JP3404563B2 - Pressure sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a pressure sensor,
For example, the present invention relates to an improvement of a pressure sensor suitable for measuring pressure of a fluid (chemical) having strong acidity. 2. Description of the Related Art As an apparatus for handling a strongly acidic fluid, for example, there is a semiconductor manufacturing apparatus. This semiconductor manufacturing apparatus employs a so-called wet etching method in which an etching solution mainly composed of nitric acid containing hydrofluoric acid is circulated by a pump to etch a semiconductor substrate, and a flow pressure of the etching solution is measured by a pressure sensor. While running. Conventionally, a pressure sensor used in such a semiconductor manufacturing apparatus is provided with a hollow portion penetrating a cylindrical pressure guiding portion made of a corrosion-resistant material, and a capacitive sensor is formed so as to close the hollow portion. A strain element as a pressure element is placed on the pressure guide,
A configuration is known in which the strain body is housed in a cylindrical case together with the pressure guiding portion so as to be pressed against the pressure guiding portion. In addition, from the viewpoint of preventing corrosion by the etching solution on the pressure receiving (liquid contacting) surface of the flexure element, a protective diaphragm made of fluororesin having good corrosion resistance is overlaid, and the protective diaphragm comes into contact with the etching solution via the protective diaphragm. With the double structure, accurate pressure measurement over time is ensured. In this pressure sensor, the etching liquid flowing from one end of the hollow portion is brought into contact with the protection diaphragm, and the strain sensor is displaced in accordance with the pressure of the etching liquid to output an electric signal corresponding to the displacement. ing. [0005] However, the above-mentioned pressure sensor has the following solution even if it has a double structure in which a protective diaphragm made of fluororesin is superimposed on the liquid contact surface side of the flexure element. There are issues to be addressed. In other words, although fluororesin is a material with excellent chemical resistance, depending on a chemical such as hydrofluoric acid or fuming nitric acid, the chemical gradually penetrates the protective diaphragm over a long period of time and reaches the strain-generating body, causing a rise. There is a problem in that a chemical gas is accumulated between the strain body and the protection diaphragm, and a state in which a small pressure is applied therebetween is generated, and the zero point of the strain body changes, so that a measurement error easily occurs. If this state continues, there is a concern that the chemical solution diffuses into the strain body, gradually corrodes the electrodes and terminals of the strain body, the cables connected thereto, and the like, and the measurement becomes impossible. . Furthermore, protective diaphragms are generally manufactured by cutting fluororesin, but the cutting process has limitations on the surface roughness and the processing accuracy of flatness. Is easily reduced. In order to improve this, conventionally, there has been proposed a method of applying a fluorine grease to a contact surface of the protective diaphragm with the strain generating body to improve a close contact state with the strain generating body. There is a problem in that transmission loss and variation in pressure occur and manufacturing costs increase. Furthermore, in the case of a protective diaphragm made of fluororesin, the flatness changes minutely due to repeated load, and the sensor output gradually changes over a long period of use, and it is difficult to maintain stable accuracy. SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional drawback, and a pressure sensor capable of accurately measuring the pressure of a strongly acidic fluid over time for a long period of time and ensuring durability. The purpose is to provide. [0009] In order to solve the above-mentioned problems, a structure according to the present invention comprises a pressure guiding portion having a hollow portion communicating with the outside, and a pressure guiding portion fixed to close the hollow portion. A pressure sensor that outputs an electric signal corresponding to a displacement based on a fluid pressure in the hollow portion. An aluminum oxide unit that transmits the pressure of the fluid to the strain member side at the hollow portion side of the pressure sensor. This is one in which a protective diaphragm made of a crystal is interposed. In this structure, trifluoride
Made of ethylene resin and its protection diaphragm
The film barrier layer that suppresses elution of metal components
Formed on the diaphragm and through its film barrier layer
It comes in contact with the fluid. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a first embodiment according to the pressure sensor of the present invention. In FIG.
