A three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution

Abstract

The present invention discloses a three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution, comprising the following steps: first, a mask is plated on the surface of a sample to be etched; a coordinate system is established according to the desired structure of the sample to be etched; for each of the to-be-etched points in the set of to-be-etched points at the current moment #imgabs0#, its unit tangent angle, actual beam incident angle, and actual etching factor are calculated; and the actual etching factor is calculated based on the actual etching factor. d t The method uses a time increment to calculate the coordinates of the next set of etched points at #imgabs2# based on the set of etched points at the current moment #imgabs1#. This iteration is repeated until the set of etched points at the next moment #imgabs3# meets the desired value. The sample to be etched is then placed in a reactive ion beam etching (RIBE) apparatus, and RIB etching is performed on each etched point in sequence based on the actual beam incident angle and etching factor of each etched point. The present invention aims to achieve three-dimensional microstructure etching using a RIB process and improve the manufacturing accuracy of three-dimensional microstructures.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional micro-nanostructure etching, and in particular to a three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution. Background Art

[0002] In recent years, with the rapid development of metasurfaces, MEMS devices, and quantum photonic devices, reactive ion beam etching (RIBE) technology has been widely used in the etching of three-dimensional micro- and nanostructures. Traditionally, techniques such as focused ion beam (FIB) and electron beam lithography (EBL) have been used to create 3D structures with nanometer precision. However, due to their extremely small range of motion, only on the micrometer scale, they are unable to achieve millimeter-scale applications. Furthermore, reactive ion etching (RIE) processes struggle to control the density of free radicals within the discharge chamber and, due to the unavoidable lateral undercutting of the structure, they make it difficult to achieve high-precision 3D structures. Applying RIE to the etching of 3D microstructures to achieve high-precision structures has become a key technical challenge that needs to be addressed. Summary of the Invention

[0003] The technical problem to be solved by the present invention: In response to the above-mentioned problems of the prior art, a three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution is provided. The present invention aims to realize three-dimensional microstructure etching based on reactive ion beam etching process and improve the manufacturing accuracy of three-dimensional microstructures.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A three-dimensional microstructure etching method based on discrete point iterative analysis of profile evolution includes the following steps:

[0006] S1, a patterned mask is plated on the surface of the sample to be etched; a coordinate system is established according to the desired structure of the sample to be etched, and the coordinate set of the contour points of the desired structure is determined. ,in ~ For the 1st The coordinates of the contour points of the desired structure;

[0007] S2, determine the etching factor and select the ion incident angle , etching factor is the angle between the sidewall and the base of the three-dimensional microstructure;

[0008] S3, according to the ion incident angle The length of the ion irradiation area is determined by the structural parameters of the mask , the length of the ion irradiation zone Divide evenly Discrete etching points ~ , thereby determining the current moment The set of points to be etched ;

[0009] S4, the current moment The set of points to be etched Determine the etching boundary control point at the boundary of the etching area;

[0010] S5, calculate the current time The set of points to be etched The unit tangent angle of each point to be etched;

[0011] S6, calculate the current moment based on the unit tangent angle The actual beam incident angle of each point to be etched;

[0012] S7, determine the current time according to the actual beam incident angle The actual etching factor of each point to be etched;

[0013] S8, according to the current time t The coordinates of the point to be etched are d t is the time increment, calculate the next moment The set of points to be etched The coordinates of n points to be etched ~ ;

[0014] S9, determine the next moment The set of points to be etched The coordinates of each point to be etched and the coordinate set of the contour points of the desired structure Whether the distance between the corresponding contour point coordinates meets the requirements, if so, record the total dwell time of all points to be etched , jump to step S10; otherwise, the next moment The set of points to be etched As the new present moment The set of points to be etched , jump to step S4;

[0015] S10, placing the sample to be etched into the reactive ion beam etching equipment, and according to the preset ion source beam current density , total beam accelerating voltage As well as the actual beam incident angle, actual etching factor and total dwell time of each point to be etched , performing reactive ion beam etching on each point to be etched in turn;

[0016] S11, detecting the etching depth of the sample to be etched. If the etching depth of the sample to be etched has not reached the requirement, jump to step S3; otherwise, end and exit.

