Vibration component measuring device, kelvin probe force spectrometer, vibration component measuring method, and interface state density measuring method

Abstract

In order to measure a change in a fluctuating component of a vibrating unit more efficiently, and to calculate an interface state density of a sample more efficiently, a vibration component measuring device (2) comprises: a vibrating unit (4); a vibration control unit (10) for causing the vibrating unit to vibrate on the basis of a first alternating current signal; a signal applying unit (14, 48) for applying at least one of a direct current signal, a second alternating current signal, and a reference alternating current signal between the vibrating unit and a sample; and a measuring unit (42, 44) for measuring a fluctuating component of the vibration of the vibrating unit. The measuring unit measures a change in the fluctuating component with respect to a change in a voltage value of the direct current signal.

Description

[Technical field]

[0001] The present disclosure relates to a method for measuring a fluctuation component of vibration of a vibrating part, or a method for measuring interface state density using said method, and an apparatus for implementing said method, and in particular, a spectrometer equipped with said apparatus. [Background technology]

[0002] In recent years, in order to improve the performance of semiconductor devices, there is a demand for a method for visualizing interface charges at the interface between a semiconductor layer and another layer, etc. Non-Patent Document 1 discloses a method for measuring the interface state density of a sample by applying low-frequency and high-frequency AC bias voltages to the sample having a MOS structure in which a fixed metal film, an oxide film, and a semiconductor film are stacked. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Description of the SiO2 Si interface properties by means of very low frequency MOS capacitance measurements, R. Castagne and A. Vapaelle, Surf. Sci. 28 (1971) 157-193 Summary of the Invention [Problem to be solved by the invention]

[0004] The method described in the above document is limited to measuring the interface state density in a macroscopic area obtained by averaging the area of ​​the metal electrode, and it is difficult to measure the interface state density on a nanometer scale. Therefore, there is a demand for an apparatus or method that can measure the behavior of a sample more efficiently or with higher precision when the signal applied to the sample is low frequency and when the signal is high frequency. [Means for solving the problem]

[0005] In order to solve the above problems, a vibration component measuring device according to one embodiment of the present disclosure includes a vibration unit, a first AC signal generator that generates a first AC signal, a second AC signal generator that generates a second AC signal having a frequency higher than the frequency of the first AC signal and different from an integer multiple of the frequency of the first AC signal, a reference AC signal generator that generates a reference AC signal having a frequency lower than the frequency of the first AC signal, a DC signal generator that generates a DC signal, a vibration control unit that vibrates the vibration unit based on the first AC signal, a signal application unit that applies the DC signal and at least one of the second AC signal and the reference AC signal between the vibration unit and a sample, and a measurement unit that measures a fluctuation component of the vibration of the vibration unit that fluctuates due to an interaction between the vibration unit and the sample.

[0006] In one aspect of the vibration component measuring device, the DC signal generator generates at least two DC signals, a first DC signal and a second DC signal having a voltage different from that of the first DC signal, and the measurement unit measures the change in the fluctuation component with respect to the change in the voltage value of the DC signal from the fluctuation component when the DC signal is the first DC signal and the fluctuation component when the DC signal is the second DC signal.

[0007] In another aspect of the vibration component measuring device, the measurement section measures a first-order differential value of the fluctuation component with respect to the voltage of the DC signal.

[0008] In another aspect of the vibration component measuring device, the measurement section measures a second-order differential value of the fluctuation component with respect to the voltage of the DC signal.

[0009] In order to solve the above problem, a vibration component measuring method according to one aspect of the present disclosure includes generating a first AC signal for vibrating a vibrating part, generating a second AC signal having a frequency higher than a frequency of the first AC signal and different from an integer multiple of the frequency of the first AC signal, generating a reference AC signal having a frequency lower than the frequency of the first AC signal, generating a DC signal, and applying the DC signal and ,before Second AC signal and Reference AC signal At least one of the following: and measuring a fluctuation component of the vibration of the vibration part that fluctuates due to an interaction between the vibration part and the sample by vibrating the vibration part based on the first AC signal while applying a first AC signal.

[0010] In one aspect of the vibration component measuring method, in generating the DC signal, at least two DC signals are generated: a first DC signal and a second DC signal having a voltage different from that of the first DC signal; and in measuring the fluctuation component, a change in the fluctuation component with respect to a change in the voltage value of the DC signal is measured from the fluctuation component when the DC signal is the first DC signal and the fluctuation component when the DC signal is the second DC signal.

[0011] In another aspect of the vibration component measuring method, the fluctuation component is measured by measuring a first-order differential value of the fluctuation component with respect to the voltage of the DC signal.

[0012] In another aspect of the vibration component measuring method, the fluctuation component is measured by measuring a second-order differential value of the fluctuation component with respect to the voltage of the DC signal. Effect of the Invention

[0013] According to one aspect of the present disclosure, it is possible to measure the change in the fluctuation component more efficiently or more precisely. In addition, it is possible to more efficiently measure the change in the behavior of the sample when the signal applied to the sample is a low frequency signal and when the signal applied to the sample is a high frequency signal, from the difference in the fluctuation component. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram for explaining a configuration of a vibration component measuring device according to a first embodiment and an operation of the vibration component measuring device. [Diagram 2] 4 is a graph showing the intensity of a signal received by the optical sensor according to the first embodiment for each frequency of the signal. [Diagram 3] 1 is a block diagram for explaining the configuration of a first phase-locked loop circuit and an automatic gain control according to a first embodiment. FIG. [Figure 4] FIG. 2 is a block diagram for explaining a configuration of a second phase-locked loop circuit according to the first embodiment. [Diagram 5] 4 is a graph showing the intensity of a signal input to a full-harmonic lock-in amplifier according to the first embodiment for each frequency of the signal. [Figure 6] 4 is a graph showing the intensity of a signal output from the first amplitude modulator according to the first embodiment for each frequency of the signal. [Figure 7] FIG. 4 is a block diagram for explaining another example of the operation of the vibration component measuring device according to the first embodiment. [Figure 8] 10 is a graph showing another example of the intensity of the signal received by the optical sensor according to the first embodiment for each frequency of the signal. [Figure 9] FIG. 1 is a band diagram for explaining how bands in the bulk of a sample are curved depending on the surface condition of the sample. [Figure 10] FIG. 1 is a band diagram for explaining how band curvature in the bulk of a sample varies with variation in an external electric field. [Figure 11] 13 is a graph showing the cutoff frequency of a signal applied to an external electrode at which no fluctuation in band curvature occurs in the bulk of the sample, for each difference between the Fermi level of the bulk of the sample and the Fermi level of the surface of the sample. [Figure 12] 10 is an equivalent circuit diagram showing a capacitance formed between a sample and an electrode when the frequency of a signal applied to an external electrode is lower than the cutoff frequency. FIG. [Figure 13]10 is an equivalent circuit diagram showing a capacitance formed between a sample and an electrode when the frequency of a signal applied to an external electrode is equal to or higher than the cutoff frequency. FIG. [Figure 14] 4 is an example of a graph showing the intensity of a signal output from the full-harmonic lock-in amplifier according to the first embodiment for each voltage value of a DC voltage. [Figure 15] FIG. 1 is a band diagram and a schematic cross-sectional side view of the vicinity of a sample, illustrating how an accumulation layer is formed near the interface of the sample due to an external electric field. [Figure 16] 1A and 1B are a band diagram and a schematic cross-sectional side view of a sample and its vicinity, showing how a depletion layer is formed near the interface of the sample due to an external electric field. [Figure 17] 1A and 1B are a band diagram and a schematic cross-sectional side view of a sample, showing how an inversion layer is formed near the interface of the sample due to an external electric field. [Figure 18] FIG. 11 is a block diagram for explaining the configuration of a vibration component measuring device according to a second embodiment and the operation of the vibration component measuring device. [Figure 19] 10 is a graph showing the intensity of a signal received by an optical sensor according to the second embodiment for each frequency of the signal. [Figure 20] 10 is a graph showing the intensity of a signal input to a first harmonic lock-in amplifier and a second harmonic lock-in amplifier according to the second embodiment for each frequency of the signal. [Figure 21] FIG. 10 is a block diagram for explaining another example of the operation of the vibration component measuring device according to the second embodiment. [Figure 22] FIG. 11 is a block diagram for explaining the configuration of a vibration component measuring device according to a third embodiment and the operation of the vibration component measuring device. [Diagram 23] FIG. 11 is a block diagram for explaining the configuration of a vibration component measuring device according to a fourth embodiment and the operation of the vibration component measuring device. [Figure 24] FIG. 13 is a block diagram for explaining the configuration of a vibration component measuring device according to a fifth embodiment and the operation of the vibration component measuring device. [Diagram 25]FIG. 13 is a block diagram for explaining the configuration of a vibration component measuring device according to a sixth embodiment and the operation of the vibration component measuring device. [Figure 26] FIG. 13 is a block diagram for explaining the configuration of a vibration component measuring device according to a seventh embodiment and the operation of the vibration component measuring device. [Figure 27] FIG. 13 is a block diagram for explaining the configuration of a vibration component measuring device according to an eighth embodiment and the operation of the vibration component measuring device. [Figure 28] FIG. 13 is a block diagram for explaining the configuration of a vibration component measuring device according to a ninth embodiment and the operation of the vibration component measuring device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Embodiment 1] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the drawings used in the following description are schematic diagrams and do not strictly represent the dimensional ratios of the respective members in the drawings.

[0016] 1 is a block diagram for explaining the configuration of a vibration component measuring device 2 according to this embodiment and the operation of the vibration component measuring device 2. The vibration component measuring device 2 according to this embodiment includes a first switch S1 and a second switch S2, which will be described later. Equipped with In this embodiment, first, an operation of the vibration component measuring device 2 in a state in which the first switch S1 is closed and the second switch S2 is open will be described as an example of a first operation.

[0017] <Cantilever tip and stage> The vibration component measuring device 2 according to this embodiment includes a cantilever probe 4 as a vibration part. The cantilever probe 4 includes a cantilever portion 6 and a probe portion 8 formed on an end of the cantilever portion 6. The vibration component measuring device 2 according to this embodiment is a device for measuring the vibration component of the cantilever probe 4 by bringing the probe portion 8 close to the sample X while vibrating the cantilever portion 6 of the cantilever probe 4.

[0018] In this embodiment, the sample X may include, for example, a semiconductor, or may include a semiconductor having an oxide film or the like formed on the surface. In other words, the sample X may have a plurality of layers and at least one interface between the plurality of layers. In this embodiment, an example will be described in which the interface state density at the surface or interface of the semiconductor of the sample X is measured through the measurement of the vibration component of the cantilever probe 4 described above by the vibration component measuring device 2.

[0019] In this embodiment, a method for measuring the vibration component of the cantilever probe 4 while always keeping the sample X and the cantilever probe 4 in a non-contact state will be described as an example, but the present invention is not limited to this. For example, the vibration component of the cantilever probe 4 may be measured using a method generally called a tapping mode in which the sample X and the cantilever probe 4 come into intermittent contact with each other as the cantilever probe 4 vibrates. However, from the viewpoint of preventing damage to the sample X, the vibration component of the cantilever probe 4 may be measured while always keeping the sample X and the cantilever probe 4 in a non-contact state.

[0020] The vibration component measuring device 2 includes a probe control unit 10 as a vibration control unit that vibrates the cantilever probe 4 at a vibration frequency corresponding to the frequency of the applied voltage. Specifically, the resonance frequency of the cantilever probe 4 when there is no interaction between the cantilever probe 4 and the sample is a frequency f 1 In this case, the probe control unit 10 is 1 A first AC signal having the following formula is input:

[0021] The vibration component measuring device 2 includes a stage 12 for supporting the sample X, and a stage electrode 14 for applying a voltage to the sample X. For example, as shown in Fig. 1, the stage electrode 14 and the sample X are electrically connected, and the cantilever probe 4 is grounded. This makes it possible to apply the same voltage as that applied to the stage electrode 14 between the cantilever probe 4 and the sample X when a voltage is applied to the stage electrode 14.

[0022] In addition, although details will be described later, in this embodiment, the stage electrode 14 is provided with the above-mentioned frequency f 1 and frequency f 1 A frequency f that is lower than m Furthermore, the signal applied to the stage electrode 14 includes a voltage V dc The signal includes a superimposed signal of a DC signal having the above-mentioned second AC signal.

[0023] <Detection of vibration components> In this embodiment, the vibration component of the cantilever probe 4 is detected, for example, by using a so-called optical lever method using a light source 16 and an optical sensor 18 provided in the vibration component measuring device 2.

[0024] Light source 16 is, for example, a laser diode, and irradiates light onto cantilever probe 4. The light irradiated to cantilever probe 4 and reflected is irradiated onto optical sensor 18.

[0025] Here, optical sensor 18 is an optical position sensor and may be, for example, a four-segment photodiode. The irradiation position on optical sensor 18 of the light reflected by cantilever probe 4 fluctuates due to the vibration of cantilever probe 4. Therefore, optical sensor 18 can determine the vibration component of cantilever probe 4 from the fluctuation component of the position where the light reflected by cantilever probe 4 is received.

[0026] For example, the optical sensor 18 calculates the vibration strength of the cantilever probe 4 for each vibration frequency of the cantilever probe 4 based on the periodic variation of the position receiving light and the intensity of the received light at each position. The optical sensor 18 also outputs a signal according to the detection result. In this embodiment, the signal output by the optical sensor 18 is a signal in which the vibration strength of the cantilever probe 4 for each vibration frequency of the cantilever probe 4 calculated by the optical sensor 18 is replaced with a signal strength for each frequency.

[0027] <Signal output by optical sensor> An example of the signal output by the optical sensor 18 is shown in the graph of Fig. 2. In Fig. 2, the horizontal axis represents the frequency of the signal output by the optical sensor 18, and the vertical axis represents the intensity of the signal output by the optical sensor 18.

[0028] The main component of the signal output by the optical sensor 18 is a frequency f 1 It is a component having the following structure.

[0029] Here, the vibration component measuring device 2 has a frequency of 2f between the cantilever probe 4 and the sample X. 1 +f m Therefore, the electrostatic force acting on the cantilever probe 4 as the electrostatic interaction between the cantilever probe 4 and the sample X changes according to this frequency. Therefore, the vibration of the cantilever probe 4 has a frequency of 2f 1 +f m Therefore, the signal output by the optical sensor 18 has a frequency component of 2f as shown in FIG. 1 +f m It has components in.

