CN113363127A - Ion source extraction electrode system - Google Patents
Ion source extraction electrode system Download PDFInfo
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- CN113363127A CN113363127A CN202010147462.1A CN202010147462A CN113363127A CN 113363127 A CN113363127 A CN 113363127A CN 202010147462 A CN202010147462 A CN 202010147462A CN 113363127 A CN113363127 A CN 113363127A
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- electrode
- extraction
- electric field
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- ion source
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/02—Details
- H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
- H01J37/08—Ion sources; Ion guns
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/30—Electron-beam or ion-beam tubes for localised treatment of objects
- H01J37/317—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation
- H01J37/3171—Electron-beam or ion-beam tubes for localised treatment of objects for changing properties of the objects or for applying thin layers thereon, e.g. for ion implantation for ion implantation
Abstract
The invention discloses an ion source extraction electrode system which comprises a plasma electrode and an extraction electrode group, wherein the extraction electrode group sequentially comprises a first ground electrode, a suppression electrode and a second ground electrode in the beam advancing direction, the first ground electrode and the second ground electrode are grounded, the suppression electrode is connected with negative pressure, the plasma electrode is connected with positive pressure, an electric field between the plasma electrode and the first ground electrode is an extraction electric field, and the extraction electric field is used for controlling the curvature and the shape of a plasma extraction interface. And introducing another ground electrode as a shielding ground electrode for shielding and isolating the plasma electrode and the suppression electrode by an electric field, stably leading out the electric field and an electric field lens electric field, and controlling the curvature and the shape of a plasma leading-out interface so as to control the initial shape of the beam current, thereby obtaining an ideal beam current form.
Description
Technical Field
The invention relates to an extraction electrode system.
Background
With the development of ion implanters, the continuous improvement of productivity and the wide application of more fields (semiconductor integrated circuits, single crystal photovoltaic cells, panel displays and the like), new requirements are also provided for indexes of an ion source and a beam extraction system, and the beam current is increased while the beam width, the beam density uniformity, the controllability of a beam divergence angle (minimum aberration condition), the operation stability of the ion source and the like become the current problems to be overcome.
The traditional large beam current extraction system basically takes a three-electrode system as a main part and is generally called as a plasma electrode, a suppression electrode and a ground electrode. The main functions of the suppression electrode are as the name suggests, the suppression electrode has the functions of suppressing electrons from the downstream of the beam, protecting ion source components at high potential from being damaged by electron bombardment, and the other function of the suppression electrode is to realize the effect of an electric field lens by adjusting the voltage difference between the plasma electrode and the suppression electrode, and realize the control of the extraction (ion acceleration process) and the beam divergence angle of the beam on the beam. Under the condition of relatively low beam density, the spatial electric field disturbance generated by the ion beam is basically the same or slightly different than the electric field formed between the electrodes, and the beam is in a relatively balanced metastable state, but with the increase of the beam density, the spatial electric field generated by the ion beam and the electrode field form a complex comprehensive electric field together, and at the moment, the optical characteristics (focusing, diverging and aberration) of the beam are completely dependent on the comprehensive electric field, so that once a small change of the plasma, the beam or the electrode causes the comprehensive electric field to change suddenly and cannot be reversed, and the beam is completely out of control.
Disclosure of Invention
The invention aims to overcome the defect that an electric field of an extraction electrode system is difficult to accurately control in the prior art, and provides an ion source extraction electrode system capable of properly controlling a plasma extraction interface (plasma meniscus).
The invention solves the technical problems through the following technical scheme:
an ion source extraction electrode system is characterized by comprising a plasma electrode and an extraction electrode group, wherein the extraction electrode group sequentially comprises a first ground electrode, a suppression electrode and a second ground electrode in the beam advancing direction, the first ground electrode and the second ground electrode are grounded, the suppression electrode is connected with negative pressure, the plasma electrode is connected with positive pressure, an electric field between the plasma electrode and the first ground electrode is an extraction electric field, and the extraction electric field is used for controlling the curvature and the shape of a plasma extraction interface.
Preferably, the extraction electric field is adjusted by adjusting a distance between the first ground electrode and the plasma electrode.
Preferably, the first ground electrode is used for electric field shielding the plasma electrode to stabilize the extraction electric field.
Preferably, the electric field between the first ground electrode and the suppression electrode is an electric field lens electric field, and the first ground electrode is used for electric field shielding the suppression electrode to stabilize the electric field lens electric field.
