阅读说明：本技术 激光状态方程实验用阻抗匹配靶的聚焦离子束制备方法 (Preparation method of focused ion beam of impedance matching target for laser equation of state experiment ) 是由 路超 张厚亮 张德志 孟宪东 廖益传 史鹏 于 2019-11-13 设计创作，主要内容包括：本发明公开了激光状态方程实验用阻抗匹配靶的聚焦离子束制备方法,包括以下步骤：通过减薄方法将待测材料制备得到微米厚度的靶材料薄膜；利用聚焦离子束将所述靶材料薄膜切割成靶片；使用聚焦离子束配套的机械手将靶片转移到准备好的标准材料台阶上并精确对准；使用聚焦离子束辅助的薄膜沉积方法进行靶片的装配；对所述靶片和微靶进行尺寸检测后完成阻抗匹配靶的制备。本发明通过这种基于聚焦离子束的新型制靶方法可有效解决传统靶制备工艺中存在的问题,实现阻抗匹配靶加工精度的显著提升,明显提高微靶的制备成品率,降低劳动强度及高活性材料靶的氧化程度,使检测数据可靠性得到提高,在精度提升的基础上还可进行高精复杂靶型的微靶制备。(The invention discloses a preparation method of a focused ion beam of an impedance matching target for a laser equation of state experiment, which comprises the following steps: preparing a target material film with micron thickness from a material to be detected by a thinning method; cutting the target material film into target pieces by using a focused ion beam; transferring the target plate to a prepared standard material step by using a manipulator matched with the focused ion beam and accurately aligning; assembling the target by using a film deposition method assisted by a focused ion beam; and completing the preparation of the impedance matching target after carrying out size detection on the target sheet and the micro-target. The novel target making method based on the focused ion beam can effectively solve the problems in the traditional target making process, realize the obvious improvement of the processing precision of the impedance matching target, obviously improve the preparation yield of the micro-target, reduce the labor intensity and the oxidation degree of the high-activity material target, improve the reliability of detection data, and can also carry out the preparation of the high-precision complex target type micro-target on the basis of improving the precision.)

1. A method for preparing a focused ion beam of an impedance matching target for a laser equation of state experiment is characterized by comprising the following steps:

A. preparing a target material film with micron thickness from a material to be detected by a thinning method;

B. cutting the target material film into target pieces by using a focused ion beam;

C. transferring the target plate to a prepared standard material step by using a manipulator matched with the focused ion beam and accurately aligning;

D. assembling target pieces by using a focused ion beam assisted thin film deposition method to obtain micro targets;

E. and completing the preparation of the impedance matching target after carrying out size detection on the target sheet and the micro-target.

2. The method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment according to claim 1, wherein in the step A, the thinning method is a grinding and polishing and Ar ion polishing thinning method, a reactive ion etching thinning method or an inductively coupled plasma etching thinning method.

3. The method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment according to claim 1 or 2, wherein in the step A, when the thinning method is a grinding and polishing and Ar ion polishing thinning method, the thinning method comprises the following sub-steps:

(1-1) cutting a material to be tested into target material slices with the thickness less than or equal to 1 mm;

(1-2) polishing the thickness of the target material sheet to 40 μm or less using coarse sandpaper;

(1-3) thinning the thickness of the target material thin film to below 20 μm by using fine sandpaper;

and (1-4) polishing and thinning by utilizing Ar ions to obtain a target sheet, and preparing a target material film with the required micrometer thickness.

4. The method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment as claimed in claim 3, wherein in substeps 1-4, the wide beam Ar ion polishing and thinning method is used in combination with the white light interference detection method to obtain the thinning rate of the specific Ar ion to the target material, and then the quantitative polishing and thinning of the target material film is performed to obtain the target material film with the thickness of micrometer required for preparing the target piece.

5. The method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment according to claim 1, wherein in the step B, the target material film is rapidly transferred to a high-vacuum focused ion beam system, after determining the cutting rate and precision of the focused ion beam on the target material film under different voltages and beam currents, a proper voltage and beam current are selected, and the focused ion beam is adopted to cut a target sheet required for preparing the impedance matching target on the target material film, wherein the ion beam current of the target material film cut by the focused ion beam is 40-80 nA, and the voltage is 10-50 kV.

