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Robert L. Rhoades, Entrepix, Inc., Arizona, USA & Gautam Banerjee, Air Products and Chemicals, Inc., Arizona, USA

ABSTRACT

Advanced semiconductor devices have evolved over recent years through a series of steps that included the introduction of both copper metal and low-k dielectric materials for the interconnect module.  As designs continue to push toward faster speeds and smaller linewidths (65, 45, 32 and 22nm), the dielectric constant (k) required at each successive technology node is projected to continue dropping toward effective k-values of 2.5 or below.  The new materials required to reach these values are generally referred to as ultra low-k, or ULK, dielectrics.  Developing such ULK materials is an incredible challenge, but several candidate materials are now available.  However, integrating them successfully into a reliable CMOS device manufacturing flow is proving to be extremely difficult, especially with regard to the CMP process module.

This article reviews recent progress and issues related to integrating ULK dielectrics, particularly as related to chemistry and interactions with CMP and post-CMP cleaning. In this context, the ULK material must first be mechanically and chemically stable during all phases of the CMP process.  For some integration schemes, this may include direct exposure of the ULK surface to the final step of slurry, which is used to polish away the thin barrier metal and expose the dielectric below.  The post-CMP cleaning chemistry will also be in direct contact with the ULK film and must not only perform the necessary function of cleaning away particles and other residuals from the polishing process, but also must not itself damage or inadvertently alter the ULK material.  In order to be successful at achieving future design targets, the combined system of materials, chemistries and processes must be integrated in a way that allows adequate repeatability and control for manufacturing.  This will continue to demand close cooperation between designers, integration teams, process engineers, ULK developers, CMP consumables suppliers, and post-CMP cleaning chemistry suppliers.