Preferably, the equivalent electric field lens parameters of the extraction electrode group are adjusted by adjusting the voltage of the suppression electrode to control the divergence angle of the beam current.
Preferably, the extraction electrode group is integrally translatable in the beam advancing direction.
Preferably, the spacing between the first ground electrode and the suppression electrode is fixed, and the spacing between the suppression electrode and the second ground electrode is fixed.
Preferably, the suppression electrode and the second ground electrode are fixed, and the first ground electrode is translatable in a beam advancing direction.
Preferably, the suppression electrode is for preventing electrons from downstream of the beam current from passing through the aperture of the set of extraction electrodes and the aperture of the plasma electrode into the ion source.
Preferably, the shape of the plasma leading-out interface is divergence, parallelism or focusing of the beam in the beam transmission direction.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The positive progress effects of the invention are as follows: on the basis of three electrodes in the prior art, another ground electrode is introduced as a shielding ground electrode for electric field shielding and isolating a plasma electrode and a suppression electrode, an electric field and an electric field lens electric field are stably led out, and the curvature and the shape of a plasma leading-out interface are controlled, so that the initial shape of the beam is controlled, and an ideal beam form is obtained.
Even if the ion beam current changes instantaneously and the divergence angle jumps, the divergent beam current can be blocked by the shielding ground electrode, so that the phenomenon that the suppression power supply is overloaded and protected and the beam current extraction is interrupted due to the fact that the suppression electrode is irradiated by the beam current is avoided.
The voltage of the suppression electrode is adjusted, so that the equivalent electric field lens parameters of the extraction electrode group can be changed, and the control of the beam divergence angle is achieved.
The electrode extraction system has the advantage of single-parameter corresponding adjustment for large beam adjustment, the curvature and the shape of a plasma extraction interface are mainly influenced by the distance between a plasma electrode and an extraction electrode group, and the electric field lens effect of the extraction electrode group is only related to the voltage of a suppression electrode. Under the condition of adjusting the beam current, the beam current optimization adjusting method can be independently optimized, and the characteristic of circularly adjusting multiple adjusting parameters is not needed, so that the beam current optimization adjusting method is quicker, simpler and more convenient.
Drawings
Fig. 1 is a schematic diagram of an ion source extraction electrode system according to an embodiment of the invention.
Fig. 2 is a schematic diagram of an ion beam transported through an ion source extraction electrode system in accordance with an embodiment of the present invention.
Fig. 3 is a schematic diagram of a plasma extraction interface being a concave surface (beam focusing) according to an embodiment of the present invention.
Fig. 4 is a schematic view of a plasma extraction interface being substantially planar (beam parallel transport) according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a convex plasma extraction interface (beam divergence) according to an embodiment of the present invention.
Fig. 6 is a schematic diagram of an electric field simulation of an ion source extraction electrode system according to an embodiment of the invention.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
The technical solution of the present invention is described in a specific embodiment with reference to fig. 1 to 6. The ion source extraction electrode system comprises a plasma electrode 11 and an extraction electrode group 2, wherein the plasma electrode is in close contact with a plasma 100 in an ion source cavity, the plasma electrode 11 is arranged on the ion source cavity, and the electric potential of the plasma electrode determines the electric potential of the plasma. The extraction motor group 2 sequentially includes a first ground electrode 21, a suppression electrode 22, and a second ground electrode 23 in the beam advancing direction a, and in this embodiment, an upper and a lower equipotential electrodes are used to form each electrode in the extraction electrode group. The material of the electrode is selected from high-temperature rare metal materials, such as tungsten and molybdenum. In the case of an increasing electrode size, a high purity graphite material is also the electrode material of choice, considering cost and weight considerations. According to different practical application requirements, the electrode can also adopt the combination of high-temperature nonferrous metal and graphite. The plasma electrode 11 has an opening 10 at the center for passing a beam, and similarly, the first ground electrode 21, the suppression electrode 22, and the second ground electrode 23 also have an opening 20 at the center for passing a beam. The ion source extraction electrode system described in this embodiment is suitable for electrodes with various opening shapes, for example, for opening a slit electrode, an extracted beam is in a strip shape (a wide beam), a long side direction of the beam is a direction perpendicular to the paper surface in fig. 1, and a short side direction of the beam is a direction perpendicular to a in the paper surface. For circular hole electrode openings, the electrode openings are shown as circularly symmetric structures. This structure is also applicable to the mesh-like extraction electrode.
