JP2011194313A - Bubbling device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bubbling device generating vapor of liquid starting material from which a mist component is fully removed.SOLUTION: The bubbling device 10 comprises: a container 11 for storing the liquid starting material 17; a liquid starting material feeding port 12 through which the liquid starting material 17 is fed; a carrier gas feeding port 13 through which a carrier gas is fed; a gas discharging port 14 for discharging a gas in the container 11; a lower filter 15 for bubbling the liquid starting material 17 by using the carrier gas; and an upper filter 16 for removing the mist component of the liquid starting material 17 from the carrier gas containing vapor of the liquid starting material 17 obtained by bubbling.

Description

  The present invention relates to a bubbling apparatus and method, and more particularly to a bubbling apparatus and method for vaporizing a liquid material such as hydrofluoric acid.

  Hydrofluoric acid (HF) is used for cleaning the silicon wafer. In general, an aqueous solution of hydrogen fluoride is used for cleaning with hydrofluoric acid, but it is very difficult to clean microscopic defects due to problems such as surface tension. If the cleaning is insufficient, there is a problem that the HF cleaning / etching process in the fine structure cannot be performed. Therefore, recently, an attempt has been made to clean the wafer using hydrofluoric acid vapor (hydrogen fluoride gas).

  Bubbling is known as one method for evaporating a liquid material. For example, Patent Document 1 proposes a method of supplying a high-viscosity liquid raw material to a CVD apparatus at a high flow rate accompanied with a carrier gas. Liquid material is sealed in a bubbling container, and a carrier gas is blown from a nozzle provided in the liquid material while the pressure in the container is kept at atmospheric pressure or lower, and then dissolved in the liquid material. And let the carrier gas accompany the raw material.

  Patent Documents 2 and 3 disclose liquid raw material vaporizers. The device described in Patent Document 2 includes a bubbling nozzle attached to the tip of the introduction pipe. Since the bubbling nozzle is composed of a plurality of thin tubes and is arranged radially at substantially equal intervals, fine bubbles can be generated continuously and uniformly, and the vaporization efficiency of the liquid material can be improved. The device described in Patent Document 3 includes a partition plate provided between the bubbling chamber and the stationary liquid level chamber. The liquid level in the static liquid level chamber is not undulated by the partition plate even during bubbling, and the liquid level can be accurately detected by the sensor.

  Patent Document 4 discloses a method for monitoring vaporization of a liquid material (liquid chemical product) by bubbling using a carrier gas. This method is based on the determination step for determining the sequential values of the pressure of the carrier gas phase-shifted to the container in which the liquid raw material is stored, and the sequential values of the pressure of the carrier gas determined in this determination step, A calculating step of calculating a mass flow rate of the vapor from the liquid raw material.

JP-A-6-244121 JP-A-6-267852 Japanese Patent Laid-Open No. 7-14770 Special table 2001-515200 gazette

  None of the conventional bubbling methods described above are directed to hydrofluoric acid, but when bubbling hydrofluoric acid using these methods, there is a problem that it is difficult to vaporize hydrofluoric acid at a high concentration. Further, since bubbling generates not only hydrofluoric acid vapor but also mist, the carrier gas may be transferred to the cleaning process in a state containing the hydrofluoric acid mist component. If the carrier gas contains hydrofluoric acid mist, the hydrofluoric acid vapor further dissolves in the mist adhering to the wafer, the concentration of hydrofluoric acid in the mist becomes very high, and the wafer is washed unevenly. There is.

  The present invention has been made to solve the above problems, and an object of the present invention is to stably generate a high-concentration vapor from which mist components have been removed by evaporating a liquid raw material such as hydrofluoric acid. It is an object of the present invention to provide a bubbling apparatus and method capable of performing the above.

  In order to solve the above-mentioned problems, a bubbling apparatus according to the present invention includes a container for storing a liquid material, a first filter for bubbling the liquid material using a carrier gas, the material vaporized in the container by the bubbling, and the A second filter that removes the mist component of the liquid source from the carrier gas containing the mist component of the liquid source, and the container is supplied with the liquid source supply port through which the liquid source is supplied and the carrier gas. A carrier gas supply port and a gas discharge port for the carrier gas from which the mist component has been removed are provided.

