A method for manufacturing a waveguide grating with continuously varying groove depth

Abstract

The present application relates to waveguide grating, specifically to a waveguide grating manufacturing method with continuous and gradually changing groove depth, which precisely measures and calibrates the ion beam current density distribution of the used ion beam in the working plane; establishes a coordinated control model associated with the target groove depth curve, ion beam current density distribution and scanning speed, relates the etching depth with the total dose of ion beam, precisely controls the total dose of ion beam received by each point on the waveguide grating by dynamically regulating the scanning speed of the substrate relative to the ion beam, and realizes the precise control of the groove depth distribution; based on the coordinated control model, the scanning speed corresponding to the target groove depth curve is solved in combination with the set target groove depth curve and the calibrated ion beam current density distribution; ion beam etching is carried out based on the solved scanning speed, and finally the continuous and gradually changing groove depth accurately corresponding to the target groove depth curve is formed on the waveguide grating; the present application can effectively overcome the defect that it is difficult to manufacture the waveguide grating with high-precision continuous and gradually changing groove depth.

Description

Technical Field

[0001] This invention relates to waveguide gratings, and more specifically to a method for fabricating waveguide gratings with continuously varying groove depths. Background Technology

[0002] Waveguide gratings are key optical components that achieve light control through periodic modulation of surface structures. Their applications have deeply penetrated into optical communication, sensing, spectral analysis, and the rapidly developing field of augmented reality (AR). AR grating waveguides mainly rely on two core mechanisms—total internal reflection and grating diffraction—to transmit microdisplay images to glasses for observation by the human eye. However, as the transmission distance increases, energy is continuously coupled out, and the light intensity gradually decreases, causing differences in display uniformity.

[0003] To address the aforementioned issues, it is necessary to optimize the grating diffraction efficiency at different locations within the coupling region, thereby improving the uniformity of light output in the coupling region. This can be achieved by partitioning the coupling region through modulation of grating parameters. Conventional etching methods produce partitioned gratings with distinct boundary lines and may exhibit abrupt losses, leading to unsatisfactory imaging results and a poor user experience. Continuously gradient groove depths are an effective approach to solving these problems; however, due to fabrication difficulties, a suitable method has yet to be found. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a method for fabricating waveguide gratings with continuously tapered groove depth, which can effectively overcome the defect of the prior art that it is difficult to fabricate high-precision waveguide gratings with continuously tapered groove depth.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for fabricating a waveguide grating with continuously tapered groove depth includes the following steps:

[0009] S1. Set the target trench depth curve;

[0010] S2. Accurately measure and calibrate the ion beam current density distribution in the working plane of the ion beam used;

[0011] S3. Establish a collaborative control model that associates the target trench depth curve, ion beam current density distribution, and scanning speed. Correlate the etching depth 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 at each point on the waveguide grating can be precisely controlled, thereby achieving precise control of the trench depth distribution.

[0012] S4. Based on the collaborative control model, combined with the set target cell depth curve and the calibrated ion beam density distribution, the scanning speed corresponding to the target cell depth curve is solved.

[0013] S5. Based on the solved scanning speed, ion beam etching is performed to finally form a continuous gradient groove depth on the waveguide grating that precisely corresponds to the target groove depth curve.

[0014] Preferably, setting the target trench depth curve in S1 includes:

[0015] Based on specific application requirements, the target slot depth curve d(x) is set with respect to the waveguide grating length x;

[0016] The target groove depth curve d(x) is one of the smooth curves described by any mathematical function.

[0017] Preferably, in S2, the precise measurement and calibration of the ion beam current density distribution in the working plane includes:

[0018] Before performing 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 using a beam profile analyzer.

[0019] 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 at the center and gradually decreases towards the edge, approximating a Gaussian distribution.

[0020] Preferably, before performing 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 using a beam profiler, including:

[0021] A two-dimensional Faraday cup array is placed in the working plane, and 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 as a two-dimensional Gaussian function.

[0022] ;

[0023] Where J0 is the central peak density, Let be the beam spot radius.

