JPH11153405A - Displacement sensor for scanner system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a displacement sensor for a scanner system of a compact constitution in which displacement of a stage can be detected at high precision by changing a dynamic range or a resolution. SOLUTION: A tube-shaped piezoelectric scanner 102 is fixed to a fixing base 104 at one end, a stage 108 is fixed at a free end, and a mirror 110 is fixed on the back side of it. An opening m106 is formed in the fixing base 104 at a corresponding part to the inner side of the scanner 102, and a 1/4 wavelength plate 120, a polarization beam splitter 122, a double focus optical system 130, and a position detector 124 are disposed in order under that. At a side part of the polarization beam splitter 122, a light source is disposed. The double focus optical system 130 condensates incidental light to it to either a first focus that is relatively light, or a second focus that is relatively long. The position detector 124 is disposed close to the first focus of the double focus optical system 130.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a scanning probe microscope (SPM) such as a scanning tunneling microscope (STM) or an atomic force microscope (AFM), for example, and the displacement of a scanner for scanning a probe, a sample, or the like. About the sensor.

[0002]

2. Description of the Related Art A simple configuration such as a scanning tunneling microscope (STM) or an atomic force microscope (AFM), such as "Method and Apparatus for Forming an Image of a Sample Surface" in JP-A-62-130302, is used. 2. Description of the Related Art A scanning probe microscope (SPM) having a high vertical and horizontal resolution at an atomic size level has been proposed.

In order to realize high resolution with such a scanning probe microscope, a scanner capable of controlling the relative position between the probe and the sample with high accuracy is required. Generally, a tripod-type or tube-type piezoelectric scanner is used as the scanner.

A tube-type piezoelectric scanner has, for example, a single common electrode on the inner peripheral surface of a piezoelectric member formed in a tube shape, and four drive electrodes on its outer peripheral surface in the circumferential direction. I have. By appropriately controlling the voltage application to the four drive electrodes, the end of the piezoelectric scanner is three-dimensionally displaced by bending or expansion and contraction. By fixing a stage to the end of the piezoelectric scanner and supporting the probe or sample on the stage, the probe or sample is scanned by the displacement of the end of the piezoelectric scanner.

[0005] The piezoelectric scanner is formed of PZT (lead zirconate titanate) or the like, and it is well known that displacement when voltage driving is performed exhibits hysteresis and creep. Therefore, when the probe or the sample is scanned by using the piezoelectric scanner, the movement characteristic of the stage (that is, the probe or the sample) shows nonlinearity. Such non-linearity appears as a distortion of a measurement image in a scanning probe microscope, and hinders quantitative measurement.

To solve such a problem, Japanese Patent Laid-Open No.
No. 229975 discloses a scanner system provided with an optical displacement sensor for optically detecting the amount of displacement of a stage. This optical displacement sensor irradiates a plane mirror provided on the stage with a parallel light beam, condenses the reflected light with a lens, forms a light spot on the position detector, and sets the stage based on the spot position detected by the position detector. Is calculated.

In such an optical displacement sensor,
A sensor has been proposed in which the relative position of a lens and a position detector is changed, and the size of a light spot on the position detector is changed to change the dynamic range and resolution of a displacement sensor. One example is disclosed in JP-A-7-98206.

The displacement sensor capable of changing the dynamic range and the resolution has a scanning range (several nm to 100 nm).
(μm or more) is very effective for an SPM having a large width. This is because the resolution of a normal displacement sensor, including the optical displacement sensor disclosed in Japanese Patent Application Laid-Open No. 6-229753, is at most about 1 / 10,000 of the dynamic range.
That is, in a displacement sensor having a dynamic range (the maximum scanning width of the SPM) of 100 μm or more, the resolution is about 0.01 μm. This is approximately 50 per scan.
In the SPM that captures 0 point data, the effective scanning width of the displacement sensor is 5 μm or more. Therefore, the displacement sensor used in the SPM needs to have a variable dynamic range and resolution.

[0009]

However, the optical displacement sensor disclosed in Japanese Patent Application Laid-Open No. 7-98206 mechanically changes the relative position between the lens and the position detector to change the dynamic range and the resolution. Therefore, not only the mechanism becomes huge and complicated, but that also leads to an increase in vibration noise. It is difficult to perform high-precision (nm order) positioning by a mechanical mechanism for driving a lens as disclosed in JP-A-7-98206. Therefore, such an optical displacement sensor is not desirable in SPM in which the device needs to be small and highly rigid.

The present invention has been made in view of such circumstances, and has as its object the ability to change the dynamic range and resolution without increasing the size and complexity of the mechanism.
Accordingly, it is an object of the present invention to provide a displacement sensor of a scanner system capable of detecting the position of a stage with high accuracy over a wide scanning range.

