JPH063271A - Spectroscopic analysis device - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a spectroscopic analyzer for analyzing a sample by utilizing Raman scattering, and an object thereof is to improve sensitivity and resolution. [Structure] Laser generator 1 for irradiating sample 12 with light
1, a condensing optical system 13 for condensing the scattered light scattered by the sample 12, a polychromator 14 for injecting the scattered light condensed by the condensing optical system 13 to disperse the scattered light, and this polychromator. In a spectroscopic analysis device including a one-dimensional line type CCD 15 for detecting the spectral pattern emitted from 14 and imaged, a scanning device 25 for scanning the CCD 15 along the spectral pattern,
27 and 18 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectroscopic analyzer, and more particularly to a spectroscopic analyzer for analyzing a sample by utilizing Raman scattering.

For example, a spectroscopic analyzer utilizing Raman scattering is known as one of semiconductor evaluation and analysis methods. This spectroscopic analyzer utilizes the fact that when a sample is irradiated with laser light, light having a frequency different from that of the irradiated laser light is emitted (scattered) from the sample in a certain direction. The sample is evaluated based on the above.

This scattered light is separated by a spectroscope, and the separated light is detected by a photodetector. Therefore, in order to evaluate the sample with high accuracy, it is necessary for the photodetector to accurately detect the dispersed light. Further, Raman scattering is generated by irradiating the sample with laser light as described above,
When Raman scattering is generated, it is necessary to configure so that the influence of disturbance is not included in the laser light irradiation site in order to improve the measurement accuracy.

[0004]

2. Description of the Related Art FIG. 8 is a block diagram showing an example of a conventional spectroscopic analysis apparatus 1. In the figure, 2 is a laser generator which irradiates the sample 3 with light. The sample 3 causes Raman scattering by being irradiated with the laser light and emits scattered light. The emitted scattered light is condensed by the condensing optical system 4 and then enters the spectroscope 5. As the spectroscope 5, for example, a polychromator or a monochromator is used to disperse the incident scattered light. The light split by the spectroscope 5 is a photomultiplier tube (hereinafter, abbreviated as Photomal) 6
The detection signal detected by the photomultiplier 6 is subjected to predetermined signal processing by the image processing device 7, and the output device 8
It was configured to be output to.

[0005]

As described above, the Photomar 6 is generally used as a conventional photodetector, but a CCD (Charge Coupled Device) having high sensitivity due to the remarkable development of electronic devices in recent years. Can now be created. For example, high-sensitivity CCDs having a quantum efficiency QE exceeding 80% have also appeared. Therefore, even when the light emitted from the spectroscope 5 is weak, the high-sensitivity CC
The CCD is attracting attention as a photodetector in Raman scattering measurement because it can sufficiently deal with D.

However, although the CCD has high sensitivity as described above, the standard image reading range of the two-dimensional CCD applicable to the spectroscopic analyzer 1 is about 12.5 × 8.5 mm (about 587 pixels). However, there is a problem that the measurable wave number region is considerably narrowed when the resolution is increased.

On the other hand, FIG. 9 shows a Raman spectrum of silicon (Si) obtained by a spectroscopic analysis device using a CCD (a spectroscopic analysis device having a CCD in place of Photomal). In the figure, the horizontal axis shows the Raman shift and the vertical axis shows the Raman intensity. As shown in the figure, the spectral position of Si is 520 cm ^-1 .
Further, FIG. 10 shows the same data as FIG. 8 with the horizontal axis enlarged. As remarkably appears in FIG. 10, a periodic spectrum is observed in the region of 200 cm ⁻¹ or less in the Raman spectrum (region indicated by arrow A in the figure).

According to the experiments conducted by the present inventor, the periodic spectrum in the region A is generated even when the sample is changed (when a sample other than Si is used). Therefore, if such a spectrum is observed in the low wavenumber region, it becomes difficult to observe the spectrum that is originally desired to be measured, and there is a problem that the measurement accuracy is reduced.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a spectroscopic analyzer capable of improving sensitivity and resolution.

[0010]

Means for Solving the Problems The above-mentioned problems are solved by an excitation light source for irradiating a sample with light, a condensing optical system for condensing scattered light scattered by the sample, and a condensing optical system for condensing the light. A spectroscope that receives the scattered light that has been incident and that disperses the scattered light;
In a spectroscopic analysis device including a photodetector for detecting a spectral pattern emitted from this spectroscope and imaged, a scanning device for scanning the photodetector along the spectral pattern is provided. It can be solved by a spectroscopic analysis device.

