JP7643000B2 - Capacitance-voltage characteristic measuring method and capacitance-voltage characteristic measuring device - Google Patents

Description

The present invention relates to a capacitance-voltage characteristic measuring method and a capacitance-voltage characteristic measuring device.

Insulators are used as materials in the circuits and displays of electronic devices. For example, when an insulator is used as a substrate, semiconductor elements and wiring are provided on a substrate made of the insulator, thereby forming the circuits of the electronic device or display. Such an insulator substrate insulates the semiconductor elements from each other, the wiring from each other, and the semiconductor elements and wiring from each other, to prevent unintended short circuits from occurring within the circuit.

As described above, insulators used as materials for substrates, etc., can generate electric charges when electronic devices or displays are operated for a long period of time. In such cases, the electric charges accumulated in the insulator can affect the operation of semiconductor elements, which can reduce the reliability of the electronic device or display.

In particular, in the insulator constituting the display substrate (e.g., flexible substrate), light is irradiated from light-emitting elements, etc., when the display is driven, and as a result, photoexcitation-induced charges are generated and accumulated in the insulator. The charges thus accumulated in the insulator change the operation of semiconductor elements, such as thin film transistors (TFTs), provided on the display substrate, and cause a decrease in the reliability (operational stability) of the display. Specifically, the influence of the charges in the insulator causes the driving voltage (threshold voltage) of the TFT to change, which causes the emission brightness of the light-emitting element to change over time, or the light-emitting element to unintentionally continue to emit weak light even when the power is turned off, thereby impairing normal operation of the display.

As a conventional technique for evaluating electric charges on an object, for example, there is a technique in which a capacitor is formed by contacting a semiconductor wafer to be measured with a conductivity measuring probe, the semiconductor wafer is irradiated with light, and then the capacitance of the capacitor is measured, and the charge carrier lifetime of the semiconductor wafer is measured based on the change in capacitance over time (see Patent Document 1). There is also a technique in which a voltage is applied to a MOS diode to evaluate the amount of electric charges trapped at the interface between the semiconductor (Si) and the oxide film (SiO ₂ ) in the MOS diode (see Non-Patent Document 1).

JP 2004-146831 A

S. M. Gee, "Semiconductor Devices (2nd Edition) - Basic Theory and Process Technology -", Sangyo Tosho Co., Ltd., March 30, 2015, pp. 161-166

As insulating materials for substrates and the like used in circuits and displays of electronic devices, it is preferable to select insulators that generate less charge (accumulation amount) due to photoexcitation. It is important to evaluate the amount of charge generated in the insulator due to photoexcitation and select such an insulator based on the evaluation results. In addition, in order to evaluate the amount of charge, it is essential to irradiate the insulator to be evaluated with light and measure the capacitance-voltage characteristics (hereinafter referred to as CV characteristics) of the capacitor structure including the insulator after the light irradiation. However, the above-mentioned conventional technology does not disclose any method for measuring the CV characteristics of the capacitor structure including the insulator after the light irradiation, and therefore it is difficult to measure the above-mentioned CV characteristics that are essential for evaluating the amount of charge in the insulator due to photoexcitation.

The present invention has been made in consideration of the above circumstances, and aims to provide a capacitance-voltage characteristic measuring method and a capacitance-voltage characteristic measuring device that can easily measure the CV characteristics of a capacitor structure that includes an insulator after light irradiation.

In order to solve the above-mentioned problems and achieve the object, the capacitance-voltage characteristic measuring method according to the present invention is characterized by including a light irradiation step in which a laminate including an insulator layer and a semiconductor layer is irradiated with light from the insulator layer side to generate charges in the insulator by photoexcitation, and a measurement step in which the capacitance-voltage characteristics of a capacitor structure after light irradiation is measured, the capacitor structure including a first electrode contacting the laminate from the insulator layer side, a second electrode contacting the laminate from the semiconductor layer side, and the laminate after light irradiation.

The capacitance-voltage characteristic measuring method according to the present invention is characterized in that, in the above invention, a charge blocking layer having a higher electrical resistance than the insulator is interposed between the insulator layer and the semiconductor layer in the laminate.

The capacitance-voltage characteristic measuring method according to the present invention is characterized in that, in the above invention, the first electrode is a transparent electrode that is transparent to the light irradiated onto the laminate, and the light irradiation step irradiates the laminate of a pre-illumination capacitor structure formed by the first electrode, the second electrode, and the laminate before light irradiation with the light from the insulator layer side via the first electrode.

The capacitance-voltage characteristic measuring method according to the present invention is characterized in that, in the above invention, the first electrode is a movable electrode that is in contact with the laminate and can be separated from it, the light irradiation process separates the first electrode from the laminate and irradiates the laminate with the light from the insulating layer side, and the measurement process forms the capacitor structure after light irradiation using the first electrode, the second electrode, and the laminate after light irradiation, and measures the capacitance-voltage characteristic of the capacitor structure after light irradiation.

The capacitance-voltage characteristic measuring method according to the present invention is characterized in that, in the above invention, the movable electrode is a mercury probe.

The capacitance-voltage characteristic measuring device according to the present invention is characterized by comprising: a first electrode that contacts a laminate including an insulating layer and a semiconductor layer from the insulating layer side; a second electrode that contacts the laminate from the semiconductor layer side; a light source that irradiates the laminate with light from the insulating layer side; a DC power source that applies a DC bias voltage to a capacitor structure after light irradiation that includes the first electrode, the second electrode, and the laminate after light irradiation; an AC power source that applies an AC voltage to the capacitor structure after light irradiation; a measuring unit that measures the capacitance-voltage characteristic of the capacitor structure after light irradiation; and a housing that forms a darkroom in which at least the light source, the laminate, the first electrode, and the second electrode are housed.

The capacitance-voltage characteristics measuring device according to the present invention is characterized in that, in the above invention, the laminate further includes a charge blocking layer interposed between the insulating layer and the semiconductor layer and having a higher electrical resistance than the insulating layer.

The capacitance-voltage characteristic measuring device according to the present invention is characterized in that, in the above invention, the first electrode is a transparent electrode that is transparent to the light from the light source, and the light source irradiates the light from the insulator layer side through the first electrode onto the laminate of the pre-illumination capacitor structure formed by the first electrode, the second electrode, and the pre-illumination laminate.

The capacitance-voltage characteristics measuring device according to the present invention is characterized in that, in the above invention, the first electrode is a movable electrode that is in contact with the laminate and can be separated from it, and the movable electrode separates from the laminate when the light source irradiates the laminate with light, and contacts the laminate after the light irradiation.

The capacitance-voltage characteristics measuring device according to the present invention is characterized in that, in the above invention, the movable electrode is a mercury probe.

The capacitance-voltage characteristics measuring device according to the present invention is characterized in that, in the above invention, it further comprises a wavelength changing unit that changes the wavelength of the light from the light source.

The capacitance-voltage characteristics measuring device according to the present invention is characterized in that, in the above invention, the semiconductor layer is provided on the second electrode.

The present invention has the effect of easily measuring the CV characteristics of a capacitor structure that includes an insulator after light irradiation.

FIG. 1 is a schematic diagram showing an example of the configuration of a CV characteristic measuring device according to a first embodiment of the present invention. FIG. 2 is a diagram showing an example of the CV characteristics of a capacitor structure measured in the first embodiment of the present invention. FIG. 3 is a flow chart showing an example of a photoexcited charge quantity measuring method to which the CV characteristic measuring method according to the first embodiment of the present invention is applied. FIG. 4 is a schematic diagram showing an example of the configuration of a CV characteristic measuring device according to the second embodiment of the present invention. FIG. 5 is a schematic diagram showing an example of the configuration of a CV characteristic measuring device according to the third embodiment of the present invention. FIG. 6 is a schematic diagram showing an example of the configuration of a CV characteristic measuring device according to the fourth embodiment of the present invention. FIG. 7 is a diagram showing an example of the measurement results of the CV characteristics in the first embodiment of the present invention. FIG. 8 is a diagram showing an example of the measurement results of the CV characteristics in the second embodiment of the present invention.

The following describes in detail the form for carrying out the present invention. However, the present invention is not limited to the following embodiment, and can be carried out with various modifications according to the purpose and application. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from the actual ones. The drawings may also include parts with different dimensional relationships and ratios. In addition, the same components are given the same reference numerals in each drawing.

<Embodiment 1>
(CV characteristic measuring device)
First, a CV characteristics measurement device according to a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing an example of a configuration of the CV characteristics measurement device according to the first embodiment of the present invention. The CV characteristics measurement device 1 according to the first embodiment is an example of a device (capacitance-voltage characteristics measurement device) that measures CV characteristics to evaluate the amount of charge caused by photoexcitation in a target insulator. As shown in FIG. 1, the CV characteristics measurement device 1 includes a transparent electrode 2a, a supporting electrode 2b, a light source 3, a DC bias power supply 4, an AC power supply 5, a capacitance measuring device 6 and a voltmeter 7 that constitute a measurement unit 8, and a housing 9.

The transparent electrode 2a and the support electrode 2b are an example of a pair of electrodes for forming a capacitor structure 10, which is the object of measurement of CV characteristics in this embodiment 1. In this embodiment 1, as shown in FIG. 1, the laminate 15 is sandwiched between the transparent electrode 2a and the support electrode 2b in the layer thickness direction to form the capacitor structure 10. The laminate 15 is an example of a laminate including at least a layer of an insulator 11 to be evaluated for the amount of charge due to photoexcitation, and a layer of a semiconductor 12 to enable quantitative measurement of the CV characteristics. Specifically, in this embodiment 1, the laminate 15 is composed of a layer of an insulator 11 and a layer of a semiconductor 12, as shown in FIG. 1. For example, the laminate 15 is formed by stacking a layer of an insulator 11 on a layer of a semiconductor 12.

The semiconductor material constituting the layer of semiconductor 12 may be, for example, an inorganic semiconductor such as an elemental semiconductor or a compound semiconductor, or an organic semiconductor. Elemental semiconductors may be, for example, silicon or germanium. Compound semiconductors may be, for example, zinc selenide, zinc oxide, gallium arsenide, gallium nitride, silicon carbide, silicon germanium, etc. Among these, inorganic semiconductors are preferred as the semiconductor material, and silicon, which can easily form a thermal oxide film, is particularly preferred.