[0011]

A displacement sensor of a scanner system according to the present invention based on the first subject includes a mirror fixed to the back side of a stage, a light source for emitting a light beam for displacement detection, and a light source for detecting a displacement. Means for guiding the light beam to the mirror, a bifocal optical system for converging the light beam reflected by the mirror to either the first focus or the second focus, and the first focus or the second focus The position detector is located close to the position detector, and the diameter of the spot formed on the light receiving surface is switched according to the switching of the focus by the bifocal optical system.The position detector detects the displacement of the stage based on the output of the position detector. And a calculation unit for calculating.

According to a second aspect of the present invention, there is provided a displacement sensor for a scanner system according to the present invention, comprising: a plane mirror fixed to the back side of a stage; a light source for emitting a light beam for detecting a displacement; and a light beam from the light source to the plane mirror. Guiding means, lens means for converting the light beam reflected by the plane mirror into a convergent light beam, beam splitting means for splitting the convergent light beam into two, and each of the two split convergent light beams A total of two position detectors, one on the optical path, one of which is located near the focal point of the lens means, so that a relatively small light spot is formed on its light receiving surface and the other A relatively large light spot is formed on the light receiving surface. The two position detectors and the stage displacement based on the output of each of the two position detectors And an arithmetic unit for calculating.

According to a third aspect of the present invention, there is provided a displacement sensor of a scanner system according to the present invention, comprising: a plane mirror fixed to the back side of a stage; a light source for emitting a light beam for detecting a displacement; and a light beam from the light source to the plane mirror. Guiding means, lens means for converting the light beam reflected by the plane mirror into a convergent light beam, a position detector arranged on the optical path of the convergent light beam, and an aperture provided between the plane mirror and the position detector A diaphragm whose diameter can be changed.The diaphragm whose diameter can be changed by appropriately restricting the diameter of the incident light beam can change the size of the light spot formed on the position detector. And a calculation unit for calculating the displacement of the stage based on the power.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. First, a scanner system according to the first embodiment will be described. FIG.
1 shows a schematic configuration of the scanner system according to the first embodiment, partially cut away.

Although the detailed structure of the tube-type piezoelectric scanner (tube scanner) 102 is not shown, it has a tube-shaped piezoelectric member, and a single common electrode is provided on the inner peripheral surface thereof. Are provided, and four or five drive electrodes are provided on the outer peripheral surface in the circumferential direction. The scanner 102 has one end fixed to a fixed base 104.

A stage 108 is fixed to the other end of the scanner 102, that is, a free end. Scanner 102
Is driven by a scanner driver (not shown), and as a result, the stage 108 is displaced in each of the x, y, and z directions.

A mirror 110 is fixed on the back side of the stage 108. An opening 106 is formed on the fixed base 104 at a portion corresponding to the inside of the scanner 102, and light can be guided into the mirror 110 through the opening 106.

A quarter-wave plate 12 is provided below the opening 106.
0, polarizing beam splitter 122 and bifocal optical system 1
30 and the position detector 124 are arranged in order from the top. Further, the polarization beam splitter 122
A light source 112 that generates light incident on the light source 112 is disposed on a side of the light source 112.

The light source 112 includes a semiconductor laser 114 and a lens 116. The semiconductor laser 114 is driven by an LD driver 118, and divergent light emitted from the semiconductor laser 114 is converted into parallel light by the lens 116, and the parallel light is polarized. The light enters the beam splitter 122.

The polarizing beam splitter 122 is used for the light source 1.
12 reflects the component light having a vibration surface in the y direction (perpendicular to the paper surface) of the light emitted from the mirror 12 and guides it to the mirror 110;
The light having a vibration plane in the x direction (parallel to the paper) of the light reflected back by the mirror 110 is transmitted and guided to the bifocal optical system 130.

The bifocal optical system 130 can appropriately focus the light incident thereon to one of a relatively short first focus and a relatively long second focus. The specific configuration of the bifocal optical system 130 will be described later.

The position detector 124 is arranged near the position of the relatively short first focal point of the bifocal optical system 130. The position detector 124 includes four light receiving elements as shown in FIG. 2, and outputs A, B, C, and D of these light receiving elements as shown in FIG.
Is input to the arithmetic circuit 126.

The arithmetic circuit 126 is based on the outputs A, B, C, D of the light receiving elements of the position detector 124,
The position of the spot formed on the light receiving surface of the position detector 124 is calculated. The arithmetic circuit 126 calculates the displacement of the spot position in the x direction (the displacement of the stage 108 in the x direction).
Is obtained by {(A + B)-(C + D)} / (A + B + C + D), and the displacement of the spot position in the y direction (the displacement of the stage 108 in the y direction) is expressed by {(A + D)-(B + C)} / (A + B + C + D). Ask.

