Fluid handling – Line condition change responsive valves – Pilot or servo controlled
Reexamination Certificate
2000-06-02
2001-09-18
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Line condition change responsive valves
Pilot or servo controlled
C137S487500, C251S118000
Reexamination Certificate
active
06289923
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved gas supply system equipped with a pressure-type flow rate control unit for use in semiconductor manufacturing facilities and chemical manufacturing plants. More particularly, the present invention relates to a gas supply system reduced in size and improved in flow rate control and other performances.
2. Description of the Prior Art
The mass flow rate controller has been widely used for gas flow rate control in the gas supply system in semiconductor manufacturing facilities.
But the mass flow rate controller has presented a number of problems in practice including high manufacturing costs, slow response, product-to-product control precision non-uniformity, and low control stability.
Similarly, the metal diaphragm valve of the air-driven type has found wide acceptance as a valve to control the supply of gas from the gas supply source to gas-using processes. But this valve is slow to open and close, which lowers reliability of the quality of the finished products, i.e., semiconductors, and fails to raise the production efficiency of semiconductors and other products.
Earlier, the applicants of the present invention developed a gas supply system using a pressure-type flow rate controller and a high-speed solenoid actuating type metal diaphragm valve which could solve all the problems with the prior art. The new supply system developed was disclosed in unexamined Japanese patent applications laid open under Nos. H08-338546 and H10-55218.
FIG. 11
shows a block diagram of a gas supply system equipped with the prior art pressure-type flow rate control unit.
FIG. 12
is a vertical, sectional view showing a control valve and an orifice-accompanying valve installed together which constitutes the core of the gas supply system.
In
FIGS. 11 and 12
, the numeral
1
indicates a pressure-type flow rate control unit,
2
a control valve,
3
a pressure detector,
4
a temperature detector,
5
an orifice,
6
a calculation control unit,
6
a
an temperature correction circuit,
6
b
a flow rate calculation circuit,
6
c
a comparison circuit,
6
d
an amplifier circuit,
7
a,
7
b
amplifiers,
8
a,
8
b
A/D converters,
9
an orifice-accompanying valve,
9
a
a valve block and
12
a valve block. The reference letters Qs denote flow-rate specifying signal, Qc flow-rate calculation signal and Qy control signal. The operating principle of that pressure-type flow rate control system is this: The fluid pressure between the orifice
5
and the control valve
2
is measured by the pressure detector
3
with the pressure P
1
on the upstream side of the orifice
5
held about twice or more higher than the downstream pressure P
2
. On the basis of this detected pressure P
1
, the flow rate Qc is calculated with an equation Qc=KP
1
(K: constant) in the calculation control unit
6
. The difference between the flow-rate specifying signal Qs and the calculated flow rate Qc is input in the drive
10
for the valve
2
as control signal Qy to regulate the opening of the control valve
2
for adjusting the pressure P
1
upstream of the orifice
5
so that the flow rate on the downstream side of the orifice
5
is automatically regulated to the specified flow rate Qs.
The control valve
2
and the orifice-accompanying valve
9
are formed separately as shown in FIG.
12
. The two valves
2
,
9
, which are connected to each other by means of a nipple
12
a
and a connecting bolt
13
a,
form the core of the gas supply system.
The orifice-accompanying valve
9
as used is an air-actuating type diaphragm valve or solenoid-actuating type metal diaphragm valve.
Also, in
FIGS. 11 and 12
, the numeral
11
a
indicates the gas outlet side,
11
b
the gas inlet side,
12
a
,
12
b
nipples, and
13
b
,
13
a
connecting bolts.
The gas supply system equipped with the known pressure-type flow rate control unit shown in
FIGS. 11 and 12
was much lower in manufacturing costs and more excellent in response characteristics than the system using the prior art mass flow rate controller. Also unsurpassed by the prior art mass flow rate controller in control precision, the pressure-type flow rate control unit has an excellent usefulness in practice.
Yet, the above-mentioned gas supply system equipped with the pressure-type flow rate control unit still has some problems to solve. That which requires urgent attention is the necessity:
to further reduce size;
to so design the components that the surfaces coming in contact with gas are easy to treat, thus raising the stability and reliability of the components;
to improve the transient flow rate characteristics to prevent the so-called overshoot (transient flow-in) and keep the mixture gas from fluctuating in composition ratio, thus raising the uniformity of quality of finished products or semiconductors; and
to speed up the switchover of gases to supply, thus improving the production efficiency.
SUMMARY OF THE INVENTION
The present invention seeks to solve those aforesaid problems with the known gas supply system equipped with the pressure-type flow rate control unit. And it is an object of the present invention to provide a gas supply system equipped with a pressure-type flow rate control unit that is further reduced in size and is so designed that the gas contact surfaces are easy to treat. It is another object of the present invention to provide a gas supply system equipped with a pressure-type flow rate control unit that is improved in transient flow rate characteristics to raise the quality uniformity of finished products, such as semiconductors. It is still another object of the present invention to provide a gas supply system equipped with a pressure-type flow rate control unit that is intended to speed up switchover of gases to supply for raising the production efficiency of semiconductors.
To achieve the foregoing objects, the control valve
2
and the orifice-accompanying valve
9
are formed integrally to further reduce the size of the system and to facilitate the treatment of the gas contact surfaces. In addition, the orifice
5
is placed on the downstream side of the orifice-accompanying valve
9
to improve the transient flow rate characteristics of fluid. Furthermore, the orifice-accompanying valve
9
itself is made as a small-sized quick-actuating type metal diaphragm valve to achieve a high-speed switchover of gases to supply.
To illustrate, the present invention in a preferred embodiment provides a gas supply system equipped with a pressure-type flow rate control unit which is so configured that with the pressure on the upstream side of the orifice held about twice or more higher than the downstream pressure, the gas flow rate is controlled to supply the gas to a gas-using process through an orifice-accompanying valve, the gas supply system comprising a control valve to receive gas from the gas supply source, an orifice-accompanying valve provided on the downstream side of the control valve, a pressure detector provided between the control valve and the orifice-accompanying valve, an orifice provided on the downstream side of the valve mechanism of the orifice-accompanying valve and a calculation control unit where on the basis of the pressure P
1
detected by the pressure detector, the flow rate Qc is calculated with an equation Qc=KP
1
(K: constant) and the difference between the flow-rate specifying signal Qs and the calculated flow rate Qc is then input as control signal Qy in the drive for the control valve, thereby regulating the opening of the control valve for adjusting the pressure P
1
so that the flow rate of the gas to supply can be controlled.
The present invention in another embodiment provides the gas supply system equipped with a pressure-type flow rate control unit as defined in above, wherein the control valve is a direct touch-type metal diaphragm valve provided with a piezoelectric element actuating-type drive, wherein the orifice-accompanying valve is a direct touch-type metal diaphragm valve, and wherein the pressure
Dohi Ryousuke
Ideta Eiji
Ikeda Nobukazu
Kagatsume Satoshi
Nishino Kouji
Fujikin Incorporated
Griffin & Szipl, P.C.
Michalsky Gerald A.
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