JP2004191277A - Scanning probe microscope and its measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning probe microscope technique for highly accurately measuring a distance between a desired position in an image and a reference position, assuming that at least one point outside the visual field of the measurement image is the reference position. <P>SOLUTION: This scanning probe microscope is equipped with an X-displacement detection part 141 and a Y-displacement detection part for detecting the relative position of a probe 1 to a specimen 3, an image acquisition part 9 having the function of storing the detection result obtained by the X-displacement detection part 141 and the Y-displacement detection part, and a means for obtaining the coordinates on a second image positioned outside the visual field of a first image from the detection result obtained by the X-displacement detection part 141 and the Y-displacement detection part, assuming that one point on the first image is the reference position. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a scanning probe microscope capable of observing and analyzing a sample surface with atomic resolution.
[0002]
[Prior art]
A scanning probe microscope (SPM) is a surface observation device capable of observing and analyzing a sample surface with atomic resolution. Typical examples are a scanning tunneling microscope (STM) using a tunnel current flowing between the probe tip and the sample surface, and a force acting between the probe tip and the sample surface. Atomic Force Microscope (AFM) and the like.
[0003]
AFM is capable of observing a three-dimensional shape with high resolution even on a non-conductive sample surface, and is used for evaluating the surface shape of a semiconductor device, a recording disk, or the like (for example, see Non-Patent Document 1). ).
[0004]
FIG. 3 shows a basic configuration of a conventional AFM. The cantilever 2 is arranged so that the probe 1 provided at the tip thereof faces the surface of the sample 3 held by the sample holding section of the XYZ scanner 6. The probe 1 moves relatively to the sample 3 by driving the XYZ scanner 6. When the probe 1 approaches the sample 3, the cantilever 2 bends due to the atomic force acting between them. This amount of deflection is detected by the lever displacement detecting section 4, and an output signal thereof is sent to the Z servo circuit 5. In the lever displacement detecting section 4, displacement is detected by an optical method such as an optical lever method or a laser interference method or a method utilizing a piezoresistance effect capable of simplifying the configuration. In the Z servo circuit 5, the output signal of the lever displacement detecting section 4 is compared with a reference value set by the Z servo circuit 5, and a Z drive signal corresponding to the deviation is output to the XYZ scanner 6. That is, feedback control is performed so that the interatomic force acting on the probe 1 is kept constant.
[0005]
On the other hand, the XY signal generator 8 outputs an X trigger signal and a Y trigger signal for XY scanning to the XY scanning circuit 7. The XY scanning circuit 7 applies an X drive signal and a Y drive signal corresponding to the X trigger signal and the Y trigger signal to the XYZ scanner 6, and causes the XYZ scanner 6 to perform XY scanning.
[0006]
The X trigger signal and the Y trigger signal output from the XY signal generation unit 8 are also sent to the image acquisition unit 9 to sample the Z drive signal output from the Z servo circuit 5, that is, the Z displacement signal of the XYZ scanner 6. Timing signal. The Z displacement signal sampled by the image acquisition unit 9 is stored in the image memory 10 together with the X trigger signal and the Y trigger signal at that time, that is, the XY position signal. The signal stored in the image memory becomes an image representing the surface shape of the sample 3.
[0007]
[Non-patent document 1]
Rhysical Review Letters, Vol. 56 (1986), p. 930 [0008]
[Problems to be solved by the invention]
In the conventional SPM, the dimensions of the three-dimensional shape of the sample are measured based on the obtained surface image. There, it was possible to measure the distance between two points in the image, but it was not possible to measure the relative distance from one point in the image using one point outside the field of view of the image as a reference position.
[0009]
As is generally the case with a microscope other than the SPM, in order to obtain an observation image with high resolution, it is necessary to reduce the observation area, that is, increase the magnification. The dimensions that can be measured are correspondingly smaller.
[0010]
In the field of recording discs, recording marks have been miniaturized, and have reached 100 nm or less at the research level. There is a demand for measuring such long-period pattern fluctuations of fine marks of several tens μm or more with a precision of nm. Such measurement was impossible with the conventional SPM.
