JP2006023200A - Optical probe and spectrometric apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make practical the measurement of physical quantity, such as the concentration of a component or the like at the arbitrary point of a liquid. <P>SOLUTION: This optical probe is constituted of a transparent material and equipped with a first hole which permits the insertion of a first optical fiber; an internal gap equipped with two or three planes, which become the total reflection surface due to the difference of a refractive index with the transparent material and are arranged so as to totally reflecting the incident light from the first optical fiber in the first hole successively; a second hole which permits the insertion of a second optical fiber and is provided at an incident position of the light successively reflected by the planes of the internal gap, two facing boundary surfaces which are provided on the way of the light path reaching the second optical fiber from the first optical fiber through two or three planes of the internal gap and perpendicular to the light path, and a cavity part communicating with the outside. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to optical measurement of physical quantities such as component concentration and temperature of a liquid.

  In the cleaning process in semiconductor manufacturing, a chemical solution of strong acid or strong alkali is used. For example, in the etching of a silicon wafer surface, a mixed solution of ammonia and hydrogen peroxide is used. In the etching process, the concentration of each component in the etching solution is measured in order to manage the etching amount.

  The component concentration of the liquid can be measured with a spectrophotometer using near infrared rays or the like. Analysis and quantification using a spectroscopic measurement apparatus are also used for etching semiconductors and measuring the concentration of cleaning liquid. For example, in the mixed acid concentration measuring method and concentration measuring apparatus described in JP-A-6-265471, a mixed acid is introduced into a flow cell using a calibration curve obtained by multivariate analysis, and near-infrared light is emitted. Determine the acid concentration by determining the absorbance. It is also known that temperature is a factor of absorbance, and the temperature of the liquid can be determined from absorbance measurement.

  However, in the conventional optical density measurement, the liquid to be measured is transferred from the tank in which etching and cleaning are performed (hereinafter referred to as the cleaning tank), the chemical overflow tank, or the chemical stock tank to the flow cell of the spectrometer. The method to introduce is taken. In this case, since there is a time delay until the liquid is introduced into the flow cell, it is not possible to catch the change in the concentration of the cleaning tank during the period of the liquid introduction into the flow cell. In addition, it is difficult to say that the concentration in the cleaning tank is measured in the system introduced from the stock solution tank.

In order to measure the optical concentration of the components in the etching solution, an optical probe that is directly immersed in the etching solution in the etching tank has also been proposed. The optical probe described in Japanese Patent Application Laid-Open No. 2000-88749 uses a quartz prism provided with a large number of reflecting surfaces in order to transmit measurement light by a sufficient distance. Two optical fibers from an external spectrometer are connected to this optical probe and immersed in a liquid. Light is introduced into the optical probe by one optical fiber, and incident light is totally reflected one after another on each reflecting surface, and light (transmitted light) that has passed through the optical probe passes through another optical fiber and is connected to an external spectrometer. Returned to Since a part of the optical path in the optical probe passes through the etching solution, the spectroscopic measurement device can measure the transmitted light.
JP-A-6-265471 JP-A-3-209149 JP 2000-88749 A

  The decrease in the yield in the semiconductor cleaning process largely depends on the concentration and temperature change of the chemical solution with which the silicon wafer surface comes into contact, and many of the concentration and temperature distribution of the chemical solution in the tank have not been clarified. Therefore, it is desirable that the concentration and temperature can be measured at any point in the tank.

  However, since the above-mentioned immersion type optical probe has a large number (6 or more) of reflecting surfaces, the dimensions are large. The semiconductor cleaning tank is designed to minimize the surplus space in order to maximize the use efficiency of the chemical solution. For example, in the case of a wafer, since the dimensions of the tank are matched to the wafer, the margin for installing the sensor is narrow. For this reason, it is not realistic to apply such a large optical probe to an existing semiconductor cleaning tank. Moreover, since many reflective surfaces must be processed, the difficulty of probe processing is high.

  An object of the present invention is to put into practical use the measurement of physical quantities such as component concentrations at arbitrary points of a liquid to be measured.

