Liquid metal ion source and focused ion beam device

Abstract

The present invention provides a liquid metal ion source and a focused ion beam device, which can release ion beams stably for a long period of time. The liquid metal ion source (50) comprises: a storage chamber (10) for holding ion materials (M) forming liquid metal; a needle-shaped electrode (20) whose surface is covered with ion materials supplied from the storage chamber; an extraction electrode (22) for releasing ions of the ion material from the front end of the needle-shaped electrode; a beam aperture (24) arranged on the downstream side of the extraction electrode to limit the beam diameter of the ions; and a vacuum chamber (30) for storing these and maintaining them in a vacuum. The liquid metal ion source (50) is characterized in that it further comprises an oxidizing gas introduction part (40), which is connected to the vacuum chamber to introduce oxidizing gas into the vicinity of the needle-shaped electrode.

Description

Technical Field

[0001] The present invention relates to a liquid metal ion source and a focused ion beam device which can be suitably used as an ion source of, for example, a focused ion beam device. Background Art

[0002] Conventionally, a liquid metal ion source is used as an ion source for a focused ion beam (FIB) device.

[0003] When the liquid metal ion source heats the liquid metal to wet the needle electrode and applies voltage between the needle electrode and the extraction electrode, the liquid metal at the tip of the needle electrode becomes a cone called a Taylor cone, and an electric field is generated from the tip of the cone to evaporate and release ions.

[0004] However, sometimes the molten metal is oxidized and the ion release becomes unstable. Therefore, a technique of introducing a reducing gas near the needle electrode (Patent Document 1) or a technique of irradiating ions to the liquid metal at the tip of the needle electrode (Patent Document 2) has been reported.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 61-22537

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 7-153403 Summary of the invention

[0009] Problems to be solved by the invention

[0010] In order to suppress the diffusion of the ion beam and the contamination of the focusing lens, a beam aperture that limits the beam diameter of the ions may be arranged on the downstream side of the extraction electrode.

[0011] However, there is a problem that the beam aperture is irradiated with ions and causes sputtering, and the high melting point materials such as tungsten and molybdenum that constitute the beam aperture become sputtered particles and fly and adhere to the needle electrode. The attached particles condense at the tip of the needle electrode as the liquid metal flows, hindering the flow of the liquid metal and making the release of the ion beam unstable.

[0012] As a countermeasure, heating or flushing is temporarily performed to increase the emission amount of the ion beam, but even so, the effect is limited.

[0013] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a liquid metal ion source and a focused ion beam device capable of stably emitting ion beams for a long period of time.

[0014] Means for solving problems

[0015] In order to achieve the above-mentioned purpose, the liquid metal ion source of the present invention comprises: a storage chamber, which holds the ion material that forms the liquid metal; a needle-shaped electrode, the surface of which is covered by the ion material supplied from the storage chamber; an extraction electrode, which releases ions of the ion material from the front end of the needle-shaped electrode; a beam aperture, which is arranged on the downstream side of the extraction electrode and limits the beam diameter of the ions; and a vacuum chamber, which accommodates the storage chamber, the needle-shaped electrode, the extraction electrode and the beam aperture and keeps it in a vacuum. The liquid metal ion source is characterized in that it further has an oxidizing gas introduction part, which is connected to the vacuum chamber and introduces oxidizing gas into the vicinity of the needle-shaped electrode.

[0016] According to the liquid metal ion source, an oxidizing gas is introduced around the needle-shaped electrode to actively oxidize the liquid metal on the surface of the needle-shaped electrode to form an oxide film on the outermost surface. In addition, it is believed that the sputtered particles flying from the beam aperture to the needle-shaped electrode are captured by the oxide film and do not reach the molten body inside, thereby not hindering the flow of the molten body to the front end of the needle-shaped electrode. As a result, the release of the ion beam becomes stable.

[0017] In the liquid metal ion source of the present invention, the oxidizing gas may be water vapor.

