Spectrometric apparatus and spectrometric method

Abstract

To provide a spectroscopic measurement device capable of improving detection sensitivity to changes in physical properties such as expansion of a sample to which energy is imparted by infrared rays or the like, having high resolution, and enabling accurate autofocusing, the following structure is employed. A spectroscopic measurement device characterized by comprising: an electromagnetic wave source that generates electromagnetic waves to be irradiated to a predetermined region of a sample; an objective lens that converges the electromagnetic waves to the predetermined region; two confocal point detectors that detect electromagnetic waves reflected by the sample; and a focus position determination mechanism that performs differential calculation or lock detection calculation on a signal obtained by dividing a difference signal of outputs of the two confocal point detectors by a sum signal, and determines a position at which a peak is taken as a focus position.

Description

Technical Field

[0001] This invention relates to a spectrophotometer and a spectrophotometer method. Background Technology

[0002] Spectrophotometers analyze the composition of substances or identify foreign substances mixed in by measuring the inherent absorption curve of a substance for a given wavelength of light, i.e., the absorption spectrum. In the analysis of molecular vibrations, infrared light with a wavelength about 10 times that of visible light is usually used. Therefore, the spatial resolution is limited to the 10 μm level by the diffraction limit, which is proportional to the wavelength of the light used.

[0003] To improve resolution, Patent Document 1 discloses a spectrophotometer that includes two confocal detectors for detecting electromagnetic waves reflected from the sample, and calculates the change in the physical properties of the sample when an energy beam is irradiated onto a predetermined area based on the outputs of the confocal detectors.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2022-134422 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Patent Document 1 describes a method that "autofocus can also be achieved by setting two confocal detectors," and describes adjusting the value of (PD2-PD1) / (PD2+PD1) to zero (paragraph

[0025] ). The inventors conducted additional experiments and found that the position where the above formula becomes 0 may not necessarily be the focus position. Figure 4 in Patent Document 1 assumes that PD1 and PD2 are perfectly symmetrical. This assumption holds true for samples with a mirror-like surface, but actual samples usually have uneven surfaces, and cases where PD1 and PD2 are perfectly symmetrical are rare. Therefore, the inventors found that the point where the value of (PD2-PD1) / (PD2+PD1) is zero is often not the focus position.

[0009] This invention is an improvement on the autofocus method described in Patent Document 1, and its purpose is to provide a spectrophotometer and spectrophotometer method with high resolution and accurate autofocus.

[0010] Methods for solving problems

[0011] The structure of the present invention for achieving the above objectives is as follows.

[0012] A spectrophotometer includes: an electromagnetic wave source that generates electromagnetic waves that irradiate a predetermined region of a sample; an objective lens that focuses the electromagnetic waves onto the predetermined region; two confocal detectors that detect electromagnetic waves reflected by the sample; and a focus position determination mechanism that performs differential calculations or lock-in detection calculations on the signals obtained by dividing the difference signal and the sum signal output from each of the two confocal detectors, and determines the position of the peak value as the focus position.

[0013] Another spectrophotometric method includes the following steps: irradiating a predetermined area of ​​a sample with electromagnetic waves; obtaining the outputs of two confocal detectors located at different positions that detect electromagnetic waves reflected from the sample by the irradiation of the electromagnetic waves; and performing differential calculation or lock detection calculation on the signal obtained by dividing the difference signal and the sum signal of each output, and determining the position of the peak value as the focus position.

[0014] Invention Effects

[0015] According to the present invention, a spectrophotometer and a spectrophotometer method with high resolution and accurate autofocus can be provided. Attached Figure Description

[0016] Figure 1 This is a schematic structural diagram of an example of the spectrophotometer apparatus of Example 1.

[0017] Figure 2 This is a diagram showing the energy beam irradiating the sample and the probe light.

[0018] Figure 3A This is a diagram illustrating the structure of a confocal detector.

[0019] Figure 3B This is a graph illustrating the relationship between the amount of light detected and the amount of displacement in a confocal detector.

[0020] Figure 4A This is a graph illustrating the relationship between the amount of light detected and the amount of displacement of two confocal detectors.

[0021] Figure 4B This is a graph illustrating the relationship between the sum of the detected light quantities of the two confocal detectors and the displacement.

[0022] Figure 4C It is a graph showing the ratio of the difference to the sum of the detected light quantities of two confocal detectors, and the relationship between their differential values ​​and the displacement.

[0023] Figure 5 This diagram illustrates why the amount of light detected differs at the focal position +L and the focal position -L.