  Further, in the method of bubbling a liquid material according to the present invention, the liquid material is bubbled by sending a carrier gas into a first filter immersed in the liquid material in a container, and the vapor of the liquid material obtained by the bubbling is used. When taking out the carrier gas containing from the said container, the mist component of the said liquid raw material is removed using a 2nd filter, It is characterized by the above-mentioned.

  In the present invention, the container has a vertically elongated cylindrical shape, the first filter is provided at a lower end portion in the container, and the second filter is provided at an upper end portion in the container. It is preferable that According to this configuration, it is possible to secure a sufficient distance until the bubbles of the carrier gas rise in the hydrofluoric acid solution and reach the liquid surface, and ensure a sufficient gas storage space in the upper part of the container. Can do. Furthermore, a sufficient distance from the liquid level to the second filter can be secured. Therefore, mist removal by the second filter can be performed in a space with a low mist concentration, and the load on the second filter can be reduced.

  In the present invention, the first filter is preferably a fluororesin filter having a pore size of 1 μm or less, and the second filter is also preferably a fluororesin filter having a pore size of 1 μm or less. When such a filter is used, very fine bubbles can be generated in the hydrofluoric acid, and the hydrofluoric acid can be vaporized at a high concentration.

  In the present invention, the first and second filters preferably have the same shape, structure and size. According to this configuration, parts can be shared, and stable operation can be expected at low cost.

  The bubbling device according to the present invention preferably further includes a level sensor for detecting the liquid level of the liquid raw material in the container. In this case, the level sensor detects a lower limit level of the optimum range of the liquid level during bubbling, and a second level detects the upper limit level of the optimum range of the liquid level during bubbling. It is preferable to include a sensor, a third level sensor located below the first level sensor, and a fourth level sensor located above the second level sensor. Furthermore, the third level sensor is preferably positioned above the first filter, and the fourth level sensor is preferably positioned below the second filter. According to this configuration, the liquid level during bubbling can always be maintained within the optimum range, and a highly reliable liquid level monitoring system can be ensured.

  The bubbling apparatus according to the present invention preferably further includes a concentration meter that measures the concentration of the liquid material supplied into the container and the concentration of the mist of the liquid material that fills the container by bubbling. According to this configuration, it is possible to measure the concentration of the hydrofluoric acid solution before the start of bubbling and the concentration change of the hydrofluoric acid solution after the gas is generated by bubbling, and the reliability of the bubbling process can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the bubbling apparatus and method which can vaporize liquid raw materials, such as a hydrofluoric acid, and can generate | occur | produce stably the high concentration raw material gas from which the mist component was removed can be provided.

It is a schematic perspective view which shows the structure of the principal part of the bubbling apparatus by preferable embodiment of this invention. It is side surface sectional drawing of the bubbling apparatus 10 shown in FIG. 1 is a block diagram showing the entire system of a bubbling device 10. FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic perspective view showing a configuration of a main part of a bubbling device 10 according to a preferred embodiment of the present invention. 2 is a side sectional view of the bubbling device 10 shown in FIG.

  As shown in FIGS. 1 and 2, the bubbling device 10 includes a container 11 in which a hydrofluoric acid solution 17 is stored, a liquid raw material supply port 12 for supplying the hydrofluoric acid solution 17 into the container 11, and a container 11. A carrier gas supply port 13 for supplying a carrier gas therein, a gas discharge port 14 for discharging the vapor of hydrofluoric acid (hydrogen fluoride gas) generated in the container 11 together with the carrier gas, A lower filter 15 (first filter) provided at the lower end portion and an upper filter 16 (second filter) provided at the upper end portion in the container 11 are provided.

  The container 11 has a cylindrical shape elongated in the vertical direction, and is installed on the support base 11a. If the height of the container 11 is sufficiently high, a gas atmosphere with little mist component of hydrofluoric acid can be obtained above the container 11. However, if the height is too high, the apparatus becomes undesirably large. Therefore, the height of the container 11 is preferably about 1 to 3 m.

The liquid source supply port 12 is provided on the side surface of the lower end portion of the container 11, and the hydrofluoric acid solution 17 supplied from the liquid source supply port 12 is charged into the container 11. The carrier gas supply port 13 is a lower end portion of the container 11 and is provided on the side surface opposite to the liquid raw material supply port 12 when viewed from the central axis of the container 11. The carrier gas supply port 13 is connected to a lower filter 15 provided in the container 11, and the carrier gas supplied from the carrier gas supply port 13 is always supplied into the container 11 via the lower filter 15. The carrier gas is preferably N ₂ gas, but other inert gases such as H ₂ gas and Ar gas may be used.