[0018] Water has higher oxidizing power than oxygen, and by using water vapor, the oxidation reaction can be carried out efficiently.

[0019] The liquid metal ion source of the present invention may further include a final exhaust system for exhausting the vacuum chamber to a target vacuum degree, and the final exhaust system and the oxidizing gas introduction portion are connected to the vacuum chamber via different flow paths.

[0020] According to the liquid metal ion source, since the flow paths of the final exhaust system and the oxidizing gas introduction unit are different, the oxidizing gas flows from the oxidizing gas introduction unit to the final exhaust system, and thus the oxidation reaction can be efficiently performed even if the flow rate of the oxidizing gas is small.

[0021] The liquid metal ion source of the present invention may further include a final exhaust system for exhausting the vacuum chamber to a target vacuum degree, and the final exhaust system and the oxidizing gas introduction part are connected to the vacuum chamber via the same flow path.

[0022] According to this liquid metal ion source, it is not necessary to provide a flow path for the oxidizing gas introduction part. Therefore, when it is desired to additionally provide an oxidizing gas introduction part to an existing liquid metal ion source, there is an advantage that the degree of freedom in installation is improved.

[0023] In the liquid metal ion source described in technical solution 3, the vacuum degree in the state where the oxidizing gas is introduced into the vacuum chamber can be 5.0×10-6 ~1.5×10 -5 Pa.

[0024] In the liquid metal ion source described in technical solution 4, the vacuum degree in the state where the oxidizing gas is introduced into the vacuum chamber can be 1.0×10 -5 ~3.0×10 -5 Pa.

[0025] In the liquid metal ion source described in claim 3, the flow path of the final exhaust system and the flow path of the oxidizing gas introduction portion may be at least partially opposed to each other in a direction perpendicular to the irradiation direction of the ion beam.

[0026] According to this liquid metal ion source, the two flow paths overlap in the direction perpendicular to the irradiation direction of the ion beam, so that the oxidizing gas easily flows from the oxidizing gas introduction portion to the final exhaust system.

[0027] In the liquid metal ion source of technical solution 3 or 4, the flow path of the above-mentioned final exhaust system and the flow path of the above-mentioned oxidizing gas inlet part can be respectively opposed to the needle-shaped electrode in at least a part in the direction perpendicular to the irradiation direction of the above-mentioned ion beam.

[0028] According to this liquid metal ion source, the oxidizing gas easily flows from the oxidizing gas introduction portion toward the needle-shaped electrode.

[0029] The liquid metal ion source of the present invention may further include an oxidizing gas introduction control unit for introducing the oxidizing gas into the vacuum chamber only when a voltage is applied between the needle-shaped electrode and the extraction electrode.

[0030] According to this liquid metal ion source, since the oxidizing gas is introduced only when a voltage is applied to release an ion beam, the oxidizing gas is introduced when the voltage is not applied and there is no effect of the oxidizing gas, thereby suppressing waste.

[0031] The focused ion beam apparatus of the present invention includes the above-mentioned liquid metal ion source.

[0032] Effects of the Invention

[0033] According to the present invention, a liquid metal ion source and a focused ion beam device capable of stably emitting ion beams for a long period of time are obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a diagram showing the overall structure of a focused ion beam device including a liquid metal ion source according to a first embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram showing a state where an ion beam is released from a general needle-shaped electrode.

[0036] Figure 3 This is a schematic diagram showing a state in which an ion beam is released from a needle-shaped electrode during sputtering of a material of a beam aperture.

[0037] Figure 4 This is a schematic diagram showing a state in which an ion beam is released from the needle-shaped electrode when an oxidizing gas is introduced around the needle-shaped electrode.

[0038] Figure 5 It is a diagram showing the overall structure of a focused ion beam device including a liquid metal ion source according to a second embodiment of the present invention.

[0039] Figure 6 This is a diagram showing the time change of the voltage of the suppression electrode when the oxidizing gas is not introduced into the vacuum chamber in the liquid metal ion source of the first embodiment.

