JPH09161712A - Sample machining device by ion beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To observe the change of the shape of a sample without interrupting machining and perform high-precision machining by observing the electrons generated when an electron beam is applied to the sample, and selectively detecting reflected electrons. SOLUTION: An ion beam 2 is applied to a sample 4 while being scanned in a circular region by an ion beam scanner 3 in a vacuum container 1. The SEM image displayed on a display 5 is changed to an image having a deep hole as machining proceeds. An electron beam 6 is scanned in a rectangular region corresponding to this image, and the sample reflected electrons of the electron beam 6 are detected by an MCP. They are amplified and used for the image signal 11 of the display 5, and a SEM image controller 8 is driven to draw the SEM image. When the non beam 2 and the electron beam 6 are applied, secondary electrons 9 contained in the sample 4 and reflected electrons 10 are generated. The reflected electrons 10 are selectively detected based on the energy difference between the secondary electrons 9 and the reflected electrons 10 to form the SEM image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for monitoring the progress of processing when performing fine processing using a FIB (Focused Ion Beam) processing apparatus.

[0002]

2. Description of the Related Art A FIB processing apparatus is an apparatus for irradiating a sample with a finely focused ion beam to perform fine processing of an irradiation portion. Conventionally, the following means have been disclosed as means for observing this processed portion.

As one of them, after processing the sample, the sample is tilted obliquely to the axis of the ion beam and a SIM image of the processed portion (a scanning ion microscope image obtained by using the ion beam in the same manner as SEM). There are some which observe a processed part by obtaining.

There is also a FIB processing apparatus in which an SEM is mounted so that the processing position of a sample can be seen, so that the processing result can be observed without using an ion beam and without tilting the sample. As a specific example, “Application of charged particle beam to industry, 132nd Committee, 125th Research Group Material-Japan Society for the Promotion of Science, 1993”, 160th.
As described on the page, a technique is disclosed in which the ion beam irradiation is switched to the electron beam irradiation and the processing state of the sample is observed.

The above-mentioned prior art has the following drawbacks.

[0006]

SUMMARY OF THE INVENTION SIM as described above
The means for observing the processed portion by obtaining an image is to check whether or not desired processing has been performed after the ion beam processing. That is, since the SIM image is not formed during the ion beam irradiation, it cannot be confirmed how the processing is progressing. Further, the means for observing the processed portion by the SEM as described above cannot observe the sample image during the ion beam processing. This is because during irradiation of the ion beam, a large amount of secondary electrons are generated from the sample due to the ion beam, and these secondary electrons are superposed on the secondary electrons due to the electron beam necessary for forming the SEM image.
Therefore, the S / N ratio is extremely low during ion beam irradiation.
Only SEM images can be obtained.

That is, in any of the above-mentioned prior arts, the processed portion cannot be confirmed until the processing is completed, so that the target sample may be excessively cut due to excessive processing. Alternatively, when trying to observe the SIM image or the SEM image during the processing, it is necessary to stop the processing and switch to the observation mode, which causes a lot of inconveniences in the processing such as a delay in the working time.

The present invention solves the above-mentioned drawbacks of the prior art, and provides an apparatus for processing a sample by an ion beam, which is capable of performing processing according to the intention of the operator in a short time and with high accuracy. To aim.

[0009]

In order to achieve the above object, the present invention has the following constitution. That is, an apparatus for processing a sample with an ion beam includes an observation means for observing the sample by detecting electrons generated by irradiating the sample with an electron beam, and the observation means irradiates the sample with the electron beam. A means for selecting and detecting the backscattered electrons obtained by

With the above structure, the electrons generated by the electron beam irradiation can be selected and detected without being affected by the electrons generated by the ion beam irradiation. More specifically, secondary electrons generated by ion beam irradiation and 2 generated by electron beam irradiation
Although the secondary electrons are indistinguishable, the reflected electrons returned by the elastic scattering action of the electron beam have higher energy than the secondary electrons described above.
Reflected electrons and secondary electrons can be distinguished. Since high energy electrons are hardly generated by ion beam irradiation,
By selecting and detecting the reflected electrons by electron beam irradiation, it is possible to obtain an SEM image that is not affected by the electrons generated by ion beam irradiation.

