Novel ion transmission focusing device

Abstract

The invention discloses a novel ion transmission focusing device, and belongs to the technical field of ion transmission. The flow limiting device comprises a flow limiting hole and an octupole rod device, each flow limiting hole is a metal plate with a small hole in the center, the two flow limiting holes form a vacuum differential cavity, and certain direct-current voltage is applied to the flow limiting holes. The octupole rod device comprises two insulating positioning rings and eight conical electrode rods which are arranged at equal intervals to form a cone shape, the eight conical electrode rods are fixed through the insulating positioning rings, and the two ends of the octupole rod are connected with an ion source outlet and a mass selector inlet respectively; every four adjacent electrodes are connected through a copper sheet to form two electrodes, and the two electrodes apply two radio frequency voltages with the same amplitude and opposite phases through a power supply. The ion transmission system can be used for focusing and transmission of cluster beams, and effectively improves the beam density in a low vacuum environment. The whole device is simple in structure, easy to machine and low in cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of ion transport devices, and particularly relates to a novel ion transport focusing device. Background Art

[0002] As a new material structure between the microscopic and macroscopic, clusters are widely used in fields such as semiconductor devices, chemical catalysis, and precision instrument manufacturing, showing great development prospects and application values. The preparation of clusters generates atomic gas by magnetron sputtering technology. The atomic gas condenses into clusters in the condensation chamber, and the working pressure of the condensation chamber is above 100 Pa, while the working pressure of the mass selector requires high vacuum (<10 -3 Pa). Therefore, a transition device for transmitting ions between low vacuum and high vacuum environments is needed, and the emittance of the ion beam has a crucial impact on the sensitivity and resolution of the mass selector.

[0003] Traditional ion transport technologies include multipole rod transport, ion funnel transport, etc. The parallelly arranged multipole rods cannot focus the ion beam well; the ion funnel has an obvious mass discrimination effect on low mass-to-charge ratio ions, and the ion funnel has a large number of electrodes and a large capacitance, which requires a higher requirement for the RF power supply.

[0004] The ion transport system has a crucial impact on the production and preparation of clusters, especially for the transport of ion beams. The current ion transport devices have problems such as insufficient focusing ability and large beam emittance, which affect the yield of clusters. Summary of the Invention

[0005] To solve the above problems, the present invention discloses a novel ion transport focusing device. The system has a simple structure and can reduce the emittance of the beam, focusing the ion beam while maintaining high ion transport efficiency.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A novel ion transport focusing device, comprising

[0008] An inlet electrode and an outlet electrode, which are respectively arranged at both ends of the chamber to form a vacuum differential chamber;

[0009] Two current-limiting holes, which are respectively arranged at the centers of the inlet electrode and the outlet electrode to form an ion flight path;

[0010] An octupole device, comprising two insulating positioning rings for fixing electrodes and eight conical electrode rods arranged at equal intervals. The two ends of the eight conical electrode rods are fixed by the insulating positioning rings,

[0011] The octupole device is coaxial with the two current-limiting holes, the inlet electrode, and the outlet electrode.

[0012] In the above solution, the insulating positioning ring is a ring-shaped structure with eight holes inside.

[0013] In the above solution, the insulating positioning ring is made of polyether ether ketone material or ceramic material.

[0014] In the above solution, the wire is used to connect the conical rod and is fixed to the conical rod by screws.

[0015] In the above solution, the conical electrode rod is present at any position, and the ratio of the conical radius R to the radius r of the conical rod at this point is R / r = 3 / 1.

[0016] In the above solution, the diameter of the larger end of the conical electrode rod is greater than 2 mm, and the diameter of the smaller end is less than 1 mm.

[0017] In the above solution, according to a novel ion transport focusing device described in claim 1, the surface roughness of the conical electrode rod is within 0.7 microns.

[0018] In the above solution, the inner diameter of the current-limiting hole used to form the differential chamber is not greater than 2 mm, and its axis coincides with the axis of the conical octupole rod.

[0019] In the above solution, the ion transport focusing device further includes:

[0020] A radio frequency power supply module, connected to the conical octupole rod assembly; wherein two groups of electrodes are respectively applied with radio frequency voltages with the same amplitude and opposite phases;

[0021] A DC power supply module, connected to the inlet electrode and the outlet electrode formed by the current-limiting holes.

