Diaphragm pump based liquid transport apparatus

Abstract

 A liquid transport apparatus can operate without having an object liquid directly contacting sliding sections, so that it can prevent particle contamination of the object liquid to assure delivery of a clean liquid feed to a subsequent processing station. The apparatus comprises a fixed wall having a liquid flow hole; a deformable wall for defining an object liquid space with a variable volume in conjunction with the fixed wall; and a driver device for generating a controlled movement of the deformable wall.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to apparatuses for transporting liquids, and relates in particular to a liquid supply apparatus suitable for use in a chemical vapor deposition apparatus for depositing thin film of a highly dielectric or ferroelectric material on a substrate.

Description of the Related Arts

[0002] In recent years, there has been a quantum jump in circuit density of integrated circuit devices produced by the semiconductor industries, and intense development activities are underway in anticipation of giga-bit order DRAMs replacing the prevailing mega-bit order DRAMs of today. Dielectric thin film materials used to make high capacitance devices necessary for producing DRAMs include tantalum pentaoxide (Ta₂O₅) films of dielectric constant less than 20 or barium titanate (BaTiO₃), strontium titanate (SrTiO₃) or mixtures of these compounds, having dielectric constants of about 300, or metallic oxide thin films made of a mixture of these compounds, such as barium strontium titanate, appear to be promising.

[0003] To deposit such a metal oxide compound thin film on a substrate in a vapor phase, a gaseous mixture made by mixing one or more gas feed material of organometallic compounds and an oxygen containing gas is directed to a substrate heated to a certain temperature. Organometallic gaseous feed material is chosen by the nature of the thin film to be produced; for example, a metallic oxide film comprised by barium strontium titanate is produced by first converting Ba, Sr, Ti or their compounds into their dipivaloylmethane (DPM) compounds, and dissolving these compounds in an organic solvent, for example tetrahydrofuran (THF), to produce respective liquid feed materials. After uniformly mixing these liquid feed materials in a required proportion to produce a master liquid feed, it is sent to a vaporizer device to produce a gaseous feed for use in the chemical vapor deposition apparatus.

[0004] Such master liquid feeds are extremely susceptible to degradation even in a sealed container such that it is undesirable to have it stagnate inside the delivery piping. The master feed liquid is especially susceptible to producing precipitate particles, by being exposed to heat or air, which tend to produce inferior quality films. Therefore, once the component liquids are mixed into a master liquid feed, it is necessary that the master feed liquid be maintained in a stable condition but it is also desirable that the master liquid be completely used up as quickly as practicable. Furthermore, it is desirable that the film deposition apparatus be capable of exercising a fine control over the flow rate of the master feed liquid over a wide range of flow rates, which means that a liquid transport device should be capable of providing a stringent control over the flow rates of the feed liquid.

[0005] In the past, constant flow pumps have been developed to enable fine control of flow rate of liquid materials, but these pumps are comprised by pistons and cylinders or rotary pumps that have sliding components separated by sealing parts.

[0006] However, such conventional pumps presented some operational problems outlined below:

(i) the sliding parts of the pump come into contact with the feed liquid to produce particles to make the feed liquid contaminated;

(ii) the sliding sections in the pump are usually vulnerable to failure, and during the repair and maintenance operations, the feed liquid becomes exposed to air thereby causing degradation and contaminating the entire feed path;

(iii) reciprocating cylinders, diaphragm and bellows cause alternating flows to produce pulsation in the liquid feed supply path.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to present a liquid transport apparatus that enables to operate without having an object liquid directly contacting sliding sections so as to prevent particle contamination of the object liquid to assure delivery of a clean liquid feed to a subsequent processing station, and facilitate repairs and maintenance operations for the liquid transport apparatus.

[0008] The object has been achieved in a liquid transport apparatus for delivering a controlled quantity of an object liquid comprising: a fixed wall having a liquid flow hole; a deformable wall for defining an object liquid space with a variable volume in conjunction with the fixed wall; and a driver device for generating a controlled movement of the deformable wall.

[0009] Accordingly, the object liquid is transported by the action of the altered volume of the object liquid space caused by the movement of the deformable wall, therefore, the object liquid can be transported in a clean condition, without coming into contact with sliding sections of the apparatus.

[0010] The driver device may comprise a working fluid space separated by the deformable wall and formed opposite to the object liquid space and a working fluid transport device for delivering a working fluid to the working fluid space. Accordingly, a suitable external working fluid transport device can be utilized to deliver the object in a clean condition to a subsequent processing station, without having the object liquid coming into contact with sliding sections. The deformable wall may be made of any flexible material, such as a flexible membrane, bellows that can undergo self-deformation without any sliding sections.