  The optical probe according to the present invention is an optical probe made of a transparent material, and becomes a total reflection surface due to a difference in refractive index between the first hole into which the first optical fiber can be inserted and the transparent material. An internal space having three planes, wherein the two or three planes are disposed so as to sequentially totally reflect incident light from the first optical fiber in the first hole; A second hole into which the second optical fiber can be inserted, the second hole provided at a position where the light sequentially reflected by the plane of the internal gap is incident, and the first optical fiber A cavity portion that is provided in the middle of the optical path leading to the second optical fiber through the two or three planes of the internal air gap, has two opposing boundary surfaces perpendicular to the optical path, and communicates with the outside. Prepare.

  In the optical probe, for example, the refractive index of the transparent material is 1.4142 or more, and the number of the planes is two.

  In the optical probe, for example, the refractive index of the transparent material is between 1.4142 and 1.155, and the number of the planes is three.

  In the optical probe, preferably, a condensing lens is provided on each of an emission side of the first optical fiber and an incident side of the second optical fiber.

  The spectroscopic measurement device according to the present invention transmits light to a liquid to be measured, detects each intensity of light of a plurality of wavelengths (for example, near infrared light), and determines the physical quantity of the liquid based on the detected value. It is a spectroscopic measuring device to measure. The spectroscopic measurement device includes the optical probe, a light source that splits near-infrared light into light having a plurality of wavelengths, and sends the light to the optical probe via a first optical fiber, and a second optical fiber from the optical probe. A light detection unit that receives light through the light source and generates a light intensity signal corresponding to the intensity of the received light, and the absorbance and acid concentration of light at multiple wavelengths for a plurality of mixed acid samples with known acid concentrations While maintaining the calibration curve equation obtained by the multivariate analysis method using a multi-degree polynomial of absorbance including a constant term between the light intensity signal output from the light detection unit, the absorbance of each wavelength is And a physical quantity calculating means for calculating the physical quantity of the liquid to be measured (for example, component concentration and temperature in the liquid) based on the calibration curve formula from the calculated light absorbance of each wavelength.

  A small immersion optical probe can be provided. Therefore, when the optical probe is immersed in the target liquid, the measurement target liquid can be always introduced into the optical probe. This eliminates the need for a mechanism (such as a flow cell) for introducing the target liquid into the measuring apparatus.

  Since a small optical probe can be introduced into the liquid, for example, in-line measurement of a physical quantity (component concentration, temperature) at an arbitrary point of the liquid in the etching tank can be performed. Further, by performing multi-point measurement, it is possible to know the concentration and temperature distribution in the tank, to know the concentration and temperature unevenness in the tank, and to improve the yield in the cleaning process.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference symbols denote the same or equivalent.

  The optical probe according to the present invention is made of a transparent material, and is characterized by providing a gap that causes total internal reflection. The internal gap has a refractive index of 1 substantially, and has two or three planes that serve as a total reflection surface due to a difference in refractive index from the material of the optical probe. That is, the internal gap is a prism mechanism that utilizes the difference in refractive index between the main body of the optical probe and the gap. The spectrometer and the optical probe are connected by two optical fibers, and the optical probe is immersed in the liquid to be measured. When the measurement light is introduced into the optical probe by one optical fiber, the light is sequentially reflected by the total reflection surface and exits from the other optical fiber. Since the liquid to be measured enters the cavity provided in a part of the optical path, the light transmitted through the liquid is sent to the spectrometer. Using this optical probe, in-line measurement of the physical quantity (component concentration and temperature) at an arbitrary point of the liquid becomes possible.

