JP5118768B2 - Near-field spectrometer - Google Patents

Description

  The present invention relates to near-field spectroscopy apparatus, and more particularly to background correction in near-field spectroscopy.

In recent years, scanning near-field optical microscopes based on principles different from general optical microscopes or electron microscopes have been developed, which can observe light smaller than the wavelength of light, which was difficult with general microscopes. Its application is expected.
This scanning near-field optical microscope detects so-called near-field waves. For example, a minute sample is placed on a flat substrate, and the sample undergoes total reflection from the back surface of the substrate. When light is incident, all propagating light is reflected, but surface waves called near-field waves are generated in the vicinity of the substrate and the sample surface. This surface wave is localized in a region within a distance within the wavelength of light around the sample surface.

Therefore, the distance between the probe tip and the sample surface can be defined by inserting a sharp probe into the near-field wave field to scatter the near-field wave and measuring the intensity of the scattered light.
Therefore, by scanning the probe while keeping the intensity of the scattered light constant, the probe tip position accurately reflects the unevenness of the sample surface. Moreover, since the probe tip is only in the near-field wave field and is not in contact with the sample itself, the probe tip is non-contact, non-destructive and can observe objects smaller than the light wavelength value. It is.

  Recently, by connecting a spectroscopic analyzer or the like to the scanning near-field optical microscope, the shape of the sample measurement surface is grasped, and the near-field scattered by bringing the sample and the probe tip close to the near-field region. Since light can be collected and the collected scattered light can be dispersed to obtain spectral information, it is possible to analyze the components and the like, and applications are being made in various fields.

However, even in a near-field spectroscopic device that can simultaneously acquire height information and component information at each measurement site of a sample, further improvement in spectral shape accuracy, measurement efficiency, etc. has been desired. In the past, there was no appropriate technique that could solve this problem.
The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a near-field spectroscopic device capable of efficiently obtaining true spectral information of a sample.

  As a result of intensive studies on the accuracy improvement of the spectrum shape in near-field spectroscopy by the present inventors, the key to the solution is to reduce the influence of background removal, device drift, etc. in near-field spectroscopy. It came to knowledge.

  In particular, in near-field spectroscopy, an optical fiber probe is often used to collect scattered near-field light or ooze out near-field light from the tip of the probe. Since the background overlaps the spectrum, the accuracy of the spectral shape of the sample is reduced. For this reason, it has been found that the accuracy of the spectrum shape in near-field spectroscopy can be improved by obtaining background information at a predetermined separation distance and correcting the spectrum of the sample.

In order to efficiently remove the influence of the background, acquiring the background information during the movement of the probe tip position to a certain measurement site, that is, when modulating the position in the Z-axis direction, for example, The present inventors have found that it is preferable from the viewpoint of shortening the time and reducing the influence of the drift of the apparatus, and have completed the present invention.
In other words, in order to achieve the above object, a near-field spectroscopic device according to the present invention includes a near-field information acquisition unit, a background information acquisition unit, a Z-axis scanning unit, and a calculation unit. The background information acquisition means obtains the background spectrum information of the corresponding measurement site while the Z-axis scanning means separates the sample and the probe tip in the Z-axis direction and is separated by a predetermined distance outside the near-field region. It is characterized by that.

Here, the near-field information acquisition means collects the near-field light scattered by bringing the sample and the probe tip close to each other in the near-field region, disperses the collected scattered light, and obtains the near-field spectrum information of the sample. obtain.
The Z-axis scanning unit scans in the Z-axis direction that separates or approaches the sample and the probe tip, and when obtaining near-field spectrum information by the near-field information acquisition unit, the sample and the probe tip are placed in a near-field region. When obtaining background spectrum information by the background information acquisition means, the sample and the probe tip are separated by a predetermined distance outside the near field region.

The calculation means subtracts the background spectrum information obtained by the background information acquisition means from the near-field spectrum information obtained by the near-field information acquisition means, and obtains true near-field spectrum information from which the background has been removed. obtain.
In the present invention, a plurality of measurement surfaces are set as the measurement site on the sample measurement surface, and the probe tip is scanned on the sample measurement surface in the X and Y axis directions orthogonal to the Z axis. Means. Then, the near-field information acquisition means moves the probe tip to the measurement surface in the X direction and the XY-axis scanning means in a state where the sample and the probe tip are brought close to a predetermined distance in the near-field region by the Z-axis scanning means. Scan in the Y direction to obtain near-field spectrum information of the measurement surface.

  The background correction means is configured such that when the probe tip moves to the next measurement surface, the Z-axis scanning means separates the sample and the probe tip in the Z-axis direction and separates the probe at a predetermined distance outside the near-field region. Obtain background spectrum information for the measurement surface of the tip movement source or destination.