Further, the above-mentioned problem is that an excitation light source for irradiating the sample with light, a condensing optical system for condensing the scattered light scattered by the sample, and a scattered light condensed by this condensing optical system. In a spectroscopic analyzer configured by a spectroscope that disperses incident scattered light and a photodetector that detects spectroscopic light emitted from the spectroscope, in a region near the surface of the sample irradiated with the light. This can be solved by a spectroscopic analyzer characterized in that it is provided with an unnecessary gas removing means for removing an unnecessary gas that adversely affects the measurement existing in the vicinity of the surface.

[0012]

As described above, by providing the scanning device for scanning the photodetector along the spectral pattern, it is possible to measure a wide spectral pattern even with the photodetector having a small image reading range. Further, it becomes possible to use a one-dimensional line CCD, and it becomes possible to perform highly sensitive Raman measurement by this one-dimensional line CCD.

Further, by providing unnecessary gas removing means for removing unnecessary gas existing in the vicinity of the surface of the sample, which adversely affects the measurement, in the vicinity of the surface of the sample irradiated with light, a factor that adversely affects the measurement result. Can be eliminated, and the measurement accuracy can be improved.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a spectroscopic analyzer 1 according to a first embodiment of the present invention.
2 is a block diagram showing the basic configuration of No. 0, and FIG. 2 is a detailed diagram of the spectroscopic analyzer 10.

In each figure, 11 is a laser generator such as an argon ion laser, which is a half mirror HM.
The sample 12 is irradiated with laser light having a predetermined frequency through the. The sample 12 (which uses silicon in this embodiment) is irradiated with laser light to cause Raman scattering, and scattered light corresponding to the material characteristics of the sample 12 is emitted.

The emitted scattered light is reflected by the half mirror HM,
The light enters the condensing optical system 13 via the prism P1. The condensing optical system 13 is composed of a Glan-Thompson prism, a depolarizing plate, a condensing lens and the like. The condensing optical system 13 condenses the scattered light in order to match the F number of the spectroscope 5 described later, and the scattered light condensed by the condensing optical system 13 is dispersed through the prism P2. It is incident on the container 5.

As the spectroscope 14, for example, a polychromator or a monochromator is used to disperse the incident scattered light. In this embodiment, as shown in FIG.
Differential type triple polychromator (SPEX: Triplemate
1877) is used as the spectroscope 14. The polychrometer 14 is composed of an entrance slit S ₁ , intermediate slits S _2, S ₃ , diffraction gratings G _{1 to} G _3-5 , concave mirrors M _{1 to} M _{7, and the} like.

The incident scattered light is reflected by the prism P3 and the concave mirror M.
_The light enters the diffraction grating G ₁ via ₁ and is dispersed by the diffraction grating G ₁ to form an image on the slit S ₂ . By appropriately setting the width of the slit S ₂ , only light in a specific frequency range can be passed. The light passing through the slit S ₂ is incident on the diffraction grating G ₂ via the concave mirrors M _{3 and} M ₄ . The diffraction grating G ₂ has a differential arrangement arranged so as to face the opposite direction to the diffraction grating G ₁ described above.

The dispersed light diffracted by the diffraction grating G ₂ is incident on the slit S ₃ via the concave mirror M _5, and the frequency is further specified. Then, it is passed through the concave mirrors M _6, M ₇ and the diffraction grating G _3-5 . To focus on the light receiving surface of the CCD 15. The spectroscope 14 having the above configuration functions as a bandpass filter that extracts only the wavelength to be measured.

FIG. 3 shows an example of a spectral pattern emitted from the spectroscope 14 and imaged. In the example shown in the figure, five spectrum patterns appear. Generally, the size of this spectral pattern is about 12.5 mm × 17.0 mm as shown in the same figure.

As the CCD 15, a one-dimensional line CCD is used in this embodiment, and its line length is set to 12.5 mm so as to correspond to the length on the short side of the spectrum pattern shown in FIG. ing. One-dimensional line type CC
The D15 has a large degree of freedom in the line direction, and CCDs of various lengths are provided. However, two-dimensional C
As described above, CD has the largest detection range of about 12.5 mm x 8.5 mm, and does not provide a package that can detect the spectrum pattern of a region larger than 12.5 mm x 17.0 mm at once. is there.

