JP6229218B2 - Scanning probe microscope - Google Patents

Description

  The present invention relates to a scanning probe microscope, and more particularly to a scanning probe microscope capable of measuring the tip of a sharp specimen.

  A scanning probe microscope (SPM) is an apparatus that obtains information on the surface of a measurement object by scanning the surface of the measurement object with a probe (probe) having a sharp tip.

  The scanning probe microscope includes a scanning tunneling microscope (STM), an atomic force microscope (AFM), a scanning magnetic force microscope (MFM), a scanning SQUID microscope, and a superconducting quantum interferometer. (SQUID), Scanning Hall Element Microscope (SHPM), Scanning Kelvin Probe Force Microscope (KFM), Scanning Maxwell Stress Microscope (SMM), Scanning Piezoelectric Response Microscope (PFM), Scanning Nonlinear Dielectric Constant Microscope (SNDM) There are various types such as a scanning near-field optical microscope (SNOM).

  As such a scanning probe microscope, Patent Document 1 includes a measurement head mounted on a sample stage, and the measurement head scans the cantilever three-dimensionally with a cantilever having a probe at a free end. A rotating mechanism that rotatably supports the measurement head; and a handle provided on the casing. The measuring head includes the rotation mechanism. A scanning probe microscope connected to an installation table on which the sample stage is installed is described.

JP2013-238430A

  However, since the conventional scanning probe microscope as described in Patent Document 1 cannot align the probe tip with the tip of a sharp sample such as a needle, the tip of the sharp sample cannot be observed. Therefore, for example, in order to develop a high-intensity electron source, it is necessary to elucidate the fine structure of the tip of the electron source. It is difficult to observe the fine structure. As described above, the scanning probe microscope cannot be observed because the probe cannot be aligned with the tip of the sharp specimen, which hinders the development of a high-intensity electron source. I was coming.

  More specifically, in order to elucidate the fine structure of the tip of the electron source, a scanning probe microscope having high spatial resolution is expected, but the tip curvature is applied to the tip of the electron source having a tip curvature radius of 100 nm to 10 μm. It has been impossible with a conventional scanning probe microscope to approach a probe of a scanning probe microscope having a radius of 1 nm to 10 nm.

  The present invention has been made in view of such circumstances, and intends to provide a scanning probe microscope capable of aligning a probe to the tip of a sharp specimen and observing the tip of the sharp specimen. Is.

The above problems can be solved in each of the following inventions.
That is, the scanning probe microscope of the present invention includes a sample stage for holding a sharp specimen, an enlarged observation means for magnifying and observing the specimen from above, and the sharp specimen. A light source for irradiating light from a lateral direction, a probe for scanning the tip surface of the sharp specimen, a cantilever on which the probe is installed at an end, and the tip of the probe positioned on the tip face of the sharp specimen Fine adjustment means for aligning, and by causing the light source to irradiate light on the sharp specimen from the lateral direction, the tip of the sharp specimen is illuminated when observed from above, and the fine movement means The main feature is that the probe tip can be aligned with the tip of the sharp specimen.

  The main feature of the scanning probe microscope of the present invention is that it further includes a magnification observation means for magnifying and observing the sample from the lateral direction.

  Furthermore, in the scanning probe microscope of the present invention, the light source continues to irradiate the sharp sample during the approach of aligning the probe with the tip surface of the sharp sample and during the scanning of the tip surface. This is the main feature.

  The main feature of the scanning probe microscope of the present invention is that the scanning probe microscope further includes a measuring means based on the Kelvin probe method.

  The probe can be aligned with the tip of the sharp specimen, and a scanning probe microscope that can observe the tip of the sharp specimen can be provided.

It is the schematic of a probe microscope. It is a photograph of a sample stage. It is a photograph when a sharp sample is observed from above with a magnification observation means while irradiating light from the lateral direction. It is the photograph which observed the sharp sample and the cantilever with the side expansion observation means. It is a figure of the surface shape of the tungsten electron source front end measured by AFM. It is a figure of the surface shape of the tungsten electron source front end measured by AFM.

The scanning probe microscope of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram of a probe microscope.
The scanning probe microscope of the present invention includes a sample stage 10 for holding a sharp sample 12, magnified observation means 11 for magnifying the sharp sample 12 from above, and irradiating the sharp sample 12 with light from the lateral direction. Light source 16, probe 13 for scanning the tip surface of sharp specimen 12, cantilever 14 provided with probe 13 at the end, and tip for aligning the tip of probe 13 with the tip face of sharp specimen 12 It mainly comprises fine movement means (not shown).

  The sharp sample 12 is a sample with a sharp tip, such as an electron source used in an electron microscope, an electron beam diffractometer, an electron beam vapor deposition apparatus, or the like. The sample stage 10 is a sample stage capable of stably holding the sharp sample 12 in an upright state with the sharp part up. For example, the sample stage 10 can be configured to hold the end of the sharp specimen 12 as shown in FIG. 2 (photo of the sample stage 10).

