JPH0620638A - Complex charged particle beam processing observation device - Google Patents

Abstract

PURPOSE:To provide a complex charged particle beam processing observation device enabling observation of not only an image of a sample cross section but also an in-depth inner surface image or a stereoscopic image and the like of a sample, with high resolution. CONSTITUTION:Various pieces of information on the cross section of a sample are stored in a memory circuit 34. When a vertical image of the sample cross section is to be observed, the signal of the cross section is drawn from the memory circuit 34 by designating the position of the sample in the direction Y, and the signal is transferred to an image memory 37, and the image is displayed on a cathode-ray tube 40. When an optionally horizontal image of the sample surface is to be observed, only the signals of the designated position Z of each secondary scanning image signal are drawn out of a plurality of image signals stored in the memory circuit 34, and the signals are re-constructed to form a secondary image signal, which is transferred to the image memory 37. When a stereoscopic image is to be observed, a stereoscopic image is constructed based on the plurality of image signals stored in the memory circuit 34, and the result is transferred to the image memory 37.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention scrapes a sample such as a semiconductor device with an ion beam, scans the scraped sample portion with an electron beam, and displays a secondary electron image or the like by a signal obtained based on the scanning. The present invention relates to a composite charged particle beam processing / observing device.

[0002]

2. Description of the Related Art FIG. 1 shows that a sample such as a semiconductor device is shaved with an ion beam, the shaved sample portion is scanned with an electron beam, and a secondary electron image or the like is displayed by a signal obtained based on the scanning. 1 shows an example of a combined charged particle beam processing and observation apparatus that has been used.
Are placed. An ion beam irradiation column 3 and an electron beam irradiation column 4 are provided on the sample chamber 1. In the ion beam irradiation column 3, an ion gun 5, an extraction electrode 6 for extracting ions from the ion gun 5, an acceleration electrode 7, a focusing lens 8, a beam blanking electrode 9, an aperture 10, a beam deflection electrode 11, an objective lens. 12 are included. In the electron beam irradiation column 4, an electron gun 13, an extraction electrode 14 for extracting ions from the electron gun 13, an anode 15, a focusing lens 16, a beam blanking electrode 17, an aperture 18, a beam deflection electrode 19, an objective. A lens 20 is included. Further, the sample chamber 1 is provided with a secondary electron detector 21 for detecting secondary electrons generated from the sample 2. The operation in such a configuration will be described below.

First, the sample 2 in the sample chamber 1 is irradiated with an ion beam from the ion beam irradiation column 3. That is, ions are extracted from the ion gun 5 by the extraction electrode 6, and the ions are accelerated by the acceleration electrode 7. Then, the accelerated ions are finely focused on the sample 2 by the focusing lens 8 and the objective lens 12. Sample 2
The irradiation position of the ion beam at the beam deflection electrode 1
1 is scanned by supplying a scanning signal, so that a desired portion of the sample is cut by the ion beam. By this processing, the cross section of the desired portion of the sample appears, and then this cross section is irradiated with the electron beam from the electron beam irradiation column 4. When the electron beam is irradiated, the ion beam is deflected by supplying a blanking signal to the beam blanking electrode and is irradiated on the aperture 10, so that the irradiation of the sample 2 with the ion beam is stopped.

In the electron beam irradiation column 4, electrons are extracted from the electron gun 13 by the extraction electrode 14, and the electrons are accelerated by the acceleration electrode 7. Then, the accelerated electrons are focused by the focusing lens 16 and the objective lens 20.
It is focused on the sample 2 in a thin manner. The irradiation position of the electron beam on the sample 2 is scanned by supplying a scanning signal to the beam deflecting electrode 19, and as a result, the sample portion exposed by the ion beam is two-dimensionally scanned. Secondary electrons generated from the sample as the electron beam is scanned are detected by the secondary electron detector 21. Although not shown, the detection signal of the detector 21 is supplied to a cathode ray tube to which an electron beam scanning signal is supplied, and a secondary electron image of the cross section of the sample is displayed on the cathode ray tube.

