JP3361268B2 - Method for evaluating polarization characteristics of ferroelectric capacitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating polarization characteristics of a ferroelectric capacitor.

[0002]

2. Description of the Related Art In recent years, a ferroelectric non-volatile memory utilizing the polarization hysteresis characteristic of a ferroelectric capacitor has been actively developed, and with this, the polarization characteristic of a ferroelectric capacitor formed on a semiconductor substrate. Evaluation devices and polarization characteristics evaluation methods are important. At present, a Sawyer tower circuit is generally used as a polarization characteristic evaluation device for a ferroelectric capacitor.

FIG. 29 is a diagram showing the structure of a conventional polarization characteristic evaluation device for a ferroelectric capacitor. In FIG. 29, 1 is a semiconductor substrate, 2 is a ferroelectric capacitor, 3 and 4 are wirings, and 5 and 6 are pads. Further, 2 a is a first electrode of the ferroelectric capacitor 2 and 2 b is a second electrode of the ferroelectric capacitor 2. The ferroelectric capacitor 2, the wirings 3 and 4, and the pads 5 and 6 are formed on the semiconductor substrate 1. Reference numeral 7 is a reference capacitor, 8 is an arbitrary waveform pulse generator, 9 is an oscilloscope, and 10, 11 and 12 are wiring cables. Further, 7a is a first electrode of the reference capacitor 7, 7b is a second electrode of the reference capacitor 7, 8a is an output terminal of the arbitrary waveform pulse generator 8, 9a is a first input terminal of the oscilloscope 9, and 9b. Is a second input terminal of the oscilloscope 9.
The capacitance of the reference capacitor 7 is known.

FIG. 30 is a flow chart showing steps of a polarization characteristic evaluation method by a conventional polarization characteristic evaluation apparatus for a ferroelectric capacitor. FIG. 31 is a diagram showing a voltage pulse and a voltage waveform measured by an oscilloscope when a polarization characteristic is evaluated using a conventional ferroelectric capacitor polarization characteristic evaluation apparatus. In FIG. 31, (a) and (d)
Is a waveform of a voltage pulse output from the arbitrary waveform pulse generator 8, (b) and (e) are voltage waveforms measured at the first input terminal 9a of the oscilloscope 9,
(C) and (f) are voltage waveforms measured at the second input terminal 9b of the oscilloscope 9. Here, the scales of the vertical axes of (c) and (f) are (a) and (d),
It is assumed to be sufficiently smaller than the scales of the vertical axes in (b) and (e). In FIG. 31, 51, 52 and 53 are voltage pulses generated by the arbitrary waveform pulse generator 8,
54 and 55 are voltage waveforms measured at the first input terminal 9a of the oscilloscope 9, and 56 and 57 are voltage waveforms measured at the second input terminal 9b of the oscilloscope 9. Further, in FIG. 31, t1 is the time when the voltage waveform 54 starts to change, and t2 is the time when the voltage waveform 55 starts to change.

FIG. 32 is a diagram showing polarization characteristics measured by a conventional polarization characteristics evaluation apparatus for ferroelectric capacitors. In FIG. 32, 71 and 72 are polarization hysteresis curves, and 7
3 is the polarization at time t1, and 74 is the polarization at time t2. The polarization characteristic evaluation method by the conventional polarization characteristic evaluation device for a ferroelectric capacitor will be described below with reference to FIGS.

First, in step P1, the arbitrary waveform pulse generator 8 applies a voltage pulse 51 to the ferroelectric capacitor 2.
Apply to. The polarization state of the ferroelectric capacitor 2 is adjusted to the first predetermined state by the step P1. In step P2, the arbitrary waveform pulse generator 8 applies the voltage pulse 52 to the ferroelectric capacitor 2, and the voltage waveform 54 is applied at the first input terminal 9a of the oscilloscope 9 and the voltage is applied at the second input terminal 9b of the oscilloscope 9. Waveform 56 is measured. In step P3, the time change of the electric field applied to the ferroelectric capacitor 2 is calculated from the film thickness of the capacitive thin film of the ferroelectric capacitor 2 and the voltage waveform 54, and the capacitance and voltage waveform 56 of the reference capacitor 7 is calculated. The time change of the charge amount in the second electrode 2b of the ferroelectric capacitor 2 when the voltage pulse 52 is applied is calculated, and the electric field applied to the ferroelectric capacitor 2 and the second electrode 2b of the ferroelectric capacitor 2 are calculated. Then, the relationship between the electric field and the polarization, that is, the polarization hysteresis curve 71 is calculated with the midpoint between the maximum value and the minimum value of the charge amount as the zero point of the polarization.

In step P4, the voltage pulse 53 is applied to the ferroelectric capacitor 2 by the arbitrary waveform pulse generator 8. The polarization state of the ferroelectric capacitor 2 is adjusted to the second predetermined state by the step P4. In process P5,
A voltage pulse 52 is applied to the ferroelectric capacitor 2 by the arbitrary waveform pulse generator 8, and a voltage waveform 55 is applied to the first input terminal 9a of the oscilloscope 9 and a voltage waveform 57 is applied to the second input terminal 9b of the oscilloscope 9. taking measurement. In step P6, the time variation of the electric field applied to the ferroelectric capacitor 2 is calculated from the thickness thin film of the ferroelectric capacitor 2 and the voltage waveform 55, and the voltage pulse is calculated from the capacitance of the reference capacitor 7 and the voltage waveform 57. 52
The time change of the charge amount in the second electrode 2b of the ferroelectric capacitor 2 at the time of application is calculated to calculate the ferroelectric capacitor 2
The relation between the electric field and the polarization is determined by finding the relation between the electric field applied to the capacitor and the amount of charge in the second electrode 2b of the ferroelectric capacitor 2, and setting the midpoint between the maximum and minimum values of the charge as the zero point of polarization. That is, the polarization hysteresis curve 72 is obtained. In step P7, the polarization 73 is subtracted from the polarization 74 to calculate the non-volatile polarization.

[0008]

However, the above-mentioned conventional structure has the following drawbacks. In the measurement system shown in FIG. 29, the wiring cable 10 has a stray capacitance of several tens pF.
There is more. Therefore, it is a ferroelectric capacitor of about 1 nF that can ignore this stray capacitance and perform accurate measurement.

When the change in polarization of the ferroelectric capacitor 2 due to a voltage pulse having a pulse width of 100 ns or less, which is necessary for analyzing the operation of the ferroelectric non-volatile memory, is evaluated using the measurement system shown in FIG. However, since the wiring has a large stray capacitance, it takes a long time to perform switching, ringing, that is, waveform disturbance occurs, an accurate voltage pulse cannot be applied, and the nonvolatile polarization cannot be accurately evaluated. Therefore, there is a problem that the short pulse cannot be used for measurement.

Further, in the measurement system shown in the same figure, the reference capacitor 7 has a frequency characteristic in capacitance, and it is difficult to obtain a constant capacitance at a frequency of several MHz or more. The change in polarization of the dielectric capacitor 2 cannot be evaluated accurately.
In addition, it is not possible to evaluate the change in polarization due to a voltage pulse from an arbitrary polarization state, which is necessary in the analysis of the operation of the ferroelectric nonvolatile memory. Further, if the pulse width of the AC voltage pulse and the pulse width applied to the ferroelectric capacitor in the ferroelectric non-volatile memory are different, an accurate reliability simulation test cannot be performed.

Further, by applying an AC voltage pulse to the ferroelectric capacitor 2 by using the measurement system shown in the same figure, the polarization characteristic of the ferroelectric capacitor in the ferroelectric nonvolatile memory is deteriorated due to repeated rewriting operation. When performing the reliability simulation test of, the pulse width needs to be larger than 100 ns, and the test time becomes long. Furthermore, since the arbitrary waveform pulse generator is used for a long time in this reliability simulation test, a large number of evaluation equipments are required and a large amount of cost is required.

The present invention has been made in view of the above circumstances, and an object thereof is to perform highly reliable polarization characteristic evaluation in a short time. That is, in the present invention, the pulse width is 100
It is an object of the present invention to provide a polarization characteristic evaluation method for a ferroelectric capacitor that can evaluate the change in polarization due to a voltage pulse of ns or less.

Further, there is provided a device for evaluating polarization characteristics of a ferroelectric capacitor and a method for evaluating polarization characteristics capable of performing a reliability simulation test of deterioration of polarization characteristics by repeating polarization reversal with an AC voltage pulse having a pulse width of 100 ns or less. The purpose is to provide. Further, a polarization characteristic evaluation device for a ferroelectric capacitor capable of evaluating polarization characteristics by using a voltage pulse having the same waveform as that of the voltage pulse waveform used in the reliability simulation test for deterioration of polarization characteristics, and polarization characteristic evaluation The purpose is to provide a method.

