JPH06231719A - Charged beam device for sectional working observation and working method - Google Patents

Abstract

PURPOSE:To work a transmission electron microscope sample in a specified position of a sample into a simple and more suitable form, and observe and analyze it in the site. CONSTITUTION:An ion optical system for emitting a converged ion beam 3 to a sample 4 from the transverse direction to the electron beam 7 of a transmission electron microscope is arranged, and a transmission type electron microscope sample is formed by ion beam etching. The secondary electrons by excitation of the beams 2, 7 are detected by a secondary electron detector 5 to confirm the working position, working form and section of the sample. The electron beam 7 transmitted by the sample 4 is detected by a transmitted electron detector 12 to observe a fine part. The X-ray by electron beam cooling is detected by an X-ray detector 10 to analyze the fine part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects secondary particles generated from a sample by focused ion beam irradiation and observes the sample surface, and ion beam etching and ion beam chemical vapor deposition CVD are performed on a predetermined region of the sample surface. By equipping a transmission electron microscope (hereinafter referred to as TEM) with a focused ion beam irradiation system and a gas supply device for processing, TEM sample preparation can be processed into a simpler and more optimal shape. A beam device and a processing method.

[0002]

2. Description of the Related Art A conventional focused ion beam processing apparatus, as disclosed in Japanese Patent Laid-Open No. 59-168652, extracts ions from a liquid metal ion source by an extraction electrode, and the ions are extracted by an aperture and an electrostatic lens. It is a device that forms a focused ion beam and deflects and scans the focused ion beam by a deflection electrode so as to irradiate a predetermined region on the sample surface.

By repeatedly irradiating the surface of the sample with the focused ion beam scanned as described above, a predetermined region of the sample is sputtered by the ion beam and is not scraped off. Also, by supplying a deposition gas from a nozzle, Form a metal film by ion beam in the irradiation area of the sample (Chemic
al Vaper Deposition; hereinafter abbreviated as CVD). These functions are used for modifying the prototype IC circuit and process evaluation, etc., and drastically shortened the debug time of IC development (Monthly Senmi-conductor World, 1987.9 [New evaluation and analysis technology for VLSI using FIB], Japan. Society for the Promotion of Science 132nd Committee 101st Workshop Material, 1987.11 "E
Failure analysis of high-speed bipolar LSI by B tester ”,
"IC analysis and wiring change by focused ion beam", "Electron beam testing technology using focused ion beam"). Recently, a cross-section TEM sample was prepared using a focused ion beam device, and the results of cross-section TEM observation at a specific location of the sample have been reported (The 37th Japan Society of Applied Physics, 1990.3 “Cross-section TEM using a focused ion beam”). Sample preparation method "). Compared with the conventional method using ion milling, this method allows the cross-section TE of a specific location of a sample to be taken in a shorter time.
It is possible to prepare M samples.

FIG. 3 shows a focused ion beam processing apparatus which is an example of a conventional apparatus. A liquid metal ion source is used for the ion gun 1, and an ion beam 2 extracted from the ion gun
Is focused and scanned by the ion optical system 3 to irradiate the surface of the sample 4. The ion optical system 3 scans a predetermined area on the surface of the sample 4 with the aperture 30 that passes only the portion near the optical axis of the ion beam 2, the electrostatic lens 31 that focuses the ion beam 2, and the focused ion beam 2. The scanning electrode 32 is provided with a scanning electrode 32, a blanker 33 for turning on / off the irradiation of the focused ion beam 2 onto the surface of the sample 4, and the like.

The ion beam 2 etches the surface of the sample 4 and simultaneously emits secondary particles excited by the ion beam. Secondary electrons in the secondary particles are detected by a secondary electron detector, and a SIM image is displayed on an observation CRT (not shown). At the same time as the irradiation of the ion beam 2, the CVD gas is supplied from the gas gun 16 nozzle to locally form a film on the surface of the sample 4. This ion beam processing apparatus has been conventionally used for cutting / connecting IC wiring and for processing / observing a cross section.

[0006]

However, in order to observe a cross section of a semiconductor sample using a focused ion beam processing apparatus as in the conventional example, when a sample for a semiconductor cross section TEM is prepared, mechanical polishing is first performed. The width of the surface of the semiconductor sample is the number 1
The area before and after the observation location of the sample that has been carved with 0 μm left is removed by ion beam etching to leave a wall of 0.5 μm or less. Next, confirm the processed shape and cross section by scanning electron microscopy (Sc) to avoid damage due to ion beam irradiation.
anning Electron Microscope (hereinafter abbreviated as SEM) Image observation is performed, and reprocessing is performed if necessary. Then, the sample after processing is observed by TEM, and when the processing is not possible due to insufficient processing, it is necessary to perform ion beam etching processing again. In this method, since the sample is taken in and out between a plurality of vacuum devices, there are problems that it takes time to evacuate and position the sample, and that it is difficult to manufacture an optimum cross-sectional TEM sample.