The spectrum pattern detected by the CCD 15 is converted into an analog / digital (A / D) converter 16,
Image processing apparatus 1 including frame memory 17 and the like
9 and the computer 18 perform image processing, and output from the output device 22 such as the monitor 20 and the printer 21.

The relationship between the reading range of the CCD 15 and the size of the spectral pattern will be described with reference to FIG. As described above, the CCD 15 is a one-dimensional line type CCD, and is configured to be able to read a hatched area (indicated by reference numeral 23 in the figure) in the figure.
Therefore, in order to image the entire region of the spectral pattern having a size of 12.5 mm × 17.0 mm, it is necessary to scan the CCD 15 in the direction along the spectral pattern (direction of arrow A in the figure). The direction along this spectral pattern is also indicated by arrow A in FIG.

As described above, the one-dimensional line CCD 1
In 5, C to capture the entire spectral pattern
It is necessary to scan the CD 15. Therefore, the spectroscopic analyzer 10 according to the present invention is provided with a CCD scanning device 24 for scanning the CCD 15. This CCD
As shown in FIG. 2, the scanning device 24 includes a motor 25, a scanning mechanism 26, a drive circuit 27, a computer 18, and the like. The motor 25 is a stepping motor, which is driven via a drive circuit 27 based on a control signal generated by the computer 18.

The motor 25 is connected to a scanning mechanism 26. The scanning mechanism 26 converts the rotational force of the motor 25 into a linear motion to scan the CCD 15 in the direction of arrow A in the figure. The computer 18 performs image processing on the signal detected by the CCD 15 as described above, and
It is configured to also control the drive of the scanning device 24.

By providing the CCD scanning device 24 having the above-mentioned configuration and making the CCD 15 movable along the spectral pattern, the entire CCD image can be imaged even by the CCD 15 having the reading area as shown in FIG. It becomes possible.

At this time, the CCD 15 continuously reads the spectral pattern frame by frame, and the read image data is stored in the frame memory 19 in synchronization with the scanning speed of the CCD 15. Therefore, the image generated based on the data stored in the frame memory 19 becomes a continuous and clear image with no breaks, and CC
Since D15 is a high-sensitivity photodetector, high resolution can be enhanced, and highly accurate light scattering spectrum measurement can be performed.

Further, in the conventional two-dimensional CCD, it was necessary to remove the two-dimensional CCD from the fixed position and move it in order to take an image of the entire frame memory, and then take an image again. Moves continuously to pick up the image of the frame memory 19, so that it is not necessary to move the CCD to pick up the image of the entire frame memory, and the measurement time can be shortened.

The intensity of the light emitted from the spectroscope 14 greatly differs depending on the characteristics of the sample 12. Therefore, the spectroscope 14
If the light emitted from is weak, it is necessary to lengthen the detection time (imaging time) by the CCD 15 (for example, 20 minutes or more), and if it is strong, the detection time can be shortened (for example, several seconds). In this way, the sample 12 to be measured
Since the detection time varies depending on the type, it is necessary to change the scanning speed accordingly. The scanning speed can be set by the input device 28. Computer 1
8 is configured to control the CCD scanning device 24 according to the scanning speed (or sample type data) input from the input device 28 and set the scanning speed according to the characteristics of the sample 12.

Next, a spectroscopic analyzer 30 according to a second embodiment of the present invention will be described below with reference to FIG. In the figure, parts having the same configurations as those of the spectroscopic analysis device 10 according to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The spectroscopic analyzer 30 according to the present embodiment is characterized in that the spectroscopic analyzer 10 is provided with an unnecessary gas removing device 31. This unnecessary gas removing device 3
Reference numeral 1 denotes an apparatus for blowing helium gas (He gas) to a position in the vicinity of the irradiation surface where the laser light is irradiated on the sample 12, which is composed of a He gas cylinder, a compressor (both not shown), a blowing nozzle 32 and the like. ing.

By providing the unnecessary gas removing device 31, it is possible to remove the air in the vicinity of the portion of the sample 12 irradiated with the laser beam during the measurement, and the irradiation position can be partially set to the helium atmosphere. .

Hereinafter, the unnecessary gas removing device 31 as described above
The effect produced by setting the position near the laser light irradiation surface of the sample 12 in the helium atmosphere will be described.