The transparent electrode 2a is an example of a first electrode that contacts the laminate 15 including the layer of the insulator 11 and the layer of the semiconductor 12 from the layer side of the insulator 11. In this embodiment 1, as shown in FIG. 1, the transparent electrode 2a is arranged so as to be in surface contact with the upper surface of the insulator 11 in the laminate 15 (the upper surface in the layer thickness direction of the insulator 11). The transparent electrode 2a is also electrically connected to the DC bias power supply 4, the AC power supply 5, and the measurement unit 8 (the capacitance meter 6 and the voltmeter 7 in this embodiment 1) via wiring or the like. The transparent electrode 2a is an electrode that is transparent to the light 3a emitted from the light source 3, and is composed of a transparent conductive film such as indium tin oxide (ITO).

The support electrode 2b is an example of a second electrode that contacts the laminate 15 including the layer of the insulator 11 and the layer of the semiconductor 12 from the layer side of the semiconductor 12. In this embodiment 1, as shown in FIG. 1, the support electrode 2b is arranged so as to be in surface contact with the lower surface of the semiconductor 12 in the laminate 15 (the lower surface in the layer thickness direction of the semiconductor 12). Although not shown in FIG. 1, the support electrode 2b is provided on a support such as a mounting table (stage) and is configured to support the laminate 15 from below. In addition, the support electrode 2b is electrically connected to the DC bias power supply 4, the AC power supply 5, and the voltmeter 7 of the measurement unit 8 via wiring or the like. The support electrode 2b is made of a conductive metal film such as copper, and faces the transparent electrode 2a in the direction perpendicular to its surface (the layer thickness direction of the laminate 15). In this embodiment 1, the layer of the semiconductor 12 in the laminate 15 is placed on the upper surface of the support electrode 2b. On the other hand, a layer of semiconductor 12 may be provided in advance on the upper surface of support electrode 2b, and stack 15 may be formed by stacking (placing) a layer of insulator 11 on the layer of semiconductor 12 provided on support electrode 2b.

The light source 3 is an example of a light source for generating charges in the insulator 11 by photoexcitation. As shown in FIG. 1, the light source 3 irradiates the laminate 15 with light 3a from the layer side of the insulator 11. In this embodiment 1, the light source 3 irradiates the laminate 15 of the capacitor structure 10 before light irradiation with light 3a from the layer side of the insulator 11 through the transparent electrode 2a. The capacitor structure 10 before light irradiation is a capacitor structure formed by the transparent electrode 2a, the support electrode 2b, and the laminate 15 before light irradiation. The light source 3 irradiates the insulator 11 of the laminate 15 with light 3a by irradiating the laminate 15 as described above with light 3a, thereby generating charges by photoexcitation in the insulator 11. The charges generated by photoexcitation in this way are mainly stored in the insulator 11.

As such a light source 3, for example, a light source that emits light including multiple wavelength bands, such as a xenon light source, a halogen light source, a krypton light source, a deuterium tungsten light source, a tungsten halogen light source, an argon light source, etc., may be used, or a single-wavelength light source that emits light of a single wavelength band, such as an LED light, may be used. Among these, a single-wavelength light source is preferable as the light source 3. In addition, it is preferable that the intensity of the light 3a from the light source 3 is such that the change in the amount of charge of the insulator 11 before and after light irradiation can be confirmed, and that the insulator 11 is not damaged.

The DC bias power supply 4 is an example of a DC power supply that applies a DC bias voltage to a measurement target of CV characteristics. In this embodiment 1, as shown in FIG. 1, the DC bias power supply 4 is configured by an output variable DC power supply that can change the output of the DC bias voltage within a predetermined range, and is circuit-configured so as to apply a DC bias voltage to a capacitor structure 10 that is a measurement target of CV characteristics. When the light source 3 is before irradiating the insulator 11 with light 3a, the DC bias power supply 4 applies a DC bias voltage to the capacitor structure 10 before light irradiation, which includes the transparent electrode 2a, the support electrode 2b, and the laminate 15 before light irradiation. When the light source 3 is after irradiating the insulator 11 with light 3a, the DC bias power supply 4 applies a DC bias voltage to the capacitor structure 10 after light irradiation, which includes the transparent electrode 2a, the support electrode 2b, and the laminate 15 after light irradiation. In either case, the DC bias power supply 4 applies a DC bias voltage to the capacitor structure 10 while continuously or intermittently changing the output of the DC bias voltage within a preset voltage range.

The AC power source 5 is an example of an AC power source that applies an AC voltage to a measurement target of CV characteristics. In this embodiment 1, as shown in FIG. 1, the AC power source 5 is configured in a circuit so as to apply an AC voltage to a capacitor structure 10, which is a measurement target of CV characteristics. Before the light source 3 irradiates the insulator 11 with light 3a, the AC power source 5 applies an AC voltage to the capacitor structure 10 before light irradiation, which includes the transparent electrode 2a, the support electrode 2b, and the laminate 15 before light irradiation. After the light source 3 irradiates the insulator 11 with light 3a, the AC power source 5 applies an AC voltage to the capacitor structure 10 after light irradiation, which includes the transparent electrode 2a, the support electrode 2b, and the laminate 15 after light irradiation.

The measurement unit 8 measures the CV characteristics of the capacitor structure 10 before the light source 3 irradiates the insulator 11 with light 3a, and measures the CV characteristics of the capacitor structure 10 after the light source 3 irradiates the insulator 11 with light 3a. In this embodiment 1, as shown in FIG. 1, the measurement unit 8 is composed of a capacitance measuring device 6 and a voltmeter 7.

The capacitance measuring device 6 is a device for measuring the capacitance C in the CV characteristics of the capacitor structure 10. In detail, the capacitance measuring device 6 is configured with an LCR meter or the like, and is configured as a circuit so as to read an AC signal and measure the capacitance C of the capacitor structure 10 as shown in FIG. 1. The capacitance measuring device 6 measures the capacitance C of the capacitor structure 10 in which a charge is accumulated in the laminate 15 by application of a DC bias voltage from the DC bias power supply 4 and application of an AC voltage from the AC power supply 5 before the light source 3 irradiates the insulator 11 with light 3a. In addition, the capacitance measuring device 6 measures the capacitance C of the capacitor structure 10 in which a charge is accumulated in the laminate 15 by application of a DC bias voltage from the DC bias power supply 4, application of an AC voltage from the AC power supply 5, and irradiation of light 3a from the light source 3 after the light source 3 irradiates the insulator 11 with light 3a. In either case, the capacitance measuring device 6 measures the capacitance C of the capacitor structure 10 corresponding to each value of the DC bias voltage applied to the capacitor structure 10 while changing it within a predetermined voltage range. The capacitance measuring device 6 also displays the measured capacitance C.

The voltmeter 7 is a device for measuring the applied voltage V in the CV characteristics of the capacitor structure 10. In detail, as shown in FIG. 1, the voltmeter 7 is connected in parallel to a pair of electrodes (the transparent electrode 2a and the support electrode 2b in this embodiment 1) constituting the capacitor structure 10 via wiring, and measures the voltage (applied voltage V) applied to the capacitor structure 10. For example, the voltmeter 7 measures the DC bias voltage applied to the capacitor structure 10 by the DC bias power supply 4 as the applied voltage V of the capacitor structure 10. The voltmeter 7 also displays the measured applied voltage V.

The housing 9 is an example of a housing that forms a darkroom in which at least the light source 3, the laminate of the capacitor structure that is the target of light irradiation by the light source 3, the first electrode, and the second electrode are accommodated. In this embodiment 1, as described above, the capacitor structure that is the target of light irradiation by the light source 3 is the capacitor structure 10 shown in FIG. 1, and the laminate, the first electrode, and the second electrode of this capacitor structure 10 are the laminate 15, the transparent electrode 2a, and the support electrode 2b, respectively. That is, the housing 9 in this embodiment 1 forms a darkroom in which at least the light source 3, the laminate 15, the transparent electrode 2a, and the support electrode 2b are accommodated. More specifically, the housing 9 is a hollow structure that forms a darkroom that can block light other than the light 3a from the light source 3 (hereinafter, appropriately referred to as external light). As shown in FIG. 1, the darkroom formed by the housing 9 accommodates the light source 3, the transparent electrode 2a, the support electrode 2b, the laminate 15, the DC bias power supply 4, the AC power supply 5, the capacitance meter 6, and the voltmeter 7. Of these, the laminate 15 is housed in a removable darkroom of the housing 9. When the semiconductor 12 layer is previously provided on the support electrode 2b, the insulator 11 of the laminate 15 is housed in a removable darkroom of the housing 9. By housing the light source 3, the laminate 15, the transparent electrode 2a, the support electrode 2b, etc. in the darkroom, the housing 9 can block external light from these contents. As a result, the light 3a from the light source 3 can be appropriately irradiated onto the laminate 15 (particularly the insulator 11) of the capacitor structure 10, which is the subject of CV characteristic measurement.

(CV characteristics of capacitor structure)
Next, a description will be given of the CV characteristics of the capacitor structure 10 measured by the CV characteristic measuring device 1 according to the present embodiment 1. Fig. 2 is a diagram showing an example of the CV characteristics of the capacitor structure measured in the present embodiment 1. As shown in Fig. 2, the CV characteristics of the capacitor structure 10 in the present embodiment 1 are represented by the correlation between the electrostatic capacitance C of the capacitor structure 10 and the applied voltage V.

In detail, the capacitance C of the capacitor structure 10 is measured by the capacitance measuring device 6 in response to the applied voltage V of the capacitor structure 10 before and after the light irradiation of the capacitor structure 10 by the light source 3. The applied voltage V of the capacitor structure 10 is measured by the voltmeter 7 in conjunction with the measurement of the capacitance C by the capacitance measuring device 6 before and after the light irradiation of the capacitor structure 10 by the light source 3. The CV characteristics of the capacitor structure 10 before light irradiation are represented by the correlation between the capacitance C of the capacitor structure 10 before light irradiation measured by the capacitance measuring device 6 and the applied voltage V of the capacitor structure 10 before light irradiation measured by the voltmeter 7. The CV characteristics of the capacitor structure 10 after light irradiation are represented by the correlation between the capacitance C of the capacitor structure 10 after light irradiation measured by the capacitance measuring device 6 and the applied voltage V of the capacitor structure 10 after light irradiation measured by the voltmeter 7.

