JP4571422B2 - Liquid level detection device and chemical treatment device - Google Patents

Description

  The present invention relates to a liquid level detection device capable of inducing bubbles discharged from a gas introduction pipe when an air pressure detection type liquid level sensor is used for liquid level control and preventing loss due to scattering of the liquid, and the liquid The present invention relates to a chemical processing apparatus provided with a surface detection device.

  2. Description of the Related Art Conventionally, in the manufacturing process of various electronic devices that require generation of thin films and patterning, including semiconductor devices, it has been popular to process objects such as semiconductor wafers, glass, and ceramic substrates with chemicals. . For example, resist coating by immersion, patterning by development and etching, crystal growth from a liquid phase, and the like are treatments related to chemicals. However, in any treatment, what is indispensable is a cleaning process for cleaning the surface of the object to be processed, which is the most important process in the manufacturing process.

  The cleaning process in the manufacturing process of a semiconductor device or the like includes a dry process using a gas and a wet process using a liquid including water.

  In the past, organic solvents such as chlorofluorocarbon compounds and chlorinated hydrocarbons have been frequently used in cleaning processes such as degreasing. However, in recent years, wet cleaning using pure water or chemicals is frequently used from the viewpoint of environmental conservation of the atmosphere and soil.

  In wet cleaning, an object to be cleaned is immersed in a cleaning tank filled with a chemical solution. There are immersion cleaning in which an object to be cleaned is immersed for a predetermined time, ultrasonic cleaning in which ultrasonic waves are applied, rocking cleaning in which the object to be cleaned is moved in a chemical solution, and bubbling cleaning in which liquid bubbles are generated in the chemical solution. Regardless of which cleaning is performed, the chemical solution is controlled so as to maintain a predetermined amount, that is, a predetermined liquid level in the cleaning tank.

  In order to control the liquid level of the cleaning tank, a so-called overflow method is known in which the tank has a two-tank structure consisting of an inner tank and an outer tank, and the chemical liquid overflows from the lower edge of the tank to the outer tank with a higher tank height. (For example, refer to Patent Document 1).

  However, in the liquid level control by overflow, it is impossible to control that the chemical liquid in the cleaning tank decreases due to evaporation, volatilization, etc., and in the extreme case, there is a problem that emptying may occur.

  On the other hand, a method for detecting the liquid level itself has been proposed. In this method, the tip of the gas introduction pipe is submerged below the liquid level via the air pressure sensor. When a predetermined flow rate of gas flows through the gas inlet pipe, the air pressure sensor electronically detects changes in the gas back pressure caused by the liquid level, and the liquid level is controlled by controlling the liquid supply amount. This is an adjustment method (for example, see Patent Document 2).

  However, when this method is applied to a cleaning tank, gas is discharged from the gas introduction pipe into the chemical solution and released into the chemical solution. In the case of detecting the liquid level of the chemical liquid, the gas is discharged by submerging the tip of the gas introduction tube in a portion close to the liquid surface. However, in order to detect the presence or absence of a chemical in the cleaning tank in order to prevent emptying of the cleaning tank, the gas is discharged by submerging the tip of the gas introduction tube in the bottom part of the chemical. As a result, the chemical liquid is bubbled by the gas released from the gas introduction pipe, and bubbles are released from the liquid surface.

  As a method of degassing the bubbles released into the liquid, a gas discharge hole is provided at the uppermost part of the cylindrical container, and the liquid is provided with a liquid outflow hole at a midway height of the cylindrical container to overflow. A separation method has been proposed (see, for example, Patent Document 3).

  However, in this gas-liquid separation method, it is difficult to cover the upper part like a chimney in a container such as a washing tank. In addition, the discharged bubbles adhere to the surface of the object to be processed, causing a cleaning failure, or the bubbles rapidly expand due to the temperature of the chemical solution and the chemical solution is bubbled, the liquid level is disturbed, or the bubbles burst on the liquid level. As a result, there is a problem that the chemical solution is scattered.

  Therefore, in order to prevent the defective behavior of the gas bubbles released from the gas introduction tube in the chemical solution, it was considered to provide a bubble induction tube that covers the gas introduction tube. FIG. 5 is a schematic view of the main part of the bubble guide tube.