Further, in the conventional method of evaluating the polarization characteristic of the ferroelectric capacitor, the polarization inversion amount when the voltage pulse is applied is evaluated. However, the polarization characteristics have a history, and the amount of polarization reversal differs depending on the polarization state before that, and it was not possible to analyze the operating state of FeRAM (ferroelectric non-volatile memory) with high accuracy. Therefore, it is an object of the present invention to provide an evaluation method capable of evaluating the polarization inversion amount when a voltage pulse is applied without being affected by the polarization state before that.

Further, there is provided an evaluation method capable of coping with reading from an insufficient written state, that is, capable of evaluating the polarization inversion amount when a voltage pulse is applied from an intermediate polarized state. The purpose is to

[0016]

In order to solve this problem, according to the present invention, a ferroelectric capacitor, a pulse generator connected to the ferroelectric capacitor, and a first capacitor are provided on a semiconductor substrate. Has a reference capacitor whose capacity is known and which is detachably connected to the second electrode of the ferroelectric capacitor, and the first electrode of the ferroelectric capacitor and the arbitrary waveform pulse generator can be disconnected. A polarization characteristic evaluation method for a ferroelectric capacitor using a polarization characteristic evaluation device connected to, wherein a first voltage pulse is applied from the pulse generator of the ferroelectric capacitor to set a polarization state to a predetermined state. And the first polarization initialization step, the ferroelectric capacitor, the arbitrary waveform pulse generator and the reference capacitor are connected, the second of the reference capacitor With a first electrode of the reference capacitor when a second voltage pulse is applied from the arbitrary waveform pulse generator to the first electrode of the ferroelectric capacitor with a constant voltage applied to the electrode. The first potential change measurement step of measuring the potential change of, the ferroelectric capacitor, the arbitrary waveform pulse generator and the reference capacitor are cut off, and measured in the first potential change measurement step. Based on the potential change and the capacitance of the reference capacitor, the first of the ferroelectric capacitors in the first potential change measurement step.
A first charge amount change calculation step of calculating a change in charge amount at the second electrode; a second polarization initialization step of performing polarization initialization similar to the first polarization initialization step; A polarization reversal step of applying a third voltage pulse from the pulse generator to the body capacitor to invert the polarization state, and a second potential change measurement step of performing the same potential change measurement as the first potential change measurement step. And a second charge amount change calculation for calculating the change in the charge amount at the second electrode of the ferroelectric capacitor in the second potential change measurement process in the same manner as the first charge amount change calculation process. It is characterized by including a step and a non-volatile polarization calculation step of calculating non-volatile polarization from the respective charge amounts obtained in the first and second charge amount change calculation steps.

Preferably, after the step of calculating the non-volatile polarization, the pulse width of the third pulse is changed to change the pulse width of the second pulse.
The process similar to each process from the polarization initialization step to the non-volatile polarization calculation step is repeated to obtain the pulse width dependence of the non-volatile polarization.

Further preferably, after the nonvolatile polarization calculating step, the pulse voltage of the third pulse is changed to be the same as each step from the second polarization initializing step to the nonvolatile polarization calculating step. Is repeated to obtain the pulse voltage dependence of the non-volatile polarization.

Preferably, at least the third pulse is a voltage pulse having a pulse width of 100 ns or less.

According to the second aspect of the present invention, on the semiconductor substrate,
A ferroelectric capacitor, a pulse generator connected to the ferroelectric capacitor, and a reference capacitor with a known capacitance in which a first electrode is disconnectably connected to a second electrode of the ferroelectric capacitor. A method for evaluating a polarization characteristic of a ferroelectric capacitor using a device for evaluating a polarization characteristic, wherein the first electrode of the ferroelectric capacitor and an arbitrary waveform pulse generator are detachably connected. After applying a first voltage pulse from the pulse generator of the body capacitor to bring the polarization state to a predetermined state, a second voltage pulse is applied from the pulse generator to bring the polarization state to near zero. The first polarization initialization step to do, the ferroelectric capacitor, the arbitrary waveform pulse generator and the reference capacitor are connected, and the reference capacitor The first voltage of the reference capacitor when the third voltage pulse is applied from the arbitrary waveform pulse generator to the first electrode of the ferroelectric capacitor with a constant voltage applied to the second electrode. A first potential change measuring step of measuring a potential change at the electrode of, the ferroelectric capacitor, the arbitrary waveform pulse generator and the reference capacitor are cut off, the first
Based on the potential change measured in the potential change measurement step and the capacitance of the reference capacitor,
A first charge amount change calculation step of calculating a change in the charge amount at the second electrode of the ferroelectric capacitor in the potential change measurement step of 1, and a polarization initialization similar to the first polarization initialization step. A second polarization initialization step for performing the above step; a polarization reversal step for reversing the polarization state by applying a fourth voltage pulse from the pulse generator to the ferroelectric capacitor;
The second procedure for measuring potential changes similar to the potential change measurement step 1
Second step of calculating the change in the charge amount at the second electrode of the ferroelectric capacitor in the second potential change measuring step in the same manner as the potential change measuring step and the first charge amount changing calculating step. And the charge amount change calculation step of
And a non-volatile polarization calculating step of calculating non-volatile polarization from the respective charge amounts obtained in the charge amount change calculating step.

Preferably, after the nonvolatile polarization calculating step, the pulse width of the fourth pulse is changed to change the second pulse to the second pulse.
The process similar to each process from the polarization initialization step to the non-volatile polarization calculation step is repeated to obtain the pulse width dependence of the non-volatile polarization.

Further preferably, after the nonvolatile polarization calculating step, the pulse voltage of the fourth pulse is changed to be the same as each step from the second polarization initializing step to the nonvolatile polarization calculating step. Is repeated to obtain the pulse voltage dependence of the non-volatile polarization.

Preferably, at least the fourth pulse is a voltage pulse having a pulse width of 100 ns or less.

