Spectroscopic measuring device, and spectroscopic signal processing method

Abstract

To provide a spectroscopic measuring device capable of achieving high S / N and high spatial resolution, and a spectroscopic signal processing method.SOLUTION: The spectroscopic measuring device includes: a first electromagnetic source that generates electromagnetic waves modulated at frequency fa; a second electromagnetic source that generates the electromagnetic waves with shorter wavelengths than the first electromagnetic source; an optical system that radiates the electromagnetic waves generated by the first electromagnetic source and the second electromagnetic source to a sample; and a detection unit that detects the electromagnetic waves generated by the vibration of the sample due to the electromagnetic waves radiated by the optical system. The detection unit performs spectrometry by detecting the electromagnetic waves based on the vibration of the sample having a frequency different from Fa.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a spectroscopic measurement device and a spectroscopic signal processing method.

Background Art

[0002] A spectroscopic measurement device is a device that analyzes the composition of a substance or identifies foreign substances mixed in the substance by measuring the absorption curve unique to the substance with respect to the wavelength of light, that is, the absorption spectrum. For the analysis of molecular vibrations and the like, infrared rays, which have a wavelength about 10 times that of visible light, are generally used. Therefore, the spatial resolution limited by the diffraction limit proportional to the wavelength of the light used remains on the order of 10 μm.

[0003] As a method exceeding the spatial resolution, Patent Document 1 discloses that when a certain energy such as light is applied to a measurement target sample and the absorption rate of the measurement target with respect to this energy is to be measured, instead of directly measuring the physical quantity corresponding to this energy, the vertical displacement (for example, thermal expansion) of the measurement target sample generated when this energy is applied is measured, thereby disclosing a measurement method that exceeds the conventional performance (resolution).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, a short-wavelength detection electromagnetic wave beam is used to achieve spectroscopic analysis with a relatively high spatial resolution, but further improvement in resolution is required.

[0006] An object of the present invention is to provide a spectroscopic measurement device and a spectroscopic signal processing method capable of realizing high S / N and high spatial resolution.

Means for Solving the Problems

[0007] frequency f a a second electromagnetic wave source that generates an electromagnetic wave having a shorter wavelength than the first electromagnetic wave source; an optical system that irradiates a sample with the electromagnetic waves generated from the first electromagnetic wave source and the second electromagnetic wave source; and a detection unit that detects an electromagnetic wave generated by the sample being vibrated by the electromagnetic wave irradiated by the optical system, wherein the detection unit detects an electromagnetic wave generated by the sample being vibrated by the electromagnetic wave irradiated by the optical system. a A spectroscopic measurement device that performs spectroscopic measurement by detecting electromagnetic waves based on the vibration of a sample having a frequency different from that of the sample.

[0008] The frequency f a a step of irradiating a measurement location with a first electromagnetic wave modulated by a wavelength of a first electromagnetic wave source, a step of irradiating a measurement location with a second electromagnetic wave having a shorter wavelength than that of the first electromagnetic wave source, a step of detecting electromagnetic waves generated by the sample vibrating due to the irradiation of the first electromagnetic wave and the second electromagnetic wave, and a step of performing a lock-in detection calculation for the modulation frequency of the detection target from the detected electromagnetic wave. Effect of the Invention

[0009] The present invention provides a spectroscopic measurement device and a spectroscopic signal processing method capable of achieving a high S / N ratio and high spatial resolution. Other problems, configurations, and effects will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0010]

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Figure 8

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Example

[0012] <Configuration Example of Spectroscopic Measurement Apparatus> FIG. 1 is a schematic diagram showing the overall configuration of a spectroscopic measurement apparatus 100 according to a first embodiment. In FIG. 1, the vertical direction (vertical direction) is defined as the Z direction, and the horizontal directions are defined as the X direction and the Y direction. The spectroscopic measurement apparatus 100 includes a stage 101 on which a sample 1 is placed, an objective lens 102, a stage 103 for focus adjustment, a beam splitter 105, a first electromagnetic wave generation unit 201, a modulation application unit 1 202, a second electromagnetic wave generation unit 301, a modulation application unit 302, a detection unit 120, and a control unit 140.

[0013] The stage 101 is configured to be movable in the X direction, the Y direction, and the Z direction. By moving the stage 101 in the X direction and the Y direction, any region on the surface of the sample 1 can be analyzed. By moving the stage 101 in the Z direction, focusing can be performed on different surface heights of the sample 1, and the surface region can be analyzed.