[0007]

In order to solve the above problems, the present invention provides an electron beam emitted from an electron gun, which is narrowed down by an irradiation lens system to irradiate a thin film processed sample,
A secondary electron emitted from the sample by irradiation with the electron beam is applied to a transmission electron microscope that magnifies the electron beam that has passed through the sample with an objective lens and a magnifying lens system of several stages and projects it on a fluorescent screen for microscopic observation. And a device equipped with a secondary electron detector for capturing X-rays and an X-ray detector, wherein a focused ion beam irradiation system capable of irradiating the sample with an ion beam laterally to the electron beam is arranged. Is a charged beam device for cross-section processing observation.

[0008]

Since the focused ion beam is scanned, secondary electrons excited by the focused ion beam are detected, the SIM image is observed, and the processing observation position of the sample is set, and then the sample surface to be processed can be subjected to ion beam etching processing. A cross-sectional TEM sample at a specific location of the sample to be processed can be manufactured. Then, if necessary, the ion beam is switched to the electron beam, and the processing state can be observed by the SEM image and the TEM image.
Further, elemental analysis of minute portions can be performed by detecting the X-rays excited by the electron beam with the X-ray detector. further,
Prior to ion beam etching, the sample observation surface is protected from damage due to ion beam irradiation by locally forming a film on the processing observation surface of the sample to be processed by the ion beam CVD to flatten the sample surface, and thus the unevenness of the sample surface is processed. The roughness of the processed surface (TEM observation surface) can be reduced, and the sample to be processed is tilted by several degrees during the ion beam etching process, so that the tilt of the processed cross section due to the spread of the focused ion beam is perpendicular to the surface. The thickness of the thin wall on the TEM observation surface can be made uniform. Therefore, the present invention is a TEM
Since the sample preparation and the TEM image observation can be performed on the spot, it is possible to observe and analyze a limited minute portion.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a charged beam device for cross-section processing and observation according to the present invention. Hereinafter, description will be given with reference to the drawings. A liquid metal ion source is used as the ion source 1, and the ion beam 2 extracted from the ion source 1 is an ion optical system 3
Sample 4 on the 5-axis sample stage accelerated / focused / scanned by
Is irradiated. Secondary electrons excited by the ion beam emitted from the sample 4 which is a semiconductor integrated circuit are detected by the secondary electron detector 5
Detected by a SIM (Scanning Ion mic)
roscope) image is displayed. Thereby, the surface of the sample 4 is observed, the processing position is set, the focused ion beam 2 is repeatedly irradiated to the processing position while being irradiated, and the TEM sample can be prepared by the sputter etching processing by the irradiation of the focused ion beam 2.

As shown in FIG. 2, the sample 4 is a slice of a semiconductor integrated circuit, and the left end 4a of the sample 4 in FIG. 2 is the surface of the semiconductor integrated circuit. The upper and lower surfaces of the left side portion 4b of the sample 4 expose the circuit cross section of the semiconductor integrated circuit. That is, the focused ion beam 2 is repeatedly scanned and irradiated from the surface direction of the sample 4 (the surface direction of the semiconductor integrated circuit) so as to scrape the upper and lower surfaces of the left side portion 4b of the sample 4 by sputtering. After the upper and lower surfaces of the left side portion 4b of the sample 4 have been ground by a predetermined amount, the focused ion beam 2 is switched to the electron beam 7.

The electron gun 6 is arranged so that the electron beam 7 irradiates the sample 4 perpendicularly to the irradiation direction of the focused ion beam 2 on the sample 4. The electron beam 7 extracted from the electron gun 6 is accelerated, focused, and scanned by the irradiation lens system 8 and the objective lens 9, and is irradiated on the sample 4. In the vicinity of the sample 4, a secondary electron detector 5 for detecting secondary electrons generated from the sample 4 and an X-ray detector 10 for detecting X-rays.
Are arranged.

Secondary electrons and X-rays excited by the electron beam emitted from the sample 4 are detected by a secondary electron detector 5 and an X-ray detector 10, respectively, and an SEM image and an X-ray spectrum are displayed on a display CRT (not shown).・ X-ray image is displayed. Further, the electron beam 7 transmitted through the sample 4 is magnified by the magnifying lens system 11 and projected on the transmission electron detector (fluorescent plate) 12 to TE.
M image observation is possible.

