JP5699105B2 - Surface measurement method and apparatus - Google Patents

Description

The present invention relates to a surface measurement method and apparatus.

As a method for measuring the amount of displacement or movement of an object, a method using optical interference is widely known. For example, a scanning probe microscope (SP known as a fine three-dimensional shape measurement tool)
M: Atomic Force Microscope (AFM), which is a type of Scanning Probe Microscope (MFM), is replaced by a conventional capacitive sensor as a displacement sensor for measuring the position of the probe. As a means that can be measured, a displacement sensor using optical interference as disclosed in Non-Patent Document 1 is about to be applied. In this optical interference displacement sensor, the laser light from the laser light source is divided into two, one is irradiated to the reference mirror, the other is irradiated to the target mirror mounted on the probe scanning mechanism, and both reflected light (reference light and After the phase difference of 0, π / 2, π, 3π / 2 is provided between the measurement light), the four phase shift interference lights generated are received and converted into electrical signals,
Desired arithmetic processing is performed on the four phase shift interference signals to determine the movement amount of the probe.

Semiconductor MIRAI Project Lithography Related Measurement Technology Workshop (October 19, 2004), p.28 (2004)

However, in the above-described optical interference displacement sensor, 0, π / 2, π between the reference light and the measurement light
As a method of providing a phase difference of 3π / 2, a prism for combining reference light and measurement light,
A non-polarizing beam splitter for separating the combined light into two optical paths and two polarizing beam splitters for providing a phase shift between the reference light and the measuring light constituting the combined light in the two optical paths are used. For this reason, the entire optical system is enlarged, and the optical interference displacement sensor is increased in size to limit the application target.

For this reason, it is not possible to mount three large optical interference displacement sensors for the x, y, and z axes as compared with conventional capacitance sensors in an AFM applied to a mass production line such as a semiconductor manufacturing process. It was close to possible. Further, since the optical paths of the four interference lights given the phase shift are separated from each other, when disturbances such as different temperature distribution, humidity distribution, atmospheric pressure distribution, density distribution, and air flow change are superimposed on the four optical paths, 4 There is an essential problem that an error occurs in the calculation processing for obtaining the amount of movement of the object from two phase shift interference signals.

Therefore, in the present invention, a displacement measuring method that can generate at least four phase shift interference lights without using a large optical system and can accurately determine the amount of displacement or movement of an object without the influence of disturbance. And an apparatus for the same.

In order to achieve the above object, in the present invention, a surface measuring device includes a probe and an actuator that scans the probe relative to the object and contacts the probe with the object. When the four-divided position sensor for detecting the contact force between the object and the probe, separating means for separating a light source, the light from the light source into a first light and second light, the Interference light is generated by causing a plurality of optical phase differences on the same plane between the first light transmitted through the separating means and reflected by the actuator and the second light reflected by the separating means . Interference means and detection means for determining the position of the probe from the interference light are provided.

In the present invention, the interference means for generating a plurality of interference lights by causing a plurality of optical phase differences between the reflected light from the object and the second light on the same plane to interfere with each other, A polarizing element array was used.

  In the present invention, the polarizing element array is a photonic crystal array.

In the present invention, the method for separating the light from the light source into the first light and the second light is constituted by a diffractive polarizing element.
In the present invention, the method for separating the light from the light source into the first light and the second light is composed of a photonic crystal.

According to the present invention, at least four phase shift interference lights can be generated by an extremely small optical interference displacement sensor without using a large interferometer, and the displacement or movement amount of an object can be accurately detected without being affected by disturbance. The scope of application will be greatly expanded. As a result, probe scanning of scanning probe microscopes including AFM can be performed with sub-nanometer precision, and fine three-dimensional structure elements such as semiconductor devices can be achieved with sub-nanometer resolution and high reproducibility. There is an effect that it is possible to measure optical information and minute unevenness information. In addition, there is an effect that it becomes possible to inspect a semiconductor wafer, a magnetic disk, a micro unevenness distribution of sub nanometers or less and a micro uneven defect on the air bearing surface of the magnetic head.

2 is a perspective view and a block diagram illustrating a configuration of an optical interference displacement sensor in Embodiment 1. FIG. It is a perspective view which shows the structure and function of a reference mirror using a diffractive polarizing element. 3 is a perspective view illustrating a configuration of a phase shift element using a photonic crystal in Example 1. FIG. It is a perspective view which shows the structure of the reference mirror using a photonic crystal, and a quarter wavelength plate. FIG. 6 is a perspective view and a block diagram illustrating a schematic configuration of an AFM according to a second embodiment. FIG. 6 is a sample cross section and a perspective view of a cantilever showing step-in scanning of an AFM probe in Example 2. It is a graph which shows the relationship between the step-in scanning in Example 2, and the probe-sample contact force. It is the perspective view and block diagram which show the schematic structure of the surface unevenness | corrugation defect inspection apparatus in Example 3. FIG. FIG. 6 is a perspective view and a block diagram showing a configuration of an optical interference displacement sensor in Embodiment 4. 6 is a perspective view showing a configuration of a phase shift element using a photonic crystal in Example 4. FIG. 6 is a front view showing a light receiving surface of a split photoelectric conversion element in Example 4. FIG. FIG. 10 is a perspective view and a block diagram showing a configuration of an optical interference displacement sensor in Embodiment 5. FIG. 10 is a perspective view illustrating a configuration of a phase shift element using a photonic crystal in Example 5. 10 is a front view showing a light receiving surface of a split photoelectric conversion element in Example 5. FIG.

In recent years, photonic crystals that can control the polarization and transmission / reflection characteristics of incident light with a fine structure of a wavelength or less have attracted attention. In the present invention, phase shift interference light is generated using this photonic crystal, and the amount of displacement or movement of the object is obtained with high accuracy without the influence of disturbance.

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

A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the optical interference displacement sensor of this embodiment includes a light source unit (not shown), a sensor unit 100 and a displacement output unit 70.

In the light source unit, for example, a linearly polarized laser beam having a wavelength of 632.8 nm from a frequency-stabilized He—Ne laser is applied to the sensor unit 100 in a polarization direction of 45 ° by the polarization plane preserving fiber 2.
To guide the light.

The sensor unit 100 includes an interferometer 600 and a displacement calculation processing unit 50. In the interferometer 600, the 45 ° polarized light emitted from the polarization preserving fiber 2 is converted into parallel light 4 by the collimator 3.
Further, the light is transmitted through the polarizing element 5 such as a Glan-Thompson prism, and the transmitted light 6 is reflected by the prism mirror 7 and the non-polarizing beam splitter 8 to enter the reference mirror 9. As shown in FIG. 2, the reference mirror 9 is made of a diffraction grating 9b made of a metal material such as Al on a synthetic quartz substrate 9a.
Is formed. The polarized beam 6 in the 45 ° direction incident on the diffraction grating is composed of two orthogonally polarized components that are vector-resolved, and the S-polarized component 25s parallel to the longitudinal direction of the diffraction grating is reflected by the diffraction grating and is orthogonally polarized P-polarized component. 25p is transmitted through the diffraction grating. In other words, this diffraction grating is a so-called diffractive polarizing element (Wire Grid Polarizer).
As a property. In this embodiment, the pitch of the diffraction grating 9b is 144 nm, and the line width is 65.
nm and height were set to 165 nm.

