Coating apparatus – Gas or vapor deposition – Crucible or evaporator structure
Reexamination Certificate
1998-09-29
2001-07-17
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
Crucible or evaporator structure
C118S715000, C118S7230VE, C156S345420
Reexamination Certificate
active
06261374
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to gas delivery systems for processing chambers, and specifically to a clog resistant gas delivery system for delivering vaporized liquid precursors; particularly triethylphosphate (TEPO) and tetraethyl orthosilicate (TEOS), to a chemical vapor deposition (CVD) chamber.
BACKGROUND OF THE INVENTION
CVD processing requires a number of vaporized processing liquids. These vaporized liquids are generated and supplied to a CVD chamber via a system of pipes (or “lines”) and vaporizing mechanisms known as a gas delivery system. Typically a separate vaporizing mechanism is provided for vaporizing each processing liquid, and is coupled to a source of processing liquid and a source of carrier gas. Each vaporizing mechanism and processing liquid source combination within a gas delivery system is referred to as a vaporization stage. Although a number of vaporizing mechanisms exist (e.g., bubblers, injection valves, etc.), most conventional gas delivery systems employ a plurality of injection valves for vaporizing processing liquids to be delivered to a CVD chamber.
A typical injection valve comprises a processing liquid inlet for receiving a pressurized processing liquid, a carrier gas inlet for receiving a pressurized inert carrier gas, and an outlet for delivering a vaporized processing liquid/carrier gas mixture. The injection valve is heated such that when the processing liquid is injected into the carrier gas, the heat and the low partial vapor pressure of the processing liquid in the carrier gas causes the processing liquid to vaporize. A high carrier gas pressure produces more processing liquid vaporization by lowering the partial vapor pressure of the processing liquid within the carrier gas. Accordingly, when designing a gas delivery system, maintenance of adequate carrier gas pressure is an important consideration, as is minimizing overall system size and complexity.
To achieve a low partial vapor pressure for each processing liquid while minimizing system size, conventional gas delivery systems are configured such that a carrier gas is delivered (via a mass flow controller) to a first injection valve, where it is used to vaporize a first processing liquid, forming a first vaporized processing liquid/carrier gas mixture. The first vaporized processing liquid/carrier gas mixture then is delivered to the carrier gas inlet of a second, consecutive injection valve where it is used to vaporize a second processing liquid. A mixture of the first and second vaporized processing liquids and the carrier gas then is delivered to the carrier gas inlet of a third consecutive injection valve, etc. These configurations provide a compact and cost effective system as they employ a single gas line, and a single carrier gas source controlled by a single mass flow controller to achieve vaporization within each of the various vaporization stages. Additionally, conventional gas delivery systems facilitate processing liquid vaporization as the entire mass flow of carrier gas is applied to each injection valve.
Despite their overall compact and efficient design, maintenance of conventional gas delivery systems is expensive due to injection valve clogging. A clogged injection valve can cause downtime not only of the chamber to which the clogged injection valve is coupled, but also of upstream and/or downstream chambers. In addition to costly chamber downtime, injection valves themselves are expensive, typically costing more than two thousand dollars to replace, exclusive of labor costs. Thus, considerable effort has been devoted to developing clog resistant gas delivery systems, and numerous advances have been achieved.
A particularly worthy advance is the recognition by Applied Materials, Inc., that alloys containing nickel react with the CVD processing liquid TEPO, causing residue formation and clogging, and the recognition that chromium can repress the nickel/TEPO reaction. Thus, gas delivery components made with less than 1% nickel and with 16-27% chromium significantly reduce clogging as described in commonly assigned U.S. Pat. No. 5,925,189 (application Ser. No. 08/568,193, filed Dec. 6, 1995). Despite such advances, clogging within gas delivery systems remains a problem, particularly when a gas delivery system must be configured with existing nickel-containing components.
Accordingly, a need exists for a clog resistant gas delivery system that can be easily and inexpensively repaired, should clogging occur, and that resists clogging regardless of component composition.
SUMMARY OF THE INVENTION
The present invention recognizes that processing liquids and/or contaminants within the various processing liquids react among themselves forming coagulates which clog gas delivery components. Specifically, the present inventors have discovered a reaction between TEOS and H
3
PO
4
(an impurity frequently found in TEPO, and a by-product of TEPO and nickel reactions) creates a residue responsible for most clogs within TEPO gas delivery systems. As used herein impurities are considered part of the processing liquid. For example, a processing liquid is referred to as comprising H
3
PO
4
whether H
3
PO
4
is a constituent of the liquid, or an impurity.
To substantially reduce or eliminate clogging an inventive gas delivery system is provided which routes gas delivery lines in a parallel format such that within each vaporization stage only a single processing liquid is present. The parallel gas delivery lines are joined, and the vaporized processing liquids are mixed within a gas line rather than within an injection valve or bubbler. Because vaporized processing liquids mixing occurs within a gas line, there are no small diameter orifices (such as those contained within injection valves or bubblers) which residue may clog. Further, in the unlikely event of clogging, the gas line can be easily and inexpensively replaced.
In its most preferred embodiment, the inventive gas delivery system comprises a single source of carrier gas and a single mass flow controller for supplying carrier gas to each vaporization stage, thus reducing the number of parts required to vaporize processing liquids in parallel. Generally, however, the present invention may be used to reduce clogging within any processing environment wherein mixed processing constituents form an undesirable reaction product that can clog the various components within a processing constituent delivery system.
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.
REFERENCES:
patent: 5186120 (1993-02-01), Ohnishi et al.
patent: 5204314 (1993-04-01), Kirlin et al.
patent: 5536323 (1996-07-01), Kirlin et al.
patent: 5702532 (1997-12-01), Wen et al.
patent: 5711816 (1998-01-01), Kirlin et al.
patent: 5766360 (1998-06-01), Sato et al.
patent: 5876503 (1999-03-01), Roeder et al.
patent: 5925189 (1999-07-01), Nguyen et al.
Bang Won
Chen Chen-An
Applied Materials Inc.
Dugan & Dugan
Hassanzadeh P.
Mills Gregory
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