Abstrict A method and apparatus for preventing flow rate errors derived
from an ultrasonic flow meter utilized in semiconductor fabrication
operations. The ultrasonic flow meter is generally configured to
include an extension chamber connected to a thin branch tube of
the ultrasonic flow meter. A venturi tube can be positioned at an
outflow location of the ultrasonic flow meter, such that the thin
branch tube is broached into the venturi tube, wherein bubbles contained
in a slurry flow are forced directly into the outflow location to
thereby prevent inaccurate flow measurements derived from the ultrasonic
flow meter. The extension chamber may be configured to reduce an
inflow velocity associated with the slurry slow and ensure that
the bubbles with not drift with the slurry flow. Additionally, a
diameter of the branch tube may be configured such that the diameter
is much smaller than a diameter associated with an inflow and/or
outflow tube of the ultrasonic flow meter.
Claims What is claimed is:
1. A method for preventing flow rate errors derived from an ultrasonic
flow meter utilized in semiconductor fabrication operations, said
method comprising the step of: configuring said ultrasonic flow
meter to include an extension chamber connected to a thin branch
tube of said ultrasonic flow meter; positioning a venturi tube at
an outflow location of said ultrasonic flow meter, such that said
thin branch tube is broached into said venturi tube, wherein bubbles
contained in a slurry flow are forced directly into said outflow
location to thereby prevent inaccurate flow measurements derived
from said ultrasonic flow meter.
2. The method of claim 1 further comprising the step of: configuring
said extension chamber to reduce an inflow velocity associated with
said slurry slow and ensure that said bubbles with not drift with
said slurry flow.
3. The method of claim 1 further comprising the step of: configuring
a diameter of said thin branch tube such that said diameter is much
smaller than a diameter associated with an inflow tube of said ultrasonic
flow meter.
4. The method of claim 1 further comprising the step of: configuring
a diameter of said thin branch tube such that said diameter is much
smaller than a diameter associated with an outflow tube of said
ultrasonic flow meter.
5. The method of claim 1 further comprising the step of: connecting
a first terminal of said thin branch tube to said venturi tube to
establish an outflow tube.
6. The method of claim 1 further comprising the step of: configuring
said ultrasonic flow meter such that a differential pressure exists
form said extension chamber toward an outflow tube of said ultrasonic
flow meter.
7. The method of claim 1 further comprising the step of: configuring
said ultrasonic flow meter such that said slurry flows into an outlet
tube of said ultrasonic flow meter and does not pass through said
ultrasonic flow meter.
8. The method of claim 1 wherein said ultrasonic flow meter is
adapted for use in Chemical Mechanical Polishing (CMP) operations.
9. The method of claim 1 wherein said bubbles comprise a plurality
of mini-bubbles.
10. A method for preventing flow rate errors derived from an ultrasonic
flow meter utilized in semiconductor fabrication operations, said
method comprising the step of: configuring said ultrasonic flow
meter to include an extension chamber connected to a thin branch
tube of said ultrasonic flow meter; positioning a venturi tube at
an outflow location of said ultrasonic flow meter, such that said
thin branch tube is broached into said venturi tube, wherein bubbles
contained in a slurry flow are forced directly into said outflow
location to thereby prevent inaccurate flow measurements derived
from said ultrasonic flow meter; and configuring said extension
chamber to reduce an inflow velocity associated with said slurry
slow and ensure that said bubbles with not drift with said slurry
flow.
11. An ultrasonic flow meter utilized in semiconductor fabrication
operations, said ultrasonic flow meter comprising: an extension
chamber connected to a thin branch tube of said ultrasonic flow
meter; and a venturi tube positioned at an outflow location of said
ultrasonic flow meter, such that said thin branch tube is broached
into said venturi tube, wherein bubbles contained in a slurry flow
are forced directly into said outflow location to thereby prevent
inaccurate flow measurements derived from said ultrasonic flow meter.
12. The ultrasonic flow meter of claim 11 wherein said extension
chamber is configured to reduce an inflow velocity associated with
said slurry slow and ensure that said bubbles with not drift with
said slurry flow.
13. The ultrasonic flow meter of claim 11 wherein a diameter of
said thin branch tube is much smaller than a diameter associated
with an inflow tube of said ultrasonic flow meter.
14. The ultrasonic flow meter of claim 11 wherein diameter of said
thin branch tube is much smaller than a diameter associated with
an outflow tube of said ultrasonic flow meter.