The arithmetic means subtracts each corresponding background spectrum information from the near-field spectrum information of each measurement surface, and obtains true near-field spectrum information from which each corresponding background is removed for each measurement surface. Is preferred.
In the present invention, as the measurement site, a plurality of measurement rows are set in the uniaxial direction in the X and Y axis planes on the sample measurement surface, and the probe tip is orthogonal to the Z axis on the sample measurement surface. XY axis scanning means for scanning in the Y axis direction is provided. The near-field information acquisition unit obtains near-field spectrum information sequentially from each measurement row.

The background correction means is configured such that when the probe tip moves to the next measurement line, the sample and the probe tip are separated in the Z-axis direction by the Z-axis scanning means and the probe tip is separated by a predetermined distance outside the near-field region. The background spectrum information for the measurement line of the movement source or movement destination of the tip is obtained.
The arithmetic means subtracts each corresponding background spectrum information from the near-field spectrum information of each measurement row, and obtains true near-field spectrum information from which each corresponding background is removed for each measurement row. Is preferred.

Further, in the present invention, an XY axis scanning unit that sets a plurality of measurement points on the sample measurement surface as the measurement site and scans the probe tip in the X and Y axis directions perpendicular to the Z axis on the sample measurement surface. Is provided. And the said near field information acquisition means obtains near field spectrum information sequentially from each said measurement point.
The background correction means is configured such that when the probe tip is moved to the next measurement point, the sample and the probe tip are separated in the Z-axis direction by the Z-axis scanning means and the probe is being separated by a predetermined distance outside the near-field region. The background spectrum information for the measurement point of the moving source or the moving destination of the tip is obtained.

Preferably, the calculation means subtracts each corresponding background spectrum information from the near field spectrum information of each measurement point to obtain true near field spectrum information from which each background corresponding to each measurement point is removed. It is.
In the present invention, an optical distance characteristic acquisition unit and a selection unit are provided. When obtaining the background spectrum information by the background information acquisition means, the Z-axis separation distance between the sample measurement surface and the probe tip is set to the distance selected by the selection means by the Z-axis scanning means. Is preferred.

Here, the optical distance characteristic obtaining unit obtains the relationship between light and distance by obtaining spectral information of the sample while changing the separation distance between the sample measurement surface and the probe tip by the Z-axis scanning unit.
Further, the selection unit selects a distance at which a desired optical characteristic can be obtained from the relationship between the light and the distance obtained by the optical distance characteristic acquisition unit.

As described above, according to the near-field spectroscopic device according to the present invention, the background information acquisition means can be used while the sample and the probe tip are separated in the Z-axis direction by the Z-axis scanning means and separated by a predetermined distance outside the near-field region. Thus, the background spectrum information of the measurement site is obtained and the near-field spectrum information of the corresponding measurement site is corrected, so that the influence of drift is reduced and the background is efficiently removed from the near-field spectrum information. be able to.
In the present invention, the distance between the sample to be measured for the background and the tip of the probe is obtained by obtaining the relationship between the spectrum and the distance by the optical distance characteristic acquiring means while changing the distance between the sample and the probe tip by the Z-axis scanning means. Therefore, it is possible to significantly reduce the deterioration of spectral information during background correction in near-field spectroscopy.

It is explanatory drawing of schematic structure of the near-field spectrometer concerning one Embodiment of this invention. It is explanatory drawing of the Z-axis direction position of a sample and a probe tip at the time of background spectrum information acquisition by the near-field spectrometer shown in FIG. 1 and near-field spectrum acquisition. It is explanatory drawing of the scanning for every measurement surface by the near-field spectrometer shown in FIG. , It is explanatory drawing of the scanning for every measurement line by the near-field spectrometer shown in FIG. , It is explanatory drawing of the scanning for every measurement point by the near-field spectrometer shown in FIG. It is explanatory drawing of the optical distance characteristic measuring means suitable for using with the near-field spectroscopy apparatus shown in FIG. It is explanatory drawing of the light-distance characteristic obtained with the optical distance characteristic measuring means shown in FIG.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a near-field spectrometer according to an embodiment of the present invention. In this embodiment, an optical fiber probe that scatters or reflects near-field light oozing from the tip as a probe and collects the scattered or reflected light is used.

A near-field optical microscope (near-field spectroscopic device) 10 shown in the figure includes a separation information acquisition unit and a near-field information acquisition unit.
The separation information acquisition means includes, for example, an optical fiber probe 12, a near-field head 14, a Z-axis position control optical system 16, an XYZ stage 18, a stage controller 20, and a computer main body 22.

  The XYZ stage 18 and the stage controller 20 scan the sample 24 and the tip of the probe 12 in the Z-axis direction so that the sample 24 and the tip of the probe 12 are separated or close to each other. Within a predetermined distance.

  In the present embodiment, a sample 24 is placed on the XYZ stage 18, and the sharp probe 12 is inserted into the field of the near-field light 25 to scatter the near-field light 25. At this time, the probe 12 is minutely vibrated at the resonance frequency by the near-field head 14. The Z-axis direction position control optical system 16 irradiates the tip of the probe 12 with light 26, detects the modulated reflected light 28 from the tip of the probe 12, and detects the change in vibration amplitude at the tip of the probe 12 from the light. . The probe 12 is scanned by driving the XYZ piezo stage 18 by the stage controller 20 while keeping the vibration amplitude at the tip of the probe 12 constant. As a result, the XY position information of each measurement point is obtained from the XYZ stage 18 and the like at the same time as the height information at each measurement point in the separation information storage unit 32 of the hard disk (HDD) 30 of the computer main body 22. Thus, the distance between the probe 12 tip and the sample 24 measurement surface can be defined.