For example, as shown in FIG. 2, the CV characteristics of the capacitor structure 10 before light irradiation are represented by a correlation line Y1 (solid line in FIG. 2) showing the correlation between the capacitance C of the capacitor structure 10 before light irradiation and the applied voltage V. The CV characteristics of the capacitor structure 10 after light irradiation are represented by a correlation line Y2 (dashed line in FIG. 2) showing the correlation between the capacitance C of the capacitor structure 10 after light irradiation and the applied voltage V. Regardless of whether the capacitor structure 10 is before or after light irradiation, as exemplified by the correlation lines Y1 and Y2, the capacitance C of the capacitor structure 10 shows a correlation of a high value including a maximum value, a correlation of a steep decline from the high value, and a correlation of a gradual increase or decrease or a constant value after the steep decline.

Here, in the CV characteristic of the capacitor structure 10 after light irradiation, the applied voltage V when the capacitance C drops sharply is increased compared to the CV characteristic of the capacitor structure 10 before light irradiation, as is clear from a comparison between the correlation lines Y1 and Y2 shown in FIG. 2. That is, the correlation line Y2 representing the CV characteristic of the capacitor structure 10 after light irradiation is shifted in the increasing direction of the applied voltage V (to the right in the drawing of FIG. 2) by the increase in the applied voltage V when the capacitance C drops sharply, compared to the correlation line Y1 representing the CV characteristic of the capacitor structure 10 before light irradiation. This shift phenomenon of the correlation line Y2 relative to the correlation line Y1 occurs due to the generation and accumulation of charges due to photoexcitation in the insulator 11 when the insulator 11 of the capacitor structure 10 is irradiated with the light 3a from the light source 3.

By using the above-mentioned CV characteristics of the capacitor structure 10 before and after light irradiation, parameters such as a flat band voltage required to derive the amount of charge excited in the insulator 11 by irradiation with the light 3a from the light source 3 (hereinafter referred to as the amount of photoexcited charge) and a capacitance in the charge storage state of the capacitor structure 10 (hereinafter referred to as the capacitance in the charge storage state) can be obtained. Specifically, as shown in FIG. 2, the flat band voltage V _FB 1 of the capacitor structure 10 before light irradiation can be derived from the applied voltage V when the capacitance C drops sharply in the CV characteristics of the capacitor structure 10 before light irradiation (see correlation line Y1). The flat band voltage V _FB 2 of the capacitor structure 10 after light irradiation can be derived from the applied voltage V when the capacitance C drops sharply in the CV characteristics of the capacitor structure 10 after light irradiation (see correlation line Y2). In addition, the capacitance C _I in the charge storage state is, for example, a capacitance in a state in which charges are stored in the layer of the semiconductor 12 included in the capacitor structure 10 before light irradiation. The capacitance C _I of such a charge storage state coincides with the capacitance of the insulating region of the capacitor structure 10 (the layer of insulator 11 in this embodiment 1), and can be derived from the capacitance C at which the capacitance becomes maximum according to the applied voltage V in the CV characteristics of the capacitor structure 10 before light irradiation.

The photoexcited charge amount Q of the insulator 11 can be derived based on the following formulas (1) and (2) on the basis of the parameters obtained from the CV characteristics of the capacitor structure 10 as described above. In particular, the flat band voltage _VFB1 of the capacitor structure 10 before light irradiation and the flat band voltage _VFB2 of the capacitor structure 10 after light irradiation are used, and the absolute value of the difference between the flat band voltage _VFB1 and the flat band voltage _VFB2 is calculated based on formula (1) to derive the flat band voltage difference _ΔVFB of the capacitor structure 10 before and after light irradiation. In addition, the photoexcited charge amount Q of the insulator 11 is derived by multiplying the flat band voltage difference _ΔVFB by the capacitance C _I in the charge storage state based on formula (2).

ΔV _FB = | V _FB 2 - V _FB 1 | ... (1)
Q=C _I ×ΔV _FB ...(2)

(Method of measuring CV characteristics of capacitor structure)
Next, a CV characteristic measuring method according to the first embodiment of the present invention will be described. FIG. 3 is a flow chart showing an example of a photoexcited charge measuring method to which the CV characteristic measuring method according to the first embodiment of the present invention is applied. This photoexcited charge measuring method is a method for measuring the charge amount (i.e., the photoexcited charge amount Q) due to photoexcitation accumulated in the target insulator 11, and is realized, for example, by sequentially performing each process of steps S101 to S106 shown in FIG. 3. The CV characteristic measuring method according to the first embodiment is a method for measuring the CV characteristics of the capacitor structure 10 required for measuring the photoexcited charge amount Q of the insulator 11, and is realized, for example, by performing at least each process of steps S103 and S104 shown in FIG. 3 using the above-mentioned CV characteristic measuring device 1 (see FIG. 1).

3, in the CV characteristic measurement method according to the present embodiment 1, first, a first CV characteristic measurement step is performed (step S101). This first CV characteristic measurement step is a step of measuring the CV characteristics of the capacitor structure 10 before light irradiation. In the present embodiment 1, the capacitor structure 10 before light irradiation is a capacitor structure including a transparent electrode 2a that contacts the laminate 15 from the layer side of the insulator 11, a support electrode 2b that contacts the laminate 15 from the layer side of the semiconductor 12, and the laminate 15 before light irradiation. For example, in step S101, the laminate 15 before light irradiation is disposed between the transparent electrode 2a and the support electrode 2b of the CV characteristic measurement device 1, thereby forming the capacitor structure 10 before light irradiation. The laminate 15 may be formed in advance by stacking a layer of the insulator 11 on the layer of the semiconductor 12 in a stage before step S101, or may be formed by stacking a layer of the insulator 11 on the layer of the semiconductor 12 during the process of step S101.

In step S101, the CV characteristic measuring device 1 measures the CV characteristics of the capacitor structure 10 before light irradiation using the capacitance measuring device 6 and the voltmeter 7. At this time, the capacitance measuring device 6 measures the capacitance C of the capacitor structure 10 in a state in which charges are stored in the laminate 15 by applying a DC bias voltage from the DC bias power supply 4 and an AC voltage from the AC power supply 5, corresponding to each value of the DC bias voltage applied to the capacitor structure 10 while changing within a predetermined voltage range. The voltmeter 7 measures the DC bias voltage applied to the capacitor structure 10 before light irradiation by the DC bias power supply 4 as the applied voltage V of the capacitor structure 10 before light irradiation. The CV characteristics of the capacitor structure 10 before light irradiation are represented by a correlation line Y1 (see FIG. 2) showing the correlation between the capacitance C of the capacitor structure 10 before light irradiation measured by the capacitance measuring device 6 and the applied voltage V of the capacitor structure 10 before light irradiation measured by the voltmeter 7. The correlation line Y1 is displayed, for example, on a display unit (not shown) provided in the capacitance measuring device 6 or the CV characteristic measuring device 1 as a measurement result of the CV characteristic of the capacitor structure 10 before light irradiation.

After the above-mentioned step S101 is performed, a first flat band voltage deriving step is performed (step S102) as shown in Fig. 3. This first flat band voltage deriving step is a step of deriving a flat band voltage _VFB1 in the CV characteristics of the capacitor structure 10 before light irradiation.

In step S102, the flat band voltage V _FB 1 is derived based on the CV characteristics of the capacitor structure 10 before light irradiation measured in the above-mentioned step S101. In detail, the applied voltage V when the capacitance C drops sharply on the correlation line Y1, which is the measurement result of the CV characteristics of the capacitor structure 10 before light irradiation, is derived as the flat band voltage V _FB 1. The process of deriving this flat band voltage V _FB 1 can be executed by, for example, an arithmetic processing unit (not shown) provided in the capacitance measuring instrument 6 or the CV characteristics measuring device 1.

After the above-mentioned step S102 is performed, a light irradiation step is performed as shown in FIG. 3 (step S103). This light irradiation step is a step in which light is irradiated from the insulator 11 layer side onto the laminate 15 including the insulator 11 layer and the semiconductor 12 layer, and charges are generated in the insulator 11 by photoexcitation.

In this embodiment 1, as shown in FIG. 1, the first electrode that contacts the laminate 15 from the layer side of the insulator 11 is a transparent electrode 2a that is transparent to the light 3a irradiated to the laminate 15 by the light source 3. In step S103, the light source 3 of the CV characteristic measuring device 1 irradiates the laminate 15 of the capacitor structure 10 before light irradiation with light 3a from the layer side of the insulator 11 through the transparent electrode 2a. In detail, the light source 3 irradiates the capacitor structure 10 before light irradiation that has already been formed in the CV characteristic measuring device 1 in the above-mentioned step S101 with light 3a from the transparent electrode 2a side. The light 3a emitted from the light source 3 penetrates the transparent electrode 2a and reaches the insulator 11 of the laminate 15. In this way, the light source 3 irradiates the light 3a to the insulator 11 through the transparent electrode 2a. In the insulator 11 irradiated with the light 3a from the light source 3, charges are generated due to photoexcitation. The charges due to this photoexcitation are mainly accumulated in the insulator 11.

After the above-mentioned step S103 is performed, as shown in FIG. 3, a second CV characteristic measurement step is performed (step S104). This second CV characteristic measurement step is a step of measuring the CV characteristics of the capacitor structure 10 after light irradiation. In this embodiment 1, the capacitor structure 10 after light irradiation is a capacitor structure including a transparent electrode 2a contacting the laminate 15 from the layer side of the insulator 11, a support electrode 2b contacting the laminate 15 from the layer side of the semiconductor 12, and the laminate 15 after light irradiation. The capacitor structure 10 after light irradiation in step S104 is the capacitor structure 10 before light irradiation described above irradiated with light 3a from the light source 3.

In step S104, the CV characteristic measuring device 1 measures the CV characteristics of the capacitor structure 10 after light irradiation using the capacitance measuring device 6 and the voltmeter 7. At this time, the capacitance measuring device 6 measures the capacitance C of the capacitor structure 10 in a state in which charges are accumulated in the laminate 15 by application of a DC bias voltage from the DC bias power supply 4, application of an AC voltage from the AC power supply 5, and irradiation with light 3a from the light source 3, corresponding to each value of the DC bias voltage under the same conditions as in step S101 described above. The voltmeter 7 measures the DC bias voltage applied to the capacitor structure 10 after light irradiation by the DC bias power supply 4 under the same conditions as in step S101 described above as the applied voltage V of the capacitor structure 10 after light irradiation. The CV characteristics of the capacitor structure 10 after light irradiation are represented by a correlation line Y2 (see FIG. 2) showing the correlation between the capacitance C of the capacitor structure 10 after light irradiation by the capacitance measuring device 6 and the applied voltage V of the capacitor structure 10 after light irradiation by the voltmeter 7. The correlation line Y2 is displayed, for example, on a display unit (not shown) provided in the capacitance measuring device 6 or the CV characteristic measuring device 1 as a measurement result of the CV characteristic of the capacitor structure 10 after light irradiation.