The following may be considered as other examples of the present invention. That is, the first device for evaluating polarization characteristics includes a ferroelectric capacitor formed on a semiconductor substrate, a first pulse generator formed on the semiconductor substrate, and a first pulse generator formed on the semiconductor substrate. A second pulse generator, a reference capacitor having a known capacitance formed on the semiconductor substrate, and a switch formed on the semiconductor substrate, wherein the first and second electrodes of the ferroelectric capacitor are provided. And the output electrodes of the first and second pulse generators are electrically connected to each other, and the second electrode of the ferroelectric capacitor and the first electrode of the reference capacitor of known capacitance are connected to each other. It is characterized in that it is electrically connected through the switch. As a result, the stray capacitance of the wiring between the pulse generator and the ferroelectric capacitor is reduced, and a voltage pulse having a pulse width of 100 ns or less can be applied to the ferroelectric capacitor. Therefore, it is possible to evaluate the polarization characteristics with high accuracy. Further, the second polarization characteristic evaluation device is configured such that the pulse width of at least one of the voltage pulses output from the first and second pulse generators can be adjusted. Is characterized by.
With this configuration, a pulse having an appropriate pulse width can be applied very easily, and a pulse having a short wavelength can be applied without ringing, so that highly accurate evaluation can be performed. Becomes The third polarization property evaluation apparatus further comprises an oscillator formed on the semiconductor substrate, wherein the first and second output electrodes of the oscillator are the first and second output electrodes of the ferroelectric capacitor. It is characterized in that the electrodes are electrically connected to each other. A fourth aspect of the present invention is a polarization characteristic evaluation apparatus according to the third aspect, wherein the first pulse generator output and the oscillator first
, The output of the second pulse generator and the second output of the oscillator are connected to a ferroelectric capacitor via a common buffer, respectively. As a result, the polarization characteristic can be evaluated by using the voltage pulse having the same waveform as the voltage pulse waveform used for the reliability simulation test of the deterioration of the polarization characteristic, so that an accurate reliability simulation test can be performed. it can. The device for evaluating polarization characteristics according to a fifth aspect is the device according to claim 1 or 2, further comprising an oscillator, wherein trigger signal input electrodes of the first and second pulse generators are respectively the first and the first of the oscillator. It is characterized in that it is electrically connected to the second output electrode. As a result, the reliability simulation test by the AC voltage pulse can be performed without occupying the arbitrary waveform pulse generator, and the stray capacitance of the wiring between the oscillator and the ferroelectric capacitor is reduced, and the pulse width is 100 ns or less. Since the voltage pulse can be applied to the ferroelectric capacitor, the reliability simulation test using the AC voltage pulse can be accurately performed in a short time.
A polarization characteristic evaluation apparatus according to a sixth aspect is characterized in that, in the fifth apparatus, the oscillator is formed outside the semiconductor substrate. According to such a configuration, the oscillator is arranged on a substrate different from the integrated circuit which constitutes the polarization characteristic evaluation device, and therefore it is possible to prevent a measurement error due to a temperature change due to heat generation of the oscillator. A polarization characteristic evaluation device according to a seventh aspect is characterized in that, in the sixth device, the semiconductor substrate and the oscillator are housed in the same package. According to this configuration, since the oscillator and the integrated circuit that constitutes the device for evaluating the polarization characteristics are housed in the same package, the wiring capacitance between the output electrode of the oscillator and the trigger signal input electrode of the pulse generator field. Can be reduced, a higher frequency AC voltage can be applied, and the size of the entire apparatus can be reduced. An eighth polarization characteristic evaluation apparatus is characterized in that, in any one of the third to seventh apparatus, the oscillator is configured so that the oscillation frequency can be changed. A polarization characteristic evaluation method according to a ninth aspect is directed to a ferroelectric capacitor formed on a semiconductor substrate, a first pulse generator formed on the semiconductor substrate, and a second pulse formed on the semiconductor substrate. A step of preparing an evaluation device comprising a generator and a device for evaluating polarization characteristics of a ferroelectric capacitor, which comprises a reference capacitor of known capacity formed on the semiconductor substrate; Polarization reversal step of applying a first voltage pulse to at least one of the first electrode and the second electrode of the body capacitor, the second electrode of the ferroelectric capacitor and the first of the reference capacitor of known capacitance. And a second step of electrically connecting the second electrode of the reference capacitor to the first electrode of the ferroelectric capacitor with a constant voltage applied to the second electrode of the reference capacitor. A potential change measuring step of measuring a potential change of the first electrode of the reference capacitor when the voltage pulse of is applied, and the potential change measured in the potential change measuring step and the capacitance of the reference capacitor And a charge amount change calculating step of calculating a change in the charge amount at the second electrode of the ferroelectric capacitor in the potential change measuring step. As a result, the capacitance of the reference capacitor is not affected by the frequency characteristic, and
It is possible to evaluate the change in polarization characteristics due to the voltage pulse of 0 ns or less. According to the tenth aspect, a polarization reversal step of applying a first voltage pulse to at least one of the first electrode and the second electrode of the ferroelectric capacitor, and the second electrode of the ferroelectric capacitor and the known capacitance. Connection step of electrically connecting the first electrode of the reference capacitor of
Measuring a potential change of the first electrode of the capacitor when a second voltage pulse is applied to the first electrode of the ferroelectric capacitor while a constant voltage is applied to the second electrode of the capacitor And a charge for calculating a change in the amount of charge in the second electrode of the ferroelectric capacitor in the potential change measuring step based on the potential change measured in the potential change measuring step and the capacitance of the capacitor. And a polarization initialization step of applying a third voltage pulse to at least one of the first electrode and the second electrode of the ferroelectric capacitor prior to the polarization inversion step. It is characterized by

According to this method, since the polarization initializing step is provided, it is possible to evaluate the polarization inversion amount when the voltage pulse is applied, without being affected by the polarization state before that.

According to the eleventh method, in the tenth method,
A polarization setting step of applying a fourth voltage pulse to at least one of the first electrode and the second electrode of the ferroelectric capacitor is further provided between the polarization initialization step and the polarization inversion step. It is characterized by According to this method, since the polarization setting step is provided, it is possible to cope with reading from an insufficient write state, which is important in the operation of FeRAM, that is, when a voltage pulse is applied from an intermediate polarization state. It is possible to evaluate the polarization inversion amount of.

According to a twelfth aspect, in any one of the tenth and eleventh methods, the method further comprises a pulse width changing step of changing the pulse width of the first voltage pulse. According to a thirteenth aspect of the present invention, in any one of the tenth to twelfth methods, the method further comprises a pulse voltage changing step of changing the pulse voltage of the first voltage pulse.

[0028]

1 is a diagram showing the configuration of a polarization characteristic evaluation apparatus for a ferroelectric capacitor according to a first embodiment of the present invention. In this device, a ferroelectric capacitor 100 to be measured is formed on a semiconductor substrate 99, and a first pulse generator 102, a second pulse generator 103, and a capacitance are formed on the same semiconductor substrate 99. Known reference capacitor 101 and electric switches 107, 1
08 are formed to form the first and second electrodes 100a and 100b of the ferroelectric capacitor 100,
The output electrodes 102a and 103a of the first and second pulse generators 102 and 103 are electrically connected to each other, and the second electrode 100 of the ferroelectric capacitor is provided.
b and the first of the reference capacitors of known capacitance
The electrode 101a is electrically connected via the electric switch 108, and at least one of the voltage pulses output from the first and second pulse generators 102, 103 has a pulse width of It is configured to be adjustable.

Here, the oscilloscope 122, the arbitrary waveform pulse generator 121, the trigger generator 600, and the first and second pulse generators 102 and 103 are each controlled by the controller 500.
In FIG. 1, 104 and 105 are buffers, 106 is an impedance converter, 109, 110, 111, 11
2, 113, 114, 115 and 116 are wirings, 11
7, 118, 119 and 120 are pads.

Ferroelectric capacitor 100, reference capacitor 101, pulse generators 102 and 103,
Buffers 104 and 105, impedance converter 10
6, electrical switches 107 and 108 are wirings 109 and 11
0, 111, 112, 113, 114, 115 and 11
6, the pads 117, 118, 119 and 120 are formed on the same semiconductor substrate 99.

The capacitance of the reference capacitor 101 is known. 121 is an arbitrary waveform pulse generator, 122 is an oscilloscope, and 123, 124, 125 and 126 are wiring cables. Further, 121a is an output terminal of the arbitrary waveform pulse generator 121, and 122a is an oscilloscope 1.
22 is a first input terminal 22 and 122b is an oscilloscope 12
2nd input terminal, 122c is oscilloscope 122
Is a third input terminal of the oscilloscope 122, and 122d is a fourth input terminal of the oscilloscope 122.

2 and 3 are flow charts showing steps of a polarization characteristic evaluation method by the polarization characteristic evaluation device for a ferroelectric capacitor according to the first embodiment of the present invention. FIG. 4 shows an example of an observation result of a voltage waveform by an electron beam tester when a voltage pulse is applied to the ferroelectric capacitor by using the polarization characteristic evaluation device for the ferroelectric capacitor according to the first embodiment of the present invention. It is a figure. The voltage waveform of FIG. 4 shows that when the voltage pulse generated by the pulse generator 103 is applied to the ferroelectric capacitor 100.
It is observed with the second electrode 100b of 0.

FIG. 5 shows a voltage pulse and an example of a voltage waveform measured by an oscilloscope when the polarization characteristic is evaluated by using the polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the first embodiment of the present invention. It is a figure. In FIG.
(A) and (d) are waveforms of voltage pulses output from the pulse generators 102 and 103 and the arbitrary waveform pulse generator 121, and (b) and (e) are oscilloscopes 1.
22 is a voltage waveform measured at the first input terminal 122a of 22 and (c) and (f) are voltage waveforms measured at the fourth input terminal 122d of the oscilloscope 122. In FIG. 5, 151 is a voltage pulse generated by the pulse generator 103, 152 is a voltage pulse generated by the pulse generator 102, and 153 is an arbitrary waveform pulse generator 1.
21 is a voltage pulse generated by 21; 154, 155 are voltage waveforms measured at the first input terminal 122a of the oscilloscope 122; 156, 157 are oscilloscope 122.
3 is a voltage waveform measured at a fourth input terminal 122d of. Further, in FIG. 5, t3 is the time when the voltage waveform 154 starts to change, and t4 is the time when the voltage waveform 155 starts to change.

FIG. 6 is a diagram showing an example of the polarization characteristics measured by the polarization characteristics evaluation apparatus for a ferroelectric capacitor according to the first embodiment of the present invention. In FIG. 6, 171,
172 is the polarization hysteresis curve, 173 is the polarization at time t3, and 174 is the polarization at time t4. Figure 7
FIG. 3 is a diagram showing an example of the pulse width dependency and the pulse voltage dependency of the non-volatile polarization measured by the polarization characteristic evaluation device for the ferroelectric capacitor according to the first example of the present invention.

