JP4858987B2 - Scanning probe microscope - Google Patents

Description

  The present invention relates to a scanning probe microscope capable of measuring the spatial distribution of in-band levels present in a semiconductor.

  Crystal defects and process-induced defects existing under the surface of the semiconductor substrate form deep levels in the band and become carriers capture / emission sources, and thus have a very serious influence on device reliability. Conventionally, the levels existing in these bands have been evaluated by depositing a metal such as gold or aluminum to a diameter of about 100 μm on a semiconductor surface terminated with an oxide film to form a metal / oxide film / semiconductor (MOS) diode. In addition, a photocapacitance (PHCAP) method has been adopted in which the variation of the capacitance of the diode is measured by sweeping the wavelength (ie, photon energy) while irradiating monochromatic light (see, for example, Non-Patent Document 1). ). By this method, the energy level of the in-band level can be measured easily and accurately.

Y. Furukawa et.al. Jpn. J. Appl. Phys. 6 (1967) 67 (published by the Association for Physics Journals (IPAP)), H. Kukimoto et.al. Phys. Rev. B 7 (1973 ) 2486 (published by American Physical Society)

  The aforementioned optical capacity (PHCAP) method has the advantage that the energy level of crystal defects and process-induced defects can be determined with good sensitivity from the wavelength of the light to be irradiated, but on the other hand, knowledge about the spatial distribution of these defects Has the disadvantage of being scarce. The spatial distribution of these crystal defects and process-induced defects affects the yield of semiconductor devices. Further, if the energy levels of individual defects can be seen individually rather than a large number of defects, it is expected to lead to a significant improvement in the semiconductor device process.

  In view of the above problems, an object of the present invention is to provide a scanning probe microscope capable of individually viewing the energy levels of individual crystal defects and process-induced defects.

  In order to achieve the above object, the present invention basically irradiates excitation light onto the oxide film directly under and near the tip of the conductive probe and has an energy level corresponding to the wavelength of the excitation light. Analyzes the distribution of crystal defects and process-induced defects existing inside the semiconductor substrate by emitting carriers from crystal defects and process-induced defects inside the semiconductor substrate and detecting the deviation of the depletion layer spread due to the diffusion of majority carriers. Adopt a means to do.

Specifically, it is as follows.
(1) The scanning probe microscope includes a conductive probe, a means for controlling the position of the conductive probe so as to have a predetermined interval with respect to the sample to be measured, and a gap between the conductive probe and the sample to be measured. Means for applying a voltage; means for irradiating excitation light between the conductive probe and the sample to be measured; and photoexcitation capacitance detection for detecting capacitance information between the conductive probe and the sample to be measured. A scanning probe microscope having means comprising:
In a scanning probe microscope having photoexcitation capacitance difference detection means for acquiring a component depending on the intensity of the excitation light from capacitance information between the conductive probe and the sample to be measured detected by the photoexcitation capacitance detection means ,
The photoexcitation capacitance difference detection means extracts a ΔC / ΔZ signal, which is a difference signal, of the capacitance information between the conductive probe and the sample to be measured detected by the photoexcitation capacity detection means, and further detects the ΔC / A component depending on the intensity of the excitation light is extracted from the ΔZ signal .
( 2) In the scanning probe microscope described in the above (1 ), the photoexcitation capacitance difference detecting means is configured such that the conductive probe vibrates in a direction perpendicular to the surface of the sample to be measured, and the conductive probe is the sample to be measured. Detecting a component that changes at the vibration frequency of the conductive probe, among the capacitance between the conductive probe and the sample to be measured. Features.
( 3) In the scanning probe microscope according to the above (1 ), the photoexcitation capacitance difference detecting means periodically displaces the position of the sample to be measured with respect to the conductive probe, and the conductive probe Of the vertical position of the sample to be measured out of the capacitance between the conductive probe and the sample to be measured when the distance between the sample and the sample to be measured is periodically modulated It is characterized in that a component synchronized with the above is detected.
( 4) The scanning probe microscope according to any one of (1) to (3 ), wherein the photoexcitation capacitance difference detecting means irradiates between the conductive probe and the sample to be measured. When the light intensity is intermittently modulated, a component synchronized with the modulation frequency is detected.
( 5) The scanning probe microscope according to any one of (1) to (4 ), wherein the photoexcitation capacitance difference detecting means irradiates the excitation light between the conductive probe and the sample to be measured. The light intensity modulation frequency is set to be lower than the frequency of the distance modulation between the conductive probe and the sample.
( 6) In the scanning probe microscope according to any one of (1) to (5 ), the photoexcitation capacitance difference detection unit is configured to emit the excitation light irradiated between the conductive probe and the sample to be measured. It is characterized in that it is configured to measure while sweeping the wavelength.
( 7) In the scanning probe microscope according to any one of (1) to (6 ), the means for controlling a relative position between the conductive probe and the sample to be measured is the conductive probe microscope. It is characterized by detecting a change in resonance frequency, resonance amplitude, or resonance Q value of a mechanical resonator composed of a probe and a piezoelectric element.

