JPH04162341A - Sample surface picture forming method and device thereof - Google Patents

Abstract

PURPOSE:To high accurately detect displacement of a vibrator by detecting a shift of a vibration frequency of the vibrator from a natural frequency as a phase difference between two measuring points of the vibrator. CONSTITUTION:In a cantilever(vibrator)2, a probe 4 is fixed to a free end of the cantilever 2 and arranged approximately to a sample surface 1a by holding a fixed end by a piezoelectric element 6. Now, when predetermined voltage is applied to the piezoelectric element 6 so as to vibrate the cantilever 2 in a natural frequency, the cantilever 2 is vibrated by the natural frequency. This vibration is changed by interatom mutual action between the pointed end of the probe 4 and the sample surface 1a, and the change of this vibration is detected by a displacement phase difference between two measuring points A, B on the cantilever 2 by the laser interference method or the like. In this way, high accurate displacement measurement can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for forming an image of a surface of a sample, which enables observation of the surface of a sample with atomic-order resolution. More specifically, it is a type of scanning that detects short-range forces such as atomic force and magnetic force that act between microscopic particles between the tip of the probe and the sample surface as data for forming an image of the sample surface. Type probe microscopy is within the technical field of the present invention.

[Prior Art] As a scanning probe microscope, for example, a scanning tunneling microscope (Scanning Tunneling Microscope) is used.
crossscope (STM), atomic force microscope (At
omic Force Microsc.

pe; AFM), magnetic force microscope (Magnetic
Force Microscope (MPM) and the like are known.

In a scanning tunneling microscope (hereinafter abbreviated as STM), 3
A conductive probe is attached to a fine movement element that is movable in the axial direction, and the tip of the probe is brought close to a distance of about 1 nm from the sample surface. This distance of approximately 1 nm is the distance at which the atoms at the tip of the probe and the electron seismic waves of the sample overlap. When a voltage is applied between the probe and the sample in this state, a tunnel current flows between them. The magnitude of this tunneling current varies depending on the distance between the probe tip and the sample. By controlling the voltage applied to the fine movement element in the direction perpendicular to the sample surface so as to keep this tunnel current value constant, the distance between the probe tip and the sample surface can be kept constant. In this state, if the probe is scanned along the sample surface in two-dimensional directions, the locus of the tip of the probe will represent the uneven shape of the sample surface. Therefore, by plotting the voltages applied to the fine movement elements in the three axial directions as coordinate values, an enlarged image of the shape of the sample surface can be obtained. The principle of STM is explained, for example, by G. Binnig (1982) in Physical Review Letters (Phys, Rev, LetterS), Volume 49, Page 57 (1982).
Binnig), H, o-ler (Rohrcr), CH
.

Gerber, E. Weibe
l) paper (Surface 5 studies by
Scanning Tunneling old er.

5cope).

However, since STM detects tunneling current as described above, observable samples are limited to those with conductivity = 6-, and insulating samples cannot be observed.

In contrast, an atomic open force microscope (hereinafter abbreviated as AFM) has been proposed as a microscope capable of observing insulating samples with atomic-order accuracy. In this AFM, the probe is fixed to the free end of the cantilever. If the sample is an insulator, no tunneling current will flow even if a voltage is applied, but when the distance between the atoms at the tip of the probe and the atoms on the sample surface (interatomic distance) becomes about lnm, as in STM,
An attractive force due to van der Waals interaction acts between the probe and the sample, and when the interatomic distance becomes smaller to the extent of the atomic bond distance, a repulsive force occurs between the probe and the sample due to the Pauli prohibition principle. These attractive and repulsive forces (atomic forces) are IQ-
Although the force is minute on the order of 19 to 10-12N, the cantilever is displaced in response to this force. The AFM detects the displacement of this cantilever and controls the voltage applied to the fine movement element so that this displacement becomes constant. Therefore, based on this applied voltage, an image of the shape of the persimmon sample surface can be obtained, similar to STM. The principle of this AFM is described, for example, in Physical Review Letters Vol. 56 (1986), No. 9.
G, Binitzhi, CF, Quait, listed on page 30.
te) paper (Atomic Force Mlero
seope).

Further, a magnetic force microscope (hereinafter abbreviated as MFM) has basically the same structure as the above-mentioned AFM, except that the probe is made of a magnetic material. In this MFM, the magnetic force that exists between the probe and the magnetic particles of the sample is detected as the displacement of the cantilever.