[0024] Figure 6A This is a diagram illustrating an example of XY scanning of the spectrophotometer apparatus of Example 2.

[0025] Figure 6B This is a diagram illustrating another example of XY scanning of the spectrophotometer apparatus of Example 2.

[0026] Figure 7 This is a diagram illustrating an example of the confocal detector of the spectrophotometer apparatus of Example 3.

[0027] Figure 8A This is a diagram illustrating an example of energy beam irradiation of the spectrophotometer apparatus of Example 4.

[0028] Figure 8B This is a diagram illustrating another example of energy beam irradiation of the spectrophotometer apparatus of Example 4. Detailed Implementation

[0029] Hereinafter, embodiments of the spectrophotometer of the present invention will be described with reference to the accompanying drawings.

[0030] Example 1

[0031] use Figure 1 The overall structure of the spectrophotometer of Example 1 will be described. Furthermore, the device structure, which is the hardware of this invention, is substantially the same as the device structure described in Japanese Patent Application Publication No. 2022-134422, which is the earlier application of this application.

[0032] Will Figure 1 The vertical direction is defined as the Z direction, and the horizontal direction is defined as the X and Y directions. The spectrophotometer includes a stage mechanism system with a sample 113, an energy imparting system for imparting energy to the sample 113, a measurement system for measuring the physical properties of the sample 113, and a control system for processing the data output from each part and controlling each part.

[0033] The stage mechanism system has an XY stage 112 on which a sample 113 is placed and which moves in the X and Y directions. By moving the XY stage 112 in the X and Y directions, arbitrary areas of the surface of the sample 113 can be analyzed.

[0034] The energy imparting system includes an energy source 100, beam expanders 101 and 102, a partial reflector 103, an energy detector 104, a dichroic mirror 110, and an objective lens 111. Furthermore, the dichroic mirror 110 and the objective lens 111 are shared with the measurement system.

[0035] Energy source 100 generates an energy beam 500, such as an infrared beam, that energizes sample 113. The beam diameter of the energy beam 500 is enlarged by beam expanders 101 and 102 and directed toward partial reflector 103. Partial reflector 103 allows a portion of the energy beam 500 to pass through energy detector 104, while reflecting the remaining portion toward sample 113. Energy detector 104 measures the intensity of the energy beam 500 transmitted through partial reflector 103. The energy beam 500 reflected by partial reflector 103 passes through dichroic mirror 110, is focused by objective lens 111, and then irradiates sample 113. Sample 113, irradiated by the energy beam 500, absorbs the energy, causing a change in its physical properties, such as thermal expansion.

[0036] The measurement system includes a light source 120, a collimating lens 121, a beam splitter 122, a filter 123, a condenser lens 124, a semi-reflective mirror 125, pinholes 126 and 128, photodetectors 127 and 129, a dichroic mirror 110, and an objective lens 111. Furthermore, while referred to as a "light source" in this embodiment, the electromagnetic waves emitted can achieve the effects of this invention even if they are not "light," so using the term "electromagnetic wave generating source" is technically accurate. Additionally, "condenser lens," "photodetector," etc., should also be referred to as "electromagnetic wave converging lens" and "electromagnetic wave detector," respectively, but "light" is used for ease of understanding.

[0037] Light source 120 generates probe light 501, such as a visible light beam or an ultraviolet light beam, to measure changes in the physical properties of sample 113. The probe light 501 generated by light source 120 has a shorter wavelength than the energy beam 500 and is preferably a beam focused on a smaller spot, such as a green or blue beam. After being collimated into a substantially parallel beam by collimating lens 121, the probe light 501 passes through beam splitter 122 and filter 123, and is directed toward dichroic mirror 110. Dichroic mirror 110 reflects the probe light 501 toward objective lens 111. The probe light 501 reflected by dichroic mirror 110 is then focused by objective lens 111 and illuminates sample 113.

[0038] use Figure 2The energy beam 500 and probe beam 501 irradiating the sample 113 will be described. As described above, both the energy beam 500 and the probe beam 501 are focused by the objective lens 111 and irradiate the sample 113. Since the beam diameter of the probe beam 501 is smaller than that of the energy beam 500, and it is irradiated in a region narrower than the area irradiated by the energy beam 500, changes in physical properties in the region irradiated by the energy beam 500 can be measured with high spatial resolution. In particular, when the probe beam 501 is a visible light beam, the beam diameter of the probe beam 501 focused on the surface of the sample 113 is approximately 0.5 μm. Furthermore, by using a confocal detector in the measurement system, the spatial resolution of the measurement system becomes approximately 0.3 μm. In addition, the measured changes in physical properties include the displacement of the surface of the sample 113 due to the absorption of the energy beam 500, changes in curvature, changes in surface refractive index / reflectivity, etc.