The first embodiment of the present invention will be described below with reference to FIGS.
A polarization characteristic evaluation method by the polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the example will be described. First, the process Pa
In No. 1, by driving the trigger generator 600, the voltage pulse 151 is output by the pulse generator 103 and is applied to the ferroelectric capacitor 100. Process P
The polarization state of the ferroelectric capacitor 100 is adjusted to a predetermined state by a1. In step Pa1, the electric switches 107 and 108 are turned off. Process Pa
At 2, the electrical switches 107 and 108 are turned on.
In step Pa3, the arbitrary waveform pulse generator 121 applies the voltage pulse 153 to the ferroelectric capacitor 100 and the first input terminal 1 of the oscilloscope 122.
22a, the voltage waveform 154, the fourth oscilloscope 122
The voltage waveform 156 is measured at the input terminal 122d of.

In step Pa4, the electric switch 107
And 108. In step Pa5, the time change of the electric field applied to the ferroelectric capacitor 100 is calculated from the thin film thickness of the ferroelectric capacitor 100 and the voltage waveform 154, and the voltage pulse is calculated from the capacitance and voltage waveform 156 of the reference capacitor 101. The time change of the charge amount in the second electrode 100b of the ferroelectric capacitor 100 when 153 is applied is calculated to calculate the ferroelectric capacitor 10
Electric field applied to 0 and the second of the ferroelectric capacitor 100.
The relationship between the electric field and the polarization, that is, the polarization hysteresis curve 171 is obtained with the midpoint between the maximum value and the minimum value of the charge amount as the zero point of the polarization. In step Pa6, the voltage pulse 151 is applied to the ferroelectric capacitor 100 by the pulse generator 103. In step Pa6, the polarization state of the ferroelectric capacitor 100 is adjusted to a predetermined state. In step Pa7, the voltage pulse 152 is applied to the ferroelectric capacitor 100 by the pulse generator 102. In step Pa7, the polarization state of the ferroelectric capacitor 100 is changed to the voltage pulse 152.
Changes depending on the pulse width and pulse voltage of the.

In step Pa8, the electric switch 107
And 108. In step Pa9, the arbitrary waveform pulse generator 121 applies the voltage pulse 153 to the ferroelectric capacitor 100 and the oscilloscope 12
The voltage waveform 155 is measured at the first input terminal 122a of No. 2 and the voltage waveform 157 is measured at the fourth input terminal 122d of the oscilloscope 122. In step Pa10, the electric switches 107 and 108 are turned off. In step Pa11, the thin film thickness of the ferroelectric capacitor 100 and the voltage waveform 15
5, the time change of the electric field applied to the ferroelectric capacitor 100 is calculated, and the reference capacitor 1
From the capacity and voltage waveform 157 of 01, the voltage pulse 153
Second electrode 100 of ferroelectric capacitor 100 during application
The change over time in the amount of charge in b is calculated, and the electric field applied to the ferroelectric capacitor 100 and the ferroelectric capacitor 1 are calculated.
The relationship between the electric field and the polarization, that is, the polarization hysteresis curve 172 is determined with the midpoint between the maximum value and the minimum value of the charge amount as the zero point of the polarization. In step Pa12, the polarization 173 is subtracted from the polarization 174 to calculate the non-volatile polarization.

In the structure of the polarization characteristic evaluation apparatus for a ferroelectric capacitor shown in FIG. 1, the wirings 110 and 111 are formed on the semiconductor substrate 99 as an integrated circuit, so that the stray capacitance is small. As a result, as shown in FIG. 4, the pulse width generated by the pulse generators 102 and 103 is 100.
A voltage pulse of ns or less can be applied. Also,
By measuring the non-volatile polarization by changing the pulse width and the pulse voltage of the voltage pulse 152, it is necessary to analyze the operation of the ferroelectric non-volatile memory. The pulse voltage dependence can be evaluated.

Although the voltage pulse 151 of FIG. 5 is a rectangular wave voltage pulse, the same effect can be obtained by using a trapezoidal wave voltage pulse, a triangular wave voltage pulse, or a sine voltage pulse. Further, although the trapezoidal wave voltage pulse is used as the voltage pulse 153 in FIG. 5, the same effect can be obtained by using a triangular wave voltage pulse, a sine voltage pulse, or a rectangular wave voltage pulse.

The construction of the polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the second embodiment of the present invention is exactly the same as the construction of the polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the first embodiment. 8 to 13 are flowcharts showing the steps of the polarization characteristic evaluation method by the polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the second embodiment of the present invention.

14 to 16 show examples of voltage pulses and voltage waveforms measured by an oscilloscope when the polarization characteristics are evaluated by using the polarization characteristics evaluation apparatus for ferroelectric capacitors according to the second embodiment of the present invention. It is the figure shown. 14-
In FIG. 16, (a) and (d) are pulse generators 10.
2 and 103 and waveforms of voltage pulses output from the arbitrary waveform pulse generator 121, (b) and (e) are voltage waveforms measured at the first input terminal 122a of the oscilloscope 122, and (c). And (f) are voltage waveforms measured at the fourth input terminal 122d of the oscilloscope 122.

14 to 16, 181 is a voltage pulse generated by the pulse generator 103, 182 is a voltage pulse generated by the pulse generator 102, 183 is a voltage pulse generated by the arbitrary waveform pulse generator 121, 184, 185 are voltage waveforms measured at the first input terminal 122a of the oscilloscope 122, 186, 187
Are voltage waveforms measured at the fourth input terminal 122d of the oscilloscope 122, 188 and 189 are pulse generators 10.
2, 190, 191 are voltage waveforms measured at the first input terminal 122a of the oscilloscope 122, 192, 193 are voltage waveforms measured at the fourth input terminal 122d of the oscilloscope 122, 194
Is a voltage pulse generated by the pulse generator 102, 1
95 is a voltage pulse generated by the pulse generator 103, 196 and 197 are voltage waveforms measured at the first input terminal 122a of the oscilloscope 122, 198 and 199.
Is a voltage waveform measured at the fourth input terminal 122d of the oscilloscope 122.

14 to 16, t5 is the time when the voltage waveform 184 starts to change, t6 is the time when the voltage waveform 185 starts to change, t7 is the time when the voltage waveform 190 starts to change, and t8 is the voltage waveform 191 changes. Time to start, t
9 is the time when the voltage waveform 196 starts to change, and t10 is the time when the voltage waveform 197 starts to change. 17 to 19 are diagrams showing an example of polarization characteristics measured by the polarization characteristics evaluation apparatus for a ferroelectric capacitor according to the second embodiment of the present invention. In FIG. 17, 201 and 202 are polarization hysteresis curves, 203 is polarization at time t5, and 204
Is the polarization at time t6. In FIG. 18, 20
5, 206, polarization hysteresis curve, 207, time t7
, And 208 is the polarization at time t8.
In FIG. 19, 209 and 210 are polarization hysteresis curves, 211 is polarization at time t9, and 212 is time t1.
Polarization at 0.

20 to 22 are views showing an example of the pulse width dependency and the pulse voltage dependency of the non-volatile polarization measured by the polarization characteristic evaluation apparatus of the ferroelectric capacitor according to the second embodiment of the present invention. is there. The polarization characteristic evaluation method by the polarization characteristic evaluation device for a ferroelectric capacitor according to the second embodiment of the present invention will be described below with reference to FIGS.

First, in step Pb1, the voltage pulse 181 is applied by the pulse generator 103 to the ferroelectric capacitor 1.
00 is applied. The polarization state of the ferroelectric capacitor 100 is adjusted to a predetermined state by the step Pb1. In the process Pb1, the electric switches 107 and 108 are turned off. In the process Pb2, the electric switch 10
Put 7 and 108. In step Pb3, the arbitrary waveform pulse generator 121 applies the voltage pulse 183 to the ferroelectric capacitor 100 and the oscilloscope 1
The voltage waveform 184 is measured at the first input terminal 122a of 22 and the voltage waveform 186 is measured at the fourth input terminal 122d of the oscilloscope 122. In step Pb4, the electric switches 107 and 108 are turned off.

