Method for testing nanometer scale film dielectric constant and Q value by network analyzer

Abstract

This invention relates to the field of electrical performance testing technology for nanoscale thin films, and in particular to a method for testing the dielectric constant and Q value of nanoscale thin films using a network analyzer. The method includes the following steps: S1: Preparing electrodes on the surface of the thin film to be tested, and forming a capacitor with the film; S2: Connecting the electrodes to the network analyzer using a probe station, and performing impedance matching on the circuit before connection; S3: Measuring the resonant frequency of the thin film under test at different frequencies and the S21 parameter at those resonant frequencies; S4: Calculating the capacitance and Q value of the thin film at different frequencies using the S parameters measured in S3; S5: Calculating the dielectric constant of the thin film at different frequencies using the capacitance obtained in S4. This invention has the advantage of simultaneously measuring the Q value of the thin film; and it can be tested at GHz frequencies, offering the advantage of high testing frequency. This invention achieves simultaneous testing of the dielectric constant and Q value of nanoscale thin film dielectrics, featuring accurate test results and high testing frequency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrical performance test of nanoscale thin film, in particular to a method for testing dielectric constant and Q value of nanoscale thin film by using network analyzer. BACKGROUND

[0002] Dielectric thin film has been widely used in the field of advanced electronic devices such as tunable capacitor, super capacitor, sensor, microwave radio frequency device and military radar. Compared with bulk, dielectric thin film has smaller volume, which is conducive to the miniaturization of devices and the integration of semiconductor related to chips. High dielectric constant and high Q value (low loss) mean better performance of dielectric thin film. However, as a nanoscale thin film, the smaller volume also increases the difficulty of measuring the dielectric constant and Q value. Although the network analyzer can be used to test the dielectric constant of the thin film by testing the waveguide reflection coefficient, it cannot test the Q value. Although the impedance analyzer can be used to directly test the dielectric constant and Q value at the same time, it is difficult to realize the test under the condition of GHz required by high frequency device.

[0003] In view of the above reasons, the present application provides a method for testing dielectric constant and Q value of nanoscale thin film by using high frequency network analyzer. Compared with the method for testing dielectric constant by using waveguide reflection coefficient, the present application has the advantage of measuring the Q value of the thin film at the same time. Compared with the method for testing dielectric constant by using semiconductor analyzer, the present application can test at GHz frequency, which has the advantage of high test frequency. The present application realizes the simultaneous test of dielectric constant and Q value of nanoscale thin film medium, and has the characteristics of accurate test result and high test frequency. SUMMARY

[0004] The present application provides a method for testing dielectric constant and Q value of nanoscale thin film by using network analyzer. The present application solves the problem that the impedance analyzer cannot realize the test under the condition of GHz required by high frequency device in the prior art. The method of the present application determines the network parameters by scanning measurement in the frequency band. The method has the advantages of simple operation, wide frequency band and accurate test.

[0005] The technical scheme of the present application is a method for testing dielectric constant and Q value of nanoscale thin film by using network analyzer, which comprises the following specific steps:

[0006] S1: preparing an electrode on the surface of the thin film to be tested, and forming a capacitor with the thin film to be tested;

[0007] S2: connecting the electrode and the network analyzer by using a probe station, and performing impedance matching on the circuit before connection;

[0008] S3: measuring the resonant frequency of the thin film to be tested at different frequencies and the S21 parameter at the resonant frequency.

[0009] S4: Calculate the capacitance and Q value of the film at different frequencies by using the S parameter tested in S3;

[0010] S5: Calculate the dielectric constant of the film at different frequencies by using the capacitance obtained in S4.

[0011] Preferably, in S1, the prepared electrodes are distributed on the surface of the measured film.

[0012] Preferably, in S1, the area of the prepared electrodes is adjusted according to the 1:100 scale of the film size. The electrode preparation method can be selected as physical vapor deposition, chemical vapor deposition, and laser pulse deposition.

[0013] Preferably, in S2, the network analyzer is calibrated for open circuit, short circuit, and load before being connected to the electrodes.

[0014] Preferably, the prepared capacitor is connected to the network analyzer using a two-port parallel through method, i.e., the two ends of the capacitor are connected to the microstrip line and ground line of the two ports of the network analyzer.

[0015] Preferably, in S3, during the testing of the S parameter, the sample is placed in a signal shielding box to reduce environmental interference.

[0016] Preferably, the number of test points in a certain frequency domain should be ensured as much as possible at different frequencies. For example, the number of sampling points should be greater than 1000 within a frequency range of 1 MHz.

[0017] Preferably, in S4, the impedance of the measured sample is calculated using the S parameter, and then the capacitance and Q value are calculated.

[0018] Preferably, in S5, the dielectric constant of the electrode coplanar capacitance is calculated using the conformal mapping method.

[0019] Compared with the prior art, the present application has the following beneficial technical effects:

[0020] 1. Compared with the method of testing dielectric constant using waveguide reflection coefficient in the prior art, the present application has the advantage of being able to simultaneously measure the Q value of the film. Compared with the method of testing dielectric constant using a semiconductor analyzer, the present application can be tested at GHz frequency, having the advantage of high test frequency. The present application realizes the simultaneous testing of nanoscale film medium dielectric constant and Q value, having the characteristics of accurate test results and high test frequency.

[0021] 2. Network analyzers are common comprehensive microwave measurement instruments. They can provide the amplitude, phase, and frequency characteristics of various scattering parameters using a frequency sweep method. Compared to semiconductor analyzers of the same price range, they offer a wider scanning frequency range and faster scanning speed. Furthermore, in addition to testing the dielectric constant and Q value of dielectric thin films at high frequencies, this invention can simultaneously obtain important electrical parameters of the device under test, such as impedance, resonant frequency, reactance, equivalent series inductance, and equivalent series resistance. It has strong practicality in the field of electrical testing. Attached Figure Description

[0022] Figure 1 The flowchart illustrates one example of the method described in this invention.

