Metal Ion Source

Abstract

A metal ion source capable of easily obtaining a high degree of vacuum required in an electron beam emission chamber is provided. [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, in which the raw material 32 is evaporated by the electron beam 21 and the gas of the evaporated raw material 32 is ionized 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 evacuation 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, respectively.

Description

[Technical field]

[0001] The present invention relates to a metal ion source for use in an ion implantation device, an ion beam etching device, a thin film manufacturing device, and the like. [Background technology]

[0002] Known metal ion sources that evaporate metal or other solid raw materials at room temperature, ionize the generated raw material gas to a plasma state, and extract an ion beam from the plasma are described in the following Patent Documents 1 and 2. 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 of the raw material gas are separated by a partition, the solid raw material is evaporated with an electron beam emitted from a deflection type electron gun disposed in the raw material evaporation chamber, the evaporated gas is introduced into the plasma generation chamber to convert the raw material gas into a plasma state in the plasma generation chamber, and an ion beam is extracted from this plasma.

[0003] Patent Document 2 discloses a metal ion source in which a raw material evaporation chamber and a plasma generation chamber are integrated to form an evaporation / plasma generation chamber, raw material placed in the evaporation / plasma generation chamber is evaporated by an electron beam emitted from a deflection type electron gun, this raw material gas is converted into plasma by electrodes placed in the evaporation / plasma generation chamber, and an ion beam is extracted from the plasma. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4440304 [Patent Document 2] Patent No. 6178526 Summary of the Invention [Problem to be solved by the invention]

[0005] In both of the ion sources in Patent Documents 1 and 2, the evaporation of the raw material is performed by irradiating an electron beam from a deflection type electron gun, without using resistance heating. In addition, in the plasma generation chamber or the evaporation / plasma generation chamber, plasma is generated by using PIG discharge. -1 ~10 -2 While a vacuum of about 10 Pa is required, the electron beam injection chamber where the electron gun is located has a higher vacuum (10 -2 Pa~10 -5 A pressure of about 100 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 because a deflection-type electron gun is used, it is difficult to perform multi-stage differential pumping, and only a single-stage differential pumping is required. Therefore, it is difficult to achieve the high degree of vacuum required in the electron beam emission chamber.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a metal ion source which can easily obtain a high degree of vacuum required in an electron beam emission chamber. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a metal ion source comprising an electron beam emission chamber equipped with an electron beam source that emits an electron beam, a plasma generation chamber having a raw material evaporation source loaded with raw material, in which the raw material is evaporated by the electron beam and the evaporated raw material gas is ionized to form a source plasma, and an ion beam extraction chamber that extracts an ion beam from the source plasma, characterized in that 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 evacuation is performed between the differential pressure chamber and the electron beam emission chamber, and between the differential pressure chamber and the plasma generation chamber, respectively.

[0008] In the present invention, since a linear electron gun that emits an electron beam in a linear direction is used, the electron beam emission chamber, the differential pressure chamber, and the plasma generation chamber can be arranged in a stacked state. Therefore, it is possible to easily realize differential evacuation in multiple stages, and it is possible to gradually increase the degree of vacuum in each chamber toward the electron beam emission chamber. Therefore, it is easy to maintain the plasma generation chamber at a low degree of vacuum suitable for plasma generation, while maintaining the electron beam emission chamber at a high degree of vacuum that does not cause arc discharge, and it is possible to stably operate the metal ion source.

[0009] In this metal ion source, a plurality of differential pressure chambers are arranged in line 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] In addition, in this metal ion source, the ion beam can be extracted horizontally from the ion beam extraction chamber.

[0012] By extracting the ion beam in the horizontal direction in this manner, the ion implantation apparatus connected to the ion beam extraction chamber can be easily installed, maintained, and connected to various devices. Effect 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 a high degree of vacuum required in an electron beam emission chamber. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing the overall configuration of a metal ion source according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0016] As shown in FIG. 1, the metal ion source 1 of this embodiment has 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 disposed at the top of the vacuum vessel 6, the plasma generation chamber 3 is disposed at the bottom immediately below the electron beam injection chamber 2, and the differential pressure chamber 4 is disposed between the electron beam injection chamber 2 and the plasma generation chamber 3. In addition, the ion beam extraction chamber 5 is disposed on the side of the plasma generation chamber 3. A plasma generating electrode 7 is disposed between the plasma generation chamber 3 and the ion beam extraction chamber 5.

