Continued reduction in resistance-capacitance (RC) delays in nano-electronic Cu interconnect structures will require new materials with increasingly lower dielectric constants (i.e. low-k). Significant reductions in RC delay can be achieved by reducing the dielectric constant of the relatively high dielectric constant Cu capping/etch stop layer. However, this risks comprising the required barrier performance of this material to the diffusion of Cu, H 2 O, and other species. In this regard, critical thresholds for the diffusion of water and solvents through low-k a-SiO x C y N z :H dielectrics of varying composition were investigated using a combination of X-ray reflectivity mass density and positronium annihilation lifetime spectroscopy pore size metrologies. It was observed that hermetic low-k a-SiO x C y N z :H dielectrics were achieved only at mass densities >2.0 g/cm 3 and when the pore diameter was less than twice the molecular diameter of water. The implications of these critical nano-porosity thresholds on continued scaling of low-k diffusion barrier and ILD materials are discussed as well as methods for overcoming these limitations.

International audienceIn a parallel investigation, the etch characteristics of materials within the Si-CO -N-H system were surveyed using two common fluorinated plasma etches used to etch SiO 2 interlayer dielectrics and SiN:H etch stop layers (CHF 3 and CF 4 /O 2 , respectively) with the goal of identifying new materials or " colors " to assist in the simplification of advanced multi-pass optical lithography. In this study, we investigat

New multipass optical lithography patterning methods needed to print features for future <10 nm technologies will demand an increasingly complex combination of hardmasks, antireflection coatings, spacers, and etch stopping materials with distinct yet complementary properties. Finding the right mix, however, has proven particularly challenging given that the materials most commonly used are drawn from a limited set of Si- and C-based solids comprising Si, C, O, N, and H. To understand and maximize the limits of this composition space, the authors have performed a combinatorial survey of the dry etch characteristics for the Si-C-O-N-H system with the goal of understanding material composition–etch interactions and identifying material subclasses with distinct etch properties. Over 50 thin films sampling Si-C-O-N-H composition space were surveyed using two fluorinated etches commonly utilized for selective patterning of SiO2 and a-SiN:H dielectrics (CHF3 and CF4/O2, respectively). It was found that the incorporation of oxygen in a-SiN:H allowed for significant tuning of the etch rate of a-SiON:H materials relative to SiO2. Additionally, increasing hydrogen content and nanoporosity significantly increased the etch rate of the various dielectric materials independent of the Si, C, O, and N content. The influence of carbon depended on whether it was incorporated as terminal organic groups, where it resulted in increased etch rates, or directly within the network of the material, where it resulted in decreased etch rates. Silicon- and carbon-rich materials exhibited very low etch rates in both etches and were found to have the most distinct and potentially complementary etch properties relative to SiO2 and a-SiN:H. Accordingly, a-C:H, a-Si:H, and a-SiC:H merit further examination as hardmask or spacer materials in future multipass patterning processes.

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