JPH07260678A - Method and device for measuring light - Google Patents

Abstract

PURPOSE:To obtain an exciting spectrum with suppressed distorsion by positively changing the incident angle for making an irradiation light incident into a sample in correspondence with the change in wavelength of irradiation light and making the penetrating depth of the irradiation light constant. CONSTITUTION:A light emitted from a light source 1 consisting of a xenon lamp is selected by a spectroscope unit 2 so that only a light 3 with specified irradiation wavelength may be obtained. The obtained light is converged on the focal face 6 of a total reflection plate 5 by an incident optical system 4. A substrate 5 is formed of semi-cylindrical sapphire with large refraction index. A sample 7 to be measured is placed in contact with the plane side of the substrate 5. The irradiation light 3 is made incident to the sample 7 through the substrate 5. The light emitted from the sample 7 during irradiation is observed by a detection optical system 8. The detected light 9 is formed into a monochromatic light, and it is converted into an electrical signal by a photomultiplier 11 and amplified by a preamplifier 12, then the result is inputted to a computer 13 for controlling. The light source 1, spectroscope unit 2 and optical system 4 are placed on a stage 15 where the sample 7 is the rotational center, allowing the incident angle to be set as desired by the computer 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical measuring method utilizing the total reflection phenomenon and an apparatus therefor, and in particular, an optical measuring method suitable for measuring a minute region of a sample to be measured which is equal to or shorter than the wavelength of light. And its device.

[0002]

2. Description of the Related Art In the semiconductor and medical industries, the characteristics of the surface and interface of a product are important factors that determine the quality of the product. For that reason, methods for measuring surfaces and interfaces have been actively studied. Related to this, for example, Japanese Patent Application Laid-Open No. 4-337447 discloses an optical measuring device utilizing the total reflection phenomenon. That is, laser light is used as a light source, and the laser light is applied to the sample on the total reflection substrate having a high refractive index from the total reflection substrate side, and is totally reflected at the interface between the total reflection substrate and the sample. This is a measurement device that selectively excites only the vicinity and observes the light emitted from the sample to obtain information near the interface of the sample.
Using such a device, the excitation spectrum of the sample was measured by changing the excitation wavelength while the incident angle was fixed, and the optical characteristics of the sample were obtained.

[0003]

In the conventional excitation spectrum measuring method, since it is necessary to continuously change the wavelength of the irradiation light in a constant wavelength region, the irradiation light is irradiated from the interface between the total reflection substrate and the sample to the sample side. The depth that penetrates into the body changes as the wavelength of the irradiation light changes.

As a result, the measured excitation spectrum is
It contained information from various depths and was distorted to the extent that it could not be used for practical purposes.

An object of the present invention is to provide a method and apparatus for measuring an excitation spectrum with little distortion and which can withstand practical use.

[0006]

The above object is to irradiate a sample with light of a plurality of wavelengths from a light source so that the depths of infiltration into the sample are the same, and to detect light from the sample. Can be achieved by measuring

[0007]

In the light measurement utilizing the total reflection phenomenon, the present inventor has noticed that the depth at which the irradiation light penetrates into the sample can be changed by changing the incident angle when the irradiation light enters the sample. It has been found that the incident angle when the irradiation light is incident on the sample can be positively changed in accordance with the change in the wavelength of the light to make the depth of the irradiation light soaked into the sample constant. Came to.

The details will be described below. The depth d by which the irradiation light permeates the sample is given by the relational expression of Equation 1. (For example, it is disclosed in Japanese Patent Laid-Open No. 4-337447.)

[0009]

[Equation 1]

Where λ is the wavelength of the irradiation light, n ₁ is the refractive index of the total reflection substrate, n ₂ is the refractive index of the sample, θ _i is the incident angle of the irradiation light, and κ is the attenuation factor of the sample. Therefore, by using the relational expression of the mathematical expression 1, even if the wavelength λ of the irradiation light changes, the incident angle θ required to keep the penetration depth d constant.
_i is obtained quantitatively. Accordingly, by changing the stage to a rotary stage and changing the incident angle of the irradiation light with respect to the sample, the depth at which the incident light penetrates into the sample can be maintained at a constant value, and the surface on which the incident light is irradiated to the sample, or It is possible to measure the excitation spectrum of the sample in a region of a certain depth from the interface.

The sample may have a structure composed of a plurality of films.

