JP3285342B2 - Hall effect measuring apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the Hall effect of a sample such as a semiconductor, and more particularly to an apparatus for measuring a Hall effect voltage by applying an AC magnetic field to the sample.

[0002]

2. Description of the Related Art A constant current is applied to a sample such as a semiconductor placed in a magnetic field, and a Hall electromotive force generated in a direction perpendicular to the magnetic field and the current is measured (Hall effect measurement) to obtain a sample. Important physical properties such as carrier type (P-type / N-type), carrier concentration, and hole mobility can be obtained. The Hall effect measurement device that measures such a Hall electromotive voltage with high accuracy is one of the indispensable analyzers for the development of new materials and the like.

Conventionally, as a method for measuring the Hall electromotive voltage with high accuracy by removing the effects of noise and voltage drift generated in the sample and the measurement circuit, an AC magnetic field is applied to the sample, and the Hall electromotive voltage at that time is measured. There is a so-called AC Hall effect measurement for measuring. For example, JP-A-8-
The Hall effect measuring device described in JP-A-36039 corresponds to this.

This conventional measuring apparatus applies an AC magnetic field of, for example, 91 Hz to a sample having a low resistance, and
For a sample having a high resistance of MΩ or more, an AC magnetic field of 9.1 Hz is applied, and for a sample having a high resistance of 3 GΩ or more, positive feedback is provided to the input side of a buffer amplifier connected to the sample. To measure the Hall EMF. As a result, the measurement limit of the sample resistance is increased from about 5 GΩ to about 100 GΩ.

[0005]

However, this conventional Hall effect measuring apparatus is no longer said to be sufficiently high in the limit of measuring the sample resistance in today's fierce competition for the development of new materials. . New materials used in the latest liquid crystal display devices and solar cells, such as a-Si, poly-Si, diamond, and CIS, which are subject to sample analysis, are, for example, 1T (10 12) Ω or This is because it has an extremely high resistance exceeding

Accordingly, the present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-described problems, and is intended to provide a Hall measuring device capable of measuring the Hall effect with high accuracy even for a sample having a high resistance of about 1 TΩ. The purpose is to provide.

[0007]

To achieve the above object, according to the Invention The Hall effect measurement apparatus according to the present invention is an apparatus for measuring the Hall effect of a sample using an alternating magnetic field, 0.0
Signal generating means for generating an AC signal in a frequency range of 1 to 0.2 Hz, AC magnetic field generating means for generating a magnetic field synchronized with the AC signal and applying the same to the sample, and applying current to apply the current to the sample Means, a buffer means for detecting a Hall electromotive voltage generated in the sample, and outputting a detection signal of a voltage proportional to the voltage, and a filter means for passing only the same frequency component of the detection signal as the AC signal And a plurality of vectors consisting of the absolute value of the voltage of the signal and the phase of the signal with respect to the AC signal at each sampling time are measured by repeating sampling at a fixed time interval for the signal indicating the passed frequency component. Vector measuring means for calculating, and calculating means for calculating a physical property value for specifying the Hall effect of the sample based on a plurality of measured vectors Characterized in that it comprises a.

The present invention also relates to a method for measuring the Hall effect of a sample using an alternating magnetic field, wherein the signal generating means comprises:
Generating an AC signal in a frequency range of 0.01 to 0.2 Hz ; generating a magnetic field synchronized with the AC signal by an AC magnetic field generating means to apply the magnetic field to the sample; Applying a current to the sample; allowing the filter means to pass only the same frequency component as the AC signal among the detection signals indicating the Hall EMF generated in the sample; By repeating the sampling for a signal indicating the component at a fixed time interval, measuring a plurality of vectors consisting of the absolute value of the voltage of the signal at each sampling time and the phase of the signal with respect to the AC signal, Based on the plurality of measured vectors, calculating a physical property value specifying the Hall effect of the sample, May be included.

Further, the present invention can be realized as a computer-readable recording medium on which a program including these steps is recorded.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an external view of an AC hole measuring apparatus 100 according to the present embodiment. The AC Hall measuring device 100 is a low frequency (0.01 to
An automatic measurement apparatus for the Hall effect, characterized by an AC magnetic field of 0.2 Hz) and vector measurement of the Hall electromotive voltage (measurement of the absolute value and phase of the Hall electromotive voltage by a synchronization loop). 20, a sample holder part 30 and an electromagnet 40.

The measuring unit 20 includes various measuring instruments and signal generators (hereinafter, referred to as “hereafter”) for measuring the Hall effect.
It is called "measuring device". ). Control unit 10
Is a personal computer or the like connected to these measuring instruments and the like by a GPIB cable, and controls these measuring instruments and the like and reads out the obtained measured values based on dedicated measurement control software installed in a built-in hard disk. Perform an automatic measurement of the Hall effect.

The electromagnet 40 is a magnet for applying an AC magnetic field to the sample, and has a cooling coil wound around an iron core. The sample holder 30 includes a sample holder 32 that holds a sample connected to the measurement unit 20 by a signal cable 33, a cryostat 31 that houses the sample holder 32, and holds the sample at a constant temperature.

FIG. 2 is an external view of the tip of the sample holder 32. FIG. 2A shows the surface of an insulating plate ( polytetrafluoroethylene ) 35 on which a sample 34 is mounted, and FIG. ) Shows the back surface. The insulating plate 35 has
A rectangular sample 34 is attached, and 4
Four signal cables 33 for applying a current and measuring a Hall electromotive voltage are connected to the two electrodes (Nos. 1 to 4).

Here, each of the four signal cables 33 is a cable having a triaxial structure (having a core wire, an inner shield and an outer shield) having a diameter of about 3 mm, and the sample is twisted (twisted) with each other. At a location close to the sample 34 (that is, a location near the center of the magnetic pole of the electromagnet 40) wound around the rod portion of the holder 32, only the core wire is wired and exposed to form an unshielded structure.

This is because the magnetic field applied to the sample 34 is an alternating current, and the effect of electromagnetic induction noise is greater than that of a direct current. In other words, the signal cables 33 are mutually twisted in order to avoid the occurrence of a current loop due to electromagnetic induction, and the non-shield structure at the distal end is formed by the physical field of the core located inside the shield due to the magnetic field. This is for avoiding the occurrence of a parasitic current on the order of several pA based on the triboelectric effect caused by the movement of the position.

FIG. 3 shows the measuring unit 2 shown in FIG.
FIG. 2 is a functional block diagram showing a detailed configuration of the first embodiment. In addition, in this figure, the electromagnet 40 and the sample 34 are also shown. The constant current source 21 is, for example, a 220 type DC current source manufactured by Keithley of the United States, and has a 5 pA based on an instruction from the control unit 10.
A current is applied to the sample 34 at a maximum resolution of 0.5 pA within a range of ５００500 mA.

The ammeter 23 is a company type 6514 ammeter or the like, and measures the current actually flowing through the sample 34 at a maximum resolution of 10f (10 minus 14) A. Scanner 2
Reference numeral 2 denotes a matrix switch including a 7001 type scanner and a 7152 type minute current card of the same company.
Based on the instruction from 0, the four electrodes of the sample 34 are switched and connected to any one of the constant current source 21, the ammeter 23 and the buffer amplifiers 24a and 24b. For example, in the measurement of the Hall effect, a current from the constant current source 21 is applied to one diagonal of two diagonals connecting the pair of electrodes of the sample 34, and the current is measured by the ammeter 23. , So that the Hall electromotive voltage generated in the other diagonal direction is input to the buffer amplifiers 24a and 24b.
The connection between the four electrodes and the four measuring devices 21, 23, 24a, b is switched.