FIG. 1 shows a front view of an example of a two-reflection optical probe, and FIG. 2 shows a cross section through a hole 22 and a gap 34. A main body 10 having a substantially rectangular parallelepiped shape of the optical probe includes a cavity 12 at a substantially central portion thereof. The cavity 12 is a space filled with a liquid when the optical probe is immersed in the liquid. In this example, the cavity 12 is provided with upper and lower parallel surfaces 12a extending in the left-right direction in the drawing and perpendicular to the longitudinal direction of the main body, and light incident perpendicularly to one surface 12a is transmitted through the other surface 12a as it is. To do. Reinforcing side portions 14 and 16 are disposed on both sides of the main body 10 and are integrated with the main body 10. The side portions 14 and 16 reinforce the main body and define the side surface of the cavity portion 12, and the liquid enters the cavity portion 12 from the front side of the figure. On the upper side of the cavity 12, holes 22 and 24 for inserting two optical fibers (for example, φ0.5 mm) 18 and 20 are provided in parallel to the longitudinal direction of the main body, and below the holes 22 and 24. Are provided with spaces 30 and 32 for holding the convex lenses 26 and 28. The optical fibers 18 and 20 are made of, for example, quartz, sapphire, or fluororesin (not including a metal element). Two total internal reflection spaces (gaps) 34 and 36 are provided below the cavity 12. The internal gaps 34 and 36 include flat surfaces 34a and 36a that form an angle of 45 degrees with the longitudinal direction of the main body. The internal voids 34 and 36 contain a gas such as air or are in a vacuum, and the refractive index n is substantially 1.0. The main body 10 is made of a material having a refractive index of n of 1.4142 (= 2 ^1/2 ) or more (a transparent material that does not contain a metal element, such as quartz, sapphire, and diamond). When n is made of a material having a refractive index of 1.4142 or more, two total reflections occur on the surfaces 34a and 36a. In the example of FIG. 1, the internal cavities 34 and 36 have a triangular cross section, and the surfaces 34 a and 36 a corresponding to the longest side of the triangle form an angle of 45 degrees with the longitudinal direction of the main body. Due to this refractive index difference, when light is incident on this surface at an incident angle of 45 degrees, the light is totally reflected. That is, the incident surface and the exit surface of the measurement light are the same plane, and the internal gaps 34 and 36 act as prisms. Since the number of light reflections is only two, there is an advantage that the optical path length between the two optical fibers 18 and 20 can be shortened. Thereby, it can prevent that transmitted light becomes dark. Since the number of reflecting surfaces is small, the dimensions of the optical probe can be reduced (for example, 1 cm wide × 3 cm high). The cavity 12 may be provided on only one side of the two reciprocating optical paths of the main body 10 so that the light passes through the liquid only once.

  In measurement, when the measurement light is incident from the spectroscopic measurement device through one optical fiber 18, the light is collected by the lens 26 and then incident perpendicularly to the surface 12 a of the cavity 12 as indicated by an arrow. Then, the liquid in the cavity 12 is permeated and travels below the cavity 12. Further, light that enters perpendicularly to the surface 12 a from below the cavity portion is again transmitted through the liquid in the cavity portion 12, passes through the lens 28, and enters the other optical fiber 20. Therefore, the light incident from the optical fiber 18 passes through the liquid in the cavity 12, is reflected in one space 34, is subsequently reflected in the other space 36, and again passes through the liquid in the cavity 12, Head up. In this way, the transmitted light of the liquid is sent to the spectroscopic device.

  The spaces 34 and 36 need to have total reflection surfaces 34a and 36a, but other shapes are not limited. Preferably, when the other two surfaces that do not correspond to the longest sides 34a and 36a of the triangles of the spaces 34 and 36 are roughened, light from the outside of the probe does not enter.

  FIG. 3 shows another example of a two-reflection optical probe. This optical probe is different from the optical probe shown in FIGS. 1 and 2 in that the position of the cavity 12 ′ is positioned between the two internal cavities 34, 36 on the lower side of the main body 10 ′, and the reinforcement. Do not use the side parts 14 and 16 for. Two opposing surfaces 12a 'are parallel to the longitudinal direction of the body. Since the position of the cavity 12 'is located below the main body 10', the vertical length of the main body 10 'can be shortened compared to the optical probe shown in FIGS. 1 and 2, but the length in the width direction is become longer.

  In the above two examples, the two optical fibers 18 and 20 are installed in parallel to make the optical probe small. However, generally, as shown in FIG. 4 as an example, the two optical fibers 18 and 20 do not necessarily have to be parallel.

