Concentration measuring device

Abstract

Accurately measure the concentration of hydrogen peroxide gas. [Solution] The device comprises a measuring cell provided with a transmissive window, a first sensor that measures the temperature of the gas and generates a first electrical signal, a second sensor that measures the pressure of the gas and generates a second electrical signal, a first photodetector that converts the amount of light of a predetermined wavelength incident on the gas from the transmissive window into a fourth electrical signal, a second photodetector that receives the amount of light that has passed through the gas and exits the transmissive window into a fifth electrical signal, and a calculation unit that calculates the gas concentration based on the first electrical signal, the second electrical signal, the fourth electrical signal, and the fifth electrical signal.

Description

Technical Field

[0001] The present invention relates to a concentration measuring device, and more particularly to a concentration measuring device for accurately measuring the concentration of hydrogen peroxide gas.

Background Art

[0002] First, the background of hydrogen peroxide utilization will be explained. In general industrial fields and medical fields where high-temperature and high-humidity steam sterilization cannot be used, hydrogen peroxide gas is used as a room-temperature or low-temperature sterilization treatment. In the sterilization treatment field, sterilization treatment with hydrogen peroxide gas has advantages such as being easy to handle, being easily soluble in water, and becoming non-toxic oxygen and water when decomposed. However, hydrogen peroxide gas may corrode the object by condensing on the surface of the object. In addition, since hydrogen peroxide gas is highly reactive and unstable, the concentration in the sterilization chamber may become non-uniform, resulting in an insufficient sterilization effect.

[0003] In the semiconductor manufacturing field, concentration management of oxidants used in processes such as film formation of insulating oxide films that affect the performance of semiconductor devices during the production process of semiconductor devices is very important. Although hydrogen peroxide gas has high oxidizing power and merits as an oxidant when used, its high reactivity causes problems with the attenuation of hydrogen peroxide gas concentration in the supply piping from the hydrogen peroxide gas generation source to the film formation apparatus. In particular, when supplying hydrogen peroxide gas from one hydrogen peroxide generator to multiple film formation apparatuses to ensure production volume, the supply piping lengths may differ due to physical layout constraints, and there have been problems such as the hydrogen peroxide gas being decomposed before reaching the film formation apparatus and variations in the hydrogen peroxide gas concentration at each film formation apparatus use point. Therefore, there is a desire to perform concentration management at the nearest use point of each film formation apparatus.

[0004] Next, let's explain the importance of concentration control. Hydrogen peroxide exists as a liquid under normal temperature and pressure conditions. To use hydrogen peroxide as a gas, it needs to be generated and transported under heating conditions. However, as mentioned above, hydrogen peroxide gas is unstable due to its high oxidizing power and reactivity, and the problem is that it decomposes if the temperature rises too high. Therefore, temperature control and concentration measurement are extremely important when using hydrogen peroxide gas.

[0005] The conventional technique for measuring hydrogen peroxide gas concentration is described, and a measuring device is known that measures the hydrogen peroxide gas concentration in a hydrogen peroxide gas fluid at a temperature of 100 to 200°C and a concentration of 5,000 to 20,000 ppm, comprising: a sampling path branching off from a hydrogen peroxide gas transport pipe; a catalyst case containing a hydrogen peroxide decomposition catalyst layer located immediately adjacent to the transport pipe side within the sampling path; gas temperature measuring instruments arranged on the gas inlet and outlet sides of the catalyst case; and a calculation device that calculates the hydrogen peroxide gas concentration from the temperature difference between the gas inlet and outlet sides (see, for example, Patent Document 1 (pages 5-7)).

[0006] Furthermore, a method for determining the concentration of hydrogen peroxide vapor or gas within a certain containment area is known, comprising the steps of: reducing the pressure of the containment area to evacuate it; introducing hydrogen peroxide into the containment area to form a sample; measuring the absorbance of the sample at wavelengths between 200 nanometers and 400 nanometers; and determining the concentration of hydrogen peroxide vapor or gas in the sample based on the absorbance (see, for example, Patent Document 2 (pages 3-4)).

[0007] Patent documents 1 and 2 employ methods for measuring hydrogen peroxide gas concentration from the heat of reaction between hydrogen peroxide and a catalyst, or from absorbance at wavelengths between 200 nanometers and 400 nanometers. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2014-020826 [Patent Document 2] Japanese Patent Application Publication No. 11-230899 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, in applications involving sterilization or disinfection, problems arose because hydrogen peroxide gas was not uniformly dispersed within the treatment chamber, preventing the target concentration of hydrogen peroxide gas from reaching the vicinity of the object to be sterilized or disinfected. As a result, the desired sterilization or disinfection effect could not be achieved.

[0010] Furthermore, controlling the concentration of oxidizing agents used in processes such as the deposition of insulating oxide films, which significantly impact device performance, is crucial in the semiconductor device production process. While hydrogen peroxide gas offers advantages as an oxidizing agent due to its high oxidizing power, its high reactivity leads to problems with attenuation within the supply piping from the hydrogen peroxide source to the deposition equipment. In particular, when supplying hydrogen peroxide gas from a single hydrogen peroxide generator to multiple deposition equipment to ensure sufficient production volume, physical placement constraints may result in different supply piping lengths for each unit. Therefore, there is a demand for concentration control at the immediate use point of each deposition equipment, but conventional technology has been unable to meet this requirement.

[0011] Furthermore, as mentioned above, hydrogen peroxide gas is unstable due to its high oxidizing power and reactivity, and it decomposes if the temperature rises too high. Therefore, temperature control and concentration measurement are extremely important when using hydrogen peroxide gas, but conventional technology has the problem of not being able to control the temperature and measure the concentration.

