JP2009042123A - Atomic force microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an atomic force microscope that reduces the effect of the relative positional fluctuations of a cantilever with an article to be inspected and enables high-accuracy measurements. <P>SOLUTION: The measurement standard for the displacement of the cantilever 12 is set as the article 1 to be inspected, and one of two types of polarized light separated by a lotion prism 28 is irradiated on the article 1 to be inspected to be set as a reference light; while the other polarized light is irradiated on the cantilever 12 to be set as light to be inspected. The relative displacement of the leading end of the cantilever 12 and the article 1 to be inspected is measured directly by using an interference optical system, and the reference light and the light to be inspected are set to a common light path to remove the ghost factor, and in order to further perform high-accuracy measurements even with respect to various articles to be inspected, the quantity ratio of the reference light and the light to be inspected can be regulated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an atomic force microscope that is a scanning probe microscope using atomic force.

  The atomic force microscope scans a cantilever with a fine probe along the surface of the specimen, and the amount of displacement of the cantilever due to the atomic force acting between the probe and the specimen Is a device that can measure the fine structure of the surface of the test object. The principle is disclosed in Patent Document 1. In Patent Document 1, the amount of displacement of the cantilever is detected by detecting a tunnel current, but methods using an optical lever method or an optical interference method have also been proposed.

  However, the general atomic force microscope does not acquire displacement information of the test object when measuring the cantilever displacement. The same applies to the atomic force microscope disclosed in Patent Document 1. When the relative position between the cantilever and the test object fluctuates due to disturbance such as vibration or temperature change, the fluctuation amount is superimposed on the measurement result. There was a problem. For example, in the AC mode in which measurement is performed while the cantilever is vibrated in the vicinity of the resonance frequency, an atomic force that varies depending on the distance between the probe and the test object is detected by a change in amplitude. At this time, it is assumed that the distance between the probe and the test object changes according to the surface shape of the test object, but if the relative position fluctuation between the cantilever and the test object occurs, the assumption does not hold and the error is Will occur.

  Patent Document 2 has been proposed as an atomic force microscope capable of reducing the influence of relative position fluctuation between a cantilever and a test object. In Patent Document 2, the displacement amount of the cantilever is detected by an optical heterodyne method using an optical system including a bifocal lens, and the configuration thereof is as shown in FIG.

  In this apparatus, a laser light source apparatus 110 that can output laser light including two types of linearly polarized light having orthogonal polarization planes and slightly different frequencies is used. Two types of linearly polarized light output from the laser light source device 110 are incident on the bifocal lens 122, and one of the linearly polarized light becomes parallel light and is irradiated on a relatively wide range of the test object 130. The other linearly polarized light becomes focused light and is condensed on the back surface of the cantilever 126. The reflected light from the back surface of the cantilever and the reflected light from the surface of the test object enter the measurement optical sensor 136. Here, the reflected light from the back surface of the cantilever is subjected to a frequency change because the optical path length changes with the amount of displacement of the cantilever 126 due to the atomic force. Therefore, the displacement amount of the cantilever 126 can be calculated from the beat signal of the optical interference detected by the measurement optical sensor 136.

  When the measurement in the AC mode is applied to Patent Document 2, the maximum value and the minimum value of the cantilever displacement are measured with respect to the surface of the test object, and the amplitude is obtained. Therefore, even when the relative position fluctuation between the cantilever and the test object occurs, the maximum value and the minimum value of the cantilever displacement change equally by the relative position fluctuation, and the amplitude measurement result is not affected. For this reason, it becomes possible to reduce the influence of the relative position fluctuation | variation of a cantilever and a test object.

JP-A-62-130302 Japanese Patent No. 2998333

  However, in the case of the atomic force microscope disclosed in Patent Document 2, the influence of the relative position fluctuation between the cantilever and the test object can be reduced, but the measurement accuracy of the cantilever displacement is degraded due to the following three factors. There was a problem to do.

