Flow control structure

Abstract

The present invention provides a flow control structure that can suppress the incorporation of foreign matter into the controlled fluid and maintain a high level of cleanliness of the controlled fluid. [Solution] The valve has a diaphragm 1 and a valve block 2. The flow rate of the fluid that flows into one channel 2a leading to the valve block 2 is controlled by the minute pressure exerted on the diaphragm 1, and the fluid is discharged from the other channel 2b leading to the valve block 2 via channels 5a and 5b formed within the valve block 2. The diaphragm 1 and the valve block 2 are in contact with each other on a flat surface.

Description

Technical Field

[0001] The present invention particularly relates to a flow control structure for controlling the flow rate of corrosive fluids such as corrosive chemicals and corrosive gases used for cleaning a silicon wafer during semiconductor manufacturing such as a silicon wafer.

Background Art

[0002] In semiconductor manufacturing and the like, extremely high cleanliness is required for fluids such as pure water for cleaning a silicon wafer and chemicals for etching treatment. Contamination and inclusion of fine dust (particles) in the fluid flow path within the semiconductor manufacturing process greatly affect the product yield, so members for flowing the fluid while maintaining its cleanliness are very important.

[0003] Conventionally, in the semiconductor manufacturing process, a cleaning process has been performed to remove impurities, oxides, etc. adhering to the surface of a silicon wafer. In this cleaning process, by sufficiently removing impurities, oxides, etc., patterning of an electronic circuit can be accurately performed in the patterning process. For this reason, in the cleaning process, for example, corrosive chemicals or corrosive gases such as hydrofluoric acid, nitric acid, hydrochloric acid, phosphoric acid, hydrofluoric acid-nitric acid, sulfuric acid, ammonia are used to remove impurities, oxides, etc. adhering to the surface of the silicon wafer.

[0004] Therefore, piping through which corrosive chemicals and gases used in the cleaning process flow employs valve structures made of materials that can withstand corrosive chemicals and gases. For example, as shown in Figures 4 and 5, Patent Document 1 describes a diaphragm valve composed of a laminated structure comprising a wetted sheet layer 21 made of a perfluorocarbon resin that comes into contact with the chemical on one side, an intermediate sheet layer 22 made of a polyvinylidene fluoride resin with a tensile modulus of elasticity of 1000 MPa or less, which is located on the other side of the wetted sheet layer 21 that does not come into contact with the chemical, and a cushion rubber layer 23 made of a rubber elastic material located on the opposite side of the intermediate sheet layer 22 from the wetted sheet layer 21. In Figure 4, 24 is the spindle, 25 is the compressor, 26 is the inlet flow path, and 27 is the outlet flow path.

[0005] Patent Document 2 describes a pressure sensor that, as shown in Figure 6, includes a sensor part including a sensor chip 32 having a diaphragm 31, a pressure introduction hole 33 on the back side of the diaphragm 31 that transmits pressure corresponding to the pressure of a pressure medium to be measured, and a protective substance 34 that protects the diaphragm 31 and transmits pressure corresponding to the pressure of the pressure medium to the back side of the diaphragm 31, and outputs a detection signal corresponding to the pressure of the pressure medium applied to the diaphragm 31, wherein the protective substance 34 includes a protective oil 36 filled in a through hole 35 and a silicone gel 37. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-86098 [Patent Document 2] Japanese Patent Publication No. 2009-103602 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the diaphragm valve described in Patent Document 1 has the drawback that foreign matter tends to accumulate in the fitting portion between the wetted seat layer 21 and the valve body 28. In addition, because the wetted seat layer 21 has a complex curved surface shape, the flowing chemical solution tends to stagnate, and foreign matter does not discharge smoothly, which is another drawback. Furthermore, the pressure sensor described in Patent Document 2 has a stepped shape from the lower case 38 through the fitting portion 39 to the pressure introduction hole 33, which has the disadvantage that foreign matter tends to accumulate in the narrow gap between the silicone gel 37 and the stepped portion 40. As described above, many conventional flow control structures have stepped sections and narrow gaps, where foreign matter tends to accumulate. In semiconductor manufacturing processes, the presence of fine particles is a significant problem, and strict measures are required to address this. However, conventional flow control structures cannot meet such stringent requirements. Therefore, there is a need for a new flow control structure that can meet the stringent requirements of the semiconductor industry.

