Optical measuring cell, optical analyzer, window forming member, and method for manufacturing an optical measuring cell

Abstract

To prevent cracking of a window material when manufacturing an optical measurement cell that meets various performance requirements, including airtightness and heat resistance, by atomic diffusion bonding.SOLUTION: An optical measurement cell 2 provided with translucent windows W1, W2 for transmitting light and designed to have a sample introduced therein is provided, the optical measurement cell comprising a window material 221 forming the translucent windows W1, W2, and flange members 222, each having the window material 221 bonded thereto via a metallic thin film M. A ratio of a thermal expansion coefficient of the flange member 222 to a thermal expansion coefficient of the window material 221 is in a range of 0.5 times or more and 1.5 times or less.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an optical measurement cell and an optical analyzer using the optical measurement cell.

Background Art

[0002] Conventionally, for example, an optical measurement cell used in an optical analyzer such as NDIR may be configured to attach a window forming member having a window material to a cell body as shown in Patent Document 1.

[0003] When an O-ring is used as a structure for airtightly fixing the window material in this window forming member, although it is slight, gas leaks through the gap between the O-ring and the sealing portion or through the O-ring itself, and a highly airtight seal cannot be achieved. Further, when the gas is reactive, the O-ring may be deteriorated by the gas.

[0004] Although it is conceivable to use a metal O-ring instead of this O-ring, in this case, if the line load during sealing is small, the sealing performance can be maintained temporarily, but leakage will occur when the thermal cycle is repeated. On the other hand, if the line load is increased, the window material will crack.

[0005] Therefore, as a structure for ensuring airtightness, as shown in FIG. 7, a structure in which a joint portion formed on a flange member is joined to a flat portion (main surface) of the window material is considered.

[0006] And for the joint portion of this structure, not only a very low leak rate is required, but also heat resistance that can withstand the temperature (200°C) during the process is required, and moreover, it is necessary to prevent cracking of the window material during the manufacturing process. Thus, various performances are required.

[0007] Under such circumstances, the inventor of the present application has considered methods such as adhesives and brazing as methods for airtightly joining the window material to the joint portion of the flange member, but has come to the conclusion that it is extremely difficult for any method to satisfy all the various performances required.

[0008] Therefore, after further intensive research, the inventors of this application discovered the possibility of satisfying all the required performance characteristics by joining the window material and the joint by atomic diffusion bonding.

[0009] However, if there is a large difference in the coefficients of thermal expansion between the flange member and the window member, such as when using stainless steel as the flange member and ZnSe as the window member, problems can arise where the window member cracks due to thermal effects during the process, such as the window member bending or the flange member undergoing thermal deformation. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2017-40655 [Overview of the project] [Problems that the invention aims to solve]

[0011] Therefore, the present invention was made to solve the above-mentioned problems all at once, and its main objective is to prevent cracking of the window material when manufacturing an optical measurement cell that satisfies various required performance characteristics such as airtightness and heat resistance by atomic diffusion bonding. [Means for solving the problem]

[0012] In other words, the optical measurement cell according to the present invention is an optical measurement cell having a light-transmitting window into which a sample is introduced, comprising a window material forming the light-transmitting window and a flange member to which the window material is joined via a thin metal film, characterized in that the ratio of the thermal expansion coefficient of the flange member to the thermal expansion coefficient of the window material is 0.5 times or more and 1.5 times or less.

[0013] In an optical measurement cell configured in this way, the window material is bonded to the flange member via a metal film; in other words, the window material is atomically diffuse-bonded to the flange member, thus satisfying various performance requirements such as airtightness and heat resistance between them. Furthermore, the ratio of the thermal expansion coefficient of the flange member to the thermal expansion coefficient of the window material is between 0.5 and 1.5 times, and since the thermal expansion coefficients of both members are close, cracking of the window material can be prevented.

[0014] Specific embodiments include a configuration in which the window material is made of zinc selenide or sapphire and the flange member is made of titanium or stainless steel invar, or a configuration in which the window material is made of barium fluoride and the flange member is made of stainless steel or nickel. Furthermore, the configuration using a window material made of zinc selenide or barium fluoride is useful for analysis using long-wavelength light (e.g., infrared light of 7 μm or longer).

[0015] Furthermore, the optical analysis apparatus according to the present invention is characterized by comprising the above-mentioned optical measurement cell, a light irradiation unit that irradiates the optical measurement cell with light, a light detection unit that detects the light transmitted through the optical measurement cell, and a concentration calculation unit that calculates the component concentration in the sample using the light intensity signal obtained by the light detection unit.