[0012] The present invention has been made in view of these problems, and its objective is to provide a concentration measuring device for accurately measuring the concentration of hydrogen peroxide gas by measuring the absorbance, temperature, and pressure of hydrogen peroxide gas. [Means for solving the problem]

[0013] A concentration measuring device according to one aspect of the present invention includes a measuring cell through which hydrogen peroxide gas flows, a first sensor that measures the temperature of the hydrogen peroxide gas and generates a first electrical signal, a second sensor that measures the pressure of the hydrogen peroxide gas and generates a second electrical signal, a third sensor that measures the temperature of a constant temperature block and generates a third electrical signal, a constant temperature block having a heater for heating the constant temperature block, an insulating material enclosing the constant temperature block, a light source that emits wavelengths for measuring the concentration of hydrogen peroxide gas, and a device that converts the amount of light emitted by the light source into a fourth electrical signal. The device includes a first light-receiving element, a second light-receiving element that converts the amount of light transmitted through hydrogen peroxide gas flowing through the measurement cell into a fifth electrical signal, a distributor that splits the light emitted from the light source into light directed toward the first light-receiving element and light directed toward the second light-receiving element, and an embedded system provided on the outside of the insulating material, which includes a control unit that controls the heater based on a third electrical signal, and a calculation unit that calculates the concentration of hydrogen peroxide gas based on the first electrical signal, the second electrical signal, the fourth electrical signal, and the fifth electrical signal.

[0014] This configuration makes it possible to accurately measure the hydrogen peroxide gas concentration while maintaining a predetermined temperature.

[0015] Another aspect of the present invention is a measuring cell suitable for a concentration measuring device according to one aspect of the present invention. The measuring cell in this aspect comprises a measuring gas channel for introducing hydrogen peroxide gas into the measuring cell, a first transmissive window through which light enters the measuring cell, a cell spacer for determining the optical path length, and a first transmissive window housing a second transmissive window through which light not absorbed by the hydrogen peroxide gas introduced into the measuring cell exits, a second cell block sandwiching the first transmissive window, the cell spacer, and the second transmissive window with the first cell block, a first O-ring disposed between the first transmissive window and the second cell block, and a second O-ring disposed between the second transmissive window and the first cell block.

[0016] This configuration of the measurement cell makes it possible to prevent a decrease in the airtightness of the measurement cell due to temperature changes outside the measurement cell, pressure fluctuations of the measurement gas, or deterioration of the measurement cell due to reactions between the measurement cell and the measurement gas, thereby enabling accurate measurement of hydrogen peroxide gas concentration.

[0017] A concentration measuring device according to one aspect of the present invention comprises: a measuring cell through which gas flows and which is provided with a transmission window; a first sensor that measures the temperature of the gas and generates a first electrical signal; a second sensor that measures the pressure of the gas and generates a second electrical signal; a first photodetector that converts the amount of light of a predetermined wavelength incident toward the gas from the transmission window into a fourth electrical signal; a second photodetector that receives the amount of light that has passed through the gas and exits from the transmission window into a fifth electrical signal; and a built-in system that calculates the gas concentration according to the Lambert-Beer law based on the first electrical signal, the second electrical signal, the fourth electrical signal, and the fifth electrical signal.

[0018] This configuration makes it possible to accurately measure the concentration of hydrogen peroxide gas. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a concentration measuring device and measuring cell capable of accurately measuring the hydrogen peroxide gas concentration. This makes it possible to perform appropriate concentration control to obtain sterilization or disinfection effects, which was not possible with conventional technology, and to control the concentration at the immediate use point of each film deposition device, thereby enabling strict control of the hydrogen peroxide gas concentration required for sterilization or disinfection treatment or film deposition in the semiconductor manufacturing process. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic diagram illustrating a concentration measuring device according to one aspect of the present invention. [Figure 2] This is a front view of a constant temperature block covered with an insulating material according to one embodiment of the present invention (the insulating material on the front is not shown). [Figure 3]It is a side view of a measurement cell according to an aspect of the present invention. [Figure 4] It is a schematic diagram for explaining a cross section of a conventional measurement cell. [Figure 5] It is a schematic diagram for explaining a cross section of a measurement cell according to an aspect of the present invention. [Figure 6] It is a schematic diagram for explaining a cross section of a measurement cell according to an aspect of the present invention. [Figure 7] It is a flowchart of the processing of a concentration measurement device according to an aspect of the present invention. [[ID=**15**]]**[Mode for Carrying Out the Invention]**

[0021] Hereinafter, aspects of the present invention will be described in detail by taking utilization in the semiconductor manufacturing field as an example while referring to the drawings. In the drawings, the same reference numerals represent the same elements.

[0022] The concentration measurement device of the present invention measures the concentration by Lambert-Beer's law from the ratio at which hydrogen peroxide gas absorbs ultraviolet light in a measurement cell, using the property that hydrogen peroxide gas absorbs ultraviolet light.

[0023] Particularly for the measurement of hydrogen peroxide gas, it is necessary to maintain a high temperature (for example, between 90°C and 200°C, for example, 120°C, etc.) so that the hydrogen peroxide gas does not condense, and the measurement cell is heated to a high temperature. Further, since the high-temperature measurement cell part and the concentration calculation circuit formed of semiconductor components coexist inside the concentration measurement device of the present invention, it is necessary to thermally insulate the semiconductor circuit, and heat separation and heat insulation of the electronic circuit are performed. Furthermore, since the atmosphere of the measurement environment varies depending on the process and the temperature or pressure changes, it is necessary to correct the pressure and temperature in order to display the hydrogen peroxide concentration in the standard state, and the concentration is displayed in the standard state.

[0024] Regarding the constant temperature control of the measurement cell at a high temperature, the measurement cell is covered with a material having high thermal conductivity (for example, aluminum, etc.) to form a constant temperature block, heated by a heater, and feedback control is performed by a temperature sensor for control.