[0008] The present invention has been made in view of the problems of the prior art, and its purpose is to provide a flow control structure that can suppress the mixing of foreign matter into the controlled fluid and maintain a high level of cleanliness of the controlled fluid. [Means for solving the problem]

[0009] To achieve the above objective, the flow control structure of the first invention has a diaphragm and a valve block, and controls the flow rate of fluid that flows into one flow path leading to the valve block, and is discharged from the other flow path leading to the valve block through a flow path formed in the valve block by a minute pressure acting on the diaphragm, characterized in that the diaphragm and the valve block are in contact with each other on a flat surface.

[0010] The flow control structure of the second invention has a diaphragm and a valve block, and controls the flow rate of fluid that flows into one flow path leading to the valve block, and is discharged from the other flow path leading to the valve block through a flow path formed in the diaphragm by a minute pressure acting on the diaphragm, characterized in that the diaphragm and the valve block are in contact with each other on a flat surface. [Effects of the Invention]

[0011] According to the flow control structure of the present invention, in the fluid flow path formed by the diaphragm and the valve block, the diaphragm and the valve block are welded together to form a single unit, so that the diaphragm and the valve block are in contact on a flat surface. This eliminates steps within the flow path, suppresses the mixing of foreign matter into the controlled fluid, and maintains a high level of cleanliness of the controlled fluid. At the same time, the flow rate of the fluid that flows into one flow path leading to the valve block is controlled by the minute pressure exerted on the diaphragm, and is discharged from the other flow path leading to the valve block via a flow path formed within the valve block or a flow path formed within the diaphragm. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1(a) is a schematic diagram including a longitudinal cross-section of one embodiment of the flow control structure of the present invention, Figure 1(b) is a plan view thereof, and Figure 1(c) is a diagram showing the area around the dashed line C circled in Figure 1(a). [Figure 2] Figures 2(a), 2(b), and 2(c) show improved forms of the embodiments shown in Figures 1(a), 2(b), and 2(c). [Figure 3] Figure 3(a) is a schematic diagram including a longitudinal section of another embodiment of the flow control structure of the present invention, Figure 3(b) is a plan view thereof, and Figure 3(c) is a diagram showing the area around the dashed line C circled in Figure 3(a). [Figure 4] Figure 4 is a longitudinal cross-sectional view of the diaphragm valve described in Patent Document 1. [Figure 5]Figure 5 is a cross-sectional view showing the undeformed state of the diaphragm in the closed state of the diaphragm valve shown in Figure 4. [Figure 6] Figure 6 is a cross-sectional view of the pressure sensor described in Patent Document 2. [Modes for carrying out the invention]

[0013] The embodiments of the present invention will be described in detail below. The embodiments described below are illustrative examples, and the present invention is not limited to these embodiments. Various changes and modifications are possible without departing from the technical scope of the present invention.

[0014] In the present invention, a piezoelectric actuator can be used as the device for operating the diaphragm. The piezoelectric effect is a long-known phenomenon in which, when mechanical pressure is applied to a crystal, an electric charge is generated on the surface of a piezoelectric element in proportion to the pressure. However, the piezoelectric effect is a reversible phenomenon, and this inverse piezoelectric effect is utilized in piezoelectric actuators. That is, by attaching electrodes to a piezoelectric element and applying a voltage, an electric field is generated inside the element, causing the piezoelectric element to expand. An electric field applied parallel to the polarization direction of the piezoelectric element crystal generates a rotational force on the straight-lined electric dipoles, producing a strong torque. This causes a change in length within the crystal, leading to the expansion of the crystal. The change in length of the piezoelectric element appears as an extremely minute change in expansion in the nanometer range by changing the applied voltage. Piezoelectric actuators have the fastest response speed among various actuators, and their expansion speed can achieve an acceleration several thousand times that of gravity. Therefore, piezoelectric actuators are preferred as the device for operating the diaphragm of the flow control structure of the present invention.

[0015] The fluids whose flow rate is controlled by the flow rate control structure of the present invention include corrosive chemicals and gases used as cleaning fluids for industrial equipment. In semiconductor manufacturing, for example, pure water used to clean silicon wafers and chemicals and gases used in etching processes are corrosive, so it is preferable that the components of the flow rate control valve used in semiconductor manufacturing equipment be made of materials that can withstand corrosive chemicals and gases.