[0016] Furthermore, the present invention relates to a method for manufacturing an optical measuring cell having a light-transmitting window through which a sample is introduced, wherein the light-transmitting window comprises a window material and a flange member that supports the window material, and the ratio of the thermal expansion coefficient of the flange member to the thermal expansion coefficient of the window material is 0.5 times or more and 1.5 times or less, and the window material and the flange member are atomically diffuse-bonded.

[0017] In addition, the window forming member according to the present invention is a window forming member used for an optical measurement cell into which a sample is introduced, and includes a window material that forms a light-transmitting window through which light passes, and a flange member to which the window material is joined via a metal thin film. The ratio of the coefficient of thermal expansion of the flange member to the coefficient of thermal expansion of the window material is 0.5 times or more and 1.5 times or less.

[0018] According to these optical analysis devices, manufacturing methods for optical measurement cells, and window forming members according to the present invention, the same operational effects as those of the above-described optical measurement cell can be achieved.

Advantages of the Invention

[0019] According to the present invention described above, while manufacturing an optical measurement cell that satisfies various required performances such as airtightness and heat resistance by atomic diffusion bonding, cracking of the window material can be prevented.

Brief Description of the Drawings

[0020] [Figure 1] It is an overall schematic diagram of a gas analysis device according to an embodiment of the present invention. [Figure 2] It is a (a) perspective view and (b) front view showing the structure of the window forming member of the embodiment. [Figure 3] It is a cross-sectional view showing the structure of the window forming member of the embodiment. [Figure 4] It is a schematic diagram showing an example of a method for forming the window forming member of the embodiment. [Figure 5] A photograph showing the experimental results using the window forming member of the embodiment. [Figure 6] A photograph showing the experimental results using the window forming member of other embodiments. [Figure 7] It is a cross-sectional view showing the structure of a conventional window forming member.

Modes for Carrying Out the Invention

[0021] Hereinafter, a gas analysis device according to an embodiment of the present invention will be described with reference to the drawings.

[0022] <1. Overall Structure> The gas analyzer 100 of this embodiment analyzes the components in a sample gas using, for example, non-dispersive infrared absorption spectroscopy (NDIR). The sample gas could be a material gas used in semiconductor manufacturing processes or exhaust gas emitted from an internal combustion engine.

[0023] Specifically, as shown in Figure 1, the gas analyzer 100 comprises an optical measurement cell 2 into which the sample gas is introduced, a light irradiation unit 3 that irradiates the optical measurement cell 2 with infrared light, a light detection unit 4 that detects the infrared light that has passed through the optical measurement cell 2, and a concentration calculation unit 5 that calculates the component concentration in the sample gas using the light intensity signal obtained by the light detection unit 4.

[0024] The optical measurement cell 2 has a pair of light-transmitting windows W1 and W2 that allow infrared light to pass through, and is a flow cell type in which the sample gas is introduced from the introduction port P1 and discharged from the outlet port P2.

[0025] Specifically, the optical measurement cell 2 comprises a cell body 21 provided with an input port P1 and an output port P2, and a window-forming member 22 fixed to the cell body 21 and having a window material 221 that forms light-transmitting windows W1 and W2. The detailed structure of the window-forming member 22 of the optical measurement cell 2 will be described later.

[0026] The light irradiation unit 3 irradiates the optical measurement cell 2 with infrared light, and is, for example, an infrared lamp. Alternatively, it may be an LED that emits infrared light. The infrared light emitted from this light irradiation unit 3 passes through one of the light-transmitting windows W1 of the optical measurement cell 2, through the internal space of the optical measurement cell 2, and through the other light-transmitting window W2, where it is detected by the light detection unit 4.

[0027] The photodetector 4 detects infrared light that has passed through the optical measurement cell 2. It includes a photodetector 41 that detects infrared light emitted from the other light-transmitting window W2 of the optical measurement cell 2, and a wavelength-selective filter 42 provided in the optical path between the other light-transmitting window W2 and the photodetector 41, which allows only a portion of the infrared light wavelengths to pass through. The light intensity signal obtained by the photodetector 41 is output to the density calculation unit 5.

[0028] The concentration calculation unit 5 calculates the concentration of a predetermined component in the sample gas using the light intensity signal obtained by the photodetector 41. Specifically, the concentration calculation unit 5 calculates the absorbance from the light intensity signal and determines the partial pressure of the predetermined component in the sample gas based on the absorbance and a calibration curve that has been created in advance and recorded in memory. Then, the concentration calculation unit 5 calculates the concentration of the predetermined component (= partial pressure of the predetermined component / total pressure of the sample gas) based on the total pressure of the sample gas in the optical measurement cell 2, which is measured by a pressure gauge (not shown) installed in the optical measurement cell 2 or the piping before and after it. The concentration calculation unit 5 is operated by a computer consisting of, for example, a CPU, memory, AD converter, input / output interface, etc.

