JPH05119094A - Ferroelectric thin film measuring instrument - Google Patents

Abstract

PURPOSE:To obtain a ferroelectric thin film measuring instrument which can simultaneously measure the residual polarization and switching time of a ferroelectric thin film with the same measuring system. CONSTITUTION:A voltage generator 13 is connected so that the generator 13 can generates a testing voltage of a square wave and apply the voltage between electrodes 11 and 12 through a capacitor 14. Both ends of the capacitor 14 are respectively connected to the (+) and (-) input terminals of a differential amplifier 15. In case residual polarization exists in a ferroelectric thin film 10 when the generator 13 generates the testing voltage and applies the voltage the electrodes 11 and 12 through the capacitor 14, a voltage Vr proportional to the residual polarization is generated across the capacitor 14. Therefore, when the voltage Vr proportional to the residual polarization is fetched through the amplifier 15 and observed on an oscilloscope, the residual polarization of the thin film 10 can be measured. In addition, by differentiating the output signal of the amplifier 15 by means of a differentiation circuit 16, the differentiated waveform corresponding to an inverted current generated when polarization inversion takes place in the thin film 10 is obtained and, when the differentiated waveform is observed on the oscilloscope, the switching time of the thin film 10 can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric thin film measuring device for measuring remanent polarization and switching time of a ferroelectric thin film.

[0002]

2. Description of the Related Art Conventionally, an apparatus for measuring remanent polarization of a ferroelectric thin film uses a measuring system having a Soyer-Tauer circuit as a basic structure, and a voltage is applied to the ferroelectric thin film to make a DE hysteresis loop. And the residual polarization voltage when the applied voltage is “0” is measured. On the other hand, the device for measuring the switching time of the ferroelectric thin film is configured to apply a positive and negative square wave to the ferroelectric thin film and measure the time change of the reversal current accompanying the polarization reversal of the ferroelectric thin film. ing.

[0003]

Generally, it is desirable that the measurement of the remanent polarization and the switching time of such a ferroelectric thin film can be performed as easily as possible.

However, since the configuration and measuring method of the above-mentioned remanent polarization measuring device and the configuration and measuring method of the switching time measuring device are completely different from each other, the remanent polarization and the switching time are simultaneously measured in order to simplify the measurement. It is not possible.

The present invention has been made in view of the above-mentioned conventional problems, and a ferroelectric thin film measuring apparatus capable of simultaneously measuring the remanent polarization of a ferroelectric thin film and the switching time in the same measuring system. The task is to provide.

[0006]

In order to achieve the above-mentioned object, the ferroelectric thin film measuring device of the present invention comprises a capacitor connected in series to the ferroelectric thin film to be measured and a capacitor connected in series. A test wave generating means for applying a positive and negative square wave to the ferroelectric thin film via the detecting means; a detecting means for detecting the voltage across the capacitor; and a differentiating circuit for differentiating the voltage detected by the detecting means. Characterize.

[0007]

When performing the measurement with the ferroelectric thin film measuring apparatus of the present invention, the capacitor is first connected in series to the ferroelectric thin film to be measured. In this state, when the test wave generating means applies positive and negative square waves to the ferroelectric thin film via the capacitor, a voltage proportional to the remanent polarization existing in the ferroelectric thin film is generated across the capacitor. Here, since the detection means detects the voltage across the capacitor, the residual polarization of the ferroelectric thin film can be measured by the detected voltage. At the same time, the differentiating circuit differentiates the voltage detected by the detecting means, so that the switching time of the ferroelectric thin film can be measured by the differentiated waveform. As a result, the remanent polarization of the ferroelectric thin film and the switching time can be simultaneously measured by the same measuring system.

From the following examples of the present invention, such an effect of the present invention will be further clarified, and further another effect of the present invention will be clarified.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main configuration of a ferroelectric thin film measuring apparatus according to an embodiment of the present invention, and FIG. 2 is a waveform diagram showing main signals in the ferroelectric thin film measuring apparatus of FIG.

In FIG. 1, the ferroelectric thin film measuring device is
Electrodes 11 and 12 for sandwiching the ferroelectric thin film 10 to be measured as a sample, a voltage generator 13 as an example of test wave generating means, and a capacitor connected in series to the ferroelectric thin film 10.
14 and.