The first ground electrode 21 and the second ground electrode 23 are grounded, the suppression electrode is connected with negative voltage, the plasma electrode is connected with positive voltage, an electric field between the plasma electrode 11 and the first ground electrode 21 is an extraction electric field, and the extraction electric field is used for controlling the curvature and the shape of a plasma extraction interface. The extraction electric field is adjusted by adjusting the distance between the first ground electrode 21 and the plasma electrode 11. The first ground electrode 21 serves to electric field shield the plasma electrode to stabilize the extraction electric field. In this solution, grounding the first ground electrode 21 ensures that its potential is fixed and always at 0 volts. Compared with other electrodes controlled by a power supply, the voltage control of the electrodes is limited by the output power, the maximum current and the like of the power supply, and the problem of power supply overload is often encountered, so that the output voltage of the power supply is out of control, the beam current state is out of control, and the recovery cannot be realized. The technical scheme of the invention well avoids the problem.
The electric field between the first ground electrode 21 and the suppression electrode 22 is an electric field lens electric field, and the first ground electrode 21 is used for electric field shielding the suppression electrode 22 to stabilize the electric field lens electric field. The equivalent electric field lens parameters of the extraction electrode group are adjusted by adjusting the voltage of the suppression electrode 22 so as to control the divergence angle of the beam current. Referring to fig. 2, it is desirable to obtain a beam 3 traveling substantially parallel in the beam advancing direction, instead of the beam 31 having a large divergence angle, it is necessary to adjust the voltage of the suppression electrode 22 so that the divergence angle is controlled within a desired range. Specifically, the voltage of the suppression electrode is adjusted, so that the equivalent electric field lens parameters of the extraction electrode group can be changed, and the control of the beam divergence angle is achieved. Because the divergence, collimation and focusing characteristics of the beam mainly depend on the shape of a plasma emission surface (also called plasma meniscus), only an extraction electrode group formed by combining a first ground electrode 21, a suppression electrode 22 and a second ground electrode 23 which are used as shielding ground electrodes forms an electric field lens, the parameters of the electric field lens can be changed by adjusting the voltage of the suppression electrode, and the optical characteristics of the beam can be optimized.
Specifically, the extraction electrode group 2 is integrally translatable in the beam advancing direction.
One way is that the spacing between the first ground electrode 21 and the suppressor electrode 22 is fixed, and the spacing between the suppressor electrode 22 and the second ground electrode 23 is fixed. It is only necessary to integrally translate the extraction electrode group to adjust the interval between the first ground electrode 21 and the plasma electrode 11 to control the curvature and shape of the plasma extraction interface.
Alternatively, the suppression electrode 22 and the second ground electrode 23 are fixed, and the first ground electrode 21 is translatable in the beam advancing direction. The curvature and shape of the plasma-extracting interface can be adjusted by just moving the first ground electrode 21 at this time. Since in an ion implantation apparatus both the ion source and the beam transport system operate under vacuum, and the control apparatus is generally disposed in an atmospheric environment, the fewer objects that need to be moved is a design advantage for the connection between the control apparatus and the vacuum system.
In addition to controlling the divergence angle of the beam, the suppression electrodes serve to prevent electrons from the beam downstream from passing through the aperture of the set of extraction electrodes and the aperture of the plasma electrode into the ion source.
Referring mainly to fig. 3-5, the plasma extraction interface is shaped as either divergent (convex in fig. 5), parallel (fig. 4) or focused (concave in fig. 3) beam in the direction of beam travel. Specifically, since the first ground electrode 21 is held at a stable potential (0 v) and the ion energy determines the potential of the plasma electrode 11, the ion beam extraction electric field between the two potential-determining electrodes is adjusted by the distance between the two electrodes. The beam geometry (divergence, parallelism, focusing) of the extracted ion beam depends on the plasma density and the extraction electric field strength. Under a certain working plasma density, the distance between the first ground electrode 21 and the plasma electrode 11 is adjusted, so that the extraction electric field can be adjusted, and the shape of a plasma emission surface (also called plasma meniscus) at the opening of the plasma electrode can be effectively changed. The space is reduced, the electric field is increased, the shape of the plasma emission surface is concave, and the ion beam has a focusing characteristic; gradually increasing the distance, flattening the shape of the emitting surface from concave, and enabling the ion beam to have the characteristic of parallel collimated beam current; further increasing the spacing causes the emitter surface to begin to change shape to a convex shape, at which point the ion beam becomes divergent.