[0014] The objective lens 102 is fixed to the stage 103 for focus adjustment. The stage 103 for focus adjustment is configured to be movable in the Z direction. Focus adjustment may be performed by driving the stage 101 in the Z direction instead of the stage 103 for focus adjustment.

[0015] The first electromagnetic wave generation unit 201 (electromagnetic wave source) is controlled by the modulation application unit 1 202 and emits an electromagnetic wave beam 10 (electromagnetic wave) having a predetermined modulation frequency. The electromagnetic wave beam 10 includes light of one or more wavelengths in a wide band from, for example, ultraviolet rays to infrared rays. The first electromagnetic wave generation unit 201 is configured to be able to convert the wavelength of the electromagnetic wave beam 10 in the range of, for example, 19 nm to 30 μm. The electromagnetic wave beam 10 passes through the beam splitter 105, is focused by the objective lens 102, and then irradiates the sample 1. The sample 1 irradiated with the electromagnetic wave beam 10 absorbs the applied energy and causes periodic physical and chemical property changes related to the modulation frequency, such as thermal expansion, refractive index change, and magnetic property change.

[0016] The second electromagnetic wave generation unit 301 (electromagnetic wave source) is controlled by the modulation without (CW) or the modulation application unit 2 302 and emits an electromagnetic wave beam 20 (electromagnetic wave) having CW or a predetermined modulation frequency. The modulation application unit 2 controls the frequency of the electromagnetic wave beam 20 emitted from the second electromagnetic wave generation. The electromagnetic wave beam 20 includes light of one or more wavelengths in a wide band from, for example, ultraviolet rays to mid-infrared rays. The second electromagnetic wave generation unit 301 is configured to be able to convert the wavelength of the electromagnetic wave beam 20 in the range of, for example, 19 nm to 3 μm. It is desirable that the electromagnetic wave beam 20 generated by the second electromagnetic wave generation unit 301 has a shorter wavelength than the electromagnetic wave beam 10 generated by the first electromagnetic wave generation unit 201 and is a beam focused on a smaller spot.

[0017] The electromagnetic wave beam 20 passes through the beam splitter 405, is reflected by the beam splitter 105, is focused by the objective lens 102, and then irradiates the sample 1. The electromagnetic wave beam irradiated on the sample 1 is reflected on the surface of the sample 1, returns on the original optical path, and is reflected toward the detection unit 120 (electromagnetic wave beam 30).

[0018] The detection unit 120 detects the electromagnetic wave beam 30 that is reflected by the sample 1 and then reflected by the beam splitters 105 and 405. Note that the characteristics of the electromagnetic wave beam 20 emitted from the second electromagnetic wave generation unit 301 and the characteristics of the electromagnetic wave beam 20 (other electromagnetic waves caused by the electromagnetic waves incident on the sample) detected by the detection unit 120 may be different. The detection unit 120 outputs the detection result of the electromagnetic wave beam 20 to the control unit 140.

[0019] As shown in FIG. 3, the detection unit 120 includes a dichroic beam splitter 130, an optical filter 131, a condenser lens 124, a half mirror 125, pinholes 126 and 128, photodetectors 127 and 129, and a spectroscope (spectrum meter) 123.

[0020] The electromagnetic wave beam 30 reflected from the surface of the sample 1 and incident on the detection unit 120 has a part of the light components with wavelengths different from the original wavelength separated by the dichroic mirror (dichroic beam splitter) 130. This part of the light components passes through the optical filter 131 and is incident on the spectroscope 123. The other light components are reflected by the dichroic mirror (beam splitter) 132.

[0021] The dichroic beam splitter 130 reflects part or almost all of the electromagnetic wave beam 10 toward the aperture stop 131. That is, if the beam splitter 132 is a partial reflection mirror, a part of the electromagnetic wave beam 30 goes toward the aperture stop 1313, and if the beam splitter 132 is a total reflection mirror, almost all of the electromagnetic wave beam 30 goes toward the aperture stop 131.

[0022] The photodetector 134 measures the scattering state of the surface of the sample 1 by detecting the electromagnetic wave beam 30 that has passed through the aperture stop 133.

[0023] The light component that has passed through the beam splitter 132 is incident on the condenser lens 124, focused, and then incident on the half mirror 125. At the half mirror 125, approximately half of the focused electromagnetic wave beam 30 is transmitted toward the pinhole 126, and the remaining approximately half is reflected toward the pinhole 128. Among the electromagnetic wave beams that have passed through the half mirror 125, the electromagnetic wave beam 10 that has passed through the pinhole 126 is detected by the photodetector 127. Among the electromagnetic wave beams that have been reflected by the half mirror 125, the electromagnetic wave beam that has passed through the pinhole 128 is detected by the photodetector 129. Note that the pinhole 126 and the pinhole 128 are arranged at positions deviated from the focal position of the condenser lens 124.

