Accurate calculation method for transverse simulation of surface acoustic wave device

Abstract

The invention belongs to the technical field of filters, and particularly relates to an accurate calculation method for transverse simulation of a surface acoustic wave device. The method comprises the following steps: constructing an initial transverse mode suppression structure model; performing photoetching calculation simulation on the initial transverse mode suppression structure model; obtaining a morphology contour after photoetching simulation; establishing a finite element model based on the morphology contour; according to the finite element model, simulating the transverse model suppression structure by using a finite element simulation technology to obtain a transverse simulation result; comparing the transverse simulation result with the performance requirement of the target device; according to a comparison result, optimizing structure parameters such as the width, the period and the morphology characteristics of the finger strips, and further improving the transverse mode suppression effect of the surface acoustic wave device; according to the method, the consistency of the transverse mode simulation and the actual measurement result is improved, the debugging time and cost between design and manufacturing are reduced, and the transverse mode suppression effect of the surface acoustic wave device is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of filters, and particularly relates to an accurate calculation method for the lateral mode simulation of surface acoustic wave devices. Background Art

[0002] Surface acoustic wave filters are key components indispensable in modern wireless communication and sensing technologies, and their performance plays a crucial role in the quality and reliability of communication systems. To improve the performance of filters, various lateral mode suppression structures are widely applied in surface acoustic wave devices. These structures suppress the excitation of lateral modes by precisely designing the shape and arrangement of electrodes, thereby optimizing the acoustic wave propagation characteristics and enhancing the signal quality of the filters. However, this design process faces numerous challenges.

[0003] Currently, the design and simulation of lateral mode suppression structures are usually based on ideal geometric models. In this method, the electrode shape of the filter is assumed to be a regular and precise geometric structure. However, in the actual manufacturing process, the lithography process inevitably introduces processing errors. These errors include edge roughness, width deviation, and contour irregularity caused by non-ideal development of photoresist, resulting in a significant difference between the actual processed structure morphology and the design model. This difference directly affects the excitation and propagation characteristics of lateral modes, making it difficult for the simulation results based on the ideal model to accurately reflect the performance of the actual device.

[0004] In addition, existing simulation methods often ignore the error sources between the processed morphology and the design model when calculating the lateral mode suppression effect. This neglect not only leads to a large deviation between the simulation results and the measured data but also makes it impossible to effectively predict the influence of lateral modes during the design iteration process, thereby increasing the debugging time and cost between design and manufacturing. In complex devices, this problem is particularly prominent and may ultimately result in the failure to meet the filter performance standards. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention proposes an accurate calculation method for the lateral mode simulation of surface acoustic wave devices, which includes:

[0006] S1: Construct an initial lateral mode suppression structure model;

[0007] S2: Conduct lithography calculation simulation on the initial lateral mode suppression structure model;

[0008] S3: Obtain the morphology profile after lithography simulation;

[0009] S4: Establish a finite element model based on the morphology profile;

[0010] S5: According to the finite element model, use finite element simulation technology to simulate the lateral mode suppression structure and obtain the lateral mode simulation result;

[0011] S6: Compare the lateral simulation results with the performance requirements of the target device;

[0012] S7: When the comparison result does not meet the requirements, optimize the structural parameters of the finger bars. When the comparison result meets the requirements, generate the layout of the surface acoustic wave device and perform tape-out.

[0013] Preferably, the process of constructing the initial lateral mode suppression structure model includes: generating an ideal geometric model according to the design parameters, where the design parameters include the width, length, period, and arrangement of the finger bars.

[0014] Preferably, the process of performing lithography calculation and simulation on the initial lateral mode suppression structure model includes:

[0015] Construct a mask pattern according to the initial lateral mode suppression structure model;

[0016] Set the spatial sampling interval and lithography system parameters, where the lithography system parameters include wavelength and numerical aperture;

[0017] Define the optical transfer function according to the numerical aperture and wavelength;

[0018] Discretize the optical transfer function according to the spatial sampling interval;

[0019] Using the Fourier optics method, transform the mask pattern into the frequency domain and multiply it by the discretized optical transfer function to obtain the frequency domain diffraction response of the lateral mode suppression structure;

[0020] Restore the frequency domain diffraction response of the lateral mode suppression structure to the spatial domain through inverse Fourier transform to obtain the light intensity distribution of the mask pattern.

[0021] Preferably, the process of obtaining the topographical profile after lithography simulation includes:

[0022] Select 20% and 40% of the maximum light intensity in the light intensity distribution as thresholds to obtain two contour lines;

[0023] Determine the contour shape according to the center line of the strip area between the two contour lines;

[0024] Extract the topographical profile of the lateral mode suppression structure according to the determined contour shape, including edge roughness, width deviation, and irregularity.

[0025] Preferably, the process of establishing a finite element model based on the topographical profile includes: importing the topographical profile obtained from lithography simulation into the finite element simulation model; establishing a finite element model according to the actual processing material parameters and structural topographical features.

[0026] Preferably, the lateral simulation results include modal excitation efficiency, amplitude distribution, and energy leakage.