FIG. 3 shows a specific example of the bifocal optical system 130. The bifocal optical system 130 is a bifocal lens 1
32, a liquid crystal element 134, a power supply 136, and a switch 138. In the liquid crystal element 134, the arrangement of the liquid crystal molecules changes according to the on / off state of the switch 138. FIG.
As shown in (A), when the switch 138 is turned on, the arrangement of the liquid crystal molecules is aligned, and the incident light is transmitted without changing its polarization direction. That is,
Incident light having a vibration surface in the x direction has a vibration surface in the x direction even after transmission. As shown in FIG.
When the light is turned off, the alignment of the liquid crystal molecules is twisted, and the incident light is transmitted by rotating its polarization direction by 90 degrees. That is, incident light having a vibration surface in the x direction has a vibration surface in the y direction after transmission. Thus, the liquid crystal element 134
The polarization direction of the light incident on the bifocal lens 132 is switched according to the ON / OFF of the switch 138.

The bifocal lens 132 is made of a birefringent crystal having a different refractive index from the direction in which the crystals are arranged, and has a different refractive index depending on the polarization direction of incident light.
That is, as shown in FIG.
The light in the direction is collected by the bifocal lens 132 at the focal position indicated by OA, and as shown in FIG.
The light whose polarization direction is the y direction is condensed by the bifocal lens 132 at a focal position indicated by OB. In this bifocal optical system, the condensed light beam whose focal position is OA is an ordinary light beam, and the condensed light beam whose focal position is OB is an extraordinary light beam.
The glass material used for the bifocal lens 132 is not limited to quartz, but is not limited to birefringent crystals such as calcite.

FIG. 4 shows another specific example of the bifocal optical system 130. The bifocal optical system 130 is a lens 142
, A liquid crystal element 144, and a liquid crystal driving section 146. The liquid crystal driving section 146 includes a power supply for supplying a voltage to be applied to the liquid crystal element 144 and a switch for turning on / off the application of the voltage to the liquid crystal element 144.
The refractive index of the liquid crystal element 144 changes depending on whether or not a voltage is applied from the liquid crystal driver 146.

The liquid crystal element 144 has two states, a high refractive index and a low refractive index, depending on whether or not a voltage is applied. For example, the liquid crystal element 144 has a low refractive index when the voltage is turned off, and the light incident on the liquid crystal element 144 is condensed at a focal position indicated by OA. And the light incident thereon is collected at the focal position indicated by OB.

FIG. 5 shows another specific example of the bifocal optical system 130. The bifocal optical system 130 includes a variable focus lens 152 and a focus control unit 160.
The variable focus lens 152 has a liquid crystal section 154 whose refractive index changes according to the presence or absence of the application of a voltage. Transparent plates facing each other with the liquid crystal section 154 are composed of lenses 156 and 158. In other words, the variable focus lens 152 is functionally equivalent to a lens in which the lens 142 and the liquid crystal element 144 in the bifocal optical system of FIG. 4 are integrated.

In the variable focus lens 152, for example, the liquid crystal unit 154 has a low refractive index when the voltage is turned off, and the light incident on the variable focus lens 152 is condensed at a focal position indicated by OA. Liquid crystal unit 154
Has a high refractive index, and the light incident on the variable focus lens 152 is collected at a focal position indicated by OB.

Although some specific examples of the bifocal optical system 130 have been described, the configuration is not limited thereto. For example, a liquid crystal lens disclosed in JP-A-60-50510 may be used. The bifocal optical system 130 may have any configuration as long as it has a function of appropriately switching the focal position.

Next, the operation of the displacement sensor of the scanner system configured as described above and shown in FIG. 1 will be described. The light converted into parallel light by the lens 116 of the light source 112 has a specific polarization component reflected by the polarization beam splitter 122, and the reflected light is linearly polarized light having a polarization component in only one direction. This linearly polarized light is a １ ／ wavelength plate 12
When the light passes through 0, the light becomes circularly polarized light and reaches the mirror 110 provided inside the scanner 102 through the opening 106 of the fixed base 104. The light reflected by the mirror 110 becomes 1 /
By passing through the four-wavelength plate 120, the １ ／ wavelength plate 120
Is a linearly polarized light having a polarization plane orthogonal to the linearly polarized light before entering the. Therefore, the linearly polarized light passes through the polarization beam splitter 122 without being reflected, and is condensed by the bifocal optical system 130 to form a spot on the light receiving surface of the position detector 124.

If the light emitted from the bifocal optical system 130 is a condensed light beam condensed at the focal position OA, a relatively large spot is formed on the light receiving surface of the position detector 124 as shown in FIG. If the light beam is formed and condensed at the focal position OB, a relatively small spot is formed on the light receiving surface of the position detector 124 as shown in FIG.

When the scanner 102 is not displaced,
The spot is formed at the center of the light receiving surface of the position detector 124. That is, if the light from the bifocal optical system 130 is a condensed light beam condensed on the focal position OA, as shown in FIG. 6A, a condensed light beam condensed on the focal position OB Then, as shown in FIG.
The spot is located at the center of the light receiving surface of the position detector 124.

