JP5156432B2 - Eddy current sample measurement method and eddy current sensor - Google Patents

Description

  In the present invention, for example, resistance of an object to be measured (sample) such as a metal thin film (conductive film) formed on various substrates such as a semiconductor wafer and a glass substrate by various methods such as sputtering, CVD, and PVD. The present invention relates to an eddy current type sample measuring method and an eddy current type sensor capable of measuring electrical characteristics such as rate and sheet resistance, physical conditions such as film thickness and scratches, etc. without contacting the sample.

  An eddy current type sample measuring method and an eddy current sensor used for the method are conventionally known. An example of a conventional eddy current sensor is shown in FIGS. The eddy current sensor of FIG. 24 is a single-sided system, and the eddy current sensor of FIG. 25 is a double-sided system. 24 and 25, when an alternating current oscillated from the self-excited oscillator A is applied to a sensor coil (excitation coil) C wound around a ferrite core B, an eddy current flows through the sample D, The physical constant of the conductive film of the sample D can be measured using the fact that the current flowing through the exciting coil C changes due to the influence of the current. In this case, the alternating current oscillated from the self-excited oscillator A is detected by the detector E, and the detected voltage and the reference voltage generated from the reference voltage generator F are compared by the error amplifier G. The amplitude voltage controller H is controlled by the output, and the AC voltage oscillated from the self-excited oscillator A is controlled to be constant. The current detector I can detect the current change due to the influence of the eddy current, and can process the detection signal to measure the sheet resistance, resistivity, film thickness, etc. of the sample D. There are various other eddy current sensors and eddy current measurement methods (see, for example, Patent Documents 1 and 2).

JP2007-333439A JP 2006-208331 A

As described above, the measurement principle of the eddy current method is to control the high-frequency voltage supplied to the exciting coil C to be constant, and to detect a current that changes depending on the resistance value of the sample D to be measured. There were the following problems.
1. Since the magnetic flux generated by the AC magnetic field applied to the sample spreads throughout the core, the spatial resolution (measurement resolution) detected is limited by the size of the magnetic path cross-sectional area of the magnetic core, and a resolution smaller than that of the magnetic core is obtained. I can't.
2. In actual measurement, a connecting lead wire is required between the exciting coil C wound around the core B and the self-excited oscillator A. The length of the lead wire depends on the size of the sample to be measured, but is long. Several tens of centimeters or more may be required, and an equivalent circuit thereof is as shown in FIG. In FIG. 26, L1 is the inductance of the exciting coil C, R1 is the equivalent resistance of the sample D, R2 is the resistance caused by the iron loss of the magnetic core, L2 and L3 are the lead wire inductances, R3 and R4 are the lead wire resistance components, and V2 Is an applied voltage, and I is a current detector. In actual measurement, since the amplitude voltage of the self-excited oscillator A in FIGS. 24 and 25 is controlled to be constant, the effects of the inductances L2 and L3 of the lead wires and the resistance components R3 and R4 existing in series with the excitation coil C are affected. As a result, the high-frequency voltage supplied to the exciting coil C cannot be kept constant, causing a measurement error.

  When Mn-Zn ferrite, etc., which has a remarkable dielectric property in addition to the magnetic property, is used as the magnetic core material of the eddy current sensor, for example, a phenomenon in which the electromagnetic wave inside the magnetic core becomes a standing wave under high frequency excitation in the MHz band Is known and is referred to as dimensional resonance. Dimensional resonance is resonance caused by the magnetic path cross-sectional area (magnetic core dimension) of the magnetic core. Therefore, even if the resonance frequency is changed with the excitation frequency kept constant, the magnetic path cross-sectional area is made constant and the excitation frequency is changed. However, the state of dimensional resonance or standing wave can be controlled.

The first eddy current type sample measuring method of the present invention is a measuring method applying the principle of dimensional resonance, and as described in claim 1, the magnetic core is made of a material in which the dielectric characteristics become remarkable in addition to the magnetic characteristics. Using the eddy current sensor, the eddy current sensor is operated at a frequency at which the electromagnetic wave inside the magnetic core generated by the combined action of magnetic and dielectric characteristics becomes a standing wave (frequency at which dimensional resonance occurs) or a frequency in the vicinity thereof. Concentrate the magnetic flux on the peak part of the standing wave (exciting the magnetic core), make the magnetic field generation area (magnetic flux cross-sectional area) of the peak part smaller than the magnetic path cross-sectional area of the magnetic core, and use the magnetic flux as a sample This is the measurement method that is given.

