JPH1194860A - Scanner system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain measured information of superior reproducibility with no distortions without being affected by a measurement environment, by directly detecting a displacement of a stage with the use of a displacement detection system with a built-in scanner. SOLUTION: A laser light entering a Wollaston prism 26 is branched to projection laser lights La, Lb, reflected at a bi-reflection plane of a reflecting mirror 24, and brought into the Wollaston prism 26 again to interfere with each other. The interference light is converted by a laser displacement detection system 28 to electric signal A, B phases corresponding to counts of fringes of interference fringes. When a stage 10 loading a sample 4 moves, the reflecting mirror 24 alike moves, whereby optical path lengths of the projection laser lights La, Lb are changed. A movement amount, a movement direction of the reflecting mirror 24 are measured from a change of phase amounts of the electric signal A, B phases. Synchronously with a pulse signal Sp output from a pulse generator 50 to which the measured values are input, a sampling part 18 samples a Z driving signal Sz, XY scan signals Sx, Sy, processes an image, and constructs an image signal S2. Accordingly, a surface information without distortions of the sample 4 is obtained three-dimensionally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanner system used for obtaining a minute displacement, for example, a scanner system used for a scanning probe microscope for measuring surface information of a sample with a resolution of the order of nanometers. .

[0002]

2. Description of the Related Art A scanning probe microscope (SPM:
An example of a scanner system will be described using a Scanning Probe Microscope. 2. Description of the Related Art Conventionally, as an example of a scanning probe microscope, a scanning tunneling microscope (STM: Scanning T) has been used with a Binnig or a roller (Rohrer) or the like.
unnelingMicroscope) has been invented. However, ST
In M, the sample that can be observed is limited to a conductive sample. Therefore, an atomic force microscope (AFM: Atm) is used as a device that can observe an insulating sample with a resolution of the order of nanometers by using elemental technologies of the STM such as the servo technology.
omic Force Microscope) has been proposed (Japanese Unexamined Patent Publication No.
JP-A-2-130302).

[0003] The AFM structure is positioned as one of the SPMs. For example, as shown in FIG. 4A, the cantilever 2 and the positional relationship between the cantilever 2 and the sample 4 are relatively changed. A scanner 6 (for example, a tube-type piezoelectric scanner) and a cantilever displacement sensor 8 capable of optically detecting a bending displacement of a free end of the cantilever 2.
With. Note that the sample 4 is mounted on a stage 10 fixed to the scanner 6.

In such an AFM structure, the sample 4 is driven by driving the scanner 6 based on the Z drive signal Sz from the Z scan driver 12 so that the cantilever 2 is moved.
When approached in the direction, the free end of the cantilever 2 is displaced by an interaction (for example, an atomic force, a contact force, a viscosity, a frictional force, a magnetic force, etc.) acting between the sample 4 and the cantilever 2.

The cantilever displacement sensor 8 optically detects the amount of displacement, and outputs the detected value, that is, a displacement signal S 1 to the Z scan driver 12. Z scan driver 1
2 controls the distance between the cantilever 2 and the sample 4 so that the displacement signal S1 from the cantilever displacement sensor 8 is maintained at a preset signal value, and the interaction between the two is constant. ), The Z drive signal S
z is output to the scanner 6 and the scanner 6 is feedback-controlled.

On the other hand, X from the scan controller 14
XY based on the trigger signal Tx and the Y trigger signal Ty
The scan driver 16 sends an X scan signal Sx to the scanner 6.
And the Y scan signal Sy, the cantilever 2 is relatively scanned in XY along the sample 4.

While the XY scanning is being performed while performing the feedback control, the X trigger signal Tx and the Y trigger signal Ty
, The Z drive signal Sz is sampled by the sampling unit 18 and stored in the image memory 20 together with the sampled XY scanning signal as the image signal S2. Then, based on the image signal S2 taken into the image memory 20, surface information (for example, surface unevenness information) of the sample 4 can be obtained three-dimensionally.

[0008]

The scanner 6 typified by a tube-type piezoelectric scanner can be driven with a high resolution, but the displacement characteristic of the scanner 6 with respect to an applied voltage is actually a straight line. Instead of the target, for example, a hysteresis as shown in FIG. Also,
A creep phenomenon in which the amount of displacement of the scanner 6 changes as the voltage application time elapses also occurs.

