Method for evaluating probe for atomic force microscope and method for measuring surface shape of measurement sample

Abstract

To evaluate a deterioration degree due to a use of a probe quantitatively and easily.SOLUTION: A method of evaluating deterioration of a probe to be used in an atomic force microscope has the steps of: putting an unused probe into contact with a surface of a measurement sample to measure a surface shape, and acquiring a force curve; obtaining absorption power K1 in an initial state from the force curve to be acquired using the unused probe; setting a threshold of the absorption power on the basis of the absorption power K1 in the initial state; putting a post-used probe in which the number X of uses is more than once into contact with the surface of the measurement sample to measure the surface shape, and acquiring the force curve; obtaining post-used absorption power KX from a force curve to be acquired using the post-used probe; and when the post-used absorption power KX exceeds the threshold of the absorption power, evaluating that the post-used probe gets deteriorated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating a probe for an atomic force microscope and a method for measuring the surface shape of a measurement sample. [Background technology]

[0002] In the field of precision measurement, one of the high-resolution measurement devices is the scanning probe microscope (SPM), which is a general term for various microscopes that share a common device configuration and operating principle.

[0003] Commonly known scanning probe microscopes include atomic force microscopes (AFM), scanning tunneling microscopes (STM), and scanning near-field optical microscopes (SNOM).

[0004] For example, an atomic force microscope basically consists of a sample stage, a probe with a probe tip at the end of a cantilever, and a detector that detects the displacement of the cantilever.When the probe approaches or comes into contact with the sample, the atomic force acting between the sample and the probe is detected, and by controlling this atomic force to remain constant, information about the sample's surface shape, surface roughness, and other irregularities can be obtained.

[0005] When measuring the surface shape and roughness of a sample using an atomic force microscope, the shape and condition of the probe tip have a significant effect on the measurement results. For example, if measurements are performed repeatedly with the same probe, the tip may become thicker or break due to wear, or the tip may become dirty, causing the probe to deteriorate and making it impossible to accurately measure the surface shape. For this reason, the selection of the probe and condition management are extremely important.

[0006] Non-Patent Document 1 proposes that probes be managed in accordance with the probe evaluation method standardized in JIS R 1683:2014 (Measurement of surface roughness of fine ceramic thin films using an atomic force microscope). It also proposes a method in which a commercially available standard sample for probe evaluation is used, and the standard sample is measured before, after, and between measurements of the sample, and the shape and condition of the probe tip are determined based on whether the results are within the specified range of the standard sample. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Japanese Standards Association, "Method for measuring surface roughness of fine ceramic thin films using an atomic force microscope (JIS R 1683:2014)", revised October 20, 2014, pp. 1-23 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the method described in Non-Patent Document 1 is limited to cases where the applicable range of the arithmetic mean roughness Ra of the target sample is 1 to 30 nm in the probe evaluation method standardized in JIS R 1683: 2014. Therefore, when measuring a sample with an arithmetic mean roughness Ra of 1 nm or less, there is no guarantee of probe inspection accuracy, and it is not possible to determine the reliability of the obtained data.

[0009] Furthermore, the operator had to visually judge the state of the probe shape (degree of deterioration) from the surface shape image obtained from the measurement results using an atomic force microscope, and the method of visually judging the state of the probe shape was prone to variations in the level of skill (experience) between operators and variations between lots.

[0010] On the other hand, atomic force microscopes are known to have atomic-level resolution, and there is a growing need for their use in analyzing samples with an arithmetic mean roughness Ra of 1 nm or less.

[0011] Therefore, an object of the present invention is to provide a technique that can quantitatively and easily evaluate the degree of deterioration of a probe due to use. [Means for solving the problem]

[0012] The inventors conducted extensive research to solve the above-mentioned problems and focused on the force curve obtained by measurements using an atomic force microscope. A force curve can be obtained when measuring the surface profile of a sample with a probe. It shows the correlation between the probe displacement and the cantilever deflection (the force acting on the cantilever) during the process of bringing the probe tip close to the sample surface, bringing it into contact with the sample surface, and then releasing the probe tip from the sample surface. The force curve contains information about the adhesive force between the sample and the probe. The adhesive force (f) is calculated, for example, from the cantilever displacement (ΔX) and the cantilever spring constant (k) using the formula f = kΔX. This adhesive force is inherently a value specific to the material of the sample. However, as the probe deteriorates and the contact area between the probe tip and the sample increases, it becomes greater than the inherent value. Based on this, the inventors discovered that the degree of probe deterioration can be evaluated by understanding the fluctuations in adhesive force.

