Temperature measuring structure

Abstract

To provide a temperature measurement structure that exhibits good temperature response without causing corrosion from the fluid being measured, such as corrosive chemicals or corrosive gases. [Solution] A temperature measuring protective member 4, whose part 3 in contact with the corrosive chemical 1 is made of silicon carbide, is immersed in a pipe 2 through which the corrosive chemical 1 flows. The temperature of the corrosive chemical 1 flowing through the pipe 2 is measured by a resistance thermometer 5 protected by and held by the temperature measuring protective member 4.

Description

Technical Field

[0001] The present invention relates to a temperature measurement structure using a temperature sensor for measuring the temperature of a measurement fluid such as a chemical solution used for cleaning a silicon wafer during semiconductor manufacturing, for example, a silicon wafer.

Background Art

[0002] Conventionally, in the semiconductor manufacturing process, a cleaning process is performed to remove impurities, oxides, etc. adhering to the surface of a silicon wafer. In this cleaning process, by sufficiently removing impurities, oxides, etc., the patterning of an electronic circuit can be accurately performed in the patterning process.

[0003] Therefore, in the cleaning process, for example, hydrofluoric acid, nitric acid, hydrochloric acid, phosphoric acid, hydrofluoric acid-nitric acid, sulfuric acid, ammonia, etc. are used as corrosive chemicals to remove impurities, oxides, etc. adhering to the surface of the silicon wafer.

[0004] In addition, since the removal ability of corrosive chemicals and corrosive gases used in the cleaning process to remove oxides, etc. varies greatly depending on the temperature of the corrosive chemicals and corrosive gases, temperature control of the corrosive chemicals and corrosive gases is necessary, and the temperature control of the corrosive chemicals and corrosive gases is performed using a temperature sensor.

[0005] Such a temperature sensor includes a temperature measuring body composed of a thermocouple, a platinum resistance thermometer element, etc., and the temperature measuring body has a structure covered with a protective tube made of a metal such as stainless steel such as SUS316L or titanium.

[0006] The metal protective tube prevents the temperature measuring body from being corroded by corrosive chemicals and corrosive gases by increasing the wall thickness of the protective tube. However, doing so dulls the temperature responsiveness of the temperature sensor and increases the size of the temperature sensor itself, resulting in poor handling.

[0007] Therefore, as disclosed in Patent Document 1, the corrosion resistance of the protective tube is improved by constructing it from synthetic resins such as PFA (perfluoroalkoxyalkane) and PTFE (polytetrafluoroethylene) resin, which have excellent chemical resistance. However, this results in a slower temperature response, and the temperature sensor itself becomes larger, making it difficult to handle. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2001-83018 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, even with protective tubes made of synthetic resins such as PFA resin, as disclosed in Patent Document 1, corrosive chemicals and gases can permeate the protective tube over time, damaging internal components such as temperature sensors inside the tube.

[0010] Furthermore, temperature sensors are used, for example, to maintain a constant temperature even when the chemical solution temperature fluctuates during the cleaning of silicon wafers. However, if the protective tube is made of synthetic resin, the temperature response of the temperature sensor becomes sluggish, making it impossible to respond immediately, and sometimes resulting in the inability to obtain silicon wafers of consistent quality.

[0011] Furthermore, resin protective tubes are weaker in strength compared to metal protective tubes, so their wall thickness must be increased to prevent deformation due to fluid pressure from the chemical solution, which further slows down the temperature response of the temperature sensor.

[0012] In view of the above problems, the object of the present invention is to provide a temperature measurement structure that has good temperature response without causing corrosion by the fluid to be measured, such as corrosive chemicals or corrosive gases. [Means for solving the problem]

[0013] To achieve the above objective, the present invention provides a temperature measurement structure characterized by immersing a temperature measurement protective member, whose part in contact with the corrosive chemical solution or corrosive gas is made of silicon carbide, in a pipe through which a corrosive chemical solution or corrosive gas flows, and measuring the temperature of the corrosive chemical solution or corrosive gas flowing through the pipe using a temperature sensor protected by and held by the temperature measurement protective member.

