JPH08153762A - Instrument and method for measuring contact potential difference of two-layer film - Google Patents

Abstract

PURPOSE: To provide an instrument and a method for measuring contact potential difference of two-layer film for checking multilayered thin films for reliability and stability of laminated state. CONSTITUTION: An instrument for measuring contact potential difference of two-layer film is provided with a pair of sample holding tools 1 and 2 which respectively hold samples 5 and 6 composed of conductive substrates and metallic or semiconductor thin films formed on the substrates in such states that the samples 5 and 6 are faced to each other in parallel, electrode terminals 3 and 4 which are respectively provided on the tools 1 and 2 and electrically connected to the samples 5 and 6, an exciter 7 which is coupled with the tool 2 and excites the sample 6, a constant-voltage power source 8 which applies a voltage across the sample 6, a current detector 9 which detects an electric current generated in the sample 5, and an amplifier 10. The instrument detects the alternating current generated in the sample 5 while the instrument vibrates the samples 5 and 6 by supplying a potential to the sample 6. The potential at which the current generated in the sample becomes '0' becomes the contact potential difference of the samples.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-layer film contact potential difference measuring apparatus and method for investigating the reliability of a multi-layer thin film, particularly the stability of a laminated state.

[0002]

2. Description of the Related Art Many devices and files (for example, LSIs, MR heads, thin film recording media, etc.) which are currently being researched and developed are composed of a multi-layered thin film in which several films are laminated. Products using such multi-layer thin films have a phenomenon of deterioration of characteristics due to alloying of materials of each layer and local batteries formed between the layers, and these become a problem because they impair the reliability of the multi-layer thin films. There is.

It is considered that such alloying and formation of local cells in the multilayer thin film are often caused by an electric gradient generated between the films, that is, a contact potential difference.

[0004]

However, conventionally, there is no apparatus for quantitatively measuring the contact potential difference generated between thin films, and the reliability of the multilayer thin film cannot be clarified.

An object of the present invention is to provide a measuring device and a measuring method for quantitatively measuring a contact potential difference between two layers, and a method for examining the reliability of a multilayer thin film based on the contact potential difference obtained here. To provide.

[0006]

A two-layer film contact potential difference measuring device of the present invention is a sample A, B to be measured having a metal thin film or a semiconductor thin film respectively formed on a pair of conductive substrates.
And a pair of sample holders A and B for holding the measured samples A and B in parallel and facing each other at a predetermined interval, and the sample holder A coupled to the sample holders A to measure the measured sample A at regular intervals. An exciter for vibrating, a constant voltage power source for applying a voltage to the sample A to be measured, and a current detection unit for detecting a current generated in the sample B to be measured are provided.

Further, in the method for measuring a two-layer film contact potential difference of the present invention, a sample to be measured composed of a metal thin film or a semiconductor thin film respectively formed on a pair of conductive substrates is made to face each other in parallel at a predetermined interval. One of the samples to be measured is vibrated at a constant cycle and a voltage is applied to the sample to be measured, and the charge transfer amount generated in the other sample to be measured is detected as an alternating current, and the alternating current value is zero. It is characterized in that a voltage value that becomes

[0008]

As the sample to be measured for measuring the contact potential difference of the multi-layered thin film, for example, two kinds of films A and B, which are in contact with each other in the metal thin film or the semiconductor thin film forming the device and the file, are independently conductive. A film having a capacitance C is formed by forming a film on a flexible substrate and facing them in parallel with each other with a distance of several microns to several millimeters.

Here, assuming that the work functions of the films A and B in vacuum are φA and φB, respectively, this capacitor has an electrical quantity Q represented by the following equation due to the contact potential of the films.
Movement occurs.

Q = C (φB−φA) At this time, the desired contact potential difference Vex is given by Vex = φB−φA. When a voltage V is applied to the sample to be measured from the outside, the charge transfer amount Q of the capacitor is Q = C (φB−φA + V). Therefore, the charge transfer amount Q with respect to the applied voltage (bias voltage) V If the dependency is examined and V that Q = 0 is obtained, this is the contact potential difference.

Thus, in principle, the contact potential difference can be obtained by the method described above. However, in this method, since it is necessary to measure the DC electric charge, it is difficult to obtain V at which Q = 0, and it is difficult to improve the measurement accuracy of the contact potential difference. Therefore, in order to improve the measurement accuracy, it is effective to detect the charge transfer amount as an alternating current.

Therefore, alternating vibration is applied to the sample to be measured to change the distance between the electrodes. Then, since the capacitance of the capacitor changes depending on the distance between the electrodes, the charge transfer amount also changes periodically. Here, when the capacitance variation of the capacitor is ΔC and the charge transfer amount is ΔQ, the change in the charge transfer amount due to the vibration between the electrodes is given by ΔQ = ΔC (φB−φA + V), and the contact potential difference can be easily obtained. You can

[0013]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the construction of a two-layer membrane contact potential difference measuring device of the present invention. As shown in FIG. 1, the two-layer film contact potential difference measuring device of the present embodiment includes samples to be measured (hereinafter referred to as samples) 5 and 6 each having a metal or semiconductor thin film formed on two conductive substrates. , This sample 5,6
A pair of flat plate-shaped sample holders 1 and 2 for holding the two in parallel at predetermined intervals, electrode terminals 3 and 4 respectively provided on the sample holders 1 and 2, and a sample holder 2. A vibration exciter 7 for vibrating the sample 6, a constant voltage power source 8 for applying a voltage to the sample 6, a current detector 9 for detecting an alternating current generated in the sample 5, and an amplifier 10 are included.