[0016] Figure 1(a) is a schematic diagram including a longitudinal cross-section of one embodiment of the flow control structure of the present invention, Figure 1(b) is a plan view thereof, and Figure 1(c) is a diagram showing the area around the dashed line C circled in Figure 1(a). 1 is a diaphragm, 2 is a valve block, 3 is a piezo actuator, and 4 is the input / output operating end of the piezo actuator 3. This input / output operating end 4 is connected to the diaphragm 1. When the diaphragm 1 expands and contracts due to the minute pressure received from the input / output operating end 4 of the piezo actuator 3, the fluid that flows into one of the flow paths formed in the upstream portion 2a leading to the valve block 2 (indicated by the arrow to the left in Figure 1(a)) can be discharged from the flow path formed in the upstream portion 2a of the valve block 2 (indicated by the arrow to the left in Figure 1(a)), through flow paths 5a and 5b formed in the valve block 2, and out of the flow path formed in the downstream portion 2b leading to the valve block 2 (indicated by the arrow to the left in Figure 1(a)). In addition to a piezo actuator, other actuators such as electric linear DC motors, linear synchronous motors, linear induction motors, linear stepping motors, hydraulic cylinders, and pneumatic cylinders can also be used to operate the diaphragm of the flow control structure of the present invention. As shown in Figure 1(a), the diaphragm 1 and the valve block 2 are in contact with each other on a flat surface, and there is no step. Furthermore, as shown in Figure 1(c), the upper right surface of the valve block 2, which forms a flow path within the valve block 2 for fluid to flow through, is cut out in a triangular shape downwards, as indicated by reference numeral 6. Having such a cutout portion 6 has the effect of making the fluid flow smoother and preventing the accumulation of foreign matter.

[0017] Figs. 2(a), 2(b), and 2(c) are diagrams showing an improved form of the embodiment shown in Figs. 1(a), 1(b), and 1(c). In this case, the micro-protrusions P1 formed on the diaphragm 1 are inserted into the valve block 2. According to this improved form, it can be expected that the operating stability of the diaphragm 1 will be improved.

[0018] Fig. 3(a) is a schematic configuration diagram including a longitudinal section of another embodiment of the flow rate control structure of the present invention, Fig. 3(b) is a plan view thereof, and Fig. 3(c) is a diagram showing an extraction of the vicinity of the broken line portion C surrounded by a circle in Fig. 3(a). 8 is a diaphragm, 9 is a valve block, 10 is a piezo actuator, and 11 is an input / output operating end of the piezo actuator 10. This input / output operating end 11 is connected to the diaphragm 8. In this embodiment, when the diaphragm 8 expands and contracts due to the minute pressure received from the input / output operating end 11 of the piezo actuator 10 for the fluid flowing into one of the flow paths (the arrow indicating leftward in Fig. 3(a)) formed in the upstream portion 9a leading to the valve block 9, the fluid can be discharged from the flow path (the arrow indicating leftward in Fig. 3(a)) formed in the upstream portion 9a of the valve block 9, through the flow path 12a formed in the valve block 9, the cylindrical space 8a in which the central portion formed in the diaphragm 8 is recessed, and the flow path 12b formed in the valve block 9, to the flow path (the arrow indicating leftward in Fig. 3(a)) formed in the downstream portion 9b leading to the valve block 9. As shown in Fig. 3(a), the diaphragm 8 and the valve block 9 are in contact with a flat surface and there is no step.

[0019] When the flow rate control structure of the present invention is used in a semiconductor manufacturing apparatus, the materials constituting the diaphragm and the valve block are preferably chemical-resistant materials (materials resistant to corrosive chemical solutions). As such chemical-resistant materials, fluorine resins such as PFA (perfluoroalkoxy alkane) and PTFE (polytetrafluoroethylene), which are excellent in acid resistance, alkali resistance, and organic solvent resistance, are preferable. Further, considering the functions required for the diaphragm and the valve block, it is preferable that the diaphragm is excellent in wear resistance, bending characteristics, chemical solution permeation resistance, and weldability. Therefore, the material of the diaphragm is more preferably modified PTFE or PFA.

[0020] Modified PTFE is obtained by introducing a very small amount (less than 1%) of a perfluorinated modifier during the polymerization process. The modifier functions as an intentional defect in the uniform polymer chain, and the slight disruption of this crystal structure improves the physical properties. That is, modified PTFE has a low melt viscosity and enables self-welding or welding, which is impossible with standard PTFE. Also, modified PTFE is extremely high-density, and its permeability to gases and liquids is extremely low. Being high-density also leads to a smoother machined surface finish, which is an important factor for sealing members. Furthermore, modified PTFE has excellent stress crack resistance.