[0011]
An object of the present invention is to provide a scanning probe microscope capable of performing the above-described length measurement and a measuring method thereof in the technical field of the scanning probe microscope.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a scanning probe microscope according to the present invention includes: a position detecting unit that detects a relative position between a probe facing a sample and a sample; a storage unit that stores a detection result of the position detecting unit; Means for obtaining, from at least one point on the one image as a reference position, coordinates on the second image located outside the field of view of the first image from the detection result of the position detecting means.
[0013]
According to the present invention, since the position detecting means for detecting the relative position between the probe and the sample detects a position signal on the observation image, the relative position between the first image and the second image located outside the visual field is detected. A positional relationship can be obtained.
[0014]
Hereinafter, typical configuration examples of the present invention will be listed.
[0015]
(1) A scanning probe microscope according to the present invention includes a probe provided to face a sample, moving means for moving the probe relative to the sample, and an interaction between the probe and the sample. Detecting means for detecting, based on the detection result obtained from the detecting means by scanning the probe surface of the sample by the moving means, and means for forming an image reflecting information on the sample surface, and A position detecting means for detecting a relative position between the probe and the sample; and a storage means for storing a detection result of the position detecting means, wherein at least one point on a first image is a reference position and the first The present invention is characterized in that a desired position coordinate on the second image arranged outside the field of view of the image is measured based on the stored detection result of the position detecting means.
[0016]
(2) The scanning probe microscope of the present invention includes a probe installed to face the sample, a moving unit for moving the sample three-dimensionally, a fine moving unit for finely moving the probe three-dimensionally, Detecting means for detecting an interaction between the probe and the sample, and scanning the sample surface with the probe to form an image reflecting information on the sample surface based on a detection result obtained from the detecting means; Means, and a position detecting means for detecting a relative position between the probe and the sample, and a storage means for storing a detection result of the position detecting means, wherein at least one point on the first image is provided. A desired position coordinate on the second image located outside the field of view of the first image with reference to the reference position is measured based on the stored detection result of the position detecting means. To.
[0017]
(3) The measuring method of the scanning probe microscope of the present invention includes the steps of: bringing a probe close to or contacting a sample; scanning the probe; and detecting an interaction between the sample and the probe. Obtaining an image reflecting the surface of the sample based on the result, and measuring the relative position of the sample and the probe; storing the measured relative position; And obtaining a desired position coordinate on the second image outside the field of view of the first image from the stored relative position with reference to at least one point on the image.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in order to facilitate understanding, in the drawings described below, elements performing the same operations as those described with reference to FIG. 3 are given the same names and reference numerals as those in FIG.
[0019]
FIG. 1 is a block diagram showing one embodiment of a scanning probe microscope according to the present invention. A sharpened probe 1 is provided at the free end of the cantilever 2. The sample 3 is held by a sample holder provided on the Z stage 111 for approaching and retracting the probe 1 and the sample 3. The Z stage 111 is set on an XY stage 112 for moving the sample 3 to a desired observation position. The cantilever 2 is arranged on the XY fine movement mechanism 602 such that the probe 1 faces the sample 3. The XY fine movement mechanism 602 is fixed to the Z fine movement mechanism 601, and by driving them, the probe 1 can finely move on the sample 3 in the XYZ directions.
[0020]
As the XY fine movement mechanism 602 and the Z fine movement mechanism 601, a tube type fine movement mechanism made of a piezoelectric material, a tripod type fine movement mechanism configured by combining three stacked piezoelectric elements, or an elastic body driven by driving a piezoelectric element. A parallel plate type fine movement mechanism utilizing elastic deformation is used. Further, a tube type, a tripod type, and a parallel plate type fine movement mechanism may be appropriately combined.
[0021]
As an example, the parallel plate type fine movement mechanism shown in FIG. 2 will be described. Although only one axis is shown here, for example, an XY fine movement mechanism can be configured by combining two basic one-axis fine movement mechanisms so as to be orthogonal to each other.
[0022]
As shown in FIG. 2, the fixed portion 603, the moving portion 604, and the elastically deforming portion 606 are formed as an integral structure by wire cutting. By driving the laminated piezoelectric element 605 sandwiched and fixed between the fixed unit 603 and the moving unit 604 in the direction of the arrow to apply a force, the elastic deformation unit 606 is elastically deformed, and The moving unit 604 moves. In this case, the moving direction of the moving unit 604 is limited to a direction parallel to the fixed unit 603 according to the deformation direction of the elastic deformation unit 606. Therefore, since the parallel plate type fine movement mechanism does not include a rotational component in the moving direction unlike a tube type scanner or the like, it is convenient when correcting nonlinearity of the piezoelectric element.
