Copper Sulfate Plating Research Articles

Investigation of poly (2-methyl imidazole co 1,4-butanediol diglycidyl ether) as a leveler for blind hole copper plating

<p>The current synthetic leveler agents are complex to operate, troublesome to purify, and low to pore filling rates. Herein, we report a new, simple, green, and inexpensive method for the synthesis of leveler agents and study their properties systematically. In acidic copper sulfate plating solutions, including polyethylene glycol (PEG), sodium 3,3’-dithiodipropane sulfonate (SPS), and chloride ions, the relation between leveler agents (dimethylimidazole and 1,4-butanediol diglycidyl ether) and the filling of blind holes have been investigated. The synthesized leveler agent was structurally characterized by infrared spectroscopy and gel chromatography tests. The plating containing the leveler agent passed plating tests as well as reliability tests and met PCB production requirements. The electrochemical behavior of the leveler agent was investigated using electrochemical tests. The X-ray diffractometer (XRD) was used to observe the differences in crystal orientation on the surface of the plated layers.<strong></strong></p>

TSV Filling with Copper Electro-deposition by Using Sodium 3-[[(dimethylamino) thioxomethyl] thio] Propane Sulphonate

Through Silicon Via (TSV) is a promising microelectronic interconnection technology in Three-D integration (3D). Three-component additives are used for non-porous TSV filling. However, various experiments must be carried out to optimize the concentrations of various additives. To avoid this costly process, Two-component additives were developed. In this paper, Sodium 3-[[(dimethylamino) thioxomethyl] thio] propane sulphonate (DPS) in the TSV filling is investigated. Only by DPS in TSV copper sulfate plating, copper ions cannot reach the bottom of the micro-hole, and copper deposits at the TSV orifice. The addition of dimethyl formamide based on the structure of MPS enhances the inhibition of DPS and may show a weak inhibition during the copper plating and filling process of TSV. 0.1 g/L DPS and 1 g/L AESS, with ampere density2 mA/cm2 and a plating time of 12 h, can obtain perfect defect-free TSV filling.

(Invited) In-Situ Observation of Copper Electroplating with Additives Using Micofluidic Devices

Recent advances in integrated circuit have been driven by packaging technology. 3D packaging using TSV (Through-Silicon Via) is becoming common in commercial products. TSVs are formed by filling deep holes with a conductive material. Copper is widely used as the conductive material, since filling the deep holes with copper is enabled by bottom-up electrodeposition using a combination of several additives. Suppressors, levelers, and accelerators are well known categories of additive to acid copper sulfate plating solutions. Bottom-up deposition is realized by various additive formulas. Using leveler alone as additive, extreme bottom-up filling has been demonstrated, and levelers are considered to be essential for bottom-up deposition. But the mechanism is not yet clear with multiple additives addition.Therefore, understanding of additive behaviors is important. Cyclic voltammetry using a rotational disk electrode has been widely used in additive studies, but interpretation of the results is not easy because adsorption occurs simultaneously with deactivation. The history of additive supply onto the plating surface also influences the hysteretic behavior. Recently, we constructed a microfluidic device in which flow cell experiments and rapid switching of the plating solution are enabled. Using the device, characteristic behavior of leveler, strong suppression and rapid deactivation, was directly observed optical microscopically and electrochemically, and difference with levelers and suppressors was clarified. Further, a TSV-like structure with similar dimensions to real TSVs was constructed in a microchannel, and real-time optical observation of bottom-up deposition was demonstrated.References T. Akita, et al., J. Electrochem. Soc., 166(1), D3058 (2019)M. Tomie, et al., J. Electrochem. Soc., 167, 082513 (2020)T. Akita, Y. Otsuka, M. Hayase, J. Electrochem. Soc., 167, 162515 (2020)

Advances in mechanistic understanding of additives for copper electroplating in high-end electronics manufacture

<p indent=0mm>Copper interconnect electroplating is one of the core technologies for the manufacture of high-end electronic devices including but not limited to chips. To promote the development of advanced copper interconnect process, it is necessary to clarify the mechanisms of copper electroplating additives. Herein, we provide a brief overview of the research progress on the interfacial structures and mechanisms of the three types of additives (accelerator, suppressor and leveler) in copper sulfate plating baths from a methodological perspective. Besides, the advantages and limitations of different research methods are discussed and the scientific issues related to the Damascene copper electroplating are summarized, to afford a hint for the further research and development of the additives in advanced chip fabrication.