After the above-mentioned step S104 is performed, a second flat band voltage deriving step is performed (step S105) as shown in Fig. 3. This second flat band voltage deriving step is a step of deriving a flat band voltage _VFB2 in the CV characteristics of the capacitor structure 10 after light irradiation.

In step S105, the flat band voltage V _FB 2 is derived based on the CV characteristics of the capacitor structure 10 after light irradiation measured in the above-mentioned step S104. In detail, the applied voltage V when the capacitance C drops sharply on the correlation line Y2, which is the measurement result of the CV characteristics of the capacitor structure 10 after light irradiation, is derived as the flat band voltage V _FB 2. The process of deriving this flat band voltage V _FB 2 can be executed by, for example, an arithmetic processing unit (not shown) provided in the capacitance measuring instrument 6 or the CV characteristics measuring device 1.

The CV characteristics measurement method according to the present embodiment 1 includes each of the steps S101 to S105 described above. After each step of this CV characteristics measurement method is performed, that is, after the above-mentioned step S105 is performed, a photoexcited charge amount derivation step is performed (step S106) as shown in FIG. 3, and the photoexcited charge amount measurement method according to the present embodiment 1 is completed. This photoexcited charge amount derivation step is a step of deriving the amount of charge excited in the insulator 11 by irradiation with light 3a from the light source 3, that is, the photoexcited charge amount Q of the insulator 11.

In step S106, the photoexcited charge amount Q of the insulator 11 is derived based on the flat band voltage V _FB 1 in step S102, the flat band voltage V _FB 2 in step S105, and the capacitance C _I in the charge storage state. For example, in step S106, the maximum value of the capacitance C in the CV characteristic of the capacitor structure 10 before light irradiation measured in step S101 is derived as the capacitance C _I in the charge storage state. In addition, by using these flat band voltages V _FB 1 and V _FB 2 and performing a calculation process based on the above-mentioned formula (1), the flat band voltage difference ΔV _FB of the capacitor structure 10 before and after light irradiation is calculated. Next, by using this flat band voltage difference ΔV _FB and the above-mentioned capacitance C _I , the photoexcited charge amount Q of the insulator 11 is calculated by performing a calculation process based on the above-mentioned formula (2). The calculation process in step S106 can be performed, for example, by a calculation processing unit of a photoexcited charge quantity measuring device applied to the photoexcited charge quantity measuring method or a calculation processing unit of the above-mentioned CV characteristics measuring device (neither shown).

The photoexcited charge amount Q thus derived can be used to evaluate the photoexcited charge amount of the target insulator 11. For example, the photoexcited charge amount Q of the insulator 11 is compared with a preset charge amount threshold (upper limit value), and based on the comparison result, an insulator 11 with a smaller amount of charge accumulated due to photoexcitation (i.e., an insulator 11 with excellent light resistance characteristics) can be selected. Specifically, if the photoexcited charge amount Q is larger than the threshold value, the insulator 11 is determined to have insufficient light resistance characteristics, and if the photoexcited charge amount Q is equal to or less than the threshold value, the insulator 11 is determined to have good light resistance characteristics. An insulator 11 with good light resistance characteristics is expected to be adopted as an insulating material constituting a substrate of a TFT mounted on an organic EL display or the like. In addition, when evaluating the amount of photoexcited charge of the insulator 11, the amount of photoexcited charge Q is divided by the volume of the insulator 11 to calculate the amount of photoexcited charge per unit volume of the insulator 11, and this calculated value is compared with a preset upper threshold value, and the light resistance characteristics of the insulator 11 can be evaluated based on the comparison result.

In the above-mentioned first CV characteristic measurement step (step S101), the laminate 15 formed by laminating the semiconductor 12 layer and the insulator 11 layer is interposed between the transparent electrode 2a and the support electrode 2b of the CV characteristic measurement device 1, thereby forming the capacitor structure 10, but the CV characteristic measurement method according to the present embodiment 1 is not limited to this. For example, in the CV characteristic measurement method according to the present embodiment 1, the semiconductor 12 layer is fixedly arranged on the support electrode 2b in advance, and the insulator 11 before light irradiation is interposed between the semiconductor 12 layer on the support electrode 2b and the transparent electrode 2a, thereby forming the capacitor structure 10 before light irradiation. With this method, it is sufficient to prepare a single layer of the insulator 11 as the measurement sample, and the effort of preparing the laminate 15 can be saved, and the measurement sample can be easily prepared. In addition, even if the capacitor structure 10 is reformed by sequentially switching between the multiple insulators 11 each time the measurement of the CV characteristics of the capacitor structure 10 after light irradiation is completed, the difference in characteristics of the semiconductor 12 can be eliminated between the multiple capacitor structures 10 whose CV characteristics are measured. This reduces the measurement error of the CV characteristics, so that the CV characteristics of the capacitor structure 10 can be measured with high accuracy, and the photoexcited charge amount Q of the insulator 11 can be derived with high accuracy.

As described above, in the first embodiment of the present invention, the laminate 15 including the insulator 11 layer and the semiconductor 12 layer is irradiated with light 3a from the light source 3 from the insulator 11 layer side, and charges are generated in the insulator 11 by this light irradiation due to photoexcitation, and the CV characteristics of the capacitor structure 10 after light irradiation, which includes the first electrode (transparent electrode 2a in this first embodiment) contacting the laminate 15 from the insulator 11 layer side, the second electrode (support electrode 2b in this first embodiment) contacting the laminate 15 from the semiconductor 12 layer side, and the laminate 15 after light irradiation, are measured.

Therefore, it is possible to easily measure the CV characteristics of the capacitor structure 10 that is affected by the charge generated in the insulator 11 by photoexcitation, i.e., the CV characteristics of the capacitor structure 10 including the insulator 11 after light irradiation. By using the CV characteristics of the capacitor structure 10 after light irradiation and the CV characteristics of the capacitor structure 10 before light irradiation, it is possible to easily derive parameters (specifically, the above-mentioned flat band voltage _VFB1 , flat band voltage _VFB2 , flat band voltage difference _ΔVFB , and capacitance C _I in the charge storage state) that are essential for evaluating the amount of charge in the insulator 11 due to photoexcitation. As a result, it is possible to easily derive the amount of photoexcited charge Q of the insulator 11.

In addition, in the first embodiment of the present invention, a transparent electrode 2a is used as the first electrode that contacts the laminate 15 from the layer side of the insulator 11, and the laminate 15 of the capacitor structure 10 before light illumination is irradiated with light 3a from the light source 3 from the layer side of the insulator 11 via the transparent electrode 2a. Therefore, compared to the conventional case where a probe electrode is brought into contact with the laminate 15 from the layer side of the insulator 11, the light irradiation area of the insulator 11 can be made wider, and the probe electrode can be prevented from scratching the target surface of the insulator 11 that is irradiated with light. As a result, the CV characteristics of the capacitor structure 10 including the insulator 11 after light irradiation can be measured more easily and stably.

<Embodiment 2>
(CV characteristic measuring device)
Next, a CV characteristic measuring device according to the second embodiment of the present invention will be described. FIG. 4 is a schematic diagram showing one configuration example of the CV characteristic measuring device according to the second embodiment of the present invention. As shown in FIG. 4, the CV characteristic measuring device 21 according to the second embodiment has a laminate 25 interposed between the transparent electrode 2a and the support electrode 2b instead of the laminate 15 of the CV characteristic measuring device 1 according to the first embodiment. That is, in the second embodiment, the CV characteristic measuring device 21 has a capacitor structure 20 including the transparent electrode 2a, the support electrode 2b, and the laminate 25 formed therein as a measurement target of CV characteristics instead of the capacitor structure 10 in the first embodiment. In addition, the laminate 25 in the second embodiment further includes a charge blocking layer 23 between the layer of the insulator 11 and the layer of the semiconductor 12. The other configurations are the same as those in the first embodiment, and the same components are given the same reference numerals.

As shown in FIG. 4, the capacitor structure 20 is formed by sandwiching the laminate 25 between the transparent electrode 2a and the support electrode 2b in the layer thickness direction. In this embodiment 2, the capacitor structure 20 before light irradiation by the light source 3 is formed by the transparent electrode 2a, the support electrode 2b, and the laminate 25 before light irradiation. The capacitor structure 20 after light irradiation by the light source 3 is formed by the transparent electrode 2a, the support electrode 2b, and the laminate 25 after light irradiation.

The laminate 25 is an example of a laminate including at least the above-mentioned layer of insulator 11 and layer of semiconductor 12. In this embodiment 2, as shown in FIG. 4, the laminate 25 includes the same layer of insulator 11 and layer of semiconductor 12 as in embodiment 1, and further includes a charge blocking layer 23. The charge blocking layer 23 is a layer for blocking the movement of charges from the layer of insulator 11 to the layer of semiconductor 12. The charge blocking layer 23 is made of an insulator having a higher electrical resistance than the insulator 11, and is interposed between the layer of insulator 11 and the layer of semiconductor 12. The laminate 25 is formed by stacking the charge blocking layer 23 on the layer of semiconductor 12, and stacking the layer of insulator 11 on the charge blocking layer 23.

The insulator constituting the charge blocking layer 23 may be either an organic insulator or an inorganic insulator, but is preferably an inorganic insulator, more preferably an oxide insulator, and particularly preferably an oxide insulator formed by thermal oxidation (hereinafter referred to as a thermal oxide film). In addition, the thickness of the charge blocking layer 23 is preferably thinner than the thickness of the insulator 11 as the measurement sample, but is not particularly limited to this.

In the second embodiment, a layer of semiconductor 12 in the laminate 25 is placed on the upper surface of the support electrode 2b. On the other hand, a layer of semiconductor 12 may be provided in advance on the upper surface of the support electrode 2b, and the laminate 25 in the second embodiment may be formed by placing a laminate consisting of a charge blocking layer 23 and a layer of insulator 11 on the layer of semiconductor 12 provided on the support electrode 2b. Alternatively, the charge blocking layer 23 may be laminated on the layer of semiconductor 12 provided on the support electrode 2b, and a layer of insulator 11 may be laminated on the charge blocking layer 23, thereby forming the laminate 25.

