Atomizer

Details Atomizer Atomizer

2002-02-28

2004-12-28

Bushey, Scott (Department: 1724)

Gas and liquid contact apparatus

With external supply or removal of heat

Heat exchange means at or downstream of contact zone

C261S066000, C261S078200

Reexamination Certificate

active

06834848

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates, in general, to a fluid delivery system. More particularly, this invention provides an integrated fluid delivery system (IFDS) for providing high purity fluid streams, such as for a wafer processing chamber.
BACKGROUND OF THE INVENTION
High purity fluid delivery systems are employed in demanding manufacturing environments such as the semiconductor manufacturing industry. The delivery systems are designed to precisely dispense fluids which may be hazardous in nature (i.e., corrosive, poisonous) and/or expensive. For example, in semiconductor processing/manufacturing, various stages such as low pressure chemical vapor deposition (LPCVD), oxidation, and plasma enhanced chemical vapor deposition (PECVD), require corrosive precursors such as boron, silicon and phosphorous to be delivered to a wafer processing chamber for the manufacture of semiconductor devices.
Typically, high purity fluid systems in the semiconductor manufacturing industry employ a complex network of tubing (plumbing) that require high integrity welds between tube sections and conduit assemblies for channeling the fluids to a variety of fluid control, metering, and operational devices. As the layout of each system is dependent upon the number and location of the control, metering and operational devices, the “system schematic” is equal in complexity to the number of high integrity welds and corresponding conduit arrangement.
As can be appreciated, the number of high cost conduit assembly (i.e., valving) and high integrity welding connections, as well as the increased complexity of the corresponding system schematic leads to liquid delivery systems which are costly to both maintain and manufacture. Indeed, bulky conduit assemblies requiring even a mere additional square foot can be cost prohibitive in the valuable real estate of clean room environments, where the cost to build per square foot is especially expensive.
Moreover, repairing a faulty weld or replacing a flow device component often necessitates disassembly of a substantial portion of the liquid delivery system. This also increases the down time of the process incorporating the component. For example, there is shown in
FIG. 1
, a typical prior art liquid delivery system
5
. Liquid delivery system
5
utilizes a conduit assembly
7
which employs a plurality of conduit sections
10
, high integrity welds (not shown) and flow devices
12
for delivering high purity liquid streams from system
5
. Flow devices
12
can be any device known in the art for processing a fluid, but typically include flow controllers, valves, filters and pressure transducers. As shown in
FIG. 1
, conduit based system
7
requires a large degree of available area inside the cabinet of liquid delivery system
5
. Thus, in the case where a particularly hard to reach component or weld requires maintenance and/or replacement, a significant portion of system
7
would need to be disassembled. As can be appreciated, conduit system
7
is complex and costly to assemble and operate. For example, conduit system
7
has a higher overall resistance to fluid flow than lesser complex systems, thus an increased “down time” is required to purge the system of fluids where necessary.
To provide a precise volume of fluid to a processing application, fluid delivery systems may comprise a flow controller. Typically, flow controllers couple a sensor for measuring flow volume with a valve for adjusting flow volume. Measuring the flow volume of an entire fluid stream, however, can lead to long response time. Some flow controllers employ a fluid bypass, measuring the flow volume of a small portion of the flow and inferring the flow volume in the bypass. These flow controllers, however, employ methods for maintaining the necessary pressure differential that are expensive, have high part counts that add tolerances and cost, or are difficult to manufacture yielding inadequate accuracy or repeatability. Examples of such bypass flow controllers include those using a bundle of tubes or a sintered metal slug.
Additionally, atomizing and/or vaporizing a liquid in a gas stream is often necessary in high purity fluid processing applications. For example, these processes may be employed to deposit high-purity, metal oxide films on a substrate. Moreover, the liquid mixtures may also be utilized for spray coating, spin coating and sol-gel deposition of materials. In particular, chemical vapor deposition (CVD) is an increasingly utilized high purity fluid delivery process for forming solid materials, such as coatings or powders by way of reactants in a vapor phase. Typically, a reactant vapor is created by heating a liquid to an appropriate temperature and bubbling a flow of carrier gas through the liquid (i.e. high purity fluid stream) to transport the vapor into a CVD chamber. Specifically, a gas stream and liquid stream are introduced into a single channel or conduit at a T-junction. The CVD system pumps a fluid stream at a steady, controlled rate into a hot region which may include ultrasonic energy for effecting the mixture components. However, this technique creates a dead volume of material upon discontinuance of the process. Further, bubbling can often be an unpredictable method of vaporization, in which the precise quantity of the liquid reactant is difficult to control.
Accordingly, there is a need for an atomizer which predictably atomizes a fluid while eliminating dead volume upon discontinuance of the atomization process. Also, there is a need for an accurate, reliable and inexpensive flow controller. Similarly, there is a need for an integrated liquid delivery system wherein the system schematic can be consolidated to a single modular manifold device.
SUMMARY OF THE INVENTION
The present invention provides an atomizer for precisely combining separate gas and liquid streams. A base member of the atomizer has a mixing slot formed therein for producing a venturi effect at a mixing point. The mixing slot has a gas input side and a mixture side. A liquid inlet is in fluidic communication with the mixing slot. The mixing point is defined by the junction of the liquid inlet to the mixing slot. A gas stream inlet is in fluidic communication with the gas input side of the mixing slot. A mixture outlet is in fluidic communication with the mixture side of the mixing slot. The gas stream flowing into the mixing point is accelerated by the tapered mixing slot, drawing portions of the liquid into the gas stream by venturi effect to produce a mixture of atomized liquid and gas in a generally laminar flow. The atomized mixture of gas and liquid streams is presented at the mixture outlet.
It is to be understood that both the foregoing general description of the invention and the following detailed description are exemplary, but are not restrictive, of the invention.


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