[0021] A very important feature in the present invention is that the diaphragm and the valve block are welded and integrated, and as shown in Fig. 1(a), Fig. 2(a), or Fig. 3(a), the diaphragm and the valve block are in contact with each other on a flat surface and there is no step in the flow path. For example, as shown in Fig. 1(a), the diaphragm 1 and the valve block 2 are in contact with each other on a flat surface. The welding portion of the diaphragm and the valve block can be formed, for example, as follows.

[0022] (1) Formation of the diaphragm 1 and the valve block 2 PTFE, modified PTFE, and PFA can be used as materials for the diaphragm 1 and valve block 2. However, considering that the bending life of the diaphragm 1 is directly related to the life of the valve, modified PTFE, which has excellent bending characteristics and weldability, is preferred as the material for the diaphragm 1, and PFA is preferred when considering chemical permeability resistance and wear resistance. Alternatively, one of either modified PTFE or PFA (for example, modified PTFE) can be used as the main material for the diaphragm 1, and a portion can be made of the other material (for example, PFA). The valve block 2 may be made of any of PTFE, modified PTFE, or PFA, while considering productivity. Alternatively, one of PTFE, modified PTFE, or PFA (for example, PTFE) can be used as the main material for the valve block 2, and a portion can be made of one of the other two materials (for example, PFA). The diaphragm 1 and valve block 2 with the cross-sectional shape shown in Figure 1(a) can be obtained by machining for PTFE and modified PTFE, and by injection molding and machining for PFA.

[0023] (2) Pre-processing of the surfaces to be welded In Figure 1(a), the lower surface of the diaphragm 1 and the upper surface of the valve block 2, where the diaphragm 1 and valve block 2 contact each other on a flat surface, are precision machined so that the arithmetic mean roughness Ra is 0.2 μm or less and the maximum height Ry is 0.8 μm or less. In this invention, the diaphragm 1 and valve block 2 can be welded together without using adhesives or joining members, as described below. Therefore, no impurities leach into the welded area.

[0024] (3) Welding of diaphragm 1 and valve block 2 To weld the diaphragm 1 and valve block 2 obtained as described above, there are two methods: inserting them into a heating furnace in an atmospheric environment and welding them (the former heating method), or locally heating only the necessary parts and welding them (the latter heating method). In the former heating method, although it is adjusted as appropriate depending on the size of the material, the temperature is above the melting point of the material, the pressure is up to about 30 MPa, and the heating time is up to about 200 minutes. In the latter heating method, although it is adjusted as appropriate depending on the size of the material, the temperature is above the melting point of the material, the pressure is about 1.0 MPa, and the heating time is about 10 minutes. Since there is no step between the diaphragm 1 and valve block 2 obtained in this way, no foreign matter is generated at the welding site, and no foreign matter accumulates or remains at the welding site.

[0025] Next, one embodiment of the operation of the flow control structure of the present invention will be described. (1) Initial purge Before starting flow control, the entire flow path, including the flow path shown in Figure 1(a), is flushed with pure water for cleaning. (2) Flow control By connecting an electrode (not shown) to the piezo actuator 3 shown in Figure 1(a) and applying a voltage to the electrode, an electric field is generated inside the piezo actuator 3. This slightly pulls the input / output operating end 4 of the piezo actuator 3 toward the piezo actuator 3, creating a minute gap between the diaphragm 1 and the projection 7 inside the valve block 2 and the downstream portion 2b leading to the valve block 2 via the input / output operating end 4, allowing fluid to flow from the upstream portion 2a leading to the valve block 2 to the downstream portion 2b leading to the valve block 2. In other words, in Figure 1(a), which shows the normally closed type, the slight pull of the input / output operating end 4 toward the piezo actuator 3 creates a minute gap between the diaphragm 1 and the projection 7 inside the valve block 2 and the downstream portion 2b leading to the valve block 2. Furthermore, a spring is inserted inside the piezo actuator 3 to extend the input / output operating end 4 outward from the piezo actuator 3. Therefore, in order to pull the input / output operating end 4 towards the piezo actuator 3, it is necessary to overcome this spring force. Accordingly, the fluid flow rate through the minute gap can be adjusted by increasing or decreasing the electric field strength generated inside the piezo actuator 3. If the electric field strength generated inside the piezo actuator 3 becomes smaller than the spring force, the input / output operating end 4 will try to return to its original position, so a minute gap will not be formed between the diaphragm 1 and the projection 7 inside the valve block 2 and the downstream portion 2b leading to the valve block 2. The fluid flow path will be closed, and fluid will not flow from the upstream portion 2a leading to the valve block 2 to the downstream portion 2b leading to the valve block 2.

