JP3689838B2 - Ferroelectric property evaluation system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dielectric property evaluation apparatus for evaluating characteristics of a ferroelectric material, in particular, PE hysteresis characteristics.
[0002]
[Prior art]
In recent years, research has been progressing to realize a nonvolatile memory using the hysteresis characteristics of ferroelectric materials, and from this point of view, ferroelectric evaluation devices that evaluate the electrical characteristics of ferroelectric materials are attracting attention. .
[0003]
A P (polarization) -E (electric field) hysteresis curve 13 shown in FIG. 6, which is a main electrical characteristic of the ferroelectric, can be measured and created using a Sawer-Power circuit as shown in FIG.
[0004]
In the Sawer-Power circuit, as shown in the figure, a ferroelectric capacitor 2 and a reference dielectric capacitor 3 are connected in series, and an input voltage Vin from the voltage waveform generation circuit 1 is connected between terminals of the series connection circuit. Is applied to the horizontal axis terminal of the oscilloscope 4, and the input voltage Vin applied to the series connection circuit of the ferroelectric capacitor 2 and the reference dielectric capacitor 3 is input to the horizontal axis terminal of the oscilloscope 4. The divided voltage Vc at the connection point between the Vin ferroelectric capacitor 2 and the reference dielectric capacitor 3 is input.
[0005]
In this case, the electrode area of the ferroelectric capacitor 2 is A, the charge (P + ε0 · E) · A = D · A stored in the ferroelectric capacitor 2 and the capacitance of the reference dielectric capacitor 3 is Cs, Since the charge CsVc stored in the dielectric capacitor 3 is equal, Vc = D · A / Cs is input to one vertical axis terminal of the oscilloscope 4.
[0006]
The voltage Vf applied to the ferroelectric capacitor 2 is considerably larger than Vc, and if Vin≈Vf, generally the polarization P in the ferroelectric is sufficiently large with respect to ε0 · E, so that D = P. By taking the Vc-Vin curve into consideration, a PE hysteresis curve is formed using the known film thickness t of the ferroelectric Cf, the voltage division ratio, the electrode area A, and the capacitance Cs of the reference dielectric capacitor 3. .
[0007]
A Sawyer-Tower circuit currently used as a PE thin film characteristic measurement circuit for a ferroelectric thin film is a circuit for observing the nonlinearity of a thick ferroelectric of about 0.5 cm in the late 1920s. Sawyer and C.I. H. Proposed by Tower. The horizontal axis (electric field E) of the ferroelectric PE hysteresis curve 13 shown in FIG. 6 is an electric field applied to the ferroelectric itself and is a value proportional to Vin-Vc. E = (Vin−Vc) / t, where t is the thickness of the body.
[0008]
Here, in the region where Vin≈Vf cannot be considered, E is not proportional to the input voltage Vin, but at first, the ferroelectric to be measured is thick and the electric field showing nonlinearity is It is necessary to apply a voltage of several hundred volts to several hundreds of volts to the ferroelectric, and it is difficult to directly define Vin-Vc, and the resistance partial pressure of the voltage Vin has been measured.
[0009]
The oscilloscope used for measuring the voltages Vin and Vc measures the voltages Vin and Vc by measuring the current flowing through the resistor Ry (1 MΩ to 10 MΩ), and is stored in the ferroelectric capacitor 2. In order to accurately measure the charge Q, it is necessary to use the input voltage Vin having a frequency at which the time constant given by the capacitance Cs of the ferroelectric capacitor 2 and the resistor Ry can be ignored, and the frequency dependence of the polarization P is separated. I can't think about it.
[0010]
In order to solve this problem, in Japanese Patent Application Laid-Open No. 6-249900, a ferroelectric and a known dielectric element are connected in series, an input voltage is applied to both ends of the series connection circuit, and the ferroelectric is known. A method of electrostatically measuring a potential difference between both ends of each of the dielectrics is disclosed.
