JPH0752155B2 - Scanning surface film analysis method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a Raman spectroscopic analysis method using a laser beam as a light source, and in particular, distribution of components and concentrations (hereinafter referred to as components / concentrations) of a sample to be measured is present. The present invention relates to a scanning surface film analysis method suitable for measurement in the case of performing.

[Background of the Invention]

When the sample to be measured is irradiated with strong monochromatic visible light, the incident light changes in frequency due to the molecular vibration of the sample, and Raman scattered light having a frequency different from that of the incident light is generated. What measured the Raman scattered light intensity with respect to the frequency change is called a Raman spectrum, and qualitative analysis can be performed from the frequency position where this Raman spectrum shows a peak, and quantitative analysis can be performed from the scattered light intensity.

Current laser Raman spectroscopy is disclosed in, for example, Japanese Patent Laid-Open No. 55-1125.
As disclosed in Japanese Patent Publication No. 49, if a solid sample is placed on a sample table, if it is a liquid sample, put it in a cell, and introduce Raman scattered light generated by irradiating the sample with laser light in a sample chamber into a spectrometer. The Raman scattered light intensity at each frequency is measured.

In the above-mentioned laser Raman spectroscopy method, the positioning of the measurement point of the sample in the XY direction is performed by moving the sample itself, and
Since it was done manually, the measurement cannot be performed if the sample itself cannot be moved in the sample chamber, such as when the sample may be damaged by moving it or when the sample cannot be put in the sample chamber. It was Even if the sample itself can be moved in the sample chamber, the X-
It was difficult to perform positioning in the Y direction with high accuracy.
For this reason, there is a drawback that the accuracy of the distribution of the obtained components / concentration decreases.

[Object of the Invention]

An object of the present invention is to provide a scanning surface film analysis method for automatically measuring a component / concentration distribution on a sample surface,
In particular, it aims to improve the efficiency of data sampling (minimum necessary sampling) and accuracy.

[Outline of Invention]

The scanning surface film analysis method of the present invention guides laser light to a sample to be measured by an optical fiber, irradiates the sample and guides Raman scattered light generated from the sample to a Raman spectrometer by the optical fiber, and measures components and concentrations. In the analysis, the optical fiber is horizontally scanned, the Raman scattered light is guided to the Raman spectrometer, and the horizontal scanning is performed while determining the scanning step width and the data sampling interval from the gradient of the concentration distribution. In this case, it is desirable to horizontally scan at least the optical fiber while keeping the distance between the sample and the optical fiber constant.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

The embodiment shown in FIG. 1 is a basic mode of the present invention. Laser light emitted from a laser light source 1 such as an argon ion laser passes through an optical fiber 2 for laser light and a sample 4 is measured by a laser focusing lens 3. Focus on the part. Then, the optical fiber 2 for laser light and the optical fiber 5 for Raman light were attached to an XY axis stage 6 and installed in an XY mechanism driven by two stepping motors (a DC motor may be used, not shown). The Raman scattered light 8 is generated from the sample 4 by program-controlling the stepping motor to automatically scan in the XY directions and irradiating the laser light 7 at each scanning point. The generated Raman scattered light 8 was condensed by the Raman condensing lens 9, passed through the Raman light optical fiber 5 and the Raman spectrum measured by the known Raman spectrometer 10 was measured, and processed by the computer 11. From this Raman spectrum, the components of sample 4
This is the concentration obtained.

The Raman spectrum obtained by the Raman spectrometer 10 is processed by the computer 11 to obtain the gradient of the concentration distribution, and the sequential scanning step width and the data sampling interval are determined by the computer 11 according to the size of the gradient, and the two stepping motors ( It is also possible to drive (not shown). When the gradient of the density distribution becomes large, the scanning step width and the data sampling interval are made small, and when the gradient becomes small, they become large. Then, the Raman spectrum is measured by the Raman spectrometer 10 at each scanning point and processed by the computer 11 to obtain the components and concentrations of the sample 4.

The embodiment shown in FIG. 2 is a basic mode of another invention, and is a laser fiber 2 and a Raman light fiber 5.
Mounted on the XYZ axis stage 6 together with the Z direction positioning sensor 12 and two stepping motors (not shown)
And an XYZ mechanism driven by one motor (not shown). The stepping motor is program-controlled to automatically scan in the XY directions, and at the same time, Z
The position of the optical fibers 2 and 5 in the Z direction is kept at a constant distance from the surface of the sample 4 by the directional positioning sensor 7 and the motor driven by this signal, and the laser beam 7 is emitted in each scan. The Raman scattered light 8 generated from the sample 4 is condensed by the Raman condensing lens 9, condensed by the Raman light optical fiber 9, passes through the Raman light optical fiber 5, and passes through the Raman spectrometer.
The spectrum is measured at 10 to measure the Raman spectrum, and processed by the computer 11. The component / concentration of sample 4 is obtained from this Raman spectrum.