The buffer amplifiers 24a and 24b
It is a 6512 type buffer amplifier or the like having an input impedance of TΩ or more. In order to enable measurement of the Hall electromotive voltage generated in the sample 34 having a high resistance of about 10 TΩ, the signal source resistance is subjected to impedance conversion. The outputs (unity gain outputs) of the buffer amplifiers 24a and 24b are connected to the inputs of the preamplifier 25 and also to the inner shield covering the core wires of the respective input cables and the inner shield of the signal cable 33 via the scanner 22. Have been. This is because the stray capacitance of the signal cable 33 is canceled by the guarding technique that makes the core wire of the three coaxial cable and the inner shield that covers the same potential equal to each other, and the current leakage generated between the core wire of the signal cable 33 and the outer shield. This is to prevent

The preamplifier 25 is manufactured by ITHACO 1201 of the United States.
And two buffer amplifiers 2
The difference between the output voltages from 4a and 4b, that is, the Hall electromotive voltage generated in the sample 34 is amplified to a voltage suitable for the input of the AC synchronization signal analyzer 26. AC sync signal analyzer 26
Is a 1253 type frequency response analyzer or the like manufactured by Solartron of the United Kingdom.
A reference signal generator 26a for generating a reference signal having a constant frequency and amplitude (a sine wave without distortion) in a frequency range including up to 0.2 Hz, and the same frequency as the reference signal among the input signals sent from the preamplifier 25 A band-pass filter 26b that passes only the signal component of the above, an AC voltage measuring unit 26c that calculates an effective voltage (absolute value) of the signal component,
And a phase measuring unit 26d for calculating a phase difference between the signal component and the reference signal.

The electromagnet current source 27 is a 647 type bipolar power supply manufactured by Lake Shore of the United States, and the like.
A current proportional to the voltage of the reference signal from “a” (alternating current synchronized with the reference signal) is generated and supplied to the coil of the electromagnet 40. As described above, the measurement system of the AC hall measurement apparatus 100 applies an AC magnetic field synchronized with the AC signal from the reference signal generation unit 26a to the sample 34, and responds (Hall electromotive voltage) from the sample 34 thereto. A synchronized loop is formed in which the signal is extracted in synchronization with the AC signal (the same frequency component is measured as a vector).

Although not shown in FIG. 3, the measuring unit 20 includes a measuring device directly contributing to the Hall effect measurement, and also facilitates automatic control by the control unit 10. (A voltmeter that measures the compliance voltage of the constant current source 21, a voltmeter that measures the difference between the output voltages of the two buffer amplifiers 24a and b, and the temperature of the sample 34 in the cryostat 31.
Control device for controlling the temperature).

FIG. 4 is a block diagram showing a detailed functional configuration of the control unit 10 of the AC hole measuring apparatus 100.
FIG. 5 is a screen display example for the operator to select and instruct processing by each functional block shown in FIG. The control unit 10 is a controller of the AC hall measurement device 100, and has seven large functions that can be selected by the operator using the menu shown in FIG. 5A, that is, the setting unit 11, the display unit 12, Graph unit 13, file unit 14,
It comprises a measurement unit 15, a confirmation function unit 16, and an option unit 17.

The setting unit 11 has a function of acquiring an instruction on the type of measurement, conditions, and the like from the operator and storing the instruction as a file, as listed in the pull-down menu shown in FIG. 5B. Having. Specifically, a comment such as a sample name added to the measurement data is acquired as in the screen display example shown in FIG. 6, or the sample is displayed on the sample as in the screen display example shown in FIG. Acquisition of measurement conditions such as the applied current value, acquisition of measurement conditions related to temperature control of the sample 34 by the cryostat 31 as in the screen display example shown in FIG. 8, and display of the screen table shown in FIG. As shown in the example,
Analysis conditions such as the number of digits when performing arithmetic processing using the measured values are obtained, and the specifications and correction coefficients of each measuring device constituting the measuring unit unit 20 are acquired as in the screen display example shown in FIG. Or get system setup information.

The "kind of measurement" includes an ohmic measurement for measuring a resistance between electrodes of a sample, a specific resistance measurement by a Van Der Pauw method, and the like, in addition to a Hall effect measurement for measuring a Hall electromotive voltage. The display unit 12 has a function of displaying and outputting the measurement results obtained by the measurement unit 15 on a CRT or the like, and as detailed in the pull-down menu shown in FIG. Displays results, displays detailed results of resistivity measurement, displays detailed results of Hall effect measurement, displays a list of measurement results that summarizes only the main results of each measurement for each temperature And display data such as measured values obtained during the measurement in real time.

The graph section 13 has a function of graphing the measurement results obtained by the measurement section 15 and displaying and outputting the graph on a CRT or the like. As shown in the pull-down menu shown in FIG. In addition, a graph of ohmic characteristics indicating the current dependency of the inter-electrode resistance is displayed, and a graph of temperature characteristics indicating the temperature dependency of the Hall electromotive voltage is displayed.

The file section 14 has a function of managing a data file in which parameters acquired from the operator by the setting section 11 and measured values read from the measuring unit section 20 by the measuring section 15 are recorded. Then, as listed in the pull-down menu shown in FIG.
Displays a detailed list of the contents of each file stored on the hard disk, etc., opens a specified file and reads data into memory, saves measurement results in memory along with measurement conditions, etc. to the hard disk, performs measurement Saves only the conditions to the hard disk, saves only the measurement results to the hard disk, prints out the measurement results and the like in the memory to a printer, sets the printer model, and terminates the operation of the AC hole measurement device 100 Or let it.

The measuring section 15 has a function of automatically measuring the Hall effect and the like while communicating with each measuring instrument of the measuring unit section 20, and is listed in the pull-down menu shown in FIG. In the meantime, the measurement is started according to the measurement conditions set by the setting unit 11, the obtained measured values and the like are displayed on the screen and saved on a hard disk, or the measurement is started from the middle of the designated temperature sweep, When the obtained measurement value is not stable with time, the state is not exited from the stability determination processing loop. For example, the measurement value is forcibly exited, or the measurement is forcibly terminated during the measurement.

The confirmation function unit 16 has a function of individually confirming the operation of measuring instruments and the like constituting the measuring unit unit 20.
As enumerated in the pull-down menu shown in FIG. 5 (g), manual settings such as transmitting a specific command to each measuring device based on an instruction from the operator are performed, and the measuring devices and the like are set. It returns to the initial state and terminates this confirmation function.

The optional section 17 is an additional function provided in the AC hole measuring apparatus 100, and is shown in FIG.
As shown in the pull-down menu shown in (1), all the measuring instruments and the like connected to the control unit 10 are initialized, and when saving data, the data is saved in a dedicated file format designated by the operator. To determine whether the measurement result is within the range specified by the operator, display the version of the control program of the AC hall measurement device 100, and perform other measurements. (Magnetic resistance measurement, Seebeck measurement).

Next, the characteristic operation of the AC hole measuring apparatus 100 configured as described above will be described. FIG.
FIG. 13 shows a large flow of an operation procedure in the Hall effect measurement in an AC magnetic field by the AC Hall measurement device 100,
That is, it is a hierarchical flow chart showing the flow of processing when the measuring unit 15 executes the Hall effect measurement using the AC magnetic field in accordance with the measurement conditions set by the setting unit 11. FIG. 11 shows the overall flow of the Hall effect measurement, and FIG. 12 shows the details of the measurement (hereinafter, referred to as “single measurement”) common to each of the two steps S50 and S51 shown in FIG. The flow is shown in FIG.
Further includes three steps S60 shown in FIG.
A detailed flow of measurement common to each of S61 and S62 (hereinafter, referred to as “basic unit measurement”) will be described.

In this Hall effect measurement, as shown in FIG.
The electrode No. of the sample 34. 1 and No. 3 is used as a current application terminal to perform a single measurement (step S50).
Electrode No. 2 and No. 4 is used as a current application terminal to perform the same single measurement (step S51). And
Based on the measured values obtained by these two single measurements (hereinafter, these two “single measurements” are referred to as “double measurements”), processing and evaluation of the absolute value of the Hall electromotive voltage (vector) and ( (Step S52), phase processing and evaluation (Step S53), estimation of a range of variation in measured values, that is, estimation of a true value (Step S54), and determination of a carrier type are performed (Step S55). Next, a display output of the result obtained by those processes is performed (step S55).

