The 16nm pitch metallic strains have been fabricated utilizing a semi-damascene integration movement optimized for cost-effective manufacturability, making it a gorgeous method for fabricating the primary native interconnect metallic layer of the A7 and past expertise nodes.
Ruthenium (Ru) semi-damascene has been initially proposed by imec as a gorgeous module method to deal with the rising resistance-capacitance (RC) delay considerations related to Cu dual-damascene when metallic pitches scale beneath 20nm. Semi-damascene is a two-level metallization module that begins with the direct etch of the primary native interconnect metallic layer (M0) and is probably expandable to a number of layers.
In 2022, imec for the primary time experimentally demonstrated direct etched low-resistance Ru strains at 18nm metallic pitch and expanded the combination scheme in direction of a two-metal-level module utilizing absolutely self-aligned vias (FSAVs).
Imec now presents 16nm pitch direct etched Ru strains with a record-low common resistance of 656W/µm. 40% of the 16nm pitch Ru line buildings have been proven to satisfy the resistance goal (as predicted based mostly on skinny movie resistivity), akin to 8nm-wide native interconnects. For the 18-22nm pitch vary, full-wafer yields of 90% and better have been obtained.
The offered semi-damascene integration movement depends on a modified EUV-based self-aligned double patterning (SADP) method – known as spacer-is-dielectric (SID) SADP – together with direct etch of Ru. Three key components from the combination movement are important to attaining low resistance values and guaranteeing cost-effective manufacturability.
First, the selection of low cost oxide and nitride-based supplies for the exhausting masks, spacers and hole fill. Second, the implementation of a sample inversion step together with an optimized SiO2 hole fill. And third, an improved Ru etch step throughout which the oxidation of the SiN exhausting masks was minimized to keep away from line bridge defectivity.
“Now that trade is choosing up Ru direct metallic etch, imec is looking forward to future generations and discusses additional optimizations to its semi-damascene movement in addition to new integration choices,” says Seongho Park, imec’s nano-interconnect programme director, “imec reveals advances in pillar-based FSAV approaches which can be key to increasing the combination in direction of a two-metal-level scheme. In different papers offered at 2025 IITC, in addition to Ru patterning optimization, methods to mitigate thermally induced morphology modifications are investigated. Wanting additional forward, imec experimentally demonstrates an epitaxially grown 25nm skinny movie of Ru to lead to a lot decrease resistive interconnects, approaching for the primary time the majority resistivity of Ru within the skinny movie regime.”
