Evaluating the Filling Performance of a Copper Plating Formula Using a Simple Galvanostat Method

Abstract

This work presents a feasible galvanostat method using a copper working electrode that was individually operated at two different rotation speeds to accurately predict the filling performance of a copper plating formula for microvia filling. This approach is based on the convection-dependent adsorption ͑CDA͒ of additives. Of six copper-plating formulas, formulated to examine the applicability of this method, four were effective for bottom-up filling and two were ineffective. In contrast with the microvia cross sections, it was demonstrated that this approach is effective to evaluate the workability of a plating formula in microvia filling. A relationship between the filling performance and the leveler concentration of a plating formula that was composed of polyethylene glycol, bis͑3-sulfopropyl͒ disulfide, and Janus Green B was also examined by using the galvanostatic measurement. The final results showed that the variation trend of the filling performance with the leveler concentration coincided with that of the potential difference obtained from the galvanostatic measurement.

Towards Structural Analysis of Polymeric Contaminants in Electrodeposited Cu films

“…In this way, the suppressing effect of the PAG chemistry is effective predominantly at the upper feature side walls and the 3 topmost wafer surface whereas the SPS accelerated copper deposition occurs preferentially at the feature bottom, thus leading to the desired differential electrodeposition. The third constituent of the electroplating bath, the so-called leveler (type-II suppressor) is meant to hinder undesired sustained copper growth (overplating, momentum plating) at the final stage of the deposition process over filled features [20,21]. The leveler action prevents the formation of Cu bumps and their coalescence over dense fields of filled trenches or vias (mounding) which is highly disadvantageous in the subsequent CMP (chemical mechanical polishing) process step [21].…”

Superconformal Filling of High Aspect Ratio through Glass Vias (TGV) for Interposer Applications Using TNBT and NTBC Additives

“…[15][16][17] Dow observed that systems employing these additives, without the use of an accelerator, could be manipulated to suppress deposition on the outer surfaces and near the entrances of holes while allowing the fastest plating to occur in the middles of the holes. Low current densities (1 to 1.6 mA cm −2 ) and long plating times (9 to 12 h) were required.…”

“…Plugging is then followed by continued filling of the 'blind' holes formed on either side of the plugs. [15][16][17]19 The degree of convection, 15,20 the solution pH, and the specific acid 20 used were found to be important factors in achieving void-free Cu filling of through-holes. These parameters also affect the degree of incorporation of organic species into the Cu deposit and the morphology of the Cu deposit.…”

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

“…This phenomenon should stem from a convection-dependent competitive adsorption of additives, whose original occasion was attributed to the potentialdependent adsorption of chloride ions. 13,29,31,34 Figure 7b showed that the cathodic potential was not significantly changed after SPS injection, implying that there was no significant interaction among Polyquaternium-2, chloride ion, and SPS at the low potential. The deposition rate of copper was Cu (II) diffusion-controlled when Polyquaternium-2, chloride ions, and SPS presented in plating solution.…”

“…The potential difference at different rotating speed, "©, defined by "© = © 1 (100 rpm) ¹ © 2 (1000 rpm), was used to evaluate the performance of plating. [29][30][31] If the value is positive, it meant that strong convection resulted in less copper deposition; 20 thus, the plating solution might be effective for TH plating, whereas it was ineffective for TH plating if "© was zero or negative. In this study, it was used to characterize the electrochemical behavior of Polyquaternium-2 and it's interaction with other additives in the system.…”