JP3132938B2 - Charged beam device for cross-section processing observation and processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting secondary particles generated from a sample by irradiating a focused ion beam, observing the surface of the sample, ion beam etching and ion beam chemical vapor deposition CVD of a predetermined region of the sample surface. By equipping a transmission electron microscope (hereinafter abbreviated as TEM) with a focused ion beam irradiation system and a gas supply device to be processed, the charge for cross-section processing observation can be processed into a simple and more optimal shape for TEM sample preparation. The present invention relates to a beam device and a processing method.

[0002]

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

By repeatedly irradiating the sample surface with the scanned focused ion beam, a predetermined region of the sample is sputtered by the ion beam and is not cut off. Further, by supplying a deposition gas from a nozzle, Form a metal film by ion beam on the irradiation area of the sample (Chemic
al Vapo r D eposition; may be abbreviated as CVD) it is. These functions are used to modify the prototype IC circuit and process evaluation, etc., and greatly reduce the debugging time of IC development ( Semiconductor World, 1987.9 [New VLSI evaluation and analysis technology using FIB], Japan Society for the Promotion of Science 132nd Committee, 101st meeting, 1987.11 "E
Failure analysis of high-speed bipolar LSI using B tester ",
"Operation analysis and wiring change of IC using focused ion beam", "Electron beam testing technology using focused ion beam"). Recently, a cross-sectional TEM sample has been produced using a focused ion beam apparatus, and the results of cross-sectional TEM observation at a specific location of the sample have been reported (37th Japan Society of Applied Physics, 1990.3, “Cross-sectional TEM using focused ion beam”). Sample preparation method ”). This method has a shorter cross-section TE at a specific location of the sample than the conventional ion milling method.
It can produce M samples.

FIG. 3 shows a focused ion beam processing apparatus which is an embodiment of the conventional apparatus. A liquid metal ion source is used for an ion gun 1 and an ion beam 2 extracted from the ion gun
Is focused and scanned by the ion optical system 3 and irradiates the surface of the sample 4. The ion optical system 3 includes an aperture 30 for passing only the portion near the optical axis of the ion beam 2, an electrostatic lens 31 for focusing the ion beam 2, and a scanning of the focused ion beam 2 over a predetermined area on the surface of the sample 4. A scanning electrode 32 to be turned on and a blanker 33 for turning on / off the irradiation of the focused ion beam 2 on the surface of the sample 4 and the like.

The ion beam 2 emits secondary particles excited by the ion beam at the same time as etching the surface of the sample 4. The secondary electrons in these secondary particles are detected by a secondary electron detector.
5 , and a SIM image is displayed on an observation CRT (not shown). Simultaneously with the irradiation of the ion beam 2, a CVD gas is supplied from a gas gun 16 nozzle to form a local film on the surface of the sample 4. This ion beam processing device cuts and cuts IC wiring.
It was conventionally used for connection, cross-section processing, observation, etc.

[0006]

However, in order to observe a cross section of a semiconductor sample using a focused ion beam processing apparatus as in the prior art, when preparing a sample for a semiconductor cross section TEM, first, mechanical polishing is performed. The width of the semiconductor sample surface is
The portion before and after the observation site of the sample, which has been cut down to leave 0 μm, is removed by ion beam etching to leave a wall of 0.5 μm or less. Next, check the processing shape and cross section by using a scanning electron microscope (Sc
Anning Electron Microscope (hereinafter abbreviated as SEM) is performed by image observation, and reworked as necessary. Then, the sample after processing is observed with a TEM, and if the processing is not possible due to insufficient processing, it is necessary to perform ion beam etching again. In this method, since a sample is taken in and out between a plurality of vacuum apparatuses, 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]

SUMMARY OF THE INVENTION 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.
The electron beam transmitted through the sample is magnified by an objective lens and a several-stage magnifying lens system, and is projected onto a fluorescent screen for microscopic observation by a transmission electron microscope. And 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 from a lateral direction with respect to the electron beam is arranged. This 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 sample is observed at the processing observation position. Then, the surface of the sample to be processed can be subjected to ion beam etching. Thus, a cross-sectional TEM sample at a specific portion 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 with the SEM image and the TEM image.
Further, by detecting the X-ray excited by the electron beam with the X-ray detector, elemental analysis of a minute portion can be performed. further,
Prior to ion beam etching, a film is locally formed on the processing observation surface of the sample to be processed by the ion beam CVD, and the sample surface is flattened, thereby protecting the sample observation surface from damage due to ion beam irradiation, and asperity on the surface of the sample to be processed. The roughness of the processing surface (TEM observation surface) due to the above can be reduced, and by tilting the sample to be processed several degrees during the ion beam etching processing, the inclination of the processing cross section due to the spread of the focused ion beam is perpendicular to the surface. The thickness of the thin wall of the TEM observation surface can be made uniform. Therefore, the present invention provides a TEM
Since preparation of a sample for use and observation of a TEM image can be performed on the spot, observation and analysis of a limited minute portion are possible.