In the single measurement (steps S50 and S51 in FIG. 11), first, as shown in FIG. 12, two sample electrodes (No. 1 and No. 3 or N
o. 2 and No. 4), the current Is in the forward (positive) direction
Is applied to perform a basic unit measurement (step S60), and then a current Is is applied in the reverse (negative) direction to perform the same basic unit measurement (step S61), and again in the forward (positive) direction. The same basic unit measurement is performed by applying the current Is (step S62). Finally, the absolute values are processed and evaluated for the measured values (vectors) obtained by the three basic unit measurements (step S62). In step S63, the phase is processed and evaluated (step S64).

Further, in the basic unit measurement (steps S60, S61 and S62 in FIG. 12), as shown in FIG.
After applying the current Is to the sample electrodes in the designated direction (step S70), the reference signal generator 26a
, The AC magnetic field B is applied to the sample 34, and a Hall electromotive voltage (vector) that changes following the magnetic field is continuously sampled N times by the AC synchronous signal analyzer 26 (step). S71). Then, the average value D of the sampling values
(Step S72)
The absolute value Sd of the standard deviation with respect to the average value D is calculated (step S73), and the gains of the buffer amplifiers 24a and 24b, the gain of the preamplifier 25, and the AC synchronization signal analyzer 26 are calculated for the average value D and the standard deviation Sd. Correcting the frequency characteristic of the amplifier system (step S7)
5). Finally, the current is flowing through the sample is actually measured by the ammeter 23 (step S75).

Next, the detailed contents of the control and calculation processing in each step shown in FIGS. 11 to 13 will be described.
"Basic unit measurement", "Single measurement", "Double measurement"
Will be described in this order. FIG. 14 is a diagram showing the meanings of symbols used in the detailed description and the calculation process. That is, FIG. 14A shows the meanings of the symbols constituting the measurement conditions and the initial conditions set by the setting unit 11, and FIG.
(B) indicates the measurement values obtained in the three types of measurement (“basic unit measurement”, “single measurement”, and “double measurement”) and the symbols of the values derived from the measurement values by arrows corresponding to the derivation process. It is shown with a line. [Basic unit measurement] (Details of each step shown in the flowchart of FIG. 13) a. Step S70 The constant current source 21 applies the current Is to the sample 34, and waits until the system reaches a stable state. Specifically, a-1. The value of the ammeter 23 is read at regular intervals (sampling time). If the rate of change of the readings for N consecutive times (the number of stable times) is equal to or less than the reference value (stability condition%), it is determined that the stability has been reached and the process proceeds to the next step. However, if stability is not reached even after a certain number of measurements (maximum number of measurements), such a "wait for stability"
Abandon and proceed. In this case, the data is marked and output for display.

A-2. Compliance voltage of constant current source 21
(Vcomp.) Is read by a voltmeter (not shown) at regular time intervals (sampling time). If the rate of change of the readings for N consecutive times (the number of stable times) is equal to or less than the reference value (stability condition%), it is determined that the stability has been reached and the process proceeds to the next step. If the stability has not been reached even after a certain number of measurements (maximum number of measurements), such a "stability wait" is abandoned, and the process proceeds to the next step. In this case, the data is marked and output for display. b. Step S71 Apply the magnetic field B (specifically, the AC synchronization signal analyzer 2
6), while measuring the Hall electromotive voltage (voltage between Vhi and Vlo) of the sample 34, extracting only the frequency Freq [Hz] component, and using a complex number (vector) model. The expressed values (specifically, the measurement values of the AC voltage measurement unit 26c and the phase measurement unit 26d of the AC synchronization signal analyzer 26) are continuously recorded. Let these readings (vectors) be a1, a2,... Ai,... And wait until the readings reach a stable value. Specifically, a value obtained by differentiating b-1.aj with respect to j at a differentiation interval sk is defined as bj as follows. When sk is 1, continuous differentiation is performed.

[0036]

(Equation 1)

B-2. The number of smoothing times sm is determined in consideration of the sheet resistance value rsheet of the sample and the magnetic field frequency Freq, and bj is smoothed (simple moving average) as follows.
And

[0038]

(Equation 2)

B-3. The absolute value of the value obtained by differentiating the phase of the cj vector with respect to j is defined as the phase variation angle pj as follows.

[0040]

(Equation 3)

B-4. When the phase variation angle pj exceeds rph degrees consecutively rnd times, it is determined that the measured value has been stabilized. For example
If rnd = 4, rph = 45,

[0042]

(Equation 4)

Is determined to be stable. Note that in a state where the reading has not yet reached the stable value and is drifting toward the stable value, it means that the drift speed is higher than random fluctuation due to noise. That is, the differential vector of the reading value is directed in a certain direction, and the differential value of the angle (phase) falls within a range of approximately ± 45 degrees centering on 0 degree. However, once the stable value is reached, the readings show random wander around the stable value, and the direction of the differential vector becomes random without being constant. That is, the differential value of the phase angle also takes a random value in the range of ± 180 degrees.

Here, when calculating the probability P that the absolute value of the derivative of the phase angle exceeds 45 degrees,

[0045]

(Equation 5)

The probability P4 that this occurs four times in succession is

[0047]

(Equation 6)

Assuming that the measurement is repeated L times, the probability PL of 45 degrees or more for four consecutive times during the measurement is as follows:

[0049]

(Equation 7)

For example, if L = 9,15

[0051]

(Equation 8)

From this, it can be seen that this phenomenon occurs with a probability of approximately 90% when the measurement is repeated at least 9 times, and 99% when the measurement is repeated 15 times. b-5. The readings aj-N + that are (N-1) retrospective readings from the reading aj of the j-th AC synchronous signal analyzer 26 corresponding to pj at this time
Up to 1 are defined as N measurement results (raw data).

[0053]

(Equation 9)

As shown in the screen display example of FIG. 9, when the AC magnetic field analysis mode is Fast, sk = 1, rnd = 4, r
ph = 30, Normal: sk = 2, rnd = 4, rph = 45, HiAccu
For racy, set sk = 3, rnd = 4, rph = 45, respectively. Therefore, N can take values from 6 to 8. c. Step S72 The average (simple vector addition) value of the N pieces of data d1, d2,.

[0055]

(Equation 10)

D. Step S73 The absolute value of the standard deviation (vector) of d1,... DN with respect to the average value D is defined as Sd as follows.

[0057]

[Equation 11]

E. For steps S74 D and Sd, the buffer amplifier 24
The correction is performed by the gain Gba of a and b, the gain Gpa of the preamplifier 25, and the frequency characteristic Famp (vector) of the amplifier system.

[0059]

(Equation 12)

F. Step S75 The current actually flowing through the sample is actually measured by the ammeter 23, and is set as is (scalar). However, if the measured current is equal to the applied current Is because the sample has low resistance, the applied current value is relatively large (for example, is> 1 μA), and is stable, Is the value signed with Is
Is used as the value of. [Single measurement] (Details of each step shown in the flowchart of FIG. 12) a. Step S60 A basic unit measurement is performed by applying Is in the forward (positive) direction, and the obtained vector value D is D1 +, standard deviation. Sd is Sd1 +, current value is
Is Is1 +. b. Step S61 Basic unit measurement is performed by applying Is in the reverse (negative) direction, and the obtained vector value D is D1-, the standard deviation Sd is Sd1-, and the current value is
Is Is1-. c. Step S62 The basic unit measurement is performed by applying Is again in the forward (positive) direction, and the obtained vector value D is set as D2 +, the standard deviation Sd is set as Sd2 +, and the current value is set as Is2 +. d. Step S63 Process and evaluate the measurement data (absolute value). Specifically, the difference between d-1.D1 + and D1- is calculated, and 1 /
Let 2 be Dv1.

