JP2015076302A - Ion beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion beam device with a cooling mechanism which prevents vibration generated by the cooling mechanism from being transmitted to the ion beam device and enables heat insulation.SOLUTION: A cooling mechanism of the invention includes: a refrigerant for cooling an emitter tip; a refrigeration machine for cooling the refrigerant; refrigerant discharge means; and refrigerant supply means. The invention stops the operation of the refrigeration machine when observing a high resolution image and discharges the refrigerant which cools the emitter tip.

Description

The present invention relates to an ion beam apparatus. For example, the present invention relates to an ion beam apparatus such as an ion microscope and an ion beam processing observation apparatus, a combined apparatus of an ion beam processing observation apparatus and an ion microscope, and a combined apparatus of an ion microscope and an electron microscope. The present invention relates to an analysis / inspection apparatus using an ion microscope and an electron microscope.

  By irradiating the sample while scanning electrons and detecting secondary charged particles emitted from the sample, the structure of the sample surface can be observed. This is called a scanning electron microscope (hereinafter abbreviated as “SEM”). On the other hand, the structure of the sample surface can be observed even when the sample is irradiated with the ion beam and the secondary charged particles emitted from the sample are detected. This is called a scanning ion microscope (hereinafter abbreviated as “SIM”). In particular, if the sample is irradiated with a light ion species such as hydrogen or helium, the sputtering effect becomes relatively small, which is suitable for observing the sample.

  A gas field ion source is suitable as the ion source of the ion microscope. A gas field ion source is an ion source that is used as an ion beam by ionizing a gas by an electric field created by an emitter tip. The ion source has a gas ionization chamber having a needle-like emitter tip to which a high voltage can be applied. An ionized gas is supplied from the gas source to the gas ionization chamber through a gas supply pipe. A potential barrier in which electrons in a gas (gas molecule) are reduced by an electric field when an ionized gas (or gas molecule) supplied from a gas supply pipe approaches the tip of a needle-like emitter tip to which a high voltage is applied and a strong electric field is applied. Is released as positive ions by tunneling. This is used as an ion beam. The gas field ion source can generate an ion beam having a narrow energy width. Further, since the size of the ion generation source is small, a fine ion beam can be generated.

  In order to observe a sample with a high signal / noise ratio in an ion microscope, it is necessary to obtain an ion beam having a large current density on the sample. For this purpose, it is necessary to increase the ion emission angular current density of the field ion source. In order to increase the ion radiation angle current density, the molecular density of the ionized gas (ion material gas) in the vicinity of the emitter tip may be increased. The gas molecule density per unit pressure is inversely proportional to the gas temperature. Therefore, the emitter tip may be cooled to a very low temperature, and the temperature of the gas around the emitter tip may be lowered. Thereby, the molecular density of the ionized gas near the emitter tip can be increased. Further, the molecular density of the ionized gas near the emitter tip can be increased by increasing the pressure of the ionized gas near the emitter tip. For example, the pressure of the ionized gas around the emitter tip is about 10-2 to 10 Pa.

In Patent Document 1, as an ion beam device that can prevent vibration generated by a refrigeration mechanism from being transmitted to an emitter tip of a gas field ion source, a container that holds a coolant that cools the emitter tip, and the temperature of the coolant There is disclosed a cooling mechanism having a temperature measuring device for measuring the temperature and a cooling mechanism composed of a refrigerator for cooling the refrigerant, and operating and stopping the refrigerator according to the temperature of the refrigerant. Also, there are two containers for holding the refrigerant for cooling the emitter tip, and it has a temperature measuring device that measures the temperature of the refrigerant and a cooling mechanism that includes a refrigerator that cools the refrigerant. And a cooling mechanism for determining which refrigerant is connected to the container holding the refrigerant. It also has a cooling mechanism consisting of a container that holds the refrigerant that cools the emitter tip, a temperature measurement device that measures the temperature of the refrigerant, and a vacuum pump that evacuates the container that holds the refrigerant. A cooling mechanism for operating and stopping the pump is disclosed.