[0011] In the above apparatus, the working fluid is preferably an incompressible fluid, and the working fluid transport device is a constant flow pump.

[0012] In the above apparatus, the object liquid space and the working fluid space are substantially symmetrical with respect to a mid-plane. When the deformable wall is a membrane, the fixed wall may have an interior contour shape substantially conforming to a deformed shape of the membrane.

[0013] In the basic apparatus, the driver device has an external driving device for mechanically deforming the deformable wall. Accordingly, the external arrangement of the apparatus can be simplified while still maintaining the basic premise of preventing the object liquid from contacting sliding sections.

[0014] Therefore it is clear that the liquid transport apparatus of the invention is designed to operate by altering the volume of the object liquid space by the action of the altered shape of the deformable wall. Since no sliding sections need to be involved directly in moving the object liquid, the apparatus enables to prevent contamination by particles so that the object liquid is always delivered to the next process in an utmost clean condition. It is also clear that the apparatus is designed for lesser repair and maintenance requirements compared with conventional designs liquid transport apparatus, and that, when necessary, the components can be taken apart quite readily for maintenance purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 

Figure 1 is a schematic cross sectional view of a first embodiment of the liquid transport apparatus of the present invention;

Figure 2 is a schematic cross sectional view of a second embodiment of the liquid transport apparatus of the present invention; and

Figure 3 is a schematic cross sectional view of a third embodiment of the liquid transport apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Preferred embodiments will be presented with reference to the drawings. The apparatus is designed to deliver a liquid feed material to a vaporizer to produce a gaseous feed for use in a chemical vapor deposition apparatus, for example.

[0017] The apparatus comprises a housing (casing structure) 10 having a roughly flat interior space and a dividing membrane 12 (deformable wall) for separating the interior space into an upper section and a lower section. The housing 10 is comprised by an upper housing 14 (fixed wall), a lower housing 16 and a dividing membrane 12 attached therebetween by a suitable method so as to produce two liquid tight compartments in the interior. More specifically, the space defined by the upper housing 14 and the membrane 12 constitutes an object liquid space 18 for containing an object liquid to be transported (in this case, a feed liquid), and the space defined by the lower housing 16 and the membrane 12 constitutes a working fluid space 20 for containing an incompressible working fluid.

[0018] The upper housing 14 has a feed liquid flow hole 22 connected to the feed distribution pipe 24 for passage of the feed liquid. The feed distribution pipe 24 is branched into an inflow pipe 28 connected to a liquid feed tank 26 and a delivery pipe 30 to connect to a vaporizer (not shown) with their respective shut-off valves 32, 34. On the other hand, the lower housing 16 has a working fluid flow hole 36 connected to a working fluid pipe 38.

[0019] The working fluid pipe 38 is branched into a pressurized fluid pipe 40 and a return pipe 42, and the pressurized fluid pipe 40 is connected to a discharge port of a constant flow pump 44, and the input opening of the constant flow pump 44 is connected to a working fluid tank 46 through a shut-off valve 48. It should be noted that, if the feed liquid exhibits a tendency to infiltrate into the membrane, the working fluid should be the same liquid as the solvent used to prepare the feed liquid. If there is no danger of infiltration, a liquid most suitable as a working fluid, such as water, silicone oil may be chosen.

[0020] The membrane 12 may be made of a polymeric resin material having suitable properties, for example, synthetic rubber or flexible Teflon group materials, which are compatible with the liquid media being transported. Standards for selection should include strength, elasticity properties as well as chemical compatibility with the feed liquid and working fluid. As illustrated in Figure 1, the interior space of housing 10 is vertically symmetrical with respect to a plane clamping the membrane 12, and is extended in a horizontal direction. That is, the interior space is shaped to be compatible with the contour of the deforming membrane 12.

[0021] The operation of the liquid transport apparatus, having the construction described above, will be presented. First step is to fill the feed liquid space 18 with the feed liquid. In this case, the constant flow pump 44 is stopped, the shut-off valve 48 in the return pipe 42 in the working fluid system is opened, the shut-off valve 32 in the inflow pipe 28 is opened, and the shut-off valve 34 in the delivery pipe 30 is closed. A pressurizing gas (e.g., Helium) is supplied from the pressure pipe 48 to the liquid feed tank 26 to deliver the liquid feed through the feed liquid flow hole 22 into the feed liquid space 18 in the upper housing 14.