  The lower filter 15 is provided at the lower end in the container 11. The lower filter 15 converts the carrier gas injected from the carrier gas supply port 13 into fine bubbles and discharges them into the hydrofluoric acid solution 17 in the container 11. The lower filter 15 is preferably a fluororesin membrane filter having excellent chemical resistance (hydrofluoric acid resistance). In particular, it is preferable to use a PTFE (polytetrafluoroethylene) filter medium having a pore size of 1 μm or less. Since the PTFE filter medium is an extremely fine continuous porous body, the carrier gas can be converted into very fine bubbles.

  The upper filter 16 is provided at the upper end in the container 11. The upper filter 16 removes the mist of hydrofluoric acid contained in the carrier gas containing the hydrogen fluoride gas sent out to the gas exhaust port 14, and sends only the carrier gas containing the hydrofluoric acid vapor into the gas exhaust port 14. The upper filter 16 is preferably a fluororesin membrane filter having excellent chemical resistance (hydrofluoric acid resistance). In particular, it is preferable to use a PTFE (polytetrafluoroethylene) filter medium having a pore size of 1 μm or less. If the pore size is 1 μm or less, mist of hydrofluoric acid can be surely removed, and a filter medium common to the lower filter 15 can be used.

  The flow rate of the gas that can pass through the lower filter 15 and the upper filter 16 is preferably about 50 to 200 NL / min. This is because the flow rate range is appropriately determined in consideration of the process, but if a certain amount of flow rate cannot be secured, the hydrofluoric acid vapor cannot be sufficiently supplied. For that purpose, the pore size should not be extremely small, and it is necessary to consider not only the pore size but also the filter area. For example, in the case of a cylindrical filter having a radius of about 60 mm and a height of about 76 mm (about 3 inches), If the pore size is 0.1 μm or more, the above flow rate can be secured.

  In the present embodiment, the upper filter 16 is particularly preferably the same product (the same shape, structure and size) as the lower filter 15. Although the usage purpose of the lower filter 15 and the upper filter 16 is different, when the above fluororesin membrane filter is used, different purposes can be achieved by using the same product. Therefore, parts can be shared, and stable operation can be expected at low cost.

  The gas discharge port 14 is provided on the side surface of the upper end portion of the container 11. The carrier gas is always supplied to the gas discharge port 14 via the upper filter 16, discharged from the gas discharge port 14 to the outside of the container 11, and transferred to a process chamber (not shown). Various processes such as wafer cleaning are performed in the process chamber.

  FIG. 3 is a block diagram showing a configuration of the entire bubbling system including the bubbling device 10.

  As shown in FIG. 3, this bubbling system measures the concentration of hydrofluoric acid, the bubbling device 10 according to this embodiment, the chemical tank 20 in which the hydrofluoric acid liquid is stored, the carrier gas tank 30 in which the carrier gas is stored. And an HF densitometer 40. The chemical liquid tank 20 is connected to the liquid raw material supply port 12 of the bubbling apparatus 10 via a pump 21 and a valve 22, and the supply amount of hydrofluoric acid is controlled by the operation of the pump 21 and the valve 22. The carrier gas tank 30 is connected to the carrier gas supply port 13 via a regulator 31 and a mass flow controller 32, and the flow rate of the carrier gas pumped from the carrier gas tank 30 is controlled by the mass flow controller 32.

  The liquid level 17S of the hydrofluoric acid solution in the bubbling device 10 is monitored by level sensors 25-28. Both ends of the pipe 29 are connected to the upper end portion and the lower end portion (hydrofluoric acid solution supply system) of the bubbling device 10, and the liquid level of the hydrofluoric acid solution in the pipe 29 is the same as the liquid level 17 S in the container 11. I'm doing it. Level sensors 25 to 28 provided at appropriate positions of the pipe 29 respectively monitor the minimum level of the hydrofluoric acid solution, the lower limit level of the optimum range, the upper limit level of the optimum range, and the highest level. In particular, the level sensor 25 is positioned slightly above the lower filter 15 and is used to determine whether the lower filter 15 is completely immersed in the hydrofluoric acid solution. The level sensor 28 is provided at substantially the same height as the connection position 41 a on the container 11 side of the pipe 41 that connects the HF concentration meter 40 and the container 11, and the concentration of the hydrofluoric acid vapor-containing gas by the HF concentration meter 40. Used to determine whether measurement is possible.