In-Situ Observation of Electrodeposition in a Microfluidic Device with through Silicon Via Model

Nowadays, the high performance of integrated circuits is due to packaging technologies, and 3d-packaging using TSVs (Through Silicon Vias) have entered use in commercial products. Copper electroplating is used to form TSVs, since bottom-up filling is available using a combination of several additives, but the filling mechanism is not clear yet. Recently, we have observed the adsorption and deactivation behavior of typical suppressing additives by using a disk electrode with a diameter of 100 μm in a microchannel that allows precise control of mass transport [1]. In this study, in order to understand the details of the TSV filling behavior, we propose a microfluidic device that has TSV feature in the channel, and in-situ observation of the electrodeposition behavior is enabled.The microfluidic device was fabricated using the silicon substrate. First, Au is sputtered on the silicon substrate and the Au film is patterned by photolithography and wet etching. Then, the micro channel is defined by a 19 μm thick photoresist pattern on the silicon substrate. In the micro channel, a rectangular area on Au film is exposed. The exposed Au film and the surrounding resist pattern model the TSV. The width, height, and depth of the via are 20 μm, 19 μm and 100 μm, respectively. Finally, a glass cover plate is put on the substrate, and the microchannel is mounted on a base. A mercury sulfate electrode (MSE) is connected to the resin base and works as a reference electrode. A copper wire is inserted into the outlet tube and works as a counter electrode.An acid copper sulfate plating solution was prepared as a VMS (Virgin Makeup Solution). Initially, additive-free VMS was supplied, and the working electrode was pre-plated with copper. Then, the solution was switched to the VMS + Leveler and open circuit potential was maintained for 120 s. Finally, -600 mV vs. MSE was applied on the working electrode, and plating behavior was observed. Figure 1 shows the appearance of the working electrode along time. At 5 s, clear interface was observed at the depth around 20 μm from the opening of the via. Below the interface, the working electrode became dark because the deposition proceeded. While no obvious change was observed above the interface and it was found that the deposition was strongly suppressed by the leveler adsorption. The interface line inclined and it was assumed that the leveler penetrated deeper in downstream side because of the solution flow.Reference[1] T. Akita, M. Tomie, R. Ikuta, H. Egoshi, and M. Hayase, J. Electrochem. Soc., 166(1), D3058 (2019). Figure 1

Application of Fluid Simulation in High-Speed Copper Sulfate Plating Using a Jet Flow Device

Application of Fluid Simulation in High-Speed Copper Sulfate Plating Using a Jet Flow Device

Physical Properties of Deposits and Three-Dimensional Structures Prepared By High-Speed Electrolytic Copper Plating Using a Jet Flow Device