By scanning the probe along the sample surface while keeping the displacement caused by this magnetic force constant, an image of the sample surface can be formed.

In these AFM and MFM, the following three methods are known as methods for detecting displacement of a cantilever.

In the first method, a dielectric film is formed on the upper surface of the cantilever, an STM is formed on the dielectric film, and displacement is detected by a tunnel current of the STM.

In the second method, an optical reflection surface is formed at the tip of the cantilever, and a laser beam such as a ruby solid-state laser or an argon gas laser is made incident on this reflection surface via a fiber and reflected. By detecting this reflected beam with a PDS (optical position detector) provided on the reflection side, a change in the reflection angle of the cantilever is detected.

In the third method, the beam emitted from the laser light source similar to the second method is divided into a reference beam and a beam incident on the cantilever reflecting surface, and the reference beam is caused to interfere with the reflected beam from the cantilever.

The displacement of the cantilever is detected by photoelectrically detecting the interference output.

It is also known that instead of the displacement of the cantilever, changes in the natural vibration of the cantilever are detected using the three methods described above (for example, Journal Applied Physics, Vol. 61 (1).
987), p. 4723.

(Article by Martin et al.). This change in natural vibration occurs because when the cantilever is brought close to a sample while causing natural vibration, the frequency of the cantilever deviates (shifts) from the natural frequency due to the influence of short-range force.

[Problems to be Solved by the Invention] In AFM and MFM, in order to facilitate displacement measurement by increasing the displacement of a cantilever, it is preferable to form the cantilever into an elongated shape using a lightweight and highly elastic material. However, as the cantilever becomes longer, the natural frequency decreases, which deteriorates the response characteristics that follow the irregularities of the sample during scanning, and makes it difficult to remove external vibration noise.

On the other hand, if the cantilever length is suppressed to 1000 μm or less in order to maintain the natural frequency at several 10 KH7, the displacement of the cantilever warp will be reduced, and a sensitive detection means or detection method will be required.

Although the three methods described above can provide good detection sensitivity, they have the following problems.

The first method using STM as a detection means is 0.1nrr in the distance direction between the STM probe and the cantilever dielectric surface.
The change in tunnel current is 10 times as large as the change in i, and has sufficient sensitivity. However, atomic forces also exist between the probe and the back surface of the cantilever, and this is difficult to separate from the atomic forces from the sample to be measured, thus hindering accurate measurements.

In the second method of detecting changes in the reflection angle, if the incident angle of the laser beam is increased to increase sensitivity, the device configuration becomes larger in the lateral direction and the natural frequency of the cantilever decreases. Furthermore, since the laser beam spot spreads on the cantilever surface, it is not easy to improve the accuracy of the flatness of the reflection surface so as to achieve the required reflection angle resolution.

In the third method using a laser interferometer as a detection means, the optical path lengths of the reference optical path system and the detection optical path system are made equal to cancel out the influence of the external environment (distortion due to temperature, atmospheric pressure, etc.) in order to increase sensitivity. However, as a result, the device configuration becomes complicated. Furthermore, if the optical structures of the reference optical path system and the detection optical path system are configured separately, it is difficult to equalize the natural frequencies of the arms of each optical path, so the sensitivity will be affected by the external environment and the sensitivity will decrease. to degrade.

The present invention has been made in view of the above problems, and its purpose is to have good detection sensitivity to short-range forces such as atomic force and magnetic force, and to be stable against changes in the external environment. An object of the present invention is to provide a method and apparatus for forming an image on a sample surface.

[Means for Solving the Problems] In order to solve the above problems, the method for forming an image on the surface of a sample according to the present invention provides a method for forming an image on the surface of a sample by directing the tip of a probe fixed to one end of a vibrating body to the surface of a sample to be inspected. The microscopic particles at the tip of the probe and the microscopic particles on the surface of the sample are brought close to each other within a predetermined distance that allows interaction by short-range force to occur, and in this state,
While scanning the probe in a two-dimensional direction along the sample surface, the vibrating body is moved such that the natural frequency of the vibrating body changes depending on the distance between the tip of the probe and the sample surface. In a method for forming an image of a vibrating sample surface, a shift in the frequency of the vibrating body from its natural frequency due to the interaction is detected by detecting a phase difference in displacement at two measurement points of the vibrating body. According to this detected frequency shift, = 12 - such that the frequency of the vibrating body is maintained at the natural frequency,
The size of the distance between the tip of the probe and the sample surface is controlled, and based on the fact that the controlled amount of this distance corresponds to the unevenness of the sample surface, the controlled amount is adjusted to the scanning position of the probe with respect to the sample surface. It is characterized by forming an image of the sample surface by plotting it in correspondence with the .

