Electrodeposition of Cu Films with Low Resistivity and Improved Hardness Using Additive Derivatization

Abstract

The adsorption mechanism of thiourea (TU) and its effect on Cu electrodeposition were verified using TU derivatization. Contrary to the previously reported behavior of TU as an inhibitor, TU either promoted or inhibited Cu reduction according to the derivatization time. During the short derivatization time, the adsorbed TU with low surface coverage was oxidized to spontaneously reduce Cu 2+ to Cu + , thereby, accelerating the Cu deposition. However, TU inhibited the Cu deposition as the coverage of TU-Cu + increased with the derivatization time. Furthermore, a deterioration in the resistivity of the Cu film, which occurred when TU was added, was largely improved by the derivatization method while maintaining an enhancement in the film hardness. TU derivatization resulted in a 9.2% enhancement in the film hardness and only a 26.0% deterioration in the film resistivity compared to those of Cu films deposited in the absence of TU, which were not simultaneously obtainable upon the direct addition of TU to the deposition bath.

Communication—Acceleration of TSV Filling by Adding Thiourea to PEG-PPG-SPS-I−

“…13 Furthermore, TU can chemically adsorb onto the Cu surface via sulfur atoms in TU, forming the significant suppression layer against Cu electrodeposition. [14][15][16] Therefore, we expected that TU can stabilize PEG-PPG adlayers on the Cu surface, and improve TSV filling at a higher current density.…”

Monitoring of SPS Concentration by the Ring Current Using a Rotating Ring-Disk Electrode with Dissolving Disk Copper to Refresh a Void Free Solution

“…2,3 Though the amount of accelerator is small, it plays an important role on accelerating the bottom-up filling, leads to void free filling. [4][5][6][7][8][9][10][11][12][13] One of the most widely used accelerators is SPS, a dimer of MPS. However, SPS contains a disulfide linkage which is unstable, easily decomposed through oxidation reactions at anode or reduction reactions at cathode.…”

Accuracy Improvement in Cyclic Voltammetry Stripping Analysis of Thiourea Concentration in Copper Plating Baths

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Examples of organic additives in electroplating baths include bis(3-sulfopropyl) disulfide, polyethylene glycol (PEG), janus green b (JGB), polyethylene imine (PEI), 1,2,3-benzotriazole (BTA), and thiourea (TU). 1,2,[6][7][8][9][10][11][12][13][18][19][20][21][22][23][24][25][26][27][28][29] TU is a common additive in Cu and Ag electrodeposition baths and induces leveling and grain refining properties. [18][19][20][21][22][23][24][25][26] TU has been used as an additive either solely or in combination with Cl − (TU-Cl − ) in baths used for electrodeposition processes involving various c...…”

“…18,19,[23][24][25][26] TU is known to form thiolate complexes such as [Cu-(TU)] 2+ , [Cu-TU] + , and [Cu-(TU) 2 ] 2+ with Cu 2+ ions in acidic Cu plating solutions. [20][21][22][23][24][25][26][27][28][29] Additionally, TU can be oxidized to formamidine disulfide (FDS), which forms other thiolate complexes with Cu + and Cu 2+ ions. [27][28][29] Owing to the various derivatives and their different electrochemical responses, TU shows unique electrochemical behavior unlike typical suppressors or levelers.…”

“…[20][21][22][23][24][25][26][27][28][29] Additionally, TU can be oxidized to formamidine disulfide (FDS), which forms other thiolate complexes with Cu + and Cu 2+ ions. [27][28][29] Owing to the various derivatives and their different electrochemical responses, TU shows unique electrochemical behavior unlike typical suppressors or levelers. Although TU commonly reduces the Cu deposition rate, it often acts in an opposite role as an accelerator under specific conditions such as low concentrations and low overpotentials.…”