The component / concentration of the sample 4 obtained from the Raman spectrum measured by the Raman spectrometer 10 is processed by the computer 11 to obtain the gradient of the component / concentration distribution, and the sequential scanning step width and the data sampling interval are determined by the size. It is also possible to drive two stepping motors (not shown) determined by 11. As the gradient of the component / concentration distribution becomes larger, the scanning step width and the data sampling interval are made smaller. On the contrary, when the gradient of the component / concentration distribution becomes smaller, they are made larger. Then, the Raman spectrum is measured at each scanning point, processed by the computer 11, and the components / concentrations are obtained.

FIG. 3 shows the laser beam 14 reflected by the Z-direction position sensor 12
In the embodiment in which the light is received by and the distance between the fibers 2 and 5 and the surface of the sample 4 is kept at a constant distance, such a structure has an effect that the sensor light emitting portion is unnecessary and the structure is simplified.

FIG. 4 shows an embodiment in which a laser is used as the positioning sensor 12.

In the figure, the laser beam 15 emitted from the positioning sensor 12 to the surface of the sample 4 to be measured becomes a bright spot 16 when the distance to the surface of the sample 4 to be measured is large. The diffusely reflected light from the laser light 15 is condensed by the lens 17 and forms an image on the image forming point 18a on the image sensor 18. When the distance to the surface of the sample 4 to be measured becomes small and the sample reaches the position 4a, the brightness shifts to 16a. Accordingly, the image forming point 18a on the image sensor 18 becomes the image forming point 1
Move to 8b. The image sensor 18 is formed by arranging a large number of light receiving elements on a straight line, and the distance between the positioning sensor 12 and the surface of the measured sample 4 can be known by reading the position of the image forming point. Therefore, if the distance between the positioning sensor 12 and the tips of the optical fibers 2 and 5 in the Z direction is defined in advance, the optical fiber 2
And the distance between the tip of 5 and the surface of the sample 4 to be measured is known. Thus, by processing the signal from the positioning sensor 12 by the computer 11 and driving a motor (not shown),
The positions of the optical fibers 2 and 5 in the Z direction can be maintained at a constant distance from the surface of the measured sample 4. Then, the Raman spectrum is measured at each scanning point and processed by the computer 11 to obtain the component / concentration.

The embodiment shown in FIG. 5 is an example of an optical non-contact sensor using a laser as the positioning sensor 12. In the figure, the laser light 20 emitted from the laser light source 19 of the positioning sensor 12 passes through the lenses 21 and 22, the half mirror 23 and the objective lens 24, and has a diameter of 1 μm on the surface of the measured sample 4.
Focused below. Further, the reflected light enters the light receiving element 26 through the half mirror 23 and the lens 25 in the objective lens 24. The diameter of the beam incident on the light receiving element 26 changes depending on the size of the bright spot 27 on the surface of the sample 4 to be measured, and the size of this bright spot 27 is the distance L between the objective lens 24 and the surface of the sample 4 to be measured. Depends on. For example, when the distance L is equal to the focal length of the objective lens 24, the size of the bright spot 27 becomes the minimum and the light receiving element
The incident beam diameter on 26 is also minimal. Objective lens at distance L
When the focal length is smaller or larger than 24, the bright spot
27a and the incident beam diameter increase. Such a light receiving element 2
If we find the relationship between the incident beam diameter to 6 and the distance L,
The distance L can be obtained by measuring the incident beam diameter. Therefore, if the distance in the Z direction between the positioning sensor 12 and the tips of the optical fibers 2 and 5 is defined in advance, the distance between the tips of the optical fibers 2 and 5 and the surface of the sample 4 to be measured can be known. Thus, the signal from the positioning sensor 12 is processed by the computer 11 and the motor (not shown) is driven to keep the positions of the optical fibers 2 and 5 in the Z direction at a constant distance from the surface of the sample 4 to be measured. You can Then, measure the Raman spectrum at each scanning point,
Processing is performed by the computer 11, and the components and concentrations are obtained.

The embodiment shown in FIG. 6 is an example in which a non-contact type sensor using a light emitting / receiving element is used as the positioning sensor 12. In the figure, the light emitting element of the positioning sensor 12
A voltage is applied to 24 to project light on the surface of the sample 4 to be measured. When the reflected light 29 from the surface of the measured sample 4 is received by the light receiving element 30, the distance L between the positioning sensor 12 and the surface of the measured sample 4 can be obtained by measuring the amount of received light.