[0027] The beneficial effects of the present invention are as follows: The precise calculation method for the lateral mode simulation of the surface acoustic wave device proposed by the present invention introduces lithography calculation simulation into the lateral mode simulation process. By replacing the ideal geometric model with the actual processing topography, it can effectively reduce the error between the ideal model and the processing topography, improve the consistency between the lateral mode simulation and the measured results, reduce the debugging time and cost between design and manufacturing, and improve the lateral mode suppression effect of the surface acoustic wave device. Brief Description of the Drawings

[0028] Figure 1 It is a flow chart of the precise calculation method for the lateral mode simulation of the surface acoustic wave device in the present invention;

[0029] Figure 2 It is a schematic diagram of the shape of the initial lateral mode suppression structure in the present invention;

[0030] Figure 3 It is a schematic diagram of the mask pattern in the present invention;

[0031] Figure 4 It is a schematic diagram of the optical transfer function in the present invention;

[0032] Figure 5 It is a light intensity distribution diagram of the mask pattern in the present invention;

[0033] Figure 6 It is a finger strip shape contour diagram after lithography simulation in the present invention. Detailed Embodiments

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] To solve the problem of insufficient simulation accuracy of the lateral mode suppression structure in the design of existing surface acoustic wave devices and the problem of significant differences between traditional simulation methods and design models; the present invention proposes a precise calculation method for the lateral mode simulation of surface acoustic wave devices, as Figure 1 shown, the method includes the following contents:

[0036] S1: Construct an initial lateral mode suppression structure model.

[0037] Generate an ideal geometric model with clear geometric shapes and periodicity according to the design parameters, including the width, length, period, and arrangement of the finger strips. This model provides a basis for subsequent lithography simulation and lateral mode analysis.

[0038] For example, two different initial transverse mode suppression structure shapes are as follows Figure 2 shown Figure 2 Figure A shows the designed shape and geometric parameters of the initial transverse mode suppression structure. The structure includes bus bars, where there are 11 bus bars, and the distance between two bus bars is w1. Two finger bars are connected to the bus bars, and the shapes of the two finger bars are rotationally symmetric along the center of the structure. The finger bars are divided into a conventional region 12 and an end structure region 13. The left edges of the two finger bars are spaced by p, the width of the conventional region is w2, the length is l2, the width of the end structure region is w3, and the length is l3. Figure 2 In Figure B, there is a gap with a width of w4 between the end structure region and the conventional region of the finger bars.

[0039] In some preferred embodiments, specific design parameters are set, namely the width, length, period, and arrangement of the finger bars; specifically: as Figure 2 in the initial transverse mode suppression structure of Figure A, w1 is 40 μm, p is 1 μm, w2 is 32 μm, w3 is 6 μm, l2 is 0.5 μm, and l3 is 0.7 μm. And the x coordinates of the center points of the conventional region 12 and the end structure region 13 are the same.

[0040] S2: Perform lithography calculation simulation on the initial transverse mode suppression structure model.

[0041] Construct a mask pattern according to the initial transverse mode suppression structure model. Specifically: Generate a mask pattern of a rectangular or periodic structure according to the initial transverse mode suppression structure model, as Figure 3 shown, and the calculation area size is 2 μm * 50 μm.

[0042] Set the lithography system parameters (wavelength and numerical aperture) and the spatial sampling interval (usually taken from 5 nm to 20 nm). For example: Determine the wavelength of the lithography light source (λ = 193 nm), the numerical aperture (NA = 0.85), and the spatial sampling interval is 10 nm.

[0043] Define the optical transfer function according to the numerical aperture and wavelength. For example: Use the numerical aperture and wavelength of the system to define the transfer function in the frequency domain. Discretize the optical transfer function according to the spatial sampling interval to obtain a discretized optical transfer function that is a circular aperture in the two-dimensional frequency domain, as Figure 4 shown. Among them, the size of the spatial sampling interval determines the discretization accuracy in the spatial domain and affects the spectral resolution in the frequency domain, thereby affecting the final calculation accuracy and the amount of calculation.

[0044] Using the Fourier optics method, the mask pattern is transformed into the frequency domain and multiplied by the discretized optical transfer function to obtain the frequency-domain diffraction response of the lateral mode suppression structure. Specifically: perform a fast Fourier transform (FFT) on the mask pattern to obtain its spectral distribution, multiply the spectral distribution by the optical transfer function to simulate the diffraction effect in the optical imaging process, and obtain the frequency-domain diffraction response of the lateral mode suppression structure.

[0045] The lithography system restores the frequency-domain diffraction response of the lateral mode suppression structure to the spatial domain through an inverse Fourier transform to obtain the intensity distribution of the mask pattern.

[0046] The intensity distribution of the mask pattern is as Figure 5 shown, and the intensity distribution truly reflects the finger imaging characteristics in the lithography system and the influence of this characteristic on the topography error of the finally processed fingers.

[0047] S3: Obtain the topography profile after lithography simulation.

