Patent Application
20120057990
This invention relates generally to fluid pumps. More particularly, embodiments of the present invention relate to multi-stage pumps. Even more particularly, embodiments of the present invention relate to a multi-stage pump with reduced form factor.
There are many applications for which precise control over the amount and/or rate at which a fluid is dispensed by a pumping apparatus is necessary. In semiconductor processing, for example, it is important to control the amount and rate at which photochemicals, such as photoresist chemicals, are applied to a semiconductor wafer. The coatings applied to semiconductor wafers during processing typically require a flatness across the surface of the wafer that is measured in angstroms. The rates at which processing chemicals are applied to the wafer has to be controlled in order to ensure that the processing liquid is applied uniformly.
Many photochemicals used in the semiconductor industry today are very expensive, frequently costing as much as $1000 a liter. Therefore, it is preferable to ensure that a minimum but adequate amount of chemical is used and that the chemical is not damaged by the pumping apparatus. Current multiple stage pumps can cause sharp pressure spikes in the liquid. Such pressure spikes and subsequent drops in pressure may be damaging to the fluid (i.e., may change the physical characteristics of the fluid unfavorably). Additionally, pressure spikes can lead to built up fluid pressure that may cause a dispense pump to dispense more fluid than intended or dispense the fluid in a manner that has unfavorable dynamics.
Some previous pump designs for photo-resist dispense pumps relied on flat diaphragms in the feed and dispense chambers to move exert pressure on the process fluid. Hydraulic fluid was typically used to assert pressure on one side of the diaphragm to cause the diaphragm to move, thereby displacing the process fluid. The hydraulic fluid could either be put under pressure by a pneumatic piston or a stepper motor driven piston. In order to get the displacement volume required by dispense pumps, the diaphragm had to have a relatively large surface area, and therefore diameter. Moreover, in previous pumps the various plates defining various portions of the pump were held together by external metal plates that were clamped or screwed together. The spaces between the various plates increased the likelihood of fluid leakage. Additionally, valves were distributed throughout the pump, making replacement and repair more difficult.
Embodiments of the present invention provide a multi-stage pump with a reduced form factor, gentler fluid handling capabilities and various features to reduce fluid usage and increase reliability. One embodiment of the present invention includes a multi-stage pump comprising an pump inlet flow path, a pump outlet flow path, a feed pump in fluid communication with the pump inlet flow path, a dispense pump in fluid communication with the feed pump and the pump outlet flow path, and a set of valves to selectively allow fluid flow through the multi-stage pump. The feed pump can comprise a feed stage diaphragm movable in a feed chamber, a feed piston to move the feed stage diaphragm and a feed motor coupled to the feed piston to reciprocate the feed piston. The dispense pump can comprise a dispense rolling diaphragm movable in a dispense chamber, a dispense piston to move the dispense diaphragm and a dispense motor coupled to the dispense piston to reciprocate the dispense piston. According to various embodiments of the present invention the feed stage diaphragm can also be a rolling diaphragm. Additionally, the feed motor and dispense motor can each be stepper motors or brushless DC motors or, for example, the feed motor can be a stepper motor and the dispense motor a brushless DC motor. The multi-stage pump, according to one embodiment can include a single piece dispense block that at least partially defines the dispense chamber, the feed chamber and various flow paths in the multi-stage pump.
Another embodiment of the present invention includes a multi-stage pump comprising a pump inlet flow path, a pump outlet flow path, a single piece dispense block defining at least a portion of a dispense chamber in fluid communication with the pump outlet flow path, and at least a portion of a feed chamber in fluid communication with the pump inlet flow path. The pump can further comprise a filter in fluid communication with the feed chamber and the dispense chamber, a feed stage diaphragm movable in the feed chamber, a feed piston to move the feed stage diaphragm, a feed motor coupled to the feed piston to reciprocate the feed piston, a dispense diaphragm movable in the dispense chamber, a dispense piston to move the dispense diaphragm and a dispense motor coupled to the dispense piston to reciprocate the dispense piston.
The dispense block can further define a first and second portion of the pump inlet flow path, a first and second portion of the feed stage outlet flow path, a first and second portion of the dispense stage inlet flow path, a first and second portion of a vent flow path, a first and second portion of a purge flow path and at least a portion of the pump outlet flow path. According to one embodiment the flow paths can be configured as follows: the first portion of the pump inlet flow path leads from an inlet to an inlet valve and the second portion of the pump inlet path leads from the inlet valve to the feed chamber; the first portion of the feed stage outlet flow path leads from the feed chamber to an isolation valve and the second portion of the feed stage outlet flow path leads to the filter; the first portion of the dispense stage inlet flow path leads from the filter to a barrier valve and the second portion of the dispense stage inlet flow path leads from the barrier valve to the dispense chamber; the first portion of the vent flow path leads from the filter to a vent valve and the second portion of the vent flow path leads from the vent valve to a vent outlet; the first portion of the purge flow path leads from the dispense chamber to a purge valve and the second portion of the purge flow path leads from the purge valve to the feed chamber.
