Compositions: coating or plastic – Coating or plastic compositions – Silicon containing other than solely as silicon dioxide or...
Reexamination Certificate
2000-03-09
2003-07-08
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Silicon containing other than solely as silicon dioxide or...
C106S287180, C427S253000, C427S099300, C556S112000
Reexamination Certificate
active
06589329
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to copper precursor compositions and their synthesis, and to a method for production of copper circuits in microelectronic device structures, as for example in formation of metal interconnects for the manufacture of semiconductor integrated circuits, thin-film recording heads and packaging components, or otherwise for metallizing or forming copper-containing films on a substrate by metalorganic chemical vapor deposition (MOCVD) utilizing such precursor compositions. The precursor compositions of the invention are also usefully employed for forming seed layers of copper for subsequent electroless or electrochemical plating of copper and other metals.
2. Description of the Related Art
The process of fabricating semiconductor integrated circuits generally includes the formation of metal interconnect lines. The metal interconnect lines often may be formed from multiple conductive layers. For example, a thin conductive layer generally termed a barrier layer may be formed from a metal, metal nitride, metal silicide, or metal silicon nitride and a thicker conductive layer, e.g., composed of aluminum, may be formed on the barrier layer.
In order to enhance circuit speed performance and reduce the resistance-capacitance (RC) signal delay, the use of copper layers has been proposed and implemented to replace the use of aluminum layers, wherein one or more metal layers of a semiconductor integrated circuit may be formed utilizing a copper based layer. Copper is of great interest for use in metallization of VLSI devices because of its low resistivity, low contact resistance, and ability to enhance device performance through the reduction of RC time delays. Many semiconductor device manufacturers are adopting copper metallization for use in production of microelectronic chips, thin-film recording heads and packaging components.
Chemical vapor deposition (CVD) of copper provides uniform coverage for the metallization. Liquid CVD precursors and/or solid precursors dissolved into solvents or excess ligands enable direct injection and/or the liquid delivery of precursors into a CVD vaporizer unit. The accurate and precise delivery rate can be obtained through volumetric metering to achieve reproducibility in CVD metallization of in VLSI device manufacturing.
Currently only a few liquid copper precursors are commercially available. These include (hfac)Cu(MHY), (hfac)Cu(3-hexyne), (hfac)Cu(DMCOD) and (hfac)Cu(VTMS), wherein hfac=1,1,1,5,5,5-hexafluoroacetylacetonato, MHY=2-methyl-1-hexen-3-yne, DMCOD=dimethylcyclooctadiene, and VTMS=vinyltrimethylsilane.
In order to prevent detrimental effects which may be caused by the interaction of a copper layer with other portions of the integrated circuit, a barrier layer is typically utilized in conjunction with copper layers. Any of a wide range of barrier materials may be utilized including materials comprising metals, metal nitrides, metal suicides, and metal silicon nitrides. Exemplary barrier materials include titanium nitride, titanium silicide, titanium silicon nitrides, niobium nitrides, niobium silicon nitrides, tantalum nitride, tantalum silicide, tantalum silicon nitrides, tungsten nitride, tungsten silicide and tungsten silicon nitride. After the formation of a barrier layer, the copper is deposited on the barrier layer. The initial copper deposition may function as an adhesion seed layer, an electrochemical or CVD seed layer, and the initial copper deposition may be followed by electrochemical plating or CVD of copper. Alternatively, the copper deposition may be employed to fully deposit the desired amount or thickness of copper.
The use of various copper precursors in CVD reactors to create copper interconnects in semiconductor integrated circuits, for example, is well known. See, for instance, U.S. Pat. Nos. 5,085,731; 5,098,516; 5,144,049; and 5,322,712; and the references cited in those patents. New and useful compositions and processes for the production of copper that improve on, or provide alternatives to, these known compositions would be highly desirable and embody a significant advance in the art.
In this respect, copper CVD processes suitable for large-scale manufacture of integrated circuits are extremely valuable to the electronics industry. Towards these ends, copper CVD can be used in two ways:
1. deposition of an adherent and conductive thin-film layer as a plating base for electroplating processes.
2. full-fill deposition of copper interconnects, thin-film circuitry, recording head coils and other features.
In electroplating applications, several critical features must be achieved in the deposition of the plating base, or “seed” layer, for the subsequent electroplating to be successful. The deposition of a useful “thin-film seed layer” must satisfy the following film requirements:
1. The film requires low resistivity and uniform thickness, thereby allowing uniform current densities to be realized during plating.
2. The film requires uniform conformality in high aspect ratio features to satisfy complex device geometries, multi-level metal layers and damascene processing.
3. The film must exhibit excellent adhesion between the deposited copper metallurgy and the barrier layer, and between subsequent levels of metal interconnect metallurgy.
In an attempt to achieve these results, copper precursor alternatives to the current commercial materials, such as (hfac)Cu(vinyltrimethylsilane), commercially available as CupraSelect (Schumacher Division of Air Products & Chemicals, Inc., Allentown, Pa.) are badly needed. (Hfac)Cu(vinyltrimethylsilane), suffers from inherent thermal instability and therefore requires additives to enhance the molecule's physical properties, including thermal stability, and to facilitate uniform nucleation and film growth. Further, these chemical additives can induce process complexities and negatively alter device integration, such as by creating high contact resistances due to contamination of contacting surfaces (with fluorine and/or oxygen impurities).
For example, one additive that has been employed is hexafluoro-2,4-pentanedionate hydrate. The addition of such a hydrate to the vinyltrimethylsilane Cu(hfac), or corresponding addition of small amounts of water, has generally been found to substantially increase the deposition rate of the CVD process. Such additives, however, may lead to contamination of the interfacial surface regions and/or copper film, either during nucleation or steady-state film growth. In both cases, the electrical properties of the film or contact region may be compromised, resulting in high film resistivity and/or high contact resistance. In multi-layered structures, both of these electrical properties are critical in respect to device integration and manufacture.
Such contamination of the product film incident to the use of hfac-hydrate in the CVD formulations is attributable to the fact that hfac is susceptible to decomposition during the film growth process especially at the barrier-copper interface. In fact, Hhfac has been used to attack and etch metal surfaces, showing a strong tendency to remain on the surface of the barrier layer and/or copper nucleation layer during subsequent metallization. In addition, over time precursors such as vinyltrimethylsilane Cu(hfac) show decomposition to green Cu(II) species. Thus, the inherent thermal instability of this precursor and the required chemical additives pose significant deficiencies in the prior and current art. There is, therefore, a significant need in the art for copper formulations that deliver improved copper precursors to the CVD process without undesirable side effects. There is particularly a need for formulations that exhibit greater thermal stability without undesirable side effects due to the presence of fluorine substituents and/or aging of the precursor solution.
Alternative commercial alkyne and ene-yne Cu(I)(hfac) precursors are volatile and afford rapid deposition rates, but these compounds are also
Baum Thomas H.
Xu Chongying
Advanced Technology & Materials Inc.
Brunsman David
Chappuis Margaret
Hultquist Steven J.
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