[0022] In the above solution, defining the vacuum degree before the inlet electrode as P1, the vacuum degree in the environment where the conical octupole rod is located as P2, and the vacuum degree after the outlet electrode as P3, then there is:

[0023] The beneficial effects of the present invention are:

[0024] The device has a simple structure, strong ion focusing ability, and high ion transmission rate, is applicable to the process of cluster production and preparation, and improves the deposition flux density of the beam current. Description of the Drawings

[0025] Figure 1 It is a structural diagram of the ion transport focusing device.

[0026] Figure 2 It is a schematic diagram of the ion advancing direction.

[0027] Figure 3 It is a device power connection diagram.

[0028] Figure 4It is a schematic diagram of the application of an ion transport focusing device of the present invention in a cluster beam system.

[0029] List of attached drawing reference numerals:

[0030] 1. Inlet electrode, 2. First insulating fixing ring, 3. Second insulating fixing ring, 4. Octupole device, 5. Outlet electrode. Detailed implementation manners

[0031] The present invention will be further clarified below in conjunction with the attached drawings and specific implementation manners. It should be understood that the following specific implementation manners are only used to illustrate the present invention and not to limit the scope of the present invention.

[0032] As shown in the figure, an ion transport focusing device according to the present invention enables the efficient transport of ions with a simple mechanical structure, and can focus the ions and reduce the emittance of the beam during the ion transport process.

[0033] Specifically, it includes

[0034] The inlet electrode 1 and the outlet electrode 5 are respectively arranged at both ends of the chamber to form a vacuum differential chamber;

[0035] Two current-limiting holes are respectively arranged at the centers of the inlet electrode and the outlet electrode to form an ion flight path;

[0036] The octupole device 4 includes two insulating positioning rings 2 and 3 for fixing the electrodes and eight conical electrode rods arranged at equal intervals. The two ends of the eight conical electrode rods are fixed by the insulating positioning rings.

[0037] In the above solution, it is defined that the vacuum degree in front of the inlet electrode 1 is P1, the vacuum degree in the environment where the conical octupole 4 is located is P2, and the vacuum degree behind the outlet electrode 5 is P3. Then there is:

[0038] Combined with the figure, the vacuum degree in front of the inlet electrode 1 is P1 = 20 Pa. Correspondingly, the vacuum degree in the environment where the flight path is located is about P2 = 0.2 Pa or lower than 0.2 Pa, and the vacuum degree behind the outlet electrode is about P1 = 0.001 Pa or lower than 0.001 Pa.

[0039] The inlet electrode 1 and the outlet electrode 5 of the present invention are circular wafers with an outer diameter of 24 mm, an inner diameter of the current-limiting hole of 2 mm, and a thickness of 2 mm.

[0040] Correspondingly, there is a conical octupole 4 on the ion flight path, and the octupole 4 is coaxial with the two current-limiting holes, the inlet electrode 1, and the outlet electrode 5; as Figure 1 shown, there is a gap between the inlet electrode 1, the outlet electrode 5, and the octupole device 4.

[0041] For further illustration, the inlet electrode 1 and the outlet electrode 5 form a vacuum differential cavity, and there is a gap with a reserved distance of 2 mm between both ends of the octupole 4 and the inlet electrode 1 and the outlet electrode 5.

[0042] During assembly, the diameter of the thin end of the cone formed by the eight conical rods 4 is about 1 mm, and the diameter of the thick end of the conical rod 4 is about 4 mm. In specific applications, the length of the conical octupole is about 60 mm. If it is shorter than this length, the ion cooling is insufficient, and if it is longer than this length, the ion kinetic energy is insufficient.

[0043] Specifically, in this embodiment, the outer diameter of the insulating positioning ring is 24 mm, the material is polyether ether ketone material, and a fixed arc for the conical octupole is provided inside to fix the octupole 4.

[0044] Specifically, in this embodiment, at any position of the conical rod, the ratio R / r of the conical radius R to the radius r of the conical rod at this point is 3 / 1. In actual machining, the surface roughness of the octupole 4 is not higher than 0.7 microns to avoid an additional electric field caused by insufficient surface roughness of the conical rod.

[0045] The eight conical electrode rods altogether form two groups of electrodes. Inside the same group of electrodes, the electrodes are connected by wires, and the wires connecting the conical rods can be fixed to the conical electrode rods with screws.

[0046] The RF power supply module applies an RF voltage to the two groups of electrodes of the octupole. The amplitudes of the two groups of RF voltages are the same, and the phases differ by 180°. Generally, the amplitude of the RF voltage is set below 200 V, and the RF frequency is about 1 MHz. At this parameter setting, the ion transmission rate of the conical octupole is relatively high.