In the present invention, since the measurement end of the conductive probe is sharpened, the area of the semiconductor substrate facing the sharpened measurement end can be made extremely small, so that the sample to be measured can be measured for every very small area. become.
Since the carriers emitted by crystal defects and process-induced defects having energy levels corresponding to the respective wavelengths are measured, accurate measurement corresponding to each defect can be performed.

The capacitance of the MOS capacitor changes at the timing shown in FIG. 3 (d) according to the change of the excitation light intensity. By detecting these changes, the distribution of crystal defects and process-induced defects existing in the semiconductor substrate can be accurately analyzed.
Further, when the wavelengths of the excitation light are swept, crystal defects and process-induced defects having energy levels corresponding to the respective wavelengths emit carriers. Therefore, by measuring while sweeping the wavelength of the excitation light, it is possible to obtain information on the distribution of crystal defects and process-induced defects having different energy levels.

  Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of an essential part of an embodiment for explaining a measurement principle using a conductive probe of the present invention.
FIG. 1 illustrates a MOS (Metal-Oxide-Semiconductor) capacitor formed between a conductive probe 3 and an oxide film 2 that is a dielectric thin film formed on a semiconductor substrate 1.
The conductive probe 3 is made of a metal material having a very small resistance value, preferably made of a metal material having elasticity, and has a pointed shape so that the measurement point can be easily specified.

Since the semiconductor substrate 1 has a depletion layer formed inside the semiconductor substrate 1, not only the capacitance derived from the oxide film 2 that is a dielectric thin film but also the capacitance derived from this depletion layer affects the measurement. In that case, the depletion layer capacitance can be canceled out by applying a DC voltage to the semiconductor substrate 1 to bring it into a charge storage state. Therefore, only the capacitance derived from the dielectric thin film 2 can be handled as in the case where the substrate 1 is a metal.
Any semiconductor substrate 1 can be used. For example, a semiconductor substrate 1 in which impurities are uniformly dispersed in an organic or inorganic material can be used.
The DC voltage source 6 is used to apply a bias voltage between the conductive probe 3 and the semiconductor substrate 1, and a depletion layer 4 due to diffusion of majority carriers in the semiconductor substrate 1 immediately below the tip of the conductive probe 3. Form.

  When the excitation light 7 is irradiated onto the oxide film 2 immediately below and near the tip of the conductive probe 3 in the state where the depletion layer 4 is formed by the diffusion of majority carriers in the semiconductor substrate 1 as described above, the excitation light 7 Since crystal defects or process-induced defects in the semiconductor substrate 1 having an energy level corresponding to the wavelength of light emit carriers, the spread of the depletion layer due to the diffusion of majority carriers described above is caused by the depletion layer 5 changed by photoexcitation. To change. That is, by detecting the difference in the spread of these depletion layers, the distribution of crystal defects and process-induced defects existing in the semiconductor substrate 1 can be found.