In a conventional three-electrode system, voltages applied to different electrodes, such as a voltage of a plasma electrode (ion energy electron volt voltage) and a voltage of a suppression electrode (suppression voltage) and a plasma density, are relatively closely related to each other. One of the parameters changes and the other parameters need to be followed up for optimization. But after the first ground electrode 21 is inserted, the influence of the voltage of the suppression electrode 22 on the extracted beam is effectively isolated, which greatly simplifies the beam optimization operation.
Referring to fig. 6, the electric field distribution using the extraction electrode system of the present embodiment is simulated by ibsimulu simulation electric field (ibsimulu software is european JYFL laboratory development simulation software, and the calculation language is C + +) beam current simulation calculation. The abscissa is the reference distance of the beam propagation direction from the ion source and the ordinate is the electrode half-aperture dimension (dimension from the beam center to the edge of the electrode aperture, which represents the aperture circle radius if the aperture is circular, the ordinate represents the half-aperture width of the slot if the slot is open). The leftmost side is the plasma 100 reaction zone. In the simulation calculation, a positive voltage of 9kV was applied to the plasma electrode 11, and a negative voltage of-3 kV was applied to the suppression electrode.
The invention describes a large ion beam ion source extraction electrode system, which overcomes the problem of unstable control of an electric field of an ion source extraction electrode caused by large beams, thereby greatly improving the operation stability of the ion source and simultaneously meeting the requirements of ultra-wide beam amplitude, uniformity and small divergence angle.
While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that these are by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.
Claims (10)
1. An ion source extraction electrode system is characterized by comprising a plasma electrode and an extraction electrode group, wherein the extraction electrode group sequentially comprises a first ground electrode, a suppression electrode and a second ground electrode in the beam advancing direction, the first ground electrode and the second ground electrode are grounded, the suppression electrode is connected with negative pressure, the plasma electrode is connected with positive pressure, an electric field between the plasma electrode and the first ground electrode is an extraction electric field, and the extraction electric field is used for controlling the curvature and the shape of a plasma extraction interface.
2. The ion source extraction electrode system of claim 1, wherein said extraction electric field is adjusted by adjusting a spacing between said first ground electrode and said plasma electrode.
3. The ion source extraction electrode system of claim 1, wherein a first ground electrode is used to electric field shield said plasma electrode to stabilize said extraction electric field.
4. The ion source extraction electrode system of claim 1, wherein the electric field between the first ground electrode and the suppression electrode is an electric field lens electric field, the first ground electrode for electric field shielding the suppression electrode to stabilize the electric field lens electric field.
5. The ion source extraction electrode system of claim 4, wherein the equivalent electric field lens parameters of an extraction electrode set are adjusted by adjusting the voltage of said suppression electrode to control the beam divergence angle.
6. The ion source extraction electrode system of claim 1, wherein said set of extraction electrodes is integrally translatable in a direction of beam current travel.
7. The ion source extraction electrode system of claim 6, wherein the spacing between the first ground electrode and the suppression electrode is fixed, and the spacing between the suppression electrode and the second ground electrode is fixed.
8. The ion source extraction electrode system of claim 1, wherein the suppression electrode and the second ground electrode are fixed, and the first ground electrode is translatable in a direction of beam current travel.
9. The ion source extraction electrode system of any one of claims 1 to 8, wherein the suppression electrode is configured to prevent electrons from the beam downstream from passing through the aperture of the set of extraction electrodes and the aperture of the plasma electrode into the ion source.
10. The ion source extraction electrode system of any one of claims 1 to 8, wherein the plasma extraction interface is shaped to diverge, collimate or focus the beam in the direction of beam travel.
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| CN202010147462.1A CN113363127A (en) | 2020-03-05 | 2020-03-05 | Ion source extraction electrode system |
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| CN202010147462.1A CN113363127A (en) | 2020-03-05 | 2020-03-05 | Ion source extraction electrode system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117438265A (en) * | 2023-11-27 | 2024-01-23 | 青岛四方思锐智能技术有限公司 | Speed regulation deflection assembly and ion implanter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117438265A (en) * | 2023-11-27 | 2024-01-23 | 青岛四方思锐智能技术有限公司 | Speed regulation deflection assembly and ion implanter |
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