JPH10208652A - Ion current stabilizing method and ion beam device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize an ion current by introducing oxygen to the vicinity of a liquid metal ion source, guiding the secondary electrons from an optical part irradiated by discharged ions to the liquid metal ion source and removing impurities on the liquid metal surface. SOLUTION: When a discharged ion current becomes unstable, oxygen is introduced from a gas cylinder 10, by applying a potential negative to an extraction electrode 3 to a beam limiting aperture 4, most of the secondary electrons generated in the aperture 4 pass a hole 6 and rush in a emitter. The quantity of generated secondary electrons is approximately equal to that of the irradiation ion current. As a result of the interaction between the electrons generated by positive irradiation of the emitter and the introduced oxygen, an insoluble film including carbides as the main component formed on the liquid metal surface is decomposed and removed so that a clean liquid metal surface can be exposed. In this way, the tailor cone is stabilized both in position and time and a discharge ion current is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ion current stabilizing method and an ion beam apparatus using the same.

[0002]

2. Description of the Related Art Liquid metal ion source (Liquid Metal Ion S)
Focused Ion Beam (Focused Ion Beam: Abbreviated below) using ource: LMIS (abbreviated below)
IB) or a stencil mask having an aperture pattern and an appropriate lens configuration can form a projection ion beam (PJIB). FIB is used for forming local cross sections and correcting wiring of semiconductor devices, and PJIB is being applied to ion exposure and maskless ion implantation.

FIG. 2 is a schematic configuration example of a conventional FIB device 29. An LMIS having a needle-like emitter serving as an ion emitting portion of a substantially point-like region; an extraction electrode for forming a high electric field at the tip of the emitter; a beam limiting aperture for selecting only a central portion of the emitted ions; A focusing lens (also referred to as a condenser lens) 15 for suppressing or converging the beam, deflectors 17a and 17b for correcting the trajectory of the ion beam 16, and a stop for improving the convergence of the ion beam 16, particularly having different diameters Selectable aperture 1 having a plurality of openings 18a, 18b, 18c and selectable
9. FIB by focusing ion beam 16 on sample 23
16 ′, the objective lens 21 and the FIB 16 ′
The scanner 22 includes a scanner 22 that scans and sweeps the sample, a sample stage 24 that finely moves while holding the sample 23, and a secondary electron detector 25 that detects secondary electrons emitted by irradiating the sample 23 with the FIB 28. The optical components are held in a vacuum container 28.

However, there are various types of arrangements and positional relationships of these ion optical components in order to enhance the ion beam characteristics, and this diagram is merely an example. A power supply for supplying a voltage to the LMIS 2, the focusing lens 15, the deflectors 17a and 17b, the objective lens 21, the scanner 22, and the sample stage 24 is provided, but is omitted in the drawing.

As shown in FIG. 3A, a LMIS 2 connects a current introduction terminal 31 fixed to a base 30 of an insulator, and a heater 32 for converting an ionic material to be ionized into a liquid.
A reservoir 34 for storing the ionic material 33;
It is composed of a needle-like emitter 35 which substantially serves as an ion emitting portion. An acceleration voltage is applied to the emitter 35, and a negative potential (extraction voltage) is applied to the opposing extraction electrode 3 with respect to the emitter 30.
As shown in FIG. 3B, a small projection 36 called a Taylor cone is formed at the tip of the emitter 35, and the ions 5 are emitted from the tip. Most of the emitted ions 5 are blocked by the beam limiting aperture 4, and only the central portion is guided to the downstream ion optical system and formed in the FIB.

[0006] For an LMIS, FIB apparatus and an application using the FIB, see John Melingairis.
Melngailis) has published a book, Journal of V Science and Technology (Journal of V)
acuum Science and Technology), Volume B5 (1987)
) From page 469 to page 495.

Regarding PJIB, A. Chalupka et al. Published a paper collection “Microelectronic Engine”.
ering) Vol. 17 (1992), pp. 229 to 2
On page 40, a reduced ion exposure apparatus using a plasma ion source as an ion source is described in detail as an example.

[0008]

Whatever the application of an ion beam apparatus equipped with an LMIS, the ion beam current must be stable for a long time. In order for the ion current to be stable, the liquid metal in the LMIS is smoothly supplied from the reservoir to the tip of the emitter without stagnation,
The tailor cone at the tip of the emitter must be positionally and temporally stable. However, the LMIS used in the current ion beam apparatus is not always highly stable depending on its operating environment and operating conditions.