However, in this method, when the potential difference between both ends of the ferroelectric and the known dielectric is measured electrostatically, the voltage amplifier connected to the ferroelectric has both ends of the input terminal floating from the ground, There is a problem that the circuit configuration becomes complicated.
[0011]
In order to solve this problem, a virtual ground circuit configured as shown in FIG. 8 has been proposed.
In this circuit, as shown in the figure, one end of a ferroelectric capacitor 2 is connected to the other end of the voltage waveform generating circuit 1 whose one end is grounded, and the other end of the ferroelectric capacitor 2 is connected to a non-inverting input terminal. Is connected to the inverting input terminal of the differential amplifier 5 which is grounded, the reference dielectric capacitor 3 is connected between the inverting input terminal and the output terminal of the differential amplifier 5, and the voltage waveform generating circuit 1 and the ferroelectric capacitor 2 are connected. Are connected to the horizontal axis terminal of the oscilloscope 4, and the output terminal of the differential amplifier 5 is connected to the vertical axis terminal of the oscilloscope 4.
[0012]
In this circuit, the input voltage Vin is applied to the ferroelectric capacitor 2 as it is, and the internal voltage of the ferroelectric capacitor 2 is determined based on the voltage Vf applied to the ferroelectric capacitor 2 by measuring Vin from Vf = Vin. The electric field E can be obtained.
Further, the charge D · A stored in the ferroelectric capacitor 2 and the charge CsVc stored in the reference dielectric capacitor 3 are equal, and by measuring the voltage Vc (= DA / Cs) proportional to D, D is obtained. In this case, since Vin = Vf, the condition of Vf >> Vc is not necessary.
[0013]
In the Sawer-Tower circuit of FIG. 7, the input impedance of the oscilloscope 4 is usually 1 MΩ to 10 MΩ, and when the capacitance of the ferroelectric capacitor 2 is about 100 pF, the charge accumulated in the ferroelectric capacitor 2 is During measurement, it flows out through the oscilloscope 4 with a time constant of about 100 μs. For this reason, when the frequency of the voltage from the voltage waveform generation circuit 1 is low, the measurement accuracy is lowered, and accurate measurement of the polarization hysteresis becomes impossible.
In addition, parasitic capacitance exists in the reference dielectric capacitor 3, the input terminal of the oscilloscope 4 and the cable, and the influence of this parasitic capacitance can be ignored when the ferroelectric capacitor 2 is about 100 pF or more.
[0014]
However, when a ferroelectric capacitor formed on a semiconductor substrate and constituting a non-volatile memory or the like is to be evaluated, the electrode area is about 100 μS or less and the capacitance is about 10 pF or less, and exists in the measurement system. The influence of parasitic capacitance cannot be ignored, and the variation in polarization hysteresis cannot be accurately evaluated.
[0015]
[Problems to be solved by the invention]
In order to solve this problem, Japanese Patent Laid-Open No. 9-129694 discloses a method for evaluating a polarization capacitor of a ferroelectric capacitor capable of evaluating accurate polarization hysteresis at a low frequency, and a ferroelectric used in a nonvolatile memory or the like. A polarization hysteresis evaluation method capable of evaluating variations in polarization hysteresis of a capacitor is disclosed.
[0016]
In Japanese Patent Laid-Open No. 9-129694, the potential of the other electrode when an alternating voltage is applied to one electrode of a ferroelectric capacitor to be evaluated for polarization hysteresis is not directly measured by an oscilloscope, but is saturated. By measuring through the MOS-FET operating in step, the charge accumulated in the ferroelectric capacitor is prevented from flowing out through the oscilloscope.
[0017]
This method is equivalent to using the differential amplifier 5 whose input resistance value is high resistance in the virtual ground circuit already described with reference to FIG. 8. In the virtual ground circuit, the voltage Vc of the reference capacitor is further reduced. By virtual grounding the detection circuit, the voltage Vf applied to the ferroelectric capacitor 2 can be calculated from the input voltage Vin.
