U.S. patent application number 11/778002 was filed with the patent office on 2009-01-15 for precision pump with multiple heads.
This patent application is currently assigned to INTEGRATED DESIGNS L.P.. Invention is credited to Greg Gray, Jack Laessle, Raymond T. Savard.
Application Number | 20090016903 11/778002 |
Document ID | / |
Family ID | 40253299 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090016903 |
Kind Code |
A1 |
Savard; Raymond T. ; et
al. |
January 15, 2009 |
Precision Pump With Multiple Heads
Abstract
A high purity, high precision pump capable of pumping more than
one type of chemistry or process fluid without requiring cleaning
or changing of surfaces contacting the processing fluid. The pump
employs a single drive mechanism coupled in parallel with multiple
pumping chambers, each capable of handling a different type of
manufacturing fluid. The pump can be utilized as part of a single
stage or multi-stage pump system.
Inventors: |
Savard; Raymond T.; (Pilot
Point, TX) ; Gray; Greg; (The Colony, TX) ;
Laessle; Jack; (Plano, TX) |
Correspondence
Address: |
CAESAR, RIVISE, BERNSTEIN,;COHEN & POKOTILOW, LTD.
11TH FLOOR, SEVEN PENN CENTER, 1635 MARKET STREET
PHILADELPHIA
PA
19103-2212
US
|
Assignee: |
INTEGRATED DESIGNS L.P.
Carrollton
TX
|
Family ID: |
40253299 |
Appl. No.: |
11/778002 |
Filed: |
July 13, 2007 |
Current U.S.
Class: |
417/244 ;
417/270; 417/349; 438/427 |
Current CPC
Class: |
F04B 25/00 20130101;
F04B 13/00 20130101 |
Class at
Publication: |
417/244 ;
417/270; 417/349; 438/427 |
International
Class: |
F04B 25/00 20060101
F04B025/00 |
Claims
1. A pump system for use in selectively dispensing a plurality of
different process fluids, comprising: a plurality of process fluid
displacement mechanisms; one or more actuation mechanisms coupled
with the plurality of displacement mechanisms for actuating each of
the plurality of process fluid displacement mechanisms, the number
of process fluid displacement mechanisms being greater than the
number of actuation mechanisms; and valves in fluid communication
with the plurality of process fluid displacement mechanisms
operable for controlling flow of process fluid from the plurality
of fluid displacement mechanisms during dispensing and for
permitting flow of process fluids into each of the plurality of
fluid displacement mechanisms during recharging of pumping
means.
2. The pump system of claim 1, further comprising a controller for
operating the valves to permit flow of process fluid from only one
of the plurality of fluid displacement mechanisms at a time during
dispensing.
3. The pump system of claim 1, wherein each of the plurality of
fluid displacement mechanisms receives process fluid from a
different one of a plurality of fluid sources.
4. The pump system of claim 1, wherein each of the plurality of
fluid displacement mechanisms is in fluid communication with a
different one of a plurality of nozzles.
5. The pump system of claim 1, wherein more than one of the
plurality of dispense points is located at a single dispense
point.
6. The pump system of claim 1, wherein the actuating mechanism
includes a hydraulic actuating mechanism.
7. A pump system for use in handling a plurality of different
process fluids in applications imposing constraints on handling
process fluid, comprising: an actuation mechanism for pumping
actuating fluid; a plurality of pump chambers, each including at
least one process fluid inlet and at least one process fluid outlet
to the pumping chamber; a diaphragm for dividing each pump chamber
and for separating process fluid from actuation fluid; and each
pump chamber in fluid communication with the actuation mechanism
through at least one channel permitting unrestricted flow into the
pump head of substantially incompressible actuation fluid, the at
least one process fluid outlet coupled to at least one valve for
selectively preventing and allowing the flow of process fluid
through the pump head; whereby operation of the hydraulic actuating
mechanism to displace actuating fluid causes actuating fluid to
flow only into each of the plurality pump chambers coupled with
opened at least one valve, resulting in pumping.
8. The pump system of claim 7, wherein the at least one fluid
channel permits unrestricted flow from the pump chamber and into
the actuating mechanism of actuation fluid.
9. The pump system of claim 7, wherein actuation mechanism is
comprised of a displacement mechanism for moving actuation fluid
coupled with an incremental advancement mechanism.
10. The pump system of claim 7, wherein the displacement mechanism
is comprised of a piston translated by a screw turned by a stepper
motor.
11. The pump system of claim 7, further comprising a controller for
selectively operating the at least one valve to which each of the
plurality of pump heads is coupled to selectively allow and stop
flow of process fluids.
12. The pump system of claim 7, wherein the at least one valve
includes a controllable valve for selectively opening and closing a
line coupled with the outlet.
13. The pump system of claim 12, further comprising a one-way
check-valve coupled with the process fluid outlet of each of the
plurality of pump chambers for allowing fluid to flow only in one
direction out of the pump head, and a one-way check valve coupled
with the process fluid inlet of each of the plurality of pump
chambers for allowing fluid to flow only in one direction into the
pump head.
14. The pump system of claim 7, wherein each of the plurality of
pump chambers is coupled with a process fluid nozzle for dispensing
process fluid.
15. The pump system of claim 14, wherein the process fluid nozzles
coupled to plurality of pump chambers are located and arranged on a
processing line for dispensing process fluids onto the same
semiconductor substrate.
16. The pump system of claim 7, wherein the outlet of each of the
plurality of pump chambers is in fluid communication with a filter
for filtering the process fluid.
17. The pump system of claim 7, wherein the actuating mechanism is
mounted within a central structure, and the plurality of pump
chambers is at least partially formed by at least one removable
pump head structure supported on the central structure.
18. The pump system of claim 12, further comprising a plurality of
pump head structures, the plurality of pump head structures being
arrayed around the support structure.
19. The pump system of claim 7 comprised of a plurality of
actuation mechanisms, wherein the number of the plurality of pump
chambers exceeds the number.
20. A pump for use in concurrently handling a plurality of
different process fluids in applications imposing constraints on
handling process fluid, comprising: a structure forming a central
reservoir for storing substantially incompressible actuation fluid,
in which a displacement member is disposed for moving actuating
fluid into and out of the central reservoir; a plurality of pump
chambers, each pump chamber including at least one process fluid
inlet and at least one process fluid outlet to a pumping chamber;
each of the plurality of pump chambers including at least a portion
of a diaphragm dividing the pump chamber and separating actuation
fluid from process fluid from within the pump chamber; at least one
channel permitting unrestricted flow between the pump chamber and
the reservoir of substantially incompressible actuation fluid; and
at least one valve coupled with the at least one process fluid
outlet coupled for preventing and allowing the flow of process
fluid through the pump chamber; whereby operation of the hydraulic
actuating mechanism to displace actuating fluid causes fluid to
flow only into pump chambers with outlets coupled with at least one
valve that is opened.
21. The pump of claim 20, further comprising, for each pump
chamber, a one-way check-valve coupled with the process fluid
outlet for allowing fluid to flow only in one direction out of the
pump chamber, and a one-way check valve coupled with the process
fluid inlet of each of the pump heads for allowing fluid to flow
only in one direction into the pump chamber.
22. The pump of claim 20, wherein the displacement mechanism is
coupled with an incremental advancement mechanism.
