CN1253722C - Ferroelectric thin film material dielectric performance multi-frequency automatic testing method and device - Google Patents

Abstract

The present invention relates to a ferroelectric thin film material dielectric performance multi-frequency automatic testing method and a device thereof, which is a testing method and a device of ferroelectric functional ceramic materials. The testing method is characterized in that any end of a ferroelectric thin film to be tested is connected with a negative electrode of an output end of a signal generator, an electrode on the other end of the ferroelectric thin film is in series connected with any end of a resistor, the resistance quantity of which is known, the other end of the resistor is connected with a positive electrode of the output end of the signal generator, wherein the negative electrode of the output end of the signal generator is used as a reference ground; sampled signals are calculated by a sensitive detection method of a digital phase to obtain amplitudes V0 and Vp of signals of both ends and phase difference theta between the signals of the both of the two ends, wherein the sensitive detection method of a digital phase is characterized in that after converted through analog/digital, a signal to be tested is digitally demodulated and calculated by a microprocessor. Thus, the equivalent capacitance quantity Cp and an equivalent resistance value Rp of the ferroelectric thin film to be tested are obtained, and a relative dielectric constant epsilon r and the dielectric loss tg delta of the ferroelectric thin film to be tested are also obtained.

Description

Multi-frequency automatic test method and device for dielectric properties of ferroelectric thin film materials

Technical field

The invention relates to a method and device for testing ferroelectric functional ceramic materials, in particular to a method and device for testing the dielectric properties of lead zirconate titanate (PZT) ferroelectric film materials.

Background technique

Ferroelectric material is a kind of functional material, which has a wide range of uses in the fields of electronics industry, computing, laser, infrared, micro-acoustic, automatic control, measurement and energy engineering. Lead zirconate titanate (molecular formula: Pb(Zr,Ti)O ₃ , referred to as PZT) is a ferroelectric material with excellent performance, which has long been used in the manufacture of non-volatile dynamic random access memory. In recent years, with the rapid development of MEMS technology, PZT ferroelectric thin film has been favored because of its advantages of high piezoelectric constant and high electromechanical coupling coefficient, and is considered to be the most promising sensor in MEMS. It is widely used in the manufacture of micro-motors, micro-mirrors and micro-piezoelectric cantilever beams in micro-electromechanical systems. At present, there are a variety of techniques for the preparation of PZT ferroelectric thin films in MEMS, such as: sol-gel method, magnetron sputtering method, pulsed laser deposition method, hydrothermal method, and spray casting method, etc. However, , the properties of PZT ferroelectric films prepared by different methods are very different, and the properties of PZT ferroelectric films prepared by the same method under different process conditions are also quite different, so for the dielectric properties of PZT ferroelectric films There are high requirements for the adaptability and test convenience of the test method. In addition, the performance test of tiny PZT patterns in the process of micro-device processing also puts forward higher requirements for the sensitivity and resolution of the test device. Therefore, the research on the performance testing technology of PZT ferroelectric thin film has become one of the key issues in the research of PZT ferroelectric thin film preparation technology and the design of microsensors and microdrivers based on PZT ferroelectric thin film.

The dielectric properties of ferroelectric materials include relative permittivity (ε _r ), dielectric loss (tgδ) and other parameters. The measurement of the relative permittivity (ε _r ) of the ferroelectric material is calculated by measuring the capacitance of the sample. There are many methods, such as resonance method, beat method, comparison method, substitution method, voltage division method, Q meter method and bridge method, etc. The dielectric loss (tgδ) measurement methods of ferroelectric materials include Q meter method, impedance bridge method, tgδ meter direct reading method, etc. These commonly used methods have various disadvantages, for example, they require standard variable capacitors or high-precision frequency meters or high-precision dedicated capacitance measuring instruments; The relative permittivity and dielectric loss, and the above methods are all aimed at the relative permittivity and dielectric loss of the sample at a single frequency.

Contents of Invention

Technical problem: the object of the present invention is to provide a multi-frequency automatic test of the dielectric properties of ferroelectric thin film materials with high precision, which can accurately, conveniently and quickly automatically measure the dielectric properties of ferroelectric thin film materials at various frequencies Methods and devices.