[0039] use Figure 3A and Figure 3B The confocal detector will be described below. The confocal detector is configured such that when light from a point source is focused on the surface of the sample, light reflected from the sample is focused on the detection surface. Specifically, the light source 120, collimating lens 121, beam splitter 122, objective lens 111, sample 113, condenser lens 124, pinhole 126, and photodetector 127 are as follows: Figure 3A As shown in the example, the probe light 501 emitted from the point source of the light source 120 is collimated into a parallel beam by the collimating lens 121 and then reflected by the beam splitter 122 before entering the objective lens 111. The objective lens 111 converges and focuses the probe light 501.

[0040] With the focus aligned with the surface of the sample 113, the reflected probe light 501... Figure 3A The solid line in the diagram represents the optical path passing through objective lens 111, beam splitter 122, and condenser lens 124, and focusing at pinhole 126. As a result, most of the probe light 501 reflected by sample 113 passes through pinhole 126 and is detected by photodetector 127. Sample 113 expands due to the irradiation of energy beam 500, and its surface... Figure 3A In the case of the displacement shown by the dashed line, the probe light 501 travels along the dashed light path and is not focused on the pinhole 126. As a result, the amount of light detected by the photodetector 127 through the pinhole 126 is reduced compared to the case of the solid light path. That is, the amount of light detected by the photodetector 127 varies according to the amount of displacement of the surface of the sample 113, and therefore the change in the physical property value of the sample 113 after being energized can be measured by the photodetector 127.

[0041] Figure 3B This is a graph showing the relationship between the detected light intensity I of the confocal detector and the displacement Z of the sample 113. For example... Figure 3BAs shown, the detected light intensity I is maximum when the surface of sample 113 is in focus, and decreases as it deviates from the focus position. On the other hand, the absolute value of the ratio ΔI / ΔZ (the change in detected light intensity I to the change in displacement Z) is the displacement detection sensitivity, which is minimum at the focus position and approximately zero near the focus position. Therefore, in Example 1, the detection sensitivity is improved by using two confocal detectors.

[0042] return Figure 1 The measurement system will now be described. The probe light 501 illuminating the sample 113 is reflected from the surface of the sample 113, returning to the beam splitter 122 along its original path and reflecting towards the condenser lens 124. The probe light 501 incident on the condenser lens 124 is converged and travels towards the semi-reflecting mirror 125. In the semi-reflecting mirror 125, approximately half of the converged probe light 501 passes through the pinhole 126, and approximately the remaining half is reflected towards the pinhole 128. Of the probe light 501 that has passed through the pinhole 126, which has passed through the semi-reflecting mirror 125, it is detected by the photodetector 127. Alternatively, the photodetector 129 detects the probe light 501 that has passed through the pinhole 128, which has been reflected by the total reflection mirror 125. Furthermore, the pinholes 126 and 128 are positioned offset from the focal point of the condenser lens 124. That is, the pinhole 126 is disposed in a direction away from the focal position of the condenser lens 124 by a distance L, while the pinhole 128 is disposed in a direction closer to the sample 113 by a distance L from the focal position. In addition, the distance L is set to be below the focal depth, that is, within the distance of focal alignment.

[0043] Figure 4A This is a graph showing the relationship between the amount of light detected by photodetectors 127 and 129 and the displacement of sample 113 when pinholes 126 and 128 are arranged at a distance L apart. The peak values ​​of the light detection curve PD1 of photodetector 127 and the light detection curve PD2 of photodetector 129 are offset by a distance L from the focusing position.

[0044] Figure 4B This is a graph that sums the detection light intensity curves PD1 and PD2. (This is achieved through...) Figure 4B The illustrated graph shows a high detection sensitivity at locations where the absolute value of the displacement ΔI / ΔZ is the most significant factor. Figure 4B The displacement is measured at the position indicated by the middle circle. That is, if it is a region within the focal depth, the detection sensitivity can be improved by measuring the displacement at a position away from the focal point.

[0045] Patent document 1 describes using the position where the value calculated using the following formula is zero as the focus position.

[0046]

[0047] The value calculated by (Equation 1) changes approximately linearly with respect to the displacement Z, ideally becoming zero at the focal position. That is, for an ideal specimen with an ultra-smooth surface, as described above. However, due to the unevenness on the surface of the actual specimen, the amount of light measured at a position close to the specimen at a distance L from the focal position is different from the amount of light measured at a position far from the specimen at a distance L from the focal position.