[0030] Also, the cantilever tip 4 vibrates at a frequency f 1 Since the cantilever 4 is vibrating at a frequency of f 1 +f m and frequency 3f 1 +f m Therefore, the signal output by the optical sensor 18 has a frequency f 1 +f m and frequency 3f 1 +f m Also has components in

[0031] Furthermore, if there is a difference in charge density due to local charge bias or the like at any interface between the probe portion 8 of the cantilever probe 4 and the sample X facing it, the electrostatic interaction between the cantilever probe 4 and the sample X changes depending on the charge density. The change in the electrostatic interaction between the cantilever probe 4 and the sample X due to the charge density shifts the resonance frequency of the cantilever probe 4 by Δf. Furthermore, the fluctuation component of the vibration of the cantilever probe 4 is observed as a change in the amplitude R and phase θ in the sidebands of the modulation component of the signal output by the optical sensor 18.

[0032] In other words, in this embodiment, it is possible to measure the change in the electrostatic interaction between the cantilever probe 4 and the sample X by observing the change in the amplitude R and the phase θ in the sideband of the modulation component of the vibration of the cantilever probe 4. From the change in the electrostatic interaction, the capacitance virtually formed between the cantilever probe 4 and the sample X can be measured.

[0033] The signal in the sideband of the modulation component of the vibration of the cantilever probe 4 may be either the upper sideband or the lower sideband. m may take either a positive or negative value.

[0034] When the frequency of the second AC signal is increased relative to the vibration frequency of the cantilever probe 4, the intensity of the sideband of the modulated component of the vibration of the cantilever probe 4 decreases rapidly. Therefore, simply increasing the frequency of the second AC signal may make it difficult to observe the sideband because it is buried in white noise.

[0035] However, increasing the frequency of the second AC signal to nearly twice the vibration frequency of the cantilever probe 4 increases the intensity of the sidebands of the modulated components of the vibration of the cantilever probe 4. Therefore, by setting the frequency of the second AC signal to nearly twice the vibration frequency of the cantilever probe 4, the intensity of the sidebands increases, making it easier to carry out the measurement.

[0036] In this embodiment, the frequency of the second AC signal is a frequency f 1 At twice the frequency f 1 A frequency lower than f m Therefore, the frequency of the second AC signal is approximately twice the vibration frequency of the cantilever probe 4, and the modulation component of the vibration of the cantilever probe 4 can be made sufficiently strong.

[0037] However, in this embodiment, the present invention is not limited to this, and the frequency of the second AC signal may be higher than that of the first AC signal and may be different from the frequency of the first AC signal by an integer multiple. In this way, when a signal on which the second AC signal is superimposed is applied to the sample X, at least a sideband of the modulated component of the vibration of the cantilever tip 4 is obtained.

[0038] <First phase-locked loop circuit and automatic gain control circuit> The signal output from the optical sensor 18 is input to a first phase-locked loop circuit 20 and a second phase-locked loop circuit 22, which are provided as phase-locked loop circuits (PLL circuits) in the vibration component measuring device 2. The first phase-locked loop circuit 20 generates a further signal based on the input signal, and inputs the generated signal to an automatic gain control circuit 24 and a stage control unit 26, which are provided in the vibration component measuring device 2.

[0039] Here, the configurations and operations of the first phase-locked loop circuit 20 and the second phase-locked loop circuit 22 will be described in detail with reference to FIGS.

[0040] Fig. 3 is a block diagram showing the configuration and operation of the first phase-locked loop circuit 20. Note that with reference to Fig. 3, an automatic gain control circuit 24 to which a part of the signal output from the first phase-locked loop circuit 20 shown in Fig. 1 is input will also be described.

[0041] The first phase-locked loop circuit 20 includes a PLL lock-in amplifier 28, a PID controller 30, and a voltage-controlled oscillator 32. The automatic gain control circuit 24 includes a PID controller 34 and a multiplier 36.

[0042] The signal input from the optical sensor 18 to the first phase-locked loop circuit 20 is input to the PLL lock-in amplifier 28. The PLL lock-in amplifier 28 is used as a phase comparator that compares the phase of the signal input from the optical sensor 18 with a reference signal input from a voltage-controlled oscillator 32, which will be described in detail later. In this embodiment, the PLL lock-in amplifier 28 outputs a signal in which the phase difference and amplitude difference between the signal from the optical sensor 18 and the reference signal are converted into voltages.

[0043] Specifically, the PLL lock-in amplifier 28 has a multiplier that multiplies two input signals, and a low-pass filter for extracting only low-frequency components from the signal generated by the multiplier. Therefore, in the PLL lock-in amplifier 28, a high frequency having a frequency equivalent to the sum of the frequencies of the two input signals and a low frequency having a frequency equivalent to the difference are output from the multiplier, but only the low frequency is extracted by the low-pass filter.

[0044] The signal output from the PLL lock-in amplifier 28, in which the phase difference between the signal from the optical sensor 18 and a reference signal is converted into a voltage, is input to a voltage controlled oscillator 32 via a PID controller 30. The voltage controlled oscillator 32 outputs a signal having a constant frequency based on the signal input from the PID controller 30.

[0045] The voltage controlled oscillator 32 may be, for example, a voltage controlled crystal oscillator (VCXO) including a crystal resonator as a resonator. In this embodiment, the voltage controlled oscillator 32 generates a frequency f 1 In other words, the resonator of the voltage controlled oscillator 32 generates a signal having a frequency f 1 Therefore, the first phase-locked loop circuit 20 oscillates at a frequency f 1 The second AC signal also functions as an oscillator with a frequency multiplication factor of 1 that generates an AC signal of

[0046] The PID controller 30 determines the phase of the first AC signal output by the voltage controlled oscillator 32 and the frequency f 1 The phase of the component is fed back to the voltage controlled oscillator 32 so that it is shifted by π / 2 from that of the component of the

[0047] For this reason, among the signals output from PLL lock-in amplifier 28, a signal in which the phase difference between the signal from optical sensor 18 and the first AC signal is replaced with a voltage has a frequency equivalent to the difference in frequency between the signal from optical sensor 18 and the first AC signal. Also, among the signals output from PLL lock-in amplifier 28, a signal in which the amplitude difference between the signal from optical sensor 18 and the first AC signal is replaced with a voltage has an amplitude equivalent to the difference in amplitude between the signal from optical sensor 18 and the first AC signal.

[0048] Of the signals output from the PLL lock-in amplifier 28, a signal in which the amplitude difference between the signal from the optical sensor 18 and the first AC signal is replaced with a voltage is input to a multiplier 36 via a PID controller 34 of the automatic gain control circuit 24. In addition, the first AC signal output from the voltage controlled oscillator 32 is input to the multiplier 36, and is multiplied by the signal from the PID controller 34.

[0049] As a result, the PID controller 34 performs feedback of the gain of the first AC signal output from the voltage controlled oscillator 32 based on the signal from the PLL lock-in amplifier 28. Therefore, the amplitude of the first AC signal output from the automatic gain control circuit 24 is kept approximately constant.

[0050] 1, the first AC signal output from the automatic gain control circuit 24 is applied to the probe control unit 10. Since the amplitude of the first AC signal is fed back by the automatic gain control circuit 24, a first AC signal of a substantially constant amplitude is input to the probe control unit 10. Therefore, the first phase-locked loop circuit 20 and the automatic gain control circuit 24 function as a first AC signal generator that generates the first AC signal.

[0051] Therefore, the first phase-locked loop circuit 20 detects the frequency of the vibration of the cantilever probe 4 and generates a first AC signal based on the frequency. Therefore, there is no need to prepare a separate device for generating the first AC signal, and once the cantilever probe 4 is oscillated, the first phase-locked loop circuit 20 can continue to generate the first AC signal.

[0052] <Second phase-locked loop circuit> 4 is a block diagram showing the configuration and operation of the second phase-locked loop circuit 22. Like the first phase-locked loop circuit 20, the second phase-locked loop circuit 22 includes a PLL lock-in amplifier 28, a PID controller 30, and a voltage-controlled oscillator 32.

[0053] The signal input from the optical sensor 18 to the second phase-locked loop circuit 22 is input to the PLL lock-in amplifier 28, which outputs a signal in which the phase difference and amplitude difference between the signal from the optical sensor 18 and a reference signal are converted into voltages.

[0054] The PID controller 30 included in the second phase-locked loop circuit 22 has the same function as the PID controller 30 included in the first phase-locked loop circuit 20. In other words, the PID controller 30 outputs a signal having a frequency corresponding to the difference between the frequency of the signal from the optical sensor 18 and the frequency of the reference signal, from the signal input from the PLL lock-in amplifier 28.

[0055] Here, the voltage controlled oscillator 32 included in the second phase locked loop circuit 22 is set to a frequency multiplication factor of 2 compared to the voltage controlled oscillator 32 included in the first phase locked loop circuit 20. Therefore, the voltage controlled oscillator 32 included in the second phase locked loop circuit 22 is set to a frequency of 2f based on the signal input from the PID controller 30. 1 In other words, the resonator of the voltage controlled oscillator 32 generates a signal having a frequency 2f 1 Therefore, the second phase-locked loop circuit 22 oscillates at a frequency of 2f 1The second AC signal also functions as an oscillator with a frequency multiplication factor of 2, generating an AC signal having a frequency twice that of the first AC signal.

[0056] <Signal output from phase-locked loop circuit> As shown in FIG. 2, the signal output from the optical sensor 18 has a frequency f 1 and frequency f 1 +f m Therefore, the PLL lock-in amplifier 28 of the first phase-locked loop circuit 20 receives a signal of frequency f 1 and frequency f 1 +f m A signal having the following components is input.

[0057] Therefore, the signal input to the PLL lock-in amplifier 28 has a frequency f 1 The PID controller 30 of the first phase-locked loop circuit 20 outputs a first AC signal having a frequency f m Therefore, the first phase-locked loop circuit 20 outputs a signal having a fluctuation component of the vibration of the cantilever probe 4 and a frequency component of m A measurement signal is output, which includes the components:

[0058] As described above, the vibration component measuring device 2 includes a light source 16, an optical sensor 18, and a first phase-locked loop circuit 20 as a measurement signal generator that generates a measurement signal.

[0059] The signal output from the optical sensor 18 has a frequency of 2f 1 +f m Components and frequency 3f 1 +f m However, in this embodiment, the PLL lock-in amplifier 28 uses a low-pass filter to not output a signal having frequency components other than those near the DC component, as described above. In addition, the PLL lock-in amplifier 28 according to this embodiment uses a low-pass filter to filter out the frequency f mIt is configured not to output a signal having a frequency component higher than that of the neighboring signals.

[0060] <Feedback to the stage> Of the measurement signals output from the first phase-locked loop circuit 20, a signal having a DC component is input to the stage control unit 26. The stage control unit 26 controls the position of the stage 12 based on the measurement signal. This allows the stage control unit 26 to control the position of the probe unit 8 on the sample X and the distance between the sample X and the probe unit 8.

[0061] For example, in this embodiment, the stage control unit 26 controls the distance between the sample X and the probe unit 8. This allows the stage control unit 26 to apply feedback so that the value of the frequency shift Δf, which corresponds to the vibration frequency shift of the cantilever probe 4, among the frequencies of the measurement signal, is kept constant.

[0062] When the distance between the sample X and the probe portion 8 when the cantilever probe 4 is not vibrating is constant, the value of the frequency shift Δf is constant. Therefore, while keeping the value of the frequency shift Δf constant, the probe portion 8 scans the sample X and sequentially records the position of the stage 12, whereby the vibration component measuring device 2 can measure the shape of the interface of the sample X.

[0063] The stage control unit 26 may include a filter for filtering the measurement signal output from the first phase-locked loop circuit 20. When the sample X has a plurality of interfaces, the stage control unit 26 may adjust the target of the interfaces to be measured by the vibration component measuring device 2 by controlling the distance between the cantilever probe 4 and the stage 12.

[0064] <Amplitude Modulator> In this embodiment, the vibration component measuring device 2 generates the above-mentioned second AC signal by using an amplitude modulator. As shown in Fig. 1, the vibration component measuring device 2 includes a first amplitude modulator 38. The first amplitude modulator 38 is, for example, an SSB modulator (single sideband modulator).

[0065] The first amplitude modulator 38 includes, for example, a multiplier, and generates a signal having a frequency obtained by adding together the frequencies of the two input signals, and a signal having a frequency obtained by subtracting the frequency of one of the two input signals from the frequency of the other. In this embodiment, the first amplitude modulator 38 extracts and outputs only the signal having a frequency obtained by adding together the frequencies of the two input signals, out of the two signals.

[0066] The first amplitude modulator 38 receives the first AC signal having a frequency f 1 In this embodiment, the double frequency signal is generated by the second phase-locked loop circuit 22 described above.

[0067] Furthermore, a reference AC signal output from an AC power source 40 included in the vibration component measuring device 2 is input to the first amplitude modulator 38. The AC power source 40 outputs a reference AC signal having a frequency f m In other words, the vibration component measuring device 2 includes the AC power supply 40 as a reference AC signal generator that generates the reference AC signal.

[0068] Therefore, the first amplitude modulator 38 outputs a frequency 2f 1 +f m This makes it possible to generate the second AC signal by the first amplitude modulator 38 from the double frequency signal generated by the second phase-locked loop circuit 22 and the reference AC signal from the AC power supply 40, and the second AC signal can be generated with a simple configuration. In other words, the vibration component measuring device 2 includes the second phase-locked loop circuit 22, the first amplitude modulator 38, and the AC power supply 40 as a second AC signal generator that generates the second AC signal.

[0069] The vibration component measuring device 2 may include a doubler that doubles the frequency of an input signal as a double frequency generator, instead of the second phase-locked loop circuit 22. In this case, the first AC signal output by the first phase-locked loop circuit 20 may be input to the doubler, and a double frequency signal may be generated from the doubler.

[0070] <Measurement of fluctuating components> The vibration component measuring device 2 according to this embodiment further includes at least one lock-in amplifier to which the measurement signal from the first phase-locked loop circuit 20 is input as a comparison signal. Specifically, the vibration component measuring device 2 according to this embodiment includes a unitary harmonic lock-in amplifier 42. The unitary harmonic lock-in amplifier 42 may have the same configuration as the PLL lock-in amplifier 28.

[0071] In this embodiment, a signal including a frequency shift Δf component output from the first phase-locked loop circuit 20 is input to the equal harmonic lock-in amplifier 42 as a comparison signal. m A reference AC signal having a frequency f is input as an equal-harmonic reference signal having the same frequency as the frequency of the reference AC signal. In this embodiment, the equal-harmonic lock-in amplifier 42 compares the comparison signal from the first phase-locked loop circuit 20 with the reference signal from the AC power supply 40. As a result, the equal-harmonic lock-in amplifier 42 extracts the frequency f m The modulation component Δf(f m ) as a fluctuation component of the vibration of the cantilever probe 4, which is the vibration part, and outputs a signal including the fluctuation component.