[0024] The configuration of the detection unit 120 is not limited to the above-described configuration and can be arbitrarily changed. The spectrometer 123 and the photodetectors 127, 129, and 134 do not necessarily all need to be present, and it is sufficient if one or more are present. As the photodetectors 127, 129, and 132, for example, those that can convert photons into current or voltage signals, such as a photodiode (PD), an avalanche photodiode (APD), a photomultiplier tube (PMT), a CCD sensor, or a CMOS sensor, can be used.

[0025] <Functions of the control device> FIG. 4 is a functional block diagram of the control unit 140. The control unit 140 includes an overall control unit 141, an energy source control unit 142, a modulation signal detection unit 143, a detected electromagnetic wave beam amount correction unit (abbreviated as "probe light amount correction unit" in the figure) 144, a spectrometer control unit 145, a focus deviation amount calculation unit 146, and an XY scanning control unit 147. The functions of each part of the control unit 140 can be realized by the processor executing a program stored in the memory.

[0026] The overall control unit 141 is an arithmetic unit that controls each unit and processes and transmits data generated by each unit. The overall control unit 141 can be constituted by, for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Each unit other than the overall control unit 141 may be constituted by dedicated hardware using, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array), or may be constituted by software operating on an arithmetic unit.

[0027] The energy source control unit 142 controls the wavelength of the electromagnetic wave beam 10 emitted from the first electromagnetic wave generation unit 201. By scanning the wavelength, spectroscopic measurement of the absorption spectrum of the sample 1 can be realized. Further, by modulating the intensities of the electromagnetic wave beams 10 and 20 by controlling the modulation application units 1 and 2, modulation detection by the modulation signal detection unit 143 described later becomes possible.

[0028] The modulation signal detection unit 143 detects the modulation signal by comparing the detected light amounts of the photodetector 127, the photodetector 129, and the photodetector 134 with the modulation signals transmitted from the modulation application units 1 and 2.

[0029] Instead of modulation signal detection, so-called AM detection may be used, in which a displacement signal related to the modulation frequency of the electromagnetic wave beams 10 and 20 is extracted by a filter and then the amplitude is measured. Further, the displacement signal may be spectroscopically analyzed using a fast Fourier transform (FFT) or the like, and the intensity of the spectral peak corresponding to the modulation frequency may be measured. Furthermore, other general amplitude detection methods may be used.

[0030] The detected electromagnetic wave beam amount correction unit 144 monitors and corrects the intensity of the electromagnetic wave beam 10 based on the output of the above detection.

[0031] The spectrum meter control unit 145 executes parameter adjustment and signal recovery of the spectrum meter 123.

[0032] The focus deviation amount calculation unit 146 drives the stage 101 or the stage 103 for focus adjustment to control the position of the objective lens 102 in the Z direction. By controlling the position of the objective lens 102 in the Z direction, it becomes possible to follow the electromagnetic wave beam 10 with respect to the unevenness of the surface of the sample 1.

[0033] The XY scanning control unit 147 moves the stage 101 or the stage 103 for focus adjustment in the X direction and the Y direction. By moving the stage 101 or the stage 103 for focus adjustment, the electromagnetic wave beam 10 can be irradiated to an arbitrary position of the sample 1, and two-dimensional plane spectroscopic measurement on the surface of the sample 1 becomes possible. Or when combined with the stage unit 101 that can move in the Z axis or the stage 103 for focus adjustment, three-dimensional optical measurement becomes possible.

[0034] In the first embodiment, when measuring with a measurement method that exceeds the conventional resolution by converting a certain physical quantity (for example, light) into another physical quantity (thermal expansion) and measuring, instead of point measurement, it is also possible to perform two-dimensional surface measurement using a white light interferometer. Thereby, in the two-dimensional displacement measurement device, it is possible to perform measurement over a large area and at high speed.

[0035] Subsequently, with reference to FIG. 5, the physical phenomenon generated in the irradiated portion of the sample 1 is explained by modulating the intensity of the electromagnetic wave beam 10 emitted from the first electromagnetic wave generation unit 201. Periodic vibration is generated inside the sample by energy injection with the electromagnetic wave beam 10 modulated at the frequency f a on the sample surface. Most of this vibration is a fundamental vibration similar to the frequency f a but there are minute f other than the fundamental vibration aPeriodic vibrations that are integer multiples, i.e., vibrations of higher-order harmonics, also occur. As shown in the lower part of FIG. 5, the periodic vibrations of these higher-order harmonics occur closer to the center as the order increases. By detecting the sample vibrations of these higher-order harmonics, the spatial resolution of the spectroscopic measurement by the detection unit 120 and the control unit 140 can be improved.

