JP2016173314A - Device and method for measuring electric characteristics of minute object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for measuring electric characteristics of a minute object that can precisely measure the electric characteristics of a low-resistance minute object.SOLUTION: A measuring device 100 for measuring the electric resistance of a minute object includes: a pair of conductive arms 10a and 10b capable of holding a minute object therebetween; a pair of electrodes 25a and 25b connected to the pair of arms 10a and 10b sandwiching the minute object, via the minute object; a power source circuit with a power source connected between the pair of arms 10a and 10b; and a voltmeter connected between the pair of electrodes 25a and 25b. With that configurations, the electric characteristics of a low-resistance minute object can be precisely measured.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a minute object electrical property measuring apparatus and a minute object electrical property measuring method, and more particularly to a minute object electrical property measuring apparatus and a minute object electrical property measuring method for measuring the electrical property of a minute object.

  In recent years, techniques for measuring electrical characteristics (for example, electrical resistance, dielectric constant, etc.) of minute objects have been actively developed.

  For example, Patent Documents 1 to 4 disclose techniques for measuring the electrical resistance (electric characteristics) of a minute object by pressing a minute electrode against both ends of the minute object (particle) to form a series circuit.

  However, the techniques disclosed in Patent Documents 1 to 4 cannot accurately measure the electrical characteristics of a low-resistance minute object.

  The present invention includes a pair of conductive arms capable of sandwiching a minute object, two electrodes connected to the pair of arms sandwiching the minute object via the minute object, the pair of arms, A micro object comprising: a power source connected between any two of the two electrodes; and a voltmeter connected between two of the pair of arms and the two electrodes not connected to the power source. It is an electrical property measuring device.

  According to the present invention, it is possible to accurately measure electrical characteristics of a low-resistance minute object.

It is FIG. (1) which shows schematic structure of the micro electrical resistance measuring apparatus of one Embodiment. It is FIG. (2) which shows schematic structure of the micro electrical resistance measuring apparatus of one Embodiment. It is a figure for demonstrating the micro / nano gripper which is an example of a clamping member. FIG. 4A is a diagram illustrating a state in which a minute object is collected using a sandwiching member, and FIG. 4B is a diagram illustrating a state in which the minute object sandwiched by the sandwiching member and the cantilever are opposed to each other. It is. It is a figure for demonstrating the specific example 1 of a power supply circuit. It is a figure for demonstrating the specific example 2 of a power supply circuit. FIG. 7A and FIG. 7B are diagrams (No. 1 and No. 2) for explaining the minute object electric resistance measuring device of Modification 1. FIG. FIGS. 8A and 8B are diagrams (No. 1 and No. 2) for explaining the minute object electric resistance measuring apparatus according to the second modification. FIGS. 9A and 9B are views (No. 1 and No. 2) for explaining a case where a pair of electrodes is made of an electrode material formed in a thin film on a cantilever. FIGS. 10A and 10B are views (No. 1 and No. 2) for explaining inconveniences when the distance between a pair of electrodes is too large with respect to the size of a minute object. FIG. 11A and FIG. 11B are diagrams (No. 1 and No. 2) for explaining a countermeasure when the distance between a pair of electrodes is too wide with respect to the size of a minute object. FIG. 12A and FIG. 12B are diagrams (No. 1 and No. 2) for explaining the minute object electric resistance measuring device of Modification 3. FIG. FIG. 13A to FIG. 13C are diagrams for explaining appropriate electrode intervals with respect to the diameter of a minute object. It is a figure for demonstrating the case where a laser displacement meter is used as a measuring apparatus which measures the displacement of a cantilever. It is a figure for demonstrating the case where the apparatus of an optical lever system is used as a measuring apparatus which measures the displacement of a cantilever. It is a figure for demonstrating the micro electrical resistance measuring apparatus of the modification 4. It is a figure for demonstrating the micro electrical resistance measuring apparatus of the modification 5. FIG. It is a figure for demonstrating the micro electrical resistance measuring apparatus of the modification 6. FIG. It is a figure for demonstrating the 4 terminal method. It is a figure for demonstrating a comparative example.

<< First Embodiment >>
Below, 1st Embodiment is described based on FIGS. 1 and 2 show a schematic configuration of a minute object electrical resistance measuring apparatus 100 as the minute object electrical property measuring apparatus according to the first embodiment. In the following description, an XYZ three-dimensional orthogonal coordinate system with the Z-axis direction shown in FIG.

  As shown in FIG. 1 and FIG. 2, the minute object electric resistance measuring apparatus 100 includes, for example, a holding member 10 including a pair of arms 10a and 10b having conductivity capable of holding a minute object to be measured, and a cantilever. 20 (cantilever), a pair of electrodes 25a and 25b provided on the cantilever 20, a power supply circuit (power supply unit) including a power source connected between the pair of arms 10a and 10b, and a pair of electrodes 25a , 25b, a laser displacement meter 30 for measuring the displacement (deformation amount) of the cantilever 20, a fine movement stage 50 provided with the cantilever 20, and a processing device 60. In FIG. 1, the pair of electrodes 25a and 25b are not shown. In FIG. 2, the laser displacement meter 30, the fine movement stage 50, and the processing device 60 are not shown.