As a specific configuration, first, electrons having an energy of a certain value or less are configured not to reach the detection element of the observation means. Further, as another configuration example, an equivalent action can be obtained by providing the observing means with a detection element that senses electrons having an energy of a certain value or more, instead of preventing electrons having low energy from reaching the detection element.

[0012]

FIG. 1 shows an embodiment of the present invention.
In the vacuum container 1, the ion beam 2 irradiates the sample 4 while the circular region is scanned by the ion beam scanner 3. A circular hole digs as time passes.
This state is displayed as an SEM image on the display 5 by the SEM installed in a direction oblique to the axis of the ion beam. In this embodiment, the image of 5 gradually changes into an image having deep holes as time passes, that is, as the processing progresses.

The image of 5 scans the electron beam 6 of the mounted SEM in a rectangular area corresponding to the field of view of 5, the sample reflected electrons of 6 are detected and amplified by the MCP detector 12, and the image signal of 5 is obtained. 11 is an SEM image drawn by driving the SEM image controller 8 for use in FIG. By the irradiation of the ion beam and the electron beam, secondary electrons 9 originally contained in the sample and reflected electrons 10 due to the electron beam are generated from the sample. The secondary electrons 9 include those generated by ion beam irradiation and those generated by electron beam irradiation, but these cannot be distinguished.

However, the secondary electrons 9 and the reflected electrons 10
Can be clearly distinguished. That is, as shown in FIG. 2, since the reflected electrons are generated by the elastic scattering action, they have energy almost equal to the energy of the irradiated electron beam, while the energy of the secondary electrons is 2 Most of the secondary electrons are 50 eV or less.

In the embodiment of the present invention, the SEM image is formed by selecting and detecting the reflected electrons generated by the electron beam irradiation based on the energy difference between the secondary electrons and the reflected electrons.

Here, in this embodiment of FIG. 1, since only the backscattered electrons are used for the image signal of the SEM, the MCP in which the voltage (V ₁ ) on the incident surface is maintained at -500V as a detector.
A (microchannel plate) detector 12 is used. The SEM is operating at 1 kV. V ₁ to -500
By maintaining the voltage at V, electrons having an energy of 500 eV or less do not enter the detector, and reflected electrons of an electron beam having an energy substantially equal to that of the electron beam 6 of 1 keV enter the detecting element at an energy of 500 eV. The signal excitation efficiency of the MCP detector used in this example depends on the energy of incident particles, and is 500 eV.
In order excitation efficiency for particles incident on the MCP detector 12 was maximum, was set V ₁ and -500 V.

In the embodiment shown above, the electron beam energy is 1 keV. However, when the SEM is used at a high voltage for reasons such as resolution enhancement, for example, when the electron beam energy is 30 keV. , V ₁ to -2
If set to 9.5 kV, the MCP detector can be used most efficiently in terms of signal excitation efficiency.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the present invention is applied to an LSI wiring correction work. In this wiring correction work, as shown in the image of 5, the gap of one wiring that has been disconnected is connected by the FIB-assisted deposition method.

The FIB-assisted deposition method is a method of irradiating a processed portion with FIB while irradiating a sample with an organic gas containing a metal, and depositing a metallic substance only on the irradiated portion of the FIB. Tungsten, hexa, and
Carbonyl is supplied from the gas supply device 14. In this embodiment, in order to detect backscattered electrons, a phosphor / scintillator 16 that emits light upon receiving electron irradiation and a photomultiplier tube 15 that converts the light into an electric signal and amplifies it are used. On the irradiation surface of the scintillator 16, the detector control power source 1
3, the voltage of +10 kV (V ₂ ) is applied. 2
An energy filter 17 is installed in front of the scintillator 16 so that the next electron does not irradiate the scintillator 16.
A voltage (V ₁ ) of −200 V is applied to the energy filter 17 by 13. Reference numeral 17 is a mesh electrode having a high aperture ratio. Of the electrons generated from the sample by the irradiation of the ion beam and the electron beam, the secondary electrons are driven back to the side of the sample in front of 17, and only the reflected electrons by the irradiation of the electron beam pass through 17, and further 10 by V ₂ .
It is accelerated to keV and 16 is emitted. Scintillator 1
Unlike the embodiment of FIG. 1, the light emission of No. 6 requires high energy of about 10 keV. As described above, since the secondary electrons generated by the ion beam irradiation do not enter the detector, a clear SEM image of the processed portion is displayed on 5. The wiring repair worker monitors the image of 5 which changes from moment to moment,
When the deposit has the thickness and size necessary for conducting the wiring, the repair work is finished.

