JP3158159B2 - Cantilever lever with tall probe for atomic force microscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cantilever with a tall probe for an atomic force microscope. More specifically, the invention of this application is useful for atomic force microscope observation of grain boundaries with large irregularities used to elucidate the mechanism of delayed fracture and fatigue fracture of high-strength steel in the form of grain boundary fracture. The present invention relates to a cantilevered lever with a tall probe for an atomic force microscope.

Conventionally, a cantilever provided with a fine probe has been known as a means for observing a solid surface with an atomic force microscope (AFM). Figure 1 of the attached drawings
FIG. 1 is a schematic view showing a conventional cantilever lever and a method for producing the same. Conventionally, as a method of forming a cantilever, as shown in FIG. 1, a silicon nitride layer formed on a silicon wafer (1) is patterned according to the shape of a cantilever including a probe (2). A method is known in which the probe (2) and the lever (3) are integrally formed by etching.

[0003] The cantilever lever comprises a probe (2), a lever (3) and a lever fixing part (4) which are integrally formed as described above.
And is formed by. There are two types of AFM observation methods using such a cantilever lever, a contact mode and a tapping mode. The contact mode is an AFM observation method in which the tip of the probe (2) is in contact with the sample surface. The mode is an AFM observation method in which the lever (3) is swung at a high frequency and the tip of the probe (1) hardly touches the sample surface.

FIG. 2 of the accompanying drawings shows an example of the use of the conventional cantilever lever (3). The height (H) of the probe (2) in either mode of the lever (3) is shown. Is several μm
And at most about 20 μm. For example, Table 1 shows the probe height and spring constant of the cantilever lever up to now. The height (H) of the probe (2) is 20 μm or less.

[0005]

[Table 1]

However, the conventional cantilever lever (3)
In the AFM observation using the method, since the height (H) of the probe (2) is limited, the AFM observation can be used only for observation of an object sample (11) having a relatively small uneven surface such as a semiconductor material. there were. The most extreme example of small irregularities is observation of an atomic image of a mica surface. Because of the limitations of such conventional cantilever levers for AFM observation, there has been a problem that it is conventionally difficult to observe a surface with more irregularities.

For example, as shown in FIG. 3, in order to elucidate the mechanisms of delayed fracture and fatigue fracture of steel materials, the distribution of precipitates at the nm level on the grain boundary fracture surface caused by these fractures, It is necessary to investigate the relationship between and slip deformation. However, in the conventional cantilever lever (3), since the height of the probe (2) is low at a grain boundary fracture surface or the like having large irregularities, the lever (3) surface collides with the sample convex portion and observation is not possible. And so on.

In order to solve such a problem, it is conceivable to increase the height (H) of the probe (2).
However, it is not easy to increase the height (H) of the probe (2). How to make the structure, how to process, etc. is a big problem in practice. Also, it is not easy to set the height (H).

Accordingly, the invention of this application is to provide a new piece having a higher probe height and a tall probe, which enables observation on the nanometer level on a surface with large irregularities such as a grain boundary fracture surface. It is an object to provide a holding lever.

[0010]

Means for Solving the Problems The invention of the present application solves the above-mentioned problems. First, a cantilever with a probe for an atomic force microscope is provided on the lever. The probe has a structure in which the probe is inserted into the hole.
It has a collar at the end opposite to the end so that it can be inserted into the lever hole.
In this case, the collar contacts the lever surface,
A cantilever lever for an atomic force microscope, wherein the probe height from the back of the lever to the tip of the probe in the inserted state is 50 μm or more. .

[0011]

[0012] And also, the invention of this application, the second, a cantilever for an atomic force microscope of the first aspect, one location or multiple locations in the laser beam spot of the lever the hollow portion cantilever is provided lever, the third, and the lever portion of the cut out portion and provided adjacent thereto to provide a cantilever which is the laser beam spot portion.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention of this application has the features described above, and the embodiments will be described below with reference to the drawings and examples.

[0014]

4 to 6 are views illustrating a cantilever lever with a tall probe according to the present invention and a method of forming the same. FIG.
1 shows a method for producing a metal probe with a flange by applying a method for producing a metal probe for a scanning tunneling microscope (STM). The procedure is as follows.