Since copper has excellent properties such as malleability and conductivity, it is widely used in the electronics field. Copper sulfate plating is expanding further in fields requiring thick deposits such as for heat dissipation boards and bumps for stress relaxation during semiconductor mounting. In order to improve productivity and reduce cost, high speed electroplating using high current density is desired. However, in electroplating under high current density, abnormal deposition such as burnt deposits and dendrites due to insufficient supply of the metal ion. In order to facilitate the supply of the metal ion, our group focused on mechanical agitation type jet devices rather than conventional air or paddle agitation. In this study, the physical properties of deposits prepared by conventional copper sulfate plating at 5 A/dm2 and the high speed copper plating at 30 or 50 A/dm2 were compared. Furthermore, the high-speed copper sulfate plating method was applied to wiring and bump resist patterns where production of three-dimensional structures was demonstrated. 20×30 mm cut copper plates were used as the test substrate, which were treated with the alkaline degreasing and the acid activation prior to plating. Three kinds of additives Bis-(3-sulfopropyl) disulfide (SPS), Janus Green B (JGB) and Polyethelene glycol-20000 (PEG-20000) were used in the copper sulfate plating solution. Samples were annealed at 120°C for 60 min after plating. Investigation of physical properties was conducted by comparison of crystal orientation measured by X-ray diffraction (XRD) and electrical conductivity measured by sheet resistance. Furthermore, the etching rate of each film was calculated from the mass loss per unit etching time. The additives were optimized for preparation of the three-dimensional structures. The current density was swept at an arbitrary speed from 0 A/dm2 to a target current density, and once reached, the current density was maintained until the target film thickness was obtained. The test substrate after plating was subjected to resist observation and then to observation using a scanning electron microscope (SEM). Fig. 1 shows the crystal orientation attained at each current density. It was confirmed that both films produced at the current densities of 30 and 50 A/dm2 by high speed copper plating and the film produced at 5 A/dm2 using the conventional method were oriented with 60% of the 111 crystal phase. The sheet resistance values of all three films exhibited approximately the same value of 0.93 to 0.95 Ω/sq. . On the other hand, the etching rate of the films produced by high-speed copper plating were 2.5 µm/min, whereas that of the film produced by the conventional method was 1.7µm/min. Fig. 2 shows the wiring pattern filled with 30 A/dm2. It was confirmed that pattern filling by high speed plating can be accomplished 10 times faster than with the conventional method. Resist pattern filling by plating at higher current density will be discussed in detail. The high-speed copper plating film using a jet flow device has the near physical properties as the conventional method. Furthermore, since filling of the pattern substrate can be performed in a short time, it is considered that it can contribute to improvement of productivity in the electronic field. Figure 1

Accumulation and Analysis of Cuprous Ions in a Copper Sulfate Plating Solution.

Knowledge of the behavior of cuprous ions (monovalent copper ion: Cu(I)) in a copper sulfate plating bath is important for improving the plating process. We successfully developed a method to quantitatively and easily measure Cu(I) in a plating solution and used it for evaluation of the solution. In this paper, a quantitative absorption spectrum measurement and a time-resolved injection measurement of Cu(I) concentrations by a color reaction are described. This procedure is effective as a method to reproduce and elucidate the phenomenon occurring in the plating bath in the laboratory. First, the formation and accumulation process of Cu(I) in solution by electrolysis of a plating solution is shown. The amount of Cu(I) in the solution is increased by electrolysis at higher current values ​​than the usual plating process. For the determination of Cu(I), BCS (bathocuproinedisulfonic acid, disodium salt), a reagent that selectively reacts with Cu(I), is used. The concentration of Cu(I) can be calculated from the absorbance of the Cu(I)-BCS complex. Next, the time measurement of the color reaction is described. The color reaction curve of Cu(I) and BCS measured by the injection method can be decomposed into an instantaneous component and a delay component. By analysis of these components, the holding structure of Cu(I) can be clarified, and this information is important when predicting the quality of the plating film to be produced. This method is used to facilitate the evaluation of the plating bath in the production line.

Accumulation and Analysis of Cuprous Ions in a Copper Sulfate Plating Solution

Accumulation and Analysis of Cuprous Ions in a Copper Sulfate Plating Solution

Quenching characteristics of bathocuproinedisulfonic acid, disodium salt in aqueous solution and copper sulfate plating solution

Bathocuproinedisulfonic acid, disodium salt (BCS) is generally used to detect Cu(I) through a color reaction. We newly found BCS fluorescence in the visible blue region in an aqueous solution. However, the fluorescence mechanism of BCS is not well known, so we should investigate its fundamental information. We confirmed that the characteristics of fluorescence are highly dependent on the molecular concentration and solvent properties. In particular, owing to the presence of the copper compound, the fluorescence intensity extremely decreases. By fluorescence quenching, we observed that a copper compound concentration of 10−6 mol/L or less could easily be measured in an aqueous solution. We also observed BCS fluorescence in copper sulfate plating solution and the possibility of detecting monovalent copper by fluorescence reabsorption.