[0023]
Here, the basic operation of the present invention will be described with reference to FIG. When the probe 1 and the sample 3 are brought close to each other by the Z stage 111, the cantilever 2 bends due to the atomic force acting between them. This amount of deflection is detected by the lever displacement detector 4 and output to the Z servo circuit 5. In the Z servo circuit 5, the deflection signal is compared with a reference value set in the Z servo circuit 5, and a Z drive signal corresponding to the deviation signal is output to the Z fine movement mechanism 601. By this feedback control, the amount of deflection of the cantilever 2 is kept constant, and the Z fine movement mechanism 601 is driven in the Z direction so that the atomic force acting between the probe 1 and the sample 3 becomes constant.
[0024]
On the other hand, the XY signal generator 8 outputs an X trigger signal and a Y trigger signal for causing the XY fine movement mechanism 602 to perform XY scanning to the XY scanning circuit 7. In the XY scanning circuit 7, the XY stage 112 and the XY fine movement mechanism 602 detected by the X displacement detection unit 141 and the Y displacement detection unit having a configuration similar to that of the X displacement detection unit 141 which is omitted in FIG. The displacement signal corresponding to the relative displacement in the X and Y directions is compared with the X and Y trigger signals, respectively, and the X and Y drive signals corresponding to the deviation signals are output to the XY fine movement mechanism 602. That is, at the time of the XY scanning operation, feedback control is performed so that the XY fine movement mechanism 602 is accurately displaced to the XY coordinate position indicated by the X trigger signal and the Y trigger signal generated by the XY signal generation unit 8, and the XY fine movement is performed. The nonlinearity error of the mechanism 602 is corrected.
[0025]
Here, the X and Y displacement detectors 141 and 142 will be described with reference to the X displacement detector 141 shown in FIG. In the X displacement detection section 141, the laser light emitted from the light source 17 enters the polarization beam splitter 15. In the polarization beam splitter 15, the incident laser light is split into two. One laser beam A passes through a quarter (1/4) wavelength plate A18, is reflected by a mirror A12 fixed to the XY stage 112, and is again polarized through the quarter wavelength plate A18. The light enters the splitter 15. The other laser beam B is turned 90 degrees by the right-angle prism 16, passes through a quarter (板) wavelength plate B 19, is reflected by a mirror B 13 fixed to the XY fine movement mechanism 602, and then again. The light enters the polarization beam splitter 15 via the quarter-wave plate B19 and the right-angle prism 16.
[0026]
The quarter-wave plate A18 and the quarter-wave plate B19 each have an optical axis at an angle of 45 degrees with respect to the polarization directions of the two laser beams A and B split by the polarization beam splitter 15. Thus, the polarization direction of the laser beam reflected from the mirror and returned to the polarization beam splitter 15 is different from the polarization direction of the original emission light by 90 degrees. Therefore, the laser beam A reflected from the mirror A12 passes through the polarization beam splitter 15 and is incident on the laser interferometer 14, and the laser beam B reflected from the mirror B13 is reflected by the polarization beam splitter 15 to be reflected. Are incident on the laser interferometer 14.
[0027]
In the laser interferometer 14, these two laser beams A and B are superimposed and interfere with each other due to the optical path difference between them. This interference phenomenon appears as an optical path difference corresponding to twice the relative displacement amount of the XY stage 112 and the XY fine movement mechanism 602 in the X direction. By optically detecting this interference phenomenon, the relative displacement amount in the X direction between the XY stage 112 and the XY fine movement mechanism 602 can be measured with high resolution.
[0028]
The Y-displacement detecting section has the completely same configuration, and can measure the relative displacement in the Y-direction between the XY stage 112 and the XY fine movement mechanism 602 with high resolution.