  According to a second eddy current type sample measuring method of the present invention, as described in claim 2, in the eddy current type sample measuring method according to claim 1, one or more detection coils are wound separately from the exciting coil. An eddy current sensor is used to measure the sample by the eddy current type sample measurement method according to claim 1, and the induced voltage of the one or more detection coils of the eddy current sensor affected by the eddy current by the sample measurement Is measured with a detector having a high input impedance connected to each detection coil.

  According to a third eddy current type sample measuring method of the present invention, as described in claim 3, in the eddy current type sample measuring method according to claim 2, one or more detection coils are wound separately from the exciting coil. Two sets of eddy current sensors are used, one for measurement and the other for non-measurement. The detection coils of both eddy current sensors are connected in series so that their induced voltages are in the opposite direction. When the sample is not set, voltage is not generated in the series circuit, the sample is not set in the non-measurement eddy current sensor, the sample is set in the measurement eddy current sensor, and the excitation voltage is applied to both eddy current sensors. The eddy current sensor for measurement is subjected to sample measurement by the eddy current type sample measurement method according to claim 1, and the induced voltage of the detection coil of the measurement eddy current sensor affected by the eddy current by the sample measurement is not measured. Eddy current sensor The voltage difference between the induced voltage of the coil in the series circuit is a measurement method for detecting by a detector of a high input impedance.

According to the eddy current sensor of the present invention, as described in claim 4, the magnetic core of the eddy current sensor is made of a material in which the dielectric characteristics become remarkable in addition to the magnetic characteristics, and the combined action of the magnetic and dielectric characteristics during excitation is used. When the generated electromagnetic wave inside the magnetic core is operated at a frequency where the standing wave becomes a standing wave or a frequency in the vicinity thereof, the generated magnetic flux is concentrated on the peak portion of the standing wave, and the magnetic field generation area (magnetic flux cross section) of the peak portion is reduced. It is made smaller than the magnetic path cross-sectional area of the magnetic core so that the magnetic flux can be given to the sample . In this case, as described in claim 5, the magnetic core material can be Mn-Zn ferrite. 7. The eddy current sensor according to claim 6, wherein an induced voltage of the eddy current sensor affected by the eddy current is detected by a sample measurement separately from the exciting coil that generates an alternating magnetic field in the magnetic core of the eddy current sensor. One or more detection coils may be provided.

The eddy current measurement method according to claim 1 of the present application has the following effects.
(1) Since the magnetic field is concentrated in a range smaller than the magnetic path cross-sectional area of the magnetic core (the peak portion of the standing wave) and the magnetic field of the peak portion is applied to the sample, the magnetic path cross-sectional area of the magnetic core of the eddy current sensor A smaller spatial resolution can be obtained and detection accuracy is improved.
(2) The spatial resolution of the measured conductivity of the sample can be improved with the same voltage value as the voltage applied to the winding of the conventional Ni—Zn ferrite core.

The eddy current measurement method according to claim 2 of the present application uses an eddy current sensor in which one or two or more detection coils are wound separately from the excitation coil, and the influence of the eddy current is measured by the sample measurement during the sample measurement. The induced voltage of the one or more detection coils of the eddy current sensor that has been subjected to detection is detected by a high input impedance detector connected to each of the detection coils.
(1) Excitation coil excitation voltage can be detected without being affected by excitation coil lead wire inductance, resistance, etc., and the sample resistivity, sheet resistance, film thickness, etc. are more accurate and sensitive than conventional methods. It becomes possible to detect a potential problem of a sample, which is difficult to detect with the conventional measurement method in which the excitation voltage is detected at the input terminal of the excitation coil.
(2) Since the detection voltage detected by the detector with high input impedance is used to control the applied voltage applied to the exciting coil, the applied voltage can be stabilized.

  The eddy current measurement method according to claim 3 of the present application uses two sets of eddy current sensors each having one or two or more detection coils wound separately from the exciting coil, one for measurement and the other for non-measurement. Because this is a differential method that detects the voltage difference between the induced voltage of the detection coil of the non-measuring eddy current sensor and the induced voltage of the detection coil of the measuring eddy current sensor affected by the eddy current due to the sample measurement. Only the voltage applied to the exciting coil affected by the eddy current can be detected with high accuracy and high sensitivity.

In the eddy current sensor according to the fourth to sixth aspects of the present invention, the magnetic core is made of a material having a remarkable dielectric characteristic in addition to the magnetic characteristic. When the magnetic core is operated at a frequency that becomes a standing wave, the generated magnetic flux concentrates on the peak portion of the standing wave, and a high-density magnetic field can be applied to the sample portion. However, the spatial resolution of the measured conductivity of the sample is improved even with the same voltage value as the voltage applied to the winding of the conventional Ni—Zn ferrite core.

  In the eddy current sensor according to claim 5 of the present invention, since the magnetic core material is Mn—Zn ferrite, the dielectric property becomes remarkable in addition to the magnetic property and the detection sensitivity is improved as compared with the Ni—Zn system.