15. The ultrasonic flow meter of claim 11 wherein a first terminal
of said thin branch tube is connected to said venturi tube to establish
an outflow tube.
16. The ultrasonic flow meter of claim 11 wherein said ultrasonic
flow meter is configured such that a differential pressure exists
form said extension chamber toward an outflow tube of said ultrasonic
flow meter.
17. The ultrasonic flow meter of claim 11 wherein ultrasonic flow
meter is configured such that said slurry flows into an outlet tube
of said ultrasonic flow meter and does not pass through said ultrasonic
flow meter.
18. The ultrasonic flow meter of claim 11 wherein said ultrasonic
flow meter is adapted for use in Chemical Mechanical Polishing (CMP)
operations.
19. The ultrasonic flow meter of claim 11 wherein said bubbles
comprise a plurality of mini-bubbles.
20. An ultrasonic flow meter utilized in semiconductor fabrication
operations, said ultrasonic flow meter comprising: an extension
chamber connected to a thin branch tube of said ultrasonic flow
meter; a venturi tube positioned at an outflow location of said
ultrasonic flow meter, such that said thin branch tube is broached
into said venturi tube, wherein bubbles contained in a slurry flow
are forced directly into said outflow location to thereby prevent
inaccurate flow measurements derived from said ultrasonic flow meter;
and said extension chamber configured to reduce an inflow velocity
associated with said slurry slow and ensure that said bubbles with
not drift with said slurry flow.
Description TECHNICAL FIELD
The present invention relates ultrasonic flow meter devices and
methods thereof. The present invention also relates to ultrasonic
flow meter devices utilized in semiconductor fabrication processes,
including CMP (Chemical Mechanical Polishing) operations.
BACKGROUND OF THE INVENTION
Ultrasonic flow meters have many advantages over other methods
of determining flow rates. Ultrasonic flow meters can continuously
measure the flow rate, while other methods generally measure average
flow rates. In addition, ultrasonic flow meters are obstructionless
and work with non-conductive fluids.
Ultrasonic flow meters are generally configured, such that a generated
ultrasonic wave is caused to propagate through a fluid flowing through
a tubular path of the ultrasonic flow meter. In typical ultrasonic
flow meters, the velocity of the fluid flowing through the tubular
path is determined on the basis of the difference between the rate
of propagation of the ultrasonic wave that propagates from an upstream
to a downstream and that, which propagates from the downstream to
the upstream.
A typical prior art flow meter includes a conduit through which
a fluid flows and a pair of ultrasonic transducers disposed in the
conduit along a line, which is inclined by a predetermined angle
with respect to a fluid flowing direction. In the operation, initially,
an ultrasonic wave is emitted from the ultrasonic transducer disposed
on the upstream side with respect to the flowing direction, toward
the downstream side, and is received by the ultrasonic transducer
on the downstream side. Then the propagation time from the emission
to the reception of the ultrasonic wave is determined. Subsequently,
an ultrasonic wave can be emitted from the ultrasonic transducer
disposed on the downstream side with respect to the flowing direction,
toward the upstream side, and is received by the ultrasonic transducer
on the upstream side, and the propagation time from the emission
to the reception of the ultrasonic wave is determined. Substituting
the two propagation times into a well-known equation yields the
velocity of the fluid, with which the rate of flow may be determined.
Ultrasonic flow meters are thus precision-sensitive devices utilized
to measure flow rates. Such devices, however, have a number of disadvantages
when applied to particular operations requiring precision measurements.
These disadvantages are particularly noticeable in CMP (Chemical
Mechanical Polishing) operations utilized in semiconductor device
fabrication environments. One of the primary disadvantages of prior
art ultrasonic flow meters in CMP operations involves the formation
of bubbles within a slurry flow. In such scenarios, the ultrasonic
wave in the flow is typically scattered by such bubbles, resulting
in poor and inaccurate measurements. Thus, it is necessary to avoid
bubbles passing through ultrasonic flow meters utilized in semiconductor
device CMP operations in order to avoid influencing the flow rate.
BRIEF SUMMARY OF THE INVENTION
The following summary of the invention is provided to facilitate
an understanding of some of the innovative features unique to the
present invention, and is not intended to be a full description.
A full appreciation of the various aspects of the invention can
be gained by taking the entire specification, claims, drawings,
and abstract as a whole.
It is therefore one aspect of the present invention to provide
an improved ultrasonic flow meter and methods thereof.