JP 2009-289670 A

  As a result of intensive studies on the cooling mechanism for preventing the vibration generated by the cooling mechanism from being transmitted to the ion beam device, the present inventors have obtained the following knowledge.

  Patent Document 1 is very effective in preventing vibration generated by the refrigeration mechanism from being transmitted to the emitter tip of the gas field ion source. However, it has been found that the time during which an image can be acquired after the operation of the refrigerator is stopped is very short unless thermal insulation is taken into consideration, and may not be able to withstand practical use.

An object of the present invention is to provide an ion beam apparatus having a cooling mechanism that can prevent vibration generated by the cooling mechanism from being transmitted to the ion beam apparatus and can also be thermally insulated.

The present invention employs the configurations described in the claims. For example, when the cooling mechanism has a refrigerant that cools the emitter tip, a refrigerator that cools the refrigerant, a means that discharges the refrigerant, and a means that supplies the refrigerant. Stop driving. And it is related with discharging | emitting the refrigerant | coolant which cools an emitter tip.

When the refrigerator is stopped, the temperature of the refrigerator cooler starts to rise. If the refrigerator and the emitter tip are not thermally insulated, this increased temperature continues to flow from the refrigerator to the emitter tip via the refrigerant that cools the emitter tip. Then, the temperature of the emitter tip continuously rises. According to the present invention, when the operation of the refrigerator is stopped, the refrigerant that cools the emitter tip is discharged, so that the increased temperature of the refrigerator cold temperature portion flows from the refrigerator to the emitter tip via the refrigerant that cools the emitter tip. There is no. That is, the refrigerator and the emitter tip are thermally insulated. Therefore, even when the refrigerator is stopped, the temperature of the emitter tip can hardly be increased. And since the temperature of an emitter tip does not rise easily, the time which can acquire an image becomes long.

1 is a schematic configuration diagram of a first embodiment of an ion beam apparatus according to Embodiment 1. FIG. 2 is an example of refrigerant discharge of the first embodiment. It is a schematic diagram of the temperature change of the emitter tip when the refrigerator is stopped. It is an operation | movement flow at the time of high-resolution image observation. FIG. 6 is a schematic configuration diagram of a second embodiment of the ion beam apparatus according to Embodiment 2. FIG. 6 is a schematic configuration diagram of a third embodiment of the ion beam apparatus according to Embodiment 3. FIG. 6 is a schematic configuration diagram of a fourth embodiment of an ion beam device according to Embodiment 4.

  The ion beam apparatus described below is more sensitive to information on the sample surface than an apparatus using an electron beam. This is because the excitation region of the secondary charged particles is localized on the sample surface as compared with the irradiation of the electron beam. In addition, since the electron beam property cannot be ignored in the electron beam, aberration occurs due to the diffraction effect. On the other hand, since the ion beam is heavier than electrons, the diffraction effect can be ignored.

  As an ion beam apparatus taking advantage of these features, for example, there is a scanning ion microscope. A scanning ion microscope is an apparatus that irradiates a sample while scanning an ion beam, detects secondary charged particles emitted from the sample, and observes the structure of the sample surface. In particular, if the sample is irradiated with a light ion species such as hydrogen or helium, the sputtering effect becomes relatively small, which is suitable for observing the sample.

  In addition, if an ion beam is irradiated on a sample and ions that have passed through the sample are detected, information reflecting the structure inside the sample can be obtained. This is called a transmission ion microscope. In particular, if the sample is irradiated with a light ion species such as hydrogen or helium, the rate of transmission through the sample is increased, which is suitable for observation.