In the eddy current sensor according to claim 6 of the present invention, a detection coil for detecting the induced voltage of the eddy current sensor affected by the eddy current by the sample measurement is provided in the magnetic core separately from the excitation coil for generating the alternating magnetic field. Has the following effects.
(1) By connecting a detector with a high input impedance to the detection coil and detecting the voltage, the applied voltage of the excitation coil can be accurately and highly sensitive without being affected by the inductance, resistance, etc. of the lead wire of the excitation coil. It can be detected.
(2) Since the detection voltage can be used to control the high frequency voltage applied to the excitation coil, the high frequency excitation voltage applied to the excitation coil can be stabilized.

(Embodiment 1 of Eddy Current Method and Eddy Current Sensor)
In the eddy current sensor of the present invention, the core (magnetic core) B having the shape shown in FIG. 1 (d) is made of a material that exhibits remarkable dielectric characteristics in addition to magnetic characteristics, for example, made of Mn-Zn ferrite, and a sensor coil. (Excitation coil) C is wound, and both terminals of the excitation coil C are used as AC voltage application terminals. For the core B, materials other than the above materials, for example, Ni—Zn ferrite can be used.

  The eddy current measurement method of the present invention can measure a sample with the sample measurement system shown in FIG. FIG. 2 shows a single-sided sensor type in which the eddy current sensor 2 shown in FIG. 1A is opposed to one side of the sample D, and the excitation coil C wound around the core B of the eddy current sensor 2 is self-excited. In this method, an alternating voltage (high frequency voltage) oscillated from the oscillator A is applied to generate a magnetic field in the magnetic core, and the magnetic field is applied to the sample D to generate an eddy current in the sample D. Since this eddy current is lost as Joule heat, high-frequency power is absorbed in the sample D, and the current flowing through the exciting coil C changes. Since the absorption and conductivity have a positive correlation, the resistivity of the sample D can be measured without contact. That is, the conductive film of the sample D can be measured using the current change due to the influence of the eddy current. In this case, the alternating current oscillated from the self-excited oscillator A is detected by the detector E, and the detected voltage and the reference voltage generated from the reference voltage generator F are compared by the error amplifier G. The amplitude voltage controller H is controlled by the output, and the AC voltage oscillated from the self-excited oscillator A is controlled to be constant. The current detector I detects the current change due to the influence of the eddy current, and can process the detection signal to measure the sheet resistance, resistivity, film thickness, etc. of the sample D.

  In the eddy current measurement method of the present invention, the frequency of the alternating voltage (high frequency voltage) oscillated from the self-excited oscillator A is set to a frequency at which the electromagnetic wave inside the magnetic core generated by the combined action of magnetic and dielectric characteristics becomes a standing wave. Then, the magnetic field is concentrated (converged) on the peak portion of the standing wave, and the cross-sectional area of the magnetic field (magnetic flux) is made smaller than the magnetic path cross-sectional area and applied to the sample D. At the frequency where the magnetic field is concentrated on the peak portion of the standing wave, the power absorption increases and the current loss increases rapidly, so that the current loss can be detected reliably. In this case, since the magnetic flux cross-sectional area is smaller than the magnetic path cross-sectional area of the magnetic core, a spatial resolution smaller than the magnetic path cross-sectional area of the magnetic core can be obtained.

磁界の強さＨの単位は〔Ａ／ｍ〕、磁束密度Ｂの単位は〔Ｔ〕又は〔ｗｂ／ｍ²〕、磁束φの単位は〔ｗｂ〕である。 The relationship between the frequency of the high-frequency voltage (excitation frequency) applied to the exciting coil, the magnetic path cross-sectional area of the magnetic core, and the magnetic flux density can be obtained from the following calculation data, which is illustrated in FIGS. 4 to 15. . 4 to 15, the horizontal axis of the graph is obtained by normalizing the distance from the center of the circular magnetic path cross section of the central portion b of the core B in FIG. Shows the maximum amplitude value B _m of the magnetic flux density. In FIG. 1 (d), c is the contour portion of the core B.

The unit of magnetic field strength H is [A / m], the unit of magnetic flux density B is [T] or [wb / m ² ], and the unit of magnetic flux φ is [wb].

  4 is an excitation frequency of 0.6 MHz, FIG. 6 is an excitation frequency of 0.8 MHz, FIG. 7 is an excitation frequency of 1 MHz, FIG. 8 is an excitation frequency of 1.2 MHz, and FIG. FIG. 10 shows an excitation frequency of 1.6 MHz, FIG. 11 shows an excitation frequency of 1.8 MHz, FIG. 12 shows an excitation frequency of 2 MHz, FIG. 13 shows an excitation frequency of 3 MHz, FIG. 14 shows an excitation frequency of 5 MHz, and FIG. is there.