FIG. 4 shows still another embodiment of the present invention. In this example, the present invention is applied to a thin sample 1 for a transmission electron microscope.
I use it to make 8. SEM is used with an acceleration voltage of 10 kV. The backscattered electrons are detected by the emission of YAG (yttrium aluminum garnet) crystal 19. Light emitted from 19 by irradiation of 19 of backscattered electrons having an energy of about 10 keV is guided to 15 by the light pipe 20 and converted into an electric signal. In this embodiment, unlike the embodiment shown in FIGS. 1 and 3, there are 19 secondary electrons.
Is irradiated. However, the energy is 50 eV or less as already mentioned, so this irradiation of secondary electrons causes Y
The AG crystal does not emit light. That is, since the energy filter is not used in this embodiment, the configuration is simple, and the reflected electrons can be detected by utilizing the energy dependency of the signal excitation of the detection element.

The creator of the sample for an electron microscope monitors the images of 5 and performs FIB processing on both sides of the thin piece portion to be created, and when the thin piece portion becomes sufficiently thin, the sample preparation is completed. The required thinness as a sample for a transmission electron microscope is usually as thin as about 0.1 μm or less. If it is not processed enough, it cannot be made this thin, and if it is processed too much, it will break. Therefore,
In the conventional FIB processing apparatus that does not use the present invention, it is necessary to constantly stop the processing and continue the processing while confirming the thinning state of the sample by the SEM image or the SIM image.

In the embodiment of the present invention, it is possible to prevent the breakage of the sample due to the excessive processing without interrupting the processing, and it is effective in improving the processing success rate and the processing speed. Further, since it becomes possible to finely adjust the processing conditions while observing the processed portion, it is effective in improving the precision and miniaturization of the processing.

Further, when it is desired to observe the processed portion by using the secondary electrons when the ion beam is not irradiated, for example, in the embodiment shown in FIG. 3, the energy filter 17 is positive voltage instead of negative voltage. If a voltage is applied to improve the secondary electron acquisition efficiency of the detector, the processed site can be observed using the secondary electrons. That is, observation by secondary electrons can be performed as necessary by simply adding a simple configuration in which the detector control power supply is provided with a voltage switching means for positive voltage and negative voltage.

Further, also in the embodiment shown in FIG. 1, as the voltage applied to the electron incident surface of the channel plate 12, a voltage depending on the excitation efficiency in the channel plate is selectively applied to cause a secondary electron. Can be observed.

That is, as shown in the embodiment of FIG. 1, 500e
When a channel plate that maximizes the excitation efficiency when incident at V is used, when the FIB processing monitor is used, the channel plate incident surface voltage is set to -500V, and when detecting secondary electrons, the incident surface is set. Voltage +500
By setting V, observation with reflected electrons or observation with secondary electrons can be performed with optimum excitation efficiency, if necessary.

Further, according to the present invention, since it is possible to perform processing while observing a micro device to be processed, it is possible to perform sputtering of a fine portion and correction of a fine mask pattern, and the micro devices are arranged in parallel at narrow intervals. Even when one of the two wirings is disconnected by the deposition method, it is possible to avoid a situation in which the two wirings are erroneously connected.

Further, the SEM image of the backscattered electrons by the low-velocity electron beam of about 2 keV or less used in the present invention has a stereoscopic effect in which the outer shape of the sample is faithfully reflected as compared with the image by the secondary electrons. It is an image. Therefore, like the present invention,
In the case of an apparatus which is applied to a FIB processing apparatus and observes the processing progress, using the SEM image using the backscattered electrons makes it possible to correctly recognize the external shape of the sample that changes from moment to moment, and It was extremely effective for the purpose of the present invention to perform the processing according to the intention with high accuracy.

In the embodiment of the present invention described above, the case where the present invention is applied to a processing apparatus using a finely focused ion beam has been described, but it is generally not limited to FIB, and is an apparatus for irradiating ions, and
It is needless to say that the present invention is effectively applied to an apparatus configured so that the irradiation section can be observed by SEM.