[0072] The vibration component measuring device 2 according to this embodiment further detects the modulation component Δf(f m The analyzer 44 receives a signal including a modulation component Δf(f m ) and the voltage V of the DC signal applied to the sample X using the method described below. dcThe modulation component Δf(f m ) to calculate the capacitance between the interface of sample X and cantilever tip 4.

[0073] For this reason, the equal harmonic lock-in amplifier 42 and the analysis unit 44 obtain the modulation component Δf(f m The equal harmonic lock-in amplifier 42 and the analyzer 44 function as a measurement unit that measures the modulation component Δf(f m Also included in the measurement section are a light source 16, a light sensor 18, and a first phase-locked loop circuit 20 for generating a comparison signal for measuring (.lambda.).

[0074] The vibration component measuring device 2 according to this embodiment further includes a DC power supply 46 and an adder 48. The DC power supply 46 outputs a voltage V dc In other words, the DC power supply 46 functions as a DC signal generator that generates a DC signal.

[0075] The adder 48 superimposes the input signals and applies the superimposed signal to the stage electrode 14. In a first operation of the vibration component measuring device 2, the second AC signal output from the first amplitude modulator 38 is input to the adder 48 through the first switch S1. A DC signal from the DC power supply 46 is also input to the adder 48. Therefore, in the first operation of the vibration component measuring device 2, the adder 48 applies a signal in which the second AC signal and the DC signal are superimposed to the sample X via the stage electrode 14. Therefore, the stage electrode 14 and the adder 48 function as a signal application unit that applies a signal between the cantilever probe 4 and the sample X.

[0076] The adder 48 is connected to the AC power supply 40 via the second switch S2. However, as shown in Fig. 1, when the second switch S2 is open, the reference AC signal from the AC power supply 40 is not applied to the adder 48. Therefore, in the first operation of the vibration component measuring device 2, the reference AC signal is not superimposed on the signal applied to the stage electrode 14.

[0077] The vibration component measuring device 2 is, for example, a voltage V dc While changing the value of f, the modulation component Δf(f m ) is measured. At least, the vibration component measuring device 2 measures whether the DC signal applied to the sample X is a voltage V dc The modulation components Δf(f m ) is measured.

[0078] <Other operations of the vibration component measuring device> Next, an operation of the vibration component measuring device 2 in a state where the first switch S1 is open and the second switch S2 is closed will be described as a second operation with reference to Fig. 7. Fig. 7 is a block diagram for explaining the second operation of the vibration component measuring device 2 according to this embodiment.

[0079] In the second operation of the vibration component measuring device 2, the first switch S1 is open, and therefore the signal output by the first amplitude modulator 38 is not applied to the adder 48. On the other hand, in the second operation of the vibration component measuring device 2, the second switch S2 is closed, and therefore the reference AC signal from the AC power supply 40 is applied to the adder 48 via the second switch S2. Therefore, the adder 48 applies the reference AC signal and the voltage V dc A signal in which a DC signal is superimposed on the DC signal is applied.

[0080] An example of a signal output by the optical sensor 18 in the second operation of the vibration component measuring device 2 is shown in the graph of Fig. 8. In Fig. 8, similarly to Fig. 2, the horizontal axis indicates the frequency of the signal output by the optical sensor 18, and the vertical axis indicates the intensity of the signal output by the optical sensor 18.

[0081] In the second operation of the vibration component measuring device 2, a vibration having a frequency f m Therefore, the vibration of the cantilever probe 4 has a frequency f m Therefore, the signal output by the optical sensor 18 has a frequency fm It has components in.

[0082] Also, the cantilever tip 4 vibrates at a frequency f 1 Since the cantilever 4 is vibrating at a frequency of f 1 +f m and frequency f 1 -f m Therefore, the signal output by the optical sensor 18 has a frequency f 1 +f m and frequency f 1 -f m Also has components in

[0083] As shown in FIG. 8, even in the second operation of the vibration component measuring device 2, the signal output from the optical sensor 18 contains a frequency f 1 and frequency f 1 +f m Therefore, the first phase-locked loop circuit 20 outputs a frequency f 1 and a measurement signal including a component of the frequency shift Δf are output. In the second operation of the vibration component measuring device 2, the signal from the first amplitude modulator 38 does not contribute to the application of a signal to the sample X. For this reason, the signal from the optical sensor 18 does not need to be input to the second phase-locked loop circuit 22.

[0084] Therefore, in the second operation of the vibration component measuring device 2, the same harmonic wave lock-in amplifier 42 receives a signal including a frequency shift Δf component as a comparison signal and a reference AC signal as a reference signal. m The modulation component Δf(f m ) is output. Furthermore, the analysis unit 44 outputs a signal including the voltage V dc The modulation component Δf(f m ) to calculate the capacitance between the interface of sample X and cantilever tip 4.

[0085] In particular, in the second operation of the vibration component measuring device 2, the frequency of the signal applied to the sample X is equal to or greater than the frequency 2f 1 +f m A frequency lower than f m The vibration component measuring device 2 measures the modulation component Δf(f m ) is measured. This enables the vibration component measuring device 2 to measure the difference in electric capacitance between the cantilever probe 4 and the sample X when the signal applied to the sample X is a low frequency signal and when the signal applied to the sample X is a high frequency signal.

[0086] <Band bending> Before describing a method for calculating the interface state density at the interface of the sample X using the vibration component measuring device 2, the curvature of the valence band and the conduction band near the interface of the sample X due to the interface charge of the sample X will be described. In the following description, an MIS structure is considered as a model in which the gap between the cantilever tip 4 and the sample X is regarded as a vacuum gap. Also, it is assumed that there is no thin film such as an oxide film on the semiconductor surface.

[0087] 9 shows band diagrams for explaining how the valence band and conduction band near the surface of sample X are curved due to the surface charge of sample X. Each band diagram shown in FIG. 9 shows the state in bulk 50 of n-type semiconductor sample X and the state at surface 52 of bulk 50. Band diagrams B1 and B2 show examples of the behavior of each state when an electronic defect occurs at surface 52 of sample X. Band diagrams B3 and B4 show examples of the behavior of each state when a local charge occurs at surface 52 of sample X.

[0088] When an electronic defect occurs on the surface 52 of the sample X, as shown in the band diagram B1, the Fermi level E FB The Fermi level E of the surface 52 is lower than FS In this state, the Fermi level E FBand the Fermi level E of surface 52 FS Electrons move from the bulk 50 to the electronic defects at the surface 52 so as to align the Fermi level E FB and the Fermi level E of surface 52 FS The difference between these two becomes smaller, so that the bulk 50 near the electronic defect becomes locally positively charged, and the surface 52 near the electronic defect becomes locally negatively charged.

[0089] For this reason, an electric field is generated between the bulk 50 near the electronic defect and the surface 52 due to the local charge. Here, since the bulk 50 is positively charged and the surface 52 is negatively charged, as shown in the band diagram B2, in the bulk 50 near the surface 52, the valence band level E V and the conduction band level E C Both of these curve upward in the band diagram.

[0090] On the other hand, when local electrons exist on the surface 52 of the sample X, the Fermi level E FS is the Fermi level E of the bulk 50 FB In this state, the Fermi level E FB and the Fermi level E of surface 52 FS As a result, as shown in the band diagram B4, a part of the local electrons at the surface 52 moves to the bulk 50 so as to align with the Fermi level E FB and the Fermi level E of surface 52 FS The difference between these becomes smaller, and in the vicinity of the location where the electron transfer occurs, the bulk 50 becomes locally negatively charged and the surface 52 becomes locally positively charged.

[0091] Therefore, in the vicinity of the above position, an electric field is generated between the bulk 50 and the surface 52 due to the local charge. Here, since the bulk 50 is negatively charged and the surface 52 is positively charged, as shown in the band diagram B4, in the bulk 50 near the surface 52, the valence band level E V and the conduction band level E C Both of these curve downward in the band diagram.

[0092] <Band bending behavior under external electric field> Next, the behavior of the valence band and conduction band near the surface of sample X when an external electric field is applied near the surface in a state where the valence band and conduction band near the surface of sample X are curved will be described. Each band diagram shown in Fig. 10 shows the state in the bulk 50 of the n-type semiconductor sample X, the state on the surface 52 of the bulk 50, and further the state of an external electrode 54 placed close to the surface 52. Note that each band diagram shown in Fig. 10 shows an equilibrium state in which sufficient electron transfer has occurred between the bulk 50 and the electronic defects in the surface 52.

[0093] When the potential of the external electrode 54 is negative, the Fermi level E EF 10, the band diagram shifts upward compared to when the potential of the external electrode 54 is 0. As a result, an external electric field is generated between the external electrode 54 and the surface 52 of the sample X, and the Fermi level E FS is further shifted downward in the band diagram. In this case, the transfer of electrons from the bulk 50 to the electronic defects in the surface 52 progresses further, so that the valence band level E V and the conduction band level E C and further curves upward in the band diagram.

[0094] On the other hand, when the potential of the external electrode 54 is positive, the Fermi level E EF 10, the potential of the external electrode 54 is shifted downward in the band diagram compared to when the potential of the external electrode 54 is 0. As a result, an external electric field is generated between the external electrode 54 and the surface 52 of the sample X, and the Fermi level E FS shifts further upward in the band diagram. In this case, the transfer of electrons from the bulk 50 to the electronic defects at the surface 52 is reduced, and the valence band level E V and the conduction band level E C The curvature becomes smaller.

[0095] Furthermore, by increasing the potential of the external electrode 54, the Fermi level E FS is the Fermi level E of bulk 50 F , and electrons may move from the electronic defects at the surface 52 to the bulk 50, as shown in the band diagram B6. In this case, the valence band level E V and the conduction band level E C means that the band is curved downward in the band diagram.

[0096] In this way, when band curvature occurs in the bulk 50 of sample X, the magnitude or direction of the band curvature of the bulk 50 changes by varying the external electric field generated in the vicinity of the surface 52.

[0097] Here, when the external electrode 54 is replaced with the cantilever probe 4 according to this embodiment, applying a potential to the external electrode 54 corresponds to applying a potential to the stage electrode 14 according to this embodiment. When a band is curved near the surface 52 of the bulk 50, a fluctuation occurs in the vibration component of the cantilever probe 4.

[0098] <Charge transfer reaction rate> Next, we consider the reaction rate of charge transfer between the bulk 50 and the surface 52. The reaction rate of electron capture from the bulk 50 at the surface state of the surface 52 is expressed by the following formula (1), and the reaction rate of electron release to the bulk 50 at the surface state of the surface 52 is expressed by the following formula (2).

[0099]

number

[0100]

number

[0101] In the above formula (1) and formula (2), n sindicates the electron occupancy rate of the surface state. In formula (1), C n is the electron capture coefficient, and in equation (2), e n is the electron emission coefficient. When attention is paid to the emission of electrons from the surface 52 to the bulk 50, a time constant τ corresponding to the time it takes for an electron to move from the surface 52 to the bulk 50 is defined by the following equation (3).

[0102]

number

[0103] In equation (3), τ 0 is the steady-state lifetime, and k B is the Boltzmann constant, and T is the temperature of the sample X. η in equation (3) is a correction term, which usually takes a value between 1 and 2. ΔE in equation (3) is the Fermi level E of the surface 52 before electron emission from the surface 52 to the bulk 50 occurs. FS and the Fermi level E of bulk 50 F Using the above formula (3), the above formula (2) can be transformed into the following formula (4).

[0104]

number

[0105] From equation (4), the time required for electron emission from the surface 52 to the bulk 50 is proportional to the time constant τ, and as the time constant τ increases, the time required for electron emission from the surface 52 to the bulk 50 becomes longer. In other words, the larger the time constant τ, the longer the time required for band bending of the bulk 50 to occur due to electron emission from the surface 52 to the bulk 50. Therefore, the external electric field generated in the vicinity of the surface 52 fluctuates, and the Fermi level E FS When the variation occurs faster than a certain rate, the bending of the band in the bulk 50 causes the Fermi level E FS may not be able to keep up with fluctuations in

[0106] <Cutoff frequency> Here, for example, suppose that an AC signal is applied to the external electrode 54, and the external electric field generated between the external electrode 54 and the surface 52 is periodically changed. In this case, while the frequency of the AC signal is low, the band curvature of the bulk 50 causes the Fermi level E FS However, when the frequency of the AC signal becomes higher than a certain value, the bending of the band in the bulk 50 causes the Fermi level E FS The bending of the band in the bulk 50 causes the Fermi level E FS The frequency at which the change in the frequency of the c Then, the cutoff frequency f c is expressed by the following equation (5).

[0107]

number

[0108] According to equations (3) and (5), the Fermi level E FS and the Fermi level E of bulk 50 F The larger the difference ΔE between c The higher the temperature of the sample X, the lower the cutoff frequency f c will be lower.

[0109] Cutoff frequency f c The relationship between the cutoff frequency f and ΔE will be described in more detail with reference to the graph in FIG. c The axis of the graph is [Hz] and the axis of the graph is ΔE [eV]. In the graph shown in Figure 11, the case where the temperature of sample X is 300K is shown by a solid line, and the case where the temperature is 80K is shown by a dotted line.

[0110] For example, if the temperature of sample X is 80K and ΔE is 0.1 eV, the cutoff frequency f c Therefore, in the above case, when a signal having a frequency of 166 kHz or more is applied to the external electrode 54 and the external electric field is varied, the curvature of the band generated in the bulk 50 of the sample X does not follow the variation of the external electric field and does not vary significantly.

[0111] <Calculation method of interface state density: Consideration of electrostatic force> Next, a method for calculating the interface state density at the interface of the sample X from the electric capacitance between the cantilever tip 4 and the sample X will be described. In the following description, a MIS structure in which the contact potential difference between the cantilever tip 4 and the sample X is set to 0 will be considered as a model.

[0112] First, for simplicity, it is assumed that the cantilever probe 4 and the sample X form a parallel plate capacitor. The cantilever probe 4 is excited by the probe control unit 10 and has a capacitance of Acos2πf 1 Assume that the cantilever probe 4 is vibrating at a frequency of f 1 It vibrates at .

[0113] When a bias voltage is applied between the cantilever tip 4 and the sample X, the electrostatic force F acting on the cantilever tip 4 is ele is expressed by the following formula.

[0114]

number

[0115] where Q is the charge density induced on the surface of the sample X, and ε 0 is the dielectric constant of a vacuum.

[0116] A voltage V is applied between the cantilever tip 4 and the sample X. dc The DC signal has a modulation frequency f and a vibration amplitude V ac AC voltage V ac Voltage V superimposed with cos2πft = V dc +V ac In this case, the modulation frequency f component of the electrostatic force acting between the cantilever probe 4 and the sample X is expressed by the following equation using Taylor series expansion:

[0117]

number

[0118] Here, V s is the surface potential of sample X.