The rotating portion may be the sample, the incident optical system, the detection optical system, or a combination thereof, as long as the incident angle of the irradiation light with respect to the sample can be set to a predetermined value. Even without using a mechanical rotation stage, optical fibers with a small diameter are arranged and installed so that the incident angle of the irradiation light on the sample changes for each optical fiber, and the incident light permeates the sample within the optical fiber. The object can also be achieved by using fiber light having a predetermined constant depth as irradiation light. Since no mechanical mechanism is used, there is an advantage that there are few failures. Furthermore, since an optical fiber is used, it has the advantages of excellent mobility and ease of use.
For the selection of the optical fiber, only the light of the optical fiber corresponding to the predetermined incident angle may be passed through the opening / closing shutter, or the light from a plurality of optical fibers may be collectively measured and analyzed by a computer.

Instead of the optical fiber, a plurality of light sources arranged side by side may be used.

It is known that even when detecting light from a sample, an equation similar to the relational expression of Equation 1 holds. For example, Toriumi et al., "Absorption effect in total reflection fluorescence spectroscopy",
Applied Optics, Vol. 31, No. 30, pp. 6376 to 6382, 1992 (Minor
u Toriumi et al, "Absorbt
ion effects on total-int
rnal-reflection fluoresce
nce spectroscopy ”, Applied
Optics, 31 (30), 6376-6382.
(1993)). Therefore, even if the wavelength λ of the irradiation light changes, the detection angle necessary for keeping the detection depth constant can be quantitatively obtained. Therefore, by changing the detection angle of the detection light with respect to the sample to a rotating stage, the depth to be measured of the sample can be maintained at a predetermined constant value, and the surface irradiated with the incident light on the sample, or It is possible to measure the excitation spectrum of the sample in a region of a certain depth from the interface.

Optical fibers having a minute diameter are arranged side by side so that the incident angle of the irradiation light with respect to the sample can be changed,
The object can also be achieved by using as the irradiation light the light from the optical fiber corresponding to the predetermined measured depth of the sample in the optical fiber.

[0016]

EXAMPLES Next, specific examples of the present invention will be described. It should be noted that these examples are merely examples under favorable specific conditions within the scope of the present invention, and the present invention is not limited to these examples.

Example 1 First, it is shown that by adjusting the incident angle using a rotary stage, it is possible to measure the excitation spectrum of only a region of a certain depth in the sample.

An outline of a configuration example of an optical measuring device for realizing the optical measuring method of the present invention will be described with reference to FIG. The light emitted from the light source 1 composed of a xenon lamp is selected by the spectroscope 2 as only the light 3 having a predetermined irradiation wavelength. This light is focused on the focal plane 6 of the total reflection substrate 5 by the incident optical system 4. The incident optical system 4 is composed of a lens in which the focal plane of the total reflection substrate and the focal plane of the condensing lens are matched, but if necessary, a mirror for adjusting the optical axis, a lens, a filter,
A polarizing plate, a slit, and the like can be used as appropriate. The total reflection substrate 5 is made of sapphire having a high refractive index and has a semi-cylindrical shape. The sample 7 to be measured is brought into close contact with the flat surface side of the total reflection substrate 5. The irradiation light 3 is incident on the sample 7 via the total reflection substrate 5. The light emitted from the sample 7 caused by this light irradiation is observed by the detection optical system 8. The detection optical system 8 is composed of a lens in which the focal plane 6 of the total reflection substrate 5 and the focal plane of the lens coincide with each other. If necessary, a mirror for adjusting the optical axis, a lens, a filter, a depolarizer and a slit. And the like can be used as appropriate. The light 9 detected by the detection optical system 8 is monochromaticized by the spectroscope 10, converted into an electric signal by the photomultiplier tube 11, amplified by the preamplifier 12, and then input to the control computer 13. It The light source 1, the spectroscope 2, and the incident optical system 4 are the rotary stage 1 with the sample 7 as the center of rotation 14.
It is mounted on No. 5 and can be set to an arbitrary incident angle by the control computer 13. The spectroscope 2 and the spectroscope 10 are also connected to the control computer 13 and can be set to any wavelength.

