JPH1010139A - Apparatus for measuring light physical-property of minute part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To identify a substance at an atomic level with good positional resolution, by injecting electrons to the substance from a probe of a scanning probe microscope and detecting a light emitted from the substance immediately below a front end of the probe. SOLUTION: A window 15 is formed of a transparent substance to light in order to take a light condensed by a concave mirror 8 out of an atmosphere bath 13. The light is condensed by the concave mirror 8 and at the same time turned to a parallel light, then taken out of the atmosphere bath 13 through the window 15. The light is reduced by a lens 6 and brought into a spectroscope 9. The light condensed by the concave mirror 8 is not directly brought into the spectroscope 9, but sent to the spectroscope after turned to the parallel light, because the light might be scattered or reflected and weakened in intensity unless the light were parallel to the Window 15 when taken out of the atmosphere bath 13. A driving mechanism moves an optical fiber 7 from outside of the atmosphere bath 13 to bring the fiber close to a front end of a probe 1. The apparatus can measure a surface shape of a sample 2, perform spectrometry and measure an emission intensity at the same time, so that a measurement time is shortened and influences by a heat drift are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring optical properties of minute parts.

[0002]

2. Description of the Related Art Scanning Tunnel
ing Microscope (STM) and Atomic Force Microscope (Atomi)
c Force Microscope (AFM) is an ultra-high resolution microscope that can measure the surface shape of a sample at the atomic level. In addition to measuring the shape of the sample surface, tunneling spectroscopy and atomic force measurement can clarify the electronic state of the sample surface at the atomic level. In addition, a multifunctional microscope (collectively referred to as a scanning probe microscope) developed by applying these microscope technologies measures the magnetism, potential, frictional force, etc. of the sample surface with a positional resolution of less than a micron. It is possible.
Further, unlike conventional optical microscopes and electron microscopes, since a lens system is not used, it has the characteristic that it is not affected by the measurement atmosphere.

However, in order to obtain useful information from a sample by using an STM, an AFM, and a scanning probe microscope (SPM), the composition and structure of the sample surface must be well defined. In other words, in the case of a sample whose surface shape is complex and consists of many types of elements, only the measurement results of the surface shape are reliable, and even if the measurement results of potential, frictional force, and magnetism are obtained, the analysis is very difficult and beneficial. It is impossible to extract important information. This is because the surface material cannot be identified by the scanning probe microscope, and the obtained information cannot be correlated with the surface material. On the other hand, there is an Auger electron spectroscopy or the like as a method for identifying a substance on the surface. However, since the positional resolution is submicron, it cannot be used as a nano-order decomposition method that has been increasingly required in recent years. Further, since a high vacuum is required for the measurement, devices such as an exhaust system and a vacuum tank are required, and the device becomes large-scale. There is a demand for a method for identifying a substance utilizing the excellent positional resolution of SPM. Under such circumstances, a light emission phenomenon using STM was reported (Z.Phys.B Vo
l.72 P497 1988). This is a phenomenon in which light is emitted from the sample when electrons are injected into the sample from the probe of the STM. Since the injected electrons have only an atomic level spread on the sample surface, the light emitted therefrom contains atomic level information. Therefore, by analyzing the emitted light, the optical properties at the atomic level can be determined. For example, it is considered that a substance on the sample surface can be identified by analyzing emitted light and analyzing the shape of the spectrum. In particular, when a surface metal is used as a sample, the shape of the spectrum differs depending on the type of metal, so that decomposition such as measurement of the distribution of metal species on the surface of the sample in which many types of metal are present is possible.

Since the emitted light is extremely weak, a photon counting method called photon counting, which counts each photon one by one, is used. However, since this method requires an integration time, the probe is stopped at a place where measurement is desired. I have to do it. However, since the sample and the SPM apparatus have a thermal drift, the position of the probe and the sample is shifted during the measurement, and the position resolution is reduced. In particular, in spectrometry, since an optical spectrum is measured, the integration time is long, and the positional resolution is further reduced.