[0048] Figure 5 This diagram illustrates how light incident on the sample surface is reflected at the focal position +L and the focal position -L. The area of ​​the sample surface illuminated by the incident light is the same at both the focal position +L and the focal position -L, but the angle of incidence on the sample at the focal position +L and the focal position -L is different, therefore the angle of reflection of the reflected light is different.

[0049] That is, at the focal position +L, the reflected light is reflected in the direction that does not return to the detector, but at the focal position -L, the reflected light is reflected in the direction that returns to the detector, so the latter detects more light.

[0050] Therefore, in this invention, instead of controlling the position of the sample 113 in the Z direction by making the value of (Equation 1) zero as described in Patent Document 1, the position in the Z direction is controlled by taking the position of the peak as the focus position by differentiating (Equation 1) as shown in (Equation 2).

[0051]

[0052] Figure 4C Examples of graphs for (Equation 1) and (Equation 2) are shown. In the case of an ideal specimen with a smooth surface, the position where the value of (Equation 1) is zero is the focal position. However, as mentioned above, the surface of a real specimen is almost not smooth, so the position where the value of (Equation 1) is zero is not necessarily the focal position. In this case, the value of (Equation 1) varies depending on the surface roughness of the real specimen, etc., so it is unclear what value constitutes the focal position, and the focal position cannot be determined.

[0053] In contrast, in Equation 2, the peak value is always located at the focal point. Therefore, even if the peak value is affected by the roughness of the sample surface, the peak value will remain constant. Figure 4C You can also determine the focus position by shifting up, left, or right.

[0054] By controlling the Z-direction position of the sample 113, the shift in the focal position caused by drift in the distance between the objective lens 111 and the sample 113 can be absorbed. Furthermore, measurements can be performed while the focal position follows the surface irregularities of the sample 113. Moreover, even when the reflectivity or refractive index of the sample 113 surface differs, or when the intensity of the light source 120 varies, their effects can be suppressed.

[0055] In addition, the above describes a calculation method based on differentiation, but it can also replace differentiation by performing frequency component analysis based on high-speed Fourier transform (FFT), etc., to lock and detect specific frequency components and find their peak values, thereby determining the focus position.

[0056] Here, the beam splitter 122 will be explained. When the transmission and reflection in the beam splitter 122 are approximately one-to-one, the amount of light from the probe light 501 passing through the beam splitter 122 twice is reduced to 1 / 4. Therefore, in order to suppress the reduction in the amount of light from the probe light 501, a polarization beam splitter can also be used as the beam splitter 122.

[0057] When using a polarizing beamsplitter, if the light emitted from the collimating lens 121 is polarized vertically relative to the plane of the paper, most of the light passes through the beamsplitter 122. Furthermore, if a λ / 4 plate with its axis rotated 45 degrees relative to the polarization direction is used as a filter 123, the probe light 501 emitted from the filter 123 becomes circularly polarized light. This circularly polarized probe light 501 is reflected from the surface of the sample 113 and returns to the filter 123 along its original path, passing through the λ / 4 plate, thus transforming from circularly polarized light into linearly polarized light perpendicular to the plane of the paper. Furthermore, due to the characteristics of the polarizing beamsplitter, almost all of the linearly polarized probe light 501 is reflected towards the condenser lens 124. In other words, by using a polarizing beamsplitter as the beamsplitter 122 and configuring a λ / 4 plate as the filter 123, the probe light 501 can be guided towards the photodetectors 127 and 129 without reducing its intensity.

[0058] In addition, a wavelength filter that allows only the wavelength of the probe light 501 to pass through can be added as filter 123. By adding a wavelength filter, the detection of light other than the probe light 501 can be suppressed, reducing detection noise.

[0059] The control system is described below. The control system is a control device 300 comprising an overall control unit 301, an energy source control unit 302, a lock detection unit 303, a detection light quantity correction unit 304, an energy intensity correction unit 305, a focus offset calculation unit 306, and an XY scan control unit 307. The overall control unit 301 is an arithmetic unit that controls each unit and processes or transmits the data generated by each unit; for example, it is a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The units other than the overall control unit 301 can be composed of dedicated hardware using ASICs (Application Specific Integrated Circuits), FPGAs (Field-Programmable Gate Arrays), etc., or they can be composed of software running on the arithmetic unit. Furthermore, the display device, printer, or storage device mentioned in the above and subsequent descriptions can be part of the control device 300 or external devices.

