JP2006244796A - Sample holder of electron microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample holder of an electron microscope doing away with pretreatment of a sample for having it electrically conducted, and enabling electricity conduction to the sample and image observation during measurement of electric resistance only by thrusting it down on a sample pedestal. <P>SOLUTION: The sample holder is provided with a sample pedestal 2 holding a sample 6 by electrically insulating it from the pedestal 2 with an electric insulator 15 arranged between the sample 6 and the pedestal 2, two electrode members 8a, 8b arranged between the pedestal 2 and the sample 6 and electrically insulated from the pedestal 2, and sample-thrusting members 5a, 5b that can be used as electrodes in contact with different positions on the surface of the sample to thrust the sample on the pedestal and electrically insulated from the pedestal. Current is passed to the sample through lead wires 9a, 9b and wires 7a, 7b are connected with a voltmeter 10 to measure voltage fall. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sample holder for holding a sample in an electron beam path in an electron microscope apparatus, and more particularly to a sample holder that enables image observation while energizing the sample or taking out an electrical signal from the sample.

  An electron microscope that performs observation or analysis by irradiating a sample with an electron beam has high spatial resolution, and is therefore widely used for evaluating materials in a very small region. Electron microscopes can not only perform image observation with high spatial resolution, but also obtain more knowledge about the sample by observing changes in the sample while heating, cooling, pulling, applying voltage, etc. .

For example, in a sample in the semiconductor field or the like, knowledge about a material property of a sample is obtained by measuring a resistance value of the sample by taking out an electric signal from the sample while the sample is energized or before and after. Techniques relating to sample holders for enabling such measurement and observation are disclosed in Japanese Utility Model Laid-Open No. 5-6966, Japanese Patent Laid-Open Nos. 10-185781 and 2003-263969.

Japanese Utility Model Publication No. 5-6966 Japanese Patent Laid-Open No. 10-185781 JP 2003-263969 A

  Japanese Utility Model Laid-Open No. 5-6966 discloses a sample holder for measuring electric resistance used in an electron microscope by a four-terminal method. In the sample holder, the sample is placed across the opposing sample stage. Lead wires for energizing the sample are connected in advance to the opposing sample stage. In addition, two terminals for measuring the voltage drop of the sample are brought into contact with the sample via two support bases. However, the two contacts necessary for measuring the voltage drop must be installed avoiding the sample pressing member. As a concretely possible method for this purpose, it is conceivable to solder the lead wire directly to the sample, or to take electrical conductivity with a wire having a spring property, but the sample in the electron microscope is usually about several mm in size. Therefore, in order to install a terminal for direct contact with the sample, it is a work requiring careful attention and skill. In particular, when soldering is performed, when the sample is replaced, the solder is removed and wiring is performed again to a new sample.

  In the sample holder disclosed in Japanese Utility Model Laid-Open No. 5-6966, it is essential that the sample pressing member is electrically insulated. Therefore, an insulator member is provided between the sample and the sample pressing member. The sample pressing member itself must be made of an insulator. Therefore, the thickness of the entire sample holder increases. Since the sample holder is mounted close to a distance of several mm from the magnetic pole piece of the objective lens, when it is desired to perform image observation by tilting the sample holder, the sample holder, the pole piece, and the There is a problem in that the interference is likely to occur and the tilt angle is limited.

  Japanese Patent Application Laid-Open No. 10-185781 discloses another sample holder for measuring electric resistance used in a four-terminal method in an electron microscope. When the sample holder is placed on the sample holder, the current-carrying terminal provided insulated from the sample stage and the electrode pad formed on the sample are brought into contact with each other, so wire bonding to the sample is necessary. However, it is possible to energize the sample and observe the image at the same time. However, in this method, it is necessary to form an electrode pad on the sample itself, and there is a problem that the sample pretreatment is troublesome because the electrode pad is produced every time the sample is changed.

  Japanese Patent Laid-Open No. 2003-263969 discloses a sample holder for measuring an electric signal used in an electron microscope such as an electron microscope. Since the sample holder shares a sample holding member for holding the sample against the sample holder and a terminal for applying a voltage to the sample, the sample holder can be easily replaced and the sample can be electrically connected. Good electrical connection can be achieved with the terminal from which the signal is extracted. In addition, the thickness of the sample holder can be reduced. However, there is a problem that the electrode for extracting an electric signal from the sample is only two terminals shared with the sample pressing member, and the electric resistance measurement by the four-terminal method cannot be performed.

