JPH02207443A - Ion beam device - Google Patents

Abstract

PURPOSE:To disable foul particles to approach the inner face of a solid insulator even when a jumping movement of foul particles is repeated by forming electrodes to be arranged in multiple steps in a prescribed form. CONSTITUTION:Electrodes 10, 11 and 12 for ion pullout or acceleration in the vacuum atmosphere are arranged in multiple steps while solid insulators 3 are interposed between respective mutually adjacent pairs of them. The shape of each electrodes is so formed that an interval between mutually opposing adjacent electrodes may form a part widening on the side of an ion running path from the respective solid insulators in the peripheral direction around the ion running path for instance, broken line shape in multiple steps where the sectional shapes of the respective electrodes enlarge their tilting angles successively in the axial direction. Thereby, a wall of an electric line of force convexly curing from the solid insulator side to the ion running path side so that foul particles are shifted in the direction of a weak electric field while performing jumping movement.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an ion implanter used in a semiconductor manufacturing process, etc., in which an electrode for extracting or accelerating or decelerating ions in a vacuum atmosphere is connected in the direction of ion extraction. Alternatively, the present invention relates to an ion beam device having an electrode system arranged in multiple stages with solid insulators interposed in the acceleration/deceleration direction.

[Conventional technology]

FIG. 4 is a schematic diagram showing an example of a conventional electrode system configuration for accelerating and decelerating ions in a vacuum atmosphere. The vacuum container that forms the vacuum atmosphere consists of a high pressure housing 1 degree and a low pressure housing 2 degrees. It is formed using a solid insulator 3, and is provided with an ion source and a vacuum evacuation device, etc., although not particularly shown, in this vacuum container. The electrode system that accelerates and decelerates ions is a high-voltage electrode 4. Medium voltage electrode5. The ion beam 7 coming from the left in the figure has a low voltage electrode 6, which is fixed in position by a solid insulator 3 and insulated from each other.
The ion beam accelerates and decelerates to the right due to the action of the electrostatic field formed by the electrode system, and in order to prevent the vacuum-side creeping surface of the solid insulator 3 from being contaminated, the creeping surface is directly visible from the ion beam travel path as shown in the figure. Generally, each electrode is formed into a cylindrical shape and arranged coaxially to prevent this. Note that contamination is mainly caused by sputtered particles generated when the ion beam hits an electrode or the like.

[Problem to be solved by the invention]

Generally, when an ion beam hits an electrode or housing, metal atoms are generated by sputtering, which travel straight in a vacuum atmosphere and collide with and adhere to structures. These attached atoms accumulate over time and eventually separate into fine particles. This deposition and separation occur everywhere in the vacuum chamber, but when the deposition occurs between the electrodes, as shown in Figure 3, the electric field is concentrated at the tip of the particle, and an electrostatic force acts in the direction of the electric field. .

Here, the reference numeral 8 means one electrode surface. in particular,
If the electric field in the direction perpendicular to the particle surface is E, then the electrostatic stress P-□Black. Elayu: Vacuum permittivity occurs, and when particle surface area is taken into account, electrostatic force ΔF-□. E8Δ
SAS:ll small area acts. By determining this over the entire particle surface, the vertical electrostatic force acting on the particle is determined.

This electrostatic force increases the average electric field E0 in the electric field space by 10'V/m (
IKV/m), for example, a zero particle that is large enough to lift a steel ball with a diameter of 50μ receives and takes away a true charge from the electrode when it floats, but the lifted particle collides with the counter electrode. It loses its charge and now receives a charge of the opposite polarity and descends. As the jumping motion is repeated in this way, a part of it finally reaches the inner surface of the solid insulator and stains the inner surface, resulting in a decrease in withstand voltage.

Since the generation of contamination particles and their jumping motion are unavoidable, an object of the present invention is to construct an electrode system in which contamination particles cannot approach the inner surface of a solid insulator even if the jumping motion is repeated.

[Means to solve the problem]

In order to solve this problem, in the present invention, each electrode constituting the electrode system is arranged so that the opposing distance between adjacent electrodes widens from the solid insulator side to the ion traveling path side in the circumferential direction around the ion traveling path. A wall of electric lines of force curved convexly from the solid insulator side to the ion travel path side is formed in this portion.