[0009] The instability of the ion current is caused by the formation of an oxide film or a carbon film on the surface of the liquid metal due to the oxygen or carbon of the residual gas particles in the vacuum vessel. When reached, it is interpreted as inhibiting the stable formation of the Taylor cone and destabilizing the ionic current. On the other hand, if the ion current becomes unstable during the operation of the ion beam apparatus, the apparatus operator customarily raises the LMIS to a higher temperature than the normal operation state, discharges a large current, or performs both at the same time. We are trying to restore stability. As another method of stabilizing the ion current, the method disclosed in Japanese Patent Publication No. 6-18109, "Method for Cleaning Liquid Metal Ion Source" (known example 1) introduces hydrogen or argon around the LMIS. LM
This is a method in which a high voltage is applied to the IS to discharge the LMIS, and carbon attached to the liquid metal is removed as a hydrocarbon gas or removed physically. As another example, Japanese Patent Application Laid-Open
JP-153403A, "Liquid metal ion source and method for stabilizing ion current" (known example 2), also discloses a method of irradiating hydrogen ions or hydrogen radicals.

Many oxide films formed on the surface of the liquid metal can be removed relatively easily by heating the liquid metal. For example, in the case of gallium (Ga), which is most widely used as a liquid metal, Ga oxide volatilizes at about 600 ° C.
The clean Ga surface is exposed, and the ionic current is stabilized. However, carbon films and organic compound films are difficult to remove by heating,
In the case of Ga-LMIS, it cannot be removed even by heating to 600 ° C. If the temperature is further increased, Ga itself evaporates, which promotes unnecessary evaporation of Ga to shorten the life of the LMIS, and causes secondary problems such as dielectric breakdown due to evaporation of the evaporated Ga on an insulator. Further, in the method in which the LMIS emits a larger current than in the normal operation state, a slight impurity at the tip of the emitter can be temporarily removed, but not all the impurities attached to the surface of the liquid metal can be removed. It becomes unstable, and a large current must be emitted each time, which is not a drastic stabilization method.

Further, in the method of the prior art 1, although the carbon film on the surface of the liquid metal can be removed, a discharge occurs even in a high-potential metal portion to which the liquid metal does not adhere, such as a heater portion and a current introduction terminal portion of the LMIS. In addition, metal particles other than the liquid metal are scattered in the vacuum vessel, which becomes a source of contamination to the liquid metal and the sample. In particular, although the carbon film on the surface of the liquid metal can be removed even by physical sputtering by introducing argon, since the heater, the current introduction terminal, and the liquid metal are sputtered, the sputtered particles from the high-potential metal portion to which the liquid metal is not adhered. It involves the problem of scattering and unnecessary consumption of liquid metal. Further, the method of the known example 2 requires a hydrogen ion source and a radical generation source to be irradiated toward the emitter, and also requires a power supply and the like. This has a problem that the device configuration is complicated and the efficiency of the device is not good, such as mounting a power source for a hydrogen ion source or a radical source that is used less frequently.

Under such circumstances, the FIB device and the PJI
In an ion beam apparatus equipped with an LMIS such as an apparatus B, if the ion current becomes unstable, some method of recovering the ion current without causing a secondary problem with a simple apparatus configuration is desired. I was

The present invention has been made in view of the above problems, and a first object of the present invention is to provide a method for stabilizing an ion current in an ion beam apparatus. A second object is to provide an ion beam apparatus that can realize an ion current stabilizing method.

[0014]

The cause of destabilizing the ion current is other than the oxide film and carbon film formed by adsorbing the residual oxygen and carbon in the vacuum vessel on the surface of the liquid metal as described above. I understand. FIG. 4A is a cross-sectional view of the vicinity of the tip of the LMIS emitter. A liquid metal 33 to be ionized is attached on the emitter 35, and ions are emitted by applying an extraction voltage to the extraction electrode 3 (FIG. 4A). 4 in the figure
1 indicates the trajectory of the emitted ions).