FIG. 7 shows the relationship between the distance L and the amount of received light. In FIG. 7, if the areas (a) and (c) are used, the distance L
And the amount of received light can be obtained in a linear relationship. Therefore, if the distance between the positioning sensor 12 and the tips of the optical fibers 2 and 5 in the Z direction is defined in advance, the optical fiber 2
And the distance between the tip of 5 and the surface of the sample 4 to be measured is known. Thus, by processing the signal from the positioning sensor 12 by the computer 11 and driving a motor (not shown),
The positions of the optical fibers 2 and 5 in the Z direction can be maintained at a constant distance from the surface of the measured sample 4. Then, the Raman spectrum is measured at each scanning point and processed by the HIP computer 11 to obtain the component / concentration.

The embodiment shown in FIG. 8 is an example in which a non-contact type sensor using a semiconductor laser is used as the positioning sensor 12. This sensor utilizes the optical feedback effect of intensity-modulating the output light by changing the phase of the light returning to the semiconductor laser. In the figure, when the emitted light 32 of the semiconductor laser 31 of the positioning sensor 12 is reflected on the surface of the sample 4 to be measured and returns to the semiconductor laser 31, the output of the laser changes depending on the phase of the returned light 33. This intensity-modulated outgoing light
The light output is measured by making 34 incident on the photoelectric conversion element 35.

FIG. 9 shows the relationship between the distance L between the positioning sensor 12 and the surface of the sample 4 to be measured and the output light power. In FIG. 9, if the regions (f) and (h) are used, the distance L And the light output can be obtained in a linear relationship. In FIG. 8, if the output from the photoelectric conversion element 35 is linearized using a linearizer (not shown) and then the signal is sent to the computer 11, a wider range than that shown in FIG. 9 is obtained. In the area, the distance L and the light output can be obtained in a linear relationship. Therefore, if the distance in the Z direction between the positioning sensor 12 and the tips of the optical fibers 2 and 5 is defined in advance, the distance between the tips of the optical fibers 2 and 5 and the surface of the sample 4 to be measured can be known. Thus, the signal from the positioning sensor 12 is processed by the computer 11 and the motor (not shown) is driven to keep the positions of the optical fibers 2 and 5 in the Z direction at a constant distance from the surface of the sample 4 to be measured. You can Then, the Raman spectrum is measured at each scanning point and processed by the computer 12 to obtain the component / concentration.

The embodiment shown in FIG. 10 is an example in which a non-contact type sensor using ultrasonic waves is used as the positioning sensor 12. In the figure, the ultrasonic oscillator 36 of the positioning sensor 12 is
The pulsed electric energy generated in step 3 is applied to the ultrasonic wave device 37, which is converted into ultrasonic wave energy by the electrostrictive effect and emitted in the vertical direction. This ultrasonic pulse 38 propagates in the vertical direction in the air, and when it hits the surface of the sample 4 to be measured, it is reflected and returned. This is received by the wave receiver 39, converted into electric energy again, amplified by the receiver 40, and output. If the speed of sound in air is checked, the distance between the positioning sensor 12 and the surface of the sample 4 to be measured can be known from the time required for the ultrasonic waves to reciprocate at this time. Therefore, if the distance in the Z direction between the positioning sensor 12 and the tips of the optical fibers 2 and 5 is defined in advance, the distance between the tips of the optical fibers 2 and 5 and the surface of the sample 4 to be measured can be known. Thus, the signal from the positioning sensor 12 is processed by the computer 11 and the motor (not shown) is driven to keep the positions of the optical fibers 2 and 5 in the Z direction at a constant distance from the surface of the sample 4 to be measured. it can. Then, the Raman spectrum is measured at each scanning point and processed by the computer 11 to obtain the component / concentration.

The embodiment shown in FIG. 11 is an example in which a capacitance type non-contact type sensor is used as the positioning sensor 12. In the figure, when a potential is applied between the measurement electrode 41 at the tip of the positioning sensor 12 and the surface of the sample 4 to be measured, electric charge is accumulated, and the capacitance C is expressed by the following equation.

C = (ε _O · ε _S · S) / L (1) where ε _{O is the} vacuum permittivity, ε _S is the relative permittivity of the dielectric, S:
Area of the measurement electrode 41, L: distance between the measurement electrode 41 and the surface of the sample 4 to be measured.

If the relative permittivity ε _S and the area S are constant, the capacitance C is determined by the distance L from the equation (1). That is, the distance L between the positioning sensor 12 and the surface of the measured sample 4 is obtained by measuring the electrostatic capacitance C. In this embodiment, a guard ring (a type of electrode) is provided around the measurement electrode 37 so that the electrostatic force lines 42 between the measurement electrode 41 and the surface of the sample 4 to be measured are uniform as shown in FIG. The same potential as that of the measuring electrode 41 is applied. By using this guard ring 43, the equation (1) is accurately established. From the above, if the distance in the Z direction between the positioning sensor 12 and the tips of the optical fibers 2 and 5 is defined in advance, the distance between the tips of the optical fibers 2 and 5 and the surface of the sample 4 to be measured can be known. Thus, the signal from the positioning sensor 12 is processed by the computer 11 and the motor (not shown) is driven to keep the positions of the optical fibers 2 and 5 in the Z direction at a constant distance from the surface of the sample 4 to be measured. You can Then, the Raman spectrum is measured at each scanning point and processed by the computer 11 to obtain the component / concentration.