Yet another embodiment of the present invention includes a multi-stage pump method comprising: forming a dispense block of a single piece of material, the dispense block at least partially defining a feed chamber, a dispense chamber, a pump inlet flow path and a pump outlet flow path, mounting a dispense rolling diaphragm between the dispense block and a dispense pump piston housing, mounting a feed stage rolling diaphragm between the dispense block and a feed pump piston housing, coupling a feed pump piston to a feed pump motor via a feed pump lead screw, coupling a dispense pump piston to a dispense pump motor via a dispense pump lead screw, coupling the feed motor to the feed pump piston housing, coupling the dispense motor to the dispense motor piston housing and coupling a filter to the dispense block such that the filter is in fluid communication with the dispense chamber and the feed chamber.
Still another embodiment of the present invention includes a pump comprising, a pump inlet flow path, a pump outlet flow path, a single piece dispense block defining at least a portion of a pump chamber in fluid communication with the pump outlet flow path and the pump inlet flow path, a diaphragm movable in the feed chamber, a piston to move the diaphragm; and a motor coupled to the piston to reciprocate the piston.
Various embodiments of the present invention can include features to make the pump drip proof, such as offsets at intersections between PTFE and metal parts, features to guide drips away from electronics and various seals. Additionally, embodiments of the present invention can include features to reduce the effects of heat on the fluid in the pump. For example, electronic components that generate heat, such as solenoids or microchips, can be positioned away from the dispense block to the extent allowed by space constraints.
Embodiments of the present invention provide a multi-stage pump that has a small form factor (e.g., approximately ½ the size of previous multi-stage pumps) with gentler fluid handling properties and a wider range of operation. Multi-stage pumps according to embodiments of the present invention have 35% fewer parts than previous multi-stage pumps, leading to a reduction in cost and complication, and do not require significant if any hydraulics. Multi-stage pumps, according to embodiments of the present invention, are easily maintained in the field, use less process chemical for dispense operations, reduce outgassing for sensitive chemistries and provide for more precise control. Other advantages include increased resist savings, increased uptime, higher yield and lower maintenance costs. Additionally, multi-stage pumps according to embodiments of the present invention provide significant space savings, allowing more pumps to be fit in the same amount of space as previous pumps.
These and other aspects of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. The following description, while indicating various embodiments of the invention and numerous specific details thereof, is given by way of illustration and not of limitation. Many substitutions, modifications, additions or rearrangements may be made within the scope of the invention, and the invention includes all such substitutions, modifications, additions or rearrangements.
A more complete understanding of the present invention and the advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings in which like reference numbers indicate like features and wherein:
Preferred embodiments of the present invention are illustrated in the FIGUREs, like numerals being used to refer to like and corresponding parts of the various drawings. To the extent dimensions are provided, they are provided by way of example for particular implementations and are not provided by way of limitation. Embodiments can be implemented in a variety of configurations.
Embodiments of the present invention are related to a pumping system that accurately dispenses fluid using a multiple stage (“multi-stage”) pump with reduced form factor. Embodiments of the present invention can be utilized for the dispense of photo-resist and other photosensitive chemicals in semiconductor manufacturing.
Feed stage 105 and dispense stage 110 can include rolling diaphragm pumps to pump fluid in multi-stage pump 100. Feed-stage pump 150 (“feed pump 150”), for example, includes a feed chamber 155 to collect fluid, a feed stage diaphragm 160 to move within feed chamber 155 and displace fluid, a piston 165 to move feed stage diaphragm 160, a lead screw 170 and a stepper motor 175. Lead screw 170 couples to stepper motor 175 through a nut, gear or other mechanism for imparting energy from the motor to lead screw 170. According to one embodiment, feed motor 175 rotates a nut that, in turn, rotates lead screw 170, causing piston 165 to actuate. Dispense-stage pump 180 (“dispense pump 180”) can similarly include a dispense chamber 185, a dispense stage diaphragm 190, a piston 192, a lead screw 195, and a dispense motor 200. Dispense motor 200 can drive lead screw 195 through a threaded nut (e.g., a Torlon or other material nut).
According to other embodiments, feed stage 105 and dispense stage 110 can be a variety of other pumps including pneumatically or hydraulically actuated pumps, hydraulic pumps or other pumps. One example of a multi-stage pump using a pneumatically actuated pump for the feed stage and a stepper motor driven hydraulic pump is described in U.S. patent application Ser. No. 11/051,576 entitled “PUMP CONTROLLER FOR PRECISION PUMPING APPARATUS” by inventors Zagars et al., filed Feb. 4, 2005, hereby incorporated by reference. The use of motors at both stages, however, provides an advantage in that the hydraulic piping, control systems and fluids are eliminated, thereby reducing space and potential leaks.