[0047] The two DC power supply modules apply a DC voltage to the inlet electrode 1 and the outlet electrode 5 to guide ions through the conical octupole device. The magnitude of the DC voltage is about 10 V and should not be too high. An excessively high voltage will cause ions to be unable to enter the device due to the too high electric potential.

[0048] The power controller is placed outside the vacuum chamber, and the octupole 4, the inlet electrode 1, and the outlet electrode 5 are led out by wires. The sealing performance and installation convenience should be considered at the interface.

[0049] To further verify the characteristics of the ion transmission system of the present invention, the SIMION software is used to simulate the ion trajectory. During the simulation, the amplitude of the RF voltage is set to 400 V (peak-to-peak), the working pressure of the conical octupole is 0.4 Pa, and when the RF frequency is changed from 0.4 MHz to 2 MHz, the change in the ion transmission rate of the device is investigated. The initial kinetic energy of the ions is about 3 eV, and the collision between the ions and the buffer gas is a hard sphere collision. The simulation results of the ion transmission rate are as Figure 4As shown, appropriately increasing the radio frequency can improve the ion transmission rate of the device. However, when the radio frequency is higher than 0.8 MHz, further increasing the radio frequency has little effect on the ion transmission rate of the device.

[0050] While maintaining a high transmission rate, the device reduces the emittance of the beam through the action of the buffer gas. An ion beam with a smaller emittance has a higher beam quality and is more easily utilized by the mass selector device.

[0051] The present invention is applicable to the ion guiding of the first-stage vacuum system of a cluster beam transmission device, reducing the emittance of the beam while maintaining a high ion transmission efficiency, simultaneously compressing the radius of the beam, increasing the ion density of the beam, and thus increasing the deposition density of the beam. The device has a simple structure and is easy to assemble, and can also be applied to the field of mass spectrometry for ion transmission focusing.

[0052] It should be noted that the above content only illustrates the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements all fall within the protection scope of the claims of the present invention.

Claims

1. A novel ion transport focusing device, characterized in that, Comprising: An inlet electrode and an outlet electrode, respectively arranged at both ends of the chamber to form a vacuum differential chamber; Two current-limiting holes, respectively arranged at the centers of the inlet electrode and the outlet electrode to form an ion flight path; An octupole device, including two insulating positioning rings for fixing electrodes and eight conical electrode rods arranged at equal intervals, and both ends of the eight conical electrode rods are fixed by the insulating positioning rings; There is a gap between the inlet electrode, the outlet electrode and the octupole device; The octupole device is coaxial with the two current-limiting holes, the inlet electrode and the outlet electrode.

2. A novel ion transport focusing device according to claim 1, characterized in that, The insulating positioning ring is a ring structure with eight holes inside.

3. A novel ion transport focusing device according to claim 1, characterized in that, The insulating positioning ring is made of polyetheretherketone material or ceramic material.

4. A novel ion transport focusing device according to claim 1, characterized in that, The conductor is connected to the surface of the guide rod through a mechanical fastener.

5. A novel ion transport focusing device according to claim 1, characterized in that, At any position of the conical electrode rod, the ratio of the conical radius R to the radius r of the conical rod at this point is R / r = 3 / 1.

6. A novel ion transport focusing device according to claim 1, characterized in that, The maximum diameter of the conical electrode rod is not less than 2 mm, and the minimum diameter is not more than 1 mm.

7. A novel ion transport focusing device according to claim 1, wherein, The surface of the conical electrode rod is polished, and the surface roughness is controlled within 0.7 um.

8. A novel ion transport focusing device according to claim 1, characterized in that, The inner diameter of the current-limiting hole used to form the differential chamber is not greater than 2 mm.

9. A novel ion transport focusing device according to claim 1, characterized in that, The ion transport focusing device further includes: An RF power supply module, connected to the conical octupole device; wherein two groups of electrodes are respectively applied with RF voltages having the same amplitude and opposite phases; A DC power supply module, connected to the inlet electrode and the outlet electrode composed of the current-limiting holes, and the DC power supply module applies a DC voltage to the inlet electrode and the outlet electrode to guide ions to pass through the conical octupole device.

10. The novel ion transport focusing device according to claim 1, wherein Define the vacuum degree before the inlet electrode as P1, the vacuum degree in the environment where the conical octopole is located as P2, and the vacuum degree after the outlet electrode as P3. Then we have:

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