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| United States Patent | 5409310 |
| Link to this page | http://www.wikipatents.com/5409310.html |
| Inventor(s) | Owczarz; Aleksander (Kalispell, MT) |
| Abstract | A semiconductor processor blending system for diluting a concentrated
liquid additive into an actively flowing primary liquid. The concentrated
additive is stored in a reservoir and transferred to a drained mixing tank
via a metering pump. A diluent supply adds a measured amount of diluent to
the mixing tank to provide a diluted additive. Primary fluid flows through
aspirator-injectors having a suction port which draws from the mixing
tank. This provides two-stage dilution which can easily achieve very
dilute ratios of the additive. |
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Title Information  |
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Drawing from US Patent 5409310 |
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Semiconductor processor liquid spray system with additive blending |
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| Publication Date |
April 25, 1995 |
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| Filing Date |
September 30, 1993 |
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Title Information |
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Description |
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TECHNICAL FIELD
The field of this invention is semiconductor processing equipment spray
liquid additive blending systems, particularly those for blending very
concentrated additives into a highly purified spray liquid to achieve a
very dilute resultant concentration of the additive.
BACKGROUND OF THE INVENTION
In the processing of semiconductors it is not uncommon to use liquid sprays
or other liquid delivery systems. This is often done in the context of
centrifugal machines which rotate one or more wafers or other
semiconductor pieces being processed while a liquid spray is directed
against one or more surfaces of the pieces.
Many of these liquid delivery systems have need to provide a liquid which
is a combination of two or more additive liquid constituents. It is
sometimes the case that one or more of the constituents is in very dilute
concentration relative to water or another primary liquid. Producing such
very dilute concentrations of liquid additives is now done by batch
dilution in other mixing equipment. This requires additional handling to
mix the liquids and additional time in repeatedly loading the diluted
mixtures into the processing machinery.
Thus there is a continuing and substantial need for liquid handling systems
which can blend a concentrated liquid additive into an actively flowing
liquid stream in very dilute proportions. Such systems need also provide
consistent concentrations and extremely high purity levels of the blended
liquids.
BRIEF DESCRIPTION OF THE DRAWINGS
One or more preferred forms of the invention are described herein with
reference to the accompanying drawings. The drawings are briefly described
below.
FIG. 1 is a fluid schematic diagram showing a preferred semiconductor
processor liquid spray additive blending system according to this
invention.
FIG. 2 is an enlarged sectional view showing a preferred construction of
aspirator-injector forming a part of the system of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
This disclosure of the invention is submitted in furtherance of the
constitutional purposes of the U.S. Patent Laws "to promote the progress
of science and useful arts" (Article 1, Section 8).
FIG. 1 shows a preferred semiconductor processor liquid blending system in
accordance with this invention. The system includes a concentrate
reservoir 10. Reservoir 10 advantageously is provided by a stock or supply
container having a suitable concentrated liquid additive which is to be
injected into a primary liquid. An example of a preferred system is use of
a surfactant 11 stored within reservoir 10 which is injected into
deionized water serving as the primary liquid. The surfactant must be
injected in concentrations which remain uniform with time, but which are
very dilute, for example 1:10,000. Reservoir 10 is preferably provided
with a detachable top closure assembly 9 which supports a suction line 13
and a recycle line 21. This allows the surfactant container to be changed
and fitted with the top closure. Suction line 13 is connected to a pump
12. Pump 12 is preferably a metering pump such as that shown in U.S. Pat.
No. 5,085,560 which is hereby incorporated in its entirety by reference.
Other suitable pumps may also be used.
Pump 12 is preferably constructed so as to provide a means for determining
the amount of additive delivered from reservoir 10 to a mix tank 20. The
outflow from pump 12 is connected to a series of valves 15, 17, and 18
which are ganged together. Valve 15 controls application of a gas purge to
the pump and related valves. The purge has an orifice 16 which controls
the rate of gas flow into the valve and pump assembly. Purge 15 is
supplied with nitrogen, clean dry air, or other suitable purge gas.
Valve 17 is a mix tank delivery control valve. This valve is most
preferably an electrically controlled, pneumatically operated valve. The
output of valve 17 is connected to a mix tank concentrate delivery or feed
line 19. Recycle valve 18 is connected to valve 17 and provides recycle
flow back to reservoir 10 via concentrate recycle line 21 when valve 17 is
in a closed condition.
