JP2003162973A - Focused ion beam processing method and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focused ion beam processing method and the device by which a sectional structure can be easily observed even when each layer constituting a layered structure is extremely thin. <P>SOLUTION: When a sectional processing is carried out as a pre-treatment to observe a cross section of a testpiece, the testpiece is processed with the testpiece inclined to a first angle with regard to the angle of incidence of the ion beam, and after processing is finished, the testpiece is observed with the testpiece inclined to a second angle. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention uses a focused ion beam,
The present invention relates to a processing method and apparatus for obtaining a cross section of a sample.

[0002]

2. Description of the Related Art A method for obtaining a cross section of a sample using a focused ion beam device is disclosed in, for example, Japanese Patent Laid-Open No. 174918/1987. That is, an ion beam is vertically applied to the surface of the sample at the cross-section creation position to form a vertical cross-section, and the cross-section is observed. As a method that does not use a focused ion beam, a method of cleaving or polishing a sample is known, but none of them can accurately determine a processing target position. On the other hand, the method using the focused ion beam has a feature that the processing target position can be accurately determined and processed by combining the microscope function and the processing function.

[0003]

However, with the progress of semiconductor manufacturing technology and the like, the shape of the sample for observing the cross-sectional shape has become finer and finer. The thinnest layered structure used for semiconductor devices, which has been developed in recent years, has a thickness of 1 Onm or less. Therefore, a vertical cross section is formed, and the observation is scanned and irradiated to observe the exposed sample surface. In this case, the resolution is very close to the resolution of the observation device, which makes observation difficult. Furthermore, when performing composition analysis of a cross-sectional structure, the energy beam to be irradiated cannot be narrowed down as much as the energy beam of the observation device. Therefore, it is becoming impossible to perform analysis by the conventional method.

[0004]

In order to solve the above problems, in the present invention, the incident angle of the ion beam is made shallow, the sample is etched obliquely, and the angle is perpendicular to or close to the exposed sample surface. Irradiate with an ion beam and observe the exposed sample surface.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION First, a focused ion beam apparatus will be described with reference to FIG. FIG. 1 is a diagram showing a schematic configuration of a focused ion beam device. As shown in FIG. 1, the ion source unit 3 has a liquid metal ion source 1 made of, for example, Ga and an extraction electrode 2. The ion source 3 is mounted on the XY direction moving device 4 and is provided so as to be movable in XY directions which are two directions orthogonal to the beam generated. On the beam irradiation side of the ion source unit 3, a first aperture 5 that allows only a central portion of the high-intensity ion beam B1 generated from the ion source unit 3 having a high current density to pass therethrough.
Are arranged.

Further, a charged particle optical system 9 including a condenser lens 6, a second aperture 7 and an objective lens 8 is arranged on the beam exit side of the first aperture 5, and the high brightness generated by the ion source 1 is obtained. The ion beam B1 is focused by the charged particle optical system 9 into a focused ion beam B2.
Here, the second aperture 7 has a plurality of through holes 7 a having different diameters and can be switched by the through hole switching device 10. Note that only one through hole 7a is shown in the drawing. That is, the second aperture 7 can be changed to a plurality of through holes 7a having different sizes by the through hole switching device 10. In this example, the diameter of the through hole 7a can be changed by sliding a member having a plurality of through holes 7a having different diameters, but the diameter of the single through hole 7a can be changed continuously or in stages. You may make it changeable.
As described above, the structure of the through hole switching device 10 is not particularly limited, but a specific example thereof is, for example, Japanese Patent Laid-Open No. 62-2237.
The configuration disclosed in Japanese Patent Publication No. 56 can be mentioned.

Further, the second aperture 7 can be moved in the XY directions by the XY direction moving device 11 in the radial position of each through hole 7a. A blanking means including a blanking electrode 12 and a blanking aperture 13 is provided on the beam exit side of the charged particle optical system 9 to turn on / off the focused ion beam. That is, when the focused ion beam B2 is turned off, a voltage is applied to the blanking electrode 12 to apply the focused ion beam B2.
Is deflected so that the blanking aperture 13 blocks the light. The arrangement of the blanking electrode 12 and the blanking aperture 13 is not limited to this, and may be arranged above the charged particle system 9, for example.