[0018]
However, the most serious problem here is the leakage resistance 6 existing in parallel with the ferroelectric capacitor 2 as shown in FIG. 9, and when the input voltage Vin is applied, the leakage does not occur in the ferroelectric capacitor 2. The leakage current Ir flowing through the resistor 6 flows into the reference dielectric capacitor 3 and appears as a voltage at the output terminal of the differential amplifier 5, so that the accurate polarization amount of the ferroelectric capacitor 2 cannot be measured. In particular, there is a dielectric degradation characteristic as an important evaluation item as a characteristic of the ferroelectric memory material. However, it is necessary to separately evaluate whether the characteristic deteriorated by applying a pulse is leakage resistance or deterioration of PE history. There is.
[0019]
The present invention has been made in view of the current state of operation of this type of ferroelectric characteristic measuring apparatus as described above, and its object is to obtain a P− due to the leakage resistance of the ferroelectric during PE hysteresis measurement. An object of the present invention is to provide a ferroelectric characteristic evaluation apparatus capable of preventing the formation error of an E hysteresis curve and evaluating the electric field E and the polarization P with high accuracy.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a series connection circuit of a ferroelectric whose characteristics are evaluated and a reference dielectric whose characteristics are known, and a predetermined voltage waveform are supplied to the ferroelectric. Voltage waveform generating means and the series connection circuit Of the series connection circuit from the connection point of Both ends Each potential Measuring means for measuring, and current exclusion means connected to a connection point between the ferroelectric and the reference dielectric, and prohibiting leakage current flowing in a leakage resistance of the ferroelectric from flowing into the reference dielectric It is characterized by having.
[0021]
Similarly, in order to achieve the above object, the invention according to claim 2 is different from the invention according to claim 1 in that a resistance is provided between the voltage waveform generating means and the connection point of the ferroelectric substance and the current exclusion means. A resistor is connected whose value is adjusted so that the leakage current is completely eliminated by the current exclusion means.
[0022]
Similarly, in order to achieve the above object, according to a third aspect of the present invention, in the invention according to the first aspect, the current eliminator generates a similar voltage waveform having a polarity different from that of the voltage waveform generator. A resistor having a resistance value adjusted between the connection points of the current exclusion means and the ferroelectric and reference dielectric so that the leakage current is completely eliminated by the current exclusion means Are connected to each other.
[0023]
Similarly, in order to achieve the object, the invention according to claim 4 is a series connection circuit of a ferroelectric whose characteristics are evaluated and a reference dielectric whose characteristics are known, and a predetermined voltage waveform applied to the ferroelectric. Voltage waveform generating means to be supplied and the series connection circuit Of the series connection circuit from the connection point of Both ends Each potential Measuring means for measuring the voltage waveform generating means and the connection point of the ferroelectric material and the connection point of the ferroelectric material and the reference dielectric material, and the gain k is a negative value, and the voltage waveform generating means A DC amplifier that generates a similar voltage waveform having a polarity different from that of the DC amplifier, Flow through ferroelectric leakage resistance And a series connection circuit with a resistor whose resistance value is adjusted so that the leakage current is completely eliminated.
[0024]
Similarly, in order to achieve the object, the invention according to claim 5 is a series connection circuit of a ferroelectric whose characteristics are evaluated and a reference dielectric whose characteristics are known, and a predetermined voltage waveform applied to the ferroelectric. Voltage waveform generating means to be supplied and the series connection circuit Of the series connection circuit from the connection point of Both ends Each potential And a first impedance and a second impedance that are connected in parallel to the voltage waveform generating means and whose connection point is grounded Connected second A series connection circuit; Second Connected between one end of a series connection circuit and a connection point of the ferroelectric and the reference dielectric, Second By means of a series connection circuit, said Flow through ferroelectric leakage resistance And a resistor whose resistance value is adjusted so that the leakage current is completely eliminated.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
A first embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a circuit diagram showing a configuration of the present embodiment.