The emitted ions pass through the hole 6 of the extraction electrode 3 and collide with the beam limiting aperture 4. Secondary electrons 42 are generated from the beam limiting aperture 4 which has been subjected to ion irradiation,
The beam returns to the emitter 35 which is at a positive potential with respect to the beam limiting aperture 4 and the extraction electrode 3, particularly to the liquid metal 33 at the tip (43 in the figure indicates the trajectory of secondary electrons). For example, if the emitted ion current is 2 μA, the emitted secondary electrons are about 1.
At 5 μA, most of it passes through hole 6 and strikes emitter 35.

On the other hand, a part of the residual gas 44 (in particular, carbon) floating near the emitter is adsorbed on the liquid metal 33.
The adsorbed residual gas 44, secondary electrons 42 and liquid metal 3
3 react with each other to form a liquid metal carbide. For example, when the liquid metal is Ga, a Ga / C compound is formed.

The carbide grows by the operation of the ion source (FIB formation) for a long time, and as shown in FIG.
An insoluble carbonized film 45 is formed on the surface. This carbonized film 45
Cannot be removed by simple heating or high-current ion emission, so if it covers the tip of the liquid metal 33, it becomes difficult to maintain a stable Taylor cone, the ion current becomes unstable, and finally the ion current stops. It will fall until.

In the present invention, the following method is used to solve such instability of the ion current. This will be described with reference to FIG. Oxygen 50 is introduced near the LMIS, and ions are released as usual. As described above, the emitted ions irradiate the ion optical component, for example, the beam limiting aperture 4, and secondary electrons 42 are generated from the irradiated portion and collide with the emitter 35. At this time, the insoluble carbonized film 45 on the liquid metal surface is
Due to the interaction between the oxygen 50 and the rushing secondary electrons 42, the oxygen 50 changes into a hydrocarbon gas or the like, and becomes a gas and separates from the liquid metal 33.

More specifically, in the present invention, the following configuration is employed to achieve the first object.

(1) A method of stabilizing an ion current in an ion beam apparatus using a liquid metal ion source, wherein oxygen is introduced into the vicinity of the liquid metal ion source, and secondary electrons from an optical component irradiated with emitted ions are irradiated. To the liquid metal ion source to remove impurities on the surface of the liquid metal.

(2) In the ion current stabilizing method of the above (1), the optical component irradiated with the emitted ions is particularly a beam limiting aperture.

(3) A step of measuring the ion current by the ion current stabilizing method of (1) or (2), a step of comparing the ion current with a predetermined fluctuation width of the ion current, and a fluctuation width of the ion current Introducing oxygen into the vicinity of the liquid metal ion source when the predetermined fluctuation range is exceeded, and discharging the secondary electrons generated in the ion optical component irradiated with ions emitted from the liquid metal ion source to the liquid metal ion source. And a step of leading to an ion source.

(4) A liquid metal ion source, an extraction electrode for controlling the ion emission of the liquid metal ion source, and a beam limiting aperture for limiting a substantial opening angle of the ion beam emitted from the liquid metal ion source. Wherein the beam limiting aperture is electrically insulated from the extraction electrode, and the beam limiting aperture is at the same potential or positive potential with respect to the extraction electrode during normal ion emission. age,
When it is necessary to recover the stability of the ion current, oxygen is introduced into the vicinity of the liquid metal ion source, and the beam limiting aperture is set to a negative potential with respect to the extraction electrode, and the secondary generated by the beam limiting aperture is set. A step of guiding electrons to at least the liquid metal ion source to remove impurities floating on the surface of the liquid metal.

(5) In the ion current stabilizing method according to any one of the above (1) to (4), gallium is particularly used as the liquid metal.

(6) A method for removing impurities on the surface of a liquid metal in a liquid metal ion source, wherein oxygen is introduced into a vacuum vessel in which the liquid metal ion source is installed, and the liquid metal is irradiated with electrons. Remove impurities on the metal surface.

(7) In the impurity removing method of (6), the liquid metal is gallium.

The second object of the present invention is achieved by the following constitution.

(8) An ion source chamber in which a liquid metal ion source is mounted, an extraction electrode for emitting ions from the liquid metal ion source, and a substantial opening angle of an ion beam emitted from the liquid metal ion source is limited. 1. An ion beam apparatus comprising at least a beam limiting aperture for introducing a gas, comprising: gas introducing means for introducing oxygen at least near the liquid metal ion source; and a power supply for applying a potential to the beam limiting aperture.