[0005] In addition to the measurement of spectroscopy of the emitted light, there have been reported methods of measuring the surface intensity and simultaneously measuring the light intensity. This is to obtain the correlation between the surface shape and the light intensity, and to clarify the optical properties of the minute part of the sample. Since there is no need for spectroscopy, no spectroscope is required, and since almost no integration time is required, measurement can be performed without stopping the probe. However, conventionally, the wavelength range to be observed is measured only at one place (for example, all the light in the visible region is measured together), and many different wavelength ranges are measured simultaneously with the surface shape measurement. Absent. Simultaneous measurement of different wavelength ranges is necessary to analyze the optical properties of the sample surface in a very small area, as in spectroscopy. is there.

[0006]

As described above, the SPM
Can only measure the shape of the surface of a sample having a complicated composition or structure. In addition, although there is a possibility that the surface substance can be identified by dispersing the light emitted from the sample using the STM, there is a disadvantage that the integration time is required due to the extremely weak light and the positional resolution is reduced. The simultaneous measurement of the surface shape and the light intensity has the disadvantage that only one wavelength range can be measured because there is only one condensing system. An object of the present invention is to provide an apparatus capable of condensing light efficiently, shortening the integration time, increasing the position resolution, and identifying a substance at an atomic level. Further, a large number of light collecting systems are provided to measure the surface shape and simultaneously measure the light intensity in a large number of wavelength ranges.

[0007]

SUMMARY OF THE INVENTION The present invention provides a scanning probe microscope for measuring the shape of a surface, an optical system for condensing light emitted from a sample immediately below the tip of the probe, and a spectroscope for separating the light. This is a minute-part optical property measuring apparatus using a scanning probe microscope provided with a spectroscope and a photodetector for detecting light.

Further, the present invention is a minute-part optical property measuring apparatus which uses a concave mirror as an optical system for efficiently condensing emitted light and uses SPM which shortens the integration time at the time of spectroscopy as much as possible. .

Further, the present invention uses a large number of optical fibers as an optical system for condensing emitted light, and at the time of measuring light intensity, changes the measurement wavelength range of each optical fiber by using a filter. This is a microscopic optical property measuring apparatus using a scanning probe microscope capable of measuring the surface shape with a scanning probe microscope and obtaining emission intensity images having different wavelength ranges at the same time.

When a sample having a complicated composition or structure is measured by the conventional SPM, only the surface shape is measured.
This is because the substance on the sample surface cannot be identified by SPM. In recent years, the phenomenon of light emission from STM has been reported, and by detecting and analyzing this light, the possibility of identifying substances on the sample surface has emerged. Since the emitted light is extremely weak, even if a photodetector with the highest sensitivity is used, an integration time of about 10 minutes is required. During that time, the probe must be stopped at the place where you want to measure the sample. No. Therefore, since the sample and the SPM device have a thermal drift, the positional relationship between the probe and the sample is constantly changed, and the longer the integration time is, the lower the position resolution is. Conventionally, since a lens or a fiber is used as a condensing system, the solid angle of condensing is small (up to about 0.1 sr), and only about 1/60 of the emitted light can be collected, and the integration time becomes long. is there. Therefore, by collecting the emitted light as much as possible, the integration time can be shortened and the positional resolution can be expected to be improved. Therefore, in order to collect the emitted light as much as possible and shorten the integration time and improve the position resolution, a concave mirror was used in the light-collecting system. With the concave mirror, spectrometry can be performed with an integration time of about 1/60 of that of a conventional light collecting system. Also, conventionally, when simultaneously measuring the surface shape and the emission intensity, only light in a certain wavelength range is detected, and when measuring the light intensity in various wavelength ranges, there is only one condensing system, First, one wavelength range must be measured, and then the wavelength range must be changed and measured. This takes time to measure and the effect of thermal drift increases. Therefore, by providing a large number of optical fibers and changing the measurement wavelength range for each optical fiber, the surface shape and the light intensity in a large number of wavelength ranges can be measured simultaneously, reducing the measurement time and reducing thermal drift. Becomes