[0061]

(Equation 13)

At this time, the Hall coefficient (Hall electromotive voltage) is not obtained by dividing D by the individual current value is. This is because if they are divided individually, the offset vector (noise) cannot be canceled well. d-2. The value obtained by dividing the square root of the mean square of Sd1 + and Sd1- (the variance of D1 + and D1- should be the same condition, the standard deviation can be obtained by the root mean square) As follows,
Sdv1, which is regarded as a range of variation with respect to Dv1.

[0063]

[Equation 14]

The reason for dividing by the square root of N is as follows. That is, in general, the measurement values of a measuring instrument in which the fluctuations occur completely at random have a normal distribution centered on the true value. Therefore, taking the average of N measurements,
The standard deviation is 1 for one measurement as follows:
/ N.

[0065]

(Equation 15)

However, when the variation is not random and the variation is caused by a certain factor, for example, when the measured value changes due to a change in the temperature of the measured object, the measured values are averaged. Nor does the standard deviation decrease. That is, the following holds.

[0067]

(Equation 16)

In reality, it is considered that both of these factors are mixed.

[0069]

[Equation 17]

Is calculated. d-3. Half of the difference between Is1 + and Is1-
Isv1.

[0071]

(Equation 18)

D-4. D1- and D2 + to Dv2 in the same manner as in the above item d-1.
Is determined from Sd1- and Sd2 + to Dv2 in the same manner as in the above section d-2, and the average current Isv2 from Is1- and Is2 + in the same manner as in the above section d-3.

[0073]

[Equation 19]

D-5. The difference between Dv1 and Dv2 is calculated, and
Is Ds as follows.

[0075]

(Equation 20)

D-6. The difference between Isv1 and Isv2 is calculated, and
Is Isv as follows.

[0077]

(Equation 21)

D-7. When the double measurement is not performed (only one single measurement), the data Ds obtained here is used.
Is used as the final Hall electromotive voltage value, the Hall resistance Rs, the Hall coefficient RH, the carrier concentration CC, and the mobility MO are calculated as follows.

[0079]

(Equation 22)

D-8. Based on the same concept as in the above section d-2, the range Sds of the variation of Ds is as follows: the root 2 of Sdv1 and Sdv2.
It is a root mean square.

[0081]

(Equation 23)

D-9. The ratio of Sds to the size of Ds is SDratio
As shown below, noise is displayed in units of%, which is one of the reliability measures.

[0083]

(Equation 24)

D-10. SDratio (% noise) is ideally 0,
If it is smaller than 0.1 (10%), it is considered good. Conversely, if it is larger than 1 (100%), the determination of the carrier type as well as the Hall coefficient becomes suspicious. If it exceeds the square root of N (see section d-2 above) (eg, 245% or more if N = 6), the measurement fails completely. e. Step S64 Process and evaluate the phase data. Specifically, the phase angle of e-1.Ds is Phs as follows. When Ph is 0 degree, it is determined to be a P-type carrier, and when 180 degree, it is determined to be an N-type carrier.

[0085]

(Equation 25)

E-2. Since Dv1 and Dv2 are originally of the same magnitude and of opposite phase (inverted), the sum of Dv1 and Dv2 should be zero. However, since there is a value when the variation error is large, half of this sum is defined as Inv as follows.

[0087]

(Equation 26)

E-3. The ratio of the absolute value of Inv to Ds described above is standardized by setting Inv.ratio as follows:
alize), and this is used as an index of phase inversion. Also, the unit is converted to% and displayed as a drift rate.

[0089]

[Equation 27]

E-4. Inv.ratio (drift rate) is ideally 0, and usually shows a value almost equal to SDratio (noise%). S
When the ratio is larger than Dratio (noise%) or larger than 1 (100%), the phase is not inverted, that is, the possibility that the voltage other than the Hall effect is dominant increases. e-5.Phs
Must be 0 or 180 degrees. When taking other values, the following two cases can be considered.

E-5-1. When the Inv. Ratio (drift rate) of the above item e-3 is large: the Hall electromotive voltage is not remarkable, and the reliability of the phase information itself is low. That is, it is highly likely that the value indicates a random value including the absolute value. e-5-2. When the sample has high resistance: The internal resistance of the Hall electromotive voltage is high, so that the time constant of the input section of the measurement system increases, and the phase of the input signal (AC Hall electromotive voltage) shifts (delays). In this case, Inv.ratio (drift rate) is not large. It can be said that the measurement is normal if the shift amount is commensurate with the sample resistance, but it seems difficult to measure accurately if the shift amount exceeds 45 degrees. However, it can be confirmed more reliably by double measurement. [Double measurement] (Details of each step shown in the flowchart of FIG. 11) a. Step S50 A single measurement is performed using the sample terminal No. 1-3 as a current application terminal, and the obtained data Ds and Rs are converted to Ds5 and Rs5. , Standard deviation Sds
ds5, the applied current value Isv is Is5, and the phase angle Phs is Phs5. b. Step S51 A single measurement is performed using the sample terminal No. 2-4 as a current application terminal, and the obtained data Ds and Rs are Ds6 and Rs6, and the standard deviation Sds is S
ds6, the applied current value Isv is Is6, and the phase angle Phs is Phs6.

Note that among the above data, Ds5, Rs5, Ds6, Rs
6 is a vector, and Sds5, Sds6, Is5 and Is6 are scalar quantities, respectively. c. Step S52 Process and evaluate the measurement data (absolute value). Specifically, c-1. Ds5 and Ds6 divided by the applied currents IS5 and IS6 (R
s5 and Rs6) and calculate the half of the sum as follows:
The average Hall resistance Rw (vector) is used.

[0093]

[Equation 28]

C-2. The simple and average value of Is5 and Is6 is defined as Iw (scalar) as follows.

[0095]

(Equation 29)

C-3. The average Hall electromotive voltage Dw (scalar) is obtained by multiplying the absolute value of Rw by Iw as follows.

[0097]

[Equation 30]

C-4. Using the absolute value of Rw as the final value of the Hall measurement, the Hall coefficient RH, the carrier concentration CC, and the mobility MO are calculated as follows.

[0099]

(Equation 31)

C-5. The root of the sum of squares of Sds5 and Sds5
And Sdw as follows. The ratio of Sdw to the magnitude of Dw is defined as SDw.ratio as one of the reliability measures as follows. Also, convert the unit to%,
Displayed as noise% during double measurement.

[0101]

(Equation 32)

C-6. SDw.ratio (noise% at the time of double measurement) may be about the same value as the sum of two SDratio (noise% at the time of single measurement). When SDratio (noise% during single measurement) is small but SDw.ratio (noise% during double measurement) is particularly large, non-operating of sample or electrode
Mickiness is considered. d. Step S53 Process and evaluate the phase data. Specifically, the phase angle of d-1.Rw is defined as a phase Phw indicating the polarity of the Hall electromotive voltage as follows. When Phw is 0 degree, it is determined to be a P-type carrier, and when Phw is 180 degrees, it is determined to be an N-type carrier. I do.

[0103]

[Equation 33]

D-2. Rs5 and Rs6 should originally be the same value, but the values may be different. Therefore, Rw of these differences
The ratio of the absolute value to
io, the unit converted to% is displayed as direction dependency, and is used as an index indicating the anisotropy (heterogeneity) of the sample (electrode).

[0105]

(Equation 34)

D-3. Aratio (direction dependency) is ideally 0,
Normally, it shows a value similar to SDratio (noise% during single measurement). If it is larger than 1 (100%), the reliability as a measured value is extremely low. In this case, the following can be considered. d-3-1. When Ds5 and Ds6 are generated due to unbalance and magnetoresistance or induction of the sample electrode: Since the actual electrode positions of Ds5 and Ds6 are symmetrical from the viewpoint of the logical electrode arrangement,
In this case, the phases are opposite to each other (original phases are the same).
Therefore, Ds has poor data reliability because Ds5 and Ds6 cancel each other. In this case, SDw.ratio (noise% during double measurement) takes a value smaller than Ratio (direction dependency).

