JP2005087975A - Gas-liquid separator and its producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas-liquid separator which has a function not permeating liquid, but permeating gas, and is hard to produce any slack and loose. <P>SOLUTION: The gas-liquid separator provided with an opening portion 10 not permeating the liquid, but permeating the gas on a silicon membrane 1 is provided. The opening portion 10 has inner wall surfaces 11 and 13 inclined in a thickness direction of the silicon membrane 1 such that an opening area expands toward the surface. The inner wall surfaces 11 and 13 are subjected to a water repellent treatment. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a gas-liquid separator having a function of transmitting gas without transmitting liquid, and a manufacturing method thereof.

For example, a porous membrane filter produced by stretching a fluorine compound such as polytetrafluoroethylene is used as a gas-liquid separation membrane of a coulometric gas sensor that is currently in practical use (Patent Document 1 below [1] 0004] to [0006]).
JP 2002-263458 A

However, such a porous membrane filter has a problem that since the membrane itself is flexible, it is easy to loosen and shape accuracy and dimensional accuracy are liable to be lowered. Moreover, since it is easy to bend, when the distance of an electrode etc. and a porous membrane filter is very small, it is difficult to manage these positional relationships strictly, and there also existed a problem that it also had difficulty at the time of an assembly operation.
In order to solve such a problem, in the above-mentioned Patent Document 1, two silicon substrates are bonded, and a shallow groove at a submicron level is formed along one of the bonding surfaces along the bonding surface. It is described that a gas-liquid separation membrane having a robust structure can be obtained by using gas permeation holes. However, the gas-liquid separation membrane having such a structure has a complicated manufacturing process.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a gas-liquid separator having a function of transmitting gas without transmitting liquid and hardly causing bending and loosening, and a method for manufacturing the same. .

  In order to solve the above-mentioned problems, the gas-liquid separator of the present invention is a gas-liquid separator in which an opening that does not transmit liquid but transmits gas is provided in a silicon film, and the opening includes an inner wall surface. However, the opening area is inclined with respect to the thickness direction of the silicon film so as to increase toward the surface, and the inner wall surface is water-repellent.

  The present invention also relates to a method of manufacturing a gas-liquid separator in which an opening that allows gas to pass through without passing through a liquid is formed in the silicon film, wherein the opening is formed in the silicon film by anisotropic etching. There is provided a method for producing a gas-liquid separator comprising a step and a step of water-repellent treatment of an inner wall surface of the opening.

In the gas-liquid separator of the present invention, an opening is provided in a silicon film, and the opening is provided with a gas-liquid separation function by applying a water repellent treatment to the inner wall surface of the opening. The opening is a tapered surface inclined with respect to the thickness direction of the silicon film, and the opening area is enlarged toward the surface. Therefore, even if the thickness of the silicon film is increased, the silicon A minute hole can be easily and accurately formed on the back side of the film. Therefore, the thickness of the silicon film can be increased to improve the rigidity, whereby it is possible to obtain a gas-liquid separator that is unlikely to be bent or loosened and that is difficult to change in size, shape, and fine positional relationship. .
In addition, since the inner wall surface of the opening portion is a tapered surface, the inner wall surface is easy to be subjected to water repellent treatment, and the effect of improving the water pressure resistance by the water repellent treatment can be effectively obtained to achieve high water resistance. it can.

In addition, according to the method of manufacturing a gas-liquid separator of the present invention, the opening is formed using anisotropic etching, and therefore the opening whose inner wall surface is inclined with respect to the thickness direction is easily formed. be able to. In addition, since reproducibility is good, minute holes can be formed with high accuracy, and design and process management are easy.
Therefore, the thickness of the silicon film is increased to improve the rigidity, and a minute hole can be easily and accurately formed in the silicon film, so that bending and loosening are difficult to occur. A gas-liquid separator that does not easily change its positional relationship can be manufactured easily and with good reproducibility.

  1 to 3 schematically show an embodiment of the gas-liquid separator of the present invention. FIG. 1 is a plan view of an opening, and FIG. 2 is a cross-sectional view taken along line AA in FIG. 3 is a cross-sectional view taken along line BB in FIG. Reference numeral 1 in the figure denotes a silicon film, and for convenience, 1a is a front surface and 1b is a back surface.