  FIG. 5 shows an example of a three-reflection optical probe. The optical probe differs from the optical probe shown in FIGS. 1 to 4 in the material of the main body 10 and the shape of the internal gap 35 that enables three-time reflection. The main body 10 is made of a material having a refractive index of 1.155 to 1.4142 or higher that does not include a metal element, such as PTFE and PFA which are transparent fluorine compounds (Cytop manufactured by Asahi Glass Co., Ltd.). The internal space 35 includes three reflecting surfaces 35a and forms an angle of 120 degrees with each other. Incident light enters each reflecting surface 35a at an incident angle of 60 degrees and is totally reflected.

  An optical probe or an optical fiber, when immersed in a bath where semiconductor etching and cleaning are performed, is a transparent material (for example, in a two-reflection optical probe, which can suppress corrosion or elution due to strong acid or strong alkali to a very small amount or zero. Quartz) is used. Sapphire glass can be used in a liquid to be measured, such as dilute hydrofluoric acid, in which quartz cannot be used in a two-reflection optical probe. The reason why the optical probe or the like is made of a material that does not contain a metal element is that if a material that does not dissolve in the semiconductor chemical solution is used, even if the optical probe breaks, no adverse effect is exerted. On the other hand, if a mirror by metal vapor deposition is provided as a reflective surface, for example, when the probe breaks, the metal melts and has an adverse effect.

  The above-described optical probe can be manufactured by combining and integrating materials having various shapes. For example, in the optical probe shown in FIGS. 1 and 2, a total reflection surface can be configured by fitting a triangular prism into a rectangular opening.

  By using any of the optical probes described above, as in the case of using a conventional flow cell, the absorbance can be obtained with a spectroscopic measurement device, and the physical quantity (component concentration, liquid temperature, etc.) in the liquid can be measured. As a measuring method, for example, a method described in JP-A-6-265471 can be employed. In this method, light is transmitted through a mixed acid to be measured, the respective intensities of light having a plurality of wavelengths are detected, and the concentration of the acid in the mixed acid is measured based on the detected value. First, an optical probe to which an optical fiber is attached is immersed in a liquid target liquid having a known component concentration, light of a plurality of wavelengths in the near infrared region having different wavelength regions is transmitted, and the intensity value of the transmitted light is measured. This measurement is repeated for a plurality of samples. Then, the absorbance is calculated from the intensity values of the plurality of samples, and a calibration curve equation between the absorbance and the physical quantity in the liquid is obtained. Next, the optical fiber and the optical probe are immersed in the liquid to be measured, the light having a plurality of different wavelengths is transmitted, and the intensity value of the transmitted light is measured. Then, the absorbance is calculated from the intensity value, and the physical quantity (component concentration, liquid temperature) in the liquid is determined using the absorbance and the calibration curve equation.

  FIG. 6 comprises a system for cleaning in semiconductor manufacturing. This system includes an etching bath 100 for cleaning a semiconductor wafer, the above-described optical probe 110 that can be immersed in an etching solution in the etching bath 100, and spectroscopic measurement devices 120 to 150. The spectroscopic measurement apparatus has the same configuration as the conventional one except that the sample is introduced into the optical probe 110 in-line. The optical probe 110 is connected to the spectrometer by optical fibers 18 and 20.

  The etching tank 100 includes an overflow tank 104. The stock solution is supplied from the stock solution tank 102 to the etching tank 100.

  In the light source 120 of the spectroscopic measurement apparatus, as shown in FIG. 7, the emitted light from the light emitting element 120 made of, for example, tungsten or a halogen lamp is condensed by the convex lens 122. The light that has passed through the diaphragm 124 arranged at the focal position of the convex lens 122 is split by the interference filter 126. The rotating disk 128 holds eight interference filters 126 having a selected transmission wavelength at equal angular intervals, and is rotated by a driving motor 127 at, for example, 1000 rpm. As the interference filter 126, a filter having a wavelength that has a large spectrum fluctuation with respect to a concentration change of a specific component and has little influence of interference and interference of other components in the near infrared region where the characteristic absorption band of water appears conspicuously is selected. The Specifically, the fluctuation of the near-infrared absorption spectrum in each of the ionic species at 980 nm, which is the characteristic absorption band of water, in the vicinity thereof, in the vicinity of 1200 nm, in the vicinity of 1460 nm, in the vicinity of 1940 nm, and in the vicinity of 2500 nm. Gives a unique spectrum. Acetic acid has characteristic absorption at 1680 nm, 1720 nm, 2260 nm, 2480 nm, and 2510 nm. Therefore, as the interference filter 126, for example, eight wavelengths are selected from wavelengths in the range of 800 nm to 2600 nm including light of these wavelengths according to the concentration to be measured, and light of these eight wavelengths is respectively selected. Use 8 filters to transmit.