[0005]

In the above-mentioned apparatus, only the cross section processed by the ion beam is observed. Therefore, in the case of a sample such as a semiconductor device, pinholes, voids, etc. in the scraped sample portion are observed. If the defect portion of the sample is included, it will be difficult to find the defect. In addition, it took a long time to find defects in the sample. Further, in the above-mentioned device, the cross section of the sample can be exposed and the secondary electron image of the cross section can be observed, but the demand for observing the internal surface image in the depth direction of the sample perpendicular to the cross section corresponds. I can't.

Further, there are cases where it is desired to see a stereoscopic image of a target portion of a sample, but the above device cannot meet such a request. The method currently used to view a stereoscopic image is that a sample is cut into a large number of thin slices, an image of each slice is photographed by a transmission electron microscope, and a three-dimensional image is obtained based on the images of the large slices. This is a method of observing a stereoscopic image.
However, high-resolution stereoscopic images cannot be obtained unless the sample is extremely thinly cut, but there is a limit to the technique for thinly cutting, and the sample cutting is performed in the atmosphere outside the electron beam, which causes sample contamination problems. Therefore, there is a drawback that a high-resolution stereoscopic image cannot be obtained, and an electron microscope image is acquired for each section, which takes time.

The present invention has been made in view of such a point, and an object thereof is to observe not only an image of a sample cross section but also an arbitrary internal surface image in the depth direction of the sample, a stereoscopic image, etc. with high resolution. It is to realize a compound charged particle beam processing and observation apparatus that enables the above.

[0008]

A composite charged particle beam processing / observing apparatus according to the present invention comprises a sample chamber, an ion beam irradiation system for irradiating a sample placed in the sample chamber with an ion beam, and an electron beam irradiation system. The electron beam irradiation system for irradiating the beam, the scanning means for scanning the electron beam on the sample, the detector for detecting the signal generated as a result of irradiating the sample with the electron beam, and the signal from the detector Supplied,
A storage unit that stores the signal in synchronization with the scanning of the electron beam, and a predetermined area of the sample is irradiated with the ion beam to grind a certain amount of the sample, and then the sampled part is scanned with the electron beam, and a signal based on the scanning And a control means for repeatedly executing a series of steps for storing a number of times.

[0009]

The combined charged particle beam processing / observing apparatus according to the present invention irradiates a predetermined region of a sample with an ion beam to grind a certain amount of the sample, and then scans the sampled electron beam with the electron beam to generate a signal based on the scanning. Repeat a series of steps to store a number of times, and obtain a large number of 2 based on each step.
A vertical sectional image, a horizontal sectional image, and a stereoscopic image are displayed based on the next electron detection signal.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 shows a control unit of an embodiment of the present invention, and the controlled ion beam irradiation column and electron beam irradiation column have the configuration shown in FIG. Reference numeral 25 denotes a scanning signal generation circuit. From this circuit 25, a blanking signal is supplied to the blanking electrode 9 of the ion beam irradiation column 3 via an amplifier 26, and an electron beam irradiation column 4 is supplied via an amplifier 27. Blanking electrode 17 inside
Is supplied to. The circuit 25 generates a two-dimensional scanning signal,
The scan signal is converted into an analog signal by the DA converter 28 and then supplied to the switch 29. Switch 2
Reference numeral 9 switches the scanning signal and supplies it to either the deflection electrode 11 for the ion beam via the magnification control circuit 30 or the deflection electrode 19 for the electron beam via the magnification control circuit 31. The detection signal of the secondary electron detector 21 is supplied to the large-capacity storage circuit 34 via the amplifier 32 and the AD converter 33. A scanning signal is also supplied from the scanning signal generating circuit 25 to the storage circuit 34, and the storage circuit 34 outputs 2 signals in response to the scanning signal.
The next electron detection signal is stored.