On the other hand, the sample surface image forming apparatus according to the present invention includes a vibrating body to which a probe to be placed close to the sample surface is fixed at one end, and a vibrating body that vibrates at its natural frequency. vibrating means for supporting the other end of the body; and scanning means for moving at least one of the vibrating body and the sample relative to the other so as to scan the probe in a two-dimensional direction along the sample surface. and a phase difference detecting means for detecting a phase difference between displacements at two measurement points of the vibrating body, and a phase difference detected by the phase difference detecting means in the natural vibration state of the vibrating body. A control means for controlling the distance between the tip of the probe and the sample surface so that a phase difference is obtained, and the control amount is determined based on the fact that the control amount of this control means corresponds to the unevenness of the sample surface. The present invention is characterized by comprising an image forming means for forming an image of the sample surface by plotting the probe in correspondence with the scanning position of the probe relative to the sample surface by the scanning means.

According to one embodiment of the present invention, the phase difference detection means includes a reflecting surface formed on the vibrating body so as to include the two measurement points, and a reflection surface formed on the vibrating body to include the two measurement points, and An input optical system that makes the laser beam enter the reflective surface; a pair of photoelectric elements that respectively receive the reflected beams of the laser beam that entered the two measurement points; and detection means for detecting a phase difference in displacement of the vibrating body.

Further, according to another embodiment of the present invention, the phase difference detection means includes a reflecting surface formed on the vibrating body so as to include the two measurement points, and a reflection surface formed on the vibrating body to include the two measurement points. an input optical system for making a laser beam incident on the reflective surface; a reference beam generating means for generating a reference beam having the same phase as the laser beam before being incident on the reflective surface;
a pair of photoelectric elements each receiving an interference beam formed by each of the reflected beams of the laser beam incident on the two measurement points interfering with the reference beam; and based on the photoelectric outputs of these photoelectric elements, the and detection means for detecting a phase difference in displacement of the vibrating body.

The two measurement points are preferably located at positions corresponding to the antinode and node of the natural vibration of the vibrating body, respectively.

[Function] According to the present invention, a shift in the frequency of the vibrating body from the natural frequency is detected as a phase difference between displacements at two predetermined measurement points of the vibrating body. In this case, since the displacement of the vibrating body is measured at two points, it is possible to measure the displacement with higher precision than the conventional measurement at one point. For example, if positions corresponding to the antinode and node of the natural vibration of the vibrating body are used as measurement points, the phase difference between the displacements at the two measurement points becomes large, making it easy to measure displacement with high precision.

The phase difference of the detected displacement, that is, the frequency shift, is due to the short-range force between the microscopic particles between the tip of the probe and the sample surface (for example, the atomic force acting between the atoms of the two, or the force between the magnetic particles of the two). (magnetic force acting on the magnetic field). The magnitude of this short-range force is proportional to the distance between the tip of the probe and the sample surface.

Therefore, if the distance between the tip of the probe and the sample surface is controlled to cancel the frequency shift, the trajectory of the tip of the probe during the scanning period will draw a shape that corresponds to the uneven shape of the sample surface. . Therefore, an image of the sample surface can be formed by plotting the control amount of the distance between the probe tip and the sample surface according to the scanning position of the probe with respect to the sample surface.

[Example] Prior to detailed explanation of the present invention, the basic principle of the present invention will be briefly explained using an atomic force microscope (AFM) as an example.

In FIG. 1, a cantilever (vibrating body) 2 has a probe 4 fixed to its free end, and the fixed end is held by a piezoelectric element 6. Probe 4 is on sample surface 1a
located close to. When a predetermined voltage is applied to the piezoelectric element 6 so as to cause the cantilever 2 to vibrate at its natural frequency, the cantilever 2 naturally vibrates in the fundamental mode or triple frequency mode as shown in FIG. 2A or FIG. 2B. . This vibration changes due to atomic interaction between the tip of the probe 4 and the sample surface 1a. This change in vibration is detected by the phase difference between the displacements of the two measurement points A and B on the cantilever 2. The following laser interferometry can be applied to this detection. Referring again to FIG. 1, two laser beams Ll are emitted from a laser light source (not shown) and separated.