[0119] <Calculation method of interface state density: Consideration of charge density> Next, let us consider the charge density Q induced on the surface of the sample X. When a bias voltage is applied between the cantilever tip 4 and the sample X, a surface potential is generated on the surface of the sample X. This causes charge accumulation, the formation of a depletion layer, the formation of an inversion layer, etc. on the surface of the sample X. For this reason, the charge density on the surface of the sample X must take the surface potential of the sample X into consideration.

[0120] On the other hand, as described above, there is a surface potential on the surface of the sample X. Also, as described above, when an AC signal is applied to the sample X, the capture or release of charges between the bulk 50 and the surface 52 due to the change in the surface potential contributes to the interaction between the cantilever tip 4 and the sample X. For this reason, the charge density on the surface of the sample X must also take into account the surface state of the sample X.

[0121] Therefore, the total charge density Q on the surface of sample X is the charge density Q due to the surface potential of sample X. s and the charge density due to the surface states Q ss In other words, Q = Q s +Q ss holds true.

[0122] <Calculation method of interface state density: Consideration of charge density when bias voltage is low frequency> The bias voltage applied to the sample X is the cutoff frequency f c A frequency f that is lower than m With AC bias voltage V ac cos2πfm Consider the charge density Q when t. When the bias voltage applied to the sample X is low frequency, charge transfer occurs between the bulk 50 and the surface 52, and it is necessary to consider that the surface state contributes to the charge density Q. Therefore, the following equation holds:

[0123]

number

[0124]

number

[0125]

number

[0126]

number

[0127] Here, C g is the capacitance due to the gap between the cantilever tip 4 and the sample X. C D is the capacitance due to the depletion layer of the semiconductor. C it is the capacitance due to the interface charge. Therefore, the modulation frequency component of the electrostatic force F ele (f m ) is expressed by the following formula:

[0128]

number

[0129] Here, C LF is the capacitance between the cantilever probe 4 and the sample X when a low-frequency AC bias is applied to the sample X, and is expressed by the following formula:

[0130]

number

[0131] Capacity C LF is expressed by the equivalent circuit shown in Fig. 12. This is equivalent to the equivalent circuit of the Shockley-Read model, which is an impedance model of the MIS structure, ignoring the resistance component. This suggests that the technique for evaluating the surface or interface of sample X is a technique similar to conventional impedance measurement or electrostatic force measurement.

[0132] The electrostatic force acting between the cantilever tip 4 and the sample X is finally generated by mixing the electrostatic force due to the AC bias voltage and the vibration of the cantilever, and has a frequency f 1 ±f m Electrostatic force F has components ele,L (f 1 ±f m ) where z is the average distance between the tip and the sample. t0 If the vibration amplitude of the cantilever is A, the distance z between the tip and the sample is z=z t0 +Acos2πf 1 Here, we note that the following equation holds:

[0133]

number

[0134] Therefore, the frequency f 1 ±f m Electrostatic force F has components ele,L (f 1 ±f m ) is expressed by the following formula:

[0135]

number

[0136] When the electrostatic force is demodulated from the signal obtained by the optical sensor 18 by the frequency modulation method as in the vibration component measuring device 2 according to the present embodiment, the electrostatic force Fele,L (f 1 ±f m ) modulates the frequency shift signal of the cantilever. As a result, the frequency shift modulation component Δf L (f m ) is expressed by the following formula:

[0137]

number

[0138] In the above formula, z t0 is sufficiently smaller than the depth of the depletion region of sample X. In other words, z t0 <<ε 0 / (C D +C it ) is satisfied. In this case, the modulation component Δf L (f m ) is the capacitance C of the sample X at the low frequency AC bias. D +C it It can be said to be proportional to

[0139] <Calculation method of interface state density: Consideration of charge density when bias voltage is high frequency> Next, the bias voltage applied to the sample X is set to the cutoff frequency f c Frequency 2f, which is higher than 1 +f m With AC bias voltage V ac cos2π(2f 1 +f m )t. When the bias voltage applied to the sample X is high frequency, charge transfer between the bulk 50 and the surface 52 does not occur, so the charge density Q due to the surface states ss to the charge density Q can be neglected. Therefore, the following equation holds:

[0140]

number

[0141]

number

[0142]

number

[0143]

number

[0144] Therefore, the modulation frequency component of the electrostatic force F ele (2f 1 +f m ) is expressed by the following formula:

[0145]

number

[0146] Here, C HF is the capacitance between the cantilever probe 4 and the sample X when a high-frequency AC bias is applied to the sample X, and is expressed by the following formula:

[0147]

number

[0148] Capacity C HF is expressed by the equivalent circuit shown in FIG. 13. This is the equivalent circuit shown in FIG. 12 with the additional capacitance C it is equivalent to ignoring the

[0149] The electrostatic force acting between the cantilever tip 4 and the sample X is finally generated by mixing the electrostatic force due to the AC bias voltage and the vibration of the cantilever, and has a frequency f 1 +f m Electrostatic force F has components ele,H (f 1 +f m) Here, we note that the following formula holds:

[0150]

number

[0151] Therefore, the frequency f 1 +f m Electrostatic force F has components ele,H (f 1 +f m ) is expressed by the following formula:

[0152]

number

[0153] When the electrostatic force is demodulated from the signal obtained by the optical sensor 18 by the frequency modulation method as in the vibration component measuring device 2 according to the present embodiment, the electrostatic force F ele,H (f 1 +f m ) modulates the cantilever frequency shift signal. As a result, the modulation component of the frequency shift Δf H (f m ) is expressed by the following formula:

[0154]

number

[0155] In the above equation, z t0 is sufficiently smaller than the depth of the depletion region of sample X. In other words, z t0 <<ε 0 / C D In this case, the modulation component Δf H (f m The slope of the DC bias voltage dependence of D It can be said that the modulation component Δf H (f m) the modulation components of both sidebands are demodulated, whereas the modulation component Δf L (f m In the derivation of , the modulation component of one sideband is demodulated. Therefore, the modulation component Δf H (f m ) is the coefficient of the modulation component Δf L (f m ) is half of

[0156] <Calculation method of interface state density: Consideration of interface charge> Next, from the relational equation of the modulation components when the bias voltage applied to the sample X is low frequency and high frequency, the charge density Q at the interface is calculated. ss When a measurement is performed using the vibration component measuring device 2 with a low-frequency AC bias voltage, the modulation component Δf L (f m ) is set to 0 at DC bias voltage V DC(LF) is expressed by the following formula:

[0157]

number

[0158] From the above formula, when a measurement is performed using a low-frequency AC bias voltage, the contact potential difference between the cantilever probe 4 and the sample X can be obtained to obtain information on the surface potential, which is the sum of the surface potential due to the surface state and the surface potential due to the bulk state of the sample X. On the other hand, when a measurement is performed using the vibration component measuring device 2 with a high-frequency AC bias voltage, the modulation component Δf of the frequency shift H (f m ) is set to 0 at DC bias voltage V DC(HF) is expressed by the following formula:

[0159]

number

[0160] From the above formula, when a measurement is performed using a high-frequency AC bias voltage, it is possible to obtain only information about the surface potential due to the bulk state of the sample X by obtaining the contact potential difference between the cantilever probe 4 and the sample X. Therefore, by using the vibration component measuring device 2 according to this embodiment and obtaining the difference in the contact potential difference using low-frequency and high-frequency AC bias voltages, it is possible to obtain information about the surface potential due to the surface state.

[0161] <Calculation method of interface state density: Derivation of interface state density from modulation component> Next, from the relational equation of the modulation components when the bias voltage applied to the sample X is low frequency and high frequency, the interface state density D it When the AC bias voltage applied to the sample X is low frequency, the modulation component Δf L (f m ) with respect to the DC bias voltage is the internal capacitance C of sample X. D +C it On the other hand, when the AC bias voltage applied to the sample X is high frequency, the modulation component Δf L (f m ) with respect to the DC bias voltage is the internal capacitance C of sample X. D is proportional to.

[0162] From these equations, the interface state density D on the surface of sample X when each bias voltage is applied to the sample is it is the modulation component Δf when the bias voltage is low frequency and high frequency. L (f m ) for the DC bias voltage. Therefore, when the elementary charge e is used, the interface state density D it is expressed by the following formula:

[0163]

number

[0164] The vibration component measuring device 2 according to this embodiment performs the above-mentioned analysis in the analysis unit 44, and while switching the frequency applied to the sample X between a high frequency and a low frequency, calculates the modulation component Δf(f m ) DC signal voltage V dc Thus, the vibration component measuring device 2 according to the present embodiment can measure the interface state density of the sample X by calculating the difference in the slope when the frequency applied to the sample X is a high frequency and when the frequency applied to the sample X is a low frequency in the analysis unit 44.

[0165] More specifically, the vibration component measuring device 2 converts the DC signal into at least a first DC signal and a second DC signal having a voltage different from that of the first DC signal, and calculates a modulation component Δf(f m ) is measured. As a result, the vibration component measuring device 2 measures the modulation component Δf(f m From the slope of the cantilever tip 4 and the sample X, the capacitance between the cantilever tip 4 and the sample X can be measured.

[0166] Furthermore, the vibration component measuring device 2 switches the AC signal included in the voltage applied to the sample X between the second AC signal and the reference AC signal, and adjusts the modulation component Δf(f m ) is measured. As a result, the vibration component measuring device 2 measures the modulation component Δf(f m From the difference in the slope of the line, the difference in capacitance between the cantilever tip 4 and the sample X when the signal applied to the sample X is a high frequency signal and a low frequency signal can be measured.

[0167] In particular, in the first operation of the vibration component measuring device 2 according to this embodiment, the frequency of the signal applied to the sample X is equal to or exceeds the cutoff frequency f c and the frequency of the signal applied to the sample X in the second operation is higher than the cutoff frequency f c In this case, the vibration component measuring device 2 can measure the interface state density of the sample X from the difference in capacitance between the cantilever probe 4 and the sample X measured in each of the first and second operations.

[0168] <Consideration of sample surface condition by measuring modulation components> Next, the modulation component Δf(f m ) to consider the surface condition of the sample X. FIG. 14 shows the relationship between the voltage V of the DC signal and the first and second operations of the vibration component measuring device 2. dc While changing the modulation component Δf(f m 14 is a graph showing the results of measurements of the DC signal voltage V dc , the vertical axis is the modulation component Δf(f m )

[0169] As shown in FIG. 14, in the first and second operations of the vibration component measuring device 2, each voltage V dc Modulation component Δf(f m ) and voltage V dc This indicates that the capacitance between the cantilever tip 4 and the sample X changes depending on whether the AC signal included in the signal applied to the sample X is high frequency or low frequency.

[0170] As can be seen clearly in the graph of the first operation in FIG. 14, the modulation component Δf(f m ) voltage V dc The slope with respect to the voltage V dc Here, the voltage V dc The modulation component Δf(f m ) voltage V dc The change in slope for represents the change in the state of the charge induced on the surface of sample X.

[0171] As shown in FIG. 14, in the first operation, the modulation component Δf(f m ) voltage V dc The slope of the voltage V changes significantly dc The value of V p and low voltage V n And V p >V n Here, referring to Figs. 15 to 17, Vdc >V p , V p ≧V dc ≧V n , and V n >V dc Let us consider the state of charge induced on the surface of sample X at each of the points.

[0172] 15 to 17 are V dc >V p , V p ≧V dc ≧V n , and V n >V dc 15 to 17 show a state in which an external electrode 54 is placed close to the surface 52 of sample X, and the sample X is a p-type semiconductor.

[0173] V dc >V p In this case, as shown in the band diagram B7 of Fig. 15, each band of the bulk 50 near the surface 52 of the sample X is curved upward. As a result, holes 56 are induced in the valence band near the surface 52 of the sample X. As a result, an accumulation layer 58 is formed by the induced holes 56 near the surface 52 of the sample X facing the external electrode 54, as shown in the band diagram B7 and the side cross-sectional view R7 of Fig. 15.

[0174] V p ≧V dc ≧V n In this case, as shown in the band diagram B8 of Fig. 16, each band of the bulk 50 near the surface 52 of the sample X is curved slightly downward. This induces negative acceptor ions 60 near the surface 52 of the sample X. As a result, a depletion layer 62 is formed by combination of holes 56 in the bulk 50 and the acceptor ions 60 near the surface 52 of the sample X facing the external electrode 54, as shown in the band diagram B8 and the side cross-sectional view R8 of Fig. 16.

[0175] V n >V dcIn this case, as shown in the band diagram B9 of Fig. 17, each band of the bulk 50 in the vicinity of the surface 52 of the sample X is bent further downward. As a result, more conduction electrons 64 are induced in the conduction band in the vicinity of the surface 52 of the sample X. As a result, an inversion layer 66 is formed by the conduction electrons 64 in the depletion layer 62 in the vicinity of the surface 52 of the sample X facing the external electrode 54, as shown in the band diagram B9 and the side cross-sectional view R9 of Fig. 17.

[0176] As described above, the voltage V of the DC signal applied to the sample X dc Therefore, the surface condition of the sample X changes. m ) for voltage V dc By measuring while changing the temperature, the surface condition of the sample X can be measured.

[0177] <Summary of the First Embodiment> The vibration component measuring device 2 according to this embodiment applies a signal between the cantilever probe 4 and the sample X, while measuring the above-mentioned modulation component Δf (f m ) is measured. Here, the signal is a signal in which a DC signal and at least one of a second AC signal and an AC signal are superimposed. Furthermore, the vibration component measuring device 2 applies at least two signals, a first DC signal and a second DC signal, having at least different voltages from each other, between the cantilever probe 4 and the sample X as DC signals.

[0178] As a result, the vibration component measuring device 2 can measure the modulation component Δf(f m ) for both the low and high frequencies of the AC component of the signal applied to the sample X. As a result, the vibration component measuring device 2 can measure the change in the measured modulation component Δf(f m ) can be used to measure the difference in the fluctuation component when the signal applied to the sample X is a low frequency signal and when it is a high frequency signal.m ) the interface state density at an interface such as the surface of sample X can be measured.

[0179] The vibration component measuring device 2 according to this embodiment measures the modulation component Δf(f m ) can be obtained by modulating a measurement signal including a signal from the optical sensor 18. Therefore, the vibration component measuring device 2 can perform measurement more efficiently or with higher precision than the above-mentioned measurement of the interface state density in a macro area obtained by averaging the area of ​​the metal electrode.

[0180] The vibration component measuring device 2 can more easily interpret the obtained fluctuation component and can more efficiently measure the interface state density of the sample X compared to a case where the electrostatic force between the cantilever probe 4 and the sample X is directly measured. Furthermore, the vibration component measuring device 2 can more easily measure the fluctuation component because it is not necessary to consider the stray capacitance between the probe 4 and the sample X compared to a case where the capacitance between the cantilever probe 4 and the sample X is directly measured. Furthermore, the vibration component measuring device 2 can measure the fluctuation component by the optical sensor 18, which is relatively inexpensive and has a simple structure compared to a capacitance sensor for measuring the capacitance between the probe 4 and the sample X. Furthermore, the vibration component measuring device 2 can be operated under various environments regardless of the temperature, magnetic field, type of atmosphere, etc., around the sample X.