In the conventional measuring method, the Z drive signal Sz and the XY scanning signal are simultaneously sampled while changing the applied voltage at a fixed step width. That is,
Sampling is performed assuming that the relationship between the displacement of the scanner 6 and the applied voltage is linear, and no consideration is given to the effects of hysteresis and creep. For this reason, it was difficult to obtain surface information of the sample 4 having no distortion and excellent reproducibility.

Therefore, for example, Nanotechnology 6 (1995)
121-126, `` Three-dimensional displa
cement measurement of a tube scanner for a scannin
g tunneling microscope by optical interferometer ''
, The displacement of the stage 10 on which the sample 4 is mounted (for example, the displacement in two directions orthogonal to each other) is directly detected using a laser interferometer (not shown), and the sample 4 A method for correcting surface information has been proposed.

However, in this method, the scanner 6
(Specifically, positions at which the displacement of the stage 10 in two directions perpendicular to each other can be directly detected), the SPM device is increased in size. .

Further, when the measurement environment of each of these laser interferometers changes, a length measurement fluctuation as if the stage 10 is moving occurs even though the stage 10 is not moving. And the fluctuation of the measurement length is superimposed on the surface information of the sample 4 as noise.

The present invention has been made to solve such a problem, and an object of the present invention is to obtain measurement information excellent in reproducibility without distortion without being affected by a measurement environment. It is to provide a compact scanner system.

[0014]

In order to achieve the above object, a scanner system according to the present invention comprises a scanner for moving an object to be measured and a displacement of the object to be measured without being affected by a measurement environment. And a displacement detection system disposed inside the scanner so as to directly detect the light, the reflection means disposed near the object to be measured, and incident light at a predetermined angle. Branching means for irradiating the reflecting means with each other, and causing the respective reflected lights reflected from the reflecting means to interfere with each other; and a predetermined light can be incident on the branching means, and the branching means And a displacement detection system capable of detecting the displacement of the measurement object based on the optical characteristics of the interference light that has interfered via the light source.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A scanner system according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2 by taking as an example a case where the scanner system is incorporated in a scanning probe microscope. In the description of the present embodiment,
The same components as those shown in FIG. 4A are denoted by the same reference numerals, and description thereof will be omitted.

A measuring method applicable to a scanning probe microscope is to scan the probe along the sample without exciting the cantilever while maintaining the bending state of the cantilever at the time of setting the probe contact pressure. With the static mode measurement method that measures the surface information of the sample, and with the cantilever excited at a predetermined resonance frequency, the tip is moved to the sample while maintaining a constant distance between the center of vibration and the sample surface. A dynamic mode measurement method for measuring surface information of a sample by scanning along the line is known. In the following description, both measurement methods will be simply referred to as SPM measurement.

Further, the scanning probe microscope has a probe scanning type for measuring the surface information of the sample by SPM by moving the probe in a predetermined direction with respect to the fixed sample, and a sample scanning type with respect to the fixed probe. Is moved in a predetermined direction to roughly classify the surface information of the sample into a sample scanning type, which can be applied to the present embodiment.

In the probe-type scanning probe microscope, a cantilever is attached to a movable portion of a scanner (for example, a tube-type piezoelectric scanner), and the probe is controlled by controlling a voltage applied to the scanner. Can be moved by a predetermined amount in a predetermined direction along the sample. On the other hand, the scanning probe microscope of the sample scanning type can place the sample on the movable part of the scanner, and controls the voltage applied to the scanner to move the sample to a predetermined position with respect to the probe. It is configured to be able to move in the direction.

As shown in FIG. 1, in this embodiment, as an example, a sample scanning type scanning probe microscope incorporating a scanner system is assumed.
The scanner 6 is mounted on a stage 10 fixed to a movable part of the scanner 6. The scanner 6 is fixed to a fixed base 22.