  The first factor that degrades the measurement accuracy is that the two types of linearly polarized light output from the laser light source device reflect on the back surface of the cantilever and the surface of the test object and reenter the bifocal lens. It is a passing point. If the optical paths are different, the optical path length difference between the two types of linearly polarized light varies due to atmospheric refractive index fluctuations accompanying fluctuations in temperature, pressure, etc., resulting in a measurement error of cantilever displacement.

  The second factor that degrades the measurement accuracy is that part of the light that becomes parallel light after being incident on the bifocal lens and irradiates the test object is reflected on the back surface of the cantilever and incident on the measurement optical sensor. This is a point that causes measurement noise. In this regard, Patent Document 2 is configured such that unnecessary light reflected on the back surface of the cantilever does not reach the measurement optical sensor by tilting the cantilever to some extent with respect to the optical axis. However, if the light incident as parallel light and reflected by the back surface of the cantilever does not reach the measurement light sensor, the principal ray of the light focused on the back surface of the cantilever as measurement light of the cantilever displacement also does not reach the measurement light sensor, Measurement is not possible. Therefore, it is impossible to avoid generation of measurement noise due to unnecessary light reflected on the back surface of the cantilever only by tilting the cantilever.

  The third factor that degrades the measurement accuracy is that the atomic force microscope disclosed in Patent Document 2 cannot adjust the light quantity ratio between the linearly polarized light incident on the cantilever and the linearly polarized light incident on the test object. . Accordingly, when the reflectance is different between the cantilever and the test object, the contrast of the interference fringes detected by the measurement optical sensor 36 is lowered, and the measurement accuracy of the cantilever displacement is deteriorated.

  The present invention has been made to solve the above-described problems, and an atomic force microscope that can reduce the influence of relative positional fluctuation between a cantilever and a test object and can measure the cantilever displacement with higher accuracy. The purpose is to provide.

  In the atomic force microscope of the present invention, a cantilever having a probe is brought close to a test object, an atomic force generated between the probe and the test object is detected, and the atomic force is kept constant. In an atomic force microscope that measures the surface shape of the test object by scanning while scanning, a light source, a polarizing optical element that divides light from the light source into two types of polarized light, and the two types of polarized light An optical system that collects interference fringes by two kinds of reflected light obtained by condensing one of the light onto the cantilever and condensing the other polarized light onto the test object and reflecting the collected light, respectively, Detecting means for detecting displacement of the cantilever from interference fringes.

  Since the cantilever displacement can be measured using the surface of the test object as a position reference, the influence of the relative position variation between the cantilever and the test object on the measurement result can be reduced.

  The two types of polarized light divided by the polarizing optical element are both reflected at the apex at the tip of the cantilever and the surface of the test object. As a result, the optical path from the light source until it is split by the polarizing optical element and the optical path after being reflected by the cantilever tip and the surface of the test object and reentering the polarizing optical element can be shared.

  Furthermore, since the exit directions of the two types of polarized light divided by the polarizing optical element are different, the cantilever can be arranged avoiding the optical path of the polarized light incident on the surface of the test object. As a result, part of the polarized light incident on the surface of the test object is not reflected on the back surface of the cantilever, and measurement noise that has been a problem in the prior art can be eliminated.

  Even when the reflectance differs between the cantilever and the test object, it is possible to keep the interference fringes detected by the detection means at a high contrast by using the means for adjusting the light quantity ratio.

  As described above, in the present invention, there are many common optical path portions, generation of measurement noise due to unnecessary light can be avoided, and interference fringes can be kept at high contrast regardless of the reflectance of the test object. Measurement can be performed with higher accuracy than before.