[0022] The working fluid space 20 is compressed by the action of the pressurizing gas, and the working fluid in the working fluid space 20 is pushed back to the working fluid tank 46 through the return pipe 42. This filling step is normally performed until the membrane 12 reaches the bottom surface of the working fluid space 20. The pressure exerted by the pressurizing gas is extremely low and lasts only briefly during this feed liquid charging step such that there is little chance for the pressurizing gas to penetrate into the feed liquid to cause processing problems in the subsequent steps.

[0023] Next step is concerned with delivering a small quantity of feed liquid contained within the feed liquid space 18 to the vaporizer at the downstream side. To perform this step, the shut-off valve 48 of the return pipe 42 in the working fluid system is closed, the shut-off valve 32 of the inflow pipe 28 in the feed distribution system is closed and the shut-off valve 34 of the delivery pipe 30 is opened and the constant flow pump 44 is operated. This causes the working fluid to flow through the working fluid flow hole 36 formed on the lower housing 16 into the working fluid space 20. The working fluid pushes the membrane 12 upward so as to deliver a given volume of the feed liquid through the delivery pipe 30 to the vaporizer apparatus.

[0024] In this process of liquid delivery, the discharge volume of the feed liquid is identical to the volume of the working fluid supplied to the working fluid space 20, in other words, the flow volume of the feed liquid is identical to the discharge volume of the constant flow pump 44. Therefore, by using a constant flow pump capable of discharging a small quantity of working fluid precisely, it is possible to precisely control the delivery of a required small volume of the feed liquid. Also, the action of the membrane 12 reduces pulsation in the flow pattern to provide a smooth delivery of the feed liquid.

[0025] During the initial stage of the feed transport process, the membrane 12 becomes thinner because of its elastic stretching, but when the pressure is stabilized, thinning does not cause deviations in the delivered volume. Normally, the feed liquid received during the initial stage of delivery is discarded and is not used for film deposition so as to avoid quantity control problems of initial liquid delivery. Also, the volume of the feed liquid space 18 can be enlarged depending on the feed liquid requirement so that one charging of the feed liquid space 18 with the feed liquid is sufficient for a long hour device production process.

[0026] In this type of liquid delivery apparatus, particles are not generated at the sliding sections because the feed liquid is not exposed to such sliding parts inherently, so that a clean liquid feed can be delivered to the vaporizer at all times. Also, because sliding parts are not used, there is not many chances of degrading the feed liquid by its exposure to air during repair or maintenance of these sliding parts. Also, because the liquid transport process is carried out by the movement of the membrane 12, there is almost no mixing of gases in the feed liquid compared with the case of direct gas pressurization on the liquid.

[0027] Also, in this embodiment, the shape of the interior contour of the housing 10 is shaped to match a swollen shape of the membrane 12, the membrane 12 is able to prolong its service life by preventing localized deformation. Furthermore, there is minimal degradation of the feed liquid, because there is no dead zone in the liquid movement and the pumping section is shaped flatter (rather than deeper) to prevent stagnation.

[0028] Also, in this embodiment, the radius of the housing 10 is larger than its height to make its overall shape flat so that small deformation of membrane 12 would be effective in moving the liquid, compared with the case of a vertically elongated shape of the pumping section. However, in a flat shape, it is necessary to provide a thicker housing 10 to prevent the housing 10 from deforming due to the pressure. When the housing 10 itself is deformed due to the pressure, precise control of liquid flow rates could be affected. If the membrane 12 could be made of a stiffer material to provide sufficient service life, it is preferable to make the diameter smaller and the height taller to provide a proper volume capacity of the housing 10.

[0029] Figure 2 shows a second embodiment of the liquid transport apparatus. Those parts which are the same as those in the previous embodiment are referred to by the same reference numerals. In this embodiment, a metallic bellows 52 replaces the membrane 12 of the first embodiment. The housing 50 is roughly cylindrical in shape and includes the coaxial inner bellows 52, having a closed top, whose bottom section is attached to the bottom section of the housing 50. The external space between the bellows 52 and the housing 50 constitutes the feed liquid space 18, and the interior space of the bellows 52 constitutes the working fluid space 20 with their respective piping. The material for making bellows 52 should be non-reactive to both the feed liquid and working fluid.

[0030] The operation of the liquid transport apparatus of this embodiment is basically the same as that in the first embodiment, and explanations will be omitted. It suffices to mention that, because the deformable wall is made of a metallic material, it is much more durable and service life is longer than a membrane made of a resin material.