[0029]

According to the present invention, it is possible to observe how the shape of the sample changes during FIB processing without interrupting the processing, so that the processing success rate is improved to almost 100%. Further fine and high-precision machining is possible,
It also contributed to the reduction of work time.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram concerning energy distribution of electrons generated from a sample by irradiation with an ion beam and an electron beam having an energy of 1 keV.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing still another embodiment of the present invention.

[Explanation of symbols]

1 ... Vacuum container, 2 ... Ion beam, 3 ... Ion beam scanner, 4 ... Sample, 5 ... Display, 6 ... Electron beam,
7 ... Electron beam scanner, 8 ... SEM image controller, 9 ... Secondary electron, 10 ... Reflected electron, 11 ... Image signal, 12 ... MC
P detector, 13 ... Detector control power source, 14 ... Gas supply device, 15 ... Photomultiplier tube, 16 ... Phosphor / scintillator, 17 ... Energy filter, 18 ... Thin sample for transmission electron microscope, 19 ... YAG crystal , 20 ... Light pipe.

Claims (12)

[Claims] 1. An apparatus for processing a sample with an ion beam, comprising observation means for observing the sample by detecting electrons generated by irradiating the sample with an electron beam, and the observation means is provided with the electron beam. An ion beam sample processing apparatus comprising means for selecting and detecting reflected electrons of an electron beam generated by irradiating a sample. 2. The sample processing apparatus using an ion beam according to claim 1, wherein the means for selecting and detecting the reflected electrons selects and detects electrons having a certain range of energy. 3. The means for selecting and detecting the reflected electrons is a channel plate detector, wherein the electrodes on the electron incident side take in the reflected electrons generated by irradiating the sample with the electron beam. The ion beam sample processing apparatus according to claim 1, further comprising a voltage applying unit that applies a voltage that does not take in electrons having low energy generated by irradiating the target sample with the electron beam and the ion beam. . 4. The voltage applying means applies a voltage for shaving the energy of the reflected electrons to the electron incident side electrode so that the reflected electrons are incident on the channel plate at the energy which shows the optimum excitation efficiency of the channel plate. The sample processing apparatus using an ion beam according to claim 3, wherein 5. An ion beam sample processing apparatus according to claim 3, wherein the voltage applying means is provided with a switching means for applying the voltage or a voltage suitable for detection of secondary electrons. . 6. The energy of the electron beam is set to 2 [ke
V] or less, The sample processing apparatus using an ion beam according to claim 1, wherein 7. The means for selecting and detecting the reflected electrons comprises a fluorescent plate or a scintillator, a photomultiplier tube, and an energy filter arranged between an electron entrance of the scintillator and a sample. The sample processing apparatus using an ion beam according to claim 1, further comprising: a voltage applying unit that applies a negative voltage that repels electrons having an energy less than that of the reflected electrons. 8. A voltage of (optimum voltage of incident surface for signal excitation-acceleration voltage of the electron beam) is applied to the front surface of the detection element of the means for selecting and detecting backscattered electrons. A sample processing apparatus using the described ion beam. 9. The means for selecting and detecting an electron having an energy in a certain range includes a voltage switching means for applying a voltage suitable for detecting the reflected electron or the opposite of the secondary electron and the reflected electron. The sample processing device using an ion beam according to claim 2. 10. The means for selecting and detecting the reflected electrons comprises:
A detection element is provided, in which the signal excitation amount by secondary electrons generated by irradiating the target sample with the ion beam is lower than the signal excitation amount by the reflected electrons having high energy. 1. A sample processing apparatus using an ion beam according to 1. 11. A method of manufacturing a microdevice including a processing step using an ion beam, wherein backscattered electrons obtained by irradiating the microdevice with an electron beam are selected and detected as the microdevice is processed by the ion beam. A method for manufacturing a microdevice including an ion beam processing step, the method including a step. 12. An apparatus for processing a sample by an ion beam, comprising observation means for detecting electrons generated by irradiating the sample with an electron beam to form a SEM image, and an electron entrance of the observation means. A sample processing apparatus using an ion beam, comprising an electrode, and a voltage applying means for preventing secondary electrons having low energy from entering the detector in the electrode.