  In addition, in order to measure the cantilever displacement with higher accuracy, there is provided sensitivity information acquisition means for actually measuring the sensitivity of the detection signal fluctuation amount with respect to the cantilever displacement amount. Sensitivity changes depending on the state of interference fringes detected by the detection means and affects the measurement result of the cantilever displacement, but it is measured by sensitivity reduction by performing calibration using the sensitivity information measured using the sensitivity information acquisition means. The error can be reduced.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of an atomic force microscope according to the first embodiment. This apparatus detects an atomic force generated between an atom of a needle-like probe and an atom on the surface of the test object 1 and performs scanning while keeping the atomic force constant. An XYZ stage 3 and a tip tilt stage 4 are provided on a base 2 that is fixed to the ground. A test object 1 is fixed to the tip tilt stage 4, and a housing 6 is fixed to the XYZ stage 3. Various optical components and sensors are built in the housing 6, and an XY scanner 7 is fixed as a fine movement mechanism in the XY directions. A tube scanner 8 is fixed to the XY scanner 7 as a fine movement mechanism in the Z direction. A cantilever 12 having the probe is attached to the tube scanner 8 via a cantilever unit attachment block 9, a piezoelectric actuator 10 for vibration, and a cantilever holder 11. A reflective surface is formed on the back surface of the tip of the cantilever 12.

  A measurement operation using the various drive mechanisms described above will be described. First, the test object 1 is fixed to the tip tilt stage 4, and the relative positional relationship between the test object 1 and the cantilever 12 is adjusted using the XYZ stage 3 and the tip tilt stage 4. Thereafter, the tube scanner 8 is used to bring the cantilever 12 closer to the test object 1 until an atomic force acts between the test object 1 and a probe (not shown) provided at the tip of the cantilever. The cantilever is scanned using the XY scanner 7 while keeping the atomic force constant, and the surface shape of the surface of the test object 1 is measured. In order to keep the interatomic force constant, in this embodiment, the displacement of the tip of the cantilever is measured using optical interference. In this embodiment, the piezoelectric actuator 10 for vibration is provided, and measurement in the AC mode is also possible.

  Next, an optical system of the atomic force microscope in this embodiment and a method for measuring the cantilever tip displacement using this optical system will be described.

  The light output from the light source 21 is guided to the inside of the housing 6 through the optical fiber 22 and converted into parallel light by the collimator 23. The parallel light emitted at this time is adjusted to be linearly polarized light. Thereafter, the light transmitted through the half-wave plate 24 and the half mirror 26 is reflected by the dichroic mirror 27 and enters the lotion prism 28 which is a polarization optical element. The lotion prism 28 is made of a birefringent material (for example, calcite), and separates incident light into two kinds of polarized light (S-polarized light and P-polarized light) orthogonal to each other and then emits them in different directions. The S-polarized light is condensed by the condensing lens 29 onto the reflecting surface provided on the back surface of the cantilever 12 and is reflected at the apex. Thereafter, the light enters the lotion prism 28 again through the same optical path as the incident optical path. On the other hand, the P-polarized light is condensed on the surface of the test object 1 and reflected at the apex. The reflected light enters the lotion prism 28 again through the same optical path. Both S-polarized light and P-polarized light transmitted through the lotion prism 28 pass through a common optical path as parallel light and are reflected by the dichroic mirror 27 and the half mirror 26. Then, the light passes through the quarter-wave plate 30, the half-wave plate 31, the half mirror 33, and the half mirror 34, and reaches the polarization beam splitter 35. The light is again split into S-polarized light and P-polarized light by the polarization beam splitter 35, and enters the photodetector 36 and the photodetector 37. The two photodetectors acquire light intensity information and transmit it to the arithmetic unit 38. The computing device 38 analyzes two types of intensity information and calculates the amount of cantilever displacement caused by interference fringes.

  The analysis contents in the arithmetic unit 38 will be described in further detail. If the optical information acquired by the photodetector 36 is A1, and the optical information acquired by the photodetector 37 is A2, the following information can be expressed.