  The near-field information acquisition means includes, for example, an excitation laser 36, an optical fiber probe (probe) 12, a spectroscope 38, a detector 40, a computer main body 22, and an XYZ stage (XY axis scanning means, Z axis scanning means). ) 18 and a stage controller (XY-axis scanning means, Z-axis scanning means) 20.

  The laser light 42 from the excitation laser 36 is incident on the fiber probe 12 and the near-field light 25 oozes out from the opening at the tip of the probe 12. The near-field light 25 is localized in a region narrower than the wavelength of light at the tip of the probe 12, and the stage controller 20 causes the tip of the probe 12 and the sample measurement surface 24 to be narrower than the wavelength of light (in the near-field region). ), The light 25 oozing out from the probe tip 12 is scattered or reflected on the sample measurement surface 24, and the scattered light or reflected light 44 is collected from the opening at the tip of the probe 12, and is dispersed by the spectroscope 38. Is done. The dispersed light is detected by the detector 40, and the light intensity is stored in the near field information storage unit 42 of the HDD 30 of the computer main body 22 together with the wavelength information obtained from the spectrometer 38.

  As described above, the near-field optical microscope 10 includes the separation information acquisition unit and the near-field information acquisition unit, so that the height information and the component information at each measurement site on the sample surface can be acquired simultaneously. The computer main body 22 can display the mapping measurement result obtained as described above on the display 45.

By the way, even with such a near-field optical microscope 10, further improvements in the accuracy of the spectral shape of the sample and the efficiency of measurement have been desired. However, in a conventional near-field optical microscope, It was only a mapping measurement of the intensity of the optical signal, and there was no concept of background correction.
Further, in the mapping measurement with a long measurement time, the background spectrum gradually changes with time, so it was necessary to update the background spectrum during the measurement.

  Therefore, what is characteristic in the present invention is that a certain measurement site at the probe tip position during the mapping measurement in order to improve the accuracy of the spectral shape of the sample, shorten the measurement time, and reduce the influence of the drift of the apparatus. That is, background information is obtained every time the movement to the position, that is, at the time of Z-axis direction position modulation, and this is used for background correction of the corresponding measurement site.

For this purpose, the present embodiment includes background information acquisition means, Z-axis scanning means, and calculation means.
The background information acquisition means includes, for example, an excitation laser 36, an optical fiber probe 12, a spectroscope 38, a detector 40, and a computer main body 22.
The Z-axis scanning unit includes, for example, an XYZ stage 18 and a stage controller 20, and scans in the Z-axis direction in which the sample 24 and the tip of the probe 12 are spaced apart or close to each other. When obtaining background spectrum information, the sample 24 and the tip of the probe 12 are separated by a predetermined distance outside the near-field region.

  The laser light 42 from the excitation laser 36 is incident on the fiber probe 12 and the near-field light 25 oozes out from the opening at the probe tip. The stage controller 20 drives the XYZ stage 18 in the Z-axis direction, and obtains background spectrum information in a state where the sample 24 and the probe tip 12 are separated by a predetermined distance outside the near-field region by the spectroscope 38 and the detector 40. . This is stored in the background information storage unit 44 of the HDD 30 of the computer main body 22.

  The calculation means is composed of, for example, the CPU 46 of the computer main body 22, and subtracts the corresponding background spectrum information in the background information storage unit 44 from the near field spectrum information of a certain measurement site in the near field information storage unit 42, Obtain true near-field spectrum information with the background removed for the measurement site.

  That is, in the present embodiment, when obtaining near-field spectrum information of a certain measurement site, as shown in FIG. 2A, the stage controller 20 drives the XYZ stage 18 in the + Z-axis direction upward in the drawing. As shown in (B), the distance H1 between the measurement site of the sample 24 and the position of the probe tip 12 is brought close to a predetermined distance in the near-field region W.

  In this embodiment, when the probe tip position is moved to the next measurement site after measurement of this measurement site, the stage controller 20 moves the XYZ stage 18 in the Z-axis direction, downward in the figure, as shown in FIG. When driving, the background spectrum of the corresponding measurement site is obtained at the time of Z-axis direction position modulation in which the measurement site of the sample 24 and the position of the probe tip 12 are separated by a predetermined distance H2 outside the near-field region W.

  In the present embodiment, the background spectrum information obtained in the state shown in FIG. 10C is subtracted from the near-field spectrum information obtained in the state shown in FIG. To do. As a result, true near-field spectrum information from which the background has been removed can be obtained for the corresponding measurement site. In the present embodiment, this is repeated for each measurement site.

