JPH11271341A - Cantilever displacement detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cantilever displacement detection device for accurately detecting the displacement of a cantilever by securing reading only reflection light from the cantilever. SOLUTION: A cantilever displacement detection device 16 is provided with a displacement detection device body 18 that is mounted to the movable end of an actuator 14 and a displacement detection optical system that is supported at the displacement detection device body 18. A cantilever 10 is mounted to the displacement detection device body 18 at a specific inclination angle via a holder 22. The displacement detection optical system is provided with a light source part 20 for condensing light for detecting displacement on the rear surface of the cantilever and a light reception part 21 for receiving only reflection light from the rear surface of the cantilever 10. Then, the light reception part 21 is provided with a light reception element 28 that receives reflection light from the cantilever 10 and outputs an electrical signal corresponding to the quantity of received light and a light reception position and a diaphragm unit 30 that emits only reflection light from the cantilever 10 toward the light reception element 28 and nearly shields light other than it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cantilever displacement detector for detecting a displacement of a cantilever used in, for example, a scanning probe microscope.

[0002]

2. Description of the Related Art Conventionally, a scanning probe microscope using a cantilever displacement detecting device of this kind includes a cantilever having a sharpened probe at a free end and a scanner for relatively moving the probe and the sample. Have. When the tip is brought close to the sample, the free end of the cantilever is displaced by the interaction (atomic force, repulsion, attractive force, viscosity, magnetic force, etc.) between the tip of the probe and the sample surface. I do. While electrically or optically detecting the amount of displacement occurring at the free end, the probe is relatively scanned in the X and Y directions along the sample surface, so that surface information and the like (for example, unevenness information) of the sample can be tertiary. Originally measured.

It is desired that the cantilever used in such a scanning probe microscope be as flexible as possible and have a high resonance frequency so that extremely weak interactions can be detected. Therefore, in order to satisfy such conflicting demands, it is desired that the cantilever be miniaturized as much as possible. Actually, the width 40μ
m, cantilevers having a length of about 100 to 200 μm are frequently used.

As a cantilever displacement detecting device for detecting the displacement of such a small cantilever, for example, an optical lever type displacement sensor disclosed in Japanese Patent Application Laid-Open No. 9-15250 is generally used. I have.

As shown in FIG. 3, when the displacement detection light L emitted from a light source (not shown) is collected on the back surface of the cantilever 2 (the surface opposite to the surface on which the probe 4 is formed),
When the cantilever 2 is not displaced, the reflected light from the cantilever 2 enters the center of the two-segment photodetector 6. On the other hand, when the cantilever 2 is displaced by the interaction between the tip of the probe 4 and the surface of the sample 8, the spot position on the two-segment photodetector 6 is changed in accordance with the amount of the displacement.

Since the two-segment photodetector 6 can output a displacement signal corresponding to a change in the spot position, the change in the cantilever 2 can be detected by measuring the change in the displacement signal. Becomes possible.

[0007]

However, in the conventional cantilever displacement detecting device, a small cantilever 2 is used.
It is difficult to accurately condense the displacement detection light L with respect to, and a part of the displacement detection light L becomes leakage light La,
There is a case where the sample 8 comes off the cantilever 2 and is irradiated. When the surface of the sample 8 is irradiated with the leakage light La, reflected light or scattered light corresponding to the unevenness of the surface of the sample 8 or a difference in reflectance is generated from the sample 8 and is incident on the two-segment photodetector 6. There are cases.

When such reflected light or scattered light enters the two-divided photodetector 6, an electric signal corresponding to the change in the amount of the reflected light or scattered light becomes noise and is superimposed on the displacement signal. The displacement of the cantilever 2 cannot be detected accurately.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a cantilever capable of accurately detecting the displacement of a cantilever by reliably capturing only reflected light from the cantilever. An object of the present invention is to provide a displacement detection device.

[0010]

In order to achieve such an object, a cantilever displacement detecting device according to the present invention comprises a light source unit capable of condensing displacement detecting light toward the cantilever, and a cantilever. It has a light receiving section that can receive only the reflected light, and this light receiving section can receive the reflected light reflected from the back of the cantilever and output an electric signal corresponding to the received light amount And a stop unit that emits only reflected light reflected from the cantilever toward the light receiving element and can substantially block other light.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cantilever displacement detecting device according to an embodiment of the present invention will be described below with reference to FIGS. As a measuring method of a scanning probe microscope using the cantilever displacement detecting device of the present embodiment, the probe can be excited without exciting the cantilever while maintaining the bending state of the cantilever at the time of setting the probe contact pressure. By scanning along the sample, the static mode measurement method of measuring the surface information of the sample, and in a state where the cantilever is excited at a predetermined resonance frequency,
A dynamic mode measurement method for measuring surface information of a sample by scanning a probe along the sample while maintaining a constant distance between the vibration center and the sample surface is known. In the description, both measurement methods are collectively referred to simply as SPM measurement.

As shown in FIG. 1, in the present embodiment, as an example, the probe 12 at the tip of the cantilever 10 is moved (scanned) in a predetermined direction with respect to a fixed sample (not shown). A probe scanning type probe microscope that measures the surface information of the sample by SPM is assumed.