(Calculated data)

  When the excitation frequency is 100 kHz or less, the magnetic flux is uniformly distributed in the magnetic path cross section, but at the excitation frequency of 0.4 MHz to 1.4 MHz (FIGS. 4 to 9), the magnetic flux density at the center of the magnetic path is high. From 6 MHz to 10 MHz (FIGS. 10 to 15), the magnetic flux density at the outer periphery of the magnetic path is high. Among these, the magnetic flux density distributions of 0.4 MHz, 1 MHz, 1.2 MHz, 1.4 MHz, 2 MHz, and 10 MHz are displayed with respect to the diameter of the circular magnetic path cross-sectional area as shown in FIG. In the present invention, an excitation frequency at which the magnetic flux density tends to concentrate is selected and applied to the excitation coil.

(Embodiment 2 of Eddy Current Method and Eddy Current Sensor)
The eddy current measurement method of the present invention can also be measured by the sample measurement system shown in FIG. The measurement system of FIG. 3 is a double-sided sensor system in which the eddy current sensor 2 of FIG. 1A is opposed and the sample D is placed (set) in the gap between the two eddy current sensors 2. As for the winding direction of the exciting coil C wound around the core B of the two eddy current sensors 2 in FIG. 3, the generation direction of the magnetic flux φ of the two eddy current sensors 2 (the magnetic force generation direction based on Fleming's right-hand rule) is added to each other. To be in the direction. The direction in which the magnetic flux φ is generated is reversed according to the change in the high-frequency current flowing through the exciting coil C.

  In FIG. 3, when a high frequency voltage oscillated from the self-excited oscillator A is applied to the exciting coil C wound around the core B of both eddy current sensors 2, eddy current flows through the sample D set in the gap, and As a result, the current flowing through the exciting coil C changes. In this case, the alternating current oscillated from the self-excited oscillator A is detected by the detector E, and the detected voltage and the reference voltage generated from the reference voltage generator F are compared by the error amplifier G. The amplitude voltage controller H is controlled by the output, and the AC voltage oscillated from the self-excited oscillator A is controlled to be constant. The current detector I detects the current change due to the influence of the eddy current, and can process the detection signal to measure the sheet resistance, resistivity, film thickness, etc. of the sample D. The frequency of the high-frequency voltage is a frequency at which an electromagnetic wave inside the magnetic core generated by the combined action of magnetic and dielectric characteristics becomes a standing wave.

(Embodiment 3 of Eddy Current Method and Eddy Current Sensor)
In the eddy current measurement method of the present invention, as an eddy current sensor, a detection coil 1 is wound around a magnetic core B separately from an excitation coil C as shown in FIG. Can also be used. The detection coil 1 can be wound over the exciting coil C or can be wound at a different location from the exciting coil C. The number of turns of the exciting coil C and the number of turns of the detection coil 1 can be arbitrarily selected.

  The eddy current measurement of the present invention can also be performed by the sample measurement system of FIG. As shown in FIG. 1B, the sample measurement system in FIG. 17 uses an eddy current sensor 2 having a detection coil 1 in addition to the excitation coil C in a magnetic core B as a single-sided sensor type, and both ends of the detection coil 1 (measurement). A high input impedance detector J is connected to the end. The impedance of the high input impedance detector J is several times higher than the inductance and resistance (impedance) of the lead wire of the detection coil 1. Also in the measurement method of FIG. 17, an alternating voltage (high frequency voltage) oscillated from the self-excited oscillator A is applied to the exciting coil C of the eddy current sensor 2. The frequency of this high-frequency voltage (excitation frequency) is also set to a frequency at which the electromagnetic wave inside the magnetic core generated by the combined action of magnetic and dielectric characteristics becomes a standing wave, and the magnetic field is concentrated on the peak portion of the standing wave. The area is made smaller than the magnetic path cross-sectional area of the magnetic core so that it can be given to the sample D.