L2 is reflected by the beam splitter 20 and incident on two points A- and B- of the reference image 22, respectively. These two points A-, B
A beam incident on - is partially reflected there and becomes a reference beam. The other part passes through the reference image 22 and enters measurement points A and B on the reflective surface 2a of the cantilever 2, where it is reflected and becomes a signal beam. Two signal beams from these measurement points A and H are generated at two points A on the reference image 22.
″.

Two interference beams are formed by interfering with the two reference beams from B-, respectively. These two interference beams each pass through the beam splitter 20 and are received by the photoelectric elements 24a and 24b. If the sample surface 1a is sufficiently far away from the probe 4, the optical power received by the photoelectric elements 24a and 24b remains constant in phase at a frequency determined by the natural frequency of the cantilever 2, as shown in FIG. 3A. Light is received. Next, when the probe 4 is brought close to the sample surface 1a, the frequency of the cantilever 2 increases from its natural frequency due to the atomic force acting on the probe 4 and the sample surface 1a. Therefore, the phase of the optical signals received by the photoelectric elements 24a and 24b varies as shown in -18=FIG. 3B. This phase variation is detected by a phase difference meter (detection means) 26, and the position of the sample surface 1a is controlled by a piezoelectric body (not shown) or the like according to the detection output so as to cancel out the phase variation of the optical signal. . The value of this control output can be regarded as data corresponding to the unevenness of the sample surface 1a. Therefore, an image of the sample surface 3a can be formed based on this unevenness data.

An example in which the present invention is applied to an AFM will be described below.

In the first embodiment shown in FIG.
The length is 500 to 2000 μm, the thickness is 5 μm, and the width is 200 μm.
μm, and a probe 4 fixed to the lower surface of its free end
The tip is sharpened to have a radius of curvature of about 0.1 μm. Further, the upper surface 2a of the cantilever 2 is formed as a reflective surface on which silver or aluminum is deposited. Such a cantilever 2 has its fixed end held by a piezoelectric element 6, and can vibrate according to the voltage applied to the piezoelectric element 6. The material of the cantilever 2 may be phosphor bronze in the form of a sufficiently thin foil made by a known method, but in this embodiment it is made of Si2N3.

When creating this cantilever 2, devices that involve mechanical movement, such as microapplication and micromachining based on semiconductor device manufacturing technology, are used.
Alternatively, it is preferable to use a technique for creating a device having a mechanically ultra-fine shape.

A sample 1 to be inspected is placed on an XYz drive device (scanning means) 10 so that its surface 1a faces the tip of the probe 4. This drive device 10 is a tri-bod type or tube-shaped piezoelectric element, and moves the sample 1 in the XY force directions so that the probe 4 scans the sample surface 1a in a two-dimensional direction along the sample surface 1a. Further, the drive device 10 moves the sample in the Z direction so that the distance between the sample surface 1a and the tip of the probe 3 is constant. This drive device 10 is controlled by a control device (control means) 12. The control device] 2 includes a drive amplifier that drives the drive device 10 and a feedback circuit (both not shown) that provides negative feedback of the drive amount.

Two measurement points A on the cantilever reflective surface 2a.

Laser light source 28a for inputting a laser beam to B
has a single frequency, such as a He-Ne laser. The beam expander 30 that shapes the laser beam emitted from the light source 28a is formed by combining a simple convex lens and a concave lens. The beam splitter 2° that polarizes the shaped beam produced by the beam expander 3o is a half prism, a pellicle splitter, or the like. The cylindrical lens 32 that makes the beam polarized by the beam splitter 2o enter two points A and B is made of an optical glass material such as BN2, and has a reflective film as a reference surface 22 (reference beam generating means) on the plane side. It is vapor-deposited. Each of these components 20, 28a, 30.3
2 constitutes an input optical system.