[0026]
In the present embodiment, as shown in FIG. 1, one end of a ferroelectric body 10 in which a ferroelectric capacitor 2 and a leakage resistor 6 are connected in parallel to the other end of the voltage waveform generating circuit 1 whose one end is grounded. The other end of the ferroelectric 10 is connected in parallel with the inverting input terminal of the differential amplifier 5 whose non-inverting input terminal is grounded and the current elimination circuit 7A into which leakage current flows. Yes.
The reference dielectric capacitor 3 is connected between the inverting input terminal and the output terminal of the differential amplifier 5, and the connection point between the voltage waveform generation circuit 1 and the ferroelectric 10 is connected to the horizontal axis terminal of the oscilloscope 4. The output terminal of the differential amplifier 5 is connected to the vertical axis terminal of the oscilloscope 4.
[0027]
In the present embodiment having such a configuration, the input voltage Vin from the voltage waveform generation circuit 1 is applied to the ferroelectric 10, and the applied voltage waveform is measured by the oscilloscope 4, and at the same time, the reference dielectric The voltage induced in the capacitor 3 is also measured.
At this time, a current equal to the leakage current Ir flowing through the leakage resistor 6 flows into the current elimination circuit 7A and is eliminated, and the leakage current Ir is prevented from flowing into the reference dielectric capacitor 3, and the ferroelectric capacitor of the ferroelectric 10 Only two charges are detected with high accuracy based on the capacitance Cs of the reference dielectric capacitor 3.
[0028]
The other operations of the present embodiment are the same as the operations of the virtual ground circuit already described with reference to FIG.
[0029]
As described above, according to the present embodiment, a current equal to the leakage current Ir flowing through the leakage resistance 6 is eliminated by the current elimination circuit 7A by the current elimination circuit 7A, and the leakage current Ir flows through the reference dielectric capacitor 3. And only the electric charge of the ferroelectric capacitor 2 is detected based on the capacitance Cs of the reference dielectric capacitor 3, and the polarization of the ferroelectric capacitor 2 is increased without an error in the polarization amount due to the leakage current Ir. It becomes possible to evaluate to accuracy.
[0030]
[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG.
FIG. 2 is a circuit diagram showing a configuration of the present embodiment.
[0031]
In the present embodiment, as shown in FIG. 2, a current mirror circuit 7B is provided in place of the current exclusion circuit 7A as compared with the first embodiment already described with reference to FIG. A resistor 8A is connected between the connection point between the generation circuit 1 and the ferroelectric 10 and the current mirror circuit 7B. The current mirror circuit 7B generates a leakage current Ir proportional to the current Is flowing through the resistor 8A. A function of flowing from the ferroelectric 10 into the current mirror circuit 7B is provided.
[0032]
Since the configuration of the other parts of the present embodiment is the same as that of the first embodiment already described, duplicate description will not be given.
[0033]
In the present embodiment having such a configuration, the resistance value of the leakage resistor 6 of the ferroelectric substance 10 is measured in advance, so that the current equal to the leakage current Ir flowing through the leakage resistor 6 can be eliminated. The resistance value is adjusted and set. In this case, when the leakage current Ir is relatively small, the current Is is adjusted to be large.
In the present embodiment, the leakage current Ir proportional to the current Is flowing through the resistor 8A having the adjusted resistance value flows into the current mirror circuit 7B, and the leakage current Ir is prevented from flowing into the reference dielectric capacitor 3. Only the electric charge of the ferroelectric capacitor 2 of the ferroelectric 10 is detected with high accuracy based on the capacitance Cs of the reference dielectric capacitor 3.
[0034]
Other operations of the present embodiment are the same as those of the first embodiment already described, and redundant description will not be given.
[0035]
Thus, according to the present embodiment, the leakage current Ir proportional to the current Is flowing through the resistor 8A having the adjusted resistance value flows into the current mirror circuit 7B, and the leakage current Ir enters the reference dielectric capacitor 3. Since it is prevented from flowing, only the electric charge of the ferroelectric capacitor 2 is detected with high accuracy on the basis of the capacitance Cs of the reference dielectric capacitor 3, and there is no error in the polarization amount due to the leakage current Ir. 2 can be evaluated with high accuracy, and when the leakage current Ir of the ferroelectric 10 is relatively small, the current Is can be increased to reduce the measurement error.