23. The pump of claim 20, wherein the central structure has formed
thereon a plurality of faces, to which a plurality of pump heads
are respectively mounted, each face cooperating with one of a
plurality of the pump heads in order to form one of the plurality
of pump chambers, the diaphragm for each pump chamber being mounted
between respective ones of the plurality of pump heads and the
central structure.
24. The pump of claim 20 wherein the plurality of pump chambers are
integrated with, and arrayed around, the structure forming the
reservoir.
25. In a pump comprised of an actuation mechanism for pumping
actuating fluid and a plurality of pump chambers, each in fluid
communication with the actuation mechanism through at least one
fluid communication channel permitting unrestricted flow of
actuating fluid between the pump chamber and actuating mechanism,
each of the plurality of pump chambers including at least one
process fluid outlet coupled to at least one outlet valve, a method
comprising: charging each of the plurality of pump chambers with
process fluid; displacing a predetermined amount of actuating fluid
from the actuating mechanism; selectively opening for process fluid
flow at least one outlet for one or more of the plurality of pump
chambers; and closing the at least one outlet for each of the other
ones of the plurality of pump chambers in order to create
back-pressure with the process fluid in the pump chambers that
tends to prevent actuation fluid from flowing into the pump
chamber; whereby actuating fluid flows only into the ones of the
plurality of pump chambers with the at least one outlet opened,
resulting in displacement of process fluid from the pumping
chamber.
26. The method of claim 25, wherein each pump chamber includes a
diaphragm separating process fluid from actuation fluid.
27. The method of claim 25, wherein the actuation mechanism is
comprised of a displacement mechanism for moving actuation fluid
coupled with an incremental advancement mechanism.
28. The method of claim 25, wherein the displacement mechanism is
comprised of a piston translated by a screw turned by a stepper
motor.
29. The method of claim 25, wherein the pump further comprises a
one-way check-valve coupled with the process fluid outlet for each
pump head for allowing fluid to flow only in one direction out of
the pump head, and a one-way check valve coupled with the process
fluid inlet of each of the pump heads for allowing fluid to flow
only in one direction into the pump head.
30. The method of claim 25, wherein the actuating mechanism is
mounted within a central structure, and each of the pumping
chambers is formed at least in part by a pump head structure
supported on the central structure.
31. The method of claim 30, wherein the plurality of pump heads are
arrayed around the support structure.
32. The pump of claim 30, wherein the central structure has formed
thereon a plurality of faces, to which the pump head structure is
mounted, each face cooperating with the pump head in order to form
one of the plurality of pump chambers; and wherein each pump
chamber includes a diaphragm for each pump chamber mounted between
respective ones of the pump head and the central structure.
33. A substrate with structures formed in part by using a pump, the
pump being comprised of an actuation mechanism for pumping
actuating fluid and a plurality of pump chambers, each in fluid
communication with the actuation mechanism through at least one
fluid communication channel permitting unrestricted flow of
actuating fluid between the pump chamber and actuating mechanism,
each of the plurality of pump chambers including at least one
process fluid outlet coupled to at least one outlet valve; wherein
using the pump comprises: charging each of the plurality of pump
chambers with process fluid; selectively opening at least one
outlet for one or more of the plurality of pump chambers; closing
the at least one outlet for each of the other ones of the plurality
of pump chambers in order to create back-pressure with the process
fluid in the pump chambers that tends to prevent actuation fluid
from flowing into the pump chamber; displacing a predetermined
amount of actuating fluid from the actuating mechanism for delivery
to a dispense point near the substrate; whereby actuating fluid
flows only into the ones of the plurality of pump chambers with the
at least one outlet opened, resulting in displacement of process
fluid from the pumping chamber.
34. The substrate of claim 33, wherein each pump chamber includes a
diaphragm separating process fluid from actuation fluid.
35. The substrate of claim 33, wherein the actuation mechanism is
comprised of a displacement mechanism for moving actuation fluid
coupled with an incremental advancement mechanism.
36. The substrate of claim 33, wherein the displacement mechanism
is comprised of a piston translated by a screw turned by a stepper
motor.
37. The substrate of claim 33, wherein the pump further comprises a
one-way check-valve coupled with the process fluid outlet for each
pump head for allowing fluid to flow only in one direction out of
the pump head, and a one-way check valve coupled with the process
fluid inlet of each of the pump heads for allowing fluid to flow
only in one direction into the pump head.
38. The substrate of claim 33, wherein the actuating mechanism is
mounted within a central structure, and each of the pumping
chambers is formed at least in part by a pump head structure
supported on the central structure.
39. The substrate of claim 38, wherein the plurality of pump heads
are arrayed around the support structure.
40. The substrate of claim 38, wherein the central structure has
formed thereon a plurality of faces, to which the pump head
structure is mounted; each face cooperating with the pump head in
order to form one of the plurality of pump chambers; and wherein
each pump chamber includes a diaphragm for each pump chamber
mounted between respective ones of the pump head and the central
structure.
41. The substrate of claim 33, wherein each of the plurality of
pump chambers is in fluid communication with a separate one of a
plurality of nozzles oriented for dispensing process fluid onto the
substrate.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates generally to apparatus used in
metering fluids with high precision, particularly in fields such as
semiconductor manufacturing.
BACKGROUND OF THE INVENTION
[0002] Many of the chemicals used in manufacturing integrated
circuits, photomasks, and other devices with very small structures
are corrosive, toxic and expensive. One example is photoresist,
which is used in photolithographic processes. In such applications,
both the rate and amount of a chemical in liquid phase--also
referred to as process fluid or "chemistry"--that is dispensed onto
a substrate must be very accurately controlled to ensure uniform
application of the chemical and to avoid waste and unnecessary
consumption. Furthermore, purity of the process fluid is often
critical. The smallest of foreign particles contaminating a process
fluid causes defects in the very small structures formed during
such processes. The process fluid must therefore be handled by a
dispensing system in a manner that avoids contamination. See, for
example, Semiconductor Equipment and Material International, "SEMI
E49.2-0298 Guide For High Purity Deionized Water And Chemical
Distribution Systems In Semiconductor Manufacturing Equipment"
(1998). Improper handling can also result in introduction of gas
bubbles and damage the chemistry. For these reasons, specialized
systems are required for storing and metering fluids in
photolithography and other processes used in fabrication of devices
with very small structures.
[0003] Chemical distribution systems for these types of
applications therefore must employ a mechanism for pumping process
fluid in a way that permits finely controlled metering of the fluid
and avoids contaminating and reacting with the process fluid.
Generally, a pump pressurizes process fluid in a line to a dispense
point. The fluid is drawn from a source that stores the fluid, such
as a bottle or other bulk container. The dispense point can be a
small nozzle or other opening. The line from the pump to a dispense
point on a manufacturing line is opened and closed with a valve.
The valve can be placed at a dispense point. Opening the valve
allows process fluid to flow at the point of dispense. A
programmable controller operates the pumps and valves. All surfaces
within the pumping mechanism, lines and valves that touch the
process fluid must not react with or contaminate the process fluid.
The pumps, bulk containers of process fluid, and associated valving
are sometimes stored in a cabinet that also houses a
controller.
