JP2006308312A - Probe tip evaluation method for scan type probe microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a probe tip evaluation method for scan type probe microscope capable of evaluating the degradation of sharpness of the probe tip with a simple procedure, when the tip of the probe under use is worn. <P>SOLUTION: The probe tip evaluation method for scan type microscope is constituted of a step S13 for measuring the groove A1 with the probe 12A and 12B regarding the reference specimen 11 on which the V-shape groove A1 is formed, the size of which is known, and a step S15 for estimating the sharpness of the tip of the probe, based on the measurement data obtained at the measurement step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a probe tip evaluation method for a scanning probe microscope, and more particularly to a probe tip evaluation method for a scanning probe microscope suitable for estimating the thickness of the tip of the probe.

As a conventional probe evaluation method using a scanning probe microscope, there is a method disclosed in Patent Document 1. In the probe evaluation method disclosed in Patent Document 1, a plurality of standard samples having two or more protrusions (repetition of the same uneven pattern) are prepared, and measurement is performed with a scanning probe microscope using these standard samples. This is a method for estimating the tip shape of the inspection probe used for the measurement. The projections and depressions patterns (parameters such as radius R, height H, pitch P, etc.) are different among a plurality of standard samples. In this probe evaluation method, first, an appropriately selected standard sample is used, and this is scanned with a probe to be inspected to obtain a concavo-convex image (real image). Next, the tip shape of the probe is expressed by a function using appropriate parameters. The above-mentioned standard sample is scanned by simulation using the probe expressed by the function to obtain an uneven image (simulation image). Next, the simulation image is compared with the real image, and the parameters of the function expressing the probe are determined so that the difference is reduced. Thereafter, the simulation image creation step and the function parameter determination step are repeated again, and finally the tip shape of the probe to be inspected is estimated.
JP-A-6-117844

  In the probe tip evaluation method disclosed in Patent Document 1, it is necessary to prepare a plurality of standard samples having different concavo-convex pattern parameters, and furthermore, a concavo-convex image is obtained using a certain standard sample. Then, it is necessary to repeat the procedure of simulating the shape of the probe from the result, exchanging it with a standard sample optimal for evaluation, and acquiring an image again. Therefore, there is a problem that the procedure is complicated.

  In view of the above problems, an object of the present invention is to provide a probe tip evaluation method for a scanning probe microscope that can evaluate the deterioration of the tip tip thickness in a simple procedure when the tip of the probe in use is worn. There is to do.

  In order to achieve the above object, a probe tip evaluation method for a scanning probe microscope according to the present invention is configured as follows.

  The probe tip evaluation method for a scanning probe microscope according to the first aspect of the present invention (corresponding to claim 1) is to measure a V-groove opening with a probe for a reference sample having a V-groove opening of known dimensions. And a estimating step for estimating the thickness of the tip of the probe based on the measurement data obtained in this measuring step.

  In the above-described probe tip evaluation method, when a reference sample having a V-groove opening of a known size formed on the surface is measured by a probe using a normal method, the probe with a thicker tip has a smaller depth than the original depth of the V-groove. The depth is measured. Therefore, record the depth measurement value when measuring the V groove with the probe before using the probe, and obtain the depth measurement value when measuring the V groove again with the probe after using the probe. In addition, by comparing the depth measurement values before and after use, it becomes possible to easily know the state of deterioration due to wear of the probe tip.

  In the probe tip evaluation method (corresponding to claim 2) of the scanning probe microscope according to the second aspect of the present invention, preferably, the measurement data is depth data of a V-groove opening. It is characterized by.

According to the present invention, a reference sample in which a V-groove opening having a known dimension is prepared, the reference sample is measured with a probe to be inspected, and the tip of the probe is based on the measurement data. Since the wear state of the shape is evaluated, changes in the tip of the probe before and after wear can be reliably captured. Furthermore, if the opening angle of the V-groove is known as a known dimension, the radius of the tip of the probe can be estimated from the measured depth data.
Further, according to the present invention, it is possible to evaluate without error due to the slip of the probe during measurement.

  DESCRIPTION OF EMBODIMENTS Preferred embodiments (examples) of the present invention will be described below with reference to the accompanying drawings.

  The basic configuration of an atomic force microscope (AFM) will be outlined as an example of a scanning probe microscope (SPM). Usually, a sample such as a semiconductor substrate having an integrated circuit formed on the surface is placed on a sample stage, and a probe is placed close to the surface of the sample. The probe is a needle member formed at the tip of the cantilever and having a very fine shape. During the measurement, the probe is brought close to the sample at such a distance that an atomic force is generated. Further, when measuring a specific region of the sample surface, the probe is moved so as to scan the sample surface. The relative scanning movement of the probe with respect to the sample surface is performed by a coarse movement mechanism on the sample side and a fine movement mechanism on the probe side. The sample stage functions as a coarse movement mechanism. The fine movement mechanism moves the probe in a direction parallel to the sample surface and in a direction substantially perpendicular to the sample surface. The fine movement mechanism is configured using, for example, a piezoelectric element.

