JPH0980060A - Scanning probe microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a scanning probe microscope for obtaining the accurate information of the height of surface of a sample. SOLUTION: A tubular piezoelectric element 36 is supported on a mirror base 43 and a cantilever displacement detecting part 39 is secured to the lower end thereof. The cantilever displacement detecting part 39 is fixed with a cantilever 40 provided with a probe at the forward end thereof. A member 38 having a concave surface to be measured is secured to the upper surface of cantilever displacement detecting part 39 on the inside of tubular piezoelectric element 36. A Z sensor 37 for detecting the displacement of the surface to be measured of member 38 in z-direction is supported by the mirror base 43 and disposed on the inside of tubular piezoelectric element 36. A sample 41 is mounted on a sample stage 42 fixed to the mirror base 43.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a scanning probe microscope.

[0002]

2. Description of the Related Art In a scanning probe microscope, height information of a sample surface is usually calculated from a voltage applied to a piezoelectric element. However, since the piezoelectric element has hysteresis in its operation characteristics and exhibits a creep phenomenon, the applied voltage does not accurately indicate the displacement of the piezoelectric element. For this reason,
A scanning probe microscope provided with a means for detecting the displacement of the piezoelectric element in the Z direction has also been considered.

FIG. 5 shows an example of a scanning probe microscope provided with a Z displacement detection mechanism. The x-scan signal output from the X-scan signal generator 11 and the y-scan signal output from the Y-scan signal generator 12 are supplied to the cylindrical piezoelectric element 2 via the high-voltage amplifier 13, and the cylindrical piezoelectric element 2 is the sample. 3 is scanned in the xy direction. During scanning, the displacement of the cantilever 4 is monitored by the optical system including the laser diode 5, the mirror 6, the photodiode 7, and the differential amplifier 8, and the servo circuit 9 outputs the cantilever 4 based on the output of the differential amplifier 8.
Output a z-servo signal for keeping the displacement of the. z
The servo signal is transmitted through the high voltage amplifier 13 to the cylindrical piezoelectric element 2
The cylindrical piezoelectric element 2 expands and contracts in the z direction so as to keep the displacement of the cantilever 4 constant.

A mirror 18 is provided on the lower surface of the free end of the cylindrical piezoelectric element 2, and the end of the optical fiber 14 connected to the optical interferometer 15 is arranged toward the mirror 18, and the amount of movement of the mirror 18 is set. That is, z of the cylindrical piezoelectric element 2
The directional displacement is measured by the optical interferometer 15. The computer 10 measures z measured by the optical interferometer 15.
The sample 3 based on the displacement and the x-scan signal and the y-scan signal.
Forming an image of the surface of.

[0005]

In this scanning probe microscope, while servo is applied in the z direction and xy scanning is performed,
The optical interferometer 15 detects z displacement of the mirror 18 provided on the lower surface of the free end of the cylindrical piezoelectric element 2, and uses this as height information of the surface of the sample 3. However, the optical interferometer 1
The z displacement of the mirror 18 measured at 5 includes an error due to the tilting of the mirror 18 during xy scanning, which also does not accurately indicate the height information of the sample 3.

This is not limited to the case where an optical interferometer is used, and the same can be said when another optical sensor or an electric sensor such as a capacitance sensor is used.
The measured z displacement includes an error due to the inclination of the measured surface corresponding to the mirror 18.

The situation around this will be described in detail with reference to FIG. Here, in order to facilitate comparison with the examples described later, a probe scanning type will be described as an example, which is different from the sample scanning type scanning probe microscope described above.

As shown in FIG. 6 (A), a cantilever displacement detecting portion 39 is fixed to the lower end of the cylindrical piezoelectric element 36, and a cantilever 40 is attached below it. A Z sensor 37 is arranged inside the cylindrical piezoelectric element 36, and a member to be measured 19 such as a plane mirror, which is an object of measurement, is fixed to the upper surface of a cantilever displacement detecting section 39.