[0004] Pumps for these types of systems are typically some form of
a positive displacement type of pump, in which the size of a
pumping chamber is enlarged to draw fluid into the chamber, and
then reduced to push it out. Types of positive displacement pumps
that have been used include hydraulically actuated diaphragm pumps,
bellows type pumps, piston actuated, rolling diaphragm pumps, and
pressurized reservoir type pumping systems. U.S. Pat. No. 4,950,134
is an example of a typical pump. It has an inlet, an outlet, a
stepper motor and a fluid displacement diaphragm. When the pump is
commanded electrically to dispense, the outlet valve opens and the
motor turns to force flow of displacement or actuating fluid into
the pumping chamber, resulting in the diaphragm moving to reduce
the size of the pumping chamber Movement of the diaphragm forces
process fluid out of the pumping chamber and through the outlet
valve.
[0005] Due to concerns over contamination, current practice in the
semiconductor manufacturing industry is to use a pump only for
pumping a single type of processing fluid or "chemistry." In order
to change chemistries being pumped, all of the surfaces contacting
the processing fluid have to be changed. Depending on the design of
the pump, this tends to be cumbersome and expensive, or simply not
feasible. It is not uncommon to see processing systems that use up
to 50 pumps in today's fabrication facilities.
SUMMARY OF THE INVENTION
[0006] The invention pertains generally to high precision pumps for
use in dispensing process fluids in applications imposing
constraints on handling due to corrosiveness of the process fluid,
and/or due to sensitivity to contamination (e.g. from other fluids,
particulates, etc.), bubbles and/or mechanical stresses. It is
particularly useful for pumps in semiconductor processing
operations.
[0007] In contradistinction to typical deployments of pumps in such
applications, particularly those used for high-precision metering,
an exemplary pump employing teachings of a preferred embodiment of
the invention is capable of pumping more than one type of chemistry
or process fluid without requiring cleaning or changing of surfaces
contacting the processing fluid. The pump employs multiple pumping
heads, each capable of handling a different type of manufacturing
fluid. At least two of the pumping heads share a common actuating
mechanism. Although a multi-headed pump might be larger when
compared to a pump with a single head, utilizing fewer actuating
mechanisms than pumping heads saves valuable space in crowded
processing facilities, such as those used for fabricating
semiconductor components, which use a large number of pumps. Since
actuation mechanisms are sometimes the most complex part of a pump,
fewer actuating mechanisms in a factory saves money and maintenance
time.
[0008] Sharing a single actuating mechanism among multiple heads
may seem undesirable, particularly for fluid metering applications.
Having a shared actuation mechanism typically means that only one
pumping head may be actuated at a time. However, in one exemplary
embodiment, the multi-headed pump is capable of fast and frequent
switching between pump heads. With actuation between pump heads
capable of being switched quickly, there is little delay between
demand for dispense and dispense in applications having very short
dispense cycles due to relatively small amounts of fluid that are
being dispensed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic view of a multiple head pump, shown in
context of a high precision, high-purity fluid dispensing
system.
[0010] FIG. 2 is an exploded view of an exemplary, preferred
embodiment of a multiple head pump.
[0011] FIG. 3 is an exploded view from a different angle of the
multiple head pump of FIG. 2.
[0012] FIG. 4 is a side view of the pump of FIGS. 2 and 3,
assembled.
[0013] FIG. 5 is a cross section of the pump of FIG. 4, taken along
section line 5-5.
[0014] FIG. 6 is a cross-section of the pump of FIG. 4 taken along
section line 6-6.
[0015] FIG. 7 is an isometric view of the pump of FIG. 4.
[0016] FIG. 8 is a front view of the pump of FIG. 4.
[0017] FIG. 9 is a back view of the pump of FIG. 4.
[0018] FIG. 10 is view of an application of the pump of FIGS.
2-9.
[0019] FIGS. 11A, 11B and 11C constitute a flow chart of an
exemplary dispense process of a controller for the pump of FIGS.
2-9.
[0020] FIG. 12 is a schematic diagram for one, preferred embodiment
of a two-stage pumping system utilizing a multi-head pump.
[0021] FIG. 13 is a schematic diagram of an alternate of a
two-stage pumping system utilizing a multi-head pump.
[0022] FIG. 14 is a schematic diagram of another alternate
embodiment of a two-stage pumping system utilizing a multi-head
pump.
[0023] FIG. 15 is a schematic diagram of an example of a two-stage
pumping system utilizing two or more multi-head pumps.
DETAILED DESCRIPTION
[0024] FIG. 1 schematically illustrates one example of a high
precision, multiple head dispense pump for pumping a plurality of
different chemicals in a high purity application. A pumping head is
a portion of a pump that, among other possible functions, contacts
and applies force to the process fluid in order to move it. In a
high precision, multiple head pump, more than one pumping head is
actuated by a common actuating mechanism. In the illustrated
example, a multiple head pump is used to dispense chemicals or
process fluids from three separate bulk sources 101, 103 and 105 to
each of three separate dispense points 107, 109 and 111,
respectively. Each source and dispense point is coupled through a
pump head 113, 115, or 117. Each pump head functions to move a
predetermined amount of fluid from the source to the corresponding
dispense point. Because each pump head functions independently and
does not share with the other pump heads any surfaces that contact
process fluids, each bulk source is permitted to be a different
type of chemical. Output valves 119, 121, and 123 open and close
output lines 120, 122, and 124, respectively, between the pump
heads to their corresponding dispense points. Each is independently
controlled by a controller (not shown) that coordinates opening of
the valve with pump operation. Because the illustrated pump is
employable to particular advantage in semiconductor manufacturing
operations, where chemicals are pumped to a dispense point for
dispensing onto a semiconductor wafer, the output lines in the
illustrated example are coupled suck back valves 125, 127 and 129.
After a dispense, a suck back valve is used to draw fluid back from
a dispense tip, nozzle or similar element in order to prevent
dripping.
[0025] In the illustrated example, the pumping heads move fluid by
drawing it into a pumping chamber and then displacing it. Positive
displacement is advantageous for applications requiring precise
metering of fluid. The volume of each pumping chamber is increased
to suck-in process fluid, and then decreased to push it out. A
member that is used to change the volume of a chamber will be
called a displacement member. A pumping chamber and displacement
member can be implemented a number of different ways. One example
includes a piston or piston-like device moving within a cylinder.
Other examples include bellows, tubular diaphragms, and rolling
diaphragms. The instant example contemplates use of a flexible
diaphragm that cooperates with the walls of the pumping chamber to
displace fluid. Moving the diaphragm in one direction increases the
volume of the pumping chamber, and moving it another direction
decreases the volume of the pumping chamber, thus displacing fluid
from it. The diaphragms for pump heads 113, 115 and 117 are
schematically illustrated in the figure as elements 131, 133 and
135, respectively.
[0026] A number of different arrangements can be used to ensure
that fluid flows only in one direction through the pump head. In
the illustrated example, the pump head includes an inlet (not
indicated) for coupling the pump head to a process fluid source,
such as sources 101, 103 or 105, and an outlet (not indicated) for
coupling the pump head to a dispense point, such as dispense point
107, 109 or 111. The pumping chamber in the pump head has at least
one opening, and preferably at least two openings, one being in
communication with the inlet and the other in communication with
the outlet. Fluid is drawn into the pumping chamber through the
inlet opening and is expelled through the outlet opening. This
allows for creation of a generally unidirectional flow of process
fluid through the pumping chamber, which can assist in reducing
pooling of process fluid and accumulation of contaminants in the
pump head. The inlet and outlet of each pump head is coupled
through valving that ensures, at least normal operation, that fluid
flows into the pumping chamber only from the inlet and exits the
pumping chamber only through the outlet.