The upper portion of the thin metal wire is coated with a resin or the like. The exposed portion of the thin metal wire is thinned by electrolytic etching. A thin metal wire is pulled up and the tip of the probe is processed at the gas-liquid interface. The coating layer is removed, and the upper excess part is cut off to obtain a metal probe with a collar.

For example, by the above procedure, a metal probe having a flange portion illustrated in FIG. 4 is obtained. The probe having the brim portion is effectively used when accurately determining the probe height. On the other hand, when it is not necessary to determine the height accurately unlike a metal probe with a collar, a metal probe for STM can be used. The radius of curvature at the tip is 50 nm.
Any material can be used for the probe, as long as the probe can be formed to the degree.

FIG. 5 shows an example of a lever cut out from a SUS304 stainless steel thin plate having a thickness of 10 μm by photolithography. At present, the thickness of the stainless steel thin film is 5 μm intervals, so that the thickness of the lever is 15,
It can be changed to 20, 25 μm. Further, the length of the width of the lever can be arbitrarily determined by newly forming a photomask. Further, a silicon thin plate or the like can be used as the thin film.

FIG. 6 shows a method for assembling a lever with a tall probe. The procedure is as follows. For example, a thin plate of stainless steel or the like is set to a predetermined size by an etching process. This produces a lever (3) having a hole. A metal probe with a brim (2) is inserted into a hole provided in the lever (3), and is fixed with, for example, an adhesive.

As a result, assembling is completed, the probe is inserted into the hole provided in the lever, and the probe height (H) from the lever back surface to the probe center in the inserted state is, for example, shown in FIG. The probe is 0.5 mm (500 μm) as shown.
Because of the collar, the collar contacts the surface of the lever (3), and the probe height (H) is set to a predetermined value by this contact.

According to the present invention, the probe height (H) from the lever surface to the tip in the inserted state is 50 μm.
It is required to be above. The height (H) is more preferably 80 μm or more, and still more preferably 100 μm or more, from the viewpoint of grain boundary observation by AFM observation and the like, and from the viewpoint of processing and production.

Tables 2 and 3 show examples of specifications of the tall probe-equipped lever of the present invention for contact and tapping.

[0022]

[Table 2]

[0023]

[Table 3]

Referring to FIG. 7, the spring constant k, the rotation angle θ of the probe mounting portion, and the resonance frequency ω are given by the following equations.

[0025]

(Equation 1)

Here, W is the measuring force, b, l, and h are the width, length, and thickness of the lever, and m is the mass 1 = (b · h ＾ 3) of the probe.
/ 12 is the bending stiffness. In the contact mode, b, h, and l have the same dimensions as those shown in FIG. 5, and in the tapping mode, h is set to 100 μm. Table 1
As shown in the conventional example, since the spring constant of the tall probe lever for the contact mode is larger than that of the normal probe lever, when the measuring force is the same, the rotation angle is reduced to 1/20. . In the AFM observation, the rotation angle is controlled to be constant by the optical lever method. However, since the accuracy of the detector is high, it is possible to measure even if the lever displacement becomes about 1/20. On the other hand, in order to make the rotation angle the same, the measuring force of the tall probe lever must be increased to 20 times that of the normal probe lever.
When a hard material such as a grain boundary surface of steel is targeted, the sample will not be damaged even if the measuring force is increased by a factor of 20.

In the tapping mode, the piezo is vibrated at the resonance point of the lever, and the piezo is controlled so that the probe approaches the sample or taps lightly so that the decrease in amplitude is constant, and a three-dimensional image is formed. obtain. 10KH for normal AFM
The lever is excited by a piezo actuator in the range of z to 1 MHz. Since the height of the tall probe lever is larger than that of a normal cantilever lever, in order to increase the resonance frequency of the lever, the spring constant must be increased. In the tapping mode, the probe does not completely contact the sample, so that even if the spring constant is increased, the measuring force does not become excessive. Therefore, as shown in Table 3, the plate thickness is increased and the spring constant is increased. Is increased, and the resonance frequency can be set to an appropriate value.

As described above, a surface having large irregularities such as a grain boundary fracture surface of a steel is measured by AF using a tall probe cantilever lever.
M observations are possible. With respect to the lever with the tall probe as described above, further improvements and optimizations are proposed in the present invention. Therefore, the contrivance and optimization will be described below. <1> AF by cantilever lever with tall probe of the present invention
M Observation FIG. 8 of the attached drawings shows the measurement principle of AFM.