FIG. 6A shows a state in which a flat sample 41 is scanned in the x direction by applying z servo and measured.
As can be seen from the figure, when the cylindrical piezoelectric element 36 bends, the member to be measured 19 tilts and the measurement location of the Z sensor 37 shifts to the end, so that the member to be measured 19 measured by the Z sensor 37 in the z direction is moved. The position includes an error of ΔZ = D1. Therefore, even though the flat sample 41 is being measured, the surface shape to be measured becomes a hilly shape having a height D1 as shown in FIG. 6B.

Therefore, when the sample having the shape shown in FIG. 6C is measured, the surface shape is measured as the shape shown in FIG. 6D.

It is an object of the present invention to provide a scanning probe microscope which can accurately obtain height information on the surface of a sample.

[0012]

The scanning probe microscope of the present invention comprises a probe, a piezoelectric element for causing relative movement between the probe and the sample in three directions, and a surface direction of the sample ( The XY drive means for driving the piezoelectric element so that the relative movement between the probe and the sample occurs in the xy direction) and the relative movement between the probe and the sample in the height direction (z direction) of the sample. Drive means for driving the piezoelectric element so as to cause the measurement, a member to be measured fixed to the piezoelectric element, the member to be measured having the surface to be measured, and the displacement of the surface to be measured of the member to be measured in the z direction are detected. Z
The surface to be measured of the member to be measured is a curved surface having a displacement detection means, and the measurement position by the Z displacement detection means is always the same position in the z direction regardless of the driving of the piezoelectric element in the xy directions.

More specifically, the piezoelectric element is a cylindrical piezoelectric element, the member to be measured is fixed to the inner free end of the cylindrical piezoelectric element, and the surface to be measured is a concave surface.

When the probe is scanned in the surface direction (xy directions) of the sample, the measured surface of the member to be measured always has the same position in the z direction at the measurement point of the Z displacement detecting means. Therefore, if the servo control is performed in the height direction (z direction) of the sample surface so that the distance between the tip of the probe and the sample surface is always constant, the z direction of the measured surface detected by the Z displacement detecting means can be adjusted. The displacement truly reflects the unevenness of the sample surface.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A scanning probe microscope according to an embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the cylindrical piezoelectric element 36 is supported by a mirror base 43, and a cantilever displacement detecting section 39 is fixed to the lower end (free end) of the cylindrical piezoelectric element 36. Cantilever 40 equipped with a probe
Is attached. A member to be measured 38 having a concave surface to be measured is fixed to the upper surface of the cantilever displacement detecting portion 39 inside the cylindrical piezoelectric element 36, and the member to be measured 3
Z sensor 37 for detecting the displacement of the surface 8 to be measured in the z direction
Are supported by the mirror base 43 and are arranged inside the cylindrical piezoelectric element 36.

A sample stage 42 is attached to a mirror base 43 below the cantilever 40, and a sample 41 is placed on it.

The cantilever displacement detector 39 detects the displacement of the cantilever 40 and outputs a lever displacement signal S5 to the servo circuit 34. The servo circuit 34 outputs the z servo signal S4 to the cylindrical piezoelectric element 36 so as to keep the lever displacement signal S5 constant. The XY scanning circuit 33 uses the X scanning signal S
2 and Y scanning signal S3 are output to the cylindrical piezoelectric element 36.
As a result, the cylindrical piezoelectric element 36 is deformed so that the probe of the cantilever 40 traces the surface of the sample 41.

The Z sensor 37 detects the displacement in the z direction of the surface to be measured of the member to be measured 38 provided at the free end of the cylindrical piezoelectric body 36, and outputs the z displacement signal S1 to the Z displacement detection circuit 32. . The microprocessor 30 takes in the x-scan signal and the y-scan signal from the XY scanning circuit 33 as xy position data, and in synchronization with this, the z-displacement signal from the Z-displacement detection circuit is the z-displacement data which is height information of the sample surface. Take in as. The microprocessor 30 transfers the xy position data and the z displacement data to the host computer 31, and the host computer 31 forms an image of the unevenness of the sample surface based on the xy position data and the z displacement data.