The S-polarized beam 6r reflected by the reference mirror 9 is used as reference light. The transmitted P-polarized beam 6m is used as measurement light. The P-polarized beam 6m becomes circularly polarized light after passing through the quarter-wave plate 10, is reflected by the target mirror 12 placed on the measurement object 31, and is again 1/4.
After passing through the wave plate 10, it becomes S-polarized light, reflected by the reference mirror 9, passed through the quarter-wave plate 10 and then reflected by the target mirror 12 as circularly polarized light, and after passing through the quarter-wave plate 10, it becomes P-polarized light. It passes through the mirror 9. In other words, the measurement light 6m travels back and forth two times along the optical path between the reference mirror 9 and the target mirror 12, and the movement amount 31d of the measurement object 31 is doubled and detected. The S-polarized beam 6 r reflected by the reference mirror 9 and the transmitted P-polarized beam 6 m are combined as an orthogonally polarized beam 14 and transmitted through the non-polarized beam splitter 8.

After passing through the opening 13 for removing stray light, the orthogonally polarized beam 14 is split into four orthogonally polarized beam beams 17 by two opposing pyramid-shaped quadrangular pyramid prisms 15a and 15b. The beam splitting method is not limited to such a prism, and a diffractive optical element or the like can also be applied. The four orthogonally polarized beam beams 17 are transmitted through the phase shift elements 18 and 19 so that 0, π / 2, π, 3π
Polarization interference occurs in a state where a phase shift of / 2 is given, and four phase shift interference lights 20 are generated.

As shown in FIG. 3, the phase shift element 18 is divided into two parts, the lower half is made of synthetic quartz 18d, and the upper half is made of a photonic crystal 18c. As shown in the enlarged view, the photonic crystal 18c forms a horizontal line-and-space diffraction grating having a pitch smaller than the wavelength of incident light on the synthetic quartz substrate 18c1, and a dielectric having a different refractive index thereon. The thin films 18c2 and 18c3 are laminated. The cross section of the thin film layer deposited on the diffraction grating maintains a triangular corrugated shape in the film thickness direction due to the unevenness of the diffraction grating. Thin film materials include Si, S
iO ₂ , TiO ₂ , Ta ₂ O ₅ , and Nb ₂ O ₅ are applicable. A multilayer thin film structure based on such a diffraction grating becomes a photonic crystal whose crystal axis direction is the direction of the diffraction grating, exhibits birefringence characteristics due to diffraction and interference action between the multilayer thin films, and polarization and transmission of incident light. -It is possible to control the reflection characteristics (see: Photonic Lattice product catalog).

The diffraction grating pitch, depth, and film thickness of each thin film are controlled in consideration of the wavelength of incident light and the desired characteristics. Another major feature is that polarizing elements and wavelength elements having different crystal axis directions can be formed in an array on a single substrate by using a film forming technique such as photolithography technique or sputtering used in semiconductor element manufacturing. is there. The photonic crystal 18c has a function as a quarter-wave plate, and a thick arrow indicates the crystal axis direction. That is, as shown in FIG. 1, 2 of the four orthogonally polarized beams 17 that pass through the photonic crystal 18c.
For two orthogonally polarized beams, a phase difference of π / 2 occurs between the two polarization components. On the other hand, the remaining two orthogonally polarized beams are transmitted through the synthetic quartz 18d and no phase difference occurs.

The phase shift element 19 is divided into two as shown in FIG. 3, and the left half is composed of a photonic crystal 19a having a crystal axis direction of 45 °, and the right half is a photo having a crystal axis direction of 45 ° in the opposite direction. It consists of a nick crystal 19b. Like the photonic crystal 18c, the photonic crystal 19a forms a line and space diffraction grating in the 45 ° direction with a pitch smaller than the wavelength of the incident light on the synthetic quartz substrate 19a1, as shown in the enlarged view. The dielectric thin films 19a2 and 19a3 having different refractive indexes are stacked on top. The structure of the photonic crystal 19b is the same. The photonic crystals 19a and 19b have a function as a polarizing element, and a thick arrow indicates the crystal axis direction. That is, as shown in FIG. 1, of the four orthogonal polarization beam beams 17, two polarization components constituting two orthogonal polarization beams that pass through the photonic crystal 19a and two orthogonal polarization beams that pass through the photonic crystal 19b. Both polarization components interfere with each other in a state where a phase difference of π is given between the two polarization components constituting the beam.

That is, polarization interference occurs in a state where phase shifts of 0, π / 2, π, and 3π / 2 are given between the respective orthogonal polarization components of the four orthogonal polarization beams 17 transmitted through the phase shift elements 18 and 19. Four phase shift interference lights 20 are generated. In order to avoid the influence of disturbance light, the four phase shift interference lights 20 pass through an interference filter 21 having a transmission center wavelength at a wavelength of 632.8 nm, and then are respectively received by 22 by four photoelectric conversion elements such as photodiodes. , Amplifier 23
Are output as four phase shift interference signals 41a, 41b, 41c and 41d.

The four phase shift interference signals 41a, 41b, 41c, and 41d are represented by (Equation 1) to (Equation 4), respectively.
).

I _a = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ) (
Number 1)

I _b = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ + π)
= I _m + I _r -2 (I _m · I _r ) ^1/2 cos (4πnD / λ)
(Equation 2)

I _c = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ + π / 2)
= I _m + I _r +2 (I _m · I _r ) ^1/2 sin (4πnD / λ)
(Equation 3)

I _d = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ + 3π / 2)
= I _m + I _r -2 (I _m · I _r ) ^1/2 sin (4πnD / λ) (
(Equation 4)

Here, I _m is the detected intensity of the probe light, the detection intensity of I _r is the reference light, n is the refractive index of the air, D
Is the amount of movement 31d of the measuring object 31, and λ is the wavelength of the laser beam 4.

In the displacement calculation processing unit 50, the movement amount D of the measurement object 31 is calculated based on (Equation 5) and displayed on the displacement output unit 70 as the movement amount signal 61.

D = (λ / 4πn) tan ⁻¹ {(I _c −I _d ) / (I _a −I _b )} (Equation 5)

In this embodiment, a diffractive polarizing element (Wire Grid Polari) is used as the reference mirror 9.
However, as is apparent from the above description, it is possible to use a photonic crystal 9c having a crystal axis direction in the horizontal direction as shown in FIG. Also, the quarter wave plate 1
Similarly for 0, it is also possible to use a photonic crystal 10c having a crystal axis direction in the 45 ° direction. In order to further simplify the interferometer 600, the phase shift element 1 in FIG.
9 is constituted only by the photonic crystal 19a, phase shift interference signals 41a and 41c represented by (Equation 1) and (Equation 3) are obtained, and the movement amount D of the measurement object 31 is obtained from these two interference signals. It is also possible to ask for it.

