Role of Chloride Ions in Suppression of Copper Electrodeposition by Polyethylene Glycol

Abstract

Chloride ions and polyethylene glycol ͑PEG͒ are used together as additives to copper damascene electroplating baths, in which they suppress deposition. When the Cl − concentration is lower than the order of 1 mM, suppression abruptly breaks down below a critical potential, around which hysteresis between active and inhibited deposition is observed. A mathematical model is presented which successfully predicts the observed Cl − concentration-dependent breakdown of PEG suppression and currentpotential hysteresis. The model assumes that adsorbed Cl − ions are involved in binding of PEG to the Cu surface, and that these ions are incorporated in the deposited film. The expressions for Cl − incorporation and adsorption are consistent with experimental measurements of Cl in deposits. Hysteresis was found to depend on the high sensitivity of polymer surface coverage to the concentration of adsorbed Cl − ions, possibly because each PEG molecule has a small number of binding sites to the surface.

Filling TSV of different dimension using galvanic copper deposition

“…Chloride acts as a specific anchor for suppressor molecules like polyethylene glycol (PEG). [4,5,6] In galvanostatic chronopotentiometric injection experiments a rapid increase of overpotential is obtained after suppressor addition. [1,7] (Figure 1 test 1 and 2) Accelerators are small molecules as mercaptopropane sulfonic acid (MPS) and MPS delivering molecules.…”

Communication—Conical TSV Filling within 30 Seconds

“…10 The charge for stripping copper is less than the requirement, because, instead of becoming the cupric ions, a part of copper atoms becomes cuprous ions then disperses to the electrolyte especially at a higher rotating rate. 10,[16][17][18] Then, they are oxidized to cupric by dissolving oxygen in bulk.…”

Polyquaternium-2: A New Levelling Agent for Copper Electroplating from Acidic Sulphate Bath

“…The synergy of these additives stemmed from the adsorptive and transport characteristics of chloride ions and from the competitive interaction between the suppressor, accelerator, and leveler. 13,[35][36][37][38][39][40][41][42][43][44][45][46][47] In order to further analysis the function of Polyquaternium-2 in TH electroplating process, the addition sequence was changed again (the addition sequence followed the description in Table 1) and the result was shown in Fig. 9.…”