Scanning Tunneling Microscopy of Superfilling in Formula Containing Chloride, Polyethylene Glycol and Bis-3-Sodiumsulfopropyl-Disulfide

Abstract

In situ scanning tunneling microscopy (STM) was used to study copper deposition at vacancy defects on a copper thin film under potentiostatic conditions at −0.20 V (vs. Ag/AgCl) in a formula containing sulfuric acid, chloride, polyethylene glycol (PEG), and bis-3-sodiumsulfopropyl-disulfide (SPS) -the widely used mixture to facilitate Cu superfilling at recessed features in semiconductor processing. The vacancy island measuring ∼70 nm wide and 12 nm deep sat in the middle of a facetted surface structure at the beginning. Cu deposit nucleated mainly at the rim of the vacancy and grew into stacked Cu(111) facets. These local pyramidal Cu stacks could restructure into wider Cu(111) terraces by transferring Cu atoms rapidly from higher to lower planes. Voltammetric results showed that Cu deposition was suppressed in a plating bath containing 1 mM KCl + 88 μM PEG8000 + 10 −7 M SPS.Steps with sharp edges bunched in the course of Cu deposition. The vacancy island was filled with Cu deposit assuming smooth terraces with sharp step edges aligned mainly in the 121 directions of the Pt(111) electrode, suggesting crystalline packing in the Cu deposit. Atomic-resolution STM imaging revealed a hexagonal array presumed to be the ( √ 3 × √ 3)R30 • -Cl − adlattice.

In Situ Measurement for Diffusion-Adsorption Process of Cl− and SPS in Through-Silicon Via Using SERS Effect Produced by Cu Nanodot Arrays

“…[12][13][14][15][16] Many studies have attempted to determine the additive behavior at the electrode surface, using various techniques such as electrochemical measurements and scanning tunneling microscopy (STM). [17][18][19][20][21] Dow et al analyzed the behavior of additives by STM and suggested that an accelerator with the thiol and sulfonate groups promoted electrodeposition. This is because the sulfonate group attracts and transfers Cu ions to chloride ions (Cl − ) on the electrode surface, which promotes electron transfer from the electrode toward the Cu ions through the Cl − .…”

Contrasts in Copper Deposition on Pt(111) Modified by 1-Mercaptopropionic and 1-Mercaptoacetic Acids as Probed by Voltammetry and STM

“…[8][9][10] The real-time and real-space imaging capability of scanning tunneling microscopy (STM) has been used to examine Cu deposition on Au and Pt single crystal electrodes. [11][12][13][14][15] Molecular-resolution STM imaging of the interface of the Cu deposit on these electrodes has revealed the spatial structures of adspecies, giving insights into the segregation of thiol molecules pre-deposited on the substrates. The MPA modifier to Au(111) results in marked differences in Cu deposition, although it is not imaged by in situ STM.…”

Rapid Determination of the Electrodeposition Potential for Cu Superfilling Using a Nanocones Array Structured Electrode

“…Bis-(3-sulfopropyl) disulfide (SPS) functionalized by disulfide bonds and sulfonic head groups is a typically accelerator and polyethylene glycol (PEG) is by far the most widely studied suppressor. [7][8][9] Complex competitive adsorption of the two additives has been extensively studied by electrochemical analysis of flat electrodes [10][11][12] and morphological characterization of feature filling. [13][14][15] Based on the fundamental knowledge regarding additive interactions, adsorption, desorption, and incorporation, several theoretical models have been developed to describe the additive behavior and the evolution of shape profiles during feature filling.…”