Feed motor 175 and dispense motor 200 can be any suitable motor. According to one embodiment, dispense motor 200 is a Permanent-Magnet Synchronous Motor (“PMSM”). The PMSM can be controlled by a digital signal processor (“DSP”) utilizing Field-Oriented Control (“FOC”) or other type of position/speed control known in the art at motor 200, a controller onboard multi-stage pump 100 or a separate pump controller (e.g. as shown in
During operation of multi-stage pump 100, the valves of multi-stage pump 100 are opened or closed to allow or restrict fluid flow to various portions of multi-stage pump 100. According to one embodiment, these valves can be pneumatically actuated (i.e., gas driven) diaphragm valves that open or close depending on whether pressure or a vacuum is asserted. However, in other embodiments of the present invention, any suitable valve can be used. One embodiment of a valve plate and corresponding valve components is described below in conjunction with
The following provides a summary of various stages of operation of multi-stage pump 100. However, multi-stage pump 100 can be controlled according to a variety of control schemes including, but not limited to those described in U.S. Provisional Patent Application No. 60/741,682 entitled “SYSTEM AND METHOD FOR PRESSURE COMPENSATION IN A PUMP” by Inventors Cedrone et al., filed Dec. 2, 2005; U.S. patent application Ser. No. 11/502,729 entitled “SYSTEMS AND METHODS FOR FLUID FLOW CONTROL IN AN IMMERSION LITHOGRAPHY SYSTEM” by Inventors Clarke et al., filed Aug. 11, 2006; U.S. patent application Ser. No. 11/602,472, entitled “SYSTEM AND METHOD FOR CORRECTING FOR PRESSURE VARIATIONS USING A MOTOR” by Inventors Gonnella et al., filed Nov. 20, 2006, U.S. patent application Ser. No. 11/292,559 entitled “SYSTEM AND METHOD FOR CONTROL OF FLUID PRESSURE” by Inventors Gonnella et al., filed Dec. 2, 2005; U.S. patent application Ser. No. 11/364,286 entitled “SYSTEM AND METHOD FOR MONITORING OPERATION OF A PUMP” by Inventors Gonnella et al., filed Feb. 28, 2006, U.S. patent application Ser. No. 11/602,508, entitled “SYSTEM AND METHOD FOR PRESSURE COMPENSATION IN A PUMP” by Inventors Cedrone et al., filed Nov. 20, 2006; U.S. patent application Ser. No. 11/602,449, entitled “I/O SYSTEMS, METHODS AND DEVICES FOR INTERFACING A PUMP CONTROLLER” by Inventors Cedrone et al., filed Nov. 20, 2006, each of which is fully incorporated by reference herein, to sequence valves and control pressure. According to one embodiment, multi-stage pump 100 can include a ready segment, dispense segment, fill segment, pre-filtration segment, filtration segment, vent segment, purge segment and static purge segment. During the feed segment, inlet valve 125 is opened and feed stage pump 150 moves (e.g., pulls) feed stage diaphragm 160 to draw fluid into feed chamber 155. Once a sufficient amount of fluid has filled feed chamber 155, inlet valve 125 is closed. During the filtration segment, feed-stage pump 150 moves feed stage diaphragm 160 to displace fluid from feed chamber 155. Isolation valve 130 and barrier valve 135 are opened to allow fluid to flow through filter 120 to dispense chamber 185. Isolation valve 130, according to one embodiment, can be opened first (e.g., in the “pre-filtration segment”) to allow pressure to build in filter 120 and then barrier valve 135 opened to allow fluid flow into dispense chamber 185. According to other embodiments, both isolation valve 130 and barrier valve 135 can be opened and the feed pump moved to build pressure on the dispense side of the filter. During the filtration segment, dispense pump 180 can be brought to its home position. As described in U.S. Provisional Patent Application No. 60/630,384, entitled “SYSTEM AND METHOD FOR A VARIABLE HOME POSITION DISPENSE SYSTEM” by Laverdiere, et al. filed Nov. 23, 2004 and PCT Application No. PCT/US2005/042127, entitled “SYSTEM AND METHOD FOR VARIABLE HOME POSITION DISPENSE SYSTEM”, by Applicant Entegris, Inc. and Inventors Laverdiere et al., filed Nov. 21, 2005, both of which are hereby incorporated by reference, the home position of the dispense pump can be a position that gives the greatest available volume at the dispense pump for the dispense cycle, but is less than the maximum available volume that the dispense pump could provide. The home position is selected based on various parameters for the dispense cycle to reduce unused hold up volume of multi-stage pump 100. Feed pump 150 can similarly be brought to a home position that provides a volume that is less than its maximum available volume.
At the beginning of the vent segment, isolation valve 130 is opened, barrier valve 135 closed and vent valve 145 opened. In another embodiment, barrier valve 135 can remain open during the vent segment and close at the end of the vent segment. During this time, if barrier valve 135 is open, the pressure can be understood by the controller because the pressure in the dispense chamber, which can be measured by pressure sensor 112, will be affected by the pressure in filter 120. Feed-stage pump 150 applies pressure to the fluid to remove air bubbles from filter 120 through open vent valve 145. Feed-stage pump 150 can be controlled to cause venting to occur at a predefined rate, allowing for longer vent times and lower vent rates, thereby allowing for accurate control of the amount of vent waste. If feed pump is a pneumatic style pump, a fluid flow restriction can be placed in the vent fluid path, and the pneumatic pressure applied to feed pump can be increased or decreased in order to maintain a “venting” set point pressure, giving some control of an otherwise un-controlled method.
At the beginning of the purge segment, isolation valve 130 is closed, barrier valve 135, if it is open in the vent segment, is closed, vent valve 145 closed, and purge valve 140 opened and inlet valve 125 opened. Dispense pump 180 applies pressure to the fluid in dispense chamber 185 to vent air bubbles through purge valve 140. During the static purge segment, dispense pump 180 is stopped, but purge valve 140 remains open to continue to vent air. Any excess fluid removed during the purge or static purge segments can be routed out of multi-stage pump 100 (e.g., returned to the fluid source or discarded) or recycled to feed-stage pump 150. During the ready segment, inlet valve 125, isolation valve 130 and barrier valve 135 can be opened and purge valve 140 closed so that feed-stage pump 150 can reach ambient pressure of the source (e.g., the source bottle). According to other embodiments, all the valves can be closed at the ready segment.