  Conversely, if the sample is irradiated with a heavy ion species such as argon, xenon, or gallium, it is suitable for processing the sample by sputtering. In particular, a focused ion beam apparatus (Focused Ion Beam, hereinafter abbreviated as FIB) using a liquid metal ion source (hereinafter abbreviated as LMIS) is known as a focused ion beam processing observation apparatus. Furthermore, in recent years, a combined machine FIB-SEM apparatus of a scanning electron microscope (SEM) and a focused ion beam (FIB) is also used. In the FIB-SEM apparatus, the cross section can be observed by SEM by irradiating the FIB and forming a square hole at a desired location. The sample can also be processed by generating gas ions such as argon and xenon by a plasma ion source or a gas field ion source and irradiating the sample.

  The present invention can be applied to an ion microscope, an ion beam processing observation apparatus, a combined apparatus of an ion beam processing observation apparatus and an ion microscope, and a combined apparatus of an ion microscope and an electron microscope. Moreover, it is applicable also to the analysis / inspection apparatus which applied the ion microscope and the electron microscope. These are collectively referred to as an ion beam apparatus. The ion beam apparatus of the present invention is not limited to the above apparatus as long as it is an ion beam apparatus using a gas field ion source.

  In an embodiment, in an ion beam apparatus that irradiates a sample with an ion beam generated from a gas field ion source, the gas field ion source includes an emitter tip serving as an anode, an extraction electrode serving as a cathode, and at least an emitter tip. A gas container that supplies gas through a gas inlet to the space between the tip of the emitter tip and the extraction electrode, a gas exhaust that exhausts gas by a vacuum pump through the gas exhaust, and a gas electric field And a cooling mechanism for cooling the ionization ion source.

  In the embodiment, it is disclosed that the cooling mechanism includes a refrigerant for cooling the emitter tip, a refrigerator for cooling the refrigerant, a means for discharging the refrigerant, and a means for supplying the refrigerant.

  Moreover, in an Example, it discloses that the gas exhaust port or the gas introduction port is provided in the structure of the ground potential.

  The above and other novel features and effects will be described below with reference to the drawings. It should be noted that the drawings are used exclusively for understanding the invention and do not limit the scope of rights.

  Further, illustration of a vacuum exhaust system including a valve for evacuating the vacuum vessel, a sample stage for placing and moving the sample, and a control means for controlling each mechanism are omitted.

  Also, the focusing lens, objective lens / beam deflector / aligner, blanking electrode, and power source of the beam deflector are not shown.

An image generation unit that generates an image based on a signal output from the detector is not shown.

A first embodiment of the ion beam apparatus will be described with reference to FIG.
The ion beam apparatus evacuates the ion source chamber 5 having the emitter tip 1, the extraction electrode 2, the gas supply pipe 4, the gas exhaust port 52, the cooling mechanism 60, the cooling conduction mechanism 61, and the radiation shield 12, and the ion source chamber 5. Ion source evacuation pump 20 for evacuation, valve 21, ionized gas source 15, acceleration power supply 7 for supplying voltage to emitter tip 1, extraction power supply 8 for supplying voltage to extraction electrode 2, and vacuum vessel 10 A connection port (or a connection port with the radiation shield 12) between the gas supply pipe 4 and the ion source chamber 5 is generically referred to as a gas introduction part. In this embodiment, the gas exhaust port 52 is referred to as a gas exhaust unit. The ion source chamber 5 and the vacuum vessel 10 are connected via an opening 18. The ion source is a gas field ionization ion source (abbreviated as a gas ion source), which is connected to a gas ionization chamber 6 having a needle-like emitter tip 1 to which a high voltage can be applied from a gas source 15 through a gas supply pipe 4. To supply ionized gas. When the ionized gas (or gas molecule) supplied from the gas supply pipe 4 approaches the tip of the needle-like emitter tip 1 to which a high electric field is applied and a strong electric field is applied, electrons in the gas (gas molecule) are reduced by the electric field. The potential barrier is tunneled and released as positive ions. The gas ion source is an ion source that uses this as an ion beam.