[0036]
[Third Embodiment]
A third embodiment of the present invention will be described with reference to FIG.
FIG. 3 is a circuit diagram showing the configuration of the present embodiment.
[0037]
In the present embodiment, as shown in FIG. 3, the current exclusion circuit 7A is removed from the first embodiment already described with reference to FIG. 1, and the connection between the ferroelectric 10 and the reference dielectric capacitor 3 is performed. A resistor 8B and a similar waveform generating circuit 7C are connected in series between the point and the ground.
The similar waveform generation circuit 7C has a function of generating a similar waveform having a polarity different from that of the voltage waveform generation circuit 1.
[0038]
Since the configuration of the other parts of the present embodiment is the same as that of the above-described embodiment, redundant description will not be given.
[0039]
In the present embodiment, the similar waveform generation circuit 7C operates in conjunction with the voltage waveform generation circuit 1, and at the same time, the input voltage Vin is applied to the ferroelectric 10, and the input voltage from the voltage waveform generation circuit 1 is Vin. When the output voltage of the similar waveform generation circuit 7C is kVin (k is a negative value), the leakage current Ir is set by setting the resistance value of the resistor 8B to -kRf with the resistance value of the leakage resistance 6 as Rf. And the leakage current Ir is prevented from flowing through the reference dielectric capacitor 3, and only the charge of the ferroelectric capacitor 2 of the ferroelectric 10 is based on the capacitance Cs of the reference dielectric capacitor 3. It is detected with high accuracy.
[0040]
Since other operations of the present embodiment are the same as those of the first embodiment already described, duplicate description will not be given.
[0041]
Thus, according to the present embodiment, when the input voltage from the voltage waveform generation circuit 1 is Vin and the output voltage of the similar waveform generation circuit 7C is kVin (k is a negative value), the resistance value of the resistor 8B. Is set to −kRf with the resistance value of the leakage resistor 6 as Rf, the leakage current Ir is eliminated with high accuracy and the leakage current Ir is prevented from flowing into the reference dielectric capacitor 3. Only the electric charge of the dielectric capacitor 2 is detected with high accuracy based on the capacitance Cs of the reference dielectric capacitor 3, and the polarization of the ferroelectric capacitor 2 is evaluated with high accuracy without any error in the polarization amount due to the leakage current Ir. It becomes possible to do.
[0042]
[Fourth Embodiment]
A fourth embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a circuit diagram showing the configuration of the present embodiment.
[0043]
In this embodiment, as shown in FIG. 4, the resistor 8B and the similar waveform generation circuit 7C are removed from the third embodiment already described with reference to FIG. A DC amplifier 11 and a resistor 8 </ b> C are connected in series between a connection point between the ferroelectric substance 10 and a connection point between the ferroelectric substance 10 and the reference dielectric capacitor 3.
[0044]
Since the configuration of the other parts of the present embodiment is the same as that of the third embodiment already described, duplicate description will not be given.
[0045]
In the present embodiment, the gain k of the DC amplifier 11 is set to a negative value, the resistance value Rs of the resistor 8C is set to −kRf, where the resistance value of the leakage resistor 6 is Rf, and the leakage current Ir is Excluded with high accuracy, the leakage current Ir is prevented from flowing through the reference dielectric capacitor 3, and only the charge of the ferroelectric capacitor 2 of the ferroelectric 10 is high based on the capacitance Cs of the reference dielectric capacitor 3. Detected with accuracy.
[0046]
The other operations of the present embodiment are the same as those of the third embodiment already described, and therefore will not be described repeatedly.