[0029]
Since the wavelength of the laser beam used here is 670 nm, when the relative displacement in the X direction between the XY stage 112 and the XY fine movement mechanism 602 is 335 nm corresponding to a half wavelength, the phase change of this interference phenomenon is 2π radians. Appears. Usually, this phase is detected by being divided into 100 to 1000, so that the relative displacement is detected with a resolution of 3.3 to 0.3 nm. Therefore, the nonlinearity error of the XY fine movement mechanism 602 can be corrected with such high resolution.
[0030]
Further, the X trigger signal and the Y trigger signal output from the XY signal generation unit 8 are also input to the image acquisition unit 9 and become timing signals for sampling the Z drive signal of the Z fine movement mechanism 601. Further, in this embodiment, the X and Y displacement signals from the X displacement detector 141 and the Y displacement detector are sampled together with the Z drive signal. The X, Y, and Z displacement signals sampled by the image acquisition unit 9 are stored in a storage unit in the image acquisition unit 9 together with the X trigger signal and the Y trigger signal at that time. The signal stored in the storage unit is displayed on the display unit 10 as an image representing the surface shape of the sample 3.
[0031]
Next, the measurement operation of this embodiment will be described with reference to FIGS. Here, a row of fine pits 301 having a length of 100 nm, a width of 70 nm, and a depth of 120 nm will be described with reference to a sample 3 such as a recording disk formed on the surface as shown in FIG.
[0032]
First, the XY stage 112 is operated to position the probe 1 at the measurement start point (1) of the measurement area 302. The above-described surface shape image acquisition operation is performed, and as a result, a first measurement image representing the surface shape at that position is obtained. The image acquisition operation is completed by returning the probe 1 to the measurement start point. The XY coordinates at each position in the image are detected by the X displacement detection unit 141 and the Y displacement detection unit and stored in the image acquisition unit 9.
[0033]
Next, the XY stage 112 is operated to position the probe 1 at the measurement start point (2) of the measurement area 303. In this positioning operation, the relative displacement amounts of the measurement areas 302 and 303 are detected with high precision using the X displacement detection section 141 and the Y displacement detection section, and stored in the image acquisition section 9. That is, the relative coordinate values of the measurement start point (1) and the measurement start point (2) are stored.
[0034]
Next, a surface shape measurement operation is performed in the measurement region 303, and a second measurement image representing the surface shape at that position is obtained. The XY coordinates at each position in the image are detected by the X displacement detection unit 141 and the Y displacement detection unit, and stored in the image acquisition unit 9. From the pit position indicated by at least one coordinate (x0, y0) on the first image, the relative coordinates of each position on the second image are calculated based on the data stored in the image acquisition unit 9.
[0035]
As described above, according to the present embodiment, the relative coordinates of the arbitrary position on the second image located outside the field of view of the first image with respect to the arbitrary position on the first image are the X displacement detection unit 141 and the Y coordinate. Since the displacement detection unit can obtain a detection resolution of 3.3 nm to 0.3 nm, it is possible to evaluate a long-period pattern fluctuation of a fine pit row having a size of several hundred nm to several tens nm with a resolution of nm.
[0036]
In this embodiment, the case of the measurement mode in which the control is performed in a state where the probe 1 is always in contact with the sample 3 has been described. The present invention is applicable to all other measurement modes, such as a case where the contact 3 intermittently repeats contact and non-contact.
[0037]
Further, the present invention is not limited to an atomic force microscope utilizing a force acting between a probe and a sample, but also a scanning tunnel microscope utilizing a tunnel current flowing between the probe and the sample, and leakage from a magnetic sample. A magnetic force microscope that detects magnetic fields to obtain magnetic information, a capacitance microscope that detects the capacitance between the probe and the sample, an electrostatic force microscope that uses the electrostatic force between the probe and the sample, or It can be applied to all other scanning probe microscopes, such as a near-field optical microscope that uses the near-field light to obtain optical information on the sample surface, without depending on the physical quantity detected by the probe. Needless to say.
[0038]
As described above, according to the present invention, since the position detecting means for detecting the relative position between the probe and the sample and the means for storing the detected position signal are provided, the first image and the position outside the field of view are provided. Can be obtained relative to each other. Therefore, it is possible to evaluate a long-period pattern fluctuation of, for example, 100 μm or more of the surface shape measured with a resolution of 1 nm or less at a resolution of 1 nm or less.
