Superconformal Film Growth: From Smoothing Surfaces to Interconnect Technology

• DOI: 10.1021/acs.accounts.2c00840
• Publication Date: 2023-04-20T04:25:35Z
• Authors: Thomas P. Moffat; Trevor M. Braun; David Raciti; Daniel Josell

ConspectusElectronics manufacturing involves Cu electrodeposition to form 3D circuitry of arbitrary complexity. This ranges from nanometer-wide interconnects between individual transistors increasingly large multilevel intermediate and global scale on-chip wiring. At larger scale, similar technology is used micrometer-sized high aspect ratio through-silicon vias (TSV) that facilitate chip stacking printed circuit board (PCB) metallization. Common all these applications void-free filling lithographically defined trenches vias. While line-of-sight physical vapor deposition processes cannot accomplish this feat, the combination surfactants electrochemical or chemical enables preferential metal within recessed surface features known as superfilling. The same superconformal film growth account for long-reported but poorly understood smoothing brightening action provided by certain electroplating additives. Prototypical surfactant additives acid-based CuSO4 electrolytes include a halide, polyether suppressor, sulfonate-terminated disulfide, and/or thiol accelerator possibly N-bearing cationic leveler. Many competitive coadsorption dynamics underlie functional operation Upon immersion, surfaces are rapidly covered saturated halide layer makes interface more hydrophobic, thereby supporting formation suppressor layer. Also, serves cosurfactant adsorption amphiphilic molecular disulfide species on while inhibiting copper sulfide incorporation into growing deposit. Furthermore, dangling hydrophilic sulfonate end group activated hindering assembly. A common thread in feature additive-derived positive feedback reaction re-entrant regions. For submicrometer optically rough surfaces, area reduction accompanies motion concave segments results most strongly bound adsorbates' enrichment, which suppressor-accelerator systems species. superfilling process quantitatively captured curvature-enhanced adsorbate coverage mechanism. features, such TSV, whose depths approach thickness hydrodynamic boundary layer, significant compositional electrical gradients couple with give negative differential resistance related nonlinear effects morphological evolution. suppressor-only electrolytes, remarkable bottom-up occurs where disrupts adsorbates at bottom TSV overruns ability due kinetic transport limitations. Because response changes chemistry rapid than mass processes, planar substrates proceeds bifurcation passive active zones, generating Turing patterns. On patterned substrates, zone development biased toward distinction packaging metallization will be blurred dimensions former merge those early day