Metal ion source

Abstract

This invention provides a metal ion source that can easily achieve the high vacuum required in an electron beam emission chamber. [Solution] The metal ion source 1 comprises an electron beam emission chamber 2 equipped with an electron beam source 22 that emits an electron beam 21, a plasma generation chamber 3 having a raw material evaporation source 33 loaded with raw material 32, which evaporates the raw material 32 with the electron beam 21 and ionizes the evaporated raw material 32 gas to form a source plasma, and an ion beam extraction chamber 5 that extracts an ion beam from the source plasma. A linear electron gun is used as the electron beam source 22. A differential pressure chamber 4 through which the electron beam 21 passes is provided between the electron beam emission chamber 2 and the plasma generation chamber 3, and differential pumping is performed between the differential pressure chamber 4 and the electron beam emission chamber, and between the differential pressure chamber 4 and the plasma generation chamber 3.

Description

[Technical Field]

[0001] This invention relates to a metal ion source used in ion implantation equipment, ion beam etching equipment, thin film manufacturing equipment, and the like. [Background technology]

[0002] As metal ion sources that evaporate metals and other solid raw materials at room temperature, ionize the resulting raw material gas to form a plasma state, and extract an ion beam from the plasma, the following are known: Patent Documents 1 and 2 below. Patent Document 1 discloses a metal ion source in which a raw material evaporation chamber for evaporating the raw material and a plasma generation chamber for generating plasma from the raw material gas are separated by a partition wall, a solid raw material is evaporated with an electron beam emitted from a deflection-type electron gun placed in the raw material evaporation chamber, the evaporated gas is introduced into the plasma generation chamber to form a plasma state of the raw material gas, and an ion beam is extracted from this plasma.

[0003] Furthermore, Patent Document 2 discloses a metal ion source that integrates a raw material evaporation chamber and a plasma generation chamber to form an evaporation and plasma generation chamber, evaporates a raw material placed in the evaporation and plasma generation chamber with an electron beam emitted from a deflection type electron gun, plasmaizes this raw material gas with electrodes placed in the evaporation and plasma generation chamber, and extracts an ion beam from the plasma. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 4440304 [Patent Document 2] Patent No. 6178526 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In both ion sources described in Patent Documents 1 and 2, the evaporation of the raw material is not performed using resistance heating, but by irradiation with an electron beam from a deflection-type electron gun. Furthermore, plasma is generated in the plasma generation chamber or the evaporation and plasma generation chamber using PIG discharge. For plasma generation by PIG discharge, 10 -1 ~10 -2 While a vacuum of around Pa is required, the electron beam emission chamber where the electron gun is located requires a higher vacuum (10) than the plasma generation chamber to prevent discharge. -2 Pa~10 -5 A vacuum of approximately Pa is required. Patent document 2 describes providing a differential pumping structure between the evaporation / plasma generation chamber and the electron beam emission chamber (paragraph 0046), but since a deflection type electron gun is used, it is difficult to perform multi-stage differential pumping and is limited to a single-stage differential pumping. Therefore, it is difficult to achieve the high vacuum level required in the electron beam emission chamber.

[0006] Therefore, the present invention aims to provide a metal ion source that can easily obtain the high vacuum required in an electron beam emission chamber. [Means for solving the problem]

[0007] To achieve the above objectives, the present invention provides a metal ion source comprising an electron beam emission chamber equipped with an electron beam source for emitting an electron beam, a plasma generation chamber having a raw material evaporation source loaded with raw materials, which evaporates the raw materials with the electron beam and ionizes the evaporated raw material gas to form a source plasma, and an ion beam extraction chamber for extracting an ion beam from the source plasma, wherein the electron beam source is a linear electron gun, a differential pressure chamber through which the electron beam passes is provided between the electron beam emission chamber and the plasma generation chamber, and differential pumping is performed between the differential pressure chamber and the electron beam emission chamber, and between the differential pressure chamber and the plasma generation chamber.

[0008] In the present invention, since a linear electron gun that emits an electron beam in a linear direction is used, an electron beam emission chamber, a differential pressure chamber, and a plasma generation chamber can be arranged in a stacked state. Therefore, multiple-stage differential pumping can be easily realized, and the degree of vacuum in each chamber can be gradually increased toward the electron beam emission chamber side. As a result, while the plasma generation chamber is set to a low degree of vacuum suitable for plasma generation, it becomes easy to maintain the electron beam emission chamber at a high degree of vacuum such that arc discharge does not occur, and the metal ion source can be stably operated.