[0027] The valving can take different arrangements, depending in
part on the number of openings into the pumping chamber and other
considerations. In the illustrated example, the valving is
comprised of two valves. Check valve 137 ensures one-way flow from
the inlet into the pumping chamber, and check valve 139 ensures
one-way flow of process fluid exiting the chamber through the
outlet. The check valves are self-actuating or lifting, which tends
to reduce complexity by avoiding having to implement a mechanism
for synchronizing their opening with the pumping action of the pump
head. However, it might be advantageous in some circumstances, such
as those described below, to incorporate valves whose opening can
be independently controlled. Furthermore, use of check valves may
not be appropriate for some applications. If the pumping chamber
has only one opening, one example of suitable valving includes a
three-way valve that selectively couples either the inlet or outlet
to the opening, or closes the opening altogether, depending on the
stroke of the pump. Other types of valving could be chosen to
achieve the same functionality, although possibly at the expense of
greater complexity and less reliability.
[0028] The plurality of pumping heads share a common actuation
mechanism, represented in the figure by drive motor and piston
assembly 135. An actuating mechanism includes a force generating
component, such as a motor, and a coupling for communicating the
force to a fluid displacement member. Sometimes, these components
are one and the same. Examples of actuating mechanisms include
mechanical, pneumatic and hydraulic mechanisms, and combinations of
them. One example of a mechanical actuator is a driver motor
coupled to a diaphragm through a purely mechanical coupling, such
as a transmission or other mechanical linkage or piston. The
linkage or piston converts the output of the motor into movement of
the fluid displacement member. A hydraulic coupling can also be
used, with the motor moving a piston, which in turn moves hydraulic
fluid that pushes against the displacement member. In a purely
pneumatic system, for example, gases under high pressure are used
to move the displacement member.
[0029] In the illustrated example, the force generated by the
common actuating mechanism is preferably applied in parallel,
rather than serially, to each of the pump heads. Although applying
the force in parallel will lead all pump heads to actuate
simultaneously, avoiding serial application of the force reduces
the complexity by avoiding a mechanism for selectively applying or
switching the actuation force between the pump heads. Complexity
tends to increase costs and reduce reliability.
[0030] In order to avoid undesirable, simultaneous actuation of all
pump heads, yet maintain simplicity, the actuating mechanism in the
illustrated example preferably utilizes a fluidic coupling for
communicating forces from a motor or other force generating
mechanism to the process fluid. The drive assembly for the
actuation mechanism in the illustrated example includes a drive
motor (not shown) for supplying force for moving the actuating
fluid. The drive motor moves a displacement member (e.g. a piston)
that, in turn, moves fluid in a manner that causes the pumping head
to actuate. Actuating fluid is moved in and out of a chamber on the
side of the diaphragm opposite the pumping chamber. Displaced
actuating fluid moves into the pumping head, reducing the volume of
the pumping chamber and pushing fluid out. Reverse movement of the
displacement member causes the actuating fluid to flow from the
pumping head, increasing the volume of the pumping chamber and
consequently drawing in process fluid. If the fluid is not
compressible at least at the pressures at which the pump functions
(such fluid being referred to herein as incompressible), and only
one pumping chamber is open, the amount of actuating fluid
displaced by actuating assembly is proportional to the amount of
process fluid displaced from within the pumping chamber.
[0031] Blocking flow of process fluid out of the pumping chamber of
a pump head in effect blocks the flow of actuating fluid into the
pump head, thus causing actuating fluid to be redirected to, and to
flow into, another pump head without internal valving to redirect
the fluid to different pump heads. Therefore, although internal
valving could be used, it is not required in order to ensure only
one head is pumping at a time. In this example, a preexisting valve
at the outlet--a valve that would otherwise be present for this
application--is sufficient, therefore allowing reduction in
complexity and the size of the pump without a corresponding
increase in the number of external valves that would otherwise be
required. Furthermore, existing external valving can be utilized
for blocking process fluid flow through the pump heads. In the
illustrated example, which uses self-actuating check valves, output
valves 119, 121 and 123 are selectively closed to block flow of
fluid from the pump heads that are not intended to be pumping
during actuation of the pump. The output valves may be located
anywhere along the line carrying fluid from the pump head to the
dispense point. A controllable valve can be substituted for one or
both check valves, or used in addition to them, if an output valve
is not available or if there is a preference not to use the output
valve. However, this would be at the expense of more cost and
complexity. Furthermore, other valving arrangements that are used
to ensure one way flow of process fluid through the pump head, such
as the three-way valve mentioned above, can also be used for this
purpose.
[0032] When used for metering fluids, the pump is operated so that
only one pump head is active at a time. All actuating fluid is
thereby directed only into or out of the active pump. By allowing
actuating fluid to flow only out of one pump head at a time, the
amount of process fluid being pumped is determined from movement of
the displacement member within the actuation mechanism. If more
than one pump head is opened for pumping during actuation, a mass
flow meter is coupled with the pump head to determine the amount
process flowing out of the pump head. However, in applications such
as semiconductor manufacturing, dispense cycles are short and
demand for dispense from a particular dispense point is not
constant and, in some cases, relatively infrequent. Given the
absence of internal valving for redirecting the actuating fluid and
the simplicity of the mechanism controlling flow of process fluid
through a pump head, fast activation of pump heads is possible,
thus allowing the actuating fluid to be, in effect, time
multiplexed to the pump heads without unduly slowing
dispensing.
[0033] Referring now to FIGS. 2 through 9, exemplary, single-stage
pump 200 is comprised of an exemplary structure for the multi-head
pump shown in FIG. 1, suitable for high purity applications, such
as those in semiconductor manufacturing. The pump 200 includes, in
this example, three pumping head structures 202, 204 and 206, which
cooperate with a central body 208 to form respective pump heads.
The heads are arrayed around a central axis of a central body 208.
The central body 208 supports the pump heads and preferably also
provides channels in the form of holes or passageways through the
body for supplying hydraulic actuating fluid to each pump head. By
integrally forming the fluid passageways as part the body, such as
by machining a monolithic block, additional connections can be
avoided, thus reducing the risk of a leak of actuation fluid. In
high purity applications such as semiconductor fabrication, even
the smallest leak contaminates the clean environment and is
therefore very undesirable.
[0034] The body in the illustrated example possesses a square
cross-section with four sides. Formed on three of the four sides
are faces to which the pumping heads are coupled. The fourth side
is used, in this example, to receive a pressure sensor 210. The
pressure sensor is used to measure the pressure of hydraulic fluid
within the actuation mechanism. Arraying the pumping heads at least
partially around channels supplying hydraulic actuation fluid tends
to result in more efficient utilization of space as compared to,
for example, a configuration in which the heads are arranged in a
linear fashion. However, other of the advantages of the exemplary
pump illustrated in these figures can be achieved without the
pumping heads being arrayed around the central axis. For example,
the pumping heads can be arranged in a stacked configuration. More
pumping heads can be coupled to the central body by increasing the
cross-sectional size, increasing the number of faces disposed
around a central axis of the central body, by reducing the size of
the pumping heads, and/or by extending the body along its central
axis. The size of the pumping head depends in part on the desired
volume of the pumping chamber. Preferably, the size of the pumping
chamber is such that multiple, incremental dispenses, in which only
a portion of the process fluid within the pumping chamber is
dispensed during a dispense cycle, are completed before having to
draw in more fluid. A face need not be flat, but can be curved if
desired. Thus, for example, the central body can have either a
polygonal or a generally circular cross section. Although a
circular cross-section may take up less space, flat faces have the
advantage of a simpler fabrication and connection with the pumping
head.