[0029] <2. Detailed structure of the window-forming member 22 of the optical measurement cell 2> Next, the detailed structure of the window-forming member 22 of the optical measurement cell 2 will be described. Since the detailed structure of the window-forming member 22 that forms one of the light-transmitting windows W1 and the detailed structure of the window-forming member 22 that forms the other light-transmitting window W2 are the same or similar, the detailed structure of the window-forming member 22 that forms one of the light-transmitting windows W1 will be described as representative below.

[0030] As shown in Figures 2 and 3, the window-forming member 22 has a flat window material 221 that forms a light-transmitting window W1 and a flange member 222 that supports the window material 221 by joining them, and is also called a flanged observation window. Here, "flat" refers not only to a completely flat plate, but also to a spherical or aspherical plano-convex lens shape, or a wedge shape with a wedge angle.

[0031] The window material 221 is formed from a material that transmits infrared light and is a flat plate that forms a circular shape in plan view. The window material 221 in this embodiment transmits infrared light with a long wavelength of 7 μm or more, and in this embodiment it is formed from zinc selenide (ZnSe).

[0032] As shown particularly in Figure 3, the flange member 222 has a cylindrical joint support portion 222a that supports the window material 221, and a flange portion 222b that is continuously provided to the joint support portion 222a so as to surround the window material 221. In addition, a through hole H1 is formed in the central part of the flange member 222 through which infrared light that has passed through the window material 221 passes. Furthermore, in this embodiment, the joint support portion 222a and the flange portion 222b are integrally formed.

[0033] The joint support portion 222a supports the main surface (flat portion) of the window material 221, and in this embodiment, it has a cylindrical shape.

[0034] The flange portion 222b has a joining support portion 222a on one of its surfaces and, in this embodiment, has an annular shape. This flange portion 222b is attached to the cell body 21 via, for example, a metal gasket (not shown), and the mounting surface of the flange portion 222b to the cell body 21 has an ICF standard knife edge portion 222x formed thereon. In addition, the flange portion 222b has multiple through holes 222h formed in the circumferential direction for screw fixing to the cell body 21.

[0035] In the above-described configuration, a method for airtightly joining the window material 221 and the flange member 222 could be to join these members by means of adhesive, brazing, or the like. However, when using adhesives, concerns arise regarding degassing from the adhesive, deterioration due to corrosive gases, and cracking of the window material 221 due to the difference in thermal expansion coefficients between the window material 221 and the flange member 222. Furthermore, if brazing is to be performed, the brazing material cannot be used if it contains silver or copper, as this would constitute metal contamination in the semiconductor process. In that case, there is no brazing material suitable for the window material 221 made of zinc selenide. Even if a usable brazing material were available, there would be concerns about cracking of the window material 221, similar to adhesives.

[0036] Therefore, the window-forming member 22 in this embodiment is constructed by joining the window material 221 and the flange member 222 by atomic diffusion bonding.

[0037] Atomic diffusion bonding is a method of joining two members by interposing a metal film between the joining surfaces of each member and applying pressure to these members. In this embodiment, the window material 221 and the flange member 222 are pressure-bonded via a thin metal film M, such as an Au film of several hundred nanometers in size.

[0038] Incidentally, as mentioned above, the window-forming member 22, which is formed by atomic diffusion bonding of the window material 221 and the flange member 222, is affected by thermal influences during the process. Therefore, if the difference between the thermal expansion coefficient of the window material 221 and the thermal expansion coefficient of the flange member 222 is large, the window material 221 may bend or the flange member 222 may undergo thermal deformation, potentially causing cracks in the window material 221.

[0039] Therefore, the window-forming member 22 of this embodiment is configured such that the ratio of the thermal expansion coefficient of the flange member 222 to the thermal expansion coefficient of the window material 221 is 0.5 times or more and 1.5 times or less, and more preferably this ratio is 0.66 times or more and 1.5 times or less. The thermal expansion coefficients described below are values ​​obtained by measuring the length of a sample when the temperature is changed, known values ​​listed in, for example, the Science Almanac, or values ​​measured according to, for example, the standards listed below. ·JIS K 0129 General rules for thermal analysis

[0040] More specifically, the window material 221 in this embodiment is made of zinc selenide (ZnSe), as described above, and its coefficient of thermal expansion is 7.1 × 10⁻⁶. -6Since it is / K, in view of the above ratio, the flange member 222 of this embodiment is made of titanium, and its coefficient of thermal expansion is 8.9 × 10 -6 It is / K. Furthermore, the flange member 222 has a thermal expansion coefficient of 11.3 × 10 -6 Experimental results have shown that when Hastelloy with a / K rating is used, cracks occur in the window material 221.