As shown in FIG. 8, when the cantilever lever (3) having the probe (2) is brought close to the sample (11), the cantilever lever (3) is bent, and the lever fixing portion (4).
The lever (3) rotates. The rotation angle of the lever (3) at this time is measured by irradiating the lever (3) with the laser beam (6) and detecting the position of the reflected light with the photo sensor (9), and the probe (2) And sample (1
The measuring force during 1) is determined. By controlling the rotation angle of the lever (3), that is, the measuring force to be constant, the piezo (10) moves up and down in the Z direction, that is, the height direction of the irregularities on the surface of the sample (11), and height information, that is, an AFM image is obtained. Can be

An AFM operating in the atmosphere usually has a CC
A D camera (5) is provided, and a position to be measured by the AFM can be determined to some extent on a surface of a semiconductor or the like having a small unevenness. However, since observation by the CCD camera (5) is performed from directly above, observation cannot be performed in a state where the tip of the probe (2) is in direct contact with the surface of the sample (11).
Recently, it has become possible to install an SEM (8) in an AFM operating in a vacuum. In this case, the sample (1
Although the observation is oblique to 1), the tip of the probe (2) and the surface of the sample (11) can be observed simultaneously.

FIG. 9 of the accompanying drawings shows the positional relationship between the cantilever lever (3) and the laser spot (12) when the conventional cantilever lever (3) is irradiated with laser light (6). FIG. 10 shows the shape of incident light obtained by a conventional lever and the positional relationship of the photosensor (9) (as viewed from the laser incident direction). The dimensions of the conventional cantilever lever (3) are 20 μm in width and 1 in length.
It is a strip of 100 to 500 μm. Since the diameter of the laser spot (12) of the laser light (6) is larger than the width of the lever (3), the laser light (6) reflected on the surface of the lever (3) is as shown in FIG. It is incident on the photosensor (9) as a laser spot (12) having a simple shape. And a photo sensor (9) divided into two parts up and down
The rotation angle of the lever (3) is detected from the difference in the amount of received light. Therefore, the accuracy of the AFM is determined by the shape of the lever (3) rather than the diameter of the laser spot (12).

The tall probe (2) of the present invention (particularly 0.5 m
By combining the cantilever lever (3) having a height of at least m with the AFM, it is possible to perform AFM observation of a highly uneven surface such as a grain boundary fracture surface formed by delayed fracture or fatigue fracture of high-strength steel. However, as shown in FIG. 8, by combining the SEM (8), a portion where the tip of the probe (2) is in contact with the surface of the sample (11) can be observed. In particular, since the grain boundary fracture surface has an irregular surface shape, the support of the SEM (8) is indispensable.

FIG. 11 of the accompanying drawings shows a cantilever lever (3) with a tall probe of the present invention and a laser spot (1).
It shows the positional relationship of 2). FIG. 12 is an enlarged plan view of the tip of the lever showing the laser spot (12). As shown in FIGS. 7A and 7B, the cantilevered lever (3) with a tall probe of the present invention that enables such AFM observation uses the tall probe (2). The lever dimensions are as large as, for example, 500 μm in width and 1.5 mm in length. Therefore, all the laser light (6) is reflected on the lever (3) surface and is incident on the photo sensor (9).

FIG. 13 of the accompanying drawings shows a laser spot (1) obtained by the lever with a tall probe of the present invention.
FIG. 3 shows the positional relationship between the shape of 2) and the photosensor (9) (as viewed from the laser incident direction). However, as shown in FIG.
Since 2) may protrude from the photosensor (9), the difference in the amount of received light between the two detectors is less likely to occur than in the case of the conventional lever (3) shown in FIG. A problem arises in that the measurement accuracy of the rotation angle of the light source is reduced. <2> Optimization of the structure of the cantilevered lever with a tall probe of the present invention Therefore, the measurement of the rotation angle of the lever (3) during the measurement using the cantilevered lever with a tall probe of the present invention (3) In order to improve the accuracy, it is considered to optimize the lever (3).

<Optimization Method for Laser Irradiation Section (A)> FIG. 14 of the accompanying drawings shows a method for optimizing one laser irradiation section (A) for the cantilever lever (3) with a tall probe of the present invention. FIG. 15 shows the positional relationship (as viewed from the laser incident direction) between the laser spot (12) of the incident light and the photosensor (9) in the optimization method (A). It is.