[0025] This section describes thermal isolation and insulation of electronic circuits. The ultraviolet light source, incident light detector, transmitted light detector, amplifier circuit, control unit, and calculation unit are composed of semiconductor components, and the upper temperature limit of general-purpose components is approximately 80°C. Therefore, it is necessary to allow light for measuring ultraviolet absorption to pass through while preventing heat conduction and radiation from the high-temperature constant-temperature block. As a countermeasure, insulation material is applied to the entire outer surface of the constant-temperature block, except for the light transmission path, to maintain the temperature of the constant-temperature block and prevent heat transfer to the outside. Furthermore, an exhaust port is provided at the top of the enclosure, and an air intake port is provided at the bottom along the perimeter of the insulation material surrounding the constant-temperature block to prevent air stagnation and create a thermal insulation layer of air to block heat conduction from the high-temperature parts. A ventilation fan may also be provided at the exhaust port.

[0026] This section explains the display of concentration under standard conditions. Because the atmospheric conditions of the hydrogen peroxide gas measurement environment differ depending on the process, even if the temperature or pressure of the hydrogen peroxide gas changes, a correction temperature sensor and a pressure sensor are installed to measure the pressure and temperature of the hydrogen peroxide gas in the piping of the measurement gas flow path. By performing pressure and temperature correction according to the Lambert-Beer law, the display of hydrogen peroxide concentration under standard conditions of 0°C and 1 atm is always maintained. Standard conditions are merely an example, and the conditions used for comparison with the changed temperature or pressure do not necessarily have to be standard conditions; any other temperature or pressure is acceptable as long as it is under the same conditions that allow for comparison with the changed temperature or pressure.

[0027] Figure 1 is a schematic diagram illustrating a concentration measuring device according to one aspect of the present invention. For illustrative purposes, the concentration measuring device 100 according to one aspect of the present invention is located between, for example, a hydrogen peroxide gas supply device (not shown) that generates hydrogen peroxide gas and, for example, a semiconductor manufacturing apparatus (not shown) that uses the generated hydrogen peroxide gas. The concentration measuring device 100 measures the absorbance of the hydrogen peroxide gas and applies the Lambert-Beer law to the measured absorbance to continuously measure the hydrogen peroxide gas concentration.

[0028] The concentration measuring device 100 has a measuring cell 101 installed inside the concentration measuring device 100. The measuring cell 101 is used to measure the absorbance of hydrogen peroxide gas flowing inside the measuring cell 101. The concentration measuring device 100 has a measuring gas channel 102a attached to the measuring cell 101 for introducing hydrogen peroxide gas from an external hydrogen peroxide gas supply device (not shown) into the measuring cell 101. The concentration measuring device 100 also has a measuring gas channel 102b attached to the measuring cell 101 for discharging the hydrogen peroxide gas introduced from the measuring gas channel 102a to an external semiconductor manufacturing device (not shown). The concentration measuring device 100 has a temperature sensor 103 (also called the first sensor) attached to either the measuring cell 101, the measuring gas channel 102a, or 102b for measuring the temperature of the hydrogen peroxide gas flowing through the measuring cell 101, the measuring gas channel 102a, and 102b. The concentration measuring device 100 has a pressure sensor 104 (also called a second sensor) attached to either the measuring cell 101, the measuring gas flow path 102a, or 102b, which measures the pressure of the hydrogen peroxide gas flowing through the measuring cell 101, the measuring gas flow path 102a, and 102b.

[0029] In Figure 1, the temperature sensor 103 is attached to the measuring gas flow path 102a, but a temperature sensor 1031 may be attached to the constant temperature block 105, which will be described next. Also, in Figure 1, the pressure sensor 104 is attached to the measuring gas flow path 102a, but a pressure sensor 1041 or pressure sensor 1042 may be attached to the piping from the hydrogen peroxide gas supply device (not shown) to the concentration measuring device 100 or from the concentration measuring device 100 to the semiconductor manufacturing equipment (not shown). The positions of the temperature sensor 103 and the pressure sensor 104 are not limited to those shown in Figure 1.

[0030] The concentration measuring device 100 has a constant temperature block 105 inside the concentration measuring device 100 that encloses the measuring cell 101 and maintains the temperature of the measuring cell 101 at a constant level. The concentration measuring device 100 has a temperature sensor 106 (also called a third sensor) mounted on the outside of the constant temperature block 105 inside the concentration measuring device 100 to measure the temperature of the constant temperature block 105. The concentration measuring device 100 also has a heater 107 (also called a warmer) mounted on the outside of the constant temperature block 105 inside the concentration measuring device 100 to heat the hydrogen peroxide gas passing through the measuring cell 101 to maintain a constant temperature. The positions of the temperature sensor 106 and heater 107 are such that they are directly attached to the constant temperature block in order to heat the constant temperature block and measure its temperature, and they do not need to be directly attached to the constant temperature block in order to heat the constant temperature block and measure its temperature; their positions may differ from those shown in Figure 1.

[0031] The concentration measuring device 100 has an insulating material 108 that is installed inside the concentration measuring device 100 so as to cover the entire constant temperature block 105, including the heater 107, and blocks heat dissipation from the constant temperature block 105 to keep the inside of the measuring cell 101 warm. The insulating material 108 prevents heat from the heater 107 from being transferred to the surrounding electronic circuits.

[0032] The concentration measuring device 100 has a light source lamp 109 (also called a light source) installed inside the concentration measuring device 100 that emits light of the wavelength necessary to measure the absorbance of hydrogen peroxide gas. The concentration measuring device 100 has a transmission window 110a installed inside the measuring cell 101 that transmits the light emitted from the light source lamp and causes it to enter the measuring cell 101. The concentration measuring device 100 also has a transmission window 110b installed inside the measuring cell 101 that transmits the light that has passed through the hydrogen peroxide gas from the measuring cell 101. Note that if the measuring cell 101 itself is made of a material that transmits light of the wavelength in the absorption band of hydrogen peroxide, such as glass, the transmission windows 110a and 110b are not necessarily required. The concentration measuring device 100 has a light distributor 113 (also called a distributor) installed inside the concentration measuring device 100 that reflects some of the light emitted from the light source lamp 109 and transmits some of it. The concentration measuring device 100 includes a photodetector 111 (also called the first photodetector) installed inside the concentration measuring device 100, which converts light reflected by the light distributor 113 into an electrical signal (also called the fourth electrical signal), and a photodetector 112 (also called the second photodetector) installed inside the concentration measuring device 100, which converts light that has passed through the light distributor 113 and through the hydrogen peroxide gas flowing in from the measurement gas channel 102a into an electrical signal (also called the fifth electrical signal).