[0017] Optionally, the calculation function expression of the unit tangent angle in step S5 is:

[0018] ,

[0019] in, For the current moment No. Points to be etched The unit tangent angle of and The current moment No. Points to be etched The line segment formed by the adjacent points to be etched at a specified distance on both sides Axis angle.

[0020] Optionally, the calculation function expression of the actual beam incident angle in step S6 is:

[0021] ,

[0022] in, For the current moment No. Points to be etched The actual beam incident angle, is the etching factor according to the desired structure The selected ion incident angle, For the current moment No. Points to be etched The unit tangent angle of .

[0023] Optionally, in step S2, the etching factor is determined and select the ion incident angle When including the etching factor of the desired structure Substitute the pre-fitted etching factor and ion incident angle The relationship function is used to obtain the corresponding ion incident angle .

[0024] Optionally, the calculation function expression of the actual etching factor in step S7 is:

[0025] ,

[0026] in, For the current moment No. Points to be etched The actual etching factor, is the pre-fitted etching factor and ion incident angle The relationship function, For the current moment No. Points to be etched The actual beam incident angle.

[0027] Optionally, in step S8, the next moment is calculated The set of points to be etched middle The coordinates of the points to be etched ~ When any The calculation function expression of the coordinates of the points to be etched is:

[0028] ,

[0029] in, For the next moment The set of points to be etched Middle The coordinates of the points to be etched, For the current moment No. The coordinates of the points to be etched, The pre-fitted etching efficiency and ion incident angle The relationship function, For the current moment No. Points to be etched The actual beam incident angle, For the current moment No. Points to be etched Ion incident angle A unit length vector, For the current moment No. Points to be etched The etching time increment.

[0030] Optionally, it also includes pre-fitting the etching factor and the ion incident angle The relationship function between etching efficiency and ion incident angle The steps of the relationship function:

[0031] S101, selecting a plurality of samples of the same material as the sample to be etched and coating a patterned mask on the surface thereof;

[0032] S102, a plurality of samples are respectively placed on the reactive ion beam etching equipment in step S10, using the same ion source beam current density as in step S10. , total beam accelerating voltage Perform various specified ion incident angles Etching processing under the condition of ion incidence angle is detected by depth detection equipment. The etching factor and etching depth of the etching process under the condition of ion incidence angle are calculated. The etching factor of the etching process under the condition of ion incident angle is obtained by fitting the etching factor with a cubic polynomial. The relationship function for various ion incident angles The etching efficiency of the etching process under the condition of the third degree polynomial fitting is used to obtain the relationship between the etching efficiency and the ion incident angle. The relationship function.

[0033] Optionally, the function expression for calculating the etching efficiency according to the etching depth is:

[0034] ,

[0035] in, is the etching efficiency, is the etching depth, is the etching processing time of the sample.

[0036] Optionally, in step S1, when a patterned mask is formed on the surface of the sample to be etched, the etching ratio of the mask material to the substrate material of the sample to be etched is greater than 1:10, and the width of the mask is greater than satisfy , the height of the mask satisfy , and are the width and height of the three-dimensional microstructure, respectively.

[0037] Optionally, the three-dimensional microstructures are distributed in an array on the substrate of the sample to be etched, and each three-dimensional microstructure consists of a lower frustum at the bottom and an upper frustum inverted on the top of the lower frustum.