As is apparent from FIG. 1, 2 of the measurement light 6m and the reference light 6r directed to the target mirror 12
One beam is emitted from the light source unit, enters the sensor unit 100, reaches the reference mirror 9, and further receives light from the reference mirror 9 by the four photoelectric conversion elements 22.
It passes through the same optical path. That is, the configuration is a common optical path type interferometer. Therefore, even if a temperature distribution, refractive index distribution, or mechanical vibration occurs due to air fluctuations in the optical path, these disturbances affect both beams equally, so when both beams interfere, The influence is completely cancelled, and the interference light is not affected by the disturbance.

Only the measurement light 6m exists only in the optical path between the reference mirror 9 and the target mirror 12. For example, since the stroke of the scanning probe microscope or the like is about several hundred microns at most, the reference mirror 9 and the target mirror 12 This gap can be set to 1 mm or less, and the influence of disturbance in such a minute gap can be ignored. The intensity variation of the laser beam itself, the (number 1) to the probe light detected intensity I _m in equation _(4), but the variation of the reference light detection intensity I _r, the displacement processing unit (5) in 50 It is canceled out by the subtraction process and the division process.

Furthermore, in the optical interference displacement sensor of this embodiment, four orthogonally polarized beams are generated with a simple configuration, and four phase shift interference lights are generated in parallel and spatially received by phase shift elements arranged in an array. As a result, the optical components are significantly reduced compared to the conventional phase shift interferometer, and the displacement sensor is greatly reduced in size. Specifically, the interferometer 60
The size of 0 can be reduced to about 20 × 15 × 50 mm or less. In addition, because the four phase-shift interference lights pass through close optical paths, even if disturbances such as temperature distribution, humidity distribution, atmospheric pressure distribution, density distribution, and airflow change due to air fluctuations are superimposed between the optical paths, The effect can be minimized.

As described above, the movement amount and position of the measurement object can be changed from sub-nanometers to picometers or less without controlling environmental factors such as temperature, humidity, atmospheric pressure, density, and acoustic vibration with high accuracy by the optical interference displacement sensor of this embodiment. It is possible to measure stably with high accuracy.

A second embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 5, in this embodiment, the optical interference displacement sensor shown in the first embodiment is mounted on an AFM. The AFM in this embodiment is a stage unit 7 on which a sample can be placed and moved in the three-dimensional direction of XYZ.
00, AFM unit 800 that measures the sample surface by scanning the probe, AF from the measurement data
A signal processing / control unit 900 that generates an M image and controls the whole, and a monitor optical system unit 500 for observing and positioning a measurement target part on the sample are configured.
The stage unit 700 is an XY that can place the sample 200 and move in a three-dimensional direction of XYZ.
A Z stage 300 and a driver 301 are provided. Sample 200 is XYZ stage 300
The sample is placed on and driven by the driver 301 and positioned at a desired measurement position while observing the surface of the sample 200 by the monitor optical system unit 500.

The AFM unit 800 has an HDC (High Density Carbon) at the tip.
) Or the like to which the probe 170 is fixed, the XYZ piezoelectric element actuator 150, the driver 151, and the position of the probe 170 (XYZ piezoelectric element actuator 15).
X, y, z-axis sensor units 100x, 100y, 100z for measuring (zero position), light source unit 1, polarization plane preserving fiber 2x for guiding linearly polarized laser light from light source unit 1 to each optical interference displacement sensor, 2y, 2z, laser light (wavelength 405) on the back of the cantilever 160
nm) a semiconductor laser 180 that irradiates 185, a quadrant position sensor 190 that detects reflected light from the cantilever 160, and a drive circuit 181 that controls the semiconductor laser 180.
It has. On the surface of the XYZ piezoelectric element actuator 150, target mirrors 12x (not shown), 12y (not shown), and 12z for an optical interference displacement sensor are mounted.

The monitor optical system unit 500 includes an imaging lens and an imaging camera. While observing an optical image of the surface of the sample 200 with the imaging camera, the XYZ stage 300 on which the sample 200 is placed is driven by the driver 301, and the sample 200. The desired measurement position is positioned under the probe 170.

The image forming unit 410 of the signal processing / control unit 900 processes the position measurement signals 61x, 61y, 61z of the XYZ piezoelectric element actuator 150 based on the output signal 195 from the quadrant position sensor 190 to generate an AFM image. . Image forming unit 4
10 is sent to the overall control unit 420 and displayed on the output screen of the output unit 430 such as a display.

Next, a method for measuring an AFM image using the optical lever principle will be described. The AFM image shows the probe 170 on the sample 20 while keeping the contact force between the probe 170 and the sample 200 constant.
0 is scanned and obtained from the movement amount of the probe 170 at that time (movement amount of the XYZ piezoelectric element actuator 150). First, how to obtain the contact force between the probe 170 and the sample 200 will be described. Laser light (wavelength 405 nm) 185 from the semiconductor laser 180 driven by the drive circuit 181 is irradiated on the back surface of the cantilever 160 having the probe 170 fixed to the tip, and the reflected light is reflected by the four-division position sensor 190. Received light. The XYZ piezoelectric element actuator 150 is driven by the driver 151 to lower the cantilever 160, and the probe 170 fixed to the tip is brought into contact with the sample 200. When the cantilever 160 is further lowered in this state, the inclination of the cantilever 160 is changed, the reflection direction of the laser irradiated on the back surface of the cantilever 160 is changed, and the incident position of the laser beam on the four-division position sensor 190 is changed. As a result, the output signal 195 from the quadrant position sensor 190 changes. The contact force can be obtained by comparing the changed signal with contact force data based on the relationship between the output signal from the four-division position sensor 190 and the inclination of the cantilever 160 obtained in advance.

Next, a procedure for measuring the surface of the sample will be described. First, the XYZ stage 300 is driven, and the probe 17 is attached to the tip of the cantilever 160 in the measurement region of the sample 200.
Position at the bottom of zero. Next, as shown in FIG.
The contact state (contact force) between the probe 170 and the sample surface 200a is determined by a four-division position sensor 19.
While monitoring with the output signal from 0, the cantilever 160 is lowered by the XYZ piezoelectric element actuator 150 (Z direction scanning 175), and the descent is stopped when a predetermined contact force is reached.