  The light transmitted through the interference filter 126 is collected by the convex lens 129 and introduced into the optical probe 110 in the etching tank 100 through the optical fiber 18. The light transmitted through the etching solution in the optical probe 110 enters the spectroscopic unit 130 through the other optical fiber 20.

The spectroscopic unit 130 includes a convex lens (not shown) that condenses the above-described transmitted light and a light receiving element (not shown) that converts light incident from the convex lens into a photocurrent. The amplifier 132 amplifies the transmitted light intensity signal output from the spectroscopic unit 130 and corresponding to the intensity of the transmitted light from the optical probe, and the A / D converter 134 converts the output of the amplifier 132 into a digital signal.

  The data processing device 140 calculates the absorbance of light of each wavelength from the transmitted light intensity signal input from the A / D converter 134, and then calculates the absorbance based on the calculated absorbance of each wavelength of light and the calibration curve formula. The concentration of acid in the mixed acid is calculated from the absorbance at each wavelength. The data processor 140 receives a microprocessor 142 that controls the whole, a ROM 144 that stores a program for operating the microprocessor 142, a RAM 146 that stores the calibration curve and various data, and data and various commands. An input device 148 such as a keyboard, a printer that outputs the result of the data processing, an output device 150 such as a display, and the like are included.

  When the small immersion type optical probe 110 is immersed in the chemical solution in the etching tank 100, the measurement target solution can be always introduced into the optical probe. This eliminates the need for a mechanism (such as a flow cell) for introducing the target liquid into the measuring apparatus. In addition, for example, in-line measurement of a physical quantity (component concentration, temperature) at an arbitrary point of the liquid in the etching bath 100 is possible. Further, by performing multi-point measurement, it is possible to know the concentration and temperature distribution in the tank, to know the concentration and temperature unevenness in the tank, and to improve the yield in the cleaning process. (In FIG. 6, the optical probe 110 is positioned near the liquid surface, but can be installed at a desired position in the tank.) Even if the optical probe 110 is broken during the measurement, the composition of the chemical solution is reduced. There is no effect.

  FIG. 8 shows more specific contents of data processing by the microprocessor 142. First, transmitted light intensity measurement data is input (step 10). Here, the rotating disk 128 is rotated by the rotation of the drive motor 127 of the measuring apparatus of FIG. 6, and the light having the transmission wavelength of the eight interference filters 126 held by the rotating disk 128 is separated by the spectroscopic unit 130. Receive the transmitted light that has passed through the mixed acid in the optical probe, and generate an analog signal proportional to the sample transmittance. These signals are amplified by the amplifier 132 and then converted into digital signals by the A / D converter 134. Then, the digital signal (transmitted light intensity) from the A / D converter 134 is input.

の演算を実行し、吸光度Ａ_ｉを求める（ステップＳ１２）。ここで、ｉ＝１〜８、Ｒ_ｉは測定対象サンプルのｉ番目の波長での透過強度値、Ｂ_ｉは基準濃度の混酸（たとえば、フッ酸＋硝酸＋酢酸）または水を光学プローブ１１０に入れたときのｉ波長の透過強度値、Ｄ_ｉは光学プローブ１１０を遮光したときのｉ番目の波長での透過強度値、である。透過強度値Ｂ_ｉおよびＤ_ｉは予め測定しておき、入力装置１４８からＲＡＭ１４６に格納しておく。 Next, with respect to the measurement data of the transmitted light intensity, the following equation (1)

The absorbance A _i is obtained (step S12). Here, i = 1 to 8, R _i is a transmission intensity value at the i-th wavelength of the sample to be measured, B _i is a mixed acid (for example, hydrofluoric acid + nitric acid + acetic acid) of reference concentration or water to the optical probe 110. The transmission intensity value at the i wavelength when the optical probe 110 is inserted, and D _i is the transmission intensity value at the i th wavelength when the optical probe 110 is shielded from light. The transmission intensity values B _i and D _i are measured in advance and stored in the RAM 146 from the input device 148.