[0013] A first aspect of the present invention is A method for evaluating deterioration of a probe used in an atomic force microscope, comprising: a step of bringing an unused probe into contact with the surface of a measurement sample to measure the surface shape and obtain a force curve; determining an initial chucking force K1 from the force curve obtained using the unused probe; setting a threshold value of the suction force based on the suction force K1 in the initial state; a step of bringing a used probe, the number of uses of which is one or more, into contact with the surface of a measurement sample to measure the surface shape and obtain a force curve; The post-use adhesive force K is calculated from the force curve obtained using the post-use probe. X and The adsorption force K after use Xand evaluating the used probe as having deteriorated when the adsorption force exceeds the threshold value. This is a method for evaluating a probe for an atomic force microscope.

[0014] A second aspect of the present invention is a method for producing a composition comprising the steps of: When the threshold value of the adsorption force is A, A=α×K1, where α is 1 or more and 10 or less.

[0015] A third aspect of the present invention is A method for measuring the surface shapes of a plurality of measurement samples using an atomic force microscope equipped with a probe, comprising: a step of bringing an unused probe into contact with the surface of a measurement sample to measure the surface shape and obtain a force curve; determining an initial chucking force K1 from the force curve obtained using the unused probe; setting a threshold value of the suction force based on the suction force K1 in the initial state; a step of repeatedly measuring the surface shape of each of a plurality of measurement samples using an atomic force microscope equipped with a probe for which the adsorption force threshold value has been set; and evaluating deterioration of a probe used in the atomic force microscope in parallel with the measurement of the surface shape, The step of evaluating deterioration of the probe includes: The used probe, which has been used once or more times, is brought into contact with the surface of the measurement sample to measure the surface shape, and the post-use adhesive force K is obtained from the force curve. X and The adsorption force K after use X and evaluating the used probe as having deteriorated when the adsorption force exceeds the threshold value. This is a method for measuring the surface shape of a measurement sample.

[0016] A fourth aspect of the present invention is the third aspect, When the threshold value of the adsorption force is A, A=α×K1, where α is 1 or more and 10 or less.

[0017] A fifth aspect of the present invention is A method for measuring the surface shape of each of a plurality of measurement samples using an atomic force microscope equipped with a probe, comprising: a step of bringing an unused probe into contact with the surface of a standard sample prepared separately from the measurement sample to measure the surface shape and obtain a force curve; determining an initial chucking force K1 from the force curve obtained using the unused probe; setting a threshold value of the suction force based on the suction force K1 in the initial state; a step of repeatedly measuring the surface shape of each of the plurality of measurement samples using an atomic force microscope equipped with a probe for which the threshold value of the adsorption force is set; and evaluating deterioration of a probe used in the atomic force microscope during the measurement of the surface shape, The step of evaluating deterioration of the probe includes: a step of bringing a used probe, the number of uses of which is one or more, into contact with the surface of the standard sample to measure the surface shape and obtain a force curve; The post-use adhesive force K is calculated from the force curve obtained using the post-use probe. X and The adsorption force K after use X and evaluating the used probe as having deteriorated when the adsorption force exceeds the threshold value. This is a method for measuring the surface shape of a measurement sample.

[0018] A sixth aspect of the present invention is the method according to the fifth aspect, When the threshold value of the adsorption force is A, A=α×K1, where α is 1 or more and 10 or less. [Effects of the Invention]

[0019] According to the present invention, the degree of deterioration of a probe due to use can be quantitatively and easily evaluated. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an atomic force microscope. [Figure 2] FIG. 2 is a plan view of the measurement surface of the measurement sample observed using the probe of the sample 1 with an atomic force microscope, viewed from above. [Figure 3] FIG. 3 is a plan view of the measurement surface of the measurement sample observed using the probe of the sample 2 with an atomic force microscope, viewed from above. [Figure 4] FIG. 4 is a plan view of the measurement surface of the measurement sample observed using the probe of the sample 3 with an atomic force microscope, viewed from above. [Figure 5] FIG. 5 is a plan view of the measurement surface of the measurement sample observed using the probe of the sample 4 with an atomic force microscope, viewed from above. [Figure 6] FIG. 6 is a plan view of the measurement surface of the measurement specimen observed using the probe of the sample 5 with an atomic force microscope, viewed from above. [Figure 7] FIG. 7 is a plan view of the measurement surface of the measurement specimen observed using the probe of the sample 6 with an atomic force microscope, viewed from above. [Figure 8] FIG. 8 is a plan view of the measurement surface of the measurement specimen observed using the probe of the sample 7 with an atomic force microscope, viewed from above. [Figure 9] FIG. 9 is a front view showing the tip state of the probe used in Samples 1 to 7. [Figure 10] FIG. 10 is a diagram showing the correlation between the chucking force, tip state, and arithmetic mean roughness obtained by measurement when the probes of Samples 1 to 7 are used. DETAILED DESCRIPTION OF THE INVENTION