[0014] The temperature sensor may also be a resistance thermometer. The portion of the temperature measuring protective member that comes into contact with corrosive chemicals or corrosive gases may have a hemispherical shape. The portion of the temperature measuring protective member that comes into contact with corrosive chemicals or corrosive gases may have a cylindrical shape. Piping through which corrosive chemicals or corrosive gases flow may be made of fluororesin. [Effects of the Invention]

[0015] According to the present invention, since the portion of the temperature measuring protective member that comes into contact with corrosive chemicals or corrosive gases is made of silicon carbide, corrosion by the fluid being measured does not occur, and the temperature sensor held by the temperature measuring protective member, protected by the silicon carbide temperature measuring protective member with high thermal conductivity, can measure temperature with high response. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic cross-sectional view of one embodiment of the temperature measurement structure of the present invention. [Figure 2] Figure 2 illustrates a temperature measurement method using a three-wire resistance thermometer. [Figure 3]FIG. 3(a) shows the temperature measurement protection member of the F1 type of the present invention, (a)-1 is a side view of the member, (a)-2 is a view of the member seen obliquely from below, (a)-3 is a longitudinal sectional view of the member; FIG. 3(b) shows the temperature measurement protection member of the F2 type of the present invention, (b)-1 is a side view of the member, (b)-2 is a view of the member seen obliquely from below, (b)-3 is a longitudinal sectional view of the member; FIG. 3(c) shows the temperature measurement protection member of the R type of the present invention, (c)-1 is a side view of the member, (c)-2 is a view of the member seen obliquely from below, (c)-3 is a longitudinal sectional view of the member; FIG. 3(d) shows the temperature measurement protection member of the C type of the present invention, (d)-1 is a side view of the member, (d)-2 is a view of the member seen obliquely from below, (d)-3 is a longitudinal sectional view of the member. [Figure 4] FIG. 4 shows the results of investigating the temperature responsiveness when switching a temperature measurement structure provided with a C-type temperature measurement protection member that had been initially immersed in running water at 5°C (1.5 L / min) to running water at 24°C (1.5 L / min). [Figure 5] FIG. 5 shows the results of investigating the temperature responsiveness when switching a temperature measurement structure provided with a C-type temperature measurement protection member that had been initially immersed in running water at 24°C (1.5 L / min) to running water at 5°C (1.5 L / min). [Figure 6] FIG. 6 shows the results of investigating the temperature responsiveness when switching a temperature measurement structure provided with a temperature measurement protection member of the F1 type, F2 type, R type or C type that had been initially immersed in running water at 21°C (1.0 L / min) to running water at 10°C (1.0 L / min). **Embodiments for Carrying Out the Invention**

[0017] Hereinafter, embodiments of the present invention will be described in detail.

[0018] In FIG. 1, a silicon carbide temperature measurement protection member 4 with a hemispherical portion 3 in contact with the chemical solution is immersed in a PFA pipe 2 through which a corrosive chemical solution 1 flows. A wiring 6 extends from a resistance temperature detector (temperature sensor) 5 that is protected by the temperature measurement protection member 4 and adhesively held by an appropriate adhesive by the temperature measurement protection member 4. The wiring 6 is connected to a substrate (not shown) to which a predetermined voltage is applied. As will be described later, the temperature of the corrosive chemical solution 1 flowing through the pipe 2 can be measured by the resistance temperature detector 5, the wiring 6, and the substrate to which a predetermined voltage is applied. The pipe 2 may be made of PTFE (polytetrafluoroethylene).

[0019] For example, corrosive chemical solutions include high-purity chemicals used for etching and cleaning in semiconductor manufacturing, sulfuric acid, hydrochloric acid, nitric acid, hydrogen peroxide solution, hydrofluoric acid, ammonium fluoride, acetic acid, phosphoric acid, aqueous ammonia, etc., and high-purity solvent-based resists and diluting solvents used for semiconductor processes, liquid crystal displays, etc., such as methyl alcohol, ethyl alcohol, isopropyl alcohol, xylene, isobutyl alcohol, ethylene glycol, acetone, ethyl acetate, toluene, dimethylformamide, ethylene glycol acetate, methoxypropyl acetate, butyl cellosolve, tetramethylammonium hydroxide, propylene glycol methyl ether acetate, dimethyl sulfoxide, N-methyl-2-pyrrolidone, etc.

[0020] For example, corrosive gases include hydrogen sulfide (H2S), sulfurous acid (SO2), nitrous acid (NO2, NO), chlorine (Cl2), ammonia (NH3).

[0021] A resistance thermometer is a device that measures temperature according to Ohm's law, and comes in 2-wire, 3-wire, and 4-wire types. When a weak current (0.5mA, 1.0mA, or 2.0mA) is passed through the resistance thermometer, the resistance Rt of the resistance thermometer can be determined from the voltage V applied to the resistance thermometer, and the temperature of the measurement point can be obtained. In the embodiment of the present invention, the temperature of a corrosive chemical solution was measured using a resistance thermometer, but of course, the temperature of a corrosive chemical solution can also be measured using a thermocouple. Furthermore, the temperature of a corrosive chemical solution can also be measured using a thermistor or a silicon carbide element.