On the other hand, when the scanner 102 is displaced, the plane direction of the mirror 110 is inclined with respect to the incident direction of the light from the polarizing beam splitter 122 toward the mirror 110, so that the light incident on the mirror 110 Are reflected in different directions. Therefore, the spot is formed at a position shifted from the center of the light receiving surface of the position detector 124. That is, if the light from the bifocal optical system 130 is a condensed light beam condensed at the focal position OA, as shown in FIG. If so, the spot moves from the center of the light receiving surface of the position detector 124 as shown in FIG.

The amount of movement from the center of the spot is
, That is, the displacement amount of the free end of the scanner 102, and this displacement amount is obtained by performing the above-described calculation in the calculation circuit 126.

As can be seen by comparing FIGS. 6B and 7B, since the spot sizes are different, the same mirror 110 is used.
, Ie, the same amount of displacement of the scanner 102, the calculation result by the calculation circuit 126 is different. In other words, the dynamic range and the resolution can be switched by changing the focusing position in the bifocal optical system 130.

That is, when a large spot is formed on the light receiving surface of the position detector 124, a large dynamic range can be obtained, but the light receiving amount per unit area of the position detector 124 decreases.
The resolution of displacement detection decreases. Conversely, when a small spot is formed on the light receiving surface of the position detector 124, the dynamic range is reduced, but the amount of received light per unit area of the position detector 124 is increased, so that the resolution of displacement detection is increased.

In this embodiment, the semiconductor laser 114 is used as the light emitting means of the light source 112, but other light emitting means such as an LED may be applied. When an LED is applied, there is no adverse effect due to interference, so that the １ ／ wavelength plate 120
Can be omitted, or a half mirror can be used instead of the polarization beam splitter 122, and the configuration can be simplified.

Next, a scanner system according to a second embodiment will be described. FIG. 8 shows a schematic configuration of a scanner system according to the second embodiment, partially cut away.

The tube type piezoelectric scanner 202 is
Although not shown in detail, a single common electrode is provided on the inner peripheral surface of a piezoelectric body formed in a tubular shape, that is, a cylindrical shape having both ends opened, and a driving electrode is provided on the outer peripheral surface.
Generally, the number of driving electrodes is four or five.
One end of the scanner 202 is fixed to a fixed base 204. A stage 208 is fixed to a free end of the scanner 202, and a plane mirror 210 is provided on the back side thereof.

An opening 206 is provided at a portion of the fixed base 204 located inside the scanner 202. Opening 2
06, a quarter-wave plate 220, a polarizing beam splitter 222, a lens 232, a half mirror 234,
A position detector 236 is coaxially arranged. A semiconductor laser 214 and a collimator lens 216 are arranged on the side of the polarization beam splitter 222, and a position detector 238 is arranged on the side of the half mirror 234.

The position detectors 236 and 238 have the same structure, and both have light receiving sections divided into four. That is, the position detector 236 has four light receiving parts 236a, 236b, 236c, and 236d, and the position detector 238 has four light receiving parts 23.
8a, 238b, 238c, and 238d. The outputs of these light receiving sections are input to the arithmetic circuit 240.

The optical path length from the lens 232 to the position detector 236 is set shorter than the optical path length from the lens 232 to the position detector 238. That is, with respect to the optical path, the position detector 236 is disposed closer to the lens 232 than the position detector 238 is.

Next, the operation of the displacement sensor of the scanner system will be described. Semiconductor laser 214
Receives a current supply from the LD driver 218 and generates a divergent light beam having a one-way linear polarization component. The divergent light beam emitted from the semiconductor laser 214 is converted into a parallel light beam by the lens 216 and is reflected by the polarization beam splitter 222. The reflected light is 1
The light passes through the 波長 wavelength plate 220 and is converted from linearly polarized light to circularly polarized light. The parallel light beam composed of this circularly polarized light is
The light enters the inside of the scanner 202 through the opening 206 formed on the fixed base 204, reaches the plane mirror 210, and is reflected there.

The reflected light beam is again transmitted to the 波長 wavelength plate 22.
0, which results in linearly polarized light whose azimuth is rotated by 90 ° with respect to the first linearly polarized light. This linearly polarized beam passes through the polarizing beam splitter 222,
The light is converted into a focused light beam by a lens 232 and is split into two by a half mirror 234. The convergent light beam that has passed through the half mirror 234 enters the position detector 236, while the convergent light beam reflected by the half mirror 234 enters the position detector 238.

The position detector 238 is a lens 2
32, the position detector 236 is disposed closer to the lens 232 than the focal plane, and therefore a spot larger than the spot formed on the position detector 238 is formed on the position detector 236. .

When the scanner 202 is not displaced,
The spots formed on the position detectors 236 and 238 are formed at the centers of the respective light receiving surfaces. That is, the four light receiving units 236a, 236b, 236c, and 23
A beam of the same amount of light enters each of the four light receiving units 238a, 238b, 238c, and 238d.