  As described above, in the present embodiment, the sample 24 and the probe 12 when the position of the tip of the probe 12 is moved to the next measurement site during the modulation of the Z-axis position during the mapping measurement, that is, after the near-field spectrum of the measurement site is collected. When the tip position is separated by a predetermined distance H2 outside the near field region, the background spectrum information of the corresponding measurement site is obtained. Thus, in the present embodiment, one background spectrum measurement is separately performed after acquisition of near-field spectrum information of all measurement sites, and uniform correction is performed using one background spectrum information for all measurement sites. Compared to the above, it is possible to reduce the influence of the drift of the apparatus system and to efficiently obtain a true near-field spectrum from which the influence of the background is largely removed for each measurement site.

Especially for the measurement of a plurality of measurement sites, since the background spectrum information is obtained at the time of Z-axis direction position modulation during mapping measurement, the measurement time of only the conventional near-field spectrum information is almost the same, Near-field spectrum information and background spectrum information can be obtained.
Each background spectrum information can be used for background correction of near-field spectrum information obtained from the measurement site at the movement source or movement destination of the probe tip position.

Hereinafter, specific examples of various scans of the probe tip position on the sample measurement surface will be described.
<Surface scanning>
A plurality of measurement surfaces are set in the measurement region of the sample, and near-field spectrum information is obtained sequentially from each measurement surface by the near-field information acquisition unit. That is, mapping measurement is performed for each measurement surface.

FIG. 3 shows a measurement surface as a certain measurement site. In the figure, the solid line shows the movement trajectory of the probe tip position on the measurement surface when mapping measurement is performed with the probe tip and the measurement surface in proximity to the near field region. A circle indicated by a broken line indicates a background measurement point in a state where the probe tip and the measurement surface are separated by a predetermined distance outside the near-field region.
As shown in the figure, at the background measurement point Q1 for the measurement surface A1, the probe tip position is separated by a predetermined distance outside the near-field region of the measurement surface to obtain background spectrum information.

After the background measurement, the probe tip is positioned above the starting point P1 of the first measurement surface A1 by driving the X axis, and the probe tip is brought close to a predetermined distance in the near field region on the starting point P1 by driving the Z axis.
While maintaining the separation distance between the first measurement surface A1 and the probe tip position, the probe tip position is scanned from the start point P1 to the end point Pn of the first measurement surface A1 in the X and Y directions as shown by the solid lines in the figure, Obtain near-field spectrum information of the measurement surface A1. At this time, the XY coordinates on the measurement surface A1 are obtained from the XYZ stage or the like, and the light intensity obtained by the detector is stored together with the wavelength information obtained from the spectroscope, so that each measurement site on the measurement surface A1 is measured. Near field spectrum information is obtained.

  After acquiring the near-field spectrum information on the first measurement surface A1, in order to acquire near-field spectrum information on the next second measurement surface, on the end point Pn of the first measurement surface A1, the probe tip is modulated by Z-axis direction position modulation. The positions are separated by a predetermined distance outside the near field region above the end point Pn, and background spectrum information for the second measurement surface is obtained. After obtaining the background spectrum information for the second measurement surface, the probe tip position is positioned above the starting point on the next second measurement surface by XY axis driving, and the probe tip is moved to the near field on the starting point by Z axis driving. Close to a predetermined distance in the area.

While maintaining the separation distance between the second measurement surface and the probe tip position, the probe tip position is scanned in the X and Y directions from the start point to the end point of the measurement surface in the same manner as the first measurement surface, and the near field of the second measurement surface Obtain spectral information.
As described above, in this embodiment, the probe during the Z-axis direction position modulation during mapping measurement of each measurement surface, that is, after acquisition of near-field spectrum information of a certain measurement surface and before acquisition of near-field spectrum information of the next measurement surface. While the tip position is separated by a predetermined distance outside the near-field region, background spectrum information of the measurement surface of the probe tip position movement source or movement destination is obtained.

  In this embodiment, the CPU subtracts the corresponding background spectrum information from the near-field spectrum information of the measurement surface to obtain true near-field spectrum information from which the background is removed for the measurement surface. This is repeated for each measurement surface.

  As a result, in this embodiment, background measurement is separately performed after acquisition of near-field spectrum information on all measurement surfaces, and background correction is uniformly performed on all measurement surfaces using one background spectrum information. As compared with the above, it is possible to obtain a true near-field spectrum in which the influence of the drift of the apparatus system is reduced and the influence of the background is largely removed for each measurement surface.

  Moreover, in the present embodiment, when a plurality of measurement surfaces are set in the measurement region of the sample and the near-field spectrum information is sequentially obtained from each measurement row by the near-field information acquisition unit, Z during the mapping measurement of each measurement surface is obtained. Since the background spectrum information is acquired as described above during axial position modulation, the measurement time is almost the same as the time of mapping measurement alone, compared to the case of performing background measurement separately after all mapping measurements are completed. Can be significantly shortened.