When the target portion of the sample 4 is thick and the transmission of the electron beam is insufficient and the TEM image is dark, the irradiation of the electron beam 7 is stopped and the irradiation of the focused ion beam 2 is turned on.
Switch their irradiation to. The scanning region of the focused ion beam is further set so that the thickness of the left end portion 4b of the sample 4 becomes thinner. Then, the TEM sample is additionally processed,
The electron beam 7 is irradiated again to observe the TEM image. As described above, according to the present invention, since optimum TEM sample preparation can be performed on the spot and the TEM image can be observed on the spot, it is possible to observe and analyze a limited minute portion.

FIG. 2 is an enlarged sectional view of the peripheral portion of the sample of the present invention. Secondary electrons 1 excited by ions and electron beams by irradiating the sample 4 with the focused ion beam 2 and the electron beam 7 scanned by the scanning electrode 32 of the ion beam irradiation system and the scanning coil 14 of the electron beam irradiation system alternately or simultaneously.
5 is detected by the secondary electron detector 5, and the SIM image and SE are detected.
After obtaining the M image, the processing position, processing shape, and cross section of the sample can be confirmed.

Further, a gas gun 16 for locally spraying a metal-organic compound vapor is provided at the irradiation position of the focused ion beam on the sample 4. The metal-organic compound vapor from the gas gun 16 is sprayed on the left end face 4a (corresponding to the surface of the semiconductor integrated circuit) of the sample 4, and at the same time, the left end face 4a of the sample 4 is repeatedly scanned and irradiated with the focused ion beam 2. . The metal film 23 is formed on the left end face 4a by blowing the metal organic compound vapor onto the left end face 4a and irradiating the left end face 4a with the focused ion beam 2.

As described above, a TEM sample is prepared by performing a sputter etching process by irradiation with a focused ion beam 2 and a local organic metal film process by spraying a CVD organic compound gas from the gas gun nozzle 16 to the irradiation position of the ion beam 2. The purpose of forming the metal film 23 on the left end surface 4a of the sample 4 is as follows. The cross-section of the semiconductor integrated circuit is formed by irradiating the focused ion beam 2 from the surface side (left end surface 4a) of the semiconductor integrated circuit which is the sample 4, but the surface of the semiconductor integrated circuit is microscopically rough. Due to the unevenness, the cross section formed by the irradiation of the focused ion beam 2 also has unevenness in the direction perpendicular to the focused ion beam irradiation direction. Therefore, simultaneously with the irradiation of the focused ion beam 2 on the surface of the semiconductor integrated circuit, a metal organic compound vapor is sprayed to form a metal film 23 on the surface of the semiconductor integrated circuit by CVD. The surface of the metal film 23 has an effect of smoothing (smoothing) the unevenness of the surface of the underlayer, and the focused ion beam is radiated from the surface of the metal film 23 to smooth the cross section formed by etching, When observing the cross section, a clear image is obtained.

As described above, the electron beam irradiation system irradiates the sample 4 whose cross section is processed with the focused ion beam 2 to the cross section of the left side portion 4b of the sample 4 and the electrons transmitted through the left side portion 4b of the sample 4 are irradiated. Beam 7 intensity is transmitted electron detector 12
The thickness of the TEM sample can be optimized because the thickness of the sample 4 at the time of processing can be estimated by monitoring with. In addition, X-rays excited by the electron beam 7
By detecting with the line detector 10, it is possible to analyze the minimum portion.

FIG. 4 is a diagram showing an embodiment for explaining the processing method of the present invention. The surface layer (device formation region) including the observation planned range of the semiconductor integrated circuit (IC) sample which is the cross-sectional TEM observation sample 4 is cut into a shape as shown in FIG. 4A by mechanical polishing. Sample 4 has a semiconductor integrated circuit of 0.
Slice it to a width of 5 to 1 mm, and further cut the device portion formed on the surface 4a to a depth of 50 to 100 μm and 100 μm.
Remove leaving behind:

Next, the surface 4a of the sample 4 is irradiated with the focused ion beam 2 while being scanned by the focused ion beam irradiation system, and secondary electrons due to the irradiation are detected by the secondary electron detector 5 to observe the SIM image. The observed image is, for example, as shown in FIG. Next, the cross-section observation position 22 is set from the SIM observation image. The cross-section observation position 22 in this embodiment is the cross-section of the contact hole 19. Then, the contact hole portion 19 which is the observation position 22
The local film formation area 20 of the CVD metal film 23 in a wide range including
And the CVD gas is sprayed from the gas gun 16 and the focused ion beam 2 in the local film forming area 20 is repeatedly irradiated to perform the film forming process of the metal film 23. This metal film 2
3 has the effect of reducing damage to the sample surface 4a due to irradiation with the focused ion beam 2.