Two points A of the reference surface 22 and the cantilever reflective surface 2a,
A pair of photoelectric elements 24 a that receive the reflected beam from B
, 24b are photodiodes. Light other than that to be detected is blocked by a field stop 34 arranged on the incident side of the photodiodes 24a and 24b. The field stop 34 is made of a copper plate or the like with two pinholes formed on it. The phase difference meter 26 for determining the phase difference between the photoelectric outputs of the photodiodes 24a and 24b is a normal commercially available product constructed from a simple electric circuit. In addition, the sample surface 1a
The image display device (image forming means) 36 that displays the image is, for example, a microcomputer equipped with a CRT 368 and a drawing circuit (not shown).

The operation of the AFM configured as described above is as follows. - As an example, the natural vibration of the cantilever 2 is assumed to be a triple frequency mode. Also, the measurement point A of the displacement of the cantilever 2
, B are positions corresponding to the antinode and node of vibration, respectively.

Here, 411 fixed point A is located at the tip of cantilever 2,
Measurement point B is 2/3 of the length of cantilever 2 from measurement point A.
It is located at

When the cantilever 2 is vibrated by the piezoelectric element 6 so as to cause natural vibration in the triple frequency mode, the cantilever 2 repeats displacement at a constant period unless another external force is applied. Here, when the sample surface 1a approaches the probe 4 and the cantilever 2 is affected by atomic force, the above-mentioned period decreases.

This cycle change is detected as follows.

The laser beam emitted from the light source 28a is expanded to an appropriate spot diameter by a beam expander 30, and then enters the beam splinter 20. This spot diameter corresponds to at least the distance between measurement points A and B on the cantilever 2. The beam polarized by the beam splitter 20 is
The light is incident on the reference surface 22 on the cylindrical lens 32.

Of the beam incident on the reference surface 22, 40 to 50% is reflected by the reference surface 22 and becomes a reference beam. In addition, the beam transmitted through the reference surface 22 is transmitted through the lindrical lens 32.
The light is condensed into a line on the cantilever reflecting surface 2a and reflected there, forming a signal beam.

These reference beams and signal beams are connected to the beam splitter 2
The light passes through the pinholes of the field diaphragm 34 and -23= and is received by the photodiodes 24a and 24b, respectively. Due to interference between these reference beams and signal beams,
The displacement of the cantilever 2 is obtained as interference fringe information. Therefore, a sinusoidal signal is detected in the photodiodes 24a and 24b corresponding to the two points A and B of the cantilever 2 undergoing natural vibration. The phase difference between these two sinusoidal signals is determined by a phase difference meter 26. This change in phase difference represents a shift in the frequency of the cantilever 2 from the frequency of the mount, that is, a change in the distance between the sample surface [a] and the probe 3. The control device 12 drives the drive device 10 in the Z direction so as to cancel this change in phase difference, and maintains the distance between the sample surface 1a and the probe 3 constant. The control output of the control device 12 in the Z direction (data indicating the unevenness of the sample surface 1a) and the XY force direction control output (data indicating the scanning position of the probe 4 with respect to the sample surface 1a) are the drawings of the image display device 36. given to the circuit. This drawing circuit displays a three-dimensional image of the sample surface 1a on the display screen 34 by plotting the unevenness data in correspondence with the scanning position data.
Enlarged display in a.

FIG. 5 shows a second embodiment of the invention. The input optical system in this embodiment includes a laser light source 28b1 a beam splitter 2
0, a disbracing prism 38 is provided. The laser light source 28b is a light source, such as a Zeeman laser, which emits two-frequency beams whose polarization planes are orthogonal to each other. The displacing prism 38 for separating the beams of the lights ri and 28b on the incident side and the Wollaston prism 40 for separating the beams on the detection side can be formed of calcite. Further, the reference surface 22 is formed by depositing a reflective film on an optical flat plate. Other components are the same as those in the first embodiment.

The two-frequency beam emitted from the light source 28b is reflected by the beam splitter 20, and then passes through the disbracing prism 38.
The beam is separated into two beams by , and is incident on the reference surface 22 . 40 to 50% of each beam incident on the reference surface 22 is reflected and becomes a reference beam. This reference beam passes through the disbracing prism 38, is made into one beam, and passes through the beam printer 20. Next, the light is reseparated by the Wollaston prism 40 into two linearly polarized beams having vibration planes perpendicular to each other, and each is received by the photodiodes 24a and 24b.