の変換を行なう（ステップＳ１４）。この変換を行なうのは次の理由による。式（１）により演算される吸光度Ａ_ｉは、光源の明るさの変動、受光素子の感度変動、光学系のひずみ等により変化する。しかしこの変化はあまり波長依存性はなく、８波長の各吸光度データに同相、同レベルで重畳する。したがって、式（２）のように、各波長間の差を取ることにより、上記変化を相殺できる。また、サンプル自体の温度変動による吸光度Ａ_ｉの変動は、たとえば出願人による特開平３−２０９１４９号公報に記載の方法を採用して除去できる。 Next, with respect to the absorbance A _i , the following formula (2)

Is converted (step S14). This conversion is performed for the following reason. The absorbance A _i calculated by the equation (1) varies depending on the brightness variation of the light source, the sensitivity variation of the light receiving element, the distortion of the optical system, and the like. However, this change is not very wavelength-dependent, and is superimposed in the same phase and at the same level on each absorbance data of 8 wavelengths. Therefore, the above change can be canceled by taking the difference between the wavelengths as shown in Equation (2). The change in absorbance A _i due to temperature variations of the sample itself, for example removal by adaptation of the methods described in JP-A-3-209149 by the applicant.

の演算を行い、フッ酸濃度Ｃ₁、硝酸濃度Ｃ₂および酢酸濃度Ｃ₃を演算する（ステップＳ１６）。ここで、混酸がたとえばフッ酸＋硝酸＋酢酸である場合を考えていて、Ｆ（Ｓ_ｉ）、Ｇ（Ｓ_ｉ）、Ｈ（Ｓ_ｉ）は、それぞれ、フッ酸、硝酸、酢酸の検量線式である。 Next, based on S _i obtained by the equation (2), the following equation (3)

The hydrofluoric acid concentration C ₁ , nitric acid concentration C ₂ and acetic acid concentration C ₃ are calculated (step S16). Here, a case where the mixed acid is, for example, hydrofluoric acid + nitric acid + acetic acid is considered, and F (S _i ), G (S _i ), and H (S _i ) are calibration curves of hydrofluoric acid, nitric acid, and acetic acid, respectively. It is a formula.

ここで、Ｓ_ｉ，Ｓ_ｉ＋１は式（１），式（２）により得られたデータ、α，β，γは検量線式の係数、Ｚ₀は定数項である。式（４）は、既知濃度の混酸（フッ酸＋硝酸＋酢酸）の標準サンプルを用いて、図６の分光測定装置により予め求めておき、データ処理装置１４０のＲＡＭ１４６に格納しておく。 Calibration curve equation of hydrofluoric acid F (S _i), together with the respective first-order of S _i including higher order terms, comprises S _i and S _{i + 1} or cross section and a constant term is the multiplication of the higher order terms Is expressed by the following equation (4).

Here, S _i and S _{i + 1} are data obtained by the equations (1) and (2), α, β, and γ are coefficients of the calibration curve equation, and Z ₀ is a constant term. Equation (4) is obtained in advance by the spectroscopic measurement device of FIG. 6 using a standard sample of mixed acid (hydrofluoric acid + nitric acid + acetic acid) of a known concentration and stored in the RAM 146 of the data processing device 140.

The calibration curve formula G (S _i ) for nitric acid and the calibration curve formula H (S _i ) for acetic acid are both similar to the formula (4) for hydrofluoric acid. Similarly, these calibration curve types are obtained in advance using the standard sample of a mixed acid (hydrofluoric acid + nitric acid + acetic acid) having a known concentration by a concentration measuring device and stored in the RAM 146 of the data processing device 140. .