Using such a device, the excitation spectrum at 300 to 400 nm in the measured region of 50 nm near the interface of the organic thin film sample in which pyrene, which is a low molecular weight compound, is dispersed in a polymer thin film is measured as follows. went. First, the control computer 13 sets the wavelength of the spectroscope 2 on the incident optical system side to a value of 300 nm. Next, the incident angle at which the penetration depth of the incident light 3 at this wavelength becomes 50 nm is calculated based on the relational expression of the equation 1, and the rotary stage 15 is driven so that the incident angle at which the sample hits becomes that value. . After that, the spectroscope 10 is set to a predetermined spectral wavelength by the control computer 13, and the intensity of the detection light 9 is set to the control computer 1.
Taken in 3. Thereafter, the same procedure is repeated while increasing the wavelength of the spectroscope 2, and the intensity of the detection light 9 is set while the penetration angle of the incident light 3 is set to a constant 50 nm until the incident wavelength becomes 400 nm. Was taken into the control computer 13. The result 16 is also shown in FIG. 2 together with the result 17 under the condition that the penetration depth of the incident light 3 is constant at 100 nm. The result of the conventional method described later is shown in FIG.
Compared with, the change in the excitation spectrum at each depth, which is a feature of the total internal reflection spectroscopy, is clearly shown. With the present invention, it becomes possible to measure the excitation spectrum for each depth for the first time,
Practical useful information has come to be obtained.

Alternatively, the light from the spectroscope 2 may be guided to the incident optical system 4 on the rotary stage 15 by using an optical fiber without mounting the light source 1 and the spectroscope 2 on the rotary stage 15. In this case, since the load on the rotary stage 15 is reduced, there is an advantage that it is easy to handle.

Comparative Example Next, it is shown that the conventional excitation spectrum is not practical.

The conventional excitation spectrum is measured by sweeping the incident wavelength while keeping the incident angle constant. Using the apparatus of Example 1, the same operation as in Example 1 was repeated except that the rotary stage 15 was not driven and the incident angle was kept constant (at 70 degrees and 45 degrees). As a result (18
And 19) are shown in FIG. When the incident wavelength changes, the penetration depth of the incident light 3 in the sample changes, so that the light is averaged in various depth regions, and the information in the depth direction, which is a feature of total internal reflection spectroscopy, is lost. It has been broken. Therefore, FIG. 3 is a featureless excitation spectrum with little change and is not practical.

Example 2 Next, it will be shown that the excitation spectrum in a region of a certain depth of the sample can be measured by adjusting the detection angle using a rotary stage.

In the apparatus of Example 1, the components on the rotary stage were changed as follows so that the detection angle, rather than the incident angle, could be changed. That is, the detection optical system 8, the spectroscope 10, the photomultiplier tube 11 and the preamplifier 12 are placed on the rotary stage 15 having the sample 7 as the rotation center 14, and the control computer 13 sets the detection angle to an arbitrary angle. Except that the setting was made possible, the detection depth of the sample 7 was kept constant by changing the detection angle of the detection light 9 with respect to the sample 7 using the apparatus of Example 1, and the excitation spectrum was measured. . As a result, a practical excitation spectrum was obtained.

Further, without placing the spectroscope 10, the photomultiplier tube 11 and the preamplifier 12 on the rotary stage 15, the light from the detection optical system 8 is used by an optical fiber.
It may be guided to the spectroscope 10, the photomultiplier tube 11 and the preamplifier 12 which are installed on a fixed stage different from the rotary stage 15. In this case, since the load on the rotary stage 15 is reduced, there is an advantage that it is easy to handle.

Example 3 Next, it is shown that the incident angle can be adjusted by using an optical fiber array to measure the excitation spectrum at a certain depth of the sample.

Instead of the rotary stage 15 in the apparatus of Example 1, an optical fiber 20 as shown in FIG. 4 was used as follows. That is, the light of the irradiation wavelength selected by the spectroscope 2 is made incident on the incident end of the optical fiber bundle 20 which is a bundle of optical fibers having a diameter of 0.1 mm.
The light emitting ends of are arranged on the focal plane 6 of the total reflection substrate 5 and in the incident plane so that the light from each optical fiber 20 can irradiate the sample 7 on the total reflection substrate 5 at various incident angles. A shutter 21 that is independently opened and closed by the control computer 13 is attached to the incident end of each optical fiber 20. In Example 1, the operation of Example 1 was repeated except that the rotary stage 15 was driven to open the fiber shutter 21 corresponding to a predetermined incident angle instead of controlling the incident angle. The excitation spectrum was measured while keeping the penetration depth of incident light at a constant value.
As a result, a practical excitation spectrum was obtained. In the case of the present embodiment, since the rotary stage is not used, there is an advantage that there is no mechanical driving part, the size can be reduced, and the handling is easy.