[0041] Next, an example of a method for joining the window material 221 and flange member 222 described above will be explained with reference to Figure 4.

[0042] First, as shown in Figure 4, a thin metal film M is formed on the joint surface T1, which is the opposing surface of the window material 221 and the flange member 222 (S1). In this embodiment, the thin metal film M is formed by sputtering onto the joint surface T1.

[0043] Then, the bonding surfaces T1 on which the thin metal film M is provided are brought facing each other (S2), and the window material 221 and flange member 222 are pressed in opposing directions to atomic diffusion bonding (pressure bonding) (S3).

[0044] In this way, the window material 221 and the flange member 222 are atomically diffuse-bonded to form the window-forming member 22.

[0045] In the window-forming member 22 configured in this way, as shown in Figure 3, the joint portion between the window material 221 and the joint support portion 222a is configured to be less susceptible to thermal stress due to the thermal expansion of the flange portion 222b. Specifically, on the flange portion 222b, an annular groove 222M is formed on the side facing the joint support portion 222a (the side opposite to the mounting surface), surrounding the joint support portion 222a. Here, the groove 222M is an annular shape formed coaxially with the joint support portion 222a. The depth of this groove 222M can be, for example, more than half the thickness of the flange portion 222b.

[0046] Here, the wall thickness (thickness) of the inner wall portion 222K located inside the groove 222M in the flange member 222 is configured to be smaller than the wall thickness (thickness) of the joint support portion 222a. In this way, by increasing the wall thickness of the joint support portion 222a and decreasing the wall thickness of the inner wall portion 222K, the joining area between the window material 221 and the joint support portion 222a can be increased, while thermal stress due to the thermal expansion of the flange portion 222b can be less likely to be applied to the joint portion between the window material 221 and the joint support portion 222a.

[0047] Furthermore, by providing the groove 222M in this manner, it is possible to reduce the transmission of distortion of the flange member 222 that occurs when the flange member 222 is attached to another member, for example with screws, to the joint between the window material 221 and the joint support portion 222a.

[0048] <3. Effects of this embodiment> With the gas analyzer 100 of this embodiment configured in this way, since the window material 221 is atomically diffuse-bonded to the flange member 222, various performance requirements such as airtightness and heat resistance can be met between them. Furthermore, since the ratio of the thermal expansion coefficient of the flange member 222 to the thermal expansion coefficient of the window material 221 is close, cracking of the window material 221 can be prevented.

[0049] The photograph in Figure 5 shows the results of an experiment to determine whether or not cracks occur in the window material after atomic diffusion bonding the window material to the flange member at 120°C and then cooling to room temperature. As can be seen from these experimental results, when the window material is made of zinc selenide and the flange member is made of Hastelloy (left side of Figure 5), cracks occur in the window material due to the difference in the thermal expansion coefficients of these materials. In contrast, as in this embodiment, when the window material is made of zinc selenide and the flange member is made of titanium (right side of Figure 5), no cracks occur in the window material.

[0050] Furthermore, since the window material 221 is made of zinc selenide, which has a low coefficient of thermal expansion, it is useful for analysis in the long wavelength range (e.g., 7 μm or more).

[0051] <4. Other Embodiments> For example, in the above embodiment, the window-forming member 22 was composed of a window material 221 made of zinc selenide and a flange member 222 made of titanium, but it may also be composed of a window material 221 made of zinc selenide and a flange member 222 made of stainless steel invar. The coefficient of thermal expansion of stainless steel invar is 5.0 × 10⁻⁶. -6 The value is / K. Even when these material combinations are used, it can be seen that no cracks occur in the window material, as shown in Figure 6.

[0052] Furthermore, the window-forming member 22 may be composed of a window material 221 made of sapphire and a flange member 222 made of titanium or stainless steel invar.

[0053] Furthermore, the window-forming member 22 may be composed of a window material 221 made of barium fluoride (BaF2) and a flange member 222 made of stainless steel or nickel. The thermal expansion coefficient of barium fluoride (BaF2) is 18.1 × 10⁻⁶. -6 The coefficient of thermal expansion for stainless steel (SUS316) is 16.0 × 10⁻¹⁰. -6 The coefficient of thermal expansion of nickel is 13.3 × 10⁻⁶ / K, and the coefficient of thermal expansion of nickel is 13.3 × 10⁻⁶. -6 It is / K.