  The present invention solves the above-described problems, eliminates the need for sample pretreatment for establishing electrical continuity with the sample, and provides a simple sample replacement method that simply holds the sample on the sample stage. An object of the present invention is to provide a charged particle beam sample holder that enables image observation during resistance measurement. Another object of the present invention is to provide a sample holder that can prevent the observation image from drifting due to electrification and can reduce the thickness of the tip of the sample holder 103.

In order to solve the above problems, the present invention provides:
A sample holder used for sample observation in an electron microscope apparatus,
A sample stage for holding the sample so as to close the through-hole part by having a through-hole part for an electron beam to pass through;
An electrical insulator disposed between the sample and the sample stage to electrically insulate the sample from the sample stage;
Two electrode members disposed at positions facing each other across the through hole portion between the electrical insulator and the sample and in contact with the sample surface at each position;
In order to hold the sample on the sample stage, two sample holding members that come into contact with different positions on the surface of the sample and can be used as electrodes that are electrically insulated from the sample stage are provided. It is characterized by that.

  Further, the present invention is characterized in that the two sample holding members are in contact with the sample surface at positions facing each other across the through hole portion on a line connecting the two electrodes.

  Moreover, the present invention is characterized in that an electrical insulator coating is applied to the side on which the sample is placed on the sample stage and used as the electrical insulator.

  In the invention, it is preferable that the electrical insulator is a fluororesin.

  In the present invention, the two electrode members are attached to the surface of the electrical insulator, and wiring for connecting the two electrode members to an external circuit is formed in the electrical insulator. It is characterized by.

  According to the present invention, a power source is connected between the two electrode members, and a voltage measuring means is connected between the sample pressing members.

  According to the present invention, a voltage measuring means is connected between the two electrode members, and a power source is connected between the sample pressing members.

According to the present invention, an electrical insulator disposed between the sample and the sample stage to electrically insulate the sample from the sample stage;
Two electrode members disposed at positions facing each other across the through hole portion between the electrical insulator and the sample and in contact with the sample surface at each position;
In order to hold the sample on the sample stage, two sample holding members that come into contact with different positions on the surface of the sample and can be used as electrodes that are electrically insulated from the sample stage are provided. By
There is no need to perform pre-treatment such as wiring the sample, and it is now possible to mount a sample for simple electrical resistance measurement on the sample holder simply by holding the sample on the sample stage. In addition, by using two electrodes as terminals for current introduction into the sample and the other two locations as terminals for voltage drop measurement, an electron microscope or the like can be used while measuring the electrical resistance of the sample by the four-terminal method or before and after that. It became possible to observe the microscopic image. In addition, since the thickness of the tip of the sample holder is reduced, it is possible to increase the inclination angle of the sample. In addition, since an electrical insulator is disposed on the side opposite to the side where the charged particle beam is irradiated onto the sample, it is possible to prevent a beam generated due to charging and to observe a stable high magnification image.

  FIG. 1 shows a cross-sectional view of a lens barrel of an electron microscope. The actual apparatus includes many electron lenses, deflectors, and the like (not shown), which are omitted because they are not directly related to the description of the present invention. The inside of the lens barrel 100 is held in a vacuum, and an electron beam EB is emitted from the electron gun 101. An objective lens pole piece 102 is disposed in the lens barrel 100. The sample holder 103 with the sample 6 mounted on the tip is loaded on the sample stage 104. The tip of the sample holder 103 on which the sample is mounted is inserted into the gap between the objective lens pole pieces 102 and held in the electron beam path. The sample stage includes a sample moving mechanism and an inclination mechanism, and the irradiation position of the electron beam EB on the sample can be changed while the sample is irradiated with the electron beam.