[0040] Figure 7 The first embodiment shows that 1.0×10 -5 A graph showing the time change of the voltage of the suppression electrode in the presence of Pa oxidizing gas. DETAILED DESCRIPTION

[0041] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0042] Figure 1 It is a block diagram showing the overall structure of a focused ion beam device 100 including a liquid metal ion source 50 according to the first embodiment of the present invention.

[0043] exist Figure 1 In the embodiment, the liquid metal ion source 50 includes a storage chamber 10 for holding an ion material (Ga, etc.) forming liquid metal, a needle-shaped electrode 20, an extraction electrode 22, a beam aperture 24, and a vacuum chamber 30 for storing and maintaining these in a vacuum state.

[0044] The storage chamber 10 has an internal space for winding one end of a wire in a coil shape, and the other end ( Figure 1 The front end side of the electrode has a sharpened needle-shaped electrode 20 ( Figure 1 The filament heater 14 is formed by processing a linear heater into a V-shape in side view, and the front end of the V-shape is connected to the vicinity of the coiled portion of the wire.

[0045] Both ends of the rear end side of the filament heater 14 are electrically connected to a pair of electrode terminals 11 and 12, respectively. And, by energizing the electrode terminals 11 and 12, the liquid metal-like ion material stored in the storage chamber 10 is heated by the filament heater 14, and the viscosity of the melt is reduced. And, the liquid metal flows toward the needle-shaped electrode 20 and covers the surface thereof. It should be noted that the electrode terminals 11 and 12 are supported by the support portion 13 composed of an insulator.

[0046] When a voltage is applied to the extraction electrode 22 on the downstream side of the needle-shaped electrode 20, the liquid metal becomes a cone called a Taylor cone due to the surface tension of the molten ion material (liquid metal) at the front end of the needle-shaped electrode 20 and the attraction of the electric field formed by applying the voltage to the extraction electrode 22. Then, an electric field is generated at the front end of the cone to evaporate and release the ion beam IB. The released ions are accelerated by the electric field formed by the needle-shaped electrode 20 and the extraction electrode 22, and travel toward the focusing lens 70 below.

[0047] The beam aperture 24 is disposed on the downstream side of the extraction electrode 22 to limit the beam diameter of ions. This can suppress the diffusion of the ion beam and the contamination of the following focusing lens 70.

[0048] It should be noted that when a suppression electrode (Suppressorelectrode) 26 is configured between the needle-shaped electrode 20 and the extraction electrode 22, the release amount of the ion beam can be controlled by applying a voltage to the suppression electrode 26. When the ion beam is easy to release, the voltage is increased to suppress the ion beam, and when the ion beam is not easy to release, the voltage is reduced to promote the release of the ion beam.

[0049] Furthermore, the storage chamber 10 , the needle electrode 20 , the extraction electrode 22 , and the beam aperture 24 constituting the liquid metal ion source 50 are housed in the vacuum chamber 30 and maintained in a vacuum state.

[0050] In addition, the focused ion beam device 100 according to the first embodiment of the present invention has, in addition to the components of the liquid metal ion source 50, a focusing lens 70 for converging the ion beam IB reduced by the beam aperture 24 on the downstream side of the beam aperture 24. The focusing lens 70 is also housed in the vacuum chamber 30 and maintained in a vacuum state.

[0051] Furthermore, the vacuum chamber 30 is communicated with an oxidizing gas introduction unit 40 for introducing an oxidizing gas into the periphery of the needle-shaped electrode 20 , and is communicated with an ion pump 45 and an exhaust system 46 for maintaining the vacuum chamber 30 in a vacuum.