During the dispense segment, outlet valve 147 opens and dispense pump 180 applies pressure to the fluid in dispense chamber 185. Because outlet valve 147 may react to controls more slowly than dispense pump 180, outlet valve 147 can be opened first and some predetermined period of time later dispense motor 200 started. This prevents dispense pump 180 from pushing fluid through a partially opened outlet valve 147. Moreover, this prevents fluid moving up the dispense nozzle caused by the valve opening, followed by forward fluid motion caused by motor action. In other embodiments, outlet valve 147 can be opened and dispense begun by dispense pump 180 simultaneously.
An additional suckback segment can be performed in which excess fluid in the dispense nozzle is removed. During the suckback segment, outlet valve 147 can close and a secondary motor or vacuum can be used to suck excess fluid out of the outlet nozzle. Alternatively, outlet valve 147 can remain open and dispense motor 200 can be reversed to such fluid back into the dispense chamber. The suckback segment helps prevent dripping of excess fluid onto the wafer.
Referring briefly to
The opening and closing of various valves can cause pressure spikes in the fluid within multi-stage pump 100. Because outlet valve 147 is closed during the static purge segment, closing of purge valve 140 at the end of the static purge segment, for example, can cause a pressure increase in dispense chamber 185. This can occur because each valve may displace a small volume of fluid when it closes. More particularly, in many cases before a fluid is dispensed from chamber 185 a purge cycle and/or a static purge cycle is used to purge air from dispense chamber 185 in order to prevent sputtering or other perturbations in the dispense of the fluid from multi-stage pump 100. At the end of the static purge cycle, however, purge valve 140 closes in order to seal dispense chamber 185 in preparation for the start of the dispense. As purge valve 140 closes it forces a volume of extra fluid (approximately equal to the hold-up volume of purge valve 140) into dispense chamber 185, which, in turn, causes an increase in pressure of the fluid in dispense chamber 185 above the baseline pressure intended for the dispense of the fluid. This excess pressure (above the baseline) may cause problems with a subsequent dispense of fluid. These problems are exacerbated in low pressure applications, as the pressure increase caused by the closing of purge valve 140 may be a greater percentage of the baseline pressure desirable for dispense.
More specifically, because of the pressure increase that occurs due to the closing of purge valve 140 a “spitting” of fluid onto the wafer, a double dispense or other undesirable fluid dynamics may occur during the subsequent dispense segment if the pressure is not reduced. Additionally, as this pressure increase may not be constant during operation of multi-stage pump 100, these pressure increases may cause variations in the amount of fluid dispensed, or other characteristics of the dispense, during successive dispense segments. These variations in the dispense may in turn cause an increase in wafer scrap and rework of wafers. Embodiments of the present invention account for the pressure increase due to various valve closings within the system to achieve a desirable starting pressure for the beginning of the dispense segment, account for differing head pressures and other differences in equipment from system to system by allowing almost any baseline pressure to be achieved in dispense chamber 185 before a dispense.
In one embodiment, to account for unwanted pressure increases to the fluid in dispense chamber 185, during the static purge segment dispense motor 200 may be reversed to back out piston 192 a predetermined distance to compensate for any pressure increase caused by the closure of barrier valve 135, purge valve 140 and/or any other sources which may cause a pressure increase in dispense chamber 185.
Thus, embodiments of the present invention provide a multi-stage pump with gentle fluid handling characteristics. By compensating for pressure fluctuations in a dispense chamber before a dispense segment, potentially damaging pressure spikes can be avoided or mitigated. Embodiments of the present invention can also employ other pump control mechanisms and valve timings to help reduce deleterious effects of pressure on a process fluid.
Dispense block 205 can include various external inlets and outlets including, for example, inlet 210 through which the fluid is received, vent outlet 215 for venting fluid during the vent segment, and dispense outlet 220 through which fluid is dispensed during the dispense segment. Dispense block 205, in the example of
Dispense block 205 routes fluid to the feed pump, dispense pump and filter 120. A pump cover 225 can protect feed motor 175 and dispense motor 200 from damage, while piston housing 227 can provide protection for piston 165 and piston 192 and, according to one embodiment of the present invention, be formed of polyethylene or other polymer. Valve plate 230 provides a valve housing for a system of valves (e.g., inlet valve 125, isolation valve 130, barrier valve 135, purge valve 140 and vent valve 145 of
A valve control gas and vacuum are provided to valve plate 230 via valve control supply lines 260, which run from a valve control manifold (in an area beneath top cover 263 or housing cover 225), through dispense block 205 to valve plate 230. Valve control gas supply inlet 265 provides a pressurized gas to the valve control manifold and vacuum inlet 270 provides vacuum (or low pressure) to the valve control manifold. The valve control manifold acts as a three way valve to route pressurized gas or vacuum to the appropriate inlets of valve plate 230 via supply lines 260 to actuate the corresponding valve(s). As discussed below in conjunction with
According to one embodiment, dispense block 205 can include a vertically protruding flange or lip 272 protruding outward from the edge of dispense block 205 that meets top cover 263. On the top edge, according to one embodiment, the top of top cover 263 is flush with the top surface of lip 272. This causes drips near the top interface of dispense block 205 and top cover 263 to tend to run onto dispense block 205, rather than through the interface. On the sides, however, top cover 263 is flush with the base of lip 272 or otherwise inwardly offset from the outer surface of lip 272. This causes drips to tend to flow down the corner created by top cover 263 and lip 272, rather than between top cover 263 and dispense block 205. Additionally, a rubber seal is placed between the top edge of top cover 263 and back plate 271 to prevent drips from leaking between top cover 263 and back plate 271.