ここで、Ａは光情報の大きさを定義する定数であり、λは使用している光の波長、ΔＬはカンチレバー１２と被検物１の間の相対的な変位情報、αはローションプリズム２８で分離したＳ偏光とＰ偏光の光路長差から決まる初期位相である。Ｖは位相変化に対する光情報変化の感度を表す感度係数であり、０以上１以下の値をとる。また、Φは２分の１波長板３１を回転させる回転機構３２の回転角度に応じて変化する位相である。

Here, A is a constant that defines the size of the optical information, λ is the wavelength of the light being used, ΔL is the relative displacement information between the cantilever 12 and the test object 1, and α is the lotion prism 28. This is the initial phase determined from the optical path length difference between the S-polarized light and the P-polarized light separated by. V is a sensitivity coefficient representing the sensitivity of the optical information change with respect to the phase change, and takes a value from 0 to 1. Further, Φ is a phase that changes according to the rotation angle of the rotation mechanism 32 that rotates the half-wave plate 31.

  In the arithmetic unit 38, these two types of signals are processed as follows to obtain displacement information S.

ここでΦがαを打ち消すように２分の１波長板３１の回転角度を調整し、かつ、ΔＬは非常に微小量であるとすると、変位情報Ｓは次式のように近似できる。

Here, if the rotation angle of the half-wave plate 31 is adjusted so that Φ cancels α, and ΔL is a very small amount, the displacement information S can be approximated by the following equation.

このようにして求められた変位情報Ｓを用いると、次式が得られる。

When the displacement information S obtained in this way is used, the following equation is obtained.

上式よりカンチレバー１２と被検物１との間の相対的な変位情報を得ることができる。上式に含まれる感度係数Ｖは、Ｓ偏光とＰ偏光の重ね具合の良し悪しにより変化する値である。干渉縞がいわゆる縞一色状態であり、かつ高コントラストであれば、干渉縞の感度係数Ｖは１に近づく。

From the above equation, relative displacement information between the cantilever 12 and the test object 1 can be obtained. The sensitivity coefficient V included in the above equation is a value that changes depending on whether the S-polarized light and the P-polarized light are superimposed. If the interference fringes are in a so-called fringe monochromatic state and have a high contrast, the sensitivity coefficient V of the interference fringes approaches 1.

  As will be described later, this embodiment includes an adjustment mechanism for bringing the interference fringe sensitivity coefficient V close to 1. However, for high-precision measurement, the interference fringe sensitivity coefficient V is accurately measured, It is desirable to calculate displacement information using it.

  In order to obtain an accurate value of the interference fringe sensitivity coefficient V, intensity information of the photodetector 36 is acquired while the half-wave plate 31 is rotated by the rotation mechanism 32. By rotating the half-wave plate 31, the phase α included in the following expression representing the intensity information changes.

位相Φの変化に伴って強度情報が強弱し、最小強度Ａｍｉｎと最大強度Ａｍａｘを知ることができる。最低強度Ａｍｉｎと最大強度Ａｍａｘの値を用いると、干渉縞の感度係数Ｖは次式で求めることができる。

As the phase Φ changes, the intensity information becomes stronger and the minimum intensity Amin and the maximum intensity Amax can be known. When the values of the minimum intensity Amin and the maximum intensity Amax are used, the interference fringe sensitivity coefficient V can be obtained by the following equation.

上式により求めた感度係数Ｖの実測値を用いて変位情報Ｓを計算することで、カンチレバー１２の変位を高精度に計測することができる。なお、感度係数Ｖの計測はフォトディテクタ３７より得られる強度情報により実施してもよい。

By calculating the displacement information S using the measured value of the sensitivity coefficient V obtained by the above equation, the displacement of the cantilever 12 can be measured with high accuracy. Note that the sensitivity coefficient V may be measured based on intensity information obtained from the photodetector 37.

  Next, various adjustment functions necessary for performing high-precision measurement will be described.

  In order to perform high-precision measurement in the present embodiment, it is desirable that the interference fringes detected by the photodetector 36 and the photodetector 37 are in a so-called fringe single color state. The interference fringes detected by the photodetector 37 are in a state where the phase is shifted by 180 degrees with respect to the interference fringes detected by the photodetector 36. Therefore, if one of the interference fringes is in a single color state, the other is also in a single color state.