[0021] <One embodiment of the present invention> An embodiment of the present invention will be described below, in which a schematic configuration of an atomic force microscope, a method for evaluating a probe, and a method for measuring the surface shape of a measurement sample including the method for evaluating the probe will be described in that order.

[0022] (1) Overview of atomic force microscope First, the basic configuration of an atomic force microscope will be described. Figure 1 is a schematic diagram showing the configuration of an atomic force microscope device.

[0023] As shown in FIG. 1, the atomic force microscope 1 is composed of a sample stage 10, a cantilever 20, a probe 22 with a probe tip 21 at the tip of the cantilever 20, a scanner 11 that scans the sample stage 10 or the cantilever 20 in the X and Y directions while simultaneously controlling the Z direction, a signal unit 30 that transmits X and Y scanning signals to the scanner, a laser unit 40 that irradiates the cantilever 20 with a semiconductor laser, a detection unit 50 that detects the displacement of the cantilever 20, and a control unit 60 that controls the Z direction so that the distance between the probe tip 21 and the surface of the measurement sample 12 remains constant.

[0024] A measurement sample 12 (measurement object) is placed on a sample stage 10, and a probe 21 is placed close to the surface of the measurement sample 12. The probe 21 is formed at the tip of a probe 22 of a cantilever 20, and is a needle-like member having a fine shape.

[0025] Next, a specific measurement method using the atomic force microscope 1 is described. The measurement sample 12 is placed on the sample stage 10 and brought close enough to or into contact with the probe 21 that an atomic force is generated between the sample 12 and the probe 21. Data on the measured curved surface is collected by controlling the atomic force acting between the sample 12 and the probe 21 to remain constant. This control is achieved by detecting a velocity signal from the vibration of the cantilever 20 and adding it to the excitation signal. When measuring a specific area on the surface of the measurement sample 12, the probe 21 is moved to scan the surface of the measurement sample 12. The scanning speed can be selected depending on the number of surface irregularities and the measurement sample 12. The user is then provided with a surface topography image, adhesion force, arithmetic mean roughness, and probe curvature radius using analysis software built into the atomic force microscope 1.

[0026] The probe 21 formed at the tip of the cantilever 20 has a pyramidal or conical shape with a sharp tip that contacts the measurement sample 12, but strictly speaking, the tip is hemispherical. With increased use, the tip of the probe 21 thickens due to wear and dirt accumulation, and its shape changes before and after measurement. If a probe 21 with a thick tip that does not reach the bottom of the depressions on the surface of the measurement sample 12 is used, the measured unevenness will be less pronounced than it actually is. In this case, the arithmetic mean roughness will be measured as smaller than it actually is. On the other hand, if the tip of the probe 21 thickens due to wear or dirt accumulation, the contact area between the measurement sample 12 and the probe 21 increases, increasing the apparent adhesive force. Therefore, it is necessary to monitor the shape and condition of the tip of the probe 21 before, during, and after measurement. For these reasons, when measuring surface topography using the atomic force microscope 1, it is important to use a probe suitable for tracking the uneven surface topography of the measurement sample 12.

[0027] (2) Probe evaluation method Next, a method for evaluating a probe for an atomic force microscope will be described. In this embodiment, deterioration of the tip of the probe due to wear or dirt is evaluated based on the adhesive force between the probe and the measurement sample. Below, we will explain as an example a case in which the deterioration state of the probe is evaluated when multiple measurement samples made of the same material are repeatedly measured with the probe.

[0028] First, in order to set a threshold value of the adhesive force that serves as a criterion for evaluating the deterioration state of the probe 21, the adhesive force of the probe 21 in its initial state is measured.

[0029] Specifically, first, an unused probe 21 is attached to the atomic force microscope 1, and the surface shape of the measurement sample 12 is measured using, for example, tapping mode (a mode in which the cantilever 20 is vibrated up and down by a piezoelectric element while approaching the surface of the measurement sample 12, and changes in amplitude are measured). At this time, a force curve is obtained along with information about the surface shape. Next, the adhesive force is calculated from the force curve. The adhesive force calculated here is the adhesive force in the initial state of the probe 21, i.e., in an undegraded state. This adhesive force is calculated as an average value over the entire measurement surface. Here, the adhesive force calculated using the unused probe 21 is referred to as adhesive force K1.