[0047]
Thus, according to the present embodiment, the resistance value Rs of the resistor 8C is set to -kRf, where the gain of the DC amplifier 11 is k (negative value) and the resistance value of the leakage resistor 6 is Rf. Since the leakage current Ir is eliminated with high accuracy and the leakage current Ir is prevented from flowing into the reference dielectric capacitor 3, only the charge of the ferroelectric capacitor 2 is based on the capacitance Cs of the reference dielectric capacitor 3. Therefore, the polarization of the ferroelectric capacitor 2 can be evaluated with high accuracy without error in the polarization amount due to the leakage current Ir.
[0048]
[Fifth Embodiment]
A fifth embodiment of the present invention will be described with reference to FIG.
FIG. 5 is a circuit diagram showing the configuration of the present embodiment.
[0049]
In the present embodiment, as shown in FIG. 5, an impedance 12a and an impedance 12b are connected in series between both terminals of the voltage waveform generation circuit 1. To configure the second series connection circuit The connection point between the impedance 12a and the impedance 12b is grounded. Further, a ferroelectric 10 in which a ferroelectric capacitor 2 and a leakage resistor 6 are connected in parallel and a resistor 8D are connected in series between both ends of the voltage waveform generating circuit 1. The connection point between the ferroelectric 10 and the resistor 8D is connected to the non-inverting input terminal of the differential amplifier 5 whose non-inverting input terminal is grounded, and between the non-inverting input terminal and the output terminal of the differential amplifier 5. The reference dielectric capacitor 3 is connected, the connection point between the ferroelectric 10 and the impedance 12 a is connected to the horizontal axis terminal of the oscilloscope 4, and the output terminal of the differential amplifier 5 is connected to the vertical axis terminal of the oscilloscope 4. Has been.
[0050]
In the present embodiment, by adjusting the resistance value Rs of the resistor 8D corresponding to the resistance values of the impedances 11a and 11b, a current equal to the leakage current Ir flows out of the ferroelectric 10, and this leakage current Ir is prevented from flowing to the reference dielectric capacitor 3, and only the charge of the ferroelectric capacitor 2 of the ferroelectric 10 is detected with high accuracy based on the capacitance Cs of the reference dielectric capacitor 3.
[0051]
Since other operations of the present embodiment are the same as those of the first embodiment already described, duplicate description will not be given.
[0052]
As described above, according to the present embodiment, by adjusting the resistance value Rs of the resistor 8D corresponding to the resistance values of the impedances 11a and 11b, a current equal to the leakage current Ir flows out of the ferroelectric body 10. Since the leakage current Ir is prevented from flowing into the reference dielectric capacitor 3, only the electric charge of the ferroelectric capacitor 2 is detected with high accuracy based on the capacitance Cs of the reference dielectric capacitor 3, and the leakage current is detected. It is possible to evaluate the polarization of the ferroelectric capacitor 2 with high accuracy without an error in the polarization amount due to Ir.
[0053]
【The invention's effect】
According to the first aspect of the present invention, the voltage waveform of the voltage waveform generating means is supplied to the ferroelectric whose characteristics are evaluated and the ferroelectric of the series connection circuit of the reference dielectric whose characteristics are known. Series connection circuit Of the series connection circuit from the connection point of Both ends Each potential Is measured, and the polarization characteristics of the ferroelectric are evaluated. The reference dielectric of the leakage current flowing in the leakage resistance of the ferroelectric by the current exclusion means connected to the connection point between the ferroelectric and the reference dielectric is measured. Since the inflow to the body is prohibited, only the charge of the ferroelectric capacitor is measured accurately by the reference capacitor of the reference dielectric without any error in polarization due to the leakage current. Can be evaluated with high accuracy.