[0038] Compared with the prior art, the present invention can achieve the following beneficial effects: the method of the present invention includes iteratively determining each current moment The point to be etched ; is the current moment The point to be etched Determine the etching boundary control point at the etching area boundary; calculate the current moment The point to be etched The unit tangent angle, actual beam incident angle, actual etching factor, according to the current moment t The point to be etched Calculate the next moment The point to be etched Finally, the sample to be etched is placed in the reactive ion beam etching equipment, and the ion source beam current density is set according to the preset , total beam accelerating voltage As well as the actual beam incident angle and actual etching factor of each point to be etched, reactive ion beam etching is performed on each point to be etched in turn. The above method realizes the contour evolution based on discrete point iterative analysis, which can realize three-dimensional microstructure etching based on reactive ion beam etching process, and effectively improve the manufacturing accuracy of three-dimensional microstructures. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the basic process of the method of the embodiment of the present invention.

[0040] Figure 2 Schematic diagram of the principle of reactive ion beam etching equipment in an embodiment of the present invention.

[0041] Figure 3 Schematic diagram of the required structure of the three-dimensional microstructure in an embodiment of the present invention.

[0042] Figure 4 This is an example diagram of the initial surface to be etched in an embodiment of the present invention.

[0043] Figure 5 Schematic diagram of etching point coordinate calculation and iteration in the iterative process in an embodiment of the present invention.

[0044] Figure 6 Graph 1 is the corresponding relationship between etching efficiency and ion incident angle in the embodiment of the present invention.

[0045] Figure 7 1 is the corresponding relationship between the etching factor and the ion incident angle in the embodiment of the present invention.

[0046] Figure 8 This is a schematic diagram of the initial surface to be etched of the sample in an embodiment of the present invention.

[0047] Figure 9 Schematic diagram of parameter changes during the iterative process of etching points in an embodiment of the present invention.

[0048] Figure 10 Schematic diagram of iterative results of simulation calculations at various points in an embodiment of the present invention.

[0049] Figure 11This is a structural diagram after etching for 10 minutes in an embodiment of the present invention.

[0050] Figure 12 This is a structural diagram after etching for 20 minutes in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings in the embodiments of the present invention. Figure 1 As shown, the three-dimensional microstructure etching method based on discrete point iterative analysis of profile evolution in this embodiment includes the following steps:

[0052] S1, a patterned mask is plated on the surface of the sample to be etched; a coordinate system is established according to the desired structure of the sample to be etched, and the coordinate set of the contour points of the desired structure is determined. ,in ~ For the 1st The coordinates of the contour points of the desired structure;

[0053] S2, determine the etching factor and select the ion incident angle , etching factor is the angle between the sidewall and the base of the three-dimensional microstructure;

[0054] S3, according to the ion incident angle The length of the ion irradiation area is determined by the structural parameters of the mask , the length of the ion irradiation zone Divide evenly Discrete etching points ~ , thereby determining the current moment The set of points to be etched ;

[0055] S4, the current moment The set of points to be etched Determine the etching boundary control point at the boundary of the etching area;

[0056] S5, calculate the current time The set of points to be etched The unit tangent angle of each point to be etched;

[0057] S6, calculate the current moment based on the unit tangent angle The actual beam incident angle of each point to be etched;

[0058] S7, determine the current time according to the actual beam incident angle The actual etching factor of each point to be etched;

[0059] S8, according to the current time t The coordinates of the point to be etched are d t is the time increment, calculate the next moment The set of points to be etched middle The coordinates of the points to be etched ~ ;

[0060] S9, determine the next moment The set of points to be etched The coordinates of each point to be etched and the coordinate set of the contour points of the desired structure Whether the distance between the corresponding contour point coordinates meets the requirements, if so, record the total dwell time of all points to be etched , jump to step S10; otherwise, the next moment The set of points to be etched As the new present moment The set of points to be etched , jump to step S4;

[0061] S10, placing the sample to be etched into the reactive ion beam etching equipment, and according to the preset ion source beam current density , total beam accelerating voltage As well as the actual beam incident angle, actual etching factor and total dwell time of each point to be etched , performing reactive ion beam etching on each point to be etched in turn;

[0062] S11, detecting the etching depth of the sample to be etched. If the etching depth of the sample to be etched has not reached the requirement, jump to step S3; otherwise, end and exit.