Spectroscopic and Electrochemical Analysis of Cu(I) in Electroplating Solution and Evaluation of Plated Films

In this study, we investigated the behavior of the cuprous ion (Cu(I)) in a copper sulfate plating solution and the effects of Cu(I) on the quality of the resultant copper plating film. Through spectroscopic methods, two kinds of Cu(I)-containing compounds in the plating solution were identified by analyzing the kinetics of the complex forming reactions between Cu(I) and the disodium salt of bathocuproinedisulfonic acid (BCS). The first Cu(I) component reacts slowly with BCS and probably incorporated deep inside the polyethylene glycol (PEG) matrix; thus, Cu(I) is sterically hindered by PEG, preventing interactions with the BCS in the plating solution. The other Cu(I) component can instantaneously react with BCS, forming a complex. In addition, interestingly, it has been shown that the instantaneous component affects the roughness of copper plating films. These results indicate that spectroscopic measurement and analysis is effective for the management and evaluation of plating solutions for high-quality production.

Spectroscopic and Electrochemical Analysis of Cu(I) Complex of Copper Sulfate Electroplating Solution and Evaluation of Plated Films

In this study, we investigated a behavior of cuprous ion (denoted as Cu(I)) in the copper sulfate plating solution and effects of the Cu(I) on a quality of Cu plating film. Through spectroscopic method, two kinds of holding structure of Cu(I) in the plating solution were firstly indicated by analyzing the kinetics of complex forming reaction between the Cu (I) and bathocuproinedisulfonic acid, disodium salt (BCS). One component is ignited from Cu(I) probably incorporated into deep inside of polyethylene glycol (PEG), and the Cu(I) must have steric hindrance of PEG to be interacted with the BCS in plating solution. Another one is a component for Cu(I) which can be instantaneously reacts to the BCS to be complex. In addition, interestingly, it has been shown that instantaneous component is affecting the roughness of Cu plating film. These results indicate that spectroscopic measurement and analysis is effective for the management and evaluation of the plating solution for high quality production.

Fabrication of Three-Dimensional Cu/CNT Composite Film By Electrodeposition

Introduction Three-dimensional metallic materials have large surface area and high electrical conductivity, and have thus attracted attention as electrode materials for applications such as lithium-ion batteries, electric double-layer capacitors and electrochemical sensors. Methods such as de-alloying1) and electrodeposition with a template2,3) are generally used in the fabrication of three-dimensional metallic materials. These methods, however, take great deal of times and costs. Our laboratory has reported that a three-dimensional copper structure can be simply fabricated by electrodeposition from a copper sulfate plating bath containing polyacrylic acid.4) The fabrication of thicker three-dimensional structures is desirable in order to obtain larger surface areas, though the thickness of the three-dimensional structure was only approximately several micrometers.In addition, the three-dimensional structure has low strength because it is composed of a thin copper sheet. Therefore, the three-dimensional structure could be deformed in the case of thickening the structural layer. Carbon nanotubes (CNTs) are expected to be applied in a wide range of fields. We consider that the embedding of CNTs into the copper sheets in the three-dimensional structure by means of electroplating can reinforce the structural integrity even when thickened. Therefore, in this study, the fabrication of a three-dimensional Cu/CNT composite film by electrodeposition was attempted to realize reinforcement of the three-dimensional structure and an increased surface area. Experimental A copper plating bath for three-dimensional copper film was prepared by the addition of polyacrylic acid (M.W. 5000) to a copper sulfate bath (0.85 M CuSO4·5H2O + 0.55 M H2SO4). The plating bath for the three-dimensional Cu/CNT composite film was prepared by the addition of CNTs (VGCF, Showa Denko) to the previous copper plating bath. The plating bath was treated with an ultrasonic homogenizer to disperse the CNTs. The dispersibility of the CNTs was examined by a laser diffraction particle size analyzer. Electrodeposition was performed under galvanostatic conditions at 25 °C. Pure copper plate was used as the cathode and a phosphorus-containing copper plate was used as the anode. Phase analysis of the deposits was performed using X-ray diffraction (XRD). The surface and cross-sectional morphology were observed using field–emission scanning electron microscopy (FE-SEM). Results and Discussion The measured particle size distribution suggests that the CNTs are dispersed as primary particles in the plating bath. Therefore, the dispersibility of the CNTs in the plating bath is considered to be very good. Fig. 1(a) shows cross-sectional SEM images of plated films fabricated from the plating baths containing 0 g/L CNTs. The structure is deformed, and it has lost the space between the copper sheets that constitute the three-dimensional structure. Fig. 1(b) shows the plated film fabricated from the plating bath containing 10 g/L CNTs. The spaces between the copper sheets are maintained. For this reason, the addition of CNTs to the three-dimensional copper structure is considered to be effective for reinforcement of the structure. References 1) T. Song, M. Yan, Z. Shi, A. Atrens, and M. Qian, Electrochim. Acta, 164, 288–296 (2015). 2) B. Qi, H. Yang, K. Zhao, M. M. Bah, X. Bo, and L. Guo, J. Electroanal. Chem., 700, 24–29 (2013). 3) H. Zhang, Q. Pan, and H. Zhang, Mater. Lett., 106, 360–362 (2013). 4) S. Arai and T. Kitamura, ECS Electrochem. Lett., 3 (5), D7-D9 (2014). Figure 1