[0181] As described above, the vibration component measuring device 2 according to this embodiment can more efficiently measure the change in the fluctuation component of the vibrating part, and can therefore more efficiently calculate the interface state density of the sample X. The vibration component measuring device 2 according to this embodiment employs the cantilever probe 4 as the vibrating part, and measures the light emitted from the light source 16 and reflected by the cantilever probe 4 by the optical sensor 18, thereby measuring the fluctuation component of the vibration of the cantilever probe 4. Therefore, the vibration component measuring device 2 functions as a Kelvin probe force spectrometer that can measure the interface state density of the sample X.

[0182] [Embodiment 2] <Device for measuring the first derivative of the fluctuation component: 1st operation> Other embodiments of the present disclosure will be described below. For convenience of explanation, the same reference numerals will be given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0183] FIG. 18 is a block diagram for explaining the configuration of a vibration component measuring device 68 according to this embodiment and the operation of the vibration component measuring device 68. As shown in FIG.

[0184] Compared with the vibration component measuring device 2, the vibration component measuring device 68 according to this embodiment further includes a second amplitude modulator 70, an adder 72, a double frequency lock-in amplifier 74, an AC power supply 76, and an adder 78. Except for the above, unless otherwise specified, the vibration component measuring device 68 according to this embodiment has the same configuration as the vibration component measuring device 2.

[0185] Hereinafter, the operation of the vibration component measuring device 68 will be described with reference to Fig. 18. In the present embodiment as well, first, the operation of the vibration component measuring device 68 in a state in which the first switch S1 is closed and the second switch S2 is open will be described as an example of a first operation.

[0186] In a first operation of the vibration component measuring device 68 according to this embodiment, a signal in which a DC signal and a second AC signal are superimposed is applied to the sample X via the stage electrode 14. Here, in this embodiment, the second AC signal is a signal in which a first high-frequency signal and a second high-frequency signal are superimposed.

[0187] The first high frequency signal is a 2f signal output from the first amplitude modulator 38, as described below. 1 +f m The second high-frequency signal is an AC signal having a frequency of 2f 1 -f m Therefore, the difference in frequency between the first and second high frequency signals is 2f mIn other words, the second high frequency signal has a frequency obtained by subtracting the frequency of the reference AC signal from twice the frequency of the first AC signal. Furthermore, in this embodiment, the first high frequency signal and the second high frequency signal have opposite phases.

[0188] In this embodiment as well, the vibration component of the cantilever probe 4 is detected using the optical lever method with the light source 16 and the optical sensor 18. In this embodiment as well, the signal output by the optical sensor 18 is a signal in which the vibration intensity of the cantilever probe 4 for each vibration frequency of the cantilever probe 4 calculated by the optical sensor 18 is converted into a signal intensity for each frequency.

[0189] An example of the signal output by optical sensor 18 is shown in the graph of Fig. 19. As in Fig. 2, the horizontal axis in Fig. 19 indicates the frequency of the signal output by optical sensor 18, and the vertical axis indicates the intensity of the signal output by optical sensor 18. Here, in Fig. 19, the component of the signal intensity that is negative indicates the frequency f 1 This indicates that the component has an opposite phase to that of the component of

[0190] In this embodiment, a frequency of 2f 1 +f m The first high frequency signal and frequency 2f 1 -f m Therefore, the cantilever probe 4 vibrates at a frequency of 2f 1 +f m Components and frequency 2f 1 -f m and the components are:

[0191] Therefore, the signal output by the optical sensor 18 has a frequency of 2f 1 +f m and frequency 2f 1 -f m However, since the first and second high-frequency signals have opposite phases, as shown in FIG. 1 -fm The component of frequency 2f 1 +f m It has the opposite polarity to the component.

[0192] In this embodiment, the vibration of the cantilever probe 4 is modulated by each of the first and second high frequency signals. Therefore, the vibration of the cantilever probe 4 has a frequency f 1 +f m , frequency f 1 +2f m , frequency f 1 -f m and frequency f 1 -2f m Therefore, the signal output by the optical sensor 18 has a sideband of the modulation component at the frequency f 1 +f m , frequency f 1 +2f m , frequency f 1 -f m and frequency f 1 -2f m However, since the first and second high frequency signals have opposite phases, for example, at frequency f 1 -f m and frequency f 1 -2f m The component of frequency f 1 +f m , and frequency f 1 +2f m It has the opposite polarity to the component.

[0193] The signal output by the optical sensor 18 is input to the first phase-locked loop circuit 20, as in the previous embodiment. In this embodiment, the low-pass filter of the PLL lock-in amplifier 28 of the first phase-locked loop circuit 20 has a frequency of 2f m The passband is set so as to output a signal having a frequency up to the vicinity of 1000 Hz. As a result, the first phase-locked loop circuit 20 outputs a signal having a frequency f m , and frequency 2f mA measurement signal is output, which includes the components:

[0194] In this embodiment, the first phase-locked loop circuit 20 also outputs the frequency f 1 The signal output by the optical sensor 18 is input to the second phase-locked loop circuit 22, as in the previous embodiment, to generate a first AC signal that is input to the probe control unit 10. As a result, the second phase-locked loop circuit 22 outputs a signal with a frequency of 2f 1 A signal having a frequency double that of the input signal is output.

[0195] In this embodiment, the first phase-locked loop circuit 20, the second phase-locked loop circuit 22, and the automatic gain control circuit 24 each have a phase shifter, which allows the first phase-locked loop circuit 20, the second phase-locked loop circuit 22, and the automatic gain control circuit 24 to convert an input signal, for example, from a cosine wave to a sine wave or from a sine wave to a cosine wave, and output the converted signal.

[0196] In this embodiment, for example, when the signal output from the optical sensor 18 is a cosine wave, the first phase-locked loop circuit 20 inputs a frequency f 1 and the comparison signal input to each lock-in amplifier are set to sine waves. Moreover, the second phase-locked loop circuit 22 sets the double frequency signal it outputs to a sine wave. Moreover, the automatic gain control circuit 24 sets the signal it inputs to the probe control unit 10 to a sine wave. Note that the signal for exciting the cantilever probe, in other words, the signal input to the probe control unit 10, and the displacement signal of the cantilever probe, in other words, the signal output by the optical sensor 18, are out of phase with each other by π / 2. Therefore, as described above, when the signal input to the probe control unit 10 is a sine wave, the signal output by the optical sensor 18 is a cosine wave.

[0197] The double frequency signal from the second phase-locked loop circuit 22 is input to the first amplitude modulator 38 as well as the second amplitude modulator 70. Similarly, the reference AC signal from the AC power supply 40 is input to the first amplitude modulator 38 as well as the second amplitude modulator 70. In this embodiment, the reference AC signal from the AC power supply 40 is a sine wave.

[0198] The second amplitude modulator 70 outputs a signal having a frequency obtained by subtracting the frequency of one of the two input signals from the frequency of the other signal, in comparison with the first amplitude modulator 38. Furthermore, the second amplitude modulator 70 outputs a signal having an opposite phase to the signal output by the first amplitude modulator 38. Except for the above, the second amplitude modulator 70 may have the same configuration as the first amplitude modulator 38, or may be an SSB modulator.

[0199] In this embodiment, the first amplitude modulator 38 outputs a frequency 2f 1 +f m The first high frequency signal is output from the second amplitude modulator 70, and the second high frequency signal is output from the second amplitude modulator 70. 1 -f m The first high frequency signal from the first amplitude modulator 38 and the second high frequency signal from the second amplitude modulator 70 are input to the adder 72. As a result, a signal in which the first high frequency signal and the second high frequency signal are superimposed is output from the adder 72 as a second AC signal. In the present embodiment as well, the second AC signal is superimposed on a DC signal by the adder 48 and then applied to the sample X via the stage electrode 14.

[0200] Here, both of the double frequency signals input to the first amplitude modulator 38 and the second amplitude modulator 70 have sine waves. Therefore, the first high frequency signal output by the first amplitude modulator 38 and the second high frequency signal output by the second amplitude modulator 70 have sine waves. Meanwhile, the first high frequency signal and the second high frequency signal have opposite phases to each other. Note that one of the first amplitude modulator 38 and the second amplitude modulator 70 may have a phase shifter, and may convert the phase of at least one of the first high frequency signal and the second high frequency signal so that the first high frequency signal and the second high frequency signal have opposite phases to each other.

[0201] In this embodiment, the measurement signal from the first phase-locked loop circuit 20 is input to the first harmonic lock-in amplifier 42 as well as to the second harmonic lock-in amplifier 74. Furthermore, the reference AC signal from the AC power supply 40 is input to the first harmonic lock-in amplifier 42 as well as to the second harmonic lock-in amplifier 74.

[0202] The frequency double lock-in amplifier 74 has the same configuration as the equal-frequency lock-in amplifier 42, except that a signal obtained by doubling the frequency of the input reference AC signal is used as a reference signal and compared with a comparison signal. In other words, a frequency double reference signal having a frequency twice that of the reference AC signal is input to the frequency double lock-in amplifier 74. The frequency double lock-in amplifier 74 may have a phase-locked loop circuit for doubling the frequency of the input reference AC signal. For this reason, the frequency double lock-in amplifier 74 detects the frequency 2f out of the components of the frequency shift Δf. m The modulation component Δf(2f m ) is output.

[0203] Modulation component Δf(2f m ) is the modulation component Δf(f m ) DC signal voltage V dc In other words, the modulation component Δf(2f m ) is the modulation component Δf(f m ) the voltage V of the DC signal applied to the sample X dc The analysis unit 44 receives the modulation component Δf(f m ), the modulation component Δf(2f m ) is input.

[0204] For this reason, the analysis unit 44 calculates the voltage V dc The modulation component Δf(2f m ) to obtain the modulation component Δf(f mIn other words, the vibration component measuring device 68 according to this embodiment can measure the change in the modulation component Δf(f m In order to measure the change in the input signal, it is not necessary to apply two DC signals with different voltage values.

[0205] <Device for measuring the first derivative of the fluctuation component: 2nd operation> Next, an operation of the vibration component measuring device 68 in a state in which the first switch S1 is open and the second switch S2 is closed will be described as a second operation with reference to Fig. 21. Fig. 21 is a block diagram for explaining the second operation of the vibration component measuring device 68 according to this embodiment.

[0206] In the second operation of the vibration component measuring device 68, the first switch S1 is open, and therefore the signals output from the first amplitude modulator 38 and the second amplitude modulator 70 are not applied to the adder 48. Instead, in this embodiment, as described below, a reference AC signal from the AC power source 40 and a signal from the AC power source 76 are applied to the adder 48.

[0207] The AC power source 76 is a power source having a frequency f m The frequency 2f is twice the frequency of m The phase of the AC signal from the AC power source 76 may be the same as or opposite to the phase of the reference AC signal output by the AC power source 40. The vibration component measuring device 68 according to this embodiment may have a doubler that doubles the frequency of the reference AC signal from the AC power source 40, instead of the AC power source 76.

[0208] In this embodiment, the signals from the AC power source 40 and the AC power source 76 are both input to an adder 78. Therefore, the adder 78 outputs a signal having a frequency f m Reference AC signal and frequency 2f mIn the second operation of the vibration component measuring device 68, the second switch S2 is closed, so that the signal from the adder 78 is applied to the adder 48 via the second switch S2. Therefore, the adder 48 outputs a signal having a frequency f m Reference AC signal, frequency 2f m AC signal, and voltage V dc A signal having a DC signal superimposed thereon is applied.

[0209] Therefore, in the second operation of the vibration component measuring device 68, the vibration of the cantilever probe 4 has a frequency f m and frequency 2f m Therefore, the signal output by the optical sensor 18 has components at frequency f m and frequency 2f m It has components in and.

[0210] Also, the cantilever tip 4 vibrates at a frequency f 1 Since the cantilever 4 is vibrating at a frequency of f 1 +f m , frequency f 1 +2f m , frequency f 1 -f m , and frequency f 1 -2f m Therefore, by inputting the signal output by the optical sensor 18 to the first phase-locked loop circuit 20, the first phase-locked loop circuit 20 outputs the fluctuation component of the vibration of the cantilever probe 4, the frequency f m , and frequency 2f m A measurement signal is output, which includes the components:

[0211] Also in the second operation of the vibration component measuring device 68, the measurement signal from the first phase-locked loop circuit 20 is input as a comparison signal to the equal-harmonic lock-in amplifier 42 and the double-harmonic lock-in amplifier 74. Also in the second operation of the vibration component measuring device 68, the reference AC signal from the AC power supply 40 is input as a reference signal to the equal-harmonic lock-in amplifier 42 and the double-harmonic lock-in amplifier 74. Therefore, also in the second operation of the vibration component measuring device 68, the equal-harmonic lock-in amplifier 42 outputs a modulation component Δf(f m ), and the double frequency lock-in amplifier 74 outputs a signal containing a modulation component Δf(2f m ) is output.

[0212] In the second operation of the vibration component measuring device 68, the frequency of the signal applied to the sample X is lower than the frequency of the signal applied to the sample X in the first operation of the vibration component measuring device 68. Therefore, the vibration component measuring device 68 measures the modulation component Δf(f m ), and the modulation component Δf(2f m ) can be measured.

[0213] In this embodiment, the vibration component measuring device 68 also measures the modulation component Δf(f m ) can be measured for each of the cases where the frequency of the AC component of the signal applied to the sample X is low frequency and high frequency.

[0214] In particular, the vibration component measuring device 68 measures the modulation component Δf(f m ) is the first derivative of the modulation component Δf(2f m For this reason, the vibration component measuring device 68 measures the modulation component Δf(f m ) changes can be measured.

[0215] The vibration component measuring device 68 according to this embodiment measures the modulation component Δf(f m ) and the modulation component Δf(2f m However, the vibration component measuring device 68 according to this embodiment is not limited to this, and only includes a double frequency lock-in amplifier 74 among the lock-in amplifiers to which the comparison signal is input, and measures the modulation component Δf (2f m In other words, the vibration component measuring device 68 may measure only the modulation component Δf(f m ) may be provided.

[0216] In the first operation, the vibration component measuring device 68 according to this embodiment applies a first high-frequency signal and a second high-frequency signal that are in opposite phase to each other to the sample X. However, the vibration component measuring device 68 according to this embodiment is not limited to this, and may apply a first high-frequency signal and a second high-frequency signal that are in phase to each other to the sample X in the first operation.

