A magnetic lens confined focused reactive ion beam source

Abstract

The present invention belongs to the field of plasma technology, and specifically relates to a magnetic lens constrained focused reactive ion beam source. The present invention can obtain a focused ion beam with a normal ion energy distribution, and introduce reactive gas to achieve rapid removal of the surface damage layer of the optical element. The technical solution adopted by the present invention includes an anode, an outer cathode arranged above the anode, and a central cathode arranged in the middle of the ion source. The anode, outer cathode, and central cathode are irregular circular rings, an ion beam extraction gap is provided between the outer cathode and the central cathode, an ionization zone is provided between the anode, the outer cathode, and the central cathode, an ionization magnetic coil is provided on the outside of the anode, a working gas introduction device is provided below the central cathode, a magnetic lens central pole is provided above the central cathode, a reactive gas outlet hole is provided in the middle of the magnetic lens central pole, and the reactive gas is introduced into the magnetic lens central pole through the central cathode by a gas guide tube, a magnetic lens coil is provided on the periphery of the magnetic lens central pole, and a magnetic lens outer pole is provided above the magnetic lens coil.

Description

Technical Field

[0001] The invention belongs to the technical field of plasma equipment, and in particular relates to a magnetic lens confined focusing reaction ion beam source. Technical Background

[0002] High-resolution space optical systems, inertial confinement laser fusion, high-precision lithography machines, and military high-power laser systems require mass production of ultra-precision core optical components made of hard, brittle materials such as silicon carbide, sapphire, and fused quartz. Conventional machining processes are prone to forming surface and subsurface damage layers on these optical components. This damage layer causes scattering, degrades image quality, and shortens the component's lifespan. The challenge is to efficiently remove this damage layer while ensuring rapid surface shape convergence.

[0003] Focused ion beam polishing, with its efficient surface shape convergence speed and precision, has become the mainstream method for surface shape correction of medium- to large-aperture hard and brittle optical components. China still primarily imports and imitates foreign ion sources and related polishing technologies. Focused ion beam RF sources and microwave sources are currently the core devices for the mainstream polishing of medium- to large-aperture hard and brittle optical components both domestically and internationally. However, these ion sources use graphite as the grid and anode material. The introduction of reactive gases not only increases component wear but also easily contaminates the components during the etching process, reducing the surface quality and performance of the components. Without the introduction of reactive gases, the etching efficiency of this type of ion source is low, making it unsuitable for the rapid removal of damaged layers on optical components. More importantly, my country has been unable to obtain independent intellectual property rights for the discharge principle and structure of this type of RF source.

[0004] In addition to the focused ion beam radio frequency source and microwave source produced abroad, the existing technical solutions for focused ion beam sources also include focused Kaufman source and Hall anode layer ion source. For example, "an ion beam coating focused ion source" is disclosed in "CN211125568U", which adopts the Kaufman ion source structure. The technical problem is that it is still necessary to use a two-stage grid to form a focused ion beam. During operation, the grid material will still be sputtered by the ion beam to the surface of the workpiece, causing contamination. The "a focused linear anode layer ion source" disclosed in "CN110767522B", the "a focused anode layer ion source device" disclosed in "CN106653557A", and the "a gridless focused beam ion source" disclosed in CN117912922A all adopt the Hall anode layer ion source structure. The three have three common technical problems:

[0005] 1. Without further ion beam focusing and confinement devices, the Hall effect orthogonal electromagnetic field between the anode and cathode will cause the emitted ions to generate a deflection component in the vertical extraction direction, resulting in a funnel-shaped distribution of the extracted ion beam. The ion energy at the beam waist cannot form a normal distribution, and deterministic point removal cannot be achieved.

[0006] 2. The anode is not optimized. Anode optimization can compress the plasma distribution to the extraction gap and increase the density of the extracted ion beam;

[0007] 3. Without the introduction of reactive gas, it is impossible to simultaneously achieve conformal processing of optical components and rapid removal of damaged layers.

[0008] In view of the above problems, the focused Hall anode layer ion source has not yet been successfully applied to the processing of optical components. Summary of the Invention

[0009] The present invention provides a magnetic lens constrained focused reactive ion beam source to solve the problems that the current Hall anode layer ion source cannot obtain a focused ion beam with a normal distribution of ion energy, resulting in the inability to achieve deterministic point removal on the surface of optical components; the ion source does not introduce reactive gas, and cannot simultaneously meet the requirements of conformal processing of optical components and rapid removal of damaged layers.