[0033] The concentration measuring device 100 has a control unit 114 that controls the temperature of the constant temperature block 105 on the outside of the insulating material 108, and a calculation unit 115 that calculates the hydrogen peroxide gas concentration. The concentration measuring device 100 has intake ports 117a and 117b that are opened in the housing 116 of the concentration measuring device 100 to allow outside air to flow into the interior of the concentration measuring device 100. The concentration measuring device 100 also has an exhaust port 118 that is opened in the housing 116 of the concentration measuring device 100 to discharge the air inside the concentration measuring device 100. The exhaust port 118 may also have a ventilation fan.

[0034] The cooling region 121 represents the area inside the concentration measuring device 100 where outside air flows in through the intake ports 117a and 117b and flows out through the exhaust port 118 for ventilation, and the heat from the constant temperature block 105 is shielded by the insulating material 108, resulting in a region where the temperature is lower than that of the constant temperature block 105. The heat retention region 122 represents the area inside the constant temperature block 105, which is heated by the heater 107 and insulated by the insulating material 108.

[0035] Arrow 131 represents the path of light emitted from the light source lamp 109, passing through the light distributor 113, and incident on the hydrogen peroxide gas flowing in from the measurement gas channel 102a. Arrow 132 represents the path of light emitted from the light source lamp 109, reflected by the light distributor 113, and incident on the light receiving element 111.

[0036] Arrow 141a indicates the flow of hydrogen peroxide gas from an external hydrogen peroxide gas supply device (not shown) into the concentration measuring device 100. Arrow 141b indicates the flow of hydrogen peroxide gas from the inside of the concentration measuring device 100 to a semiconductor manufacturing device (not shown) outside the concentration measuring device 100.

[0037] Next, the calculation for determining the hydrogen peroxide gas concentration using the concentration measuring device 100 will be explained. The hydrogen peroxide gas supplied by the hydrogen peroxide gas supply device (not shown) flows into the measuring cell 101 via the measuring gas flow path 102a, for example, by pressurized air supply or suction. The hydrogen peroxide gas that flows into the measuring cell 101 flows inside the measuring cell 101 and is supplied to the semiconductor manufacturing apparatus (not shown) via the measuring gas flow path 102b.

[0038] While hydrogen peroxide gas flows through the measurement cell 101, the light emitted by the light source lamp 109 and transmitted through the light distributor 113 (indicated by arrow 131) enters the transmission window 110a. Only the light that is absorbed by the hydrogen peroxide gas and then transmitted is received by the light receiving element 112 and converted into a fifth electrical signal. The converted electrical signal is transmitted to the calculation unit 115.

[0039] Furthermore, the light emitted by the light source lamp 109 and reflected by the light distributor 113 is received by the light receiving element 111 and converted into a fourth electrical signal, which is then transmitted to the calculation unit 115. Since the light intensity of the light source 109 is not always constant, by measuring the light reflected by the light distributor 113 with the light receiving element 111 and correcting the measurement result of the light transmitted through the optical cell with the light receiving element 112 for fluctuations in light intensity, it becomes possible to measure the absorbance purely due to the light absorption by hydrogen peroxide.

[0040] While the hydrogen peroxide gas flows through the measuring cell 101, the heater 107 maintains its temperature at, for example, 120°C, between 90°C and 200°C, to prevent decomposition or condensation of the hydrogen peroxide gas. The heater 107 is controlled by the control unit 114 and the temperature sensor 106 to maintain a constant temperature in the adiabatic cell block, thereby maintaining a constant temperature condition.

[0041] While the hydrogen peroxide gas flows through the measuring cell 101, the temperature sensor 103 and pressure sensor 104 accurately measure the temperature and pressure, respectively, and the measured data (also called the first electrical signal and the second electrical signal, respectively) is transmitted to the calculation unit 115. The calculation unit 115 uses the electrical signals from the light-receiving elements 111 and 112 and the data from the temperature sensor 103 and pressure sensor 104 to calculate the hydrogen peroxide gas concentration using the following equation (1). C=A / αT*log(Io / Ix)*(273+t) / 273*Po / (P+Po) ...(1) however, C: Required hydrogen peroxide gas concentration, A: A constant specific to the device. α: UV absorption coefficient of hydrogen peroxide gas, T: Optical path length (representing the distance the light emitted from the light source lamp 109 travels through the hydrogen peroxide gas inside the measurement cell 101). Io: Amount of light incident on measurement cell 101, Ix: Transmitted light amount of measurement cell 101, t: Temperature of hydrogen peroxide gas, Po: 1 atmosphere, P: Pressure of hydrogen peroxide gas The formula is as follows: log(Io / Ix) represents the absorbance. The relationship between the amount of light measured by each photodetector and the absorbance is as follows:

[0042] To measure the incident and transmitted light in the Lambert-Beer equation, a standard gas without hydrogen peroxide is first passed through the measurement cell (in Figure 1, the source of the standard gas and the switching valve for switching are not shown for the sake of simplicity in the drawing). Let S11 be the amount of light from the photodetector 111 measured against the passed standard gas, and S21 be the amount of light from the photodetector 112 measured simultaneously. S11 and S21 are stored in a memory device.