  The output signals of the level sensors 25 to 28 are supplied to a control panel (not shown) that controls the entire system, and the control panel controls the operations of the pump 21 and the valve 22 based on the detection results of the level sensors 25 to 28. Thereby, the supply amount of the hydrofluoric acid solution is controlled. When the liquid level of the hydrofluoric acid liquid is lower than the level sensor 26, the hydrofluoric acid liquid is additionally charged from the liquid raw material supply port 12, and when the liquid level exceeds the level sensor 27 due to the additional charge, the additional charge is stopped. The Therefore, the liquid level can be maintained within a certain range during bubbling.

  Basically, it is sufficient to use two intermediate level sensors 26 and 27 to control the liquid level. However, if the level sensors 26 and 27 do not operate normally, the hydrofluoric acid solution in the container 11 is insufficient. Or overflowing from the container 11. In order to prevent such an unexpected situation, level sensors 25 and 28 are provided to improve the reliability.

  The HF concentration meter 40 is connected to the upper space of the container 11 via a pipe 41 and further connected to a hydrofluoric acid solution supply system via a pipe 43. Therefore, the HF concentration meter 40 can measure both the concentration of the mist of the hydrofluoric acid solution filling the container 11 and the concentration of the hydrofluoric acid solution supplied from the chemical solution tank 20 into the container 11. Thereby, the density | concentration change of the hydrofluoric acid liquid after generating gas can be measured. In particular, when the hydrofluoric acid solution is flowed after replacing (cleaning) the inside of the piping with pure water, the concentration of the hydrofluoric acid solution may be changed by the pure water remaining in the piping. In order to reliably grasp such an unexpected situation, the concentration of the hydrofluoric acid solution supplied into the container 11 can be measured.

  When measuring the mist concentration of the hydrofluoric acid solution in the container 11, the valve 42 is opened with the valve 44 closed, and the mist component in the container 11 is taken in from the pipe 41. When measuring the concentration of the hydrofluoric acid solution, the valve 44 is opened with the valve 42 closed, and the hydrofluoric acid solution is taken in from the pipe 43. Therefore, it is possible to efficiently measure both the hydrofluoric acid mist and the hydrofluoric acid raw material liquid using one HF concentration meter 40.

  In bubbling the hydrofluoric acid solution, first, the hydrofluoric acid solution is charged into the empty container 11. At this time, as shown in FIG. 1, it is necessary to charge the hydrofluoric acid solution 17 so that the lower filter 15 is sufficiently immersed. When the charge amount of the hydrofluoric acid solution 17 is small, the bubbles released from the lower filter 15 immediately reach the liquid surface 17S, and the hydrofluoric acid vapor cannot be sufficiently contained in the bubbles. This is because the concentration of the steam-containing gas is lowered. However, if the amount of the hydrofluoric acid solution is too large, the space occupied by the gas atmosphere becomes narrow and the mist concentration of hydrofluoric acid becomes too high. When a predetermined amount of hydrofluoric acid solution is charged into the container 11, the lower space of the container 11 becomes a storage space for the hydrofluoric acid solution, and the upper space of the container 11 becomes a space filled with carrier gas. Thus, preparation for bubbling is completed.

  Next, a carrier gas is supplied to the bubbling device 10. The carrier gas sent into the container 11 passes through the lower filter 15 and is then released into the hydrofluoric acid solution. The carrier gas that has passed through the lower filter 15 is converted into fine bubbles. The lower filter 15 generates bubbles in the hydrofluoric acid solution, and these bubbles float in the hydrofluoric acid solution. At this time, the bubbles have a certain amount of hydrogen fluoride in a gas phase state, and after the bubbles reach the liquid surface 17S of the hydrofluoric acid solution, they are released into the upper space (vapor space) in the container 11, It diffuses into the gas atmosphere in the container 11.

  When the carrier gas is sent into the container 11 from the carrier gas supply port 13, the gas atmosphere existing in the container 11 is sent out in order. The gas atmosphere in the container 11 contains carrier gas and hydrofluoric acid vapor, but also contains a mist component of hydrofluoric acid generated by bubbling. However, since the mist component of hydrofluoric acid is removed by the upper filter 16, the gas that has passed through the upper filter 16 does not contain the mist component of hydrofluoric acid. A carrier gas containing only is obtained.