The embodiment shown in FIG. 12 is an example in which a non-contact type sensor using an eddy current is used as the positioning sensor 12. In the figure, a high frequency (about 1 MHz) current is passed through the active coil 44 of the positioning sensor 12 to generate a magnetic field 41. When the positioning sensor 12 is brought close to the surface of the sample to be measured 4 in this state, eddy currents flow concentrically on the surface of the sample to be measured and the impedance of the active coil 44 changes. If the distance between the positioning sensor 12 and the surface of the sample to be measured 4 decreases, the coil impedance decreases in proportion to this. Therefore, if the Wheatstone bridge is formed and the impedance of the coil is measured, The distance from the surface of the measurement sample 4 is known. Therefore, if the distance in the Z direction between the positioning sensor 12 and the tips of the optical fibers 2 and 5 is defined in advance, the distance between the tips of the optical fibers 2 and 5 and the surface of the sample 4 to be measured can be known. Thus, the signal from the positioning sensor 12 is processed by the computer 11,
By driving a motor (not shown), the positions of the optical fibers 2 and 5 in the Z direction can be kept at a constant distance from the surface of the measured sample 4. Then, the Raman spectrum is measured at each scanning point and processed by the computer 11 to obtain the component / concentration. In the figure, 45 is an inactive coil.

〔The invention's effect〕

As described above, according to the present invention, since the optical fiber or the sample is horizontally scanned and the Raman scattered light is guided to the Raman spectrometer, the component / concentration which is conventionally impossible is not uniform and the distribution exists. It is also effective for grasping the distribution of the components and concentrations of the samples.

Further, according to the present invention, if the gradient of the density distribution is gentle, the scanning step width and the sampling interval can be wide, and the number of data can be small. On the other hand, if the gradient of the density distribution is steep, the scanning can be performed. There is an effect that the accuracy can be improved by narrowing the step width and the sampling interval.

[Brief description of drawings]

1 to 3 are explanatory views of a scanning type surface film analyzing apparatus according to the present invention. FIG. 1 is a schematic diagram of a basic embodiment, FIG. 2 is another schematic diagram of the basic embodiment, and FIG. Is another schematic view of the basic embodiment, FIG. 4, FIG. 5, FIG. 6, FIG. 8, FIG.
FIG. 11 and FIG. 12 are schematic diagrams of each embodiment of the non-contact type sensor, FIG. 7 is a characteristic diagram showing the relationship between the distance and the amount of received light in the example of FIG. 6, and FIG. 9 is that of FIG. It is a characteristic view which shows the relationship between the distance and the optical output in an example. 1, 19 ... Laser light source, 2 ... Laser light optical fiber, 3 ... Laser condenser lens, 4 ... Sample, 5 ... Raman light optical fiber, 6 ... XY axis stage, 6a ...
... X-Y-Z axis stage, 7,14,15,20 ... laser light,
8 ... Raman scattered light, 9 ... Raman condenser lens, 10 ...
Raman spectrometer, 11 …… Computer for scanning control / data processing, 16,16a, 27,27a …… Bright spot, 17,21,22,25 …… Lens, 18 …… Image sensor, 18a, 18b …… Conclusion Image point, 23 ...
… Half mirror, 24 …… Objective lens, 26,30 …… Light receiving element, 28 …… Projecting element, 29 …… Reflected light, 31 …… Semiconductor laser, 32 …… Emitted light, 33 …… Returned light, 34 ...... Intensity-modulated outgoing light, 35 …… Photoelectric conversion element, 36 …… Ultrasonic oscillator, 37 …… Ultrasonic wave transmitter, 38 …… Ultrasonic wave, 39 …… Ultrasonic wave receiver, 40 …… Ultrasonic receiver, 41 …… Measurement electrode, 42 ……
Electric lines of force, 43 ... Guard ring, 44 ... Active coil, 45 ... Inactive coil.

Claims (2)

[Claims] 1. A method of guiding laser light to a sample to be measured with an optical fiber, irradiating the sample to guide Raman scattered light generated from the sample to a Raman spectrometer with the optical fiber, and measuring and analyzing components and concentrations, A scanning surface film analysis method characterized in that an optical fiber is horizontally scanned, Raman scattered light is guided to a Raman spectrometer, and the horizontal scanning is performed while determining a scanning step width and a data sampling interval from a gradient of a concentration distribution. 2. The scanning surface film analysis method according to claim 1, wherein at least the optical fiber is horizontally scanned while keeping the distance between the sample and the optical fiber constant.