  An eddy current flows through the sample D to which the magnetic field is applied, and the current flowing through the exciting coil C changes under the influence of the eddy current. The voltage change accompanying this current change is detected by the high input impedance detector J connected to both ends (measurement ends) of the detection coil 1 and detected by the detector E. The detected voltage and the reference voltage generated from the reference voltage generator F are compared by the error amplifier G, and the amplitude voltage controller H is controlled by the output from the error amplifier G, and the alternating current oscillated from the self-excited oscillator A. The voltage is controlled to be constant and applied to the exciting coil C. At this time, a change in the current flowing through the exciting coil C due to the influence of the eddy current is detected by the current detector I, and from the detected value, the power consumption caused by the generation of the eddy current in the sample D, that is, the sample D The resistivity, sheet resistance, and the like can be known, and the film thickness and scratches of the conductive film can be known based on the detection. The equivalent circuit of the eddy current sample measurement system of FIG. 17 is as shown in FIG. In FIG. 18, L1 is the inductance of the exciting coil C, R1 is the equivalent resistance of the sample D, R2 is the resistance caused by the iron loss of the magnetic core, L2 and L3 are the lead wire inductances, R3 and R4 are the lead wire resistance components, and V2 Is an applied voltage, I is a current detector, and V is a voltmeter at the measurement end of the detection coil 1.

(Embodiment 4 of Eddy Current Method and Eddy Current Sensor)
FIG. 19 shows a sample measurement system in which the eddy current sensor 2 of FIG. 1B is opposed to a double-sided sensor type. A high input impedance detector J is connected to the measurement end of the detection coil 1 of both eddy current sensors 2. It is. Also in this case, the winding direction of the exciting coil C wound around the core B of the eddy current sensor 2 in FIG. 19 is the direction of generation of the magnetic flux φ of the eddy current sensor 2 (the direction of magnetic force generation based on Fleming's right-hand rule). In such a direction that they are added to each other. Also in this case, the direction in which the magnetic flux φ is generated is reversed according to the change of the high-frequency current flowing in the exciting coil C.

  When an alternating voltage (high-frequency voltage) oscillated from the self-excited oscillator A is applied to the exciting coil C of both the eddy current sensors 2 in FIG. 19, an eddy current flows through the sample D set in the gap. The current flowing through the exciting coil C changes. A voltage change accompanying this current change is detected by a high input impedance detector J connected to both ends (measurement ends) of the detection coil 1. The detected voltage is detected by the detector E, the detected voltage and the reference voltage generated from the reference voltage generator F are compared by the error amplifier G, and the amplitude voltage controller H is controlled by the output from the error amplifier G. Thus, the AC voltage oscillated from the self-excited oscillator A is controlled to be constant and applied to the exciting coil C. Also at this time, a change in the current flowing through the exciting coil C due to the influence of the eddy current is detected by the current detector I, and from the detected value, the power consumption caused by the generation of the eddy current in the sample D, that is, the sample D It is possible to know the resistivity, sheet resistance, etc., and to know the film thickness, scratches, etc. of the conductive film based on the detection. In this case, the excitation frequency is also a frequency at which the electromagnetic wave inside the magnetic core generated by the combined action of the magnetic and dielectric characteristics becomes a standing wave, and the magnetic field is concentrated on the peak portion of the standing wave so that the magnetic flux cross-sectional area is the magnetic path of the magnetic core. It is made smaller than the cross-sectional area so that it can be applied to the sample D.

(Embodiment 5 of Eddy Current Type Sample Measuring Method and Eddy Current Sensor)
Another example of the eddy current type sample measuring method of the present invention is shown in FIG. FIG. 20 shows a single-sided sensor differential method using two sets of single-sided eddy current sensors 2. The first eddy current sensor 2 is a measurement sensor that measures sample D by passing an exciting current through the exciting coil C. The second eddy current sensor 2 is used for non-measuring only by passing an exciting current through the exciting coil C without setting a sample, and the detection coils 1 of both eddy current sensors 2 have their induced voltages in opposite directions. When there is no sample in series connection, an induced voltage is not generated in the series circuit even if an excitation voltage is applied to the excitation coil C.

  In FIG. 20, when an AC voltage oscillated from the self-excited oscillator G is applied to the excitation coil C of both eddy current sensors 2, the sample D set in the gap of the measurement eddy current sensor (first eddy current sensor) 2 is applied. An eddy current flows and the current flowing through the exciting coil C changes due to the eddy current. However, since no sample is set in the gap of the non-measuring eddy current sensor (second eddy current sensor) 2, the eddy current loss is reduced. Does not occur. At this time, a voltage is induced in the detection coils 1 of the two eddy current sensors 2, but the voltage at both ends (measurement ends) of the two detection coils 1 connected in series becomes a differential voltage between the two induced voltages. This differential voltage is detected by the high input impedance detector J. The impedance of the high input impedance detector J is several times higher than the inductance and resistance (impedance) of the lead wires of both detection coils 1, so that the differential voltage is measured by the eddy current sensor for measurement. Only the voltage due to the influence of the eddy current of the lead wire, and the impedance of the lead wire between the detection coils 1 and the high input impedance detector J becomes a negligible value (cancelled value).