In the present embodiment, the obtained background spectrum information can be used for background correction of either the near-field spectrum information obtained from the measurement surface of the probe tip position movement source or movement destination.
In the above configuration, an example in which the near-field spectrum information of the measurement surface is corrected using the background spectrum information collected from the background measurement point near the start point of the measurement surface is described. A background spectrum collected from the background measurement points may be used.

  In the present embodiment, the background correction can be performed at an arbitrary time as long as the near-field spectrum information on each measurement surface is corrected with the corresponding background spectrum information. For example, each time the near-field spectrum information of each measurement surface is obtained, the corresponding background spectrum information is corrected in real time, and the mapping measurement results are sequentially displayed on the display, or the near-field spectrum information of all measurement surfaces can be obtained. After that, it is possible to perform correction with the corresponding background spectrum information and display the mapping measurement result on the display at a time.

<Line scan>
As shown in FIG. 4, a plurality of measurement rows L1 to Ln are set in the X-axis direction in the drawing in the sample measurement area, and near-field spectrum information is obtained sequentially from each measurement row L1 to Ln by the near-field information acquisition means. That is, mapping measurement is performed for each measurement row Li.
In the figure, the solid line shows the movement trajectory of the probe tip position on the sample when the probe tip and the sample are brought close to each other in the near field region and mapping measurement is performed. A broken line indicates a movement locus of the probe tip position in a state where the probe tip position and the sample are separated by a predetermined distance outside the near-field region. Circles indicated by broken lines indicate background measurement points in a state in which the probe tip position and the sample are separated by a predetermined distance outside the near-field region.

  As shown in the figure, the measurement region of the sample is scanned for each measurement row Li. That is, first, before acquiring near-field spectrum information of the first measurement row L1, the acquisition of background spectrum information for the first measurement row L1 is performed by separating the probe tip position and the sample by a predetermined distance outside the near-field region, Performed from background measurement point Q1.

  After the background measurement, the probe is positioned above the start point P11 of the first measurement row L1 by driving the XY axis, and at the start point P11 of the first measurement row L1, the probe tip position is brought close to the near field region by driving the Z axis. Start collecting spectral information. That is, the probe tip is scanned in the X-axis direction to the end point Pn on the first measurement row L1 while maintaining this separation distance. At this time, the XY coordinates of the measurement row L1 are obtained from an XYZ stage or the like, and the light intensity obtained by the detector is stored together with the wavelength information obtained from the spectrometer, so that the proximity in each measurement site of the measurement row L1 is obtained. Field spectrum information is obtained.

  After acquiring near-field spectrum information of the end point P1n on the first measurement line L1, in order to acquire near-field spectrum information of the next second measurement line L2, at the end point P1n, the probe tip position is determined by driving the Z axis. Separated by a predetermined distance outside the area. Then, by driving the XY axis, the probe tip position is moved, for example, in the diagonally left direction in the figure, and is positioned above the start point P21 on the next second measurement row L2.

Here, in the present embodiment, for example, background spectrum information for the second measurement row is backed up in a state where the probe tip position is separated by a predetermined distance outside the near-field region when moving to the next measurement row. Obtained from ground measurement point Q2.
In this embodiment, the probe tip position is close when the Z-axis direction position modulation during mapping measurement of each measurement line, that is, after the near-field spectrum information of one measurement line is acquired and before the near-field spectrum information of the next measurement line is acquired. When the sensor is separated by a predetermined distance outside the field area, background spectrum information is obtained for the measurement line L1 from which the probe tip position is moved to the measurement line L2 which is the movement destination.

In this embodiment, the CPU subtracts the corresponding background spectrum information from the near-field spectrum information of a certain measurement line, and obtains true near-field spectrum information from which the corresponding background is removed for the measurement line. In the present embodiment, this is repeated for each measurement line.
Therefore, in the present embodiment, during the mapping measurement of each measurement row, the back-end for the measurement row of the movement source or the movement destination of the probe tip position is separated to a predetermined distance outside the near-field region at the time of the Z-axis direction position modulation. It was decided to obtain ground spectrum information and perform this for each measurement line.

  As a result, in this embodiment, after acquiring near-field spectrum information of all measurement rows, background measurement is separately performed, and background correction is performed uniformly using one background spectrum information for all measurement rows. Compared to the above, it is possible to reduce the influence of the drift of the apparatus system and to obtain a true near-field spectrum in which the influence of the background is largely removed for each measurement line.

  In addition, in the present embodiment, when a plurality of measurement rows are set in the measurement region of the sample and the near-field spectrum information is sequentially obtained from each measurement row by the near-field information acquisition unit, Z in the mapping measurement of each measurement row is obtained. Since the background spectrum information as described above is acquired while being separated by a predetermined distance outside the near-field region at the time of axial position modulation, the measurement time is compared with that separately performing background measurement. The time can be greatly shortened to almost the same time as the information only acquisition time.

  In the present embodiment, certain background spectrum information can be used for background correction of either near-field spectrum information obtained from the measurement line at the probe tip position movement source or movement destination.