Reference numeral 35 denotes a central control unit, and the central control unit 35 is connected to a scanning signal generating circuit 25, a storage circuit 34, an image memory 37, and a lens control circuit 38 via an interface 36. The lens control circuit 38 controls the objective lens 20 in the electron beam irradiation column 4. The image signal stored in the image memory 37 is supplied to the display cathode ray tube 40 via the DA converter 39.
A scan signal is supplied to 0 from the scan signal generation circuit 41 via the DA converter 42. The operation of such a configuration will be described below.

First, a basic operation for cutting a sample with an ion beam and observing a processed cross section with an electron beam will be described. Based on a command from the central controller 35, the scanning signal from the scanning signal generation circuit 25 is supplied to the deflection electrode 11 in the ion beam irradiation column 3 via the DA converter 28, the switch 29, and the magnification control circuit 30. As a result, the observation portion of the sample 2 in the sample chamber 1 is cut by the ion beam. After shaving the sample of the desired portion, the switch 29 is switched, and this time, the scanning signal is supplied to the deflection electrode 19 of the electron beam irradiation column 4 via the magnification control circuit 31. As a result, the electron beam is two-dimensionally scanned at a desired portion of the sample cross section. Secondary electrons generated by the scanning of the electron beam are detected by the detector 21, and the detection signal is supplied to the storage circuit 34 via the amplifier 32 and the AD converter 33 and stored therein. At this time, if the signal supplied to the memory circuit 34 is sent to the image memory 37, the secondary electron image of the cross section of the sample obtained by the scanning of the electron beam on the cathode ray tube 40 can be obtained.

Next, a more specific embodiment of the apparatus will be described.
Describe. Figure 3 shows the blanket of the ion beam irradiation column 3.
Blanking signal (a) applied to
Applied to the blanking electrode 17 of the column irradiation column 4.
The blanking signal (b) is shown. Each signal is high
Each beam without blanking at the time of bell
The beam is emitted to the
Is called. Period T₁Is the processing area before processing the sample
This is the period for observing the vicinity, and the sample 2 alternates with ions.
The beam and the electron beam are emitted at a predetermined interval. This a
On-beam irradiation time is short, weakening irradiation energy
As a result, the surface of the sample is hardly scraped. And the electronic bill
Electron beam travels two-dimensionally on the sample surface during irradiation
The image of the sample surface based on this scanning is examined.
It is possible to observe with this image and see the image.
Is set. Next period T_TwoIs the pretreatment processing stage of the observation position
In the sample model shown in FIG. 4, the ion beam is
Irradiation along the Y direction, y in the Y direction₀Until the surface appears
During irradiation where the ion beam with relatively high irradiation energy is long
The sample 2 is irradiated at intervals. y₀Preliminary addition until the surface appears
After the work is completed, the beam irradiation period T for observing the sample_Three
Is started. Period T_ThreeWhen entering, the focused ion beam
Is controlled to be more tightly focused, y₀Try from the surface
It becomes a mode that thins the material, and AE
The sample is exposed to the sample, and after the ion beam irradiation
The mode in which the scanning period of the electron beam continues is repeated. Term
Interval T_ThreeOf I₁At y₀By the ion beam
Y after being scraped₁The surface is exposed and then ionic
Period E instead of beam₁At the electron beam
Of the cut cross section of S (x₁~ X_L・ Z₁~ Z_n)of
The area is scanned. From the area of S obtained by scanning
Of the secondary electron signal of y₁Together with surface position information
Memorized in. Next, period I_TwoSo y₁Scraping the surface, y_Twosurface
Expose that y _TwoScan the surface with an electron beam for period E_Two
Done in y_TwoStorage circuit 3 for the secondary electron detection signal of the surface
Store in 4. Thus the sample y₁From the surface y_m
The secondary electron detection signal of the sample cross section up to the surface is stored in the memory circuit 3
4 is stored.

In the series of steps of cutting the sample with the ion beam and two-dimensionally scanning the cut part with the electron beam, the sample is sequentially cut with the ion beam, so that the electron beam is irradiated after cutting. The central control unit 35 controls the lens control circuit 38 of the objective lens 20 to adjust the focus of the electron beam based on the cutting position information of the ion beam, and the electron beam cuts the sample 2 in a state where the electron beam is always in focus. The irradiated cross-section is irradiated.