Technical solution: the technical solution of the present invention is as follows:

The test method (plan 1) is:

1). Connect any end of the ferroelectric film to be tested to the negative electrode of the output terminal of the signal generator, and connect the electrode at the other end of the ferroelectric film to be tested in series with any end of a resistor with a known resistance value. The other end is connected to the positive electrode of the output terminal of the signal generator, and the negative electrode of the output terminal of the signal generator is used as the reference ground:

2). Set the signal generator so that it outputs a sine wave at the frequency point to be tested; synchronously collect the sine voltage signal at both ends of the known resistance, at least one complete cycle of the signal is collected, and the sampling frequency depends on the specific used The requirements of the digital phase-sensitive detection algorithm are set; the sampled signal is calculated by the digital phase-sensitive detection method, and the amplitude V ₀ and V _p of the signals at both ends and the phase difference θ between the signals at the two ends are obtained ;

3). According to formula $C_P=\frac{\left|\sin \mathrm{\θ}\right|*V_0}{R*2*\mathrm{\π}*f*V_P},$ $R_P=\frac{R}{\frac{\left|\mathrm{COS\θ}\right|*V_0}{V_P}-1}---\left(1\right)$

Obtain the equivalent capacitance _Cp and equivalent resistance value _Rp of the ferroelectric thin film to be tested;

According to formula ${\mathrm{\ϵ}}_r=\frac{C_{p}t}{{\mathrm{\ϵ}}_{0}A},$ $\mathrm{tg\δ}=\frac{1}{2\mathrm{\πf}{C}_p{R}_p}---\left(2\right)$

Obtain the relative permittivity ε _r and the dielectric loss tgδ of the ferroelectric thin film to be measured;

In the formula, _V0 is the amplitude of the sinusoidal voltage signal at the end of the auxiliary voltage dividing resistor connected to the positive electrode of the signal generator output; _Vp is the amplitude of the sinusoidal voltage signal at the connecting end of the auxiliary voltage dividing resistor and the ferroelectric film to be measured, θ In order to measure the phase difference between the sinusoidal voltage signals at both ends of the auxiliary voltage divider resistor (namely the above two circuits), f is the frequency of the sine wave generated by the signal generator, R is the resistance value of the known resistor; t is the iron to be tested The thickness of the electric film, A is the electrode area of the ferroelectric film to be tested, and _ε0 is the vacuum permittivity.

The test method (plan 2) is:

1). Connect any terminal electrode of the ferroelectric film to be tested to the negative electrode of the output terminal of the signal generator, connect the other terminal electrode of the ferroelectric film to be tested in series with any terminal of a resistor with a known resistance value, and the other terminal of the resistor Connect to the positive electrode of the output terminal of the signal generator, and use the negative electrode of the output terminal of the signal generator as the reference ground;

2). Set the signal generator so that it outputs a sine wave signal at the frequency point to be measured, and use a commercial lock-in amplifier to measure the amplitudes V ₀ and V _p of the sinusoidal voltage signals at both ends of the known resistance and the two channels The phase difference θ ₀ and θ _p of the signal relative to the synchronous reference signal output by the signal generator, and the phase difference θ=θ ₀ -θ _p between the two signals is calculated from these two phase differences;

3) According to the formula $C_P=\frac{\left|\sin \mathrm{\θ}\right|*V_0}{R*2*\mathrm{\π}*f*V_P},$ $R_P=\frac{R}{\frac{\left|\cos \mathrm{\θ}\right|*V_0}{V_P}-1}---\left(1\right)$

Obtain the equivalent capacitance _Cp and equivalent resistance value _Rp of the ferroelectric thin film to be tested;

According to formula ${\mathrm{\ϵ}}_r=\frac{C_{p}t}{{\mathrm{\ϵ}}_{0}A},$ $\mathrm{tg\δ}=\frac{1}{2\mathrm{\πf}{C}_p{R}_p}---\left(2\right)$

The relative permittivity ε _r and dielectric loss tgδ of the ferroelectric thin film to be tested are obtained.