  Therefore, in this embodiment, a CCD sensor 53 is provided as a sensor for adjusting the interference fringes to the one-color fringe state. Light that has been split by the half mirror 34, transmitted through the polarization beam splitter 51, and expanded by the beam expander 52 is incident on the CCD sensor 53. Accordingly, the interference fringes observed by the CCD sensor 53 are the same as the interference fringes detected by the photodetector 36. For this reason, by adjusting the tip tilt stage 4 so that the interference fringes observed by the CCD sensor 53 are in a striped color state, the interference fringes detected in the photo detector 36 and the photo detector 37 can be in a striped color state. .

  However, when the test object 1 is fixed with a large inclination, there is a possibility that the interference fringes cannot be observed in the CCD sensor 53. Therefore, in this embodiment, a position sensor 55 is provided. The light split by the half mirror 33 is incident on the position sensor 55. Therefore, the reflected light from the cantilever 12 and the reflected light from the test object 1 enter the position sensor 55. Then, the tip tilt stage 4 is adjusted so that two bright spots observed by the position sensor 55 overlap. Thereby, it can adjust so that the reflected light from the cantilever 12 and the reflected light from the to-be-tested object 1 may take a substantially common optical path. Therefore, the interference fringes can be observed in the CCD sensor 53, and the interference fringes can be adjusted to be in a single color state.

  In addition, the present embodiment includes a camera 56 and can observe the state of the tip of the cantilever. By using the camera 56, it is possible to adjust so that the light condensed by the condenser lens 29 is irradiated to a predetermined place on the back surface of the cantilever.

  The difference between the present embodiment described above and the conventional example shown in FIG. 5 is that the light incident on the test object 1 is focused light. As a result, the range in which the S-polarized light and the P-polarized light pass through different optical paths is from passing through the lotion prism 28 to being reflected by the cantilever 12 and the test object 1 and entering the lotion prism 28 again. There are many. Therefore, it is possible to reduce the influence of atmospheric refractive index fluctuations associated with fluctuations in temperature, atmospheric pressure, etc., as compared with the prior art, and the displacement measurement of the cantilever 12 can be made highly accurate.

  The present embodiment is also different from the conventional example in that the principal rays of S-polarized light and P-polarized light take different optical paths. As a result, it is possible to adopt a configuration in which the cantilever 12 is not disposed in the optical path where the P-polarized light enters the test object 1, and the generation of measurement noise can be suppressed.

  The angle at which the S-polarized light and the P-polarized light are separated by the lotion prism 28 is preferably designed according to the inclination (inclination angle) of the cantilever 12 with respect to the test object 1. More specifically, in FIG. 2, which is an enlarged view of the vicinity of the cantilever 12, it is desirable to design the lotion prism 28 and the condenser lens 29 so that θ1 and θ2 are equal. Here, θ1 is an angle formed by the S-polarized chief ray incident on the back surface of the cantilever 12 and the P-polarized chief ray incident on the test object 1. Θ2 is a design value of an angle formed between the reflection surface provided on the back surface of the cantilever 12 and the test object 1. In general, in order to avoid mechanical interference between the cantilever holder 11 and the test object 1, the device is designed with a certain angle θ 2, and θ 2 is also set to 10 degrees in this embodiment. In this embodiment, since the P-polarized chief rays are aligned and measured so that they are perpendicularly incident on the test object 1, when θ1 and θ2 are different and θ1 is smaller than necessary, the cantilever holder 11 and the test object 1 are measured. May cause mechanical interference.