[0026] Flow control in the normally open type can be performed as follows. In the normally open type, as shown in Figure 1(a), there is a small gap between the diaphragm 1 and the projection 7 inside the valve block 2 and the downstream portion 2b leading to the valve block 2. By connecting an electrode (not shown) to the piezo actuator 3 shown in Figure 1(a) and applying a voltage to the electrode, an electric field is generated inside the piezo actuator 3. This extends the input / output operating end 4 of the piezo actuator 3, closing the small gap between the diaphragm 1 and the projection 2c inside the valve block 2 and the downstream portion 2b leading to the valve block 2 via the input / output operating end 4. As a result, fluid does not flow from the upstream portion 2a leading to the valve block 2 to the downstream portion 2b leading to the valve block 2. Note that a spring is inserted inside the piezo actuator 3 to pull the input / output operating end 4 back towards the piezo actuator 3. Therefore, in order for the input / output operating end 4 to extend, it is necessary to overcome this spring force. Therefore, if the electric field strength generated inside the piezo actuator 3 becomes smaller than this spring force, the input / output operating end 4 will try to return to its original position, creating a small gap between the diaphragm 1 and the projection 7 inside the valve block 2 and the downstream portion 2b leading to the valve block 2, allowing fluid to flow from the upstream portion 2a leading to the valve block 2 to the downstream portion 2b leading to the valve block 2. Thus, by increasing or decreasing the electric field strength generated inside the piezo actuator 3, the fluid flow rate through the small gap can be adjusted.

[0027] The upstream flow path of the upstream portion 2a leading to the valve block 2 and the downstream flow path of the downstream portion 2b leading to the valve block 2 are equipped with a flow sensor, a pressure sensor, and a temperature sensor to sense the fluid flow rate, pressure, and temperature, respectively, and signals from each sensor are fed back to electrodes (not shown). The electric field strength generated inside the piezo actuator 3 differs depending on the signals fed back from these flow sensor, pressure sensor, and temperature sensor.

[0028] Electrostatic discharge Electrostatic discharge can occur when highly purified chemical solutions flow through piping or when these solutions come into contact with silicon wafer substrates. For example, fluororesins have the characteristic of easily becoming negatively charged (easily attracting electrons). Due to this electrostatic discharge, foreign matter may adhere to fluororesin piping. Effective measures to prevent this electrostatic discharge include grounding, static elimination (neutralizing the charge by applying the opposite charge to the charged object), coating with an antistatic agent (surfactant), and humidification (increasing the moisture content in the air to suppress charging by discharge from the material surface). [Explanation of Symbols]

[0029] 1. Diaphragm 2 Valve block 2a Upstream part 2b Downstream part 3. Piezo actuator 4. Input / Output Operating Ends of Piezo Actuator 5a, 5b channel 8 diaphragm 9 Valve block 9a Upstream part 9b Downstream part 10 Piezo actuators 11 Input / Output Operating Ends of Piezo Actuator 12a, 12b channel

Claims

1. A flow control structure comprising a diaphragm and a valve block, wherein the flow rate of a fluid that flows into one flow path leading to the valve block is controlled by a minute pressure acting on the diaphragm, and the fluid is discharged from the other flow path leading to the valve block via a flow path formed within the valve block, wherein the lower surface of the diaphragm consists of a central projection that protrudes downward and a flat lower surface surrounding the projection, and the flat lower surface of the diaphragm and the flat upper surface of the valve block are in contact by placing the flat lower surface of the diaphragm on the flat upper surface of the valve block, and there is no step between the flat lower surface of the diaphragm and the flat upper surface of the valve block.

2. A flow control structure comprising a diaphragm and a valve block, wherein the flow rate of a fluid that flows into one flow path leading to the valve block is controlled by a minute pressure on the diaphragm, and the fluid is discharged from the other flow path leading to the valve block via a flow path formed in the valve block and a flow path formed in the diaphragm, the lower surface of the diaphragm having a central projection that protrudes downward, a recess surrounding the projection, and an extension having a flat lower surface extending outward from the recess, the flat lower surface of the diaphragm and the flat upper surface of the valve block are in contact by placing the flat lower surface of the diaphragm on the flat upper surface of the valve block, and there is no step between the flat lower surface of the diaphragm and the flat upper surface of the valve block.

3. The flow control structure according to claim 1, characterized in that the minute protrusions formed on the diaphragm are inserted into the valve block.

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