In step Pb5, the time variation of the electric field applied to the ferroelectric capacitor 100 is calculated from the capacitance thin film thickness of the ferroelectric capacitor 100 and the voltage waveform 184, and the capacitance and voltage waveform 186 of the reference capacitor 101 is calculated. The time change of the amount of charge in the second electrode 100b of the ferroelectric capacitor 100 when the voltage pulse 183 is applied is calculated, and the electric field applied to the ferroelectric capacitor 100 and the second electrode of the ferroelectric capacitor 100 are calculated. The relationship between the electric field and the polarization at 100b is determined, and the relationship between the electric field and the polarization, that is, the polarization hysteresis curve 201 is determined with the midpoint between the maximum value and the minimum value of the charge amount as the zero point of the polarization. In step Pb6, the voltage pulse 181 is applied to the ferroelectric capacitor 100 by the pulse generator 103. The polarization state of the ferroelectric capacitor 100 is adjusted to a predetermined state by the step Pb6. In the process Pb7,
A voltage pulse 182 is applied to the ferroelectric capacitor 100 by the pulse generator 102. By the step Pb7, the polarization state of the ferroelectric capacitor 100 changes depending on the pulse width and the pulse voltage of the voltage pulse 182.

In step Pb8, the electric switch 107
And 108. In step Pb9, the arbitrary waveform pulse generator 121 applies the voltage pulse 183 to the ferroelectric capacitor 100 and the oscilloscope 12
2 has a voltage waveform 185 at the first input terminal 122a and a voltage waveform 1 at the fourth input terminal 122d of the oscilloscope 122.
87 is measured. In step Pb10, the electric switches 107 and 108 are turned off. In step Pb11, the capacitance thin film thickness of the ferroelectric capacitor 100 and the voltage waveform 185
The time change of the electric field applied to the ferroelectric capacitor 100 is calculated from the
From the capacitance and the voltage waveform 187 of No. 1, the second electrode 100b of the ferroelectric capacitor 100 when the voltage pulse 183 is applied.
Of the electric charge applied to the ferroelectric capacitor 100 and the ferroelectric capacitor 10
The relationship between the electric field and the polarization, that is, the polarization hysteresis curve 202 is calculated with the zero point of the polarization as the midpoint between the maximum value and the minimum value of the charge amount. In step Pb12, the polarization 203 is subtracted from the polarization 204 to calculate the non-volatile polarization. The pulse width and pulse voltage of the voltage pulse 182 are changed, and steps Pb6 to 12 are repeated. The above steps Pb1 to 1
Step 2 is exactly the same as steps Pa1 to 12 in the first embodiment.

Next, in step Pb13, the voltage pulse 181 is applied to the ferroelectric capacitor 100 by the pulse generator 103. The polarization state of the ferroelectric capacitor 100 is adjusted to a predetermined state by the step Pb13. In step Pb14, the voltage pulse 188 is applied to the ferroelectric capacitor 100 by the pulse generator 102. In step Pb14, the polarization state of the ferroelectric capacitor 100 is set so that the polarization amount is near zero. In step Pb15, the electric switches 107 and 108 are turned on. Process Pb
16, the arbitrary waveform pulse generator 121 applies the voltage pulse 183 to the ferroelectric capacitor 100, and at the same time, the first input terminal 122a of the oscilloscope 122 is input.
Then, the voltage waveform 190 is measured, and the voltage waveform 192 is measured at the fourth input terminal 122d of the oscilloscope 122. Process Pb1
At 7, the electrical switches 107 and 108 are turned off.

In step Pb18, the time variation of the electric field applied to the ferroelectric capacitor 100 is calculated from the capacitance thin film thickness of the ferroelectric capacitor 100 and the voltage waveform 190, and the capacitance and voltage waveform 192 of the reference capacitor 101 is calculated. The time change of the amount of charge in the second electrode 100b of the ferroelectric capacitor 100 when the voltage pulse 183 is applied is calculated, and the electric field applied to the ferroelectric capacitor 100 and the second electrode of the ferroelectric capacitor 100 are calculated. The relationship with the amount of charge at 100b is determined, and the relationship between the electric field and the polarization, that is, the polarization hysteresis curve 205 is determined with the midpoint between the maximum value and the minimum value of the charge amount as the zero point of the polarization. In step Pb19, the voltage pulse 181 is applied to the ferroelectric capacitor 100 by the pulse generator 103. The polarization state of the ferroelectric capacitor 100 is adjusted to a predetermined state by the step Pb19. In step Pb20, the voltage pulse 188 is applied to the ferroelectric capacitor 100 by the pulse generator 102. In step Pb20, the polarization state of the ferroelectric capacitor 100 is set so that the polarization amount is near zero. In step Pb21, the voltage pulse 189 is applied to the ferroelectric capacitor 1 by the pulse generator 102.
00 is applied. In step Pb21, the polarization state of the ferroelectric capacitor 100 changes depending on the pulse width and pulse voltage of the voltage pulse 189.

In step Pb22, the electric switch 10
Put 7 and 108. In step Pb23, the arbitrary waveform pulse generator 121 applies the voltage pulse 183 to the ferroelectric capacitor 100, and the first input terminal 122a of the oscilloscope 122 outputs the voltage waveform 191.
The voltage waveform 193 is measured at the fourth input terminal 122d of the oscilloscope 122. In step Pb24, the electric switches 107 and 108 are turned off. In step Pb25, the time variation of the electric field applied to the ferroelectric capacitor 100 is calculated from the capacitance thin film thickness of the ferroelectric capacitor 100 and the voltage waveform 191, and the voltage pulse is calculated from the capacitance and voltage waveform 193 of the reference capacitor 101. The time change of the charge amount in the second electrode 100b of the ferroelectric capacitor 100 when 183 is applied is calculated, and the electric field applied to the ferroelectric capacitor 100 and the charge in the second electrode 100b of the ferroelectric capacitor 100 are calculated. The relationship between the electric field and the polarization, that is, the polarization hysteresis curve 206, is obtained by setting the midpoint between the maximum value and the minimum value of the charge amount as the zero point of the polarization. Polarization 2 in the process Pb26
The polarization 207 is subtracted from 08 to calculate the non-volatile polarization. The pulse width and pulse voltage of the voltage pulse 189 are changed, and steps Pb19 to 26 are repeated.

Next, in step Pb27, the voltage pulse 181 is applied to the ferroelectric capacitor 100 by the pulse generator 103. The polarization state of the ferroelectric capacitor 100 is adjusted to a predetermined state by the step Pb27. In step Pb28, the voltage pulse 194 is applied to the ferroelectric capacitor 100 by the pulse generator 102. In step Pb28, the polarization state of the ferroelectric capacitor 100 is set so that the polarization amount is near zero. In step Pb29, the electric switches 107 and 108 are turned on. Process Pb
At 30, the voltage pulse 183 is applied to the ferroelectric capacitor 100 by the arbitrary waveform pulse generator 121, and the first input terminal 122a of the oscilloscope 122 is displayed.
And the voltage waveform 196 is measured at the fourth input terminal 122d of the oscilloscope 122.

In step Pb31, the electric switch 10
Cut 7 and 108. In step Pb32, the time variation of the electric field applied to the ferroelectric capacitor 100 is calculated from the thickness thin film of the ferroelectric capacitor 100 and the voltage waveform 196, and the voltage pulse is calculated from the capacitance and voltage waveform 198 of the reference capacitor 101. The time change of the charge amount in the second electrode 100b of the ferroelectric capacitor 100 when 183 is applied is calculated, and the electric field applied to the ferroelectric capacitor 100 and the charge in the second electrode 100b of the ferroelectric capacitor 100 are calculated. Calculate the relationship with the amount of charge, and set the midpoint between the maximum and minimum values of the amount of charge as the zero point of polarization,
Relationship between electric field and polarization, that is, polarization hysteresis curve 20
Ask for 9.

In step Pb33, the pulse generator 10
3, the voltage pulse 181 is applied to the ferroelectric capacitor 100.
Apply to. Ferroelectric capacitor 1 by process Pb33
The polarization state of 00 is adjusted to a predetermined state. Process Pb3
4, the voltage pulse 19 is generated by the pulse generator 102.
4 is applied to the ferroelectric capacitor 100. Process Pb3
4, the polarization state of the ferroelectric capacitor 100 is set so that the polarization amount is near zero. In step Pb35, the voltage pulse 195 is applied to the ferroelectric capacitor 100 by the pulse generator 103. By the step Pb35, the polarization state of the ferroelectric capacitor 100 changes depending on the pulse width and pulse voltage of the voltage pulse 195.