After measuring the position of the probe 170 (position of the XYZ piezoelectric element actuator 150) at the descending point 176 by the optical interference displacement sensors 100x, 100y, 100z, the cantilever 1 is measured.
60 (Z-direction scanning 177), based on the output signal from the four-division position sensor 190, if the probe 170 is completely detached from the sample 200, it is determined whether or not measurement in the measurement region has been completed. If not completed, the XYZ piezoelectric element actuator 150 is driven to move the cantilever 160 to the next measurement point (X scanning 178). The amount of movement (feed pitch) in X scanning is determined according to the resolution required for observation. At the next measurement point, the cantilever 160 is lowered again, and the position of the probe 170 is measured.

The above step-in operation is repeatedly performed over the two-dimensional measurement region (XY region) by the XYZ piezoelectric element actuator 150, and then the measurement is completed. Here, the method of measuring the two-dimensional measurement area is scanned in the same manner as a raster scan in a television. The feed pitch (adjacent scanning interval) in the Y direction at this time is determined according to the resolution required for observation.

The XYZ piezoelectric element actuator 150 driven by the driver 151 scans in the XYZ directions and the positioning of the sample 200 by the XYZ stage 300 is performed by the signal processing / control unit 9.
Centralized control is performed by the 00 scan control unit 400. The control of the contact force between the probe 170 and the sample 200 and the measurement of the position of the probe 170 (the position of the XYZ piezoelectric element actuator 150) by the optical interference displacement sensors 100x, 100y, 100z are all signal processing / control units. Centralized control is performed by an overall control unit 420 in 900. Scan control unit 400
To XYZ scanning signals of the XYZ piezoelectric element actuator 150 are also sent to the overall control unit 4.
20, the position measurement signal of the probe 170 is sent to the image forming unit 410, respectively.
An FM image is generated and output to the output unit 430 such as a display via the overall control unit 420.

FIG. 7 shows the relationship between the step-in scanning and the probe-sample contact force. Contact force change curve 17
As shown in FIG. 9, as the probe 170 rises and retreats from the sample 200, the contact force changes from the push-in direction to the pull-in direction, and the pull-in force becomes maximum at the moment of separation from the sample. After detachment, the contact force is not received at all while moving to the next measurement point and approaching the sample again. When the probe 170 starts to approach again, a force in the pushing direction is applied at the moment when the probe 170 comes into contact with the sample 200, and when the set contact force is reached, the cantilever 160 stops descending. It is desirable that the set contact force is 1 nN or less, preferably sub nN to pN. The detection of the contact force is not limited to the above-mentioned optical lever method, and the cantilever is finely vibrated in the Z direction with a sub-nanometer order amplitude and MHz order frequency from a separately provided piezoelectric element actuator. It is also possible to detect from a change in vibration frequency.

Further, the present invention is not limited to the step-in scanning AFM, and can be applied to the measurement of the probe position in the AFM such as tapping scanning. In addition, the present invention is not limited to the AFM, and other scanning probe microscopes such as SNOM (Scanning)
The present invention is also applicable to probe position measurement and control in Near-Field Optical Microscope (Near Field Scanning Microscope) and STM (Scanning Tunneling Microscope).

As shown in FIG. 5, according to the present embodiment, since the small optical interference displacement sensor shown in the first embodiment can be mounted on the AFM and the position of the probe can be measured, The same effect as the embodiment can be obtained, and the position of the probe can be stably measured with an accuracy of sub-nanometer to picometer. As a result, the resolution of the two-dimensional AFM image is improved and the image reproducibility can be dramatically improved.

A third embodiment of the present invention will be described with reference to FIG. As shown in FIG.
The optical interference displacement sensor shown in the first embodiment is mounted on a surface irregularity inspection apparatus.
The surface irregularity inspection apparatus according to the present embodiment includes a stage unit 1000 on which a sample can be placed and scanned in a three-dimensional direction of XYZ, and a surface inspection unit 1100 that inspects the sample surface by relatively scanning a probe. It comprises a signal processing / control unit 1200 for generating a defect detection image from the measurement data and controlling the whole, and a monitor optical system unit 500 for observing and positioning a portion to be inspected on the sample.

The stage unit 1000 includes an XYZ stage 350 and a driver 351 on which the sample 210 is placed and can be scanned in the XYZ three-dimensional direction. Sample 210 is XYZ stage 3
50, and is driven by a driver 351, and the sample optical system unit 500
After being positioned at a desired inspection position while observing the surface of 0, the surface irregularities are inspected by scanning in the XY directions.

The surface inspection unit 1100 is a polarization plane that guides linearly polarized laser light from the optical interference displacement sensor 100, the condensing lens 215, the light source unit 1, and the light source unit 1 to the optical interference displacement sensor 100. A storage fiber 2 is provided. For example, a solid-state laser having a wavelength of 532 nm is used for the light source unit. Since the configuration and function of the optical interference displacement sensor 100 are the same as those in the first embodiment, description thereof is omitted. The measurement light 6 m emitted from the optical interference displacement sensor 100 is condensed on the surface of the sample 210 by the condenser lens 215. When the NA (Numerical Aperture) of the condensing lens 215 is 0.8, the condensing spot diameter is about 0.8 μm. In order to maintain this spot diameter during XY scanning of the sample 210, an autofocus unit (not shown) may be provided as necessary.

The monitor optical system unit 500 includes an imaging lens and an imaging camera. While observing an optical image on the surface of the sample 210 with the imaging camera, the XYZ stage 350 on which the sample 210 is mounted is driven by a driver 351, and the sample 210. The desired inspection position is positioned under the condensing lens 215 stored in advance.

In the defect detection unit 460 of the signal processing / control unit 1200, the optical interference displacement sensor 1
Based on the 00 measurement signals 61 and 230 and the XY drive signal of the XYZ stage 350, a surface unevenness image is generated. Further, in the defect detection unit 460, a defect having an unevenness higher than a preset height is extracted, sent to the overall control unit 470 together with the surface unevenness image, and displayed on the output screen of the output unit 480 such as a display. Is done.

Next, a procedure for inspecting the uneven state of the surface of the sample 210 will be described. First, the surface inspection unit 1100 is retracted from the optical axis of the monitor optical system unit 500, the XYZ stage 350 is driven, and the inspection area of the sample 210 is stored in advance.
Position at the bottom of 5. Next, as shown in FIG. 8, after the surface inspection unit 1100 is moved on the optical axis of the monitor optical system unit 500, the XYZ stage 350 is driven in the XY directions, and the sample is scanned in the same manner as raster scanning on a television. 210 is scanned (continuous scanning in the X direction). The feed pitch (adjacent scanning interval) in the Y direction at this time is determined according to the resolution required in the inspection. Sample 210 at each scanning position based on (Equation 5)
Since the surface unevenness amount D is calculated and output as the unevenness measurement signals 61 and 230, the surface unevenness image of the inspection region can be generated from the XY scanning signal of the XYZ stage 350 and the measurement signals 61 and 230.