[0024] Preferably, in S3, a collaborative control model is established that correlates the target trench depth curve, ion beam current density distribution, and scanning speed. This model links the etching depth to 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 at each point on the waveguide grating is precisely controlled, achieving precise control of the trench depth distribution. This includes:

[0025] For the target trench 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 dose received at that point:

[0026] ;

[0027] Where dose(x) is the total ion beam dose received at the waveguide grating length x, R m The etching depth per unit ion beam dose was determined experimentally.

[0028] For the ion beam current density distribution J(x',y') and the scanning speed v(x), when the stage drives the waveguide grating to scan along its length direction at the scanning speed v(x), the total ion beam dose received at any point on the waveguide grating is the integral of the ion beam current density over time when the ion beam passes through that point. This integral is inversely proportional to the scanning speed v(x). When the stage drives the waveguide grating to scan along its length direction 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).

[0029] Considering the relationships between the target trench depth curve d(x) and the ion beam current density distribution J(x',y'), and between the ion beam current density distribution J(x',y') and the scanning speed v(x), the etching depth d(x0) of any point x0 on the waveguide grating centerline y=0 can be expressed as an integral equation:

[0030] ;

[0031] in, This represents the effective intensity of the ion beam current density at other locations (x', y') relative to the etching depth d(x0) at the current calculation point (x0, y0) during the scanning process. For the waveguide grating centerline, y0=0, and L is the total length of the waveguide grating.

[0032] Preferably, the etching depth R per unit ion beam dose m Through experimental determination, including:

[0033] A SiO2 sample was subjected to uniform ion beam etching for a fixed time. The etching depth was measured using a profilometer or atomic force microscope (AFM), and the etching depth R of the SiO2 sample under unit ion beam dose was calculated. m .

[0034] Preferably, in S4, based on the cooperative control model, and combining the set target trench depth curve and the calibrated ion beam current density distribution, the scanning speed corresponding to the target trench depth curve is calculated, including:

[0035] For solving the inverse problem of the cooperative control model, a numerical iterative algorithm is adopted, which combines the target trench depth curve d(x), the known ion beam current density distribution J(x',y'), and the etching depth R per unit ion beam dose. m Substitute the data into the collaborative control model and solve in reverse for the scanning speed v(x) corresponding to the target groove depth curve d(x);

[0036] The scanning speed v(x) is approximately inversely proportional to the target groove depth curve d(x). That is, for areas with deeper etching depth, the scanning speed should be slowed down; for areas with shallower etching depth, the scanning speed should be accelerated.

[0037] Preferably, in step S5, ion beam etching is performed based on the solved scanning speed, ultimately forming a continuously gradient groove depth on the waveguide grating that precisely corresponds to the target groove depth curve, including:

[0038] S51. Fix the photoresist grating mask fabricated by holographic interference lithography onto the worktable inside the vacuum chamber of the ion beam etching system.

[0039] S52. The scanning speed v(x) corresponding to the target trench depth curve d(x) is programmed and loaded into the high-precision motion control system of the stage. The process parameters are set, the ion beam source is turned on, and the process parameters are kept constant during the scanning process to ensure the etching depth R per unit ion beam dose. m Stability;

[0040] S53. The motion control system drives the worktable to scan the waveguide grating along its length direction 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 continuous gradient groove depth is finally formed on the waveguide grating that precisely corresponds to the target groove depth curve d(x).

[0041] The process parameters include ion energy, beam current, beam pressure, and the composition and flow rate of the reactant gas.

[0042] (III) Beneficial Effects

[0043] Compared with the prior art, the waveguide grating fabrication method with continuously tapered groove depth provided by the present invention has the following advantages:

[0044] 1) Extremely high precision and controllability: By establishing a precise mathematical model, the complex problem of continuous gradient groove depth control is transformed into a relatively simple scanning speed control problem. At the same time, the speed control precision of the high-precision motion control system is extremely high. Combined with the precise ion beam density distribution calibration, it is possible to accurately reproduce the groove depth profile at the sub-nanometer level, thereby obtaining a grating structure with extremely high fidelity.

[0045] 2) Excellent design flexibility: It can create continuous gradient groove depth curves described by any mathematical function. Whether it is a simple linear gradient or a complex Gaussian, sine or other non-periodic groove depth profile, new grating structures can be generated simply by changing the target groove depth curve, which greatly enhances the freedom of device design and R&D efficiency.

