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Precision pump with multiple heads

Precision pump with multiple heads description/claims

The present invention relates generally to apparatus used in metering fluids with high precision, particularly in fields such as semiconductor manufacturing.

Many of the chemicals used in manufacturing integrated circuits, photomasks, and other devices with very small structures are corrosive, toxic and expensive. One example is photoresist, which is used in photolithographic processes. In such applications, both the rate and amount of a chemical in liquid phase—also referred to as process fluid or “chemistry”—that is dispensed onto a substrate must be very accurately controlled to ensure uniform application of the chemical and to avoid waste and unnecessary consumption. Furthermore, purity of the process fluid is often critical. The smallest of foreign particles contaminating a process fluid causes defects in the very small structures formed during such processes. The process fluid must therefore be handled by a dispensing system in a manner that avoids contamination. See, for example, Semiconductor Equipment and Material International, “SEMI E49.2-0298 Guide For High Purity Deionized Water And Chemical Distribution Systems In Semiconductor Manufacturing Equipment” (1998). Improper handling can also result in introduction of gas bubbles and damage the chemistry. For these reasons, specialized systems are required for storing and metering fluids in photolithography and other processes used in fabrication of devices with very small structures.

Chemical distribution systems for these types of applications therefore must employ a mechanism for pumping process fluid in a way that permits finely controlled metering of the fluid and avoids contaminating and reacting with the process fluid. Generally, a pump pressurizes process fluid in a line to a dispense point. The fluid is drawn from a source that stores the fluid, such as a bottle or other bulk container. The dispense point can be a small nozzle or other opening. The line from the pump to a dispense point on a manufacturing line is opened and closed with a valve. The valve can be placed at a dispense point. Opening the valve allows process fluid to flow at the point of dispense. A programmable controller operates the pumps and valves. All surfaces within the pumping mechanism, lines and valves that touch the process fluid must not react with or contaminate the process fluid. The pumps, bulk containers of process fluid, and associated valving are sometimes stored in a cabinet that also houses a controller.

Pumps for these types of systems are typically some form of a positive displacement type of pump, in which the size of a pumping chamber is enlarged to draw fluid into the chamber, and then reduced to push it out. Types of positive displacement pumps that have been used include hydraulically actuated diaphragm pumps, bellows type pumps, piston actuated, rolling diaphragm pumps, and pressurized reservoir type pumping systems. U.S. Pat. No. 4,950,134 is an example of a typical pump. It has an inlet, an outlet, a stepper motor and a fluid displacement diaphragm. When the pump is commanded electrically to dispense, the outlet valve opens and the motor turns to force flow of displacement or actuating fluid into the pumping chamber, resulting in the diaphragm moving to reduce the size of the pumping chamber Movement of the diaphragm forces process fluid out of the pumping chamber and through the outlet valve.

Due to concerns over contamination, current practice in the semiconductor manufacturing industry is to use a pump only for pumping a single type of processing fluid or “chemistry.” In order to change chemistries being pumped, all of the surfaces contacting the processing fluid have to be changed. Depending on the design of the pump, this tends to be cumbersome and expensive, or simply not feasible. It is not uncommon to see processing systems that use up to 50 pumps in today's fabrication facilities.

The invention pertains generally to high precision pumps for use in dispensing process fluids in applications imposing constraints on handling due to corrosiveness of the process fluid, and/or due to sensitivity to contamination (e.g. from other fluids, particulates, etc.), bubbles and/or mechanical stresses. It is particularly useful for pumps in semiconductor processing operations.

In contradistinction to typical deployments of pumps in such applications, particularly those used for high-precision metering, an exemplary pump employing teachings of a preferred embodiment of the invention is capable of pumping more than one type of chemistry or process fluid without requiring cleaning or changing of surfaces contacting the processing fluid. The pump employs multiple pumping heads, each capable of handling a different type of manufacturing fluid. At least two of the pumping heads share a common actuating mechanism. Although a multi-headed pump might be larger when compared to a pump with a single head, utilizing fewer actuating mechanisms than pumping heads saves valuable space in crowded processing facilities, such as those used for fabricating semiconductor components, which use a large number of pumps. Since actuation mechanisms are sometimes the most complex part of a pump, fewer actuating mechanisms in a factory saves money and maintenance time.

Sharing a single actuating mechanism among multiple heads may seem undesirable, particularly for fluid metering applications. Having a shared actuation mechanism typically means that only one pumping head may be actuated at a time. However, in one exemplary embodiment, the multi-headed pump is capable of fast and frequent switching between pump heads. With actuation between pump heads capable of being switched quickly, there is little delay between demand for dispense and dispense in applications having very short dispense cycles due to relatively small amounts of fluid that are being dispensed.

FIG. 1 is a schematic view of a multiple head pump, shown in context of a high precision, high-purity fluid dispensing system.

FIG. 2 is an exploded view of an exemplary, preferred embodiment of a multiple head pump.

FIG. 3 is an exploded view from a different angle of the multiple head pump of FIG. 2.

FIG. 4 is a side view of the pump of FIGS. 2 and 3, assembled.

FIG. 5 is a cross section of the pump of FIG. 4, taken along section line 5-5.

FIG. 6 is a cross-section of the pump of FIG. 4 taken along section line 6-6.

FIG. 7 is an isometric view of the pump of FIG. 4.

FIG. 8 is a front view of the pump of FIG. 4.

• Provisional Patent
• Utility Patent

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