In FIG. 5, when the liquid level detection gas 2 is discharged from the gas introduction pipe 1 into the liquid 5 through an air pressure sensor (not shown), the liquid introduction column 1 of the liquid 5 is filled in the gas introduction pipe 1. Pressure is applied. Accordingly, the bubbles 21 are intermittently released from the lower opening 11 of the gas introduction pipe 1 while resisting this back pressure. The bubble 21 is guided to the bubble guide tube 3 that covers the gas introduction tube 1, floats on the liquid surface 51, and is discharged from the liquid surface 51. In this way, the behavior of the bubbles 21 in the liquid 5 can be controlled.
Japanese Patent Laid-Open No. 10-284456 (see FIG. 1) Japanese Patent Laid-Open No. 11-351943 (see FIG. 1) JP-A-6-201230 (see FIG. 1)

  As shown in FIG. 5, if a double tube structure in which a bubble guide tube 3 is provided outside the gas introduction tube 1, the liquid level detection gas 2 discharged from the lower opening 11 of the gas introduction tube 1 is used. It is possible to prevent the bubbles 21 from being guided into the bubble guide tube 3 and diffusing into the liquid 5.

  However, FIG. 6 shows a schematic diagram of the behavior of bubbles at the upper and outlet of the bubble guide tube. The liquid 5 is a chemical solution for performing chemical treatment, and the temperature is high, for example, exceeding 100 ° C. In this case, the bubble 21 formed by discharging the liquid level detection gas 2 press-fitted into the gas introduction tube 1 from the lower opening 11 of the gas introduction tube 1 is rapidly expanded in the bubble induction tube 3. As a result, the volume increases. When the bubble guide tube 3 floats toward the liquid surface 51, the liquid 5 in the bubble guide tube 3 becomes a liquid bubble 52 confined between the vertically adjacent bubbles 21. And rise with the bubbles 21. The bubble 21 bursts at the moment when it is discharged from the upper opening 31 of the bubble guide tube 3 at the liquid level 51.

  Therefore, the bubble 21 bursts at the liquid level 51 and at the same time the liquid bubble 52 is scattered. When the liquid 5 is hot, the tendency is particularly large because the bubbles 21 are heated and expanded. Moreover, although not shown, when the liquid level detection device 100 is applied to a chemical treatment tank such as a washing tank, it is difficult to completely cover the tank with a lid or the like. For this reason, the liquid bubbles 52 are scattered outside the tank and the processing liquid is reduced.

  Therefore, the present invention guides bubbles discharged from the gas introduction tube to the liquid level by the bubble guide tube, and provides a liquid outflow hole in the bubble guide tube to allow the liquid bubbles to flow out into the liquid and to release only the bubbles from the bubble guide tube. An object of the present invention is to provide a liquid level detection device that prevents the liquid from splashing and a chemical solution processing apparatus provided with the liquid level detection device.

  The above-described problem is to detect a change in the liquid level of the liquid according to claim 1, wherein the gas introduction pipe for press-fitting the gas into the liquid and the change in the back pressure of the gas are electrically detected. A gas pressure sensor that converts the signal into a gas; and a bubble guide tube that covers the gas introduction tube. The bubble guide tube guides bubbles that are discharged from the lower opening of the gas introduction tube and float to the liquid level. This is solved by a liquid level detection device configured to have a liquid outflow hole on the upper side surface in the vicinity of the liquid level.

  That is, the gas introduction tube is covered with the bubble induction tube, and the bubbles discharged from the lower opening of the gas introduction tube are guided to the liquid level with the bubble induction tube. However, the bubbles floating in the bubble guide tube are floated together in a liquid bubble state in which a liquid is sandwiched.

  Therefore, a liquid outflow hole is provided on the upper side surface of the bubble guide tube near the liquid surface, and the bubbles are discharged from the bubble guide tube. However, the liquid bubbles that have floated in the bubble guide tube together with the bubbles flow out of the liquid outflow hole. Then, before reaching the upper opening of the bubble guide tube, it escapes to the outside of the tube.

  As a result, only the bubbles are released from the upper part of the bubble guide tube, so that the liquid will not scatter even if the bubbles that have risen in the bubble guide tube burst from the upper opening. .