  In the eddy current type sample measurement method of FIG. 20, even if the AC voltage applied to the exciting coil C fluctuates, the output detected by the high input impedance detector J is the differential voltage, that is, for measurement as described above. Only the power consumption caused by the generation of eddy current in the sample D of the eddy current sensor 2, that is, the resistivity of the sample D, the sheet resistance, and the like. This output is used for calculation processing of the film thickness, scratches, etc. of the conductive film of the sample, and is not used for control of the amplitude voltage controller H. In FIG. 20, the amplitude voltage controller H controls the reference voltage generated from the reference voltage generator F and the detected voltage detected from the self-excited oscillator A by the error amplifier G, and outputs from the error amplifier G. Thus, the amplitude voltage controller H is controlled so that the AC voltage oscillated from the self-excited oscillator A is controlled to be constant and applied to the exciting coil C. In this case, the excitation frequency is also a frequency at which the electromagnetic wave inside the magnetic core generated by the combined action of the magnetic and dielectric characteristics becomes a standing wave, and the magnetic field is concentrated on the peak portion of the standing wave so that the magnetic flux cross-sectional area is the magnetic path of the magnetic core. It is made smaller than the cross-sectional area so that it can be applied to the sample D.

(Embodiment 6 of Eddy Current Type Sample Measuring Method and Eddy Current Sensor)
Another example of the eddy current type sample measuring method of the present invention is shown in FIG. FIG. 21 shows a double-sided sensor differential system using two sets of double-sided eddy current sensors 2. The winding direction of the exciting coil C wound around the core B of both the eddy current sensors 2 in FIG. 21 is also set so that the direction of generation of the magnetic flux φ of the both eddy current sensors 2 is the direction in which they are added together as shown in FIG. is there. The direction of generation of this magnetic flux φ is also reversed in response to a change in the high-frequency current flowing through the exciting coil C.

  The detection coils 1 of the two eddy current sensors 2 in FIG. 21 are connected in series so that the induced voltages thereof are in opposite directions, and the first eddy current sensor 2 applies an excitation current to the excitation coil C to pass the sample D. The measuring sensor to be measured, the second eddy current sensor 2, is a non-measuring eddy current sensor in which an exciting current is simply passed through the exciting coil C without setting a sample. When excitation current flows through the respective excitation coils C of both eddy current sensors 2, an induced voltage is induced in each detection coil 1 of both eddy current sensors 2. In FIG. 21, both detection coils 1 are connected in series so that the induced voltage is in the reverse direction.

  In FIG. 21, when an AC voltage oscillated from the self-excited oscillator G is applied to the excitation coil C of both eddy current sensors 2, the sample D set in the gap of the measurement eddy current sensor (first eddy current sensor) 2 is applied. Eddy current flows, and the current flowing in the exciting coil C changes due to the eddy current, but since no sample is set in the gap of the non-measuring eddy current sensor (second eddy current sensor) 2, There is no loss. At this time, an induced voltage is induced in both detection coils 1, but the voltage at both ends (measurement ends) of the two detection coils 1 connected in series becomes a differential voltage between the two induced voltages. This differential voltage is detected by the high input impedance detector J. As in the case of FIG. 5, the detected output is only the differential voltage, that is, the power consumption caused by the generation of eddy current in the sample D of the eddy current sensor 2 for measurement, that is, only the resistivity and sheet resistance of the sample. Therefore, it is not used for the control of the amplitude voltage controller H, but is used for arithmetic processing such as the film thickness and scratches of the conductive film of the sample. In FIG. 6, the reference voltage generated from the reference voltage generator F and the detected voltage detected from the self-excited oscillator A are compared by the error amplifier G, and the amplitude voltage controller H is controlled by the output from the error amplifier G. The AC voltage oscillated from the self-excited oscillator A is controlled to be constant and applied to the exciting coil C. In this case, the excitation frequency is also a frequency at which the electromagnetic wave inside the magnetic core generated by the combined action of the magnetic and dielectric characteristics becomes a standing wave, and the magnetic field is concentrated on the peak portion of the standing wave so that the magnetic flux cross-sectional area is the magnetic path of the magnetic core. It is made smaller than the cross-sectional area so that it can be applied to the sample D.

(Embodiment 7 of Eddy Current Type Sample Measuring Method and Eddy Current Sensor)
Another example of the eddy current type sample measuring method of the present invention is shown in FIG. FIG. 22 shows a double-sided sensor differential system using two sets of eddy current sensors 2 provided with a second detection coil 3 in addition to the excitation coil C and the detection coil 1 as shown in FIG. The second detection coil 3 is wound around the set of eddy current sensors 2, and the second detection coils 3 of the two sets of eddy current sensors 2 are connected in series so that the induced voltages thereof are in the same direction. The winding direction of the exciting coil C of both the eddy current sensors 2 in FIG. 22 is also set so that the generation directions of the magnetic flux φ of both the eddy current sensors 2 are added to each other. The direction of generation of this magnetic flux φ is also reversed in response to a change in the high-frequency current flowing through the exciting coil C.