[0046] 3) Simplified process and improved processing efficiency: This method belongs to the "digital control" unobstructed mask processing technology. It adopts continuous scanning, which significantly improves the processing efficiency for making one-dimensional gratings with continuously gradient groove depth. The entire manufacturing process has a high degree of automation and good repeatability, which helps to reduce production costs and shorten the R&D cycle.

[0047] 4) Improve the performance of grating devices: Because it is possible to precisely manufacture an ideal continuous gradient groove depth profile, the optical performance of the grating can be effectively optimized;

[0048] 5) High versatility: 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 the process parameters, including ion energy and reactive gas composition (reactive ion beam etching), it can adapt to the etching requirements of different materials. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0050] Figure 1 This is a schematic diagram of the process of the present invention;

[0051] Figure 2 This is a schematic diagram of ion beam etching performed in this invention;

[0052] Figure 3 This is a schematic diagram of the target trench depth curve in this invention;

[0053] Figure 4 This is a schematic diagram showing the ion beam etching rate at different positions on the worktable in this invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0055] The following describes the specific process of the waveguide grating fabrication method with continuously tapered groove depth provided by this invention, using a concrete example (e.g.) Figure 1 (as shown) and technical effects.

[0056] 1. Set the target trench depth curve.

[0057] Based on specific application requirements, the target slot depth curve d(x) is set with respect to the waveguide grating length x;

[0058] The target groove depth curve d(x) is one of the smooth curves described by any mathematical function, which can be a linear, exponential, Gaussian, sine or other smooth curves described by any mathematical function.

[0059] For a 12-inch waveguide grating, a photoresist grating mask with a period of 350 nm was fabricated using holographic interference lithography. The mask pattern needs to be transferred to the substrate via ion beam etching. The total length of the waveguide grating is L = 100 mm. The target groove depth curve d(x) varies linearly along the length of the waveguide grating; that is, as the waveguide grating length x increases from 0 to L, the corresponding target groove depth curve d(x) linearly changes from 50 nm to 200 nm. Figure 3 As shown. At this point, the expression for the target trench depth curve d(x) is:

[0060] (Unit: nm)

[0061] 2. Accurately measure and calibrate the ion beam current density distribution in the working plane.

[0062] Before performing 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 using a beam profile analyzer.

[0063] 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 at the center and gradually decreases towards the edge, approximating a Gaussian distribution.

[0064] Specifically, before ion beam etching, the ion beam current density distribution J(x',y') of the ion beam in the working plane is precisely measured and calibrated using a beam profiler, including:

[0065] A two-dimensional Faraday cup array is placed in the working plane, and 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 as a two-dimensional Gaussian function.

[0066] ;

[0067] Where J0 is the central peak density, Let be the beam spot radius.

[0068] Third, establish a collaborative control model that associates the target trench depth curve, ion beam current density distribution, and scanning speed. Correlate the etching depth 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 at each point on the waveguide grating can be precisely controlled, thereby achieving precise control of the trench depth distribution.

[0069] 1) For the target trench 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 dose received at that point:

[0070] ;

[0071] Where dose(x) is the total ion beam dose received at the waveguide grating length x, R m The etching depth per unit ion beam dose, i.e., the ion beam etching rate, is determined experimentally.

[0072] 2) For the ion beam current density distribution J(x',y') and the scanning speed v(x), when the stage drives the waveguide grating to scan along its length direction at the scanning speed v(x), the total ion beam dose received at any point on the waveguide grating is the integral of the ion beam current density over time when the ion beam passes through that point. This integral is inversely proportional to the scanning speed v(x). When the stage drives the waveguide grating to scan along its length direction 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).

[0073] 3) Considering the relationship between the target trench 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), the etching depth d(x0) of any point x0 on the waveguide grating centerline y=0 can be expressed as an integral equation:

[0074] ;

[0075] in, This represents the effective intensity of the ion beam current density at other locations (x', y') relative to the etching depth d(x0) at the current calculation point (x0, y0) during the scanning process. For the waveguide grating centerline, y0=0, and L is the total length of the waveguide grating.

[0076] Specifically, the etching depth R per unit ion beam dose m Through experimental determination, including:

[0077] A SiO2 sample was subjected to uniform ion beam etching for a fixed time. The etching depth was measured using a profilometer or atomic force microscope (AFM), and the etching depth R of the SiO2 sample under unit ion beam dose was calculated. m .