  Next, in claim 2, the liquid outflow hole is solved by the liquid level detection device according to claim 1, wherein one opening area is configured such that at least the bubble cannot penetrate.

  In other words, the liquid outflow hole provided on the upper side surface of the bubble guide tube is designed to have a size that prevents bubbles that have been levitated from the bubble guide tube from penetrating.

  As a result, only the liquid flows out from the liquid outflow hole, and the bubble does not pass through the liquid outflow hole and comes out from the upper opening of the bubble guide tube and bursts outside the liquid surface. Therefore, it is possible to prevent the liquid from scattering.

  Next, in claim 3, the liquid level detection device according to claim 1, wherein the distance between the tip of the bubble guide tube and the upper end of the liquid outflow hole is larger than the vertical length of the bubble. .

  In other words, while the bubble guide tube is always filled with liquid, the gas is intermittently discharged from the gas introduction tube into the bubble guide tube against the liquid pressure to form bubbles. When the gas expands and extends vertically in the bubble guide tube due to high liquid temperature, etc., if the bubble passes through the liquid outflow hole, the bubble will disperse the liquid in the bubble guide tube, that is, the liquid bubble. I will carry it up. As a result, when bubbles are ruptured on the liquid surface, the liquid bubbles are scattered.

  Therefore, the length from the tip of the bubble guide tube to the upper end of the liquid outflow hole is set to be equal to or longer than the length of the bubble so that the liquid outflow hole effectively allows the liquid to flow out without escaping the bubble.

  Next, in claim 4, the problem is solved by a chemical processing apparatus in which the liquid level detection apparatus according to claim 1 is attached to the chemical processing tank.

  That is, if the liquid level detection device according to the present invention is attached to a chemical liquid processing apparatus that cleans an object to be processed such as a cleaning tank, the liquid level of the chemical liquid in the chemical liquid processing apparatus can be detected. In addition, it is possible to prevent the chemical solution such as a high-temperature strong oxidant in the apparatus from being scattered or diminished.

  According to the present invention, by providing the liquid outflow hole in the bubble guide tube, it is possible to prevent the bubbles discharged from the gas introduction tube from bursting on the liquid surface and scattering of the liquid. Therefore, in particular, when applied to a chemical processing apparatus in which the temperature of the liquid is high and the expansion of bubbles is large, there is an effect that the loss due to the scattering of the chemical can be greatly reduced.

A bubble guide tube that covers a gas introduction tube for injecting a liquid level detection gas into the liquid is provided, and a liquid outflow hole is provided in the upper side surface of the bubble guide tube near the liquid surface. Bubbles of gas discharged from the lower opening of the gas inlet pipe are guided and floated to the liquid level by the bubble guide pipe, and the liquid bubbles that are lifted at the same time by being sandwiched between the bubbles are released into the liquid from the liquid outflow hole, and only the bubbles are guided to the bubbles. Release from the tube.
[First embodiment]
FIG. 1 is an enlarged cross-sectional view of a main part of the first invention of the present invention, FIG. 2 is a perspective view illustrating an undesired liquid outflow hole, and FIG. 3 is a perspective view illustrating a liquid outflow hole.

  In FIG. 1, the liquid level detection apparatus 100 includes a liquid 5 in a gas introduction pipe 1 through a pressure sensor 110, for example, a chemically stable gas 2 such as nitrogen gas. The back pressure (back pressure) commensurate with the liquid column H1 that is discharged into the pressurized gas 2 is detected by the pressure sensor 110 and converted into an electrical signal, and converted to the height of the liquid column H1. Knowing the height of the liquid level.

  As the pressure sensor 110, for example, if the liquid column H1 is several tens of centimeters at most, the back pressure is a minute pressure difference of several thousand Pa, so a so-called micro pressure gauge is used. An elastic differential pressure gauge such as a bellows is convenient because the diaphragm is converted into an electrical signal.

  By the way, the gas 2 press-fitted into the gas introduction pipe 1 is discharged as a bubble 21 into the liquid 5 from the lower opening 112. The behavior of the bubbles 21 in the liquid 5 is controlled by the bubble guide tube 3. In the vicinity of the upper opening 31 of the bubble guide tube 3, a liquid outflow hole 4 having a size that the bubble 21 cannot penetrate is provided.