The measuring device (Scheme 1) includes: a test signal generator, a measuring auxiliary voltage dividing resistor, an A/D conversion and interface control unit, a microprocessor main control unit and a computer for realizing digital phase-locking calculation and sampling control. Connect any end electrode of the ferroelectric film to be tested to the negative electrode of the output terminal of the test signal generator, connect the other end of the ferroelectric film to be tested with any end of the auxiliary voltage dividing resistor in series, and connect the other end of the measuring auxiliary voltage dividing resistor to The positive electrode of the output terminal of the test signal generator is connected. In this way, the ferroelectric thin film to be tested, the auxiliary voltage dividing resistor for measurement and the test signal generator are connected in series to form a loop, and the loop uses the negative electrode at the output end of the test signal generator as a reference ground. The two input ends of the A/D conversion and interface control unit are respectively connected with the two ends of the measuring auxiliary voltage dividing resistor. The digital signal output and control signal of the A/D conversion and interface control unit are connected with the digital and control bus of the microprocessor main control unit. The microprocessor main control unit is connected with the computer through a printer parallel interface or an RS232 serial interface or a USB interface or a PCI bus.

Or the device (solution 2) of the present invention includes: a test signal generator, a measuring auxiliary voltage dividing resistor, a commercial lock-in amplifier unit and a computer. Any end of the ferroelectric film to be tested is connected to the negative electrode of the output terminal of the test signal generator, the other end electrode of the ferroelectric film to be tested is connected in series with any end of the measuring auxiliary voltage dividing resistor, and the other end of the measuring auxiliary voltage dividing resistor is connected to the test The positive electrode of the output terminal of the signal generator is connected. In this way, the ferroelectric thin film to be tested, the auxiliary voltage dividing resistor for measurement and the test signal generator are connected in series to form a loop, and the loop uses the negative electrode at the output end of the test signal generator as a reference ground. The sync output of the test signal generator is connected to the reference input of a commercial lock-in amplifier unit. The input terminal of the commercial lock-in amplifier unit is connected to both ends of the measuring auxiliary voltage dividing resistor. The commercial lock-in amplifier unit is connected with the computer through a printer parallel port or an RS232 serial port or a USB port or a PCI bus.

The test signal generators described in Scheme 1 and Scheme 2 are general-purpose function generators, which are used to generate standard sine waves of various frequencies. The test system uses the sine wave signal generated by the signal generator as the reference signal for the test, that is to say, the test system tests the relative permittivity and Dielectric loss.

The measurement auxiliary voltage dividing resistance described in scheme one and scheme two is the standard resistance of known resistance value, and its value is of the same order of magnitude as the equivalent resistance value of the ferroelectric film to be measured at the intermediate frequency of the measurement frequency range; The auxiliary voltage divider resistor is connected in series with the ferroelectric film to be tested, and the other ends of the voltage divider resistor and the ferroelectric film are respectively connected to the positive and negative electrodes of the output terminal of the signal generator; the series circuit takes the negative output terminal of the signal generator as a reference land.

The A/D conversion and interface control unit described in the first solution includes: an analog signal amplification and adjustment circuit, an A/D conversion part, an interface control part and a power supply part.

The A/D conversion part includes exactly the same two A/D conversion channels, each channel includes an A/D conversion circuit, and an analog signal amplification and adjustment circuit corresponding to it. The A/D conversion circuit and the analog signal amplification and adjustment circuit also use the negative output terminal of the aforementioned signal generator as a reference ground. The two A/D conversion channels must be able to perform A/D conversion completely synchronously, and the two A/D conversion channels can output valid data notification signals independently. The input terminals of the analog signal amplification and adjustment circuits of the two A/D conversion channels are respectively connected to the two ends of the aforementioned measurement auxiliary voltage dividing resistors which have been connected in series with the ferroelectric film to be tested and the signal generator to form a loop. The outputs of the two analog signal amplification and adjustment circuits are respectively connected to the inputs of the corresponding A/D conversion circuits. The data line and control line of the A/D conversion part are connected with the data line and control line of the interface control part. The interface control part has interface control and data buffering functions. The interface control part can access the data, control and state memory of two A/D conversion channels, and can choose to read, write and control any A/D conversion channel. The output of the power supply part is connected with the analog signal amplification and adjustment circuit, the A/D conversion circuit and the corresponding power input of the interface control part to provide power for these three parts.

