Pore Characterization in low-k Dielectric Films using X-ray Reflectivity: X-ray Porosimetry

Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. iii FOREWORD The persistent miniaturization or rescaling of the integrated chip (IC) has led to interconnect dimensions that continue to decrease in physical size. This, coupled with the drive for reduced IC operating voltages and decreased signal-to-noise ratio in the device circuitry, requires new interlayer dielectric (ILD) materials to construct smaller and more efficient devices. At the current 90 nm technology node, fully dense organosilicate materials provide sufficient ILD shielding within the interconnect junctions. However, for the ensuing 65 nm and 45 nm technology nodes, porous ILD materials are needed to further decrease the dielectric constant k of these critical insulating layers. The challenge to generate sufficient porosity in sub-100 nm features and films is a significant one. Increased levels of porosity are extremely effective at decreasing k, but high levels of porosity deteriorate the mechanical properties of the ILD structures. Mechanically robust ILD materials are needed to withstand the stresses and strains inherent to the chemical–mechanical polishing steps in IC fabrication. To optimize both k and the mechanical integrity of sub-100 nm ILD structures requires exacting control over the pore formation processes. The first step in achieving this goal is to develop highly sensitive metrologies that can accurately quantify the structural attributes of these nanoporous materials. This Recommended Practice Guide is dedicated to developing X-ray Porosimetry (XRP) as such a metrology. It is envisaged that XRP will facilitate the development of nanoporous ILD materials, help optimize processing and fabrication parameters, and serve as a valuable quality control metrology. Looking beyond CMOS technology, many attributes of XRP will be useful for the general characterization of nanoporous materials which are becoming increasingly important in many emerging fields of nanotechnology.