Pumps – Expansible chamber type – Mechanically actuated distributor
Reexamination Certificate
1999-07-24
2001-11-27
Walberg, Teresa (Department: 3742)
Pumps
Expansible chamber type
Mechanically actuated distributor
Reexamination Certificate
active
06322337
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to dispensing liquids in precise volumes and more particularly to the transfer of liquid from a reservoir to a point of use by a pump having a displacement piston and a rotating piston valve communicating with one of a plurality of liquid ports.
The ability to deliver precise small volume amounts of liquids without introduction of contaminants is quite important in the manufacture of many products, especially in the electronics industry. A semiconductor foundry has several principal areas—metrology, lithography, and track where resist and developer must be rapidly and precisely dispensed. More specifically, photolithography requires precise repeatable delivery of photoresist and developer at different rates such as volumes of 0-10 ml±0.1%, repeatable to within ±0.1 volume % with substantially no contaminants or air bubbles. If these requirements cannot be met consistently, it adversely impacts the yield of the process. See, e.g., Chang & Sze,
ULSI Technology
(1996) hereby incorporated by reference.
The semiconductor industry provides, for example, different pumps such as piston pumps, diaphragm pumps, and peristalic pumps to transfer liquid from a liquid reservoir to a dispense nozzle above a silicon wafer in a spin station. After the liquid is dispensed any residual liquid left in the tip of the nozzle is drawn back slightly so that the resulting meniscus force prevents uncontrolled drips on the wafer and the wafer is rotated at high rpm to spread the liquid uniformly over the wafer.
The liquid dispensing system must also provide a filter to capture contaminants which might be introduced in the liquid dispensed. When the filter is upstream of the pump, it captures the contaminants generated for example at the reservoir and/or the reservoir line leading to the pump but will be ineffective at capturing contaminants generated in the pump which then enter the liquid dispensed on the wafer. When the filter is downstream of the pump, the filter may capture pump generated contaminants but may still release air bubbles and contaminants into the dispensing system during draw back mode when the liquid reverses direction through the filter which tends to dislodge some of the particles caught in the filter.
SUMMARY OF THE INVENTION
The invention provides systems and methods of rapid delivery of liquids in precise volumes and with accuracy. The systems include a pump operating under the positive displacement principle. The pump includes at least one displacement piston, and at least one piston valve with a fluid slot, where the pistons in a cylinder define a pumping chamber. In general the displacement piston travels back and forth in the cylinder, producing suction, and discharging pumping action. The distance traveled by the displacement piston determines the dispensing volume of the pumping chamber and the direction of travel determines the direction of flow through any cylinder port. The piston valve rotates to align the fluid slot with a given cylinder port to communicate with the pumping chamber.
In refill mode, the piston valve rotates until the slot aligns with the intake port of the cylinder so the pumping chamber can communicate with the reservoir. The displacement piston retracts in the cylinder, expanding the pumping chamber, and drawing liquid from the reservoir though the intake port and into the pumping chamber. In dispense mode, the piston valve rotates closing the intake port so that the pumping chamber no longer communicates with the reservoir until the piston valve slot aligns with the discharge port out of the pumping chamber. The displacement piston slides forward, reducing the volume of the pumping chamber, expelling liquid through the discharge port.
In one embodiment, the piston valve includes a plurality of ports, such as an intake port, a discharge port, and a drawback port to permit precise delivery of liquids through a dispense nozzle without introducing contaminants, air bubbles, or liquid dripping. In drawback mode, in this embodiment, after the discharge step, the piston valve rotates closing the discharge port and the piston valve slot aligns with the drawback port, then the displacement piston slides back, expanding the volume of the pumping chamber, drawing liquid back in the dispense nozzle. The embodiment of the system also prevents contaminants and air bubbles from being introduced into the liquid to be dispensed from the nozzle by placing a filter across the discharge line downstream from the pump, and providing a separate drawback line for performing the drawback of the liquid in the dispensing nozzle so that drawback does not occur through the filter. This embodiment has special advantage in the precise control of semiconductor equipment used in dispensing liquid chemicals in ULSI technology.
REFERENCES:
patent: 5044889 (1991-09-01), Pinkerton
patent: 5312233 (1994-05-01), Tanny et al.
patent: 5863187 (1999-01-01), Bensley et al.
patent: 5996620 (1999-12-01), Bensley
Babikian Dikran
Barney John E.
Bensley Douglas S.
Dimaggio Frank
Tanny Mark
@Patent Planet
Ivek Corporation
Moll Robert
Patel Vinod D
Walberg Teresa
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