The electrodes 11 and 12 are electrically insulated from each other, and the electrode 12 is grounded. The voltage generator 13 is connected so that one end thereof generates a square-wave test voltage as shown in A of FIG. 2 and applies it to the electrode 11 via the capacitor 14, and the other end of the voltage generator 13 is connected. Are grounded together with the electrode 12. That is, the voltage generator 13 applies positive and negative square wave test voltages to the series circuit of the capacitor 14 and the ferroelectric thin film 10.

Here, the peak value Va of the test voltage generated by the voltage generator 13 is set to a value equal to or higher than the voltage at which the ferroelectric thin film 10 can be completely polarized. Furthermore, the capacitor 14 is
Those having no remanent polarization are selected, and their capacitance C1 is selected so as to have a relationship of Cx << C1 with the capacitance Cx of the ferroelectric thin film 10.

In FIG. 1, the ferroelectric thin film measuring device further includes a differential amplifier 15 and an differentiating circuit 16 which constitute an example of a detecting means.

Both ends of the capacitor 14, that is, the voltage generator 13 side,
The electrode 11 side is connected to the + input terminal and the − input terminal of the differential amplifier 15, respectively. As a result, with respect to the square-wave test voltage as shown in FIG. 2A, the differential amplifier 15 obtains a detected waveform as shown in FIG. 2B as its output signal, which is observed at the oscilloscope. Further, the output signal of the differential amplifier 15 is input to the differentiating circuit 16, and the differentiating circuit 16 further obtains a detection waveform as shown in C of FIG. 2 as its output signal, which is observed by the oscilloscope.

Next, the operation of the ferroelectric thin film measuring device configured as described above will be described with reference to FIGS. 1 and 2. When the voltage generator 13 applies a square wave test voltage of voltage ± Va to the electrode 11 via the capacitor 14 as shown in A of FIG. 2, when the ferroelectric thin film 10 has remanent polarization, B of FIG. As indicated by circle d in the detection waveform of
A voltage Vr proportional to the remanent polarization is generated at both ends of. That is, when the test voltage has a positive polarity, a voltage Vr / 2 proportional to the residual polarization is generated, and when the test voltage has a reverse polarity, a reverse polarity voltage (-Vr / 2) proportional to the residual polarization is generated. Therefore,
By taking out the voltage Vr proportional to the remanent polarization through the differential amplifier 15 and observing it with an oscilloscope,
The remanent polarization of the ferroelectric thin film 10 can be measured.

Further, at this time, when the output signal of the differential amplifier 15 is differentiated by the differentiating circuit 16, as shown in C of FIG.
Since it is possible to obtain a differential waveform corresponding to the reversal current accompanying the polarization reversal of the ferroelectric thin film 10, the switching time of the ferroelectric thin film 10 can be measured by observing this differential waveform with an oscilloscope. .

As described above, according to this embodiment, the remanent polarization and the switching time can be measured at the same time.

[0018]

As described in detail above, a capacitor connected in series to a ferroelectric thin film, a test wave generating means for applying a positive and negative square wave to the ferroelectric thin film via the capacitor, and both ends of the capacitor. Since the detection means for detecting the voltage and the differentiation circuit for differentiating the voltage detected by the detection means are provided, the remanent polarization of the ferroelectric thin film and the switching time can be simultaneously measured by the same measurement system.

[Brief description of drawings]

FIG. 1 is a block diagram showing a ferroelectric thin film measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing main signals in the ferroelectric thin film measuring apparatus of FIG.

[Explanation of symbols]

 10 Ferroelectric thin film 13 Voltage generator 14 Capacitor 15 Differential amplifier 16 Differentiation circuit

Claims (1)

[Claims] 1. A capacitor connected in series to a ferroelectric thin film to be measured, test wave generating means for applying a positive and negative square wave to the ferroelectric thin film via the capacitor connected in series, and A ferroelectric thin film measuring apparatus comprising: a detection unit that detects the voltage across the capacitor; and a differentiation circuit that differentiates the voltage detected by the detection unit.