[0052] The exhaust system 46 is connected to the vacuum chamber 30 via a valve 46a, and exhausts the vacuum chamber 30 to a (low) vacuum degree at which the ion pump (final exhaust system) 45 starts to work. Specifically, after the exhaust system 46 exhausts to a vacuum degree at which the ion pump starts to work, the ion pump 45 is operated for a period of time, and then the valve 46a is closed to allow the ion pump 45 to continue to work. Thus, the vacuum chamber 30 is exhausted to a higher target vacuum degree by the ion pump 45. The flow paths of the exhaust system 46 and the ion pump 45 merge, and are connected to the vacuum chamber 30 by a flow path F1 at one place.

[0053] It should be noted that, in the first embodiment, the oxidizing gas introduction part 40 is connected to the vacuum chamber 30 by another flow path F2 at a position at least partially opposed to the flow path F1 of the exhaust system 46 and the ion pump 45 in the horizontal direction (the direction perpendicular to the irradiation direction of the ion beam IB). In addition, each flow path F1, F2 is arranged at a position at least partially opposed to the needle-shaped electrode 20 in the horizontal direction.

[0054] In addition, if Figure 1 As shown, in the first embodiment, the oxidizing gas G introduced from the oxidizing gas introduction part 40 through the flow path F2 into the vacuum chamber 30 passes through the needle electrode 20 and is exhausted from the other flow path F1 by the ion pump 45 .

[0055] As described above, by making the flow paths F1 and F2 different from each other, the oxidizing gas G flows from the flow path F2 to the flow path F1 , so that even if the flow rate of the oxidizing gas G is small, the oxidation reaction can be efficiently performed.

[0056] In this example, the oxidizing gas introduction unit 40 includes a cylinder 41 storing the oxidizing gas and a flow rate adjustment unit 42 for limiting the flow rate of the oxidizing gas. The oxidizing gas in the cylinder 41 is introduced into the vicinity of the needle-shaped electrode 20 in the vacuum chamber 30 via the flow rate adjustment unit 42 .

[0057] As the material of the oxidizing gas, water, oxygen, ozone, nitrous oxide, nitric oxide, nitrogen dioxide, etc. can be cited, and liquid can also be used. In the case of liquid, there are two phases of vapor (vapor pressure corresponding to the temperature of the cylinder 41) and liquid of the oxidizing gas in the cylinder 41, and the vapor (for example, water vapor) is supplied. In addition, hydrates that retain water in the crystals such as copper nitrate, copper sulfate, and iron iodide can also be used. Compared with oxygen, water has a high oxidizing ability, so that the oxidation reaction is carried out efficiently.

[0058] The flow rate adjustment unit 42 may be a variable valve, a throttle device, a mass flow controller, a material that transmits oxidizing gas, etc. Alternatively, a control valve may be used to feedback-control the supply flow rate according to the vacuum degree of the vacuum chamber 30 .

[0059] Next, refer to Figure 2 to Figure 4The reason why the oxidizing gas is introduced around the needle-shaped electrode 20 in the vacuum chamber 30, which is a characteristic part of the present invention, is described below.

[0060] First, if Figure 2 As shown, the melt M of the ion material that normally covers the surface of the needle-shaped electrode 20 flows toward the tip 20t of the needle-shaped electrode 20 and is released as the ion beam IB.

[0061] However, when the beam aperture 24 is sputtered by the ion beam IB, Figure 3 As shown, the material of the beam aperture 24 adheres to the needle electrode 20 as sputtered particles 24s. The sputtered particles 24s aggregate at the tip 20t of the needle electrode 20 along with the flow of the melt M, hinder the flow of the melt M, and destabilize the release of the ion beam IB.

[0062] Therefore, when the oxidizing gas is introduced around the needle-shaped electrode 20, Figure 4 As shown, the molten body M on the surface of the needle-shaped electrode 20 is actively oxidized to form an oxide film Ox on the outermost surface. In addition, it is considered that the sputtered particles 24s flying to the needle-shaped electrode 20 are captured by the oxide film Ox and do not reach the molten body M inside, so that the molten body M does not flow toward the front end 20t of the needle-shaped electrode 20. As a result, the release of the ion beam IB becomes stable.