On the other hand, when the scanner 202 is displaced, for example, as shown in FIG. 9, the plane mirror 210 is inclined with respect to the optical axis of the light beam incident on the inside of the scanner 202. For example, when the scanner 202 is displaced in the y direction, the plane mirror 210 is tilted about the x axis. Specifically, when the tip of the scanner 202 has an inclination of θ with respect to the reference state, the light beam incident on the plane mirror 210 is reflected at an angle of 2θ with respect to the incident beam.
As a result, the spots formed on the position detectors 236 and 238 are shifted from the centers of the light receiving surfaces of the position detectors 236 and 238 in accordance with the inclination angle of the plane mirror 210.

Here, the relationship between the tilt angle θ of the plane mirror 210 and the movement amount of the spot will be described with reference to FIG. The position detector 238 is disposed on the focal plane of the lens 232, and the relative positional relationship between the two is schematically shown in FIG. The position detector 236 is disposed closer to the lens than the focal plane of the lens 232, and the relative positional relationship between the two is schematically shown in FIG.
It is shown by (B).

The lens 232 and the position detector 2
Assuming that the distance between the spots 38 is f1 (this is equal to the focal length of the lens 232), the displacement d1 of the spot on the position detector 238 with respect to the inclination angle .theta.
(Θ) is given by d 1 (θ) = f 1 sin (2θ). Also, the lens 232 and the position detector 23
Assuming that the interval of 6 is f2, the movement amount d2 (.theta.) Of the spot on the position detector 236 with respect to the inclination angle .theta. Of the plane mirror 210 is given by d2 (.theta.) = F2 sin (2.theta.).

Since f1> f2, the same plane mirror 210
It can be seen that the displacement d1 of the spot on the position detector 238 is larger than the displacement d2 of the spot on the position detector 236 with respect to the inclination θ.

The above discussion is based on the fact that the plane mirror 21 corresponds to the displacement of the free end of the scanner 202 in the y direction in FIG.
Although it is assumed that the inclination angle θ is generated at 0, this can be applied to the displacement in the x direction as it is.

The angle of inclination of the free end of the scanner 202 depends on the amount of displacement thereof. Therefore, the amount of movement of the scanner 202, that is, the stage 208, can be obtained from the amount of movement of the spot formed on the position detectors 236 and 238.

The outputs of the light receiving sections 236a and 238a are typically represented by A, and similarly, the light receiving sections 236b and 2
The output of 38b is typically B, the light receiving section 236c and the light receiving section 2
The output of 38c is typically C, the light receiving unit 236d and the light receiving unit 2
When the output of 38d is typically represented by D, the amount of movement of the spot in the x-direction (in other words, the displacement of the stage 208 in the x-direction) dx is within the range in which the spot does not deviate from the boundary between the light receiving sections. The amount of movement of the spot in the y-direction (in other words, the displacement of the stage 208 in the y-direction) dy is determined by {(A + D)-(B + C)}. Dy = k {(A + D)-(B + C)} Here, k is a predetermined proportional constant k.

This calculation is performed by the arithmetic circuit 240 in which the light receiving sections 236a and 236 of the position detector 236 are connected.
b, 236c, and 236d, and the light receiving sections 238a, 238b, and 238c of the position detector 238.
And 238d for each output.

As shown in FIG. 10, the spot formed on the light receiving surface of the position detector 236 is larger than the spot formed on the light receiving surface of the position detector 238. Since the amount of movement of the spot on the position detector 238 relative to is larger than the amount of movement of the spot on the position detector 236, the light receiving portions 238a, 238b, and 23 of the position detector 238
The displacement signals obtained based on the outputs of 8c and 238d have a narrow dynamic range but high sensitivity, and conversely, the displacement signals obtained based on the outputs of the light receiving portions 236a, 236b, 236c, and 236d of the position detector 236. Shows that the sensitivity is low but the dynamic range is wide.

Next, a scanner system according to a third embodiment will be described. FIG. 11 shows a schematic configuration of a scanner system according to the third embodiment, partially cut away.

Although the detailed configuration of the tube-type piezoelectric scanner (tube scanner) 302 is not shown, a single tube is formed on the inner peripheral surface of the piezoelectric member formed in a cylindrical shape having both ends opened. Are provided, and four or five drive electrodes are provided on the outer peripheral surface in the circumferential direction. The lower end of the scanner 302 is fixed to a fixed base 304. A stage 308 is fixed to an upper end, that is, a free end, of the scanner 302. A sample or a probe is mounted on the stage 308.

A flat mirror 310 is provided on the lower surface of the stage 308.
Is fixed with its reflecting surface facing downward. Fixed base 30
4, a hole 306 is formed coaxially with the scanner 302, and is arranged in a straight line with the quarter-wave plate 320, the polarizing beam splitter 320, and the plane mirror 310. Below the polarizing beam splitter 322, a light source unit 312 supported by a support member (not shown) is arranged. The light source unit 312 includes a semiconductor laser 314,
It comprises an LD driver 318 for driving this and a collimator lens 316 arranged on the emission side of the semiconductor laser 314.