At this time, the both ends of the cross-section observation position 22 are irradiated with the focused ion beam 2 and marked 21 by the drilling process by etching so that the observation position can be easily found and processed accurately. Then, as shown in FIG. 4C, the central portion of the contact hole portion 19 has a width of 0.05 to 0.2 μm.
The left and right etching areas 24 are removed by sputter etching with a focused ion beam 2 having a depth of about 10 μm.

At this time, by tilting the sample 4 by several degrees (2 to 5 °) as shown in FIG. 4D, the tilt of the etching cross section due to the shape of the focused ion beam 2 is corrected and a vertical thin wall is produced. can do. Then, the electron beam 7 is irradiated from the electron beam irradiation system to the observation position of the device cross section 4b of the sample 4, and the transmitted electrons are detected by the transmitted electron detector 12.
Confirm that the transmitted electron intensity is sufficient. When the transmitted electron intensity is low, the etching area 2 in FIG.
4 near the cross-section observation position 22 and focus ion beam 2
Irradiation. As shown in FIG. 1, the electron beam is perpendicular to the optical axis of the focused ion beam, and irradiates the cross section of the sample 4 perpendicularly. 4E and 4F show the shapes of the sample 4 on the upper surface and the cross section after processing, respectively.

FIG. 5 (a) is an SEM image when the processed cross section of the sample 4 is irradiated with the electron beam 7 from the vertical direction. This SEM image observation can be performed by switching the ion beam 2 to the electron beam 7 as needed during the ion beam processing operation, so that the processing position, processing shape, cross section, etc. can be easily confirmed. In addition, FIG. 5B shows the spectrum of the X-rays excited by the electron beam 7 detected by the X-ray detector, and FIG. 5C shows the X-ray image of aluminum (Al). In this way, it is possible to easily perform elemental analysis of a minute portion at a specific place. Therefore, the present invention is based on TEM sample preparation and FIG.
Since the cross-sectional TEM image observation as shown in (d) can also be performed on the spot, it is possible to observe and analyze a specific portion.

[0023]

As described above, according to the present invention, a sample for a cross-section TEM at a specific place can be processed by ion beam processing, and during processing work, the ion beam is switched to an electron beam as necessary and SEM image observation and Since X-ray analysis can be performed, it is easy to confirm the processing position, processing shape, and cross section and analyze minute parts. Also, the local film formation and sample inclination protect the surface of the sample to be processed and make a vertical and flat cross section. In addition, since the cross-sectional TEM image can be observed on the spot, the cross-sectional TEM at a specific place can be observed.
It is effective for observation.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a sample peripheral portion of the present invention.

FIG. 3 is a schematic sectional view showing an embodiment of a conventional device.

FIG. 4 is a diagram for explaining a working example of the present invention.

FIG. 5 is a diagram for explaining an observation / analysis example of the present invention.

[Explanation of symbols]

 1 ion source 2 focused ion beam 3 ion optical system 4 sample 5 secondary electron detector 6 electron gun 7 electron beam 8 electron beam lens system 9 objective lens 10 X-ray detector 11 magnifying lens system 12 transmission electron detector 14 scanning coil 15 Secondary Electron 16 Gas Gun (Nozzle) 17 Aluminum Wiring 18 Polysilicon Wiring 19 Contact Hole 20 Local Film Formation Area 21 Mark (Drilling by Ion Etching) 22 Cross Section Observation Position 23 Metal Film (Local Film Formation by Ion Beam CVD) 24 Etching area 25 Protective film 26 Silicon substrate 32 Scan electrode

Claims (3)

[Claims] 1. An electron gun for generating an electron beam, an electron beam lens system for narrowing the electron beam to irradiate a sample surface, a magnifying lens system for magnifying the electron beam transmitted through the sample, and the magnifying lens. A transmission electron detector for projecting an electron beam expanded by the system onto a fluorescent plate for microscopic observation; an ion gun for generating an ion beam at a right angle to the sample irradiation direction of the electron beam; and for focusing the ion beam An ion optical system that irradiates the sample at right angles to the sample irradiation direction of the electron beam while scanning, and captures secondary electrons and X-rays emitted from the sample by the electron beam irradiation and the focused ion beam irradiation. A charged beam device for cross-section processing observation, which comprises a secondary electron detector and an X-ray detector. 2. The charged particle beam apparatus for cross-section processing observation according to claim 1, further comprising a gas gun for spraying a metal compound vapor at a focused ion beam irradiation position of the sample. 3. S obtained by focused ion beam irradiation
A focused charged beam characterized in that a processing position of the sample is set by observing an IM image, and a mark is made at both ends of the processing position by drilling by the focused ion beam etching, and a specific place of the sample is accurately processed. Processing method.