  For the gas introduction pipe 1 and the bubble guide pipe 3, for example, a fluororesin pipe is used in consideration of chemical resistance, heat resistance, etc. with respect to the liquid 5 such as a chemical solution. The gas introduction tube 1 has an inner diameter of about several mmΦ, the bubble induction tube 3 has an inner diameter of about 10 mmΦ, and the bubbles 21 discharged from the lower opening 11 of the gas introduction tube 1 are guided to the liquid level 51 in the bubble induction tube 3. It will surface.

  However, when the liquid 5 is at a high temperature such as a phosphoric acid aqueous solution heated to 130 ° C., for example, the bubbles 21 discharged from the lower opening 11 of the gas introduction tube 1 initially have small bubbles of several mmΦ. It expands due to thermal expansion. FIG. 1 schematically shows such a state.

  When the bubble 21 expands, the bubble 21 rises with the bubble 21 in the state of the liquid bubble 52 in which the liquid 5 is confined between the bubbles 21 in the bubble guide tube 3. Since the bubble 21 cannot pass through the liquid outflow hole 4, it rises as it is and bursts and disappears at the upper opening 31 of the bubble guide tube 3.

  On the other hand, the liquid bubble 52 which has been lifted by being sandwiched between the bubbles 21 is pressed from below by the bubbles 21 rising from the liquid outflow hole 4, and as shown by the shaded arrows, the bubble guide tube is formed from the liquid outflow hole 4. 3 flows out into the liquid 5 outside. That is, since only the bubbles 21 are discharged from the upper opening 31 of the bubble guide tube 3, the liquid 5 does not scatter even if it bursts.

  By the way, in order to prevent the bubbles 21 from coming out of the liquid outflow hole 4, it is necessary to be stably maintained when the bubbles 21 reach the liquid outflow hole 4. The bubble 21 generated here is generated by discharging the gas 2 into the liquid and is not a floating microbubble such as a bubble sol but a large visible bubble. There are several factors that determine the stability of such bubbles, but the nature of the liquid 5 is significant.

  That is, if the liquid contains a surfactant or if the liquid has high viscosity and appropriate elasticity, the liquid 21 is stable. Since the membrane is completely independent and isolated in the fluid 5 rich in fluidity, it is stable.

  Therefore, if the bubble 21 that is guided and floats by the bubble guide tube 3 is not an opening large enough to contain the bubble 21, the bubble 21 is kept at the top of the bubble guide tube 3. It has been confirmed that the light reaches the opening 31 and is discharged.

  In FIG. 2, the liquid outflow hole 4 in the liquid level detection device 100 opens below the liquid level in the vicinity of the upper opening 31 of the bubble guide tube 3. That is, as shown in FIG. 2 (A), when the liquid outflow hole 4 has a configuration in which the upper part of the bubble guide tube 3 exposed from the liquid surface 51 is cut out, the liquid outflow hole 4 As in the case where it does not exist, the liquid bubbles are scattered when the bubbles burst, although not shown.

  Further, as shown in FIG. 2B, when the liquid outflow hole 4 opens to a deep part from the liquid surface 51, the liquid bubbles floating between the bubbles (not shown) and the bubbles are not in the liquid 5. It cannot flow out from the liquid outflow hole 4 by pressure, and the function as the liquid outflow hole 4 is impaired.

  In FIG. 3, the liquid outflow hole 4 in the liquid level detection device 100 can be configured in the bubble guide tube 3 in various shapes. That is, FIG. 3A shows a case where the liquid outflow hole 4 is square, and FIG. 3B shows a case where the liquid outflow hole 4 is circular. When the liquid contains a surfactant, or when the liquid has a high viscosity and the bubbles are stable, it is only necessary to provide one large opening that does not exceed the passage cross-sectional area of the bubbles.

  FIG. 3C shows a case where a plurality of circular liquid outflow holes 4 are provided around the bubble guide tube 3, and FIG. 3D shows a rectangular liquid outflow hole 4 around the bubble guide tube 3 in an interdigital manner. Is provided. The outflow amount of the liquid bubbles as the liquid outflow holes 4 is compensated by the number of holes, and even when the bubbles are small and divided, only the liquid bubbles can flow out without passing through the bubbles. Will not be damaged.

