Fluid handling – Systems – With flow control means for branched passages
Reexamination Certificate
1999-08-10
2001-02-27
Fox, John (Department: 3753)
Fluid handling
Systems
With flow control means for branched passages
C137S271000
Reexamination Certificate
active
06192938
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates in general to gas handling systems for semiconductor processing and in particular, to gas panel systems whether of a localized nature or distributed around a semiconductor processing tool.
Wafer fabrication facilities are commonly organized to include areas in which chemical vapor deposition, plasma deposition, plasma etching, sputtering and the like are carried out. In order to carry out many of these processes, it is necessary that the tools which are used for the process, be they chemical vapor deposition reactors, vacuum sputtering machines, plasma etchers or plasma enhanced chemical vapor deposition, be supplied with various process gases which gases may be reactive or inert or provide reactive species.
For instance, in order to perform epitaxial deposition, silicon tetrachloride has bubbled through it a carrier gas such as dry nitrogen, which then carries silicon tetrachloride vapor into an epitaxial deposition chamber. In order to deposit a silicon oxide dielectric coating, also known as a deposited oxide coating, silane (SiH
4
) is flowed into the tool and oxygen is flowed into the tool where they react to form (SiO
2
) on the surface of the wafer. Plasma etching is carried out by supplying carbon tetrachloride and sulfur hexafluoride to a plasma etcher tool. The compounds are ionized, to form reactive halogen species which then etch the silicon wafer. Silicon nitride may be deposited by the reaction of dichlorosilane and ammonia in a tool. It may be appreciated that in each instance pure carrier gases or reactant gases must be supplied to the tool in contaminant-free, precisely metered quantities.
In a typical wafer fabrication facility the inert and reactant gases are stored in tanks which may be located in the basement of the facility and which are connected via piping or conduit to a valve manifold box. The tanks and the valve manifold box are considered to be part of the facility level system. At the tool level an overall tool system, such as a plasma etcher or the like, includes a gas panel and the tool itself. The gas panel contained in the tool includes a plurality of gas paths having connected therein manual valves, pneumatic valves, pressure regulators, pressure transducers, mass flow controllers, filters, purifiers and the like. All have the purpose of delivering precisely metered amounts of pure inert or reactant gas from the valve manifold box to the tool itself.
The gas panel is located in the cabinet with the tool and typically occupies a relatively large amount of space, as each of the active devices are plumbed into the gas panel, either through welding tubing to the devices or combinations of welds and connectors such as VCR connectors available from Cajon Corporation or the like.
Gas panels are relatively difficult to manufacture and hence expensive. In a combination VCR connector and welded tubing system the individual components are held on shimmed supports to provide alignment prior to connections at VCR fittings. Misalignment at a VCR fitting can result in leakage.
In addition, it has been found that VCR fittings often tend to come loose in transit and some gas panel manufacturers assume that the VCR fittings have loosened during transit, possibly admitting contaminants to the system.
Welds are relatively expensive to make in such systems but are typically carried out using a tungsten inert gas (TIG) system, having an orbital welding head to weld a tube stub and a tube together. The welding must take place in an inert atmosphere, such as argon, and even then leads to deterioration of the surface finish within the tubes. One of the important characteristics of modern-day gas panel systems and gas handling systems is that the surfaces of the gas handling equipment that tend to have the gas or vapor contact them must be made as smooth and nonreactive as possible in order to reduce the number of nucleation sites and collection sites where contaminants may tend to deposit in the tube, leading to the formation of particulates or dust which would contaminate the wafers being processed.
Additional problems with conventional gas panels relate to the fact that a combination VCR and welded system of the type currently used today typically requires a significant amount of space between each of the components so that during servicing the VCR connections can be accessed and opened. In-addition, in order to remove an active component from a contemporary gas panel, many of the supports of the surrounding components must be loosened so that the components can be spread out to allow removal of the active component under consideration.
Most wafer fabricators are aware that it is only a matter of time until, for instance, the silane lines in the gas panels are “dusted.” “Dusting” occurs when air leaks into an active silane line causing a pyrophoric reaction to take place yielding loose particulate silicon dioxide in the tube, thereby contaminating the line. Other lines also can be contaminated. For instance, those which carry chlorine gas used in etchers or which carry hydrogen chloride used in other reactions. Hydrogen chloride mixing with moisture present in the humidity of air produces hydrochloric acid which etches the interior of the tube, roughening it and increasing the number of nucleation sites and the likelihood that unwanted deposition would occur inside the tube. In both of these cases, as well as in others, it would be necessary then to open the particular line in the gas panel in order to clean it.
In addition, individual component failures may require a line being opened in order to clean it and is time consuming and expensive.
What is needed, then, is a new type of gas panel which is compact, inexpensive to manufacture and easy to service.
SUMMARY OF THE INVENTION
In accordance with the present invention, a gas panel assembly is provided including a plurality of active device receiving one-piece gas or vapor manifolds. The active device receiving manifolds are arranged so that they receive gas or vapor at an inlet end, pass the gas or vapor along to a plurality of interior channels to a plurality of active device receiving stations which may be connected to an active device or have connected thereto a gas return cap and ultimately deliver the gas or vapor from an outlet for ultimate supply to a tool.
The inventive gas panel assembly is easy to manufacture, in that a standardized manifold is used with a standardized footprint for connection to the active devices. Each of the active device sites is positioned along the face of the substantially rectangular manifold and is oriented to extend at substantially right angles to the face of the active device manifold and therefore out of the general flow path. Each of the devices is connected to the manifold by a plurality of Allen-head bolts which hold the device base onto the manifold and which may be quickly and easily removed in order to remove a particular device from the system without disturbing other portions of the system.
The manifolding system is also self-aligning, in that each manifold is a repeatable machined component which has been prefabricated. There is no necessity either to provide welded connections or VCR and tube connections directly to the active devices as the connections are made through and support provided by the manifold itself. By tucking within the manifold each of the inlet and outlet connection loops from the manifold between adjacent stations, this greatly saves space and allows a great reduction in the amount of space over that required by a prior gas panel assembly.
The gas panel assembly embodying the present invention is easy to manufacture in that each of the active devices is separately aligned. If misalignment were to occur, for instance, between a pressure regulator and the device receiving station on the surface of a one-piece manifold, an adjacent valve mass flow controller or the like would not be positioned out of alignment with the general manifolding structure as a result thereof. Thus, any misalignment which m
Redemann Eric J.
Vu Kim N.
Fox John
Unit Instruments, Inc.
Wolf Greenfield & Sacks P.C.
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