6. The method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment as claimed in claim 1 or 5, wherein in step B, the ion source of the focused ion beam is a liquid metal ion source or a gaseous ion source, and the target sheet has a rectangular, circular or triangular shape.

7. The method of claim 1, wherein in step C, the manipulator is contacted with the target in the focused ion beam system, the target and the manipulator are fixed together by a focused ion beam assisted platinum deposition method, and the movement of the target and the precise alignment between the target and the step of the standard material are realized by the precise movement of the manipulator, wherein the step size of the manipulator is controlled to be greater than 30 μm/step at the beginning of the target transfer process, the step size of the manipulator is controlled to be less than 5 μm/step at the end of the target transfer process, and the step size of the manipulator is controlled to be less than 1 μm/step during the precise alignment of the target.

8. The method of claim 1, wherein in step D, after the target plate is precisely aligned with the step of the standard material, the target plate is fixed to the standard material substrate by a focused ion beam assisted platinum deposition method, so as to complete the assembly of the impedance matching target, wherein the assembly of the target plate is performed by platinum deposition on the edge or corner of the target plate.

9. The method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment according to claim 1, wherein in the step E, the size detection is performed by combining a scanning electron microscope with white light interference detection or by using a step profiler.

10. The method for preparing the focused ion beam of the impedance matching target for the laser state equation experiment as claimed in claim 9, wherein when the size detection is performed by combining a scanning electron microscope and a white light interference detection, the in-situ size detection of the target sheet and the micro-target is performed by using a nano-resolution scanning electron microscope equipped in a focused ion beam system; and (4) taking out the formed micro target, detecting the sizes of the target sheet and the micro target by using a white light interference method, and confirming that the target design requirements are met.

Technical Field

The invention belongs to the field of preparation of impedance matching targets required by laser loading state equation research, and relates to a preparation method of a high-precision impedance matching target for laser state equation experiments based on a focused ion beam technology.

Background

The dynamic high-pressure equation of state experiment of the material is used for researching the equation of state of different materials under the condition of dynamic loading. The state equation data obtained through experiments are used for obtaining a material state equation, so that a function expression of the relation among state parameters in a matter system is described, and the method has important theoretical and practical values in the field of extreme conditions such as celestial physics, geophysical, nuclear physics and the like. Strong laser loading is an important means for obtaining extreme conditions such as ultrahigh pressure, ultrahigh strain rate and the like. Equation of state experiments under laser-loaded dynamic high pressure conditions require micro-target preparation as the sample of the experiment.

At present, because an absolute detection technology is immature, a relative detection technology is generally adopted, and a micro target required to be prepared is an impedance matching target. The impedance matching target mainly comprises a standard material and a material to be tested, and the structure is shown in figure 1. The standard material is generally selected from aluminum, the standard material substrate and the step can be integrally formed through a single-point diamond lathe, and the step (target sheet) of the material to be detected is generally only a few micrometers to tens of micrometers in thickness and is assembled on the standard material substrate after preparation.

For the impedance matching target for the equation of state experiment, the precision, the surface oxidation and the like of the target have great influence on the experimental precision and the data reliability. The traditional target preparation process comprises the processes of grinding and polishing preparation of a target material film, manual cutting of a target sheet, manual alignment and assembly of the target sheet and an aluminum step under a stereoscopic microscope, white light interference detection of finished target size parameters and the like. The process has the defects of low micro-target precision, single target type, high target making labor intensity, low target yield and the like, and is not suitable for the target preparation of high-activity materials, so that the requirements of high-pressure equation of state experiments can not be met gradually.

In order to improve the precision of the impedance matching target for the laser equation of state experiment, improve the target type, improve the rate of finished micro-target preparation and reduce the oxidation degree of the high-activity material target, the target making process needs to be improved to solve the bottleneck problem of the traditional target preparation process and meet the requirement of the high-pressure equation of state experiment.