A substantially rectangular opening 10 is formed in the silicon film 1. The inner wall surfaces 11 and 13 of the opening 10 are inclined with respect to the thickness direction (Z direction in the drawing) of the silicon film 1 so that the opening area increases toward the front surface 1a side, and on the back surface 1b side. A slit hole 12 having a line shape in plan view is formed in a lowermost part (bottom).
Here, the opening area of the opening 10 refers to the area of a portion that becomes a hole when the opening 10 is cut in a cross section perpendicular to the thickness direction (Z direction) of the silicon film 1.
That is, as shown in FIG. 2, the cross-sectional shape perpendicular to the length direction (X direction in the drawing) of the opening 10 is formed in a substantially V shape. Further, as shown in FIG. 3, the inner wall surfaces 13 at both ends in the length direction of the opening 10 are also inclined with respect to the Z direction, and the length of the opening 10 in the X direction is the lowest (bottom). The slit hole 12 is the smallest and gradually expands from the slit hole 12 toward the surface 1a side.

The inner wall surfaces 11 and 13 of the opening 10 are subjected to water repellent treatment. Specifically, a thin film made of a water repellent is provided on the inner wall surfaces 11 and 13, and the static contact angle of the inner wall surfaces 11 and 13 with respect to a predetermined liquid is within a predetermined range. The static contact angles of the inner wall surfaces 11 and 13 are designed in a range where a suitable water pressure resistance can be obtained at the opening 10.
That is, if the water pressure resistance in the opening 10 is high to some extent, the liquid does not flow out from the opening 10 while the back surface 1b side of the silicon film 1 is filled, and a gas-liquid separation function is obtained. The water pressure resistance in the opening 10 changes according to the surface tension of the liquid, the size of the slit hole 12 in the opening 10 (the length in the X direction and the width in the Y direction), and the liquid and the inner wall surfaces 11 and 13. The contact angle can be controlled. The contact angle between the liquid and the inner wall surfaces 11 and 13 can be controlled by the type of the water repellent formed on the inner wall surfaces 11 and 13.
The water repellent treatment of the inner wall surfaces 11 and 13 is sufficient if at least the periphery of the slit hole 12 of the opening 10 is water repellent, but the entire inner wall surfaces 11 and 13 of the opening 10 are subjected to water repellent treatment. It is preferable. Further, the surface 1 a of the silicon film 1 following the inner wall surfaces 11 and 13 may be subjected to water repellent treatment. On the other hand, it is preferable that the back surface 1b of the silicon film 1 that is in contact with the liquid is hydrophilic.

In order to obtain a gas-liquid separation function, the water pressure resistance in the opening 10 is preferably 20 kPa or more.
The size of the opening 10 may be within a range in which a preferable water pressure resistance is obtained. For example, in this embodiment, the length in the X direction of the slit hole 12 in the back surface 1b of the silicon film 1 is 1 to 2 mm. The width in the Y direction is preferably in the range of 0.0001 to 0.002 mm (0.1 to 2 μm).
In order to obtain a preferable rigidity, the thickness of the silicon film 1 is preferably 50 μm or more, and is preferably set to about 100 μm, for example. The upper limit of the thickness of the silicon film 1 is not particularly limited. However, since the time required for processing increases as the thickness increases, the thickness is preferably set to 450 μm or less.
The inclination angle of the inner wall surfaces 11 and 13 of the opening 10 with respect to the Z direction is determined by the etching conditions (etching rate). Therefore, the length in the X direction and the width in the Y direction of the opening 10 on the surface 1 a of the silicon film 1 are set to a desired size at the bottom of the opening 10 based on the inclination angle determined by the etching conditions and the thickness of the silicon film 1. The slit hole 12 is designed to be formed.
The static contact angle between the liquid and the inner wall surfaces 11 and 13 may be within a range in which a preferable water pressure resistance can be obtained. For example, in the present embodiment, it is preferably 120 ° or more.