[0217] For example, when the signal output by the optical sensor 18 is a cosine wave, the first phase-locked loop circuit 20 outputs a frequency f 1 The signal from the second phase-locked loop circuit 22 is made a sine wave, and the comparison signal input to each lock-in amplifier is left as a cosine wave. The second phase-locked loop circuit 22 makes the double frequency signal it outputs a cosine wave. The automatic gain control circuit 24 makes the signal input to the probe control unit 10 a sine wave.

[0218] In the above configuration, even if the first and second high-frequency signals are in phase with each other, the vibration of the cantilever probe 4 has a frequency f 1 +f m , frequency f 1 +2f m , frequency f 1 -f m , and frequency f 1 -2f mIn this way, even if the first and second high-frequency signals are in phase with each other, the vibration component measuring device 68 can measure the modulation component Δf(f m ) and the modulation component Δf(2f m ) can be measured.

[0219] In this embodiment, the first high frequency signal has a frequency of 2f 1 +f m and the second high frequency signal has a frequency 2f 1 -f m However, in this embodiment, the present invention is not limited to this, and the difference in frequency between the first high-frequency signal and the second high-frequency signal may be 2f m As long as the first and second high frequency signals are equal to or lower than the second AC signal, the first and second high frequency signals may be higher or lower in frequency. For example, the first and second high frequency signals may have a frequency in the gigahertz range. In this case, the vibration component measuring device 68 measures the modulation component Δf (f m ) and the modulation component Δf(2f m ) can be measured.

[0220] [Embodiment 3] <Accumulator> FIG. 22 is a block diagram for explaining the configuration of a vibration component measuring apparatus 80 according to this embodiment and the operation of the vibration component measuring apparatus 80. As shown in FIG.

[0221] Compared with the vibration component measuring device 68, the vibration component measuring device 80 according to this embodiment includes an integrator 82 instead of the first amplitude modulator 38, the second amplitude modulator 70, and the adder 72. Except for the above, unless otherwise specified, the vibration component measuring device 80 according to this embodiment has the same configuration as the vibration component measuring device 68. In Fig. 22, an operation of the vibration component measuring device 80 in a state in which the first switch S1 is closed and the second switch S2 is open will be described as a first operation.

[0222] In a first operation of the vibration component measuring device 80 according to this embodiment, the double frequency signal from the second phase-locked loop circuit 22 and the reference AC signal from the AC power supply 40 are input to an integrator 82. The integrator 82 outputs a signal obtained by integrating the multiple input signals. For this reason, the integrator 82 according to this embodiment integrates the frequency 2f of the double frequency signal. 1 and the frequency of the reference AC signal f m The signal obtained by adding and the frequency of the double frequency signal, 2f 1 from the frequency of the reference AC signal f m In other words, the signal in which the first high frequency signal and the second high frequency signal that are in phase with each other are superimposed, as described in the previous embodiment, is output as the second AC signal.

[0223] The second AC signal from the integrator 82 is input to the adder 48 via the first switch S1. Therefore, in the first operation of the vibration component measuring device 80 according to this embodiment, the second AC signal and the voltage V dc A signal having a DC signal superimposed thereon is applied.

[0224] In this embodiment, the frequency f output by the first phase-locked loop circuit 20 is 1 The signal of frequency 2f is a sine wave. 1 The frequency-multiplied signal of is a cosine wave. Therefore, as described in the previous embodiment, the vibration component measuring device 80 according to this embodiment can measure the modulation component Δf(f m ) and the modulation component Δf(2f m The second operation of the vibration component measuring apparatus 80 according to this embodiment is realized by the same method as the second operation of the vibration component measuring apparatus 68.

[0225] In this embodiment, the vibration component measuring device 80 also measures the modulation component Δf(f m ) and the modulation component Δf(2f m) can be measured for both cases where the frequency of the AC component of the signal applied to the sample X is low and high. Furthermore, unlike the vibration component measuring devices according to the above-mentioned embodiments, the vibration component measuring device 80 does not require an amplitude modulator. Therefore, the vibration component measuring device 80 can measure the modulation component Δf(f m ) and the modulation component Δf(2f m ) value can be measured.

[0226] [Embodiment 4] <Device for measuring second derivative of fluctuation component> FIG. 23 is a block diagram for explaining the configuration of a vibration component measuring device 84 according to this embodiment and the operation of the vibration component measuring device 84. As shown in FIG.

[0227] The vibration component measuring device 84 according to this embodiment further includes an AC power supply 85 and a third harmonic lock-in amplifier 86, as compared with the vibration component measuring device 68. Except for the above, unless otherwise specified, the vibration component measuring device 84 according to this embodiment has the same configuration as the vibration component measuring device 68. In Fig. 23, an operation of the vibration component measuring device 84 in a state in which the first switch S1 is closed and the second switch S2 is open will be described as a first operation.

[0228] AC power source 85 has a frequency of 3f m In addition, a signal from the AC power source 85 is always input to the adder 48. Therefore, in this embodiment, the adder 48 outputs an AC signal of frequency 3f in addition to the first high frequency signal, the second high frequency signal, and the DC signal. m The signal on which the AC signal is superimposed is input to the sample via the stage electrode 14. Therefore, the vibration of the cantilever probe 4 is performed at a frequency f 1 +3f m and frequency f 1 -3f m Therefore, the first phase-locked loop circuit 20 outputs the fluctuation component of the vibration of the cantilever probe 4, the frequency f m , frequency 2f m , and frequency 3f mA measurement signal is output, which includes the components:

[0229] In this embodiment, the measurement signal from the first phase-locked loop circuit 20 is input to the first harmonic lock-in amplifier 42, the second harmonic lock-in amplifier 74, and also to the third harmonic lock-in amplifier 86. Furthermore, the reference AC signal from the AC power supply 40 is input to the first harmonic lock-in amplifier 42, the second harmonic lock-in amplifier 74, and also to the third harmonic lock-in amplifier 86.

[0230] The third frequency lock-in amplifier 86 has the same configuration as the equal frequency lock-in amplifier 42, except that a signal having a frequency three times the frequency of the input reference AC signal is used as a reference signal and compared with a comparison signal. In other words, a third frequency reference signal having a frequency three times the frequency of the reference AC signal is input to the third frequency lock-in amplifier 86. The third frequency lock-in amplifier 86 may have a phase-locked loop circuit for doubling the frequency of the input reference AC signal by three. For this reason, the third frequency lock-in amplifier 86 detects the frequency 3f out of the components of the frequency shift Δf. m The modulation component Δf(3f m ) is output.

[0231] Except for the above, the first and second operations of the vibration component measuring device 84 according to this embodiment are realized by the same methods as the first and second operations of the vibration component measuring device 68, respectively.

[0232] In this embodiment, the vibration component measuring device 84 measures the modulation component Δf(f m ), modulation component Δf(2f m ), plus the modulation component Δf(3f m ) can be measured. m ) is the modulation component Δf(2f m ) DC signal voltage V dc In other words, the modulation component Δf(3f m ) is the modulation component Δf(f m) the voltage V of the DC signal applied to the sample X dc The analyzer 44 receives the modulation component Δf(f m ), and the modulation component Δf(2f m ), as well as the modulation component Δf(3f m ) is input.

[0233] As described above, the state on the surface of sample X is determined by the voltage V of the DC signal applied to sample X. dc When the state at the surface of the sample X changes, the modulation component Δf(f m In other words, if the conditions at the surface of the sample X change, the slope of the modulation component Δf(2f m ) value changes.

[0234] Here, for example, the voltage V of the DC signal applied to the sample X is dc While changing the modulation component Δf(3f m ) is measured. In this case, the voltage V at which the state of the surface of sample X changes is dc When the modulation component Δf(3f m ) changes. Therefore, the vibration component measuring device 84 according to this embodiment changes the value of the modulation component Δf(3f m ) can be used to measure changes in the state of the surface or interface of sample X.

[0235] Furthermore, when the measurement is performed by the vibration component measuring device 84 while changing the position of the surface of the sample X to be measured, the polarity of the charge at that position may change depending on the position on the surface of the sample X. m ) changes. Therefore, the vibration component measuring device 84 measures the modulation component Δf(3f m ) allows the polarity of the surface charge of the sample X at the measurement position to be measured.

[0236] [Embodiment 5] <Simultaneous application of low and high frequencies> FIG. 24 is a block diagram for explaining the configuration of a vibration component measuring device 88 according to this embodiment and the operation of the vibration component measuring device 88. As shown in FIG.

[0237] The vibration component measuring device 88 according to this embodiment includes an AC power supply 90 and an AC power supply 92 instead of the AC power supply 40, as compared with the vibration component measuring device 2. Moreover, the vibration component measuring device 88 according to this embodiment includes a first lock-in amplifier 94 and a second lock-in amplifier 96 instead of the equal harmonic lock-in amplifier 42, as compared with the vibration component measuring device 2. Moreover, the vibration component measuring device 88 according to this embodiment does not include the first switch S1 and the second switch S2, as compared with the vibration component measuring device 2. Except for the above, unless otherwise specified, the vibration component measuring device 88 according to this embodiment has the same configuration as the vibration component measuring device 2.

[0238] The AC power source 90 outputs a first reference AC signal having a frequency f m1 The AC power source 92 generates an AC signal having a frequency of f m2 where frequency f m1 and frequency f m2 are both at frequency f 1 Also, the frequency f of the second reference AC signal is m2 is the frequency f of the first reference AC signal m1 In the present embodiment, the AC power sources 90 and 92 are reference AC signal generators that generate the first reference AC signal and the second reference AC signal, respectively, as the reference AC signal.

[0239] The first lock-in amplifier 94 and the second lock-in amplifier 96 have the same configuration as the unitary harmonic lock-in amplifier 42, for example.

[0240] In the operation of the vibration component measuring device 88 according to this embodiment, the double frequency signal from the second phase-locked loop circuit 22 and the first reference AC signal from the AC power supply 90 are applied to the first amplitude modulator 38. Therefore, the first amplitude modulator 38 outputs a frequency 2f 1 +f m1 In the present embodiment, the second AC signal from the first amplitude modulator 38 is constantly applied to the adder 48 while the vibration component measuring device 88 is in operation.

[0241] In the operation of the vibration component measuring device 88 according to this embodiment, the second reference AC signal from the AC power source 92 is constantly applied to the adder 48. Therefore, in this embodiment, the adder 48 is always supplied with a frequency of 2f 1 +f m1 and a second AC signal of frequency f m2 The adder 48 further superimposes a DC signal from the DC power source 46. Therefore, the adder 48 outputs a signal obtained by superimposing the second AC signal, the second reference AC signal, and the voltage V dc The signal obtained by superimposing the DC signal on the DC signal is applied to the sample X via the stage electrode 14.

[0242] Therefore, in the operation of the vibration component measuring device 88, the vibration of the cantilever probe 4 always has a frequency f m1 and frequency f m2 Therefore, the signal output by the optical sensor 18 always has a frequency f m1 and frequency f m2 It has components in and.

[0243] Also, the cantilever tip 4 vibrates at a frequency f 1 Here, the vibration of the cantilever probe 4 is caused by the high-frequency second AC signal and has a frequency f 1 +f m , and frequency 3f 1 +f m1At the same time, the vibration of the cantilever tip 4 has a frequency f 1 +f m2 , and frequency f 1 -f m2 , has sidebands of the modulation components.

[0244] Therefore, the first phase-locked loop circuit 20, to which the signal from the optical sensor 18 is input, outputs a comparison signal that includes both the component of the frequency shift Δf caused by the second AC signal and the component of the frequency shift Δf caused by the second reference AC signal.

[0245] The first lock-in amplifier 94 receives a first reference signal having a frequency f m1 A first reference AC signal having a frequency f is applied to the second lock-in amplifier 96. m2 Therefore, the first lock-in amplifier 94 receives a second reference AC signal having a frequency of 2f 1 +f m1 The modulation component Δf(f m1 On the other hand, the second lock-in amplifier 96 outputs a signal having a frequency f m2 The modulation component Δf(f m2 The signals from the first lock-in amplifier 94 and the second lock-in amplifier 96 are both input to the analysis unit 44.

[0246] Therefore, the vibration component measuring device 88 measures the modulation component Δf(f m1 The vibration component measuring device 88 also measures the modulation component Δf(f m2 ). Furthermore, the vibration component measuring device 88 measures the modulation component Δf(f m1 ) and the modulation component Δf(f m2 ) can be measured simultaneously.

[0247] Therefore, the vibration component measuring device 88 according to this embodiment can simultaneously measure the change in the fluctuation component of the vibration of the cantilever probe 4 when the frequency of the AC component of the signal applied to the sample X is both low and high. Therefore, the vibration component measuring device 88 can more easily measure the change in the above-mentioned fluctuation component with respect to the change in the frequency of the AC component of the signal applied to the sample X.

[0248] In this embodiment, the first lock-in amplifier 94 and the second lock-in amplifier 96 each have the same configuration as the equal-harmonic lock-in amplifier 42. However, the present invention is not limited to this, and the vibration component measuring device 88 according to this embodiment may further include two lock-in amplifiers having the same configuration as the equal-harmonic lock-in amplifier 74, to which the first reference AC signal and the second reference AC signal are respectively applied as reference signals. As a result, the vibration component measuring device 88 can measure the modulation component Δf (2f m1 ) and the modulation component Δf(2f m2 ) may be measured simultaneously. In this way, the vibration component measuring device 88 can measure a plurality of voltages V dc The above-mentioned modulation component Δf(2f m1 ) and the modulation component Δf(2f m2 ) changes can be measured.

[0249] [Embodiment 6] <Amplitude shift measurement> FIG. 25 is a block diagram for explaining the configuration of a vibration component measuring device 98 according to this embodiment and the operation of the vibration component measuring device 98. As shown in FIG.

[0250] The vibration component measuring device 98 according to this embodiment does not include the first phase-locked loop circuit 20, the second phase-locked loop circuit 22, and the automatic gain control circuit 24, as compared with the vibration component measuring device 2. Instead, the vibration component measuring device 98 according to this embodiment further includes a first harmonic lock-in amplifier 42, and also includes an AC power source 100 and an AC power source 102.

[0251] Except for the above, unless otherwise specified, the vibration component measuring device 98 according to this embodiment has the same configuration as the vibration component measuring device 2. In Fig. 25, an operation of the vibration component measuring device 98 in a state in which the first switch S1 is closed and the second switch S2 is open will be described as a first operation.

[0252] The AC power source 100 has a frequency f 1 and inputs it to the probe control unit 10. For this reason, the AC power supply 100 is a first AC signal generator that generates a first AC signal for vibrating the cantilever probe 4. The AC power supply 102 generates a first AC signal having a frequency of 2f 1 and inputs it to the first amplitude modulator 38.