XY scanning for positioning and inspection of the sample 210 by the XYZ stage 350 is comprehensively controlled by the scanning control unit 450 of the signal processing / control unit 1200. The inspection of the surface of the sample 210 by the optical interference displacement sensor 100 is comprehensively controlled by the overall control unit 470 in the signal processing / control unit 1200. The XY scanning signal of the XYZ stage 350 is sent from the scanning control unit 450, and the optical interference displacement sensor 100 is sent from the overall control unit 470.
Measurement signals 61 and 230 are sent to the defect detection unit 460, respectively, and a surface unevenness image is generated, and a defect having an unevenness higher than a preset height is extracted to control the overall control unit 470. To the output unit 480 such as a display.

As shown in FIG. 8, according to the present embodiment, the concave / convex defect on the sample surface can be inspected by the small optical interference displacement sensor shown in the first embodiment, and therefore, the same as the first embodiment. As a result, it is possible to stably measure irregularities on the sample surface with a sensitivity of sub-nanometers to picometers or less. As a result, for example, it is possible to dramatically improve the sensitivity of inspection of irregularities on semiconductor wafers, magnetic disks, magnetic head floating surfaces, and the like.

A fourth embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 8, the optical interference displacement sensor of the present embodiment includes a light source unit (not shown), a sensor unit 100, and a displacement output unit 70.

In the light source unit, for example, a linearly polarized laser beam having a wavelength of 632.8 nm from a frequency-stabilized He—Ne laser is applied to the sensor unit 100 in a polarization direction of 45 ° by the polarization plane preserving fiber 2.
To guide the light.

The sensor unit 100 includes an interferometer 600 and a displacement calculation processing unit 51. In the interferometer 600, as in the first embodiment, the 45 ° polarized light emitted from the polarization-maintaining fiber 2 is converted into parallel light 4 by the collimator 3, and further transmitted through the polarization element 5 such as a Glan-Thompson prism, and the transmitted light 6 is transmitted. The light is reflected by the prism mirror 7 and the non-polarizing beam splitter 8 and is incident on the reference mirror 9. As shown in FIG. 2, the reference mirror 9 has a configuration in which a diffraction grating 9b is formed of a metal material such as Al on a synthetic quartz substrate 9a. The polarized beam 6 in the 45 ° direction incident on the diffraction grating is composed of two orthogonally polarized components that are vector-resolved, and the S-polarized component 25s parallel to the longitudinal direction of the diffraction grating is reflected by the diffraction grating and is orthogonally polarized P-polarized component. 25p is transmitted through the diffraction grating. That is, this diffraction grating is a so-called diffractive polarizing element (Wire Grid).
Polarizer). In this embodiment, the pitch of the diffraction grating 9b is 1
The thickness was 44 nm, the line width was 65 nm, and the height was 165 nm.

The S-polarized beam 6r reflected by the reference mirror 9 is used as reference light. The transmitted P-polarized beam 6m is used as measurement light. The P-polarized beam 6m becomes circularly polarized light after passing through the quarter-wave plate 10, is reflected by the target mirror 12 placed on the measurement object 31, and is again 1/4.
After passing through the wave plate 10, it becomes S-polarized light, reflected by the reference mirror 9, passed through the quarter-wave plate 10 and then reflected by the target mirror 12 as circularly polarized light, and after passing through the quarter-wave plate 10, it becomes P-polarized light. It passes through the mirror 9. In other words, the measurement light 6m travels back and forth two times along the optical path between the reference mirror 9 and the target mirror 12, and the movement amount 31d of the measurement object 31 is doubled and detected. The S-polarized beam 6 r reflected by the reference mirror 9 and the transmitted P-polarized beam 6 m are combined as an orthogonally polarized beam 14 and transmitted through the non-polarized beam splitter 8.

After passing through the opening 13 for removing stray light, the orthogonally polarized beam 14 is converted into a rectangular beam 81 by a beam shaping element 80 such as a diffractive optical element, a hologram element, or an anamorphic prism pair. This rectangular orthogonal polarization beam 81 is transmitted through the phase shift elements 82, 83 and 84, so that 0, π / 4, π / 2 are present between the orthogonal polarization components.
Polarization interference occurs in a state where phase shifts of 3π / 4, π, 5π / 4, 3π / 2, and 7π / 4 are given, and eight phase shift interference lights 85 are generated.

The phase shift element 82 is divided into two as shown in FIG. 10, the left half is composed of synthetic quartz 82d, and the right half is composed of a photonic crystal 82c. Since the configuration and principle of the photonic crystal 82c are the same as those in the first embodiment, description thereof is omitted. Photonic crystal 82c is 1
It has a function as an / 8 wavelength plate, and a thick arrow indicates the crystal axis direction. That is, as shown in FIG. 9, a phase difference of π / 4 is generated between two polarization components with respect to the orthogonal polarization beam that passes through the photonic crystal 82 c in the rectangular orthogonal polarization beam 81. On the other hand, with respect to the orthogonally polarized light beam that passes through the synthetic quartz 82d, there is no phase difference between the two polarization components.

The phase shift element 83 is divided into four as shown in FIG. 10, and a synthetic quartz 83d, a photonic crystal 83c, a synthetic quartz 83d, and a photonic crystal 83c are arranged from the left. Like the phase shift element 82, the photonic crystal 83c has a function as a quarter wavelength plate,
A thick arrow indicates the crystal axis direction. That is, as shown in FIG. 9, a phase difference of π / 2 is generated between two polarization components of an orthogonally polarized beam 81 that passes through the photonic crystal 83 c in the rectangular orthogonally polarized beam 81. On the other hand, with respect to the orthogonal polarization beam transmitted through the synthetic quartz 83d, there is no phase difference between the two polarization components.

The phase shift element 84 is divided into eight as shown in FIG. 10, and the photonic crystal 84a having a 45 ° crystal axis direction and the photonic crystal 84 having a 45 ° crystal axis direction opposite to each other.
b is arranged alternately. The photonic crystals 84a and 84b have a function as a polarizing element, and a thick arrow indicates the crystal axis direction. That is, as shown in FIG. 9, two polarization components constituting an orthogonal polarization beam that passes through the photonic crystal 84a out of the rectangular orthogonal polarization beam 81 and 2 constituting an orthogonal polarization beam that passes through the photonic crystal 84b. Both polarization components interfere with each other in a state where a relative phase difference of π is given between the two polarization components.

That is, 0, π / 4, π / 2, 3π / 4, π, 5π / 4, 3π / between the orthogonal polarization components of the rectangular orthogonal polarization beam 81 transmitted through the phase shift elements 82, 83, and 84. 2, 7π
Polarization interference occurs with a phase shift of / 4, and eight phase shift interference lights 85 are generated. The eight phase shift interference lights 85 have a wavelength of 632.8 nm in order to avoid the influence of disturbance light.
Are transmitted through an interference filter 86 having a transmission center wavelength and then received by a divided photoelectric conversion element 87 such as an eight-divided photodiode array composed of eight light receiving areas corresponding to the eight areas of the phase shift element 84, and an amplifier. After being amplified at 88, eight phase shift interference signals 89
a, 89b, 89c, 89d, 89e, 89f, 89g, and 89h are output. FIG.
1 shows a light receiving surface of the split photoelectric conversion element 87. The light receiving areas 87a and 87b are respectively shown in FIG.
This corresponds to the photonic crystals 84 a and 84 b of the zero phase shift element 84.

