Double pressure vessel chemical dispenser unit

Details Double pressure vessel chemical dispenser unit Double pressure vessel chemical dispenser unit

1999-09-01

2001-10-09

Dawson, Robert (Department: 1712)

Electrolysis: processes, compositions used therein, and methods

Electrolytic coating

Coating predominantly semiconductor substrate

C204S275100, C204S237000

Reexamination Certificate

active

06299753

ABSTRACT:

BACKGROUND OF THE INVENTION
1. b Field of the Invention
The present invention relates to a fluid delivery system with particular application to an electroplating system.
2. Background of the Related Art
Semiconductor processing systems typically require fluid delivery apparatus to supply chemicals and other fluids to various components of the processing system. For example, electroplating involves the use of an electrolytic solution to plate a conductive surface formed on device features of a substrate. The substrate is positioned in a processing chamber, or cell, to expose a surface of the substrate to the electrolytic solution. The cell typically includes a cell body, an anode and a cathode on which the substrate is mounted. The solution is flowed into the cell and over the exposed surface of the substrate while a power supply biases the surface of the substrate with respect to the anode and solution to attract ions from the electrolytic solution, thereby plating the surface with a metal, such as copper. After flowing past the substrate, the fluid is emptied into a fluid source such as a tank or reservoir and then cycled back to the cell. In order to maintain a uniform chemical composition, the electrolytic solution is continuously circulated between the processing cells and the fluid source which also acts to replenish the chemical components of the electrolytic solution. Thus, a continuous supply of the electrolyte can be flowed past the substrate.
FIG. 1
is a simplified schematic of an electrolyte delivery system
10
. A main tank
12
provides a bulk source of an electrolytic solution. The composition of the solution in the main tank
12
is controlled by a dosing module
14
which supplies the various constituents of the solution in the desired proportions. A supply line
16
couples the main tank
12
to processing cells
18
located downstream wherein substrates (not shown) are disposed during processing. A pump
17
disposed in the supply line
16
causes the solution to flow from the main tank
12
to the cells
18
. The electrolytic solution is flowed through the cells
18
and subsequently expelled from the cells
18
via outlet lines
20
. The outlet lines
20
dispense the electrolyte to an electrolyte return module (ERM)
22
which is fluidly coupled to the main tank
12
by a return line
24
. A pump
26
disposed in the return line
24
pumps the spent electrolyte from the ERM
22
back to the main tank
12
.
One problem with current fluid delivery systems, such as the system
10
shown in
FIG. 1
, is the use of pumps
17
,
26
to circulate the fluid from the main tank
12
to the cells
18
and back to the main tank
12
. Pumps
17
,
26
are typically positive displacement pumps employing the use of diaphragms to provide lift at a suction inlet and pressure at an outlet. Such pumps require periodic maintenance or replacement as components, such as the diaphragm, become worn. Additionally, pump components, such as the diaphragm, are a source of contamination for the electrolyte as the components degrade over time. The resulting contamination can become lodged in device features formed on the substrate during processing and lead to defective devices. While filtration systems may be used to capture and remove larger particles from the electrolytic solution, some particles are too small for state-of-the-art filtration equipment. As the device geometry's continue to shrink the relative size of particles becomes larger.
Another problem with the use of pumps is the detrimental effect on the flow rate of the electrolyte over the surface of the substrate. In order to ensure uniform plating over a substrate surface at a constant rate, the flow rate of electrolytic solution in the cells must be maintained substantially constant during processing. However, the rapid action of pumps creates massive impulses in the system resulting in pulsed flow of the electrolyte in the cell. Thus, the flow pulses caused by the pumping action of the pumps causes the flow rate of solution in the cells to vacillate. Further, the pulsed flow can also force particles through filters disposed in the delivery system, thereby rendering the filters ineffective even for larger particles normally captured by the filters. Thus, the use of pumps in a fluid delivery system can present considerable cost in parts, labor, down-time and defective devices.
Therefore, there is a need for a fluid delivery system which eliminates or minimizes contamination of the fluid as well as flow pulses by use of components such as pumps.
SUMMARY OF THE INVENTION
The present invention generally relates to a fluid delivery system with particular application to an electroplating system.
In one aspect, the invention includes two or more reservoirs fluidly connected to one or more processing cells by a supply line and a return line. The upper fluid levels in the two or more reservoirs are maintained vertically displaced by a height from the processing cells to facilitate gravity-assisted flow of fluid from the processing cells to the reservoirs via the return line. A gas source is coupled to the reservoirs to selectively pressurize the reservoirs and cause fluid flow therefrom to the processing cells through the supply line. Valves disposed in the supply line and return line control the direction and rate of fluid flow and ensure equal flow rates into each cell. In a first position, the valves communicate the first reservoir and processing cell along the supply line and the second reservoir and the processing cell along the return line. In a second position, the valves communicate the first reservoir and processing cell along the return line and the second reservoir and the processing cell along the supply line. The reservoirs are alternately filled and emptied with a fluid circulated between the reservoirs and the processing cells.
In another aspect, a method of circulating a fluid between two or more reservoirs and a processing system is provided, wherein the lowest fluid level in the processing system is maintained at a level higher than the highest fluid level in the two or more reservoirs to provide a positive fluid pressure differential between the processing system and the pair of reservoirs. Pressurizing a first reservoir induces fluid flow from the first reservoir to the processing system. Fluid is flowed from the processing system to a second reservoir by gravity. Upon reaching a low fluid level in the first reservoir and a high fluid level in the second reservoir, the direction of fluid flow is reversed so that fluid is flowed from the second reservoir to the processing system and from the processing system to the first reservoir. Fluid flow from the second reservoir is induced by pressurizing the second reservoir. Fluid flow from the processing system to the first reservoir is provided by gravity. The flow rates to and from the processing system is preferably maintained substantially constant to allow for a uniform flow rate and constant fluid level in the processing system.


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patent: 4326940 (1982-04-01), Eckles et al.
patent: 4789445 (1988-12-01), Goffman et al.
patent: 5092975 (1992-03-01), Yamamura et al.
patent: 5148945 (1992-09-01), Geatz
patent: 5330072 (1994-07-01), Ferri, Jr. et al.
patent: 5447615 (1995-09-01), Ishida
patent: 5516412 (1996-05-01), Andricacos et al.
patent: 5722447 (1998-03-01), Morgan et al.
patent: 5803599 (1998-09-01), Ferri, Jr. et al.
PCT Written Opinion citing additional references for PCT/US 99/28159, dated Dec. 8, 2000.

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