On the other hand, the two beams that have passed through the reference surface 22 are incident on measurement points A and B on the cantilever reflective surface 2a, and are reflected there to become signal beams. After passing through the reference surface 22, these two signal beams pass through the same optical path as the reference beam and are received by photodiodes 24a and 24b, respectively. Therefore, in the photodiodes 24a and 24b,
An interference beam between the signal beam and the reference beam will be received. Based on the outputs of these photodiodes 24a and 24b, an image of the sample surface is obtained in the same manner as in the first embodiment.

FIG. 6 shows a third embodiment of the invention. In the input optical system in this embodiment, a triangular prism 42 is used as a means for splitting the beam emitted from the He-Ne laser light source 28a and polarized by the beam splitter 20. This triangular prism 42 is made of an optical glass material such as BK7.

In addition, photoelectric elements 44a and 44b that detect reflected beams from measurement points A and B on the cantilever reflective surface 2a,
It is a silicon photodiode with a light-receiving surface divided into two parts. Subtractors 46a and 46b for determining the output difference between the light receiving surfaces of these two-divided photodiodes 44a and 44b are constructed of operational amplifiers and the like. Other components are the same as those in the first embodiment.

The beam emitted from the light source 28a is polarized by the beam splitter 20 and enters the apex 42a of the triangular prism 42. This incident beam has the optical path shown in FIG.
The light beam is split into two parts at the apex 42a of the triangular prism 42, and is refracted and incident on measurement points A and B on the cantilever reflecting surface 2a so that the angle of incidence is as small as possible. The beams incident on these measurement points A and B are reflected at measurement points A and B, respectively, and become reflected beams f1. f″2, but its reflection angle and reflection position change according to the vibration of the cantilever 2. In this way, the reflected beams fl and f2, which contain information on the displacement of the cantilever 2, are refracted by the triangular prism 42 and turned into beams. The light passes through the splitter 20 and is received by the two-split photodiodes 44a and 44b.11111 Fixed point A
Two outputs corresponding to the two light receiving surfaces of the photodiode 44a corresponding to the subtracter 46a are respectively given to the positive and negative side terminals of the subtracter 46a. The subtracter 46a is the photodiode 4
4a, that is, the reflected beam f1 for measurement point A.
The displacement and deflection angle are determined and provided to the phase difference meter 26. Similarly, the displacement and deflection angle of the reflected beam f2 at the measurement point B are determined by the subtracter 44b based on the two outputs of the two-split photodiode 44b, and are provided to the phase difference meter 26. The phase difference meter 26 determines the phase difference between the displacement and deflection angle of the reflected beams fl and f2, ie, the phase difference between the displacement of the cantilever 2 at the measurement points A and B, based on the outputs of the subtractors 46a and 46b. As a result, a shift in the frequency of the cantilever 2 from its natural vibration is detected, and an image of the sample surface 1a is obtained as in the first embodiment.

According to this third embodiment, the measurement point A of the cantilever 2,
High detection accuracy is achieved because the smaller the angle of incidence with respect to B, the greater the change in the angle of reflection of the reflected beam. Furthermore, since the triangular prism 42 is simply used as a means for reducing the angle of incidence with respect to the measurement points A and B, it is easy to downsize the device configuration.

Three embodiments have been described above, and each embodiment has a smaller device configuration and is less expensive than when a conventional laser interferometer is used.

In each of the above embodiments, an example has been described in which the natural vibration of the cantilever 2 is set to the triple mode of the first harmonic of the fundamental wave, but the fundamental wave mode and other harmonic modes as shown in FIG. However, the same effects as in each of the above embodiments can be achieved.

In each of the above embodiments, the sample 1 is moved by the XYz drive device 1 in order to move the sample surface 1a and the probe 3 relative to each other.
Although the sample 1 is moved by 0, the cantilever 2 may be moved while the sample 1 is fixed.