[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 apparatus for cross-section processing observation according to the present invention. Hereinafter, description will be made with reference to the drawings. A liquid metal ion source is used as an ion source 1, and an ion beam 2 extracted from the ion source 1 is applied to an ion optical system 3.
Sample 4 on a 5-axis sample stage
Is irradiated. Secondary electrons excited by an ion beam emitted from a sample 4 which is a semiconductor integrated circuit are output from a secondary electron detector 5.
SIM (Scanning Ion Mic)
roscope ) image is displayed. Thus, the surface of the sample 4 is observed, the processing position is determined, the focused ion beam 2 is repeatedly irradiated to the processing position while scanning, and the TEM sample can be manufactured by the sputter etching by the irradiation of the focused ion beam 2.

[0010] Sample 4, as shown in FIG. 2, a slice piece of the semiconductor integrated circuit, the left end portion 4 of the sample 4 in Fig. 2
a is the surface of the semiconductor integrated circuit. The circuit cross section of the semiconductor integrated circuit is exposed on the upper and lower surfaces of the left portion 4b of the sample 4. 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 cut the upper and lower surfaces of the left portion 4b of the sample 4 by sputtering. After the upper and lower surfaces of the left portion 4b of the sample 4 have been cut by a predetermined amount, the focused ion beam 2 is switched to the electron beam 7 next.

The electron gun 6 is arranged so that the electron beam 7 irradiates the sample 4 perpendicularly to the direction in which the focused ion beam 2 irradiates 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
Is 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 the SEM image and the X-ray spectrum are displayed on a display CRT (not shown). -An X-ray image is displayed. Further, the electron beam 7 transmitted through the sample 4 is expanded by a magnifying lens system 11 and projected on a transmission electron detector (fluorescent plate) 12 to be TE
M images can be observed.

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 .
Irradiation Cum switched to the beam. The scanning area of the focused ion beam is further set so that the thickness of the left end 4b of the sample 4 is reduced. Then, additional processing of the TEM sample is performed and again
Perform the switching of the beam, that by the irradiation of the electron beam 7 TEM
Observe the image. As described above, according to the present invention, since an optimal TEM sample can be prepared on the spot and a TEM image can be observed on the spot, observation and analysis of a limited minute portion can be performed.

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

Furthermore, the focused ion beam irradiation position on the sample 4 is provided with a gas gun 16 for Ru spraying an organic metal compound vapor locally. Organic gold from gas gun 16
The group compound vapor 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 focused ion beam 2 is repeatedly scanned and irradiated on the left end face 4a of the sample 4. The metal film 23 is formed on the left end face 4a by spraying the organic metal compound vapor on the left end face 4a and irradiating the focused ion beam 2 on the left end face 4a.

As described above, a TEM sample is prepared by performing a sputter etching process by irradiation with the focused ion beam 2 and a local metal film forming process by spraying a CVD organometallic compound gas from the gas gun nozzle 16 to the ion beam 2 irradiation position. . The purpose of forming the metal film 23 on the left end face 4a of the sample 4 is as follows. The focused ion beam 2 is irradiated from the surface side (left end face 4a) of the semiconductor integrated circuit which is the sample 4 to form a cross section of the semiconductor integrated circuit, but the surface of the semiconductor integrated circuit is microscopically highly uneven. The cross section formed by the irradiation of the focused ion beam 2 is also affected by the unevenness, so that the unevenness occurs in a direction perpendicular to the irradiation direction of the focused ion beam. Therefore, at the same time as the irradiation of the focused ion beam 2 on the surface of the semiconductor integrated circuit, an organometallic compound vapor is sprayed, and as shown in FIG.
To form a metal film 23 that by the VD. The surface of the metal film 23 has an effect of smoothing (smoothing) irregularities on the surface of the base, and a focused ion beam is irradiated from the surface of the metal film 23 to make the cross section formed by etching smooth. When observing the cross section, a clear image is obtained.