As described above with reference to FIGS. 9 and 10.
In addition, in the conventional spectroscopic analyzer 1, the measurement is performed.
200 cm of Raman spectrum^-1The periodic space is
Cuttle (area indicated by arrow A in Fig. 10: this periodic
That spectrum is referred to below as the disturbance spectrum)
It Generally, in Raman scattering measurement, 0 to 1000 cm
^-1Spectral measurements in the range of are required. Obey
Therefore, such a disturbance spectrum is observed in the low frequency region.
Is difficult to measure the spectrum that you want to measure.
As described above, it becomes difficult and the measurement accuracy decreases.
It is Ri.

Then, in order to investigate the cause of the disturbance spectrum, the same measurement was performed using a sample other than Si, and the same disturbance spectrum was generated for the other samples. Also, an experiment was conducted to change the excitation wavelength of the laser light, and it was found that the generation of the disturbance spectrum did not depend on the excitation wavelength of the laser light.

On the basis of the above experimental results, the present inventor assumed that the generation of the disturbance spectrum is related to the Raman effect of atmospheric components on the sample surface, and conducted an experiment to change the atmosphere on the sample surface. The results are shown in FIGS. 5 and 6.

In FIG. 5, Si was used as the sample 12, and the surface of the sample 12 irradiated with the laser beam was sprayed with nitrogen gas (N ₂ gas), and the surface was in an N ₂ gas atmosphere. It shows a Ramans pentle when performing. Comparing FIG. 5 with FIG. 10 described above,
It can be seen that when the sample surface is in an N ₂ gas atmosphere, a disturbance spectrum that is substantially the same as that in the conventional case (the surface is in the atmosphere) is generated.

On the other hand, FIG. 6 shows a Raman spectroscope in the case where the He gas is sprayed on the surface of the sample 12 irradiated with the laser beam and the Raman scattering is measured in the He gas atmosphere on the surface of the sample. Is shown. From the figure, it can be seen that by setting the He gas atmosphere on the surface of the sample, all the disturbing disturbance spectra have disappeared. That is, the cause of the disturbance spectrum is nitrogen in the air, and since the sample 12 was conventionally measured by Raman scattering in the atmosphere, the disturbance spectrum was generated by the N ₂ gas contained in the air. Seem.

The spectroscopic analyzer 30 is provided with an unnecessary gas removing device 31 on the basis of the above experimental results to remove N ₂ gas from a position near the laser light irradiation surface of the sample 12 and create a He gas atmosphere to generate a disturbance spectrum. It is configured to prevent the above. Therefore, according to the spectroscopic analysis device 30,
Since the generation of the disturbance spectrum in the low frequency region is suppressed, the measurement sensitivity can be improved especially in the low frequency region. Therefore, it becomes possible to measure weak light, which was hardly noticeable with the conventional measurement sensitivity, and the range of application of Raman scattering measurement can be expanded.

FIG. 7 shows a modification of the second embodiment. In the spectroscopic analysis device 30 according to the second embodiment, the sample 12
In order to create a helium atmosphere in the vicinity of the laser light irradiation surface, the unnecessary gas removing device 31 is provided and He gas is blown out from the blowing nozzle. However, with this configuration, the He gas must be continuously blown during the measurement, and it is difficult to create a complete He gas atmosphere, and there is a possibility that N ₂ gas may enter the sample surface. Therefore, the present modification is characterized in that the sample 12 is housed in the cell 40 in an airtight state.

The cell 40 is composed of a body portion 41 and a lid portion 42, and the lid portion 42 is fixed to the body portion 4 by screws 43.
It is configured to be airtightly fixed to 1. Further, in order to improve airtightness, a rubber packing material 44 is arranged between the main body 41 and the lid 42. Also, the lid portion 4
At the central position of 2, a transparent window portion 45 through which the laser light emitted from the laser generator 11 is incident and the generated scattered light is emitted is provided.

Further, an introduction pipe 46 for introducing He gas and a discharge pipe 47 for discharging the gas in the cell 40 are arranged on the side of the main body 41. He is introduced into the introduction pipe 46.
The gas supply device 48 is connected, and He gas is
It is introduced into the cell 40 by the e gas supply device 48 and the introduction pipe 46. Further, the discharge pipe 47 is provided with a check valve (not shown) that allows the gas to proceed only in the exhaust direction. Therefore, by introducing the He gas into the cell 40 from the introduction pipe 46, the inside of the cell 40 can be made into a helium atmosphere in a short time, and the He gas is introduced after the inside of the cell 40 becomes the helium atmosphere. There is no need, and He gas need not be introduced for the entire time during the measurement, so that the He gas supply device 48 can be downsized.