Next, the measurement results obtained by the apparatus of this embodiment will be described with reference to FIG. FIG. 2A shows a state in which a flat sample 41 is scanned in the x direction by applying z servo and measured. Measured member 38
Regarding the position in the z direction of the surface to be measured, the portion measured by the Z sensor 37 is always at the same position regardless of the bending of the cylindrical piezoelectric element 36. In other words, as the surface to be measured of the member to be measured 38, a curved surface whose z position at the measurement position by the Z sensor 37 does not change is selected. Therefore, the error ΔZ due to the bending of the cylindrical piezoelectric element 36 is ΔZ = 0.

Therefore, when the flat sample 41 as shown in FIG. 2A is measured, the surface shape to be measured becomes flat as shown in FIG. 2B. FIG.
When a sample having a shape as shown in (C) is measured, the measured surface shape is as shown in FIG. 2 (D).

As described above, according to the present invention, the measurement result showing the shape of the sample surface faithfully can be obtained. The advantage of the present invention is clear when comparing the measurement result of this embodiment in FIG. 2 with the measurement result of the conventional example in FIG.

In the above description, the structure of the Z sensor 37 was not particularly mentioned, but as the Z sensor 37, for example, an electric displacement detection sensor 44 such as a capacitance sensor shown in FIG. 3 is used. You can In this case, a conductive film is provided on the measured surface of the measured member 38. Further, the optical displacement detection sensor 47 such as the optical interferometer shown in FIG. 4 can be used. In this case, an optical reflection film is provided on the measured surface of the measured member 38.

The shape of the surface to be measured of the member to be measured 38 may be a spherical surface or an aspherical surface.
8 is manufactured by applying an optical reflection film or a conductive film to the concave lens, for example.

In the embodiment, an atomic force microscope (AFM) is taken as an example of the scanning probe microscope, but of course, the present invention is an excitation for exciting the cantilever to measure the sample surface shape. It is also applicable to other types of scanning probe microscopes such as a mode AFM, a magnetic force microscope (MFM) for detecting magnetic information on the sample surface, and a tunneling electron microscope (STM).

Further, in the embodiment, the surface to be measured of the member to be measured 38 is a concave surface, but it may be a convex surface depending on the arrangement of the Z sensor 37, the cylindrical piezoelectric body 36, the cantilever 40, and the sample 41. is there.

[0027]

According to the scanning probe microscope of the present invention, since the height information of the sample surface which does not include the error due to the inclination of the member to be measured can be obtained, the true unevenness of the sample surface can be measured.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a scanning probe microscope according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining measurement results by the scanning probe microscope shown in FIG.

FIG. 3 is a diagram showing a state in which an electric displacement detection sensor is used as a Z sensor.

FIG. 4 is a diagram showing a state in which an optical displacement detection sensor is used as a Z sensor.

FIG. 5 is a diagram showing an example of a scanning probe microscope provided with a Z displacement detection mechanism.

FIG. 6 is a diagram illustrating a measurement result by a conventional scanning probe microscope having a Z displacement detection mechanism.

[Explanation of symbols]

32 ... Z displacement detection circuit, 33 ... XY scanning circuit, 34 ... Servo circuit, 36 ... Cylindrical piezoelectric element, 37 ... Z sensor,
38 ... Member to be measured, 40 ... Cantilever.

Claims (2)

[Claims] 1. In a scanning probe microscope, a probe, a piezoelectric element for causing relative movement in three directions between the probe and the sample, and a probe in a surface direction (xy direction) of the sample. The XY drive means for driving the piezoelectric element so that the relative movement between the sample occurs, and the piezoelectric element so that the relative movement between the probe and the sample occurs in the height direction (z direction) of the sample. A Z drive means for driving, a member to be measured fixed to the piezoelectric element and having a surface to be measured, and a Z displacement detecting means for detecting displacement of the surface to be measured of the member to be measured in the z direction. On the surface to be measured of the member to be measured, the measurement position by the Z displacement detecting means is independent of the driving of the piezoelectric element in the xy directions.
A scanning probe microscope, which is a curved surface that always has the same position in the z direction. 2. The scanning probe according to claim 1, wherein the piezoelectric element is a cylindrical piezoelectric element, the member to be measured is fixed to the inner free end of the cylindrical piezoelectric element, and the surface to be measured is a concave surface. microscope.