[0010] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a magnetic lens constrained focusing reaction ion beam source, comprising a cylindrical shell arranged on a base plate, an anode, an outer cathode and a central cathode arranged in the cylindrical shell, a working gas introduction device arranged at the center of the base plate in the cylindrical shell, the central cathode arranged on the working gas introduction device, and the gap between the downward-inclined inner ring of the outer cathode and the upward-inclined inner ring of the central cathode relatively arranged is the ion beam extraction gap; an ionization zone is arranged between the anode and the outer cathode and the central cathode, an ionization magnetic coil is arranged on the inner side wall of the cylindrical shell, a magnetic lens central pole is arranged above the central cathode, a reaction gas derivation hole is arranged in the middle of the magnetic lens central pole, the reaction gas is introduced into the magnetic lens central pole by a gas guide tube through the central cathode, and then derivation is conducted by the derivation hole arranged in the magnetic lens central pole, and a magnetic lens coil and a magnetic lens outer pole are arranged in sequence from bottom to top on the upper part of the outer cathode.

[0011] Furthermore, the outer end surface of the central magnetic pole of the magnetic lens is tilted upward to form a Y shape, the air guide tube extends from the center of the bottom of the central magnetic pole of the magnetic lens, the inner end surface of the outer magnetic pole of the magnetic lens is tilted downward, the tilt angle is 0 to 50 degrees, and the tilted parts of the central magnetic pole of the magnetic lens and the outer magnetic pole of the magnetic lens are in the same conical surface.

[0012] Furthermore, the upper structure of the outer magnetic pole of the magnetic lens is the same as the upper structure of the outer cathode.

[0013] Furthermore, the width of the upper end surface of the anode is consistent with the width of the ion beam extraction gap.

[0014] Furthermore, the vertical distance from the inner end surface of the outer magnetic pole of the magnetic lens to the outer cathode is greater than the vertical distance from the inner end surface of the outer magnetic pole of the magnetic lens to the outer end surface of the center magnetic pole of the magnetic lens.

[0015] Furthermore, the angle of the reaction gas outlet hole in the central magnetic pole of the magnetic lens is set to 0 to 60 degrees.

[0016] Furthermore, the magnetic lens coil and the ionization magnetic coil are coreless electromagnetic coils, which are wound with insulating enameled wires with a diameter of more than 1 mm.

[0017] Furthermore, depending on different processing scenarios, the ion beam source adopts a cylindrical or rectangular design.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] 1. The structure of the present invention uses a magnetic lens to further constrain the drawn ion beam, so that the ion energy at the focus of the focused ion beam is normally distributed, solving the problem that the focused Hall ion source cannot be used for deterministic fixed-point processing of optical components.

[0020] 2. The present invention optimizes the anode structure so that the plasma distribution is concentrated at the extraction gap, which improves the ionization rate of the working gas on the one hand and the density of the extracted ion beam on the other hand.

[0021] 3. The present invention introduces reactive gas and adopts a design that separates working gas and reactive gas, which can effectively avoid the corrosion of the anode by the reactive gas, and fundamentally solves the problem that the filament electrode, graphite anode and grid in the existing mainstream Kaufman source and RF source are easily corroded and cannot be used for reactive etching.

[0022] 4. Since the present invention is based on the design of a gridless focused Hall anode layer ion source, it fundamentally solves the problem of contamination of the workpiece surface by the focusing grid during operation of existing radio frequency or microwave ion sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of a cylindrical magnetic lens confined focusing reactive ion beam source;

[0024] Figure 2 for Figure 1 A-direction view;

[0025] Figure 3 Schematic diagram of anode design

[0026] Figure 4 This is a schematic diagram of the design of the central magnetic pole of the magnetic lens;

[0027] Figure 5 A is the view in the direction of the rectangular source;

[0028] Figure 6 This is the ion beam distribution state diagram when the magnetic lens is not working;

[0029] Figure 7 This is a diagram of the ion beam distribution state when the magnetic lens is working.

[0030] Marking instructions: 1—anode, 2—outer cathode, 3—center cathode, 4—center magnetic pole of magnetic lens, 5—outer magnetic pole of magnetic lens, 6—magnetic lens coil, 7—ionization magnetic coil, 8—working gas introduction device, 9—reaction gas guide pipe. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. The technical solutions provided by each embodiment of the present invention are described in detail below in conjunction with the drawings.