[0060] The energy source control unit 302 controls the wavelength, intensity, and other parameters of the energy beam 500 generated by the energy source 100. By scanning the wavelength, the absorption spectrum of the sample 113 can be measured. Furthermore, by modulating the intensity, the locking detection unit 303, described later, can perform locking detection.

[0061] The lock detection unit 303 performs so-called lock detection by comparing the detection light quantities PD1 and PD2 of the photodetectors 127 and 129 with the modulation signal sent from the power source control unit 302. Using the modulation signal as a reference, for example, the amplitude of PD2-PD1 is determined by locking the detection signal PD2-PD1.

[0062] Alternatively, the difference between PD1 and PD2 can be calculated after performing lock detection on the modulation signal as a reference, or the value of (Equation 1) can be used for lock detection.

[0063] Alternatively, instead of lock-on detection, a so-called AM detector can be used, which measures the amplitude after extracting a displacement signal that corresponds to the modulation frequency of the energy beam 500 through a filter.

[0064] Alternatively, FFT or similar methods can be used to perform spectral analysis on the displacement signal to determine the intensity of the spectral peak corresponding to the modulation frequency. Furthermore, other general amplitude detection methods can also be used.

[0065] The detection light quantity correction unit 304 divides the amplitude of PD2-PD1 obtained by the locking detection unit 303 by PD2+PD1. The value obtained by the division operation is proportional to the amplitude of the displacement of the surface of the sample 113, and is therefore referred to as the sample displacement measurement value below.

[0066] The energy intensity correction unit 305 calculates a value proportional to the energy absorptivity by dividing the sample displacement measurement value obtained by the probe light quantity correction unit 304 by the intensity of the energy beam 500 measured by the energy detector 104. The absorption spectrum of the sample 113 is obtained by calculating this value proportional to the energy absorptivity while scanning the wavelength of the energy beam 500. The obtained absorption spectrum can be output externally in tabular or graphical form. For example, the graphical absorption spectrum can be displayed on a display device such as a liquid crystal display, stored in a storage device, or printed by a printer. Furthermore, the focus offset calculation unit 306 controls the Z-direction position of the objective lens 111 based on the value in (Equation 2). By controlling the Z-direction position of the objective lens 111, the probe light 501 can follow the surface irregularities of the sample 113.

[0067] The XY scanning control unit 307 moves the objective lens 111 or the XY stage 112 in the X and Y directions. By moving the objective lens 111 or the XY stage 112, the energy beam 500 and the probe light 501 can be irradiated to any position on the sample 113, enabling the measurement of the absorption spectrum distribution on the surface of the sample 113. In particular, with the wavelength of the energy beam 500 fixed, measurements based on two confocal detectors are performed while moving the objective lens 111 or the XY stage 112, thereby generating a mapping image of the absorbance for that wavelength.

[0068] Furthermore, the focus offset calculation unit 306 and the XY scan control unit 307 operate in cooperation, enabling the lens or stage to move while simultaneously tracking the focus of the probe light 501 on the uneven surface of the sample 113. As a result, XY scanning can be performed while maintaining high detection sensitivity of the energy absorption rate. Additionally, the generated absorbance mapping image can be directly output externally as an image or as a graph. For example, the mapping image can be displayed on a display device such as a liquid crystal display, stored in a storage device, or printed by a printer. The graph display is, for example, a two-dimensional graph in the case of one-dimensional scanning by the XY scan control unit 307, and a three-dimensional graph in the case of two-dimensional scanning by the XY scan control unit 307.

[0069] As explained above, in Example 1, changes in physical properties such as expansion of the sample 113, which is energized by infrared radiation, are detected based on the outputs PD1 and PD2 of the two confocal detectors, thus improving detection sensitivity. Furthermore, by calculating the differential value of (PD2-PD1) / (PD2+PD1) based on each output, the effects of surface reflectivity, refractive index, surface unevenness, variations in the amount of energy beam 500 and probe light 501, and drift in the distance between the objective lens 111 and the sample 113 can be suppressed. Moreover, by using visible light with a shorter wavelength than infrared light as the probe light 501, spatial resolution can be improved.

[0070] Furthermore, by using the outputs PD1 and PD2 of the two confocal detectors, in addition to measuring changes in physical properties, autofocus can also be performed, thus eliminating the need for a separate autofocus mechanism and achieving space-saving in the spectrophotometer. Moreover, by using autofocus with two confocal detectors, the focal position can be rapidly followed to track the surface of a sample with large irregularities, thereby shortening the measurement time.