As described above, the electron beam 7 is applied to the cross section of the left portion 4b of the sample 4 from the electron beam irradiation system to the sample 4 which has been processed in cross section by the focused ion beam 2, and the electron transmitted through the left portion 4b of the sample 4 is irradiated. Transmitted electron detector 12
By monitoring the above, the thickness of the sample 4 at the time of processing can be estimated, so that the thickness of the TEM sample can be optimized. Further, X-rays excited by the electron beam 7 are converted into X-rays.
By detecting with the line detector 10, it is possible to analyze a minimal part.

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

Next, the surface 4a of the sample 4 is irradiated by the focused ion beam irradiation system while scanning the focused ion beam 2, and secondary electrons due to the irradiation are detected by the secondary electron detector 5, and the SIM image is observed. The observed image is, for example, as shown in FIG. Next, the section observation position 22 is set from the SIM observation image. The section observation position 22 in the case of this embodiment is a section of the contact hole 19. Then, extensively specify the local deposition area 20 of the CVD metal layer 23 including the observation position 22 der Turkey contact hole 19, and the blowing CVD gas from the gas gun 16, the focused ion in the local deposition area 20 By repeatedly irradiating the beam 2, the metal film 23 is formed. The metal film 23 has an effect of reducing damage to the sample surface 4a due to irradiation of the focused ion beam 2.

At this time, both ends of the cross-section observation position 22 are irradiated with the focused ion beam 2 to make marks 21 by drilling by etching, so that the observation position can be easily found and processed accurately. Then, as shown in FIG. 4C, the center portion of the contact hole portion 19 is set to a width of 0.05 to 0.2 μm.
The left and right etching areas 24 are removed by sputter etching with the 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 inclination of the etching cross section due to the shape of the focused ion beam 2 is corrected, and a vertical thin wall is formed. can do. Then, the electron beam 7 is irradiated from the electron beam irradiation system onto the observation position of the device section 4 b 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 small, the etching area 2 shown in FIG.
4 and the focused 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. FIGS. 4E and 4F show the shapes of the sample 4 on the top surface and the cross section after processing, respectively.

FIG. 5A shows an SEM image of the sample 4 when a processing section 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, processed shape, cross section, and the like can be easily confirmed. FIG. 5B shows the X-rays excited by the electron beam 7 detected by the X-ray detector and the spectrum is displayed, and FIG. 5C shows the X-ray image of aluminum (Al). In this manner, element analysis of a minute portion at a specific location can be easily performed. Therefore, the present invention is based on the TEM sample preparation and FIG.
Since a cross-sectional TEM image observation as shown in FIG. 4D can be performed on the spot, observation and analysis of a specific portion are possible.

[0023]

As described above, according to the present invention, a cross-sectional TEM sample at a specific location can be processed by ion beam processing. During the processing operation, the ion beam is switched to an electron beam as needed, and SEM image observation and the like are performed. Because X-ray analysis can be performed, it is easy to confirm the processing position, processing shape, cross-section, and to analyze minute parts. In addition, by local film formation and sample inclination, the surface of the sample to be processed can be protected and a vertical and flat cross-section can be manufactured. In addition, since a cross-sectional TEM image can be observed on the spot, the cross-sectional TEM at a specific location can be observed.
It is effective for observation.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of a sample peripheral part according to the present invention.

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

FIG. 4 is a view 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]

 DESCRIPTION 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 Reference Signs List 15 secondary electron 16 gas gun (nozzle) 17 aluminum wiring 18 polysilicon wiring 19 contact hole 20 local film formation area 21 mark (drilled by ion etching) 22 cross-sectional 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)

(57) [Claims] 1. An electron gun for generating an electron beam, an electron beam lens system for narrowing the electron beam and irradiating a sample surface, an expanding lens system for expanding an electron beam transmitted through the sample, and the expanding lens. A transmission electron detector for projecting the electron beam expanded by the system onto a fluorescent screen for microscopic observation, an ion gun for generating an ion beam at right angles to a sample irradiation direction of the electron beam, and converging the ion beam; And an ion optical system for irradiating the sample at right angles to the sample irradiation direction of the electron beam while scanning,
A charged beam apparatus for cross-section processing observation, comprising: a secondary electron detector for capturing secondary electrons and X-rays emitted from the sample by the electron beam irradiation and the focused ion beam irradiation; and an X-ray detector. . 2. The charged beam apparatus for cross-section processing observation according to claim 1, further comprising a gas gun for spraying a metal compound vapor onto the focused ion beam irradiation position of the sample. 3. A charged beam processing method, wherein a thin film of a sample is processed using a focused ion beam for preparing a TEM sample, and TEM observation is performed in a place where the TEM sample is prepared.