[0078] Figure 4 This diagram illustrates the ion beam etching rate at different positions on the worktable. The etching rate was calibrated experimentally by placing 20-line coarse photoresist grating masks at different positions, etching for 10 minutes under static conditions on the worktable, and then using a profilometer to measure the depth of the coarse grating mask. The result shows the relationship between the ion beam etching rate and the ion beam current density.

[0079] IV. Based on the collaborative control model, and combined with the set target cell depth curve and the calibrated ion beam density distribution, the scanning speed corresponding to the target cell depth curve is solved.

[0080] For solving the inverse problem of the cooperative control model, a numerical iterative algorithm is adopted, which combines the target trench depth curve d(x), the known ion beam current density distribution J(x',y'), and the etching depth R per unit ion beam dose. m Substitute the data into the collaborative control model and solve in reverse for the scanning speed v(x) corresponding to the target groove depth curve d(x);

[0081] The scanning speed v(x) is approximately inversely proportional to the target groove depth curve d(x). That is, for areas with deeper etching depth, the scanning speed should be slowed down; for areas with shallower etching depth, the scanning speed should be accelerated.

[0082] V. Ion beam etching based on the solved scanning speed, such as... Figure 2 As shown, a continuous gradient groove depth is finally formed on the waveguide grating that precisely corresponds to the target groove depth curve.

[0083] 1) Fix the photoresist grating mask fabricated by holographic interference lithography onto the worktable inside the vacuum chamber of the ion beam etching system;

[0084] 2) The scanning speed v(x) corresponding to the target trench depth curve d(x) is programmed and loaded into the high-precision motion control system of the stage. The process parameters are set, the ion beam source is turned on, and the process parameters are kept constant during the scanning process to ensure the etching depth R per unit ion beam dose. m Stability;

[0085] 3) The motion control system drives the stage to scan the waveguide grating along its length direction 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 continuous gradient groove depth is finally formed on the waveguide grating that precisely corresponds to the target groove depth curve d(x).

[0086] The process parameters include ion energy, beam current, beam pressure, and the composition and flow rate of the reactant gas.

[0087] After ion beam etching, the fabricated waveguide grating was characterized using atomic force microscopy (AFM). 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%.

[0088] This embodiment fully demonstrates the feasibility and superiority of the 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, the precise and efficient manufacturing of gratings with complex deep groove structures has been successfully achieved, providing strong technical support for the development of high-performance integrated photonic devices.

[0089] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a waveguide grating with continuously tapered groove depth, characterized in that: Includes the following steps: S1. Set the target trench depth curve; S2. Accurately measure and calibrate the ion beam current density distribution in the working plane of the ion beam used; S3. Establish a collaborative control model that correlates the target trench depth curve, ion beam current density distribution, and scanning speed. This model links the etching depth to 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 at each point on the waveguide grating is precisely controlled, achieving precise control of the trench depth distribution. This includes: For the target trench depth curve d ( x ) and ion beam current density distribution J ( x' , y' The etching depth at any point on the waveguide grating. d Proportional to the total dose of the ion beam received at that point dose : ； in, dose ( x ) is the length of the waveguide grating x The total dose of the ion beam received at the location, R m The etching depth per unit ion beam dose was determined experimentally. For ion beam current density distribution J ( x' , y' ) and scanning speed v ( x When the worktable is at a scanning speed v ( x When the waveguide grating is scanned along its length, the total ion beam dose received at any point on the waveguide grating is the integral of the ion beam current density over time when the ion beam passes that point. This integral is related to the scanning speed. v ( x The ratio is inversely proportional when the worktable operates at a scanning speed. v ( x When the waveguide grating is scanned along its length, the ion beam bombardment time experienced by any point on the waveguide grating is 1 / v ( x Related; Taking into account the target trench depth curve d ( x ) and ion beam current density distribution J ( x' , y' ), Ion beam current density distribution J ( x' , y' ) and scanning speed v ( x The relationship between ) for any point on the waveguide grating centerline y=0 x 0, its etching depth d ( x 0) can be represented as an integral equation: ； in, This indicates that during the scanning process, relative to other positions ( x' , y' The ion beam current density at the current calculation point () x 0, y 0) etching depth d ( x The effective intensity of y0 is 0, for the waveguide grating centerline, y0=0. L This is the total length of the waveguide grating; S4. Based on the collaborative control model, combined with the set target cell depth curve and the calibrated ion beam density distribution, the scanning speed corresponding to the target cell depth curve is solved. S5. Based on the solved scanning speed, ion beam etching is performed to finally form a continuous gradient groove depth on the waveguide grating that precisely corresponds to the target groove depth curve.

