JPH05231860A - Interatomic force microscope and its scanning method - Google Patents

Abstract

PURPOSE:To obtain an interatomic force microscope which is provided with a probe composed of an acicular crystal having a high aspect ratio and can accurately measures a sample without receiving any influence from a frictional force in the initial stage of horizontal scanning. CONSTITUTION:This microscope is provided with a probe 1 composed of an acicular crystal and at least a runway section 4 in which no picturing is made in the initial stage of each horizontal scanning for raster scanning. Then the unevenness on the surface of a sample is pictured except the runway section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an atomic force microscope (hereinafter referred to as AFM) and its scanning method, and more particularly to an AFM having a probe having a small tip curvature and a large aspect ratio.
And its scanning method.

[0002]

2. Description of the Related Art In recent years, an AFM has been developed as an apparatus for observing a solid surface in atomic order. In the AFM, in order to detect a minute force, a cantilever 12 having a probe 11 as shown in FIG. 3 and having a length of about 100 μm to 200 μm is required. The sample is observed by raster scanning. Conventionally, as the above-mentioned probe, one using the edge portion of the cantilever tip as a probe, one prepared by using a crystal etch pit as a template, one prepared by anisotropic etching [Journal of Vacuum Science・ And Technology A8 (1990) From page 3386
Page 3396 (J. Vac. Sci. Technol. A8, 3386-3396, 199
0)] etc. are used. The resolution of the AFM depends on the radius of curvature of the tip of the probe, and the smaller the radius of curvature, the higher the resolution. At present, a probe with a radius of curvature of 20 nm to 30 nm is manufactured, and an atomic image of mica or the like is observed using this probe.

However, as an application of the AFM, there is an observation of the sample surface at the atomic level, and at the same time, an observation of the sample having large irregularities on the order of nanometers or microns. In the case of such a sample observation, particularly for a sample having a deep groove shape such as a grating, the above-mentioned probe cannot reach the bottom of the groove portion and accurate shape measurement is difficult. In (1), a probe having a high aspect ratio that reaches the bottom of the groove at the same time as the tip curvature of the probe is small is required, and a probe using needle crystals is promising.

[0004]

In an AFM in which a probe is brought into contact with a sample and a repulsive force generated perpendicularly to the sample surface is detected, when a sample surface is raster-scanned using a probe with a high aspect ratio, At the beginning of the horizontal scanning, the influence of the frictional force generated between the sample and the probe becomes large. Due to this frictional force, the cantilever is twisted, and it is difficult to accurately measure the unevenness of the sample surface at the initial stage of each lateral scanning.

In order to solve the problem of the atomic force microscope having such a high aspect ratio probe, the present invention is an atomic force microscope capable of observing unevenness of a sample surface with high accuracy and a scanning method thereof. The purpose is to provide.

[0006]

Means for Solving the Problems A probe having a ratio of a diameter of a root to a length of 1: 2 or more is provided, and a run-up section which is not imaged is provided at least in the initial stage of each horizontal scanning, and raster scanning is performed. The unevenness of the sample surface other than the run-up section is imaged.

[0007]

According to the above-mentioned scanning method, the initial range of each lateral scan in which the high aspect ratio probe is greatly affected by the frictional force is not imaged, and only the range where the influence of the frictional force disappears is imaged. As a result, it becomes possible to accurately measure the unevenness of the sample surface.

[0008]

EXAMPLES The present invention will be described in more detail below with reference to examples.

