JP2004047341A - Method and device for observation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a sample 3 from charging up when it is irradiated by an electron beam E1 for observation. <P>SOLUTION: As an observed area of the sample 3 is irradiated by the electron beam E1 during observation with a scanning electron microscope, the area is negatively charged. A positively charged Ar ion beam 10 is irradiated at least one part around the observed area of the sample 3 except for the area. The irradiation of the Ar ion beam neutralizes the observed area of the sample 3 and prevents the sample from charging up. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Field of the Invention]
The present invention relates to an observation method using an observation device such as a scanning electron microscope and the observation device.
[0002]
[Prior art]
The scanning electron microscope detects secondary electrons, reflected electrons, and the like generated based on the irradiation of the sample with the electron beam, and detects information about the sample based on the detection result.
[0003]
In such a scanning electron microscope, a semi-in-lens type having a small aberration coefficient has been used as an objective lens, and a scanning electron microscope with improved resolution has been developed. FIG. 4 shows a main part of such a scanning electron microscope, and reference numeral 101 denotes a semi-in-lens type objective lens.
[0004]
The objective lens 101 is configured such that an outer magnetic pole 103 is disposed outside an inner magnetic pole 102, and a magnetic field formed by the objective lens 101 reaches a sample 104. Secondary electrons E2 generated by irradiating the observation region of the sample 104 with the electron beam E1 are constrained by the magnetic field of the objective lens 101, are wound up on the sample 104, and travel upward in the objective lens 101.
[0005]
A secondary electron detector 105 is provided inside the objective lens 101 at a position away from the axis of the electron beam E1. Then, the secondary electrons E <b> 2 wound up from the observation region of the sample 104 and taken out to the inside of the objective lens 101 are turned on by the action of an electric field based on the voltage applied to the secondary electron detector 105. 105 and is detected by the secondary electron detector 105.
[0006]
[Problems to be solved by the invention]
As described above, the observation region of the sample 104 is irradiated with the electron beam E1, and the irradiation of the electron beam E1 is continued. Negative charges will be charged. Negative charges due to the irradiation of the electron beam E1 accumulate in the region to be observed of the sample 104, and when the charge amount increases, the charge is increased. The next electron is affected. As a result, the secondary electron detection result of the secondary electron detector 105 is affected, and there is a need for improvement such that information such as a surface observation image of the sample 104 cannot be appropriately detected based on the detection result. .
[0007]
[Means for Solving the Problems]
The observation method based on the present invention, while irradiating the charged particle beam to the observed region of the sample, avoiding the observed region of the sample, irradiating at least a part of the periphery of the observed region with an ion beam, It is characterized in that information from an observation region of the sample is detected.
[0008]
Another observation method based on the present invention is an observation method of irradiating a charged particle beam on an observed region of a sample and observing the observed region, wherein the charged particle beam is irradiated on the observed region of the sample. A charged particle beam irradiating step of irradiating, an ion beam irradiating step of irradiating at least a part of a periphery of the observed area with an ion beam avoiding the observed area of the sample, and information from the observed area of the sample And an information detecting step of detecting
[0009]
Further, the observation device according to the present invention is a charged particle beam irradiation means for irradiating a charged particle beam to the observation region of the sample, and at least a part of the periphery of the observation region, avoiding the observation region of the sample. It is characterized by having ion beam irradiation means for irradiating an ion beam, and information detection means for detecting information from the observed region of the sample.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 is a schematic configuration diagram showing an observation device according to the present invention. In the figure, the observation device 1 is a scanning electron microscope.
[0012]
An electron gun 2 is arranged above the observation device, and an electron beam (charged particle beam) E1 is irradiated from the electron gun 2 toward a region of the sample 3 to be observed. Here, as the electron gun 2, for example, a field emission type (FE type) electron gun is used. The electron beam E1 emitted from the electron gun 2 and accelerated is narrowly focused on a predetermined observation region of the sample 3 by the condenser lens 4 and the objective lens 5. As the objective lens 5, a semi-in-lens type objective lens having an inner magnetic pole 5a, an outer magnetic pole 5b, and a lens coil 5c is used.
[0013]
Above the objective lens 5, a scanning coil 6 for deflecting the electron beam E1 is arranged. A scanning signal for scanning the observation area of the sample 3 with the electron beam E1 is supplied to the scanning coil 6 from a scanning signal generation circuit (not shown).
[0014]
An opening 7 is provided at a predetermined position below the lens coil 5 c in the objective lens 5, and a secondary electron detector 8 is arranged inside the opening 7. The secondary electron detector 8 is located off the axis of the electron beam E1 in the objective lens 5.
[0015]
Here, the electron gun 2, the condenser coil 4, the scanning coil 6, the objective lens 5 and the like constitute an electron beam irradiation unit (charged particle beam irradiation unit).