  The atomic force microscope has a function of measuring the concavo-convex shape of the sample surface by utilizing the atomic force generated between the probe and the sample when the probe approaches the sample surface. The interatomic force between the probe and the sample is controlled so as to be kept constant when the probe scans the sample surface. In order to perform this control, for example, an optical lever type optical detection device is provided for detecting bending and twisting of a cantilever provided with a probe. The displacement / deformation detection information of the cantilever detected by the optical lever type optical detection device is input to the control unit, where it is compared with a reference value. A control signal is generated so that the detected data matches the reference value, the control signal is fed back to the fine movement mechanism that determines the position of the probe (cantilever), and the displacement / deformation state of the cantilever matches the reference value Control is performed to

  By moving the probe along the surface of the sample so as to maintain the above state, and obtaining information related to the change in position of the probe with respect to the sample surface at that time, the uneven shape at the atomic level on the sample surface is measured. It becomes possible.

  The sharpness of the tip of the probe is an important factor for measuring the uneven shape of the sample surface with high accuracy. Therefore, a method for accurately evaluating the sharpness (or wear) of the tip of the probe will be described below with reference to the drawings.

  An embodiment of a probe evaluation method according to the present invention will be described with reference to FIGS. FIG. 1 shows a state in which the inspection probes 12A and 12B measure a plurality of grooves A1 formed on the surface of the reference sample 11. In FIG. 1, the probe 12A to be inspected is a probe having a tip 13A before wear, and the probe 12B to be inspected is a probe having a tip 13B after wear. FIG. 2 shows a flowchart for implementing the probe tip evaluation method. FIG. 3 is a diagram mathematically expressing the relationship between the probe to be inspected and the groove when the angle θ of the V-shaped groove is known in the measurement of FIG.

  FIG. 1 shows a probe 12A before the tip is worn and a probe 12B after the tip is worn. In the reference sample 11 having the groove A1, the groove A1 has a V-shaped cross section, and the depth D of the groove A1 is known. When the reference sample 11 having the groove A1 is used as a measurement object and the groove A1 is measured by the probe 12A according to the principle of an atomic force microscope, data of the measurement depth Da is acquired as shown in FIG. Similarly, when the groove A1 is measured with the probe 12B with respect to the reference sample 11, the measurement depth Db is obtained as shown in FIG.

  Accordingly, when the groove A1 of the reference sample 11 is measured by an atomic force microscope equipped with the probe to be inspected, V depends on the thickness of the tip (13A, 13B) of the probe to be inspected (12A, 12B). The measured depth of the groove A1 is different. The deeper the tip of the probe, the deeper the depth of the groove A1 is measured, which is closer to the original depth value D of the groove A1, and the deeper the tip, the shallower the depth of the groove A1 is measured. As a result, the deterioration of the probe before and after wear can be reliably captured.

  Based on the above, the probe tip evaluation method according to this embodiment, as shown in FIG. 2, attaches the inspection probe (step S11), sets the reference sample 11 (step S12), and sets the reference sample 11 by the inspection probe. It consists of measurement (step S13), acquisition of measurement depth data (step S14), and evaluation of the tip of the probe to be inspected (step S15).

  In addition, when the angle θ of the V-shaped groove A1 in the reference sample 11 is known as shown in FIG. 3, the radius of the roundness forming the tip 13C of the probe 12C is “r”. Based on the measurement depth value D and the measurement depth d, the radius r of the probe tip 13C can be estimated by the following equation (2).

D−d = r / sin θ−r (1)
r = (D−d) sin θ / (1-sin θ) (2)

  Therefore, when the angle θ is known, the probe evaluation method according to the present embodiment can be configured so that the tip evaluation step S15 of the probe tip to be inspected is executed using the above formulas (1) and (2). Accordingly, it is possible to estimate the radius of the tip of the probe.

  The configurations, shapes, sizes, and arrangement relationships described in the above embodiments are merely shown to the extent that the present invention can be understood and implemented, and the numerical values and the compositions (materials) of the respective configurations are as follows. It is only an example. Therefore, the present invention is not limited to the described embodiments, and can be variously modified without departing from the scope of the technical idea shown in the claims.

For example, the plurality of V-shaped grooves A1 formed in the reference sample 11 can be formed continuously without a gap as shown in FIG. 1, or can be formed at intervals.
In addition, by using a reference sample in which V-shaped grooves are formed or combined in a plurality of directions, the tip evaluation direction of the probe becomes a plurality, and consistency with an object to be measured by a scanning probe microscope (SPM) is improved. improves.
The probe radius in the present invention intends to mainly estimate the portion in contact with the V-shaped groove, and it goes without saying that a more complicated needle shape can be estimated by using various V-shapes.

  The present invention is used for accurate evaluation of the tip of a probe used in measurement with a scanning probe microscope.

It is a figure for demonstrating embodiment of the probe tip evaluation method which concerns on this invention. It is a flowchart which implements the probe tip evaluation method of this embodiment. It is the figure which expressed mathematically the relationship between a to-be-inspected probe and a groove | channel when the angle ((theta)) of a V-shaped groove | channel is known by the measurement of FIG.

Explanation of symbols

11 Reference Sample 12A, 12B, 12C Inspection Probe 13A, 13B, 13C Tip of Inspection Probe A1 Groove

Claims (2)

A measuring step of measuring the V-groove opening with a probe with respect to a reference sample having a V-groove opening of known dimensions;
An estimation step for estimating the thickness of the tip of the probe based on the measurement data obtained in the measurement step;
A probe tip evaluation method for a scanning probe microscope, comprising: 2. The probe tip evaluation method for a scanning probe microscope according to claim 1, wherein the measurement data is depth data of the V groove opening.

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