[0031] Figure 3 shows still another embodiment, in which the bellows 52 is operated by a driving device. That is, the bottom section of the housing 50 has an opening section 54 to eliminate the space corresponding to the working fluid space in the previous embodiments. Instead of the working fluid, a push rod 58 is inserted through the opening section 54 to fix the tip of the push rod 58 to the ceiling 56 of the bellows 52. The proximal end of the push rod 58 is attached to an elevator device 60 for raising and lowering the push rod 58. The elevator device 60 comprises a motor 64 having a speed reducer 62 with a large speed reduction ratio and a gear mechanism 66 for converting rotation to linear movement so as to provide finely controlled up and down movements to the push rod 58. The operation of this apparatus is basically the same as that of the previous embodiments, and the explanation is omitted.

[0032] According to its broadest aspect the invention relates to a liquid transport apparatus for delivering a controlled quantity of an object liquid comprising: a fixed wall having a liquid flow hole; and a wall for defining an object liquid space with a variable volumne in conjunction with said fixed wall.

[0033] It should be noted that the objects and advantages of the invention may be attained by means of any compatible combination(s) particularly pointed out in the items of the following summary of the invention and the appended claims.

SUMMARY OF THE INVENTION

[0034] 

1. A liquid transport apparatus for delivering a controlled quantity of an object liquid comprising: a fixed wall having a liquid flow hole; a deformable wall for defining an object liquid space with a variable volume in conjunction with said fixed wall; and a driver device for generating a controlled movement of said deformable wall.

2. An apparatus , wherein said driver device comprises a working fluid space separated by said deformable wall and formed opposite to said object liquid space and a working fluid transport device for delivering a working fluid to said working fluid space.

3. An apparatus , wherein said deformable wall is a membrane.

4. An apparatus , wherein said membrane is made of a material compatible with both said object liquid and said working fluid.

5. An apparatus , wherein said object liquid space and said working fluid space are formed substantially flat.

6. An apparatus , wherein said working fluid is an incompressible fluid.

7. An apparatus , wherein said working fluid transport device comprises a constant flow pump.

8. An apparatus , wherein said object liquid space and said working fluid space are substantially symmetrical with respect to a symmetry plane.

9. An apparatus , wherein said fixed wall has an interior contour shape substantially conforming to a deformed shape of a dividing membrane.

10. An apparatus , wherein said deformable wall comprises a bellows.

11. An apparatus , wherein said bellows is made of a material compatible with both said object liquid and said working fluid.

12. An apparatus , wherein said driver device has an external driving device for mechanically deforming said deformable wall.

13. An apparatus , wherein said deformable wall comprises a bellows.

14. An apparatus , wherein said bellows is made of a material compatible with said object liquid.

15. An apparatus , further comprising a push rod connecting said deformable wall to said external driving device.

Claims

1. A liquid transport apparatus for delivering a controlled quantity of an object liquid comprising: a fixed wall having a liquid flow hole; a deformable wall for defining an object liquid space with a variable volume in conjunction with said fixed wall; and a driver device for generating a controlled movement of said deformable wall.

2. An apparatus according to claim 1, wherein said driver device comprises a working fluid space separated by said deformable wall and formed opposite to said object liquid space and a working fluid transport device for delivering a working fluid to said working fluid space.

3. An apparatus according to claim 2, wherein said deformable wall is a membrane.

4. An apparatus according to claim 3, wherein said membrane is made of a material compatible with both said object liquid and said working fluid.

5. An apparatus according to claim 2, wherein said object liquid space and said working fluid space are formed substantially flat.

6. An apparatus according to claim 2, wherein said working fluid is an incompressible fluid.

7. An apparatus according to claim 2, wherein said working fluid transport device comprises a constant flow pump.

8. An apparatus according to claim 2, wherein said object liquid space and said working fluid space are substantially symmetrical with respect to a symmetry plane.

9. An apparatus according to any of the preceding claims, wherein said fixed wall has an interior contour shape substantially conforming to a deformed shape of a dividing membrane, and/or wherein preferably said deformable wall comprises a bellows, and/or wherein preferably said bellows is made of a material compatible with both said object liquid and said working fluid, and/or wherein preferably said driver device has an external driving device for mechanically deforming said deformable wall, and/or wherein preferably said deformable wall comprises a bellows, and/or wherein preferably said bellows is made of a material compatible with said object liquid, and/or preferably further comprising a push rod connecting said deformable wall to said external driving device.

10. A liquid transport apparatus for delivering a controlled quantity of an object liquid comprising: a fixed wall having a liquid flow hole; and a wall for defining an object liquid space with a variable volumne in conjunction with said fixed wall.

Drawing