[0063] It should be noted that since the oxide film Ox at the tip 20t of the needle-shaped electrode 20 is thin or the applied voltage of the extraction electrode 22 is concentrated at the tip 20t, it is considered that the molten body M at the tip 20t easily destroys the oxide film Ox and becomes the ion beam IB.

[0064] As described above, when the amount of the introduced oxidizing gas is too small, the sputtered particles 24 s adhere to the needle-shaped electrode 20 and the emission of the ion beam IB becomes unstable.

[0065] On the other hand, when the amount of the introduced oxidizing gas is too large, the oxide film Ox at the tip 20 t of the needle-shaped electrode 20 becomes thick, and the emission of the ion beam becomes unstable.

[0066] The amount of oxidizing gas introduced into the vacuum chamber 30 varies depending on the exhaust speed of the exhaust system 46 and the ion pump 45 or the volume of the vacuum chamber 30 , and therefore an appropriate range may be required to stabilize the actual release of the ion beam in each device.

[0067] like Figure 1 As shown, the liquid metal ion source 50 may further include an oxidizing gas introduction control unit 48 for introducing oxidizing gas into the vacuum chamber 30 only when a voltage is applied between the needle-shaped electrode 20 and the extraction electrode 22 .

[0068] The oxidizing gas introduction control unit 48 is composed of a computer such as a microcomputer, and can monitor the voltage between the needle electrode 20 and the lead-out electrode 22, for example, and can control the flow adjustment unit 42 to open at a specified opening while the voltage is applied between the needle electrode 20 and the lead-out electrode 22, and to close the flow adjustment unit 42 when the voltage between the needle electrode 20 and the lead-out electrode 22 is detected to be zero.

[0069] The effect of the oxidizing gas is exerted when a voltage is applied between the needle electrode 20 and the extraction electrode 22 to make the melt M flow on the surface of the needle electrode 20. Therefore, when the voltage between the needle electrode 20 and the extraction electrode 22 is zero, it is possible to suppress the wasteful introduction of the oxidizing gas and reduce the amount of the oxidizing gas used.

[0070] It should be noted that the introduced gas is adsorbed on the surface in the vacuum chamber and is gradually released from the surface into the vacuum chamber. Thus, the same effect can be obtained by adsorbing the gas in advance when high pressure is not applied and supplying it from the surface.

[0071] Next, refer to Figure 5 A focused ion beam device 100B including a liquid metal ion source 50B according to a second embodiment of the present invention will be described.

[0072] The focused ion beam device 100B including the liquid metal ion source 50B of the second embodiment has the same structure as the first embodiment except that the communicating flow path between the oxidizing gas introduction part 40 and the vacuum chamber 30 is different. The same components as those of the first embodiment are marked with the same reference numerals. Figure 1 The same symbols are used and the description is omitted.

[0073] That is, in the second embodiment, the exhaust system 46 and the flow path of the oxidizing gas introduction unit 40 merge at F3, and the flow path F3 and the flow path of the ion pump 45 merge, and communicate with the vacuum chamber 30 through a single flow path F4. The operation of the exhaust system 46 and the ion pump 45 is the same as that of the first embodiment.

[0074] The flow channel F4 is arranged at a position opposing the needle-shaped electrode 20 at least partially in the horizontal direction.

[0075] In the second embodiment, the flow path F2 ( Figure 1 ), therefore, when it is desired to additionally provide an oxidizing gas inlet portion to an existing liquid metal ion source, there is an advantage of increased freedom of configuration.

[0076] On the other hand, Figure 5As shown, in the second embodiment, the oxidizing gas G introduced from the oxidizing gas introduction part 40 via the flow path F3 is divided into two parts, and flows not only to the vacuum chamber 30 side through the flow path F4, but also to the ion pump 45 side. Therefore, assuming that the oxidizing gas G is evenly divided in molecular flow, it is considered that the introduction amount of the oxidizing gas G for effectively acting on the oxidation reaction needs to be about twice that of the first embodiment.