FIG. 1 is an explanatory diagram of the AFM scanning method of the present invention. The probe 1 scans the sample surface laterally (X direction).
After performing the reciprocal scanning 2 for one line, the raster scanning is performed by moving in the vertical direction (Y direction) 3 and reciprocally scanning in the horizontal direction again. At the beginning of each lateral scan of the raster scan, the run-up section 4 is provided, and the remaining section is the imaging area 5. FIG. 2 shows a schematic view of the AFM of the present invention using the above scanning method. For the AFM probe 7, a tetrapod-shaped acicular crystal of zinc oxide provided at the tip of the cantilever 6 made of a Si ₃ N ₄ thin film was used. The aspect ratio of the needle crystals is about 20. The force was controlled so that the repulsive force generated when the probe 7 was brought into contact with the sample 8 was constant. For the scanning, a piezoelectric body combined in a tripod type is used, and the sample 8 fixed to the piezoelectric body is scanned. In the scanning, a voltage with a triangular waveform is applied to the piezoelectric body 9 for scanning in the horizontal direction (X direction) so that a region larger than the region to be observed can be scanned.
Raster scanning was performed by applying a stepwise voltage to the scanning piezoelectric body 10. Using the AFM, a polyimide alignment film for liquid crystal was observed. Scanning is performed in the range of 700 nm in the horizontal direction and 500 nm in the vertical direction, and 200 nm at the initial stage of the horizontal scanning is the run-up section. 500 remaining
The area of nm x 500 nm was imaged. By this scanning method, the groove formed on the surface of the alignment film was accurately observed.

The run-up section for removing the influence of the frictional force varies depending on the probe shape, the probe material, the cantilever shape, the material of the sample to be measured, the scanning speed, and the like. In this example,
An approach section of 100 nm or more was required. When a probe having an aspect ratio smaller than that of the present embodiment is used,
The influence of frictional force was eliminated when the run-up area was 100 nm or less. Further, with a probe having an aspect ratio of 2 or less, the influence of frictional force did not appear in the AFM image, and the approach section was not necessary.

The production of the tetrapod-shaped acicular crystals of zinc oxide itself is, for example, a method of oxidizing the surface of zinc fine particles in water and then heating in an oxygen atmosphere [Journal of Crystal Growth 102 ( 1990) No. 965
Pages 973 (J. Crystal Growth 102, 965-973, 199
0)] and the like are known, but the method of the present invention can widely apply such known techniques.

Further, in this embodiment, the Si ₃ N ₄ film is used as the cantilever material, but a SiO ₂ thin film or a metal thin film such as tungsten or gold can be used.

Further, as the tetrapod-shaped acicular crystals, not only those containing zinc oxide as a main component but also those containing zinc selenide as a main component can achieve the same effect.

Further, as needle crystals, SiC, Al
₂ O ₃ , W, graphite, Fe, Cu, B, Sn, Pb, In,
Needle-like crystals having high mechanical strength such as potassium titanate can be used. However, since these crystals are two-dimensional needle crystals, the production yield of cantilevers is worse than that of tetrapod-shaped needle crystals.

[0015]

According to the present invention, an atomic force microscope having a high aspect ratio probe and capable of accurately measuring a sample without being affected by a frictional force at the initial stage of lateral scanning was obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a scanning method of an atomic force microscope according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an outline of an atomic force microscope according to an embodiment of the present invention.

FIG. 3 is a perspective view showing an outline of a conventional cantilever for an atomic force microscope.

[Explanation of symbols]

 1 probe 2 horizontal (X direction) scanning 3 vertical (Y direction) scanning 4 run-up area 5 imaging area 6 cantilever 7 zinc oxide probe 8 sample 9 horizontal (X direction) scanning piezoelectric 10 vertical ( Y direction) Piezoelectric body for scanning 11 Probe 12 Cantilever

Claims (5)

[Claims] 1. In a scanning method of an atomic force microscope, wherein a raster scan is repeated to repeat the horizontal scan while changing the position of the horizontal scan on the sample surface, at least an initial run section is provided at the beginning of each horizontal scan. And a scanning method of an atomic force microscope. 2. A probe having a ratio of the diameter of the root to a length of 1: 2 or more is provided, and at least an initial run section not imaged is provided at the initial stage of each lateral scan, and raster scanning is performed, except for the run section. An atomic force microscope characterized by imaging the unevenness of the sample surface of. 3. The atomic force microscope according to claim 2, wherein the probe is formed of a needle crystal. 4. The atomic force microscope according to claim 3, wherein the acicular crystals have a tetrapod shape containing zinc oxide as a main component. 5. The atomic force microscope according to claim 3, wherein the acicular crystals have a tetrapod shape containing zinc selenide as a main component.