[0030] The surface profile measurement conditions are not particularly limited. For example, when measuring the surface profile of a sample 12 with an arithmetic mean roughness Ra of 1 nm or less, the measurement range should be 1 μm square to 1.5 μm square, the scanning speed should be 0.5 to 1 Hz, and the number of pixels should be 256 × 256 or 512 × 512. For a sample 12 with a sharp tip or a large number of irregularities, the scanning speed can be set to 0.5 Hz or less. Furthermore, when the number of irregularities is small, the measurement area can be increased. This allows the surface area of ​​the irregularities in the surface profile of the sample 12 to be determined with high accuracy, even when the arithmetic mean roughness Ra is 1 nm or less. The tapping mode of the atomic force microscope 1 can measure the surface profile of a sample in air or liquid.

[0031] Next, based on the initial adhesive force K1, a threshold value for the adhesive force is set, which serves as a standard for evaluating the deterioration state of the probe 21. As mentioned above, repeated use of the same probe 21 can cause the tip of the probe 21 to become dirty or wear out, leading to deterioration of the probe. In particular, when measuring a surface profile with an arithmetic mean roughness Ra of 1 nm or less, if the tip of the probe 21 is too thick, the tip of the probe 21 will not reach the bottom of the recess, resulting in a profile that is measured as being less uneven than it actually is. This increases the contact area between the tip of the probe 21 and the measurement sample 12, resulting in an increase in the apparent adhesive force. Therefore, a threshold value is set to ensure the reliability of data such as the surface profile measured when the probe 21 is used repeatedly.

[0032] Because the adhesive force of the probe 21 tends to increase with the number of times the probe 21 is used, it is preferable to set the adhesive force threshold value so that the surface profile of the measurement sample 12 can be accurately measured even if the probe 21 has deteriorated. Specifically, when the threshold value is A, the threshold value is expressed as A = α × K1, and α can be appropriately changed depending on the type of measurement sample 12, etc. Here, α represents the adhesive force increase factor and can be set arbitrarily depending on the threshold value A. If the increase factor α is too small, the probe 21 may be determined to be deteriorated even when it is not significantly deteriorated. If the increase factor α is too large, the probe 21 may be determined to be not deteriorated even when it is deteriorated. In this regard, the increase factor α is preferably between 1 and 10, and more preferably between 3 and 6. By using such an increase factor, the threshold value A can be set to a value that allows the deterioration state of the probe 21 to be appropriately determined. As a result, the surface profile of a measurement sample 12 having an arithmetic mean roughness Ra of 1 nm or less can be accurately measured.

[0033] The number of times the probe 21 is used is counted as one time when the surface shape of one measurement sample 12 is measured, and if the surface shape of each of multiple measurement samples 12 is measured, the number of times it is used is counted as the number of measurement samples 12.

[0034] Next, the probe 21 for which the threshold value has been set is evaluated for deterioration after repeated use.

[0035] Specifically, first, a probe 21 that has been used repeatedly is prepared, and the probe 21 is brought into contact with the surface of the measurement sample 12 to measure the surface shape and obtain a force curve. Then, the adhesive force is calculated from the obtained force curve. The adhesive force calculated at this time is the adhesive force in the state after use of the probe 21, that is, the adhesive force in the deteriorated state of the probe 21. Here, the adhesive force calculated using the used probe 21 is defined as the adhesive force after use K XThe conditions for measuring the surface shape can be changed as appropriate depending on the type of measurement sample 12, but since the adsorptive force may vary depending on the measurement conditions, it is advisable to use the same measurement conditions as those for the unused probe 21 described above.

[0036] Adsorption power after use K X becomes larger than the adsorption force K1 in the initial state due to deterioration of the tip of the probe 21.

[0037] Next, the adsorption force after use K X is compared with the threshold value A of the chucking force set above, and the deterioration state of the probe 21 after use is evaluated. X If the suction force K is equal to or less than the threshold A of the suction force, it can be evaluated that the probe 21 is in a good condition after use and that high accuracy can be obtained in measuring the surface shape. X If the adhesion force exceeds the adhesion force threshold value A, this indicates that the tip of the probe 21 has deteriorated. For example, if the tip of the probe 21 becomes worn or dirty, the tip becomes thicker, the contact area with the measurement sample 12 increases, and the apparent adhesion force increases. In this case, the minute irregularities on the surface of the measurement sample 12 cannot be measured accurately, and the obtained surface shape image is observed as gentle irregularities, making it impossible to obtain the original surface shape. Furthermore, for example, if the tip of the probe 21 is damaged and splits into two, the contact area with the measurement sample 12 increases, and the apparent adhesion force increases. In this case, the damaged probe 21 scans the surface of the measurement sample 12 more than once, and the obtained surface shape image is observed as multiplexed, making it impossible to obtain the original surface shape.

