Fluid handling – Line condition change responsive valves – Pilot or servo controlled
Reexamination Certificate
1997-07-15
2001-06-12
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Line condition change responsive valves
Pilot or servo controlled
C137S487500
Reexamination Certificate
active
06244293
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a mass flow controller, commonly termed MFC. More particularly, the present invention provides a novel technique including a device and method for maintaining a fluid flow rate of fluids used in, for example, semiconductor processing or the like. Merely by way of example, the present invention is illustrated using a device and methods related to integrated circuit processing. But it will be recognized that the present invention also can be applied to the manufacture of products such as flat panel displays, hard disk drives, and others.
In the manufacture of semiconductor integrated circuits, process complexity and wafer size tends to increase with time. For instance, wafer size has increased from one inch up to six inch over the past thirty years. Larger sized wafers such as eight inch are now being used. Twelve inch wafers and larger are being proposed. As wafer size and complexity of processing increase, gases used for the manufacture of the integrated circuits also become more important. In particular, control of a selected flow rate range for a process step (e.g., plasma etching (“PE”), chemical vapor deposition (“CVD”)) becomes rather important. Accordingly, mass flow controllers have been used to selectively control fluid flow rates of selected process steps.
Numerous mass flow controllers are presently on the market today. Manufacturers of mass flow controllers include, among others, Unit Instruments, Inc. (“Unit”), Brooks Instruments (“Brooks”), and Tylan General (“Tylan”). These manufacturers generally have a broad range of products to cover a variety of flow ranges, which are used in the manufacture of integrated circuit devices. For instance, Unit has at least ten different products for the purpose of covering a variety of flow rate ranges. Tylan has at least seven different products. As for Brooks, it has about eight products or more for covering different fluid flow ranges.
A limitation with these conventional mass flow controllers is their sheer number, where each controller can often be used for a limited fluid flow range. The sheer number of these mass flow controllers often translates into large numbers of different controller units being used and stored for replacement in the manufacturing line or semiconductor fabrication plant, commonly termed wafer fab. Accordingly, it is often quite expensive and time consuming to keep available all necessary spare parts to replace faulty or broken mass flow controllers.
Additionally, conventional mass flow controllers can often be adjusted to accommodate a relatively narrow flow rate range, which makes it often impossible or highly impractical to modify such conventional mass flow controllers to accommodate a different and often higher fluid flow rate. Therefore, companies such as Unit generally introduce a new mass flow controller to replace pre-existing controllers. This replacement process often translates into discarding older mass flow control units for newer ones at the expense of the wafer fab or wafer manufacturer.
From the above, it is seen that a mass flow controller which is cost effective and efficient is often desirable.
SUMMARY OF THE INVENTION
According to the present invention, a technique including a device and method for maintaining a fluid flow rate of a fluid used in, for example, semiconductor processing or the like is provided. In an embodiment, the present invention provides a device having wide fluid operating ranges, which are used in a variety of semiconductor processing operations.
In a specific embodiment, the present invention provides a fluid mass flow control device having a novel body design to allow for a wide variety of fluid flow rates. The device includes a main body, and an elongated fluid flow cavity in the main body. The fluid flow cavity is coupled (e.g., connected) to a fluid inlet/outlet. A control valve is coupled or connected by way of at least one orifice(s) between the fluid flow cavity and a fluid outlet/inlet. To increase capacity of fluid flow, the elongated fluid flow cavity is disposed underlying a portion of the control valve (or overlaps a region occupied by the valve) to increase a fluid flow path of the elongated fluid flow cavity. This fluid flow cavity allows for a variety of fluid flow rates.
In an alternative specific embodiment, the present invention provides a method for controlling fluid flow in a fluid flow device. The method includes a step of providing a fluid flow at an inlet of an elongated fluid flow cavity. The fluid is flowed through the elongated fluid flow cavity in a first direction in a laminar flow manner. The fluid is also flowed from the elongated fluid flow cavity to a control value through a first orifice in a second direction. The second direction has a directional element that is opposite of the first direction. By traversing in the direction opposite to the first direction, the present method can provide a longer elongated fluid flow cavity, which provides, for example, a wider variety of fluid flow ranges.
In yet another embodiment, the present invention provides a method of fabricating a fluid flow controller using a novel body design. The method includes a step of providing a main body, which has an elongated fluid flow cavity in the main body. This elongated fluid flow cavity is generally capable of more than one fluid flow range. To provide a desired fluid flow range, a selected by-pass element is chosen to provide fluid flow operable within the desired fluid flow range. The by-pass element is placed and assembled into the elongated fluid flow cavity. Other by-pass elements can also be selected to provide numerous other fluid flow ranges, depending upon the application.
The present invention further provides a method for modifying a fluid flow controller from a first fluid flow range to a second fluid flow range, which is different from the first fluid flow range. The method includes a step of providing a first fluid flow controller operable in a first range of fluid flow. The first fluid flow controller includes a first by-pass element for the first fluid flow rate. The method uses a step of replacing the first by-pass element with a second by-pass element for the second fluid flow rate to form a second fluid flow controller operable in the second range of fluid flow. The second fluid flow rate can be different from the first fluid flow rate. This sequence of steps allows for modification of MFCs according to the present invention to provide desired flow rates. That is, the present MFC is not designed or limited to provide a single range of narrow flow rates as pre-existing techniques.
Numerous benefits are achieved by way of the present invention over preexisting techniques. In particular, the present invention can provide a single mass flow control body for low and high fluid flow rates, which cannot be accurately detected by way of pre-existing techniques. Additionally, the present invention provides a main chamber housing that is easily modifiable to use numerous by-pass elements for use with selected ranges of fluid flow, which are generally wider than preexisting techniques. The present invention also provides a technique for modifying a first fluid flow controller designed for and operable at a first fluid flow range to a second fluid flow controller operable at a second fluid flow range, which cannot be done with pre-existing techniques. Additionally, the present invention provides a single mass flow controller operable over a wide range of flows, typically much wider than pre-existing techniques. Accordingly, the present invention achieves these benefits and others, which will be described in further detail throughout the specification.
The present invention achieves these benefits and others in the context of known process technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.
REFERENCES:
patent: 3335748 (1967-08-01), Klemm
Michalsky Gerald A.
Townsend and Townsend / and Crew LLP
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