[0054]
According to the second aspect of the present invention, the voltage waveform of the voltage waveform generating means is supplied to the ferroelectric substance whose characteristics are evaluated and the ferroelectric substance of the series connection circuit of the reference dielectric whose characteristics are known. Series connection circuit Of the series connection circuit from the connection point of Both ends Each potential Is measured, and the polarization characteristics of the ferroelectric are evaluated. The reference dielectric of the leakage current flowing in the leakage resistance of the ferroelectric by the current exclusion means connected to the connection point between the ferroelectric and the reference dielectric is measured. Inflow to the body is prohibited. At this time, the resistance value of the resistor connected between the voltage waveform generating means and the connecting point of the ferroelectric substance and the current exclusion means increases the leakage current value excluded by the current exclusion means. Since it is adjusted to be set with accuracy, even if the leakage current of the ferroelectric substance is small, the value of the current flowing through the resistor can be increased to reduce the measurement error, and the ferroelectric capacitor of the ferroelectric substance can be reduced. Only the electric charge is accurately measured by the reference capacitor of the reference dielectric without an error in the polarization amount due to the leakage current, and the polarization characteristic of the ferroelectric can be evaluated with higher accuracy.
[0055]
According to the third aspect of the present invention, the voltage waveform of the voltage waveform generating means is supplied to the ferroelectric substance whose characteristics are evaluated and the ferroelectric substance of the series connection circuit of the reference dielectric whose characteristics are known. Series connection circuit Of the series connection circuit from the connection point of Both ends Each potential Is measured to evaluate the polarization characteristics of the ferroelectric, but is connected to the connection point between the ferroelectric and the reference dielectric, and the current exclusion means generates a similar voltage waveform having a polarity different from that of the voltage waveform generation means. The leakage current flowing through the ferroelectric leakage resistance is prohibited from flowing into the reference dielectric. At this time, the resistance value of the resistor connected between the current exclusion means and the connection point of the ferroelectric and the reference dielectric However, since it is adjusted to completely eliminate the leakage current, only the charge of the ferroelectric capacitor of the ferroelectric is accurately measured by the reference capacitor of the reference dielectric without an error in the polarization amount due to the leakage current, This makes it possible to evaluate the polarization characteristics of the ferroelectric material with higher accuracy.
[0056]
According to the invention of claim 4, the voltage waveform of the voltage waveform generating means is supplied to the ferroelectric whose characteristics are evaluated and to the ferroelectric of the series connection circuit of the reference dielectric whose characteristics are known. Series connection circuit Of the series connection circuit from the connection point of Both ends Each potential Is measured, and the polarization characteristics of the ferroelectric are evaluated. The voltage waveform with a negative gain k between the voltage waveform generating means and the connecting point of the ferroelectric and the connecting point of the ferroelectric and the reference dielectric is measured. A series connection circuit of a DC amplifier and a resistor that generates a similar voltage waveform having a polarity different from that of the generating means is connected. By this DC connection circuit, an inflow of a leakage current flowing through the ferroelectric leakage resistance into the reference dielectric is prevented. In this case, since the resistance value of the resistor is adjusted so as to completely eliminate the leakage current, only the charge of the ferroelectric capacitor of the ferroelectric is reduced by the reference capacitor of the reference dielectric. Therefore, it is possible to accurately measure the polarization characteristics of the ferroelectric material without making an error in the amount of polarization due to.
[0057]
According to the fifth aspect of the present invention, the voltage waveform of the voltage waveform generating means is supplied to the ferroelectric whose characteristics are evaluated and the ferroelectric of the series connection circuit of the reference dielectric whose characteristics are known. Series connection circuit Of the series connection circuit from the connection point of Both ends Each potential Is measured, and the polarization characteristics of the ferroelectric are evaluated. The first impedance and the second impedance, which are connected in parallel to the voltage waveform generating means and whose connection point is grounded, are measured. Connected second The series connection circuit prohibits inflow of the leakage current flowing through the ferroelectric leakage resistance into the reference dielectric. (Second) Since the resistance value of the resistor connected between one end of the series connection circuit and the connection point of the ferroelectric and reference dielectric is adjusted so as to completely eliminate the leakage current, the ferroelectric capacitor of the ferroelectric capacitor Only the electric charge is accurately measured by the reference capacitor of the reference dielectric without an error in the polarization amount due to the leakage current, and the polarization characteristic of the ferroelectric can be evaluated with higher accuracy.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of a first exemplary embodiment of the present invention.