[0063] like Figure 2As shown, the reactive ion beam etching apparatus in this embodiment includes: a three-dimensional motion platform 5, a control device 7, and a gas distribution unit 8. The three-dimensional motion platform 5 is provided with a reactive etching ion source 3, and the wide beam ion source 3 is provided with an ion source water cooling module 4. A tiltable and rotatable water cooling fixture 1 is arranged in the ion source emission direction of the reactive etching ion source 3, and the water cooling fixture 1 is connected to a water chiller 6 and can rotate 180 degrees in the YZ plane and 360 degrees in the XY plane. The gas distribution unit 8 includes a gas mixing tank 9 and multiple groups of gas cylinders 11, and each gas cylinder 11 is connected to the gas mixing tank 9 via a corresponding gas flow control valve 10. The output end of the gas mixing tank 9 is connected to the reactive etching ion source 3. The water chiller 6, the wide beam ion source 3, the three-dimensional motion platform 5, and the gas flow control valve 10 are all connected to the control device 7. Placing the sample to be etched into the reactive ion beam etching apparatus means mounting the sample to be etched on a water-cooled fixture 1. In this embodiment, this also includes applying vacuum thermal grease to the back of the sample to be etched to ensure good contact between it and the water-cooled fixture 1. Turning on the water chiller 6 ensures that the water cooling cycle and the ion source water cooling module 4 operate normally, and that the surface temperature of the sample to be etched does not exceed 30°C. Then, the gas mass flow meter is controlled by the control device 7 to introduce reactive ion beam etching process gas into the reactive etching ion source 3, causing the ion source to discharge.

[0064] In step S1, when a patterned mask is plated on the surface of the sample to be etched, the etching ratio of the mask material to the substrate material of the sample to be etched is greater than 1:10, and the width of the mask is greater than satisfy , the height of the mask satisfy , and are the width and height of the three-dimensional microstructure respectively. Figure 3 As shown, the three-dimensional microstructures in this embodiment are distributed in an array on the substrate of the sample to be etched, and each three-dimensional microstructure is composed of a lower frustum at the bottom and an upper frustum inverted on the top of the lower frustum. This structure is often used for metasurface infrared band reflectors and optical phase control. Figure 3 middle, is the top width of the three-dimensional microstructure, is the height of the three-dimensional microstructure, is the structural period of the three-dimensional microstructure, is the etching factor (the angle between the sidewall of the three-dimensional microstructure and the processing base surface), is the structural height of the upper cone, is the bottom width of the three-dimensional microstructure. In this embodiment, the substrate material of the sample to be etched is single crystal silicon, and the top width is ， Bottom width , etching factor , structural cycle ， Structural height of upper cone , the height of the three-dimensional microstructure The patterned mask is circular, and the width of the mask is , the height of the mask The mask material is chromium, and the etching ratio to the substrate material is 1:12 under the bombardment of the ion beam formed by SF6 gas.

[0065] In step S2 of this embodiment, the etching factor is determined and select the ion incident angle When including the etching factor of the desired structure Substitute the pre-fitted etching factor and ion incident angle The relationship function is used to obtain the corresponding ion incident angle ,Right now: ,in is the pre-fitted etching factor and ion incident angle For example, in this embodiment, according to the etching factor of the desired structure Select the initial ion incident angle is 70°.

[0066] In step S3 of this embodiment, according to the ion incident angle The length of the ion irradiation area is determined by the structural parameters of the mask , the length of the ion irradiation zone Divide evenly discrete points to be etched ( ), thereby determining the current moment The point to be etched , the initial moment , its coordinates can be determined according to the coordinate system; Figure 4 This is an example of the initial surface to be etched in this embodiment. The points to be etched are all ion irradiation area length The discrete points within are specifically divided into 10nm intervals.

[0067] In this embodiment, step S4 is the current time The point to be etched The etching boundary control point is determined at the etching area boundary, and 100 outside the etching area boundary nm Determine the boundary point and Since the ion beam irradiation energy of these two points is basically zero, the two etching boundary control points and are all considered as fixed points, such as Figure 4 The two etching boundary control points specifically determined in this embodiment are as follows: and The coordinates are: and .

[0068] The calculation function expression of the unit tangent angle in step S5 of this embodiment is:

[0069] ,

[0070] in, For the current moment No. Points to be etched The unit tangent angle of and The current moment No. Points to be etched The line segment formed by the adjacent points to be etched at a specified distance on both sides Axis angle.

[0071] The calculation function expression of the actual beam incident angle in step S6 of this embodiment is:

[0072] ,

[0073] in, For the current moment No. Points to be etched The actual beam incident angle, is the etching factor according to the desired structure The selected ion incident angle, For the current moment No. Points to be etched The unit tangent angle of .

[0074] The calculation function expression of the actual etching factor in step S7 of this embodiment is:

[0075] ,

[0076] in, For the current moment No. Points to be etched The actual etching factor, is the pre-fitted etching factor and ion incident angle The relationship function, For the current moment No. Points to be etched The actual beam incident angle.

[0077] In step S8 of this embodiment, the next moment is calculated The set of points to be etched middle The coordinates of the points to be etched ~ When any The calculation function expression of the coordinates of the points to be etched is:

[0078] ,

[0079] in, For the next moment The set of points to be etched Middle The coordinates of the points to be etched, For the current moment No. The coordinates of the points to be etched, The pre-fitted etching efficiency and ion incident angle The relationship function, For the current moment No. Points to be etched The actual beam incident angle, For the current moment No. Points to be etched Ion incident angle A unit length vector, For the current moment No. Points to be etched The etching time increment.

[0080] In step S9 of this embodiment, the next moment is determined The set of points to be etched The coordinates of each point to be etched and the coordinate set of the contour points of the desired structure Whether the distance between the corresponding contour point coordinates meets the requirements, if so, record the total dwell time of all points to be etched , jump to step S10; otherwise, the next moment The set of points to be etched As the new present moment The set of points to be etched , jump to step S4. It should be noted that the time for each point to be etched is the time increment , so the total residence time of all the points to be etched is calculated The way is: ,and Initially it is 0. As an optional implementation, in this embodiment, the time increment 0.01min (for easy observation, Figure 4 Only data points with integer etching time t are shown in the figure. The total dwell time For 20 minutes.

[0081] In addition, this embodiment also includes pre-fitting the etching factor and the ion incident angle The relationship function between etching efficiency and ion incident angle The steps of the relationship function:

[0082] S101, selecting a plurality of samples of the same material as the sample to be etched and coating a patterned mask on the surface thereof;

[0083] S102, a plurality of samples are respectively placed on the reactive ion beam etching equipment in step S10, using the same ion source beam current density as in step S10. , total beam accelerating voltage Perform various specified ion incident angles Etching processing under the condition of ion incidence angle is detected by depth detection equipment. The etching factor and etching depth of the etching process under the condition of ion incidence angle are calculated. The etching factor of the etching process under the condition of ion incident angle is obtained by fitting the etching factor with a cubic polynomial. The relationship function, such as Figure 7 As shown, for various ion incident angles The etching efficiency of the etching process under the condition of the third degree polynomial fitting is used to obtain the relationship between the etching efficiency and the ion incident angle. The relationship function, such as Figure 6 As shown. Among them, the depth detection equipment can be selected according to the needs. White light interferometer, atomic force microscope (AFM, Atomic Force Microscope), scanning electron microscope (SEM, Scanning Electron Microscope), profilometer, confocal microscope, etc. can be selected. In this embodiment, the depth detection equipment is used to detect various ion incident angles. The etching factor and etching depth of the etching process at 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, and 80°, and the dwell time is t= 5min. Use SEM (scanning electron microscope) to detect the etching depth at 9 angles in step S5 and the etching factor (i.e. the angle between the sidewall and the initial base surface). . Using a cubic polynomial to fit the ion incident angle (i.e., the direction of the ion beam and x Axis positive angle) corresponding relationship ，Obtain etching efficiency and ion incident angle The relationship function is as follows Figure 6 As shown, the etching factor and ion incident angle are obtained The relationship function is as follows Figure 7 As shown, the function expressions are:

[0084] ,

[0085] ,

[0086] in, is the etching factor, is the etching efficiency; is the independent variable, i.e., the ion incident angle .

[0087] In this embodiment, the function expression for calculating the etching efficiency according to the etching depth is:

[0088] ,

[0089] in, is the etching efficiency, is the etching depth, such as Figure 5 As shown, is the etching processing time of the sample.

[0090] In this embodiment, the sample is etched from top to bottom through the previous process, and after the etching is completed, it serves as the initial structure in the method of this embodiment, such as Figure 8 In step S10 of this embodiment, the sample to be etched is placed in a reactive ion beam etching device, and the ion source beam current density is preset. , total beam accelerating voltage As well as the actual beam incident angle and actual etching factor of each point to be etched, when the reactive ion beam etching process is carried out on each point to be etched in turn, the process gas ratio of the material to be etched is selected to be pure SF6, and the ion source beam density is 7mA / cm 2 , total beam accelerating voltage 500V (screen grid DC regulated power supply voltage V s =450V, accelerating gate DC regulated power supply voltage V c =50V).

[0091] Figure 9 Schematic diagram of parameter changes during the iterative process of the points to be etched in this embodiment, wherein the black circles represent the points to be etched, that is, the black circle points are the initial points to be etched, one iteration is represented by a black triangle, and another iteration is represented by a black square. Figure 10This is a schematic diagram of the iterative results of the simulation calculation at each point in this embodiment. For ease of observation, only the etching time is shown in the figure. t The data points are integers (5 min, 10 min, 15 min, and 20 min).

[0092] Since the result requires a bilaterally symmetrical structure, the above process is a single-sided etching process. After the solidification process is completed, the sample is rotated to a symmetrical orientation and processed at the same beam angle. J 0, total beam accelerating voltage V t Beam angle ɑ Total dwell time T t The sample is etched. Since the result is required to be a bilaterally symmetrical structure, the above process is a single-sided etching. After the solidification process is completed, the sample is rotated to a symmetrical orientation and processed at the same beam angle. Figure 11 This is the structural diagram after etching for 10 minutes in this embodiment. Figure 12 This is a structural diagram after etching for 20 minutes in this embodiment.

[0093] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution, characterized in that The steps include: S1, a patterned mask is plated on the surface of the sample to be etched; a coordinate system is established according to the desired structure of the sample to be etched, and the coordinate set of the contour points of the desired structure is determined. ,in ~ For the 1st The coordinates of the contour points of the desired structure; S2, determine the etching factor and select the ion incident angle , etching factor is the angle between the sidewall and the base of the three-dimensional microstructure; S3, according to the ion incident angle The length of the ion irradiation area is determined by the structural parameters of the mask , the length of the ion irradiation zone Divide evenly Discrete etching points ~ , thereby determining the current moment The set of points to be etched ; S4, the current moment The set of points to be etched Determine the etching boundary control point at the boundary of the etching area; S5, calculate the current time The set of points to be etched The unit tangent angle of each point to be etched; S6, calculate the current moment based on the unit tangent angle The actual beam incident angle of each point to be etched; S7, determine the current time according to the actual beam incident angle The actual etching factor of each point to be etched; S8, according to the current time t The coordinates of the point to be etched are d t is the time increment, calculate the next moment The set of points to be etched middle The coordinates of the points to be etched ~ ; S9, determine the next moment The set of points to be etched The coordinates of each point to be etched and the coordinate set of the contour points of the desired structure Whether the distance between the corresponding contour point coordinates meets the requirements, if so, record the total dwell time of all points to be etched , jump to step S10; Otherwise, the next moment The set of points to be etched As the new present moment The set of points to be etched , jump to step S4; S10, placing the sample to be etched into the reactive ion beam etching equipment, and according to the preset ion source beam current density , total beam accelerating voltage As well as the actual beam incident angle, actual etching factor and total dwell time of each point to be etched , performing reactive ion beam etching on each point to be etched in turn; S11, detecting the etching depth of the sample to be etched. If the etching depth of the sample to be etched has not reached the requirement, jump to step S3; otherwise, end and exit.