  Here, the range of irradiation with the excitation light 7 does not necessarily need to be exactly under the tip of the conductive probe, and is near the periphery of the region where the tip of the conductive probe 3 and the oxide film 2 are in contact, for example, the widest range. The depletion layer 5 is in a region in contact with the oxide film 2 and in a range outside the region in which the tip of the conductive probe 3 is in contact with the oxide film 2. If the difference in the spread of the depletion layer is detected by irradiating the excitation light 7 within this range, the distribution of crystal defects and process-induced defects in the semiconductor substrate 1 can be found.

FIG. 2 is a block diagram of the scanning probe microscope of the present invention.
The scanning probe microscope shown in FIG. 2 includes a semiconductor substrate 1 on which a dielectric measurement sample 2 is placed as a depletion layer forming means, and a conductive probe 3 facing the semiconductor substrate 1. , A light source 9, a condenser 11, and a condenser lens 12.
In FIG. 2, the conductive probe 3 is made of an L-shaped elastic metal material having a very small resistance value, and one end facing the sample is sharpened.

  The conductive probe 3 is formed by bending a metal wire such as W (tungsten), Pt (platinum) / Ir (iridium), or Ni (nickel) having a diameter of about 50 μm into an L shape, and one end of the conductive probe 3 has, for example, a cone shape. It is formed by sharpening as follows. This sharpening of the tip is achieved by subjecting the metal wire to an electrolytic polishing process by chemical etching or an electric discharge machining process. Furthermore, the tip radius of curvature of the processed tip can be controlled by the chemical concentration, applied voltage, etching time, discharge voltage, machining time, etc. Therefore, the radius of curvature of the tip can be realized with good reproducibility. . The conductive probe 3 is located on the surface of the semiconductor substrate 1 having the oxide film 2 that is a sample to be measured between the contact portion with the piezoelectric element 8 that is a tuning fork crystal resonator and the tip of the conductive probe 3. It has a bent portion that is perpendicular to it.

When detecting electrical information between the tip of the conductive probe 3 and the sample to be measured, the electrical information is taken in only when the tip of the conductive probe 3 is closest to the sample 2 to be measured.
When detecting electrical information between the tip of the conductive probe 3 and the sample to be measured, only when the piezoelectric element 8 that excites the conductive probe 3 maintains a certain range of phases in its vibration state. , To take in electrical information. That is, in the vibration state of the piezoelectric element 8 detected by the vibration detection device, the tip of the conductive probe 3 is closest to the sample 2 to be measured if the vibration phase is π / 2. Therefore, electrical information is taken in only during a period in which the vibration phase is around π / 2, for example, during a period in which π / 4 to 3π / 4 is maintained.

  As the piezoelectric element 8, a tuning fork type crystal resonator is used. This tuning fork type crystal resonator is made of a piezoelectric material, and has two plate-like spring portions (hereinafter referred to as “pronge”; long side portions) connected at right angles to both ends of the connecting portion (short side portion), It is U-shaped as a whole. The piezoelectric element 5, which is a tuning fork type crystal resonator, vibrates in a direction orthogonal to the long side portion of the conductive probe 3 (length direction of the sharpened portion). The conductive probe 3 is in light contact with the outer edge of the prongage so as to face the direction perpendicular to the direction of the longitudinal axis of the prongage. The piezoelectric element 8 is used for the purpose of exciting the conductive probe 3 and simultaneously detecting the vibration of the conductive probe 3.

  An AC voltage (angular frequency ω 1) is applied to the piezoelectric element 8 by an AC voltage source 10 to vibrate the piezoelectric element 8. As a result, the conductive probe 3 vibrates at an angular frequency ω 1 so that the sharpened tip approaches and separates from the surface of the sample to be measured formed on the semiconductor substrate 1 in the vertical direction.

  The other end of the conductive probe 3 (on the side opposite to the sharpened end) is electrically connected to the capacitance detector 17. Further, the conductive probe 3 falls to the ground potential through the capacitance detector 17. The capacitance detector 17 constitutes means for detecting capacitance information between the conductive probe 3 and the semiconductor substrate 1 having the oxide film 2 as a sample to be measured. It is used to measure the capacitance of the MOS capacitor formed between the oxide film 2 and the oxide film 2 formed in general, and an LCR meter, an LC resonance circuit, etc. can be generally used. The capacitance detector 17 is also a photoexcitation capacitance detection unit that acquires a component depending on the intensity of excitation light in the capacitance information between the conductive probe and the sample to be measured.

