Drying and gas or vapor contact with solids – Process – Gas or vapor pressure is subatmospheric
Reexamination Certificate
1999-08-03
2001-01-30
Ferensic, Denise L. (Department: 3749)
Drying and gas or vapor contact with solids
Process
Gas or vapor pressure is subatmospheric
C034S092000, C034S216000, C034S257000
Reexamination Certificate
active
06178660
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to processing of semiconductor wafers and, more specifically, to treatment of moving semiconductor wafers.
BACKGROUND OF THE INVENTION
Semiconductor processing comprises a complex series of sequential steps through a number of semiconductor processing tools adapted to perform various operations. Such operations include, but are by no means limited to, photoresist deposition, exposure, and development; etching; deposition of conductive and dielectric layers; and planarization. Often, a single wafer may undergo the same operations multiple times as each layer of circuit design is created. Frequently, it is desirable to clean the wafer to reduce interfacial contamination before certain process steps. Such cleaning may comprise exposing the wafer surface to reactive ion plasma or to other cleaning gases.
Wafer cleaning steps may be ex-situ or in-situ. An ex-situ cleaning step is one in which the wafer is cleaned in one process tool before the main processing occurs in another processing tool. Ex-situ cleaning may have certain disadvantages, including the potential for recontamination between the cleaning step and the next processing step. In this case, a limited time window between the cleaning step and the next processing step is required. An in-situ cleaning step is one in which the wafer is cleaned in the process tool which performs the main processing step. The existing art for in-situ cleaning of wafers requires placing the wafer in a fixed separate chamber or a fixed position within a transfer chamber. Such a separate chamber increases the cost, the processing time, and the space dedicated to the tool.
During cleaning, a wafer is typically placed on a chuck or similar support that keeps the wafer stationary while processing occurs. To accommodate the support, the chamber in which the wafer is cleaned is typically at least as wide and deep as the wafer diameter. The wafer is typically handled before cleaning to set it in place for the cleaning step which is to be performed and again after cleaning to remove the wafer from the chamber. In-situ cleaning offers the benefit of a cleaner and more controlled wafer surface as compared to ex-situ cleaning.
Other wafer cleaning processes or chemical treatment processes such as sputtering or vapor deposition are also typically performed in chambers that are at least as large as the wafer, in which the wafer remains stationary during treatment, and in which the wafer is typically handled to place and remove the wafer. There is a need in the art, therefore, for a more compact apparatus, especially one with reduced dimension in the direction of wafer movement. A related need is for an apparatus that permits plasma cleaning of wafers while the wafer is in transit from the load area to the main processing area.
SUMMARY OF THE INVENTION
To meet these and other needs, and in view of its purposes, the present invention provides a pass-through, wafer-processing tool for directing process gas onto a moving semiconductor wafer. The tool comprises an open-ended, non-isolated processing module having a wafer entry, a wafer exit, and a wafer passage connecting the wafer entry and wafer exit. The wafer passage is dimensioned to accommodate travel of the wafer through the passage. The tool further comprises two vacuum manifolds, one mounted adjacent the wafer entry and one mounted adjacent the wafer exit, and a gas manifold between the vacuum manifolds adapted to direct process gas onto the moving wafer. The pass-through, wafer-processing tool has a depth between the entry and exit that is less than the wafer diameter.
The process gas may comprise ammonia, hydrogen, or nitrogen but is not limited to those gases. The tool is adapted to provide a cleaning step, a sputtering step, a chemical vapor deposition step, a plasma treatment step, or a reactive ion etching step.
One or more pass-through, wafer-processing tools of the present invention may be part of an integrated system of semiconductor wafer-processing stations in a cluster configuration. A wafer handler is adapted to carry a wafer sequentially from a processing station before the pass-through, wafer-processing tool; through the pass-through, wafer-processing tool; and into a processing station after the pass-through, wafer-processing tool. Such a wafer handler is a robotic handler adapted to control the speed of the wafer through the pass-through, wafer-processing tool. In particular, the pass-through, wafer-processing tool is a pre-cleaner adapted to clean the wafer in preparation for the process performed in the sequential processing station.
The gas manifold is connected to a remote plasma unit outside the module and adapted to deliver plasma ions generated by the remote plasma unit to the moving wafer. Alternatively, the process gas is a reactive gas from which a plasma is generated in the pass-through, wafer processing tool. In such a case, the tool comprises a top electrode mounted in the module above the wafer passage and a wafer handler carrying the wafer through the wafer passage from underneath the wafer, functioning as a bottom electrode, and having DC-biasing capability. A radio-frequency (RF) source connected to the top electrode delivers sufficient RF energy to generate a plasma from the reactive gas bounded by the top electrode, the wafer, and the vacuum manifolds. The top electrode may be a baffle plate of the gas manifold.
The process of the present invention comprises generating a plasma from reactive gas supplied by the gas manifold. The process further comprises moving the semiconductor wafer on a robotic handler functioning as a bottom electrode underneath the wafer in a path underneath a top electrode mounted above the moving wafer. RF energy is delivered to the top electrode sufficient to generate a plasma from the reactive gas in a region bounded by the vacuum manifolds, the top electrode, and the wafer. The wafer handler is DC-biased to attract plasma ions from the plasma to impinge upon the wafer. In the alternative, the process gas may comprise a plasma containing plasma ions, and the process may comprise directing the plasma ions onto the moving wafer by generating the plasma ions in a remote plasma unit outside the module and delivering the plasma ions onto the moving wafer through the gas manifold.
The present invention also includes any plasma-generating device for exposing a moving semiconductor wafer to a plasma. The device comprises a robotic handler adapted to move the wafer and to serve as a bottom electrode underneath the wafer, a top electrode mounted above the moving wafer, reactive gas between the top electrode and the wafer, and an RF source connected to the top electrode and capable of delivering sufficient RF energy to generate a plasma from the reactive gas between the top electrode and the wafer. A process for exposing a moving semiconductor wafer to a plasma comprises placing the semiconductor wafer on a robotic handler adapted to serve as a bottom electrode underneath the wafer, moving the wafer with the robotic handler in a path underneath a top electrode mounted above the moving wafer, delivering a reactive gas between the top electrode and the moving wafer, and delivering RF energy to the top electrode sufficient to generate a plasma from the reactive gas between the top electrode and the wafer.
The present invention may also comprise a process for treating a moving semiconductor wafer with process gas in a pass-through, wafer-processing tool comprising an open-ended, non-isolated processing module enclosure. The process comprises moving the wafer into the pass-through, wafer-processing tool through a wafer entry port in the module and along a wafer passage dimensioned to accommodate travel of the wafer through the module. Then, the wafer is moved past an entry vacuum manifold adjacent the wafer entry port, past a gas manifold that directs process gas onto the moving wafer, and past an exit vacuum manifold adjacent the wafer exit port in the module through which the wafer then exits the to
Emmi Peter A.
Park Byeongju
Ferensic Denise L.
International Business Machines - Corporation
Mattera Michelle A.
Ratner & Prestia
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