JPH1030997A - Method and apparatus for measuring light absorption distribution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To locally measure a temperature change of a sample due to light absorption by a minute temperature measuring means, thereby to change a spatial distribution such as a light absorption efficiency and a light absorption spectrum of a sample to a wavelength of irradiation light. Can be measured with higher spatial resolution. SOLUTION: Light from a light source 1 is irradiated through a spectroscope 2 from the back surface of a light-transmitting thin film 4 supporting a sample 5. At the tip of the probe of the cantilever 6 in the atomic force microscope,
A thermocouple contact 7 is provided. The light emitted from the back surface of the thin film 4 passes through the thin film 4 and is absorbed by the sample 5, and the temperature of the surface of the thin film 4 where the sample 5 exists is locally increased. This temperature change is measured by scanning the contact 7 of the thermocouple,
The distribution of the presence or absence of the sample 5 on the surface of the thin film 4, that is, the distribution of the light absorption efficiency is measured. In addition, the spectroscope 2 can be used to scan the wavelength of the irradiation light on the sample 5 and measure the absorption spectrum of the sample 5 from the temperature change accompanying the wavelength change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring a light absorption distribution capable of measuring the light absorption characteristics of a substance with a spatial resolution higher than the wavelength of measurement light.

[0002]

2. Description of the Related Art Conventionally, in order to evaluate and identify a thin film material, its light absorption spectrum, particularly infrared absorption spectrum, is often used. Further, in evaluating a thin film material, it has been desired to be able to evaluate not only the average property of the material but also the distribution of physical properties or composition thereof.

[0003] In a conventional light absorption spectrum apparatus, a light absorption spectrum of a sample is measured by irradiating the sample with light and measuring the intensity of light transmitted through the sample.

[0004]

By the way, when measuring the distribution of the light absorption spectrum characteristics of a sample using the above-mentioned conventional light absorption spectrum apparatus, the irradiation light is narrowed down using an optical system such as a lens. Was going by. Therefore, the spatial resolution of the measurement depends on the size of the irradiation light narrowed down by the optical system, and therefore, the spatial resolution can be realized only up to about half the wavelength of the irradiation light.

According to the present invention, the spatial distribution such as the light absorption efficiency and the light absorption spectrum of the sample is made smaller than the wavelength of the irradiation light by locally measuring the temperature change of the sample due to light absorption by a minute temperature measuring means. It is an object of the present invention to provide a method and apparatus for measuring a light absorption distribution that can be measured with high spatial resolution.

[0006]

The light absorption distribution measuring method according to the present invention uniformly irradiates a sample placed on a support with light, and locally absorbs the sample due to light absorption in the irradiated region. The temperature distribution is sequentially measured by a temperature measuring means to measure the spatial distribution of light absorption of the sample.

When a light-absorbing sample is irradiated with light, the sample absorbs light, most of which is converted to heat, and the temperature of the sample rises. The temperature change of the sample due to the heat of light absorption is locally measured one after another using a temperature measuring means. By this temperature measurement, the spatial distribution such as the light absorption efficiency of the sample can be determined. As described above, in the present invention, the irradiation light is not narrowed down by the optical system, but the irradiation light is applied with a certain spread, and each portion of the irradiation area is locally measured one after another by the temperature measuring means. I have. For this reason, the spatial resolution of the measurement can be measured with a higher spatial resolution provided by the temperature measuring means, regardless of the wavelength of the irradiation light.

In the above, in order to prevent the irradiation light on the sample from being blocked by the temperature measuring means, the side opposite to the temperature measuring means with respect to the sample, or the side or oblique side of the sample and the temperature measuring means. When the light is irradiated from above, accurate measurement can be performed. Alternatively, the support is formed of a transparent material that allows irradiation light to pass therethrough, a sample is placed on the support, and the sample is irradiated with light while transmitting the support,
The measurement may be performed on the sample from the side opposite to the support by the temperature measuring means.

In the above, the spatial distribution of the absorption spectrum of the sample can be measured by scanning the wavelength of the light irradiated on the sample.

A light absorption distribution measuring apparatus according to the present invention comprises a light-transmitting support for supporting a sample, an irradiation means for uniformly irradiating light from the back surface of the support, and a device for measuring a local temperature change of the sample. Temperature measuring means for measuring the spatial distribution.

The irradiation light from the irradiation means strikes the back surface of the support, passes through the support and irradiates the sample. The local temperature change of the sample whose temperature has increased by absorbing the irradiation light is measured by the temperature measuring means.