  The DC voltage source 6 is means for applying a voltage between the conductive probe 3 and the semiconductor substrate 1 and applies a DC voltage.

Of the output signal from the capacitance detector 17, the ω1 component, which is the vibration angular frequency of the conductive probe 3, is demodulated and detected by the lock-in amplifier LA1 (19).
The conductive probe 3 vibrates in the vertical direction (that is, the Z direction) in the figure at a frequency ω1. At this time, the distance Z between the conductive probe 3 and the semiconductor substrate 1 having the oxide film 2 as the sample to be measured is modulated at the frequency ω1. The capacitance C between the conductive probe 3 and the semiconductor substrate 1 having the oxide film 2 as the sample to be measured also changes at the frequency ω1. The lock-in amplifier LA1 detects the change in the frequency ω1 of the capacitance C. This detection signal corresponds to a variation of the capacitance C with respect to a change in the distance Z, that is, a ΔC / ΔZ signal. This detection signal corresponds to a ΔC / ΔZ signal which is a difference signal of the capacitance of the MOS capacitor formed between the conductive probe 3 and the oxide film 2 formed on the semiconductor substrate 1.
However, ΔC represents the change in capacitance, and ΔZ represents the distance between the conductive probe 3 and the semiconductor substrate 1 having the oxide film 2 as the sample to be measured. As described above, since the measurement is performed using frequency detection by a lock-in amplifier, it is not necessary to obtain the absolute value of Z.
The lock-in amplifier LA1 (19) extracts a ΔC / ΔZ signal that is a difference signal of capacitance information between the conductive probe and the sample to be measured . As shown in the block diagram, the component depending on the intensity of the excitation light is extracted by the lock-in amplifier LA2 (20).

  The pressure strain-voltage signal from the piezoelectric element 8 is input to the vibration detection device 14, such as a signal related to the vibration amplitude of the piezoelectric element 8, the resonance frequency of the piezoelectric element 5, or the Q value of the mechanical resonance of the piezoelectric element 8. Get the output signal.

Here, when the conductive probe 3 approaches the surface of the oxide film 2 formed on the semiconductor substrate 1 that is the sample to be measured, an interaction force (vibrates due to vibration) acting between the tip of the conductive probe 3 and the surface of the oxide film 2. When the tip of the conductive probe 3 is in contact with the surface of the oxide film 2, a repulsive force is received from the surface of the oxide film 2. This is an interaction force), and the vibration amplitude of the piezoelectric element 8 attached to the conductive probe 3; Alternatively, the signal related to the resonance frequency of the piezoelectric element 8 or the Q value of the mechanical resonance of the piezoelectric element 8 changes. A semiconductor substrate 1 as a sample to be measured and an oxide film 2 formed thereon are arranged on a scanning stage 16 for moving in the XYZ directions. The scanning control device 15 determines the position of the conductive probe 3 in the XY plane and receives the output signal of the vibration detection device 14 that detects the vibration frequency of the piezoelectric element 8, and changes in these signals are determined in advance. A scanning voltage is supplied to the scanning stage 16 so as to be a certain value, and the conductive probe 3 and the surface of the oxide film 2 are controlled so as to maintain a certain distance. Specifically, as described above, when the tip of the vibrating conductive probe 3 comes into contact with the surface of the oxide film 2, it receives a repulsive force from the surface of the oxide film 2. Then, the vibration amplitude of the conductive probe 3 is reduced by this repulsive force. Further, the vibration frequency of the conductive probe 3 is increased. Here, since the conductive probe 3 is fixed to the piezoelectric element 8, the vibration amplitude and vibration frequency of the conductive probe 3 coincide with the vibration amplitude and vibration frequency of the piezoelectric element 8. That is, if the scanning voltage is supplied to the scanning stage 16 so that the vibration amplitude of the piezoelectric element 8 detected by the vibration detection device 14 or the vibration frequency thereof is maintained at a certain value, the conductive probe 3 and the oxide film 2 are supplied. The distance between the surfaces remains constant.
The scanning stage 16 operates so as to periodically modulate the distance between the conductive probe and the sample by periodically displacing the position of the sample to be measured with respect to the conductive probe in the vertical direction. May be.