As shown in FIGS. 1 and 2, the scanner system of the present embodiment is capable of displacing the object to be measured (the stage 10 on which the sample 4 is mounted) (in the XY directions) without being affected by the measurement environment. A displacement detection system capable of directly detecting the displacement of the stage 10 is built in the scanner 6 so that the displacement can be directly detected.

The displacement detection system includes a reflecting means fixed to the back surface of the stage 10 (a surface opposite to the surface on which the sample 4 is mounted), and a reflecting means which branches incident light at a predetermined angle to the reflecting means. Along with irradiating, a branching unit that causes the respective reflected lights reflected from the reflecting unit to interfere with each other, and a laser beam that can be incident on the branching unit and based on the optical characteristics of the interference light that interfered through the branching unit, A laser displacement detection system 28 capable of detecting the displacement of the stage 10.

As an example of the reflecting means in the present embodiment, a reflecting mirror 24 having two reflecting surfaces 24a and 24b which are respectively orthogonal to the optical axes of the two laser beams split by the splitting means is applied. Have been.

As an example of the branching means in the present embodiment, the incident laser light is split into, for example, two outgoing laser lights La and Lb having polarization components orthogonal to each other, and these two outgoing laser lights La and Lb are used. Is applied to the two reflecting surfaces 24a and 24b of the reflecting mirror 24 at right angles.

The laser displacement detection system 28 includes a fixed base 2
2, the laser light source 30 capable of emitting laser light having linearly polarized light orthogonal to each other, for example, and the displacement of the stage 10 based on the optical characteristics of the interference light interfering via the Wollaston prism 26. That is, a displacement detection unit 32 capable of detecting the movement amount and the movement direction in the XY directions is provided.

Next, the operation of this embodiment will be described. In a state where the SPM measurement is being performed while the scanner 6 is feedback-controlled by the Z drive signal Sz from the Z scan driver 12, the laser light having, for example, linearly polarized light orthogonal to each other emitted from the laser light source 30 is reflected by the half mirror 34 , And enters the Wollaston prism 26, and is split into two outgoing laser beams La and Lb having a predetermined deflection angle.

Then, these two emitted laser beams L
a, Lb are the two reflecting surfaces 24 a, 2 of the reflecting mirror 24.
4b, these two reflecting surfaces 24a, 24a,
The reflected laser beams La and Lb respectively reflected from 24b are:
Again, the light enters the Wollaston prism 26 and interferes with each other.

At this time, the interference light emitted from the Wollaston prism 26 is reflected from the half mirror 34,
The light is guided to the displacement detector 32. In the displacement detection unit 32, the interference light is guided to the beam splitter 38 via the λ / 4 plate 36, and is distributed in two directions.

From the interference light transmitted through the beam splitter 38, only light having a linear polarization component parallel to the plane of the drawing (referred to as first linear polarization) is extracted by the first polarizing plate 40. The first linearly polarized light is the first linearly polarized light.
Is converted into an electric signal (A phase) corresponding to the optical characteristics (specifically, the number of interference fringes).

On the other hand, the interference light reflected from the beam splitter 38 is extracted by the second polarizing plate 44, for example, only light having a linear polarization component perpendicular to the plane of the drawing (referred to as second linear polarization). Then, the second linearly polarized light is converted by the second photoelectric conversion element 46 into an electric signal (B) corresponding to its optical characteristics (specifically, the number of interference fringes).
Phase).

In the present embodiment, the reflected light from the first and second polarizing plates 40 and 44 is prevented from entering the optical path including the Wollaston prism 26 via the half mirror 34. Thus, the direction of the optical axis of the λ / 4 plate 36 is adjusted.

At this time, the first and second photoelectric conversion elements 4
Electric signals (A-phase, B-phase) respectively output from 2, 46
Have a phase difference of 90 ° from each other. Where, for example,
If the stage 10 moves by the distance x in the X direction, the reflection mirror 24 also moves with the movement of the stage 10, so that the optical path lengths of the two emitted laser beams La and Lb change.

Specifically, the two reflecting surfaces 24a, 24b
Respectively form an angle θ (see FIG. 2) with respect to the horizontal plane H, the optical path length change amount Δx1 of the emitted laser light La
Decreases by Δx1 = xsinθ, while the optical path length variation Δx2 of the emitted laser light Lb increases by Δx2 = xsinθ.