[0071] Example 2

[0072] In Example 1, it was explained that scanning the position illuminated by the energy beam 500 and the probe light 501 was performed by moving the objective lens 111 in the X and Y directions. In Example 2, it was explained that scanning the position illuminated by the energy beam 500 and the probe light 501 was performed with the objective lens 111 fixed. Furthermore, the same reference numerals are used for structures identical to those in Example 1, and descriptions are omitted.

[0073] use Figure 6A as well as Figure 6B The main parts of Example 2 will be described below. The spectrophotometer of Example 2 is an improvement on the structure of Example 1 by adding an x-scanning mirror 115 and a y-scanning mirror 116, and a Z-stage 114.

[0074] The x-scanning mirror 115 and the y-scanning mirror 116 are mirrors that reflect the energy beam 500 and the probe light 501. The energy beam 500 and the probe light 501 are scanned in the X direction by the rotation of the x-scanning mirror 115, and scanned in the Y direction by the rotation of the y-scanning mirror 116. The rotation of the x-scanning mirror 115 and the y-scanning mirror 116 is controlled by the XY scan control unit 307.

[0075] The Z-stage 114 is disposed on the XY-stage 112, on which the sample 113 is placed and moves in the Z direction. The movement of the Z-stage 114 in the Z direction is controlled by the focal offset calculation unit 306. That is, based on the value of (Equation 1), the position of the Z-stage 114 in the Z direction is controlled, so that, similar to Embodiment 1, the probe light 501 can follow the unevenness of the surface of the sample 113.

[0076] exist Figure 6A In this embodiment, an x-scanning mirror 115 and a y-scanning mirror 116 are disposed between the dichroic mirror 110 and the objective lens 111. By rotating the two mirrors, the energy beam 500 and the probe light 501 are scanned on the surface of the sample 113. By scanning the energy beam 500 and the probe light 501 on the surface of the sample 113, the distribution of the absorption spectrum can be determined in the same manner as in Example 1.

[0077] exist Figure 6B In this configuration, an x-scanning mirror 115 and a y-scanning mirror 116 are positioned between the filter 123 and the dichroic mirror 110. By rotating these two mirrors, only the probe light 501 is scanned on the surface of the sample 113. That is, in... Figure 6B In this structure, even if the x-scanning mirror 115 and y-scanning mirror 116 rotate, the energy beam 500 is not scanned. Furthermore, the probe light 501 is scanned in the region illuminated by the energy beam 500. By scanning the probe light 501 in the region illuminated by the energy beam 500, the distribution of the absorption spectrum in that region can be determined.

[0078] As explained above, in Example 2, by rotating the x-scanning mirror 115 and the y-scanning mirror 116, the probe light 501 is scanned at least on the surface of the sample 113, thus enabling the determination of the distribution of the absorption spectrum. Furthermore, similar to Example 1, changes in the thermal expansion and other physical properties of the sample 113, which is energized by infrared radiation, are detected based on the outputs PD1 and PD2 of the two confocal detectors, thereby improving detection sensitivity.

[0079] Furthermore, scanning of the probe light 501 and the energy beam 500 can be performed not only by rotating the x-scanning mirror 115 and the y-scanning mirror 116, but also by combining this with the horizontal movement of the XY stage 112 and the objective lens 111. For example, in Figure 6B In this structure, after the probe light 501 is aligned with the area of ​​the irradiated energy beam 500 by rotating the x-scanning mirror 115 and the y-scanning mirror 116, the surface of the sample 113 can be scanned by moving the objective lens 111 and the like.

[0080] Furthermore, similar to Example 1, by using the outputs PD1 and PD2 of the two confocal detectors, autofocus can be performed in addition to measuring changes in physical properties. Therefore, there is no need to set up a separate autofocus mechanism, which can save space in the spectrophotometer. In addition, by using the autofocus of the two confocal detectors, the focal position can be rapidly followed to track the surface of the sample with large irregularities, thus shortening the measurement time.

[0081] Example 3

[0082] In Example 1, the use of two confocal detectors to detect the probe light 501 reflected from the surface of the sample 113 was described. In Example 3, it was described that detection was performed using a confocal detector, and the probe light 501 before being converged by the condenser lens 124 was detected via an aperture, thereby determining the scattering state of the surface of the sample 113. Furthermore, structures identical to those in Example 1 are labeled with the same symbols, and descriptions are omitted.

[0083] use Figure 7 The main parts of Example 3 will be described below. The spectrophotometer of Example 3 adds a reflector 130, an aperture stop 131, and a photodetector 132 to the structure of Example 1. The reflector 130 is positioned between the beam splitter 122 and the condenser lens 124, reflecting a portion or almost all of the probe light 501 reflected from the surface of the sample 113 toward the aperture stop 131. That is, if the reflector 130 is a partial reflector, a portion of the probe light 501 is directed toward the aperture stop 131; if the reflector 130 is a total reflector, almost all of the probe light 501 is directed toward the aperture stop 131. The photodetector 132 detects the probe light 501 that has passed through the aperture stop 131, thereby determining the scattering state of the surface of the sample 113.

