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Porous Low-K Deposition and Characterization Research

Final Activity Report Summary - POLDER (Porous Low-K Deposition and Characterization Research)

In the first month of the project, new equipment, the ASM Eagle #174; 12, was delivered at IMEC. It was installed and the basic processes accepted within the original chronogramme. Initially, two types of low-k films were studied. The first one, Aurora #174; ELK HM, is a film with a dielectric constant of 2.55 and a Young's modulus of 9 GPa, compatible with integration in the 45 nm node. The second one, Aurora #174; ELK, is a film with a dielectric constant of 2.3 and a Young's modulus of 4 GPa, compatible with integration in the 32 nm node. The final films are obtained after a two-step process: the first process consists of the deposition of a film, which contains a porogen within a Si-O-C type of skeleton; the second process consists of a UV cure in which this porogen is removed (and nanopores are created) and the skeleton is restructured in such a way that the mechanical characteristics (as characterized by E modulus and hardness) are improved. Both deposition and cure processes had to be optimised for both films during the course of the project and eventually the final material and film characteristics were state of the art.

In the same equipment and in another, similar equipment (also an Eagle #174; 12 cluster system), barrier layers were developed and characterised. The interaction of the UV cure with these films was characterised. A special hermeticity test was developed which showed that the standard barrier is excellent against moisture diffusion. All these films were used for integration in single and dual damascene flows.

This integration proved to be quite difficult and special optimisation of the etch, strip and clean steps were necessary to limit the increase of the effective dielectric constant. The final processes showed good electrical results and EFTEM analysis showed very little carbon depletion in the low k films.