  In the present embodiment, the background correction can be performed at an arbitrary time as long as the near-field spectrum information of each measurement row is background-corrected with the corresponding background spectrum information. For example, each time the near-field spectrum information of each measurement line is obtained, the corresponding background spectrum information is corrected in real time, and the mapping measurement results are sequentially displayed on the display, or the near-field spectrum information of all measurement lines can be obtained. After that, it is possible to perform correction with the corresponding background spectrum information and display the mapping measurement result on the display at a time.

  In this embodiment, the background measurement point is preferably set to the background measurement point during the movement of the probe tip position to the next measurement line from the viewpoint of shortening the measurement time. If there is a predetermined separation distance, as shown in FIG. 5, the background measurement point Qi can be set near the start point or end point of each measurement row Li.

<Point scanning>
As shown in FIG. 6, a plurality of measurement points are set in the measurement region of the sample, and near-field spectrum information is obtained sequentially from each measurement point by the near-field information acquisition means. That is, mapping measurement is performed for each measurement point.

In the figure, each point indicated by a solid line indicates a measurement point that obtains near-field spectrum information by bringing the probe tip position and the sample measurement surface close to each other in the near-field region. A circle indicated by a broken line indicates a background measurement point in a state where the probe tip position and the sample measurement surface are separated by a predetermined distance outside the near-field region.
As shown in the figure, the measurement area of the sample is scanned for each measurement point. That is, first, above the first measurement point P1, the probe tip position is separated by a predetermined distance outside the near-field region, and by the XY axis drive, as shown by the broken line in the figure, the probe tip position is set around the first measurement point P1. While turning the position, background spectrum information for the measurement point P1 is obtained from the background measurement point Q1.

  In this embodiment, after obtaining background spectrum information from the background measurement point Q1, the probe tip is positioned above the first measurement point P1 by XY axis driving. Then, the probe tip position is brought close to a predetermined distance in the near-field region on the first measurement point P1 by Z-axis driving, and near-field spectrum information is acquired. At this time, the XY coordinates of the measurement point P1 are obtained from XYZ or the like, and the light intensity obtained by the detector is stored together with the wavelength information obtained from the spectrometer, whereby the spectrum information at the measurement point P1 is obtained.

In the present embodiment, after the near-field spectrum information of the first measurement point P1 is obtained, the near-field spectrum information of the next second measurement point P2 is obtained. Therefore, on the first measurement point P1, the probe is driven by the Z axis. The tip position is separated by a predetermined distance outside the near-field region, and the probe tip position is positioned above the second measurement point P2 by driving the X axis.
Above the second measurement point P2, with the probe tip position separated by a predetermined distance outside the near-field region, the periphery of the second measurement point P2 is swung as shown by the broken line in the figure by XY axis drive. In the meantime, the background spectrum information for the measurement point P2 is obtained from the background measurement point Q2.

In the present embodiment, after obtaining the background spectrum information from the background measurement point Q2, the probe tip position is positioned above the second measurement point P2 by XY axis driving. The probe tip position is brought close to a predetermined distance in the near-field region on the second measurement point P2 by driving the Z axis. Near field spectrum information of the second measurement point P2 is acquired.
As described above, in the present embodiment, during the modulation of the Z-axis direction position during the mapping measurement of each measurement point, that is, after the acquisition of the near-field spectrum information of the next measurement point after the acquisition of the near-field spectrum information of the next measurement point. When the probe tip position is separated by a predetermined distance outside the near-field region, background spectrum information for the measurement point of the probe tip position movement source or destination is obtained.

In this embodiment, the CPU subtracts the corresponding background spectrum information from the near-field spectrum information of the measurement point, and obtains true near-field spectrum information from which the corresponding background is removed for the measurement point. This is repeated for each measurement point.
Therefore, in this embodiment, during the mapping of each measurement point during the mapping measurement, the probe is separated at a predetermined distance outside the near-field region when moving the probe tip position to the next measurement point. The background spectrum information for the measurement point of the movement position or movement destination of the tip position is obtained, and this is performed for each measurement point.

  As a result, in this embodiment, after obtaining near-field spectrum information of all measurement points, background measurement is separately performed, and background correction is uniformly performed for all measurement points using one background spectrum information. Compared to the above, it is possible to obtain a true near-field spectrum in which the influence of the drift of the apparatus system is reduced and the influence of the background is largely removed at each measurement point.

  Moreover, in this embodiment, when a plurality of measurement points are set in the measurement region of the sample and the near-field spectrum information is sequentially obtained from each measurement point by the near-field information acquisition unit, Z during the mapping measurement of each measurement point is obtained. Since the background spectrum information as described above is acquired when the axial position is modulated, the measurement time is greatly increased to approximately the same time as that for normal mapping measurement alone, compared to a separate background measurement. Can be shortened.

  In the present embodiment, the background spectrum information obtained when moving from the measurement point at the probe tip position to the measurement point at the destination is obtained from the measurement point at the source or destination of the probe tip position. It can also be used for background correction of either near-field spectral information.

