Recent progress in materials, processes and integration schemes to reduce line resistance (Line-R) of damascene Cu and alternative conductors (damascene Co and subtractive Ru) are reviewed, including (1) graphene/Co capped Cu to achieve both EM reliability and Line-R reduction (2) nanosecond laser anneal of Ru blanket films for subtractive-etched interconnects, (3) single damascene Cu, which is potentially one way to extend Cu to extreme nodes, and (4) Co/Cu composite integration to preserve Cu power rails. Finally, the technology shift from Cu to alternative conductors is discussed from the viewpoint of Line-R crossover.

The published paper will discuss the impact of exhaust pressure and velocity on particle performance in wet clean process chambers. Correlations are drawn from chamber exhaust pressure, exhaust velocity, and exhaust duct condition to explain the observed degradation in particle performance. Based on the observations, key solutions including periodic preventative maintenance on exhaust duct lines, chamber wipe downs, exhaust rebalancing are recommended to improve chamber stability and particle performance.

Feasibility of single damascene Cu BEOL nanowires with TaN/Ta barrier (i.e. omitting a CVD-Co liner) was studied. Successful Cu gap-fill in 36 nm pitch trenches demonstrated 30% line resistance (Line-R) reduction vs. leading-edge Cu with conventional TaN/Co liner. This was attributed to larger Cu volume fraction and 15% lower intrinsic Cu resistivity. In order to assess the Line-R crossover point, comparable Ru nanowires were estimated through analysis of electron scattering components, based on Rs of blanket Ru films. The calculation predicts Line-R of subtractive-etched Ru lines (larger grains) crosses conventional Cu with TaN/Co liner at 12 nm linewidth, but never crosses Cu with TaN/Ta liner. Analysis of electron scattering components shows the resistivity of Ru lines will be dominated by grain boundary scattering, suggesting that the key for subtractive-etched Ru wires crossing over Cu would be innovations that enhance grain growth of blanket Ru films.

A novel extreme low-k (ELK) porous SiCOH (pSiCOH) dielectric has been developed by adding a third carbosilane precursor to the diethoxymethylsilane and bicycloheptadiene precursors used in the plasma enhanced chemical vapor deposition fabrication process of ultralow-k pSiCOH interconnect dielectrics. By adjusting the plasma parameters, the dielectric constant (k) has been lowered to k < 2.1. The k value of the ELK dielectric has been further reduced to 1.8 by extracting the porogen from the as-deposited films before subjecting them to ultraviolet cure using hydrogen radicals. It was found that the carbon concentration and the porosity of the ELK film can be tuned with different porogen extraction times in order to control the final k value of the dielectric.