  The cooling mechanism 60 includes a refrigerator 62, a bellows 63, a refrigerant 64 (in this embodiment, helium gas is used as a refrigerant), a high temperature side stage 65 that cools the radiation shield 12, a low temperature side stage 66 that cools the emitter tip 1, A compressor (compressor unit) 69 that uses helium gas as a working gas, a high-pressure pipe 67 that supplies high-pressure helium gas to the refrigerator 62, and the high-pressure helium gas that is periodically expanded inside the refrigerator 62 causes cooling. And a low-pressure pipe 68 that recovers the low-pressure helium gas that has expanded to a low pressure in the compressor 69, a refrigerant discharge means, and a refrigerant supply means. The refrigerant discharge means includes a refrigerant discharge pipe 84, a valve 8, and a refrigerant discharge mechanism 86 (a vacuum pump is used in this embodiment). The refrigerant supply means includes a refrigerant supply pipe 81, a valve 82, and a refrigerant source 83.

  A voltage is applied to the emitter tip 1 by the acceleration power supply 7, and a voltage is applied to the extraction electrode 2 from the extraction power supply 8. The ion source chamber 5 is fixed to the ground potential (GND) regardless of the operation of the ion beam apparatus. The ion source chamber 5 is a vacuum container configured to surround the emitter tip 1. In this embodiment, the space surrounded by the ion source chamber 5 and the radiation shield 12 is a gas ionization chamber 6 that ionizes the gas. In this embodiment, the gas ionization chamber 6 refers to a structure that is composed of one or more members so as to surround at least the emitter tip 1 and into which gas is introduced.

  Ions emitted from the emitter tip 1 are focused on the sample 72 by the focusing lens 70 and the objective lens 71. Between both lenses are a beam deflector / aligner 73, a movable beam limiting aperture 74, a blanking electrode 75, a blanking beam stop plate 76, and a beam deflector 77. Secondary electrons emitted from the sample 72 are detected by a secondary electron detector 78. The control means (not shown) includes an acceleration power source 7, a drawing power source 8, a focusing lens 70, an objective lens 71, a beam deflector / aligner 73, a movable beam limiting aperture 74, a blanking electrode 75, a beam deflector 77, and secondary electrons. The detector 78 and the like are controlled. The control means (not shown) may be configured as hardware by a dedicated circuit board, or may be configured by a program executed by a computer (not shown) connected to the ion beam apparatus. In this embodiment, the number of the exhaust ports 80 and the vacuum pumps 22 of the vacuum container 10 is one, but a plurality of them may be provided.

  The vacuum vessel 10 is fixed to a base plate 24, and the base plate 24 is fixed by a vibration isolation mechanism 23 and a mount 25 that reduce vibration transmitted from the floor to the apparatus. The refrigerator 62 is fixed to the gantry 25 by a column 26.

  A method of observing a high resolution image will be described with reference to FIGS.

  FIG. 1 shows a state where the helium gas refrigerant 64 is filled with 1 atm and the emitter tip 1 is cooled by the cooling mechanism 60. The refrigerator 62 and the compressor 69 are operating, and each is a mechanical vibration source. A refrigerant 64 and a bellows 63 are disposed between the refrigerator 62 and the ion source 5 serving as a vacuum container. Therefore, the vibration of the refrigerator 62 has a characteristic that it is difficult to transmit to the ion source 5 which is a vacuum container. The vibration of the compressor 69 is transmitted to the apparatus main body via the floor where the apparatus is installed. An anti-vibration mechanism 23 is disposed between the base plate 24 and the gantry 25. Therefore, the high-frequency vibration of the floor is difficult to transmit to the apparatus. Thereby, the vibration of the compressor 69 is difficult to transmit to the apparatus via the floor. Here, the compressor 69 has been described as the cause of the floor vibration, but the cause of the floor vibration is not limited to this. The anti-vibration mechanism 23 may be configured by an anti-vibration rubber, a spring, a damper, or a combination thereof.