[0253] Since the first amplitude modulator 38 is also supplied with a reference AC signal from the AC power source 40, the first amplitude modulator 38 operates at a frequency of 2f 1 +f m Therefore, in the first operation of the vibration component measuring device 98 according to the present embodiment, the sample X also receives the second AC signal and the voltage V dc A signal having a DC signal superimposed thereon is applied.

[0254] As a result, the vibration of the cantilever tip 4 is 1 +f m and frequency 3f 1 +f m Therefore, the signal output by the optical sensor 18 has a sideband of the modulation component at a frequency f 1 +f m and frequency 3f 1 +f m Also has components in

[0255] Here, the AC power supply 102 is synchronized with the AC power supply 100 so that the phase of the double frequency signal it outputs is the same as the phase of the first AC signal output by the AC power supply 100. Therefore, the intensity of the sidebands of the measurement signal output by the optical sensor 18 correlates with the magnitude of the amplitude shift ΔA of the vibration of the cantilever probe 4 caused by the interaction between the cantilever probe 4 and the sample X.

[0256] The measurement signal output by the optical sensor 18 is input to one of the equal-harmonic lock-in amplifiers 42. The first AC signal from the AC power supply 100 is input to the equal-harmonic lock-in amplifier 42 as a reference signal. As a result, the equal-harmonic lock-in amplifier 42 compares the measurement signal from the optical sensor 18 with the first AC signal, and outputs a comparison signal including a component of the amplitude shift ΔA of the cantilever probe 4.

[0257] The comparison signal is input to the other equal harmonic lock-in amplifier 42. The equal harmonic lock-in amplifier 42 receives a reference AC signal from the AC power source 40 as a reference signal. As a result, the equal harmonic lock-in amplifier 42 detects the frequency f m The modulation component ΔA(f m ) as a fluctuation component of the vibration of the cantilever probe 4, which is the vibration part, and outputs a signal including the fluctuation component.

[0258] The modulation component ΔA(f m ) is input to the analyzer 44. The analyzer 44 calculates the modulation component ΔA(f m ) and measure the voltage V dc The modulation component ΔA(f m ) to calculate the capacitance between the interface of the sample X and the cantilever probe 4. The modulation component ΔA(f m ) is calculated from the modulation component Δf(f m ) can be performed in the same manner as the calculation of the capacitance between the interface of the sample X and the cantilever probe 4.

[0259] The vibration component measuring device 98 measures, for example, a voltage V dc While changing the value of m More specifically, the vibration component measuring device 98 measures the voltage V dc The modulation components ΔA(fm ) is measured.

[0260] In the second operation of the vibration component measuring device 98, the first switch S1 is closed and the second switch S2 is opened. Therefore, in the second operation of the vibration component measuring device 98, the adder 48 outputs the reference AC signal from the AC power source 40 and the voltage V dc A signal superimposed with a DC signal is applied to the sample X.

[0261] As a result, the vibration of the cantilever tip 4 is 1 +f m and frequency f 1 -f m Therefore, the signal output by the optical sensor 18 has a sideband of the modulation component at a frequency f 1 +f m and frequency f 1 -f m Also has components in

[0262] Here, the AC power supply 40 is synchronized with the AC power supply 100 so that the phase of the reference AC signal it outputs is the same as the phase of the first AC signal it outputs. Therefore, the intensity of the sidebands of the measurement signal output by the optical sensor 18 correlates with the magnitude of the amplitude shift ΔA of the cantilever probe 4 caused by the interaction between the cantilever probe 4 and the sample X. As a result, the equal-harmonic lock-in amplifier 42 to which the measurement signal from the optical sensor 18 is applied outputs a comparison signal including a component of the amplitude shift ΔA of the cantilever probe 4.

[0263] Therefore, even in the second operation of the vibration component measuring device 98, the same harmonic wave lock-in amplifier 42 to which the comparison signal is input detects the frequency f m The modulation component ΔA(f m ) is output. Furthermore, the analysis unit 44 outputs a signal including the voltage V dc The modulation component ΔA(f m), the capacitance between the interface of the sample X and the cantilever probe 4 is calculated. From the above, the vibration component measuring device 98 calculates the modulation component ΔA(f m ) can be measured.

[0264] The vibration component measuring device 98 according to this embodiment, compared to the vibration component measuring device 2, has a modulation component Δf(f m ) instead of the modulation component ΔA(f m In the present embodiment as well, the vibration component measuring device 98 can more efficiently measure the change in the fluctuation component of the vibrating part, and therefore can more efficiently calculate the interface state density of the sample X.

[0265] [Embodiment 7] <Phase shift measurement> FIG. 26 is a block diagram for explaining the configuration of a vibration component measuring apparatus 104 according to this embodiment and the operation of the vibration component measuring apparatus 104. As shown in FIG.

[0266] The vibration component measuring device 104 according to this embodiment has the same configuration as the vibration component measuring device 98. In Fig. 26, an operation of the vibration component measuring device 104 in a state in which the first switch S1 is closed and the second switch S2 is open will be described as a first operation.

[0267] In the first operation of the vibration component measuring device 104 according to this embodiment, the sample X is also supplied with the second AC signal and the voltage V dc This causes the cantilever probe 4 to vibrate at a frequency of f 1 +f m and frequency 3f 1 +f m Therefore, the signal output by the optical sensor 18 has a sideband of the modulation component at a frequency f 1 +f m and frequency 3f 1 +f m Also has components in

[0268] Here, the AC power supply 102 is synchronized with the AC power supply 100 so that the phase of the double frequency signal it outputs is identical to the phase of the first AC signal output by the AC power supply 100. Therefore, the intensity of the sidebands of the measurement signal output by the optical sensor 18 correlates with the magnitude of the phase shift Δφ of the oscillation of the cantilever probe 4 caused by the interaction between the cantilever probe 4 and the sample X.

[0269] The measurement signal output by the optical sensor 18 is input to one of the equal-harmonic lock-in amplifiers 42. As a result, the equal-harmonic lock-in amplifier 42 compares the phase of the measurement signal from the optical sensor 18 with that of the signal from the AC power supply 100, and outputs a comparison signal including a component of the amplitude shift Δφ of the cantilever probe 4.

[0270] The comparison signal is input to the other equal harmonic wave lock-in amplifier 42. The equal harmonic wave lock-in amplifier 42 receives a reference AC signal from the AC power source 40 as a reference signal. As a result, the equal harmonic wave lock-in amplifier 42 detects the frequency f m The modulation component Δφ(f m ) as a fluctuation component of the vibration of the cantilever probe 4, which is the vibration part, and outputs a signal including the fluctuation component.

[0271] The modulation component Δφ(f m ) is input to the analyzer 44. The analyzer 44 calculates the modulation component Δφ(f m ) and measure the voltage V dc The modulation component Δφ(f m ) to calculate the capacitance between the interface of the sample X and the cantilever tip 4. The modulation component Δφ(f m ) is calculated from the modulation component Δf(f m ) can be performed in the same manner as the calculation of the capacitance between the interface of the sample X and the cantilever probe 4.

[0272] The vibration component measuring device 104 is, for example, a voltage V dcWhile changing the value of m More specifically, the vibration component measuring device 104 measures the voltage V dc The modulation components Δφ(f m ) is measured.

[0273] In the second operation of the vibration component measuring device 104, the first switch S1 is closed and the second switch S2 is opened. Therefore, in the second operation of the vibration component measuring device 104, the adder 48 outputs the reference AC signal from the AC power source 40 and the voltage V dc A signal superimposed with a DC signal is applied to the sample X.

[0274] As a result, the vibration of the cantilever tip 4 is 1 +f m and frequency f 1 -f m Therefore, the signal output by the optical sensor 18 has a sideband of the modulation component at a frequency f 1 +f m and frequency f 1 -f m Also has components in

[0275] Here, the AC power supply 40 is synchronized with the AC power supply 100 so that the phase of the reference AC signal it outputs is the same as the phase of the first AC signal it outputs. Therefore, the intensity of the sidebands of the measurement signal output by the optical sensor 18 correlates with the magnitude of the phase shift Δφ of the cantilever probe 4 caused by the interaction between the cantilever probe 4 and the sample X. As a result, the first phase-locked loop circuit 20 outputs a comparison signal including a component of the phase shift Δφ of the cantilever probe 4.

[0276] Therefore, even in the second operation of the vibration component measuring device 104, the same harmonic wave lock-in amplifier 42 to which the comparison signal is input receives the frequency f m The modulation component Δφ(f m) is output. Furthermore, the analysis unit 44 outputs a signal including the voltage V dc The modulation component Δφ(f m ), the capacitance between the interface of the sample X and the cantilever probe 4 is calculated. From the above, the vibration component measuring device 104 calculates the modulation component Δφ(f m ) can be measured.

[0277] The vibration component measuring device 104 according to this embodiment, compared to the vibration component measuring device 2, has a modulation component Δf(f m ) instead of the modulation component Δφ(f m In the present embodiment as well, the vibration component measuring device 104 can more efficiently measure the change in the fluctuation component of the vibrating part, and therefore can more efficiently calculate the interface state density of the sample X.

[0278] [Embodiment 8] <Increasing measurement speed with lock-in amplifiers> FIG. 27 is a block diagram for explaining the configuration of a vibration component measuring apparatus 106 according to this embodiment and the operation of the vibration component measuring apparatus 106. As shown in FIG.

[0279] Compared with the vibration component measuring device 2, the vibration component measuring device 106 according to this embodiment further includes a third amplitude modulator 108. Except for the above, unless otherwise specified, the vibration component measuring device 106 according to this embodiment has the same configuration as the vibration component measuring device 2. In Fig. 27, an operation of the vibration component measuring device 106 in a state in which the first switch S1 is closed and the second switch S2 is open will be described as a first operation.

[0280] In this embodiment, the third amplitude modulator 108 may have the same configuration as the first amplitude modulator 38 or the second amplitude modulator 70 described above, or may be an SSB modulator. 1 and a signal of frequency f from AC power source 40 mIn this embodiment, the third amplitude modulator 108 outputs a signal having a frequency obtained by adding the frequencies of the input signals together, specifically, a frequency f 1 +f m The signal is output.

[0281] The signal output by the third amplitude modulator 108 is input to the equal harmonic lock-in amplifier 42 as a reference signal. Furthermore, in this embodiment, the signal from the optical sensor 18 is input to the equal harmonic lock-in amplifier 42 as a comparison signal. The signal input from the optical sensor 18 to the equal harmonic lock-in amplifier 42 has a frequency of, for example, f 1 +f m Alternatively, the signal may pass through a bandpass filter that transmits only frequency components in the vicinity of

[0282] In the first operation of the vibration component measuring device 106 according to this embodiment, the sample X also receives the frequency 2f 1 +f m a second AC signal having a voltage V dc Therefore, even in the first operation of the vibration component measuring device 106, the measurement signal output by the optical sensor 18 contains the component of the frequency shift Δf at the frequency f 1 +f m Included in the sidebands of.

[0283] Therefore, the same harmonic lock-in amplifier 42 converts the frequency shift Δf component into a frequency f 1 +f m A comparison signal containing frequency f 1 +f m As a result, the equal harmonic lock-in amplifier 42 detects the frequency f 1 +f m The modulation component Δf(f 1 +f m ) as a fluctuation component of the vibration of the cantilever probe 4, which is the vibration part, is outputted and inputted to the analysis part 44.

[0284] The analyzer 44 calculates the modulation component Δf(f1 +f m ) and the voltage V of the DC signal applied to the sample X is measured using the method described above. dc The modulation component Δf(f 1 +f m ) to calculate the capacitance between the interface of the sample X and the cantilever probe 4. The modulation component Δf(f 1 +f m ) is calculated from the modulation component Δf(f m ) can be performed in the same manner as the calculation of the capacitance between the interface of the sample X and the cantilever probe 4.

[0285] The vibration component measuring device 106 is, for example, a voltage V dc While changing the value of f, the modulation component Δf(f 1 +f m More specifically, the vibration component measuring device 106 measures the voltage V dc The modulation components Δf(f 1 +f m ) is measured.

[0286] In the second operation of the vibration component measuring device 106 according to the present embodiment, the first switch S1 is opened and the second switch S2 is closed. Therefore, the sample X is supplied with the frequency f m a reference AC signal having a voltage V dc Therefore, even in the second operation of the vibration component measuring device 106, the measurement signal output by the optical sensor 18 contains the component of the frequency shift Δf at the frequency f 1 +f m Included in the sidebands of.

[0287] Therefore, in the second operation of the vibration component measuring device 106, the same harmonic wave lock-in amplifier 42 also detects the modulation component Δf(f 1 +f m) as a fluctuation component of the vibration of the cantilever probe 4, which is a vibration part, and inputs it to the analysis unit 44. For this reason, the vibration component measuring device 106 calculates the modulation component Δf(f 1 +f m ) can be measured.

[0288] The vibration component measuring device 106 according to this embodiment, compared to the vibration component measuring device 2, has a modulation component Δf(f m ) instead of the modulation component Δf(f 1 +f m In the present embodiment as well, the vibration component measuring device 106 can more efficiently measure the change in the fluctuation component of the vibrating part, and therefore can more efficiently calculate the interface state density of the sample X.

[0289] In addition, in each operation of the vibration component measuring device 106 according to this embodiment, the frequency of the reference signal input to the equal-harmonic lock-in amplifier 42 is higher than the frequency of the reference signal input to the equal-harmonic lock-in amplifier 42 in each of the above-mentioned embodiments. Therefore, the equal-harmonic lock-in amplifier 42 according to this embodiment can detect the modulation component Δf(f 1 +f m ), thus improving the measurement speed of the sample X.

[0290] [Embodiment 9] <Vibration component measuring device equipped with a micro vibration mechanism> FIG. 28 is a block diagram for explaining the configuration of a vibration component measuring apparatus 110 according to this embodiment and the operation of the vibration component measuring apparatus 110. As shown in FIG.

[0291] The vibration component measuring device 110 according to this embodiment is different in configuration from the vibration component measuring device 2 in that it includes a micro-vibration detection mechanism 112 instead of the cantilever probe 4, the probe control unit 10, the light source 16, and the optical sensor 18. The micro-vibration detection mechanism 112 includes a leaf spring 114, a leaf spring control unit 116, a leaf spring holding unit 118, a fixed electrode 120, and a capacitance sensor 122.

[0292] The micro vibration detection mechanism 112 includes a leaf spring 114 as a vibrating part. The leaf spring 114 is a thin plate-like member including, for example, silicon or a silicon oxide film. Since the leaf spring 114 is made of silicon or a silicon oxide film, micro-machining of the leaf spring 114 is facilitated during manufacturing of the leaf spring 114. The leaf spring 114 may have a metal coating.