  This control is always executed while the conductive probe 3 is scanning the surface of the oxide film 2. The scanning control device 15 applies a voltage to drive the scanning stage 13 in the XY directions, and controls the conductive probe 3 to scan a predetermined region on the surface of the oxide film 2. With the above control, the conductive probe 3 causes the conductive probe 3 and the surface of the oxide film 2 to have a predetermined interval (as described above, the vibration amplitude of the piezoelectric element 8 detected by the vibration detection device 14). If the scanning voltage is supplied to the scanning stage 16 so that the vibration frequency is kept at a certain value, the distance between the conductive probe 3 and the surface of the oxide film 2 is kept constant. Then, the surface of the oxide film 2 is scanned.

The display device 1 (18) has a monitor and a computer function, and the output of the lock-in amplifier LA1 (19) is made to correspond to the position in the XY direction of the conductive probe 3 in the storage means built in the computer function. A certain ΔC / ΔZ signal is stored, and the stored data is subjected to image processing by a storage and arithmetic processing function, and ΔC / ΔZ () at each point on the surface of the oxide film 2 formed on the semiconductor substrate 1 as a sample to be measured. Z represents the distance between the conductive probe 3 and the semiconductor substrate 1 having the oxide film 2 as the sample to be measured.) A signal distribution image is created and displayed on the monitor.
Here, the process of deriving the ΔC / ΔZ signal will be described. As described above, when the conductive probe 3 vibrates in the longitudinal direction (that is, the Z direction) in the figure at the frequency ω1, the distance Z between the conductive probe 3 and the semiconductor substrate 1 having the oxide film 2 as the sample to be measured. Is modulated at the frequency ω1, and the capacitance C between the conductive probe 3 and the semiconductor substrate 1 having the oxide film 2 as the sample to be measured also changes at the frequency ω1. The lock-in amplifier LA1 detects the change in the frequency ω1 of the capacitance C. This detection signal corresponds to a variation of the capacitance C with respect to a change in the distance Z, that is, a ΔC / ΔZ signal.

  The monochromatic excitation light 10 emitted from the excitation light source 9 is divided into pulsed light having a frequency ω 2 by an optical chopper 11, and further condensed on the oxide film 2 immediately below the conductive probe 3 by a condenser lens 12. In addition, the position where the excitation light 10 is irradiated does not necessarily need to be exactly below the conductive probe 3, and may be irradiated near the region of the oxide film 2 that is in contact with the conductive probe 3. The optical system including the excitation light source 9, the light chopper 11, and the condenser lens 12 constitutes means for irradiating excitation light between the conductive probe and the sample to be measured. Positioning is performed so that the above capacity is detected. This positioning operation can be performed automatically or manually while monitoring the capacity output.