[0043] Next, the hydrogen peroxide gas to be measured is passed through the measurement cell. The light intensities measured by the photodetectors 111 and 112 for the passed hydrogen peroxide gas are denoted as S12 and S22, respectively. Here, S21, measured when hydrogen peroxide is not present, is taken as the incident light in equation (1). Then, by correcting the change from S11 to S12 measured by the photodetector 111 (the change in the light intensity of the light source) for S22 after passing the hydrogen peroxide gas through, it becomes possible to measure the absorbance of hydrogen peroxide gas without being affected by the change in the light intensity of the light source. The formula for calculating absorbance: log(Io / Ix) is as follows. log(Io / Ix)=log((S21 / (S22×S11 / S12))...(2) By substituting the absorbance obtained using equation (2) into Lambert-Beer equation (1), it becomes possible to accurately measure the hydrogen peroxide gas concentration without being affected by fluctuations in the light source.

[0044] By repeating the above steps, continuous measurement becomes possible.

[0045] The measuring cell 101 may, for example, have a housing made of a metal material. The metal material may be, for example, stainless steel. Details of the measuring cell 101 are described below with reference to Figures 3 to 5. The measuring gas flow paths 102a and 102b must be made of a material that is corrosion-resistant to highly reactive hydrogen peroxide gas and in which hydrogen peroxide does not easily decompose.

[0046] The measuring gas channels 102a and 102b may, for example, be made of fluororesin. The fluororesin may be, for example, PFA (perfluoroalkoxyalkane) resin, or a similar material suitable for flowing gases whose concentration is to be measured. Furthermore, measuring gas channels 102a and 102b may be the same or different. Measuring gas channels 102a and 102b may be an integrated channel. Measuring gas channels 102a and 102b may be made of, for example, glass.

[0047] The temperature sensor 103 measures t in equation (1) described above. Temperature sensors 103 and 106 may, for example, be platinum resistance thermometers. Alternatively, temperature sensors 103 and 106 may be copper resistance thermometers, for example.

[0048] The pressure sensor 104 may, for example, be a strain gauge type pressure sensor. Alternatively, the pressure sensor 104 may be a piezoelectric pressure sensor, a silicon pressure sensor, or the like.

[0049] The heater 107 is a heating device, and the heating device may be, for example, a resistance heater.

[0050] The thermal insulation material 108 may, for example, be melamine. As an example, melamine is a thermosetting foam material having open or discontinuous cells and is excellent in flame retardancy, heat resistance, and thermal insulation. Furthermore, the thermal insulation material 108 may be a thermal insulation material with heat resistance of 120°C or higher.

[0051] The light source lamp 109 may, for example, be an excimer lamp. Alternatively, the light source lamp 109 may be, for example, an LED, a mercury lamp, a deuterium lamp, a zinc lamp, a cadmium lamp, or any similar lamp suitable for emitting light at wavelengths covering the absorption band of hydrogen peroxide (e.g., 200-400 nm).

[0052] The transmissive windows 110a and 110b may, for example, be quartz glass. Alternatively, the transmissive windows 110a and 110b may be, for example, sapphire glass, or a similar material suitable for transmitting light of wavelengths within the absorption band of hydrogen peroxide gas.

[0053] The light-receiving elements 111 and 112 may, for example, be photodiodes. Alternatively, the light-receiving elements 111 and 112 may be similar devices that are sensitive to the absorption band of hydrogen peroxide, such as photocells, photomultiplier tubes, or silicon photodiodes.

[0054] The optical distributor 113 is, for example, quartz glass, which may be coated with, for example, a metal oxide, aluminum, nickel-chromium, etc., to control its transmittance and reflectance.

[0055] The control unit 114 and the arithmetic unit 115 may be included in an embedded system 120, which may include, for example, a microcontroller (MCU). The embedded system 120 described above is composed of, for example, a semiconductor integrated circuit, which includes a processor and memory, and executes computer programs, such as operating systems and application software, stored in, for example, memory. The processor described above may be a general-purpose processor, such as an MPU (microprocessor) or a CPU (central processing unit). The memory described above may be a storage device, such as a ROM (Read Only Memory), PROM (Programmable ROM), EPROM (Erasable Programmable ROM), EEPROM (Electrically EPROM), RAM (Random-Access Memory), DRAM (Dynamic RAM), or SRAM (Static RAM).

[0056] The control unit 114 receives data (also called the third electrical signal) regarding the temperature of the constant temperature block 105 measured by the temperature sensor 106. If the temperature indicated by the received data is lower than a preset temperature, the control unit 114 starts energizing the heater 107 to warm the constant temperature block 105. If the temperature indicated by the received data is higher than a preset temperature, the control unit 114 stops energizing the heater 107. The operation of the calculation unit 115 will be explained in detail with reference to Figure 7.

[0057] The housing 116 may, for example, be made of a metal material, which may be, for example, stainless steel.

[0058] The intake ports 117a and 117b allow outside air to flow into the concentration measuring device 100. The intake ports 117a and 117b have a position and shape suitable for allowing outside air to flow into the concentration measuring device 100 to provide insulation between the constant temperature block 105 and the electronic circuit including the control unit 114 and the calculation unit 115. The shape of the intake ports 117a and 117b can be various shapes, such as slits. Furthermore, if the exhaust port 118 has a ventilation fan, for example, the ventilation fan can forcibly draw outside air into the concentration measuring device 100.

[0059] The exhaust port 118 may have a ventilation fan, such as a cooler fan, that is suitable for drawing outside air into the concentration measuring device 100 and expelling the air inside the concentration measuring device 100 to the outside.

[0060] All of the above is for illustrative purposes only and is not limited to all of the above.