Example 4 Next, it is shown that the detection angle can be adjusted by using an optical fiber array to measure the excitation spectrum in a region of a certain depth of the sample.

Instead of the rotary stage in the apparatus of Example 2, an optical fiber was used as follows. That is, the same incident end of the optical fiber bundle 20 as in the third embodiment is arranged on the focal plane 6 of the total reflection substrate 5 and in the emission plane so that the light from the sample 7 can be detected by each optical fiber at various detection angles. did. A shutter 21 that is opened and closed independently by the control computer 13 is attached to the emission end of the optical fiber bundle 20. The exit end of this optical fiber is a spectrometer 10.
Connected to. Other than this, the optical measurement device of the second embodiment is the same. In Example 7, the operation of Example 2 was repeated except that the shutter 21 of the fiber 20 corresponding to the predetermined detection angle was opened instead of driving the rotary stage 15 to control the detection angle. The excitation spectrum was measured while the detection depth of was kept constant. As a result, a practical excitation spectrum was obtained. In the case of the present embodiment, since the rotary stage is not used, there is an advantage that there is no mechanical driving part, the size can be reduced, and the handling is easy.

[0030]

According to the present invention, by adjusting the incident angle and the detection angle, the surface on which the sample is irradiated with the incident light,
Alternatively, since only a sample in a region of a certain depth from the interface can be measured, a good practical excitation spectrum can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram of an optical measurement device according to a first embodiment of the present invention.

FIG. 2 is an excitation spectrum diagram measured by the optical measurement method of Example 1 of the present invention.

FIG. 3 is an excitation spectrum diagram measured by an optical measurement method of a comparative example of the present invention.

FIG. 4 is a diagram of an optical measurement device according to a third embodiment of the present invention.

[Explanation of symbols]

1 ... Light source, 2 ... Spectrometer, 3 ... Incident light, 4 ... Incident optical system,
5 ... Total reflection substrate, 6 ... Focal plane of total reflection substrate 5, 7 ... Sample, 8 ... Emission optical system, 9 ... Emission light, 10 ... Spectroscope, 11
... Photomultiplier tube, 12 ... Preamplifier, 13 ... Control computer, 14 ... Rotation center of rotation stage 15, 15 ... Rotation stage, 16 ... Excitation spectrum under the condition that the penetration depth of incident light 3 is 50 nm , 17 ... Excitation spectrum under the condition that the penetration depth of incident light 3 is 100 nm, 18 ... Excitation spectrum under the condition that the incident angle is 70 degrees, 19 ... Excitation spectrum under the condition that the incident angle is 45 degrees, 20 ... Optical fiber, 21 ... Shutter.

Claims (6)

[Claims] 1. A light measuring method characterized by measuring detection light generated from a region of the same depth of a sample irradiated with light of a plurality of wavelengths from a light source. 2. The light measuring method according to claim 1, wherein at least one of an incident angle of the irradiation light with respect to the sample and a detection angle of the light generated by the irradiation is changed by using a rotary stage. 3. The sample is installed so that the light from the light source can be irradiated through a plurality of fibers having different incident angles of the irradiation light with respect to the sample, or through the plurality of fibers having a different detection angle of the detection light from the sample. The light measuring method according to claim 1, wherein at least one of the two is installed so that light from the sample can be detected. 4. A light measuring device comprising at least a light source, an incident optical system for irradiating the sample with irradiation light from the light source, and a photodetector for detecting detection light from the sample on which the irradiation light is incident. An optical measurement device, which measures light generated from a region of the same depth of a sample irradiated with light of a plurality of wavelengths from a light source. 5. The light measuring device according to claim 4, wherein at least one of an incident angle of the irradiation light to the sample and a detection angle of the light generated by the irradiation is changed by using a rotary stage. 6. A sample is installed so that light from a light source can be irradiated through a plurality of fibers having different incident angles of irradiation light, or a plurality of fibers having different detection angles of detection light from the sample are used. The light measuring device according to claim 4, wherein at least one of the two is installed so that light from the sample can be detected.