The probe-scanning probe microscope includes an actuator 14 (for example, a tube-type piezoelectric scanner) that allows the probe 12 of the cantilever 10 to scan the sample surface in a three-dimensional direction. The cantilever displacement detecting device 16 of the present embodiment is supported by the actuator 14. The probe scanning type probe microscope is configured so that the probe 12 of the cantilever 10 can be moved by a predetermined amount in a predetermined direction along the sample by controlling a voltage applied to the actuator 14. I have.

The cantilever displacement detecting device 16 is provided with a displacement detecting device main body 18 attached to a movable end of the actuator 14 and a displacement detecting optical system supported by the displacement detecting device main body 18.
Is attached to the displacement detecting device main body 18 via the holder 22 at a predetermined inclination angle.

The displacement detection optical system includes a light source unit 20 capable of condensing displacement detection light toward the back surface of the cantilever 10 (the surface opposite to the surface on which the probe 12 is disposed);
The light source unit 20 and the light receiving unit 21 can receive only the reflected light reflected from the back surface of the cantilever 10. The light source unit 20 and the light receiving unit 21 respectively receive the displacement detection light from the light source unit 20 on the back surface of the cantilever 10. The position can be adjusted so that the light is guided to a desired position (described later) of the light receiving unit 21 via the light receiving unit.

The light source section 20 includes, for example, a semiconductor laser 24
And a condensing lens 26 for condensing the laser light emitted from the semiconductor laser 24, that is, the light for displacement detection, toward the back surface of the cantilever 10.

The light receiving section 21 receives light reflected from the back of the cantilever 10 and outputs a light signal corresponding to the amount of received light and the light receiving position (for example, a two-divided photodetector). Diode) and only the light reflected from the back of the cantilever 10
And an aperture unit 30 that emits light toward and can substantially block other light.

The diaphragm unit 30 is fixed at a desired position by a fixing member (not shown). As shown in FIG. 2A, a thin plate member 32 having a light shielding property and a predetermined member formed on the thin plate member 32 are formed. And a circular hole 34 having a diameter. The material of the thin plate member 32 is not particularly limited as long as it is optically opaque.

The diameter D1 of the circular hole 34 is such that even when the cantilever 10 is displaced during the SPM measurement, the reflected light from the back surface of the cantilever 10 can be guided to the light receiving element 28 through the circular hole 34. Designed for

In this case, in order to reliably guide the reflected light from the back of the cantilever 12 to the circular hole 34, for example, a condenser lens 36 is disposed in the optical path between the aperture unit 30 and the back of the cantilever 10. Then, this condenser lens 3
6, it is preferable that the reflected light from the back surface of the cantilever 10 is focused on the center of the circular hole 34 of the aperture unit 30.

According to such a configuration, the cantilever 1
In a state where 0 is not displaced, the reflected light from the back surface of the cantilever 10 is condensed by the condenser lens 36 at the center of the circular hole 34 of the diaphragm unit 30 and then the circular hole 34 is formed.
Illuminates the center of the light receiving element 28.

On the other hand, during the SPM measurement, the interaction between the tip of the probe 12 and the sample surface (atomic force, repulsive force,
Cantilever 10 by attractive force, viscosity, magnetic force, etc.
When the tip is displaced, the reflected light from the back surface of the cantilever 10 condensed in the circular hole 34 of the diaphragm unit 30 corresponding to the displaced state is indicated by an arrow S in the drawing (hereinafter referred to as a converging point moving direction S). Go to).

Therefore, if the diameter D1 of the circular hole 34 is sufficiently ensured, the reflected light from the back surface of the cantilever 10 guided by the condenser lens 36 toward the circular hole 34 during the SPM measurement is circular. The light passes through the circular hole 34 and irradiates the light receiving element 28 without being kicked by other parts than the hole 34.

According to such a configuration, during SPM measurement,
The reflected light from the back of the cantilever 10
After being condensed on the circular hole 34 of the aperture unit 30 via 6, the reflected light mostly passes through the circular hole 34 and is irradiated on the light receiving element 28. Further, the reflected light reflected from a portion other than the back surface of the cantilever 10 (for example, the surface of the sample) during the SPM measurement is almost shielded by the thin plate member 32 of the aperture unit 30, so that the light receiving element 28 is hardly irradiated. There is no. As a result, the electric signal output from the light receiving element 28 is hardly superimposed with noise as in the related art, and the electric signal indicates the displacement state (for example, displacement amount, displacement direction, etc.) of the cantilever 10. Output characteristics. Therefore, the displacement of the cantilever 10 can be accurately detected by measuring the change of the electric signal.

In the above-described embodiment, the diaphragm unit 30 in which the circular hole 34 is formed in the thin plate member 32 is used. For example, as shown in FIG.
The above-described operation and effect can be realized even if the thin plate member 32 is formed with the oval hole 38 extending along the line.

According to such an oval hole 38, a sufficient light passage area can be secured along the focusing point moving direction S.
The reflected light from the back surface of the cantilever 10 condensed in the oval hole 38 passes through the oval hole 38 without being kicked by other parts other than the oval hole 38 and is transmitted to the light receiving element 28. Irradiated.

