JPH09274883A - Fib/sem compounded apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out SEM(scanning electron microscope) observation of a cross section of a specimen which is processed with high precision by FiB (focused ion beam) processing while preventing charging up. SOLUTION: A means to radiate beam to an electrode is installed in a SEM apparatus 2 which accelerates and converges electrons to scan a specimen 4 and forms on observation image be secondary electrons and reflected electrons generated by the specimen 4. This compounded apparatus comprises a SEM apparatus part of which a normal SEM mode and a secondary electron generating mode by irradiation of the electrode can be selectively employed, an FIB apparatus part 1 having a scanning ion microscopic function to accelerate and converge ions 11 and scan the specimen 4 and form an observation image by secondary electron signals emitted out of the specimen 4 and a function to irradiate a defined region of the specimen 4 selectively with converged ions and process the specimen 4, and a specimen chamber part 3 to hold the specimen in vacuum and the FIB 1 and the SEM 2 are so arranged as to cross respective beam axes of the FIB 1 and the SEM 2 approximately at the same position of the same specimen.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a focused ion beam (F
ocused Ion Beam (hereinafter referred to as FIB) is used to process the cross section of the sample, and the cross section is scanned with an electron scanning electron microscope (Scanning Ele
The present invention relates to an apparatus for observing with a ctron microscope: SEM), and particularly to an apparatus effective for observing a fine structure of a sample.

[0002]

2. Description of the Related Art As a conventional technique, there is Japanese Patent Laid-Open No. 1-181529. This describes a configuration in which an electron beam shower gun dedicated to neutralization is attached to a combined device of FIB and SEM. With this configuration, it is possible to perform high-precision FIB processing that prevents charge-up and in-situ SEM observation of the FIB processing portion.

[0003]

Since the prior art is equipped with a dedicated electron beam shower gun, electrons with low acceleration energy can be amply supplied to the sample. Therefore, even if samples of various materials and sizes are processed with various FIB currents, it is possible to reliably prevent charge-up. However, the dedicated hardware must be placed near the sample,
There are problems in terms of cost and space.

From the viewpoint of cost and space, it may be considered to use an SEM electron probe for neutralizing charge-up during FIB processing. Thereby, the hardware of the electron beam shower gun can be omitted. However, if neutralization is performed using the beam conditions of SEM observation as they are, the amount of beam current is extremely limited. Therefore, under conditions where the sample insulation, the area of the insulating portion, and the FIB processing beam current are large,
There is a drawback that a sufficient neutralizing effect may not be obtained.
In order to reliably perform neutralization under various conditions, it is necessary to supply low energy electrons to the sample in abundance. A method of changing the accelerating voltage of the SEM and the focusing condition of the lens may be considered in order to supply a lot of low-energy electrons.
The operating conditions of the EM are (1) Search for a processed part on the sample (SEM
Mode), (2) Neutralization during FIB processing (neutralization mode),
(3) It is necessary to change in a series of operations of cross-section observation (SEM mode) after FIB processing, which is not desirable from the viewpoint of stable operation of the apparatus.

[0005]

According to the present invention, the primary beam of the SEM is not directly used but is irradiated onto the electrode and converted into secondary electrons, thereby lowering the energy of the electron beam and increasing the amount of current. Plan. This is either (1) mounting an electron-electron conversion electrode near the beam irradiation point on the sample of the SEM column and irradiating the conversion electrode with a beam by deflection, or
(2) It can be realized by either mechanically inserting the conversion electrode near the beam irradiation point on the sample of the SEM column or by any method. In the case of (1), since only beam deflection control is required, S
It has the feature that EM mode and neutralization mode can be switched instantly. In the case of (2), there is a feature that the neutralizing function can be realized without modifying the SEM part.

During FIB processing, secondary electrons are generated from the conversion electrode to neutralize the charge up of the insulating sample due to FIB irradiation. When the electrode potential is set to the ground potential, the energy of the secondary electrons generated from the electrode is several eV, so that it can be immediately attracted to the charged-up place. Since this is a physical equilibrium phenomenon, the amount of secondary electrons supplied is automatically controlled according to the degree of charge-up. Therefore, even if there is a difference in the insulation property, area, and FIB processing current of the sample,
Charge-up can be prevented under appropriate neutralization conditions. The amount of secondary electrons depends on the amount of the primary beam of the SEM, but if the electrode is made of a material having a high secondary electron yield (for example, aluminum), a secondary electron current larger than the primary beam current can be obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the FI used in the first embodiment.
It is explanatory drawing of B / SEM. First, the FIB section will be described. Ions emitted from the liquid metal ion source 11 are focused on the sample 4 by the condenser lens 12 and the objective lens 14. A deflector 13 is arranged in front of the objective lens 14, and a beam is deflected by a deflection electric field generated by the deflector 13, so that an arbitrary place on the sample can be irradiated with the FIB.
Secondary particles generated from the sample 4 by FIB irradiation are detected by the detector 15 and sent to the control device 50 as a luminance signal, and are imaged as a scanning ion microscope (abbreviated as SIM) image on the CRT of the computer 51. Is displayed. Secondary electrons and secondary ions can be selectively detected in the secondary particles. The FIB has not only an image acquisition similar to that of the SEM, but also a function of selectively processing a specific portion based on the obtained image.