In step Pb36, the electric switch 10
Put 7 and 108. In step Pb37, the arbitrary waveform pulse generator 121 applies the voltage pulse 183 to the ferroelectric capacitor 100, the voltage waveform 197 is applied to the first input terminal 122a of the oscilloscope 122, and the voltage is applied to the fourth input terminal 122d of the oscilloscope 122. Waveform 199 is measured. In step Pb38, the electric switches 107 and 108 are turned off. In process Pb39,
Capacitive thin film thickness of ferroelectric capacitor 100 and voltage waveform 1
97, the time change of the electric field applied to the ferroelectric capacitor 100 is calculated, and the voltage pulse 18 is calculated from the capacitance of the reference capacitor 101 and the voltage waveform 199.
Second electrode 10 of ferroelectric capacitor 100 when 3 is applied
0b, the time change of the charge amount is calculated to obtain the relationship between the electric field applied to the ferroelectric capacitor 100 and the charge amount at the second electrode 100b of the ferroelectric capacitor 100, and the maximum and minimum values of the charge amount are calculated. The relationship between the electric field and the polarization, that is, the polarization hysteresis curve 210 is determined with the midpoint of the values as the zero point of the polarization. Polarization 212 in the process Pb40
The polarization 211 is subtracted from this to calculate the non-volatile polarization. The pulse width and pulse voltage of the voltage pulse 195 are changed, and steps Pb33 to 40 are repeated.

In the configuration of the polarization characteristic evaluation apparatus for a ferroelectric capacitor shown in FIG. 1, the first and second pulse generators 102 and 103, the ferroelectric capacitor 100 to be measured and the reference capacitor 101, and these are connected. Since the wirings 110 and 111 are formed on the semiconductor substrate 99 as an integrated circuit, the wiring length is short and the stray capacitance is small. As a result, as shown in FIG. 4, the pulse width generated by the pulse generators 102 and 103 is 100.
A voltage pulse of ns or less can be applied. Also,
By measuring the non-volatile polarization by changing the pulse width and the pulse voltage of the voltage pulse 182, it is necessary to analyze the operation of the ferroelectric non-volatile memory. The pulse voltage dependence can be evaluated. In addition, the voltage pulse 1 is applied to correspond to the difference in the writing state of the ferroelectric non-volatile memory.
After changing the polarization state at 88 and 194, the pulse width and pulse voltage of the voltage pulses 189 and 195 are changed to measure the non-volatile polarization, so that the operation of the ferroelectric non-volatile memory from an arbitrary writing state can be performed. It is possible to evaluate the pulse width dependency and the pulse voltage dependency of the non-volatile polarization as shown in FIGS. 21 and 22, which are necessary for highly accurate analysis.

As described above, according to this structure, since the pulse generator and the ferroelectric capacitor are formed on the same semiconductor substrate, the stray capacitance of the wiring between them is reduced and the pulse width is reduced. A voltage pulse of 100 ns or less can be applied to the ferroelectric capacitor. In addition,
Since all the polarization states of the ferroelectric capacitor 100 are intermediate between the polarization state in which the polarization is aligned in one direction and the polarization state in which the polarization amount is zero, as shown in FIGS. Evaluating the pulse width dependence and pulse voltage dependence of the non-volatile polarization is effective for highly accurate analysis of the operation of the ferroelectric non-volatile memory.

The voltage pulse 181 in FIGS. 14 to 16 uses a rectangular wave voltage pulse, but a trapezoidal wave voltage pulse,
The same effect can be obtained by using a triangular wave voltage pulse or a sine voltage pulse. Also, the voltage pulse 18 of FIGS.
Although 3 uses a trapezoidal wave voltage pulse, the same effect can be obtained by using a triangular wave voltage pulse, a sine voltage pulse, and a rectangular wave voltage pulse.

In the above embodiment, the trigger generator 60
Although 0 (see FIG. 1) is provided, the trigger generator is not necessarily provided, and the first and second pulse generators may be appropriately switched. Next, a third embodiment of the present invention will be described. FIG. 23 is a diagram showing the configuration of a polarization characteristic evaluation device for a ferroelectric capacitor according to the third embodiment of the present invention. In this example, the semiconductor substrate 99 that constitutes the device of the first embodiment of the present invention shown in FIG.
An oscillator 300 is further disposed on the first and second output electrodes 300a and 300b of the oscillator 300 and the first and second electrodes 100a and 100 of the ferroelectric capacitor.
b are electrically connected to the
The inversion signal of the signal output from the output electrode 300a of (1) can be output from the second output electrode 300b of the oscillator. Further, the voltage pulse generated by the pulse generators 102 and 103 and the voltage pulse generated by the oscillator are configured to be applied to the ferroelectric capacitor 100 via the buffers 301 and 302, and used for evaluation of non-volatile polarization. It is characterized in that the waveform of the voltage pulse and the waveform of the voltage pulse used for evaluating the deterioration of the polarization characteristics due to the AC voltage pulse can be made substantially the same. The other structure is exactly the same as that of the first embodiment, and the same parts are designated by the same reference numerals. By the way, in FIG. 23, 99
Is a semiconductor substrate, 100 is a ferroelectric capacitor, 101 is a reference capacitor, 102 and 103 are pulse generators, 104 and 105 are buffers, 106 is an impedance converter, 107 and 108 are electrical switches, 10
9, 112, 113, 114, 115 and 116 are wirings, 117, 118, 119 and 120 are pads. Further, 100a is the first of the ferroelectric capacitor 100.
Electrode, 100b is the second electrode of the ferroelectric capacitor 100, 101a is the first electrode of the reference capacitor 101, and 101b is the reference capacitor 101.
2 is an output electrode of the pulse generator 102, and 103a is an output electrode of the pulse generator 103.

Ferroelectric capacitor 100, reference capacitor 101, pulse generators 102 and 103,
Buffers 104 and 105, impedance converter 10
6, electrical switches 107 and 108 are wirings 109 and 11
2, 113, 114, 115 and 116, pad 11
7, 118, 119 and 120 are formed on the semiconductor substrate 99.

The capacitance of the reference capacitor 101 is known. 121 is an arbitrary waveform pulse generator, 122 is an oscilloscope, and 123, 124, 125 and 126 are wiring cables. Further, 121a is an output terminal of the arbitrary waveform pulse generator 121, and 122a is an oscilloscope 1.
22 is a first input terminal 22 and 122b is an oscilloscope 12
2nd input terminal, 122c is oscilloscope 122
Is a third input terminal of the oscilloscope 122, and 122d is a fourth input terminal of the oscilloscope 122. Also, in FIG.
Is an oscillator, 301 and 302 are buffers, 303 and 3
04 is an electric switch, 305, 306, 307, 30
Reference numerals 8, 309 and 310 are wirings. Oscillator 300, buffers 301 and 302, electric switches 303 and 30
4, wirings 305, 306, 307, 308, 309 and 310 are formed on the semiconductor substrate 99. Also, 3
00a is a first output electrode of the oscillator 300, and 300b is a second output electrode of the oscillator 300.

In the configuration of the polarization characteristic evaluation apparatus for the ferroelectric capacitor shown in FIG. 23, the wirings 305, 306, 307, 30 are used.
8, 309 and 310 are semiconductor substrates 99 as integrated circuits.
The stray capacitance is small because it is formed on top. As a result, as shown in FIG. 24, it is possible to perform a reliability simulation test of deterioration of nonvolatile polarization due to an AC voltage pulse having a pulse width of 100 ns or less. Further, the pulse generator 102
And 103, oscillator 300, buffers 301 and 302
On a semiconductor substrate 99, and pulse generators 102 and 1
Since the voltage pulse generated in 03 and the voltage pulse generated in the oscillator are applied to the ferroelectric capacitor 100 via the buffers 301 and 302, it depends on the waveform of the voltage pulse used for the evaluation of the non-volatile polarization and the AC voltage pulse. The waveform of the voltage pulse used to evaluate the deterioration of the polarization characteristics can be made substantially the same, and the reliability simulation test of the deterioration of the non-volatile polarization can be accurately performed.

Next, a fourth embodiment of the present invention will be described. FIG. 25 is a diagram showing the configuration of the polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the fourth example of the present invention. In this example, the buffer 30 used in FIG.
The pulse from the pulse generator is directly applied to the ferroelectric capacitor 100 without using 1 and 302. Here, the trigger signal input electrode of the trigger generator 600 and the first and second electrodes 3 of the oscillator 300 are used.
00a and 300b are the first and second pulse generators 1
It is applied to the ferroelectric capacitor 100 via 02 and 103. The output of the oscillator is input to the ferroelectric capacitor via the first and second pulse generators. Like the above-described embodiment, the same parts are designated by the same reference numerals.

Therefore, also with this configuration, the output of the oscillator is applied to the ferroelectric capacitor 100 via the pulse generator, so that the pulse width of the output of the oscillator is controlled by the pulse generator, and the evaluation of the non-volatile polarization is performed. The waveform of the voltage pulse used and the waveform of the voltage pulse used to evaluate the deterioration of the polarization characteristics due to the AC voltage pulse can be made almost the same, and the reliability simulation test of the deterioration of the nonvolatile polarization can be performed accurately. . That is, the stress waveform and the measurement waveform can be the same, and the reliability test and the measurement for evaluating the polarization characteristic can be performed under the same condition.