[0077] Furthermore, since the oxidizing gas G that has entered the vacuum chamber 30 is eventually exhausted by the ion pump 45 , the degree of vacuum is lower than that of the first embodiment.

[0078] In the second embodiment as well, the oxidizing gas is introduced around the needle-shaped electrode 20 to actively oxidize the melt M on the surface of the needle-shaped electrode 20 , thereby stabilizing the emission of the ion beam IB.

[0079] The present invention is not limited to the above-described embodiments, but extends to various modifications and equivalents included in the concept and scope of the present invention.

[0080] In the first embodiment, the flow paths F1 and F2 do not need to be opposed to each other in the horizontal direction (the direction perpendicular to the irradiation direction of the ion beam IB).

[0081] In addition, the flow paths F1 and F2 in the first embodiment and the flow path F4 in the second embodiment may not be arranged at a position facing the needle-shaped electrode 20 (in a direction perpendicular to the irradiation direction of the ion beam IB).

[0082] Example

[0083] Use respectively Figure 1 and Figure 5 In the liquid metal ion source (focused ion beam device) shown, the stability of ion beam emission based on the presence or absence of introduction of an oxidizing gas into the vacuum chamber 30 was evaluated.

[0084] It should be noted that the exhaust system 46 is separated from the system after suctioning to a vacuum level at which the ion pump 45 starts to operate. The exhaust capacity of the ion pump 45 is set to 30 L / mm, and the volume of the vacuum chamber 30 is set to 2L.

[0085] The stability of ion beam emission is evaluated by the change in the voltage applied to the suppression electrode 26. Figure 6 As shown, when the ion beam is not easily released, the voltage of the suppression electrode 26 decreases.

[0086] Specifically, the case where the voltage of the suppression electrode 26 is maintained above 0.1 kV for more than 50 hours from the start of applying voltage between the needle electrode 20 and the extraction electrode 22 is evaluated as 0 (stable ion beam release), and the case where the voltage of the suppression electrode 26 is reduced to less than 0.1 kV in less than 50 hours from the start is evaluated as × (unstable ion beam release).

[0087] The obtained results are shown in Tables 1 and 2. Figure 6-7 .

[0088] Table 1 is a table showing the relationship between the amount of oxidizing gas introduced and the stability of ion beam emission in the liquid metal ion source according to the first embodiment.

[0089] Table 2 is a table showing the relationship between the amount of oxidizing gas introduced and the stability of ion beam emission in the liquid metal ion source according to the second embodiment.

[0090] Table 1

[0091] Vacuum degree [Pa] Ion beam release stability <![CDATA[2.0×10 -6 ]]> × <![CDATA[5.0×10 -6 ]]> ○ <![CDATA[8.0×10 -6 ]]> ○ <![CDATA[1.0×10 -5 ]]> ○ <![CDATA[1.5×10 -5 ]]> ○ <![CDATA[2.0×10 -5 ]]> ×

[0092] Table 2

[0093] Vacuum degree [Pa] Ion beam release stability <![CDATA[2×10 -6 ]]> × <![CDATA[5×10 -6 ]]> × <![CDATA[7.5×10 -6 ]]> × <![CDATA[1×10 -5 ]]> ○ <![CDATA[1.25×10 -5 ]]> ○ <![CDATA[1.5×10 -5 ]]> ○ <![CDATA[3.0×10 -5 ]]> ○ <![CDATA[5.0×10 -5 ]]> ×

[0094] As shown in Table 1, in the case of the liquid metal ion source 50 of the first embodiment, the vacuum degree in the state where the oxidizing gas is introduced into the vacuum chamber 30 is 5.0×10 -6 ~1.5×10 -5 Pa range, the ion beam release is stable.