In the above description, a thermocouple, a thermistor, a platinum resistance thermometer and the like can be mentioned as the temperature measuring means. A thermocouple is suitable as a minute temperature sensor or a heat sensor. The thermocouple is a control means for mounting the contact portion on a minute leaf spring and controlling the deflection of the leaf spring to be constant while scanning the contact portion of the thermocouple while contacting or approaching the surface of the sample. Should be provided. At this time, it is desirable to apply the technique of the atomic force microscope.
The scanning may be performed while vibrating the contact portion of the thermocouple.

The irradiating means preferably has a uniform light intensity and can irradiate irradiating light having a certain spread.
Further, if the irradiating means is provided with a spectroscopic means for scanning the wavelength of the irradiation light on the sample, the absorption spectrum of the sample can be measured.

Further, it is preferable that the support is in the form of a mesh or a thin film having a thickness of 10 μm or less. It is desirable that the sample be thermally isolated except for radiation through its surface.If the support is made into a mesh or thin film, it becomes difficult for the heat of the sample to escape through the support, and changes in the temperature of the sample due to light absorption will occur. Can be measured accurately. Also,
As a material of the support, silicon, a silicon compound (such as silicon nitride, silicon oxide, silicon carbide, or a composite compound thereof), or germanium has infrared transmittance, and is preferable from the viewpoint of production and the like. This is because infrared absorption tends to produce a specific absorption spectrum due to the structure of the substance, and is suitable for evaluating the physical properties and composition of a sample and analyzing impurities.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the light absorption distribution measuring method of the present invention will be described below with reference to FIG. As shown in FIG. 1, light from a light source 1 is emitted from a back surface of a support supporting a sample 5 through a spectroscope 2.
The support comprises a support frame 3 having an opening or window 3a and a light-transmitting thin film 4 provided on the support frame 3 so as to cover the window 3a. 5
Is installed. Cantilever 6 in atomic force microscope
A contact 7 of a thermocouple is provided at the tip of the probe at the tip. The thermocouple contact 7 is connected to a thermometer 8.

Light emitted from the back surface of the thin film 4 passes through the light-transmitting thin film 4 and is absorbed by the sample 5, and the temperature of the surface of the thin film 4 where the sample 5 exists is locally increased. . By measuring the temperature change with the junction 7 of the thermocouple, the distribution of the place where the sample 5 exists on the surface of the thin film 4 and the place where the sample 5 does not exist, that is, the distribution of the light absorption efficiency can be measured. Further, the wavelength of the irradiation light to the sample 5 is scanned using a diffraction means such as a diffraction grating or a prism of the spectroscope 2, and a temperature change accompanying the scan is measured. The spectrum can be measured.

As a method of measuring the temperature change, a value obtained when a certain time has passed since the light irradiation and the temperature of the sample becomes constant may be measured, or the light irradiation may be modulated to modulate the value. The amplitude of the component that follows the modulation cycle may be measured.
In addition, if the light absorption heat of the sample is diffused into the surroundings through the support due to heat conduction, the spatial resolution of the measurement will be degraded. To prevent this, the sample should be a thin film or mesh support as described above. It is preferable to set it on. Further, the sample may be supported only by the support frame 3 or the like. Note that performing the measurement in a vacuum is also effective for reducing thermal diffusion due to convection.

In the above embodiment, the distribution of the presence or absence (presence) of the light-absorbing sample was determined. However, the light absorption efficiency and the in-plane distribution of the light absorption spectrum of the sample can also be measured. Further, from the above measurement, it is also possible to obtain the heat conduction characteristics of the sample.

[0019]

Next, an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2, a support frame 9 made of silicon is used.
A fine line 11 of a graphite sputtered film (line width 0.5 μm, film thickness 0.2 μm, interval 2 μm) was formed on a surface of a support 10 of silicon nitride (film thickness 0.2 μm) adhered to ) Was prepared. As a light source, an Nd-YAG laser 12 having a wavelength of 1064 nm is used, and a chopper 13 (modulation frequency 100H) is used.
The light whose intensity was modulated through z) was irradiated from the back surface of the support 10 (irradiation light intensity was about 100 J / m ² ). Reference numeral 17 denotes a condenser for condensing light from the laser 12 on the chopper 13, and reference numeral 18 denotes a collimator for converting divergent light from the chopper 13 into parallel light.

First, a thermocouple probe 14 attached to an atomic force microscope was brought into contact with the surface of the support 10 with a force of 1 nN to obtain a surface unevenness image of the support. In this image, the fine lines 11 of the graphite film were observed to be convex, and the portions where the thin line 11 was not present and the silicon nitride support 10 was exposed were observed to be concave.