[0017] In the electron beam emission chamber 2, an electron beam source 22 that emits an electron beam 21 is disposed. In this embodiment, a linear type electron gun that emits the electron beam 21 in a linear direction, rather than a deflection type, is used as the electron beam source 22. During operation of the metal ion source 1, the inside of the electron beam emission chamber 2 is evacuated by a first vacuum pump 23, and an arc discharge is prevented from occurring. -2 Pa~10 -5 The electron beam injection chamber 2 is maintained at a high vacuum of about 5×10 Pa. -3 The vacuum level is maintained at or above 1 Pa.

[0018] In addition, a Wernert electrode 24 and an electron acceleration electrode 25 are disposed in the electron beam emission chamber 2. In the vacuum vessel 6, a part forming the electron beam emission chamber 2 is provided with a gauge port 26 for attaching a gauge head.

[0019] In the plasma generation chamber 3, there are disposed a hearth 31 and a raw material evaporation source 33 equipped with a solid raw material 32 loaded in the hearth 31. The raw material evaporation source 33 is disposed directly below the electron beam source 22 so that the raw material 32 is irradiated with the electron beam 21 emitted linearly from the electron beam source 22. A second vacuum pump 34 is connected to the plasma generation chamber 3, and by driving this second vacuum pump 34, the plasma generation chamber 3 is maintained at a vacuum level suitable for plasma generation (which differs depending on the type of plasma generating electrode). For example, when a PIG electrode system is used as the plasma generating electrode 7 as described below, the inside of the plasma generation chamber 3 is maintained at a vacuum level of 10 -1 Pa~10 -2 The vacuum level in the electron beam emission chamber 2 is maintained at about 1 Pa. Regardless of the type of plasma generating electrode 7, the vacuum level 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 from the electron beam source 22 through the differential pressure chamber 4 to evaporate the raw material 32, and the raw material gas is diffused in the plasma generation chamber 3.

[0020] A reflector 34 for reflecting plasma is placed inside the plasma generation chamber 3. In the vacuum vessel 6, a part forming the plasma generation chamber 3 is provided with a gauge point 35 for attaching a gauge head and an observation window 36 for observing the inside of the plasma generation chamber 3.

[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 generating electrode 7. The PIG electrode system is composed of a cathode 7a, a countercathode 7c, and an anode 7b arranged between the cathodes 7a and 7c and having a slightly larger diameter than the cathodes 7a and 7c. The space located on the inner circumference of each of the electrodes 7a, 7b, and 7c opens 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 vessel 6, and can be heated by electrical current. In addition to the PIG electrode system, an electrode system for RF discharge or an electrode system for arc discharge can also be used as the plasma generating electrode 7.

[0022] An air-core coil 71 that generates a DC magnetic field having a component in approximately the same direction as the electric field between the electrodes 7a, 7b, and 7c is arranged in the atmosphere around the plasma generating electrode 7. The magnetic field generated by the air-core coil 71 makes it easier for discharge to occur, and since the plasma is confined in the radial direction of the air-core coil 71, the ion density can be increased.

[0023] A magnetic shielding member 72 is arranged in the atmosphere on the plasma generation chamber 3 side of the air-core coil 71 in order to prevent magnetic influence on the plasma generation chamber 3. An ignition gas supply unit 73 for introducing ignition gas into the plasma generation chamber 3 is provided in a portion of the vacuum vessel 6 adjacent to the plasma generating electrode 7. For example, oxygen or argon can be used as the ignition gas. The ignition gas is used only when igniting the plasma, and the ignition gas is shut off when the plasma is stably generated.

[0024] When the vapor pressure in the plasma generation chamber 3 rises, free electrons therein move in tandem between the three electrodes at high speed, generating a high-frequency discharge, which ionizes the raw material gas in the plasma generation chamber 3 to generate a plasma called a swamb (source plasma). At this time, if the potential of the countercathode 7c is set to a potential configuration several tens of volts higher than that of the cathode 7a, the swamb becomes more likely to diffuse toward the ion beam extraction chamber 5 by bipolar diffusion. Ions in the plasma enter the ion beam extraction chamber 5 by bipolar diffusion and are extracted from the source plasma by the ion extraction electrode 51 of the electrostatic electrode system arranged in the ion beam extraction chamber 5. The extraction direction of the ion beam is set to the horizontal direction. The ions accelerated by the ion extraction electrode 51 become a beam and are implanted into the ion implantation target 8.

