Coating apparatus – With indicating – testing – inspecting – or measuring means
Reexamination Certificate
1999-01-13
2002-06-25
Bueker, Richard (Department: 1763)
Coating apparatus
With indicating, testing, inspecting, or measuring means
C118S719000, C118S726000, C118S729000
Reexamination Certificate
active
06409837
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to semiconductor processing and more specifically to the deposition of a metal layer, such as copper, within a chemical vapor deposition (CVD) system, using a liquid precursor.
BACKGROUND OF THE INVENTION
In the formation of integrated circuits (ICs) it is often necessary to deposit thin material layers or films, such as films containing metal and metalloid elements, upon the surface of a substrate, such as a semiconductor wafer. One purpose of such thin films is to provide conductive and ohmic contacts for the ICs and to yield conductive or barrier layers between the various devices of an IC. For example, a desired film might be applied to the exposed surface of a contact hole formed in an insulating layer of a substrate, with the film passing through the insulating layer to provide plugs of conductive material for the purpose of making electrical connections across the insulating layer.
One well known process for depositing such films is chemical vapor deposition (CVD), in which a film is deposited on a substrate using chemical reactions between various constituent or reactant gases, referred to generally as process gases. In a CVD process, reactant gases are pumped into a process space of a reaction chamber containing a substrate. The gases react in the process space proximate a surface of the substrate, resulting in the deposition of a film of one or more reaction by-products on the surface. Other reaction by-products that do not contribute to the desired film on the exposed substrate surfaces are then pumped away or purged by a vacuum system coupled to the reaction chamber.
One variation of the CVD process, which is also widely utilized in IC fabrication, is a plasma-enhanced CVD process or PECVD process in which one or more of the reactant process gases is ionized into a gas plasma to provide energy to the reaction process. PECVD is desirable for lowering the processing temperatures of the substrate and reducing the amount of thermal energy usually necessary for a proper reaction with standard CVD. In PECVD, RF electrical energy is delivered to the process gas or gases to form and sustain the plasma, and therefore, less thermal energy is needed for the reaction.
The dimensions of the IC devices formed by such film deposition techniques have continued to decrease, while the density of such devices on the substrate wafers being processed are increasing. Particularly, IC devices having physical features that are sub-micron in dimension are becoming more common. Furthermore, the semiconductor industry has increasingly desired that such small IC devices have interconnects which are highly conductive. Whereas aluminum alloys and tungsten have been traditionally utilized for conductive interconnects within IC devices, copper has become popular for such interconnects within sub-micron devices. It has been found that IC devices utilizing copper interconnects rather than aluminum or tungsten interconnects, exhibit greater reliability and speed.
For chemical vapor deposition of copper, it has become common to utilize a liquid copper-containing precursor designated in the art as an (hfac) Cu (TMVS) precursor. As is well known in the art, such a precursor, in liquid form, includes a hexa-fluoracetylacetonate (HFAC) organic chemical ligand combined with trimethylvinylsilane (TMVS). The liquid copper precursor must then be vaporized prior to introduction into a CVD processing chamber as a process gas. The use of such metal precursors with organic molecular ligands is broadly referred to as metal-organic chemical vapor deposition or MOCVD.
Processing systems presently available for MOCVD of copper have several particular drawbacks. First, while some systems rely upon bubbling or evaporating the precursor to the gaseous state, other systems rely upon the use of a commercially- available direct liquid injection (DLI) system for delivery of the MOCVD copper precursor to the process chamber. One such DLI system is the DLI-25B available from MKS Instruments of Andover, Mass. DLI systems use liquid from a reservoir or ampule and then heat the liquid in the delivery line as it passes to a process chamber. Pumps and flow controllers are used to manage liquid flow. Such DLI systems are generally not specifically developed for MOCVD copper precursor introduction. In fact, most such DLI systems were developed for delivering water vapor within a process chamber. As a result, processing systems utilizing commercially available DLI systems often result in copper condensation or even deposition within the actual lines and flow control components of the DLI system which hinders introduction of the gaseous precursor to a process chamber. For example, condensation in the line may occur past the point at which the precursor vaporizes but before the process chamber. In addition to the inefficient delivery of the gaseous precursor, particle generation may result within the DLI system which may contaminate a substrate being processed. Deposition within the DLI system accompanied by particle generation will ultimately clog the DLI system and render it ineffective until it may be disassembled and cleaned. As will be appreciated, such factors are undesirable within a processing system as they decrease the efficiency and throughput of the processing system and require additional maintenance.
Another drawback to copper MOCVD systems, as with other CVD systems incorporated within a larger, multi-chamber processing tool, is the inability to control the transmission of CVD reaction by-products from the CVD processing chamber to a substrate handler which interfaces with the numerous processing chambers of the processing tool. The inability to control the by-product flow into the handler often precludes the use of a copper MOCVD chamber in combination in the same processing tool with a physical vapor deposition (PVD) chamber, because such PVD processes are very sensitive to background contamination which is generated by the CVD reaction by-products. With respect to copper deposition, such cross contamination is a significant drawback, because one of the most effective diffusion barriers for copper is tantalum nitride (TaN) which is deposited by a PVD method. Presently, TaN cannot be effectively deposited by CVD techniques. Accordingly, a PVD—TaN processing chamber and methodology cannot be effectively integrated with a MOCVD—Cu processing chamber in a single processing tool unless the contaminating reaction byproducts from the MOCVD chamber can be prevented from entering the PVD chamber.
Still another drawback with current copper MOCVD processing systems results from the fact that such systems allow deposition of copper up to the outer edge of the substrate. Generally, the barrier layer (e.g. TaN) deposited beneath the copper layer on the substrate, which is deposited by a PVD method as discussed above, will not extend to the edge of the wafer. Therefore, a portion of the copper layer which extends around the outer substrate edge, will not be deposited entirely upon a barrier layer. As a result, at the edges of the substrate, the copper will be free to diffuse into the silicon wafer, which may affect the operation of the IC devices formed on the substrate.
Accordingly, it is an objective of the invention to improve MOCVD deposition techniques in general and Cu MOCVD deposition techniques in particular, and thus to present a processing system which addresses the above-discussed drawbacks of current systems.
Specifically, it is an objective of the invention to uniformly introduce a gaseous copper precursor into a process chamber while reducing particle generation from such precursor introduction and reducing clogging associated with prior art precursor introduction systems.
It is another objective of the present invention to reduce cross contamination between adjacent processing systems which are necessary for the various steps associated with IC fabrication from a substrate wafer.
It is still another objective of the present invention to prevent the deposition of
Bueker Richard
Tokyo Electron Limited
Wood Herron & Evans LLP
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