The microprocessor main control unit for implementing digital phase-locking calculation and sampling control described in Scheme 1 can be composed of a system based on a digital signal processor (DSP), a system based on a single-chip microcomputer or a system based on an embedded microprocessor. , Functionally, the unit realizes digital lock-in amplification calculation, sampling control, port control and communication control, etc. For a microprocessor system with a built-in A/D conversion and interface control unit, if the performance of the built-in A/D conversion and interface control unit meets the requirements of the system, the aforementioned A/D conversion and interface control unit can be omitted. The microprocessor main control unit shall at least include a microprocessor, a host interface control unit, a program and data memory, an expansion peripheral bus control unit, a power supply and other peripherals. The expansion peripheral bus of the microprocessor main control unit is connected with the output bus of the interface control part of the aforementioned A/D conversion and interface control unit. The microprocessor main control unit can output a sampling clock signal whose frequency is continuously adjustable and used as the aforementioned two-way A/D conversion; the aforementioned two-way A/D conversion data valid notification signal and the two external interrupt inputs of the microprocessor unit The terminal is connected as the corresponding interrupt trigger signal. The microprocessor main control unit reads and controls the data of any A/D conversion channel through the interface control part in the aforementioned A/D conversion and interface control unit. The microprocessor unit communicates with the host through a host interface control unit via a parallel bus or a serial bus or a USB port or a PCI bus.

The commercial lock-in amplifier unit described in the second scheme is equivalent to the collection of the A/D conversion and interface control unit and the microprocessor main control unit in the first scheme. The input terminal of the commercial lock-in amplifier is connected to the two ends of the measurement auxiliary voltage dividing resistor which has been connected in series with the ferroelectric film to be tested and the signal generator in series. In addition, the reference input terminal of the commercial lock-in amplifier unit is connected to the test signal generator. connected to the synchronous output of the device. The commercial lock-in amplifier unit is connected to the computer through an external printer parallel interface or RS232 serial interface or USB interface or PCI bus.

The computer described in scheme one and scheme two is connected with the microprocessor main control unit or the commercial lock-in amplifier unit through a parallel port or a serial port or a USB port or a PCI bus for parameter input, measurement status monitoring and The results show that.

In summary, the present invention is to form an organic whole with the test signal generator, the auxiliary voltage dividing resistor for measurement, the A/D conversion and interface control unit, the microprocessor main control unit and the computer that realize the digital phase-locking calculation and sampling control part, or The test signal generator, measurement auxiliary voltage divider resistor, commercial lock-in amplifier unit, and computer form an organic whole, and the connection lines between each part should be as short as possible to reduce the parasitic capacitance between lines and external interference.

The testing method of the invention calculates the relative permittivity and dielectric loss of the ferroelectric film to be tested by measuring the equivalent capacitance and equivalent resistance of the ferroelectric film to be tested at various frequencies.

For scheme 1, the specific working process of the measurement is: the computer sends instructions to the microprocessor main control unit according to the parameters set by the user, that is, the frequency value to be measured and the known resistance value of the auxiliary voltage dividing resistor; The unit first initializes each part and each port including the signal generator, A/D conversion and interface control unit; then the micro-processing main control unit enters the data acquisition program, and the data acquisition program starts the timer to send out the sampling signal, and the frequency of the sampling signal is the same as that to be tested The frequency point value is related to the digital phase-locking algorithm adopted. The two-way A/D conversion circuit in the A/D conversion and interface control unit is under the control of the sampling signal and is taken from both ends of the measurement auxiliary voltage divider resistor and passed through The sinusoidal voltage signal processed by the analog signal adjustment amplifier circuit (7) is sampled, and then the data acquisition program of the microprocessor main control unit enters a waiting state; after the two A/D conversion channels have sampled the data and the conversion is completed, each sends out the data Effective signal; these two signals respectively trigger two external interrupts of the microprocessor main control unit, at this time, the data acquisition program of the microprocessor main control unit enters the interrupt routine, and reads the data collected by the two A/D conversion channels respectively. The obtained data; after all the data points at this frequency are collected, the microprocessor main control unit enters the data processing program, which performs digital phase-locking calculation on the collected data, and calculates the amplitude and phase of the two signals Then, the equivalent capacitance and equivalent resistance of the piezoelectric film to be tested can be obtained from formula (1). There are various algorithms for digital phase-locking calculation, and the purpose is to calculate and obtain the amplitude and phase of the two sinusoidal signals to be measured.