[0038] In this way, while the probe 21 is repeatedly used, the adhesion force K x If the chucking force K after use does not exceed the threshold value A, the probe 21 will not deteriorate and can continue to be used. In addition, the reliability of data such as the surface shape image of the measurement sample 12 measured at this time can be guaranteed. xexceeds threshold A, it means that the probe 21 has deteriorated or is showing signs of deterioration, and the reliability of the measured data such as the surface profile image cannot be guaranteed. In this case, it is advisable to replace the used probe 21 with an unused probe 21 and perform the measurement again.

[0039] In this way, the deterioration state of the probe can be evaluated.

[0040] (3) Measurement method for the surface shape of the measurement sample Next, we will explain a method for measuring the surface shape of measurement sample 12, including the above-mentioned method for evaluating probe 21. Here, we will explain a case where, when measuring the surface shapes of multiple measurement samples 12 repeatedly using atomic force microscope 1, the deterioration state of probe 21 is evaluated in parallel with each measurement.

[0041] First, an unused probe 21 is attached to the atomic force microscope 1 .

[0042] Next, the first measurement sample 12 is introduced into the atomic force microscope 1, and its surface shape is measured. At this time, a force curve is obtained along with information about the surface shape. The adhesive force K1 of the unused probe 21 is calculated from this force curve, and the adhesive force threshold A is set from this adhesive force K1. This threshold A may be set appropriately, for example, by the above-mentioned A=α×K1 (where the increase factor α is 1 or more and 10 or less).

[0043] Next, the first measurement sample 12 is removed from the atomic force microscope 1, and the second measurement sample 12 is introduced, and similarly, information about the surface shape and a force curve are obtained. The adhesive force obtained from this force curve is the adhesive force K2 when the probe 21 has been used twice. This adhesive force K2 is compared with the adhesive force threshold A, and if it is equal to or less than threshold A, it is determined that the probe 21 has not deteriorated, and if it exceeds threshold A, it is determined that the probe 21 has deteriorated. If the probe 21 has not deteriorated, it can be used repeatedly.

[0044] Next, the surface shape of a plurality of measurement samples 12 is repeatedly measured, and information about the surface shape and a force curve are similarly obtained for the Xth measurement sample 12. The chucking force obtained from this force curve is the chucking force K when the probe 21 is used X times. X This adsorption force K X is compared with the chucking force threshold A, and if it exceeds threshold A, it is determined that the probe 21 has deteriorated. In this case, it is advisable to replace the deteriorated probe 21 with an unused one.

[0045] As a result, the deterioration state of the probe 21 can be grasped in parallel with repeatedly measuring the surface shapes of a plurality of measurement samples 12.

[0046] Here, an example has been described in which the deterioration state of the probe 21 is evaluated each time the surface shape is measured, but the deterioration state may be evaluated every predetermined number of measurements, such as every 10 surface shape measurements.

[0047] <Effects of this embodiment> According to this embodiment, one or more of the following effects are achieved.

[0048] In this embodiment, the adsorption force K after repeated use of the probe 21 is x The deterioration state of probe 21 after use can be quantitatively and easily evaluated by comparing the initial chucking force K1 obtained using an unused probe 21 with a preset chucking force threshold A. This makes it possible to determine, for example, whether the tip of probe 21 is in a state suitable for measuring measurement sample 12 with an arithmetic mean roughness Ra of 1 nm or less, and maintain high measurement accuracy.

[0049] The chucking force threshold A is A=α×K1, and it is preferable that the increase factor α is between 1 and 10. By setting the threshold A in this way, the deterioration state of the probe 21 can be grasped more accurately, and high accuracy can be maintained when measuring the surface shape of the measurement sample 12 having an arithmetic mean roughness Ra of 1 nm or less.