Furthermore, the application of the present invention is not limited to atomic force microscopes (AFM), but also magnetic force microscopes (MFM).
It is also applicable to

[Effects of the Invention] As explained above, according to the sample surface image forming method and apparatus of the present invention, the shift of the vibration frequency of the vibrating body from the natural frequency is expressed as the phase difference between two measurement points of the vibrating body. Therefore, the displacement of the vibrating body can be detected with high precision.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram for explaining the principle of the image forming method and apparatus of the present invention, FIGS. 2A and 2B are schematic diagrams showing the vibration state of the cantilever in FIG. 1, and FIGS. 3A and 3B are The figure is a diagram showing the signal waveform of the photoelectric element in Fig. 1, Fig. 4 is a block diagram showing a first embodiment in which the image forming apparatus of the present invention is applied to an AFM, and Fig. 5 is a diagram showing the second embodiment. FIG. 6 is a block diagram similarly showing the third embodiment, and FIG. 7 is an optical path diagram showing the optical path of the triangular prism in FIG. 6. 1... Sample, 2... Cantilever (vibrating body), 4...
・Probe (deep needle), 6...Piezoelectric element, 10...X
YZ drive device (scanning means), 12...control device (control means), 20...beam splitter, 22...reference plane (reference beam generating means), 24a, 24b, 42a
, 42b...Photoelectric element, 26...Phase difference meter (detection means), 28a, 28b...Laser light source, 30-...
Beam expander, 32... Cylindrical lens, 36... Image display device (image forming means), 38...
Disbracing prism, 42...Triangular prism applicant's attorney Atsushi Tsuboi = 31-

Claims (1)

[Claims] 1. The tip of the probe fixed to one end of the vibrating body is placed against the surface of the sample to be inspected so that microscopic particles at the tip of the probe and microscopic particles on the sample surface The distance between the tip of the probe and the surface of the sample is determined while the probe is being scanned in a two-dimensional direction along the sample surface. In the image forming method of the sample surface in which the vibrating body is vibrated so that the natural frequency of the vibrating body changes according to the A shift in the frequency of the vibrating body from the natural frequency due to the interaction is detected, and the frequency of the vibrating body is maintained at the natural frequency according to the detected frequency shift. , controlling the size of the distance between the tip of the probe and the sample surface, and scanning the probe with respect to the sample surface using the control amount based on the fact that the controlled amount of this distance corresponds to the unevenness of the sample surface. A method for forming an image of a sample surface, comprising forming an image of the sample surface by plotting the sample surface in correspondence with its position. 2. The method for forming an image on a sample surface according to claim 1, wherein the two measurement points are positions corresponding to an antinode and a node of the natural vibration of the vibrating body, respectively. 3. A vibrating body to which a probe to be placed close to the surface of the sample is fixed at one end; a vibrating means for supporting the other end of the vibrating body so as to vibrate the vibrating body at its natural frequency;
a scanning means for moving at least one of the vibrating body and the sample relative to the other so as to scan the probe in a two-dimensional direction along the sample surface; a phase difference detection means for detecting a phase difference between displacements at two measurement points; and a control means for controlling the distance between the probe and the sample surface, and based on the fact that the control amount of the control means corresponds to the unevenness of the sample surface, the control amount is controlled by the scanning means to scan the probe on the sample surface. 1. An image forming device for forming an image on a surface of a sample, comprising an image forming means for forming an image of the surface of the sample by plotting the image in correspondence with the position. 4. The phase difference detection means includes a reflecting surface formed on the vibrating body so as to include the two measuring points, and a reflecting surface formed on the vibrating body so that a laser beam having the same phase is incident on at least the two measuring points. an input optical system that allows a laser beam to enter the laser beam; a pair of photoelectric elements that respectively receive the reflected beams of the laser beam that entered the two measurement points; 4. The sample surface image forming apparatus according to claim 3, further comprising a detection means for detecting a phase difference in displacement of the vibrating body. 5. The phase difference detection means includes a reflecting surface formed on the vibrating body so as to include the two measuring points, and an incident laser beam that is incident on the reflecting surface so as to be incident on at least the two measuring points. an optical system; a reference beam generating means for generating a reference beam having the same phase as the laser beam before entering the reflecting surface; and a reference beam generating means for generating a reference beam having the same phase as the laser beam before entering the reflecting surface; A pair of photoelectric elements each receiving an interference beam formed by interfering with the other beam, and a detection means for detecting a phase difference in the displacement of the vibrating body at the two measurement points based on the photoelectric outputs of these photoelectric elements. 4. The image forming apparatus for a sample surface according to claim 3. 6. The sample surface image forming apparatus according to any one of claims 3 to 5, wherein the two measurement points are positions corresponding to an antinode and a node of the natural vibration of the vibrating body, respectively. .