  The carrier gas containing hydrofluoric acid vapor is transferred to the wafer cleaning process. Since the carrier gas does not contain a mist component of hydrofluoric acid, there is no problem that the wafer is non-uniformly cleaned by the mist in which hydrofluoric acid is dissolved at a high concentration. Further, since the vapor of hydrofluoric acid penetrates deeply into the minute defects formed on the surface of the wafer, it is possible to remove the silicon oxide film formed in the minute defects.

  As described above, the bubbling device according to the present embodiment uses the lower filter 15 to sufficiently reduce the bubble size of the carrier gas, so that more hydrofluoric acid vapor can be included in the bubbles. Therefore, a hydrofluoric acid vapor-containing gas having a saturated concentration can be generated efficiently. Further, the concentration of the hydrofluoric acid vapor-containing gas obtained from the gas discharge port 14 can be adjusted by changing the concentration of the hydrofluoric acid solution in the container 11, the charge amount of the hydrofluoric acid solution, the flow rate of the carrier gas, and the like. .

  Further, the bubbling apparatus according to the present embodiment includes the lower filter 15 for bubbling the hydrofluoric acid solution and the upper filter 16 for removing the mist component of hydrofluoric acid from the carrier gas containing the hydrofluoric acid vapor. Only the vapor of hydrofluoric acid can be stably taken out from the gas outlet 14. Therefore, in the cleaning process of the silicon wafer using the hydrofluoric acid vapor, a uniform cleaning process without unevenness can be performed without being affected by the concentrated hydrofluoric acid mist.

  The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention, and it goes without saying that these are also included in the scope of the present invention. Yes.

  For example, in the above-described embodiment, the substantially cylindrical container 11 elongated in the vertical direction is used. However, the shape of the container 11 is not particularly limited, and may be, for example, a substantially rectangular parallelepiped container 11 or a substantially spherical container 11. It may be. However, when the cylindrical container 11 is used, a high concentration hydrofluoric acid vapor can be generated relatively easily. Moreover, although the case where the lower filter 15 and the upper filter 16 are the same product was demonstrated in the said embodiment, the size, a structure, a shape, a material, etc. of the lower filter 15 and the upper filter 16 may differ.

  Further, in the above embodiment, bubbling of hydrofluoric acid liquid is taken as an example. However, the bubbling apparatus according to the present invention is not limited to bubbling of hydrofluoric acid liquid, and can target various liquid raw materials. .

DESCRIPTION OF SYMBOLS 10 Bubbling apparatus 11 Container 11a Support stand 12 Liquid raw material supply port 13 Carrier gas supply port 14 Gas discharge port 15 Lower filter 16 Upper filter 17 Hydrofluoric acid liquid 17S Hydrofluoric acid liquid level 20 Chemical liquid tank 21 Pump 22 Valves 25-28 Level Sensor 29 Piping 30 Carrier gas tank 31 Regulator 32 Mass flow controller 40 HF concentration meter 41, 43 Piping 41a One end 42, 44 on the container 11 side of piping 41 Valve

Claims (6)

A container for containing a liquid raw material;
A first filter for bubbling the liquid material using a carrier gas;
A second filter that removes the mist component of the liquid source from a carrier gas containing the source material vaporized in the container by the bubbling and the mist component of the liquid source;
The container includes a liquid source supply port to which the liquid source is supplied, a carrier gas supply port to which the carrier gas is supplied, and a gas discharge port that discharges the carrier gas from which the mist component has been removed. Bubbling device characterized by. The container has a vertically elongated cylindrical shape,
The first filter is provided at a lower end in the container;
The bubbling device according to claim 1, wherein the second filter is provided at an upper end portion in the container.   The bubbling device according to claim 1 or 2, wherein the first filter is a fluororesin filter having a pore size of 1 µm or less.   The bubbling device according to claim 1 or 2, wherein the second filter is a fluororesin filter having a pore size of 1 µm or less.   3. The bubbling device according to claim 1, wherein each of the first and second filters is a fluororesin filter having a pore size of 1 μm or less, and has the same shape, structure, and size. Bubbling the liquid material by sending a carrier gas into the first filter immersed in the liquid material in the container;
A bubbling method comprising removing a mist component of the liquid material using a second filter when a carrier gas containing the vapor of the liquid material obtained by the bubbling is taken out from the container.

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