Of the ΔC / ΔZ signal that is the output signal from the lock-in amplifier LA1 (19), the ω2 component that is the frequency of the pulsed light is demodulated and detected by the lock-in amplifier LA2 (20).
Here, the process of deriving the ΔC / ΔZ signal will be described. As described above, the conductive probe 3 vibrates in the vertical direction (that is, the Z direction) in the figure at the frequency ω1. Therefore, since the distance Z between the conductive probe 3 and the semiconductor substrate 1 having the oxide film 2 as the sample to be measured is modulated at the frequency ω1, the semiconductor having the conductive probe 3 and the oxide film 2 as the sample to be measured. The capacitance C between the substrates 1 also changes at the frequency ω1. Further, as described in paragraph 0027, since the excitation light 10 is divided into pulsed light having the frequency ω2 by the optical chopper 11 and focused on the oxide film 2 immediately below the conductive probe 3, the conductive probe 3 And the capacitance C between the semiconductor substrate 1 having the oxide film 2 as the sample to be measured are doubly modulated not only by the frequency ω1 but also by the frequency ω2. As described above, the lock-in amplifier LA1 detects the change in the frequency ω1 of the capacitance C. This detection signal corresponds to a variation of the capacitance C with respect to a change in the distance Z, that is, a ΔC / ΔZ signal. Furthermore, the lock-in amplifier LA2 (20) demodulates and detects the component modulated by the frequency ω2 in the ΔC / ΔZ signal. This detection signal corresponds to the Δ ² C / ΔZΔI signal as described below.
This detection signal is a component modulated by light (basically, there is a component of the MOS capacitor capacitance formed between the conductive probe 3 and the oxide film 2 formed on the semiconductor substrate 1. Corresponds to Δ ² C / ΔZΔI (where I represents the light intensity from the monochromatic light emitted from the excitation light source 9; whether or not it changes, zero is not considered) .

This Δ ² C / ΔZΔI signal corresponds to a variation of the depletion layer due to optical excitation as shown in paragraph 0002 above (that is, the Δ ² C / ΔZΔI signal has a component modulated by the pulse frequency ω ² of the excitation light 10. As a result of demodulation detection, the physical meaning is a component modulated by light among the capacitance of the MOS capacitor formed between the conductive probe 3 and the oxide film 2 formed on the semiconductor substrate 1. It becomes.
The indicating device 2 (21) stores the Δ ² C / ΔZΔI signal, which is the output of the lock-in amplifier LA2 (20), in the built-in storage means in association with the position of the conductive probe 3 in the XY direction. Then, a distribution image of the Δ ² C / ΔZΔI signal at each point on the surface of the oxide film 2 formed on the semiconductor substrate 1 as the sample to be measured is created and displayed.
Next, FIG. 3 will be described.

  FIG. 3 is a timing chart of the capacitance measurement of the MOS capacitor formed between the conductive probe 3 and the oxide film 2 formed on the semiconductor substrate 1. 3A is a vibration waveform characteristic of the conductive probe, FIG. 3B is a DC voltage characteristic applied to the semiconductor substrate, FIG. 3C is an excitation light characteristic modulated by the optical chopper, and FIG. 3D. Is the capacitance characteristic of the MOS capacitor.

3, 31 is a vibration waveform characteristic of the conductive probe, 32 is a DC voltage V ₀ characteristic applied to the semiconductor substrate, 33 is an excitation light characteristic representing the excitation light intensity modulated to the ON or OFF level by the optical chopper, 34 Is a capacitance characteristic of the MOS capacitor modulated in a sawtooth shape by excitation light.

  For a conductive probe oscillating at an angular frequency ω1, a constant DC voltage is applied to the semiconductor substrate during the measurement period, and a depletion layer due to diffusion of majority carriers immediately below the conductive probe as shown in FIG. Is forming. On the other hand, as described in paragraph 0011, the excitation light is divided into pulsed light having a frequency ω2 by an optical chopper.

  Here, it is desirable that ω2 <ω1 because carrier emission from a crystal defect having an energy level corresponding to the wavelength of the excitation light or a process-induced defect is a relatively slow process. Specifically, ω1 is preferably about 50 kHz to 300 kHz, while ω2 is preferably about 5 kHz to 50 kHz.

  As described in the description of FIG. 1, when the excitation light is irradiated, crystal defects or process-induced defects in the semiconductor substrate having an energy level corresponding to the wavelength emit carriers. The spread of the depletion layer changes due to diffusion. For this reason, the capacitance of the MOS capacitor changes at the timing shown in FIG. 3D in accordance with the change of the excitation light intensity. By detecting these changes, the distribution of crystal defects and process-induced defects existing in the semiconductor substrate 1 can be found.

  Further, when the wavelengths of the excitation light are swept, crystal defects and process-induced defects having energy levels corresponding to the respective wavelengths emit carriers. Therefore, by measuring while sweeping the wavelength of the excitation light, information on the distribution of crystal defects and process-induced defects having different energy levels can be obtained.