(Method of measuring CV characteristics of capacitor structure)
Next, a CV characteristic measurement method according to a second embodiment of the present invention will be described. The CV characteristic measurement method according to the second embodiment is similar to the first embodiment, except that the measurement target is replaced from the capacitor structure 10 of the first embodiment to the capacitor structure 20 of the second embodiment. That is, the photoexcited charge amount measurement method to which the CV characteristic measurement method according to the second embodiment is applied is realized by sequentially performing each process of steps S101 to S106 shown in FIG. 3 with the capacitor structure 20 of the second embodiment as the measurement target of CV characteristics. The CV characteristic measurement method according to the second embodiment is a method for measuring the CV characteristics of the capacitor structure 20 required for measuring the photoexcited charge amount Q of the insulator 11, and is realized by performing at least each process of steps S103 and S104 shown in FIG. 3 using the above-mentioned CV characteristic measurement device 21 (see FIG. 4).

In detail, in the first CV characteristic measurement step (step S101) in this embodiment 2, the pre-light-irradiation laminate 25 is disposed between the transparent electrode 2a and the support electrode 2b of the CV characteristic measurement device 21, thereby forming the pre-light-irradiation capacitor structure 20. The laminate 25 may be formed in advance by sequentially stacking the charge blocking layer 23 and the insulator 11 layer on the semiconductor 12 layer before step S101, or may be formed by sequentially stacking the charge blocking layer 23 and the insulator 11 layer on the semiconductor 12 layer during the process of step S101.

In this step S101, the CV characteristic measuring device 21 measures the CV characteristics of the capacitor structure 20 before light irradiation using the capacitance measuring device 6 and the voltmeter 7. The measurement of the CV characteristics by the CV characteristic measuring device 21 in step S101 is the same as that in the above-mentioned embodiment 1, except that the CV characteristics are measured for the capacitor structure 20 before light irradiation. That is, in this step S101, the capacitance C of the capacitor structure 20 before light irradiation is measured by the capacitance measuring device 6, and the applied voltage V of the capacitor structure 20 before light irradiation is measured by the voltmeter 7. The CV characteristics of the capacitor structure 20 before light irradiation are represented by a correlation line Y1 (see FIG. 2) showing the correlation between the capacitance C of the capacitor structure 20 before light irradiation measured by the capacitance measuring device 6 and the applied voltage V of the capacitor structure 20 before light irradiation measured by the voltmeter 7.

Next, in a first flat band voltage derivation step (step S102) in this embodiment 2, a flat band voltage _VFB1 is derived based on the CV characteristics of the capacitor structure 20 before light irradiation measured in the above-mentioned step S101. The process of deriving this flat band voltage _VFB1 is similar to that of the above-mentioned embodiment 1, except that the CV characteristics of the capacitor structure 20 before light irradiation are used.

Next, in the light irradiation step (step S103) in this embodiment 2, the light source 3 of the CV characteristic measuring device 21 irradiates the laminate 25 of the capacitor structure 20 before light irradiation with light 3a from the layer side of the insulator 11 through the transparent electrode 2a. In detail, the light source 3 irradiates the capacitor structure 20 before light irradiation, which has already been formed in the CV characteristic measuring device 21 in the above-mentioned step S101, with light 3a from the transparent electrode 2a side. The light 3a emitted from the light source 3 penetrates the transparent electrode 2a and reaches the insulator 11 of the laminate 25. In this way, the light source 3 irradiates the light 3a to the insulator 11 through the transparent electrode 2a. In the insulator 11 irradiated with the light 3a from the light source 3, charges are generated due to photoexcitation.

Here, as shown in FIG. 4, a charge blocking layer 23 having a higher electrical resistance than the insulator 11 is interposed between the layer of insulator 11 and the layer of semiconductor 12 in the laminate 25. The charge blocking layer 23 can prevent the charge generated in the insulator 11 by photoexcitation from moving to the layer of semiconductor 12. As a result, the charge generated by photoexcitation in the insulator 11 does not escape to the layer of semiconductor 12, but is accumulated in the insulator 11.

Next, in the second CV characteristic measurement process (step S104) in this embodiment 2, the capacitor structure 20 before light irradiation is irradiated with light 3a from the light source 3 to become the capacitor structure 20 after light irradiation. In step S104, the CV characteristic measurement device 21 measures the CV characteristics of the capacitor structure 20 after light irradiation using the capacitance measurement device 6 and the voltmeter 7. The measurement of the CV characteristics by the CV characteristic measurement device 21 in step S104 is the same as that of the above-mentioned embodiment 1, except that the measurement target of the CV characteristics is the capacitor structure 20 after light irradiation. That is, in this step S104, the capacitance C of the capacitor structure 20 after light irradiation is measured by the capacitance measurement device 6, and the applied voltage V of the capacitor structure 20 after light irradiation is measured by the voltmeter 7. The CV characteristics of the capacitor structure 20 after light irradiation are represented by a correlation line Y2 (see FIG. 2) that shows the correlation between the capacitance C of the capacitor structure 20 after light irradiation measured by the capacitance measuring device 6 and the applied voltage V of the capacitor structure 20 after light irradiation measured by the voltmeter 7.

Next, in a second flat band voltage derivation step (step S105) in this embodiment 2, a flat band voltage _VFB2 is derived based on the CV characteristics of the capacitor structure 20 after light irradiation measured in the above-mentioned step S104. The process of deriving this flat band voltage _VFB2 is similar to that of the above-mentioned embodiment 1, except that the CV characteristics of the capacitor structure 20 after light irradiation are used.

The CV characteristics measurement method according to the second embodiment includes each of steps S101 to S105 in the second embodiment. After each step of this CV characteristics measurement method is performed, the photoexcited charge amount derivation step of step S106 is performed as in the first embodiment described above, and the photoexcited charge amount measurement method according to the second embodiment is completed.

The photoexcited charge amount derivation step (step S106) of the present embodiment 2 is similar to that of the above-mentioned embodiment 1, except that the flat band voltage V _FB 1 by step S102 of the present embodiment 2 and the flat band voltage V _FB 2 by step S105 of the present embodiment 2 are used. That is, in this step S106, the photoexcited charge amount Q of the insulator 11 in the capacitor structure 20 of the present embodiment 2 is derived based on the above-mentioned flat band voltages V _FB 1 and V _FB 2, the capacitance C _I in the charge storage state, and the formulas (1) and (2). In the present embodiment 2, the capacitance C _I in the charge storage state is, for example, the capacitance in a state in which charges are stored in the layer of the semiconductor 12 included in the capacitor structure 20 before light irradiation. Such a capacitance C _I in the charge storage state matches the capacitance of the insulating region of the capacitor structure 20 (the region of the layer of the insulator 11 and the charge blocking layer 23 in the present embodiment 2), and can be derived from the capacitance C when it becomes a maximum value according to the applied voltage V in the CV characteristic of the capacitor structure 20 before light irradiation.

In the first CV characteristic measurement step (step S101) in this embodiment 2, the laminate 25 formed by laminating the semiconductor 12 layer, the charge blocking layer 23, and the insulator 11 layer is interposed between the transparent electrode 2a and the support electrode 2b of the CV characteristic measurement device 21, thereby forming the capacitor structure 20, but the CV characteristic measurement method according to this embodiment 2 is not limited to this. For example, in the CV characteristic measurement method according to this embodiment 2, the semiconductor 12 layer is fixedly disposed on the support electrode 2b in advance, and a laminate of the insulator 11 and the charge blocking layer 23 before light irradiation is interposed between the semiconductor 12 layer on the support electrode 2b and the transparent electrode 2a, thereby forming the capacitor structure 20 before light irradiation. Alternatively, a laminate of the semiconductor 12 layer and the charge blocking layer 23 is fixedly disposed on the support electrode 2b in advance, and the insulator 11 before light irradiation is interposed between the charge blocking layer 23 in the laminate on the support electrode 2b and the transparent electrode 2a, thereby forming the capacitor structure 20 before light irradiation.

The above method reduces the effort required to prepare the laminate 25, and allows for easy preparation of a measurement sample. In addition, even if the capacitor structure 20 is re-formed by sequentially switching between the multiple insulators 11 each time the measurement of the CV characteristics of the capacitor structure 20 after light irradiation is completed, the difference in characteristics of the semiconductor 12 can be eliminated between the multiple capacitor structures 20 whose CV characteristics are measured. This reduces the measurement error of the CV characteristics, allowing the CV characteristics of the capacitor structure 20 to be measured with high accuracy, and ultimately allows the photoexcited charge amount Q of the insulator 11 to be derived with high accuracy.

As described above, in the second embodiment of the present invention, a charge blocking layer 23 having a higher electrical resistance than the insulator 11 is interposed between the layer of the insulator 11 and the layer of the semiconductor 12 in the laminate 25 for forming the capacitor structure 20 whose CV characteristics are to be measured, and the other configurations are the same as those of the first embodiment. Therefore, the same effects as those of the first embodiment can be obtained, and the charge generated in the insulator 11 by photoexcitation can be prevented from escaping to the layer of the semiconductor 12, so that the variation in the measured value of the capacitance C can be suppressed when measuring the CV characteristics of the capacitor structure 20 after light irradiation. As a result, the amount of shift of the CV characteristics after light irradiation (i.e., the flat band voltage difference ΔV _FB ) that shifts from the CV characteristics before light irradiation due to the influence of light irradiation can be accurately derived, and thus the amount of photoexcited charge Q of the insulator 11 can be accurately derived.

<Embodiment 3>
(CV characteristic measuring device)
Next, a CV characteristics measurement apparatus according to a third embodiment of the present invention will be described. Fig. 5 is a schematic diagram showing one configuration example of a CV characteristics measurement apparatus according to the third embodiment of the present invention. As shown in Fig. 5, a CV characteristics measurement apparatus 31 according to the third embodiment further includes a wavelength changing unit 33 for varying the wavelength of light 3a emitted from the light source 3, in addition to the configuration of the CV characteristics measurement apparatus 21 according to the second embodiment described above. The other configuration is the same as that of the second embodiment, and the same reference numerals are used for the same components.