Also with this structure, as in the third embodiment, the pulse generator, the oscillator, and the reference capacitor are all formed on the same semiconductor substrate as the ferroelectric capacitor to be measured. That is, in the configuration of the polarization characteristic evaluation device for a ferroelectric capacitor shown in FIG.
Since 5, 306, 307, 308, 309 and 310 are formed on the semiconductor substrate 99 as an integrated circuit, the stray capacitance is small. As a result, as shown in FIG.
It is possible to perform a reliability simulation test of deterioration of non-volatile polarization due to an AC voltage pulse having a pulse width of 100 ns or less. The stray capacitance due to the wiring is further reduced, a higher-frequency pulse can be accurately applied, and higher-precision measurement is possible.

Further, the area occupied by the chip can be made smaller. Furthermore, because the oscillator, the ferroelectric capacitor, and the pulse generator are all formed on the same semiconductor substrate, they all have the same temperature, so they are highly accurate measurement with little temperature dependence against environmental temperature changes. And, it becomes possible to perform a reliability test. Next, a fifth embodiment of the present invention will be described.

FIG. 26 is a diagram showing the configuration of a polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the fifth embodiment of the present invention. In this example, the oscillator 300, which is arranged on the same semiconductor substrate 99 as the pulse generator, the ferroelectric capacitor and the reference capacitor in the fourth embodiment of the present invention shown in FIG. A so-called multi-chip circuit formed on the semiconductor substrate. The operation and the evaluation method using the same are the same as those in the fourth embodiment. According to such a configuration, in addition to the effect of the fourth embodiment, the oscillator is not formed on the same semiconductor substrate, so that the temperature change due to the heat generation of the oscillator can be avoided, and more accurate measurement can be performed. Is possible. However, the semiconductor substrate that constitutes the integrated circuit for measuring the polarization characteristics, in terms of reducing the wiring capacitance,
It is desirable to install them as close to each other as possible in order to arrange the measurement environment.

Furthermore, in order to improve the measurement accuracy,
As a sixth embodiment of the present invention, as shown in a sectional view of FIG. 27, a semiconductor substrate 99 that constitutes an integrated circuit for measuring polarization characteristics, and a semiconductor substrate 310 for oscillator, so as to constitute a multichip module. Are preferably packaged in the same package 700. In addition, as a seventh embodiment of the present invention, as shown in FIG. 28, when it is used only for the reliability test, an integrated circuit for measuring polarization characteristics is configured without forming a pulse generator. On the semiconductor substrate 99, the oscillator 300 and the reference capacitor 1
01 and the ferroelectric capacitor 100 may be formed. Here, in the fourth embodiment shown in FIG. 25, from the top of the semiconductor substrate 99 forming the integrated circuit, the first
And the second pulse generators 102 and 103 are removed, and the trigger generator is removed, and the other configurations are formed in exactly the same manner as the fourth embodiment.

According to such an apparatus, the controller 600
Thus, the oscillation wavelength can be changed, and a pulse having a desired wavelength can be applied to the ferroelectric capacitor to be measured via the oscillator 300 to perform the reliability test.

[0069]

As described above, according to the present invention, since the pulse generator and the ferroelectric capacitor are arranged on the same substrate, the stray capacitance of the wiring connecting them is small, and the pulse generator generates them. The applied voltage pulse does not cause ringing. Therefore, a voltage pulse of 100 ns or less can be accurately applied to the electrodes of the ferroelectric capacitor.

Further, since a voltage pulse of 100 ns or less can be used, it is possible to evaluate the polarization characteristics by applying a voltage pulse of 100 ns or less to obtain 100
Changes in polarization characteristics due to voltage pulses of ns or less can be evaluated, and the applied pulse for applying stress and the pulse for measurement can be the same pulse, so a more accurate reliability test can be performed. It will be possible.

Further, since the oscillator and the ferroelectric capacitor are arranged on the same substrate, the stray capacitance of the wiring connecting the electrodes of both is small, and the voltage pulse generated by the oscillator does not ring. . Therefore, 100n
An AC voltage pulse of s or less can be accurately applied to the electrodes of the ferroelectric capacitor, and a reliability simulation test using the AC voltage pulse can be performed. You can also adjust the wavelength,
It is possible to perform a reliability simulation test using an AC voltage pulse without occupying an arbitrary waveform pulse generator.

Further, since the output electrode of the pulse generator and the output electrode of the oscillator are connected to the electrode of the ferroelectric capacitor through a common buffer, it is used for a reliability simulation test of deterioration of polarization characteristics. Since the polarization characteristic can be evaluated by using the voltage pulse having the same waveform as that of the voltage pulse, an accurate reliability simulation test can be performed.

Further, according to the evaluation method of the present invention, since the polarization initialization step is provided, it is possible to evaluate the polarization inversion amount when the voltage pulse is applied without being affected by the polarization state before that. It can be carried out. Further, according to the evaluation method of the present invention, since the polarization setting step is provided, the FeRAM
It is possible to cope with the reading from the insufficient write state, which is important in the operation of 1), that is, it is possible to evaluate the polarization inversion amount when the voltage pulse is applied from the intermediate polarization state.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a polarization characteristic evaluation device for a ferroelectric capacitor according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing steps of a polarization characteristic evaluation method by the polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing steps of a polarization characteristic evaluation method by the polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the first embodiment of the present invention.

FIG. 4 is an example of an observation result of a voltage waveform by an electron beam tester when a voltage pulse is applied to the ferroelectric capacitor by using the polarization characteristic evaluation device for the ferroelectric capacitor according to the first embodiment of the present invention. Figure shown

FIG. 5 is a diagram showing a voltage pulse and an example of a voltage waveform measured by an oscilloscope when the polarization characteristic is evaluated using the polarization characteristic evaluation device for a ferroelectric capacitor according to the first example of the present invention.

FIG. 6 is a diagram showing an example of polarization characteristics measured by a polarization characteristics evaluation device for a ferroelectric capacitor according to a first embodiment of the present invention.

FIG. 7 is a diagram showing an example of pulse width dependency and pulse voltage dependency of non-volatile polarization measured by the polarization characteristic evaluation apparatus for the ferroelectric capacitor according to the first example of the present invention.

FIG. 8 is a flowchart showing steps of a polarization characteristic evaluation method by a polarization characteristic evaluation device for a ferroelectric capacitor according to a second embodiment of the present invention.

FIG. 9 is a flowchart showing steps of a polarization characteristic evaluation method by a polarization characteristic evaluation device for a ferroelectric capacitor according to a second embodiment of the present invention.

FIG. 10 is a flowchart showing steps of a polarization characteristic evaluation method by a polarization characteristic evaluation device for a ferroelectric capacitor according to a second embodiment of the present invention.

FIG. 11 is a flowchart showing steps of a polarization characteristic evaluation method by a polarization characteristic evaluation device for a ferroelectric capacitor according to a second embodiment of the present invention.

FIG. 12 is a flowchart showing steps of a polarization characteristic evaluation method by a polarization characteristic evaluation device for a ferroelectric capacitor according to a second embodiment of the present invention.

FIG. 13 is a flowchart showing steps of a polarization characteristic evaluation method by a polarization characteristic evaluation device for a ferroelectric capacitor according to a second embodiment of the present invention.

FIG. 14 is a diagram showing an example of a voltage pulse and a voltage waveform measured by an oscilloscope when a polarization characteristic is evaluated using the polarization characteristic evaluation device for a ferroelectric capacitor according to the second example of the present invention.

FIG. 15 is a diagram showing an example of a voltage pulse and a voltage waveform measured by an oscilloscope when a polarization characteristic is evaluated using the polarization characteristic evaluation device for a ferroelectric capacitor according to the second example of the present invention.

FIG. 16 is a diagram showing an example of a voltage pulse and a voltage waveform measured by an oscilloscope when the polarization characteristic is evaluated by using the polarization characteristic evaluation apparatus for a ferroelectric capacitor according to the second example of the present invention.

FIG. 17 is a diagram showing an example of polarization characteristics measured by a polarization characteristics evaluation device for a ferroelectric capacitor according to a second embodiment of the present invention.

FIG. 18 is a diagram showing an example of polarization characteristics measured by a polarization characteristics evaluation device for a ferroelectric capacitor according to a second embodiment of the present invention.

FIG. 19 is a diagram showing an example of polarization characteristics measured by a polarization characteristics evaluation device for a ferroelectric capacitor according to a second embodiment of the present invention.