[0035] The central body preferably also houses, as in this example,
at least one hydraulic actuation mechanism. The mechanism includes
a fluid reservoir as well as a displacement element. In the
illustrated embodiment, the actuation fluid reservoir is comprised
of a cavity 207 (see FIG. 5) of circular cross-section formed
within the center of the block forming body 208, and the
displacement element is comprised of several elements functioning
as a piston and generally designed by reference number 209. Placing
the hydraulic actuation mechanism in the central body makes most
efficient use of space and avoids external connections. However,
all or part of the actuation mechanism could, alternatively, be
located outside support body 208 and hydraulically coupled with the
pumping heads, with the loss of certain advantages of the preferred
embodiment, such as loss of compactness and greater complexity and
risk of contamination from leaks due to increased numbers of
connections. For example, if the axial length of a body is extended
by joining multiple blocks, the actuation mechanism could, for
example, be located in one of the blocks and hydraulically coupled
with the other block through a passageway or external line.
[0036] In the illustrated embodiment, pumping head structures 202,
204 and 206 are coupled respectively with a face portion 211 formed
on each of three side walls of body 208.
[0037] In each of the pumping head structures, diaphragm 212
extends across the face portions and cooperates with a pumping head
to define a pumping chamber 214 on one side of the diaphragm, and
with a depression 216 formed in the body, at the face portion, to
define an actuating fluid chamber 218 on the opposite side of the
diaphragm. In this preferred embodiment of the exemplary pump the
diaphragm can be easily removed and replaced by removing the
pumping head assembly. The diaphragm is sealed against the
cooperating face of body by O-ring seal 220. Plate 222 attaches the
diaphragm to the face of the body. Among other advantages,
attaching the diaphragm with the plate allows the pump to be built
and charged with actuation fluid--preferably a substantially
incompressible fluid (at least at the pressures typically
encountered in the application), such as glycol--prior to the pump
heads being assembled with the body. The diaphragms are preferably
made from a translucent material in order to permit visual
identification of any air or gas bubbles within the actuation fluid
prior to attaching the pump heads. Although one diaphragm per pump
head is being used in the illustrated embodiment, two or more
adjacent pump heads could instead use a different area of one,
larger diaphragm, isolated by a seal or other structure so that
process fluid does not leak between the pump heads. Vent line 223
permits air to be purged from the actuation fluid chamber 218 in
each pumping head. Vent lines 223 are sealed with plugs that are
not shown in the figures. Air entrapped in the actuation fluid
and/or process fluid, pumping chamber, actuation fluid chamber,
cavity 207, or any of the channels within the pump carrying the
fluids, can also be detected by charging the pumping chambers with
process fluid, closing each of them so that process fluid cannot
flow out, pumping the actuation fluid and monitoring the pressure
of the actuation fluid using pressure sensor 210. Because air
bubbles are compressible, the measured pressure will be less than
expected if a substantial amount of air is entrapped in the
system.
[0038] Each pump head structure 202, 204 and 206 is an assembly
that includes a pumping chamber cover 224 with a cavity or
depression 226. The cover cooperates with the diaphragm 212 to form
pumping cavity 214. O-ring 225 forms a seal between the cover 224
and the diaphragm mounting plate 216. Inlet orifice 228 and outlet
orifice 230 extend through cover 224 for permitting flow of process
fluid into and out of, respectively, the pumping chamber. The inlet
orifice is located near the bottom of the pumping chamber so that
fluid flows upward, against gravity, when the pump is in a normal
operating position, toward the outlet orifice. This arrangement and
the elongated form of the pumping chamber tends to reduce pooling
of process fluid within the pumping chamber and encourages
migration of bubbles toward the outlet to assist with purging. The
generally curved shape of the depression 226 and obtuse angles at
the junctions of straight surfaces within the pumping cavity avoid
sharp corners in which process fluid and micro-bubbles might
collect and be difficult to purge, thus further reducing the risk
of entrainment of bubbles during normal operation.
[0039] Each pump head structure includes connectors for connecting
lines carrying process fluid into and out of the pump head. In
order to save space, the connectors are preferably oriented in a
direction that is generally parallel to the elongated axis of the
pumping chambers and the body 208. If oriented with their axes
perpendicular to the axis of the body 208, the pump 200 would
occupy more space in lateral directions, and additional space would
be required to accommodate the process fluid lines that will be
connected to the inlet and outlet connectors. Inlet fitting 232 and
outlet fitting 234 are threaded into a connector block 236. The
illustrated inlet and outlet fittings are examples of flare type
fittings typical in semiconductor manufacturing. They are intended
to be representative generally of fittings for connecting lines to
the pump. Other types of fittings can be used, depending on the
application. Other examples of high purity fittings used in the
semiconductor industry include Super Type Pillar Fitting.RTM. and
Super 300 Type Pillar Fitting.RTM. of Nippon Packing Co., Ltd.,
Flowell.RTM. flare fittings, Flaretek.RTM. fittings from Entegris,
"Parflare" tube fittings from Parker, LQ, LQ1, LQ2 and LQ3 fittings
from SMC Corporation, Furon.RTM. Flare Grip.RTM. fittings and
Furon.RTM. Fuse-Bond Pipe from Saint-Gobain Performance Plastics
Corporation. The connector block 236 and the cover 224 are, in this
example, fabricated separately and assembled into a head assembly.
However, the assembly could be fabricated using fewer or more
components.
[0040] The connector block 236 includes a passageway that carries
fluid from the inlet into the connector block toward the inlet
orifice 228 of the pumping chamber. In this example, the passageway
is formed by a channel 238 formed on the surface of a block and a
cooperating gasket 240. The gasket also seals the pumping chamber
cover 224 with the connector block 236. A hole 242 allows fluid to
flow into channel 244 (see FIG. 5) defined through the pumping
chamber cover 224. Channel 244 terminates at inlet orifice 228.
[0041] In the illustrated example, a one-way check valve 246 is
integrated into the connector block that allows fluid to flow only
from the inlet fitting 232 to the pumping chamber. The check valve
is inserted into the same bore as the inlet fitting 232. It is
comprised of an orifice plate 248 and an umbrella-shaped valve 250
that cooperates with the orifice plate 248. The valve's stem
attaches the valve to the orifice plate. Fluid flowing under
pressure through the holes in the orifice plate, toward the valve,
tends to cause the edges of the valve to curl up or lift, while the
center of the valve remains stationary. The valve has an inverted
shape. When it is assembled, the stem pulls the edges of the valve
against the orifice plate, thereby creating a seating force that
presses the perimeter of the valve against the plate. This forms a
good seal. More details about this particular type of check valve
can be found in commonly assigned U.S. patent application Ser. No.
11/612,408, filed on Dec. 18, 2006, which is incorporated herein by
reference.