[0048] By analyzing the intensity distribution, two contour lines are drawn using 20% and 40% of the maximum intensity as thresholds respectively. The outer contour line (20% threshold) represents the boundary of the low exposure dose after photoresist development, usually corresponding to the maximum expansion range of the contour during the processing. The inner contour line (40% threshold) reflects the boundary of the high exposure dose region of the photoresist, usually corresponding to the more concentrated part of the topography profile during processing. Determine the contour shape according to the center line of the strip-shaped area between the two contour lines, that is, the final finger topography profile is determined by the center line of the strip-shaped area enclosed by the two contour lines, as Figure 6 shown.

[0049] Extract the topography profile of the lateral mode suppression structure according to the determined contour shape, including edge roughness and width deviation.

[0050] S4: Establish a finite element model based on the topography profile.

[0051] Import the topography profile obtained from lithography simulation into the finite element simulation model; establish a finite element model according to the actual processing material parameters (such as elastic modulus, density, etc.) and structural topography characteristics (geometric characteristics such as the width, period, and shape of the structure).

[0052] S5: According to the finite element model, use finite element simulation technology to simulate the lateral mode suppression structure to obtain the lateral mode simulation result.

[0053] Add periodic boundary conditions to the finite element model, and set the electrical and mechanical boundary conditions of the bus bar and finger bars, then the admittance curve of the surface acoustic wave resonator can be calculated, and the magnitude of the lateral mode can be determined through the admittance curve and displacement distribution.

[0054] Modal excitation efficiency, amplitude distribution, and energy leakage can be calculated through simulation; analyzing the transverse mode suppression effect can provide a basis for structural optimization.

[0055] S6: Compare the transverse mode simulation results with the performance requirements of the target device;

[0056] S7: When the comparison results do not meet the requirements, optimize the structural parameters such as the width, period, and topography characteristics of the fingers to further improve the transverse mode suppression effect of the surface acoustic wave device; when the comparison results meet the requirements, generate the layout of the surface acoustic wave device and perform tape-out.

[0057] In summary, the present invention provides an accurate calculation method for transverse mode simulation of a surface acoustic wave device. By introducing lithography calculation simulation into the transverse mode simulation process and replacing the ideal geometric model with the actual processing topography, the matching degree between the simulation results and the actual performance is improved, providing an efficient and accurate technical means for the design and development of high-performance surface acoustic wave devices.

[0058] The above embodiments further illustrate the object, technical solution, and advantages of the present invention. It should be understood that the above embodiments are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made to the present invention within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An accurate calculation method for transverse simulation of surface acoustic wave devices, characterized in that, Including: S1: Construct an initial lateral mode suppression structure model; S2: Conduct lithography calculation simulation on the initial lateral mode suppression structure model; S3: Obtain the topography profile after lithography simulation; S4: Establish a finite element model based on the topography profile; S5: According to the finite element model, use finite element simulation technology to simulate the lateral mode suppression structure and obtain the lateral mode simulation result; S6: Compare the lateral mode simulation result with the performance requirements of the target device; S7: When the comparison result does not meet the requirements, optimize the structural parameters of the finger bars. When the comparison result meets the requirements, generate the layout of the surface acoustic wave device and conduct tape-out.

2. The precise calculation method for lateral simulation of a surface acoustic wave device according to claim 1, characterized in that The process of constructing the initial lateral mode suppression structure model includes: generating an ideal geometric model according to the design parameters, where the design parameters include the width, length, period, and arrangement pattern of the finger bars.

3. The accurate calculation method for lateral simulation of a surface acoustic wave device according to claim 1, characterized in that The process of conducting lithography calculation simulation on the initial lateral mode suppression structure model includes: Construct a mask pattern according to the initial lateral mode suppression structure model; Set the spatial sampling interval and lithography system parameters, where the lithography system parameters include wavelength and numerical aperture; Define the optical transfer function according to the numerical aperture and wavelength; Discretize the optical transfer function according to the spatial sampling interval; Using the Fourier optics method, transform the mask pattern into the frequency domain and multiply it by the discretized optical transfer function to obtain the frequency domain diffraction response of the lateral mode suppression structure; Restore the frequency domain diffraction response of the lateral mode suppression structure to the spatial domain through inverse Fourier transform to obtain the light intensity distribution of the mask pattern.

4. The precise calculation method for lateral simulation of a surface acoustic wave device according to claim 1, characterized in that, The process of obtaining the topography profile after lithography simulation includes: Select 20% and 40% of the maximum light intensity in the light intensity distribution as thresholds to obtain two contour lines; Determine the contour shape according to the center line of the strip area between the two contour lines; Extract the topography profile of the lateral mode suppression structure according to the determined contour shape, including edge roughness, width deviation, and irregularity.

5. The accurate calculation method for transverse simulation of a surface acoustic wave device according to claim 1, characterized in that, The process of establishing a finite element model based on the topography profile includes: importing the topography profile obtained from lithography simulation into the finite element simulation model; establishing a finite element model according to the actual processing material parameters and structural topography characteristics.

6. The precise calculation method for the lateral simulation of a surface acoustic wave device according to claim 1, characterized in that, The lateral mode simulation result includes modal excitation efficiency, amplitude distribution, and energy leakage.

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