Dispense block 205 can also include sloped feature 273 that includes a sloped surface defined in dispense block 205 that slopes down and away from the area of pump 100 housing electronics. Consequently, drips near the top of dispense block 205 are lead away from the electronics. Additionally, pump cover 225 can also be offset slightly inwards from the outer side edges of dispense block 205 so that drips down the side of pump 100 will tend to flow past the interface of pump cover 225 and other portions of pump 100.
According to one embodiment of the present invention, wherever a metal cover interfaces with dispense block 205, the vertical surfaces of the metal cover can be slightly inwardly offset (e.g., 1/64 of an inch or 0.396875 millimeters) from the corresponding vertical surface of dispense block 205. Additionally, multi-stage pump 100 can include seals, sloped features and other features to prevent drips from entering portions of multi-stage pump 100 housing electronics. Furthermore, as shown in
Returning to
Back plate 271, according to one embodiment of the present invention, can include inwardly extending tabs (e.g., bracket 274) to which top cover 263 and pump cover 225 mount. Because top cover 263 and pump cover 225 overlap bracket 274 (e.g., at the bottom and back edges of top cover 263 and the top and back edges pump cover 225) drips are prevented from flowing into the electronics area between any space between the bottom edge of top cover 263 and the top edge of pump cover 225 or at the back edges of top cover 263 and pump cover 225.
Manifold 302, according to one embodiment of the present invention can include a set of solenoid valves to selectively direct pressure/vacuum to valve plate 230. When a particular solenoid is on thereby directing vacuum or pressure to a valve, depending on implementation, the solenoid will generate heat. According to one embodiment, manifold 302 is mounted below a PCB board (which is mounted to back plate 271 and better shown in
It should be noted that the multi-stage pump 100 described in conjunction with
A flow passage is defined for each valve for the application of a valve control gas/vacuum or other pressure to cause the diaphragm to be displaced between an open position and closed position for a valve. As an example, flow passage 1050 runs from an input on valve control plate 230 to the corresponding opening in the arced surface of purge valve chamber 1040. By selective application of vacuum or low pressure through flow passage 1050, diaphragm 1002 can be displaced into chamber 1040, thereby causing purge valve 140 to open. An annular ring around each valve chamber provides for sealing with O-rings 1004. For example, annular ring 1055 is used to partially contain an o-ring to seal purge valve 140.
In the embodiment of
When positive pressure is applied through flow passage 1065, diaphragm 1002 moves to seal the inlet and outlet (in this case flow passage 295 from the dispense chamber and flow passage 305 to the feed chamber). The volume of fluid in area 1072 will therefore be moved out of purge valve 140. This will cause a pressure spike in the dispense chamber (or other enclosed space to which the fluid is moved). The amount of fluid displaced by the valve will depend on how much volume was held up in the valve. Because this volume varies with the amount of pressure applied, different pumps of the same design, but operating using different vacuum pressures, will show different pressure spikes in the dispense chamber or other enclosed space. Moreover, because diaphragm 1002 is plastic, the displacement of diaphragm 1002 for a given vacuum pressure will vary depending on temperature. Consequently, the volume of unused area 1070 will change depending on temperature. Because the displacement volume of the valve of
Embodiments of the present invention reduce or eliminate the problems associated with a valve chamber having a flat surface.
In the embodiment of
The valve chamber can be sized to allow the diaphragm to displace sufficiently to allow fluid flow from the inlet to the outlet path (e.g., from flow path 300 to flow path 305 of
It should also be noted that flow passage 1050 for the application of pressure/vacuum to the diaphragm does not have to be centered in the valve chamber, but may be off center (this is shown, for example, on the barrier valve chamber 1035 in
However, the positioning of these flow passages with respect to the valve can be reversed or otherwise changed in other embodiments so that less fluid is displaced back to the dispense chamber than displaced to the feed chamber when purge valve 140 closes. For inlet valve 125, on the other hand, the inlet flow passage can be closer to the center so that more fluid is displaced back to the fluid source than to the feed chamber when inlet valve 125 is closed (i.e., inlet valve 125 can have the inlet/outlet flow path arrangement shown in
Other configurations of inlet and outlet flow passages can also be utilized. For example, both the inlet and outlet flow passage to a valve can be off center. As another example, the widths of the inlet and outlet flow passages can be different so that one flow passage is more restricted, again helping to cause more fluid to be displaced through one of the flow passages (e.g., the larger flow passage) when the valve closes.
As can be seen from
The valves of valve plate 230 may have different dimensions. For example, the purge valve 140 can be smaller than the other valves or the valves can be otherwise dimensioned.
The size of each valve can be selected to balance the desire to minimize the pressure drop across the valve (i.e., the desire to minimize the restriction caused by the valve in the open position) and the desire to minimize the amount of hold up volume of the valve. That is, the valves can be dimensioned to balance the desire for minimally restricted flow and to minimize pressure spikes when the valve opens/closes. In the examples of
As discussed above, feed pump 150 according to one embodiment of the present invention can be driven by a stepper motor while dispense pump 180 can be driven by a brushless DC motor or PSMS motor.
PMSM 3030 can be utilized as feed motor 175 and/or dispense motor 200 as described above. In one embodiment, pump 100 utilizes a stepper motor as feed motor 175 and PMSM 3030 as dispense motor 200. Suitable motors and associated parts may be obtained from EAD Motors of Dover, N.H., USA or the like. In operation, the stator of BLDCM 3030 generates a stator flux and the rotor generates a rotor flux. The interaction between the stator flux and the rotor flux defines the torque and hence the speed of BLDCM 3030. In one embodiment, a digital signal processor (DSP) is used to implement all of the field-oriented control (FOC). The FOC algorithms are realized in computer-executable software instructions embodied in a computer-readable medium. Digital signal processors, alone with on-chip hardware peripherals, are now available with the computational power, speed, and programmability to control the BLDCM 3030 and completely execute the FOC algorithms in microseconds with relatively insignificant add-on costs. One example of a DSP that can be utilized to implement embodiments of the invention disclosed herein is a 16-bit DSP available from Texas Instruments, Inc. based in Dallas, Tex., USA (part number TMS320F2812PGFA).
BLDCM 3030 can incorporate at least one position sensor to sense the actual rotor position. In one embodiment, the position sensor may be external to BLDCM 3030. In one embodiment, the position sensor may be internal to BLDCM 3030. In one embodiment, BLDCM 3030 may be sensorless. In the example shown in
BLDCM 3030 can be run at very low speeds and still maintain a constant velocity, which means little or no vibration. In other technologies such as stepper motors it has been impossible to run at lower speeds without introducing vibration into the pumping system, which was caused by poor constant velocity control. This variation would cause poor dispense performance and results in a very narrow window range of operation. Additionally, the vibration can have a deleterious effect on the process fluid. Table 1 below and
As can be seen from TABLE 1, compared to a stepper motor, a BLDCM can provide substantially increased resolution with continuous rotary motion, lower power consumption, higher torque delivery, and wider speed range. Note that, BLDCM resolution can be about 10 times more or better than what is provided by the stepper motor. For this reason, the smallest unit of advancement that can be provided by BLDCM is referred to as a “motor increment,” distinguishable from the term “step”, which is generally used in conjunction with a stepper motor. The motor increment is smallest measurable unit of movement as a BLDCM, according to one embodiment, can provide continuous motion, whereas a stepper motor moves in discrete steps.
With the BLDCM, current is adjusted with an increase or decrease in load. At any particular point in time, the BLDCM will self-compensate and supply itself with the amount of current necessary to turn itself at the speed requested and produce the force to move the load as required. The current can be very low (under mA) when the motor is not moving. Because a BLDCM is self-compensating (i.e., it can adaptively adjust current according to load on system), it is always on, even when the motor is not moving. In comparison, the stepper motor could be turned off when the stepper motor is not moving, depending upon applications.
To maintain position control, the control scheme for the BLDCM needs to be run very often. In one embodiment, the control loop is run at 30 kHz. So, every 33 ps, the control loop checks to see if the BLDCM is at the right position. If so, try not to do anything. If not, it adjusts the current and tries to force the BLDCM to the position where it should be. This rapid self-compensating action enables a very precise position control, which is highly desirable in some applications. Running the control loop at a speed higher (e.g., 30 kHz) than normal (e.g., 10 kHz) could mean extra heat generation in the system. This is because the more often the BLDCM switches current, the more opportunity to generate heat.
According to one aspect of the invention, in some embodiments the BLDCM is configured to take heat generation into consideration. Specifically, the control loop is configured to run at two different speeds during a single cycle. During the dispense portion of the cycle, the control loop is run at a higher speed (e.g., 30 kHz). During the rest of the non-dispense portion of the cycle, the control loop is run at a lower speed (e.g., 10 kHz). This configuration can be particularly useful in applications where super accurate position control during dispense is critical. As an example, during the dispense time, the control loop runs at 30 kHz. It might cause a bit of extra heat, but provides an excellent position control. The rest of the time the speed is cut back to 10 kHz. By doing so, the temperature can be significantly dropped.
The dispense portion of the cycle could be customized depending upon applications. As another example, a dispense system may implement 20-second cycles. On one 20-second cycle, 5 seconds may be for dispensing, while the rest 15 seconds may be for logging or recharging, etc. In between cycles, there could be a 15-20 seconds ready period. Thus, the control loop of the BLDCM would run a small percentage of a cycle (e.g., 5 seconds) at a higher frequency (e.g., 30 kHz) and a larger percentage (e.g., 15 seconds) at a lower frequency (e.g., 10 kHz).
As one skilled in the art can appreciate, these parameters (e.g., 5 seconds, 15 seconds, 30 kHz, 10 kHz. etc.) are meant to be exemplary and non-limiting. Operating speed and time can be adjusted or otherwise configured to suit so long as they are within the scope and spirit of the invention disclosed herein. Empirical methodologies may be utilized in determining these programmable parameters. For example, 10 kHz is a fairly typical frequency to drive the BLDCM. Although a different speed could be used, running the control loop of the BLDCM slower than 10 kHz could run the risk of losing position control. Since it is generally difficult to regain the position control, it is desirable for the BLDCM to hold the position.
Reducing speed as much as possible during the non-dispense phase of the cycle without undesirably compromising the position control is achievable in embodiments disclosed herein via a control scheme for the BLDCM. The control scheme is configured to increase the frequency (e.g., 30 kHz) in order to gain some extra/increased position control for critical functions such as dispensing. The control scheme is also configured to reduce heat generation by allowing non-critical functions to be run at a lower frequency (e.g., 10 kHz). Additionally, the custom control scheme is configured to minimize any position control losses caused by running at the lower frequency during the non-dispense cycle.
The control scheme is configured to provide a desirable dispense profile, which can be characterized by pressure. The characterization can be based on deviation of the pressure signal. For example, a flat pressure profile would suggest smooth motion, less vibration, and therefore better position control. Contrastingly, deviating pressure signals would suggest poor position control. As far as position control is concerned, the difference between running the BLDCM at 10 kHz and at 15 kHz can be insignificant. However, if the speed drops below 10 kHz (e.g., 5 kHz), it may not be fast enough to retain position control. For example, one embodiment of the BLDCM is configured for dispensing fluids. When the position loop runs under 1 ms (i.e., at about 10 kHz or more), no effects are visible to the human eye. However, when it gets up to the 1, 2, or 3 ms range, effects in the fluid become visible. As another example, if the timing of the valve varies under 1 ms, any variation in the results of the fluid may not be visible to the human eye or by other process monitors. In the 1, 2, or 3 ms range, however, the variations can be visible. Thus, the control scheme preferably runs time critical functions (e.g., timing the motor, valves, etc.) at about 10 kHz or more.
Another consideration concerns internal calculations in the dispense system. If the dispense system is set to run as slow as 1 kHz, then there is not any finer resolution than 1 ms and no calculations that need to be finer than 1 ms can be performed. In this case, 10 kHz would be a practical frequency for the dispense system. As described above, these numbers are meant to be exemplary. It is possible to set the speed lower than 10 kHz (e.g., 5 or even 2 kHz).
Similarly, it is possible to set the speed higher than 30 kHz, so long as it satisfies the performance requirement. The exemplary dispense system disclosed herein uses an encoder which has a number of lines (e.g., 2000 lines to give 8000 pulses to the DSP). The time between each line is the speed. Even if the BLDCM is running fairly slowly, these are very fine lines so they can come very fast, basically pulsing to the encoder. If the BLDCM runs one revolution per a second, that means 2000 lines and hence 8000 pulses in that second. If the widths of the pulses do not vary (i.e., they are right at the target width and remain the same over and over), it is an indication of a very good speed control. If they oscillate, it is an indication of a poorer speed control, not necessarily bad, depending on the system design (e.g., tolerance) and application.
Another consideration concerns the practical limit on the processing power of a digital signal processor (DSP). As an example, to dispense in one cycle, it may take almost or just about 20 ms to perform all the necessary calculations for the position controller, the current controllers, and the like. Running at 30 kHz gives about 30 ms, which is sufficient to do those calculations with time left to run all other processes in the controllers. It is possible to use a more powerful processor that can run faster than 30 kHz. However, operating at a rate faster than 30 ms results a diminishing return. For example, 50 kHz only gives about 20 ms ( 1/50000 Hz=0.00002 s=20 μs). In this case, a better speed performance can be obtained at 50 kHz, but the system has insufficient time to conduct all the processes necessary to run the controllers, thus causing a processing problem. What is more, running 50 kHz means that the current will switch that much more often, which contributes to the aforementioned heat generation problem.
In summary, to reduce the heat output, one solution is to configure the BLDCM to run at a higher frequency (e.g., 30 kHz) during dispensing and drop down or cut back to a lower frequency (e.g., 10 kHz) during non-dispensing operations (e.g., recharge). Factors to consider in configuring the custom control scheme and associated parameters include position control performance and speed of calculation, which relates to the processing power of a processor, and heat generation, which relates to the number of times the current is switched after calculation. In the above example, the loss of position performance at 10 kHz is insignificant for non-dispense operations, the position control at 30 kHz is excellent for dispensing, and the heat generation is significantly reduced. By reducing the heat generation, embodiments of the invention can provide a technical advantage in preventing temperature changes from affecting the fluid being dispensed. This can be particularly useful in applications involving dispensing sensitive and/or expensive fluids, in which case, it would be highly desirable to avoid any possibility that heat or temperature change may affect the fluid. Heating a fluid can also affect the dispense operation. One such effect is called the natural suck-back effect. The suck-back effect explains that when the dispense operation warms and expands the fluid out of the nozzle, it starts to cool and as it starts to cool, it can lose a little bit. When the dispense operation retracts, the fluid in the nozzle starts to increase the volume. Therefore, with the suck-back effect the volume may not be precise and may be inconsistent.
Multi-stage pumps, according to various embodiments of the present invention, can be significantly smaller than previous multi-stage pumps, while providing gentler fluid handling characteristics and a wider range of operation. Various features of the multi-stage pump contribute to the smaller size.
Some previous pump designs relied on flat diaphragms in the feed and dispense chambers to move exert pressure on the process fluid. Hydraulic fluid was typically used to assert pressure on one side of the diaphragm to cause the diaphragm to move, thereby displacing the process fluid. The hydraulic fluid could either be put under pressure by a pneumatic piston or a stepper motor driven piston. In order to get the displacement volume required by dispense pumps, the diaphragm had to have a relatively large surface area, and therefore diameter.
As discussed above in conjunction with
For example, previous pumps that used flat diaphragms to achieve a 10 ml displacement, required a pump chamber with a 4.24 square inch (27.4193 square centimeter) cross section. A pump chamber using a rolling diaphragm can achieve a similar displacement with a 1.00 square inch (6.4516 square centimeter) diaphragm. Even taking into account the space between the piston and chamber wall for the diaphragm to roll and the sealing flange, the rolling diaphragm pump only requires a footprint of 1.25 square inches (8.064 square centimeters). Additionally, the rolling diaphragm is able handle much higher pressures than the flat diaphragm due to the reduced wetted surface area. Consequently, the rolling diaphragm pump does not require reinforcement, such as metal encasement, to handle pressures for which the flat diaphragm requires reinforcement.
Additionally, the use of a rolling diaphragm allows the flow passages into and out of feed chamber 155 and dispense chamber 185 to be advantageously placed to reduce size. As discussed in conjunction with
Another feature of embodiments of the present invention that reduces size is the use of a single piece dispense block that defines the various flow passages from inlet to outlet, including the pump chambers. Previously, there were multiple (e.g., five or more) blocks that defined the flow passages and chambers. Because dispense block 205 is a single block, seals are reduced and the complexity of the assembly is reduced.
Yet another feature of embodiments of the present invention that helps reduce the size is that all the pump valves (e.g., input, isolation, barrier, vent and purge) are in a single valve plate. Previously, valves were split between valve plates and the various dispense blocks. This provided for more interfaces that could cause fluid leaks.
Moreover, in previous pumps the various PTFE plates were held together by external metal plates that were clamped or screwed together. Screwing or otherwise attaching component to PTFE is difficult because PTFE is a relatively weak material. Embodiments of the present invention solve this problem by the use of bars (e.g., inserts) with perpendicular female threaded holes as described in conjunction with
Although described in terms of a multi-stage pump, embodiments of the present invention can also be utilized in a single stage pump.
Dispense block 4005 can include various external inlets and outlets including, for example, inlet 4010 through which the fluid is received, purge/vent outlet 4015 for purging/venting fluid, and dispense outlet 4020 through which fluid is dispensed during the dispense segment. Dispense block 4005, in the example of
Dispense block 4005 routes fluid from the inlet to an inlet valve (e.g., at least partially defined by valve plate 4030), from the inlet valve to the pump chamber, from the pump chamber to a vent/purge valve and from the pump chamber to outlet 4020. A pump cover 4225 can protect a pump motor from damage, while piston housing 4027 can provide protection for a piston and, according to one embodiment of the present invention, be formed of polyethylene or other polymer. Valve plate 4030 provides a valve housing for a system of valves (e.g., an inlet valve, and a purge/vent valve) that can be configured to direct fluid flow to various components of pump 4000. Valve plate 4030 and the corresponding valves can be formed similarly to the manner described in conjunction with valve plate 230, discussed above. According to one embodiment, each of the inlet valve and the purge/vent valve is at least partially integrated into valve plate 4030 and is a diaphragm valve that is either opened or closed depending on whether pressure or vacuum is applied to the corresponding diaphragm. In other embodiments, some of the valves may be external to dispense block 4005 or arranged in additional valve plates. According to one embodiment, a sheet of PTFE is sandwiched between valve plate 4030 and dispense block 4005 to form the diaphragms of the various valves. Valve plate 4030 includes a valve control inlet (not shown) for each valve to apply pressure or vacuum to the corresponding diaphragm.
As with multi-stage pump 100, pump 4000 can include several features to prevent fluid drips from entering the area of multi-stage pump 100 housing electronics. The “drip proof” features can include protruding lips, sloped features, seals between components, offsets at metal/polymer interfaces and other features described above to isolate electronics from drips. The electronics and manifold and PCB board can be configured similarly to the manner described above to reduce the effects of heat on fluid in the pump chamber.
Thus, similar features as used in a multi-stage pump to reduce form factor and the effects of heat and to prevent fluid from entering the electronics housing can be used in a single stage pump.
Although the present invention has been described in detail herein with reference to the illustrative embodiments, it should be understood that the description is by way of example only and is not to be construed in a limiting sense. It is to be further understood, therefore, that numerous changes in the details of the embodiments of this invention and additional embodiments of this invention will be apparent to, and may be made by, persons of ordinary skill in the art having reference to this description. It is contemplated that all such changes and additional embodiments are within the scope of this invention as claimed.
This application is a continuation of, and claims a benefit of priority under 35 U.S.C. 120 of the filing date of U.S. patent application Ser. No. 11/602,464, entitled “SYSTEM AND METHOD FOR A PUMP WITH REDUCED FORM FACTOR” by inventors Cedrone et al, filed Nov. 20, 2006, which in turn is a Continuation-in-Part and claims under 35 U.S.C. 120 benefit of and priority to PCT Patent Application No. PCT/US2005/042127, entitled “SYSTEM AND METHOD FOR A VARIABLE HOME POSITION DISPENSE SYSTEM” by Applicant Entegris, Inc. and inventors Laverdiere et al., filed Nov. 21, 2005, in the United States Receiving Office, and under 35 U.S.C. 119(e) benefit of and priority to U.S. Provisional Patent Application No. 60/742,435 entitled “SYSTEM AND METHOD FOR MULTI-STAGE PUMP WITH REDUCED FORM FACTOR” by Cedrone et al., filed Dec. 5, 2005, both of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60742435 | Dec 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11602464 | Nov 2006 | US |
| Child | 13216944 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2005/042127 | Nov 2005 | US |
| Child | 11602464 | US |