  In the third aspect, the bubble guide tube 3 is always filled with the liquid 5. The gas 2 is intermittently discharged from the gas introduction pipe 1 into the bubble guide pipe 3 against the liquid pressure corresponding to the liquid column H1, and becomes a bubble 21. When the gas 2 expands and extends in the vertical direction in the bubble guide tube 3 due to a high liquid temperature or the like, if the head of the bubble 21 passes through the liquid outflow hole 4, the bubble 21 is bubbled into the bubble guide tube 3. The liquid 5 in the liquid, that is, the liquid bubble 52 is carried to the liquid surface 51. As a result, when the bubble 21 bursts at the liquid level 51, a problem that the liquid bubble 52 scatters occurs.

Therefore, in FIG. 1, the relationship between the distance H2 between the tip of the bubble guide tube 3 and the upper end of the liquid outflow hole 4 and the vertical length H3 of the bubble 21 is set to H2> H3. If it does so, the bubble 21 will not escape from the liquid outflow hole 4, but only the liquid bubble 52 will flow out, and the original function of the liquid outflow hole 4 will work effectively.
[Second Embodiment]
FIG. 4 is a schematic diagram showing the configuration of the second invention of the present invention. In the figure, a chemical treatment apparatus 200 is filled with a chemical solution 202 in a chemical solution tank 201. For example, if the chemical solution 202 is a cleaning agent, it is a cleaning tank, and if it is an etching solution, it is an etching tank. If there is a plating tank, etc. In the chemical bath 201, for example, a semiconductor wafer as the workpiece 210 is held by the guide 211 and immersed in the chemical solution 202 for processing.

  The liquid level detector 100 is installed in the chemical tank 201. This liquid level detection device 100 branches, for example, a gas supply pipe 111 that feeds nitrogen gas or the like into two gas pressure sensors 110, one of which is a liquid that detects the liquid level 51 of the chemical liquid 202 in the chemical liquid tank 201. The upper limit detection apparatus 101 and the other are divided into a liquid lower limit detection apparatus 102 so that the presence of the chemical liquid 202 is detected and no emptying occurs. The liquid upper limit detection device 101 sinks the gas introduction tube 1 and the bubble guide tube 3 near the liquid surface 51, and the liquid lower limit detection device 102 reaches the bottom of the chemical solution tank 201 with the gas introduction tube 1 and the bubble guide tube 3. Submerged in depth.

  The liquid level 51 maintained at a predetermined position by the liquid upper limit detection device 101 is received by the chemical liquid outer tank 204 because the chemical liquid 202 overflows when the workpiece 210 is immersed, and the liquid surface 51 is outside the chemical liquid. The chemical liquid 202 accumulated in the tank 204 is returned to the chemical liquid tank 201 via, for example, a pump 205, a filter 206, and a heater 207. Although not shown here, the liquid level detection device 100 may be installed also in the chemical solution outer tank 204.

  The liquid level 51 of the chemical tank 201 is controlled by the liquid upper limit detection device 101 and can be appropriately supplied by the chemical supply pipe 203. When the chemical liquid 202 is replaced, the chemical liquid 202 is discharged through the liquid discharge port 208. Although it is difficult to hermetically seal, the lid 220 can be appropriately attached during the chemical treatment.

  In this way, when the liquid level detection device 100 according to the present invention is applied to the chemical processing apparatus 200, it is discharged from the gas introduction tube 1 by the action of the bubble guide tube 3 and the liquid outflow hole 4 provided in the bubble guide tube 3. It is possible to suppress the problem that the bubble 21 is ruptured and the chemical liquid 202 is scattered.

  The gas introduction tube and bubble induction tube are preferably fluororesin tubes in consideration of chemical resistance and heat resistance, but are not limited, and other polymer materials, metals, etc., depending on the type of chemicals and processing specifications Can be used, and various modifications are possible.

  In addition, the gas used in the liquid level detection device is inactive because nitrogen is generally used. However, the thickness of the gas introduction tube and the bubble guide tube depends on the type of gas, the depth of the processing device, the liquid ( Various deformations are possible depending on the back pressure depending on the specific gravity, viscosity, surface free energy, etc.