(9) In the above (8), further, an ammeter for measuring an ion current emitted from the liquid metal ion source, a vacuum gauge for measuring a degree of vacuum in the ion source chamber, and at least an output of the ammeter. And a signal processing means for controlling the gas introduction means.

(10) In the above (8) to (9),
The ion beam device is a focused ion beam device or a projection ion beam device.

(11) The ion beam apparatus according to (10), wherein the liquid metal ion source is a gallium liquid metal ion source.

[0032]

DETAILED DESCRIPTION OF THE INVENTION An ion beam apparatus according to the present invention is an ion beam apparatus including a liquid metal ion source and a beam limiting aperture for limiting a substantial opening angle of an ion beam emitted from the liquid metal ion source. The configuration is such that at least gas introducing means for introducing a reactive gas around the liquid metal ion source and a power supply for applying a potential to the beam limiting aperture are provided. When the emission ion current becomes unstable using this ion beam device, the LMI
Oxygen is introduced near S, and ions are released as usual. By setting the beam limiting aperture to several tens of volts positive potential with respect to the extraction voltage, most of the secondary electrons generated by the emitted ions irradiating the beam limiting aperture irradiate the emitter of the liquid metal ion source, The insoluble carbon film floating on the surface of the liquid metal is decomposed by the interaction between the introduced oxygen and the irradiation of the secondary electrons to form a clean liquid metal surface. The emitted ion current is stabilized by such a device configuration and method.

(Embodiment 1) A specific embodiment of an ion beam apparatus according to the present invention will be described with reference to FIG. FIG. 1 shows a schematic configuration of the ion beam apparatus 1, and includes an LMIS 2, an extraction electrode 3, a beam limiting aperture 4, a power supply 4 'for applying a voltage to the beam limiting aperture 4, a gas cylinder 10, an adjusting valve 12, and the like ( The description of the parts common to FIG. 2 is omitted).

Oxygen can be gradually introduced from the gas cylinder 10 to the vicinity of the LMIS 2 via the valve 11 and the regulating valve 12.
The adjustment of the gas introduction amount is performed by the adjustment valve 12 while monitoring the vacuum gauge 14.
2 is performed by the signal processing device 26. The outputs of the power supplies 2 ', 3', 4 ', 15', 17 ', and 21', the selection aperture 19 and the controller 20 'of the sample stage 24,
Control of 24 ', secondary electron detector 25 and sample 23
Is monitored by the signal processing device 26 and can be displayed on the monitor 27 as needed.

With such an apparatus configuration, the beam current flowing into the sample 23 or the ion current emitted by the LMIS 2 is monitored one by one, and if the fluctuation width is larger than a predetermined fluctuation width, the adjusting valve 12 is set to a predetermined value. Release gradually until the degree of vacuum is reached, and clean the liquid metal. To show specific numerical values, the total emission ion current is set to 3 μA and the current fluctuation width is set to within 3% per hour. The degree of vacuum during normal ion current emission was 3 × 10 to ⁵ Pa, the degree of vacuum during oxygen introduction was 3 × 10 to ² Pa, and the applied voltage to the beam limiting aperture was −40 V. In particular, setting the introduction amount of from 1 × 10 ~ ² 1
× a 10 ~ ⁴ Pa approximately, cause discharge when a large amount introduced to the ion emission can not be expected inherent effect is too small to reverse.

Details around the LMIS 2 and the beam limiting aperture 4 will be described with reference to FIG. FIG. 6A shows an example of a structure in which the beam limiting aperture 4 disconnects the electrical contact with the extraction electrode 3 via the insulating layer 60. The beam limiting aperture 4 can be set at a potential different from that of the extraction electrode 3 by the power supply 4 ′. To positively collide secondary electrons with the emitter 35, the extraction electrode 3 is set at a positive potential of several tens of volts. During normal ion emission, the output of the power supply 4 'is set to zero and set to the same potential as the extraction voltage 3.

