Additive Behavior during Copper Electrodeposition in Solutions Containing Cl[sup −], PEG, and SPS

We present a tertiary current-distribution model for copper electrodeposition under galvanostatic conditions, with detailed surface chemistry kinetics for the model system of copper electrodeposition. The values of the kinetic parameters are extracted from results of statistical chronoamperometry and linear sweep voltammetry experiments using a potential-dependent, diffusion-adsorptiondesorption model of the experimental system. The resulting surface chemistry description is combined with fundamental conservation laws, including mass transport, potential distribution, and competitive adsorption, to form the tertiary current distribution model. Two-dimensional finite element simulations of this model provide information about the causes of the thickness of the copper electrodeposition layer, including potential variations of the cathodic surface, fluctuations in the cupric ion concentration and coverage of the accelerator. The model is used to predict the filling process with different current densities and SPS concentrations and is verified by copper electrodeposition experiments. The "optimal zone" was determined for the SPS concentration and the inward current density to achieve good TSV filling. Sample points in the outer zone were selected and the failure mechanism was studied to help to infer the right direction toward the "optimal zone" in copper electrodeposition. The models are potentially useful tools for measuring the properties of electrolyte solutions and for the optimization of copper electrodeposition processes. Through-Silicon via (TSV) is one of key techniques for 3D integration with many advantages. The electroplated copper is a major interconnect material in TSV due to its high electrical conductivity, lower cost than alternative deposition methods.1,2 Copper electrodeposition as an efficient method of metallization is widely accepted, and it has been proposed by many researchers. [3][4][5] According to the feature of TSV on chip, some special additives such as accelerator (Bis-(3-sulfopropyl) disulfide, or SPS), suppressor (Polyethylene glycol, or PEG), leveler (Janus Green B) and Cl − , are usually applied in electrolyte solution to assist copper filling with void-free.6-8 An appropriate distribution of additives provides a fast growth at the bottom and the growth rate at via opening is suppressed, as improper distribution of additives result in unfilled feature.9 Hence, behaviors of additives on the cathode surface are very important for TSV filling process. However, there are still some challenges for establishing the optimal process for copper filling because the influence of feature of TSV, complicated mechanisms of additives behaviors and complicated fabricated process.2 A predictive numerical model of the copper electrodeposition process is a very helpful tool to investigate the optimal process with some advantages, such as low cost and efficiency. A typical numerical model should have the ability to predict feature evolution of copper electrodeposition under different operating conditi...

Section: 43mentioning

confidence: 99%

“…PEG concentration was kept at 300 ppm, according to the investigation by M. Tan et al 48 In Figure 1, the steady SPS surface coverage of 4 ppm SPS is 88%. It is assumed that the electrode was fully SPS-activated or PEG-inhibited as the electrolyte containing only SPS or PEG.…”

Section: 43mentioning

confidence: 99%

RETRACTED: Copper Electrodeposition in Through-Silicon Via under Galvanostatic Condition

Luo

Chen

Zhang

et al. 2016

“…As shown in Table II, 50 ppm chloride ions (Cl -as HCl), 100 ppm polyethylene glycol with a mean molecular weight of 2000 (PEG2000: PEG), 2 ppm bis(3-sulfopropyl)disulfide (SPS), and 2 ppm Janus green B (JGB) were added to the base plating bath as additives (copper filling additives). [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65] The volume of the plating baths was ca. 100 cm 3 .…”

Section: Methodsmentioning

confidence: 99%

Fabrication of Copper/Single-Walled Carbon Nanotube Composites by Electrodeposition Using Free-Standing Nanotube Film

Arai

Kirihata

Ueda

et al. 2017

Copper/single-walled carbon nanotube (SWCNT) composites were fabricated by electrodeposition using a freestanding SWCNT film as a template. The SWCNT films were directly electrodeposited to form copper/SWCNT composites. An acidic copper sulfate bath was employed as a basic plating bath, and the effects of additives to the basic bath on the morphologies of copper deposits were examined. Poly(ethylene glycol), chloride ions (Cl -), bis(3-sulfopropyl)disulfide (SPS), and Janus green B (JGB) were added individually or in combination as additives. Electrodeposition of copper occurred only on the surface of the SWCNT film when using the basic plating bath without additives. In contrast, copper was deposited not only on the surface but also in the interior of the SWCNT film when using the plating baths containing at least PEG and Cl -, resulting in copper/SWCNT composites. Electrodeposition of copper inside the SWCNT film was accelerated dramatically when all four additives (PEG, Cl -, SPS, and JGB) were added to the basic bath. This novel fabrication method of copper/CNT composites using CNT films as templates can be applied to the fabrication of various types of metal/CNT composites. Carbon nanotubes (CNTs) exhibit high thermal conductivity 1-6 and high current-carrying capacity (ampacity) 7 as well as excellent mechanical characteristics.8-10 Therefore, the development of practical applications of CNTs is an active area of research. Copper/CNT composites are promising materials, especially in the electronics field, and many fabrication methods, such as spark plasma sintering, [19][20][21][22][23] have been reported. The CNT composite plating has advantages, such as the uniform distribution of CNTs in metal matrices derived from a homogeneous dispersion of CNTs in plating baths, which results in little damage to CNTs due to dispersant addition at room temperature instead of direct grafting of hydrophilic groups that makes CNTs hydrophilic. Copper/CNT composite films possess excellent tribological 24,25 and field emission 26,27 properties. However, in general, the CNT content in electrodeposited composites is low (ca. 0.5 mass% 22 ), which could lead to insufficient thermal conductivity. 22 Therefore, other methods to obtain copper/CNT composites with a greater CNT content are needed.Recently, a freestanding, thin CNT film, 28,29 made from an aggregate of CNTs and so-called "bucky paper," has attracted considerable attention for its application as high efficiency filters, 30,31 displays, 32 lithium-ion battery anodes, 33 and supercapacitors. 34,35 Furthermore, composites using freestanding CNT films as flexible scaffolds for active materials have been investigated particularly intensively for their application to rechargeable batteries. [36][37][38][39][40][41][42][43][44][45][46][47][48] Electrodeposition of copper inside the freestanding CNT film was expected to be an effective method for forming copper/CNT composites with greater CNT content. However, few studies on direct electrodeposition not limited to copper o...

“…A ads + S bulk [1] The equilibrium constant of the adsorption reaction is defined as adsorption constant k, indicating the ratio of adsorption and desorption rate. Together with the additive bulk concentration c, the adsorption constant determines the liquid/surface additive interactions.…”

Section: A Bulk + S Adsmentioning

confidence: 99%

The Influence of Adsorption Kinetics on Copper Superfilling for Dual Damascene

Liske

Krause

Uhlig

et al. 2016

The proceeding scaling in microelectronic devices requires smaller and smaller copper wires for energy transfer in integrated devices. Voids in the copper wires lead to a resistance increase and damage of the wiring. Copper wires are fabricated by electrochemical deposition as it enables a bottom-up, void free copper growth, so-called superfilling. The present work focuses on the mechanism of the electrochemical deposition with the goal of understanding and describing the superfilling. Electrochemical measurements and partial fill experiments under production-like conditions are carried out to study the effects of bath additives. The co-adsorption theory is adopted to explain additive interaction which is presumed to be the key for superfilling. It is shown that superfilling is a result of the synergetic adsorption behavior of at least two organic additives and a kinetic balancing between additive accumulation and copper deposition rate.