  The size of the minute object to be measured is such that the maximum diameter that can be clamped by the clamping member 10 is in the range of 10 nm to 1 mm, and the more preferable size is in the range of 1 μm to 100 μm. . Specific examples of minute objects include toners used in copiers, pharmaceuticals, foodstuffs, powders used as constituent materials for electronic devices, minute foreign substances adhering to electronic substrates, and biological materials such as cells. It is done.

  Examples of the powder include toner particles, 3D printer constituent materials (about several um to several tens of um), toner charging iron powder (about 30 um to 100 um), liquid crystal spacers (about several um) and the like. It is done.

  As an example of the sandwiching member 10, as shown in FIG. 3, a so-called micro / nano gripper or micro / nano tweezers that sandwiches and holds minute objects from both ends is used.

  Here, in this embodiment, since the pair of arms 10a and 10b of the clamping member 10 is also used as an independent pair of electrodes, each arm satisfies the following two conditions.

  The first condition is that conduction is ensured in each arm from at least the contact surface with the minute object to the connection point with the power supply circuit. Specific numerical values relating to conduction may be such that a current of several uA to several mA flows in a circuit including a pair of arms, a minute object, and a power supply circuit. If the arm to be used does not have continuity as a standard, for example, use a method of depositing the surface of the arm with gold, copper, tungsten, etc., or using a deposition thin film formation technology with a focused ion beam, etc. There is a method of creating a microelectrode.

  The second condition is that a pair of arms 10a and 10b that also function as a pair of electrodes are insulated from each other. If it is not insulated, the circuit will short-circuit and current will not flow through the minute objects. As a specific numerical value for insulation, it is desirable that it is 10 times or more the resistance value of the minute object to be measured.

  As an example, the clamping member 10 includes an XYZ three-dimensional movement mechanism (hereinafter referred to as “three-dimensional”) that can move the clamping member 10 independently in the X-axis direction, the Y-axis direction, and the Z-axis direction. (Also referred to as “movement mechanism”), a sampling position (see FIG. 4A) in which a minute object can be collected in a sampling area (for example, a sample table on which the minute object is dispersed or a member to which the minute object is attached). )) And a measurement position (see FIG. 4B), which is a position where the held minute object faces the cantilever 20 (here, the + Z side position of the cantilever 20). The operation of the holding member 10 when holding (collecting) a minute object by the holding member 10 is manually performed via the operation unit. Instead of the XYZ three-dimensional movement mechanism, for example, a tilt rotation mechanism that can rotate the holding member 10 and an XY two-dimensional movement mechanism that moves the holding member 10 along the XY plane may be combined. The operations of the XYZ three-dimensional movement mechanism, the tilt rotation mechanism, and the XY two-dimensional movement mechanism may be automatic or manual via an operation unit.

  As shown in FIG. 1 and FIG. 2, the cantilever 20 is formed of a thin rectangular plate-like member, for example. The fixed end portion is fixed to the upper surface of the fine movement stage 50, and the free end portion (major portion). Protrudes from the fine movement stage 50 to the + X side and faces a minute object held by the clamping member 10 located at the measurement position.

  As the cantilever 20, for example, a cantilever for an atomic force microscope (AFM) having a very high smoothness can be used, but a cantilever having an appropriate spring constant and material is selected according to measurement contents. There is a need. Normally, a cantilever for an atomic force microscope is provided with a tip for scanning a sample at the free end, but here it is not always necessary to provide a tip. That is, when a tipless cantilever is used or when a cantilever provided with a tip is used, it is necessary to fix the cantilever so that the tip faces the laser displacement meter 30 side instead of the minute object side. The cantilever 20 preferably has high smoothness, and may be other than for AFM.

  The pair of electrodes 25a and 25b (shaded portions in FIG. 2) are provided side by side in the Y-axis direction on the upper surface of the cantilever 20 to ensure conductivity. Therefore, in order to prevent leakage between the pair of electrodes 25a and 25b, the portions other than the shaded portions in FIG. Each electrode may be called a “terminal”.

  Here, the interval between the pair of electrodes 25a and 25b is set to be narrower than the particle size of the minute object to be measured. The pair of electrodes 25 a and 25 b is made of an electrode material (conductive material) formed as a thin film on the surface of the cantilever 20. Note that the case where the pair of electrodes is made of an electrode material formed into a thin film will be described in detail in Modification 3 described later.

  As shown in FIG. 4, as the power supply circuit, for example, a configuration using a constant voltage power supply and an ammeter, or a voltage drop between both ends of the constant voltage power supply, the reference resistance, and the reference resistance as shown in FIG. It is possible to take a configuration using a voltmeter. In short, the power supply circuit as the power supply unit may be configured to include at least the power supply.