The wavelength changer 33 changes the wavelength of the light 3a emitted from the light source 3. In detail, the wavelength changer 33 is composed of a spectrometer such as a prism or a diffraction grating, and is provided on the light emitting side of the light source 3 as shown in FIG. 5. The wavelength changer 33 receives light from the light source 3 and separates the received light into light 3a of a plurality of continuous wavelength bands. The wavelength changer 33 sequentially outputs the light 3a of the plurality of wavelength bands thus separated by wavelength band in a predetermined order. That is, the light 3a output from the light source 3 through the wavelength changer 33 is irradiated onto the insulator 11 of the laminate 25 while continuously changing the wavelength in a predetermined order. The wavelength changer 33 may sequentially output the light 3a while continuously changing the wavelength from the short wavelength side to the long wavelength side, or may sequentially output the light 3a while continuously changing the wavelength from the long wavelength side to the short wavelength side.

(Method of measuring CV characteristics of capacitor structure)
Next, a CV characteristics measurement method according to the third embodiment of the present invention will be described. The CV characteristics measurement method according to the third embodiment is similar to the above-mentioned second embodiment, except that the insulator 11 is irradiated with the light 3a whose wavelength is continuously changed by the wavelength changer 33, in order for each wavelength band. That is, in the photoexcited charge measurement method to which the CV characteristics measurement method according to the third embodiment is applied, each process of steps S101 to S106 shown in FIG. 3 is sequentially repeated for each wavelength band of the light 3a that is continuously changed by the wavelength changer 33. In the CV characteristics measurement method according to the third embodiment, at least each process of steps S103 and S104 is repeated for each wavelength band of the light 3a that is continuously changed by the wavelength changer 33.

For example, when the insulator 11 is irradiated with light of a first wavelength band among the light 3a of a plurality of wavelength bands emitted from the light source 3 and dispersed by the wavelength changing unit 33, the above-mentioned steps S101 to S106 are performed for the light of the first wavelength band. Next, when the insulator 11 is irradiated with light of a second wavelength band continuous from the first wavelength band among the light 3a of the plurality of wavelength bands, the above-mentioned steps S101 to S106 are performed again for the light of the second wavelength band. In this manner, the steps S101 to S106 are repeated until the wavelength changing unit 33 finishes changing the wavelength of the light 3a. As a result, in the third embodiment, the CV characteristics of the capacitor structure 20 before and after light irradiation, the flat band voltages _VFB1 and _VFB2 , the flat band voltage difference ΔVFB, the capacitance C _I in the charge storage state, and the photoexcited charge amount Q of the insulator 11 are obtained for _each wavelength band of the continuous light 3a.

As described above, in the third embodiment of the present invention, the wavelength of the light 3a emitted from the light source 3 is changed by the wavelength changing unit 33, and the light 3a of a plurality of wavelength bands is sequentially irradiated to the insulator 11 for each wavelength band, and each step of the photoexcited charge amount measurement method (including each step of the CV characteristic measurement method) is repeated for each wavelength band of the light 3a irradiated to the insulator 11, and the rest is configured in the same manner as in the second embodiment. Therefore, the same action and effect as the second embodiment described above can be obtained, and physical data such as the CV characteristics required to derive the photoexcited charge amount Q of the insulator 11 can be obtained for each of the plurality of wavelength bands of the light 3a irradiated to the insulator 11, making it possible to evaluate the dependency of the photoexcited charge amount Q of the insulator 11 on the wavelength of the irradiated light.

<Embodiment 4>
(CV characteristic measuring device)
Next, a CV characteristic measuring device according to a fourth embodiment of the present invention will be described. FIG. 6 is a schematic diagram showing one configuration example of a CV characteristic measuring device according to the fourth embodiment of the present invention. As shown in FIG. 6, a CV characteristic measuring device 41 according to the fourth embodiment includes a movable electrode (e.g., a mercury probe 42a) instead of the transparent electrode 2a of the CV characteristic measuring device 21 according to the second embodiment. That is, in the fourth embodiment, a capacitor structure 40 including a mercury probe 42a, a support electrode 2b, and a laminate 25 is formed in the CV characteristic measuring device 41 as a measurement target of CV characteristics instead of the capacitor structure 20 in the second embodiment. The other configurations are the same as those of the second embodiment, and the same reference numerals are used for the same components.

The mercury probe 42a is an example of a movable electrode that can be moved away from the layer side of the insulator 11 to the laminate (laminate 25 in this embodiment 4) including at least a layer of the insulator 11 and a layer of the semiconductor 12. In detail, the mercury probe 42a is an electrode composed of a cylindrical structure such as a cylinder containing mercury fluid having both elasticity and conductivity, and is arranged to face the support electrode 2b as shown in FIG. 6. The mercury probe 42a has a driving unit (not shown) and can move in a direction approaching or moving away from the support electrode 2b (for example, the direction indicated by the thick double-sided arrow in FIG. 6). The mercury probe 42a moves toward the insulator 11 of the laminate 25 arranged on the support electrode 2b, for example, and contacts the insulator 11 by applying the mercury fluid exposed from the cylindrical structure to the surface of the insulator 11. The mercury probe 42a moves away from the insulator 11 by moving the mercury fluid in a direction away from the surface of the insulator 11. In the mercury probe 42a in this embodiment 4, the viscosity of the mercury fluid and the inner diameter of the cylindrical structure are set so that a portion of the mercury fluid does not remain on the surface of the insulator 11 when the mercury probe 42a is separated from the surface of the insulator 11. As shown in FIG. 6, the mercury probe 42a is electrically connected to the DC bias power supply 4, the AC power supply 5, and the measurement unit 8 (the capacitance measuring device 6 and the voltmeter 7 in this embodiment 4) via wiring or the like.

As shown in FIG. 6, the capacitor structure 40 is formed by sandwiching the laminate 25 between the mercury probe 42a and the support electrode 2b in the layer thickness direction. In this embodiment 4, the capacitor structure 40 before light irradiation by the light source 3 is formed by the mercury probe 42a, the support electrode 2b, and the laminate 25 before light irradiation. The capacitor structure 40 after light irradiation by the light source 3 is formed by the mercury probe 42a, the support electrode 2b, and the laminate 25 after light irradiation.

(Method of measuring CV characteristics of capacitor structure)
Next, a CV characteristic measuring method according to a fourth embodiment of the present invention will be described. The CV characteristic measuring method according to the fourth embodiment is the same as the above-mentioned second embodiment, except that the first electrode to be brought into contact with the surface of the insulator 11 as the measurement sample is replaced from the transparent electrode 2a to a movable mercury probe 42a. That is, the photoexcited charge amount measuring method to which the CV characteristic measuring method according to the fourth embodiment is applied is realized by using the mercury probe 42a as the first electrode and sequentially performing each process of steps S101 to S106 shown in FIG. 3. The CV characteristic measuring method according to the fourth embodiment is a method for measuring the CV characteristics of the capacitor structure 40 required for measuring the photoexcited charge amount Q of the insulator 11, and is realized by performing at least each process of steps S103 and S104 shown in FIG. 3 using the above-mentioned CV characteristic measuring device 41 (see FIG. 6).

In detail, in the first CV characteristic measurement process (step S101) in this embodiment 4, the laminate 25 is placed on the support electrode 2b of the CV characteristic measurement device 41, and the mercury probe 42a is brought into contact with the layer of the insulator 11 in this laminate 25 to form the capacitor structure 40 before light irradiation. The formation of the laminate 25 is the same as in the above-mentioned embodiment 2.

In this step S101, the CV characteristic measuring device 41 measures the CV characteristics of the capacitor structure 40 before light irradiation using the capacitance measuring device 6 and the voltmeter 7. The measurement of the CV characteristics by the CV characteristic measuring device 41 in step S101 is the same as that in the above-mentioned embodiment 2, except that the transparent electrode 2a that contacts the layer of the insulator 11 is replaced with a mercury probe 42a. That is, in this step S101, the capacitance C of the capacitor structure 40 before light irradiation is measured by the capacitance measuring device 6, and the applied voltage V of the capacitor structure 40 before light irradiation is measured by the voltmeter 7. The CV characteristics of the capacitor structure 40 before light irradiation are represented by a correlation line Y1 (see FIG. 2) that shows the correlation between the capacitance C of the capacitor structure 40 before light irradiation measured by the capacitance measuring device 6 and the applied voltage V of the capacitor structure 40 before light irradiation measured by the voltmeter 7.

Next, in the first flat band voltage derivation step (step S102) in this embodiment 4, a flat band voltage _VFB1 is derived based on the CV characteristics of the capacitor structure 40 before light irradiation measured in the above-mentioned step S101. The process of deriving this flat band voltage _VFB1 is similar to that of the above-mentioned embodiment 2, except that the CV characteristics of the capacitor structure 40 before light irradiation are used.

Next, in the light irradiation process (step S103) in this embodiment 4, the CV characteristic measuring device 41 separates the mercury probe 42a from the laminate 25 and irradiates the laminate 25 with light 3a from the light source 3 from the layer side of the insulator 11. In this step S103, the mercury probe 42a is an example of a movable electrode that can be separated from the laminate 25, and is separated from the laminate 25 when the light source 3 irradiates the laminate 25 with light 3a. In detail, the mercury probe 42a moves in a direction that separates the mercury fluid from the surface of the insulator 11, thereby separating from the layer of the insulator 11 in the laminate 25. After the mercury probe 42a is separated from the layer of the insulator 11 as described above, the light source 3 irradiates the laminate 25 before light irradiation with light 3a from the layer side of the insulator 11. At this time, the light source 3 irradiates light 3a onto a surface portion of the insulator 11 including at least the portion to be measured (preferably the entire surface of the insulator 11). The portion to be measured of the insulator 11 is the portion of the entire surface of the insulator 11 that is in contact with the mercury probe 42a. Charges are generated in the insulator 11 due to photoexcitation when the light 3a from the light source 3 is irradiated. Charges generated by photoexcitation in the insulator 11 are stored in the insulator 11 because the charge blocking layer 23 blocks the charge from moving toward the semiconductor 12 layer.