It is therefore another aspect of the present invention to provide
an improved ultrasonic flow meter method and methods thereof for
use in semiconductor fabrication operations.
It is still another aspect of the present invention to provide
an improved ultrasonic flow meter method and methods thereof for
use in Chemical Mechanical Polishing (CMP) operations.
It is yet another aspect of the present invention to provide an
improved ultrasonic flow meter method and methods thereof for limiting
measurement errors derived from ultrasonic flow meters utilized
in CMP operations.
The above and other aspects of the present invention can thus be
achieved as is now described. A method and apparatus for preventing
flow rate errors derived from an ultrasonic flow meter utilized
in semiconductor fabrication operations are disclosed herein. The
ultrasonic flow meter is generally configured to include an extension
chamber connected to a thin branch tube of the ultrasonic flow meter.
A venturi tube can be positioned at an outflow location of the ultrasonic
flow meter, such that the thin branch tube is broached into the
venturi tube, wherein bubbles contained in a slurry flow are forced
directly into the outflow location to thereby prevent inaccurate
flow measurements derived from the ultrasonic flow meter. The extension
chamber may be configured to reduce an inflow velocity associated
with the slurry slow and ensure that the bubbles with not drift
with the slurry flow.
Additionally, a diameter of the branch tube may be configured such
that the diameter is much smaller than a diameter associated with
an inflow and/or outflow tube of the ultrasonic flow meter. A first
terminal of the thin branch tube may be connected to the venturi
tube to establish an outflow tube. Additionally, the ultrasonic
flow meter may be configured such that a differential pressure exists
form the extension chamber toward an outflow tube of the ultrasonic
flow meter. The slurry flows into an outlet tube of the ultrasonic
flow meter and does not pass through the ultrasonic flow meter.
Such an ultrasonic flow meter may be adapted for use in Chemical
Mechanical Polishing (CMP) operations. The bubbles may comprise
a plurality of mini-bubbles.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying figures, in which like reference numerals refer
to identical or functionally-similar elements throughout the separate
views and which are incorporated in and form part of the specification,
further illustrate the present invention and, together with the
detailed description of the invention, serve to explain the principles
of the present invention.
FIG. 1 illustrates a prior ultrasonic flow meter device; and
FIG. 2 depicts an ultrasonic flow meter device, in accordance with
a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The particular values and configurations discussed in these non-limiting
examples can be varied and are cited merely to illustrate embodiments
of the present invention and are not intended to limit the scope
of the invention.
FIG. 1 illustrates a prior ultrasonic flow meter device 10 which
includes ultrasonic wave emitter/receiver 12 and 14. Ultrasonic
wave emitter/receiver 12 is connected to a tube 13 which in turn
is connected to an interface portion 24. The interface portion 24
is connected to a tube 20 through which inflow 28 enters. An ultrasonic
flow meter is located between ultrasonic wave emitter receiver 12
and 14 which in turn are respectively connected to signal cables
16 and 18. Ultrasonic wave emitter/receiver 14 is connected to a
tube 15 which in turn is connected to an interface portion 26.
The interface portion 26 is connected to a tube 22 through which
an outflow 30 exits.
The configuration depicted in FIG. 1 suffers from several inherent
problems. First, the ultrasonic wave in the flow will be scattered
by bubbles, resulting in error prone measurements. Additionally,
even a small amount of bubbles contained in the viscosity of the
slurry is not easy to be removed in a small diameter tube. Thus,
one of the primary disadvantages of prior art ultrasonic flow meters
in CMP operations, for example, involves the formation of bubbles
within a slurry flow. In such scenarios, the ultrasonic wave in
the flow is typically scattered by such bubbles, resulting in poor
and inaccurate measurements. It is thus necessary to avoid bubbles
passing through ultrasonic flow meters utilized in semiconductor
device CMP operations in order to avoid influencing the flow rate.
FIG. 2 depicts an ultrasonic flow meter device 40 in accordance
with a preferred embodiment of the present invention. Ultrasonic
flow meter device 40 includes a tube 44 through which inflow 42
may enter. Tube 44 is connected to an extension chamber 46 in which
a slurry 45 may be collected. Bubbles 90 are depicted within slurry
45. It is desirable to prevent such bubbles from passing from the
extension chamber 46 and into interface portion 64 and tube 60 because
tube 60 is connected not only to interface portion 64 but also to
wave emitter/receiver 54. Wave emitter/receiver 54 is connected
to a signal cable 50 while wave emitter/receiver 56 is connected
to a signal cable 52. The wave emitter/receiver 54 is additionally
connected to a tube 62 which in turn is connected to an interface
portion 66.