A deflecting electrode 16 for scanning the focused ion beam B2 which has passed through the blanking aperture 13 to a desired position is arranged on the beam exit side of the blanking aperture 13. The focused ion beam B2 scanned by the deflection electrode 16 is applied to a desired position on the sample 18 on the sample stage 17.
Then, the focused ion beam B2 can be repeatedly irradiated and scanned in a predetermined region on the surface of the sample 18. The sample stage 17 has an X that allows the sample 18 to move in the XYZ directions.
The YZ moving function is provided, and also the tilting function for tilting the sample 18 is provided.

A secondary charged particle detector 19 for detecting secondary charged particles emitted from the surface of the sample 18 irradiated with the focused ion beam B2 is arranged above the sample stage 17. The secondary charged particle detector 19 includes an image control unit 20 for amplifying the detection signal and obtaining a plane intensity distribution of the secondary charged particles, and a sample surface based on the plane intensity distribution signal from the image control unit 20. The image display device 21 that displays the formed pattern is connected.

Further, on the side of the sample stage 17, a Faraday cup 1 whose position can be exchanged with the sample stage 17 is provided.
5 are provided. Faraday cup 15 is sample 18
Instead of, the focused ion beam B2 is irradiated and the beam current is measured. The extraction electrode 2, the planning electrode 12 and the deflection electrode 16 described above are
A pull-out power supply 22, a blanking power supply 23, and a deflection power supply 24, which apply desired voltages to the respective components, are connected to each. Further, it is possible to comprehensively control the entire focused ion beam apparatus, and individually control the XY direction moving device 4, the through hole switching device 10, the XY direction moving device 11, and the above-mentioned power sources 22 to 24. A control unit 25 including a computer system is provided.

In such a focused ion beam device, the ion beam B1 extracted from the ion source 3 is focused by the charged particle optical system 9 and scanned by the deflection electrode 16 to irradiate the sample 18 to process the sample 18. It can be carried out.
Although not shown in this example, a gas irradiation nozzle is provided in the vicinity of the sample 18, and a gas is supplied from the gas irradiation nozzle at the same time as the irradiation of the focused ion beam B2 to locally perform CVD film formation. You can

When performing such processing, the processing status can be observed by the image display device 21. Although not shown in this example, for example, the surface of the sample 18 may be illuminated by general illumination so that the sample surface can be observed with an optical microscope at the same time. Hereinafter, a sample processing method using such a focused ion beam device will be described. First, a peripheral image for forming a cross section of the sample 18 is obtained as shown in FIG. In FIG. 2, the surface of the sample 18 is irradiated while scanning the focused ion beam B2, and secondary charged particles generated from the surface of the sample 18 by the irradiation are detected by the secondary charged particle detector 19 to obtain It is the image.

First, the sample 18 is arranged so that its surface is at a right angle to the irradiation axis of the focused ion beam B2. Then, the processing observation position of the sample 18 is obtained.
Then, using the tilting function of the sample stage 17, the sample 18 is tilted by an angle θ as shown in FIG. 3b. At this time, the processing position of the sample 18 is displaced with respect to the predetermined optical axis of the focused ion beam B2. Here, the focused ion beam B2 is again scanned and irradiated, and the image of the sample surface is observed.

Then, a portion AA 'having a structure to be observed in the image is designated. Then, indicate the approximate depth d of the structure to be observed. The incident angle of the focused ion beam B2 at the time of processing is θ. From these relationships, the ion beam irradiation region (processing frame 30) when the sample is tilted as shown in FIG. 3a is determined. The area of the processing frame 30,
The deflection electrode 16 sets the scanning region of the focused ion beam B2, and the scanning irradiation is performed. That is, it is processed. After a lapse of a certain time after the start of processing, the processed surface is observed and it is confirmed whether or not a desired portion is obtained. Therefore, in the beginning of processing,
While setting d to be shallow, the processing area is determined, and while confirming the processing shape, the depth d is successively increased to obtain a desired portion. The sample 18 is cross-section processed as shown in FIG. 3b. For example, the sample 18 is a semiconductor device in which the insulating film 31 is formed on the substrate 33 and the very thin wiring 32 is formed in the insulating film. The cross section to be observed is the wiring 32. As described above, the cross-section processed wiring 32 is multiplied by 1 / COSθ as a cross section.
When θ = 80 °, it is 5.8 times, and when θ = 85 °, it is 11.5 times.