The system of FIG. 1 also includes a mix tank 20. Mix tank 20 is fed with
additive concentrate via line 19, and a diluent via diluent feed line 24.
A preferred diluent for the system being described is deionized or
distilled water supplied from a purified water source 54. Water delivery
to mix tank 20 is controlled via a diluent feed control valve 25. Valve 25
is also an electrically controlled, pneumatically operated valve. Other
valves generally shown as square boxes in FIG. 1 are also of this type.
Mix tank 20 further includes means for determining the contents of the
tank. This can advantageously be provided by a level or volume measurement
gauge 23 having electronic output. Mix tank gauge 23 preferably has high,
low, and overflow alarm setpoints, as suggested by the arrows shown in the
schematic drawing of FIG. 1. Tank 20 is also preferably provided with a
vent 26 and an overflow outlet 27. Overflow outlet 27 is directed into an
overflow drain 28 which is connected to a drain outflow line 31. Drain
outflow line 31 is also connected to a drain control valve 30 which
controls emptying of mix tank 20. A mix tank drain line 29 is connected
between the mix tank and valve 30.
Mix tank 20 also has a mix tank outflow line 32 which conveys diluted
additive to a diluted additive distribution manifold 33.
The concentrate and mix tank subsystem described above is preferably
operated by first draining the contents of mix tank 20 by opening valve 30
and allowing any residual contents to discharge through the drain outflow
line 31. Valve 30 is closed and the emptied mix tank is then charged with
a suitable amount of the concentrated liquid additive 11 from reservoir
10. The concentrate is supplied by pumping concentrate 11 via suction line
13 through pump 12 with controlled delivery via concentrate delivery
control valve 17 and mix tank concentrate feed line 19. Pump 12 is most
preferably controlled so as to delivery a precise amount of surfactant or
other desired concentrate to the mix tank.
The delivery of concentrate is regulated with greater precision by
utilizing control valve 17 and recycle valve 18 in combination with
recycle line 21. Pump 12 begins operation to charge the gang of valves 15,
17, and 18 with recycle occurring back through recycle line 21 to the
interior of reservoir 10. Once this fluid loop is fully filled with
concentrate, then valve 17 is opened and the rate of delivery is
calculated either using an integrating flowmeter, or more preferably
counting of the metering pump strokes.
Once the mix tank is charged with concentrate, then it is ready to receive
diluent via line 24 as controlled by diluent feed control valve 25. In the
preferred embodiment, the diluent is deionized water which is discharged
into the mix tank from line 24. The discharging diluent causes mixing with
the previously supplied concentrate to produce a substantially homogeneous
diluted additive within mix tank 20. Diluent is supplied via line 24 until
a desired level is achieved; for example, when the level sensor 23 detects
a preset "high" level. At that point, valve 25 is closed and the relative
proportions of diluent and concentrate are fixed.
The resulting diluted additive contained within mix tank 20 is delivered
through line 32 to the diluted additive distribution manifold 33. Manifold
33 has a plurality of diluent additive branch lines 35. Diluent additive
branch lines 35 preferably have suitable means for measuring and adjusting
the flow of diluted additive. This monitoring and adjustment is
particularly important in the case where there are numerous lines so that
balanced flows can be achieved. As shown, lines 35 are each provided with
injection adjustment valves 37. Injection adjustment valves 37 are
preferably manually controlled valves which allow the flow rate in each of
the branch lines to be adjusted to approximately equal flow rates. The
flow rates through lines 35 are monitored by suitable flowmeters 38, which
are preferably flowmeters having low flow rate alarms, as indicated by the
arrows in FIG. 1. The manual adjustment valves 37 and flowmeters can
advantageously be integrated into a single combined unit such as those
available from Futurestar of Edina, Minn. under the model names Pathfinder
or Odyssey. Other flowmeters or branch line flow control valves are also
possible.
Branch lines 35 also have injection control valves 39 which are
electrically controlled, pneumatically operated valves as indicated above.
The outflow from valves 39 are fed to aspirator-injectors 40.