  Laser displacement meter 30 is fixed to the + X side surface of fine movement stage 50 so as to face cantilever 20 (here, on the −Z side of cantilever 20). Thus, since the laser displacement meter 30 is provided integrally with the cantilever 20 via the fine movement stage 50, the displacement due to deformation (warping) of the cantilever 20 can be accurately measured.

  The laser displacement meter 30 is not necessarily limited to a specific product (spec), but its spot size is approximately the same as the width of the cantilever 20 or larger than the width of the cantilever 20 so that the deformation of the cantilever 20 can be monitored. Small is desirable. Further, it is desirable that the measurement resolution is high so that minute deformation of the cantilever 20 can be detected. Specifically, a resolution of about 1 nm is required.

  The fine movement stage 50 is a moving table that can be moved minutely in the Z-axis direction. The fine movement stage 50 requires a position resolution on the order of nm, and specifically, a piezo stage (a stage using a piezo element as an actuator) is preferably used. Instead of the piezo stage, for example, a stage using a high-precision stepping motor or the like as an actuator may be used.

  The processing device 60 controls the fine movement stage 50, monitors the measurement value of the laser displacement meter 30, brings the minute object sandwiched between the clamping members 10 and the cantilever 20 into contact with each other at a desired contact pressure, and then minutely Find the electrical resistance of an object.

  As a specific flow up to the start of measurement, a three-dimensional movement mechanism is operated as necessary to position the holding member 10 at a sampling position on the sampling area, and the holding member 10 is manually operated to move a minute object from the sampling area. (See FIG. 4A), the three-dimensional movement mechanism is operated to move the holding member 10 holding the minute object to a measurement position where the minute object is opposed to the cantilever 20 (see FIG. 4B). ).

  Instead of the movement of the holding member by the three-dimensional movement mechanism, for example, the sampling area and fine movement stage 50 have a two-dimensional movement function in the XY plane, and the holding member 10 has a one-dimensional movement function in the Z-axis direction or A tilt rotation function may be provided.

  In addition, an observation system (microscope function) is required for pinching fine objects scattered / adhered to the sampling area by the holding member 10 and for positioning when the fine objects are brought close to and in contact with the cantilever 20. However, the specific means is not limited as long as a minute object of several um size can be recognized, and for example, any of an optical microscope, an electron microscope, and an atomic force microscope may be used.

  As a measurement flow, the holding member 10 that holds the minute object positioned at the measurement position is moved in the −Z direction by the three-dimensional movement mechanism to bring the minute object and the cantilever 20 close to each other, and then the processing device 60 finely moves. The stage 50 is slightly moved in the + Z direction to bring the minute object held by the pair of arms 10a and 10b into contact with the pair of electrodes 25a and 25b on the cantilever 20. As a result, the pair of arms 10a and 10b and the pair of electrodes 25a and 25b are connected via minute objects. The processing device 60 determines whether or not the minute object and the cantilever 20 are in contact with each other based on the measurement value of the laser displacement meter 30 (the amount of deformation of the cantilever 20 and the pair of electrodes 25a and 25b at the time of contact). The amount of deformation of the cantilever 20 when the minute object is brought into contact with the cantilever 20 depends on the spring constant of the cantilever 20, but is preferably set to about 1 μm or less. When receiving a processing start request via the operation unit, the processing device 60 starts controlling the fine movement stage 50 and monitoring the measured value from the laser displacement meter 30 described above.

  Since the pair of electrodes 25a and 25b are provided on the cantilever 20, the contact state (contact pressure) between the minute object and the pair of electrodes 25a and 25b can be managed with high accuracy. There are two reasons why the contact state can be managed with high accuracy. The first is that the pressure applied to the minute object can be managed by measuring the deformation amount of the cantilever 20 by the laser displacement meter 30. For example, if a cantilever with a spring constant of 0.01 N / m and a laser displacement meter 30 with a resolution of 10 nm are used, the pressure applied to a minute object can be managed in units of 0.1 nN. Second, the surface of the cantilever 20 has high smoothness. Thereby, the change of the contact area with the micro object by the surface unevenness | corrugation for every measurement can be suppressed to the minimum.

  Next, the processing device 60 has a power source connected to the pair of arms 10a and 10b in a state where the minute object sandwiched between the pair of arms 10a and 10b and the pair of electrodes 25a and 25b are brought into contact with each other with a desired contact pressure. The circuit is turned on, a current is passed through a minute object sandwiched between the pair of arms 10a and 10b, and a measured value (voltage value) of a voltmeter connected to the pair of electrodes 25a and 25b is read. Then, the processing device 60 uses the Ohm's law (resistance = voltage / current) from the read voltage value and the current value flowing through the circuit including the power supply circuit, the pair of arms 10a and 10b, and the minute object. The resistance value (electrical resistance) is obtained.