  In FIG. 22, the first eddy current sensor 2 is a measurement sensor that measures the sample D by flowing an exciting current through the exciting coil C, and the second eddy current sensor 2 allows the exciting current to flow through the exciting coil C without setting the sample. It is only a non-measuring eddy current sensor. A sample is not set in the non-measuring eddy current sensor (second eddy current sensor) 2 in FIG. 22, but a sample D is set in the measuring eddy current sensor (first eddy current sensor) 2 and both eddy current sensors 2 are used. When an excitation voltage is applied to the sensor, a high input impedance detector J detects the difference between the induced voltage of the first detection coil 1 of the non-measurement eddy current sensor 2 and the induced voltage of the first detection coil 1 of the measurement eddy current sensor 2. Is done. At this time, the induced voltage of the second detection coil 3 of the measurement eddy current sensor affected by the eddy current by the sample measurement is detected by the second high input impedance detector K (FIG. 22), and the detected voltage is detected. The signal is detected by the device E and inputted to the error amplifier G so that it can be used for controlling the amplitude voltage controller H. In this case, the excitation frequency is also a frequency at which the electromagnetic wave inside the magnetic core generated by the combined action of the magnetic and dielectric characteristics becomes a standing wave, and the magnetic field is concentrated on the peak portion of the standing wave so that the magnetic flux cross-sectional area is the magnetic path of the magnetic core. It is made smaller than the cross-sectional area so that it can be applied to the sample D.

(Embodiment 8 of Eddy Current Type Sample Measuring Method and Eddy Current Sensor)
Another example of the eddy current type sample measuring method of the present invention is shown in FIG. This is a system in which the second detection coil 3 is wound only around the core of the measurement eddy current sensor 2 and not around the core of the non-measurement eddy current sensor 2. Also in this case, if a sample is not set in the non-measuring eddy current sensor 2 but a sample D is set in the measuring eddy current sensor 2 and an excitation voltage is applied to both eddy current sensors 2, the non-measuring eddy current sensor 2 The difference between the induced voltage of the first detection coil 1 and the induced voltage of the first detection coil of the measurement eddy current sensor 2 was detected by the high input impedance detector J, and at the same time, the sample measurement was affected by the eddy current. The induced voltage of the second detection coil 3 of the measurement eddy current sensor 2 is detected by the second high input impedance detector K (FIG. 23). This detected voltage can be detected by the detector E, input to the error amplifier G, and used for controlling the amplitude voltage controller H.

(A)-(c) is a schematic diagram which shows the example of a different winding of the eddy current sensor with a detection coil of this invention, (d) is a perspective view of the core of an eddy current sensor. Explanatory drawing of an example of the eddy current type sample measuring method of the single-sided sensor system of this invention. Explanatory drawing of an example of the eddy current type sample measuring method of the double-sided sensor system of this invention. Explanatory drawing which shows the relationship between the magnetic flux density in the case of the excitation frequency of 0.4 MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the magnetic flux density in the case of the excitation frequency 0.6MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the magnetic flux density and magnetic path cross-sectional area at the excitation frequency of 0.8 MHz in the eddy current measurement method of the present invention. Explanatory drawing which shows the relationship between the magnetic flux density at the time of the excitation frequency of 1 MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the magnetic flux density at the time of the excitation frequency of 1.2 MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the magnetic flux density in the case of the excitation frequency of 1.4 MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the magnetic flux density at the time of the excitation frequency of 1.6 MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the magnetic flux density and magnetic path cross-sectional area at the excitation frequency of 1.8 MHz in the eddy current measurement method of the present invention. Explanatory drawing which shows the relationship between the magnetic flux density at the time of the excitation frequency of 2 MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the magnetic flux density at the time of the excitation frequency of 3 MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the magnetic flux density at the time of the excitation frequency of 5 MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the magnetic flux density at the time of the excitation frequency of 10 MHz in the eddy current type measuring method of this invention, and a magnetic path cross-sectional area. Explanatory drawing which shows the relationship between the excitation frequency in the eddy current type measuring method of this invention, magnetic flux density, and a magnetic path cross-sectional area (diameter). Explanatory drawing of an example of the eddy current type sample measuring method of this invention which made the magnetic core provided with the detection coil into the single-sided sensor system. FIG. 18 is an equivalent circuit diagram of the eddy current measurement system of FIG. 17. Explanatory drawing of an example of the eddy current type sample measuring method of this invention which made the magnetic core provided with the detection coil into the double-sided sensor system. Explanatory drawing of an example of the eddy current type sample measuring method of this invention which made the magnetic core provided with the detection coil the single-sided sensor differential system. Explanatory drawing of an example of the eddy current type sample measuring method of this invention which made the magnetic core provided with the detection coil into the double-sided sensor differential system. Explanatory drawing of an example of the eddy current type sample measuring method of this invention which made the magnetic core provided with the 1st detection coil and the 2nd detection coil into the double-sided sensor differential system. An eddy current sensor with a first detection coil and a second detection coil is used for the eddy current sensor for measurement, and an eddy current sensor with the first detection coil is used for the eddy current sensor for measurement. Explanatory drawing of an example of the eddy current type measurement system of this invention made into the differential system. Explanatory drawing of the conventional eddy current type sample measuring method of a single-sided sensor system. Explanatory drawing of the eddy current type sample measuring method of the conventional double-sided sensor system. The equivalent circuit diagram of the eddy current type sample measuring method of the conventional single-sided sensor system.