Disclosure of Invention

The invention aims to overcome the bottleneck problem of the traditional target making process and provides a high-precision impedance matching target preparation method based on a focused ion beam technology.

One aspect of the invention provides a method for preparing a focused ion beam of an impedance matching target for a laser equation of state experiment, which comprises the following steps:

A. preparing a target material film with micron thickness from a material to be detected by a thinning method;

B. cutting the target material film into target pieces by using a focused ion beam;

C. transferring the target plate to a prepared standard material step by using a manipulator matched with the focused ion beam and accurately aligning;

D. assembling target pieces by using a focused ion beam assisted thin film deposition method to obtain micro targets;

E. and completing the preparation of the impedance matching target after carrying out size detection on the target sheet and the micro-target.

According to an embodiment of the method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment, in the step A, the thinning method is a grinding and polishing and Ar ion polishing thinning method, a reactive ion etching thinning method or an induction coupling plasma etching thinning method.

According to an embodiment of the method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment, in the step a, when the thinning method is a grinding and polishing and Ar ion polishing thinning method, the thinning method includes the following sub-steps:

(1-1) cutting a material to be tested into target material slices with the thickness less than or equal to 1 mm;

(1-2) polishing the thickness of the target material sheet to 40 μm or less using coarse sandpaper;

(1-3) thinning the thickness of the target material thin film to below 20 μm by using fine sandpaper;

and (1-4) polishing and thinning by utilizing Ar ions to obtain a target sheet, and preparing a target material film with the required micrometer thickness.

According to an embodiment of the method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment, in substeps 1-4, a wide-beam Ar ion polishing and thinning method is combined with a white light interference detection method to obtain the thinning rate of specific Ar ions to a target material, and then quantitative polishing and thinning of the target material film are carried out to obtain the target material film with the micron thickness required by target piece preparation

According to an embodiment of the method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment, in the step B, a target material film is quickly transferred to a high-vacuum focused ion beam system, proper voltage and beam current are selected after the cutting rate and precision of the focused ion beam on the target material film under different voltages and beam currents are determined, and a target sheet required by impedance matching target preparation is cut on the target material film by the focused ion beam, wherein the ion beam current of the target material film cut by the focused ion beam is 40-80 nA, and the voltage is 10-50 kV.

According to an embodiment of the method for preparing a focused ion beam of the impedance matching target for laser equation of state experiments, in step B, the ion source of the focused ion beam is a liquid metal ion source or a gaseous ion source, and the target sheet is rectangular, circular or triangular.

According to one embodiment of the method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment, in step C, a manipulator is contacted with a target in a focused ion beam system, the target and the manipulator are fixed together by a platinum deposition method assisted by the focused ion beam, and the movement of the target and the precise alignment between the target and a standard material step are realized through the precise movement of the manipulator, wherein the step length of the manipulator is controlled to be more than 30 mu m/step at the beginning stage of the target transfer process, the step length of the manipulator is controlled to be less than 5 mu m/step at the end stage of the target transfer process, and the step length of the manipulator is controlled to be less than 1 mu m/step in the precise alignment process of the target.

According to one embodiment of the method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment, in step D, after the target sheet is accurately aligned with the step of the standard material, the target sheet and the standard material substrate are fixed together by using a platinum deposition method assisted by the focused ion beam, so as to complete the integral assembly of the impedance matching target, wherein the assembly of the target sheet is realized by performing platinum deposition on the edge or corner of the target sheet.

According to an embodiment of the method for preparing a focused ion beam of the impedance matching target for laser equation of state experiments, in step E, the size detection is performed by combining a scanning electron microscope with white light interference detection or by using a step profiler.

According to one embodiment of the preparation method of the focused ion beam of the impedance matching target for the laser equation of state experiment, when the size detection is performed by combining a scanning electron microscope and white light interference detection, the in-situ size detection of a target sheet and a micro-target is performed by using a nano-resolution scanning electron microscope equipped in a focused ion beam system; and (4) taking out the formed micro target, detecting the sizes of the target sheet and the micro target by using a white light interference method, and confirming that the target design requirements are met.