The interface portion 66 is connected to a tube 68 which in turn
is connected to a tube 70 that may be configured as a venturi tube.
A thin branch tube 80 connects tube 70 to extension chamber 46.
Note that the extension chamber 46 contains a pressure P.sub.1
while tube 70 contains a pressure P.sub.2 that is greater than P.sub.1.
Tube 70 is also connected to a tube 72 through which outflow 74
and bubbles may exist. Note also that the thin branch tube 80 contains
a diameter D.sub.1 that is much less than a diameter D.sub.2 of
ultrasonic flow meter 58.
Extension chamber 46 reduces the inflow 42 velocity of slurry 45
and ensure that bubbles 90 (i.e., mini-bubbles) will not drift with
the slurry flow. The bubbles 90 in extension chamber 46 will thus
drift toward and into thin branch tube 80 because the roof 49 of
extension chamber 46 is shaped generally like an overturned funnel.
The other terminal 94 of thin branch tube 80 is connected to tube
70 (i.e., a venturi tube), which can be established at the tube
72. Note that tube 72 comprises an outflow tube. The diameter diameter
D.sub.1 of thin branch tube 80 is much smaller than the diameter
of either tube 46 which comprises an inflow tube, or tube 72 which
comprises an outflow tube. A pressure differential also exists from
extension chamber 46 toward outflow tube 72 thereby forcing bubbles
90 away from ultrasonic flow meter 58. In fact, little slurry will
flow into outflow tube 72 and does not pass through ultrasonic flow
meter 58. This results in very little measurement errors and is
acceptable because the slurry flow false alarm percentage in CMP
(e.g., Mirra CMP) is generally about 30%.
A number of advantages can be obtained from implementing the improved
ultrasonic flow meter of the present invention. For example, bypass
bubble in the flow is successive and self-working. An additional
power or valve is not necessary. Also, less time is required to
calibrating the flow meter, while reducing wasted slurry. Additionally,
false alarms can be reduced regarding slurry flow during CMP operations.
Finally, the present invention is easy to install and when implemented
properly, is practically maintenance free.
Based on the foregoing it can be appreciated that the present invention
discloses a method and apparatus for preventing flow rate errors
derived from an ultrasonic flow meter utilized in semiconductor
fabrication operations. The ultrasonic flow meter is generally configured
to include an extension chamber connected to a thin branch tube
of the ultrasonic flow meter. A venturi tube can be positioned at
an outflow location of the ultrasonic flow meter, such that the
thin branch tube is broached into the venturi tube, wherein bubbles
contained in a slurry flow are forced directly into the outflow
location to thereby prevent inaccurate flow measurements derived
from the ultrasonic flow meter. The extension chamber may be configured
to reduce an inflow velocity associated with the slurry slow and
ensure that the bubbles with not drift with the slurry flow.
Additionally, a diameter of the branch tube may be configured such
that the diameter is much smaller than a diameter associated with
an inflow and/or outflow tube of the ultrasonic flow meter. A first
terminal of the thin branch tube may be connected to the venturi
tube to establish an outflow tube. Additionally, the ultrasonic
flow meter may be configured such that a differential pressure exists
form the extension chamber toward an outflow tube of the ultrasonic
flow meter. The slurry flows into an outlet tube of the ultrasonic
flow meter and does not pass through the ultrasonic flow meter.
Such an ultrasonic flow meter may be adapted for use in Chemical
Mechanical Polishing (CMP) operations. The bubbles may comprise
a plurality of mini-bubbles.
The embodiments and examples set forth herein are presented to
best explain the present invention and its practical application
and to thereby enable those skilled in the art to make and utilize
the invention. Those skilled in the art, however, will recognize
that the foregoing description and examples have been presented
for the purpose of illustration and example only. Other variations
and modifications of the present invention will be apparent to those
of skill in the art, and it is the intent of the appended claims
that such variations and modifications be covered. The description
as set forth is thus not intended to be exhaustive or to limit the
scope of the invention. Many modifications and variations are possible
in light of the above teaching without departing from scope of the
following claims. It is contemplated that the use of the present
invention can involve components having different characteristics.
It is intended that the scope of the present invention be defined
by the claims appended hereto, giving full cognizance to equivalents
in all respects. |