Cyclic Voltammetry Stripping Analysis to Determine Iodide Ion Concentration in Cu Plating Bath. Issue 5 (1st January 2018)

• Record Type: Journal Article
• Authors: Yoon, Young; Ham, Yu Seok; Kim, Tae Young; Choe, Seunghoe; Kim, Jae Jeong
• Is Part Of: Journal of the Electrochemical Society. Volume 165:Issue 5(2018)
• Page Start: H213
• Page End: H218
• Publication Date: 2018-01-01
• Subjects: cyclic voltammetry strpping -- iodide ion -- Through silicon via; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0471805jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Accurate monitoring of an electroplating bath's chemical balance is a key factor for maintaining its performance during a long-term plating operation. In this paper, a method is suggested to measure the concentration of iodide ion (I − ), an inorganic leveler for through-silicon via (TSV) filling, based on its electrochemical response. During the operation of plating, I − was consumed via the reaction with Cu + (Cu + + I → CuI), an oxidation reaction (2I − → I2 + 2e), as well as a physical incorporation. The I − concentration decrease resulted in a degradation of the bath, while the major byproducts (CuI and I2 ) rarely influenced on bath performance. In order to monitor the I − concentration by cyclic voltammetry stripping (CVS) analysis, the electrochemical response of I − was examined at various conditions. I − suppressed the Cu electrodeposition rate; this response was dependent on the mass transport of I − and the applied potential of cathode. A subsequent effective coverage analysis revealed that not only I − but also Cu(I) iodide (CuI) was a key inhibitor, demonstrating that the inhibition of I − becomes weaker at a negative potential. With a responsive curve (RC)-CVS analysis conducted at an optimized condition, a linear relationship between the real and measured concentrations could be found, irrespective of other additives' concentrations. The method suggested in this paper enabled the direct monitoring of the I − concentration in a Cu plating bath.