Galvanostatic bottom-up filling of TSV-like trenches: Choline-based leveler containing two quaternary ammoniums

2016

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Through silicon via (TSV) technology has been researched for 3-dimensional packaging of electronic devices, and Cu electrodeposition has been used for TSV filling. The organic additives are one of the most important factors in Cu electrodeposition affecting Cu gap-filling, and the leveler usually plays a decisive role. In this research, iodide ion (I − ) is adopted instead of organic leveler for Cu bottom-up filling. The behaviors of I − are investigated by various types of electrochemical analyses. Especially, the influences of I − on the adsorption of the accelerator and suppressor are extensively studied, and it is confirmed that I − makes the suppression layer robust while reducing the adsorption of the accelerator. Also, it was observed that the effect of I − is greater under the strong convection of electrolytes than without convection, meaning that I − could induce selective deposition at the bottom of the features. Based on this, TSV-scaled trenches are successfully filled by potentiostatic Cu electrodeposition in the presence of the accelerator, suppressor, and I − without any organic levelers.

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confidence: 60%

The Influences of Iodide Ion on Cu Electrodeposition and TSV Filling

2016

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“…[1][2][3][4] In addition, Cu electrodeposition is widely utilized to realize 3-dimensional packaging through the formation of through-silicon vias (TSVs). [5][6][7][8][9][10][11] Cu electrodeposition is used to fill features while preventing defect formation, allowing for interconnects that exhibit excellent reliability and high performance. Superconformal electrodeposition, also known as superfilling or bottom-up filling, allows for this defect-free filling in nano-and micro-sized features.…”

mentioning

confidence: 99%

Electrochemical Behavior of Citric Acid and Its Influence on Cu Electrodeposition for Damascene Metallization

Choe

et al. 2015

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The electrolyte for Cu superfilling generally consists of copper sulfate, sulfuric acid, a chloride ion, an accelerator, and a suppressor. In this study, the characteristics of citric acid-based electrolytes and the interaction between citrate species and accelerators are investigated, with the ultimate goal being the replacement of both sulfuric acid and the suppressor with citric acid. Electrochemical impedance measurements were adopted to measure the changes in solution and charge transfer resistances with respect to citric acid and accelerator concentrations. In addition to a decrease in solution resistance resulting from the addition of citric acid, charge transfer inhibition was observed during Cu electrodeposition, which is likely the result of adsorption of citrate species onto Cu surface. A competitive adsorption between the citrate species and the accelerator was also observed and the new additive system was applied to the feature filling in the absence of the conventional polyethylene glycol suppressor. Using this new copper sulfate, citric acid, chloride ion, and accelerator system, trenches were successfully bottom-up filled, resulting in no internal defects.

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The Cu plating solution typically contains small amounts of organic additives, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] which enhance the uniformity, 13 brightness, 14 and mechanical properties of the Cu film. 15 In addition, for particular application to damascene Cu plating, the additives enable bottom-up filling at trenches or vias by controlling the relative deposition rates of Cu at the top and bottom of the features.…”

mentioning

confidence: 99%

“…Owing to the merits of high throughput, low process cost, and good film quality, Cu electroplating has a wide application, from traditional Cu foil production to state-of-the-art semiconductor metallization processes. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The Cu plating solution typically contains small amounts of organic additives, 1-16 which enhance the uniformity, 13 brightness, 14 and mechanical properties of the Cu film. 15 In addition, for particular application to damascene Cu plating, the additives enable bottom-up filling at trenches or vias by controlling the relative deposition rates of Cu at the top and bottom of the features.…”

mentioning

confidence: 99%

“…15 In addition, for particular application to damascene Cu plating, the additives enable bottom-up filling at trenches or vias by controlling the relative deposition rates of Cu at the top and bottom of the features. [1][2][3][4][5][6][7][8][9][10][11][12] For this application, the organic additives are grouped as the accelerator, suppressor, and leveler based on their electrochemical behaviors and their roles in pattern filling.…”

mentioning

confidence: 99%

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High Accuracy Concentration Analysis of Accelerator Components in Acidic Cu Superfilling Bath

Choe

et al. 2015

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We have devised a modified cyclic voltammetry stripping (CVS) method to measure the concentrations of bis-(sulfopropyl) disulfide (SPS) and 3-mercapto-1-propane sulfonate (MPS) in Cu plating solutions. Though MPS, a breakdown product of SPS, enhances the Cu deposition rate on flat electrodes, it is not a superfilling-capable accelerator for the damascene structure, unlike SPS. Therefore, accurate measurement of SPS in damascene Cu plating baths is important. However, enhancement of the Cu deposition rate by MPS interferes with the electrochemical signal of SPS, leading to a significant error when using the modified linear approximation technique (MLAT)-CVS analysis method. To evaluate their concentrations individually, a two-step CVS analysis was performed in which the total accelerator concentration ([SPS] + 1/2[MPS]) and conversion ratio were separately determined. All MPS species in the bath were oxidized to SPS by controlling the plating solution pH. Subsequent MLAT-CVS analysis successfully revealed the total accelerator concentration in the Cu plating solution. Individual SPS and MPS concentrations were thereby calculated using the conversion ratio evaluated from the difference in their relative accelerating abilities. This modified method enabled determination of the SPS concentration with <10% error, suggesting a reliable and high accuracy tool to predict pattern filling capabilities of plating solutions. Owing to the merits of high throughput, low process cost, and good film quality, Cu electroplating has a wide application, from traditional Cu foil production to state-of-the-art semiconductor metallization processes. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The Cu plating solution typically contains small amounts of organic additives, 1-16 which enhance the uniformity, 13 brightness, 14 and mechanical properties of the Cu film. 15 In addition, for particular application to damascene Cu plating, the additives enable bottom-up filling at trenches or vias by controlling the relative deposition rates of Cu at the top and bottom of the features.1-12 For this application, the organic additives are grouped as the accelerator, suppressor, and leveler based on their electrochemical behaviors and their roles in pattern filling.One of the most widely used accelerators is bis-(sulfopropyl) disulfide (SPS), a dimer of 3-mercapto-1-propane sulfonate (MPS). Acceleration by SPS in Cu superfilling has been explained by the competitive adsorption theory [17][18][19][20][21] or by the catalytic action caused by the reduction of cupric ions. 22,23 In the competitive adsorption theory, acceleration is regarded as a recovery of the deposition rate previously suppressed by the polyethylene glycol (PEG)-Cl inhibition layer, and recovery occurs through the displacement of the PEG-Cl layer with SPS.17-19 A recent study revealed that the acceleration is a result of the dissociative adsorption of SPS with displacement of the well-ordered Cl − layer. 20,21 MPS, a dissociated product of SPS, reconverts to SPS with re...