Compared with the prior art, the novel target making method based on the focused ion beam can effectively solve the problems in the traditional target preparation process, realize the obvious improvement of the processing precision of the impedance matching target, obviously improve the preparation yield of the micro-target, reduce the labor intensity and the oxidation degree of the high-activity material target, improve the reliability of detection data, and can also carry out the preparation of the high-precision complex target type micro-target on the basis of improving the precision.

Drawings

Fig. 1 shows a schematic structural diagram of an impedance matching target for laser equation of state experiments.

Fig. 2 a to d are schematic diagrams illustrating a process of preparing a thin film of a target material in a method of preparing a focused ion beam of an impedance matching target for laser equation of state experiments according to an exemplary embodiment of the present invention.

Fig. 3 a to h are diagrams illustrating a path of preparing an impedance matching target based on a focused ion beam in a focused ion beam preparation method of an impedance matching target for laser equation of state experiments according to an exemplary embodiment of the present invention.

Detailed Description

All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.

Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.

The method is used for preparing the impedance matching target for the laser state equation experiment based on the focused ion beam technology, so that the method can be suitable for preparing the high-precision complex target.

The following describes the method for preparing the focused ion beam of the impedance matching target for the laser equation of state experiment in detail with reference to the accompanying drawings.

Fig. 2 a to d are schematic diagrams illustrating a process of manufacturing a target material thin film in a method of manufacturing a focused ion beam of an impedance matching target for laser equation of state experiments according to an exemplary embodiment of the present invention, and fig. 3 a to h are schematic diagrams illustrating a path of manufacturing an impedance matching target based on a focused ion beam in a method of manufacturing a focused ion beam of an impedance matching target for laser equation of state experiments according to an exemplary embodiment of the present invention.

According to an exemplary embodiment of the present invention, the method for preparing a focused ion beam of an impedance matching target for laser equation of state experiments includes the following steps.

In the step A, a target material film with the thickness of several microns is prepared from the material to be detected by a thinning method.

In this step, the thinning method may be a polishing and Ar ion polishing thinning method, a reactive ion etching thinning method, or an inductively coupled plasma etching thinning method, and different thinning methods may be adopted depending on the specific material. Wherein the thickness of the target material film is preferably 6-15 μm, and the two-dimensional size is preferably 50-200 μm.

Fig. 2 a to d are schematic diagrams illustrating a process of preparing a thin film of a target material in a method of preparing a focused ion beam of an impedance matching target for laser equation of state experiments according to an exemplary embodiment of the present invention. Wherein, a diagram shows a target material slice obtained by wire-electrode cutting of a material to be measured, the thickness d₁Less than or equal to 1 mm; b shows a slice of target material after polishing with coarse sandpaper, thickness d₂Less than or equal to 40 mu m; c shows the target material film after thinning with fine sandpaper, thickness d₃Less than or equal to 20 mu m; d is a thickness d of the final target material film after polishing with Ar ions_tA few microns (see target design requirements specifically).

As shown in fig. 2, taking the thinning method as a grinding and polishing method and an Ar ion polishing thinning method as an example, the method may specifically include the following sub-steps:

(1-1) cutting the material to be tested into target material slices with the thickness less than or equal to 1 mm. The material to be measured can be Fe, Al, W, Ce, La, Zr and other materials.

(1-2) polishing the thickness of the sheet of target material to below 40 μm using coarse sandpaper to facilitate subsequent fine grinding with fine sandpaper, for example 400# to 800# silicon carbide sandpaper.

(1-3) the thickness of the target material thin film is reduced to 20 μm or less by using fine sandpaper, for example, by using diamond sandpaper having a particle size of 3 μm. Usually thinned until crimping is imminent, depending on the particular material d₃There will be a difference.

And (1-4) polishing and thinning by utilizing Ar ions to obtain a target material film with the required micron thickness for preparing the target piece, specifically, firstly polishing and thinning by utilizing wide-beam Ar ions and combining a white light interference detection method to obtain the thinning rate of specific Ar ions to the target material, and then quantitatively polishing and thinning the target material film to obtain the target material film with the required micron thickness for preparing the target piece.