Four phase shift interference signals 89a, 89b, 89c, 89d, 89e, 89f, 89g
, 89h are given by (Equation 6) to (Equation 13), respectively.

I _a = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ) (Equation 6)

I _b = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ + π)
= I _m + I _r −2 (I _m · I _r ) ^1/2 cos (4πnD / λ) (Expression 7)

I _c = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ + π / 2)
= I _m + I _r +2 (I _m · I _r ) ^1/2 sin (4πnD / λ) (Equation 8)

I _d = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ + 3π / 2)
= I _m + I _r −2 (I _m · I _r ) ^1/2 sin (4πnD / λ) (Equation 9)

I _e = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ + π / 4)
= I _m + I _r + (2I _m · I _r ) ^1/2 {cos (4πnD / λ) −sin (4π
nD / λ)} (Expression 10)

I _f = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ + 5π / 4)
= I _m + I _r − (2I _m · I _r ) ^1/2 {cos (4πnD / λ) −sin (4π
nD / λ)} (Expression 11)

_{I g = I m + I r} +2 (I m · I r) 1/2 cos (4πnD / λ + 3π / 4)
= I _m + I _r + (2I _m · I _r ) ^1/2 {sin (4πnD / λ) + cos (4π
nD / λ)} (Equation 12)

I _h = I _m + I _r +2 (I _m · I _r ) ^1/2 cos (4πnD / λ + 7π / 4)
= I _m + I _r − (2I _m · I _r ) ^1/2 {sin (4πnD / λ) + cos (4π
nD / λ)} (Expression 13)

In the displacement calculation processing unit 51, the movement amount D of the measurement object 31 is calculated based on (Equation 14), and is displayed on the displacement output unit 70 as the movement amount signal 61.

D = (λ / 4πn) tan ⁻¹ [{2 ^1/2 (I _g −I _h ) − (I _a −I _b )} /
{2 ^1/2 (I _e −I _f ) + (I _c −I _d )}] (Equation 1
4)

In this embodiment, a diffractive polarizing element (Wire Grid Polari) is used as the reference mirror 9.
However, as in the first embodiment, it is also possible to use a photonic crystal 9c having a crystal axis direction in the horizontal direction as shown in FIG. Similarly, the quarter-wave plate 10 can also be a photonic crystal 10c having a crystal axis direction in the 45 ° direction.

As is apparent from FIG. 9, 2 of the measurement light 6m and the reference light 6r toward the target mirror 12
One beam is emitted from the light source unit, enters the sensor unit 100, reaches the reference mirror 9, and further receives light from the reference mirror 9 by the four photoelectric conversion elements 22.
It passes through the same optical path. That is, the configuration is a common optical path type interferometer. Therefore, even if a temperature distribution, refractive index distribution, or mechanical vibration occurs due to air fluctuations in the optical path, these disturbances affect both beams equally, so when both beams interfere, The influence is completely cancelled, and the interference light is not affected by the disturbance. Only the measurement light 6m exists only in the optical path between the reference mirror 9 and the target mirror 12. For example, since the stroke of the scanning probe microscope or the like is about several hundred microns at most, the reference mirror 9 and the target mirror 12 This gap can be set to 1 mm or less, and the influence of disturbance in such a minute gap can be ignored. The intensity variation of the laser beam itself, (6) the probe light detected intensity I _m to (Equation _13), but the variation of the reference light detection intensity I _r, the displacement processing unit 5
It is canceled by the subtraction process and the division process in (Equation 5) at 0.

Furthermore, in the optical interference displacement sensor of this embodiment, eight orthogonally polarized beams are generated with a simple configuration, and eight phase shift interference lights are generated and received spatially in parallel by phase shift elements arranged in an array. As a result, the optical components are significantly reduced compared to the conventional phase shift interferometer, and the displacement sensor is greatly reduced in size. Specifically, the interferometer 60
The size of 0 can be reduced to about 20 × 15 × 50 mm or less. In addition, since the eight phase shift interference lights pass through close optical paths, even if disturbances such as temperature distribution, humidity distribution, atmospheric pressure distribution, density distribution, and airflow change due to air fluctuations are superimposed between the optical paths, The effect can be minimized. Further, in this embodiment, the phase shift amount is π / 4, which is ½ that of the first embodiment, so that the movement amount D can be calculated with higher accuracy.

In addition, the measurement accuracy can be further improved by increasing the number of divisions of the phase shift elements 82, 83, and 84 and the number of divisions of the divided photoelectric conversion elements 87.

As described above, the movement amount and position of the measurement object can be changed from sub-nanometers to picometers or less without controlling environmental factors such as temperature, humidity, atmospheric pressure, density, and acoustic vibration with high accuracy by the optical interference displacement sensor of this embodiment. It is possible to measure stably with high accuracy. Further, by mounting the optical interference displacement sensor of this embodiment on the AFM shown in FIG. 5 as in the second embodiment, the same effect as in the second embodiment can be obtained, and the position of the probe can be changed to sub-nano. It is possible to stably measure with accuracy of meters to picometers or less. As a result, the resolution of the two-dimensional AFM image is improved and the image reproducibility can be dramatically improved.

Further, by mounting the optical interference displacement sensor of this embodiment on the surface unevenness defect inspection apparatus shown in FIG. 8 similarly to the third embodiment, the same effects as those of the third embodiment can be obtained, and the sample surface can be obtained. Can be stably measured with a sensitivity of sub-nanometer to picometer.
As a result, for example, it is possible to dramatically improve the sensitivity of inspection of irregularities on semiconductor wafers, magnetic disks, magnetic head floating surfaces, and the like.

A fifth embodiment of the present invention will be described with reference to FIGS. As shown in FIG.
The optical interference displacement sensor of this embodiment includes a light source unit (not shown), a sensor unit 100, and a displacement output unit 70.

In the light source unit, for example, a linearly polarized laser beam having a wavelength of 632.8 nm from a frequency-stabilized He—Ne laser is applied to the sensor unit 100 in a polarization direction of 45 ° by the polarization plane preserving fiber 2.
To guide the light.

The sensor unit 100 includes an interferometer 600 and a displacement calculation processing unit 52. In the interferometer 600, as in the first embodiment, the 45 ° polarized light emitted from the polarization-maintaining fiber 2 is converted into parallel light 4 by the collimator 3, and further transmitted through the polarization element 5 such as a Glan-Thompson prism, and the transmitted light 6 is transmitted. The beam is converted into a rectangular beam 91 by a beam shaping element 80 such as a diffractive optical element, a hologram element, or an anamorphic prism pair. The rectangular beam 91 is reflected by the prism mirror 7 and the non-polarizing beam splitter 8 and is incident on the reference mirror 9.