  FIG. 2 is a perspective view of the tip of the sample holder 103 of the present invention as viewed from the electron beam irradiation side. At the tip of the sample holder 103, the sample frame 17 is supported by the sample frame support member 21, and a sample frame opening 17a is formed inside the sample frame 17. The sample table 2 and the lever body 18 are supported by the sample table frame opening 17a via the tilt shaft 19 and the lever body shaft 22, respectively. The sample stage 2 and the lever body 18 are connected so as to be movable and rotatable at the connecting portion 24. The lever body abutting portion 18a is in contact with a lever body pushing member 23 arranged inside the sample frame support member 21. The sample table tension spring 20 pulls the sample table 2 so that the lever body contact portion 18a always contacts the lever body pushing member 23.

  In FIG. 2, when the lever body pushing member 23 pushes the lever body abutting portion 18a in the direction of the tip end of the sample frame 17, the lever 2 acts on the sample body 2 as a fulcrum. The end on the side rotates in the irradiation direction of the electron beam EB. Since the lever body 18 and the sample stage 2 are connected by the connecting portion 24, the sample stage 2 can be tilted with the tilt axis 19 as the tilt center. Further, the sample stage support member 21 can be rotated in the arrow R direction by the tilt mechanism of the sample stage 104 shown in FIG. As will be described later, since the sample is held against the back side of the sample stage 2, the sample can be tilted biaxially.

Next, the first embodiment will be described with reference to FIGS.
FIG. 3 is a plan view of the tip portion of the sample holder 103 according to the first embodiment, and is a back view as seen from the direction C in FIG. FIG. 4 is a cross-sectional view of the distal end portion of the sample holder 103 in the cross section AA of FIG. As described above, the tip of the sample holder 103 has a very thin structure in order to make the inclination angle as large as possible in the narrow gap of the objective lens pole piece, and it is easier to understand the structure than the actual dimensions. It is drawn several times in the vertical direction. In addition, the ratio of the thickness of the sample 6, the electrode members 8a and 8b, and the insulating coating 15 to the thickness of the sample stage 6 is different from the actual one, and the positional relationship in the vertical direction is shown so that it can be easily seen.

In FIG. 4, leaf springs 5a and 5b which are holding members for fixing a sample are connected to a voltmeter 10 via screws 4a and 4b, nuts 1a and 1b, and electric wires 7a and 7b. Since the nuts 1a and 1b also serve as electrodes, they should not be electrically connected to the sample stage 2. Therefore, it is insulated by the insulators 3c and 3d. The nuts 1a and 1b may be bonded to the sample table 2 together with the insulators 3c and 3d.
Since the screws 4a and 4b also serve as electrodes, they are insulated from the sample stage by the insulators 3a, 3c, 3b and 3d.

  On the sample table 2, for example, an insulating coating 15 (shown by hatching in FIG. 3) such as a fluororesin is applied. On the insulating coating 15, electrode members 8a and 8b are bonded and fixed. The sample 6 is attached across the electrode members 8a and 8b, and is held by the leaf springs 5a and 5b. When exchanging the sample, the sample 6 can be easily removed by loosening the screws 4a and 4b, and the connection between the terminals is disconnected. When the sample 6 is replaced and the screws 4a and 4b are tightened, the connection of each terminal is restored again. The insulating coating 15 and the sample 6 are electrically insulated from the sample table 2 by the insulating coating 15. Lead wires 9a and 9b are fixed to the electrode members 8a and 8b in advance by soldering or the like, and their opposite terminals are connected to the constant current power source 11.

  As described above, the resistance of the sample 6 can be measured by passing a current through the sample 6 through the electrode members 8a and 8b and measuring the voltage drop with the voltmeter 10 using the leaf springs 5a and 5b as detection terminals. Further, since the sample stage 2 and the insulator coating 15 are provided with through holes 16 through which the electron beam EB passes, the electron microscope image is observed while measuring the resistance of the sample 6 or before and after the measurement. Is possible.

  In the above description, the electrode members 8a and 8b are connected to the constant current power source 11 and the leaf springs 5a and 5b are connected to the voltmeter 10. However, how the electrodes 8a and 8b are connected to each other depends on the electrode member 8a. , 8b and the leaf springs 5a, 5b are determined as follows according to the positional relationship with each other in contact with the sample 6. In the example of FIG. 4, the positions where the electrode members 8 a, 8 b are in contact with the sample 6 are outside the position where the leaf springs 5 a, 5 b are in contact with the sample 6, so the wires 7 a, 7 b are connected to the voltmeter 10. The lead wires 9a and 9b are connected to a constant current power source 11. When the position where the leaf springs 5a, 5b and the sample 6 are in contact is outside the position where the electrode members 8a, 8b and the sample 6 are in contact, the electric wires 7a, 7b are connected to the constant current power source 11, A voltmeter 10 is connected to the lead wires 9a and 9b.