According to this modification as described above, the sample 12
Is attached to the spectroscopic analyzer in a state of being housed in the cell 40, which is composed of the main body 41 and the lid 42, and the Raman scattering measurement is performed. At this time, by keeping the inside of the cell 40 in a helium atmosphere, it is possible to perform favorable Raman scattering measurement without generating a disturbance spectrum. Further, in the case of this modification, the configuration of the He gas supply device 48 can be simplified, and the intrusion of N ₂ gas that causes the disturbance spectrum can be reliably prevented, so that the measurement accuracy can be improved.

In the above embodiment, the one-dimensional line CCD is used as the photodetector, but in the case of using the two-dimensional line CCD having a narrow imaging range with respect to the spectral pattern region. Of course, the present invention can be applied.

[0045]

As described above, according to the present invention, by providing the scanning device for scanning the photodetector along the spectral pattern, a wide spectral pattern can be measured even by the photodetector having a small image reading range. It will be possible. Further, it becomes possible to use a one-dimensional line CCD, and it becomes possible to perform highly sensitive Raman measurement by this one-dimensional line CCD.

Further, in the site near the surface of the sample irradiated with light, unnecessary gas removing means for removing nitrogen and oxygen existing in the site near the surface is provided to remove a factor adversely affecting the measurement result. The measurement accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a spectroscopic analyzer that is a first embodiment of the present invention.

FIG. 2 is a detailed configuration diagram of a spectroscopic analysis device that is a first embodiment of the present invention.

FIG. 3 is a diagram showing an example of a spectrum pattern.

FIG. 4 is a basic configuration diagram of a spectroscopic analyzer that is a second embodiment of the present invention.

FIG. 5 is a diagram showing a Raman spectrum of Si when a sample is in a nitrogen atmosphere.

FIG. 6 S in the case where the sample is in a helium atmosphere
It is a figure which shows the Raman spectrum of i.

FIG. 7 is a diagram for explaining a modification of the second embodiment.

FIG. 8 is a configuration diagram showing an example of a conventional spectroscopic analyzer.

FIG. 9 is a diagram showing a Raman spectrum of Si when the sample is in the atmosphere.

10 is an enlarged view showing the Raman spectrum shown in FIG. 9. FIG.

[Explanation of symbols]

 10, 30 Spectroscopic analyzer 11 Laser generator 12 Sample 13 Condensing optical system 14 Spectrometer (polychromator) 15 CCD 18 Computer 24 CCD scanning device 25 Motor 26 Scanning mechanism 31 Unnecessary gas removing device 32 Blowing nozzle 40 Cell 41 Main body 42 lid 45 window 46 introduction pipe 47 discharge pipe

Claims (6)

[Claims] 1. An excitation light source (11) for irradiating a sample (12) with light, a condensing optical system (13) for condensing scattered light scattered by the sample (12), and the condensing optics. The scattered light collected by the system (13) is incident, and the spectroscope (14) that disperses the scattered light and the photodetector (15) that detects the spectral pattern that is emitted from the spectroscope (14) and is imaged And a scanning device (24) for scanning the photodetector (15) along the spectral pattern. 2. The spectroscopic analyzer according to claim 1, wherein the spectroscope (14) is one or more polychromators or monochromators. 3. The spectroscopic analyzer according to claim 1, wherein the photodetector (15) is a one-dimensional or two-dimensional CCD (Charge Coupled Device). 4. An excitation light source (11) for irradiating a sample (12) with light, a condensing optical system (13) for condensing scattered light scattered by the sample (12), and the condensing optics. The scattered light collected by the system (13) is incident, and the spectroscope (14) that disperses the scattered light, and the photodetector (15) that detects the disperse light emitted from the spectroscope (14) In the spectroscopic analysis device configured by (1) and (2), an unnecessary gas removing means for removing an unnecessary gas present in the surface vicinity of the sample (12) and irradiated with the light, which adversely affects the measurement. (31, 40)
A spectroscopic analyzer characterized by being provided. 5. The unnecessary gas removing means (31, 40),
The spectroscopic analyzer according to claim 4, wherein the unnecessary gas is removed by blowing an inert gas onto the surface of the sample. 6. The cell (40) having a window (45) for transmitting the light from the excitation light source, wherein the sample (12) can be housed in an airtight state, and the unnecessary gas removing means is constituted by a cell (40). 5. The spectroscopic analyzer according to claim 4, wherein after the sample (12) is stored, the cell (40) is filled with an inert gas to perform spectroscopic analysis.