When the emission ion current becomes unstable, oxygen is introduced from the gas cylinder and a negative potential is applied to the extraction electrode 3 to the beam limiting aperture 4. A part goes to the extraction electrode, but most passes through the hole 6 and enters the emitter 35. The potential difference between the extraction electrode 3 and the emitter 35 is 5 to 1
Since it is 0 kV, electrons having energy of 5 to 10 keV are colliding with the emitter. The amount of secondary electrons generated is approximately the same as the irradiation ion current. Due to the interaction between the introduced oxygen and the electrons actively irradiated to the emitter, the insoluble coating mainly composed of carbide formed on the surface of the liquid metal is decomposed and removed, and the clean liquid metal surface is exposed. . As a result, the tailor cone is temporally stabilized in position, the emission ion current is stabilized, and the resulting FIB is also stabilized.

FIG. 6B shows an example in which a space is provided between the beam limiting aperture 4 and the extraction electrode 3 to maintain electrical insulation. The beam limiting aperture 4 is attached to a conductive support member 61, and a voltage from a power supply (not shown) is applied to the support member 61.

By using such an ion beam apparatus 1, unnecessary metal particles are not scattered by the discharge of the LMIS, and another expensive ion source or radical source for removing impurities on the surface of the liquid metal is installed. Since the ion current can be stabilized without performing, and the ions are released even during the cleaning of the liquid metal, monitoring the ion current allows the user to know the stability recovery state of the ion current,
The cleaning time can be increased or decreased as necessary, and the cleaning can be effectively terminated. Further, since a series of operations can be controlled by the signal processing device, the stability of the ionic current can be automatically restored without human intervention.

(Embodiment 2) This embodiment is an apparatus for cleaning an LMIS in which stable operation cannot be expected and restoring stable operation. This will be described with reference to FIG. At least one set of LMISs 71a, 71b and extraction electrodes 72a, 72b can be installed in the vacuum vessel 70 (two sets in FIG. 7), and has an electron generating means. The electron generating means is a filament 73. By heating the filament 73 and providing a potential difference between the LMISs 71a and 71b, the electrons generated by the filament 73 are reduced to L.
The MISs 71a and 71b can be irradiated. Further, the present apparatus has gas introducing means 74 including a gas cylinder, a valve, a regulating valve, and the like for supplying oxygen into the vacuum vessel 70.

By introducing a small amount of oxygen from the gas introducing means 74 along with the generation of electrons, the carbonized film can be decomposed and removed by the interaction between the carbonized film and oxygen and electrons at the tip of the emitter. Since this vacuum vessel has a simple configuration in which only the LMIS, the electron generating means, and the gas introducing means are arranged, it is possible to recover the stable current of the LMIS exclusively on a regular basis without installing any additional means such as a gas cylinder in the ion beam apparatus. Can be used as a device.

The present apparatus can be used for cleaning the surface of a liquid metal at the time of filling an ionic material (liquid metal) into a reservoir at the time of preparing an LMIS, and can remove carbides floating in the liquid metal before filling, thereby providing a clean liquid. It has the effect of filling metal.

The LMIS stable current recovery device shown in FIG. 7 requires an ion accelerating power source, an ion extracting power source, an electron accelerating power source, an LMIS heating power source, etc., but they are omitted in FIG.

(Embodiment 3) FIG. 8 shows a PJ using an LMIS.
This is an embodiment of the IB device 80, in which the ions extracted from the LMIS 2 are directed to the irradiation lens 81 with the opening angle limited by the beam limiting aperture 4, and the ion beam 8
Reference numeral 2 denotes a stencil mask 85 having an opening pattern 84 while changing the trajectory so as to focus on the center of the projection lens 83.
Is irradiated. The opening pattern 84 is a through hole having an enlarged beam shape to be projected onto the sample 85. The FIB scans a thin ion beam to form a desired irradiation area, whereas the PJIB is an opening pattern provided on the stencil mask 85. It is determined by 84 shapes. In this embodiment, a rectangular opening is shown, but the opening pattern 84 is not limited to this.

In such a PJIB device 80,
Since the instability of the ion beam impairs the desired projection pattern 86 to be formed, a method for restoring the stability of the beam current is an essential technique. In this embodiment, a gas cylinder filled with a reactive gas, particularly an oxygen gas, is installed and introduced into the ion source chamber via a valve, a regulating valve, and a nozzle. While monitoring the degree of vacuum in the ion source chamber with a vacuum gauge, the control valve is opened and closed to adjust the amount of gas to be introduced. The amount of reactive gas introduced may be set to 10 -1 to -5 Pascal.