A stop 330 having a variable stop diameter and a condenser lens 332 are provided beside the polarizing beam splitter 322.
And the position detector 334 are arranged on a straight line. The stop 330 is formed of, for example, a rotatably supported disk having a plurality of openings having different diameters. Alternatively, the iris diaphragm may be constituted by a plurality of feathered diaphragm plates.

The position detector 334 has four light receiving areas, and is arranged so that the center thereof is located on the optical axis. The light receiving area of the position detector 334 is connected via a preamble 336 to an arithmetic circuit 338 that calculates the displacement of the scanner 302 based on its output.

A scanner driver 344 for driving the scanner 302 is connected to a scan controller 340 that generates a control signal based on a reference waveform (reference voltage) generated by a waveform generator 346. The scan controller 340 includes a non-linearity correcting unit 342 that corrects the non-linearity of the scanner 302 based on the displacement signal input from the arithmetic circuit 338.

The arithmetic circuit 338 obtains the displacement of the scanner 302 from the amplified output signal of the position detector 334, and supplies a displacement signal indicating the displacement to the scan controller 340. Scan controller 34
A value of 0 indicates that predetermined processing (such as processing for feedback control described later and processing for rotating or shifting the movement of the scanner 302 in the xy directions) is performed on the reference voltage generated by the waveform generator 346. , X-direction control signal and y-direction control signal to the scanner driver 344. At this time, the non-linearity correcting means 342
Applies a predetermined correction to the control signal generated based on the displacement signal supplied from the arithmetic circuit 338. The scanner driver 344 selectively applies voltages to the four drive electrodes of the scanner 302 according to the supplied control signal, and displaces the scanner 302.

Next, the operation of the displacement sensor of the thus configured scanner system will be described. When the scanner driver 344 does not apply a voltage to any of the four drive electrodes of the scanner 302, the scanner 302 is not displaced and is in the reference state. In addition, the scanner driver 344 is
0 based on the control signal output from the
Are selectively applied to the four drive electrodes, the scanner 302 is displaced in accordance with the applied voltages.

The parallel beam, which is linearly polarized light, emitted from the light source unit 312 passes through the polarizing beam splitter 322 and enters the quarter-wave plate 320. This quarter wave plate 3
At 20, the linear polarization component of the incident light beam is converted to a circular polarization component.

The light beam transmitted through the quarter-wave plate 320 enters the plane mirror 310 through the hole 306 of the fixing base 304. This incident light beam is reflected by the plane mirror 310 and again enters the quarter-wave plate 320. The light beam transmitted through the quarter-wave plate 320 passes through the quarter-wave plate 320 twice, and has a linear polarization component orthogonal to the linear polarization component before entering the quarter-wave plate 320. It becomes a beam.

The light beam that has passed through the quarter-wave plate 320 is reflected by the polarization beam splitter 322. The reflected light beam is transmitted through a stop 3 that can change the stop diameter.
The light enters the condenser lens 332 via 30 and is condensed on the light receiving surface of the position detector 334 to form a light spot. This light spot is formed at a position displaced from the center corresponding to the inclination of the stage 308, that is, the displacement of the scanner 302.

When the scanner 302 is displaced as shown in the figure, the plane mirror 310 has an inclination θ with respect to the optical axis of the light beam incident inside the scanner 320. Therefore, the light beam incident on the plane mirror 310 is reflected at an angle of 2θ.

The light beam reflected by the plane mirror 310 is 1
Quarter-wave plate 320 and polarizing beam splitter 322
After that, the light enters the stop 330 whose stop diameter is variable. Aperture 3
By reducing the aperture diameter of the aperture 30, for example, the surface reflection of the polarization beam splitter 322 and the １ ／ wavelength plate 320
It is possible to remove noise light generated by surface reflection such as the above, and to extract only a light beam for measurement. Aperture 330
Form a light spot on the light receiving surface of the position detector 334 having four light receiving regions. At this time, since the light beam is reflected by the plane mirror 310 at an angle of 2θ with respect to the incident light beam, the formation position of the light spot is displaced in accordance with the tilt direction of the plane mirror 310.

When the position detector 334 is arranged at the focal position of the condenser lens 332, the light spot is small, so that the position detector 334 starts to be kicked when the movement amount increases, and the movement detection range becomes small, so that the position detector 334 is slightly shifted in the optical axis direction. . That is, the position detector 334 is
The focal point is located closer to the lens 332 than the focal point 32.

The displacement amount D of the light spot on the light receiving surface of the position detector 334 from the center of the light receiving surface is approximately expressed by D = fsin (2θ). Here, f is the focal length of the condenser lens 332.