[0022] Figure 2 illustrates a temperature measurement method using a three-wire resistance thermometer. In Figure 2, wires 11, 12, and 13 with the same resistance value (R) are prepared, and a specified current I (0.5mA, 1.0mA, or 2.0mA) is passed from a circuit board 14 to which a predetermined voltage is applied from an external power supply, through wire 11. The specified current I returns from wire 11 through the resistance thermometer 15 (resistor Rt), wires 12 and 13, and back to the circuit board 14. At this time, a potential difference V1 is generated between terminals A and B, and a potential difference V2 is generated between terminals B and C. Since the voltage across the resistance thermometer 15 with resistor Rt is V, it can be calculated as follows. V1-V2=I×(R+Rt)-I×R=I×Rt=V Since I is the specified current and V can be determined from calculations, the resistance Rt of the temperature sensor 15 can be determined, and the temperature of the measurement unit can be determined based on that resistance Rt. The two-wire system involves connecting one copper wire to each end of the resistive element. However, this method is not very practical because errors occur due to the wiring resistance. The 4-wire system is a wiring method in which two wires are connected to each end of the resistance element of the resistance thermometer, and it is somewhat more expensive.

[0023] Silicon carbide is a material with excellent chemical resistance, high strength, and high thermal conductivity. For example, regarding chemical resistance, when immersed in 60% nitric acid at 90°C for 24 hours, the weight loss (mg / cm³) is significant. 2 ) is 0.04, weight loss (mg / cm³) when immersed in 95% sulfuric acid at 95°C for 24 hours. 2) is 0.01, weight loss (mg / cm³) when immersed in 30% sodium hydroxide at 80°C for 24 hours. 2 ) is almost zero.

[0024] Next, to evaluate the responsiveness, four types of temperature measuring and protective members were adopted, as shown in Figure 3. Figure 3(a) is designated as type F1, Figure 3(b) as type F2, Figure 3(c) as type R, and Figure 3(d) as type C. A comparison of the sizes of each type is shown in Table 1 below. The temperature measuring and protective member in Figure 3(a) has a structure in which a short cylindrical member 22 extends from a cylindrical member 21. The temperature measuring and protective member in Figure 3(b) has a structure in which a slightly longer cylindrical member 32 extends from a cylindrical member 31. The temperature measuring and protective member in Figure 3(c) has a structure in which a member 42 with a hemispherical portion extends from a cylindrical member 41. The temperature measuring and protective member in Figure 3(d) is a cylindrical member 51. In Table 1, the wetted area refers to the area of ​​the part of the temperature measuring protective member that came into contact with the flowing water in the temperature response test described below, and the wetted part housing volume refers to the volume of the part of the temperature measuring protective member that came into contact with the flowing water in the temperature response test described below.

[0025] [Table 1]

[0026] Figure 4 shows the results of investigating the temperature response of a temperature measuring structure equipped with a Type C temperature measuring protective component, which was initially immersed in 5°C flowing water (1.5 L / min), when switched to 24°C flowing water (1.5 L / min). Figure 5 shows the results of investigating the temperature response of a temperature measuring structure equipped with a Type C temperature measuring protective component, which was initially immersed in 24°C flowing water (1.5 L / min), when switched to 5°C flowing water (1.5 L / min). In Figures 4 and 5, the vertical axis represents temperature (°C), and the horizontal axis represents time (seconds). As shown in Figure 4, the rise time of the 90% response from 5°C to 22.1°C is approximately 650 milliseconds, and as shown in Figure 5, the fall time of the 90% response from 24.0°C to 6.9°C is approximately 574 milliseconds. Thus, it can be seen that it exhibits extremely excellent temperature response.

[0027] Next, Figure 6 shows the results of investigating the temperature response of temperature measuring structures equipped with F1, F2, R, or C type temperature measuring protective members, which were initially immersed in 21°C running water (1.0 L / min), when switched to 10°C running water (1.0 L / min). In Figure 6, the vertical axis represents temperature (°C), and the horizontal axis represents time (seconds). In Figure 6, the thick dashed line L1 represents the temperature measuring structure equipped with the F1 type temperature measuring protective member, the thick solid line L2 represents the temperature measuring structure equipped with the F2 type temperature measuring protective member, the dashed line L3 represents the temperature measuring structure equipped with the R type temperature measuring protective member, and the dotted line L4 represents the temperature measuring structure equipped with the C type temperature measuring protective member.

[0028] As shown in Figure 6, the temperature measurement structure (L2) equipped with an F2 type temperature measurement protective member exhibits extremely excellent temperature responsiveness, with a 90% response fall time of approximately 666 milliseconds from 21°C to 11.1°C. Furthermore, the temperature measurement structure (L3) equipped with an R type temperature measurement protective member exhibits a 90% response fall time of approximately 1500 milliseconds from 21.0°C to 11.1°C. However, the temperature measurement structure (L1) equipped with the F1 type temperature measurement protection member has a very long 90% response fall time of approximately 3917 milliseconds when it reaches 11.1°C from 21°C, and the temperature measurement structure (L4) equipped with the C type temperature measurement protection member cannot reach 90% response even after 10000 milliseconds.