Next, the hydrofluoric acid concentration C ₁ , the nitric acid concentration C ₂ and the acetic acid concentration C ₃ obtained by the calculation of the equation (4) are output to the output device 150 (step S 18). For example, it is displayed on a CRT screen, outputted as a hard copy on printing paper, or transmitted to the outside.

Further, based on the obtained data of hydrofluoric acid concentration C ₁ , nitric acid concentration C _2, and acetic acid concentration C ₃ , the present state of the mixed acid tank 100 can be grasped and calculated from these data. The parameter values necessary for the management of the tank 100, for example, the stock solution addition amount, the stock solution addition time, the waste solution amount, and the waste solution time are calculated, and the results are output to the output device 150 (step S20).

  In the above example, the method for measuring the component concentration in the liquid has been described. However, since the temperature is also a factor of absorbance, the liquid temperature can be similarly determined by measuring absorbance. That is, the measurement method described above can be used for measurement of various physical quantities related to absorbance.

  In this example, the mixed acid to be measured was hydrofluoric acid + nitric acid + acetic acid, but other mixed acids, for example, hydrofluoric acid + nitric acid, phosphoric acid + nitric acid, hydrofluoric acid + nitric acid + acetic acid, phosphoric acid + nitric acid. Needless to say, data processing may be performed in the same manner for + acetic acid, hydrofluoric acid + hydrochloric acid, sulfuric acid + hydrochloric acid, and aqua regia.

Front view of a two-reflection optical probe Side sectional view of a two-reflection optical probe Front view of a modified example of a two-reflection optical probe Front view of another modified example of a two-reflection optical probe Front view of 3 times reflection type optical probe Diagram showing the configuration of the spectrometer Block diagram of a light source for a spectroscopic measurement device Flow chart of data processing of spectrometer

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Main body of optical probe, 12 Cavity part 12, 18, 20 Optical fiber, 26, 28 Convex lens, 34, 36 Internal space | gap, 34a, 36a Total reflection surface, 120 Light source, 130 Spectroscopic part, 140 Data processing part.

Claims (6)

An optical probe made of a transparent material,
A first hole into which the first optical fiber can be inserted;
An internal air gap having two or three planes to be a total reflection surface due to a difference in refractive index with the transparent material, wherein the two or three planes are used as the first light in the first hole. An internal air gap arranged so as to sequentially reflect the incident light from the fiber, and
A second hole into which a second optical fiber can be inserted, the second hole provided at a position where light sequentially reflected by the plane of the internal gap is incident;
Provided in the middle of the optical path from the first optical fiber through the two or three planes of the internal gap to the second optical fiber, and having two opposing boundary surfaces perpendicular to the optical path, An optical probe comprising: a cavity communicating with   2. The optical probe according to claim 1, wherein the refractive index of the transparent material is 1.4142 or more, and the number of the planes is two.   The optical probe according to claim 1, wherein the refractive index of the transparent material is between 1.4142 and 1.155, and the number of the planes is three.   The optical probe according to any one of claims 1 to 3, wherein a condensing lens is provided on each of an emission side of the first optical fiber and an incident side of the second optical fiber. A spectroscopic measurement device that transmits light to a liquid to be measured, detects each intensity of light of a plurality of wavelengths, and measures a physical quantity of the liquid based on the detected value,
An optical probe according to any one of claims 1 to 4,
A light source that splits near-infrared light into light of a plurality of wavelengths and sends the light to an optical probe via a first optical fiber;
A light detection unit that receives light from the optical probe via a second optical fiber and generates a light intensity signal corresponding to the intensity of the received light;
A calibration curve equation obtained by a multivariate analysis method using a multi-order polynomial of absorbance including a constant term between the absorbance of light of multiple wavelengths and the concentration of acid for a plurality of mixed acid samples with known acid concentrations On the other hand, the light absorbance of each wavelength is calculated from the light intensity signal output by the light detection unit, and the physical quantity of the liquid to be measured is calculated from the calculated light absorbance of each wavelength based on the calibration curve equation. A spectroscopic measurement apparatus comprising: a physical quantity calculating means for calculating. The spectroscopic measurement apparatus according to claim 5, wherein the physical quantity is a component concentration and temperature in a liquid.

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