Thereafter, the back surface of the support 10 was irradiated with intensity-modulated laser light. Then, the probe 14 is moved to the convex portion and the concave portion, and the thermoelectromotive force generated in the thermocouple provided with the contact at the tip of the probe 14 is applied to the preamplifier 1.
5 and the 100 kHz modulated component was measured by the lock-in amplifier 16. Although a thermoelectromotive force of about 0.2 mV was observed at the convex portion, the thermoelectromotive force observed at the concave portion was 0.1 mV.
It was 1 mV. The thermoelectromotive force observed in the concave portion indicates a temperature change due to the direct heating of the thermocouple by the irradiation light transmitted through the support 10, and the thin line 11 of the convex portion
Is a value obtained by subtracting this value from the thermoelectromotive force at the convex portion.

Further, the support 1 was examined by an atomic force microscope.
While scanning the surface of the probe with the probe, the value of the local thermoelectromotive force is plotted against the position of the probe, and the space of the heat absorber (the thin line 11 of the graphite film in this case) on the surface of the support 10 is plotted. The distribution could be imaged. The obtained image clearly resolved a fine graphite line having a line width of 0.5 μm, and it was confirmed that the optical absorption distribution measuring apparatus of this example had a high spatial resolution of 1 μm or less.

[0023]

As is apparent from the above description, according to the present invention, the sample is irradiated with irradiation light uniformly, and each part of the irradiation area is locally measured one after another by the temperature measuring means. Therefore, the spatial resolution of the measurement can measure the light absorption characteristics of the sample with higher spatial resolution provided by the minute temperature measuring means regardless of the wavelength of the irradiation light.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an embodiment of a light absorption distribution measuring method according to the present invention.

FIG. 2 is a configuration diagram showing one embodiment of a light absorption distribution measuring device according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 light source 2 spectroscope 3 support frame 3a window 4 thin film 5 sample 6 cantilever 7 thermocouple contact 8 thermometer 9 support frame 10 support 11 fine wire 12 Nd-YAG laser 13 chopper 14 thermocouple probe 15 preamplifier 16 lock-in amplifier 17 Condenser 18 Collimator

Claims (12)

[Claims] 1. A sample placed on a support is uniformly irradiated with light, and a local temperature change of the sample due to light absorption in a region irradiated with the light is sequentially measured by temperature measuring means. A method for measuring the spatial distribution of light absorption of a light absorption distribution. 2. In order to prevent the irradiation light on the sample from being blocked by the temperature measuring means, light is emitted from the side of the sample opposite to the temperature measuring means or from the side of the sample and the temperature measuring means. The method for measuring a light absorption distribution according to claim 1, wherein the light is irradiated. 3. The support is formed of a transparent material that transmits the irradiation light, the sample is placed on the support, the sample is irradiated with light through the support, and the sample is supported on the sample. 2. The method according to claim 1, wherein the temperature is measured from the side opposite to the body by the temperature measuring means. 4. The light absorption distribution according to claim 1, wherein an absorption spectrum of the sample is measured by scanning a wavelength of light applied to the sample. Measuring method. 5. A light-transmitting support for supporting a sample, irradiation means for uniformly irradiating light from the back surface of the support, and temperature measuring means for measuring a spatial distribution of a local temperature change of the sample. And a light absorption distribution measuring device. 6. The light absorption distribution measuring device according to claim 5, wherein said temperature measuring means uses a thermocouple. 7. A contact portion of the thermocouple is mounted on a minute leaf spring, and the contact portion of the thermocouple is brought into contact with or close to the surface of the sample while controlling the deflection of the leaf spring to be constant. 7. The light absorption distribution measuring device according to claim 6, further comprising control means for scanning while scanning. 8. The light absorption distribution measurement according to claim 5, wherein the irradiating means includes a spectroscopic means for scanning a wavelength of the irradiating light to the sample. apparatus. 9. The light absorption distribution measuring device according to claim 5, wherein the support is in a mesh shape. 10. The light absorption distribution measuring device according to claim 5, wherein the support is a thin film having a thickness of 10 μm or less. 11. The light absorption distribution measuring apparatus according to claim 5, wherein a material of the support is silicon, a silicon compound, or germanium. 12. The light absorption distribution measuring apparatus according to claim 11, wherein said silicon compound is silicon nitride, silicon oxide, silicon carbide, or a composite compound thereof.