  Here, the upper limit of the voltage applied to the minute object by the power supply circuit is preferably about 100 V in order to avoid discharge between the pair of arms 10a and 10b as a pair of electrodes. It is desirable to start reading the measured value of the voltmeter after leaving it for about one minute immediately after applying the voltage in order to avoid the influence of the input inrush current. To obtain accurate measurement results, change the value of the current flowing through the circuit in a single measurement, read the change in voltage, and obtain the resistance value by linear regression with Ohm's law. It is desirable.

  The minute object electrical resistance measuring apparatus 100 of the present embodiment described above includes a pair of arms 10a and 10b having conductivity capable of holding the minute object and a pair of arms 10a and 10b holding the minute object. A pair of electrodes 25a and 25b connected via a pair, a power circuit including a power source connected between the pair of arms 10a and 10b, and a voltmeter connected between the pair of electrodes 25a and 25b. ing.

In this case, a circuit for supplying a current to the minute object including a pair of arms 10a and 10b for holding the minute object and a power source is configured, and includes a pair of electrodes 25a and 25b in contact with the minute object and a voltmeter. Since a circuit for measuring the voltage drop of the minute object is configured, the electrical resistance of the minute object having a low resistance (several tens of kΩ or less) as the contact resistance between the pair of electrodes 25a and 25b and the minute object is measured. Can be made sufficiently small.
As a result, it is possible to accurately measure the electrical characteristics of a low resistance (several tens of kΩ or less) minute object.

  Moreover, since the minute object electrical resistance measuring apparatus 100 further includes the cantilever 20 having the pair of electrodes 25a and 25b provided on the surface, the amount of bending of the cantilever 20 (the amount of bending of the pair of electrodes 25a and 25b) is measured. Thus, the contact pressure between the pair of electrodes 25a and 25b and the minute object can be managed.

  Moreover, since the micro electrical resistance measuring apparatus 100 further includes a laser displacement meter 30 that measures the displacement of the cantilever 20, the deformation amount (deflection amount) of the cantilever 20 can be accurately measured.

  The cantilever 20 is a cantilever for an atomic force microscope. In this case, the lever surface of the atomic force microscope cantilever has high smoothness. Therefore, when optically measuring the amount of deformation of the cantilever, the light hitting the cantilever is not scattered and remains straight. Since it is detected, the amount of deformation can be accurately measured. In addition, since the lever surface of the atomic force microscope cantilever has high smoothness, it is possible to suppress a change in contact area due to surface irregularities for each measurement.

  Further, since the distance between the pair of electrodes 25a and 25b is narrower than the particle size of the minute object, the minute object can be brought into contact with both the pair of electrodes 25a and 25b.

  In addition, since the pair of electrodes 25a and 25b is made of an electrode material formed in a thin film on the surface of the cantilever 20, high insulation performance can be obtained between the electrodes, generation of leakage current can be suppressed, and voltage drop can be accurately measured.

In addition, the method of measuring electrical resistance of micro objects according to the present embodiment includes a step of sandwiching micro objects between a pair of conductive arms 10a and 10b, a micro object sandwiched between a pair of arms 10a and 10b, and a pair of A step of bringing the electrodes 25a and 25b into contact, a step of applying a voltage between the pair of arms 10a and 10b, and a step of measuring the voltage between the pair of electrodes 25a and 25b.
In this case, it is possible to accurately measure the electrical characteristics of a minute object having a low resistance (several tens of kΩ or less).

  Further, the minute object electrical resistance measurement method (minute object electrical property measurement method) of the present embodiment measures the deformation amount of the pair of electrodes 25a and 25b, and the minute object and the pair of electrodes 25a and 25b based on the measurement result. Since the method further includes a step of managing the contact state, the electrical characteristics of the minute object can be measured with higher accuracy.

  Further, since it is possible to perform measurement while holding only one particle of the minute object with the sandwiching member 10, the inherent electrical resistance of the one particle can be stably measured with high accuracy.

  On the other hand, when the electrical property of the micro object group is measured by holding a micro object group including a plurality of micro objects with a pair of electrodes, the micro object group and each electrode are The contact state changes, and stable and highly accurate measurement cannot be performed. That is, in this case, the measurement accuracy is affected by the filling rate of fine objects, the molding state, and the like.

  Hereinafter, some modified examples of the above embodiment will be described.

  In the minute object electrical resistance measuring apparatus 200 of Modification 1 shown in FIGS. 7A and 7B, the cantilever 21 has a bifurcated comb shape, and an electrode is provided on each crotch part.

  In the cantilever 21, the region irradiated with the laser beam for measuring the deflection can be sufficiently secured in the trunk portion that continues to the pair of crotch portions. Thereby, the pressure applied to the minute object from the cantilever 21 can be managed.