  In the first embodiment described above, for example, even when the thickness of the insulator coating 15 is about 0.1 mm, the thickness accuracy can be controlled on the order of μm, so that the insulation with a thickness suitable for the voltage applied to the sample 6 Things can be coated. Therefore, the purpose of thinning the tip of the sample holder 103 can be achieved. Further, since the insulator coating 15 is applied to the side that cannot be seen from the direction in which the electron beam is irradiated, the irradiated electron beam does not directly hit the insulator, and beam drift caused by charging can be prevented.

Next, the second embodiment will be described with reference to FIGS.
FIG. 5 is a plan view of the distal end portion of the sample holder 103 according to the second embodiment, and is a back view as seen from the direction C in FIG. 6 is a cross-sectional view of the tip end portion of the sample holder 103 in the cross section BB of FIG. As described above, the tip of the sample holder 103 has a very thin structure in order to make the tilt angle as large as possible in the gap between the narrow objective lens pole pieces. It is drawn several times in the direction. Also, the ratio of the thickness of the sample 6 and the flexible substrate 12 to the thickness of the sample stage 6 is different from the actual one, and is shown so that the vertical positional relationship can be easily seen.

In FIG. 6, leaf springs 5a and 5b which are holding members for fixing the sample are connected to the voltmeter 10 via screws 4a and 4b, nuts 1a and 1b, and electric wires 7a and 7b. Since the nuts 1a and 1b also serve as electrodes, they should not be electrically connected to the sample stage 2. Therefore, it is insulated by the insulators 3c and 3d. The nuts 1a and 1b may be bonded to the sample table 2 together with the insulators 3c and 3d.
Since the screws 4a and 4b also serve as electrodes, they are insulated from the sample stage by the insulators 3a, 3c, 3b and 3d.

  A flexible substrate 12 is bonded and fixed on the sample stage 2. FIG. 8 is a single product diagram of the flexible substrate 12. In FIG. 8, the flexible substrate 12 is provided with sample-side terminals 13a and 13b and wiring-side terminals 14a and 14b, and 13a and 14a, and 13b and 14b are pattern wirings provided inside the flexible substrate 12, respectively. It is connected. Except for the sample-side terminals 13a and 13b and the wiring-side terminals 14a and 14b, the contact surface between the flexible substrate 12 and the sample table 2 and the contact surface between the flexible substrate 12 and the sample 6 are electrically insulating materials such as polyimide. It is made with.

  Since the sample side terminals 13a and 13b are formed so as to be slightly convex from the surface of the insulator of the flexible substrate 12, when the sample 6 is mounted on the flexible substrate 12, the sample side terminals 13a and 13b and the sample 6 are Contact. The plate springs 5a and 5b serve both as sample fixing and electrodes by holding the opposite side of the surface of the sample 6 in contact with the flexible substrate 12 with the plate springs 5a and 5b. When exchanging the sample, the sample 6 can be easily removed by loosening the screws 4a and 4b, and the connection between the terminals is disconnected. When the sample 6 is replaced and the screws 4a and 4b are tightened, the connection of each terminal is restored again.

  Since the insulating part of the flexible substrate 12 is located on the surface of the sample table 2 on the sample mounting side, the sample table 2 and the sample 6 are electrically insulated. On the other hand, lead wires 9a and 9b are fixed in advance to the wiring side terminals 14a and 14b of the flexible substrate 12 by soldering or the like, and their opposite terminals are connected to the constant current power source 11.

  As described above, by passing a current through the sample 6 through the wiring side terminals 14a and 14b and the sample side terminals 13a and 13b of the flexible substrate 12, and measuring the voltage drop with the voltmeter 10 using the leaf springs 5a and 5b as detection terminals. The resistance of the sample can be measured. In addition, since the sample stage 2 and the flexible substrate 12 are provided with through holes 16 through which the electron beam EB passes, it is possible to observe an electron microscope image while measuring the resistance of the sample or before and after that. It is.