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is an explanatory diagram of a light emission phenomenon using a scanning probe microscope according to the present invention. Here, STM and A
An example using FM has been described. (A) When STM is used
(b) is a case where AFM is used. 1 is an STM probe, 2
Is a conductive sample, 3 is a voltage source for applying a voltage between the sample and the probe, 4 is an AFM probe, and 5 is an insulating film on the conductive sample. The arrow at the tip of the probe represents the trajectory of the electrons injected into the sample, and the dashed arrow represents the emitted light. In order to emit light, electrons need to be injected into the sample. Therefore, STM can measure only a sample having conductivity on the surface. AFM has conductivity inside but tens of nm on the surface.
STM is used when the probe comes into contact with the sample and breaks the sample because of the existence of the insulating film of a certain degree. Also AFM
Are usually made of an insulating material, but the AFM tip used in the present invention must be made of a conductive material. As shown in the figure, light is emitted by injecting electrons or holes into the sample.

FIG. 2 shows a conventional light collecting system (a) according to the present invention and a light collecting system (b) using a concave mirror. 6 is a lens, 7 is an optical fiber, 8 is a concave mirror, 9 is a spectroscope, 10 is a photodetector, 1
Reference numeral 1 denotes a piezoelectric element for driving the probe. The dashed arrow in (a) indicates how light is emitted, and the solid arrow in (b) indicates how light is collected. Here, an example using STM is shown. The concave mirror covers the entire top of the sample. The conventional condensing system uses a lens or an optical fiber, and the solid angle of condensing is at most 0.1 at the maximum.
Since it is sr, it only focuses about 1/60 of the emitted light. By using a concave mirror, the solid angle of light collection becomes approximately 2πsr, and almost all emitted light can be collected. In this method, it is the piezoelectric element for driving the sample and the STM probe that hinders the light collection. Therefore, it is necessary to make the sample and the piezoelectric element as small as possible. Although the light collected by the concave mirror is directly introduced into the spectroscope, it may be converted into parallel light by the concave mirror and finally condensed by a lens. Which converging method is used depends on what spectroscope and concave mirror are combined.

FIG. 3 is a method for measuring light intensity in a number of different wavelength ranges according to the present invention. Here, an example of measuring two wavelength ranges has been described. Reference numeral 12 denotes an optical filter. Since there is a concave mirror, the lens cannot be used as a light condensing system. Therefore, two optical fibers are brought close to the tip of the probe to guide light into the optical fibers. An optical filter is provided between the optical fiber and the photodetector, and only light in a wavelength range to be measured is introduced into the photodetector.

FIG. 4 is an overall view of an optical property measuring apparatus for minute parts using SPM according to the present invention.

Reference numeral 13 denotes an atmosphere tank in which a sample is placed, 14 denotes an atmosphere control device, and 15 denotes a window made of a substance transparent to the condensed light for taking out the light condensed by the concave mirror from the atmosphere tank. It is. The light is condensed by a concave mirror and converted into parallel light at the same time. The light is taken out of the atmosphere tank through the window of the atmosphere tank, and the light is made incident on the diaphragm spectroscope by the lens. Here, the light collected by the concave mirror is converted into parallel light without being directly introduced into the spectroscope because the light must be taken out of the atmosphere tank through the window, and if the light is not made incident parallel to the window, the light may diverge. This is because reflection occurs and the light intensity decreases. Reference numeral 16 denotes a drive mechanism for moving the optical fiber from outside the atmosphere tank in order to bring the optical fiber closer to the tip of the probe. With this device, the measurement of the shape of the sample surface, the spectroscopic measurement of light, and the measurement of emission intensity can be performed at the same time, so that the measurement time can be reduced and the influence of thermal drift can be reduced.