  A method for manufacturing a comb-shaped cantilever 21 provided with a pair of electrodes (hereinafter also referred to as a comb-shaped cantilever with electrodes) will be briefly described. First, a deposition thin film forming technique using a focused ion beam or the like is applied to a majority region from one end to the other end in the longitudinal direction of one rectangular cantilever whose surface is insulated. Then, a processing technique such as a focused ion beam is applied to the majority region where the thin film is formed to process it into a comb shape (form a notch). In this manner, a comb-shaped cantilever with an electrode is manufactured from one rectangular cantilever. A high insulation performance is obtained between the pair of electrodes formed on the cantilever 21 by such a procedure, generation of a leakage current is suppressed, and a voltage drop can be measured with high accuracy.

  As a shape that can obtain the same effect as the comb shape in the shape of the cantilever, a shape in which a part of a rectangular cantilever is cut out like the cantilever 22 of the minute electrical resistance measuring device 300 of the second modification shown in FIG. (A shape having an opening between portions where a pair of electrodes are provided). In this case, the bending of the cantilever 22 can be measured by irradiating the tip of the cantilever 22 with a laser beam. The cantilever 22 provided with a pair of electrodes can also be produced in the same procedure as the above-mentioned comb-shaped cantilever with electrodes.

  In the minute electrical resistance measuring device shown in FIGS. 9A and 9B, the pair of electrodes provided on the cantilever is made of an electrode material (conductive material) in which a thin film is formed. The pair of electrodes can be produced using a deposition thin film forming technique using a focused ion beam or the like. The surface of the cantilever on which the thin film is formed needs to be insulated in order to avoid a short circuit between the electrodes. Therefore, it is desirable to use a cantilever whose surface is made of silicon oxide or a cantilever whose surface is coated with resin.

  The film thickness of the electrode is set so that the minute object does not contact the region between the electrodes in the cantilever during measurement. When the minute object comes into contact with the cantilever, as shown in FIGS. 10A and 10B, the minute object does not contact the pair of electrodes, and electrical resistance measurement cannot be performed. In order to avoid such a situation, there are a method of increasing the film thickness of an electrode to be formed and a method of processing a region between portions where a pair of electrodes in a cantilever is provided. For example, by forming a recess or a notch in a region between a pair of electrodes in a cantilever, a minute object can contact the pair of electrodes without touching the cantilever (FIGS. 11A and 11B). )reference).

  As shown in FIGS. 12A and 12B, in the minute object electric resistance measuring apparatus 400 of the third modification, two rectangular cantilevers are used as a pair of electrodes. That is, a thin electrode material is formed on each rectangular cantilever, and the rectangular cantilever can be regarded as an electrode substantially. Although it is difficult in terms of apparatus space to arrange two rectangular cantilevers so that the large surfaces on which the electrode material is formed face each other, the end faces of the two rectangular cantilevers face each other as in Modification 3. Such arrangement is sufficiently possible in terms of apparatus space. The displacement measurement of the cantilever may be a measurement of only one cantilever or a configuration in which measurement of two cantilevers is performed.

  With such a configuration, it is not necessary to process the cantilever, and an increase in cost can be suppressed. The cantilever to be used needs to ensure continuity at least from the position where the surface is in contact with the minute object to the position where it is connected to the device for measuring the voltage drop. Therefore, for example, a cantilever whose surface is coated with gold or platinum can be used.

  Thus, by using two cantilevers as a pair of electrodes, high insulation performance can be obtained between the electrodes, generation of leakage current can be suppressed, and voltage drop can be accurately measured.

  As described in the first embodiment, the distance between the electrodes provided on the cantilever needs to be narrower than the diameter of the minute object to be measured. In this case, the minute object can contact the electrode without contacting the cantilever (see FIG. 13C). If the distance between the electrodes is larger than the diameter of the minute object, the minute object may contact the cantilever and cannot contact the pair of electrodes (see FIGS. 13A and 13B). Therefore, when forming a cantilever with electrodes, it is desirable to determine the interelectrode distance from the particle size distribution of the minute object to be measured.

  Here, the case where a laser displacement meter is used as a measuring device for measuring the displacement of the cantilever will be described with reference to FIG. By measuring the displacement of the cantilever, the pressure applied to the minute object from the cantilever during electrical resistance measurement can be managed, and stable and reproducible measurement is realized. In particular, when the minute object to be measured undergoes a large deformation at a low pressure, the contact area with the electrode changes greatly if the pressure cannot be managed for each measurement, and reliable results cannot be obtained. By using a laser displacement meter, the displacement of the cantilever can be accurately measured.

  Here, the laser displacement meter is not necessarily limited to a specific product, but the spot size must be the same as or smaller than the width of the cantilever so that the deformation of the cantilever can be monitored. . Further, it is desirable that the measurement resolution is high so that minute deformation can be detected, and more specifically, a resolution of about 1 nm is required. Further, such a measuring device for measuring the displacement of the cantilever may be configured to detect only one displacement when there are two cantilevers.