2. The method for fabricating a waveguide grating with continuously tapered groove depth according to claim 1, characterized in that: The target trench depth curve is set in S1, including: The waveguide grating length is set according to specific application requirements. x Target trench depth curve d ( x ); Among them, the target trench depth curve d ( x () is one of the smooth curves described by any mathematical function.

3. The method for fabricating a waveguide grating with continuously tapered groove depth according to claim 2, characterized in that: S2 performs precise measurement and calibration of the ion beam current density distribution within the working plane, including: Before ion beam etching, the ion beam current density distribution in the working plane is analyzed using a beam profiler. J ( x' , y' To perform precise measurements and calibrations; in, x' , y' The x and y coordinates of the working plane represent the ion beam current density distribution. J ( x ', y The density is highest at the center and gradually decreases towards the edge, approximating a Gaussian distribution.

4. The method for fabricating a waveguide grating with continuously tapered groove depth according to claim 3, characterized in that: Before performing ion beam etching, the ion beam current density distribution of the ion beam used in the working plane is analyzed using a beam profiler. J ( x' , y' To perform precise measurements and calibrations, including: A two-dimensional Faraday cup array is placed in the working plane, and the ion beam current density distribution is measured and plotted. J ( x' , y' The distribution pattern within the working plane is used to obtain the ion beam current density distribution through data fitting. J ( x ', y It can be approximated as a two-dimensional Gaussian function: ； in, J 0 represents the central peak density. Let be the beam spot radius.

5. The method for fabricating a waveguide grating with continuously tapered groove depth according to claim 1, characterized in that: The etching depth per unit ion beam dose R m Through experimental determination, including: A SiO2 sample was subjected to uniform ion beam etching for a fixed time. The etching depth was measured using a profilometer or atomic force microscope (AFM) to calculate the etching depth of the SiO2 sample per unit ion beam dose. R m .

6. The method for fabricating a waveguide grating with continuously tapered groove depth according to claim 1, characterized in that: In S4, based on the cooperative control model, and combining the set target trench depth curve and the calibrated ion beam current density distribution, the scanning speed corresponding to the target trench depth curve is calculated, including: For solving the inverse problem of the cooperative control model, a numerical iterative algorithm is used to obtain the target trench depth curve. d ( x ) and known ion beam current density distribution J ( x' , y' Etching depth per unit ion beam dose R m Substitute the values ​​into the collaborative control model and solve for the target trench depth curve in reverse. d ( x The corresponding scan speed v ( x ); Among them, scanning speed v ( x curves of target trench depth d ( x Approximately inversely proportional: That is, for areas with deeper etching depth, the scanning speed should be slowed down; for areas with shallower etching depth, the scanning speed should be accelerated.

7. The method for fabricating a waveguide grating with continuously tapered groove depth according to claim 6, characterized in that: In S5, ion beam etching is performed based on the solved scanning speed, ultimately forming a continuously gradient groove depth on the waveguide grating that precisely corresponds to the target groove depth curve, including: S51. Fix the photoresist grating mask fabricated by holographic interference lithography onto the worktable inside the vacuum chamber of the ion beam etching system. S52, Target trench depth curve d ( x The corresponding scan speed v ( x The program is loaded into the high-precision motion control system of the worktable, the process parameters are set, the ion beam source is turned on, and the process parameters are kept constant during the scanning process to ensure the etching depth per unit ion beam dose. R m stability; S53, The motion control system drives the worktable according to the scanning speed. v ( x The waveguide grating is scanned along its length by the ion beam, which continuously etches the waveguide grating. Due to the scanning speed... v ( x The continuous change of ) eventually forms a curve on the waveguide grating corresponding to the target groove depth. d ( x Precisely corresponding continuous gradient groove depth; The process parameters include ion energy, beam current, beam pressure, and the composition and flow rate of the reactant gas.

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