FIG. 2 shows a preferred embodiment of aspirator-injector 40 used in
accordance with this invention. Injectors 40 are advantageously formed
from a body piece 41 made of a suitable material, such as
polytetrafluoroethylene or other suitable material. The inlet end of body
piece 41 is preferably provided a first or inlet port 42 which can
advantageously be threaded to allow coupling with related liquid flow
tubing or piping. Body piece 41 is also provided with a second or outflow
port 43 at the opposite or outlet end. Body piece 41 is still further
provided with a third or suction port 44 through which is fed the diluted
additive conveyed in branch lines 35.
Injector 40 has a through passageway from the inflow or infeed port 42 to
the outfeed or outflow port 43. Adjacent to the infeed port 42 there is
mounted a flow restriction and jet forming device or venturi piece 46.
Piece 46 has internal passageway 71 which preferably has a tapered section
72 towards the inlet end and a orifice or constricted portion 73.
Primary fluid is fed through inlet 42 and is accelerated by the
constriction provided by venturi piece 46. The accelerated flow emits from
constriction section 73 and jets across remaining portions of injection
chamber 45. Injection chamber 45 is in fluid communication with suction
port 44. The jet creates a reduced pressure which generates the suction
through port 44. Diluted additive from the associated branch line 37
enters port 44 and fills chamber 45. It is entrained with the primary
liquid jet, but in a greatly diluted ratio thereto.
The jet and entrained additive are received within mixing section entrance
port 75. Port 75 joins with a mixing section neck portion 76. Neck portion
76 smoothly meets with diverging or expanding mixing section chamber 47. A
diffuser piece 48 is preferably fitted at the end of the mixing section.
Diffuser 48 includes suitable diffuser apertures 49 through which mixed
primary and additive liquids pass. As shown, apertures 49 are
advantageously six in number and arranged in an equiangularly spaced
arrangement about the longitudinal axis of injector 40.
The outflow from injector 40 is advantageously supplied to a processing
chamber 88 via processing chamber spray heads or nozzles 89. Spray nozzles
89 direct fluid towards semiconductor wafer holders, carriers, or other
semiconductor pieces or handling equipment. Examples of suitable
processors include the centrifugal wafer carrier cleaning apparatus
described in U.S. Pat. No. 5,224,503, which is hereby incorporated
hereinto by reference. The semiconductor processor liquid blending system
of FIG. 1 is advantageously incorporated into a centrifugal wafer carrier
cleaning apparatus the same or similar to that shown in U.S. Pat. No.
5,224,503, or other suitable semiconductor processor. As shown the spray
heads 89 are provided in two distinct banks, such as for inwardly directed
nozzles and outwardly directed nozzles. Other configurations are also
possible.
Primary liquid is provided to spray nozzles 89 from suitable sources of
primary liquid 54. Sources 54 are in the preferred embodiment supplies for
deionized water. The supplies of deionized water are in fluid
communication with pressure reduction regulators 56. Pressure gauges 55
are advantageously included downstream from regulators 56 to indicate the
pressure which is being delivered from the pressure regulators 56.
The deionized water or other suitable primary liquid is conveyed through
primary liquid supply lines 57. The primary liquid supply lines 57 are
advantageously provided with primary liquid flow adjustment valves 58,
which are advantageously manual throttling valves. Primary liquid
flowmeters 59 are also preferably included in lines 57 to indicate the
flow rate of primary liquid being delivered to nozzles 89. Primary liquid
supply lines 57 are advantageously connected to primary liquid
distribution manifold 60. Primary liquid branch lines 61 branch from
manifold 60 and are plumbed to primary liquid control valves 51. Recycle
bleed lines 81 tee off from branch lines 61 just upstream from valves 51
to aid in providing a continuous flow of liquid, even when control valves
51 are closed. This recycle subsystem will be explained in greater detail
below.
Valves 51 are preferably electrically controlled, pneumatically operated
valves which turn the flow of primary liquid on or off as needed for
operation of spray nozzles 89. Manual cut-off valves 50 can also
advantageously be provided between control valves 51 and
aspirator-injectors 40 for maintenance or other purposes. Cut-off valves
50 are normally open.