After the processing is completed, the ion beam is inclined with respect to the processed surface of the sample so that the ion beam is vertical or at an angle close thereto, and the processed (cross section) surface is observed. In addition, the composition of the substance appearing on the processed surface is analyzed. When the tilting function of the sample stage 17 is restored, the surface of the sample 18 and the optical axis of the focused ion beam B2 are perpendicular to each other. Therefore, the processed (cross-sectional) surface is inclined by 90-θ ° with respect to the horizontal. When observing perpendicularly to the processed (cross-sectional) surface, the sample stage 17 is further tilted by 90-θ ° by the tilting function of the sample stage 17 and observed.

At this time, the processing area may be determined automatically or interactively by the computer system. Further, the etched portion below the line BB 'shown in FIG. 3b does not contribute to observation, and thus etching is unnecessary. Therefore, the processing frame is A
The unnecessary etching amount can be reduced by increasing the width from the small one on the A ′ side with the passage of time. As a result, the time required for processing can be shortened.

Further, the sample stage generally cannot tilt the sample so much that the effect of enlarging the cross section becomes remarkable. Therefore, the sample is set on the sample tilting mechanism 34 shown in FIG. Further, a sample tilting jig 34 having a rotating shaft 35 whose tilt can be arbitrarily changed is installed on the sample stage 17 so that the incident angle of the focused ion beam B2 with respect to the sample surface can be made extremely shallow. Further, instead of the sample stage 17, a sample holder having this sample tilting mechanism can be installed in the sample chamber so that ion beam processing can be performed.

[0018]

As described above, the present invention has an effect that it is possible to observe or analyze fine vertical and horizontal structures which have been difficult to observe and analyze in the past.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a schematic configuration of an integrated ion beam device according to the present invention.

FIG. 2 is an observed image of a sample placed horizontally.

FIG. 3 shows a processed state of the present invention, FIG. 3a is a plan view, and FIG. 3b is a sectional view.

FIG. 4 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

1 ion source 2 Extractor electrode 3 Ion source section 4 XY movement device 5 First aperture 5a through hole 6 condenser lens 7 aperture 7a through hole 8 Objective lens 9 Charged particle optical system 10 Through hole switching device 11XY movement device 12 Blanking electrode 13 Blanking aperture 14 Blanking means 15 Faraday Cup 16 Deflection electrode 17 Sample stage

Claims (4)

[Claims] 1. A step of obtaining an observation processing position of a sample placed so that a sample surface is perpendicular to an irradiation axis of the focused ion beam, a step of tilting the sample, and a step of scanning and irradiating the focused ion beam, The step of observing the sample surface image again, the step of designating a portion having a structure to be observed in the image, the step of instructing the approximate depth of the step to be observed, and the focused ion beam irradiation region (processing frame) The step of determining, the step of scanning and irradiating with a focused ion beam, the step of sequentially obtaining a desired position by increasing the depth while confirming the processing shape, and the processed cross section of the sample, A focused ion beam processing method comprising the steps of observing a processing cross section by inclining the ion beam so that it is vertical or at an angle close to it. 2. The portion having the structure to be observed is AA ′.
2. The focused ion beam processing method according to claim 1, wherein the processing frame is made wider from the smaller one on the AA ′ side over time. 3. An ion source for generating an ion beam, a charged particle optical system for focusing the ion beam, a deflection electrode for scanning and irradiating the focused ion beam on a desired position of a sample, and an XYZ moving mechanism. In a focused ion beam apparatus comprising: a sample stage provided, the sample stage is configured such that when a region necessary for observation of the sample surface is processed by scanning and irradiating the focused ion beam, the focused ion beam is incident. With respect to the angle, the sample is tilted at a first angle with respect to the horizontal, and when observing the processed cross section of the sample, the sample is further moved from the state where the tilt of the sample is returned to the second position. As the angle of 9
0-The focused ion beam processing apparatus, which is equipped with a tilting mechanism for tilting the first angle or at an angle close thereto. 4. A second sample tilting mechanism is installed on the sample stage, and the second sample tilting mechanism is capable of mounting a sample tilted at a predetermined angle with respect to the surface of the sample stage. The focused ion beam device according to claim 3, further comprising a portion.