  In the above description, the sample-side terminals 13a and 13b of the flexible substrate 12 are described as being connected to the constant current power source 11 and the leaf springs 5a and 5b are connected to the voltmeter 10; Is determined as follows according to the positional relationship between the sample-side terminals 13a and 13b and the leaf springs 5a and 5b in contact with the sample 6. In the example of FIG. 6, the positions where the sample side terminals 13a, 13b are in contact with the sample 6 are outside the position where the leaf springs 5a, 5b and the sample 6 are in contact, so the wires 7a, 7b are connected to the voltmeter 10. The lead wires 9a and 9b are connected to a constant current power source 11. When the position where the leaf springs 5a, 5b and the sample 6 are in contact is outside the position where the sample side terminals 13a, 13b and the sample 6 are in contact, the electric wires 7a, 7b are connected to the constant current power source 11. The voltmeter 10 is connected to the lead wires 9a and 9b.

  In Embodiment 2 described above, it is sufficient that the thickness of the flexible substrate 12 is, for example, about 0.1 mm, so that the object of thinning the tip portion of the sample holder 103 can be achieved. In addition, since the flexible substrate 12 is disposed on the side that cannot be seen from the direction in which the electron beam is irradiated, the irradiated electron beam does not directly hit the insulator, and beam drift caused by charging can be prevented.

It is a figure which shows the lens-barrel cross section of an electron microscope. It is the perspective view which looked at the sample holder tip part from the electron beam irradiation side. It is a back view of the sample holder front-end | tip part seen from the arrow C in FIG. 2 for demonstrating Embodiment 1 of this invention. It is sectional drawing of the sample holder front-end | tip part in the cross section AA of FIG. It is a back view of the sample holder front-end | tip part seen from the arrow C in FIG. 2 for demonstrating Embodiment 2 of this invention. It is sectional drawing of the sample holder front-end | tip part in the cross section BB of FIG. It is a figure which shows the flexible substrate of FIG. 5 by a single item.

Explanation of symbols

(Those that perform the same or similar operations are denoted by a common reference.)
EB Electron beam 1a, 1b Nut 2 Sample stage 3a, 3b, 3c, 3d Insulator 4a, 4b Screw 5a, 5b Leaf spring 6 Sample 7a, 7b Electric wire 8a, 8b Electrode member 9a, 9b Lead wire 10 Voltmeter 11 Constant current power supply DESCRIPTION OF SYMBOLS 12 Flexible substrate 13a, 13b Sample side terminal 14a, 14b Wiring side terminal 15 Insulation coating 16 Through-hole part 100 Lens tube 101 Electron gun 102 Objective lens magnetic pole piece 103 Sample holder 104 Sample stage

Claims (7)

A sample holder used for sample observation in an electron microscope apparatus,
A sample stage for holding the sample so as to close the through-hole part with a through-hole part for the electron beam to pass through;
An electrical insulator disposed between the sample and the sample stage to electrically insulate the sample from the sample stage;
Two electrode members disposed at positions facing each other across the through hole portion between the electrical insulator and the sample and in contact with the sample surface at each position;
In order to hold the sample on the sample stage, two sample holding members that come into contact with different positions on the surface of the sample and can be used as electrodes that are electrically insulated from the sample stage are provided. A sample holder for an electron microscope characterized by the above. 2. The sample holder for an electron microscope according to claim 1, wherein the two sample holding members are in contact with the sample surface at positions facing each other across the through hole portion on a line connecting the two electrodes. . 3. The sample holder for an electron microscope according to claim 1, wherein an electrical insulator coating is applied to a side on which the sample is placed on the sample stage and used as the electrical insulator. 4. The sample holder for an electron microscope according to claim 3, wherein the electrical insulator is a fluororesin. The two electrode members are attached to the surface of the electrical insulator, and wiring for connecting the two electrode members to an external circuit is formed in the electrical insulator. The sample holder for an electron microscope according to claim 1 or 2. 6. The electron microscope sample holder according to claim 1, wherein a power source is connected between the two electrode members, and a voltage measuring means is connected between the sample pressing members. 6. The sample holder for an electron microscope according to claim 1, wherein a voltage measuring means is connected between the two electrode members, and a power source is connected between the sample pressing members.

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