After obtaining the equivalent capacitance and equivalent resistance of the ferroelectric film to be tested, the relative permittivity and dielectric loss of the ferroelectric film to be tested at frequency f can be obtained from formula (2). By changing the signal frequency f and repeating the above steps, the relative permittivity and dielectric loss of the ferroelectric film to be tested at various frequency values can be obtained, and the entire testing process can be completed.

For the second scheme, the specific working process of the measurement is: the user sets the parameters for the signal generator, that is, the required frequency value f; the computer sends instructions to the commercial lock-in amplifier unit through the interface, so that it can measure the aforementioned measurement aids twice. The amplitudes V ₀ , V _p of the sinusoidal voltage signals at both ends of the voltage dividing resistor and their respective phase differences θ ₀ , θ _p relative to the synchronous output signal of the signal generator. From θ ₀ and θ _p , the phase difference θ (θ=θ ₀ -θ _p ) of the signals at both ends of the auxiliary voltage dividing resistor can be calculated. Then, according to formulas (1) and (2), the relative permittivity and dielectric loss of the piezoelectric film to be tested at frequency f can be obtained. By changing the signal frequency f and repeating the above steps, the relative permittivity and dielectric loss of the ferroelectric film to be tested at various frequency values can be obtained, and the entire testing process can be completed.

Beneficial effects: In summary, the present invention organically combines the signal generator, auxiliary voltage dividing resistor, A/D conversion and interface control unit, microprocessor main control unit, and various parts of the computer to form a ferroelectric thin film medium A multi-frequency automatic test system for electrical properties, which can measure the relative permittivity and dielectric loss of ferroelectric thin films at various frequencies. It has the characteristics of simple test process, good user adjustment, high measurement accuracy, and can continuously measure the dielectric constant and dielectric loss of each frequency point, etc., and has a good application prospect.

Description of drawings

Figure 1 is the overall connection block diagram of the device. There are signal generator 1, auxiliary voltage dividing resistor 2, ferroelectric thin film 21 to be tested, A/D conversion and interface control unit 3, microprocessor main control unit 4, and computer 5.

Fig. 2 is the overall connection block diagram of the second scheme of the device. Among them is a commercial lock-in amplifier unit 6 .

FIG. 3 is an electrical functional block diagram of the A/D conversion and interface control unit 3 . There are an analog signal adjustment amplifier circuit 7 , an A/D conversion circuit ( 8 ), an interface control part 9 and a power supply part 10 .

FIG. 4 is an electrical functional block diagram of the microprocessor main control unit 4 . There are expansion peripheral bus control unit 11 , microprocessor 12 , host interface control unit 13 , program and data memory 14 , peripherals 15 and power supply 16 .

FIG. 5 is a schematic circuit diagram of the A/D conversion circuit 8 and the interface control section 9 .

FIG. 6 is a specific connection diagram of the analog signal amplification and adjustment circuit 7, which only includes one path, and the other path is the same.

FIG. 7 is a schematic circuit diagram of the power supply section 10 .

Fig. 8 is a program flowchart of the computer 5 and the DSP main control unit.

Figure 9 is a block diagram of the lock-in amplification algorithm.

FIG. 10 is a graph showing the relationship between relative permittivity and frequency of the PZT thin film sample measured in Example 1. FIG.

FIG. 11 is a graph showing the relationship between dielectric loss and frequency of the PZT thin film sample measured in Example 1. FIG.

Fig. 12 is a computer program flow chart of the second embodiment.

FIG. 13 is a graph showing the relationship between relative permittivity and frequency of the PZT thin film sample measured in Example 2. FIG.

FIG. 14 is a graph showing the relationship between the dielectric loss and the frequency of the PZT thin film sample measured in the second embodiment.

Detailed ways

The present invention will be further described below in conjunction with embodiment.

Embodiment one, the present embodiment adopts scheme one, promptly by test signal generator (1), measuring auxiliary voltage divider resistance (2), A/D conversion and interface control unit (3), realize digital phase lock calculation and sampling control A micro-processing main control unit (4) and a computer (5) form a test device.