  Further, in the present embodiment, the background correction can be performed at any time as long as the near-field spectrum information at each measurement point is background-corrected with the corresponding background spectrum information. For example, each time the near-field spectrum information at each measurement point is obtained, the corresponding background spectrum information is corrected in real time, and the mapping measurement results are sequentially displayed on the display, or the near-field spectrum information at all measurement points can be obtained. After that, it is possible to perform correction with the corresponding background spectrum information and display the mapping measurement result on the display at a time.

In the above configuration, the example in which the background spectrum information of the corresponding measurement point is obtained when the probe tip position is swung around the measurement point by a predetermined separation distance has been described. The background spectrum information of the corresponding measurement point Pi is obtained from each of the background measurement points Qi separated by a predetermined separation distance outside the near field region as shown in FIG. You can also.

  As described above, according to the near-field spectroscopic device according to the present embodiment, during the modulation of the Z-axis direction position during the mapping measurement for each of the plurality of measurement sites, that is, when the probe tip position is moved to the next measurement site. The background spectrum information for background correction of the measurement site of the movement position of the probe tip position or the movement destination is obtained while being separated by a predetermined distance outside the near field region, and this is performed for each measurement site.

  As a result, in this embodiment, after acquiring near-field spectrum information of all measurement sites, background measurement is separately performed, and background correction is performed uniformly using one background spectrum information for all measurement sites. Compared to the above, it is possible to obtain a true near-field spectrum in which the influence of the drift of the apparatus system is reduced and the influence of the background is largely removed for each measurement site.

  Moreover, in this embodiment, when a plurality of measurement sites are set in the measurement region of the sample and the near-field spectrum information is obtained sequentially from each measurement point by the near-field information acquisition unit, the measurement site next to the probe tip position is obtained. During the movement, the background spectrum is acquired as described above while being separated by a predetermined distance outside the near-field region. The time can be significantly reduced to almost the same time.

<Light distance characteristics>
By the way, in near-field spectroscopy, if the distance between the probe and the sample is far, the signal from the sample may be significantly reduced. Conventionally, however, how much spectrum is obtained at what specific distance. Did not have the ability to measure

  On the other hand, if background correction is not performed with careful consideration of the relationship between optical characteristics and distance in near-field spectroscopy, it will cause deterioration of the waveform of the near-field spectrum rather than removing the background. , Background removal may not be performed properly. For this reason, the relationship between light and distance in near-field spectroscopy is particularly important when defining a background spectrum.

Therefore, in the present embodiment, in order to measure the relationship between light and distance as described above and to appropriately remove the background without accompanying waveform deterioration, an optical distance characteristic acquisition unit and a selection unit as shown in FIG. Means. Note that portions corresponding to those in FIG. 1 are denoted by reference numeral 100 and description thereof is omitted.
The optical distance characteristic acquisition means includes, for example, an excitation laser 136, an optical fiber probe 112, a spectroscope 138, a detector 140, a computer main body 122, an XYZ stage 118, and a stage controller 120.

  In this embodiment, when the stage controller 120 causes the tip of the probe 112 and the measurement surface of the sample 24 to approach each other to a region narrower than the light wavelength (in the near-field region), the light 125 oozing out from the probe tip 112 is the sample 124. Scattered or reflected on the measurement surface. The scattered light or reflected light 144 is collected from the opening at the tip of the probe 112 and dispersed by the spectroscope 138. The separated light is detected by the detector 140. The light intensity is stored in the optical distance characteristic information storage unit 150 of the HDD 130 of the computer main body 122 together with the wavelength information obtained from the spectroscope 138.

  At this time, in this embodiment, the stage controller 120 drives the XYZ stage 118 in the Z-axis direction, and obtains spectral information while changing the separation distance between the sample 124 measurement surface and the probe 112 tip. This spectral information is stored in the optical distance characteristic storage unit 150 together with the Z-axis coordinates obtained from the stage controller 120 or the like.

In this way, the relationship between light and distance as shown in FIG. 9 is obtained. For example, as shown in the figure, as the distance between the probe tip position and the sample measurement surface approaches, the resulting spectral undulation increases, but as the distance increases, it becomes flat. Such a relationship between light and distance can be grasped.
The selection means is composed of, for example, the input device 152 and the like, and selects a distance at which a desired optical characteristic can be obtained from the relationship between the light obtained in the optical distance characteristic storage unit 150 and the separation distance. Thereby, the distance which should measure a background can be selected exactly.

  In this embodiment, when the background information is acquired by the background information acquisition unit, the CPU 146 accesses the optical distance characteristic storage unit 150 and sets the separation distance between the sample and the probe tip as described above. The distance at which the desired optical characteristic selected in this way is obtained. As a result, the distance between the tip of the probe whose background should be measured and the sample can be accurately known, and the background spectrum is obtained at the exact predetermined distance. Therefore, the spectrum information at the time of background correction in near-field spectroscopy can be obtained. Can be greatly reduced.