The pair of sample holders 1 and 2 facing each other in parallel are provided with electrode terminals 3 and 4, respectively, and a film to be measured is formed on a conductive substrate made of conductive silicon or the like. The samples 5 and 6 are fixed and electrically connected to the electrode terminals 3 and 4. One of the sample holders, in this example, the sample holder 2 is connected to the vibrator 7, and the sample 6
Is vibrated in the direction of arrow A at a constant cycle. The other sample holder 1 (sample 5) is fixed so as not to move.

Further, the electrode terminal 4 of the sample holder 2 is
The sample 6 is connected to a constant voltage power source 8 for applying a predetermined bias voltage, and the electrode terminal 3 of the sample holder 1 is provided with a current detector for detecting an alternating current generated in the sample 5 due to vibration. Connect to the container 9. The amplifier 10 is for increasing the S / N ratio of the signal detected by the current detector 9 to obtain measurement data.

Next, the results of measuring the contact potential difference using the two-layer film contact potential difference measuring device constructed as described above will be described.

(Measurement 1) First, the contact potential difference of a sample of the same metal in which gold was vapor-deposited on a conductive silicon substrate was measured. FIG. 2 is a diagram showing a measurement result of a current value generated when a sample made of evaporated gold was vibrated.
With the sample fixed, the capacitance generated between samples is 5
After deciding the interval of the samples so as to be pF, when one sample was excited in a sine wave at an oscillation frequency of 10 Hz,
The result of measuring the current generated in the other sample is shown.

According to FIG. 2, when the bias voltage is applied in the range of 0 to ± 10 V, the amplitude of the current increases as the absolute value of the bias voltage increases, regardless of whether the bias voltage is applied positively or negatively. I understand.

FIG. 3 is a graph showing the relationship between the bias voltage and the magnitude of the generated current when a sample made of evaporated gold is used. According to FIG. 3, the amplitude of the current becomes 0 at about 0.5 mV. That is, the contact potential difference is about -0.5 m.
V. And as a result of repeating the same measurement several times,
It was confirmed that the contact potential difference converged within a range of ± 0.5 mV, and that the contact potential difference due to the same metal was almost 0V.

(Measurement 2) Next, with respect to a sample made of a dissimilar metal in which gold and platinum are vapor-deposited on a conductive silicon substrate,
The contact potential difference was measured. FIG. 4 is a diagram showing a measurement result of a current value generated when a sample made of vapor-deposited gold and vapor-plated platinum was vibrated, which was measured under the same conditions as in the case of measurement 1 shown in FIG. is there. According to FIG. 4, 0 to ± 10
When the bias voltage was applied in the range of V, the amplitude of the current disappeared when the bias voltage was about -2.5V.

FIG. 5 is a diagram showing the relationship between the bias voltage and the magnitude of the amplitude of the generated current when a sample made of evaporated gold and evaporated platinum is used. According to FIG. 5, the amplitude of the current was 0 when the bias voltage was −2.535V.
Then, as a result of repeating the same measurement several times, the contact potential difference between the vapor-deposited gold and the vapor-deposited platinum was 2.540 V, and a typical contact potential difference due to different kinds of metals could be obtained.

[0023]

As described above, by using the two-layer film contact potential difference measuring device and the two-layer film contact potential difference measuring method of the present invention, the contact potential difference of a multi-layer thin film can be easily measured. As a result, it is possible to grasp the state of charge transfer accompanying the above, and to contribute to high reliability of the multilayer thin film.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a two-layer film contact potential difference measuring device of the present invention.

FIG. 2 is a diagram showing a measurement result of a current value generated when a sample made of evaporated gold was vibrated.

FIG. 3 is a diagram showing the relationship between the bias voltage and the magnitude of the amplitude of the generated current when a sample made of evaporated gold is used.

FIG. 4 is a diagram showing a measurement result of a current value generated when a sample made of evaporated gold and evaporated platinum was vibrated.

FIG. 5 is a diagram showing the relationship between the bias voltage and the magnitude of the amplitude of the generated current when a sample made of evaporated gold and evaporated platinum is used.

[Explanation of symbols]

 1, 2 Sample holder 3, 4 Electrode terminals 5, 6 Sample 7 Vibrator 8 Constant voltage power supply 9 Current detector 10 Amplifier

Claims (2)

[Claims] 1. A sample to be measured A, B having a metal thin film or a semiconductor thin film respectively formed on a pair of conductive substrates.
And a pair of sample holders A and B for holding the measured samples A and B in parallel and facing each other at a predetermined interval, and the sample holder A coupled to the sample holders A to measure the measured sample A at regular intervals. A two-layer film contact, comprising a vibrating vibrator, a constant voltage power source for applying a voltage to the sample A to be measured, and a current detection unit for detecting a current generated in the sample B to be measured. Potentiometer. 2. A sample to be measured formed of a metal thin film or a semiconductor thin film respectively formed on a pair of conductive substrates is opposed to each other in parallel at a predetermined interval, and one of the samples to be measured is vibrated at a constant cycle. And a voltage is applied to the sample to be measured, the charge transfer amount generated in the other sample to be measured is detected as an alternating current, and a voltage value at which the alternating current value becomes zero is obtained. Measuring method of membrane contact potential difference.