[0039]
【The invention's effect】
According to the present invention, it is possible to realize a scanning probe microscope capable of measuring a distance from a desired position in a measured image with high accuracy using at least one point outside the visual field of the measured image as a reference position.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an embodiment of a scanning probe microscope according to the present invention.
FIG. 2 is a diagram illustrating an example of a configuration of a parallel plate driving mechanism according to the present invention.
FIG. 3 is a block diagram illustrating a configuration of a conventional technique.
FIG. 4 is a diagram illustrating a measurement operation according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Probe, 2 ... Cantilever, 3 ... Sample, 301 ... Pit, 302, 303 ... Measurement area, 4 ... Lever displacement detector, 5 ... Z servo circuit, 6 ... XYZ scanner, 601 ... Z fine movement mechanism, 602 ... XY fine movement mechanism, 603: fixed unit, 604: moving unit, 605: piezoelectric element, 606: elastic deformation unit, 7: XY scanning circuit, 8: XY signal generation unit, 9: image acquisition unit, 10: image memory, 111 ... Z stage, 112 ... XY stage, 12 ... Mirror A, 13 ... Mirror B, 14 ... Laser interferometer, 15 ... Polarizing beam splitter, 16 ... Right angle prism, 17 ... Light source, 18 ... 1/4 wavelength plate A , 19 ... 1/4 wavelength plate B, 141 ... X displacement detector.

Claims (9)

A probe installed opposite to the sample, a moving unit for moving the probe relatively to the sample, a detecting unit for detecting an interaction between the probe and the sample, and the moving unit Means for forming an image reflecting information on the sample surface based on a detection result obtained from the detection means by scanning the probe with respect to the sample surface, and detecting a relative position between the probe and the sample Position detecting means and storage means for storing a detection result of the position detecting means are provided, and at least one point on the first image is set as a reference position and a second position is located outside the field of view of the first image. A scanning probe microscope configured to measure a desired position coordinate on an image based on a stored detection result of the position detecting means. The scanning probe microscope according to claim 1, wherein the probe has a probe provided at a free end of a cantilever, and detects an interaction between the probe and the sample surface. . The moving means detects a bending amount of the cantilever due to an atomic force acting between the probe and the sample, compares the detected bending signal with a predetermined reference value, and corresponds to the deviation. The scanning probe microscope according to claim 2, wherein the signal is controlled so that the interatomic force acting between the probe and the sample is constant. 2. The scanning type according to claim 1, wherein the moving unit includes a first moving unit that moves the sample three-dimensionally, and a second moving unit that moves the probe three-dimensionally. Probe microscope. The position detecting means has a laser light source, a polarizing beam splitter, and a laser interferometer, and transmits the laser light emitted from the laser light source to the first moving means and the second moving means via the polarizing beam splitter. 5. The scanning probe microscope according to claim 4, wherein the laser interferometer measures the relative position between the probe and the sample by causing the laser interferometer to enter and reflect each of the moving means. 5. The scanning probe microscope according to claim 4, wherein said second moving means has a mechanism for restricting a moving direction of said probe to a direction of elastic deformation of an elastic body by driving a piezoelectric element. A probe installed to face the sample, a moving unit for moving the sample three-dimensionally, a fine movement unit for finely moving the probe three-dimensionally, and detecting an interaction between the probe and the sample Detecting means for scanning the sample surface with the probe, and means for forming an image reflecting information on the sample surface based on the detection result obtained from the detecting means, and the probe and the Position detection means for detecting the relative position of the sample, and storage means for storing the detection result of the position detection means are provided, and at least one point on the first image is set as a reference position and is outside the field of view of the first image A scanning probe microscope characterized in that a desired position coordinate on a second image located at a position is measured based on a stored detection result of the position detecting means. Bringing a probe into or out of contact with a sample, scanning the probe, detecting an interaction between the sample and the probe, and acquiring an image reflecting the sample surface based on the detected result. And a step of measuring a relative position between the sample and the probe, a step of storing the measured relative position, and a step of storing the measured relative position in the first image with reference to at least one point on the first image. Obtaining a desired position coordinate on the second image outside the visual field from the stored relative position. 9. The scanning probe microscope according to claim 8, wherein a probe provided at a free end of a cantilever is used as the probe, and an interaction between a tip of the probe and the sample surface is detected. Measurement method.

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