dynamically adjusting the substrate scanning speed relative to the ion beam, the total ion beam dose received by each point on the waveguide grating is precisely controlled, achieving precise control of the groove depth distribution. This includes: For the target groove depth curve d(x) and the ion beam current density distribution J(x',y'), the etching depth d at any point on the waveguide grating is proportional to the total ion beam dose received at that point: ； Where, dose(x) is the total dose of the ion beam received at the waveguide grating length x, R m is the etching depth per unit ion beam dose, determined experimentally; For the ion beam current density distribution J(x',y') and the scanning speed v(x), when the workbench drives the waveguide grating to scan along its length at the scanning speed v(x), the total ion beam dose received by any point on the waveguide grating is the time integral of the ion beam current density when the ion beam scans through the point. This integral is inversely proportional to the scanning speed v(x). When the workbench drives the waveguide grating to scan along its length at the scanning speed v(x), the ion beam bombardment time experienced by any point on the waveguide grating is related to 1 / v(x); Taking into account the relationship between the target groove depth curve d(x) and the ion beam current density distribution J(x', y'), and the ion beam current density distribution J(x', y') and the scanning speed v(x), for any point x0 on the center line y=0 of the waveguide grating, its etching depth d(x0) can be expressed as an integral equation: ； in, It represents the effective intensity of the ion beam current density at other positions (x', y') relative to the etching depth d(x0) at the current calculation point (x0, y0) during the scanning process. For the center line of the waveguide grating, y0=0, and L is the total length of the waveguide grating.

6. The method for fabricating a waveguide grating with a continuously gradient groove depth according to claim 5, wherein: The etching depth R under the unit ion beam dose m Determined through experiments, including: A SiO2 sample is uniformly ion-beam etched for a fixed time, and the etching depth is measured by a step profiler or atomic force microscope AFM. The etching depth R of the SiO2 sample under unit ion beam dose is calculated. m .

7. The method for fabricating a waveguide grating with a continuously gradient groove depth according to claim 5, wherein: In S4, based on the collaborative control model, the set target slot depth curve and the calibrated ion beam current density distribution are combined to solve the scanning speed corresponding to the target slot depth curve, including: For solving the inverse problem of the collaborative control model, a numerical iterative algorithm is used to transform the target groove depth curve d(x) and the known ion beam current density distribution J(x', y'), the etching depth R under unit ion beam dose, and the target groove depth curve d(x) into the target groove depth curve d(x). m Substitute into the collaborative control model and reversely solve the scanning speed v(x) corresponding to the target groove depth curve d(x); Among them, the scanning speed v(x) is approximately inversely proportional to the target groove depth curve d(x): That is, for locations with deeper etching depths, the scanning speed should be slowed down; for locations with shallower etching depths, the scanning speed should be accelerated.

8. The method for fabricating a waveguide grating with a continuously gradient groove depth according to claim 7, wherein: In S5, ion beam etching is performed based on the calculated scanning speed, ultimately forming a continuously gradient groove depth on the waveguide grating that accurately corresponds to the target groove depth curve, including: S51, fixing the photoresist grating mask produced by holographic interference lithography on a workbench in the vacuum chamber of the ion beam etching system; S52, program the scanning speed v(x) corresponding to the target groove depth curve d(x) into the high-precision motion control system of the workbench, set the process parameters, turn on the ion beam source and keep the process parameters constant during the scanning process to ensure that the etching depth R under unit ion beam dose is m stability; S53, the motion control system drives the workbench to scan the waveguide grating along its length direction at a scanning speed v(x), and the ion beam continuously etches the waveguide grating. Due to the continuous change of the scanning speed v(x), a continuously gradient groove depth that accurately corresponds to the target groove depth curve d(x) is eventually formed on the waveguide grating; Among them, process parameters include ion energy, beam current, beam pressure, reaction gas composition and flow rate.

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