D-3-2. In the case where the voltage due to factors other than the Hall effect is dominant: The voltage takes on a completely dashed value. In this case, SDw.ratio (noise% in double measurement) is as large as Aratio (direction dependency), and Inv.rati in single measurement
Because of the large o (drift rate), it is often possible to confirm that the data is not reliable.

D-3-3. When the phase is shifted to the negative side due to the high resistance of the sample: If the internal resistance or the electrode resistance of the sample is different between the electrode terminals, the amount of the phase shift will be different. . In this case, Inv.ratio (drift rate) is not large, and it can be confirmed that Phw is shifted from 0 or 180 degrees. SDw.ratio (Noise% during double measurement) and Ara
When both tio (direction dependence) are particularly large, the specific resistance (Va
nDerPauw) Noise and F value (balance factor) during measurement
Need to be reviewed. e. Step S54 A range (true value) of the variation is estimated.

E-1. Estimate the range of variation in measured values.
If the Phw shifts from 0 or 180 degrees to the negative side due to the high resistance of the sample, the Hall EMF is also observed to be smaller than the actual value, and the true value shifts to a larger value than the measured value and fluctuates. Could be. So,
This shift is also estimated using the phase shift amount Ph.shift. However, when the amount of phase shift exceeds 90 degrees, estimation is impossible.

[0110]

(Equation 35)

E-2. From the sum of the variation ranges of Ds5 and Ds6,
The range of variation of Rw (Rwmin-Rwmax) is determined as follows.

[0112]

[Equation 36]

However,

[0114]

(37)

It is assumed that Note that Rwmin and Rwmax are scalar quantities. Sds' is for correcting the attenuation of the Hall electromotive force value when the sample has a high resistance. When only single measurement is performed,

[0116]

(38)

Is used. If Dw is considerably smaller than the value of Ds due to a large e-3.Aratio (direction dependency), Rwmin calculated based on the value of Ds may not be realistic. In that case, as shown below, based on the value of Dw,
Recalculate min.

If

[0119]

[Equation 39]

If

[0121]

(Equation 40)

It is assumed that e-4.Hall coefficient obtained from Rw / s.min, carrier concentration, and mobility are respectively RHmin, CCmax, and MOmin, and those obtained from Rw / s.max are RHmax, CCmin, and MOmax, as follows. RH,
The true value ranges of CC and MO are estimated respectively. However, Rw /
When s.min is negative, RHmin and MOmin are set to 0, and CCmax is set to infinity.

[0123]

[Equation 41]

E-5. If the sample has a high resistance and a phase shift, the true value of the Hall electromotive voltage can be corrected using the cosine of the phase shift amount Ph.shift. However, this is a convenient option and has no theoretical basis, and is used only as a guide.

[0125]

(Equation 42)

F. Step S55 The carrier type of the sample 34 is determined. Specifically, the carrier type is determined based on the phase angle Phw obtained by f-1. Double measurement. When only a single measurement is performed, Phs is replaced with Phs (step S64).
a)).

F-2. P-type when Phw is 0 degree, N-type when Phw is 180 degree
Although it is a rule to judge the type, since the phase angle actually varies, it is defined as follows.

[0128]

[Equation 43]

F-3. Since there is ambiguity in the phase angles other than those described above, the judgment is displayed with a mark as shown below.

[0130]

[Equation 44]

F-4. When SDw.ratio (noise% during double measurement) or Aratio (direction dependency) exceeds 100%, the reliability of the phase angle value itself is low, so that Only the mark is displayed without judging the carrier type. Inv.ratio (drift rate) at single measurement is 100%
When the number exceeds the limit, only the? Mark is displayed for the same reason. ? f-5.SDw.ratio (% of noise in double measurement) or Aratio
If the (direction dependency) exceeds 30% even if it does not exceed 100%, it is considered that there is some influence on the determination of the carrier type. To display. If the Inv.ratio (drift rate) during single measurement exceeds 30%, it is displayed with a mark for the same reason.

[0132] P? Or N? F-6. If the above item f-3. And item f- 5 . Are satisfied at the same time, two? Marks are displayed as follows. Become. P ?? or N ?? FIG. 15 is a screen display example showing the result of the Hall effect measurement by an AC magnetic field measurement apparatus 100 using an AC magnetic field. That is, the measurement unit 15 executes the measurement of the Hall effect according to the measurement conditions set by the setting unit 11, and displays and outputs the measured values and the calculation results obtained as a result.

The meaning of each of the items (1) to (27) shown in the figure is as follows. (1) Temperature sweep number This is the number in the temperature sweep of the measurement temperature (measurement point) displayed in item (2) on the right. (2) Measurement temperature This is the temperature of the sample corresponding to the measurement result displayed on this screen. (3) Connection terminal Indicates the connection terminal (electrode number of the sample) of the voltage value displayed in the list box of item (5). This item can be changed by the operator. (4) Measured voltage value The value (voltage value and phase) read by the AC synchronization signal analyzer 26 at each connection terminal is shown. (5) Terminal between 1-3 No. of sample The measurement result when a current is applied to the terminal between 1-3 is shown. (6) Terminal between 2 and 4 No. of sample The measurement results when a current is applied to the terminal between 2 and 4 are shown. (7) Current [A] Read values Is1 +, Is1 of ammeter 23 in single measurement
-, Is2 +. (8) Voltage [V] Indicates the average voltage values D1 +, D1-, and D2 + by the AC voltage measurement unit 26c in the single measurement. Buffer amplifier 24
a, b, values after performing gain correction and the like of the preamplifier 25. (9) Phase [degree] Indicates the average phase value by the phase measurement unit 26d in the single measurement. This is a value after performing phase correction and the like of each measuring instrument, connection cable, and other systems. (10) Noise [V] Values Sd1 + and Sd representing voltage and phase standard deviations by AC synchronous signal analyzer 26 in single measurement.
1-, Sd2 +. (11) << Hall voltage between terminals >> +/- Hall electromotive voltage D obtained by calculating from the voltage and phase of the AC synchronous signal analyzer 26 at the (+) current and the (-) current of each terminal.
v1, phase, and noise SdV1. (12) << Hall voltage between terminals >>-/ + Hall electromotive voltage D obtained by calculating from the voltage and phase of the AC synchronous signal analyzer 26 at the (-) current and the (+) current of each terminal.
v2, phase, and noise SdV2. (13) << Hole Voltage Between Terminals >> Noise [V] The range Sds of the variation of the Hall electromotive voltage at each terminal is shown. (14) << Hole voltage between terminals >> [%] Indicates the ratio of noise to the Hall electromotive voltage at each terminal. (15) << Hole voltage between terminals >> Drift rate [%] The current at each terminal is calculated from (+) current to (-) current, and (-) current to (+).
9 shows the phase reproducibility Inv.ratio of the AC synchronization signal analyzer 26 when the current is used. (16) << Overall result >> Hall electromotive voltage [V] Shows the Hall electromotive voltage Ds or Dw as the overall result. (17) << Comprehensive result >> Phase [degree] Indicates the phase Phw as a comprehensive result. (18) << Overall Result >> Noise [V] Indicates the noise SDw.ratio as the overall result. (19) << Comprehensive Result >> [%] Indicates the ratio of noise to Hall EMF as a comprehensive result. (20) << Comprehensive result >> Direction dependence [%] The result of the terminal between 1-3 (Rs5) and No. Indicates whether the result (Rs6) of the terminal between 2 and 4 is the same. In particular,
The ratio of the absolute value to Rw (= Dw / Is) of the overall result is defined as direction dependency, and the anisotropy (heterogeneity) of the sample is shown. (21) Carrier type Indicates the carrier type of the sample determined from the overall result phase Phw. (22) Hall coefficient Indicates the Hall coefficient determined from the Hall electromotive voltage of the overall result. (23) Carrier concentration Indicates the carrier concentration determined from the Hall electromotive voltage of the overall result. (24) Sheet carrier concentration A value obtained by dividing the carrier concentration by the thickness of the sample. (25) Mobility Shows the mobility of the sample determined from the Hall electromotive voltage of the overall result. (26) Minimum value-Maximum value The minimum value and the maximum value of the values of the items (22) to (25) are shown. (27) Others A button for switching to a screen showing other auxiliary measurement results (such as the frequency of an AC magnetic field).