Control of Accumulation of Cu(I) in Copper Sulfate Electroplating Plating Solution

With density growth of printed circuit board and the development of through-silicon via (TSV) plating technology, it becomes more important to fine management of the plating solution during the manufacturing process in order to keep high quality of product. In copper sulfate electroplating, monovalent copper ions (cuprous ion: Cu(I)) has been implicitly pointed out as one of the main cause of low quality such as high roughness and dull metallic on the Cu plated surface, therefore accurate measurement of Cu(I) concentrations has been strongly required in the plating process. In spite of the needs in industry, it has been remaining as challenge to measure and monitor the Cu(I) concentration in the process because of the unstableness of Cu(I) in solution, conceitedly rapid oxidation. In fact, although a large amount of Cu(I) can be considered to be contained in the plating solution in the production lines, there is not enough knowledge about the holding structure of Cu(I) in the plating solutions. We have succeeded in optical analyzing the Cu(I) containing in the plating solutions conducted by absorption of a chelate of Cu(I) with bathocuproinedisulfonic acid, disodium salt (BCS). Here, we will report the formation and accumulation of Cu(I) in copper sulfate electroplating solutions and discuss the relationship Cu(I) activity to electrolysis conditions such as electro density, time and dissolving gas, based on the experiments in the laboratory. These results also will be important knowledge to control a process factor such as concentrations and holding structures of Cu(I) in the plating solutions even in manufactural plating line. As experimental, a time course of Cu(I) concentrations were determined from change in absorbance originated from formation of Cu(I) and BCS chelate accompanied by applying electrolysis the copper sulfate plating solutions. The electrolysis was carried out using two electrode system; anode: copper plate, cathode: platinum plate (electrochemically active area: 20×40 mm). The plating solution (150mL) was degassed with nitrogen gas through the energization. Cu(I) does not include most in the new liquid of copper sulfate, however about 1mM Cu(I) was accumulated by electrolysis for 10 minutes at a current density of 62.5mA / cm2. Cu(I) concentration in the solutions were firstly increased depending on the electrolysis time, the decreases as longer than a certain period of time, for example, about 15 minutes in 62.5mA/ cm2. Accumulation of Cu(I) tends to increases in accordance with the current density but there was no change in the following 15.5 mA/ cm2. On the contrary, the amount of Cu(I) to be accumulated even more than 78.1mA/ cm2 was less than the amount of 62.5mA/ cm2. Accumulation of Cu(I) is considered to be proportional to the current density and time within a certain range. For optimal current value in the formation of the plating film is less than this lower limit, usually the accumulation of monovalent copper would be less likely to occur. On the other hand, if it exceeds the upper limit, the precipitation of a large amount of particles in the solution was observed. In previous discussion, Cu(I) that is formed in a solution concluded that are stabilized incorporated into PEG. Excessive Cu(I) might form the copper particles by a disproportionation reaction. Through the optical analysis of Cu(I), it found that the formation and accumulation of Cu(I) depends on other conditions in electrolysis. For example, the accumulation of Cu(I) is hardly observed using phosphorus-containing copper plate as the anode instead of Cu plate. Further, when bubbling with air instead of nitrogen gas, accumulation of Cu (I) was reduced to approximately half. It can be explained that Cu (I) was oxidized by dissolved oxygen come from the bubbled air. The oxidation is a major factor that inhibits the accumulation of Cu (I). In fact by the air bubbling, Cu (I) concentration in the solution is reduced in accordance with the bubbling time. Cu (I) is more stably maintained in the degassed solution. As conclusion, these results clarified that accumulation of Cu (I) of the copper sulfate plating solution is governed by various factors, such as current-density, operation time electrode and kind of dissolved gas in electrolysis. It also shows the possibility of controlling the density and the holding structure of Cu (I) in solution. The Cu (I) is a cause of roughness of the film, it is also considered to have a positive effect on the filling in TSV plating. By controlling the formation and accumulation of Cu (I) of the copper sulfate plating solution, thereby enabling more detailed consideration of these issues.