[Effect]

If each of the electrodes constituting the electrode system is formed in this way and a wall of electric lines of force curves convexly from the solid insulator side toward the ion travel path within the opposing spacing between the electrodes, contamination particles will Centrifugal force acts on the contamination particles as they try to make a jumping motion along the lines of electric field inside the solid insulation material, and each time the contamination particles jump, they move away from the solid insulator and can enter inside the curved wall of the electric field. This is not possible, and as a result, the contamination particles that try to move towards the solid insulator are solid 1! I The inner surface of the green material cannot be approached, and the inner surface of the solid insulator is kept clean.

〔Example〕

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

In the figure, the same members as in FIG. 4 are designated by the same reference numerals, and their explanations will be omitted. High voltage electrode 10. Medium voltage electrode 11. Low voltage electrode 12
In each case, the cross-sectional shape is a multi-step polygonal line shape with a gradually increasing inclination angle in the axial direction.

Sputtered particles can attach near the tip of each electrode, but the electric field strength on the way from that part to the solid insulator increases as it approaches the solid insulator, and this causes the electric field space between adjacent electrodes to increase. The wall of the electric line of force curves convexly from the solid insulator side to the ion travel path side.
By changing the slope of any one of the polygonal lines in the cross section of each electrode, in this example, the portion A in the opposing interval of each electrode,
It is formed in B. In other words, with such an electrode configuration, as shown in Figure 2, the electric force 1 (dashed line in the figure) is curved convexly toward a weaker electric field, so the sputtered particles are not affected by electricity at the sputtering speed at which they are generated. Even if the lines of force try to penetrate the wall and move toward the solid insulator, after colliding with the electrode surface,
It moves while receiving a force along the convexly curved lines of electric force, and simultaneously receives a centrifugal force due to this movement, so it sequentially shifts toward the weak electric field while performing a jumping motion (solid line arrow in the figure). In the case of FIG. 1, the sputtered particles move toward the tip of each electrode and are finally collected inside the high-voltage electrode 10 or in the low-voltage housing 2 where there is no electric field.

Although only one example has been described here as an embodiment of the invention, the content of the present invention is not limited to the shape shown in FIG. The object of the invention can also be achieved by providing an electrode shape such that the lines of electric force are convex in the direction, for example, by providing mutually sloped flat plate electrodes. Further, although the explanation has been given using a three-electrode configuration as an example, the number of electrodes is not limited.

(Effects of the Invention) As described above, in the present invention, each electrode constituting the electrode system is connected to a portion where the opposing distance between adjacent electrodes widens from the solid insulator side to the ion travel path side. By forming the wall in the circumferential direction, a wall of electric lines of force that curves convexly from the solid insulator side to the ion travel path side is formed in this part, so that the stubble that occurs near the tip of each electrode is eliminated. Even if the particles try to penetrate the wall of the electric field lines and move towards the solid insulator at the sputtering speed at which they are generated, once they collide with the electrode surface, they will exert force along the convexly curved electric field lines. As it moves while receiving centrifugal force and is simultaneously subjected to centrifugal force due to this movement, it is sequentially shifted towards a weaker electric field while making a jumping motion, and cannot approach the solid insulator.As a result, the inner surface of the solid insulator is always clean. kept,
A decrease in withstand voltage can be prevented without increasing the size of the device or increasing costs.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing an embodiment of the present invention, Figure 2 is a conceptual diagram showing the behavior of fine particles in the present invention, Figure 3 is a state diagram of fine particles in contact with an electrode, and Figure 4 is a diagram of the conventional It is a schematic diagram of an acceleration tube. 3: Solid insulator, 4, 5.6, 8, 10.11, 12.
20, 21: Electrode, 7: Ion beam, 22: Electric force line. 4111fu 11?1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1) In an ion beam device having an electrode system in which electrodes for extracting or accelerating or decelerating ions in a vacuum atmosphere are arranged in multiple stages via solid insulators in the direction of extracting or accelerating or decelerating ions, the electrodes Each of the electrodes constituting the system is formed in such a way that a portion where the opposing distance between adjacent electrodes widens from the solid insulator side to the ion travel path side is formed in the circumferential direction around the ion travel path, and the solid insulator is applied to this portion. An ion beam device characterized in that a wall of electric lines of force is formed that curves convexly from the side toward the ion travel path.