Thus, as shown in the noise values (items (10), (13), (18), etc.) in this display screen example, according to the AC hall measuring apparatus 100, only the measured values are used. Instead, the variation (standard deviation) of the measured value based on a plurality of samplings by the measuring instrument is shown. Further, “minimum value−maximum value” (item (2
As shown in 6)), the variation range of the final result (true value) obtained by the calculation of the measured values is 1
It is estimated and displayed within the range of sigma (standard deviation).
This can avoid the risk that the measurer mistakes the reliability of the measurement result.

Further, this AC hole measuring apparatus 100
In a single measurement, the polarity of the current applied to the sample is inverted, and the Hall electromotive voltage (vector) obtained when the current is positive, the Hall electromotive voltage (vector) obtained when the current is negative is simply calculated as the absolute value. Instead of subtracting each other, the vector is subtracted. This cancels out all unnecessary noises that do not depend on the polarity of the applied current, that is, noises having a phase difference of 0 degree or 180 degrees from the applied current, as well as noises having any phase difference. Therefore, various noise components superimposed on the Hall electromotive voltage are removed, and highly accurate Hall effect measurement is realized.

Next, among the correction functions of the AC Hall measurement device 100, a correction function for the non-linearity of the electromagnet 40 (non-linearity in the coil current vs. the magnetic field strength) will be described. 16A and 16B are diagrams for explaining the correction function. FIG. 16A is a graph showing the relationship between the coil current of the electromagnet 40 and the magnetic field strength, and FIG. 1 shows a configuration and connections of a measuring instrument and the like when performing a calibration for calculating a correction coefficient for correcting an error.

In general, when a large current is applied to the electromagnet of the iron core, the magnetic flux saturates inside the iron core. Therefore, as shown in FIG. It is in. Therefore, even when a complete sine wave current is applied from the reference signal generator 26a via the electromagnet current source 27, the generated magnetic field has a distorted waveform instead of a sine wave. Therefore, if the magnetic field strength of the electromagnet 40 is uniquely specified by simply performing a proportional conversion on the voltage value of the reference signal from the reference signal generating unit 26a (or the current value generated by the electromagnet current source 27), the magnetic field Proportional to the Hall EMF and the magnetic field strength generated depending on the temperature (that is, Hall coefficient)
Is not found exactly.

Therefore, the AC hole measuring device 100
The electromagnet 40 is preliminarily determined using a reference Hall element.
The relationship between the current vs. the magnetic field strength is measured in advance, and based on the measurement result, the current required to generate the magnetic field of the designated magnetic field strength is calculated backward and applied to the electromagnet 40. Specifically, first, as shown in FIG. 16B, a probe 28a using a Hall element as a sensor is used.
And a Gauss meter (magnetic field strength meter) 28b for outputting a voltage proportional to the Hall electromotive voltage (that is, the magnetic field strength) as an analog signal, setting the Hall element between the magnetic poles of the electromagnet 40, The signal is connected so as to be input to the AC synchronization signal analyzer 26.

Then, the operator causes the AC hall measuring apparatus 100 to execute the automatic calibration of the magnetic field by using the function of the system setup (magnetic field calibration) by the setting unit 11. Then, according to the condition regarding the automatic calibration input by the operator, the measuring unit 15 sets the AC synchronization signal analyzer 26
The reference signal generator 26a sequentially generates a plurality of reference signals having different amplitudes, and obtains a value observed by the AC synchronizing signal analyzer 26 for each amplitude reference signal (the analog signal output from the Gauss meter 28b). Of these, the effective value of the same frequency component as the reference signal) is recorded. Then, a curve equation relating the two is calculated by the least square method.

The measuring unit 15 measures the reference signal by the voltage sweep and calculates the curve equation at 0.2 Hz,
The processing is executed for each frequency of 0.01 Hz, 0.02 Hz, and 0.01 Hz, and the obtained coefficients of the curve equation are stored. FIG. 17 is a screen display example showing the function of the magnetic field calibration by the setting unit 11. In the figure, the applied current [A] to the electromagnet 40 at a frequency of 0.2 Hz (this is a value obtained by multiplying the voltage of the reference signal from the reference signal generation unit 26a by a constant conversion coefficient), A measured value field consisting of the observed magnetic field strength [T] of the electromagnet 40 (this is a value obtained by multiplying an AC voltage extracted by the AC synchronization signal analyzer 26 from an analog signal from the Gauss meter 28b by a constant conversion coefficient); , A formula (calibration formula) of an approximate cubic curve relating them and the like are shown.

In the actual measurement of the Hall effect for the sample 34, the measuring unit 15 refers to the calibration equation for each frequency calculated in this way, and determines the frequency of the applied magnetic field and the magnetic field specified by the operator. Based on the intensity, an applied current to the electromagnet 40 necessary to generate the magnetic field is specified, and a reference signal of a voltage corresponding to the applied current is referred to as a reference signal generator 26.
a. As a result, in the actual measurement of the sample 34, it is possible to accurately measure the Hall coefficient in consideration of the non-linearity of the current vs. the magnetic field strength of the electromagnet 40 without requiring a magnetic field strength meter.

Next, the significance of setting the frequency range of the AC magnetic field to 0.01 to 0.2 Hz by the AC Hall measuring apparatus 100 and the control related to the frequency will be described. FIG. 18A is a graph showing the basis for defining the upper limit of the frequency range. The voltage of the sample (Hall electromotive voltage or voltage drop) observed under each of the nine types of measurement conditions and the applied magnetic field at that time are shown. Is a plot of the relationship with the frequency of.

Note that “7065”, “6512”, and “7152” in the names given to the respective curves in the figure are the scanner 22 and the buffer amplifier 24 of Keithley, USA.
The model names of the products used as a and b. When a scanner 22 of a type called a dedicated matrix in which buffer amplifiers 24a and b are built is used, independent external buffer amplifiers 24a and 24b and a general-purpose matrix are used. Corresponds to the case where an independent external buffer amplifier 24a, b and a scanner 22 of a type called a high insulation matrix are used (however, the input resistance of the voltage measurement for the sample is All are 100T ohms or more). Also, "1T_HVG", "1T_HVG"
00G_HVG ”and“ Dire_HVG ”are pseudo samples (four 1TΩ) having an interelectrode resistance of about 1TΩ, respectively.
Of which reference resistors are connected in series and in a circulating manner), 10
This corresponds to a case where a pseudo sample of about 0 GΩ (similarly connected to four 100 GΩ reference resistors) and a compound semiconductor (GaAs) of about 1 MΩ are measured.

As shown in the figure, it can be seen that the higher the resistance of the sample, the greater the attenuation of the generated voltage at a higher frequency, that is, the worse the SN ratio. For example, 6512
When a sample of about 1 TΩ is measured using the scanner 22 and the buffer amplifiers 24 a and 24 b (the curve “651
2_1T_HVG ") has about 5 at 0.01 Hz.
The signal having a voltage of 0 V is attenuated to about 15 V at 0.2 Hz.

Although not shown in this graph,
When a magnetic field having a high frequency exceeding about 0.2 Hz is generated, the level of parasitic noise generated by electromagnetic induction from the electromagnet 40 increases, and the measurement error resulting therefrom also increases. Furthermore, depending on the sample, its response (Hall electromotive voltage) is delayed due to a magnetic field of a high frequency exceeding about 0.2 Hz due to its capacitance, resulting in a phase error, which makes it difficult to determine the carrier type of the sample. Some things have a negative effect.