Spectroscopic and Electrochemical Analysis of Cu(I) Complex of Copper Sulfate Electroplating Solution and Evaluation of Plated Films

With density growth of printed circuit board and the development of TSV plating technology, it becomes more important to management of the plating solution during the manufacturing process. In copper sulfate electroplating, accurate measurement of the monovalent copper ions (Cu(I)) concentrations in the solutions is required, because they are pointed out to cause roughness of the plated surface. We have succeeded in analyzing the Cu(I) contained in the plating solutions conducted by absorption of a chelate of Cu(I) with bathocuproinedisulfonic acid, disodium salt (BCS). Although Cu(I) in the solutions is considered to not be detected because they are oxidized immediately, in fact, a large amount of Cu(I) is contained in the plating solution of the production lines. However, there is not enough conclusions about the effect of Cu(I) in the solution is on the plated surface. We had found that formation and accumulating Cu (I) by electrolysis under suitable conditions for copper sulfate plating solutions. Here, we will discuss a mechanism of Cu(I) accumulation in CuSO4 plating solution during the electrolysis from the view point of (1) dynamics on formation of 1:2 complex between Cu(I) and BCS chelate and (2) MALDI-MS analysis of the plating solution. In addition, by considering of implicit knowledge about the role of Cu(I) for product quality in production line, we will discuss (3) the relationship of Cu(I) amount and qualities of the Cu plated surface. (1) Dynamics on formation of 1:2 complex between Cu(I) and BCS chelate Cu(I) concentration in the plating solution can be determined from the absorbance of Cu (I) and BCS chelate. Furthermore, it is possible to classify the holding structures of Cu(I) by analyzing the kinetics reaction between BCS and Cu (I). Reaction of BCS with Cu (I) can be divided into three components, the instantaneous component of the time constant is less than 1 seconds (A0), an fast component is completed within a few seconds (AS), and components having a long time constant which is slow than a few minutes (AL). Although Cu(I) concentration in the solution was increased by electrolysis, change in each of the reaction components was not uniform (AS component was not observed in this experiment). That AL component is increased in the initial (<4min) of the electrolysis, A0 component was increased with a delay to between 6 and 10 minutes. This suggests that some Cu(I) holding structures occurring at different processes in solution. (2) MALDI-MS analysis of Cu plating solution Results of MALDI-MS analysis show some intermolecular interaction between Cu(I) and BCS. It can be considered that the some of the Cu(I) ion must be incorporated into poly ethylene glycoside (PEG) and stabilized for accumulation in the Cu plating solution. In the case of deeply incorporating into the PEG chain, Cu(I) must be isolated from the solution and attack from BCS by the PEG, and formation of Cu(I)-BCS2 complex was probably inhibited to be long kinetics component (AL). On the other hand, A0 component is not be described in clear, these Cu (I) is considered to be held in a state to quickly react with BCS. (3) Relationship of Cu(I) amount and qualities of the Cu plated surface Cu(I) in these states would have played a different role each in the electroplating process. So far, the results of the plating solution analyzing of the production line, mainly A0 component is suggested to affect the roughness of the plated surface. This effect is also supported by electrochemical measurements. Changes in the A0 values for the current time are correlated well with the changes in the area values in CVS (Cyclic Voltammetry Stripping) measurement. On the other hand, no clear relationship was observed between the AL values and area values. PEG might have to reduce the impact on the film surface by incorporating excess Cu(I). In order to investigate the effect of Cu(I) to the structures of the plating, surface were electroplated onto the copper plates with electrolysis solutions (electrolysis time : 0 to 20 minutes). In the film formed in 4 min electrolysis solution (negligible A0), roughness on the plate surface did not occur. However, in the 6 to 10 min electrolysis solutions, roughness occurs on the film surface depending on the electrolysis time. It was confirmed that Cu(I) accumulation (especially A0 component) is affecting the defect occurrence of coating appearance. These results show that spectroscopic methods for the analysis of Cu(I) in solution are effective, and the performance change of the solutions can be easily evaluated.