  Further, the shape and number of the liquid outflow holes, the opening area, the position provided in the bubble guide tube, etc. are not uniquely determined by the size of the bubbles discharged from the gas introduction tube, the specifications of the liquid (chemical solution), etc. Can be modified.

(Additional remark 1) It detects the fluctuation | variation of the liquid level of a liquid, Comprising: The gas introduction pipe which press-fits gas in this liquid, The gas pressure sensor which converts the change of the back pressure of this gas into an electrical signal, A bubble induction tube for covering the gas introduction tube,
The bubble guide pipe guides bubbles that are discharged from the lower opening of the gas introduction pipe and floats to the liquid level, and has a chemical solution outflow hole provided around the upper side of the pipe near the liquid level. A liquid level detection device (Claim 1).

(Supplementary note 2) The liquid level detection device according to supplementary note 1, wherein the chemical solution outflow hole has at least one opening area in which the bubbles cannot penetrate.

(Supplementary note 3) The liquid level detection device according to supplementary note 1, wherein the chemical outflow hole has a circular shape or a square shape.

(Supplementary note 4) The liquid level detection device according to claim 1, wherein the distance between the tip of the bubble guide tube and the upper end of the liquid outflow hole is larger than the length of the bubble in the vertical direction. .

(Additional remark 5) The liquid level detection apparatus of Claim 1 is attached to the chemical | medical solution processing tank. The chemical | medical solution processing apparatus (Claim 4) characterized by the above-mentioned.

(Appendix 6) Having two sets of the liquid level detection device,
At least one of the chemical treatment apparatuses according to appendix 4, wherein the lower opening of the gas introduction pipe is closest to the bottom surface of the chemical treatment tank.

(Additional remark 7) This chemical | medical solution processing tank is a washing tank. The chemical | medical solution processing apparatus of Additional remark 4 characterized by the above-mentioned.

Industrial applicability

  The liquid level detection device according to the present invention contributes to, for example, suppressing the scattering of the chemical liquid due to the burst of bubbles in the chemical liquid processing apparatus used for various chemical liquid processing in the manufacturing process of the electronic device.

It is an expanded sectional view of the principal part of 1st invention of this invention. It is a perspective view which illustrates an undesirable liquid outflow hole. It is a perspective view which illustrates a liquid outflow hole. It is a schematic diagram which shows the structure of 2nd invention of this invention. It is a schematic diagram of the principal part of a bubble guide tube. It is a schematic diagram of the behavior of the bubble at the upper and outlet of the bubble guide tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas introduction pipe 11 Lower opening 2 Gas 21 Bubble 3 Bubble induction pipe 31 Upper opening 4 Liquid outflow hole 5 Liquid 51 Liquid surface
52 Liquid Bubble 100 Liquid Level Detection Device 101 Liquid Upper Limit Detection Device 102 Liquid Lower Limit Detection Device 110 Gas Pressure Sensor 111 Gas Supply Pipe 200 Chemical Solution Processing Device 201 Chemical Solution Tank 202 Chemical Solution
203 Chemical liquid supply pipe 204 Chemical liquid outer tank
205 Pump 206 Filter 207 Heater 208 Drainage port 210 Workpiece 211 Guide 220 Lid

Claims (3)

A gas introduction pipe for detecting a change in the liquid level of the liquid, for injecting a gas into the liquid, a gas pressure sensor for converting a change in the back pressure of the gas into an electric signal, and the gas introduction pipe And a bubble guide tube
Bubble guide tube is for inducing bubbles floats discharged from the lower opening of the gas inlet pipe on the liquid surface, and have a circumferentially provided liquid outflow hole on the top side of the liquid surface near the ,
A liquid level detection device characterized in that the distance between the tip of the bubble guide tube and the upper end of the liquid outflow hole is smaller than the length of the bubble guide tube and larger than the vertical length of the bubble . The liquid level detection device according to claim 1 , wherein the liquid outflow hole has an opening area that does not allow the bubbles to pass therethrough . 3. A chemical processing apparatus, wherein the liquid level detecting device according to claim 1 is attached to a chemical processing tank.

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