[0036] In FIG. 6, it shows that the electromagnetic wave beam 20 generated by the second electromagnetic wave generation unit is irradiated onto the surface of the sample 1, and the reflected electromagnetic wave beam 30 is detected by the detection unit 120, thereby detecting various vibrations described in FIG. 5. Here, the electromagnetic wave beam 20 generated by the second electromagnetic wave generation unit is CW oscillating, and from this reflected signal, the fundamental vibration f of the sample 1 due to the irradiation of the modulated electromagnetic wave beam 10 emitted from the first electromagnetic wave generation unit 201 a not only, but also vibrations other than the fundamental vibration, such as 2f a , 3f a , …, nf a (n is a natural number) signals that carry frequency components are detected. Here, as n increases, the detectable signals decrease sharply, so n is basically a natural number of 15 or less.

[0037] Using FIG. 7, it is explained that by modulating the intensity of the electromagnetic wave beam 10 emitted from the first electromagnetic wave generation unit 201, the physical phenomenon occurring in the irradiated portion of the sample 1 is detected by the electromagnetic wave beam 20 modulated at the frequency f b emitted from the second electromagnetic wave generation unit 301.

[0038] As described in FIG. 5, periodic vibrations are generated by injecting energy onto the sample surface by the electromagnetic wave beam 10 modulated at the frequency f a from the first electromagnetic wave generation unit 201. Here, the electromagnetic wave beam 20 generated by the second electromagnetic wave generation unit is oscillated at a frequency f a different from the modulation frequency f b at the first electromagnetic wave generation unit 201, and the fundamental vibration f of the sample 1 due to the irradiation of the modulated electromagnetic wave beam 10 emitted from the first electromagnetic wave generation unit 201 a , vibrations other than the fundamental vibration 2f a , 3f a , …, nfa Detect a signal having a frequency component of (n is a natural number). Not only suppress the detection of scattered light not related to the second electromagnetic wave that becomes noise, but also f b and f a By conveniently combining the frequencies of, f b ±f a , or f b ±2f a , f b ±3f a , …, f b ±nf a , f a +2f b , f a +3f b , …, f a +nf b (n is a natural number), etc., by detecting a modulation signal of a specific component, an improvement in measurement sensitivity and measurement resolution can be expected. However, when f b =f a , it is necessary to irradiate the sample 1 with the second electromagnetic wave before and after irradiating the sample 1 with the first electromagnetic wave. Set the irradiation interval time between the two types of electromagnetic waves as s, and it is desirable that s is less than 10 μsec.

Example

[0039] Referring to FIG. 2, the configuration of the spectroscopic apparatus of Example 2 will be described. In Example 2, the electromagnetic wave beam 10 generated by the first electromagnetic wave generation unit is not coaxial with the electromagnetic wave beam 20 generated by the second electromagnetic wave generation unit and does not irradiate the sample 1, but irradiates from an oblique direction of the sample 1. Since the other configurations are the same as those of the two-dimensional displacement measurement apparatus of Example 1 shown in FIG. 1, detailed description thereof will be omitted.

Example

[0040] Referring to FIG. 8, the configuration of the spectroscopic apparatus of Example 3 will be described. In Example 3, the electromagnetic wave beam 10 generated by the first electromagnetic wave generation unit does not irradiate the sample 1 coaxially with the electromagnetic wave beam 20 generated by the second electromagnetic wave generation unit, but is characterized by irradiating from below the sample. Since the other configurations are the same as those of the two-dimensional displacement measurement apparatus of Example 1 shown in FIG. 1, detailed description thereof will be omitted.

[0041] The embodiments of the present invention have been described above. The present invention is not limited to the above embodiments, and components may be modified or the embodiments may be appropriately combined without departing from the gist of the invention. Further, some components shown in the above embodiments may be deleted.

Explanation of Reference Numerals

[0042] 1: Sample, 10, 20, 30: Electromagnetic wave beam, 100, 200, 300: Spectrometer, 101: Stage, 102: Objective lens, 103: Focus adjustment stage, 105: Beam splitter, 120: Detection unit, 123: Spectrometer, 124: Condensing lens, 125: Half mirror, 126, 128: Pinhole, 127, 129: Photodetector, 130: Dichroic mirror, 132: Beam splitter, 133: Iris, 134: Detector, 140: Control unit, 141: Overall control unit, 142: Energy source control unit, 143: Modulation signal detection unit, 144: Detection electromagnetic wave beam energy correction unit, 145: Spectrometer control unit, 146: Focus shift amount calculation unit, 147: XY scanning control unit, 201: First electromagnetic wave generation unit, 202: Modulation application unit 1, 301: Second electromagnetic wave generation unit, 302: Modulation application unit 2.