FIG. 5 shows how the voltage applied to the sample is controlled in order to make the light emission depend on the voltage applied to the sample. It is necessary to evaluate the sample by changing the voltage applied to the sample and performing emission measurement such as emission spectrum measurement and light intensity measurement. However, due to the thermal drift, if the probe is stopped, the luminescence measurement is performed with sufficient integration time at a certain voltage, and the luminescence measurement is performed at the next voltage after the end, the position of the probe with respect to the sample is reduced. Changes greatly. Therefore, the first luminescence measurement result and the last luminescence measurement result are
Measurement results are obtained at different sample positions, and the obtained measurement results cannot be compared. Therefore, the voltage applied to the sample is set as shown in FIG. 5, and the control of the photodetector and the like is performed in synchronization with the voltage, and the influence of the thermal drift is averaged. That is, the light emission is not measured at once, but is measured in a short integration time, and the obtained measurement results are integrated later. First, the sample application voltage V1 is set to the voltage at which the luminescence is measured, and the luminescence is measured at that voltage. After the light emission measurement for a second, the data is taken in and the next voltage V2 is set, and the light emission measurement is performed similarly. After b seconds from the end of the light emission measurement at the last voltage V4, the first voltage V4
Return to 1 and repeat the luminescence measurement. After repeating the process several times in this manner, the light emission measurement results at the same voltage may be integrated.
With this method, the light emission measurement results for each sample applied voltage include the effects of thermal drift on average, so that the results can be compared. If the integration time required for the light emission analysis is x seconds and the specific voltage holding time in one cycle is a second, the number of repetitions is x / a.

(Embodiment 2) Although the method using the STM has been described, the case where the light emission is measured using the AFM will be described. Reference numeral 17 denotes an AFM probe. In the luminescence measurement method using the STM described in Example 1, 10 n
When an insulator film having a thickness of m or more exists, the STM probe and the insulator film come into contact with each other, and the probe and the insulator film are destroyed, so that measurement becomes impossible. For such a sample, AFM
The use of makes it possible to measure luminescence. The AFM originally measures the surface shape by bringing the probe and the sample into contact with each other, and at this time, controls the contact force to a very weak force of nN to pN, thereby avoiding destruction of the probe and the sample. This A
Using the FM technique, the luminescence of a sample having an insulating film on the surface is measured. The voltage applied between the AFM probe made of a conductive material and the sample is set higher than the voltage adopted in the STM. Specifically, STM is at most 2.30
In contrast, the AFM applies a maximum of several hundred volts. Since the applied voltage depends on the type and thickness of the insulator film, an optimum value must be selected. By applying a high voltage, electrons can pass through the insulator film, the electrons are injected into the sample, and light is emitted. This light can be collected and detected by the same device as in the case of the STM.

[0018]

According to the present invention, it is possible to identify a substance on a sample surface with high positional resolution by using a luminescence measuring apparatus using SPM.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a light emission phenomenon using a scanning probe microscope according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a light physical property measuring device using SPM according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a minute portion optical property measuring apparatus provided with an apparatus for measuring light intensity in a number of different wavelength ranges according to the first embodiment of the present invention. .

FIG. 4 is an explanatory view of a minute portion optical property measuring apparatus using the SPM according to the first embodiment of the present invention.

FIG. 5 is an explanatory view of a light physical property measuring device using a scanning probe microscope according to the first embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... STM probe, 2 ... conductive sample, 3 ... voltage source, 4 ... conductive AFM probe, 5 ... insulator film, 6 ... lens, 7 ... optical fiber, 8 ... concave mirror, 9 ... spectroscope 10, photodetector, 1
DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element, 12 ... Optical filter, 13 ... Atmosphere tank, 1
4 ... Atmosphere control device, 15 ... Window.

Claims (4)

[Claims] A light detector that detects light, injects electrons into a substance from a probe of a scanning probe microscope, and detects light emitted from a substance immediately below the tip of the probe.
A microscopic optical property measurement device characterized by the ability to identify the surface material and clarify the electronic state with atomic-level positional resolution. 2. A photodetector according to claim 1, further comprising a photodetector provided with a spectroscope for performing spectroscopy, and a filter for passing only light of a certain range of wavelengths for measuring the intensity of light of a specific range. Optical property measuring device for micro-parts, which has a light detector and can perform both spectroscopy and light intensity measurement at the same time. 3. An optical property measuring apparatus according to claim 1, wherein a concave mirror is used as a condensing system for the light incident on the spectroscope, and the converging solid angle is made as large as possible. 4. The optical property measuring apparatus for minute parts according to claim 1, wherein the voltage applied to the substance and the timing of light detection are synchronized in order to average the effects of thermal drift and enable comparison of measurement results.