In the second CV characteristic measurement step (step S104) in this embodiment 4, the laminate 25 before light irradiation is irradiated with light 3a from the light source 3 to become the laminate 25 after light irradiation. In step S104, the CV characteristic measurement device 41 forms a capacitor structure 40 after light irradiation using the mercury probe 42a, the support electrode 2b, and the laminate 25 after light irradiation, and measures the CV characteristics of the capacitor structure 20 after light irradiation using the capacitance measurement device 6 and the voltmeter 7. In detail, the mercury probe 42a contacts the laminate 25 after light irradiation from the light source 3 from the layer side of the insulator 11. That is, the mercury probe 42a moves toward the insulator 11 of the laminate 25 after light irradiation, and contacts the layer of the insulator 11 in the laminate 25 after light irradiation by applying mercury fluid to the surface of the insulator 11. As a result, the capacitor structure 40 after light irradiation in this embodiment 4 is formed.

The measurement of the CV characteristics by the CV characteristic measuring device 41 in step S104 is the same as that in the above-described embodiment 2, except that the first electrode in contact with the layer of the insulator 11 after light irradiation is replaced from the transparent electrode 2a to the mercury probe 42a, that is, the object of measurement of the CV characteristics is the capacitor structure 40 after light irradiation. In such step S104, the capacitance C of the capacitor structure 40 after light irradiation is measured by the capacitance measuring device 6, and the applied voltage V of the capacitor structure 40 after light irradiation is measured by the voltmeter 7. The CV characteristics of the capacitor structure 40 after light irradiation are represented by the correlation line Y2 (see FIG. 2) showing the correlation between the capacitance C of the capacitor structure 40 after light irradiation measured by the capacitance measuring device 6 and the applied voltage V of the capacitor structure 40 after light irradiation measured by the voltmeter 7.

Next, in a second flat band voltage derivation step (step S105) in this embodiment 4, a flat band voltage _VFB2 is derived based on the CV characteristics of the capacitor structure 40 after light irradiation measured in the above-mentioned step S104. The process of deriving this flat band voltage _VFB2 is similar to that of the above-mentioned embodiment 2, except that the CV characteristics of the capacitor structure 40 after light irradiation are used.

The CV characteristics measurement method according to the fourth embodiment includes each of steps S101 to S105 in the fourth embodiment. After each step of this CV characteristics measurement method is performed, the photoexcited charge amount derivation step of step S106 is performed as in the second embodiment described above, and the photoexcited charge amount measurement method according to the fourth embodiment is completed.

The photoexcited charge amount derivation step (step S106) of the present embodiment 4 is similar to that of the above-mentioned embodiment 2, except that the flat band voltage V _FB 1 by step S102 of the present embodiment 4 and the flat band voltage V _FB 2 by step S105 of the present embodiment 4 are used. That is, in this step S106, the photoexcited charge amount Q of the insulator 11 in the capacitor structure 40 of the present embodiment 4 is derived based on the above-mentioned flat band voltages V _FB 1 and V _FB 2, the capacitance C _I in the charge storage state, and the formulas (1) and (2). In the present embodiment 4, the capacitance C _I in the charge storage state is, for example, the capacitance in a state in which charges are stored in the layer of the semiconductor 12 included in the capacitor structure 40 before light irradiation. Such a capacitance C _I in the charge storage state matches the capacitance of the insulating region of the capacitor structure 40 (the region of the layer of the insulator 11 and the charge blocking layer 23 in the present embodiment 4), and can be derived from the capacitance C when it becomes a maximum value according to the applied voltage V in the CV characteristic of the capacitor structure 40 before light irradiation.

In the first CV characteristic measurement step (step S101) in this embodiment 4, the laminate 25 formed by laminating the semiconductor 12 layer, the charge blocking layer 23, and the insulator 11 layer is placed on the support electrode 2b of the CV characteristic measurement device 41, and the insulator 11 of the laminate 25 is brought into contact with the mercury probe 42a to form the capacitor structure 40, but the CV characteristic measurement method according to this embodiment 4 is not limited to this. For example, in the CV characteristic measurement method according to this embodiment 4, the layer of the semiconductor 12 is fixedly placed on the support electrode 2b in advance, and the laminate of the insulator 11 and the charge blocking layer 23 before light irradiation is interposed between the layer of the semiconductor 12 on the support electrode 2b and the mercury probe 42a, to form the capacitor structure 40 before light irradiation. Alternatively, a laminate of a semiconductor layer 12 and a charge blocking layer 23 may be fixedly disposed on the support electrode 2b in advance, and the pre-light-irradiation capacitor structure 40 may be formed by interposing the pre-light-irradiation insulator 11 between the charge blocking layer 23 in the laminate on the support electrode 2b and the mercury probe 42a.

The above method reduces the effort required to prepare the laminate 25, and allows for easy preparation of a measurement sample. In addition, even if the capacitor structure 40 is re-formed by sequentially switching between the multiple insulators 11 each time the measurement of the CV characteristics of the capacitor structure 40 after light irradiation is completed, the difference in characteristics of the semiconductor 12 can be eliminated between the multiple capacitor structures 40 whose CV characteristics are measured. This reduces the measurement error of the CV characteristics, allowing the CV characteristics of the capacitor structure 40 to be measured with high accuracy, and ultimately allows the photoexcited charge amount Q of the insulator 11 to be derived with high accuracy.

As described above, in the fourth embodiment of the present invention, a movable electrode that can be separated from the laminate 25 is used as the first electrode that contacts the laminate 25 from the layer side of the insulator 11, the movable electrode is separated from the laminate 25, the laminate 25 is irradiated with light 3a from the light source 3 from the layer side of the insulator 11, the capacitor structure 40 after light irradiation is formed by the movable electrode, the support electrode 2b, and the laminate 25 after light irradiation, and the CV characteristics of the capacitor structure 40 after light irradiation are measured, and the rest are configured in the same manner as in the second embodiment. Therefore, the same effects as those of the second embodiment can be obtained, and light can be irradiated to a wide range of surface parts including the part where the electrode is in contact with the entire surface of the insulator 11, and as a result, the CV characteristics of the capacitor structure 40 including the insulator 11 after light irradiation can be more easily measured. In addition, since the mercury probe 42a is used as the movable electrode, it is possible to prevent contact scratches and indentations of the probe electrode on the surface of the insulator 11 that is the target of light irradiation. As a result, the CV characteristics of the capacitor structure 40 including the insulator 11 after light irradiation can be stably measured.

In the above-mentioned first to fourth embodiments, the first electrode, the second electrode, the light source, the DC bias power supply, the AC power supply, the capacitance meter, and the voltmeter constituting the CV characteristics measuring device, as well as the laminate interposed between the first and second electrodes, are housed inside the darkroom formed by the housing 9, but the present invention is not limited to this. For example, the darkroom may house at least the first electrode, the second electrode, and the laminate constituting the capacitor structure to be measured, and the light source for light irradiation, which need to be shielded from external light in order to measure the CV characteristics.

In the above-mentioned third and fourth embodiments, the laminate 25 including the semiconductor 12 layer, the charge blocking layer 23, and the insulator 11 layer is exemplified as the laminate including the insulator 11 to be measured, but the present invention is not limited thereto. For example, in the CV characteristic measuring device 31 of the third embodiment including the wavelength changing unit 33 for changing the wavelength of the light 3a from the light source 3, the capacitor structure 20 for measuring the CV characteristics may be formed by interposing the laminate 15 including the semiconductor 12 layer and the insulator 11 layer between the transparent electrode 2a and the support electrode 2b. In the CV characteristic measuring device 41 of the fourth embodiment including the mercury probe 42a as a movable electrode that can be brought into contact with the insulator 11 in a separable manner, the capacitor structure 40 for measuring the CV characteristics may be formed by interposing the laminate 15 including the semiconductor 12 layer and the insulator 11 layer between the mercury probe 42a and the support electrode 2b. That is, the CV characteristic measuring device according to the present invention may be a combination of the above-mentioned first to fourth embodiments.

In addition, in the above-mentioned embodiment 4, the mercury probe 42a is exemplified as a movable electrode that can be brought into contact with the insulator 11 in a separable manner, but the present invention is not limited to this. For example, the movable electrode is not limited to the mercury probe 42a, and may be an electrode other than the mercury probe 42a.

The present invention will be explained below with reference to examples, but the present invention is not limited to the following examples.

Example 1
In Example 1, the CV characteristics of the measurement sample were measured using the CV characteristics measurement device 41 (see FIG. 6) according to the above-mentioned embodiment 4. The measurement sample of Example 1 was a laminate formed by laminating a polyimide film (an example of the insulator 11) on a P-type silicon wafer (an example of the semiconductor 12). The thickness of the polyimide film in this laminate was 1 [μm]. The electrode diameter of the mercury probe 42a was 0.17 [cm]. In Example 1, the measurement sample was stored in a darkroom by the housing 9 of the CV characteristics measurement device 41 in order to block external light other than the light 3a (irradiation light) from the light source 3. The CV characteristics of this measurement sample were measured in this darkroom.

In the measurement of the CV characteristics in Example 1, a measurement sample was placed on the support electrode 2b of the CV characteristics measurement device 41 in such a direction that the P-type silicon wafer was in contact with the support electrode 2b, and a mercury probe 42a was lowered and brought into contact with the surface of the polyimide film of the measurement sample. This formed a capacitor structure consisting of the support electrode 2b, the P-type silicon wafer, the polyimide film, and the mercury probe 42a. Next, the CV characteristics measurement device 41 applied a DC bias voltage to this capacitor structure by the DC bias power supply 4, and an AC voltage to this capacitor structure by the AC power supply 5. At this time, the DC bias voltage was set to -50 [V] or more and 50 [V] or less. The frequency of the AC voltage was set to 100 [kHz]. The CV characteristics measurement device 41 measured the capacitance C and applied voltage V of the capacitor structure in this state by the capacitance measurement device 6 and the voltmeter 7, respectively, and thereby measured the CV characteristics of this capacitor structure.

Fig. 7 is a diagram showing an example of the measurement results of the CV characteristics in Example 1 of the present invention. In Example 1, as shown in Fig. 7, a correlation line Y1 showing the correlation between the capacitance C of the capacitor structure before light irradiation and the applied voltage V was obtained as the CV characteristics of this capacitor structure before light irradiation. Furthermore, based on this obtained correlation line Y1, as shown in Fig. 7, it was possible to derive the flat band voltage _VFB1 of the capacitor structure before light irradiation.