Claims

1. Frequency f ａ a first electromagnetic wave source that generates an electromagnetic wave modulated at a second electromagnetic wave source that generates an electromagnetic wave having a wavelength shorter than that of the first electromagnetic wave source; an optical system that irradiates a sample with the electromagnetic waves generated from the first electromagnetic wave source and the second electromagnetic wave source; a detection unit that detects an electromagnetic wave generated by vibration of the sample due to the electromagnetic wave irradiated by the optical system; A spectroscopic measurement device comprising: The detection unit is the f ａ A spectroscopic measurement device characterized by performing spectroscopic measurement by detecting electromagnetic waves based on the vibration of the sample having a frequency different from that of the f

2. In the spectroscopic measurement device according to Claim 1, The electromagnetic wave generated from the second electromagnetic wave source is a continuous wave or an electromagnetic wave modulated at a frequency f ｂ A spectroscopic measurement device characterized by this.

3. In the spectroscopic measurement device according to Claim 1, A spectroscopic measurement device, comprising: an analog-digital signal processing unit including an amplifier for lock-in detection that processes a signal from the detection unit.

4. In the spectroscopic measurement device according to Claim 3, Only the electromagnetic wave generated from the first electromagnetic wave source is modulated at a predetermined first modulation frequency, and the detection of the modulated signal is performed by lock-in detection by the analog-digital signal processing unit for frequency components that are two or more times the predetermined first modulation frequency. A spectroscopic measurement device characterized by the above.

5. In the spectroscopic measurement device according to Claim 2, Said f ａ The different frequency from f is f ｂ ±f ａ 、f ｂ ±2f ａ 、f ｂ ±3f ａ 、…、f ｂ ±nf ａ、 f ａ +2f ｂ 、f ａ +3f ｂ 、…、f ａ +nf ｂ A spectroscopic measurement device characterized by having vibrations with at least any one of the frequencies of f (where n is a natural number), f ± f, f ± 2f, f ± 3f, …, f ± nf, f + 2f, f + 3f, …, f + nf.

6. In the spectroscopic measurement device according to Claim 4, The detection unit performs lock-in detection on frequency components having a frequency that is 1 times or more and 15 times or less the modulation frequency f applied to the electromagnetic wave generated from the first electromagnetic wave source. ａ A spectroscopic measurement apparatus characterized by the above.

7. In the spectroscopic measurement device according to Claim 4, The detection unit performs lock-in detection on frequency components having a frequency that is 1 times or more and 15 times or less the modulation frequency f applied to the electromagnetic wave generated from the second electromagnetic wave source. ｂ A spectroscopic measurement apparatus characterized by the above.

8. In the spectroscopic measurement device according to Claim 2, The modulation frequency f applied to the electromagnetic wave generated from the first electromagnetic wave source ａ and the modulation frequency f applied to the electromagnetic wave generated from the second electromagnetic wave source ｂ When they are the same, before or after irradiating the sample with the electromagnetic wave generated from the first electromagnetic wave source, irradiate the sample with the electromagnetic wave generated from the second electromagnetic wave source at a predetermined time interval, and detect the difference. A spectroscopic measuring device characterized by this.

9. In the spectroscopic measurement device according to Claim 8, The spectroscopic measurement device, wherein the predetermined time interval is 10 μsec or less.

10. Irradiating a first electromagnetic wave modulated at a frequency f to a measurement location of the sample ａ and a step of irradiating the first electromagnetic wave modulated at a frequency f to a measurement location of the sample irradiating the measurement location with a second electromagnetic wave having a wavelength shorter than that of the first electromagnetic wave; detecting an electromagnetic wave generated by vibration of the sample due to irradiation with the first electromagnetic wave and the second electromagnetic wave; performing lock-in detection calculation on the detected electromagnetic wave with respect to a modulation frequency of a detection target; A spectroscopic signal processing method, characterized by including:

11. In the spectroscopic signal processing method according to Claim 10, The lock-in detection calculation is performed on the frequency component of a frequency that is equal to or more than 1 times and equal to or less than 15 times the modulation frequency f ａ or f ｂ A spectroscopic signal processing method characterized by performing lock-in detection calculation on the frequency component of a frequency that is equal to or more than 1 times and equal to or less than 15 times the modulation frequency f

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