Superconformal Copper Deposition in Through Silicon Vias by Suppression-Breakdown

Abstract

The evolution of superconformal Cu electrodeposition in high aspect ratio through silicon vias (TSVs) is examined as a function of polymer suppressor concentration, applied potential and hydrodynamics. Electroanalytical measurements in a CuSO 4 -H 2 SO 4 -Cl electrolyte are used to explore and quantify the effect of such parameters on the metal deposition process. Hysteretic voltammetry due to suppressor breakdown reveals an S-shaped negative differential resistance that leads to non-linear spatial-temporal patterning during metal deposition. For the given hydrodynamic conditions, cyclic voltammetry reveals the potential regime over which positive-feedback gives rise to the superconformal feature filling dynamic. Breakdown of suppression is primarily related to polymer concentrations in the electrolyte while its reformation is dependent on its transport to the interface. Morphological evolution during the early stages of TSV filling reveals two distinct growth front geometries. For dilute polymer concentrations, an initial bifurcation into passive-active surfaces occurs on the side walls of the TSVs followed by bottom-up fill. The depth of the initial sidewall bifurcation within the via increases with polymer concentration. For higher polymer concentrations, i.e. ≥ 25 μmol/L, active metal deposition is rapidly confined to the bottom surface of the via followed by sustained bottom-up filling.

Superconformal Film Growth: From Smoothing Surfaces to Interconnect Technology

“…For higher additive concentrations, e.g., Cl – ≥ 100 μmol/L and poloxamine ≥20 μmol/L, suppressor breakdown occurs at more negative potentials where the overpotential for metal deposition is large so that substantial Cu 2+ depletion occurs adjacent to the active bottom-up growth front and constrains the growth velocity. Bottom-up growth originates near the bottom of 6 μm wide × 60 μm deep annular vias and propagates upward, with the growth front changing from concave to flat or convex profiles depending on conditions and the sampling point in the evolution (Figures and ). ,,, For larger TSVs, 125 μm in diameter and 625 μm deep, the convex shape is even more pronounced . A trend toward ⟨110⟩ texture develops normal to the active growth front, reflecting the influence of Cl – on the polymer-disrupted and/or -denuded growth surface .…”

“…Bottom-up growth originates near the bottom of 6 μm wide × 60 μm deep annular vias and propagates upward, with the growth front changing from concave to flat or convex profiles depending on conditions and the sampling point in the evolution (Figures 9 and 10). 2,8,9,75 For larger TSVs, 125 μm in diameter and 625 μm deep, the convex shape is even more pronounced. 77 A trend toward ⟨110⟩ texture develops normal to the active growth front, reflecting the influence of Cl − on the polymer-disrupted and/or -denuded growth surface.…”

“…Simulations of TSV filling based on a single suppressor additive consumed within the growing deposit are consistent with successful bottom-up filling experiments (black dots in the green zone). Adapted from refs , , and and not subject to U.S. copyright.…”

Toward Preeminent Throwing Power from a Novel Alkaline Copper Electronic Electroplating Bath with Composite Coordination Agents

“…During the acid sulfate copper electronic electroplating, it is often difficult to regulate the additives because of their complicated synergistic effects and different consumption rates. [14][15][16][17] Besides, without the assistance of expensive pulse electroplating power, the throwing power of sulfate copper electroplating bath is quite low to 56.0 % or worse in the through holes (THs) with 400 μm depth and 100 μm hole diameter. [18] Compared with acidic copper sulfate plating process, a weak alkaline copper electroplating bath with citrate as the complexant is not corrosive and does not contain phosphorus.…”

Superconductivity of Electrodeposited Sn Films

“…[1][2][3] Electrodeposited superconducting structures would naturally become a candidate choice as the copper counterparts have been manufactured using similar approaches for the conventional semiconductor integrated circuits. [4][5][6] In those processes, organic additives are typically used to tune the Cu growth rates at different locations, resulting in defect free filling of metal structures. Among the superconducting metals, Sn presents a reasonably high superconducting transition temperature, i.e., the critical temperature T c at 3.7 K, in its crystalline bulk form 7 and provides good manufacturing compatibility.…”