  A sample table 10 shown in FIG. 2 is obtained by welding a cylinder having a diameter of 1 mm and a length of 3 mm to a thin plate, and the sharp sample 12 is fixed to the cylindrical portion with solder. The edge of the sharp sample 12 may be held, for example, by fixing the sample to the sample stage 10 with solder, or using a clay-like member such as clay for the sample holder, and the sharp sample 12 in the clay-like member. It is also possible to carry out by embedding the end portion. Moreover, you may hold | maintain the edge part of the sharp sample 12 by using the adhesive member instead of a clay-like member, and attaching the edge part of the sharp sample 12 to an adhesive member.

  Furthermore, the sample stage 10 can also be configured using a jig that mechanically grips the end of the sharp sample 12. As described above, various configurations of the sample stage for holding the needle-shaped sharp sample 12 can be used, but the configuration is not limited thereto. However, in consideration of the holding property, stability, simplicity, etc. of the sharp sample 12, it is preferable to fix the sample to the sample stage 10 with solder.

  Returning to FIG. 1, the magnifying observation means 11 is installed on the sample stage and is used when the tip of the probe 13 is aligned with the tip of the sharp sample 12. Zoom in at a magnification of more than double and display to the observer. As the magnifying observation means 11, for example, a microscope, a microscope set with a monitor camera, or the like is used.

  When a microscope is used as the magnifying observation means 11, the operator of the scanning probe microscope can adjust the position of the probe by looking directly into the microscope. When a microscope with a monitor camera set is used, the operator can adjust the position of the probe while looking at a monitor that displays an image captured by the monitor camera.

  Here, a light source 18 for irradiating the sharp specimen 12 from above may be installed in the vicinity of the magnification observation means 11. As the light source 18, a light source usually used for illuminating a sample in a scanning probe microscope, such as an LED light source or a halogen bulb, can be used.

The probe 13 is a probe (probe) of a scanning probe microscope (SPM) and has a sharp tip. By scanning the probe close to the sample surface, the sample surface can be magnified.
The cantilever 14 has a cantilever structure with one end fixed, and a probe 13 is installed on the free end side.

  The light source 16 is a light source that illuminates the sharp sample 12 held on the sample stage 10 from the side in an upright state. As the light source 16, a light source that is usually used to illuminate a sample in a scanning probe microscope, such as an LED light source or a halogen light bulb, can be used.

  In the vicinity of the light source 16, there may be provided a side magnification observation means 17 that enables the sharp specimen 12 to be magnified from the side. As the side magnifying observation means 17, similarly to the magnifying observation means 11, a microscope, a microscope set with a monitor camera, or the like is used.

  When a microscope is used as the side magnification observation means 17, the operator of the scanning probe microscope can directly adjust the position of the probe by looking directly into the microscope. When a microscope with a monitor camera set is used, the operator can adjust the position of the probe while looking at a monitor that displays an image captured by the monitor camera.

  Here, the conventional scanning probe microscope cannot observe the tip (needle tip) of a sharp sample such as an electron source. The reason is that the radius of curvature of the tip of the electron source is 100 nm to 10 μm, and the radius of curvature of the tip of the scanning probe microscope is only 1 nm to 10 nm. As described above, it is extremely difficult to position and approach a very narrow needle tip close to the very thin needle tip even if the magnification observation means 11 is used.

  As a result of intensive studies, the inventors of the present invention have found that the probe can be accurately positioned and brought into contact with the needle tip with a very simple device. That is, as shown in FIG. 1, a light source 16 for irradiating the sharp specimen 12 with light from the lateral direction is provided. The inventor irradiates the sharp specimen 12 with light from the light source 16 from the lateral direction, and observes that the tip of the sharp specimen 12 looks shining when observed with the magnification observation means 11 installed above the sharp specimen 12. discovered.

  FIG. 3 shows a photograph of the sharp specimen 12 observed by the magnifying observation means 11 from above while irradiating light from the lateral direction. In FIG. 3, an electron source is used as the sharp specimen 12. As shown in the figure, since the tip of the sharp sample 12 appears to shine, the probe can be easily positioned on the tip of the sharp sample 12.

  Next, a description will be given with reference to FIG. FIG. 4 is a photograph of the sharp specimen 12 and the cantilever 14 observed by the side magnification observation means 17. A sharp sample 12 shown in FIG. 4 is a tungsten-molybdenum electron source having a tip curvature radius of 0.2 μm. As shown in FIG. 4, by observing the sharp specimen 12 and the cantilever 14 with the side magnification observation means, positioning in the left-right direction as viewed in the drawing is facilitated. However, as is apparent from this figure, even if the cantilever 14 can be observed, the probe 13 is too small to be observed, and the tip of the sharp specimen 12 is too small to be observed.

