Coating processes – Coating by vapor – gas – or smoke – Metal coating
Reexamination Certificate
2000-02-28
2001-11-20
Pianalto, Bernard (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Metal coating
C118S719000, C118S730000, C427S255500, C427S255700, C427S294000, C427S301000, C427S337000
Reexamination Certificate
active
06319553
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to processing chambers and in particular the present invention relates to a multi-station processing chamber.
BACKGROUND
Multi-station processing chambers are used to process several substrates, such as semiconductor wafers, within the same chamber. By processing several wafers at once, the throughput of the system is increased. An example of a multi-station processing chamber is the batch chemical vapor deposition (“CVD”) chamber, Concept 2 Altus model, manufactured by Novellus Systems, Inc. located in San Jose, Calif.
While the throughput of multi-station processing chambers is typically greater than single wafer processing chambers, the throughput of a multi-station processing chamber is generally limited by the inability to simultaneously perform incompatible processes. For example, in a CVD tungsten chamber, incompatible reactive gases, such as silane (SiH
4
) and tungsten hexafluoride (WF
6
) are used within the same chamber. If these reactive gases are permitted to mix at critical SiH
4
to WF
6
ratios, particles may be formed in the gas phase, which then may contaminate the wafers being processed. In conventional CVD tungsten chambers, each wafer introduced to the chamber must be brought up to temperature and exposed to silane gas in an initiation step. If the silane gas is exposed to any tungsten hexafluoride during the initiation step, unwanted particles will form. Thus, the tungsten deposition at other stations can occur only after the newly introduced wafer has completed its heating and silane initiation step.
In addition, where reactive gases, e.g., tungsten hexafluoride, migrate from one area in the chamber to other areas in an uncontrolled fashion prior to the completion of other processing steps, such as the silane initiation, the reactive gases may attack the Ti seed/barrier layers causing damage to the devices on the wafers. This mechanism can be independent of the gas phase particle producing phenomena. Thus, during the heating and silane initiation of the wafer, the other stations in the multi-station chamber must remain idle to avoid the uncontrolled migration of reactive gases or the undesirable combination of reactive gases. Consequently, the throughput of a multi-station processing chamber is limited by the idle period of the different stations while incompatible processes are performed in neighboring stations. Alternatively, a multi-station processing chamber must perform certain incompatible processing steps, such as the silane initiation, in a separate reactor, which adds cost and complexity to the system, and may reduce throughput.
SUMMARY
A multi-station processing chamber, in which incompatible processes can be performed simultaneously, includes a base with a plurality of wells in which pedestals are located. The outside edge of the wells and the pedestals define annular gaps. The chamber also includes a top portion with showerheads that are aligned above each of the plurality of pedestals. The showerheads flow reactive gases over substrates, such as semiconductor wafers, that are located on the pedestals. The reactive gases are drawn through the annular gap by a pressure gradient created by a vacuum pump connected to the wells via exhaust ports. The reactive gases are thus drawn through the annular gaps into the wells and out the exhaust port. The narrow annular gaps permit little or no recirculation of the reactive gases once the gases are drawn into the wells. Consequently, the reactive gases are not permitted to mix in an uncontrolled manner at an elevated temperature and pressure sufficient to cause a gas phase reaction, thereby avoiding unintentional creation of gas phase particles. Further, the undesirable migration of reactive gases throughout the chamber is avoided.
The showerheads are flush with the ceiling of the chamber, while the wells contain smooth contours to limit the dead space in the chamber, thereby minimizing residence time of the reactive gases.
The chamber also includes an indexing plate to move the substrates from one station to the next. The substrates are loaded and unloaded via a load/unload port adjacent to one station.
In one embodiment, a purge plate that flows an inert gas, such-as argon, is located between the showerheads on the ceiling of the chamber. The flow of an inert gas between the flow of reactive gases assists in maintaining the desired separation of reactive gases.
Using the chamber in accordance with an embodiment of the present invention, incompatible processes may be contemporaneously performed. Thus, a substrate positioned on one pedestal at one station may receive a silane initiation, while another substrate positioned on another pedestal can simultaneously receive a tungsten hexafluoride-silane nucleation or hydrogen reduction. Because each process step may be performed at the same time, there is little or no idle period, thereby increasing throughput.
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E.J. McInerney, “Study of station flow dynamics in a sequential multiwafer chemical vapor deposition batch reactor using reactor modeling”, J. Vac. Sci. Technol. A 14(3), May/Jun. 1996, 1996 American Vacuum Society, pp. 1152-1155.
Hancock Shawn D.
McInerney Edward J.
Pratt Thomas M.
Halbert Michael J.
Novellus Systems Inc.
Pianalto Bernard
Skjerven Morrill & MacPherson LLP
Steuber David E.
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