[0009] In this metal ion source, a plurality of differential pressure chambers can be arranged side by side along the emission direction of the electron beam, and the differential pressure chamber closest to the electron beam emission chamber can be evacuated by a cryopump.

[0010] This makes it easy to maintain the electron beam emission chamber at a high degree of vacuum.

[0011] Also, in this metal ion source, an ion beam can be drawn out horizontally from the ion beam extraction chamber.

[0012] By drawing out the ion beam horizontally in this way, the installation, maintenance, connection to various devices, etc. of the ion implantation device connected to the ion beam extraction chamber become easy.

Advantages of the Invention

[0013] As described above, according to the present invention, it is possible to provide a metal ion source that can easily obtain the high degree of vacuum required in the electron beam emission chamber.

Brief Description of the Drawings

[0014] [Figure 1] It is a cross-sectional view showing the overall configuration of the metal ion source according to the present invention.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the metal ion source 1 according to the present invention will be described based on FIG. 1.

[0016] As shown in FIG. 1, the metal ion source 1 of this embodiment includes an electron beam injection chamber 2, a plasma generation chamber 3, a differential pressure chamber 4, and an ion beam extraction chamber 5. The electron beam injection chamber 2, the plasma generation chamber 3, the differential pressure chamber 4, and the ion beam extraction chamber 5 are formed in a grounded vacuum vessel 6. In the embodiment shown in FIG. 1, the electron beam injection chamber 2 is arranged at the uppermost part of the vacuum vessel 6, the plasma generation chamber 3 is arranged at the lowermost part directly below it, and the differential pressure chamber 4 is arranged between the electron beam injection chamber 2 and the plasma generation chamber 3. Also, the ion beam extraction chamber 5 is arranged on the side of the plasma generation chamber 3. A plasma generation electrode 7 is arranged between the plasma generation chamber 3 and the ion beam extraction chamber 5.

[0017] An electron beam source 22 for injecting an electron beam 21 is arranged in the electron beam injection chamber 2. In this embodiment, as the electron beam source 22, a linear electron gun that injects the electron beam 21 in a straight line direction rather than a deflection type is used. During the operation of the metal ion source 1, the inside of the electron beam injection chamber 2 is evacuated by the first vacuum pump 23, and is maintained at a high vacuum of about 10 -2 Pa to 10 -5 Pa, which makes it difficult for arc discharge to occur. Specifically, the electron beam injection chamber 2 is maintained at a vacuum degree of 5×10 -3 Pa or higher. [[ID=#]]

[0018] In addition, a Wellner electrode 24 and an electron acceleration electrode 25 are arranged in the electron beam injection chamber 2. In the part of the vacuum vessel 6 that forms the electron beam injection chamber 2, a gauge port 26 for attaching a measuring element is provided.

[0019] In the plasma generation chamber 3, a raw material evaporation source 33 is arranged, which includes a hearth 31 and a solid raw material 32 loaded on the hearth 31. The raw material evaporation source 33 is arranged directly below the electron beam source 22 such that the electron beam 21 linearly emitted from the electron beam source 22 irradiates the raw material 32. A second vacuum pump 34 is connected to the plasma generation chamber 3. By driving this second vacuum pump 34, the plasma generation chamber 3 is maintained at a degree of vacuum suitable for plasma generation (which varies depending on the type of plasma generation electrode). For example, as described later, when a PIG electrode system is used as the plasma generation electrode 7, the inside of the plasma generation chamber 3 is maintained at a degree of vacuum of about 10 -1 Pa to 10 -2 Pa. Regardless of the type of the plasma generation electrode 7, the degree of vacuum in the electron beam emission chamber 2 is higher than that in the plasma generation chamber 3. The raw material 32 in the plasma generation chamber 3 is irradiated with an electron beam by passing the electron beam from the electron beam source 22 through the differential pressure chamber 4, and the raw material 32 is evaporated, so that the raw material gas diffuses into the plasma generation chamber 3.

[0020] In the plasma generation chamber 3, a reflecting plate 34 for reflecting plasma is arranged. In the part of the vacuum container 6 that forms the plasma generation chamber 3, a gauge point 35 for attaching a measuring element and an observation window 36 for observing the inside of the plasma generation chamber 3 are provided.