[0050] Furthermore, in this embodiment, since a force curve can be obtained while measuring the surface shape of the measurement sample 12, when measuring a plurality of measurement samples 12 of the same type in sequence, the adhesive force of the probe 21 at that time can be calculated, for example, every time the surface shape of the measurement sample 12 is measured, or every time a predetermined number of measurement samples 12 are measured. Therefore, the deterioration state of the probe 21 can be grasped while measuring the surface shape of the measurement sample 12. As a result, the adhesive force K after use can be calculated. x If the chucking force K after use is less than the threshold value A, it can be confirmed that the probe is not deteriorated and that the surface shape image measured by the probe is highly reliable as a measurement result at the level required by the measurer. x exceeds threshold A, it can be determined that the probe 21 is in a deteriorated state and that the reliability of the measurement result obtained at this time is low. In this way, by determining the deterioration state of the probe 21 together with the measurement of the surface shape of the measurement sample 12, it is possible to maintain high measurement accuracy.

[0051] Furthermore, according to the evaluation method of this embodiment, a threshold value determined from the adsorption force is set for the probe 21. Therefore, for example, when the probe 21 is detached from the atomic force microscope 1 and then reattached, there is no need to set the threshold value again, thereby improving evaluation efficiency.

[0052] Furthermore, when the same type of probe 21 is combined with the measurement sample 12, there is a correlation between the adhesive force of the probe 21 and the state of deterioration. Therefore, it is possible to obtain a force curve for a probe whose number of uses is unknown, and infer the state of deterioration from the adhesive force.

[0053] Furthermore, according to the method for measuring the surface shape of a measurement sample in this embodiment, by including the step of evaluating the deterioration state of the probe 21 described above, when repeatedly measuring the surface shapes of a plurality of measurement samples 12, it is possible to measure the surface shape of each measurement sample 12 using a probe 21 that is not deteriorated. In other words, high measurement accuracy can be maintained.

[0054] Furthermore, the deterioration state of the probe 21 can be evaluated based on the adsorption force calculated from a force curve obtained together with information about the surface shape of the measurement sample 12, so that measurement efficiency can be maintained without compromising it, without the need for a special evaluation process.

[0055] <Other embodiments> Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention.

[0056] In the above-described embodiment, the deterioration state of the probe 21 is evaluated using the adhesive force when the probe 21 approaches or contacts the measurement sample 12, but the present invention is not limited to this. For example, a standard sample for evaluating the adhesive force of the probe 21 may be prepared separately from the measurement sample 12 to be measured, and the deterioration state of the probe 21 may be evaluated based on the adhesive force obtained from the force curve obtained when this standard sample is measured with the probe 21. Specifically, the standard sample is measured with an unused probe 21, and the adhesive force K1 in the initial state is obtained from the obtained force curve, and the threshold value A is set. Thereafter, every time the surface shape of, for example, 10 measurement samples 12 is measured, the probe 21 is brought into contact with the standard sample to obtain a force curve, and the adhesive force K1 after use is calculated. X may be calculated and compared with threshold value A to determine the deterioration state of probe 21. The standard sample may be made of the same type of material as measurement sample 12, or may be made of a material different from that of measurement sample 12.

[0057] When repeatedly measuring the surface shape of a plurality of measurement samples 12 while evaluating the deterioration state of probe 21 using a standard sample, the following procedure may be used, for example.

[0058] First, a standard sample is introduced into the atomic force microscope 1 equipped with an unused probe 21, and its force curve is obtained along with information about its surface shape. From this force curve, the adhesive force K1 of the unused probe 21 is calculated and set as the adhesive force threshold A.

[0059] Next, the atomic force microscope 1 equipped with the probe 21 for which the threshold value A has been set is used to repeatedly measure the surface shapes of a plurality of measurement samples 12.

[0060] After measuring the surface shape of the measurement sample 12 a predetermined number of times, the surface shape of the standard sample is measured and a force curve is obtained together with information about the surface shape. From this force curve, the adsorption force K of the probe 21 after the Xth use is calculated. X is calculated and compared with threshold A to determine the deterioration state.

[0061] In this way, before measuring the surface shape of the measurement sample 12, the surface shape is measured in advance for a separately prepared standard sample, the chucking force at that time is calculated, and it is compared with the threshold value A, so that the surface shape can be measured while evaluating the deterioration state of the probe 21. [Example]

[0062] The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

[0063] In this example, an unused probe is repeatedly used to determine the initial adhesive force K1, and after setting the threshold A, the adhesive force K after use is calculated based on the number of times the probe is used. X The fluctuations in the temperature were monitored to evaluate the deterioration state of the probe.