[0042] The connector block also includes a passageway that carries
fluid exiting pumping chamber 214 to the outlet connector 234. It
also incorporates a one-way check valve 252 that allows fluid flow
in the direction of the outlet connector. Check valve 252 is
substantially similar to check valve 246. It includes an orifice
plate 254 that sits in a recess 255 formed on the back of pumping
chamber cover 224. Umbrella-shaped valve 256 is attached to the
orifice plate 254. Fluid flowing out of the pumping chamber 214,
through the outlet orifice 230, flows through the check valve 252
and into a passageway that connects with outlet fitting 234. That
passageway is formed in part by channel 258, formed in one surface
of connector block 236, and cooperating gasket 240. Segment 260
(see FIG. 6) of the passageway connects to a bore into which inlet
fitting 234 is screwed. An initial portion of channel 258
preferably forms a volume large enough to accommodate deflection of
the edges of the valve and flow of fluid from around the edges of
the valve without restricting the flow.
[0043] Incompressible actuating fluid is stored in the central
chamber or cavity 207 of the actuating mechanism. When piston 209
translates within the cavity 207, passageways 264 communicate fluid
between the cavity and an actuating fluid chamber 218, associated
with each of the pumping heads 202, 204 and 206. Fluid is capable
of moving in parallel between the cavity 207 and each actuating
fluid chamber 218. Therefore, actuating fluid will, unless
otherwise stopped, flow into each actuating chamber 218 when the
piston displaces actuating fluid from the cavity 207. Similarly,
actuating fluid will, unless otherwise stopped, flow out of the
actuating fluid chamber 218 associated with each pump head when the
piston is retracted, causing the actuating fluid to be drawn into
the cavity 207.
[0044] Assuming that the pumping chamber 214 and the corresponding
actuating fluid chamber 218 contain no gas, air or other
compressible substance, flow of fluid through a given passageway is
controlled in the illustrated embodiment by whether the diaphragm
is permitted to move in the corresponding pump head. If it cannot
move, actuating fluid will tend not to flow in either direction
through the passageway between the cavity 207 and the actuating
fluid chamber 218 that is associated with that diaphragm. Whether a
diaphragm moves depends on whether process fluid can be drawn into
the pumping chamber 214 during flow of actuating fluid out of the
actuating fluid chamber 218, and whether it can flow out of the
pumping chamber during flow of the actuating fluid from the cavity
207 and into the actuating fluid chamber 218. Given that process
fluid can only flow in one direction through the pumping chamber of
the illustrated embodiment, opening and closing a valve (not shown
in these figures) located in the outlet flow path for process fluid
from the pumping chamber 214 will thus determine whether the
diaphragm can be moved to displace the process fluid in the pumping
chamber, which in turn determines whether actuating fluid flows
into the actuating fluid chamber for the given pump head. By
opening the outlet of only one pumping head, all the actuating
fluid caused by displacement of piston 209 will be forced to flow
into only the actuating fluid chamber of the pump head with the
open outlet. The volume of actuating fluid displaced by movement of
piston 209 will equal the volume of process fluid displaced by the
diaphragm of the pump head with the open outlet. In other words,
there is a linear relationship between the movement of the piston
and the volume of process fluid pumped.
[0045] As process fluid is always permitted to flow into each of
the pumping chambers in the illustrated embodiment, actuating fluid
will always flow from each actuating fluid chamber 218 during
retraction of piston 209, at least until the diaphragm reaches the
surface of the wall forming depression 216 for that particular
process fluid chamber. The wall forming depression 216 preferably
includes a channel 217 to ensure that the diaphragm is pulled
evenly against the wall. Thus, the illustrated embodiment of pump
200 will simultaneously recharge, or will recharge in parallel,
each pumping chamber in the pump, regardless of the number of
pumping heads.
[0046] Piston 209 include a sliding seal 262. Displacement of the
piston within cavity 207 is preferably controlled by a stepper
motor 264, which turns a drive screw 266. Clamp 268 attaches the
drive screw to output shaft 270 of the motor. Thrust bearing 272
prevents the drive shaft from axially loading the output shaft of
the motor. The threads on the drive screw 266 couple with threads
on the inside of the piston 209. The angular position of the piston
is fixed by a guide 274, which is clamped to the piston and
cooperates with slot 276 to prevent rotation of the piston. Turning
the drive screw moves the piston. Other types of mechanisms for
translating the piston could, however, be substituted. An optical
sensor 278 detects when guide 274, and thus piston 209, is at a
predetermined limit during upstroke. This is used to calibrate the
pump. Cover 280 seals an opening that allows access to the cavity
207 for assembly and cleaning.
[0047] For semiconductor and other high purity applications, it is
preferred that all surfaces of the pump that contact the process
fluid are made of non-contaminating or non-reacting material. One
example of such a material is polytetrafluoroethylene, which is
sold by DuPont under the trademark Teflon.RTM..
[0048] An exemplary application of multiple head dispense pump 200
is illustrated by FIG. 10. In this application, the pump 200 is
used to dispense 3 different types of process fluids, used in the
fabrication of integrated circuits, onto a semiconductor wafer 300.
Each process fluid is stored in a bulk container 302. The
respective containers are numbered 302A, 302B and 302C. Each
container supplies process fluid to one of the dispense heads 202,
204 or 206. In this example, bulk container 302A supplies pump head
204 through supply line 304A; bulk container 302B supplies pump
head 202 through supply line 304B; and bulk container 302C supplies
pump head 206 through supply line 304C. Each of the supply lines is
connected to the inlet fitting 232 (see FIG. 2) of the pump head
that it supplies with process fluid.
[0049] The outlet fitting 234 (see FIG. 2) of each of the pump
heads 202, 204 and 206 is connected, respectively, to outlet lines
306B, 306A, and 306C. In this example, each outlet line is
connected in series with a separate one of the filters 308A, 308B
or 308C. Filtering the process fluid is optional. Furthermore,
fewer than all of the process fluids can be filtered, if desired.
Each of the filters is connected to a separate purge valve 310A,
310B and 310C, respectively. The outlets of the filters are
connected to dispense valves 312A, 312B and 312C, respectively. The
dispense valves may include, optionally, integrated suck-back
valves. The outlet of each of the dispense valves is connected to a
nozzle, from which process fluid is dispensed onto wafer 300. Not
all of the heads on pump 200 need to be used to service one wafer.
They may also be used, for example, to supply process fluid to more
than one wafer.
[0050] Operation of the pump 200 and dispense valves 312 is
controlled by a controller 314. Preferably, the controller is
programmable, microprocessor-based, but could be implemented using
any type of analog or digital logic circuitry. The same controller
can be used to control more than one multi-head pump. The
controller typically receives a demand for dispense signal from a
manufacturing line, where the wafer is being processed. However,
the control processes can be implemented in the line controller or
other processing entity associated with the fabrication
facility.
[0051] FIGS. 11A, 11B, and 11C are high level flow diagrams for an
exemplary dispense mode control process of exemplary multi-head
pump 200 of FIGS. 2-9 for the application illustrated in FIG. 10.
The process takes place within the controller 314 when the
controller is in a dispense mode. In this example, the controller
receives a request for dispense in the form of a signal sent to one
of its interfaces. There are three interfaces in this example,
corresponding to pump heads 202, 204 and 206 (see FIGS. 2-9). Each
interface may include a physical communication interface. It may
also store certain state information. Alternatively, the interfaces
may also be implemented entirely logical or virtually. For example,
the controller may communicate with one or more tracks or other
processing entities over one or more shared physical mediums, using
addressable messages. The signal would be comprised of a message
that identifies directly or indirectly a dispense head, such as by
a logical port, address, or other identifier that the controller
can map to a particular dispense head.