When the two laser beams La and Lb whose optical path lengths are changed interfere with each other, the optical path length change component becomes 2
Interference light having an optical characteristic of xsin θ is obtained. In this case, the optical characteristics of the interference light (the number of interference fringes)
, That is, a change in the optical path length, is caused by the electric signals (A-phase and B-phase) output from the first and second photoelectric conversion elements 42 and 46, respectively.
Appears as a change in the phase difference.

At this time, the interpolation circuit 48 counts the change in the phase difference between the electric signals (A-phase and B-phase) corresponding to the change in the number of interference fringes, whereby the movement amount and movement of the reflection mirror 24 are calculated. The direction is measured, and the measured value is output to the pulse generator 5.
Output to 0. Note that the measured value measured at this time is also the moving amount and moving direction of the stage 10 and the sample 4 that can be the measurement target.

The pulse generator 50 generates a predetermined pulse signal Sp every time the length measurement value changes by a predetermined value.
Output to The sampling section 18 samples the Z drive signal Sz from the Z scan driver 12 and simultaneously samples the XY scan signals Sx and Sy from the XY scan driver 16 in synchronization with the input timing of the pulse signal Sp. Then, by subjecting these signals Sx, Sy, Sz to predetermined image processing, an image signal S2 is constructed and stored in the image memory 20.

Then, based on the image signal S2 fetched into the image memory 20, surface information (for example, surface unevenness information) of the sample 4 having no distortion and excellent reproducibility can be obtained three-dimensionally.

As described above, according to the present embodiment, by applying the displacement detection system capable of directly detecting the displacement of the stage 10, the surface information of the sample 4 can be obtained without any influence of hysteresis or creep phenomenon. Obtainable.

Further, by incorporating the displacement detection system inside the scanner 6 which is isolated from the outside, it is possible to obtain measurement information having no distortion and excellent reproducibility without being affected by the measurement environment. Specifically, the scanner 6
The measurement environment between the Wollaston prism 26 and the reflection mirror 24 can be always kept constant in the scanner 6 even when the measurement environment outside the scanner changes, and the Wollaston prism 26 and the reflection mirror 24 can be maintained. Can be arranged close to the object to be measured (the sample 4 and the stage 10), so that highly accurate measurement can always be performed.

Further, by incorporating the displacement detection system inside the scanner 6 isolated from the outside, the scanner system can be made compact. Note that the present invention is not limited to the above-described embodiment, and can be variously changed without adding new matter.

In the above-described embodiment, the movement amount in the X direction and uniaxial length measurement in the movement direction have been described as an example. For example, the reflection mirror for the X direction and the reflection mirror for the Y direction are fixed to the stage 10, respectively. In addition, by disposing a pair of Wollaston prisms and a laser displacement detection system corresponding to these reflection mirrors, it is possible to measure the movement amount and movement direction in the XY directions simultaneously or separately.

In the above-described embodiment, the Z drive signal Sz applied to the scanner 6 is sampled as the Z-direction displacement information. Instead, for example, the Z-direction displacement of the scanner 6 is directly detected. A possible displacement detector may be provided in the scanner 6.

In the above-described embodiment, the method of counting the number of interference fringes is employed. For example, the emitted laser beams La and Lb are regarded as light having different frequencies from each other, and the respective frequencies are determined by the heterodyne method. The amount of movement and the direction of movement of the reflection mirror 24, that is, the stage 10, may be measured by the analysis.

In the above-described embodiment, the stage 10 and the sample 4 are applicable as the measuring objects in relation to the description of the sample scanning type scanning probe microscope, but the probe scanning type scanning probe is used. In the microscope, since the cantilever 2 is attached to the movable portion (for example, the stage 10) of the scanner 6, the object to be measured can be the cantilever 2 and the stage 10.

Further, the scanner system according to the present invention can be used not only in the scanning probe microscope used in the description of the embodiment, but also in various fields requiring quantitative minute displacement such as a stage. . For example, it may be used for driving a sample stage used for micromanipulation or a stylus for performing manipulation, and a laser scanning microscope (LSM).
It may be used for the stage of icroscope). Further, it is also effective to use the stage for an optical microscope that requires a small displacement.