As shown in FIG. 14, two hollow portions (14) are provided along the length of the lever (3). The sum of the widths of these two hollow portions (14) is made larger than the diameter of the laser spot (12), and the width of the bridge portion (15) between the hollow portions (14) is changed to the conventional lever (3). When the width is about 20 μm,
The laser spot (12) reflected from the bridge portion (15) and incident on the photo sensor (9) is shown in FIG.
5 and the difference in the amount of received light between the upper and lower detectors is likely to occur, so that the measurement accuracy of the rotation angle of the lever (3) is improved.

<Optimization Method of Laser Irradiation Section (B)> FIG. 16 of the accompanying drawings shows another optimization method (B) of the laser irradiation section for the cantilever lever (3) with a tall probe of the present invention. ). As shown in FIG.
The laser beam (6) may be applied to the edge of the laser (3) by providing the hollow portion (14) only at the location. However, the optimization method (A) having two hollow portions as shown in FIG. 14 is structurally more stable and the bridge portion (15) than the optimization method (B). The probability of damaging is low.

<Optimization Method of Laser Irradiation Section (C)> FIG. 17 of the attached drawings shows another optimization method of the laser irradiation section (3) of the cantilever lever (3) with a tall probe according to the present invention. FIG. 18 shows the positional relationship (as viewed from the laser incident direction) between the laser spot (12) of the incident light and the photosensor (9) in the optimization method (C). Things.

When two hollow portions (14) are provided side by side in the width direction of the lever (3), the bridge portion (15)
Reflected light from the photosensor (9) protrudes at the upper end and the lower end of the photosensor (9), and the accuracy of the rotation angle of the lever (3) deteriorates. Therefore, when a hollow portion (14) having a shape as shown in FIG. 17 is provided, on the photosensor, FIG.
The shape of the reflected light as shown in FIG.
The accuracy of the measurement of the rotation angle is improved, and the accuracy of the AFM observation is also improved.

<Optimization Method of Laser Irradiation Section (D)> FIG. 19 of the accompanying drawings further shows a method of optimizing the laser irradiation section of the cantilever lever (3) with a tall probe of the present invention (D).
It is shown. In order to perform the SEM observation and the AFM observation at the same time, the protrusion of the lever (3) from the portion where the probe (2) is attached comes into the field of view of the SEM. Should be smaller.

Therefore, as shown in FIG. 19, laser irradiation parts are arranged on both sides of the probe (2), and the protrusion of the lever (3) is reduced. In consideration of the balance of the lever (3), two hollow portions (14) are provided on both sides. Also in this case, the shape of the bridge portion (15) is as shown in FIG.
The shape shown in FIG. <Optimization method of laser irradiation part (E)> The above-mentioned cantilever lever (3) with a tall probe of the present invention has a contact mode in which the tip of the probe (2) is in contact with the surface of the sample (11). It can be used for two types of AFM observations: tapping mode, no touch, or only slight touch.

In the contact mode, as in the method (A) for optimizing the laser irradiation part shown in FIG. 14 or the method (D) for optimizing the laser irradiation part shown in FIG. It is important to reduce the spring force by reducing the thickness to about 10 μm to reduce the measurement force. FIG. 20 of the attached drawings shows a method (E) for optimizing the laser irradiation part of the cantilever lever (3) with a tall probe according to the present invention.

As shown in FIG. 20, in order to prevent such a twist of the lever (3), it is possible to increase the torsional rigidity by providing a large cut-out portion (14) at the center of the lever (3). It is. On the other hand, in the tapping mode, it is necessary to increase the thickness of the lever (3) and increase the resonance frequency.

The invention of this application, for example, as described above, has a high-precision AFM having a surface with large irregularities such as a new grain boundary fracture surface by a configuration as described above.
Provided is a cantilever with a tall probe for an atomic force microscope that enables observation to be realized. Of course, the present invention is not limited by the above examples.

[0045]

As described in detail above, according to the invention of this application using a cantilever with a tall probe, by combining the cantilever with a tall probe with an atomic force microscope, a new nm level can be obtained. Can contribute to the elucidation of the mechanism of delayed fracture and fatigue fracture of high-strength steel that takes the form of grain boundary fracture.