[0061] Figure 2 is a front view of a constant temperature block 105 having a measuring cell 101 inside a thermal insulation material 108 according to one aspect of the present invention, where the thermal insulation material 108 on the front is not shown. In Figure 2, the constant temperature block 105 includes temperature sensors 103, 106, and a heater 107, which were described with reference to Figure 1. The positions of the temperature sensors 103, 106, and heater 107 shown in Figure 2 are different from those of the temperature sensors 103, 106, and heater 107 shown in Figure 1, as long as the temperature sensing part of the temperature sensor is directly attached to the surface of the constant temperature block and the heating surface of the heater is directly attached to the surface of the constant temperature block.

[0062] Figure 3 is a side view of a measuring cell 101 according to one embodiment of the present invention. The measuring cell 101 is incorporated into a constant temperature block 105. In Figure 3, the measuring cell 101 has measuring gas flow paths 102a, 102b and a permeable window 110b, as described with reference to Figure 1. The measuring cell 101 also has a fixing plate 505a and fixing screws 506a, 506b, which will be described later with reference to Figure 5.

[0063] Figure 4 is a schematic diagram illustrating a cross-section of a conventional measurement cell 400. Arrow 431 indicates the path of light emitted from a light source lamp (not shown) and incident on the measurement gas flowing in from the measurement gas channel 421.

[0064] The conventional measuring cell 400 houses a conventional transmission window 410b, a conventional cell spacer 403 that determines the optical path length indicated by arrow 411, and a conventional transmission window 410a in that order inside the receiving conventional cell block 401, and is sandwiched by the cover conventional cell block 402. The conventional cell blocks 401 and 402 are fixed by fixing plates 405a and 405b which are fixed by fixing screws 406a and 406b, as illustrated in Figure 4. The structure seals the flow path of the measuring gas by placing O-rings 404b and 404a between each of the conventional transmission windows 410b and 410a and the conventional cell blocks 401 and 402.

[0065] However, in the conventional measuring cell 400, the structure seals the space between the cell block and the permeable window with only an O-ring. As a result, the O-rings 404a and 404b deteriorate elastically due to external temperature changes, pressure fluctuations of the measuring gas, and deterioration due to reactions with the measuring gas, leading to problems such as loss of airtightness.

[0066] The inventors of this application have succeeded in resolving problems such as loss of airtightness due to elastic deterioration of O-rings 404a and 404b by newly developing a measuring cell 101 according to one aspect of the present invention. Next, the structure of the measuring cell 101 of the present invention will be described with reference to Figure 5.

[0067] Figure 5 is a schematic diagram illustrating a cross-section of a measuring cell 101 according to one aspect of the present invention.

[0068] A measuring cell 101 according to one aspect of the present invention has a structure in which a transmissive window 110b, a cell spacer 503 that determines the optical path length indicated by the arrow 511, and a transmissive window 110a are housed in that order inside the receiving cell block 501, and are sandwiched by a cover cell block 502. The structure seals the flow path of the measuring gas by placing O-rings 504b and 504a between each of the transmissive windows 110b and 110a and the cell blocks 501 and 502.

[0069] A measuring cell 101 according to one aspect of the present invention includes a measuring gas flow path 102a, a transmission window 110a (also called the first transmission window), and a transmission window 110b (also called the second transmission window), as described with reference to Figure 1, and a cell block 501 (also called the first cell block) and a cell block 502 (also called the second cell block), which will be described later. The measuring cell 101 has a cell spacer 503 that determines the optical path length indicated by the arrow 511. The measuring cell 101 has an O-ring 504a (also called the first O-ring) positioned between the cell block 502 and the transmission window 110a, and an O-ring 504b (also called the second O-ring) positioned between the cell block 501 and the transmission window 110b. The measuring cell 101 has fixing plates 505a and 505b positioned to sandwich the cell block 501 and the cell block 502 and fixed by fixing screws 506a and 506b. The measuring cell 101 has gap spacers 507a and 507b that maintain a constant distance between the fixed plate 505a and the fixed plate 505b.

[0070] Cell block 501 is the receiving cell block, and houses the permeable window 110b, cell spacer 503, and permeable window 110a in that order inside cell block 501. Cell block 502 is a cover cell block 502, and cell block 501 and cell block 502 sandwich the permeable window 110a, cell spacer 503, and permeable window 110b. By placing O-ring 504b between cell block 501 and permeable window 110b, and O-ring 504a between cell block 502 and permeable window 110a, the flow path of the measured gas is sealed.

[0071] In the measuring cell 101 according to one embodiment of the present invention illustrated in Figure 5, the transparent windows 110a and 110b have chamfered edges on their circular corners, the cell spacer 503 is made of an elastically deformable resin such as PTFE or PFA, and the opposing surfaces of the transparent windows 110a and 110b also have inclined surfaces along their circumferences. The fixing plates 505a and 505b are made of metal and are configured to sandwich the cell blocks 501 and 502, and are fixed by fixing screws 506a and 506b. The gap spacers 507a and 507b are made of metal and are inserted between the fixing plates 505a and 505b so that the distance between them remains constant. When tightening between the fixing plate 505a and the fixing plate 505b, the cell spacer 503 is deformed and tightened within the elastic deformation conditions that prevent the cell spacer 503 from buckling due to the lengths of the gap spacers 507a and 507b and the length of the cell spacer 503. By deforming and tightening the cell spacer 503, it is possible to maintain the sealing performance between the transmissive windows 110a and 110b and the cell spacer 503, while simultaneously maintaining a constant optical path length indicated by arrow 511 between the transmissive window 110a and the transmissive window 110b.

[0072] With this configuration, at the contact surface between the transmissive windows 110a and 110b and the cell spacer 503, the cell spacer 503 can form a new seal structure in addition to the seal structure formed by the O-rings 504a and 504b. Simultaneously with the formation of the new seal structure, it becomes possible to control the distance between the transmissive windows 110a and 110b by controlling the cell spacer 503, which is extremely important for measuring the absorbance of the gas being measured.

[0073] O-rings 504a and 504b are, for example, made of fluororubber and form the sealing structure of the present invention. Fluororubber, as an example, does not buckle and has excellent corrosion resistance.