Here, if the diameter of the stop 330 is reduced as shown by a broken line in the figure, the aperture angle of the light beam emitted from the condenser lens 332 is reduced, and is formed on the light receiving surface of the position detector 334. The light spot diameter becomes smaller. As a result, the ratio of the amount of displacement to the diameter of the light spot increases, so that measurement with high resolution is possible.
When the diameter of the stop 330 is increased, the condensing lens 33
The aperture angle of the light beam emitted from the light source 2 increases, and the diameter of the light spot formed on the light receiving surface of the position detector 334 increases. As a result, the resolution is reduced because the ratio of the displacement amount to the light spot diameter is reduced, but measurement can be performed over a wide area.

The direction and amount of displacement of the light spot on the light receiving surface of the position detector 334 correspond to the direction and angle of inclination of the plane mirror 310, and the direction and angle of inclination of the plane mirror 310 correspond to the direction of displacement of the stage 308. Corresponds to quantity. The arithmetic circuit 338 includes the position detector 33
4 by performing a predetermined operation on the output signal of
The displacement direction and displacement amount of the light spot on the light receiving surface of the position detector 334 are calculated, the inclination direction and the inclination angle of the plane mirror 310 are obtained from the displacement direction and the displacement amount of the light spot, and the stage is determined from the inclination direction and the inclination angle of the plane mirror 310. The displacement direction and the displacement amount of 308 are obtained.

Specifically, the position detector 33
4, the displacement dx in the x direction of the light spot on the light receiving surface
And the displacement amount dy in the y direction are the position detector 33
4 is A, B, C, and D, respectively, and dx = {(A + D)-(B + C)} / (A + B + C +
D) dy = {(A + B)-(C + D)} / (A + B + C +
D).

The scan controller 340 generates a control signal in the x direction and a control signal in the y direction for displacing the stage 308 to a predetermined state based on the reference waveform output from the waveform generator 346. Desired stage 30
There is a deviation between the state of FIG. 8 and the actual state of the stage 308 due to hysteresis or creep occurring in the displacement of the piezoelectric body constituting the scanner 302. The non-linearity correcting means 342 monitors the monitor signal, determines a deviation between the state of the desired stage 308 and the actual state of the stage 308 indicated by the monitor signal, and compensates for the deviation by using the generated control signal. Make corrections to That is, the scan controller 340 includes the arithmetic circuit 338
The feedback control is performed so that the actual state of the stage 308 obtained by the above becomes a desired state.

The actual state of the stage 308 (the tilt angle θ and the tilt direction) is optically detected, and feedback control is performed so that the detected actual state of the stage 308 becomes a desired state. Is not influenced by hysteresis or creep due to the displacement of the piezoelectric body constituting the scanner 302, and the state of the stage 308 is favorably controlled.

Next, a modified example of the above-described scanner system according to the third embodiment will be described. FIG. 12 shows a schematic configuration of a scanner system according to this modification, partially cut away. In the figure, the same members as those already described in the third embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

This modified example can be understood from FIG.
The scanner system according to the third embodiment described above (FIG. 1)
In 1), a scan range setting unit 3 for setting a scan range
48, and a diaphragm adjustment unit 350 that adjusts the diaphragm diameter of the diaphragm 330 according to the set scan range.

The waveform generator 346 includes the scan setting section 34
A reference waveform (reference voltage) is generated based on the scan range set in step S8. The aperture adjustment unit 350 changes the aperture diameter of the aperture 330 according to the scan range set by the scan setting unit 348. Specifically, when a wide scan range is set in the scan setting unit 348, the aperture adjustment unit 350 adjusts the aperture 330 so that the aperture diameter increases, and a narrow scan range is set in the scan setting unit 348. The aperture adjustment unit 350
Adjusts the stop 330 so that the stop diameter becomes small.

As described above, when the aperture diameter of the aperture adjustment unit 850 is large, the sensitivity is low, but the range in which the inclination angle of the plane mirror 310 can be detected, in other words, the range in which the displacement of the stage 308 can be detected is wide. . Conversely, the aperture adjustment unit 350
Is small, the sensitivity is high.
The detectable range of the tilt angle of 0, in other words, stage 3
The detectable range of the displacement of 08 is narrow.

The aperture adjustment unit 350 adjusts the aperture diameter of the aperture 330 so that the detectable range of the displacement of the stage 308 is equal to or slightly larger than the scan range set by the scan range setting unit 348. adjust.

For example, when the stop 330 is constituted by an iris stop composed of a plurality of wing-shaped stop plates, the stop diameter is adjusted so as to best satisfy this condition. Also,
In the case where the stop 330 is formed of a disk having a plurality of openings formed with different diameters and rotatably supported, an appropriate one of the openings satisfying this condition is arranged on the optical path.

By adjusting the diaphragm 330 in this manner, the plane mirror 3 can be adjusted at an optimum sensitivity suitable for the scanning range.
Signals for detecting the ten states can be obtained.
The signal detected by the position detector 334 is processed in exactly the same manner as in the third embodiment. That is, the actual state of the stage 308 (the tilt angle θ and the tilt direction) is detected based on the information obtained by the position detector 334, and the detected actual stage 30 is detected.
Feedback control is performed so that the state of No. 8 becomes a desired state. As a result, the state of the stage 808 is well controlled by eliminating the influence of hysteresis and creep of the scanner 302.