  FIG. 15 shows a configuration provided with a mechanism for measuring the displacement of the cantilever using an optical lever method. Here, the configuration is such that the light from the laser is irradiated onto the cantilever and the reflected light is detected by a two-divided detector. In this method, a change in the traveling angle of the reflected light due to the deformation of the cantilever 20 is detected at the position of the reflected light on the two-divided detector. That is, when the cantilever 20 is warped, the center position of the laser beam that strikes the two-divided detector is shifted, and the difference in output from the two light receiving regions changes. The amount of warpage of the cantilever can be calculated from this change. Even in this case, the displacement of the cantilever can be accurately measured.

  In this case, a two-divided detector is used as the photodetector. However, the detector may be a detector (preferably a photodetector) having two or more divisions (having two or more light receiving regions).

  The circuit for passing a current through the minute object and the circuit for measuring the voltage drop of the minute object are not limited to the configuration of the embodiment shown in FIG. That is, the method for connecting the pair of arms of the clamping member and the electrode provided on the cantilever can be changed as appropriate.

  In the above embodiment, since a large amount of current flows from the power supply circuit to the holding member, there is a possibility that a large amount of noise derived from the current flowing in the electric system of the three-dimensional movement mechanism for moving the holding member may occur in the current.

  Therefore, as in the minute object electric resistance measuring apparatus 500 of the fourth modification shown in FIG. 16, a voltmeter is connected between a pair of arms that sandwich the minute object, and between the pair of electrodes that are in contact with the minute object. A power supply circuit may be connected.

  On the other hand, when a large amount of current flows from the power supply circuit to the electrode, there is a possibility that noise derived from the current flowing in the electrical system of the fine movement stage 50 may be generated in the current. It is desirable to consider.

  Therefore, like the minute object electric resistance measuring devices 600 and 700 of the modified examples 5 and 6 shown in FIGS. 17 and 18, one of a pair of arms that sandwich the minute object and two electrodes that are in contact with the minute object. A voltmeter may be connected between the two and a power supply circuit may be connected between the other of the pair of arms and the other of the two electrodes.

  As a result, the amount of noise generated from the three-dimensional movement mechanism side and the amount of noise generated from the fine movement stage 50 side are compared, and, for example, any circuit can be selected from the circuit configurations shown in FIGS. 2 and 16 to 17. By selecting the configuration, a circuit with the smallest measurement noise can be assembled, and the electrical resistance of a minute object can be measured with high accuracy. Further, the switching of these circuit configurations may be performed automatically by the processing device 60 or manually via the operation unit. That is, any two of the pair of arms and the pair of electrodes can be selectively connected to the power supply circuit, and the remaining two can be selectively connected to the voltmeter by a switch circuit including a plurality of relays. By performing the above operation, each relay may be switched on and off.

  In the above embodiment and each modification, the electrical resistance of the minute object is measured. However, instead of or in addition to this, the dielectric constant of the minute object may be measured. In order to measure the dielectric constant of a minute object, the DC power supply in the power supply circuit of the above embodiment and each modification may be replaced with an AC power supply. By using an AC power supply, the frequency response of the current flowing through the minute object can be measured to obtain the impedance. Further, the dielectric constant can be obtained by obtaining the capacitor from the impedance. In this case, the electrical resistance can be measured in addition to the dielectric constant.

  In addition, although the micro electrical resistance measuring device of the said embodiment and each modification is provided with the measuring device which measures the displacement of the cantilever 20, it does not need to be provided. In this case, regarding the contact between the minute object and the cantilever, it is necessary to rely on visual observation through a microscope or the like, but it is sufficient to measure the electrical characteristics (electrical resistance and dielectric constant) of the minute object. Is possible.

  By the way, in the said embodiment and each modification, as FIG. 1 showed, the structure which provided the fine movement stage 50, the laser displacement meter 30, and the cantilever 20 integrally was shown. The configuration in FIG. 1 is not easily affected by noise due to vibration. For example, when the configuration in FIG. 1 cannot be realized due to cost or manufacturing reasons, for example, the clamping member 10 and the fine movement stage are integrated. A configuration may be employed in which the holding member 10 is finely moved together with the fine movement stage 50.

  The measuring device is not limited to the one described in the above embodiment and each modification, and any other measuring device may be used as long as it can measure the displacement of the cantilever 20. In short, it is preferable to have a configuration that emits light waves, sound waves, radio waves, and the like toward the cantilever 20 and receives the reflected waves.

  Moreover, although the micro electrical property measuring device of the said embodiment and each modification has one clamping member, you may have multiple. For example, a plurality of holding members having different sizes may be used depending on the particle size of the minute object. Immediately after the measurement using one clamping member is completed, the other clamping member that clamps another minute object is put on standby while measuring the electrical characteristics of the minute object sandwiched by one clamping member. You may make it perform the measurement using another clamping member. In this case, the electrical characteristics of a plurality of minute objects can be measured more efficiently.