[0016]
An Ar ion gun (ion beam irradiation means) 9 is disposed obliquely above the sample 3, and a predetermined portion of the sample 3 is irradiated with an Ar ion beam 10 from the Ar ion gun 9. The Ar ion beam 10 is a positively charged ion beam.
[0017]
A secondary electron detector 8 arranged inside the opening 7 of the objective lens 5 is connected to a signal amplifier 11 and an image processing device 12 in order, and detects a secondary electron detected by the secondary electron detector 8. The detected signal is amplified by the signal amplifier 11 and then image-processed by the image processing device 12 as an observation image, which is information on the observation region of the sample 3.
[0018]
Here, the secondary electron detector 8, the signal amplifier 11, the image processing device 12, and the like constitute an information detecting means.
[0019]
The electron beam E1 and the Ar ion beam 10 are irradiated onto the sample 3 in a predetermined vacuum atmosphere, and the secondary electrons generated from the sample 3 move accordingly in the vacuum atmosphere.
[0020]
Next, an observation method according to the present invention using such an observation device will be described.
[0021]
First, the sample 3 is placed inside the observation device 1, and the inside of the observation device 1 is evacuated to a predetermined vacuum atmosphere.
[0022]
Then, an electron beam E1 is generated from the electron gun 2 and accelerated. The accelerated electron beam E1 is narrowly focused and irradiated in a predetermined observation region of the sample 3 by the condenser lens 4 and the objective lens 5 excited under predetermined conditions. At this time, the electron beam E1 focused in the observation region of the sample 3 is two-dimensionally scanned by the scanning coil 6 (a charged particle beam irradiation step).
[0023]
Here, a predetermined portion of the sample 3 is irradiated with the Ar ion beam 10 from the Ar ion gun 9 during the period in which the above-described charged particle beam irradiation step is performed. Here, the predetermined location of the sample 3 where the Ar ion beam 10 is irradiated is a location avoiding the observation area to which the electron beam E1 is irradiated, and is at least a part of the periphery of the observation area. . For example, as shown in FIG. 2, when the shape of an observation area 20 on which the electron beam E <b> 1 is scanned and irradiated on the sample 3 is a square shape having a quadrilateral 21, the Ar ion beam 10 The portion to be irradiated is a part of the periphery of the observed region 20 and is a portion 22 outside the one side 21a constituting the periphery (quadrilateral 21) of the observed region (ion beam irradiation step).
[0024]
As a result, the observation region 20 of the sample 3 is irradiated with the electron beam E1, and the Ar ion beam 10 is irradiated on at least a part of the periphery of the observation region 20 while avoiding the observation region 20 of the sample 3. You.
[0025]
Secondary electrons are generated from the observed region of the sample 3 in response to the irradiation of the electron beam E1. The generated secondary electrons are detected by the secondary electron detector 8, and the secondary electron detector 8 sends out a detection signal based on the detected secondary electrons. This detection signal is amplified by the signal amplifier 11 and then image-processed by the image processing device 12 as an observation image, which is information on the observation region of the sample 3 in association with the scanning of the electron beam E1 by the scanning coil 6. . As a result, an observation image (information) of the observation region of the sample 3 is detected (information detection step).
[0026]
Here, the behavior of secondary electrons generated from the sample 3 in the above-described information detection step will be described with reference to FIG.
[0027]
The secondary electrons E2 generated in response to the electron beam E1 applied to the observation area 20 of the sample 3 are given rotational motion by the magnetic field formed by the objective lens 5, and are collected on the axis of the electron beam E1. It is wound up on the sample 3 and goes upward in the objective lens 5. The secondary electrons E2 in the objective lens 5 are attracted in the direction of the secondary electron detector 8 by an electric field formed by the corona ring 8a of the secondary electron detector 8, accelerated, and accelerated by the scintillator of the secondary electron detector 8. 8b. As a result, the secondary electrons E2 are detected by the secondary electron detector 8.
[0028]
Here, when the same observation region 20 in the sample 3 is continuously irradiated with the electron beam E1 to continue the observation, the observation region 20 is charged with negative charges, and the negative charge due to the irradiation of the electron beam E1 is changed into the observation region. There is a possibility that the charge is accumulated in the battery 20 and the charge amount increases to cause charge-up. However, since the Ar ion beam 10 positively charged by the Ar ion gun 9 irradiates the outer peripheral portion (at least a part of the periphery) 22 of the observation region 20 of the sample 3, the outer peripheral portion 22 of the sample 3 is The observation region 20 is electrically neutralized through the connection 22, and no charge-up occurs.