The gas-liquid separator of the present embodiment performs crystal anisotropic etching by wet etching on the silicon film 1 to form the opening 10 having the slit hole 12, and then repels the inner wall surfaces 11 and 13 of the opening 10. It can be produced by water treatment.
When crystal anisotropic etching is performed from the surface 1a side of the silicon film 1, the inner wall surfaces 11 and 13 are formed to be inclined with respect to the thickness direction (Z direction) of the silicon film 1, and the etching time is suitably set. For example, a slit hole 12 is formed in which the inner wall surface reaches the bottom of the silicon film 1 and penetrates to the back surface 1b side.
The length of the slit hole 12 in the X direction and the width in the Y direction adjust the size of the etching mask used during crystal anisotropic etching when the thickness of the silicon film 1 and the etching conditions (etching rate) are determined. Can be controlled.
As an etching mask, an SiO ₂ film formed on the silicon film 1 and patterned by a photolithography method can be used. ,

The water repellent treatment of the inner wall surfaces 11 and 13 is preferably performed in a state in which a peelable adhesive sheet is in close contact with the back surface 1b of the silicon film 1 in advance. By doing so, it is possible to prevent the water repellent treatment from reaching the back surface 1b of the silicon film 1, which is preferable for making the back surface 1b hydrophilic.
Then, a liquid water repellent is coated on the surface 1a of the silicon film 1 by using an appropriate coating method such as a spray method, a coating method, or a dipping method. At this time, it is preferable to coat at least the entire inner wall surfaces 11 and 13 of the opening 10 with a water repellent. More preferably, the entire surface 1a of the silicon film 1 is coated.
Moreover, it is preferable to apply vibration to the coated water repellent by ultrasonic waves to remove bubbles in the water repellent.
Thereafter, the coated water repellent is dried. The drying conditions are set such that the solvent in the coated water repellent is removed and a thin film made of the water repellent is formed.

Here, if air bubbles are present in the coated water repellent during drying, the water repellent treatment tends to be insufficient in the vicinity of the air bubbles. In particular, if air bubbles are likely to stay in the lowermost part of the opening 10 and the water repellent treatment around the slit hole 12 becomes insufficient, the water pressure resistance cannot be obtained as designed. This can be prevented by removing bubbles in the water repellent using ultrasonic waves.
The water repellent used in the water repellent treatment has a desired contact angle after the treatment, good wettability to the surface to be coated, and a film thickness that can be coated on the inner wall surface of the minute opening 10. Those are preferred. Specifically, those containing fluorine as a main component are suitable, and specific examples include HIRECX1 (trade name; manufactured by NTT-Advanced Technology). The drying condition of the water repellent is preferably, for example, in the range of about 50 to 60 ° C. and about 60 to 120 minutes.
The thickness of the thin film of the water repellent after the drying treatment is preferably sufficiently smaller than the width of the slit hole 12 in the Y direction, and is preferably about 0.1 to 0.5 μm, for example.

The gas-liquid separator of the present embodiment is used by being arranged at the interface between the liquid and the gas so that the back surface 1b of the silicon film 1 is in contact with the liquid in the gas-liquid separator of various apparatuses.
For example, a concave portion for storing a liquid or a concave groove as a liquid flow path is formed in a plate-like substrate, and the gas-liquid separator of the present embodiment is laminated on the substrate so as to cover the concave portion or the concave groove. It can also be used.
As such a substrate, for example, the gas-liquid separator made of the silicon film 1 and the glass plate can be chemically bonded, and high sealing properties can be obtained after the bonding. Therefore, glass can be preferably used. .

In the present embodiment, since the silicon film 1 can be made thick and rigid, the silicon film 1 can be used as a single layer. Further, the silicon film 1 can be joined and integrated with another reinforcing member.
As described above, since the gas-liquid separator made of the silicon film 1 can be chemically bonded to the glass plate, an opening 6 is provided on the back surface 1b of the silicon film 1, for example, as shown in FIG. The silicon film 1 can be reinforced by joining and integrating the glass plates 5. The opening 6 of the glass plate 5 is formed so as not to block the opening 10 of the silicon film 1 and so that the opening 10 of the silicon film 1 and the opening 6 of the glass plate 5 communicate with each other.
In this way, when the glass plate 5 is bonded to the silicon film 1, the silicon film 1 can be made thinner than the case where it is used without being bonded to the glass plate 5. The thickness can be preferably set to about 100 μm, for example. Even if the size of the slit hole 12 is the same, the thinner the silicon film 1 is, the easier it is to perform high-precision processing. Therefore, it is possible to increase the porosity by providing more minute openings 10 densely. .