[0032] The present invention provides a magnetic lens confined focusing reactive ion beam source, such as Figure 1-4 As shown, it includes a cylindrical shell arranged on the bottom plate, an anode 1, an outer cathode 2 and a central cathode 3 are arranged in the cylindrical shell, an ionization zone is arranged between the anode 1 and the outer cathode 2 and the central cathode 3, a working gas introduction device 8 is arranged at the center of the bottom plate in the cylindrical shell, a central cathode 3 is arranged on the working gas introduction device 8, a magnetic lens central pole 4 is arranged above the central cathode 3, an ionization magnetic coil 7 is arranged on the inner side wall of the cylindrical shell, a magnetic lens coil 6 and a magnetic lens outer pole 5 are arranged in sequence on the upper part of the outer cathode 2, a reaction gas lead-out hole is arranged in the middle of the magnetic lens central pole 4, the reaction gas is introduced into the magnetic lens central pole 4 through the central cathode 3 by the gas guide pipe 9, and then is led out by the lead-out hole arranged in the magnetic lens central pole 4, the outer end surface of the magnetic lens central pole 4 is inclined upward to form a Y shape, and the gas guide pipe 9 extends into the bottom center of the magnetic lens central pole 4.

[0033] The inner end surface of the outer magnetic pole 5 of the magnetic lens is tilted downward and is the same as the upper structure of the outer cathode 2, with an inclination angle of 0 to 50 degrees, and the inclined parts of the central magnetic pole 4 of the magnetic lens and the outer magnetic pole 5 of the magnetic lens are in the same cone surface; the vertical distance from the inner end surface of the outer magnetic pole 5 of the magnetic lens to the outer cathode 2 is greater than the vertical distance from the inner end surface of the outer magnetic pole 5 of the magnetic lens to the outer end surface of the central magnetic pole 4 of the magnetic lens, so that the magnetic field distribution of the magnetic lens is mainly concentrated between the inner end surface of the outer magnetic pole 5 of the magnetic lens and the outer end surface of the central magnetic pole 4 of the magnetic lens, which has a converging effect on the ion beam; the angle β of the reaction gas outlet hole in the central magnetic pole 4 of the lens is set to 0 to 60 degrees, such as Figure 4 shown.

[0034] The outer cathode 2 is provided at the inner step of the cylindrical shell. The anode 1, the outer cathode 2 and the central cathode 3 are irregularly shaped circular rings. The gap between the downwardly inclined inner ring of the outer cathode 2 and the upwardly inclined inner ring of the central cathode 3 is the ion beam extraction gap. An annular water cooling device is provided below the anode 1. Figure 1-3 shown.

[0035] The upper end surface of the anode 1 is tilted toward the center, the inner end surface of the outer cathode 2 is tilted downward, and the outer end surface of the central cathode 3 is tilted upward. The tilt angles of the upper end surface of the anode 1, the inner end surface of the outer cathode 2, and the outer end surface of the central cathode 3 are consistent, and the tilt angle α is 0 to 20 degrees. Figure 3 As shown, the outer cathode 2 and the central cathode 3 are inclined at the same conical surface. An ion beam extraction gap of 2-5 mm is provided between the outer cathode 2 and the central cathode 3. The width d of the upper end face of the anode 1 is consistent with the width of the ion beam extraction gap. The vertical distance from the anode 1 to the lower end face of the outer cathode 2 and the central cathode 3 at the inclined portion is set to 2-5 mm.

[0036] The above-mentioned anode 1 is connected to a high voltage of 500~5000V, the outer cathode 2, the center cathode 3, the center magnetic pole 4 of the magnetic lens and the outer magnetic pole 5 of the magnetic lens are grounded, the magnetic lens coil 6 and the ionization magnetic coil 7 adopt a coreless electromagnetic coil design, and are wound with insulating enameled wire with a diameter of more than 1mm. The magnetic lens coil 6 is wound with 200~300 turns, and the ionization magnetic coil 7 is wound with 100~200 turns. The working current of the magnetic lens coil 6 is 5~15A, and the working current of the ionization magnetic coil 7 is 2~10A.

[0037] The working gas is transported by the working gas introduction device 8 to the ionization zone arranged between the anode 1 and the outer cathode 2 and the central cathode 3. The working gas is ionized in the Hall orthogonal electromagnetic field formed by the anode 1 and the ionization magnetic coil 7 to form a plasma. Under the action of the anode high voltage, the ion beam is drawn out from the gap between the outer cathode 2 and the central cathode 3, and cascade collides with the reaction gas transported to the periphery of the central magnetic pole 4 of the magnetic lens through the reaction gas duct 9, generating a reaction ion beam. The reaction ion beam forms a focused reaction ion beam with a normal distribution of ion energy under the constraint of the magnetic field generated by the magnetic lens coil 6.