[0064] Specifically, first, an unused probe (company name: Bruker AXS, model number: ScanAsyst-Air) was attached to an atomic force microscope (company name: Bruker AXS, product name: Dimension Icon). Next, a crystal substrate with an arithmetic mean roughness Ra of 0.3 nm was prepared as the measurement sample. This crystal substrate was introduced into the atomic force microscope, and the surface shape of the crystal substrate was measured. The measurement conditions were peak force tapping mode, with 256 x 256 points measured at a scan speed of 1 Hz over a 1 μm square area on the crystal substrate surface. Note that peak force tapping mode is a type of tapping mode.

[0065] Next, the force curve data acquired together with the surface shape data was analyzed using the built-in analysis software of the atomic force microscope (company name: Bruker AXS, product name: NanoScope Analysis). Using this, the adhesive force of the probe when it was used once (adhesive force in the initial state K1) was calculated, and the adhesive force was found to be K1 = 0.41 nN.

[0066] Next, the chucking force threshold A was set based on the chucking force K1 in the initial state. In this example, the threshold A (=α×K1) was set to 3.08 nN, with the chucking force increase factor α due to probe deterioration being set to 7.5.

[0067] Then, using a probe for which threshold value A was set, the surface shape of the crystal substrate was repeatedly measured, and the correlation between the number of times the probe was used and the chucking force was confirmed. In this example, an example in which a probe with the above-mentioned number of times X used was used was designated Sample 1, and examples in which probes with numbers of times X used of 41, 98, 142, 178, and 203, as shown in Table 1 below, were designated Sample 2 to 6. In addition, an example in which a probe with an unknown number of times used was designated Sample 7. For Samples 2 to 7, as with Sample 1, force curves were obtained along with images of the surface shape of the crystal substrate, and the chucking force K after use was measured. X Calculate the adsorption force K after use. X If the value was equal to or less than threshold A, it was judged as "◯" indicating that there was no degradation, and if it exceeded threshold A, it was judged as "×" indicating that there was degradation.

[0068] [Table 1]

[0069] 2 to 8 show plan views of the measurement surfaces of the measurement specimens obtained for Samples 1 to 7. As shown in FIG. 2, in Sample 1, where the probe was used in the initial state, it was confirmed that the surface shape of the measurement specimen with an arithmetic mean roughness Ra of 1 nm or less could be measured with high accuracy. In addition, the chucking force K after use XIn Samples 2 to 4, which were evaluated as having no degradation (determined as good) and had a resistance below threshold A (3.08 nN), it was confirmed that the surface shape could be measured with the same accuracy as in Sample 1, as shown in Figures 3 to 5. This is thought to be because, in Samples 2 to 4, the tip of the probe was not worn or chipped, or even if it was worn or chipped, the degree of wear did not affect the measurement accuracy, as shown in Figure 9.

[0070] On the other hand, the adsorption force after use K X For Samples 5 to 7, which were evaluated as having deteriorated (determined as "x") because their roughness exceeded threshold A (3.08 nN), it was confirmed that the surface profile of samples with an arithmetic mean roughness Ra of 1 nm or less could not be measured accurately, as shown in Figures 6 to 8. Specifically, for Samples 5 and 6, as shown in Figures 6 and 7, it was confirmed that the surfaces of the measured samples were observed to have unevenness that was gentler than the original unevenness. This is thought to be because the tip of the probe in Samples 5 and 6 had become thicker due to wear or chipping, as shown in Figure 9. Furthermore, for Sample 7, it was confirmed that double unevenness was observed on the surface of the measured sample, as shown in Figure 8. This is thought to be because the tip of the probe in Sample 7 was bifurcated and chipped, as shown in Figure 9, and the surface of the measured sample was scanned more than twice.

[0071] Next, the correlation between the adhesion force, tip condition, and arithmetic mean roughness measured using the probes of Samples 1 to 7 will be explained using Figure 10. In Figure 10, the left vertical axis represents the increase factor α of adhesion force, the right vertical axis represents the arithmetic mean roughness Ra [nm], and the horizontal axis represents the radius of curvature of the probe tip [nm]. In the figure, the dots (●) represent the increase factor of adhesion force for Samples 1 to 6, the squares (□) represent the arithmetic mean roughness Ra measured for Samples 1 to 6, the circles (◯) represent the increase factor of adhesion force for Sample 7 (probe with a bifurcated tip), and the triangles (△) represent the arithmetic mean roughness Ra measured for Sample 7.