Thereafter, the CV characteristic measuring device 41 separated the mercury probe 42a, which had been in contact with the polyimide film of the capacitor structure, from the polyimide film, and irradiated the surface of the polyimide film from which the mercury probe 42a had been removed with light 3a by the light source 3. At this time, the light 3a was LED light with a wavelength of 470 [nm]. The intensity of the light 3a was 4 [μW/cm ² ]. The irradiation time of the light 3a was 30 minutes. In this state, the CV characteristic measuring device 41 measured the capacitance C and applied voltage V of the capacitor structure after the light irradiation using the capacitance measuring device 6 and the voltmeter 7 under the same conditions as the CV characteristics before the light irradiation, respectively, thereby measuring the CV characteristics of the capacitor structure after the light irradiation. As a result, as shown in FIG. 7, a correlation line Y2 showing the correlation between the capacitance C and applied voltage V of the capacitor structure after the light irradiation was obtained as the CV characteristics of the capacitor structure after the light irradiation. Based on the obtained correlation line Y2, the flat band voltage _VFB2 of the capacitor structure after light irradiation could be derived as shown in FIG.

Next, in Example 1, the flat band voltage difference ΔV FB shown in FIG. 7 was derived based on the above-mentioned formula (1) using the flat band voltages V _FB 1 and V _{FB 2} before and after light irradiation. The obtained flat band voltage difference ΔV _FB was 14.7 [V]. In addition, the capacitance C _I in the charge storage state was derived based on the CV characteristics of the capacitor structure before light irradiation in Example 1 (see the correlation line Y1 shown in FIG. 7). The obtained capacitance C _I was 105.3 [pF]. Using the flat band voltage difference ΔV _FB and capacitance C _I thus obtained, the photoexcited charge amount Q of the polyimide film could be derived based on the above-mentioned formula (2). The obtained photoexcited charge amount Q was the charge amount increased by photoexcitation in the polyimide film, and was 1.5×10 ⁻⁹ [C].

Example 2
In Example 2, the CV characteristics of the measurement sample were measured using the CV characteristics measurement device 41 in the same manner as in Example 1. The measurement sample in Example 2 was a laminate in which a thermal oxide film (SiO ₂ ), which is an example of the charge blocking layer 23, was laminated on the surface of a P-type silicon wafer in the same manner as in Example 1, and a polyimide film in the same manner as in Example 1 was laminated on the thermal oxide film. That is, in this laminate, the thermal oxide film was interposed between the P-type silicon wafer and the polyimide film. The thickness of this thermal oxide film was set to 50 [nm]. The volume resistance value of this thermal oxide film was higher than the volume resistance value (=1×10 ¹⁷ [Ω·cm]) of the polyimide film, specifically, 1×10 ¹⁸ [Ω·cm]. The mercury probe 42a of the CV characteristics measurement device 41 was the same as in Example 1. The measurement sample in Example 2 was stored in a darkroom by the housing 9 of the CV characteristics measurement device 41 in order to block external light in the same manner as in Example 1. The CV characteristics of the measurement sample were measured in this darkroom.

In the measurement of the CV characteristics in Example 2, a measurement sample was placed on the support electrode 2b of the CV characteristics measurement device 41 in such a direction that the P-type silicon wafer was in contact with the support electrode 2b, and a mercury probe 42a was lowered and brought into contact with the surface of the polyimide film of the measurement sample. This formed a capacitor structure consisting of the support electrode 2b, the P-type silicon wafer, the thermal oxide film, the polyimide film, and the mercury probe 42a. Next, the CV characteristics measurement device 41 applied a DC bias voltage to this capacitor structure by the DC bias power supply 4, and an AC voltage to this capacitor structure by the AC power supply 5. At this time, the DC bias voltage was set to -50 [V] or more and 100 [V] or less. The frequency of the AC voltage was set to 100 [kHz]. The CV characteristics measurement device 41 measured the capacitance C and applied voltage V of the capacitor structure in this state by the capacitance measurement device 6 and the voltmeter 7, respectively, and thereby measured the CV characteristics of this capacitor structure.

Fig. 8 is a diagram showing an example of the measurement results of the CV characteristics in Example 2 of the present invention. In Example 2, as shown in Fig. 8, a correlation line Y1 showing the correlation between the capacitance C of the capacitor structure before light irradiation and the applied voltage V was obtained as the CV characteristics of this capacitor structure before light irradiation. Furthermore, based on this obtained correlation line Y1, as shown in Fig. 8, it was possible to derive the flat band voltage _VFB1 of the capacitor structure before light irradiation.

Thereafter, the CV characteristic measuring device 41 separated the mercury probe 42a, which had been in contact with the polyimide film of the capacitor structure, from the polyimide film, and irradiated the surface of the polyimide film from which the mercury probe 42a had been removed with light 3a by the light source 3. At this time, the light 3a was LED light with a wavelength of 470 [nm]. The intensity of the light 3a was 4 [μW/cm ² ]. The irradiation time of the light 3a was 30 minutes. In this state, the CV characteristic measuring device 41 measured the capacitance C and applied voltage V of the capacitor structure after the light irradiation using the capacitance measuring device 6 and the voltmeter 7 under the same conditions as the CV characteristics before the light irradiation, respectively, thereby measuring the CV characteristics of the capacitor structure after the light irradiation. As a result, as shown in FIG. 8, a correlation line Y2 showing the correlation between the capacitance C and applied voltage V of the capacitor structure after the light irradiation was obtained as the CV characteristics of the capacitor structure after the light irradiation. Based on the obtained correlation line Y2, the flat band voltage _VFB2 of the capacitor structure after light irradiation could be derived as shown in FIG.

Next, in Example 2, the flat band voltage difference ΔV FB shown in FIG. 8 was derived based on the above-mentioned formula (1) using the flat band voltages V _FB 1 and V _{FB 2} before and after light irradiation. The obtained flat band voltage difference ΔV _FB was 62.8 [V]. In addition, the capacitance C _I in the charge storage state was derived based on the CV characteristics of the capacitor structure before light irradiation in Example 2 (see the correlation line Y1 shown in FIG. 8). The obtained capacitance C _I was 106.7 [pF]. Using the flat band voltage difference ΔV _FB and capacitance C _I thus obtained, the photoexcited charge amount Q of the polyimide film could be derived based on the above-mentioned formula (2). The obtained photoexcited charge amount Q was the amount of charge increased by photoexcitation in the polyimide film, and was 6.7×10 ⁻⁹ [C].

The present invention is not limited to the above-mentioned embodiments 1 to 4 and examples 1 and 2. The present invention also includes configurations in which the above-mentioned components are appropriately combined. In addition, other embodiments, examples, operational techniques, etc. made by those skilled in the art based on the above-mentioned embodiments 1 to 4 are all included in the scope of the present invention.

REFERENCE SIGNS LIST 1, 21, 31, 41 CV characteristic measuring device 2a Transparent electrode 2b Support electrode 3 Light source 3a Light 4 DC bias power supply 5 AC power supply 6 Capacitance measuring device 7 Voltmeter 8 Measuring section 9 Housing 10, 20, 40 Capacitor structure 11 Insulator 12 Semiconductor 15, 25 Laminated body 23 Charge blocking layer 33 Wavelength changing section 42a Mercury probe Y1, Y2 Correlation line

Claims (10)

a light irradiation step of irradiating a laminate including an insulator layer and a semiconductor layer with light from the insulator layer side to generate charges in the insulator by photoexcitation;
a measuring step of measuring capacitance-voltage characteristics of a capacitor structure after light irradiation, the capacitor structure including a first electrode contacting the laminate from the insulator layer side, a second electrode contacting the laminate from the semiconductor layer side, and the laminate after light irradiation;
Including,
a charge blocking layer having a higher electrical resistance than the insulator is interposed between the insulator layer and the semiconductor layer in the laminate;
The capacitance-voltage characteristic measuring method according to the present invention is characterized in that: the first electrode is a transparent electrode that is transparent to the light irradiated to the laminate;
The light irradiation step includes irradiating the laminate having a capacitor structure before light illumination, which is formed by the first electrode, the second electrode, and the laminate before light irradiation, with the light from the insulator layer side via the first electrode.
2. The method for measuring capacitance-voltage characteristics according to claim 1 . the first electrode is a movable electrode that is in separable contact with the stack;
The light irradiation step includes irradiating the laminate with the light from the insulating layer side with the first electrode spaced apart from the laminate;
the measuring step includes forming the capacitor structure after light irradiation using the first electrode, the second electrode, and the laminate after light irradiation, and measuring the capacitance-voltage characteristics of the capacitor structure after light irradiation.
2. The method for measuring capacitance-voltage characteristics according to claim 1 . The movable electrode is a mercury probe.
4. The method for measuring capacitance-voltage characteristics according to claim 3 . a first electrode that is in contact with a laminate including an insulator layer and a semiconductor layer from the insulator layer side;
a second electrode in contact with the stack from the semiconductor layer side;
a light source that irradiates the laminate with light from the insulating layer side;
a DC power source that applies a DC bias voltage to a capacitor structure after light irradiation, the capacitor structure including the first electrode, the second electrode, and the laminate after light irradiation;
an AC power source that applies an AC voltage to the capacitor structure after the light irradiation;
A measurement unit for measuring the capacitance-voltage characteristics of the capacitor structure after light irradiation;
a housing forming a darkroom in which at least the light source, the laminate, the first electrode, and the second electrode are housed;
Equipped with
The laminate further includes a charge blocking layer interposed between the insulator layer and the semiconductor layer and having a higher electrical resistance than the insulator.
The capacitance-voltage characteristic measuring device is characterized by the above. the first electrode is a transparent electrode that is transparent to the light from the light source;
the light source irradiates the stack of a capacitor structure before light irradiation, which is formed by the first electrode, the second electrode, and the stack before light irradiation, with the light from the insulator layer side via the first electrode;
6. The capacitance-voltage characteristic measuring device according to claim 5 . the first electrode is a movable electrode that is in separable contact with the stack;
the movable electrode is separated from the laminate when the light is irradiated to the laminate by the light source, and is in contact with the laminate after the light irradiation.
6. The capacitance-voltage characteristic measuring device according to claim 5 . The movable electrode is a mercury probe.
8. The capacitance-voltage characteristic measuring device according to claim 7 . Further comprising a wavelength changing unit that changes the wavelength of the light from the light source.
The capacitance-voltage characteristic measuring device according to any one of claims 5 to 8 . The semiconductor layer is provided on the second electrode.
10. The capacitance-voltage characteristic measuring device according to claim 5 , wherein the capacitance-voltage characteristic measuring device is a capacitance-voltage characteristic measuring device.

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