[0023] Figure 2 This is a schematic diagram of the dual-port parallel direct connection method between the network analyzer and the device in an embodiment of the present invention. Detailed Implementation

[0024] Example 1

[0025] See appendix Figure 1 As shown, this invention provides an example of a method for testing the dielectric constant and Q value of nanoscale thin films using a network analyzer, comprising the following steps:

[0026] S1: An electrode is prepared on the surface of the thin film to be tested and a capacitor is formed with the thin film to be tested;

[0027] S2: Use a probe station to connect the electrodes to the network analyzer, and perform impedance matching on the circuit before connection;

[0028] S3: Measure the resonant frequency of the thin film under test at different frequencies and the S21 parameter at that resonant frequency;

[0029] S4: Using the S-parameters obtained from S3, calculate the capacitance and Q value of the thin film at different frequencies;

[0030] S5: Using the capacitance obtained in S4, calculate the dielectric constant of the thin film at different frequencies.

[0031] In this embodiment of the invention, the thickness of the thin film under test is 140 nm, and the dielectric constant of the substrate is 10. First, coplanar electrodes were fabricated on the surface of the thin film under test using magnetron sputtering. The electrodes were 1 mm square in shape, with a 1 mm distance between them. Then, a probe station was used to connect the electrodes to a network analyzer. Impedance matching was performed on the circuit before connection, and the network analyzer performed open-circuit calibration, short-circuit calibration, and load calibration.

[0032] The connection method adopts the attached Figure 2The schematic diagram illustrates the two-port parallel direct connection method. The S21 parameters at 100k-10GHz are scanned using a network analyzer inside the signal shielding box. The device impedance is calculated using the impedance calculation formula (1), the Q value is calculated using the Q value calculation formula (2) with the impedance, the capacitance is calculated using the capacitance calculation formula (3) with the impedance, and the dielectric constant is calculated using the conformal mapping formula (4) with the capacitance.

[0033] The impedance calculation formula (1), Q value calculation formula (2), capacitance calculation formula (3), and conformal mapping formula (4) are shown below:

[0034]

[0035]

[0036]

[0037]

[0038] Where S21 is the measured S21 parameter, img{Z} and real{Z} distributions represent the imaginary and real parts of the impedance, respectively, and ε s Let L represent the dielectric constant of the substrate, L be the electrode length, W be the electrode width, g be the electrode spacing, h be the film thickness, and K be a function of g and W, expressed by the formula (5) shown below:

[0039]

[0040] One of the advantages of this invention is that, compared to methods that use waveguide reflection coefficients to test dielectric constant, this invention has the advantage of simultaneously measuring the Q-value of thin films; and compared to methods that use semiconductor analyzers to test dielectric constant, this invention can perform tests at GHz frequencies, offering the advantage of high testing frequency. This invention achieves simultaneous testing of the dielectric constant and Q-value of nanoscale thin film dielectrics, featuring accurate test results and high testing frequency.

[0041] Furthermore, in addition to testing the dielectric constant and Q value of dielectric thin films at high frequencies, this invention can also obtain important electrical parameters of the device under test, such as impedance, resonant frequency, reactance, equivalent series inductance, and equivalent series resistance. It has strong practical applications in the field of electrical testing.

[0042] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for testing the dielectric constant and Q value of nanoscale thin films using a network analyzer, characterized in that, The specific steps include the following: S1: An electrode is prepared on the surface of the thin film to be tested and a capacitor is formed with the thin film to be tested; S2: Connect the electrodes to the network analyzer using a probe station, and perform impedance matching on the circuit before connection; perform open-circuit calibration, short-circuit calibration, and load calibration on the network analyzer before connecting it to the electrodes; connect the fabricated capacitor to the network analyzer using a two-port parallel through-through method. S3: Measure the resonant frequency of the thin film under test in the range of 100k-10GHz and the S21 parameter at that resonant frequency inside the signal shielding box; S4: Using the S-parameters obtained from S3, calculate the capacitance and Q value of the thin film at different frequencies; S5: Using the capacitance obtained in S4, calculate the dielectric constant of the thin film at different frequencies; specifically, calculate the device impedance using the impedance calculation formula, calculate the Q value by substituting the impedance into the Q value calculation formula, calculate the capacitance by substituting the impedance into the capacitance using the capacitance calculation formula, and calculate the dielectric constant by substituting the capacitance into the conformal mapping formula. The calculation formulas are as follows: ； Where S21 is the measured S21 parameter, and img{Z} and real{Z} distributions represent the imaginary and real parts of the impedance, respectively. Let L represent the dielectric constant of the substrate, L be the electrode length, W be the electrode width, g be the electrode spacing, h be the film thickness, and K be a function of g and W, expressed as follows: 。 2. The method for testing the dielectric constant and Q value of nanoscale thin films using a network analyzer according to claim 1, characterized in that, In S1: The prepared electrodes are distributed on the surface of the thin film being tested.

3. The method for testing the dielectric constant and Q value of nanoscale thin films using a network analyzer according to claim 1, characterized in that, In S1, the area of ​​the prepared electrode is adjusted proportionally to the film size at a ratio of 1:

100.

4. The method for testing the dielectric constant and Q value of nanoscale thin films using a network analyzer according to claim 1, characterized in that, In S4: First, the impedance of the sample under test is calculated using S-parameters, and then the capacitance and Q value are calculated.

5. The method for testing the dielectric constant and Q value of nanoscale thin films using a network analyzer according to claim 1, characterized in that, In S5: The dielectric constant of the coplanar capacitance of the electrodes is calculated using conformal mapping.

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