Among them, the signal generator (1), the auxiliary voltage dividing resistor (2), and the ferroelectric film to be tested (21) are connected in series to form an electric circuit, and the two ends of the auxiliary voltage dividing resistor (2) are respectively connected to A/D conversion and interface control. Unit (3). Among them, the test signal generator (1) adopts MOTECH FG503 DDS function generator, which can generate sine wave signals from 1Hz to 3MHz and square wave signals synchronized with it. The auxiliary voltage dividing resistor (2) is a carbon film resistor, and its resistance value is in the same order as the equivalent resistance value of the ferroelectric film to be measured at the middle frequency (1KHz) of the measurement frequency range.

Among them, the A/D conversion and interface control unit (3) adopts a self-made system, which is composed of an analog signal adjustment amplifier circuit (7), an A/D conversion circuit (8), an interface control part (9), and a power supply part (10) . The analog signal adjustment amplifier circuit (7) is mainly composed of operational amplifiers max410 and max4108, and a voltage reference chip max6341. The A/D conversion circuit (8) is mainly composed of an A/D conversion chip max1201. The interface control part (9) is mainly composed of a data buffer chip 74LVTH162245, an address decoding chip 74HC138, and a signal buffer chip 74HCT541. The power supply part (10) is mainly composed of chips LM7815, LM7915, LM7805, LM7905, TL783, LM337 and the like. The input terminals of the two analog signal amplification and adjustment circuits (7) are connected to the two ends of the ferroelectric film (21) to be tested. The outputs of the two analog signal amplification and adjustment circuits (7) are respectively connected to the inputs of the corresponding A/D conversion circuit (8); the data line and the control line of the A/D conversion circuit (8) are connected with the interface control part (9) The data line is connected with the control line; the output of the power supply part (10) is connected with the analog signal amplification and adjustment circuit (7), the A/D conversion circuit (8) is connected with the corresponding power input of the interface control part (9), for these three part to provide power. The output signals of the A/D conversion and interface control unit include 16-bit data lines, 3-bit address lines, two read-write control lines, one clock signal line, and two interrupt control lines. These signal lines are connected with the micro-processing unit (4 ) associated.

The microprocessor main control unit (4) adopts TMS320C6711 DSP STARTER KIT of TI Company. The DSP STARTER KIT board takes TMS320C6711 digital signal microprocessor (12) as the core, and includes host interface control unit (13), expansion peripheral bus control unit (11), program and data memory (14), power supply (16) and other peripherals (15). The data and control bus of the microprocessor (12) is connected with the corresponding data and control interface of the program and data memory (14), the expansion peripheral bus control unit (11), the host interface control unit (13) and the peripheral hardware (15) . The output of the power supply (16) is connected with the corresponding power input of the microprocessor (12), program and data memory (14), expansion peripheral bus control unit (11), host interface control unit (13) and peripheral equipment (15) . The peripheral bus of the expansion peripheral bus control unit (11) is connected with the output bus of the interface control part (9) of the aforementioned A/D conversion and interface control unit (3). The output data and control bus of the host interface control unit (13) are connected in parallel with the computer (5) through an external printer.

During the test, the computer downloads the parameters and running programs to the DSP, and gives the control right to the DSP. After the DSP collects the data and calculates the results, the results are passed to the computer to display the results. The lock-in amplification algorithm adopted is shown in Fig. 9, in which S(t) is the signal to be tested, the frequency is ω ₁ , and becomes a digital signal S(n) after sampling. R ₁ (n) and R ₂ (n) are reference sequences, which are standard sinusoidal sequences generated by a computer, with an amplitude of 1, the same frequency as ω ₂ , and a phase difference of 90 degrees. The frequency ω ₂ of the reference sequence is the same as the sampling frequency of the A/D conversion, and satisfies ω ₂ =Kω ₁ , K is a multiple of 4 and the minimum is 8, and the total number of sampling points is N. Finally, the amplitude U _r of the signal to be measured can be obtained as: U _r =2U _O . The initial phase φ of the signal to be measured relative to the reference signal is: $\cos \mathrm{\&phi;}=\frac{2{\mathrm{<figure-callout\; id="1u"\; label="Y"\; filenames="C20031010647800161.png"\; state="\{\{state\}\}">Y</figure-callout>}}_1}{u_r},\sin \mathrm{\&phi;}=\frac{2Y_2}{u_r}.$ This device tested the ferroelectric thin film prepared on the Pt/Ti/SiO ₂ /Si substrate by sol-gel technology. The ferroelectric thin film was coated with 150nm thick Au film on the surface of the thin film by sputtering method as the upper surface of the thin film. For electrodes, a 50nm Cr film was used to enhance the adhesion between PZT and Au. The relative permittivity and dielectric loss of the sample (t=1μm, A=6.1mm ² ) were tested from 100Hz to 10KHz, and the results are shown in Figures 10 and 11.