  As described above, the present embodiment has a function of reducing the vibration transmitted from the refrigerator 62 and the compressor 69 to the apparatus, but in order to completely stop the vibration from the refrigerator 62 and the compressor 69, the refrigerator 62 and the compressor 69 are used. Good to stop. However, simply stopping the refrigerator 62 and the compressor 69 causes the following problems. This problem will be described with reference to FIG. When the refrigerator 62 and the compressor 69 are operating, the emitter tip 1 is at the temperature T1. Assuming that the refrigerator 62 and the compressor 69 are stopped at the time t1, the temperature of the emitter tip 1 increases exponentially like a temperature increase curve 90 when the refrigerant remains. The temperature range of the emitter tip in which a high resolution image can be observed is from the temperature T1 to T2. The time during which the temperature of the emitter tip rises from T1 to T2 is the time from time t1 to t2. Therefore, the time during which the high resolution image can be observed is the time from the time point t1 to t2. When the refrigerant remains, the time during which this high-resolution image can be observed is too short, and the operability becomes very poor.

  Therefore, when the refrigerator 62 and the compressor 69 are stopped, the following operation is added to thermally insulate the emitter tip 1. First, after the emitter tip 1 has cooled to the desired temperature T1, the refrigerator 62 and the compressor 69 are stopped. While the vibrations of the refrigerator 62 and the compressor 69 are damped, the refrigerant discharge mechanism 86 of the vacuum pump is activated and the valve 85 is opened to discharge the helium gas refrigerant 64 filled with 1 atm from the refrigerant discharge pipe 84. And make a vacuum. When the discharge of the helium gas refrigerant 64 is completed, the valve 85 is closed and the refrigerant discharge mechanism 86 of the vacuum pump is stopped (FIG. 2). The high temperature side stage 65 and the low temperature side stage 66 are thermally insulated from the emitter tip 1 and the radiation shield 12 by a vacuum. Therefore, it is possible to prevent the rising temperature of the cooling mechanism 60 from being transmitted to the emitter tip 1 and the radiation shield 12. The temperature change of the emitter tip 1 at this time becomes a temperature rise curve 91 when the refrigerant in FIG. 3 is discharged. At this time, the time during which the temperature of the emitter tip rises from T1 to T2 is the time from time t1 to time t3. Therefore, the time during which a high-resolution image can be observed can be lengthened and operability is improved. When the temperature of the emitter tip 1 reaches T2, the observation of the high resolution image is terminated. Then, the valve 82 is opened, and the refrigerant 64 of helium gas is filled with 1 atm from the refrigerant source 83 through the refrigerant supply pipe 81. When filling is completed, the valve 82 is closed. Then, the refrigerator 62 and the compressor 69 are operated to cool the temperature of the emitter tip 1.

  The operations described so far are summarized as a flow in FIG.

Although not shown, the method for forming the gas ionization chamber 6 using the radiation shield 12 is not limited to the present embodiment. For example, the gas ionization chamber is provided with the radiation shield 12 serving as a closed space in the ion source chamber 5. It can be realized in various forms such as 6.

  A second embodiment of the ion beam apparatus will be described with reference to FIG. In the following, differences from the first embodiment will be mainly described, and description of similar parts will be omitted.

In FIG. 5, the refrigerant discharge mechanism 86 includes a buffer tank 87, a valve 88, and a vacuum pump 89. In advance, the valve 88 is opened and the buffer tank 88 is evacuated by the vacuum pump 89. When the valve 88 is closed, the buffer tank is in a vacuum regardless of whether the vacuum pump 89 is in operation. As soon as the valve 85 is opened, the refrigerant 64 can be discharged.

  A third embodiment of the ion beam apparatus will be described with reference to FIG. In the following, differences from the first embodiment will be mainly described, and description of similar parts will be omitted.

A refrigerant cooling mechanism 92 is provided in front of the refrigerant source 83. When cooling the emitter tip 1 after high-resolution observation, the cooling time of the emitter tip 1 can be shortened by filling the coolant 64 that has been cooled by the coolant cooling mechanism 92 in advance.