[0072] As shown in Figure 10, for samples 1 to 6, it was confirmed that the radius of curvature of the probe tip increases and the tip becomes thicker as the number of uses increases. It was also confirmed that as the tip becomes thicker, the contact area increases and the increase factor of the adsorptive force becomes larger. It was also confirmed that as the tip becomes thicker, the value of the arithmetic mean roughness Ra decreases, making it impossible to measure the surface shape of the measurement sample with high accuracy. In other words, it was confirmed that the degree of wear of the probe tip cannot be determined from the fluctuations in the arithmetic mean roughness Ra.

[0073] Furthermore, in sample 7, although the radius of curvature of the probe tip is small, the increase factor α of the adsorptive force is large and the contact area is increased, so it was confirmed that the tip of the probe may be broken off due to damage.

[0074] As described above, the adhesive force is sensitive to the thickness and damage state of the probe tip, and it is found to be useful for determining the tip shape of the probe. In addition, for the probe, a threshold value A is set from the adhesive force K1 in the initial state, and the adhesive force K1 after use is X By comparing with threshold A, the deterioration state of the probe can be quantitatively and easily evaluated, and the difference in the skill level of the operator and the variation between lots can be reduced. [Explanation of symbols]

[0075] 1. Atomic Force Microscope 10 Sample stage 11. Scanner 12 Measurement sample 20 Cantilever 21 Probe 30 Signal Section 40 Laser section 50 Detector 60 Control Unit

Claims

1. A method for evaluating deterioration of a probe used in an atomic force microscope, comprising: a step of bringing an unused probe into contact with the surface of a measurement sample to measure the surface shape and obtain a force curve; The initial adhesion force K is calculated from the force curve obtained using the unused probe. １ and The adsorption force K in the initial state １ setting a threshold value of the suction force based on the a step of bringing a used probe, the number of uses of which is one or more, into contact with the surface of a measurement sample to measure the surface shape and obtain a force curve; The post-use adsorption force K is calculated from the force curve obtained using the post-use probe. Ｘ and The adsorption force K after use Ｘ and evaluating the used probe as having deteriorated when the adsorptive force exceeds the threshold value, The arithmetic mean roughness Ra of the measurement sample is 1 nm or less, When the threshold value of the adsorptive force is A, A=α×K 1 , where α is 1 or more and 10 or less. A method for evaluating probes for atomic force microscopes.

2. A method for measuring the surface shapes of a plurality of measurement samples using an atomic force microscope equipped with a probe, comprising: a step of bringing an unused probe into contact with the surface of a measurement sample to measure the surface shape and obtain a force curve; The initial adhesion force K is calculated from the force curve obtained using the unused probe. １ and The adsorption force K in the initial state １ setting a threshold value of the suction force based on the a step of repeatedly measuring the surface shape of each of a plurality of measurement samples using an atomic force microscope equipped with a probe for which the adsorption force threshold value has been set; and evaluating deterioration of a probe used in the atomic force microscope in parallel with the measurement of the surface shape, The step of evaluating deterioration of the probe includes: The adsorption force K after use is calculated from the force curve obtained when the probe, which has been used once or more, is brought into contact with the surface of the measurement sample and the surface shape is measured. Ｘ and The adsorption force K after use Ｘ and evaluating the used probe as having deteriorated when the adsorptive force exceeds the threshold value, The arithmetic mean roughness Ra of the measurement sample is 1 nm or less, When the threshold value of the adsorptive force is A, A=α×K 1 , where α is 1 or more and 10 or less. A method for measuring the surface shape of a sample.

3. A method for measuring the surface shape of each of a plurality of measurement samples using an atomic force microscope equipped with a probe, comprising: a step of bringing an unused probe into contact with the surface of a standard sample prepared separately from the measurement sample to measure the surface shape and obtain a force curve; The initial adhesion force K is calculated from the force curve obtained using the unused probe. １ and The adsorption force K in the initial state １ setting a threshold value of the suction force based on the a step of repeatedly measuring the surface shape of each of the plurality of measurement samples using an atomic force microscope equipped with a probe for which the threshold value of the adsorption force is set; and evaluating deterioration of a probe used in the atomic force microscope during the measurement of the surface shape, The step of evaluating deterioration of the probe includes: a step of bringing a used probe, the number of uses of which is one or more, into contact with the surface of the standard sample to measure the surface shape and obtain a force curve; The post-use adsorption force K is calculated from the force curve obtained using the post-use probe. Ｘ and The adsorption force K after use Ｘ and evaluating the used probe as having deteriorated when the adsorptive force exceeds the threshold value, The arithmetic mean roughness Ra of the measurement sample is 1 nm or less, When the threshold value of the adsorptive force is A, A=α×K 1 , where α is 1 or more and 10 or less. A method for measuring the surface shape of a sample.

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