From the above, in order to make it possible to measure the Hall effect with an AC magnetic field substantially for a sample having a high resistance of about 1 TΩ or more, the upper limit of the frequency is about 0.2 Hz. Deemed appropriate. FIG. 18B is a graph serving as a basis for defining the lower limit of the frequency range. The reference signal output from the reference signal generation unit 26a is passed through the buffer amplifiers 24a and 24b and the preamplifier 25 to the AC synchronization signal analyzer 26 as it is. 5 is a graph showing a frequency transfer function of the AC hall measurement device 100 observed by inputting the data to the input terminal.

As shown in the figure, at a frequency close to DC of about 0.01 Hz, even if the signal is from an ideal signal source, its voltage is attenuated by about 20%. . The band-pass filter 26b and the like of the AC synchronization signal analyzer 26 form a filter that effectively removes the DC component (that is, offset drift) of noise, but has a relatively low (that is, close to DC) frequency AC. This is because the signal is also attenuated.

When a magnetic field having a frequency lower than about 0.01 Hz is used, the DC voltage due to the sample and the measuring device is reduced.
It becomes difficult to distinguish from drift, and the measurement error resulting therefrom increases. Further, it is necessary to consider that the overall measurement time required from the start to the end of the measurement is prolonged with the decrease in the frequency. From the above, it was determined that about 0.01 Hz was appropriate as the lower limit of the frequency of the applied magnetic field in the Hall effect measurement using the AC magnetic field.

In the actual measurement of the sample,
When the operator does not explicitly specify the frequency of the magnetic field, the measuring unit 15 of the AC hall measuring apparatus 100 sets the frequency to 0.2 at the start of the measurement (as a default).
Hz alternating current magnetic field is adopted. Then, the value of the phase Ph obtained in the above single measurement is 0
From 180 degrees or 180 degrees, it is determined that the frequency of the applied magnetic field is too high and not appropriate,
Re-measure at lower frequency. Specifically, if the shift amount is less than 30 degrees, re-measurement is performed at 0.01 Hz and 3
If it is 0 degrees or more, re-measure at 0.02 Hz.

As a result, in the Hall effect measurement on a sample having a high resistance, a measurement error occurs due to the deterioration of the frequency characteristic of the measurement system, that is, the measurement error is formed by the signal source resistance and the stray capacitance of the buffer amplifiers 24a and b and the scanner 22. The occurrence of the measurement error due to the phase shift based on the large time constant is automatically suppressed. As described above, the AC hole measurement device according to the present invention has been described based on the embodiment.
The present invention is, of course, not limited to this embodiment.

For example, in the present embodiment, Hall effect measurement is performed by double measurement consisting of two single measurements, that is, Hall effect measurement is performed when two different electrode pairs are used for a sample to which a current is applied. The measurement results obtained in each case were averaged, but may be completed by one single measurement. Similarly, in the single measurement, three basic unit measurements in which the direction of the current applied to the sample is positive, negative, and positive are repeated, but may be performed in two positive and negative directions.

The number of times and whether or not to perform verification-based measurement are determined in consideration of the trade-off relationship between the obtained measurement accuracy (reliability and reproducibility) and the time required for measurement. An appropriate selection may be made in consideration of the properties of the target sample (resistance value, ohmic properties of electrodes, capacitance, etc.).

[0153]

As is clear from the above description, the Hall effect measuring apparatus according to the present invention is an apparatus for measuring the Hall effect of a sample using an alternating magnetic field, and has a structure of 0.01 to 0.2.
A signal generating means for generating an AC signal in a frequency range of Hz, an AC magnetic field generating means for generating a magnetic field synchronized with the AC signal and applying the magnetic field to the sample, a current applying means for applying a current to the sample, A buffer means for detecting a Hall electromotive voltage generated in the sample and outputting a detection signal of a voltage proportional to the voltage, a filter means for passing only the same frequency component as the AC signal among the detection signals, Vector measuring means for measuring a plurality of vectors composed of an absolute value of a voltage of the signal and a phase of the signal with respect to the AC signal at each sampling time by repeating sampling at a fixed time interval for a signal indicating a frequency component. And calculating means for calculating a physical property value for specifying the Hall effect of the sample based on the plurality of measured vectors. And wherein the door.

As a result, a frequency of 0.01 to 0.2 Hz can be obtained.
Under an AC magnetic field with a very low frequency in the wave number range, only the Hall EMF component synchronized with the frequency of the magnetic field is extracted, and vector calculation considering not only the absolute value of the component but also the phase relationship with the applied magnetic field Therefore, even if the sample has an extremely high resistance of about 1 TΩ, the effect of the measurement error due to the response delay based on the time constant between the signal source resistance and the stray capacitance of the measurement system is reduced. Hall effect measurement with high accuracy is realized.

That is , a practical and valuable Hall effect measurement can be performed on a high-resistance sample of about 1 TΩ by using a measurement device that can be actually obtained from the viewpoint of both measurement accuracy and measurement time. Further, the Hall effect measuring apparatus further includes frequency optimizing means for optimizing a frequency of an AC magnetic field to be applied to the sample, and the frequency optimizing means generates an AC signal having a frequency of 0.2 Hz. Controlling the signal generation means, and controlling the vector measurement means to measure a plurality of vectors with respect to the Hall electromotive force of the sample generated under a magnetic field synchronized with the AC signal, and the measured plurality of vectors Judge whether the phase in is in a range exceeding a certain amount from a certain reference phase,
If it is in the range, the signal generating means is controlled to generate an AC signal having a frequency lower than 0.2 Hz, and the vector measuring means is configured to repeat the operation by the vector measuring means and the calculating means. And the calculation means may be controlled.

As a result, a measurement error occurs due to an excessively high frequency of the applied magnetic field, that is, a measurement error occurs due to a phase shift based on a large time constant formed by the signal source resistance and the stray capacitance of the measurement system. Are automatically suppressed. Further, the sample is connected to the tip of the core wire of a coaxial cable composed of a core wire, an inner shield and an outer shield, and is connected to the current applying means and the buffer means via the core wire. A magnetic field is applied by the AC magnetic field generating means, and at a fixed length including the tip to which the sample is connected, it is assumed that wiring is provided only by a core wire not covered with the inner shield and the outer shield. Is also good.

As a result, the generation of the parasitic current due to the movement of the core wire of the coaxial cable in the AC magnetic field is avoided, and the measurement accuracy is improved. Further, the AC magnetic field generating means includes:
A magnetic field having a magnetic field strength determined by the magnitude of the AC signal is generated, and the Hall effect measuring apparatus further includes a magnetic field correction unit that specifies a relationship between the magnitude of the AC signal and the magnetic field strength for the AC magnetic field generation unit. By referring to the specified relationship, the magnitude of the AC signal required to generate a magnetic field having a magnetic field strength to be applied to the sample is specified, and an AC signal of the magnitude is generated. Magnetic field control means for controlling the signal generation means.

As a result, the nonlinearity in the relationship between the coil current and the magnetic field strength of the AC magnetic field generating means such as an electromagnet is corrected, and the error in the calculation of the proportional coefficient (Hall coefficient) of the Hall electromotive voltage with respect to the applied magnetic field is performed. Is avoided. Further, the magnetic field correction means may include: 0.2 H
The relationship at each of a plurality of frequencies equal to or less than z is specified, and the magnetic field control unit refers to a plurality of the relationships specified by the magnetic field correction unit that correspond to the frequency of the magnetic field to be applied to the sample. Thus, the magnitude of the AC signal may be specified, and the signal generating means may be controlled.

Thus, in the correction for the non-linearity, the frequency dependence is also taken into account, so that the Hall coefficient is calculated with higher accuracy. Further, the calculation means may calculate an average value and a standard deviation for the plurality of vectors, and obtain a true value of the estimated physical property value and a variation range thereof from each of the average value and the standard deviation. This makes it possible to know the reliability of not only the measured values obtained by the measuring device but also the final measured results obtained by calculating the measured values.