  That is, if the tip of the sharp specimen 12 is illuminated by the light source 16 from the side surface direction, and the tip of the probe 13 is not positioned by observing with the magnification observation means 11 from above, the tip of the probe 13 is placed on the tip of the sharp specimen 12. It turns out to be difficult to approach. However, as described above, the probe 13 can be more easily approached to the sharp specimen 12 by using the side magnification observation means 17 together.

  Further, the scanning probe microscope of the present invention has the probe 13 by irradiating the sharp sample 12 with light during the approach of aligning the probe 13 with the tip surface of the sharp sample 12 and during the scanning of the tip surface. And the sharp sample 12 can be configured so that the positional relationship can be confirmed even during measurement.

  Usually, in SPM (AFM) measurement, in order to suppress stray light, the illumination is turned off during the approach and during the scan after the end of the approach. The scanning probe microscope of the present invention can approach and measure a sample without turning off the illumination. As a result, the success or failure of the approach to a sharp sample can be confirmed in real time through an optical microscope. The state of scanning can be confirmed during measurement.

  The scanning probe microscope of the present invention includes a scanning tunneling microscope (STM), an atomic force microscope (AFM), a scanning magnetic force microscope (MFM), a scanning SQUID microscope, a superconducting quantum device. Interferometer (SQUID), scanning Hall element microscope (SHPM), scanning Kelvin probe force microscope (KFM), scanning Maxwell stress microscope (SMM), scanning piezoelectric response microscope (PFM), scanning nonlinear dielectric microscope ( SNDM) and scanning near-field optical microscope (SNOM) are included, and the features of the present invention can be applied to all of them and can achieve the same effects. Therefore, the scanning probe microscope of the present invention can be provided with measuring means by the Kelvin probe method.

  Next, the result of actually measuring the tip of the electron source with the scanning probe microscope of the present invention will be described. Here, in order to evaluate the characteristics of the electron source, a method of observing and evaluating the distribution of the work function at the tip of the electron source with a field emission microscope as the intensity distribution of the electron beam on a fluorescent screen is generally used. However, this technique cannot examine the fine structure in the low work function plane on the tip surface of the electron source or the local work function distribution in the plane.

  Therefore, it is possible to observe the in-plane fine structure by measuring the low work function surface at the tip of the electron source with a scanning probe microscope. Furthermore, by measuring with the Kelvin probe method which is one of the measuring methods of the scanning probe microscope, it is possible to observe the local work function distribution in the plane.

  First, the sample stage shown in FIG. 2 was used, and a tungsten / molybdenum electron source having a tip curvature radius of 0.2 μm was fixed to the sample stage 10 with solder. Next, with the scanning probe microscope of the present invention, the probe was brought close to (approached to) the tip of the electron source, and measurement was performed with a scanning range of 5 μm square. The measurement results are shown in FIG.

  As shown in FIG. 5, the crystal grains at the tip of the electron source can be clearly observed. Similarly, the same electron source is further enlarged, and the surface shape of the tip of the electron source measured with a scanning range of 1 μm square is shown in FIG. As shown in FIG. 6, a flat tip surface can be clearly observed. The present invention makes it possible to measure the tip of an electron source, which is a sharp sample, with a scanning probe microscope, and to realize structural analysis within the low work function plane of the tip of the electron source, which has not been possible in the past, and use of the characteristic evaluation of the existing SPM It becomes.

DESCRIPTION OF SYMBOLS 10 Sample stand 11 Magnification observation means 12 Sharp sample 13 Probe 14 Cantilever 16 Light source 17 Side expansion observation means 18 Light source

Claims (4)

A sample stage for holding a sharp sample;
Magnification observation means installed on the sample stage and magnifying the sharp sample from above,
A light source for irradiating the sharp sample with light from a lateral direction;
A probe for scanning the tip surface of the sharp specimen;
A cantilever with the probe installed at the end;
Fine movement means for aligning the tip of the probe with the tip of the sharp specimen;
With
The light source irradiates light on the sharp sample from the lateral direction so that the tip of the sharp sample shines when observed from above, and the probe tip is positioned at the tip of the sharp sample by the fine movement means. A scanning probe microscope that can be combined. The scanning probe microscope according to claim 1, further comprising magnification observation means for magnifying and observing the sharp specimen from the lateral direction.   3. The scanning probe microscope according to claim 1, wherein the light source continues to irradiate light on the sharp sample during an approach of aligning the probe with the tip surface of the sharp sample and during scanning of the tip surface. .   The scanning probe microscope according to any one of claims 1 to 3, further comprising a measurement unit using a Kelvin probe method.

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