Embodiment 2. This embodiment adopts the scheme 2, which includes a test signal generator (1), a measurement auxiliary voltage dividing resistor (2), a commercial lock-in amplifier (6) and a computer (5).

The test signal generator (1) and measurement auxiliary voltage dividing resistor (2) used therein are the same as those used in the first embodiment. The connections of the ferroelectric thin film to be tested (21), the auxiliary measuring voltage divider resistor (2) and the test signal generator (1) are the same as those in the first embodiment.

In this embodiment, the commercial lock-in amplifier (6) model is NF LI5630. The input end of the lock-in amplifier (6) is connected with the two ends of the ferroelectric film (21) to be tested, the reference input end of the lock-in amplifier is connected with the synchronous signal output end of the signal generator, and the lock-in amplifier and the computer are connected through the RS232 port. connect. During the test, the lock-in amplifier successively tests the signal amplitude at both ends of the ferroelectric film to be tested and the phase of the signals at both ends relative to the synchronous signal of the test signal generator. The computer reads the test results from the lock-in amplifier through the RS232 port and calculates the relative permittivity and dielectric loss of the ferroelectric film to be tested. This device tested the ferroelectric thin film prepared on the Pt/Ti/SiO ₂ /Si substrate by sol-gel technology. The ferroelectric thin film was coated with 150nm thick Au film on the surface of the thin film by sputtering method as the upper surface of the thin film. For electrodes, a 50nm Cr film was used to enhance the adhesion between PZT and Au. The relative permittivity and dielectric loss of the sample (t=1μm, A=6.1mm ² ) were tested from 100Hz to 10KHz, and the results are shown in Figures 13 and 14.

Claims (6)

1, a kind of ferroelectric thin-flim materials dielectric properties multi-frequency automatic test approach is characterized in that method of testing is:

1), any end with ferroelectric thin film to be measured links to each other with the negative electrode of the output terminal of signal generator, the electrode of the other end of this ferroelectric thin film to be measured is connected with any end of the resistance of a known resistance, this resistance other end links to each other with the positive electrode of signal generator output terminal, with the negative electrode of signal generator output terminal as with reference to ground;

2), the signalization generator, make it export sine wave under the Frequency point to be measured; Sine voltage signal to the two ends of this known resistance carries out synchronous acquisition, gathers the signal of a complete cycle at least, and sample frequency is set according to the requirement of the concrete digital phase-sensitive detection algorithm that adopts; The signal that sampling is obtained calculates with the method that digital phase-sensitive detects, and draws the amplitude V of this two end signal ₀And V _pAnd these two ends phase difference between signals θ; So-called digital phase-sensitive detection method is meant behind the measured signal process analog/digital conversion, carries out digital demodulation by microprocessor and calculate.

3), according to formula $C_P=\frac{\left|\sin \mathrm{\&theta;}\right|*V_0}{R*2*\mathrm{\&pi;}*f*V_P},R_P=\frac{R}{\frac{\left|\cos \mathrm{\&theta;}\right|*V_0}{V_P}-1}$

Obtain the equivalent electric capacity C of ferroelectric thin film to be measured _pWith equivalent resistance R _p

According to formula ${\mathrm{\&epsiv;}}_r=\frac{C_{p}t}{{\mathrm{\&epsiv;}}_{0}A},\mathrm{tg\&delta;}=\frac{1}{2\mathrm{\&pi;f}{C}_p{R}_p}$

Obtain the relative dielectric constant ε of ferroelectric thin film to be measured _rWith dielectric loss tg δ;

V in the formula ₀For measuring link to each other with signal generator (1) the output terminal positive electrode amplitude of sine voltage signal of end of auxiliary divider resistance (2); V _pAmplitude for the sine voltage signal of measuring auxiliary divider resistance (2) and ferroelectric thin film link to be measured, θ is the phase differential between the sine voltage signal that to measure auxiliary divider resistance (2) two ends be above two-way, f is the sinusoidal wave frequency that signal generator produces, and R is the resistance of known resistance; T is the thickness of ferroelectric thin film to be measured, and A is the electrode area of ferroelectric thin film to be measured, ε ₀Be permittivity of vacuum.