[0293] The leaf spring 114 vibrates under the control of the leaf spring control unit 116, which functions as a vibration control unit. For example, the leaf spring control unit 116 vibrates the leaf spring 114 at a frequency corresponding to the frequency of the applied voltage. Specifically, the resonant frequency of the leaf spring 114 when there is no interaction between the leaf spring 114 and the sample X is a frequency f 1 In this case, the leaf spring control unit 116 is 1 A first AC signal having the following formula is input:

[0294] The leaf spring holding part 118 holds the leaf spring 114 together with the leaf spring control part 116, for example, at the end of the leaf spring 114. The fixed electrode 120 is disposed at a distance from the leaf spring 114 and forms a capacitance between the leaf spring 114 and the fixed electrode 120. The fixed electrode 120 is fixed in position and is not dependent on the vibration of the leaf spring 114. The capacitance sensor 122 measures the capacitance between the leaf spring 114 and the fixed electrode 120, for example, by measuring the amount of charge accumulated in the fixed electrode 120.

[0295] Here, the leaf spring 114 is vibrated by the leaf spring control unit 116 while its end is held by the leaf spring holding unit 118. Therefore, as the leaf spring 114 vibrates, the position of the leaf spring 114 near the center, which is not directly held by the leaf spring control unit 116 and the leaf spring holding unit 118, periodically changes. Therefore, as the leaf spring 114 vibrates, the distance between the leaf spring 114 and the fixed electrode 120 arranged at a distance from the leaf spring 114 and facing the leaf spring 114, periodically changes.

[0296] As described above, the magnitude of the capacitance formed between the leaf spring 114 and the fixed electrode 120 changes periodically as the leaf spring 114 vibrates. Therefore, by measuring the magnitude of the capacitance formed between the leaf spring 114 and the fixed electrode 120 with the capacitance sensor 122, the vibration component of the leaf spring 114 can be measured.

[0297] The capacitance sensor 122 calculates the vibration strength of the leaf spring 114 for each vibration frequency of the leaf spring 114 based on the variation in capacitance. The capacitance sensor 122 also outputs a signal in accordance with the detection result. In this embodiment, the signal output by the capacitance sensor 122 is a signal in which the vibration strength of the leaf spring 114 for each vibration frequency of the leaf spring 114 calculated by the capacitance sensor 122 is replaced with a signal strength for each frequency.

[0298] Except for the above, the vibration component measuring device 110 according to this embodiment has the same configuration and operates in the same manner as the vibration component measuring device 2. Therefore, in the first operation of the vibration component measuring device 110, the leaf spring 114 vibrates at a frequency f 1 The vibration occurs at a frequency of 2f 1 +f m Therefore, the signal output by the capacitive sensor 122 is the same as the signal shown in FIG. 1 , f 1 +f m , 2F 1 +f m , and 3f 1 +f m It has components in.

[0299] The measurement signal output by the capacitive sensor 122 is , No. The first phase-locked loop circuit 20 receives the signal. Capacitive Sensor 122 From the measurement signal from the sensor 114, a comparison signal including a component of the frequency shift Δf of the vibration of the leaf spring 114 is output.

[0300] The comparison signal is input to the equal harmonic wave lock-in amplifier 42. The equal harmonic wave lock-in amplifier 42 receives a reference AC signal from the AC power source 40 as a reference signal. As a result, the equal harmonic wave lock-in amplifier 42 detects the frequency f m The modulation component Δf(f m ) as a fluctuation component of the vibration of the leaf spring 114 which is a vibrating part.

[0301] The modulation component Δf(f m ) is input to the analyzer 44. The analyzer 44 calculates the modulation component Δf(f m ) and measure the voltage V dc The modulation component Δf(f m ) from the interface of sample X and Leaf spring 114 Calculate the capacitance between the modulation component Δf(f m ) is calculated from the modulation component Δf(f m ) can be performed in the same manner as the calculation of the capacitance between the interface of the sample X and the cantilever probe 4.

[0302] The vibration component measuring device 110 is, for example, a voltage V dc While changing the value of f, the modulation component Δf(f m More specifically, the vibration component measuring device 110 measures the voltage V dc The modulation components Δf(f m ) is measured.

[0303] In the second operation of the vibration component measuring device 110 according to the present embodiment, the first switch S1 is opened and the second switch S2 is closed. Therefore, the sample X is supplied with the frequency f m a reference AC signal having a voltage V dc Therefore, in the second operation of the vibration component measuring device 110, Capacitive Sensor 122The measurement signal output by the 1 +f m Included in the sidebands of.

[0304] Therefore, in the second operation of the vibration component measuring device 110, the same harmonic wave lock-in amplifier 42 also detects the modulation component Δf(f m ) as a fluctuation component of the vibration of the leaf spring 114, which is a vibrating part, and inputs it to the analysis unit 44. Therefore, the vibration component measuring device 110 calculates the modulation component Δf(f m ) can be measured.

[0305] The vibration component measuring device 110 according to this embodiment, compared to the vibration component measuring device 2, has a modulation component Δf(f m In the present embodiment as well, the vibration component measuring device 110 can more efficiently measure the change in the fluctuation component of the vibrating part, and therefore can more efficiently calculate the interface state density of the sample X.

[0306] In particular, the vibration component measuring device 110 according to this embodiment calculates the modulation component Δf(f m In other words, the vibration component measuring device 110 can measure the modulation component Δf(f m ), there is no need for a capacitive sensor having an expensive or complicated configuration for directly measuring the capacitance between the sample X and the leaf spring 114. Therefore, the vibration component measuring device 110 can measure the change in the fluctuation component of the vibrating part more efficiently than an apparatus equipped with a capacitive sensor for directly measuring the capacitance between the sample X and the leaf spring 114.

[0307] The vibration component measuring device 110 according to this embodiment can be used as a MEMS sensor equipped with the micro vibration detection mechanism 112 as a micro sensor. In this embodiment, the vibration component of the leaf spring 114 is measured by measuring the electrostatic capacitance between the leaf spring 114 and the fixed electrode 120 using the fixed electrode 120 and the capacitance sensor 122. However, the measurement of the vibration component of the leaf spring 114 is not limited to this, and may be performed using an optical fiber sensor.

[0308] Furthermore, the leaf spring 114 may include silicon having a piezo-resistance effect, or crystal having a piezoelectric effect including quartz, etc. In this case, the vibration component of the leaf spring 114 may be measured by measuring the resistance value of the silicon having a piezo-resistance effect, or the electromotive force generated in the crystal having a piezoelectric effect.

[0309] The above-mentioned method for measuring the vibration component of the leaf spring 114 is different from the optical lever method using the light source 16 and the optical sensor 18. Therefore, since it is not necessary to secure an optical path from the light source 16 to the optical sensor 18, the above-mentioned method for measuring the vibration component of the leaf spring 114 makes it possible to further miniaturize the vibration component measuring device 110.

[0310] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0311] 2. Vibration component measuring device 4 Cantilever probe 10 Probe control section 20 First phase-locked loop circuit 22 Second phase-locked loop circuit 36 Multiplier 38 1st Amplitude Modulator 40 AC power supply 42 1st harmonic lock-in amplifier 44 Analysis Department 46 DC power supply 48 Adder 70 Second Amplitude Modulator 74th harmonic lock-in amplifier 86 Triple Frequency Lock-in Amplifier 94 First Lock-in Amplifier 96 Second Lock-in Amplifier S1 First switch S2 Second switch

Claims

1. A vibration part; a first AC signal generator that generates a first AC signal; a second AC signal generator that generates a second AC signal having a frequency higher than a frequency of the first AC signal and different from an integer multiple of the frequency of the first AC signal; a reference AC signal generator that generates a reference AC signal having a frequency lower than a frequency of the first AC signal; a DC signal generator that generates at least two DC signals, a first DC signal and a second DC signal having a voltage different from that of the first DC signal; a vibration control unit that vibrates the vibration unit based on the first AC signal; a signal application unit that applies the DC signal and at least one of the second AC signal and the reference AC signal between the vibration unit and a sample; a measurement unit that measures a fluctuation component of the vibration of the vibration unit that fluctuates due to an interaction between the vibration unit and the sample, The measurement unit is a vibration component measuring device that measures the change in the fluctuation component relative to the change in the voltage value of the DC signal from the fluctuation component when the DC signal is the first DC signal and the fluctuation component when the DC signal is the second DC signal.

2. A vibration part; a first AC signal generator that generates a first AC signal; a second AC signal generator that generates a second AC signal having a frequency higher than a frequency of the first AC signal and different from an integer multiple of the frequency of the first AC signal; a reference AC signal generator that generates a reference AC signal having a frequency lower than a frequency of the first AC signal; a DC signal generator for generating a DC signal; a vibration control unit that vibrates the vibration unit based on the first AC signal; a signal application unit that applies the DC signal and at least one of the second AC signal and the reference AC signal between the vibration unit and a sample; a measurement unit that measures a first-order differential value of a fluctuation component of the vibration of the vibration unit, which fluctuates due to an interaction between the vibration unit and the sample, with respect to the voltage of the DC signal.

3. A vibration part; a first AC signal generator that generates a first AC signal; a second AC signal generator that generates a second AC signal having a frequency higher than a frequency of the first AC signal and different from an integer multiple of the frequency of the first AC signal; a reference AC signal generator that generates a reference AC signal having a frequency lower than a frequency of the first AC signal; a DC signal generator for generating a DC signal; a vibration control unit that vibrates the vibration unit based on the first AC signal; a signal application unit that applies the DC signal and at least one of the second AC signal and the reference AC signal between the vibration unit and a sample; a measurement unit that measures a second-order differential value of the voltage of the DC signal of a fluctuation component of the vibration of the vibration unit, the fluctuation component fluctuating due to an interaction between the vibration unit and the sample.

4. 4. The vibration component measuring device according to claim 2, wherein the measuring section further measures a change in the fluctuation component with respect to a change in a voltage value of the DC signal.

5. The vibration component measuring device according to claim 1 , wherein the fluctuation component includes a frequency shift of the vibration section.

6. 4. The vibration component measuring device according to claim 1, wherein the fluctuation component includes an amplitude shift of the vibrating portion.

7. The vibration component measuring device according to claim 1 , wherein the fluctuation component includes a phase shift of the vibration section.

8. 4. The vibration component measuring device according to claim 1, wherein the second AC signal has a frequency obtained by adding the frequency of the reference AC signal to a frequency twice that of the first AC signal, or a frequency obtained by subtracting the frequency of the reference AC signal from a frequency twice that of the first AC signal.

9. the second AC signal includes a first high frequency signal and a second high frequency signal, 4. The vibration component measuring device according to claim 1, wherein a difference between a frequency of the first high frequency signal and a frequency of the second high frequency signal is twice as high as a frequency of the reference AC signal.

10. 10. The vibration component measuring device according to claim 9, wherein the first high frequency signal and the second high frequency signal are in opposite phase.

11. The measurement unit includes: a measurement signal generator that detects a vibration component of the vibration unit and generates a measurement signal based on the vibration component; 4. The vibration component measuring device according to claim 1, further comprising at least one lock-in amplifier that calculates the fluctuation component by comparing a comparison signal generated based on the measurement signal with a reference signal generated based on the reference AC signal.

12. The vibration component measuring device according to claim 11, wherein at least one of the lock-in amplifiers includes a first harmonic lock-in amplifier that compares the comparison signal with a first harmonic reference signal having the same frequency as the frequency of the reference AC signal to calculate the fluctuation component.

13. The vibration component measuring device according to claim 11, wherein at least one of the lock-in amplifiers includes a double frequency lock-in amplifier that compares the comparison signal with a double frequency reference signal having a frequency twice the frequency of the reference AC signal to calculate the fluctuation component.

14. The vibration component measuring device according to claim 11, wherein at least one of the lock-in amplifiers includes a triple frequency lock-in amplifier that compares the comparison signal with a triple frequency reference signal having a frequency three times that of the reference AC signal to calculate the fluctuation component.

15. the reference AC signal generator generates at least a first reference AC signal and a second reference AC signal having a frequency different from an integer multiple of the frequency of the first reference AC signal; The vibration component measuring device according to claim 11, wherein the at least two lock-in amplifiers include a first lock-in amplifier that compares the comparison signal with a first reference signal generated based on the first reference AC signal to calculate the fluctuation component, and a second lock-in amplifier that compares the comparison signal with a second reference signal generated based on the second reference AC signal to calculate the fluctuation component.

16. A Kelvin probe force spectrometer comprising the vibration component measuring device according to claim 1 , wherein the vibration portion includes a cantilever.

17. generating a first AC signal for vibrating the vibration portion; generating a second AC signal having a frequency higher than the frequency of the first AC signal and different from an integer multiple of the frequency of the first AC signal; generating a reference AC signal having a frequency lower than a frequency of the first AC signal; generating at least two DC signals, a first DC signal and a second DC signal having a voltage different from that of the first DC signal; and measuring a fluctuation component of the vibration of the vibration unit that fluctuates due to an interaction between the vibration unit and the sample by applying the DC signal and at least one of the second AC signal and the reference AC signal between the vibration unit and the sample and vibrating the vibration unit based on the first AC signal, A vibration component measurement method in which, in measuring the fluctuation component, a change in the fluctuation component relative to a change in the voltage value of the DC signal is measured from the fluctuation component when the DC signal is the first DC signal and the fluctuation component when the DC signal is the second DC signal.

18. generating a first AC signal for vibrating the vibration portion; generating a second AC signal having a frequency higher than the frequency of the first AC signal and different from an integer multiple of the frequency of the first AC signal; generating a reference AC signal having a frequency lower than a frequency of the first AC signal; Generating a DC signal; a first-order differential value of a voltage of the DC signal of a fluctuation component of the vibration of the vibration part that fluctuates due to an interaction between the vibration part and the sample, the first-order differential value being a voltage of the DC signal of a fluctuation component of the vibration of the vibration part that fluctuates due to an interaction between the vibration part and the sample, while applying the DC signal and at least one of the second AC signal and the reference AC signal between the vibration part and the sample, and vibrating the vibration part based on the first AC signal.

19. generating a first AC signal for vibrating the vibration portion; generating a second AC signal having a frequency higher than the frequency of the first AC signal and different from an integer multiple of the frequency of the first AC signal; generating a reference AC signal having a frequency lower than a frequency of the first AC signal; Generating a DC signal; a second-order differential value of the voltage of the DC signal of the fluctuation component of the vibration of the vibration part that fluctuates due to interaction between the vibration part and the sample, the second-order differential value being a voltage of the DC signal of the fluctuation component of the vibration of the vibration part that fluctuates due to interaction between the vibration part and the sample, while applying the DC signal and at least one of the second AC signal and the reference AC signal between the vibration part and the sample, and vibrating the vibration part based on the first AC signal.

20. 20. A method for measuring interface state density, comprising: measuring an interface state density at any interface of the sample from a value measured by the vibration component measuring method according to any one of claims 17 to 19.

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