As shown in FIG. 2, the reference mirror 9 has a configuration in which a diffraction grating 9b is formed of a metal material such as Al on a synthetic quartz substrate 9a. The rectangular polarized light beam 6 in the 45 ° direction incident on the diffraction grating is composed of two orthogonally polarized components separated in vector, and the S-polarized component 25s parallel to the longitudinal direction of the diffraction grating is reflected by the diffraction grating and orthogonally crossed P. The polarization component 25p is transmitted through the diffraction grating. That is, this diffraction grating is a so-called diffractive polarizing element (Wire Grid Polar).
The property as a riser). In this embodiment, the pitch of the diffraction grating 9b is 144 nm.
The line width was 65 nm and the height was 165 nm.

The rectangular S-polarized beam 6r reflected by the reference mirror 9 is used as reference light. The transmitted rectangular P-polarized beam 6m is used as measurement light. The rectangular P-polarized beam 6m is a quarter-wave plate 1
After passing through 0, it becomes circularly polarized light and is condensed linearly on the surface of the sample 210 by the condenser lens 215 (216). NA (Numerical Aperture) of the condenser lens 215
When the numerical aperture is 0.8, the spot width (direction perpendicular to the longitudinal direction) of the linear focused spot 217 is about 0.8 μm. The reflected light from the surface of the sample 210 becomes a rectangular beam after passing through the condensing lens 215, and again passes through the quarter-wave plate 10 to become S-polarized light, is reflected by the reference mirror 9, passes through the quarter-wave plate 10, and then becomes a circle. The sample 210 is again polarized by the condenser lens 215.
The light is condensed linearly on the surface (216).

The reflected light from the surface of the sample 210 becomes a rectangular beam after passing through the condenser lens 215, becomes P-polarized light after passing through the quarter-wave plate 10, and passes through the reference mirror 9. That is, the measurement light 6m travels back and forth two times along the optical path between the reference mirror 9 and the surface of the sample 210, and the amount of unevenness on the surface of the sample 210 is doubled and detected. Rectangular S-polarized beam 6r reflected by the reference mirror 9
The transmitted rectangular P-polarized beam 6m is combined as a rectangular orthogonal polarized beam 218 and transmitted through the non-polarized beam splitter 8. The longitudinal direction of the linear focused spot 217 and the longitudinal direction of the rectangular orthogonal polarized beam 218 are in a conjugate relationship. That is, the uneven distribution information on the surface of the sample 210 in this direction is stored as the optical phase distribution in the rectangular P-polarized beam 6m.

This rectangular orthogonal polarization beam 218 is transmitted through the phase shift elements 219 and 220, so that polarization interference occurs in a state where phase shifts of 0, π / 2, π, and 3π / 2 are given between the orthogonal polarization components. Then, four phase shift interference lights 221 divided in the direction orthogonal to the longitudinal direction of the linear focused spot 217 are generated.

As shown in FIG. 13, the phase shift element 219 is divided into two in a direction perpendicular to the longitudinal direction of the linear focused spot 217, the lower half is composed of synthetic quartz 219d, and the upper half is composed of a photonic crystal 219c. The Since the configuration and principle of the photonic crystal 219c are the same as those in the first embodiment, description thereof is omitted. The photonic crystal 219c has a function as a quarter wavelength plate, and a thick arrow indicates the crystal axis direction. That is, as shown in FIG. 12, a phase difference of π / 2 is generated between two polarization components with respect to the orthogonal polarization beam that passes through the photonic crystal 219 c in the rectangular orthogonal polarization beam 218. Meanwhile, synthetic quartz 219d
As for the orthogonally polarized beam passing through, there is no phase difference between the two polarization components.

The phase shift element 220 is divided into four in a direction orthogonal to the longitudinal direction of the linear focused spot 217 as shown in FIG. 13, and a photonic crystal 220a having a crystal axis direction of 45 °,
Photonic crystals 220b having opposite 45 ° crystal axis directions are arranged alternately. The photonic crystals 220a and 220b have a function as a polarizing element, and a thick arrow indicates the crystal axis direction. That is, as shown in FIG.
18 between the two polarization components constituting the orthogonal polarization beam that transmits the photonic crystal 220a and the two polarization components that constitute the orthogonal polarization beam that transmits the photonic crystal 220b. In the state where the phase difference is given, both polarization components interfere.

That is, a phase shift of 0, π / 2, π, 3π / 2 is given between the orthogonal polarization components in the direction orthogonal to the longitudinal direction of the rectangular orthogonal polarization beam 218 transmitted through the phase shift elements 219 and 220. The phase-shifting interference light 2 that interferes with polarization in a state of being divided, is divided into four in a direction perpendicular to the longitudinal direction of the linear focused spot 217, and is conjugated to the longitudinal direction of the linear focused spot 217.
21 is generated. The phase shift interference light 221 has a wavelength 632 in order to avoid the influence of disturbance light.
. After passing through the interference filter 86 having a transmission center wavelength at 8 nm, as shown in FIG.
N corresponding to the longitudinal direction of the linear focused spot 217 and the four regions of the phase shift element 220
Each light is received by a divided photoelectric conversion element 222 such as a photodiode array having a light receiving region of pixels × 4, amplified by an amplifier 223, and then output as N × 4 phase shift interference signals 224.

As shown in FIG. 14, the light receiving regions 222a and 222b correspond to the photonic crystals 220a and 220b of the phase shift element 220 of FIG. Four phase shift interference signals corresponding to N pixels are given by (Equation 1) to (Equation 4), respectively, as in the first embodiment, and the displacement calculation processing unit 52 is based on (Equation 5). A one-dimensional distribution of the surface unevenness D of the sample 210 is calculated for each of N pixels, and is displayed on the displacement output unit 70 as the surface unevenness signal 230.

In this embodiment, a diffractive polarizing element (Wire Grid Polari) is used as the reference mirror 9.
However, as in the first embodiment, it is also possible to use a photonic crystal 9c having a crystal axis direction in the horizontal direction as shown in FIG. Similarly, the quarter-wave plate 10 can also be a photonic crystal 10c having a crystal axis direction in the 45 ° direction. In combination with the fourth embodiment, the phase shift amount can be increased by π / 8. In that case, the split photoelectric conversion element 222 may be a two-dimensional solid-state imaging element.