[0074] Arrow 511 represents the optical path length for measuring the ultraviolet absorbance of hydrogen peroxide gas and corresponds to T in equation (1) explained with reference to Figure 1. The above optical path length is the distance between the transmission windows 110a and 110b. A portion of the light transmitted through transmission window 110a is absorbed by the hydrogen peroxide gas. The light not absorbed by the hydrogen peroxide gas passes through transmission window 110b. The light transmitted through transmission window 110b is received by the photodetector 112 shown in Figure 1.

[0075] Figure 6 is a schematic diagram illustrating another cross-section of a measuring cell 101 according to one aspect of the present invention. Light emitted from the light source lamp 109 (indicated by arrow 131) passes through the portion indicated by reference numeral 601.

[0076] Figure 7 is a flowchart of the processing of the concentration measuring device 100 according to one aspect of the present invention. The processing of the concentration measuring device 100 according to one aspect of the present invention begins when the power to the concentration measuring device 100 is turned on.

[0077] In step S701, the embedded system 120, as described with reference to Figure 1, turns on the light source lamp 109. The embedded system 120 also starts controlling the heater based on the temperature data (third electrical signal) of the constant temperature block 105 measured by the temperature sensor 106. The process proceeds to step S702.

[0078] In step S702, the standard gas is introduced into the measurement cell 101 from a standard gas source (not shown) via the measurement gas flow path 102a. The process then proceeds to step S703.

[0079] In step S703, the light from the light source lamp 109, which was lit in step S701, is reflected by the light distributor 113, received by the light receiving element 111, and converted into an electrical signal which is then received by the calculation unit 115. The amount of light (S11) indicated by the received electrical signal is temporarily stored in the memory of the calculation unit 115 and then used in the calculation of the hydrogen peroxide gas concentration in step S710, which will be described below. The process then proceeds to step S704.

[0080] In step S704, light from the light source lamp 109, which was lit in step S701, passes through the light distributor 113, the transmitted light is absorbed by the standard gas, received by the light receiving element 112, and the converted electrical signal is received by the calculation unit 115. Similar to step S703, the amount of light (S21) indicated by the received electrical signal is temporarily stored in the memory device of the calculation unit 115, and then used in the calculation of the hydrogen peroxide gas concentration in step S710, which will be described below. The process proceeds to step S705.

[0081] In step S705, a switching valve (not shown) switches from the standard gas to hydrogen peroxide gas, and hydrogen peroxide gas is introduced into the measuring cell 101 from the measuring gas flow path 102a. The process then proceeds to step S706.

[0082] In step S706, the light from the light source lamp 109, which was lit in step S701, is reflected by the light distributor 113, and the reflected light is received by the light receiving element 111 and converted into an electrical signal (the fourth electrical signal), which is received by the calculation unit 115. Similar to steps S703 and S704, the amount of light (S12) indicated by the received electrical signal is temporarily stored in the memory of the calculation unit 115, and then used in step S710, which will be described below, when the calculation unit 115 calculates the hydrogen peroxide gas concentration. The process proceeds to step S707.

[0083] In step S707, light from the light source lamp 109, which was lit in step S701, passes through the light distributor 113. The transmitted light is absorbed by the hydrogen peroxide gas and received by the light receiving element 112. The arithmetic unit 115 receives the converted electrical signal (the fifth electrical signal). Similar to steps S703, S704, and S706, the amount of light (S22) indicated by the received electrical signal is temporarily stored in the memory device of the arithmetic unit 115 and then used in step S710, which will be described below, when the arithmetic unit 115 calculates the hydrogen peroxide gas concentration. The process then proceeds to step S708.

[0084] In step S708, the calculation unit 115 receives data (a first electrical signal) regarding the temperature of the hydrogen peroxide gas from the temperature sensor 103, which measures the temperature of the hydrogen peroxide gas in the measurement cell 101. Similar to steps S703, S704, S706, and S707, the received temperature data (the first electrical signal) is temporarily stored in the memory device within the calculation unit 115, and then used in step S710, which will be described below, when the calculation unit 115 calculates the hydrogen peroxide gas concentration. The process then proceeds to step S709.

[0085] In step S709, the calculation unit 115 receives data (a second electrical signal) regarding the pressure of the hydrogen peroxide gas from the pressure sensor 104, which measures the pressure of the hydrogen peroxide gas inside the measurement cell 101. Similar to steps S703, S704, and S706-S708, the received pressure data (the second electrical signal) is temporarily stored in the memory device within the calculation unit 115, and then used in step S710, which will be described below, when the calculation unit 115 calculates the hydrogen peroxide gas concentration. The process then proceeds to step S710.

[0086] In step S710, the calculation unit 115 calculates the absorbance using the light intensity (S11) stored in step S703, the light intensity (S21) stored in step S704, the light intensity (S12) stored in step S706, the light intensity (S22) stored in step S707, and equation (2) explained with reference to Figure 1. The calculation unit 115 calculates the hydrogen peroxide gas concentration using the absorbance calculated by equation (2), the temperature data stored in step S708, the pressure data stored in step S709, and equation (1) explained with reference to Figure 1. The process proceeds to step S711.

[0087] In step S711, the data regarding the hydrogen peroxide gas concentration calculated in step S710 is output to an external device of the concentration measuring device 100.

[0088] The processing of the concentration measuring device 100 is not shown in the diagram for the sake of simplicity, but the processing from step S706 to step S711 is performed continuously. When the power to the concentration measuring device 100 is turned off, the processing of the concentration measuring device 100 ends.

[0089] According to this embodiment, the hydrogen peroxide gas concentration can be measured continuously and accurately.

[0090] Although this specification describes the measurement of hydrogen peroxide gas concentration, the present invention is also applicable to the measurement of the concentration of other gases.