Next, the SEM section will be described. Electron source 2
The electrons emitted from 1 are focused on the sample 4 by the condenser lens 22 and the objective lens 24. A deflector 23 is arranged in front of the objective lens 24, and the beam is deflected by a deflection magnetic field generated by the deflector 23. When the sample is irradiated with the deflected beam, secondary electrons are generated from the sample, which pass through the objective lens 24 and are detected by the detector 25. The detection signal is sent to the control device 50 as a brightness signal,
An image is displayed on the CRT of the computer 51. The deflector 23 is provided with two windings. One is a normal S
It is for raster scanning used during EM image observation, and the other is for large-angle deflection to realize the neutralization mode. The beam deflected at a large angle irradiates the conversion electrode 5 arranged near the beam exit of the SEM column 2, and secondary electrons are generated from the electrode. When the potential of the electrode is the ground potential, the energy of the generated secondary electrons is several eV and is efficiently attracted to the charge-up generation site. Further, the potential of the electrode 5 can be changed to adjust the supply of secondary electrons to the sample.

The FIB column 1 and the SEM column 2 are mounted in the sample chamber 3, and the FIB beam axis and the SEM beam axis intersect each other on the sample.

The control device 50 controls column control of the FIB and SEM, etc., and the GUI (graphical user interface) for the operation and images of the SEM and SIM are displayed on the CRT of the computer 51. .

FIG. 2 is an explanatory diagram of a window for displaying a microscope image. This image monitor window 100
Has an image signal input switching button 101,
An image displayed on the display unit 103 is selected. For example, SE
When M is selected, the image brightness signal is connected to the signal from the detector 25, and the SEM raster scan is performed by clicking the start / stop button 102.
The SEM image is displayed on the CRT.

FIG. 3 shows an area editor window 200 for setting an important processing position when performing FIB processing.
When the get image button 201 is clicked, an image similar to the image display section 103 of the image monitor 100 is stored in the image memory for the editor in the computer,
It is displayed on the display unit 204. For example, based on the stored image, in order to perform the rectangular processing at the desired location, the rectangular processing area 205 is set by clicking the rectangular figure selection button 202 and operating the mouse on the display unit 204.

FIG. 4 shows a processing condition setting window 300. Here, the processing time and the like and the presence or absence of the charge neutralization function during processing are set. Neutralization setting button
When 301 is turned on, the deflector 23 in the SEM column 1 operates in the large-angle deflection mode during processing to enter the neutralization mode, and the secondary electrons generated from the conversion electrode 5 neutralize the charge-up. Processing is in the area editor window 2
It is started by clicking the processing button 203 in 00.

FIG. 5 shows the FIB / used in the second embodiment.
It is a block diagram of SEM. The difference from the first embodiment is
The conversion electrode is in a movable type. When observing the SEM image, the conversion electrode 5 is retracted by the conversion electrode moving mechanism 6 to a position that does not affect the beam of the SEM. At the time of charge-up neutralization, the conversion electrode 5 is moved on the beam axis of the SEM, and secondary electrons are generated from the conversion electrode. This allows
Charge-up can be prevented without adding a large-angle deflection function to the SEM.

As a method of irradiating the conversion electrode with a beam,
Although (1) beam deflection and (2) mechanical movement of the conversion electrode have been described above, they can be combined to optimize the secondary electron generation position.

When the conversion electrode is irradiated with an electron beam for a long time, a phenomenon occurs that contamination adheres to the observation part. This phenomenon largely depends on the vacuum degree of the sample chamber, and the secondary electron generation efficiency decreases under the condition of low vacuum degree. For this purpose, methods such as (1) providing heating means on the conversion electrode, (2) scanning the conversion electrode with an electron beam to reduce the beam irradiation amount per unit area, and the like can be utilized.

Although the embodiment of the combined device of FIB and SEM has been described above, it is obvious that the same effect can be expected in the combined device of FIB and FIB.

[0018]

According to the present invention, it is possible to reliably prevent charge-up in FIB processing at low cost. As a result, it becomes possible to easily observe the SEM image of the cross section of the sample processed by the FIB with high accuracy.

[Brief description of drawings]

FIG. 1 is an FIB / SEM used in the first embodiment of the present invention.
Explanatory drawing of an apparatus.

FIG. 2 is an explanatory diagram of an image monitor window.

FIG. 3 is an explanatory diagram of an area editor window.

FIG. 4 is an explanatory diagram of a processing condition setting window.

FIG. 5 is a FIB / SEM used in the second embodiment of the present invention.
Explanatory drawing of an apparatus.

[Explanation of symbols]

1 ... FIB column, 2 ... SEM column, 3 ... sample chamber, 4
... sample, 5 ... conversion electrode, 11 ... ion source, 12, 22 ...
Condenser lens, 13, 23 ... Deflector, 14, 24 ...
Objective lens, 15, 25 ... Detector, 21 ... Electron source, 50
... control device, 51 ... computer.

Claims (3)

[Claims] 1. An electron is accelerated and focused to scan on a sample,
The SEM device for forming an observation image by secondary electrons and reflected electrons generated from the sample is provided with a means for inspecting a beam on an electrode, and a normal SEM mode and a secondary electron generation mode by electrode irradiation can be selectively used. The SEM device section configured as described above, the scanning ion microscope function of accelerating and focusing the ions to scan the sample, and form an observation image by the secondary particle signal emitted from the sample, The FIB device section has a function of irradiating the region with selectively focused ions to process the sample, and a sample chamber section for holding the sample in a vacuum, and the beam axes of the FIB and the SEM respectively. FIBs, which are installed so as to intersect at almost the same position on the same sample.
/ SEM combined device. 2. The FIB / SEM composite apparatus according to claim 1, wherein the electrode is deflected and irradiated with the beam of the SEM to realize the secondary electron generation mode. 3. The SEM by which the electrodes are mechanically moved.
The FIB / SEM combined device according to claim 1 or 2, wherein the FIB / SEM combined device is inserted on the beam axis of, and realizes the secondary electron generation mode.