In the third embodiment and its modification described above, feedback control is performed to obtain a desired stage state. For example, in the case of STM or AFM, the monitor signal from the arithmetic circuit 338 is applied to the feedback control. In addition, xy coordinates are newly created on the computer, and the xy coordinates are
A desired stage state can be obtained by performing image processing for rearranging the STM signal and the AFM signal on the coordinates.

The light emitting means of the light source 312 is a semiconductor laser 3
Although 14 is used, other light emitting means such as an LED may be applied. When an LED is used, since no adverse effect is caused by interference, a half mirror can be used instead of the quarter-wave plate 320 and the polarizing beam splitter 322, and the configuration can be simplified. The present invention is not limited to the above-described embodiment at all, and includes all implementations without departing from the gist of the invention.

[0086]

According to the present invention, there is provided a displacement sensor of a scanner system capable of changing a dynamic range and a resolution without increasing the size and complexity of the mechanism. Therefore, this scanner system can be suitably applied to a scanning probe microscope requiring high rigidity, and can detect displacement of a stage supporting a probe or a sample with high accuracy over a wide scanning range.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration of a scanner system according to a first embodiment, partially cut away.

FIG. 2 schematically shows four light receiving elements included in the position detector shown in FIG.

FIG. 3 shows one specific example of the bifocal optical system shown in FIG.

FIG. 4 shows another specific example of the bifocal optical system shown in FIG.

FIG. 5 shows another specific example of the bifocal optical system shown in FIG.

FIG. 6 shows a spot formed on a position detector by a condensed light beam condensed at a focal position OA, and a relationship between the position of the spot and the inclination of the mirror.

FIG. 7 shows a spot formed on a position detector by a converged light beam condensed at a focal position OB, and the relationship between the position of the spot and the inclination of the mirror.

FIG. 8 shows a schematic configuration of a scanner system according to a second embodiment, partially cut away.

FIG. 9 shows the relationship between the inclination of the plane mirror shown in FIG. 8 and the position of a spot formed on the position detector.

FIG. 10 shows a relationship between a distance from a lens to two position detectors and a size of a spot formed on the position detector in FIG.

FIG. 11 shows a schematic configuration of a scanner system according to a third embodiment, partially cut away.

FIG. 12 shows a schematic configuration of a modified example of the scanner system shown in FIG. 11 with a part cut away.

[Explanation of symbols]

 Reference Signs List 110 mirror 112 light source 120 quarter-wave plate 122 polarizing beam splitter 124 position detector 126 arithmetic circuit 130 bifocal optical system

Claims (3)

[Claims] 1. A displacement sensor of a scanner system for detecting a displacement of a stage fixed to a free end of a tube scanner, a mirror fixed to a back side of the stage, and a light source for emitting a light beam for detecting displacement. Means for directing a light beam from a light source to a mirror; a bifocal optical system for converging the light beam reflected by the mirror to either a first focus or a second focus; and a first focus or a second focus. A position detector located near the two focal points, where the diameter of the spot formed on the light receiving surface is switched according to the switching of the focal point by the bifocal optical system, and a stage based on the output of the position detector A displacement sensor for a scanner system, comprising: a calculation unit for calculating a displacement of the scanner. 2. A displacement sensor of a scanner system for detecting a displacement of a stage fixed to a free end of a tube scanner, a plane mirror fixed on the back side of the stage, and a light source for emitting a light beam for detecting displacement. Means for guiding the light beam from the light source to the plane mirror, lens means for converting the light beam reflected by the plane mirror into a convergent light beam, beam splitting means for splitting the convergent light beam into two, A total of two position detectors, one on each optical path of the two convergent light beams, one of which is located close to the focal point of the lens means, so that its light receiving surface is relatively Two position detectors and two position detectors, where a small light spot is formed and a relatively large light spot is formed on the other light receiving surface Each displacement sensor of the scanner system and a calculation unit for calculating a displacement of the stage based on the output of. 3. A displacement sensor of a scanner system for detecting displacement of a stage fixed to a free end of a tube scanner, a plane mirror fixed on the back side of the stage, and a light source for emitting a light beam for detecting displacement. Means for guiding the light beam from the light source to the plane mirror, lens means for converting the light beam reflected by the plane mirror into a convergent light beam, a position detector arranged on the optical path of the convergent light beam, and a position from the plane mirror. This is a stop that can change the stop diameter provided before reaching the detector.The stop diameter can change the size of the light spot formed on the position detector by appropriately limiting the diameter of the incident light beam. A possible aperture, and a calculation unit that calculates the displacement of the stage based on the output of the position detector. The displacement sensor of the turbocharger toner system.