The Ar ion polishing and thinning in the invention can prepare the target material film with the required micron thickness, can effectively control the thickness of the film and reduce the labor intensity, and the polishing and thinning under high vacuum can effectively prevent the material from being oxidized. Compared with the method for preparing the target material film by grinding and polishing, the Ar ion etching method can effectively reduce the surface stress of the film and prevent the film with the thickness of several microns from curling and deforming.

Then, key steps B to E of preparing an impedance matching target based on the focused ion beam are performed.

Fig. 3 a to h are diagrams illustrating a path of preparing an impedance matching target based on a focused ion beam in a focused ion beam preparation method of an impedance matching target for laser equation of state experiments according to an exemplary embodiment of the present invention. Wherein, a illustrates transferring the prepared target material film into a high vacuum focused ion beam system and performing focused ion beam cutting of the target wafer, and b illustrates fixing the target wafer to a robot by ion beam assisted platinum deposition; the figure c shows that the target plate is driven to move by the movement of the mechanical arm; d-diagram shows the target plate being moved over the standard material step using a robot; e-diagram shows the precise alignment between the target and the standard material step by the high precision movement of the robot; f illustrates the assembly between the target and the standard material step using ion beam assisted platinum deposition; g-diagram shows in-situ measurement of micro-target size using a scanning electron microscope in a focused ion beam system; h shows the final detection of the micro-target size using white light interferometry, ensuring that the target design requirements are met.

In step B, after the target material thin film is obtained, the target material thin film is cut into target pieces by using a focused ion beam. The length of the target sheet is more than 200 μm, and the width is more than 100 μm, so as to meet the requirements of target design and laser loading equation of state experiments.

Wherein, the ion source of the focused ion beam can be a liquid metal ion source or a gaseous ion source, such as a Ga ion beam; the shape of the target sheet can be in different shapes such as rectangle, circle or triangle, and is specifically adjusted according to the target design.

As shown in a diagram in fig. 3, during operation, the target material film is rapidly transferred to a high vacuum focused ion beam system, after determining the cutting rate and precision of the focused ion beam to the target material film under different voltages and beam currents, a proper voltage and beam current are selected, and a target sheet required by the preparation of the impedance matching target is cut on the target material film by the focused ion beam. Wherein the ion beam current of the focused ion beam cutting target material film is 40-80 nA, and the voltage is 10-50 kV; the current is preferably 47nA, and the voltage is preferably 20-30 kV.

The invention cuts the target sheet by focusing the ion beam, and can realize high-precision cutting of the target sheet by utilizing the ion beam focused to the nanometer scale. The cutting process is an automatic controllable process, the cutting precision and efficiency are improved, the invalid area of the target step edge is effectively reduced, and the target slice cutting success rate is also improved to be close to 100%. One target material film can be used for cutting and subsequent assembly of a plurality of target pieces, thereby saving the consumption of the target material and saving the target manufacturing cost.

In step C, the target is transferred to a prepared step of standard material, typically Al, using a robot associated with a focused ion beam and precisely aligned.

As shown in fig. 3 b to e, in the focused ion beam system, the robot arm is first contacted with the target, the target and the robot arm are fixed together by using a focused ion beam assisted platinum deposition method, and the movement of the target and the precise alignment between the target and the step of the standard material are realized by the precise movement of the robot arm.

The step length of the manipulator is controlled to be larger than 30 mu m/step at the beginning stage of the target piece transferring process so as to improve the transferring efficiency, the step length of the manipulator is controlled to be smaller than 5 mu m/step at the end stage of the target piece transferring process so as to prevent the target piece from colliding with a standard material step, the step length of the manipulator is controlled to be smaller than 1 mu m/step in the accurate aligning process of the target piece so as to ensure the accurate alignment of the target piece and the standard material step, and the step length can be changed according to the requirements of accuracy and efficiency.