1 Detection coil (first detection coil)
2 Eddy current sensor 3 Second detection coil A Self-excited transmitter B Core (magnetic core)
C Sensor coil (excitation coil)
D Sample E Detector F Reference voltage generator G Error amplifier H Amplitude voltage controller I Current detector J High input impedance detector K Second high input impedance detector L1 Excitation coil inductance L2, L3 Lead wire inductance R1 Equivalent resistance of sample R2 Resistance due to core loss of magnetic core R3, R4 Resistance component of lead wire V2 Applied voltage

Claims (6)

In an eddy current sample measurement method that applies an alternating magnetic field to a sample to generate eddy currents, detects power absorption due to the eddy currents, and performs various measurements such as resistivity, sheet resistance, and film thickness of the sample. Using an eddy current sensor made of a magnetic core material that exhibits remarkable dielectric characteristics in addition to magnetic characteristics, and generating dimensional resonance of electromagnetic waves inside the magnetic core of the eddy current sensor, or making the eddy current sensor magnetic and dielectric characteristics core inside the electromagnetic waves caused by the combined action by exciting the core at a frequency of or near a standing wave of the magnetic flux part of the mountain by generating magnetic flux concentrated in the mountain portion of the standing wave An eddy current type sample measurement method characterized in that a cross-sectional area is made smaller than a magnetic path cross-sectional area of a magnetic core, and the magnetic flux is applied to the sample to generate an eddy current in the sample.   The eddy current type sample measurement method according to claim 1, wherein an eddy current sensor in which one or more detection coils are wound is used separately from the exciting coil, and the sample measurement is performed by the eddy current type sample measurement method according to claim 1. Then, the induced voltage of the one or more detection coils of the eddy current sensor affected by the eddy current by the sample measurement is detected by a detector with high input impedance connected to each detection coil. An eddy current sample measurement method.   In the eddy current type sample measurement method according to claim 2, two sets of eddy current sensors each having one or two or more detection coils wound are used separately from the excitation coil, one for measurement and the other for non-measurement. The eddy current sensor for non-measurement is configured so that the detection coils of both eddy current sensors are connected in series so that their induced voltages are in the opposite direction, and no sample is set in both eddy current sensors so that no voltage is generated in the series circuit. A sample is not set in the eddy current sensor, a sample is set in the eddy current sensor for measurement, and an excitation voltage is applied to both eddy current sensors. The voltage difference between the induced voltage of the detecting coil of the measuring eddy current sensor and the induced voltage of the detecting coil of the non-measuring eddy current sensor that is affected by the eddy current due to the sample measurement is measured in the series circuit. Eddy current sample measurement method characterized by detecting in-impedance of the detector. An eddy current sensor is used to generate an eddy current by applying an alternating magnetic field to a sample, detect power absorption due to the eddy current, and use it for various measurements such as resistivity, sheet resistance, and film thickness of the sample. When the excitation coil is excited at a frequency where the electromagnetic wave inside the magnetic core generated by the combined action of the magnetic and dielectric characteristics becomes a standing wave or a frequency in the vicinity thereof, the magnetic core The eddy current sensor is characterized in that the magnetic field generated in the center is concentrated on the peak portion of the standing wave so that the magnetic flux cross-sectional area of the peak portion is smaller than the magnetic path cross-sectional area of the magnetic core.   5. The eddy current sensor according to claim 4, wherein the magnetic core material is Mn-Zn ferrite.   6. The eddy current sensor according to claim 4, wherein an induced voltage of the eddy current sensor affected by the eddy current is detected by a sample measurement separately from the exciting coil that generates an alternating magnetic field in the magnetic core of the eddy current sensor. An eddy current type sample measuring method, wherein one or more detection coils are provided.

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