Fluid handling – Processes – Involving pressure control
Reexamination Certificate
2000-04-19
2002-04-02
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Processes
Involving pressure control
C137S505140, C137S505390
Reexamination Certificate
active
06363959
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates broadly to fluid pressure regulators and methods of operating the same, and more particularly to a pressure regulator having a controlled differential pressure setting capability providing improved response when utilized, for example, in batchwise gas delivery applications such as may be found in the semiconductor processing industry.
Fluid pressure regulators are used in a variety of fluid transfer applications involving the delivery or other transport of pressurized process gases or the like. Within these applications, pressure regulators are provided to deliver a flow of a pressurized gas or other fluid at a regulated outlet pressure, and to maintain that pressure at a set value generally independent of the gas flow rate. For that purpose, the pressure regulator is supplied at its inlet port by a source of fluid which typically is at a pressure substantially higher than the desired outlet pressure. The desired outlet pressure is set and the regulator automatically actuates an internal valve to adjusts the size of a variable passage between its inlet and outlet ports to minimize the offset between the actual outlet pressure and the set pressure.
As is detailed more fully in commonly-assigned U.S. Pat. Nos. 5,787,925; 5,762,086; 5,755,428; 5,732,736; 5,458,001; 5,230,359; 4,702,277; and 4,257,450, pressure regulators of the type herein involved conventionally are operated on a force balance principle. In this regard, an internal diaphragm assembly of the regulator is subjected to forces acting in opposite directions. These forces include a first force acting in a first direction and related to the pressure setting, typically developed by the manual compression of a coil or other spring, a second force acting in a second direction opposite the first direction and developed by the outlet pressure as applied to the effective area of the diaphragm exposed to that pressure. Under standard operating conditions, the first force of the pressure setting is held constant such that any variation in the inlet or outlet pressure effects a proportional change in the second, opposing force being applied to the diaphragm. The imbalance thereby created between these opposing first and second forces cause the diaphragm to deflect. This deflection is transmitted directly to the valve which cooperates with an associated valve seat to vary the open area of an orifice or other fluid passage defined between the valve and the seat and, as a result, the fluid flow from the inlet of the regulator to its outlet.
For example, a step change increase in outlet flow rate generally will tend to decrease the outlet pressure and, proportionally, the second, opposing force being applied to the diaphragm by the outlet pressure. The force imbalance thereby developed is translated to the valve element via the deflection of the diaphragm. Such deflection urges the valve element to move in a direction which increases the area of the fluid flow orifice defined between the element and its associated valve seat. This increase, in turn, effects a corresponding increase in the fluid flow rate through the regulator which ultimately balances at steady state condition wherein the decrease in the outlet pressure is modulated.
Conversely, for a step change decrease in the outlet flow rate, the flow imbalance thereby developed would have the effect of urging the valve element in an opposite direction to decrease the area of its fluid flow orifice and, proportionately, the flow rate. A new balance thus is effected in which the outlet pressure is marginally increased as compared to outlet flow prior to the step change decrease.
The above-described automatic operation illustrates that some change in outlet pressure is required to accommodate a change in outlet flow. The purpose of pressure regulation therefore is to minimize the change in outlet pressure for a given range of flow variation. In addition to outlet pressure, the response of a pressure regulator must accommodate the effect of inlet pressure changes on the regulated outlet pressure, and also the effect as the flow rate approaches zero. The latter is expressed as the ability of the pressure regulator to close under a no-flow condition.
Regarding the effects of inlet pressure changes, the inlet pressure applied to the area of the valve passage develops a force which, as aforementioned, acts in the opposite direction as that of the pressure setting force. For example, a decrease in inlet pressure results in a proportionate decrease in the force transmitted to the diaphragm assembly, with the force balance being restored by a corresponding increase in outlet pressure. Sequentially, the decrease in inlet pressure decreases the force opposing the pressure setting force which, in turn, causes the diaphragm assembly to increase the valve opening. With the flow across the valve thereby being increased, the outlet pressure is increased to a new value which again restores the force balance. As conventionally operated at inlet pressures of 30-500 psi, pressure regulators of the type herein involved typically exhibit about a 1 psi increase or, as the case may be, decrease in outlet pressure for each 100 psi change in inlet pressure.
The precise relationship between inlet pressure decrease and outlet pressure increase is determined by the ratio of the effective areas of the valve passage and the diaphragm. For a more detailed analysis of this effect, reference may be had to the present inventor's prior U.S. Pat. No. 5,230,359, entitled “Supply Pressure Compensated Fluid Pressure Regulator And Method.”
Particularly for applications involving the batchwise delivery of a process gas at the point of use, there has been an expressed interest in providing for a fast start-up at the beginning of each delivery cycle. Such a start-up may be achieved when the outlet pressure of the regulator is controlled to stabilize quickly at a steady-state value as the gas flow is increased from no flow prior to the commencement of a delivery cycle, to a given delivery flow rate.
The semiconductor industry, for example, utilizes the batchwise delivery of process gases in the manufacture of integrated circuit (IC) chips or dies. In the general mass production of semiconductor devices, hundreds of identical “integrated” circuit (IC) trace patterns are photolithographically imaged over several layers on a single semiconductor wafer which, in turn, is cut into hundreds of identical dies or chips. Within each of the die layers, the circuit traces are deposited from a metallizing process gas such as tungsten hexafluoride (WF
6
), and are isolated from the next layer by an insulating material deposited from another process gas. The process gases typically are delivered in discrete flow cycles or “batches” from pressurized supplies, thereby requiring delivery systems of a type which may be operated in alternate flow and no-flow modes.
A representative delivery system of such type is shown at
10
in the schematic of FIG.
1
. Referring then to
FIG. 1
, delivery system
10
may be seen to conventionally include, in series, a gas supply
12
, a pneumatic isolation valve,
14
, a pressure regulator,
16
, a pressure transducer,
18
, a manual valve,
20
, a mass flow controller,
22
, and a pneumatic on/off valve,
24
. Fluid flow through system
10
is in the direction reference by arrow
30
.
Prior to the initiation of a delivery cycle, system
10
is in a start-up/stand-by or “no-flow” operational mode wherein pneumatic valve
24
is commanded closed, manual valve
20
is set open, and mass flow controller
22
is set to zero. At the initiation of “flow” or delivery operational mode, pneumatic valve
24
is commanded to open and the mass flow controller
22
is set to control flow at a desired rate. Thereupon, at the termination of the flow mode, the pneumatic valve
24
is commanded closed and the setting of the mass flow controller
22
is returned to zero. At all times during both operational modes, the pressure regulator
16
remains set at a
Hepperle Stephen M.
Molnar, Jr. John A.
Parker-Hannifin Corporation
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