[0025] A third vacuum pump 52 is connected to the ion beam extraction chamber 5 in order to remove neutral gas and recombined ions. In addition, in the vacuum vessel 6, a portion forming the ion beam extraction chamber 5 is provided with an observation window 53 for observing the inside of the ion beam extraction chamber 5.

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

[0027] The uppermost differential pressure chamber 41 can be evacuated by a cryopump 44. The cryopump 44 evacuates the inside of the differential pressure chamber 41 by cooling an exhaust surface 45 disposed 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.

[0028] Each differential pressure chamber 41~4 n Differential evacuation is performed between two adjacent differential pressure chambers. Differential evacuation is performed between the electron beam emission chamber 2 and the adjacent uppermost differential pressure chamber 41, and between the plasma generation chamber 3 and the adjacent lowermost differential pressure chamber 4. n In this embodiment, differential pumping is performed between the electron beam emission chamber 2 and each of the differential pressure chambers 41 to 4. n The vacuum level of the space on the electron beam emitting chamber 2 side is set higher than the vacuum level of the other space on the plasma generating chamber 3 side among any two adjacent spaces among the plasma generating chamber 3 and the differential pressure chambers 41 to 4. nand the degree of vacuum in the electron beam emission chamber 2 increases from the plasma generation chamber 3 to the electron beam emission chamber 2, with the electron beam emission chamber 2 having the highest degree of vacuum and the plasma generation chamber 3 having the lowest degree of vacuum. The pressure difference between the two adjacent spaces is controlled to an appropriate value according to the discharge format and the type of raw material.

[0029] In the metal ion source 1 of the present embodiment, a linear electron gun that emits an electron beam in a linear direction is used, so that multi-stage differential pumping can be easily realized. n It is possible to gradually increase the degree of vacuum in the plasma generation chamber 3 toward the electron beam emission chamber 2. This makes it easy to maintain the plasma generation chamber 3 at a low degree of vacuum suitable for generating source plasma, while maintaining the electron beam emission chamber 2 at a high degree of vacuum where no arc discharge occurs, and thus enables the metal ion source 1 to operate stably. n The number of the differential pressure chambers 4 can be one or more, and the number can be selected arbitrarily. It is considered that the greater the number of the differential pressure chambers 4, the greater the ultimate vacuum of the electron beam emission chamber 2 can be.

[0030] In addition, the linear electron gun makes it easier to increase the intensity of the electron beam compared to the deflection electron gun. Therefore, the ion density in the source plasma can be increased, and it becomes easy to extract a high-density ion beam in the horizontal direction as well. Extracting the ion beam in the horizontal direction makes it easy to install, maintain, and connect the ion implantation device connected to the ion beam extraction chamber 5 to various devices. This provides an advantage that the metal ion source 1 is useful for industrial use, for example, the discovery of alloys and catalysts that do not exist in nature, and the research and development of new materials and pharmaceuticals.

[0031] In the metal ion source 1 shown in FIG. 1, a plurality of differential pressure chambers 41 to 4 are arranged toward the upper side of the plasma generation chamber 3. n In the above example, the plasma generating chamber 3 and the electron beam emitting chamber 2 are arranged in a stacked manner. nThe electron beam emitting chambers 2 may be arranged in a stacked manner. With such a configuration, the total height of the metal ion source 1 can be reduced while a large number of differential pressure chambers 41 to 4 can be provided. n In addition, the case where the plasma generating electrode 7 is disposed between the plasma generation chamber 3 and the ion beam extraction chamber 5 has been described, but the plasma generating electrode 7 can be disposed between the differential pressure chamber 4 at the lowest stage. n and the plasma generation chamber 3, or the plasma generation electrode 7 may be omitted. [Explanation of symbols]

[0032] 1. Metal ion source 2. Electron beam injection chamber 3. Plasma Generation Chamber 4(41~4 n ) Differential pressure chamber 5. Ion beam extraction chamber 6 Vacuum container 7. Plasma generating electrode 21 Electron Beam 22 Electron beam source 32 Raw materials 33 Raw material evaporation source

Claims

1. A metal ion source comprising: an electron beam emission chamber having an electron beam source for emitting an electron beam; a plasma generation chamber having a raw material evaporation source loaded with a raw material, the raw material being evaporated by the electron beam, and the evaporated raw material gas being 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 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 evacuation is performed between the differential pressure chamber and the electron beam emission chamber and between the differential pressure chamber and the plasma generation chamber, respectively; 2. A metal ion source comprising: a metal ion source extracting an ion beam in a horizontal direction from said ion beam extraction chamber.

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

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