  Moreover, the micro electrical property measuring apparatus of the above embodiment and each modification may have a plurality of cantilevers. For example, by providing a plurality of cantilevers with different intervals between the electrodes, a cantilever suitable for each particle size of the minute object to be measured can be selectively used.

  Moreover, the micro electrical property measuring apparatus of the above embodiment and each modification may have a plurality of clamping members and a plurality of cantilevers. For example, a minute object held on one clamping member and one cantilever face each other, and another minute object held on another clamping member and another cantilever face each other so that the same kind or different kinds of a plurality of minute objects You may make it measure an electrical property in parallel. When different types of characteristics of a plurality of minute objects are measured in parallel, the measurement may be performed sequentially by changing a pair of a holding member that holds the minute objects and a cantilever.

  Moreover, in the said embodiment and each modification, although the micro electrical property measuring device is provided with the processing apparatus 60, it does not need to be provided. In this case, control (for example, minute movement of the fine movement stage 50) performed by the processing device 60 may be performed manually (manual), or a calculation performed by the processing device 60 may be performed by a person. Even if the minute object electrical property measuring apparatus includes the processing device 60, the fine movement of the fine movement stage 50 may be performed manually, or a calculation performed by the processing device 60 may be performed by a person. .

  Below, the thought process in which the inventors of the present invention have come up with the above embodiment and each modification will be described.

  Currently, micron particles are used in various industrial products, pharmaceuticals, and food products. The toner used in copiers and laser printers is becoming smaller in diameter, and is the industry's smallest class with a particle size of about 5um. Silica particles for spacers between liquid crystal panels are also about 5 um. Micron particles are also commonly used for food products such as pharmaceuticals and flour. One of the promising technologies in 3D printers whose market is rapidly expanding is the powder lamination method, but the powder used in this method is also small, and particles of 10 um or less in size have been included. ing.

  As the field of handling microscopic particles expands in this way, a means for accurately evaluating electric characteristics such as electric resistance is required so that these particles can be handled more reliably and accurately. In recent years, with the development of micro object manipulation / measurement technology called nanotechnology, a technique for evaluating the characteristics of these micron particles in units of one particle is being developed.

  In response to such needs, devices such as Patent Documents 1 to 4 have been developed in which microelectrodes are pressed against arbitrary microparticles to form a series circuit and electrical resistance is measured.

  While the methods for measuring electrical resistance of minute objects as described above have been proposed, these methods can measure any single particle adhering to a component or member while achieving both evaluation accuracy and efficiency. The challenge remains difficult. In the methods of Patent Documents 1 to 4, it is necessary to prepare a dedicated manipulator for arranging particles on electrodes in order to achieve both evaluation accuracy and efficiency for any one particle. It is difficult to measure the electrical resistance of an arbitrary particle with these methods alone, and if an evaluation is performed in combination with a manipulator that should be prepared separately, a reduction in measurement efficiency is inevitable.

  In order to solve the problems as described above, the present inventors have invented a sandwiching member for sandwiching a minute object and a one-particle electrical resistance measuring device for an arbitrary minute object using a cantilever. By using the present invention, it is possible to accurately measure the electrical resistance of a minute object after collecting and holding an arbitrary minute object. Specifically, a measurement circuit is formed by holding a minute object with a holding member which is one electrode and bringing it into contact with a cantilever which is the other electrode. By applying a voltage to the formed measurement circuit and measuring the flowing current, the single-particle electrical resistance of an arbitrary minute object is measured. At this time, by measuring the displacement of the cantilever, which is an electrode, the pressure applied to the minute object can be managed, and highly accurate resistance measurement can be realized.

  However, the above one-particle electrical resistance measuring device still has a problem that the electrical resistance of a minute object having an arbitrary low resistance (several tens of kΩ or less) cannot be accurately measured. In the case of low resistance measurement, in the configuration of the conventional invention, the contact resistance between the minute object and the electrode is dominant as compared with the electrical resistance of the minute object to be measured, so the resistance value of the minute object is buried in the contact resistance, It cannot be measured accurately. As a result, in the conventional invention, the resistance of a low-resistance minute object such as a metal fine particle or graphite particle cannot be measured.

  By the way, a method called a four-terminal method is generally used for low resistance measurement. As shown in FIG. 19, the four-terminal method is a method using a parallel circuit composed of a circuit for passing a current to a measurement object (DUT) and a circuit for measuring a voltage drop of the measurement object. . If such a circuit is used, since almost no current flows through the circuit for measuring the voltage drop, it is possible to perform measurement while ignoring the contact resistance. In particular, when the measurement object is several tens of kΩ or less, the four-terminal method is effective.