Primary liquid control valves 51 are preferably ganged with primary liquid
purge valves 52. Compressed gas, such as nitrogen or clean dry air is
supplied through purge gas branch lines 66 to valves 52. When valves 51
are operated into a closed position, purge valves 52 open to allow flow of
compressed gas through remaining parts of valves 51 to blow out the
downstream portions 68 of primary liquid supply lines 57. This clears the
downstream portions 68, and the associated aspirator-injectors 40 and
nozzles 89 of any remaining mixed primary liquid and additive.
The semiconductor processing industry has high susceptibility to damage
from contamination. This leads to an exceedingly high level of cleanliness
and purity being needed in order to reduce or prevent contamination. The
system of FIG. 1 is preferably provided with a primary liquid recycle
system 80 to reduce the risk of bacterial growth in primary liquid supply
lines 57 which are upstream from valves 51. The recycle system includes
branch or bleed lines 81 which tee from the primary liquid supply branch
lines 61 near valves 51. The bleed lines 81 are piped to a suitable
collector, such as the recycle bleed line receiving manifolds 82. There is
also a recycle bleed line 81 running from immediately upstream of valve 25
to one of manifolds 82. Dual manifolds are preferably used because the
primary liquid supply system is also provided with two different
subsystems. This reduces the possibility of fluid flows being unbalanced
due to connection between the two separate flow subsystems. The outflow
from manifolds 82 are preferably provided with recycle balance valves 83.
The outputs from valves 83 are joined together at recycle return line 84.
Recycle return line 84 is directed to a suitable drain or reprocessing
subsystem as desired.
This invention also includes novel methods for blending concentrated liquid
additive into an actively flowing primary liquid. Methods are particularly
useful in blending concentrated liquid additives into a plurality of
primary liquid supply lines containing active flows of primary liquid for
delivery to spray heads of a semiconductor processor. The methods include
delivering a controlled amount of concentrated liquid additive from a
concentrate reservoir to a mix tank. This is advantageously accomplished
by sucking concentrated liquid additive from reservoir 10 through line 13
to pump 12. Pump 12 is preferably then used for pumping the concentrated
liquid additive. The concentrated liquid additive is supplied by suitably
controlling the concentrate delivery valve 17 and concentrate recycle
valve 18. This can be done to provide delivery of the concentrated liquid
additive to the mix tank 20 or by recycling the concentrate to reservoir
10. The concentrate is preferably initially recycled to charge the pump
and recycle loop prior to delivering the concentrate to mix tank 20.
Methods also preferably include draining or emptying the mix tank prior to
delivering concentrated liquid additive thereto. This allows the mix tank
to be used from a more closely controlled reference point and thus
provides a referencing function relative to the mix tank contents. This
referencing function most preferably removes all prior diluted liquid
additive from the mix tank before another batch is prepared.
Novel methods of this invention further include diluting the concentrated
liquid additive charged within the mix tank. This diluting step can most
preferably be accomplished by supplying diluent to the mix tank. The
diluent is preferably controllably supplied to provide a resulting
predetermined mix ratio. The diluent is preferably supplied to the mix
tank by jetting it into the mix tank containing concentrated additive,
thereby mixing and homogenizing the diluted liquid additive produced in
this first dilution process sequence.
The novel methods still further include flowing or supplying primary liquid
through aspirator-injectors mounted in the primary liquid supply lines.
This flowing produces actively flowing primary liquid streams into which
the diluted additive from mix tank 20 is injected. The methods
additionally include injecting diluted additive into the flowing primary
liquid flows via said aspirator-injectors. This accordingly provides a
plurality of active flows of primary liquid to provide two-stage diluted
liquid additive therein.
The invention can be made using system components which are commercially
available using typical fabrication processes. The materials of
construction vary for the intended service. As shown, most components are
either polytetrafluoroethylene or stainless steel. Other suitable
materials are also possible consistent with the liquids being handled.
In compliance with the statute, the invention has been described in
language necessarily limited in its ability to properly convey the
conceptual nature of the invention. Because of this inherent limitation of
language, it must be understood that the invention is not necessarily
limited to the specific features described, since the means herein
disclosed comprise merely preferred forms of putting the invention into
effect. The invention is, therefore, claimed in any of its forms or
modifications within the proper scope of the appended claims appropriately
interpreted in accordance with the doctrine of equivalents.
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Description |
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