[0052] When the controller receives a request for dispense of
process fluid, as indicated by blocks 402, 404, and 406, the
controller signals the other interfaces that the pump is busy and
sets a flag indicating that dispense is active for that interface.
Thus, if the request is received on interface 1, the controller
communicates to interfaces 2 and 3 at step 408 that the pump is
busy, so that production tracks or lines that communicate with it
know that dispense is not available. It also sets at step 410 a
stored flag, dispense 1, active. Similarly, if a dispense request
is received on interface 2, a pump busy signal or state is
communicated to interfaces 1 and 3 at step 412 and a dispense 2
flag is set active at step 414. Finally, if the request for
dispense is received on interface 3, the pump busy signal or state
is communicated to interfaces 1 and 2 at step 416, and the dispense
3 flag is set active at step 418.
[0053] As indicated by decision step 420, the controller determines
whether there is an optional dispense delay set up or programmed
for that interface. In a dispense delay, as indicated by steps 422,
424 and 426, the dispense valve corresponding to the active
dispense flag is opened for a predetermined period of time prior to
the pump being actuated. This might be used in applications in
which, for example, it is desirable for the rate of dispense to
start slow and then increase. If there is no dispense delay, the
pump is started at step 428. The controller can be set up or
programmed to open the dispense valve corresponding to the active
dispense flag either immediately or after a predetermined or
programmed delay, as indicated by steps 430, 432 and 434.
[0054] Once the dispense valve is opened and the pump is started,
the controller actuates the pump so that a preset or otherwise
determinable amount of process fluid is dispensed at a predefined
rate or rates (the rate can be varied by, or be a function of, time
and/or other parameters, if desired), as indicated by step 436. In
the embodiment illustrated in FIGS. 2-9, the controller steps the
stepper motor 264 at a rate corresponding to the desired rate(s).
The number of steps corresponds to the volume of process fluid to
be dispensed. Once that volume is dispensed, the pump stops and the
dispense valve corresponding to the active dispense flag is closed,
as indicated by steps 442, 444, 446, 448, 450 and 452. The closing
of the dispense valve can, optionally, be delayed, as indicated by
steps 438 and 440. Once the active dispense valve is closed, the
corresponding suck-back valve is operated, as indicated by steps
454, 456, 458, 460, 462, 464, 466, 468 and 470, after an optional
delay, as indicated by steps 472 and 474. The state of the
suck-back is communicated to the interface corresponding to the
active dispense flag, as indicated by steps 456, 462 and 468.
[0055] Once suck-back is completed, an end of dispense state or
signal is communicated to the interface with the active dispense
flag, as indicated by steps 472, 474, 476, 478, 480, and 482. The
controller then waits for the interface to release the dispense, as
indicated by steps 484, 486, and 488. The release occurs when the
track or line controller signals acknowledge the end of
dispense.
[0056] When the interface releases the dispense, the controller
clears all dispense flags at step 490, communicates to all dispense
interfaces that the pump is busy at step 492, and recharges the
pump at step 494. To recharge the pump, the stepper motor is
stepped in a direction opposite of the direction it is stepped for
dispense, until the pumping chambers in each pump are fully
charged. In the embodiment illustrated in FIGS. 2-9, an optical
sensor 278 indicates when guide 274 is in a fully retracted
position. This indicates that the piston 209 is retracted to the
point at which enough of the actuating fluid is sucked out of each
of the actuating fluid chambers 218 that the pumps are charged with
the desired amount of process fluid. Typically, this will be when
the diaphragm 212 is pulled close to the wall of depression 216
that partially forms the actuating fluid chambers. The dispense
cycle then ends at step 498, and the state of the controller
returns to a start state indicted by step 400, in which the pump
waits for a dispense request.
[0057] Referring now to FIGS. 12, 13, 14 and 15, another
application multi-headed pump, such as the ones discussed above in
connection with FIGS. 1-11, is in a two-stage pumping system. Four
examples 500, 502, 504, and 505 of two-stage pumping systems are
illustrated, respectively, in FIGS. 12, 13, 14 and 15. Example 505
demonstrates two, two-stage pumps 505 arranged in parallel, with
first stages that share one, common actuation system, and second
stages sharing a second, common actuation system. Each of the
remaining examples is of just a two-stage pumping system, with both
stages sharing the same actuation mechanism.
[0058] In each of the examples of a two-stage pumping system, a
pumping chamber 506 is used as a first stage, and pumping chamber
508 is used as a second stage. The volume of each pumping chamber
is changed to draw in and expel process fluid using a diaphragm,
bellows, rolling diaphragm, tubular diaphragm or other arrangement.
In examples 500, 502, and 504, pumping chambers 506 and 508 can be
two different heads of a multi-headed pump, such as the one
described in FIGS. 2-9. In the two, two-stage pumping systems 505,
the first stage pumping chambers 506 of the respective two stage
pump systems are, in the example, implemented with different heads
on the same multi-headed pump. Similarly, the second stage pumping
chambers 508 of these two, two-stage pumping systems are
implemented by different heads on a second multi-headed pump.
Additional heads on each multi-head pump could also be used to
drive the same stage of more than two, two-stage pumps, if
desired.
[0059] The first stage of the pump is used to pull fluid from a
source 509 and push it to a filtering system, generally designated
by filter 510. The second stage is used for pulling the fluid from
the filtering system and dispensing it, in a metered fashion, onto,
for example, a wafer 512. Fill valve 513 is opened to allow fluid
to be drawn from the source 509 and into the first stage, and then
closed when the first stage pumps. The fill valve can be
alternatively implemented as a check-valve. The filtering system
typically includes a vent, controlled in these examples by valve
514, and a drain, controlled in these examples by valve 516. Each
of the examples also includes a dispense valve 518, for controlling
dispensing, and an optional suck-back valve 520. Each of the
two-stage pumping systems in the examples includes a valve 522 for
preventing reverse flow of processing fluid from the pumping
chamber 508. A check valve is preferred. Two-way and other types of
valves can be substituted for the check valve, but they will need
to be opened and closed synchronously with the operation of the
pumping system, thereby complicating the control processes. Each
two-stage pumping system includes a recirculation loop 521 that is
opened and closed by recirculation valve 523. The two, two-stage
pumping systems 505 shown in FIG. 15 can be used to pump different
types of process fluids to the same station, and onto the same
wafer, as shown, in which case process fluid sources 509 would
contain different types of process fluid. The two pumping systems
can also be used to pump process fluids to multiple different
stations.
[0060] The two-stage pumping systems 500 and 505 shown in FIGS. 12
and 15 also include reservoir 524 in series between the filter 510
and the second stage pumping chamber 508 of each of the systems.
The reservoir is optional, and is only necessary if the filtering
system cannot also act as a reservoir for receiving process fluid
being pumped by the first stage.
[0061] In all examples 500, 502, 504, and 505, multiple pumping
chambers are driven by a single drive mechanism, which in these
examples is comprised of stepper motor 526, turning a screw 528,
which in turn causes translation of a piston within cylinder 530.
In the two-stage pumping systems 500, 502, and 504, each drive
mechanism is coupled in parallel to pumping chambers 506 and 508.
