Bottom-up Cu filling of annular through silicon vias: Microstructure and texture

Microstructural and morphological evolution during bottom-up Cu filling of annular through silicon vias (TSV) in a CuSO₄-H₂SO₄-Cl^--poloxamine electrolyte is examined. Deposition proceeds in two distinct stages beginning with a passive-to-active state transition on the via sidewalls whose depth and ultimate thickness depends on the polymer flux. Growth is conformal or tapered with columnar grains whose width and texture differ between the outer and inner sidewalls of the annulus due to area reduction and expansion respectively. The outer sidewall and bottom surface have a preferred texture; 〈111〉//ND (via normal) and 〈110〉//CD (via circumferential). With time the sidewalls passivate while further deposition is localized to the via bottom. Bottom-up growth then fills the TSV with the formation and selective expansion of the 〈110〉//ND textured grains. At higher suppressor concentrations the initial onset and transient period of sidewall deposition is displaced to greater depth and the subsequent shift to bottom-up filling with large 〈110〉//ND texture grains occurs earlier. The dominant 〈110〉//ND texture during bottom-up filling is congruent with Cl^- stabilized texture development. The absence of suppression indicates that the polymeric suppressor does not adsorb on the active upward propagating surface.