[0021] Between the plasma generation chamber 3 and the ion beam extraction chamber 5, for example, a PIG electrode system is arranged as the plasma generation electrode 7. The PIG electrode system includes a cathode 7a, a counter cathode 7c, and an anode 7b arranged between the two cathodes 7a and 7c and having a slightly larger diameter than the two cathodes 7a and 7c. The spaces located inside the circumferences of the respective electrodes 7a, 7b, and 7c are open to the plasma generation chamber 3. Each of the electrodes 7a, 7b, and 7c is connected to a heating power source arranged outside the vacuum container 6 and can be energized for heating. As the plasma generation electrode 7, in addition to the PIG electrode system, an electrode system for RF discharge or an electrode system for arc discharge can also be used.

[0022] An air-core coil 71 is placed in the atmosphere surrounding the plasma generating electrode 7, generating a DC magnetic field with a component in approximately the same direction as the electric field between electrodes 7a, 7b, and 7c. The magnetic field generated by the air-core coil 71 facilitates discharge, and the plasma is confined in the radial direction of the air-core coil 71, thereby increasing the ion density.

[0023] A magnetic shielding member 72 is placed in the atmosphere on the plasma generation chamber 3 side of the air-core coil 71 to avoid magnetic influence on the plasma generation chamber 3. Furthermore, an ignition gas supply unit 73 for introducing ignition gas into the plasma generation chamber 3 is provided in the part of the vacuum vessel 6 adjacent to the plasma generation electrode 7. For example, oxygen or argon can be used as the ignition gas. The ignition gas is used only during plasma ignition, and is shut off once a stable plasma generation state is achieved.

[0024] When the vapor pressure in the plasma generation chamber 3 increases, the free electrons within it move rapidly in tandem between the three electrodes, generating a high-frequency discharge. This high-frequency discharge ionizes the source gas in the plasma generation chamber 3, creating a plasma called a swam (source plasma). At this time, if the potential of the anticathode 7c is set to be several tens of volts higher than that of the cathode 7a, the swam will diffuse more easily towards the ion beam extraction chamber 5 due to bipolar diffusion. Ions in the plasma enter the ion beam extraction chamber 5 due to bipolar diffusion and are extracted from the source plasma by the ion extraction electrode 51 of the electrostatic electrode system located in the ion beam extraction chamber 5. The ion beam extraction direction is horizontal. The ions accelerated by the ion extraction electrode 51 become a beam and are injected into the ion implantation object 8 (target).

[0025] A third vacuum pump 52 is connected to the ion beam extraction chamber 5 to remove neutral gases and recombined ions. In addition, an observation window 53 is provided in the part of the vacuum vessel 6 that forms the ion beam extraction chamber 5 for observing the inside of the ion beam extraction chamber 5.

[0026] In this embodiment, a plurality of differential pressure chambers 41-4 are arranged between the electron beam emission chamber 2 and the plasma generation chamber 3 along the direction of emission of the electron beam 21. n A differential pressure chamber 41-4 is provided. n This is formed by arranging multiple differential pressure chamber walls 42, each having a beam passage hole 41 that serves as the path for the electron beam, at intervals within the vacuum vessel 6. The beam passage holes 41 can also be formed on the inner surface of a pipe-shaped member having vertical length. In this case, the pipe-shaped member is fitted into the inner surface of the hole provided in the differential pressure chamber wall 42. Each differential pressure chamber 41-4 n Each of these chambers, except for the uppermost differential pressure chamber 41, is connected to a vacuum pump 43 that can be controlled individually. The electron beam emission chamber 2 and the uppermost differential pressure chamber 41 adjacent to it are also separated by a differential pressure chamber wall 42 having beam passage holes 41, and the plasma generation chamber 3 and the lowermost differential pressure chamber 4 adjacent to it n The space between these areas is also partitioned by a differential pressure chamber wall 42 having beam passage holes 41.

[0027] The exhaust of the uppermost differential pressure chamber 41 can be performed by a cryopump 44. The cryopump 44 cools an exhaust surface 45 located inside the uppermost differential pressure chamber 41 to an extremely low temperature with a refrigerant such as liquid helium or liquid nitrogen, thereby capturing gas molecules on the exhaust surface 45 by condensation or adsorption, and exhausting the inside of the differential pressure chamber 41.