[0038] In this embodiment, the inclination angle α of the upper end face of the anode 1, the inner end face of the outer cathode 2 and the outer end face of the center cathode 3 is 10°, the ion beam extraction gap is set to 4 mm, the width d of the upper end face of the anode 1 is also 4 mm, the vertical distance from the anode 1 to the lower end face of the outer cathode 2 and the center cathode 3 at the inclination is set to 2.5 mm, the inclination angle of the outer end face of the center magnetic pole 4 of the magnetic lens and the inner end face of the outer magnetic pole 5 of the magnetic lens is 30°, the angle β of the reaction gas extraction hole in the center magnetic pole 4 of the magnetic lens is set to 45o, the anode 1 is connected to a voltage of 2000V, the magnetic lens coil 6 and the ionization magnetic coil 7 are wound with insulating enameled wire with a diameter of 1.2 mm, the magnetic lens coil 6 is wound with 250 turns, the ionization magnetic coil 7 is wound with 150 turns, the working current of the magnetic lens coil 6 is 10A, and the working current of the ionization magnetic coil 7 is 5A.

[0039] See also Figure 5 , the ion source can also adopt a rectangular design.

[0040] See also Figure 6 When the magnetic lens is not working, the ion beam has a certain focusing effect under the action of the tilt angles of the anode 1, the outer cathode 2 and the central cathode 3. The deflection caused by the Hall magnetic field makes the ion beam appear funnel-shaped, and the energy distribution of the ions at the center of the beam waist is low, and true focusing cannot be achieved.

[0041] See also Figure 7 When the magnetic lens is working, the magnetic field of the magnetic lens constrains the motion trajectory of the deflected ions, causing the ion beam to converge at one point.

[0042] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A magnetic lens confined focusing reaction ion beam source, comprising a cylindrical shell arranged on a bottom plate, an anode (1), an outer cathode (2) and a central cathode (3) arranged in the cylindrical shell, a working gas introduction device (8) arranged at the center of the bottom plate in the cylindrical shell, the central cathode (3) arranged on the working gas introduction device (8), and a gap between the downwardly inclined inner ring of the outer cathode (2) and the upwardly inclined inner ring of the central cathode (3) being arranged opposite to each other as an ion beam extraction gap; characterized in that: An ionization zone is provided between the anode (1) and the outer cathode (2) and the central cathode (3); an ionization magnetic coil (7) is provided on the inner side wall of the cylindrical shell; a magnetic lens central pole (4) is provided above the central cathode (3); a reaction gas outlet hole is provided in the middle of the magnetic lens central pole (4); the reaction gas is introduced into the magnetic lens central pole (4) through the gas guide tube (9) via the central cathode (3), and then is discharged through the outlet hole provided in the magnetic lens central pole (4); a magnetic lens coil (6) and a magnetic lens outer pole (5) are provided in sequence from bottom to top on the upper part of the outer cathode (2).

2. The magnetic lens confined focusing reactive ion beam source according to claim 1, characterized in that: The outer end surface of the central magnetic pole (4) of the magnetic lens is tilted upward to form a Y shape, the air guide tube (9) extends from the bottom center of the central magnetic pole (4) of the magnetic lens, and the inner end surface of the outer magnetic pole (5) of the magnetic lens is tilted downward at an inclination angle of 0 to 50 degrees, and the inclined parts of the central magnetic pole (4) of the magnetic lens and the outer magnetic pole (5) of the magnetic lens are located in the same conical surface.

3. The magnetic lens confined focusing reactive ion beam source according to claim 1 or 2, characterized in that: The upper structure of the outer magnetic pole (5) of the magnetic lens is the same as the upper structure of the outer cathode (2).

4. The magnetic lens confined focusing reactive ion beam source according to claim 3, characterized in that: The width of the upper end surface of the anode (1) is consistent with the width of the ion beam extraction gap.

5. The magnetic lens confined focusing reactive ion beam source according to claim 4, characterized in that: The vertical distance from the inner end surface of the outer magnetic pole (5) of the magnetic lens to the outer cathode (2) is greater than the vertical distance from the inner end surface of the outer magnetic pole (5) of the magnetic lens to the outer end surface of the central magnetic pole (4) of the magnetic lens.

6. The magnetic lens confined focusing reactive ion beam source according to claim 5, characterized in that: The angle of the reaction gas outlet hole in the central magnetic pole (4) of the magnetic lens is set to 0-60 degrees.

7. The magnetic lens confined focusing reactive ion beam source according to claim 6, characterized in that: The magnetic lens coil (6) and the ionization magnetic coil (7) are coreless electromagnetic coils, which are wound with insulating enameled wires with a diameter of more than 1 mm.

8. The magnetic lens confined focusing reactive ion beam source according to claim 7, characterized in that: Depending on different processing scenarios, the ion beam source adopts a cylindrical or rectangular design.

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