Also in this embodiment, the timing of introducing the reactive gas, the monitoring of the degree of vacuum, the control of the regulating valve, the regulation of the released ion current, etc. are performed by the signal processing device, but are not shown in FIG.

[0047]

According to the present invention, when the emission ion current of the LMIS in the FIB device becomes unstable, the ion current can be stabilized with a simple device configuration.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an ion beam device according to the present invention.

FIG. 2 is an explanatory diagram of a conventional FIB device.

FIG. 3 is an explanatory diagram of an LMIS in a conventional FIB device.

FIG. 4 is an explanatory diagram of a problem that occurs in a conventional LMIS.

FIG. 5 shows an LMI in the ion beam apparatus according to the present invention.
FIG.

FIG. 6 is an explanatory diagram of a setting method of a beam limiting aperture in the ion beam device according to the present invention.

FIG. 7 is an explanatory view of another embodiment of an ion beam apparatus according to the present invention, which stabilizes an ion current of an LMIS that emits unstable ions.

FIG. 8 is an explanatory view of another embodiment of the ion beam device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ion beam apparatus, 2 ... LMIS, 3 ... Extraction electrode, 4 ... Beam limiting aperture, 5 ... Ion, 33 ... Liquid metal, 35 ... Emitter, 42 ... Secondary electrons, 45 ... Carbonized film, 50 ... Oxygen.

Claims (11)

[Claims] 1. A method for stabilizing an ion current in an ion beam apparatus using a liquid metal ion source, wherein oxygen is introduced into the vicinity of the liquid metal ion source, and secondary electrons from an optical component irradiated with emitted ions are emitted from the optical element. An ion current stabilizing method, wherein the method is directed to a liquid metal ion source to remove impurities on the surface of the liquid metal. 2. The ion current stabilizing method according to claim 1, wherein the optical component irradiated with the emitted ions is a beam limiting aperture. 3. The method according to claim 1, wherein the step of measuring the ion current, the step of comparing the ion current with a predetermined fluctuation width of the ion current, and the case where the fluctuation width of the ion current exceeds the predetermined fluctuation width are performed. Introducing an oxygen into the vicinity of the liquid metal ion source, and a step of guiding secondary electrons generated in an ion optical component irradiated with ions emitted from the liquid metal ion source to the liquid metal ion source. Stabilization method. 4. A liquid metal ion source, an extraction electrode for controlling ion emission of the liquid metal ion source, and a beam limiting aperture for limiting a substantial opening angle of an ion beam emitted from the liquid metal ion source. In an ion current stabilizing method for an ion beam device including at least, the beam limiting aperture is electrically insulated from the extraction electrode, and the beam limiting aperture is set to the same potential or a positive potential with respect to the extraction electrode during normal ion emission. When it is necessary to recover the stability of the current, oxygen is introduced into the vicinity of the liquid metal ion source, and the beam limiting aperture is set to a negative potential with respect to the extraction electrode, and the secondary electrons generated in the beam limiting aperture are set. At least to the liquid metal ion source to remove impurities floating on the liquid metal surface A method for stabilizing an ion current, comprising: 5. The method according to claim 1, wherein said liquid metal is gallium. 6. A method for removing impurities on a surface of a liquid metal in a liquid metal ion source, wherein oxygen is introduced into a vacuum vessel in which the liquid metal ion source is installed, and the liquid metal is irradiated with electrons to thereby remove the surface of the liquid metal. A method for removing impurities, comprising removing impurities. 7. A method according to claim 6, wherein said liquid metal is gallium. 8. An ion source chamber for mounting a liquid metal ion source, an extraction electrode for emitting ions from the liquid metal ion source, and limiting a substantial opening angle of an ion beam emitted from the liquid metal ion source. An ion beam apparatus including a beam limiting aperture, comprising: gas introducing means for introducing oxygen near the liquid metal ion source; and a power supply for applying a potential to the beam limiting aperture. 9. An ammeter for measuring an ion current emitted from the liquid metal ion source, a vacuum gauge for measuring a degree of vacuum in the ion source chamber, and processing the output of the ammeter to produce the gas by processing the output of the ammeter. An ion beam device including signal processing means for controlling the introduction means. 10. An ion beam device according to claim 8, wherein said ion beam device is a focused ion beam device or a projection ion beam device. 11. An ion beam apparatus according to claim 10, wherein said liquid metal ion source is a gallium liquid metal ion source.