  Further, the present embodiment includes a half-wave plate 24 and a rotation mechanism 25 as means for adjusting the light quantity ratio between the S-polarized light and the P-polarized light separated by the lotion prism 28. Here, the rotation mechanism 25 is a mechanism that rotates the half-wave plate 24 about the optical axis of the parallel light emitted from the collimator 23 as the rotation axis. When the half-wave plate 24 is rotated by the rotation mechanism 25, the polarization direction of the linearly polarized light incident on the half-wave plate 24 can be freely changed and emitted. This means that the ratio between the S-polarized light and the P-polarized light included in the emitted linearly polarized light can be freely changed. As a result, the light quantity ratio between the S-polarized light and the P-polarized light separated by the lotion prism 28 can be changed. Can be adjusted freely.

  When this light quantity ratio adjusting mechanism is used, even when the reflectance is different between the cantilever 12 and the test object 1, the light quantity of the reflected light from the cantilever 12 and the light quantity of the reflected light from the test object 1 are made equal. be able to. Therefore, the contrast of the interference fringes detected by the photodetector 36 and the photodetector 37 can be increased, and the displacement measurement of the cantilever 12 can be made more accurate than the conventional example shown in FIG.

  In this embodiment, a lotion prism is used as the polarizing optical element, but the same effect can be obtained by using a Wollaston prism instead. In this embodiment, the S-polarized light is irradiated on the back surface of the cantilever and the P-polarized light is irradiated on the test object. However, the S-polarized light and the P-polarized light may be reversed.

  FIG. 3 is a diagram illustrating a configuration of an atomic force microscope according to the second embodiment. The difference from the first embodiment is that the positions of the quarter-wave plate 30 and the half-wave plate 31 and the position of the half mirror 33 are reversed, and further, between the half mirror 33 and the position sensor 55, The polarization beam splitter 54 is inserted. Only the reflected light from the test object 1 is incident on the position sensor 55 and the reflected light from the cantilever 12 is not incident. Then, the tip tilt stage 4 is adjusted using the positional information of one bright spot to be observed so that the interference fringes are in a single color state. That is, the ideal position of the bright spot where the interference fringes are in a single-colored state is known in advance, and the tip tilt stage 4 is adjusted so that the bright spot moves to the ideal position.

  The feature of the present embodiment is that the bright spot position can be calculated more accurately by calculation by a computer because there is only one bright spot detected by the position sensor 55. For this reason, the alignment state of the test object 1 can be obtained with high accuracy only by a computer, and this is a form suitable for automatic measurement.

  FIG. 4 is a diagram illustrating a configuration of an atomic force microscope according to the third embodiment. The difference from the first and second embodiments is that the number of interference fringe detection photodetectors is reduced to one. The analysis contents in the arithmetic unit 38 in this case will be described. Assuming that the optical information acquired by the photodetector 36 is A1, as described in the first embodiment, it is expressed by the following equation.

ここで、Ａは光情報の大きさを定義する定数であり、λは使用している光の波長、ΔＬはカンチレバー１２と被検物１の間の相対的な変位情報、αはローションプリズム２８で分離したＳ偏光とＰ偏光の光路長差から決まる初期位相である。Ｖは干渉縞の感度係数であり０以上１以下の値をとる。また、Φは２分の１波長板３１を回転させる回転機構３２の回転角度に応じて変化する位相である。

Here, A is a constant that defines the size of the optical information, λ is the wavelength of the light being used, ΔL is the relative displacement information between the cantilever 12 and the test object 1, and α is the lotion prism 28. This is the initial phase determined from the difference in optical path length between the S-polarized light and the P-polarized light separated by. V is a sensitivity coefficient of interference fringes and takes a value of 0 or more and 1 or less. Further, Φ is a phase that changes according to the rotation angle of the rotation mechanism 32 that rotates the half-wave plate 31.

  Here, if the rotation angle of the half-wave plate 31 is adjusted so that Φ cancels α, and ΔL is a very small amount, the optical information A1 can be approximated by the following equation.

このようにして求められた光情報Ａ１を用いると、次式が得られる。

When the optical information A1 thus obtained is used, the following equation is obtained.