[0084] The surface of the sample 113 irradiated by the energy beam 500 undergoes localized curvature changes due to thermal expansion, or localized refractive index changes due to temperature changes or changes in carrier concentration.

[0085] As a result, the scattering state of the sample 113 surface sometimes changes, and the angular distribution of the reflected light from the probe light 501 changes. This change in the angular distribution of the reflected light alters the spread of the probe light 501 within the aperture stop 131, thus changing the amount of light detected by the photodetector 132. Therefore, by detecting the probe light 501 via the aperture stop 131 through the photodetector 132, the scattering state of the sample 113 surface can be determined.

[0086] Furthermore, when the displacement on the surface of the sample 113 is small and difficult to detect, the intensity of the energy beam 500 can be used as a reference signal for locking detection. In addition, when the reflector 130 is a total reflection mirror, the scattering state can be measured by a confocal detector when the reflector 130 is removed from the optical path of the probe light 501, and when the reflector 130 is put back into the optical path.

[0087] As explained above, in Example 3, the scattering state of the surface of the sample 113 can be determined by detecting the probe light 501 before it is focused by the condenser lens 124 via the aperture stop 131. Alternatively, the determination of the scattering state can be combined with the determination of the confocal detector.

[0088] Example 4

[0089] In Example 1, the case where an infrared beam was used as the energy beam 500 to energize the sample 113 was described. In Example 4, the case where a charged particle beam such as an electron beam or ion beam was used as the energy beam 500 was described. Furthermore, structures identical to those in Example 1 are labeled with the same symbols, and descriptions are omitted.

[0090] use Figure 8A as well as Figure 8B The main parts of Example 4 will be described below. In the spectrophotometer of Example 4, a charged particle beam is used as the energy beam 500, therefore the dichroic mirror 110 and objective lens 111 cannot be shared between the energy imparting system and the measurement system. Therefore, in Figure 8A In this embodiment, compared to the structure of Example 1, the dichroic mirror 110 is replaced with a perforated mirror 110', and the objective lens 111 is replaced with a hollow objective lens 111'.

[0091] The perforated mirror 110' is a reflecting mirror with a hole in its center, and the hollow objective lens 111' is a lens with a hole in its center. An energy beam 500, which is a charged particle beam, passes through the holes in the perforated mirror 110' and the hollow objective lens 111' and irradiates the sample 113.

[0092] Furthermore, the probe light 501 is reflected towards the hollow objective lens 111' at a position outside the aperture of the perforated lens 110', converges at a position outside the aperture of the hollow objective lens 111', and illuminates the sample 113. The probe light 501, which illuminates the sample 113 together with the energy beam 500 as a charged particle beam, is detected by two confocal detectors after being reflected by the sample 113, in the same manner as in Example 1.

[0093] exist Figure 8B In this embodiment, compared to the structure of Example 1, the dichroic mirror 110 is replaced with a reflecting mirror 110". The probe light 501 is reflected by the reflecting mirror 110" and incident on the objective lens 111, where it is focused and illuminates the sample 113. Additionally, an energy beam 500, as a charged particle beam, irradiates the sample 113 from outside the axis of the objective lens 111. Figure 8B In the structure, the probe light 501, which is irradiated onto the sample 113 along with the energy beam 500, which is a charged particle beam, is detected by two confocal detectors after being reflected by the sample 113.

[0094] As explained above, in Embodiment 4, a charged particle beam is used as the energy beam 500, thus enabling the application of energy to a region narrower than that of an infrared beam, thereby further improving spatial resolution. Alternatively, an infrared beam can be used instead of a charged particle beam as the energy beam 500 in Embodiment 4.

[0095] The foregoing has described several embodiments of the present invention. The present invention is not limited to these embodiments, and modifications or appropriate combinations of the constituent elements may be made without departing from the spirit of the invention. Furthermore, several constituent elements may be deleted from all the constituent elements shown in the above embodiments.