[0029] Thus, the reason for the differences in the 90% response fall time is thought to be due to differences in the area of ​​the temperature measuring protective member in contact with the flowing water, the ratio of the area of ​​the temperature measuring protective member in contact with the flowing water to the volume of the temperature measuring protective member, and the ratio of the area of ​​the temperature measuring protective member in contact with the flowing water to the surface area of ​​the temperature measuring protective member. As shown in Table 1, the wetted area is largest for the F2 type, followed by the C type, R type, and F1 type in decreasing order.

[0030] Table 2 below shows a comparison of volume (A) / surface area (B), surface area (B) / volume (A), wetted area (C) / volume (A), wetted area (C) / surface area (B), and wetted area (C) / surface area (B'). As shown in Table 2, the ratio of the wetted area to the volume of the temperature measuring protective member (C / A) and the ratio of the wetted area to the surface area of ​​the temperature measuring protective member (C / B, C / B') are largest for the F2 type, followed by the R type, F1 type, and C type in decreasing order. This difference in the ratio of the wetted area to the volume of the temperature measuring protective member (C / A) and the ratio of the wetted area to the surface area of ​​the temperature measuring protective member (C / B, C / B') is thought to be reflected in the results shown in Figure 6. In other words, the C type temperature measuring protective member is a cylindrical member 51, has a small wetted area, and only a part of the tip of the long cylindrical member comes into contact with the flowing water. As described in paragraph 0028, Type C has a large heat capacity in the parts that do not come into contact with flowing water, resulting in extremely poor temperature responsiveness.

[0031] [Table 2]

[0032] Since the present invention is configured as described above, it has the following effects. (1) Since the temperature measurement and protection member is made of silicon carbide, which has high thermal conductivity, it has good temperature response. (2) The larger the surface area of ​​the part in contact with the chemical solution, the better the temperature response. The larger the ratio of the liquid contact area to the volume of the temperature measuring protective member and the larger the ratio of the liquid contact area to the surface area of ​​the temperature measuring protective member, the better the temperature response.

[0033] Furthermore, the temperature measurement protection component can take various shapes, including hemispherical and cylindrical sections, as well as prismatic sections, shuriken-shaped sections (with four protruding triangular pyramids), pentagonal sections, hexagonal sections, octagonal sections, star-shaped sections (with five or more protruding triangular pyramids), ellipsoidal sections, and conical sections. These shapes do not cause pressure loss of corrosive chemicals or gases flowing through the piping, and prevent the accumulation of foreign matter in the piping through which the corrosive chemicals or gases flow. [Explanation of Symbols]

[0034] 1. Corrosive chemical solution 2 Piping 3. The part that comes into contact with the chemical solution 4. Temperature measurement protective component 5. Resistance thermometer 6 Wiring 11, 12, 13 Wiring 14 circuit boards 15. Resistance thermometer 21 Cylindrical member 22 Cylindrical member 31 Cylindrical member 32 Cylindrical member 41 Cylindrical member 42 Member having a hemispherical portion 51 Cylindrical member

Claims

1. A temperature measuring structure for measuring the temperature of a corrosive chemical solution or corrosive gas flowing through a pipe, wherein a temperature measuring protective member, the portion of which contacts the chemical solution or gas is made of silicon carbide, is immersed in flowing water, and the temperature of the flowing water flowing through the pipe is measured by a temperature sensor protected by and adhering to the temperature measuring protective member, characterized in that, when the area of ​​the portion of the temperature measuring protective member that contacts the flowing water is C mm², the volume of the temperature measuring protective member is A mm³, the total surface area of ​​the temperature measuring protective member is B mm², and the surface area of ​​only the outer surface of the temperature measuring protective member is B' mm², (C / A) is greater than 0.34 / mm, (C / B) is greater than 14%, and (C / B') is greater than 15%.

2. The temperature measuring structure according to claim 1, wherein the temperature sensor is a resistance thermometer, thermocouple, thermistor, or an element made of silicon carbide.

3. The temperature measuring structure according to claim 2, wherein the portion of the temperature measuring protective member that comes into contact with the corrosive chemical solution or corrosive gas is a hemispherical portion.

4. The temperature measuring structure according to claim 2, wherein the portion of the temperature measuring protective member that comes into contact with the corrosive chemical solution or corrosive gas is a cylindrical portion.

5. The temperature measuring structure according to claim 3 or 4, wherein the piping through which the corrosive chemical solution or corrosive gas flows is made of fluororesin.

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