[0091] The embodiments described herein are for illustrative purposes only, and the present invention is not limited to the embodiments described herein. [Industrial applicability]

[0092] The concentration measuring device of the present invention can be widely used in various industries where measuring the concentration of gases is necessary. [Explanation of Symbols]

[0093] 100 Concentration measuring device 101 Measurement Cell 102a Measurement gas flow path 102b Measurement gas flow path 103 Temperature Sensor 1031 Temperature Sensor 104 Pressure Sensor 1041 Pressure Sensor 1042 Pressure Sensor 105 Constant Temperature Block 106 Temperature Sensor 107 Heater 108 Insulation 109 Light source lamp 110a Transparent window 110b Transparent window 111 Light-receiving element 112 Photodetector 113 Optical splitter 114 Control Unit 115 Arithmetic section 116 cabinets 117a Air intake 117b Air intake 118 Exhaust vent 120 Embedded Systems 121 Cooling area 122 Heat retention area 131 How Light Travels 132 How Light Travels 141a Flow of hydrogen peroxide gas 141b Flow of hydrogen peroxide gas 400 Conventional Measurement Cells 401 Conventional Cell Block 402 Conventional Cell Block 403 Conventional Cell Spacer 404a O-ring 404b O-ring 405a Fixed plate 405b Fixed plate 406a Fixing screw 406b Fixing screw 410a Conventional transparent window 410b Conventional transparent window 411 Optical path length 421 Measurement gas flow path 431 How light travels 501 Cell Block (First Cell Block) 502 Cell Block (Second Cell Block) 503 Cell Spacer 504a O-ring 504b O-ring 505a Fixed plate 505b Fixed plate 506a Fixing screw 506b Fixing screw 507a Gap Spacer 507b Gap Spacer 511 Optical path length 601 Light-transmitting part

Claims

1. A concentration measuring device for measuring the concentration of hydrogen peroxide gas, A measuring cell through which the hydrogen peroxide gas flows, A first sensor that measures the temperature of the hydrogen peroxide gas and generates a first electrical signal, A second sensor that measures the pressure of the hydrogen peroxide gas and generates a second electrical signal, A constant temperature block comprising the aforementioned measurement cell, A third sensor that measures the temperature of the constant temperature block and generates a third electrical signal, and A heater for heating the aforementioned constant temperature block. A constant temperature block having, The insulating material encompassing the constant temperature block, A light source that emits a wavelength for measuring the concentration of the hydrogen peroxide gas, A first light-receiving element that converts the amount of light emitted by the light source into a fourth electrical signal, A second light-receiving element that converts the amount of light transmitted through the hydrogen peroxide gas flowing through the measurement cell into a fifth electrical signal, A distributor that splits the light emitted by the light source into light directed toward the first light-receiving element and light directed toward the second light-receiving element, A built-in system provided on the outside of the aforementioned insulation material, A control unit that controls the heater based on the third electrical signal, A calculation unit that calculates the concentration of the hydrogen peroxide gas based on the first electrical signal, the second electrical signal, the fourth electrical signal, and the fifth electrical signal. embedded systems and A concentration measuring device characterized by being equipped with the following features.

2. The concentration measuring device according to claim 1, characterized in that the measuring cell includes a transmission window.

3. The concentration measuring device according to claim 1, further comprising a housing having an air intake port and an exhaust port for ventilating the inside of the concentration measuring device.

4. The concentration measuring device according to claim 1, characterized in that the control unit controls the heater to maintain a constant temperature of the hydrogen peroxide gas in the measuring cell.

5. The concentration measuring device according to claim 4, characterized in that the temperature is 90°C or higher and 200°C or lower.

6. A measuring cell for measuring the concentration of hydrogen peroxide gas, A measuring gas channel for introducing the hydrogen peroxide gas into the measuring cell, A first transmission window through which light enters the measurement cell, A cell spacer that determines the optical path length, and A second transmissive window through which light that was not absorbed by the hydrogen peroxide gas flowing into the measurement cell is emitted. A first cell block that houses, The first transparent window, the cell spacer, and the second transparent window are sandwiched between the first cell block and the second cell block, A first O-ring is positioned between the first transmissive window and the second cell block, A second O-ring is positioned between the second transparent window and the first cell block. A measuring cell characterized by having the following features.

7. A first fixing plate and a second fixing plate are positioned to sandwich the first cell block and the second cell block, A gap spacer is placed between the first fixing plate and the second fixing plate so as to keep the distance between the first fixing plate and the second fixing plate constant, Fixing screws for fixing the first fixing plate and the second fixing plate The measuring cell according to claim 6, further comprising the features described above.

8. A concentration measuring device for measuring the concentration of a gas, A measuring cell through which the aforementioned gas flows and which is provided with a permeable window, A first sensor that measures the temperature of the gas and generates a first electrical signal, A second sensor that measures the pressure of the aforementioned gas and generates a second electrical signal, A first light-receiving element that converts the amount of light incident on the gas from the transmissive window into a fourth electrical signal, A second light-receiving element that converts the amount of light transmitted through the gas and emitted from the transmission window into a fifth electrical signal, A built-in system that calculates the concentration of the gas according to the Lambert-Beer law based on the first electrical signal, the second electrical signal, the fourth electrical signal, and the fifth electrical signal. A concentration measuring device characterized by being equipped with the following features.

9. The concentration measuring device according to claim 8, further comprising a heater that heats the measuring cell and the permeable window to maintain the gas at a predetermined temperature.

10. The concentration measuring device according to claim 9, further comprising an insulating material that blocks the exchange of heat between the heat-insulating region, which includes the measuring cell and the heater, and a cooling region adjacent to the heat-insulating region.

11. With an additional enclosure, The aforementioned housing and the aforementioned insulation material create the aforementioned heat retention region and the aforementioned cooling region. The concentration measuring device according to claim 10, further comprising an intake port and an exhaust port that generate the cooling region inside the housing.

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