上式より、カンチレバー１２と被検物１との間の相対的な変位情報を得ることができる。上式に含まれる光情報の大きさＡと干渉縞の感度係数Ｖは、２分の１波長板３１を回転機構３２により回転させながらフォトディテクタ３６の強度情報を取得し、最小強度Ａｍｉｎと最大強度Ａｍａｘを求めることで次式のように計算することができる。

From the above equation, relative displacement information between the cantilever 12 and the test object 1 can be obtained. The magnitude A of the optical information and the sensitivity coefficient V of the interference fringes included in the above formula are obtained by obtaining the intensity information of the photodetector 36 while rotating the half-wave plate 31 by the rotation mechanism 32, and the minimum intensity Amin and the maximum intensity. By calculating Amax, it can be calculated as follows.

なお、本実施例の場合、カンチレバー変位の符号がわからない欠点がある。しかしながら、カンチレバーの振幅情報を用いて計測を行なうＡＣモードではカンチレバー変位の符号情報を必要としないため、本実施例を適用することができる。

In the case of this embodiment, there is a drawback that the sign of the cantilever displacement is not known. However, in the AC mode in which measurement is performed using the amplitude information of the cantilever, the sign information of the cantilever displacement is not required, and therefore this embodiment can be applied.

1 is a schematic diagram illustrating a configuration of an atomic force microscope according to Example 1. FIG. It is the figure which expanded the cantilever peripheral part. 6 is a schematic diagram illustrating a configuration of an atomic force microscope according to Example 2. FIG. 6 is a schematic diagram illustrating a configuration of an atomic force microscope according to Example 3. FIG. It is a schematic diagram which shows one prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Test object 2 Base 3 XYZ stage 4 Tip tilt stage 6 Housing 7 XY scanner 8 Tube scanner 9 Cantilever mounting block 10 Excitation piezoelectric actuator 11 Cantilever holder 12 Cantilever 21 Light source 22 Optical fiber 23 Collimator 24 1/2 wavelength plate 25 Rotating mechanism 26 Half mirror 27 Dichroic mirror 28 Lotion prism 29 Condensing lens 30 Quarter wavelength plate 31 Half wavelength plate 32 Rotating mechanism 33 Half mirror 34 Half mirror 35 Polarizing beam splitter 36 Photo detector 37 Photo detector 51 Polarizing beam Splitter 52 Beam expander 53 CCD sensor 54 Polarizing beam splitter 55 Position sensor 56 Camera

Claims (7)

A cantilever provided with a probe is brought close to the object to be detected, an atomic force generated between the probe and the object to be detected is detected, and scanning is performed while keeping the atomic force constant. In an atomic force microscope that measures the surface shape of an object,
A light source;
A polarizing optical element that divides light from the light source into two types of polarized light;
One of the two kinds of polarized light is condensed on the cantilever, and the other polarized light is condensed on the test object, and the interference fringes caused by the two kinds of reflected light obtained by reflecting the interference light are respectively obtained. An optical system to obtain,
An atomic force microscope comprising: detecting means for detecting displacement of the cantilever from the interference fringes.   The atomic force microscope according to claim 1, wherein the two types of polarized light take different optical paths when entering the cantilever and the test object.   The atomic force microscope according to claim 1 or 2, wherein an angle formed by the two types of polarized light is equal to an inclination angle of the cantilever with respect to the test object.   The atomic force microscope according to any one of claims 1 to 3, further comprising means for adjusting a light amount ratio of the two types of polarized light.   The means for adjusting the light amount ratio includes a wave plate that changes a polarization direction of light from the light source, and a rotation mechanism that rotates the wave plate around an optical axis of the light. Item 5. The atomic force microscope according to Item 4.   The atomic force microscope according to any one of claims 1 to 5, wherein the detection means includes sensitivity information acquisition means for acquiring sensitivity information used when calculating an optical path length difference from the interference fringes.   The sensitivity information acquisition means includes a quarter-wave plate disposed in a common optical path of the two types of polarized light, a half-wave plate, and a rotation mechanism that rotates the half-wave plate; The atomic force microscope according to claim 6, comprising:

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