FIG. 2 is a circuit diagram showing a configuration of a second exemplary embodiment of the present invention.
FIG. 3 is a circuit diagram showing a configuration of a third exemplary embodiment of the present invention.
FIG. 4 is a circuit diagram showing a configuration of a fourth embodiment of the present invention.
FIG. 5 is a circuit diagram showing a configuration of a fifth exemplary embodiment of the present invention.
FIG. 6 is a characteristic diagram of a P (polarization) -E (electric field) hysteresis curve.
FIG. 7 is a circuit diagram showing a configuration of a Sawyer-Tower circuit.
FIG. 8 is a circuit diagram showing a configuration of a virtual ground circuit.
FIG. 9 is an explanatory diagram of the influence of leakage resistance in the virtual ground circuit.
[Explanation of symbols]
1 Voltage waveform generator
2 Ferroelectric capacitors
3 Reference dielectric capacitor
4 Oscilloscope
5 Differential amplifier
6 Leakage resistance
7A current exclusion circuit
7B Current mirror circuit
7C Similar waveform generator
8A-8D resistors
10 Ferroelectric material
11 DC amplifier
12a, 12b Impedance
13 PE system histories curve

Claims (5)

A series connection circuit of a ferroelectric whose characteristics are evaluated and a reference dielectric whose characteristics are known;
Voltage waveform generating means for supplying a predetermined voltage waveform to the ferroelectric;
Measuring means for measuring the potential of each end of the series connection circuit from the connection point of the series connection circuit ;
Current exclusion means connected to a connection point between the ferroelectric and the reference dielectric, and for inhibiting leakage current flowing through a leakage resistance of the ferroelectric from flowing into the reference dielectric; Ferroelectric property evaluation equipment.   The ferroelectric characteristic evaluation apparatus according to claim 1, wherein a resistance value is set between the voltage waveform generating unit and the connection point of the ferroelectric and the current eliminating unit, and the leakage current is reduced by the current eliminating unit. A ferroelectric characteristic evaluation apparatus, wherein a resistor adjusted so as to be completely eliminated is connected.   2. The ferroelectric characteristic evaluation apparatus according to claim 1, wherein the current exclusion means is configured to generate a similar voltage waveform having a polarity different from that of the voltage waveform generation means, and the current exclusion means and the ferroelectric substance. And a resistor whose resistance value is adjusted by the current eliminator so that the leakage current is completely eliminated is connected between the connection points of the reference dielectric and the ferroelectric. Characteristic evaluation device. A series connection circuit of a ferroelectric whose characteristics are evaluated and a reference dielectric whose characteristics are known;
Voltage waveform generating means for supplying a predetermined voltage waveform to the ferroelectric;
Measuring means for measuring the potential of each end of the series connection circuit from the connection point of the series connection circuit ;
A similar voltage waveform connected between the connection point of the voltage waveform generating means and the ferroelectric and the connection point of the ferroelectric and the reference dielectric, having a negative gain k and having a polarity different from that of the voltage waveform generating means. A direct current amplifier that generates
A series connection circuit with a resistor whose resistance value is adjusted so that a leakage current flowing through the leakage resistance of the ferroelectric substance is completely eliminated by the DC amplifier;
A ferroelectric characteristic evaluation apparatus comprising: A series connection circuit of a ferroelectric whose characteristics are evaluated and a reference dielectric whose characteristics are known;
Voltage waveform generating means for supplying a predetermined voltage waveform to the ferroelectric;
Measuring means for measuring the potential of each end of the series connection circuit from the connection point of the series connection circuit ;
A second series connection circuit which is connected in parallel to the voltage waveform generating means and which connects a first impedance and a second impedance whose mutual connection point is grounded;
It is connected between the connection point of one end and the ferroelectric and the reference dielectric of the second series connection circuit, by the second series circuit, the ferroelectric leakage current flowing through the leakage resistance of the fully A ferroelectric characteristic evaluation device comprising: a resistor whose resistance value is adjusted so as to be excluded.

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