In the two-stage pumping systems 505, shown in FIG. 15, the first
stage pumping chambers 506 are driven by a common drive mechanism,
and the second stage pumping chambers 508 are driven by a second,
common drive mechanism.
[0062] For semiconductor and other high purity applications, it is
preferred that all surfaces of the pump that contact the process
fluid be made of non-contaminating or non-reacting material. One
example of such a material is polytetrafluoroethylene, which is
sold by DuPont under the trademark Teflon.RTM.. Other examples
include high density polyethylene and polypropylene, and PFA
(perfluoroalkoxy copolymer resin).
[0063] The drive mechanism operates substantially similarly to the
actuation mechanism described in connection with FIGS. 1-9.
Actuation of a drive mechanism causes actuation fluid to flow
through fluid conduits extending between drive mechanisms and each
of the two pumping chambers in a manner described below. The
conduits can be comprised of tubing, formed as passageways through
blocks of materials, or other structures capable of communicating
actuation fluid, and combinations of the foregoing. Surfaces
contacting the actuation fluid do not need to be of a type for
maintaining high-purity, such as those required for the process
fluid.
[0064] In two-stage pumping systems 500, 502 and 505, shown in
FIGS. 12, 13, and 15, the drive mechanisms are coupled to pumping
chambers through valves 532 and 534. Valves 532 and 534 are used to
control the flow of actuation fluid between the drive mechanism of
each of the two pumping chambers to which it is coupled. They
permit selectively directing flow of actuating fluid only to one of
the plurality of pumping chambers to which the pumping mechanism is
coupled. A single three-way valve can be substituted for the two
valves 532 and 534. Valves 532 and 534 are omitted from the
two-stage pumping system 504 of FIG. 14. Instead, a first stage
output valve 536 is inserted to permit selectively closing and
opening the outlet of the pumping chamber. Closing the first stage
pumping chamber prevents actuation fluid from displacing processing
fluid from the chamber, thus effectively "locking" it against
actuation, and thereby making it unnecessary to utilize valves 532
and 534. Although a coupling that utilizes valves 532 and 534 may
complicate system timing, they do not have to be suitable for
high-purity applications, like valve 536 would need to be.
Therefore, they will be less expensive. Furthermore, valves 532 and
534 may enhance dispense accuracy. Therefore, although optional,
they might be preferred for some applications.
[0065] The operation of the two-stage pumping systems, which is
described below, is controlled by one or more controllers,
executing predetermined control routines to open and close the
various valves and to cause turning of the motor of the drive
mechanism.
[0066] Referring now only to FIGS. 12-13, operation of each of the
two-stage pumping systems 500 and 502 will be first described.
Assuming that each system is completely primed and full of process
fluid, all valves are closed and a unit is ready to process a first
wafer. Dispense valve 518 is opened. Actuation fluid valve 534 for
the second stage is also opened. Drive motor 526 turns the drive
screw 528, moving the piston in cylinder 530. The piston advances
forward, pushing actuation fluid out of the cylinder. Blocked by
closed first stage actuation fluid valve 532, the actuation fluid
moves through valve 534 and into pumping chamber 508, causing
movement of a process fluid displacement member, such as some type
of diaphragm. As the actuation fluid moves in, it displaces an
equal volume of process fluid. The process fluid exits the chamber.
It is blocked by check valve 522, so it flows through output valve
518 and out a dispense tip. Output valve 518 is then closed after
the dispense is finished. The motor 526 reverses direction, pulling
the piston backward, which in turn pulls the actuation fluid back
in to the cylinder 530. This pulls the process fluid displacement
member, causing the pumping chamber to increase in volume and to
pull on the process fluid. New process fluid is drawn from the
reservoir 524 or, if there is no reservoir, from filter 510, to
replenish the dispensed amount. All valves close unit is back at
rest. Either a sensor detects a low fluid level in the reservoir
(or in the filter if there is no reservoir), or the first stage
automatically refills the reservoir (or filter) after every
dispense. In either case, first stage pumping chamber 506 is
already full of process fluid. Actuation fluid valve 532 is opened
and the motor 526 is actuated to cause actuation fluid to be pushed
into pumping chamber 506. This forces the process fluid through
filter 510 and into reservoir 524, if present. Fluid can be pushed
through the filter at any desired flow rate. Once the reservoir
524, or if there is no separate reservoir, the filter, is full, the
motor reverses, fill valve 513 opens, and fresh process fluid is
drawn into the pumping chamber 506 as the volume of the pumping
chamber increases due to actuating fluid being pulled from it. The
unit is now recharged and ready for the next dispense. If desired,
the process fluid can be recirculated, filtered, and returned to
the source bottle. To do this, valve 523 is opened so the process
fluid can be pumped back to the source through line 521. The
recirculation process keeps the fluid from becoming stagnant.
[0067] The two-stage pumping system of FIG. 14 functions similarly.
However, instead of valves 532 being closed during dispensing,
valve 536 is closed during dispensing and recharging of pumping
chamber 508. Since the pumping chamber 506 is full of process fluid
and both valves 513 and 536 are closed, actuation fluid is
effectively blocked from flowing into or out of the pumping chamber
506, forcing it to flow only between pumping chamber 508 and
cylinder 530. During actuation of the first stage pumping chamber
506, actuation fluid is forced to flow to the first stage pumping
chamber, and away from the second stage pumping chamber 508, by
having the second stage pumping chamber fully charged and closing
dispense valve 518.
[0068] Each of the two, two-stage pumping systems 505 in FIG. 15
works in a manner substantially similar to those of the preceding
examples. However, each drive mechanism drives only one of the two
stages and therefore they must be operated in a coordinated
fashion. One drive mechanism is coupled to the first stages of the
two pumping systems, which are respectively represented by pumping
chambers 506, and selectively actuates either one of the two first
stages in a manner like that described above in connection with
FIGS. 12-14. Similarly, the second drive mechanism selectively
actuates either of the pumping chambers 508 in the manner
described. This arrangement, thus, confers the benefits of having
fewer drive mechanisms than pumping chambers, yet enables the two
stages to be operated independently. Stages of more than two pumps
can be driven by the same drive mechanism, if desired.
[0069] Valves 532 and 534 are optional for each of the drive
mechanisms, although they can provide greater control and accuracy.
Furthermore, no valve 536 on the outlet of the first stage pump is
required when valves 532 and 534 are omitted, since the first stage
of each of the two pumping systems is being operated independently
of the second stage of each of the two pumping systems. However, if
the reservoirs or filters of the respective of the two-stage
pumping systems 505 need to be filled independently, then an output
valve, like valve 536, would be desirable to have.
[0070] The foregoing description is of an exemplary and preferred
embodiment of a multiple dispense head pump employing at least in
part certain teachings of the invention. The invention, as defined
by the appended claims, is not limited to the described
embodiments. Alterations and modifications to the disclosed
embodiments may be made without departing from the invention. The
terms used in this specification are, unless expressly stated
otherwise, intended to have ordinary and customary meaning and are
not intended to be limited to the details of the illustrated
structures or the disclosed embodiments. None of the descriptions
in the present application should be read as implying that any
particular element, step, or function is an essential element which
must be included in the claim scope. The scope of patented subject
matter is defined only by the allowed claims. Moreover, none of
these claims are intended to invoke paragraph six of 35 USC
.sctn.112 unless the exact words "means for" or "steps for" are
followed by a participle.
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