[0029]
In addition, normally, secondary electrons are generated separately from the portion of the sample 3 irradiated with the Ar ion beam 10 due to the irradiation of the sample 3 with the Ar ion beam 10, and the secondary electrons are generated as noise as secondary electrons. Although it is conceivable that the object is detected by the detector 8, in the present invention, Ar is added to the outer vicinity 22, which is at least a part of the periphery of the observed region 20, which is a part avoiding the observed region 20. Since the ion beam 10 is irradiated, as shown in FIG. 3, the secondary electrons E3 generated from the outer vicinity portion due to the irradiation of the Ar ion beam 10 enter the inside of the semi-in-lens type objective lens 5. It will go around outside without entering. Therefore, the secondary electrons E3 from the sample 3 due to the irradiation of the Ar ion beam 10 are not detected by the secondary electron detector 5 arranged inside the objective lens 5, and the Ar ion beam 10 is Even if the light is irradiated on 3, the detected noise can be greatly reduced.
[0030]
As described above, since the secondary electrons E3 caused by the irradiation of the Ar ion beam 10 are not detected by the secondary electron detector 8 inside the objective lens 5, the operation is performed while irradiating the electron beam E1. During observation, there is no problem if the Ar ion beam 10 is irradiated onto the predetermined portion of the sample 3 to electrically neutralize the observation region 20.
[0031]
In the above-described example, at least a part of the periphery of the observation region 20 of the sample 3 is irradiated with the Ar ion beam 10. However, by providing a plurality of Ar ion guns 9, the periphery of the observation region 20 is provided. The Ar ion beam 10 may be entirely irradiated.
[0032]
When irradiating the sample 3 with the Ar ion beam 10 from the Ar ion gun 9, if it is difficult to narrow down the Ar ion beam 10 so as to irradiate the observed region 20 of the sample 3, the objective lens 5 may be used. Can be arranged so that the Ar ion gun 9 does not directly look at the observation region 20 of the sample 3 by blocking the part of the Ar ion beam 10.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an observation device according to the present invention.
FIG. 2 is a plan view showing a region to be observed in a sample.
FIG. 3 is a schematic configuration diagram illustrating a main part of an observation device according to the present invention.
FIG. 4 is a diagram showing a main part of a semi-in-lens type observation device.
[Explanation of symbols]
1 ... observation device, 2 ... electron gun, 3 ... sample, 4 ... condenser lens,
5 ... objective lens, 6 ... scanning coil, 7 ... aperture, 8 ... secondary electron detector,
9 ... Ar ion gun, 10 ... Ar ion beam, 11 ... Signal amplifier,
12: Image processing device, E1: Electron beam, E2: Ar ion beam

Claims (16)

While irradiating a charged particle beam to the observation region of the sample, irradiating at least a part of the periphery of the observation region with the ion beam while avoiding the observation region of the sample, information from the observation region of the sample is obtained. An observation method characterized by detecting an object. An observation method of irradiating a charged particle beam to an observation region of a sample to observe the observation region, wherein the charged particle beam irradiation step of irradiating the observation region of the sample with the charged particle beam; and An ion beam irradiation step of irradiating at least a part of the periphery of the observed area with an ion beam, avoiding the observed area; and an information detecting step of detecting information from the observed area of the sample. Observation method. The observation method according to claim 2, wherein the ion beam irradiation step is performed during a period in which the charged particle beam irradiation step is performed. The observation method according to claim 1, wherein the ion beam is a positively charged ion beam. The observation method according to claim 4, wherein the ion beam is an Ar ion beam. The observation method according to claim 1, wherein the charged particle beam is an electron beam. The observation method according to claim 1, wherein the charged particle beam is scanned in an observation area of the sample. The observation method according to any one of claims 1 to 7, wherein the information detected from the observation region of the sample is detected based on secondary electrons from the observation region. Charged particle beam irradiating means for irradiating the observed area of the sample with a charged particle beam, and ion beam irradiating means for irradiating at least a part of the periphery of the observed area with an ion beam avoiding the observed area of the sample; An observation apparatus comprising: information detection means for detecting information from an observation region of the sample. 10. The observation apparatus according to claim 9, wherein the ion beam irradiation unit is a unit that irradiates a positively charged ion beam. The observation device according to claim 10, wherein the ion beam irradiation unit is a unit that irradiates an Ar ion beam. The observation apparatus according to claim 9, wherein the charged particle beam irradiation unit includes an electron gun that emits an electron beam. The observation apparatus according to any one of claims 9 to 12, wherein the charged particle beam irradiation means includes a scanning coil that scans the charged particle beam within an observation region of the sample. The observation device according to claim 8, wherein the information detection unit includes a secondary electron detector that detects a secondary electron from an observation region of the sample. 15. The observation apparatus according to claim 14, wherein the charged particle beam irradiation unit includes an objective lens, and a detection unit of a secondary electron detector in the information detection unit is disposed inside the objective lens. The observation apparatus according to claim 15, wherein the objective lens blocks a part of the ion beam.

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