  In the present invention, the scanning control device 15 performs measurement while sweeping the wavelength of the excitation light at each measurement point while moving the operation stage 16 in the X and Y directions. As a result, information on the distribution of crystal defects and process-induced defects having different energy levels can be obtained.

It is a figure which shows the mode of the Metal-Oxide-Semiconductor (MOS) junction formed with the conductive probe of SCM, and the semiconductor substrate by which the surface was covered with the dielectric thin film. It is a block diagram which shows embodiment by this invention. It is a block diagram which shows generation | occurrence | production of the vibration of a conductive probe, the DC voltage applied to a semiconductor sample, and an excitation light pulse.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Oxide film 3 Conductive probe 4 Depletion layer by diffusion of majority carriers
5 Depletion layer changed by photoexcitation 6 DC voltage source 7 Excitation light 8 Piezoelectric element 9 Excitation light source 10 Excitation light 11 Optical chopper 12 Condensing lens 13 AC voltage source 14 Vibration detection device 15 Scan control device 16 Scanning stage 17 Capacitance detector 18 Display 1
19 Lock-in amplifier 1
20 Lock-in amplifier 2
21 Display 2
31 Vibration of a conductive probe 32 DC voltage applied to a semiconductor substrate 33 Modulation of excitation light intensity 34 Capacitance modulated by excitation light

Claims (7)

A conductive probe, means for controlling the position of the conductive probe so as to have a predetermined interval with respect to the sample to be measured, means for applying a voltage between the conductive probe and the sample to be measured,
A scanning probe microscope having means for irradiating excitation light between the conductive probe and the sample to be measured, and light excitation capacitance detecting means for detecting capacitance information between the conductive probe and the sample to be measured Because
In a scanning probe microscope having photoexcitation capacitance difference detection means for acquiring a component depending on the intensity of the excitation light from capacitance information between the conductive probe and the sample to be measured detected by the photoexcitation capacitance detection means ,
The photoexcitation capacitance difference detection means extracts a ΔC / ΔZ signal , which is a difference signal, of the capacitance information between the conductive probe and the sample to be measured detected by the photoexcitation capacity detection means, and further detects the ΔC / from ΔZ signal, scanning probe microscope and extracting a component which depends on the intensity of the excitation light.   The photoexcitation capacitance difference detecting means is configured to vibrate the conductive probe in a direction perpendicular to the surface of the sample to be measured, and the conductive probe periodically modulates the distance from the sample to be measured. 2. The scanning probe microscope according to claim 1, wherein a component that changes at a vibration frequency of the conductive probe is detected from among the capacitance between the conductive probe and the sample to be measured.   The photoexcitation capacitance difference detection means periodically shifts the position of the sample to be measured with respect to the conductive probe in the vertical direction, and periodically modulates the distance between the conductive probe and the sample to be measured. 2. A component synchronized with a period of displacement of a vertical position of the sample to be measured is detected from among the capacitance between the conductive probe and the sample to be measured. The scanning probe microscope described. The optical excitation capacitance difference detection means detects a component synchronized with the modulation frequency when the intensity of the excitation light irradiated between the conductive probe and the sample to be measured is intermittently modulated. The scanning probe microscope according to claim 1, wherein the scanning probe microscope is provided. The photoexcitation capacitance difference detecting means is configured to set the modulation frequency of the light intensity of the excitation light irradiated between the conductive probe and the sample to be measured to be higher than the frequency of distance modulation between the conductive probe and the sample. The scanning probe microscope according to claim 1, wherein the scanning probe microscope has a low frequency. 6. The optical excitation capacitance difference detection means is configured to measure while sweeping the wavelength of the excitation light irradiated between the conductive probe and the sample to be measured. A scanning probe microscope according to claim 1.   The means for controlling the relative position between the conductive probe and the sample to be measured is a resonance frequency or a resonance amplitude or a resonance Q value of a mechanical resonator constituted by the conductive probe and the piezoelectric element. The scanning probe microscope according to any one of claims 1 to 6, characterized in that a change in the frequency is detected.

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