The pressure guiding portion 1 is formed into a cylindrical shape from, for example, PTFE (polytetrafluoroethylene) synthetic resin and has
It has a stepped portion, and one end (the lower end in the figure) is gradually thickened from the thinnest portion, and thread grooves 3a, 3b are formed on the outer periphery of the thinnest portion and the thickest portion. A hollow portion 5 whose inner diameter is slightly widened from the lower end to the middle thereof is formed in the pressure guiding portion 1 in the axial direction to the upper end, and expands like a funnel at the upper end surface. On the upper end surface of the pressure guiding portion 1, a groove 7 is formed annularly in a portion near the outer periphery, and an O-ring 9 having elasticity is formed in the groove 7.
The protective diaphragm 11 is overlapped with the protective diaphragm 11 so as to close the hollow portion 5. The protective diaphragm 11 is formed of a single crystal of aluminum oxide (Al 2 O 3), more specifically, a single crystal of sapphire in a flat and disc-like shape. A strain-generating body 13 as, for example, a capacitance-type pressure-sensitive element (pressure element) is overlaid on the protective diaphragm 11 so as to be in close contact with each other. The strain body 13 has a flat disk shape similar to that of the protection diaphragm 11 and has a space between opposing electrodes therein. The point at which the capacitance between these opposing electrodes changes due to the pressing displacement from the protection diaphragm 11. Is a known type that converts into an electric signal corresponding to the displacement by applying a DC voltage and outputs the electric signal from the lead wire 15. The strain body 13, the protective diaphragm 11, and the pressure guiding portion 1 are covered with a cylindrical presser screw 17 which is open at one end. Reference numeral 17a denotes an end face of the holding screw 17, reference numeral 1
7b is a lead-out hole for the lead wire 15 provided on the end face 17a. A screw groove (not shown) is formed inside the tip end of the holding screw 17, and the screw groove is screwed into the screw groove 3 b of the pressure guiding section 1.
a restricts the flexure element 13 in the direction of the pressure-guiding section 1,
The end faces of the flexure element 13, the protective diaphragm 11, the O-ring 9, and the pressure guiding portion 1 are strongly pressed. For this reason, a sealing structure is formed between the upper end side of the pressure guiding section 1 and the protection diaphragm 11 so that, for example, the etching liquid filled in the hollow section 5 does not leak. A cap or the like (not shown) is put on the outer periphery of the pressure guiding portion 1 and the holding screw 17 to produce a product.
The pressure sensor of the present invention configured as described above has a pressure guiding portion 1.
When the screw groove 3a is screwed and connected to, for example, a circulation system of an etching solution in a semiconductor manufacturing apparatus (not shown), the hollow portion 5 is filled with the etching solution and comes into contact with the protective diaphragm 11. Then, the flexure element 13 is displaced through the displacement of the protective diaphragm 11 in accordance with the pressure displacement of the etching solution, and an electric signal of a level corresponding to the pressure displacement is output from the lead wire 15. Moreover, the sapphire single crystal plate is
It has excellent chemical resistance to chemical liquids such as hydrofluoric acid and fuming nitric acid and hardly penetrates.
Even if the etching liquid comes into contact with 1, the permeation of the etching liquid into the strain body 13 is suppressed, and no gas is accumulated between the protective diaphragm 11 and the strain body 13, so that even if used for a long time, Measurement and durability can be secured. Further, the sapphire single crystal plate has a very high flatness of about 10 μm, and the protective diaphragm 11 and the strain generating element 1 can be formed without using fluorine grease as in the prior art.
Since the surface contact accuracy between the three can be kept high, accurate measurement is possible from this point as well. FIG. 2 shows a first configuration in which a protective diaphragm 11 having a thickness of about 0.1 mm is superimposed on a flexure element 13.