2, ferroelectric thin-flim materials dielectric properties multi-frequency automatic test approach according to claim 1, the step 2 that it is characterized in that above method of testing is: the signalization generator, make it export sine wave signal under the Frequency point to be measured, measure the amplitude V of sine voltage signal at the two ends of known resistance with commercial lock-in amplifier respectively ₀And V _pAnd this two paths of signals is with respect to the phase differential θ of the synchronous reference signal of signal generator output ₀, θ _p, calculate phase differential θ=θ between this two paths of signals by these two phasometers ₀-θ _p

3, a kind of ferroelectric thin-flim materials dielectric properties multi-frequency automatic testing equipment, it is characterized in that this device comprises signal generator (1), auxiliary divider resistance (2), A/D conversion and interface control unit (3), microprocessor main control unit (4), computing machine (5), signal generator (1) wherein, auxiliary divider resistance (2), ferroelectric thin film to be measured (21) is connected into an electric loop, connect A/D conversion and interface control unit (3) respectively at the two ends of auxiliary divider resistance (2), the digital signal output and the control signal of A/D conversion and interface control unit (3) link to each other with the numeral and the control bus of microprocessor main control unit (4), and microprocessor main control unit (4) and computing machine (5) link to each other by printer parallel interface or RS232 serial line interface or USB interface or pci bus.

4, ferroelectric thin-flim materials dielectric properties multi-frequency automatic testing equipment according to claim 3, it is characterized in that A/D conversion and interface control unit (3), microprocessor main control unit (4) is replaced by commercial lock-in amplifier unit (6), the input end of commercial lock-in amplifier unit (6) links to each other with the two ends that ferroelectric thin film to be measured (21) and signal generator (1) are connected into the auxiliary divider resistance (2) of measurement in loop, the reference input of commercial lock-in amplifier unit (6) links to each other with the synchronous output end of measuring signal generator (1), and commercial lock-in amplifier unit (6) passes through external printer parallel interface or RS232 serial line interface or USB interface or pci bus and links to each other with computing machine (5).

5, ferroelectric thin-flim materials dielectric properties multi-frequency automatic testing equipment according to claim 3, it is characterized in that A/D changes and interface control unit (3) is made up of simulating signal adjustment amplifying circuit (7), A/D change-over circuit (8), interface control section (9), power supply part (10), the two-way simulating signal is amplified the output of adjusting circuit (7) and is linked to each other with the input of corresponding A/D change-over circuit (8) respectively; The data line of A/D change-over circuit (8) links to each other with control line with the data line of control line with interface control section (9); The output of power supply part (10) and simulating signal are amplified adjustment circuit (7), and the corresponding power supply input of A/D change-over circuit (8) and interface control section (9) links to each other, for these three parts provide power supply.

6, ferroelectric thin-flim materials dielectric properties multi-frequency automatic testing equipment according to claim 3, it is characterized in that microprocessor main control unit (4) by expand peripheral bus control module (11), microprocessor (12), host interface control module (13), program and data-carrier store (14), peripheral hardware (15), power supply (16) is formed, the corresponding data of the data of microprocessor (12) and control bus and program and data-carrier store (14), expansion peripheral bus control module (11), host interface control module (13) and peripheral hardware (15) links to each other with control interface.The output of power supply (16) links to each other with the corresponding power supply input of microprocessor (12), program and data-carrier store (14), expansion peripheral bus control module (11), host interface control module (13) and peripheral hardware (15).The expansion peripheral bus of microprocessor main control unit (13) is connected with the output bus of the interface control section (9) of aforesaid A/D conversion and interface control unit (3).The output data of host interface control module (13) and control bus and computing machine (5) link to each other by external printer parallel interface or RS232 serial line interface or USB interface or pci bus.

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