  However, even if such a four-terminal method is simply applied to the resistance measurement of a minute object, high-precision measurement cannot be realized. This is because the pressure that the minute object receives from the electrode cannot be controlled. Since the shape of minute objects with a diameter of several um to several hundred um changes even with a small external force, the contact area between the minute object and the electrode changes every measurement if the pressure with the electrode cannot be managed during resistance measurement. Therefore, reproducible measurement is not possible. In the conventional invention, the pressure was controlled by using a cantilever as an electrode and measuring its displacement optically. Similarly, a four-terminal circuit was constructed using a cantilever as an electrode, and resistance measurement and pressure were measured. It is difficult to manage. This is because, as shown in FIG. 20, even if a configuration in which two cantilevers are simply arranged in parallel, a sufficient area for reflecting the laser beam for measuring the deflection cannot be obtained. Therefore, in order to realize highly accurate four-terminal measurement of minute objects, it is necessary to devise the structure of the electrodes.

  As the measurement of the electrical characteristics of the minute objects in the above-described embodiment and each modification for solving the above-described problems, the present inventors have made a current flow in the gripping member having two arms and the minute object gripped by the gripping member. And a device for measuring the voltage drop between the electrodes, and a device for optically measuring the deflection of the cantilever. We developed an electrical resistance measurement device for minute objects.

  By using this configuration, it is possible to accurately measure the electrical resistance of a low-resistance minute object. This is because, in this configuration, the contact resistance between the electrode and the minute object is negligibly small compared to the internal resistance of the voltmeter that measures the voltage drop between the electrodes. By eliminating the need to consider contact resistance, it is possible to accurately measure the electrical resistance of a low-resistance minute object. That is, this configuration implements a four-terminal method for measuring the electrical resistance of minute objects.

  Moreover, if this structure is used, the pressure which a micro object receives from an electrode can be managed. In this configuration, since the electrode is formed on the cantilever, the portion irradiated with the laser beam for measuring the displacement of the cantilever can be sufficiently widened, and the reflected light amount can be sufficiently obtained. Thereby, the displacement of the cantilever on which the electrode is formed can be measured, and the pressure applied to the minute object can be managed.

  DESCRIPTION OF SYMBOLS 10 ... Holding member, 10a, 10b ... A pair of arm, 20 ... Cantilever, 30 ... Laser displacement meter (measuring device), 60 ... Processing device, 100, 200, 300, 400, 500, 600, 700 ... Microscopic electric resistance Measuring device (microscopic electrical property measuring device).

JP 09-189727 A Japanese Patent Laid-Open No. 09-311150 Japanese Patent Laid-Open No. 09-196978 JP 09-189728 A

Claims (15)

A pair of conductive arms capable of holding minute objects;
Two electrodes connected via a minute object to a pair of arms holding the minute object;
A power source connected between any two of the pair of arms and the two electrodes;
And a voltmeter connected between two of the pair of arms and the two electrodes that are not connected to the power supply unit.   The micro-electrical property measuring apparatus according to claim 1, further comprising a cantilever having the two electrodes provided on a surface thereof.   The minute can electrical property measuring apparatus according to claim 2, wherein the cantilever has a notch or an opening between portions where the two electrodes are provided.   The said cantilever has a recessed part between the site | parts in which the said 2 electrode is provided, The micro electrical property measurement apparatus of Claim 2 characterized by the above-mentioned.   5. The minute electrical property measuring apparatus according to claim 2, wherein the two electrodes are made of a conductive material formed in a thin film on the surface of the cantilever.   The microscopic electrical property measuring apparatus according to claim 1, wherein the two electrodes are a pair of cantilevers having conductivity.   The device for measuring electrical characteristics of minute objects according to any one of claims 2 to 6, further comprising a measuring device for measuring the displacement of the cantilever. The measuring device irradiates the cantilever with light, detects the reflected light and measures the displacement of the cantilever,
8. The minute object electrical property measuring apparatus according to claim 7, wherein an area of a portion of the cantilever irradiated with a light spot from the measuring device is larger than a size of the light spot.   9. The minute object electrical property measuring apparatus according to claim 8, wherein the measuring apparatus is a laser displacement meter. The measuring device is
A light source that emits laser light toward the cantilever;
9. The minute object electrical property measuring apparatus according to claim 8, further comprising an N-divided detector (N is 2 or more) for detecting light emitted from the light source and reflected by the cantilever.   The said cantilever is a cantilever for atomic force microscopes, The micro electrical property measuring apparatus as described in any one of Claims 2-10 characterized by the above-mentioned.   The microscopic electrical property measuring apparatus according to claim 1, wherein a distance between the two electrodes is narrower than a particle size of the microscopic object.   The micro electrical property measuring apparatus according to claim 1, wherein the pair of arms and the two electrodes are selectively connectable to the power supply unit and the voltmeter. . Sandwiching minute objects with a pair of conductive arms;
Contacting the microscopic object sandwiched between the pair of arms with two electrodes;
Applying a voltage between any two of the pair of arms and the two electrodes;
And measuring a voltage drop between two of the pair of arms and the two electrodes to which the voltage is not applied. 15. The method according to claim 14, further comprising a step of measuring a deformation amount of the electrode and managing a contact state between the two objects and the minute object held by the pair of arms based on the measurement result. Method for measuring electrical properties of minute objects.

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