  A fourth embodiment of the ion beam apparatus will be described with reference to FIG. In the following, differences from the first embodiment will be mainly described, and description of similar parts will be omitted.

In this embodiment, the low temperature side stage 66 and the radiation shield 12 are omitted. When the required cooling temperature is high, it is effective for cost reduction.

As described above, the embodiments described above do not have to be implemented individually, but a plurality of examples can be applied simultaneously, and the scope of rights is not limited.

DESCRIPTION OF SYMBOLS 1 Emitter tip 2 Extraction electrode 4 Gas supply piping 5 Ion source chamber 6 Gas ionization chamber 7 Acceleration power source 8 Extraction power source 10 Vacuum vessel 12 Radiation shield 15 Gas source 18 Opening 20 Ion source vacuum exhaust pump 21 Valve 22 Vacuum pump 23 Prevention Shaking mechanism 24 Base plate 25 Base 26 Support column 52 Gas exhaust port 60 Cooling mechanism 61 Cooling conduction mechanism 62 Refrigerator 63 Bellows 64 Refrigerant 65 High temperature side stage 66 Low temperature side stage 67 High pressure piping 68 Low pressure piping 69 Compressor 70 Focusing lens 71 Objective lens 72 Sample 73 Beam deflector / aligner 74 Movable beam limiting aperture 75 Blanking electrode 76 Blanking beam stop plate 77 Beam deflector 78 Secondary electron detector 80 Exhaust port 81 Refrigerant supply piping 82 Valve 83 Refrigerant source 84 Refrigerant exhaust Outlet piping 85 Valve 86 Refrigerant discharge means 87 Buffer tank 88 Valve 89 Vacuum pump 90 Temperature rise curve when refrigerant remains 91 Temperature rise curve when refrigerant is discharged 92 Refrigerant cooling mechanism

Claims (6)

In an ion beam apparatus that observes or processes a sample by irradiating the sample with an ion beam generated from a gas field ion source,
The gas field ion source is:
An emitter tip to be the anode,
An extraction electrode serving as a cathode;
A vacuum vessel containing at least the emitter tip;
A gas introduction part for supplying gas through a gas introduction port to a space between the tip of the emitter tip and the extraction electrode;
A gas exhaust part for exhausting the gas by a vacuum pump through a gas exhaust port;
A cooling mechanism for cooling the gas field ion source;
A cooling conduction mechanism cooled by the cooling mechanism;
In an ion beam apparatus comprising:
The cooling mechanism includes a refrigerant for cooling the emitter tip, a refrigerator for cooling the refrigerant, means for discharging the refrigerant, and means for supplying the refrigerant,
An ion beam apparatus characterized in that a coolant for cooling the emitter tip is discharged by means for discharging the coolant to thermally insulate the cooling mechanism from the emitter tip.
The ion beam device according to claim 1.
When the temperature of the emitter tip reaches a desired temperature, stop the cooling mechanism, discharge the coolant that cools the emitter tip, and observe the resolution image,
When the emitter tip reaches or exceeds a predetermined temperature range, the observation of the resolution image is stopped, the coolant for cooling the emitter tip is supplied by means for supplying the coolant, and the cooling mechanism is operated. Ion beam device.
The ion beam apparatus according to claim 2.
An ion beam apparatus, wherein the coolant for cooling the emitter tip is helium gas.
The ion beam apparatus according to claim 3.
An ion beam apparatus characterized in that the cooling mechanism and the emitter tip are thermally insulated from each other by discharging the refrigerant for cooling the emitter tip by means of discharging the refrigerant to make a vacuum state.
The ion beam device according to claim 4.
An ion beam apparatus characterized in that the means for discharging the refrigerant is a vacuum pump, a buffer tank, or both.
In the ion beam apparatus in any one of Claim 1 to 4,
An ion beam apparatus characterized in that the means for supplying the refrigerant has a function of cooling the refrigerant in advance before supplying the refrigerant to the cooling mechanism.