Through the series of steps described above, the memory circuit 34 stores information on a number of sample cross sections. here,
If you want to observe an image of the sample cross section in any vertical direction,
By designating the position of the sample in the Y direction in FIG. 4, the signal of the cross section is taken out from the memory circuit 34, transferred to the image memory 37, and the image is displayed on the cathode ray tube 40. Next, if it is desired to observe a cross-sectional image in the direction (X) perpendicular to the cutting direction (Y) even with the same cross-sectional image, the central controller 37 selects one of the many image signals stored in the storage circuit 34 from among the many image signals. Only the signal at the designated X position (for example, k) of each two-dimensional scanning image signal is taken out, these signals are reconstructed to create a two-dimensional image signal, and the two-dimensional image signal is transferred to the image memory 37.
Further, when it is desired to observe an image of the sample surface in an arbitrary horizontal direction, that is, in the depth direction (Z), the central controller 35 selects each of the two-dimensional scanning among the many image signals stored in the storage circuit 34. Only the signal at the designated Z position (for example, p) of the image signal is taken out, these signals are reconstructed to create a two-dimensional image signal, and the two-dimensional image signal is transferred to the image memory 37. Next, when observing a stereoscopic image, the central control unit 35 constructs a stereoscopic image based on a large number of image signals stored in the storage circuit 34, and transfers the result to the image memory 37.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, in the embodiment described above, the sample was cut in the vertical direction to obtain the image signal, but the surface of the sample was gradually thinned, and each time, an image of the horizontal sample surface was acquired to obtain a large number of images. It is also possible to store a signal and perform the same processing as described above from a large number of the stored horizontal image signals to create an image of a vertical section or a stereoscopic image.

[0017]

As described above, the combined charged particle beam processing / observing apparatus according to the present invention irradiates a predetermined region of a sample with an ion beam to grind a certain amount of the sample, and then scatters the electron beam at the sample portion. A series of steps for scanning and storing a signal based on the scanning is repeated many times, and based on a large number of secondary electron detection signals obtained based on each step,
Since it is configured to display vertical cross-sectional images, horizontal cross-sectional images, and stereoscopic images, it is possible to observe not only the sample cross-sectional images but also arbitrary internal surface images in the depth direction of the sample, stereoscopic images, etc. with high resolution. It will be possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional compound charged particle beam processing / observing apparatus.

FIG. 2 is a diagram showing an embodiment of a control system of a composite charged particle beam processing / observing apparatus according to the present invention.

FIG. 3 is a diagram showing blanking signals of an ion beam and an electron beam according to an embodiment of the present invention.

FIG. 4 is a diagram showing a sample model for explaining an example of constructing a sectional image.

[Explanation of symbols]

 9,17 Blanking electrode 11,19 Deflection electrode 20 Objective lens 21 Secondary electron detector 25,41 Scan signal generation circuit 28 DA converter 29 Switch 30,31 Magnification control circuit 33 AD converter 34 Storage circuit 35 Central control unit 36 interface 37 image memory 40 cathode ray tube

Claims (2)

[Claims] 1. A sample chamber, an ion beam irradiation system for irradiating an ion beam to a sample arranged in the sample chamber, an electron beam irradiation system for irradiating an electron beam, and an electron beam on the sample. Scanning means for scanning with,
A detector that detects a signal generated as a result of irradiating a sample with an electron beam, a storage unit that is supplied with a signal from the detector and stores the signal in synchronization with scanning of the electron beam, and an ion beam for a predetermined sample A composite charged particle provided with a control means for irradiating an area to grind a certain amount of a sample, then scanning the electron beam on the shaved sample part, and repeatedly executing a series of steps for storing a signal based on the scanning. Beam processing observation device. 2. The combined charged particle beam processing and observation apparatus according to claim 1, further comprising means for readjusting the focus state of the electron beam in accordance with the depth of the sample cut by the ion beam.