[0054] The transmission wavelength of zinc selenide is 0.5 to 22 μm, and the transmission wavelength of barium fluoride is 0.15 to 12 μm. Both transmit long-wavelength infrared light (e.g., 7 μm or longer), making them useful for analysis in the long-wavelength range.

[0055] In the above embodiment, the window material 221 and the flange member 222 were atomically diffuse-bonded, but these members may be joined by, for example, welding, soldering, brazing, adhesive, anodic bonding, or by applying a surface activation method to join the members by interfacial activation using ion milling or the like.

[0056] Furthermore, although an Au thin film was used as the metal thin film M for atomic diffusion bonding in the above embodiment, the metal thin film is not limited to this, and may be a thin film made of Al, Cr, or the like, for example.

[0057] Although the optical measurement cell 2 in the above embodiment had a pair of light-transmitting windows W1 and W2, it may also have a configuration with one light-transmitting window. In this case, light is incident and emitted through the single light-transmitting window. Furthermore, the optical measurement cell 2 may also have a configuration with three or more light-transmitting windows.

[0058] In the above embodiment, the joint support portion 222a and the flange portion 222b were integrally formed, but they may be separate parts.

[0059] Although the window material 221 in the above embodiment was circular in plan view, it may also be other shapes, such as rectangular in plan view.

[0060] In addition, although the gas analyzer in the above embodiment used non-dispersive infrared absorption spectroscopy (NDIR), it may also use Fourier transform infrared spectroscopy (FTIR), or an optical analysis method using light other than infrared light. Furthermore, the optical analyzer of the present invention may analyze liquids as well as gases as samples.

[0061] Furthermore, various modifications and combinations of the embodiments are permitted, as long as they do not contradict the spirit of the present invention. [Explanation of Symbols]

[0062] 100...Gas analyzer (optical analyzer) 2. Cells for optical measurement 3. Light irradiation section 4. Light detection unit 5...Concentration calculation section W1, W2... Translucent windows 221... Window materials 222a...Joint support part 222b...Flange section T1...joint surface M...metal thin film

Claims

1. An optical measurement cell having a light-transmitting window into which a sample is introduced, The cell comprises a window material that forms the light-transmitting window and a flange member that fixes the window material to the cell body. The flange member has a flange portion fixed to the cell body and a cylindrical joining support portion extending on the side opposite to the mounting surface of the flange portion to the cell body. The window material is joined to the tip surface of the joint support portion by atomic diffusion bonding via a thin metal film. An optical measuring cell characterized in that the ratio of the thermal expansion coefficient of the flange member to the thermal expansion coefficient of the window material is 0.5 times or more and 1.5 times or less.

2. The optical measuring cell according to claim 1, wherein the window material is made of zinc selenide or sapphire, and the flange member is made of titanium or stainless steel invar.

3. The optical measuring cell according to claim 1, wherein the window material is made of barium fluoride and the flange member is made of stainless steel or nickel.

4. An optical measuring cell according to any one of claims 1 to 3, A light irradiation unit that irradiates light onto the optical measurement cell, A light detection unit for detecting light transmitted through the optical measurement cell, An optical analyzer comprising: a concentration calculation unit that calculates the concentration of a component in a sample using the light intensity signal obtained by the light detection unit.

5. A method for manufacturing an optical measurement cell having a light-transmitting window through which a sample is introduced, The optical measuring cell comprises a window material that forms the light-transmitting window and a flange member that fixes the window material to the cell body. The flange member has a flange portion fixed to the cell body and a cylindrical joining support portion extending on the side opposite to the mounting surface of the flange portion to the cell body. In cases where the ratio of the thermal expansion coefficient of the flange member to the thermal expansion coefficient of the window material is 0.5 or more and 1.5 or less, A method for manufacturing an optical measuring cell, characterized by atomic diffusion bonding the window material and the flange member.

6. A window-forming member used in an optical measurement cell into which a sample is introduced, A window material that forms a light-transmitting window, The window material is provided with a flange member for fixing it to the cell body, The flange member has a flange portion fixed to the cell body and a cylindrical joining support portion extending on the side opposite to the mounting surface of the flange portion to the cell body. The window material is joined to the tip surface of the joint support portion by atomic diffusion bonding via a thin metal film. A window-forming member characterized in that the ratio of the thermal expansion coefficient of the flange member to the thermal expansion coefficient of the window material is 0.5 times or more and 1.5 times or less.

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