[0096] Explanation of reference numerals in the attached figures

[0097] 100: Energy source; 101, 102: Beam expander lenses; 103: Partial reflector; 104: Energy detector; 110: Dichroic mirror; 110': Perforated mirror; 110”: Reflector; 111: Objective lens; 111': Hollow objective lens; 112: XY stage; 113: Sample; 114: Z stage; 115: X-scanning mirror; 116: Y-scanning mirror; 120: Light source; 121: Collimating lens; 122: Beam splitter; 123: Filter; 124: Concentrator. Lens, 125: Semi-reflecting mirror, 126, 128: Pinhole, 127, 129: Photodetector, 130: Reflecting mirror, 131: Aperture stop, 132: Photodetector, 300: Control device, 301: Overall control unit, 302: Energy source control unit, 303: Lock detection unit, 304: Probe light quantity correction unit, 305: Energy intensity correction unit, 306: Focus offset calculation unit, 307: XY scan control unit, 500: Energy beam, 501: Probe light.

Claims

1. A spectrophotometer, characterized in that, have: An electromagnetic wave source that generates electromagnetic waves that irradiate a predetermined area of ​​the sample. An objective lens that focuses the electromagnetic waves onto the predetermined region; Two confocal detectors, positioned at different locations, detect electromagnetic waves reflected by the sample; as well as The focus position determination mechanism performs differential calculation or lock detection calculation on the signal obtained by dividing the difference signal and the sum signal of the outputs of the two confocal detectors, and determines the position of the peak value as the focus position.

2. The spectrophotometer according to claim 1, characterized in that, The spectrophotometer includes a Z-direction control unit that controls the relative distance between the stage on which the sample is placed and the objective lens based on the discrimination result of the focusing position discrimination mechanism.

3. The spectrophotometer according to claim 2, characterized in that, The two confocal detectors are composed of a first confocal detector and a second confocal detector. The first confocal detector has a pinhole disposed at a distance L from the focal position in a direction away from the sample, and the second confocal detector has a pinhole disposed at a distance L from the focal position in a direction close to the sample. When the output of the focus position discrimination mechanism, the first confocal detector is PD1, and the output of the second confocal detector is PD2, the value of (PD2-PD1) / (PD2+PD1) is further differentiated or locked for detection, and the position where the peak value is taken is determined as the focus position.

4. The spectrophotometer according to claim 1, characterized in that, The spectrophotometer includes a calculation unit that calculates the change in the physical property value of the sample when the electromagnetic wave irradiates the predetermined area based on the outputs of the confocal detector.

5. The spectrophotometer according to claim 4, characterized in that, The spectrophotometer includes an electromagnetic wave intensity detector, which measures the intensity of the electromagnetic wave. The change in the physical property value is corrected based on the intensity of the electromagnetic wave.

6. The spectrophotometer according to claim 4, characterized in that, The electromagnetic wave source modulates the intensity of the electromagnetic wave. The calculation unit uses the modulation signal of the intensity of the electromagnetic wave as a reference to correct the changes in the physical property value.

7. The spectrophotometer according to claim 4, characterized in that, The spectrophotometer includes a display device that displays the absorption spectrum.

8. The spectrophotometer according to claim 4, characterized in that, The spectrophotometer includes a display device that displays a mapped image of absorbance.

9. The spectrophotometer according to claim 1, characterized in that, The spectrophotometer includes an XY scanning control unit that controls the position of the predetermined region.

10. The spectrophotometer according to claim 9, characterized in that, The XY scanning control unit controls the position of the predetermined area by moving the stage on which the objective lens or the sample is placed in the horizontal direction.

11. The spectrophotometer according to claim 9, characterized in that, The XY scan control unit controls the position of the predetermined area by rotating a reflector that is positioned on the path of the electromagnetic wave and reflects the electromagnetic wave.

12. A spectrophotometric determination method, characterized in that, Includes the following steps: Electromagnetic waves are irradiated onto a predetermined area of ​​the sample; The outputs of two confocal detectors located at different positions are obtained to detect electromagnetic waves reflected from the sample by the irradiation of the electromagnetic waves. as well as Differential calculation or lock detection calculation is performed on the signal obtained by dividing the difference signal and the sum signal of each output, and the position of the peak value is determined as the focus position.

13. The spectrophotometric determination method according to claim 12, characterized in that, The spectrophotometric method includes the following steps: based on the outputs of the confocal detector, calculating the change in the physical property values ​​of the sample when the electromagnetic wave is irradiated on the predetermined region.

14. The spectrophotometric determination method according to claim 13, characterized in that, The change in the physical property value is corrected based on the intensity of the electromagnetic wave reflected from the sample.

15. The spectrophotometric determination method according to claim 14, characterized in that, Modulate the intensity of the electromagnetic wave irradiating a predetermined area of ​​the sample. The change in the physical property value is corrected based on the modulation signal of the intensity of the electromagnetic wave.

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