FIG. 5 is a characteristic diagram showing the output of the sensor when a rated pressure is applied, and as can be seen from the graph, it can be seen that the pressure sensor of the present invention has good output accuracy with respect to the load pressure. Further, since the sapphire single crystal plate does not change its flatness due to the repeated load, by using the sapphire single crystal plate for the protective diaphragm 11, stable accuracy can be maintained for a long time. In the pressure sensor having the configuration shown in FIG. 1, the pressure-resistant seal between the pressure guiding portion 1 and the protection diaphragm 11 is about 9 kgf / cm 2. If the sealing property is improved, a higher range pressure measurement can be performed. By the way, when a sapphire single crystal plate is used for the protective diaphragm 11, the chemical resistance and
Although it is excellent in terms of preventing the penetration of the chemical solution and stabilizing the accuracy, there is some concern that a minute amount of the metal component may be eluted from the portion in contact with the chemical solution. Therefore, as shown in FIG. 3, a film barrier layer 19 as a coating layer made of an ethylene trifluorochloride resin (PCTFE) film is provided on the pressure guiding portion 1 side of the protective diaphragm 11, that is, on the surface in contact with the etching solution. It is preferable to press against the pressure guiding portion 1 via the O-ring 9 and to make it come into contact with the etching liquid. Other configurations are the same as those in FIG. In such a pressure sensor, since the ethylene trifluoride chloride (PCTFE) is a dense and hard material, the protective diaphragm 11 is provided with the film barrier layer 19 made of the ethylene trifluoride chloride (PCTFE) film. The formation of the triple protective diaphragm structure makes it possible to prevent the elution of the minute metal component into the etching solution. Next, FIG. 4 is a longitudinal sectional view for explaining a second configuration according to the present invention. In place of the sapphire single crystal plate, silicon carbide (about 0.2 mm thick) is used in the first configuration. In particular, the protective diaphragm 21 is formed by forming a film of (β-SiC) on one surface of the strain body 13 by, for example, thermal CVD, and the other configuration is the same as the first configuration. As described above, since the silicon carbide (SiC) is a dense and hard material by using the protective diaphragm 21 formed of silicon carbide itself, it is excellent in chemical resistance, prevention of penetration of a chemical solution, stability of accuracy, and the like. The characteristics can be maintained, and no minute metal components elute from the protective diaphragm 21. The above-described pressure sensor of the present invention is not limited to measuring the pressure of a strongly acidic etching liquid, but is also suitable for measuring the flow pressure of a fluid such as a strongly acidic liquid or gas. As described above, the first configuration according to the present invention comprises a pressure guiding portion having a hollow portion communicating with the outside, and a fluid pressure in the hollow portion fixed to close the hollow portion. A strain-generating body that outputs an electric signal according to the displacement based on, and a protective diaphragm made of aluminum oxide single crystal that transmits the fluid pressure to the strain-generating body side is interposed in the hollow part side of the strain-generating body, Made of chlorofluoroethylene resin for protection
Fill that suppresses elution of minute metal components from diaphragm
Forming a barrier layer on the protective diaphragm;
Since is wetted in the fluid through the Mubariya layer, excellent chemical resistance, it can also prevent chemical penetration, aluminum oxide single
Dissolution of small metal components into chemical solution from protective diaphragm of crystal
In addition, it is possible to suppress the protrusion, and it is possible to maintain stable sensor accuracy for a long period without a change in flatness due to a repeated load. Further, the second aspect of the present invention
Because the protective diaphragm itself, which is placed on the strain body and comes into contact with the chemical solution, is made of silicon carbide, it has excellent properties such as improved chemical resistance, prevention of chemical solution penetration, and stability of accuracy. And no elution of minute metal components.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing an embodiment of a pressure sensor according to a first configuration of the present invention. FIG. 2 is a characteristic diagram of the pressure sensor according to the first configuration of FIG. FIG. 3 is a longitudinal sectional view showing a modification of the first configuration in FIG. 1; FIG. 4 is a longitudinal sectional view showing an embodiment of a pressure sensor according to a second configuration of the present invention. [Description of Signs] 1 Pressure guiding portions 3a, 3b Screw groove 5 Hollow portion 7 Concave groove 9 O-ring 11, 21 Protective diaphragm 13 Strain generator 15 Lead wire 17 Holding screw 17a End face portion 17b Lead-out hole 19 Film barrier layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-138177 (JP, A) JP-A-7-326770 (JP, A) JP-A 1-128141 (JP, U) 501062 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 19/06 G01L 9/00 305

Claims (1)

(1) A pressure guiding portion having a hollow portion communicating with the outside, and an electric signal fixed to close the hollow portion and corresponding to a displacement based on a fluid pressure in the hollow portion. A protective diaphragm made of an aluminum oxide single crystal that transmits the pressure of the fluid to the strain-generating body side is formed on the hollow part side of the strain-generating body. Chlorinated ethylene resin
Elution of minute metal components from the protective diaphragm
Film barrier layer is formed on the protective diaphragm
And is in contact with the fluid through the film barrier layer.
A pressure sensor, characterized in that cause.