Ultra-Conformal Metal Coating on High-Aspect-Ratio Three-Dimensional Structures Using Supercritical Fluid: Controlled Selectivity/Non-Selectivity

Underlayer dependence can be controlled for supercritical fluid deposition (SCFD) of Cu. SCFD, which has a remarkable potential for ultra-conformal deposition and gap-filling, has previously required a metallic underlayer to initiate deposition. Here, this constraint has been overcome by depositing a novel catalytic layer, CuMn_xO_y, onto a semiconducting and insulating substrate. The stoichiometry of CuMn_xO_y affected both the morphology of CuMn_xO_y film and the catalytic effect on succeeding SCFD of Cu. By using this technique of depositing CuMn_xO_y as a catalytic layer, conformal SCFD of Cu was achieved on high-aspect-ratio trenches (aspect ratio 50) whose surfaces were SiO₂. In conclusion, a CuMn_xO_y film with graded stoichiometry in the depth direction might improve the adhesion between Cu and an insulative underlayer.