Further, the current applying means applies positive and negative currents of the same magnitude to the sample, and the calculating means operates when a positive current is applied to the sample by the current applying means. By subtracting a plurality of vectors measured when a negative current is applied to the sample from a plurality of vectors measured by the vector measuring means, calculating the physical property value after calculating a net Hall EMF. May be.

As a result, all unnecessary noise that does not depend on the polarity of the applied current, that is, noise having any phase difference from the applied current is canceled out, and measurement with a high S / N ratio is realized. As described above, the present invention is a technology that enables measurement of the Hall effect on a sample having a high resistance of about 1 TΩ, and has a very high practical value in today's fierce competition for the development of new materials.

[Brief description of the drawings]

FIG. 1 is an external view of an AC hall measurement device according to the present invention.

FIGS. 2A and 2B are external views of a tip portion of a sample holder, and FIG.
Is the insulating plate ( polytetrafluoro
(B) shows the back surface of ( ethylene ).

FIG. 3 is a functional block diagram illustrating a detailed configuration of a measurement unit of the AC hall measurement device.

FIG. 4 is a block diagram illustrating a detailed functional configuration of a control unit of the AC hall measurement device.

FIG. 5 is a screen display example for an operator to select and instruct processing by each functional block shown in FIG. 4;

FIG. 6 is a display example of a screen for setting a comment such as a sample name added to measurement data.

FIG. 7 is a display example of a screen for setting measurement conditions such as a current value applied to a sample.

FIG. 8 is a display example of a screen for setting measurement conditions related to temperature control of a sample by a cryostat, and the like.

FIG. 9 is a display example of a screen for setting analysis conditions such as the number of digits when the control unit performs arithmetic processing using measured values.

FIG. 10 is a display example of a screen for setting system setup information such as a specification and a correction coefficient of each measuring device included in the measuring unit.

FIG. 11 is a flowchart showing a flow of an entire operation in the Hall effect measurement in an AC magnetic field by the AC Hall measurement device.

12 is a flowchart showing a detailed flow of a single measurement common to each of two steps S50 and S51 shown in FIG.

FIG. 13 shows three steps S60 and S shown in FIG.
It is a flowchart which shows the detailed flow of the basic unit measurement common to each of 61 and S62.

FIG. 14A shows the meanings of symbols constituting measurement conditions and initial conditions set by a setting unit, and FIG.
It is a figure which shows the measurement value obtained in "basic unit measurement", "single measurement", and "double measurement", and the symbol of the value derived from the measurement value with the arrow line corresponding to the derivation process.

FIG. 15 is a screen display example showing a result of a Hall effect measurement by an AC hall measuring device in an AC magnetic field.

16A is a graph showing the relationship between the coil current of the electromagnet and the magnetic field strength, and FIG. 16B is a graph showing a measurement when a calibration for calculating a correction coefficient for correcting the nonlinearity is performed. 2 shows the configuration and connection of the container and the like.

FIG. 17 is a screen display example showing a magnetic field calibration function of the control unit.

18A is a graph showing the relationship between the sample voltage observed under each of the nine types of measurement conditions and the frequency of the applied magnetic field at that time, and FIG. 18B is a graph showing the relationship between the reference signal generation unit and FIG. 9 is a graph showing a frequency transfer function of an AC Hall measuring device obtained when an output reference signal is directly input to an AC synchronization signal analyzer via a buffer amplifier and a preamplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Control part 11 Setting part 12 Display part 13 Graph part 14 File part 15 Measurement part 16 Confirmation function part 17 Option part 20 Measurement unit part 21 Constant current source 22 Scanner 23 Ammeter 24a, b Buffer amplifier 25 Preamplifier 26 AC synchronous signal analyzer Reference numeral 26a Reference signal generator 26b Bandpass filter 26c AC voltage measurement unit 26d Phase measurement unit 27 Current source for electromagnet 28a Probe 28b Gauss meter 30 Sample holder unit 31 Cryostat 32 Sample holder 33 Signal cable 34 Sample 35 Insulating plate 40 Electromagnet 100 AC hole measurement apparatus

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 33/06 G01N 27/72

Claims (8)

(57) [Claims] 1. An apparatus for measuring a Hall effect of a sample using an AC magnetic field, comprising: signal generating means for generating an AC signal in a frequency range of 0.01 to 0.2 Hz; and a magnetic field synchronized with the AC signal. AC magnetic field generating means for generating and applying a current to the sample, current applying means for applying a current to the sample, detecting a Hall electromotive voltage generated in the sample, and outputting a detection signal of a voltage proportional to the voltage Buffer means for filtering, and filter means for passing only the same frequency component as the AC signal in the detection signal. By repeating sampling at a fixed time interval for a signal indicating the passed frequency component, at each sampling time Vector measuring means for measuring a plurality of vectors composed of an absolute value of a voltage of the signal and a phase of the signal with respect to the AC signal; Based on the vector number, the Hall effect measurement apparatus, characterized in that it comprises a calculating means for calculating a property value that identifies the Hall effect of the sample. 2. The coaxial cable, wherein the sample is connected to a tip of a core wire of a coaxial cable including a core wire, an inner shield and an outer shield, and connected to the current applying means and the buffer means via the core wire. Of the portions to which a magnetic field is applied by the AC magnetic field generating means, at a fixed length including the tip to which the sample is connected, wiring is performed only by the core wire not covered with the inner shield and the outer shield. The Hall effect measuring device according to claim 1, wherein 3. The AC magnetic field generating means generates a magnetic field having a magnetic field strength determined by the magnitude of the AC signal, and the Hall effect measuring device further comprises: Magnetic field correction means for specifying a relationship with the magnetic field strength, and by referring to the specified relationship, the magnitude of the AC signal necessary to generate a magnetic field having a magnetic field strength to be applied to the sample is specified. 2. The Hall effect measurement apparatus according to claim 1, further comprising: a magnetic field control unit that controls the signal generation unit so as to generate an AC signal of the magnitude. 4. The magnetic field correction means specifies the relation at each of a plurality of frequencies of 0.2 Hz or less, and the magnetic field control means determines a sample among the plurality of relations specified by the magnetic field correction means. 4. The Hall effect measuring apparatus according to claim 3 , wherein the magnitude of the AC signal is specified by referring to a frequency corresponding to a magnetic field to be applied to the control unit, and the signal generating unit is controlled. 5. The calculation means calculates an average value and a standard deviation for the plurality of vectors, and obtains a true value of the estimated physical property value and a range of variation thereof from each of the average value and the standard deviation. The Hall effect measuring device according to claim 1, wherein: 6. The current applying means applies positive and negative currents of the same magnitude to the sample, and the calculating means applies a positive current to the sample when the current applying means applies a positive current to the sample. By subtracting a plurality of vectors measured when a negative current is applied to the sample from a plurality of vectors measured by the vector measuring means, calculating the physical property value after calculating a net Hall EMF. The Hall effect measuring device according to claim 1, wherein 7. A method for measuring a Hall effect of a sample using an AC magnetic field, wherein the signal generating means generates an AC signal in a frequency range of 0.01 to 0.2 Hz ; Generating a magnetic field synchronized with the AC signal in the AC magnetic field generating means to apply the magnetic field to the sample; applying current to the sample in the current applying means; and generating holes in the sample in the filter means. Passing only the same frequency component as the AC signal in the detection signal indicating the electromotive voltage; and causing the vector measurement means to repeat sampling at a fixed time interval for the signal indicating the passed frequency component, thereby Measuring a plurality of vectors consisting of the absolute value of the voltage of the signal at the sampling time and the phase of the signal with respect to the AC signal; Calculating a physical property value specifying the Hall effect of the sample based on the plurality of measured vectors. 8. A computer-readable recording medium on which a program including the steps according to claim 7 is recorded.