  The number of openings 10 provided in the silicon film 1 may be one, but a plurality of openings 10 may be provided as long as desired strength and rigidity of the silicon film 1 can be ensured. As the total area of the slit holes 12 in the silicon film 1 increases, the amount of gas permeation through the gas-liquid separator increases. When a plurality of openings 10 are provided, each opening 10 is designed so as to obtain a preferable water pressure resistance.

  In this embodiment, the slit hole 12 has a line shape in plan view. However, the shape of the opening and the hole is not limited to this, and for example, an opening having a substantially dotted hole 22 as shown in FIGS. Similar effects can be obtained with the portion 20 as well. 5 is a plan view schematically showing the opening 20, and FIG. 6 is a cross-sectional view taken along the line AA in FIG.

  The example of this figure is different from the above embodiment in that the shape of the opening 20 in the surface 2a of the silicon film 2 is substantially square, and the hole 22 formed in the lowermost part (bottom) of the opening 20 is provided. It is a point that is a minute square shape. The inner wall surface 21 of the opening 20 is inclined with respect to the thickness direction (Z direction) of the silicon film 2 as in the above embodiment, and the inner wall surface 21 is similarly subjected to water repellent treatment.

In the opening 20 having such a configuration, since the hole 22 is small, the water pressure resistance can be easily increased as compared with the above embodiment, but the amount of gas permeation is small. Therefore, it is preferable to provide a plurality of such openings 20 as long as desired strength and rigidity of the silicon film 2 can be ensured.
In this case, the individual openings 20 are designed so as to obtain a preferable water pressure resistance.
In this example, the size of the opening 20 may be within a range in which a preferable water pressure resistance can be obtained. For example, the length in the X direction of the hole 22 in the back surface 2b of the silicon film 2 is 0.0001 to 0.002 mm. (0.1 to 2 μm), and the width in the Y direction is preferably in the range of 0.0001 to 0.002 mm (0.1 to 2 μm).
The inclination angle of the inner wall surface 21 of the opening 20 with respect to the Z direction is determined by the etching condition (etching rate). Therefore, the length in the X direction and the width in the Y direction of the opening 20 on the surface 2a of the silicon film 2 are set to a desired size at the bottom of the opening 20 from the inclination angle determined by the etching conditions and the thickness of the silicon film 2. It is designed so that a hole 22 is formed.
The static contact angle between the liquid and the inner wall surface 21 may be within a range in which a preferable water pressure resistance can be obtained, but is preferably 120 ° or more in this example, for example.

(Example)
A gas-liquid separator having the configuration shown in FIGS.
First, oxide films (SiO ₂ films) were formed on the front surface 1a and the back surface 1b of the silicon film 1, respectively. The thickness of the silicon film 1 was 100 μm, and the thicknesses of the oxide films on the front and back surfaces were both 0.8 μm. The silicon film 1 was used such that (111) planes of the crystal planes formed inner wall surfaces 11 at both ends in the width direction (Y direction) of the opening 10.
Next, the oxide film on the surface 1a was patterned by photolithography, and an opening having a length of 2 mm in the X direction and a width of 153.5 μm in the Y direction was provided in the oxide film.
Next, anisotropic etching was performed on the silicon film using the oxide film provided with the opening as an etching mask. As the etching solution, a solution (temperature of about 60 ° C.) in which 500 g of KOH was dissolved in 790 ml of distilled water, the temperature was lowered to 60 ° C., and isopropyl alcohol (IPA) was added until the liquid was saturated. The etching rate on each crystal plane when wet etching is performed on the silicon film using this etching solution is as follows:
{111}: {100}: {110} = 0.2: 22.5: 16 (μm / h).
After etching for 300 minutes, it was gradually cooled, washed with pure water, and dried using nitrogen gas.
Thereafter, the oxide films on the front and back surfaces of the silicon film 1 were removed using hydrofluoric acid to complete the formation of the opening 10. The length of the slit hole 12 in the back surface 1b of the silicon film 1 in the X direction was 2 mm, and the width in the Y direction was 1 μm ± 0.5 μm. Further, the length in the X direction of the opening 10 on the surface 1a of the silicon film 1 was 1.568 mm, and the width in the Y direction was 2.003 μm.