By the nano-grain boundary analysis method, a guideline for improving characteristics of delayed fracture and fatigue fracture can be obtained. The strength can be increased to 200 kg. Also, by combining the cantilevered lever with tall probe of the present invention, which has been optimized, and the AFM,
AFM observation of a surface having large irregularities such as a grain boundary fracture surface formed by delayed fracture or fatigue fracture becomes possible with high accuracy.

Further, in combination with the SEM, positioning for AFM observation and acquisition of low-magnification information become possible.

[Brief description of the drawings]

FIG. 1 is a schematic view of a conventional cantilever lever.

FIG. 2 is a diagram showing an example of use of a conventional cantilever lever (3).

FIG. 3 is a diagram showing a state of AFM observation of a surface having large irregularities.

FIG. 4 is a front view illustrating a method for producing a metal probe with a brim.

FIG. 5 is a plan view and a front view showing an example of a cantilever lever with a tall probe.

FIG. 6 is a perspective view illustrating assembling of a cantilever lever with a tall probe.

FIG. 7 is a schematic diagram when measuring a cantilever lever.

FIG. 8 is a diagram showing the measurement principle of AFM.

FIG. 9 shows a laser beam (6) applied to a conventional cantilever lever (3).
FIG. 4 is a plan view showing a positional relationship between a cantilever lever (3) and a laser spot (12) when the laser beam is irradiated.

FIG. 10 is a plan view showing the shape of incident light obtained by a conventional lever and the positional relationship (as viewed from the laser incident direction) of the photosensor (9).

FIG. 11 shows a cantilevered lever with a tall probe according to the present invention (3).
It is the front view and top view which showed the positional relationship of the laser spot (12).

FIG. 12 is an enlarged plan view of the tip of the lever of FIG. 11;

FIG. 13 is a plan view showing the shape of a laser spot (12) obtained by the cantilevered lever with a tall probe of the present invention and the positional relationship (as viewed from the laser incident direction) of the photosensor (9). .

FIG. 14 shows a cantilevered lever with a tall probe according to the present invention (3).
FIG. 5 is a plan view showing a method (A) for optimizing a laser irradiation section of FIG.

FIG. 15 is a plan view showing the positional relationship between the laser spot (12) of the incident light and the photosensor (9) (as viewed from the laser incident direction) in the optimization method (A).

FIG. 16 shows a cantilevered lever with a tall probe according to the present invention (3).
FIG. 6 is a plan view showing a method (B) for optimizing a laser irradiation section of FIG.

FIG. 17 shows a cantilevered lever with a tall probe according to the present invention (3).
FIG. 4 is a plan view showing a method (C) for optimizing a laser irradiation section of FIG.

FIG. 18 is a plan view showing the positional relationship between the laser spot (12) of incident light and the photosensor (9) (as viewed from the laser incident direction) in the optimization method (C).

FIG. 19 shows a cantilevered lever with a tall probe of the present invention (3).
FIG. 5 is a plan view showing a method (D) for optimizing a laser irradiation unit.

FIG. 20 shows a cantilevered lever with a tall probe of the present invention (3).
FIG. 5 is a plan view showing a method (E) for optimizing a laser irradiation section of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon wafer 2 Probe 3 Cantilever 4 Lever fixing part 5 CCD camera 6 Laser output 7 Reflection mirror 8 SEM (scanning electron microscope) 9 Photosensor 10 Piezo 11 Sample 12 Laser spot 13 Tall probe mounting hole 14 Cutout part 15 Bridge part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-320919 (JP, A) JP-A-7-253435 (JP, A) JP-A-8-21845 (JP, A) JP-A-10- 221355 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 13/10-13/24 G12B 21/00-21/24 G01B 21/30 G01B 7/34 H01J 37/28 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A cantilevered lever with a probe for an atomic force microscope having a structure in which a probe is inserted into a hole provided in the lever, wherein the probe has an end opposite to a tip. Has a brim,
When inserted into the lever hole, the collar part is on the lever surface.
The probe height is determined by this contact.
A cantilever for an atomic force microscope, wherein the height of the probe from the back surface of the lever to the tip of the probe in the inserted state is 50 μm or more. 2. A cantilever for an atomic force microscope according to claim 1.
A bar, one of which is located at the laser beam spot on the lever.
Cantilever lever with multiple or multiple cutouts . 3. A hollow portion and a lever portion adjacent to the hollow portion.
3. The cantilevered lever according to claim 2 , wherein said is a laser beam spot portion .