For example, as shown in FIG. 3, the reflection mirror 24, the Wollaston prism 26, and the laser displacement detection system 28 are arranged outside the scanner 6, and these are not affected by the fluctuation of the measurement environment. The detection environment of the displacement detection system may be protected by a detection environment holding means that can always keep the detection environment constant.

As shown in FIG. 3, in the present modification, the detection environment holding means includes first and second hollow cylindrical members 60 and 62 extending in parallel with the scanner 20. The first hollow cylindrical member 60 has a base end fixed to the stage 10 and a front end extending in the direction of the fixed base 22 in a free state. Further, the first hollow cylindrical member 60 is formed of a material having a low density, such as plastic, and is sufficiently thin, so that the entire measurement object (that is, the stage 10 on which the sample 4 is mounted) is formed. Is increased only by about 1%. For this reason, the resonance frequency of the scanner 6 in the SPM measurement is not reduced.

The second hollow cylindrical member 62 has a smaller diameter than the first hollow cylindrical member 60, and has a base end fixed to the fixed base 22 and a distal end fixed to the first hollow cylindrical member 62. It extends inside the tubular member 60 and is in a free state.

The first and second hollow cylindrical members 60,
The respective tips of 62 have a predetermined gap and partially overlap each other so that they do not collide with or press against each other when the stage 10 is moved during SPM measurement.

The diameter of the first hollow cylindrical member 60 and the diameter of the second hollow cylindrical member 62 are not particularly limited as long as they do not collide with each other or come into pressure contact with each other. In the present modification, a Z displacement sensor capable of detecting a Z-direction displacement (vertical displacement) of the measurement target may be arranged in the scanner 6. As an example of the Z displacement sensor, as an example, a capacitance sensor 64 fixed to the fixed base 22
And a capacitance sensor target 66 fixed to the stage 10. Based on a capacitance change caused by a change in the space between the capacitance sensor 64 and the capacitance sensor target 66, the stage 10 in the Z direction is used. The actual displacement (movement amount and movement direction) can be directly detected.

Therefore, when this Z displacement sensor is arranged, the actual displacement of the stage 10 in the Z direction is directly detected, and the scanner 6 is fed back in the Z direction by the Z drive signal Sz while taking the detected data into account. It becomes possible to control. For this reason, it is possible to improve the accuracy of the feedback control.

[0051]

According to the present invention, it is possible to provide a compact scanner system capable of obtaining measurement information excellent in reproducibility without distortion without being affected by the measurement environment.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration in which a scanner system according to an embodiment of the present invention is incorporated in a scanning probe microscope.

FIG. 2 is a diagram showing an internal configuration of the laser displacement detection system shown in FIG.

FIG. 3 is a diagram showing a main configuration of a scanner system according to a modified example of the invention.

FIG. 4A is a diagram illustrating a configuration of a conventional scanner system, and FIG. 4B is a diagram illustrating hysteresis characteristics of the scanner.

[Description of Signs] 2 Cantilever 4 Sample 6 Scanner 10 Stage 24 Reflection mirror 26 Wollaston prism 28 Laser displacement detection system

Claims (3)

[Claims] 1. A scanner for moving a measurement object, and a displacement detection system arranged inside the scanner so as to directly detect a displacement of the measurement object without being affected by a measurement environment. The displacement detection system includes: a reflection unit disposed near the object to be measured; and an incident light that is branched at a predetermined angle and radiated to the reflection unit, respectively, and reflected from the reflection unit. A branching unit that causes reflected light to interfere with each other, and a predetermined light that can be incident on the branching unit, and a displacement of the measurement object based on an optical characteristic of the interference light that interferes via the branching unit. And a displacement detection system capable of detecting an error. 2. The scanner system according to claim 1, wherein the reflection unit includes a reflection mirror having reflection surfaces formed at right angles to an optical axis of the light branched by the branching unit. . 3. The branching means includes a Wollaston prism capable of dividing incident light into lights having different polarization components and irradiating the light perpendicularly to the reflecting means. The scanner system according to claim 1, wherein: