KR101283259B1 - System and method for position control of a mechanical piston in a pump - Google Patents

Abstract

Embodiments of the systems and methods disclosed herein utilize a BLDCM in a pumping system useful in semiconductor manufacturing for real time control of fluid movement and discharge rate, smooth motion control, and highly accurate and repeatable position control. To drive a single stage pump or a multiple stage pump. The BLDCM can employ a position sensor that feeds back the position in real time to a processor that implements a custom field-oriented control scheme. Embodiments of the present invention can reduce heat generation without undesirably yielding accurate position control of the discharge pump by raising and lowering the operating frequency of the BLDCM in accordance with the criticality of the basic function (s) through a custom control scheme. The control scheme maintains a constant speed while driving the BLDCM at a very low speed, thereby allowing the pumping system to operate over a wide speed range while minimizing vibration and substantially increasing dispensing performance and work capacity.

Description

SYSTEM AND METHOD FOR POSITIONING CONTROL OF MECHANICAL PISTON IN PUMPS {{SYSTEM AND METHOD FOR POSITION CONTROL OF A MECHANICAL PISTON IN A PUMP}

Cross-reference to related application

This application is filed on December 2, 2005, entitled "SYSTEM AND METHOD FOR POSITION CONTROL OF A MECHANICAL PISTON IN A PUMP." / 741,660, filed on September 1, 2006, entitled "SYSTEM AND METHOD FOR POSITION CONTROL OF A MECHANICAL PISTON IN A PUMP." Application No. 60 / 841,725 is claimed as priority, in fact both patent applications are incorporated herein by reference.

The present invention relates to a fluid pump. In particular, embodiments of the present invention relate to systems and methods for controlling the position of a mechanical piston in a motor driven single or multistage pump useful in semiconductor manufacturing.

There are many applications that require precise control over the amount and / or speed at which fluid is discharged by the pumping device. In semiconductor processing, it is important to control the amount and speed at which photochemicals, such as photoresist chemicals, are applied to the semiconductor wafer. Coatings applied to semiconductor wafers during processing usually require a certain flatness and / or uniform thickness over the wafer surface, the flatness and / or thickness being measured in angstroms. The rate at which the processing chemicals are applied (ie, ejected) to the wafer must be carefully controlled to ensure that the processing liquid is applied uniformly.

Photochemicals used in the semiconductor industry today are usually very expensive, reaching $ 1000 per liter. Therefore, it is highly desirable to use the lowest but sufficient amount of chemicals and to ensure that the pumping device does not damage the chemicals.

Unfortunately, this desirable feature can be very difficult to achieve with current pumping systems because there are a number of obstacles associated with each other. For example, due to input power issues, the pressure may vary from system to system. Due to the dynamic nature and properties of the fluid, the pressure needs to vary from fluid to fluid (eg, the greater the viscosity of the fluid, the greater the pressure required). In operation, vibrations that occur in various parts of the pumping system (eg step motors) can negatively affect the performance of the pumping system, in particular in the discharge stage. In pumping systems using pneumatic pumps, large pressure spikes can be caused when the solenoid is turned on. In addition, in the case of a pumping system using a multistage pump, a small breakdown in operation may cause intense pressure spikes in the liquid. This pressure spike and subsequent pressure drop can damage the fluid (ie, change the physical properties of the fluid undesirably). In addition, the pressure spike can lead to an increase in the fluid pressure, which causes the discharge pump to discharge more fluid than intended or to discharge the fluid in a manner with undesirable dynamic properties. In addition, because the aforementioned obstacles are related to each other, sometimes the solution may cause more problems and / or worsen the problems.

In general, the pumping system cannot satisfactorily control the pressure fluctuations during the cycle. There is a need for a new pumping system that can provide real-time control of fluid movement and discharge rate, smooth motion control, and highly accurate and repeatable position control. In particular, there is a demand for accurate and repeatable positional control of mechanical pistons in pumps. Embodiments of the present invention can address these needs and more.

Embodiments of the present invention provide a system and method for accurate and repeatable position control of a mechanical piston in a pump, which substantially eliminates the disadvantages of previously developed pumping systems and methods used in semiconductor manufacturing. Or reduce it. Specifically, embodiments of the present invention provide a pumping system having a motor driven pump.

In one embodiment of the invention, the motor driven pump is a discharge pump.

In various embodiments of the present invention, the discharge pump may be a multistage pump or part of a single stage pump.

In one embodiment of the invention, the two stage discharge pump is driven by a permanent magnet synchronous motor (PMSM) and a digital signal processor (DSP) using field directed control (FOC).

In one embodiment of the invention, the discharge pump is driven by a brushless DC motor (BLDCM) having a position sensor for real time position feedback.

An advantage of the various embodiments of the present invention disclosed herein is that it can provide real time control over fluid movement and discharge amount, smooth motion control, and very accurate and repeatable position control.

It is an object of the present invention to reduce heat generation without undesirably yielding accurate position control of the discharge pump. This object is achieved by various embodiments of the present invention having a custom control scheme configured to increase the operating frequency of the position control algorithm of the motor for important functions, such as ejection, and to reduce the operating frequency to an optimal range for non-critical functions. Achievable at

Another advantage provided by embodiments of the present invention is improved speed control. The custom control scheme disclosed herein can operate the motor at a very low speed and also maintain a constant speed, thereby allowing the new pumping system disclosed herein to achieve a wide speed while minimizing vibration and substantially increasing the discharge performance and working capacity. It will work as a range.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention and its advantages will be more fully understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which like elements are denoted by like reference numerals.

1 is a schematic diagram of a motor assembly with a brushless DC motor, in accordance with an embodiment of the present invention.
Figure 2 is a schematic diagram of a multi-stage pump ("multi-stage pump) implemented with a brushless DC motor, according to one embodiment of the invention.
Figure 3 is a schematic diagram of a pumping system implemented with a multi-stage pump, according to an embodiment of the present invention.
4 is a schematic diagram showing timing of a valve and a motor in accordance with an embodiment of the present invention.
5 is a diagram showing a comparison of the range of average torque output and speed between a brushless DC motor and a step motor, according to an embodiment of the invention.
Figure 6 is a diagram showing a comparison of the average motor current and load between a brushless DC motor and a step motor, according to an embodiment of the present invention.
7 is a diagram showing the difference between motor operation at 30 kHz and motor operation at 10 kHz.
8 is a chart illustrating pressure control timing at various stages of a brushless DC motor and step motor, in accordance with an embodiment of the present invention.
9 is a chart illustrating the pressure control timing at the beginning of the filtration process of a brushless DC motor and a step motor, according to an embodiment of the invention.
10 is a schematic diagram of a single-stage pump implemented with a brushless DC motor according to an embodiment of the present invention.

In the drawings, like reference numerals are used to designate like and corresponding parts and will not be drawn to scale, with reference to the drawings.

Embodiments of the present invention relate to a pumping system having a multistage ("multistage") pump for supplying and discharging fluid onto a wafer during semiconductor fabrication. Specifically, embodiments of the present invention provide a discharge stage driven by a feed stage pump driven by a stepper motor and a brushless DC motor, in order to control the movement of the fluid and the discharge volume onto the wafer very accurately and repeatedly. Provided is a pumping system in which a multistage pump including a stage pump is implemented. Note that the multistage pumps described herein and the pumping system in which such pumps are implemented are provided by way of example and not by way of limitation, and embodiments of the invention may be practiced with other multistage pump forms. The following describes in detail an embodiment of a motor driven pumping system in which position control is very accurately and repeatedly.

1 is a schematic diagram of a motor assembly 3000 according to one embodiment of the present invention having a motor 3030 and a position sensor 3040 coupled to the motor. In the example shown in FIG. 1, the diaphragm assembly 3010 is connected to the motor 3030 through lead screws 3020. In one embodiment, the motor 3030 is a permanent magnet synchronous motor ("PMSM"). In the case of a brush DC motor, the polarity of the current is changed by the commutator and the brush. However, in the case of PMSM, reversal of polarity is performed through synchronous switching of the power transistor with the position of the rotor. Thus, a PMSM can be characterized as "brushless" and is considered more reliable than a brush DC motor. In addition, the PMSM can improve efficiency by generating rotor magnetic flux using a magnet of the rotor. Other advantages of PMSM include vibration reduction, noise reduction (by removing the brush), efficient heat dissipation, small footprint and small rotor inertia. The reverse magnetic forces induced in the stator by the movement of the rotor may have different profiles depending on how the stator is wound. One profile may have a trapezoidal shape, and the other profile may have a sinusoidal shape. The term "PMSM" is used herein to represent all types of brushless permanent magnet motors and may be used interchangeably with the term "brushless DC motor (BLDCM)".

In an embodiment of the present invention, the BLDCM 3030 may be used as a supply motor and / or a discharge motor in a pump such as the multistage pump 100 shown in FIG. In this example, the multistage pump 100 includes a feed end portion 105 and a separate discharge end portion 110. Supply stage 105 and discharge stage 110 may include a rolling diaphragm pump for pumping fluid in multistage pump 100. For example, feed stage pump 150 (“feed pump 150”) is a feed chamber 155 for collecting fluid, a feed stage diaphragm 160 that moves within the feed chamber 155 to displace the fluid, a feed stage A piston 165, lead screw 170, and feed motor 175 for moving the diaphragm 160 are included. Lead screw 170 is coupled to feed motor 175 via a nut, gear, or other mechanism for imparting energy from the motor to lead screw 170. The supply motor 175 rotates the nut, which in turn rotates the lead screw 170, which causes the piston 165 to move. Supply motor 175 may be any suitable motor (eg, step motor, BLDCM, etc.). In one embodiment of the invention, the supply motor 175 is implemented as a step motor.

The discharge stage pump 180 (“discharge pump 180”) may include a discharge chamber 185, a discharge stage diaphragm 190, a piston 192, a lead screw 195, and a discharge motor 200. . Discharge motor 200 may be any suitable motor, including BLDCM. In one embodiment of the invention, the discharge motor 200 is implemented with the BLDCM 3030 of FIG. The discharge motor 200 is controlled by a digital signal processor ("DSP") using field-oriented control ("FOC") in the discharge motor 200, by a controller mounted on the multistage pump 100, or by a separate [ Can be controlled by a pump controller that is external to the pump 100. The discharge motor 200 may further include an encoder (eg, a fine line rotational position encoder or a position sensor 3040) for feeding back the position of the discharge motor 200 in real time. Using a position sensor, the position of the piston 192 is precisely and repeatedly controlled, whereby accurate and repeatable control of the movement of the fluid in the discharge chamber 185 is made. For example, using a 2000 line encoder that provides 8000 pulses to the DSP according to one embodiment, the angle of rotation can be accurately measured and controlled in 0.045 ° increments. In addition, the BLDCM can be driven with little or no vibration at low speeds. In addition, the discharge end portion 110 may further include a pressure sensor 112 for measuring the pressure of the fluid in the discharge end (100). The pressure measured by the pressure sensor 112 can be used to control the speed of several pumps. Suitable pressure sensors include ceramic and polymer based, piezoresistive and capacitive pressure sensors, such as those manufactured by Metallux AG of Corv.

A filter 120 for filtering impurities from the process fluid is located between the feed end portion 105 and the discharge end portion 110 in terms of the flow of the fluid. A number of valves (eg, inlet valve 125, isolation valve 130, shutoff valve 135, purge valve 140, outlet valve 145, outlet valve 147, etc.) are suitably disposed to provide fluid The manner of passing through the multi-stage pump 100 can be controlled. The valve of the multistage pump 100 is opened and closed to allow or restrict fluid flow to various portions of the multistage pump 100. The valve of the multistage pump may be a diaphragm valve (ie gas driven) operated by pneumatic pressure which opens or closes depending on whether positive pressure or negative pressure (vacuum) is applied. Other suitable valves are also possible.

In operation, the multistage pump 100 may include a preparation section, a discharge section, a filling section, a preliminary filtration section, a filtration section, a discharge section, a purge section, and a static purge section (see FIG. 4). During the feed section, the inlet valve 125 is opened and the feed stage pump 150 moves (eg, pulls) the feed stage diaphragm 160 to draw fluid into the supply chamber 155. When a sufficient amount of fluid is filled in the supply chamber 155, the inlet valve 125 is closed. During the filtration section, the feed stage pump 150 moves the feed stage diaphragm 160 to displace the fluid from the feed chamber 155. Isolation valve 130 and shutoff valve 135 are opened to allow fluid to flow past filter 120 into discharge chamber 185. According to one embodiment, fluid flows into the discharge chamber 185 after the isolation valve 130 is first opened (eg, in the "preliminary filtration zone") to allow the pressure in the filter 120 to rise. The shutoff valve 135 can be opened to allow for the use. According to another embodiment, both the isolation valve 130 and the shutoff valve 135 may be open and the feed pump may move to increase the pressure on the discharge side of the filter. During the filtration section, the discharge pump 180 can be brought to the home position. US Provisional Patent Application No. 60 / 630,384 entitled "SYSTEM AND METHOD FOR A VARIABLE HOME POSITION DISPENSE SYSTEM" filed November 23, 2004 by Laverdiere et al., Laverdiere International Patent Application No. PCT / US2005 / 042127, entitled "SYSTEM AND METHOD FOR A VARIABLE HOME POSITION DISPENSE SYSTEM", filed November 21, 2005, and 2008 As described in the corresponding US National Stage Patent Application No. 11 / 666,124, filed September 30, the home position of the discharge pump may be the position that provides the largest available volume to the discharge pump during the discharge cycle. This available volume is smaller than the maximum available volume that the discharge pump can provide, the contents of which are incorporated herein by reference. In order to reduce the unused retention volume among the multistage pumps 100, the home position is selected based on several parameters related to the discharge cycle. Likewise, feed pump 150 may be brought to a home position providing a volume less than its maximum available volume.

When the fluid enters the discharge chamber 185, the pressure of the fluid increases. In US Patent Application No. 11 / 292,559 (currently patented) entitled "SYSTEM AND METHOD FOR CONTROL OF FLUID PRESSURE" filed December 2, 2005 by Gonnella et al. As described, the pressure in the discharge chamber 185 can be controlled through adjusting the speed of the feed pump 150, the contents of which are incorporated herein by reference. According to one embodiment of the invention, when the fluid pressure in the discharge chamber 185 reaches a predetermined pressure set point (e.g., determined by the pressure sensor 112), the discharge stage pump 180 is discharge stage diaphragm ( 190) start pulling back. In other words, the discharge stage pump 180 increases the available volume of the discharge chamber 185 to allow the inflow of fluid into the discharge chamber 185. This can be done, for example, by reducing the pressure in the discharge chamber 185 by rotating the discharge motor 200 at a predetermined speed. When the pressure in the discharge chamber 185 falls below the set point (within the tolerance range of the system), the speed of the supply motor 175 is increased to bring the pressure in the discharge chamber 185 to reach the set point. When the pressure exceeds the set point (within the tolerance range of the system), the speed of the feed motor 175 is reduced and the pressure in the downstream discharge chamber 185 is reduced. The process of increasing and decreasing the speed of the supply motor 175 can be repeated until the discharge stage pump reaches the home position, at which point both the supply motor and the discharge motor can be stopped.

According to another embodiment, the speed of the first stage motor during the filtration section can be controlled using a "no-response zone" control scheme. When the pressure in the discharge chamber 185 reaches an initial threshold, the discharge stage pump may move the discharge stage diaphragm 190 to allow the inflow of fluid into the freer discharge chamber 185, whereby the discharge chamber The pressure in 185 drops. When the pressure falls below the lowest pressure threshold, the speed of the supply motor 175 is increased, resulting in an increase in the pressure in the discharge chamber 185. When the pressure in the discharge chamber 185 exceeds the maximum pressure threshold, the speed of the supply motor 175 is reduced. In addition, the process of increasing and decreasing the speed of the supply motor 175 can be repeated until the discharge stage pump reaches the home position.

When the discharge zone begins, the isolation valve 130 is open, the shutoff valve 135 is closed, and the discharge valve 145 is open. In another embodiment, the shutoff valve 135 remains open during the discharge interval and may be closed at the end of the discharge interval. During this period, if the shutoff valve 135 is open, the pressure is detected by the controller because the pressure in the discharge chamber, which can be measured by the pressure sensor 112, will be affected by the pressure of the filter 120. Can be. Feed stage pump 150 pressurizes the fluid to remove air bubbles from filter 120 via open discharge valve 145. The feed stage pump 150 can be controlled to allow the discharge to occur at a predetermined rate, thereby increasing the discharge time and slowing down the discharge rate, thereby allowing accurate control of the amount of discharge. If the feed pump is a pneumatic style pump, a fluid flow resistor can be installed in the outlet flow path, and the air pressure applied to the feed pump is increased or decreased to maintain the "outlet" set pressure, slightly for a method that is not otherwise controlled. It can provide control of.

When the purge section begins, the isolation valve 130 is closed, the shutoff valve 135 is closed if it was open in the discharge section, the discharge valve 145 is closed, the purge valve 140 is open, and the inlet The valve 125 is opened. The discharge pump 180 applies pressure to the fluid in the discharge chamber 185 to discharge the bubbles through the purge valve 140. During the static purge interval, the discharge pump 180 is stopped, but the purge valve 140 remains open to continue to discharge air. Any excess fluid removed during the purge section or the static purge section may be sent out of the multistage pump 100 (eg, returned or discarded to a fluid source) or recycled to feed stage pump 150. During the preparation period, the inlet valve 125, the isolation valve 130 and the shutoff valve 135 are opened and the purge valve 140 so that the feed stage pump 150 can reach the ambient pressure of the source (eg, the supply vessel). ) May be closed. According to another embodiment, all valves may be closed in the preparation section.

During the discharge interval, the outlet valve 147 opens and the discharge pump 180 applies pressure to the fluid in the discharge chamber 185. Since the outlet valve 147 can respond to control slower than the outlet pump 180, the outlet motor 147 can be started after the outlet valve 147 is first opened and after a predetermined period of time. This prevents the discharge pump 180 to push the fluid through the partially open outlet valve 147. This also prevents the fluid from rising towards the discharge nozzle (which is a mini pump) due to the opening of the outlet valve and subsequently the fluid from moving forward due to the operation of the discharge motor. In another embodiment, the outlet valve 147 can be opened and at the same time discharge can be initiated by the discharge pump 180.

An additional suckback section may be performed to remove excess fluid in the discharge nozzle. During the intake section, the outlet valve 147 can be closed and the excess fluid can be sucked out of the discharge nozzle using an auxiliary motor or vacuum. Alternatively, the outlet valve 147 may remain open and may rotate the discharge motor 200 back to draw fluid into the discharge chamber. The suction section contributes to preventing the excess fluid from dripping onto the wafer.

3 is a schematic diagram showing a pumping system 10 in which a multistage pump 100 is implemented. The pumping system 10 may further include a fluid source 15 and a pump controller 20 that operate with the multistage pump 100 to discharge the fluid onto the wafer 25. The operation of the multistage pump 100 may be controlled by the pump controller 20. The pump controller 20 is a computer readable medium 27 (eg, RAM, ROM, flash memory, optical disk, magnetic disk, or containing a set of control instructions 30 for controlling the operation of the multistage pump 100). Other computer readable media). The processor 35 (eg, CPU, ASIC, RISC, DSP or other processor) executes the above instructions. In particular, the pump controller may be embedded in the multistage pump 100 or may be connected to the multistage pump 100 via one or more communication links for conveying control signals, data or other information. For example, the pump controller 20 is shown in FIG. 3 as being communicatively connected to the multistage pump 100 via communication links 40 and 45. The communication links 40 and 45 may be networks (eg, Ethernet, wireless networks, global networks, DeviceNet networks or other networks known or developed in the art), buses (eg SCSI buses), or other communication links. have. The pump controller 20 may be implemented as an embedded PCB substrate or remote controller, or in other suitable manner. An interface (eg, network interface, I / O interface, analog-to-digital converter and other components) suitable for allowing the pump controller 20 to communicate with the multistage pump 100 may be included in the pump controller 20. have. The pump controller 20 may include various computer components known in the art, including processors, memory, interfaces, display devices, peripherals or other computer components, and the like. The pump controller 20 controls the various valves and motors of the multistage pump to enable the multistage pump to accurately discharge fluid, including low viscosity fluids (ie, less than 100 centipoise) or other fluids. United States Provisional Patent Application No. 60 / 741,657, entitled "I / O INTERFACE SYSTEM AND METHOD FOR A PUMP," filed December 2, 2005 by Cedrone et al. (2006 I / O interface connectors, described in US Patent Application No. 11 / 602,449 and International Application No. PCT / US06 / 45127, on November 20, 2011, connect pump controller 20 to various interfaces and manufacturing tools. To provide an I / O adapter that can be used to, the contents of all of the above applications are incorporated herein by reference.

4 schematically shows the timing of the valve and the discharge motor in the various operating sections of the multistage pump 100. While several valves are shown to be closed in unison during the interval change, the closing timing of these valves can be adjusted slightly (eg, 100 milliseconds) to reduce pressure spikes. For example, between the discharge section and the purge section, the isolation valve 130 may be closed just before closing the discharge valve 145. However, note that other valve timings may be used in various embodiments of the present invention. In addition, several sections may be performed together (eg, the fill / discharge step may be performed simultaneously, in which case both the inlet and outlet valves may be opened in the fill / discharge section). Also note that a particular section does not need to be repeated every cycle. For example, the purge interval and the static purge interval are not performed every cycle. Likewise, the discharge section is not performed every cycle. In addition, several ejections may be performed before recharging.

Opening and closing several valves can cause pressure spikes in the fluid. Closing the purge valve 140 at the end of the static purge section may cause the pressure in the discharge chamber 185 to rise, for example. This pressure rise can occur because each valve can displace a small amount of fluid when it is closed. For example, when the purge valve 140 is closed, a small amount of fluid may be displaced toward the discharge chamber 185 by the purge valve. Since the outflow valve 147 closes when a pressure rise occurs due to the closing of the purge valve 140, if the pressure does not decrease, during the subsequent ejection interval, "spitting" of the fluid onto the wafer may occur. Can be. In order to release this pressure during the static purge section or during the further section, the discharge motor 200 is provided by a predetermined distance to compensate for any pressure increase caused by the closing of the shutoff valve 135 and / or the purge valve 140. It may be reversed to retract the piston 192. One embodiment for correcting the pressure rise caused by the closing of a valve (eg, purge valve 140) is described in Gonnella et al., Filed December 2, 2005, entitled "System for Correcting Pressure Fluctuations Using Motors." And US Provisional Patent Application No. 60 / 741,681 entitled "SYSTEM AND METHOD FOR CORRECTING FOR PRESSURE VARIATIONS USING A MOTOR" (US Patent Application No. 11 / 602,472 and International Application No. PCT / on November 20, 2006). Converted to US06 / 45176, the contents of all of which are incorporated herein by reference.

In addition, the pressure spike in the process fluid can be reduced by closing the valve to form confined spaces and avoiding opening the valve between these confined spaces. US Provisional Patent Application No. 60 / 742,168, entitled "SYSTEM AND METHOD FOR VALVE SEQUENCING IN A PUMP," filed December 2, 2005 by Gonnella et al. (Converted to US Patent Application No. 11 / 602,465 and International Application No. PCT / US06 / 44980 on November 20, 2006) describes one embodiment of valve opening and closing timing to reduce pressure spikes in process fluids. The contents of all of the above applications are hereby incorporated by reference.

Also, note that during the preparation period, the pressure in the discharge chamber 185 may change based on the nature, temperature, or other factors of the diaphragm. U.S. Provisional Patent Application No. 60 / 741,682, entitled "SYSTEM AND METHOD FOR PRESSURE COMPENSATION IN A PUMP," filed December 2, 2005 by James Cedrone. Discharge motor 200 can be controlled to compensate for this pressure drift, as described in US Patent Application No. 11 / 602,508 and International Application No. PCT / US06 / 45175 on November 20, All of these applications are incorporated herein by reference. Accordingly, embodiments of the present invention provide a multistage pump having smooth fluid handling characteristics that can avoid or mitigate potentially harmful pressure fluctuations. Embodiments of the present invention may also employ other pump control mechanisms and valve linings to help reduce the deleterious effects of pressure on process fluids. A further example of a pump assembly for a multistage pump 100 is described in US Patent Application No. 11/11 entitled "PUMP CONTROLLER FOR PRECISION PUMPING APPARATUS," filed February 4, 2005 by Zagars et al. 051,576 (currently US Pat. No. 7,476,087), the contents of which are incorporated herein by reference.

In one embodiment, the multistage pump 100 includes a step motor as a supply motor 175 and a BLDCM 3030 as a discharge motor 200. Suitable motors and related components are available from such sources as EAD Motors, Dover, New Hampshire. In operation, the stator of the BLDCM 3030 generates stator flux and the rotor produces rotor flux. The interaction between the stator flux and the rotor flux forms the torque and, moreover, the speed of the BLDCM 3030. In one embodiment, a digital signal processor (DSP) is used to perform all field-oriented control (FOC). The FOC algorithm is implemented as computer executable software instructions contained on a computer readable medium. Digital signal processors with computational power, speed, and programmability to control the BLDCM 3030 and fully execute the FOC algorithm in a few microseconds can now be used with on-chip hardware peripherals at relatively insignificant additional costs. One example of a DSP that may be used to implement embodiments of the invention disclosed herein is a 16-bit DSP (part number TMS320F2812PGFA) available from Texas Instruments Inc. of Dallas, Texas.

The BLDCM 3030 may include at least one position sensor that detects the actual rotor position. In one embodiment, the position sensor may be located outside of the BLDCM 3030. In one embodiment, the position sensor may be located inside the BLDCM 3030. In one embodiment, the BLDCM 3030 may not have a sensor. In the example shown in FIG. 1, the position sensor 3040 is coupled to the BLDCM 3030 to feed back the actual rotor position of the BLDCM 3030 in real time, with the DSP being the actual rotor position of the BLDCM 3030. To control the BLDCM 3030. The configuration with the position sensor 3040 is a very accurate and repeatable control of the position of the mechanical piston (eg, the piston 192 of FIG. 2), so that the discharge pump (eg, the discharge pump 180 of FIG. 2) There is an additional advantage that a very accurate and repeatable control of the movement and discharge amount of the fluid is ensured at the time of displacement of the piston. In one embodiment, the position sensor 3040 is a fine line rotational position encoder. In one embodiment, the position sensor 3040 is a 2000 line encoder. According to one embodiment of the present invention, the 2000 line encoder may provide 8000 pulses or counts to the DSP. With the 2000 line encoder, the angle of rotation can be accurately measured and controlled in 0.045 ° increments. Other suitable encoders may also be used. For example, the position sensor 3040 may be a 1000 or 8000 line encoder.

The BLDCM 3030 can be operated at very low speeds while still maintaining constant velocity, which means little or no vibration. In other technologies, such as step motors, vibrations have always been induced in the pump system during low speed operation, which is due to poor equal speed control. This vibration will worsen the discharge performance and as a result the window area of operation becomes very narrow. In addition, vibrations can have deleterious effects on process fluids. Tables 1 and 5-9 compare the step motor with the BLDCM and demonstrate many of the advantages of using the BLDCM 3030 as the discharge motor 200 of the multistage pump 100.

Item Step motor BLDCM Volume resolution (μl / step) One 0.1 (10x improvement) Default behavior Work, stop, stand by, work, stand by;
The vibration of the motor at low speed
Causes "flickering of discharge" Continuous motion,
Do not stop Motor current, power Set the current for the maximum condition,
Power consumption regardless of what is required Adaptable to the load Torque transmission lowness height Speed performance 10-30x 30,000x

As can be seen in Table 1, compared to step motors, BLDCMs can offer continuous rotational operation, low power consumption, high torque transfer rates and a wide range of speeds, with significantly increased resolution. Note that the resolution of the BLDCM can be approximately 10 times more than the resolution provided by the step motor. For this reason, the smallest unit of increment that can be provided by the BLDCM is referred to as "motor increment", distinct from the term "step" which is generally used in connection with a step motor. This motor increment is the smallest measurable unit of motion in the BLDCM according to one embodiment that can provide continuous operation, while the step motor operates in discrete steps.

FIG. 5 is a diagram illustrating an average torque output and a speed range of a BLDCM and a stepper motor according to an exemplary embodiment of the present invention. As illustrated in FIG. 5, the BLDCM can maintain a torque output that is substantially constant above the torque output of the stepper motor at high speed. In addition, the speed range of the BLDCM is wider (eg 1000 times or more) than the step motor. In contrast, step motors tend to have low torque outputs and these torque outputs also tend to drop undesirably upon increasing speed (ie, torque output decreases at high speeds).

6 is a diagram showing a comparison of the average motor current and load of the BLDCM and step motor according to an embodiment of the present invention. As illustrated in FIG. 6, the BLDCM can adapt and adapt to the load on the system and uses only the power necessary to bear the load. In contrast, the stepper motor uses a current set for maximum conditions, regardless of what is required. For example, the peak current of the stepper motor is 150 milliamps. Although a 1 lb load does not require as much current as a 10 lb load, 150 mA of current is equally used to move a 10 lb load as well as a 1 lb load. As a result, the stepper motor consumes power in terms of maximum conditions at run time, regardless of the load, which results in inefficient and inefficient use of energy.

In the case of BLDCM, the current is regulated as the load increases or decreases. At any particular point in time, the BLDCM will self-compensate, supply the BLDCM itself with the amount of current needed to rotate the BLDCM itself at the required speed, and generate only the force needed to move the load. If the motor is not moving, the current can be very low (<10 mA). The control of the BLDCM is self-compensating (ie, the current can be adjusted according to the load on the system), so it is always on even if the motor is not moving. In contrast, depending on the application, the stepper motor can be turned off when not moving.

In order to maintain position control, it is necessary to operate the control scheme regarding BLDCM very frequently. In one embodiment, the control loop operates at 30 kHz, i.e. at about 33 Hz per cycle. Therefore, every 33 ms the control loop checks if the BLDCM is in place. If in position, no action is attempted. If it is not in place, it attempts to regulate the current and force the BLDCM into position. This fast self-compensation operation allows very accurate position control, which is highly desirable in some applications. Operating the control loop at high speed (eg 30 kHz) compared to the conventional case (eg 10 kHz) means that the system is overheating. This is because the more often the BLDCM switches current, the greater the chance of heat generation.

According to one aspect of the invention, in some embodiments the BLDCM is configured in view of heat generation. Specifically, the control loop is configured to operate at two different speeds during a single cycle. During the discharge period of the cycle, the control loop operates at high speed (eg 30 kHz). During periods other than discharge during the cycle, the control loop operates at a low speed (eg 10 kHz). This configuration can be particularly useful in applications where very accurate position control during the ejection interval is important. For example, during the discharge period the control loop operates at 30 kHz, which provides excellent position control. In the remaining period, the speed returns to 10 kHz. By doing in this way, temperature can be reduced significantly.

The discharge section of the cycle can be tailored depending on the application. For example, the discharge system may perform a 20 second cycle. In one 20 second cycle, 5 seconds may be for discharging, the remaining 15 seconds may be for logging, recharging, or the like. Between cycles, there may be a preparation period of 15 to 20 seconds. Thus, the control loop of the BLDCM can operate at a high rate (e.g., 30 kHz) at a small rate (e.g., 30 seconds) during a cycle, and at a low frequency (e.g., 10 kHz) at a high rate (e.g., 15 seconds) during a cycle. will be.

Those skilled in the art will appreciate that the aforementioned parameters (eg, 5 seconds, 15 seconds, 30 kHz, 10 kHz, etc.) are exemplary and are not intended to be limiting. The speed and time of operation may be suitably adjusted or otherwise adjusted within the scope and spirit of the invention disclosed herein. Empirical methods can be used to determine these programmable parameters. For example, 10 kHz is a very common BLDCM operating frequency. Other speeds may be used, but running the control loop of the BLDCM slower than 10 kHz may risk losing position control. It is generally desirable to maintain the position of the BLDCM, since it is difficult to regain position control.

One aim of this aspect of the invention is to lower the speed as much as possible during sections other than discharge during the cycle without undesirably lowering the level of position control. In the embodiments disclosed herein, the above goal may be performed through a custom control scheme for BLDCM. The custom control scheme is intended to increase the frequency (e.g., to 30 kHz) in order to ensure slightly excess / enhanced position control for important functions such as discharge. In addition, the custom control scheme is intended to reduce heat generation by allowing non-critical functions to be operated at lower frequencies (eg 10 kHz). In addition, the custom control scheme is intended to minimize any loss of position control caused by operating at low frequencies during periods other than discharge during the cycle.

The custom control scheme is adapted to provide a desirable discharge profile that can be characterized by pressure. This characterization can be based on the deviation of the pressure signal. For example, a flat pressure profile will suggest smooth operation, small vibrations, and even better position control. In contrast, pressure signals outside the reference will suggest poor position control. 7 is a diagram illustrating the difference between motor operation at 30 kHz and motor operation at 10 kHz (10 mL at 0.5 mL / s). The first 20 seconds is the discharge phase. As can be seen in FIG. 7, during the ejection step, a 30 kHz ejection has a smoother and less noise pressure profile than a 10 kHz ejection.

As far as position control is concerned, the difference between running BLDCM at 10 kHz and running at 15 kHz can be marginal. However, if the speed drops below 10 kHz (eg, to 5 kHz), this speed may not be fast enough to maintain good position control. For example, one embodiment of the BLDCM is adapted to discharge the fluid. If the position control loop is operated below 1 kHz (ie above about 10 kHz), there is no visible effect. However, when the operating time of the position control loop rises to the 1, 2, or 3 ms range, the effect on the fluid is visible. In another example, when the timing of the valve changes to less than 1 Hz, no change in fluid can be visually confirmed. However, if the timing of the valve changes in the 1, 2, or 3 ms range, the change in fluid can be visually observed. Accordingly, the custom control scheme preferably operates time-constrained functions (eg, timing of motors, valves, etc.) at about 10 kHz or more.

Another consideration is the internal circulation of the discharge system. If the discharging system is set to run as slowly as about 1 kHz, no better resolution is achieved than in the case of 1 Hz, and calculations that need to be better than in the case of 1 Hz cannot be performed. In this case, 10 kHz is a practical frequency for the discharge system. As mentioned above, the above numerical values are exemplary. It is also possible to set rates below 10 kHz (eg 5 kHz or even 2 kHz).

Similarly, speeds in excess of 30 kHz can be set if the performance requirements are met. The example ejection system disclosed herein uses an encoder with multiple lines (eg, 8000 lines). The time taken between lines is speed. Although the BLDCM operates very slowly, the spacing between the lines is very fine, so that the next line can be reached very quickly, thereby providing a pulse to the encoder. Driving the BLDCM at 1 rps means passing 8000 lines in one second and further generating 8000 pulses. If the width of the pulse does not change (ie, the width of the pulse does not deviate from the target width and remains the same again), this suggests that the speed control is very good. If fluctuations appear in the width of the pulse, this implies poor speed control, although not necessarily bad, depending on system design (eg, tolerance) and application.

Another consideration concerns the practical limitation of the processing power of a digital signal processor (DSP). For example, for discharge in one cycle, it may take almost 20 ms to perform all necessary calculations for the position controller, current controller, and the like. The 30 kHz operation takes about 30 ms, which is enough time to run all the rest of the controller with the time left to perform the above calculations. It is also possible to use more powerful processors that can operate at speeds higher than 30 kHz. However, operation at speeds higher than 30 Hz results in a decrease in marginal utility. For example, a 50 kHz operation only takes about 20 Hz (1/50000 Hz = 0.00002 s = 20 Hz). In this case, better speed performance can be ensured at 50 kHz, but the time the system has is insufficient to perform all the processing necessary to drive the controller, thus causing processing problems. Moreover, operating at 50 kHz will make the switching of current much more frequent, which causes the above-mentioned heat generation problem.

In short, one solution to reducing heat dissipation is to configure the BLDCM to operate at high frequencies (e.g., 30 kHz) during discharging operations and to fall back or fall back to low frequencies (e.g., 10 kHz) during operations other than discharging (e.g. recharging). It is. Factors to consider in configuring a custom control scheme and associated parameters include position control performance, computational speed related to the processor's processing power, and heat generation related to the number of times the current is switched after computation. In the above example, the loss of position control performance is minimal in the 10 kHz operation performed during the operation other than the discharge, the position control is excellent in the 30 kHz operation performed during the discharge operation, and the heat generation is considerably reduced. Through reducing heat generation, embodiments of the present invention can provide technical advantages that change in temperature does not affect the fluid being discharged. This may be particularly useful in applications involving the ejection of sensitive and / or expensive fluids, in which case it would be highly desirable to rule out any possibility that heat or temperature changes may affect the fluid. In addition, heating the fluid may also affect the discharging operation. One such effect is called the natural suck back effect. The liquid cutting effect explains that when heat is generated in the discharging operation, this heat expands the fluid. When the fluid begins to cool outside of the pump, the fluid contracts and withdraws at the end of the nozzle. Thus, due to the natural liquid cutting effect, the volume may not be accurate and may be inconsistent.

8 is a chart illustrating the cycle timing of a step motor and a BLDCM at various stages in accordance with one embodiment of the present invention. According to the above-described example, the supply motor 175 is implemented as a step motor, and the discharge motor 200 is implemented as a BLDCM. The shaded areas in FIG. 8 indicate that the motor is in operation. According to one embodiment of the invention, the step motor and the BLDCM can be configured in a manner that facilitates pressure control during the filtration cycle. An example of the pressure control timing of the stepper motor and BLDCM is given in FIG. 9, where the shaded area indicates that the motor is in operation.

8 and 9 illustrate exemplary configurations of the supply motor 175 and the discharge motor 200. More specifically, once the set point of the pressure signal is reached, the BLDCM (ie, the discharge motor 200) may begin to rotate back at the programmed filtration rate. In the meantime, the speed of the step motor (i.e., the supply motor 175) is changed to maintain the set point of the pressure signal. This configuration offers several advantages. For example, no pressure spikes will occur in the fluid, the pressure acting on the fluid will be constant, no adjustments to viscosity fluctuations will be needed, no differences between systems, and no vacuum will appear on the fluid.

Although a multistage pump has been described, embodiments of the present invention may also be employed in single stage pumps. 10 is a schematic diagram of the pump assembly for the pump 4000. The pump 4000 may be similar to one stage, ie, the discharge stage, of the multistage pump 100 described above, and may include a single chamber and a rolling diaphragm driven by an embodiment of the BLDCM as described herein, The control scheme for position control is also the same as or similar to the multistage pump described above. The pump 4000 may include a discharge block 4005 that forms several flow paths through the pump 4000 and at least partially forms a chamber of the pump. The discharge block 4005 may be an integral block made of PTFE, modified PTFE, or other material. Since these materials do not react or exhibit only minimal reaction with a large number of process fluids, the use of these materials allows the flow path and pump chamber to be processed directly into the discharge block 4005 with minimal additional hardware. Thus, the discharge block 4005 reduces the need for piping by providing an integrated fluid manifold.

The discharge block 4005 includes a plurality of external inlets and outlets, such as an inlet 4010 for receiving fluid, a purge / discharge outlet 4015 for purging / draining the fluid, and a discharge outlet for discharging fluid during the discharge section ( 4020), and the like. In the example of FIG. 10, since the pump has only one chamber, the discharge block 4005 includes an external purge outlet 4015. United States Provisional Patent Application No. 60 / 741,667, entitled "O-RING-LESS LOW PROFILE FITTING AND ASSEMBLY THEREOF," filed December 2, 2005 by Iraj Gashgaee. US Patent Application No. 11 / 602,513 and International Application No. PCT / US06 / 44981, issued on November 20, 2006, provide an O- line that can be used to connect the outer inlet and outlet of the discharge block 4005 to the fluid line. An embodiment of a ringless connector is described and the entire contents of all of the above patent applications are incorporated herein by reference.

Discharge block 4005 is a fluid inlet valve (eg, at least partially formed by valve plate 4030) from the inlet to the inlet valve to the pump chamber, from the pump chamber to the purge / discharge valve, and from the pump chamber. To exit 4020. The pump cover 4225 can protect the pump motor from damage, while the piston housing 4027 can provide protection for the piston and can be formed of polyethylene or other polymer. Valve plate 4030 provides a valve housing for a valve system (eg, inlet valve and purge / discharge valve) that can be configured to direct the flow of fluid to various parts of pump 4000. The valve plate 4030 and the corresponding valve may be formed similarly to the manner described above with respect to the valve plate 230. Each of the inlet valve and the purge / discharge valve is at least partially integrated into the valve plate 4030 and is a diaphragm valve that opens or closes depending on whether a positive or negative pressure is applied to the diaphragm. Alternatively, some valves may be external to the discharge block 4005 or disposed on additional valve plates. In the example shown in FIG. 10, diaphragms of various valves are formed between the valve plate 4030 and the discharge block 4005 via a PTFE sheet. The valve plate 4030 includes a valve control inlet (not shown) for each valve for applying positive pressure or negative pressure to the corresponding diaphragm.

Like the multistage pump 100, the pump 4000 may include some features to prevent fluid droplets from entering the area of the pump 4000 that houses the electronic device. “Spinning features” may include protruding lips, bevels, seals between components, offsets of metal / polymer interfaces, and other features described above to isolate electronic devices from droplets. The electronics and manifold can be configured similarly to the manner described above to reduce the effect of heat on the fluid in the pump chamber.

Accordingly, embodiments of the systems and methods disclosed herein are useful in pumping systems useful in semiconductor manufacturing for real time control of fluid movement and discharge amount, smooth motion control, and highly accurate and repeatable position control. BLDCM can be used to drive single or multiple stage pumps. The BLDCM can employ a position sensor that feeds back the position in real time to a processor running a custom FOC scheme. The same or similar FOC scheme can be applied to the single stage pump and the multiple stage pump.

Although the invention has been described in detail herein with reference to exemplary embodiments, it is to be understood that such description is given by way of example only and is not to be construed as limiting. Accordingly, many changes in details of the embodiments according to the invention described above and further embodiments of the invention will be apparent to those skilled in the art with reference to the specification, and of course, can be practiced by those skilled in the art. All such changes and additional embodiments are considered to be within the scope of the claimed invention. Accordingly, the scope of the invention should be determined by the following claims and legal equivalents.

Claims (20)

As a pumping system,
Pump;
A brushless DC motor for driving a discharge pump in the pump;
A computer readable medium containing software instructions for controlling the pump; And
A processor in communication communication with the computer readable medium and the pump
Wherein the discharge pump includes an inlet and an outlet, and the software command controls the brushless DC motor to control the brushless DC motor in accordance with a control scheme for operation of the discharge pump that directs fluid from the inlet to the outlet. Can be executed by
Wherein the control scheme is adapted to drive the brushless DC motor at at least two controller frequencies during a single cycle. The pumping system of claim 1, wherein the at least two controller frequencies comprise a first frequency for the discharge portion of the single cycle. The pumping system of claim 2, wherein the first frequency is 30 kHz. The pumping system of claim 1, wherein the control scheme is adapted to minimize heat generation by the brushless DC motor during operation of the discharge pump. The method of claim 1, wherein the at least two controller frequencies comprise a first frequency and a second frequency, and wherein the control scheme drives the brushless DC motor to a first frequency during a discharging operation and the non-discharge during operations other than discharging. Pumping system adapted to drive a brush DC motor at a second frequency. The pumping system of claim 5 wherein the second frequency is lower than the first frequency. The pumping system of claim 6 wherein the first frequency is 30 kHz and the second frequency is 10 kHz. A pump comprising a discharge pump, wherein the discharge pump,
Entrance;
exit;
Discharge chamber;
piston;
A discharge end diaphragm disposed between the discharge chamber and the piston;
Brushless DC motor; And
Lead screw connecting the piston to the brushless DC motor
A piston displacement pump comprising: a brushless DC motor embodied on a computer readable medium and executable by a processor to perform a control scheme for operation of the discharge pump for guiding fluid from the inlet to the outlet. Controlled by software commands,
The processor is communicatively coupled to the computer readable medium and the pump,
Wherein the control scheme is adapted to drive the brushless DC motor at at least two controller frequencies during a single cycle. The pump of claim 8, wherein the at least two controller frequencies comprise a first frequency for the discharge portion of the single cycle. 10. The pump of claim 9, wherein the first frequency is 30 kHz. 9. The pump of claim 8, wherein the control scheme is adapted to minimize heat generation by the brushless DC motor during operation of the discharge pump. 9. The apparatus of claim 8, wherein the at least two controller frequencies comprise a first frequency and a second frequency, the control scheme driving the brushless DC motor at a first frequency during a discharging operation and the non-discharging during operations other than discharging. A pump configured to drive the brush DC motor at a second frequency. 13. The pump of claim 12, wherein the second frequency is lower than the first frequency. The pump of claim 13, wherein the first frequency is 30 kHz and the second frequency is 10 kHz. Connecting the brushless DC motor to the mechanical piston of the pump having an inlet and an outlet; And
And controlling the brushless DC motor to drive at a first frequency during a discharging operation and to drive the brushless DC motor at a second frequency during operations other than discharging the pump. The method of claim 15, wherein the second frequency is lower than the first frequency. 16. The method of claim 15, further comprising providing real time position feedback of the mechanical piston to a processor in communication with the pump. 16. The method of claim 15, further comprising driving the brushless DC motor at the first and second frequencies during a single cycle. 16. The method of claim 15, wherein the controlling step further comprises raising the operating frequency of the brushless DC motor to 30 kHz during the discharge portion of the cycle. 16. The method of claim 15, wherein said controlling step further comprises lowering the operating frequency of said brushless DC motor to 10 kHz during portions other than discharge during a cycle.

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