  Furthermore, in this embodiment, if the distance between the probe tip and the sample surface is greater than the interaction distance between the near-field light generated at the probe 112 tip and the sample 124 surface, the spectrum can be taken, but the peak shape is different. When the tip of the probe 112 and the surface of the sample 124 are brought close to each other, a sudden change in the spectrum peak may occur, which can be confirmed as an interaction between the near-field light generated at the probe tip and the sample surface.

In addition, although the example which used the fiber probe as a probe was demonstrated in the said structure, it is applicable to arbitrary probes. In the above configuration, the illumination-collection mode has been described as an example, but the present invention can be applied to any measurement mode. In particular, a total reflection prism can be provided and applied to total reflection measurement, and the same effect as the above configuration can be obtained.
In the above configuration, an example in which the position of the probe is fixed and the XYZ stage is moved has been described. However, the present invention can be applied to a structure in which the XYZ stage is fixed and the position of the probe is moved.

  Although the expression spectral information is used in the above configuration, a spectrum is obtained by performing an inverse Fourier transform on the interferogram, and background correction is performed on the spectrum. The present invention can be applied to both cases in which a ground-corrected spectrum is removed and an inverse Fourier transform is performed on the interferogram from which the background is removed to obtain a spectrum from which the background is removed.

  In each of the above-described configurations, when moving to each measurement site, first, the Z-axis drive alone is first separated upward on the source measurement site to a predetermined separation distance, and then the next measurement site is obtained only by XY-axis drive. However, it is also possible to simultaneously move the probe tip from the proximity position of the source measurement site to the separation position of the destination measurement site by combining the Z-axis drive and the XY-axis drive.

10 Near-field optical microscope (near-field spectrometer)
12 Optical fiber probe (Near field, background information acquisition means)
18 XYZ stage (near field, background information acquisition means, Z-axis scanning means, XY-axis scanning means)
20 stage controller (near field, background information acquisition means, Z-axis scanning means, XY-axis scanning means)
22 Computer itself (Near field, Background information acquisition means)
36 Excitation laser (Near field, background information acquisition means)
38 Spectrometer (Near field, background information acquisition means)
40 detector (near field, background information acquisition means)

Claims (2)

A near-field spectrometer that performs near-field spectrum measurement and background measurement by scanning the sample measurement surface in a row,
An XY plane consisting of an X axis and a Y axis on the sample measurement surface of the sample and a Z axis orthogonal to the XY plane are set, and the probe tip is scanned in the X axis or Y axis direction on the sample measurement surface An axial scanning means;
Z-axis scanning means for scanning in the Z-axis direction with the sample and the probe tip spaced apart or close to each other;
The Z-axis scanning means collects the near-field light scattered by bringing the sample and the probe tip close to a predetermined distance in the near-field region, disperses the near-field light, and obtains near-field spectrum information of the sample. Obtaining near field information obtaining means;
Background information for obtaining background spectrum information by separating a distance in the Z-axis direction between the sample measurement surface and the probe tip by the Z-axis scanning unit to a predetermined distance outside the near-field region from the sample. Acquisition means;
A calculation means for subtracting the background spectrum information obtained by the background information acquisition means from the near-field spectrum information obtained by the near-field information acquisition means to obtain true near-field spectrum information from which the background has been removed, and With
A plurality of measurement rows on the sample measurement surface as measurement sites are set in parallel with the X axis or the Y axis and in the same scanning direction,
The near-field information acquisition means obtains near-field spectrum information sequentially from each measurement line,
The background information acquisition unit separates the probe tip from the sample by the Z-axis scanning unit in the Z-axis direction at a predetermined distance outside the near-field region when the probe moves to the next measurement row, and measurement is performed. The probe obtains the background spectrum information for the measurement line of the movement source or the movement destination of the probe tip between the completed measurement line and the next measurement line,
The calculation means subtracts the corresponding background spectrum information from the near-field spectrum information of each measurement row, and obtains true near-field spectrum information from which the corresponding background is removed for each measurement row. A near-field spectrometer. The near-field spectroscopic device according to claim 1,
While changing the separation distance between the sample measurement surface and the probe tip by the Z-axis scanning unit, the spectral information of the sample is obtained by the near-field information acquisition unit, and the change of the spectrum peak caused by the near-field scattered light is obtained. Optical distance characteristic acquisition means for obtaining a relationship between the spectrum and the separation distance by
Selection means for selecting a distance at which a near-field spectrum or a background spectrum is obtained from the relationship between the spectrum obtained by the optical distance characteristic acquisition means and the separation distance;
A calculation means for subtracting the background spectrum information obtained by the background information acquisition means from the near-field spectrum information obtained by the near-field information acquisition means to obtain true near-field spectrum information from which the background has been removed, and Further comprising
The near-field information acquisition unit is configured to select the sample when the optical distance characteristic acquisition unit obtains the relationship between the near-field spectrum and the separation distance, or when the selection unit selects a distance from which the near-field spectrum is obtained. Has obtained near-field spectrum information of
The near field spectroscopic device, wherein the background information acquisition means obtains background spectrum information when a distance at which a background spectrum is obtained is selected by the selection means.

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