Study of the Influence of Polypropylene Fibers, Contacting with Copper Sulfate Plating Solution, on the Properties of the Electrolyte and Copper Coatings

Study of the Influence of Polypropylene Fibers, Contacting with Copper Sulfate Plating Solution, on the Properties of the Electrolyte and Copper Coatings

Study of the Influence of Polypropylene Fibers, Contacting with Copper Sulfate Plating Solution "ЦКН", on the properties of the Electrolyte and Copper Coatings

Study of the Influence of Polypropylene Fibers, Contacting with Copper Sulfate Plating Solution "ЦКН", on the properties of the Electrolyte and Copper Coatings

近接場光学センサーを用いた硫酸銅めっき液中の添加剤管理方法

近接場光学センサーを用いた硫酸銅めっき液中の添加剤管理方法

Extreme Bottom-up in Through Silicon Vias by Leveler Pre-adsorption

In the TSV copper filling process, combination of several additives, such as suppressor, accelerator and levelers, are used in the electroplating bath. Besides, strong agitation is often applied to achieve good bottom-up feature. From past studies, it is considered that levelers, which show strong suppression effect in the electroplating, have an essential role in the bottom-up feature. It is assumed that the bottom-up TSV filling is achieved based on diffusion-adsorption model, in which less suppression in the via bottom is caused by diffusional limitation of the leveler and preferential deposition happens around via bottom. However, in the practical filling process, in addition to the leveler, other additives are used, and the filling mechanism is not clear yet. In this study, only leveler is added in the plating bath, and the effect of leveler on filling feature is discussed. Experimental The leveler used in this study is a commercial product,and the composition is not opened. Besides, the product name is neither provided. At first, in order to grasp the suppression effect of the leveler, chronoamperometry was carried out with addition of only leveler in an acid copper sulfate plating bath ( 1M CuSO4 + 0.3 M H2SO4+ 1mM HCl ). It was assumed that initial adsorption of the leveler on plating surface has some impacts, and pre-immersion time before the plating start was varied. -520mV vs. MSE was applied with a rotating disk electrode at a rotational speed of 400rpm. Leveler concentrations of manufacture’s standard (x1) and 5 times concentrated one (x5) were examined. Figure 1 shows the results. Strong suppression was not obtained with standard leveler concentration, and suppression became stronger along plating time. Less current density at initial plating period was observed with longer pre-immersion. Stronger suppression was observed with 5x leveler concentration. From these results, it was supposed that suppression is limited by mass transfer of leveler. In order to clarify the diffusion-adsorption effect, TSV filling experiment with pre-immersion was performed. Figure 2 shows example results. With short pre-immersion, it is supposed that little leveler adsorbed inside the via, while strong suppression was observed on upper area of the via with 30min pre-immersion, and it was found that the leveler diffused deeper with long pre-immersion. Figure 3 shows an example result after some optimization. Extreme bottom-up was achieved with relatively high aspect ratio vias. Figure 1

A Study on the Decomposition of SPS and Its Effects on Via Filling Performance

Electrolytic copper via filling based on three additive component copper sulfate bath chemistry has been and currently is widely used in electronic packaging. Progression in copper sulfate plating chemistry is vital to development of smart phones among other devices. In order to further elucidate bath chemistry and possible methods to improve performance, degradation of the disodium 3,3'-dithiobis(1-propanesulfonate) (SPS) additive, which is employed as brightener, during copper via filling by electrodeposition and the influence of a byproduct on plating was investigated. Oxidative decomposition of SPS and formation of disodium 1,3-propanedisulfonate (PDS) at an IrO2 coated Ti insoluble anode during electrolysis was confirmed by NMR analysis. By addition to a fresh bath, PDS was then shown to compromise via filling performance. This study clarified the anodic oxidation of SPS to PDS under electrolytic filling conditions and that the PDS concentration correlated to the filling ability of the copper plating bath.