Cu post-CMP clean is important to keep both Cu and low-k dielectric clean after polishing. In this paper, two Cu post-CMP clean solutions are analyzed in electrochemical, physical and electrical characterizations, based on the material and integration scheme of imec 65nm platform. It is shown that the combination of these two PCMP clean solutions can achieve both reasonable cleaning efficiencies and reliable low-k dielectric lifetime.
This paper introduces a novel electrochemical technology called electrografting (eG™). After describing electrografting the main characteristics, it will be shown that this technology can be successfully applied to the formation of thin, conformal, and uniform seed layers for IC copper interconnects. Seed layer thicknesses down to 10nm thick are deposited on various copper diffusion barrier materials and characterized in terms of sheet resistance, morphology, conformality, adhesion, and gapfilling capability. Initial results pointed out that the technology can be extended to seedless direct filling of interconnect structures.
Electrografting FundamentalsElectrografting can be defined as a surface initiated electrochemical process for organic and organometallic film deposition, i.e. a process in which a single, usually Faradaïc, electrochemical reaction is coupled to a range of non-Faradaïc chemical reactions giving rise to the formation of a film. This technology works on any conducting and semi conducting surface. Figure 1 illustrates the main characteristics of electrografting in the example of an organic precursor:• As an electro-initiated reaction, electrografting requires very low amount of electrical current, as shown in the voltammogram of Figure 1a. This constitutes an essential feature of electrografting which induces very little ohmic drop and makes it operative and equally uniform on large substrates with a very wide range of substrate resistivities: PVD TaN, PVD TaN/Ta, ALD TaN,…etc ( Figure 1c); • Most electrografting reactions are based on electrically neutral molecular precursors: they are thus mainly fed by diffusion, and very little by migration, as the precursors are insensitive to local electric fields during the process. A straightforward consequence of this is that electrografting delivers coatings which are intrinsically conformal, even on very demanding surfaces with high aspect ratios ( Figure 1d); • Electrografted reactions are usually linked with intimate surface/molecule charge transfer leading to the formation of strong chemical bonds, which can often survive the overall coupled chemistry and sometimes be detected post-mortem in the electrografted film ( Figure 1b) (1). At a more macroscopic scale, electrografted films usually show very strong adhesion to the substrate on which they have been grafted, in line with the interface management which is forced during the initial charge transfer process.
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