In the above-described embodiment, the light receiving element 28 and the aperture unit 30 are arranged on the optical path in a separated state. For example, as shown in FIG. The aperture unit 30 may be directly attached on the surface 28a.

Specifically, the diaphragm unit 30 shown in FIG. 2C has a light shielding property and the light receiving surface 2 of the light receiving element 28.
The thin plate member 40 includes a thin plate member 40 that can be directly adhered on the thin plate member 8a, and a cutout portion 42 formed in the thin plate member 40. The cutout portion 42 extends along the light collecting point moving direction S. The material of the thin plate member 40 is not particularly limited as long as it is optically opaque.

According to such a configuration, the aperture unit 3
0 can be formed integrally with the light receiving element 28, so that the alignment between the aperture unit 30 and the light receiving element 28 can be easily performed, and the replacement thereof is also facilitated.

More specifically, when positioning between the aperture unit 30 and the light receiving element 28, for example, the cantilever 1
In a state where 0 is not displaced, the light receiving surface 28a of the light receiving element 28 from the cantilever 10 via the condenser lens 36
The spot P converged on the light receiving surface 28a is located at the center position (2
Assuming that the spot P is formed at a position symmetrical with respect to the dividing line 28b, both sides of the spot P (that is, the two dividing lines 2)
Notch 4 so that both sides along 8b) are uniformly shielded from light.
2 may be positioned.

Further, in the above-described embodiment, the light receiving element 28 and the aperture unit 30 are arranged on the optical path in a separated state. For example, as shown in FIG. The light receiving element 28 may be housed, and the aperture unit 30 and the light receiving element 28 may be integrated into a unit.

Specifically, the diaphragm unit 30 shown in FIG. 2D has a housing 44 having a light shielding property and capable of accommodating the light receiving element 28, and a notch 46 formed in the housing 44. The notch 46 is formed in the focusing point moving direction S
Extends along. The material of the housing 33 is not particularly limited as long as it is optically opaque.

According to such a configuration, the aperture unit 3
Since the light receiving element 28 can be housed in the lens unit 0 to be integrally formed, the alignment between the aperture unit 30 and the light receiving element 28 can be easily performed, and the replacement thereof is also facilitated.

More specifically, when the light receiving element 28 is housed in the aperture unit 30, for example, when the cantilever 10 is not displaced, the light receiving surface 28a of the light receiving element 28 is conveyed from the cantilever 10 via the condenser lens 36. Assuming that the focused spot P is formed at the center position of the light receiving surface 28a (a position symmetrical with respect to the dividing line 28b), both sides of the spot P (that is, both sides along the dividing line 28b) The position of the notch 46 may be determined such that the light-shielded portions are uniformly shielded.

In the above-described embodiment, a probe scanning type probe microscope is assumed. However, by moving the sample in a predetermined direction with respect to the fixed probe, the sample surface information of the sample can be measured by SPM. The cantilever displacement detection device of the present embodiment can be used for a scanning probe microscope. Although not shown, the sample-scanning scanning probe microscope allows a sample to be placed on the movable end of an actuator, and controls the voltage applied to the actuator to move the sample to the probe. It is configured to be able to move in a predetermined direction.

[0036]

According to the present invention, it is possible to provide a cantilever displacement detecting device capable of accurately detecting cantilever displacement by reliably taking in only reflected light from the cantilever.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a cantilever displacement detection device according to an embodiment of the present invention.

FIG. 2A is a diagram showing a configuration of an aperture unit applied to a cantilever displacement detection device according to an embodiment of the present invention, and FIG. 2B is a diagram showing an aperture unit according to a modification of FIG. (C) relates to a modified example of the cantilever displacement detecting device, and shows a state in which the aperture unit is attached to the light receiving surface of the light receiving element, and (d) shows a modified example of the cantilever displacement detecting device. FIG. 7E is a diagram illustrating a state where the light receiving element is integrally accommodated in the aperture unit according to the example, and FIG. 8E is a cross-sectional view taken along line ee in FIG.

FIG. 3 is a perspective view showing a configuration of a conventional cantilever displacement detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cantilever 14 Actuator 16 Cantilever displacement detecting device 18 Displacement detecting device main body 20 Light source part 21 Light receiving part 22 Holder 28 Light receiving element 30 Aperture unit

Claims (3)

[Claims] 1. A light source unit capable of condensing displacement detection light toward a cantilever, and a light receiving unit capable of receiving only reflected light reflected from the cantilever. A light-receiving element capable of receiving reflected light reflected from the back of the cantilever and outputting an electric signal corresponding to the amount of received light, and emitting only reflected light reflected from the cantilever toward the light-receiving element, and A cantilever displacement detecting device, comprising a diaphragm unit capable of substantially blocking other light. 2. The cantilever displacement detecting device according to claim 1, wherein the aperture unit is directly attached on a light receiving surface of the light receiving element. 3. The cantilever displacement detecting device according to claim 1, wherein the light receiving element is integrally accommodated in the aperture unit.