2. The three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution according to claim 1, characterized in that: The calculation function expression of the unit tangent angle in step S5 is: ， in, For the current moment No. Points to be etched The unit tangent angle of and The current moment No. Points to be etched The line segment formed by the adjacent points to be etched at a specified distance on both sides Axis angle.

3. The three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution according to claim 1, characterized in that: The calculation function expression of the actual beam incident angle in step S6 is: ， in, For the current moment No. Points to be etched The actual beam incident angle, is the etching factor according to the desired structure The selected ion incident angle, For the current moment No. Points to be etched The unit tangent angle of .

4. The three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution according to claim 1, characterized in that: Determine the etching factor in step S2 and select the ion incident angle When including the etching factor of the desired structure Substitute the pre-fitted etching factor and ion incident angle The relationship function is used to obtain the corresponding ion incident angle .

5. The three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution according to claim 4, characterized in that: The calculation function expression of the actual etching factor in step S7 is: ， in, For the current moment No. Points to be etched The actual etching factor, is the pre-fitted etching factor and ion incident angle The relationship function, For the current moment No. Points to be etched The actual beam incident angle.

6. The three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution according to claim 5, characterized in that: In step S8, the next moment is calculated The set of points to be etched middle The coordinates of the points to be etched ~ When any The calculation function expression of the coordinates of the points to be etched is: ， in, For the next moment The set of points to be etched Middle The coordinates of the points to be etched, For the current moment No. The coordinates of the points to be etched, The pre-fitted etching efficiency and ion incident angle The relationship function, For the current moment No. Points to be etched The actual beam incident angle, For the current moment No. Points to be etched Ion incident angle A unit length vector, For the current moment No. Points to be etched The etching time increment.

7. The three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution according to claim 6, characterized in that: Also includes pre-fitted etch factor and ion incident angle The relationship function between etching efficiency and ion incident angle The steps of the relationship function: S101, selecting a plurality of samples of the same material as the sample to be etched and coating a patterned mask on the surface thereof; S102, a plurality of samples are respectively placed on the reactive ion beam etching equipment in step S10, using the same ion source beam current density as in step S10. , total beam accelerating voltage Perform various specified ion incident angles Etching processing under the condition of ion incidence angle is detected by depth detection equipment. The etching factor and etching depth of the etching process under the condition of ion incidence angle are calculated. The etching factor of the etching process under the condition of ion incident angle is obtained by fitting the etching factor with a cubic polynomial. The relationship function for various ion incident angles The etching efficiency of the etching process under the condition of the third degree polynomial fitting is used to obtain the relationship between the etching efficiency and the ion incident angle. The relationship function.

8. The three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution according to claim 7, characterized in that: The functional expression for calculating the etching efficiency according to the etching depth is: ， in, is the etching efficiency, is the etching depth, is the etching processing time of the sample.

9. The three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution according to claim 1, characterized in that: In step S1, when a patterned mask is plated on the surface of the sample to be etched, the etching ratio of the mask material to the substrate material of the sample to be etched is greater than 1:10, and the width of the mask is greater than satisfy , the height of the mask satisfy , and are the width and height of the three-dimensional microstructure, respectively.

10. The three-dimensional microstructure etching method based on discrete point iterative analysis of contour evolution according to claim 9, characterized in that: The three-dimensional microstructures are distributed in an array on the substrate of the sample to be etched, and each three-dimensional microstructure consists of a lower frustum at the bottom and an upper frustum inverted on the top of the lower frustum.

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