Coating processes – Coating by vapor – gas – or smoke – Metal coating
Reexamination Certificate
1998-07-10
2002-10-08
Chen, Bret (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Metal coating
C427S255394, C427S255700, C427S553000, C438S761000
Reexamination Certificate
active
06461675
ABSTRACT:
BACKGROUND OF THE INVENTION
The fabrication of electronic devices on semiconductor substrates, such as ultra large scale integration (ULSI) device fabrication, has resulted in integrated circuit (IC) chips having substantial miniaturization of electronic device dimensions. Conventional aluminum/silicon oxide (Al/SiO2) interconnect architectures have proven inadequate to meet the demand for higher interconnect performance (e.g., IC speed and reliability lifetime) needed to support increasingly miniaturized electronic device fabrication with higher chip integrated densities. To support further miniaturization, industry has chosen copper metalization to replace aluminum.
Copper offers a number of important advantages associated with higher interconnect performance. For instance, copper can increase interconnect performance by reducing interconnect propagation delays and cross talk, and by enabling higher metalization current densities than are available with aluminum. In addition, copper offers reliability and cost advantages in the manufacturing of electronic devices. For instance, when combined with low-k dielectrics, copper's superior electromigratior performance and lower resistivity reduces the number of metalization levels needed for a given IC chip. This reduction in the number of metalization levels results in reduced manufacturing cost and/or increased yield.
A number of deposition methods allow for the deposition of copper on a substrate, including electrochemical deposition or plating, Physical-Vapor Deposition (PVD), and Metal-Organic Chemical-Vapor Deposition (MOCVD)). Plating deposits copper by creating a charge potential between a copper-containing electrochemical bath and the substrate. Although plating can deposit copper films having adequate characteristics to support interconnect functions on a substrate, plating requires additional equipment for deposition of barrier and other layers on the substrate. Moreover, electrochemical deposition (ECD) methods produce significant amounts of wet chemical waste requiring expensive disposal. These additional requirements increase manufacturing cost and complexity. By comparison, PVD and MOCVD advantageously allow clustering of copper deposition with barrier deposition and preclean processes, such as with process module reaction chambers clustered around a vacuum-integrated cluster tool available from CVC, Inc. The capability for fully vacuum-integrated deposition of the diffusion barrier and copper layers onto semiconductor substrates makes a MOCVD-based option very attractive due to the reduced complexity of the deposition process sequence and the greater equipment productivity.
Copper deposition with MOCVD provides a number of additional advantages compared with to ECD and PVD. For instance, MOCVD-deposited copper used to form integrated plugs and metal lines has excellent gap-fill characteristics at a low thermal budget, such as less than 250° C., making MOCVD deposition of copper compatible with single and dual damascene processing and compatible with low-k polymer dielectrics. The resulting interconnect architectures provide low metal resistivity, reduced interconnect propagation delay and cross-talks, and good electromigration lifetime characteristics.
Although MOCVD copper deposition can form high-quality copper films to act as integrated circuit conductive interconnects, the films frequently have poor adhesion to underlying diffusion barrier layers. Poor adhesion between the copper film and the underlying barrier is attributed to interface contamination that is formed during conventional MOCVD copper processes using commonly available precursors. The interfacial contaminates which can have a detrimental impact on copper film adhesion include carbon and fluorine, both present in common copper MOCVD precursors. A copper film formed with conventional MOCVD to interface with a substrate barrier layer frequently fails to pass the scribe plus tape pull test, and can separate from the barrier during chemical-mechanical polishing (CMP) processes used to form inlaid conductive copper plugs and metal lines. The scribe plus tape test is accomplished by physically scribing a tick-tac-toe design in the copper film and then attempting to lift the copper film from the barrier layer with a tape pull. If a copper film has adequate adhesion to the barrier layer, the tape pull force will not lift the film from the barrier. In contrast, failure to pass the scribe plus tape test indicates that the copper film has inadequate adhesion to the barrier layer, and that the process used for the deposition of the copper film will not support large scale commercial production of chips having copper interconnects.
SUMMARY OF THE INVENTION
Therefore a need has arisen for a method that deposits a copper film having good adhesion to an underlying layer.
A further need exist for a method that supports deposition of copper films with vacuum-deposition equipment that is compatible with the equipment used to deposit other films on the substrate.
A further need exist for a method that supports the deposition of copper films with reduced complexity and high reliability.
A further need exist for a method that will support a high-throughput fabrication of semiconductor integrated circuit, having copper interconnects.
In accordance with the present invention a method is provided that substantially eliminates or reduces disadvantages and problems associated with previously developed methods for depositing copper films on substrates.
A first material is deposited on the substrate to form an interface with an underlying layer associated with the substrate and to act as a seed layer for the copper layer. The seed layer is deposited to have good adhesion to the underlying layer of the substrate, such as the diffusion barrier of the substrate. The copper layer is then deposited on the seed layer to form the copper film on the substrate, such as the copper film that forms a copper interconnect. The first material forms a seed layer by using deposition according to first predetermined conditions that optimize adhesion of the seed layer to the underlying layer of the substrate. The copper layer is deposited on the seed layer according to second predetermined conditions, such as conditions that will optimize properties and maximize the throughput available for deposition of a copper bulk layer. For instance, the seed layer thickness can range from 50 to 500 angstroms depending on the adhesion enhancement method, and the bulk layer thickness can range from 200 to 15,000 angstroms.
One predetermined condition for depositing the seed layer is depositing the first material onto a substrate barrier to form an interface or a buffer layer between the barrier and the bulk copper layer that forms the copper interconnect, but to anneal the first material before deposition of the bulk copper layer. The first material can comprise a generally thin layer of copper that is thermally annealed at a predetermined temperature for a predetermined time. Thermal annealing promotes diffusion of copper into the barrier for atom-to-atom bonding and disassociates or displaces the contaminates associated with the interface (typically carbon, fluorine, and/or oxygen).
Alternatively, the first material can be an inert material that will have minimal reactivity with the precursor used to deposit copper (making it difficult for the precursor contaminants to get adsorbed on the surface). For instance, noble metals, such as platinum or iridium, are inert to contaminates associated with the MOCVD process, thus avoiding contamination of the interface during MOCVD deposition of copper. Similarly, passivated metals, such as tantalum nitride, titanium nitride, TaO
x
N
y
and TiO
x
N
y
can be used as the first material.
Alternatively, the first material can be a catalytic material, such as chromium, tin, zinc, titanium or tungsten, that alloys with copper at a relatively low temperature, and a generally thin layer of copper deposited on the catalytic layer. The catalytic material and copper are t
Campbell, Sr. David R.
Liu Zeming
Moslehi Mehrdad M.
Omstead Thomas R.
Paranjpe Ajit P.
Baker & Botts L.L.P.
Chen Bret
CVC Products Inc.
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