[0095] On the other hand, as shown in Table 2, in the case of the liquid metal ion source 50 of the second embodiment, the vacuum degree in the state where the oxidizing gas is introduced into the vacuum chamber 30 is 1.0×10 -5 ~3.0×10 -5 The reason why the vacuum degree of the liquid metal ion source 50 of the second embodiment is low (increasing the amount of oxidizing gas introduced) is considered to be that part of the oxidizing gas is exhausted by the exhaust system 46 and fails to reach the vacuum chamber 30 as described above.

[0096] Figure 6 The figure shows the time change of the voltage of the suppression electrode 26 when the oxidizing gas is not introduced into the vacuum chamber 30 in the liquid metal ion source 50 of the first embodiment. 14 hours after the start, the voltage of the suppression electrode 26 dropped to less than 0.1 kV.

[0097] Figure 7 In the liquid metal ion source 50 of the first embodiment, 1.0×10-5 Time change of the voltage of the suppression electrode 26 when the Pa oxidizing gas is used. The voltage of the suppression electrode 26 is maintained at 0.1 kV or more for more than 50 hours from the start.

[0098] Explanation of symbols

[0099] 10 Storage Room

[0100] 20 Needle Electrode

[0101] 22. Lead electrode

[0102] 24 beam aperture

[0103] 26 Suppression electrode

[0104] 30 Vacuum Chamber

[0105] 40 Oxidizing gas inlet

[0106] 45 Ion pump (final exhaust system)

[0107] 48 Oxidizing gas introduction control unit

[0108] 50, 50B Liquid Metal Ion Source

[0109] 70 Focusing lens

[0110] 100, 100B Focused ion beam device

[0111] IB Ion Beam

[0112] M Ionic materials (liquid metals)

Claims

1. A liquid metal ion source, comprising: a storage chamber that holds ionic materials that form the liquid metal; a needle-shaped electrode, the surface of which is covered with the ion material supplied from the storage chamber; An extraction electrode that releases ions of the ion material from the front end of the needle-shaped electrode; a beam aperture disposed on the downstream side of the extraction electrode to limit the beam diameter of the ions; and The vacuum chamber contains the storage chamber, the needle electrode, the extraction electrode and the beam aperture and maintains a vacuum. The liquid metal ion source is characterized in that it further comprises an oxidizing gas introduction part, the oxidizing gas introduction part is connected to the vacuum chamber and introduces the oxidizing gas into the periphery of the needle-shaped electrode. The liquid metal ion source further comprises a final exhaust system for exhausting the vacuum chamber to a target vacuum degree. When the final exhaust system and the oxidizing gas introduction part are connected to the vacuum chamber via different flow paths, the vacuum degree in the vacuum chamber when the oxidizing gas is introduced is 5.0×10 -6 Pa~1.5×10 -5 Pa; When the final exhaust system and the oxidizing gas introduction unit are connected to the vacuum chamber via the same flow path, the vacuum degree in the vacuum chamber in a state where the oxidizing gas is introduced is 1.0×10 -5 Pa~3.0×10 -5 Pa.

2. The liquid metal ion source according to claim 1, wherein The oxidizing gas is water vapor.

3. The liquid metal ion source according to claim 1, wherein The flow path of the final exhaust system and the flow path of the oxidizing gas introduction portion are at least partially opposed to each other in a direction perpendicular to the irradiation direction of the ion beam.

4. The liquid metal ion source according to claim 1, wherein The flow path of the final exhaust system and the flow path of the oxidizing gas introduction portion are respectively opposed to the needle-shaped electrode in at least a portion in a direction perpendicular to the irradiation direction of the ion beam.

5. The liquid metal ion source according to any one of claims 1 to 4, wherein The liquid metal ion source further includes an oxidizing gas introduction control unit for introducing the oxidizing gas into the vacuum chamber only when a voltage is applied between the needle-shaped electrode and the extraction electrode. 6 . A focused ion beam device comprising the liquid metal ion source according to claim 1 .

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