By transferring and aligning the target by using the manipulator, the target can be accurately aligned with the step of the standard material by using the moving step length of the manipulator in hundreds of nanometers, and the target alignment precision in nanometer scale can be realized. Therefore, the width of the groove between the step of the standard material and the step of the target to be tested can be effectively controlled, and the success rate of subsequent target assembly is facilitated.

In step D, assembling the target wafer by using a focused ion beam assisted thin film deposition method to obtain the micro target.

After the target and the standard material step are precisely aligned, the target and the standard material substrate are fixed together by using a focused ion beam assisted platinum deposition method to obtain the micro target, as shown in the f diagram in fig. 3. The assembly of the target is preferably achieved by platinum deposition at the edges or corners of the target. In order to achieve close contact between the target and the substrate, a robot may be used to apply pressure to the target to increase the contact between the target and the substrate.

In the target sheet assembling process, preferably, the voltage and the beam current of the focused ion beam when the platinum deposition rate is higher are firstly searched out so as to improve the assembling efficiency; during assembly, a manipulator is used for pressing the target piece and then platinum deposition is carried out so as to improve the close fit degree between the target piece and the aluminum substrate.

The target sheet assembly is carried out by utilizing the focused ion beam to assist the film deposition, so that the whole assembly process can be monitored in real time, the target sheet and the substrate can be ensured to be tightly fixed and attached, and the target assembly success rate is improved.

And step E, carrying out size detection on the target sheet and the assembled micro target to complete the preparation of the impedance matching target.

The size detection in the step can be realized by combining a scanning electron microscope with white light interference detection or by adopting a step profiler.

As shown in g and h in fig. 3, when the size detection is performed by combining a scanning electron microscope and white light interference detection, the in-situ size detection of the target sheet and the micro-target is performed by using a nanometer resolution scanning electron microscope equipped in a focused ion beam system; and (4) taking out the formed micro target, detecting the sizes of the target sheet and the micro target by using a white light interference method, and confirming that the target design requirements are met. The scanning electron microscope belongs to in-situ detection, and mainly obtains plane size so as to confirm that the next white light interference detection is not needed; the white light interference detection needs to obtain plane size information and thickness information as a criterion for judging whether the overall assembly of the micro-target is qualified or not.

After the target piece is cut, whether the size of the primary target piece meets the requirement needs to be detected, and after the target piece is assembled on the substrate, whether the size of the primary target piece meets the requirement needs to be detected again, because the size of the target piece is very small, the size of the target piece can be damaged in the assembling process; the thickness of the substrate and the step of the micro target needs to be detected, the positioning of the target sheet on the substrate also needs to be detected, the positioning of the target sheet on the substrate refers to the width of the groove (generally about 100 mu m), and whether the final positioning is qualified or not is determined according to the sizes of the target sheet, the substrate and the step in the delivered assembled micro target and whether the positioning of the target sheet meets the requirements or not.

Wherein the two-dimensional size of the micro-target substrate is 100-6000 μm, preferably 5000 μm, and the thickness of the micro-target substrate is 30-500 μm, preferably 50-60 μm. Wherein the detection range of the three-dimensional size of the prepared scanning electron microscope is 0.001-500 mu m; the two-dimensional size detection range of the plane of the white light interferometer is 1-20000 mu m, the thickness detection range is 0.01-100 mu m, and the thickness detection range is limited.

The invention carries out micro-target size detection by combining the in-situ scanning electron microscope with a subsequent white light interference method, and can further ensure the reliability of detection data. The in-situ scanning electron microscope detection can be used for effective screening to determine whether to enter a subsequent white light interference detection procedure.

In addition, most processes of the preparation method are operated in a high vacuum environment, so that the target material can be effectively prevented from being oxidized, and after the target precision is promoted, the method is favorable for the complexity and diversification improvement of the target type.

In conclusion, the impedance matching target manufacturing method for the laser state equation experiment based on the focused ion beam technology can obviously improve the processing precision of the impedance matching target, obviously improve the yield of the target, reduce the labor intensity and the target oxidation degree, and can increase the reliability of detection data and perform the preparation of high-precision complex target types.

The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.