Next, a dicing tape was bonded onto the back surface 1b of the silicon film 1 as a peelable adhesive sheet. Then, HIRECX1 (trade name; manufactured by NTT-Advanced Technology) as a water repellent was applied to the entire surface 1a of the silicon film 1 while applying ultrasonic vibration (frequency: 100 kHz) to the silicon film 1.
After applying the water repellent, it was dried by heating in an oven at 70 ° C. for 2 hours.
Observation with a scanning electron microscope (SEM) after drying revealed that a thin film of a water repellent was formed on the inner surfaces 11 and 13 of the opening 10 up to the bottom. The thickness of the water repellent thin film was 3.3 μm.
Further, the static contact angle when 1 μl of pure water was dropped on the water repellent treated portion was 156 °.

The gas-liquid separator obtained through such water repellent treatment was evaluated for water pressure resistance.
As shown in FIG. 7, the apparatus for measuring the water pressure resistance is configured such that the liquid delivered by the pump 41 flows into the rubber tube 43 after passing through the pressure sensor 42.
A gas-liquid separator 44 was disposed at the open end of the rubber tube 43 so as to close the open end, and was fixed in a liquid-tight manner by an O-ring 45.
The pump 41 was driven to feed distilled water at a constant flow rate of 1 μm / min. Due to the fed distilled water, a static pressure is applied to the gas-liquid separator 44, and the pressure increases as time passes. The pressure increase / decrease was monitored by the pressure sensor 42 at 1 second intervals. On the other hand, the opening 10 of the gas-liquid separator 44 was observed with an optical microscope, and the presence or absence of liquid leakage was monitored. It was confirmed that when the liquid leaked from the opening 10 of the gas-liquid separator 44, a pressure decrease in the pressure sensor 42 occurred.
It was confirmed that the slit hole 12 of the opening 10 was a through-hole due to leakage of liquid from the opening 10. Thereby, it has confirmed that gas could permeate | transmit from the slit hole 12 to the liquid side.
Before the liquid (distilled water) leaked from the opening 10 of the gas-liquid separator 44, the maximum value of the pressure measured by the pressure sensor 42 was taken as the value of the water pressure resistance.
Thus, as a result of measuring the water pressure resistance of the gas-liquid separator obtained in the present Example, it was 38 kPa.

It is a top view which shows one Embodiment of the gas-liquid separator which concerns on this invention. It is sectional drawing which follows the AA line in FIG. It is sectional drawing which follows the BB line in FIG. It is a top view which shows other embodiment of the gas-liquid separator which concerns on this invention. It is a top view which shows other embodiment of the gas-liquid separator which concerns on this invention. It is sectional drawing which follows the AA line in FIG. It is a schematic block diagram which shows the apparatus used for the measurement of water pressure resistance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Silicon film 1a, 2a Front surface 1b, 2b Back surface 10, 20 Opening part 11, 13, 21 Inner wall surface 12 Slit hole 22 Hole 44 Gas-liquid separator

Claims (2)

A gas-liquid separator provided with an opening that allows gas to pass through the silicon film without passing through the liquid,
The opening is characterized in that an inner wall surface is inclined with respect to a thickness direction of the silicon film so that an opening area is enlarged toward the surface, and the inner wall surface is subjected to water repellent treatment. Gas-liquid separator. A method for producing a gas-liquid separator provided with an opening that allows gas to pass through a silicon film without passing liquid,
Forming an opening in the silicon film by anisotropic etching;
A method for producing a gas-liquid separator, comprising a step of subjecting the inner wall surface of the opening to a water repellent treatment.

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