FIG. 20 is a diagram showing an example of pulse width dependency and pulse voltage dependency of nonvolatile polarization measured by a polarization characteristic evaluation device for a ferroelectric capacitor according to a second example of the present invention.

FIG. 21 is a diagram showing an example of pulse width dependency and pulse voltage dependency of nonvolatile polarization measured by a polarization characteristic evaluation device for a ferroelectric capacitor according to a second example of the present invention.

FIG. 22 is a diagram showing an example of pulse width dependency and pulse voltage dependency of non-volatile polarization measured by a polarization characteristic evaluation device for a ferroelectric capacitor according to a second example of the present invention.

FIG. 23 is a diagram showing a configuration of a polarization characteristic evaluation device for a ferroelectric capacitor according to a third embodiment of the present invention.

FIG. 24 is a diagram showing deterioration of non-volatile polarization due to an AC voltage pulse evaluated by using a polarization characteristic evaluation device for a ferroelectric capacitor according to a third example of the present invention.

FIG. 25 is a diagram showing a configuration of a polarization characteristic evaluation device for a ferroelectric capacitor according to a fourth example of the present invention.

FIG. 26 is a diagram showing a configuration of a polarization characteristic evaluation device for a ferroelectric capacitor according to a fifth example of the present invention.

FIG. 27 is a diagram showing the configuration of a polarization characteristic evaluation device for a ferroelectric capacitor according to a sixth embodiment of the present invention.

FIG. 28 is a diagram showing the configuration of a polarization characteristic evaluation device for a ferroelectric capacitor according to a seventh embodiment of the present invention.

FIG. 29 is a diagram showing a configuration of a conventional polarization characteristic evaluation device for a ferroelectric capacitor.

FIG. 30 is a flowchart showing steps of a polarization characteristic evaluation method by a conventional ferroelectric capacitor polarization characteristic evaluation apparatus.

FIG. 31 is a diagram showing a voltage pulse and a voltage waveform measured by an oscilloscope when a polarization characteristic is evaluated using a conventional ferroelectric capacitor polarization characteristic evaluation apparatus.

FIG. 32 is a diagram of polarization characteristics measured by a conventional polarization characteristics evaluation device for a ferroelectric capacitor.

[Explanation of symbols]

99 semiconductor substrate 100 Ferroelectric capacitor 101 Reference capacitor 102, 103 pulse generator 104, 105, 301, 302 buffers 106 Impedance converter 107, 108, 303, 304 Electric switch 121 Arbitrary waveform pulse generator 122 Oscilloscope 123,124,125,126 wiring cable 300 oscillator 500 controller 600 trigger generator

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01R 31/00 G01N 27/60 G01R 27/26 G01R 29/24 H01L 21/66 G11C 29/00 H01L 41 / twenty two

Claims (8)

(57) [Claims] 1. A ferroelectric capacitor on a semiconductor substrate,
A pulse generator connected to the ferroelectric capacitor,
A reference capacitor having a known capacitance, the first electrode of which is detachably connected to the second electrode of the ferroelectric capacitor, and the first electrode of the ferroelectric capacitor and the arbitrary waveform pulse generator A polarization characteristic evaluation method for a ferroelectric capacitor using a device for polarization characteristic evaluation that is disconnectably connected, wherein a polarization state is obtained by applying a first voltage pulse from the pulse generator of the ferroelectric capacitor. A first polarization initialization step of a predetermined state, the ferroelectric capacitor, the arbitrary waveform pulse generator and the reference capacitor are connected, a constant voltage to the second electrode of the reference capacitor. The capacitor for reference when the second voltage pulse is applied from the arbitrary waveform pulse generator to the first electrode of the ferroelectric capacitor in the applied state. The first potential change measuring step of measuring the potential change at the first electrode of, the ferroelectric capacitor, the arbitrary waveform pulse generator and the reference capacitor are cut off, the first potential change Based on the potential change measured in the measurement step and the capacitance of the reference capacitor, the first to calculate the change in the charge amount at the second electrode of the ferroelectric capacitor in the first potential change measurement step A charge amount change calculating step, a second polarization initializing step that performs the same polarization initializing step as the first polarization initializing step, and a third voltage pulse is applied to the ferroelectric capacitor from the pulse generator. And a polarization reversal step of reversing the polarization state, a second potential change measurement step of performing the same potential change measurement as the first potential change measurement step, and the same as the first charge amount change calculation step. The second of the ferroelectric capacitor in the second potential change measuring step.
A second charge amount change calculating step for calculating a change in the charge amount at each electrode, and a non-volatile polarization calculating a non-volatile polarization from each charge amount obtained in the first and second charge amount change calculating steps. A method of evaluating a polarization characteristic of a ferroelectric capacitor, comprising: a calculation step. 2. The third step after the nonvolatile polarization calculation step.
The pulse width of the pulse is changed, and the same steps as the steps from the second polarization initialization step to the nonvolatile polarization calculation step are repeated to obtain the pulse width dependence of the nonvolatile polarization. The method for evaluating the polarization characteristics of a ferroelectric capacitor according to claim 1, wherein 3. After the nonvolatile polarization calculating step, the third polarization is calculated.
The pulse voltage of the pulse is changed, and the same steps as the steps from the second polarization initialization step to the non-volatile polarization calculation step are repeated to obtain the pulse voltage dependence of the non-volatile polarization. Claim 1 characterized in that
7. A method for evaluating polarization characteristics of a ferroelectric capacitor as described in. 4. The method of evaluating the polarization characteristics of a ferroelectric capacitor according to claim 1, wherein at least the third pulse is a voltage pulse having a pulse width of 100 ns or less. 5. A ferroelectric capacitor on a semiconductor substrate,
A pulse generator connected to the ferroelectric capacitor,
A reference capacitor having a known capacitance, the first electrode of which is detachably connected to the second electrode of the ferroelectric capacitor, and the first electrode of the ferroelectric capacitor and the arbitrary waveform pulse generator A polarization characteristic evaluation method for a ferroelectric capacitor using a device for polarization characteristic evaluation that is disconnectably connected, wherein a polarization state is obtained by applying a first voltage pulse from the pulse generator of the ferroelectric capacitor. After a predetermined state, the first polarization initialization step of applying a second voltage pulse from the pulse generator so that the polarization amount is in a polarization state near zero, the ferroelectric capacitor, and The arbitrary waveform pulse generator is connected to the reference capacitor, and a second voltage of the ferroelectric capacitor is applied in a state where a constant voltage is applied to the first electrode of the reference capacitor. A first potential change measuring step of measuring a potential change at the first electrode of the reference capacitor when a third voltage pulse is applied to a pole from the arbitrary waveform pulse generator; and the ferroelectric capacitor And, disconnecting the arbitrary waveform pulse generator and the reference capacitor, based on the potential change and the capacitance of the reference capacitor measured in the first potential change measurement step, the first potential change measurement A first charge amount change calculation step of calculating a change in charge amount at the second electrode of the ferroelectric capacitor in the step, and a second polarization initialization similar to the first polarization initialization step. Polarization initialization step, polarization inversion step of inverting the polarization state by applying a fourth voltage pulse from the pulse generator to the ferroelectric capacitor, and the first potential change measurement A second potential change measurement step of performing the same potential change measurement and extent, a second of the ferroelectric capacitor in the first charge amount variation calculating step and the similarly the second potential change measurement step
A second charge amount change calculating step for calculating a change in the charge amount at each electrode, and a non-volatile polarization calculating a non-volatile polarization from each charge amount obtained in the first and second charge amount change calculating steps. A method of evaluating a polarization characteristic of a ferroelectric capacitor, comprising: a calculation step. 6. The fourth step after the nonvolatile polarization calculation step.
The pulse width of the pulse is changed, and the same steps as the steps from the second polarization initialization step to the nonvolatile polarization calculation step are repeated to obtain the pulse width dependence of the nonvolatile polarization. The method for evaluating the polarization characteristics of a ferroelectric capacitor according to claim 5, wherein 7. The fourth step after the nonvolatile polarization calculation step.
The pulse voltage of the pulse is changed, and the same steps as the steps from the second polarization initialization step to the non-volatile polarization calculation step are repeated to obtain the pulse voltage dependence of the non-volatile polarization. 6. The method according to claim 5, wherein
7. A method for evaluating polarization characteristics of a ferroelectric capacitor as described in. 8. The method for evaluating the polarization characteristics of a ferroelectric capacitor according to claim 5, wherein at least the fourth pulse is a voltage pulse having a pulse width of 100 ns or less.