[0028] Each differential pressure chamber 41-4 n Of these, differential exhaust is performed between two adjacent differential pressure chambers. In addition, differential exhaust is performed between electron beam emission chamber 2 and the uppermost differential pressure chamber 41 adjacent to it, and between plasma generation chamber 3 and the lowermost differential pressure chamber 4 adjacent to it. n Differential exhaust is performed between the electron beam emission chamber 2 and each differential pressure chamber 41-4. n In the plasma generation chamber 3, the vacuum level of one space on the electron beam emission chamber 2 side is made higher than the vacuum level of the other space on the plasma generation chamber 3 side. nThe vacuum level in the electron beam emission chamber 2 increases as you move from the plasma generation chamber 3 towards the electron beam emission chamber 2, with the highest vacuum level in the electron beam emission chamber 2 and the lowest in the plasma generation chamber 3. The differential pressure between the two adjacent spaces is controlled to an appropriate value depending on the discharge type and the type of raw material.

[0029] In the metal ion source 1 of this embodiment, a linear electron gun that emits an electron beam in a straight line is used, so multi-stage differential pumping can be easily realized. Therefore, each differential pressure chamber 41-4 n This makes it possible to gradually increase the vacuum level toward the electron beam emission chamber 2. This makes it easy to maintain a low vacuum level in the plasma generation chamber 3 suitable for source plasma generation, while maintaining a high vacuum level in the electron beam emission chamber 2 that prevents arc discharge, thereby enabling stable operation of the metal ion source 1. Differential pressure chambers 41-4 n The number of differential pressure chambers 4 can be one or more, and the number can be selected arbitrarily. It is believed that the more differential pressure chambers 4 there are, the higher the achievable vacuum level in the electron beam emission chamber 2 can be.

[0030] Furthermore, with a linear electron gun, it is easier to increase the intensity of the electron beam compared to a deflected electron gun. This allows for an increase in the ion density in the source plasma, making it easier to extract a high-density ion beam horizontally. Extracting the ion beam horizontally simplifies the installation, maintenance, and connection of the ion implanter connected to the ion beam extraction chamber 5 with various other devices. This also provides advantages that make the metal ion source 1 useful for industrial applications, such as the discovery of alloys and catalysts that do not exist in nature, and research and development of new materials and pharmaceuticals.

[0031] In the metal ion source 1 shown in Figure 1, multiple differential pressure chambers 41-4 are positioned above the plasma generation chamber 3. n Although the example shows the arrangement of the electron beam emission chambers 2 stacked on top of each other, multiple differential pressure chambers 41-4 are located diagonally upward from the plasma generation chamber 3. nFurthermore, the electron beam emission chambers 2 can be arranged in a stacked manner. With this configuration, the overall height of the metal ion source 1 can be kept low while numerous differential pressure chambers 41-4 n It becomes possible to install the plasma generating electrode 7 between the plasma generation chamber 3 and the ion beam extraction chamber 5. In addition, although the case in which the plasma generating electrode 7 is placed between the plasma generation chamber 3 and the ion beam extraction chamber 5 has been explained, the plasma generating electrode 7 can be placed in the lowest differential pressure chamber 4 n It can be placed between the plasma generation chamber 3, or the plasma generation electrode 7 can be omitted. [Explanation of Symbols]

[0032] 1. Metal ion source 2. Electron beam emission chamber 3. Plasma generation chamber 4 (41~4 n ) Differential pressure chamber 5. Ion beam extraction room 6 Vacuum container 7 Plasma generating electrode 21 Electron beam 22 Electron beam source 32 Raw materials 33. Source of raw material evaporation

Claims

1. A metal ion source comprising an electron beam emission chamber equipped with an electron beam source for emitting an electron beam, a plasma generation chamber having a raw material evaporation source loaded with raw materials, wherein the raw materials are evaporated by the electron beam and the evaporated raw material gas is ionized to form a source plasma, and an ion beam extraction chamber for extracting an ion beam from the source plasma, The electron beam source is configured as a linear electron gun. A metal ion source characterized by providing a differential pressure chamber through which the electron beam passes between the electron beam emission chamber and the plasma generation chamber, and performing differential pumping between the differential pressure chamber and the electron beam emission chamber, and between the differential pressure chamber and the plasma generation chamber.

2. The metal ion source according to claim 1, wherein a plurality of differential pressure chambers are arranged in a row along the direction of emission of the electron beam, and the differential pressure chamber closest to the electron beam emission chamber is evacuated by a cryopump.

3. The metal ion source according to claim 1, wherein an ion beam is drawn horizontally from the ion beam extraction chamber.

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