For the deposition and processing of copper films one may distinguish the following general requirements:
(1) It must be possible to deposit high-purity films for the lowest possible resistivity. In addition, it will be desirable to be able to control the texture of the Cu films, since this is a determining factor for the electromigration resistance of the material.
(2) The deposition method chosen must allow for high deposition rates for adequate throughput.
(3) A chemical-mechanical polishing technique has to be developed that makes it feasible to planarize Cu and its associated barrier layer.
(4) Given that Cu will be used in conjunction with the damascene method for patterning, the deposition method must be able to completely fill trenches and vias with high aspect ratios.
(5) Since the use of Cu necessitates a diffusion barrier, it will be desirable to perform the metal/barrier depositions in an integrated cluster tool, so that the sample does not have to be exposed to the atmosphere between the two depositions.
(6) It must be possible to maintain a low-cost, high-reliability process for low cost of ownership.
In the next two sections we will describe various chemical and physical methods for the deposition of Cu. This will be followed by a section on approaches to the patterning of Cu, both subtractive and damascene.
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