As is apparent from FIG. 12, the two beams of the measurement light 6 m and the reference light 6 r directed toward the surface of the sample 210 are emitted from the light source unit, enter the sensor unit 100, reach the reference mirror 9, and further reach the reference mirror 9. From the light to the light received by the photoelectric conversion element 222 completely passes through the same optical path. That is, the configuration is a common optical path type interferometer. Therefore, even if a temperature distribution, refractive index distribution, or mechanical vibration occurs due to air fluctuations in the optical path, these disturbances affect both beams equally, so when both beams interfere, The influence is completely cancelled, and the interference light is not affected by the disturbance. Further, the intensity variation of the laser beam itself is caused by the measurement beam 6
Since m and the reference beam 6r are equally affected, they are canceled out at the time of interference, and are also superimposed on the measured eight phase-shift interference beams. Therefore, the subtraction processing in (Expression 5) in the displacement calculation processing unit 52 is performed. Is also offset.

Furthermore, in the optical interference displacement sensor of this embodiment, four orthogonally polarized beams are generated with a simple configuration, and four phase shift interference lights are generated in parallel and spatially received by phase shift elements arranged in an array. As a result, the optical components are significantly reduced compared to the conventional phase shift interferometer, and the displacement sensor is greatly reduced in size. In addition, because the four phase-shift interference lights pass through close optical paths, even if disturbances such as temperature distribution, humidity distribution, atmospheric pressure distribution, density distribution, and airflow change due to air fluctuations are superimposed between the optical paths, The effect can be minimized.

As described above, the movement amount and position of the measurement object can be changed from sub-nanometers to picometers or less without controlling environmental factors such as temperature, humidity, atmospheric pressure, density, and acoustic vibration with high accuracy by the optical interference displacement sensor of this embodiment. It is possible to measure stably with high accuracy. Further, after removing the displacement output unit 70 from the optical interference displacement sensor of the present embodiment, FIG. 8 shows the same as in the third embodiment.
By mounting it on the surface irregularity defect inspection apparatus shown in Fig. 4, it is possible to obtain the same effect as in the third embodiment, and to stably measure irregularities on the sample surface with a sensitivity of sub-nanometers to picometers or less. . As a result, for example, it is possible to dramatically improve the sensitivity of inspection of irregularities on semiconductor wafers, magnetic disks, magnetic head floating surfaces, and the like. In particular, in the case of the present embodiment, the use of the linear focused spot 217 has an advantage that the uneven distribution information of the two-dimensional region can be obtained in a short time by scanning only in one direction of X or Y.

As described above, according to the present invention, it is possible to obtain the amount of displacement or movement of an object with high accuracy without the influence of disturbance by using an extremely small optical interference displacement sensor, and the range of applications is greatly expanded. . As a result, probe scanning of scanning probe microscopes including AFM can be performed with sub-nanometer precision, and fine three-dimensional structure elements such as semiconductor devices can be achieved with sub-nanometer resolution and high reproducibility. There is an effect that it is possible to measure optical information and minute unevenness information. In addition, there is an effect that it becomes possible to inspect a semiconductor wafer, a magnetic disk, a micro unevenness distribution of sub nanometers or less and a micro uneven defect on the air bearing surface of the magnetic head. Furthermore, by feeding back these measurement results to the element manufacturing process conditions, highly reliable production of devices and media can be achieved.

DESCRIPTION OF SYMBOLS 1 ... Light source unit 2, 2x, 2y, 2z ... Polarization plane preservation fiber 3 ...
Collimator 5 ... Polarizing element 7 ... Prism mirror 8 ... Non-polarizing beam splitter 9 ... Reference mirror 10 ... 1/4 wavelength plate 12, 12x, 12
y, 12z ... target mirror 14, 17, 81, 218 ... orthogonally polarized beam 13 ... aperture 15a, 15b ... quadrangular pyramid prism 18, 19, 82, 8
3, 84, 219, 220 ... phase shift elements 9c, 10c, 18c, 19a, 19b
82c, 82d, 83c, 83d, 84a, 84b, 219c, 220a, 220b
..Photonic crystal 20, 85, 221... Phase shift interference light 21, 86
..Interference filters 22 ... Photoelectric conversion elements 23, 88, 223 ... Amplifiers
31 ... Measurement object 41a, 41b, 41c, 41d, 89a, 89b, 89c,
89d, 89e, 89f, 89g, 89h, 224... Phase shift interference signal 50,
51, 52 ... Displacement calculation processing units 61, 61x, 61y, 61z, 230.
-Movement amount signal, unevenness measurement signal 70 ... Displacement output unit 80 ... Beam shaping element 87, 222 ... Divided photoelectric conversion element 100, 100x, 100y, 10
0z Sensor unit 150 XYZ piezoelectric element actuator 160
..Cantilever 170 ... probe 180 ... semiconductor laser 181 ...
Drive circuit 190... 4 split position sensor 200, 210.
15 ... Condensing lens 300, 350 ... XYZ stage 400, 450 ...
Scan control unit 410: Image forming unit 420, 470: Overall control unit 430, 480 ... Output unit 460 ... Defect detection unit
500 ... Monitor optical system unit 600 ... Interferometer 700, 1000 ...
Stage unit 800 ... AFM unit 900, 1200 ... Signal processing / control unit 1100 ... Surface inspection unit

Claims (10)

The actuator scans the probe relative to the object by the actuator,
The probe is brought into contact with the object until a predetermined contact force is reached,
Separating light from the light source into first light that passes through the polarizing element and second light that is reflected by the polarizing element;
Irradiating the actuator with the first light;
The reflected light from the actuator and the second light are combined by the polarizing element, a plurality of optical phase differences are generated on the same plane on the combined light, and interference light is generated.
A surface measurement method characterized in that a plurality of optical phase differences are generated on the same plane in the interference light to determine the position of the probe.   The surface measurement method according to claim 1, wherein a plurality of optical phase differences are generated between the reflected light from the actuator and the second light by the polarizing element array.   The surface measuring method according to claim 2, wherein the polarizing element array is configured by a photonic crystal array.   The surface measurement method according to claim 1, wherein a method of separating light from the light source into first light and second light is based on a diffractive polarization element.   The surface measurement method according to claim 1, wherein a method of separating light from the light source into first light and second light is based on a photonic crystal. A probe,
An actuator that scans the probe relative to the object and contacts the probe with the object;
A four-divided position sensor for detecting a contact force between the probe and the object;
A light source;
Separating means for separating light from the light source into first light and second light;
Interference light is generated by causing a plurality of optical phase differences on the same plane between the first light transmitted through the separation means and reflected by the actuator and the second light reflected by the separation means. Interference means to cause,
A surface measuring apparatus comprising: a detecting unit that obtains the position of the probe from the interference light.   The surface measuring apparatus according to claim 6, wherein the interference unit is a polarizing element array.   The surface measuring apparatus according to claim 7, wherein the polarizing element array is configured by a photonic crystal array.   The surface measuring apparatus according to claim 6, wherein the separating unit is a diffractive polarizing element.   The surface measuring apparatus according to claim 6, wherein the separating unit is a photonic crystal.

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