High-Aspect-Ratio Copper-Via-Filling for Three-Dimensional Chip Stacking

Kondo, Kazuo; Yonezawa, Toshihiro; Mikami, Daisuke; Okubo, Tatsuya; Taguchi, Yuichi; Takahashi, Kenji; Barkey, Dale P.

doi:10.1149/1.2041047

Cited by 107 publications

(87 citation statements)

References 10 publications

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“…6,9,13 The Fig. 3a, conical surfaces resulted from the columnar TSVs filling which used the PPR current, and the standard four-additive electrolyte including Cl − , SPS, PEG, and SDDACC.…”

Section: Resultsmentioning

confidence: 99%

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Communication—Conical TSV Filling within 30 Seconds

Hoang

Kondo

2017

J. Electrochem. Soc.

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Super bottom up filling of TSVs is achieved by using a new leveler NM. The leveler was characterized by CVS method, its inhibition role was exhibited at different rotating rates and concentrations. NM electrolyte built up TSVs from the bottoms and almost no deposition on the TSV walls. The electrolyte containing NM leveler was effective at a high current density for both periodic pulse reverse (PPR) current, and direct current (DC). The 2 μm diameter and 16 μm depth conical TSVs required 30 s for full filling by two steps which were the PPR current step and the DC step.

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Section: Resultsmentioning

confidence: 99%

“…7 Kondo et al archived 60 min of filling for 10 × 70 μm columnar TSVs using the PPR current. 13 TSV electrodeposition time has dramatically reduced by using conical TSV shape, and new levelers.…”

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confidence: 99%

Communication—Conical TSV Filling within 30 Seconds

Hoang

Kondo

2017

J. Electrochem. Soc.

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“…9 The addition of leveler, for example Janus Green B (JGB), can significantly enhance the performance of a plating formula because the forced convection acting on the board surface is always stronger than that at the middle of the TH during electroplating. 16,17 It is a very time-consuming work to search or design additives for TH electroplating. Until now, only few additives used for TH electroplating have been reported.…”

Section: Introductionmentioning

confidence: 99%

Polyquaternium-2: A New Levelling Agent for Copper Electroplating from Acidic Sulphate Bath

Chen

Wang

et al. 2016

Electrochemistry

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Poly[bis(2-chloroethyl)ether-alt-1,3-bis [3-(dimethylamino)propyl]urea] (Polyquaternium-2) was employed as a leveler in the through-hole (TH) electroplating experiments from an acidic sulphate bath. The interaction between Polyquaternium-2 and copper surface was investigated using Field Emission Scanning Electronic Microscope (FE-SEM) and X-ray Photoelectron Spectra (XPS). The electrochemical behavior of Polyquaternium-2 and its interaction with other additives, such as a suppressor and an accelerator were characterized using rotating disk electrode. Polyquaternium-2 could absorb on copper surface to form an adsorption layer and inhibit the copper electrodeposition. As shown in the TH electroplating experiments, a copper deposit with uniform thickness was obtained when 0.17 µmol/L Polyquaternium-2 was added. The addition of Polyquaternium-2 could also increase the cathodic polarization, which is attributed to the adsorption of Polyquaternium-2 on the cathode in the process of TH electroplating. The results indicate that Polyquaternium-2 is an effective leveler used for TH electroplating, having a good synergy with SPS, PEG and Cl − .

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“…[6][7][8][9][10][11][12][13] Copper is a good conductor but its coefficient of thermal expansion (CTE) is high. Therefore, issues related to CTE mismatch between the conducting materials and the dielectric materials arise in PCB and 3D packaging with high-density interconnections.…”

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confidence: 99%

Microvia Filling with Nickel-Tungsten Alloy to Decrease the Coefficient of Thermal Expansion of Electronic Circuit Interconnections

Lin

Huang

Wang

et al. 2015

ECS Electrochemistry Letters

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A nickel-tungsten alloy plating formula was developed to electrochemically fill the microvias of printed circuit boards and the through-silicon vias (TSVs) of wafers. The plating solution was composed of Ni(SO 3 NH 2 ) 2 , citric acid, sodium citrate, Na 2 WO 4 , chloride ions, and 2-mercapto-5-benzimidazolesulfonic acid. A void-free Ni-W superfilling of a microvia and a TSV were achieved. The tungsten content in the filled alloy varied from 1.5 atom% to 5.5 atom%, depending on the plating temperature. The coefficient of thermal expansion of the filled Ni-W was theoretically calculated according the tungsten content, which was lower than that of copper. Microvia filling by copper electroplating has been widely employed to fabricate state-of-the-art printed circuit boards (PCBs) for interconnection, especially for integrated circuit (IC) packaging substrates.1-5 Recently, through-silicon vias (TSVs) have also been metallized by copper electroplating for the interconnection of threedimensional (3D) IC chip stacking packaging. [6][7][8][9][10][11][12][13] Copper is a good conductor but its coefficient of thermal expansion (CTE) is high. Therefore, issues related to CTE mismatch between the conducting materials and the dielectric materials arise in PCB and 3D packaging with high-density interconnections.Numerous authors have reported that the high CTE of the copper filled in the TSVs results in stress impacts on silicon substrates. [14][15][16][17] Copper atoms diffuse from the TSV due to thermal cycling, leading to void formation in the TSV. 18,19 The copper protrusion on the TSV caused respectively by thermal expansion and diffusion of copper lattices and atoms may destroy stacked IC chips. [20][21][22] Copper must be replaced by tungsten 23 or nickel 24,25 to overcome the issue of CTE mismatch.Although the CTE of tungsten is very low, 14,26 it cannot be electrochemically plated in an aqueous electrolyte. Fortunately, tungsten can be induced to co-deposit with nickel. [27][28][29][30][31][32] In this work, a Ni-W alloy plating formula that can achieve Ni-W bottom-up filling of microvia was developed. This plating formula can fill the microvia of PCBs and can also fill TSVs. The Ni-W filled TSVs exhibit good thermal stability after being annealed at 500• C for 4 h. ExperimentalThe dimensions of the PCB fragments cut for the Ni-W filling plating were 4.2 × 6.0 cm 2 . The microvias were formed by CO 2 laser ablation. The diameter and depth of the microvias were 80 μm and 40 μm, respectively. The sidewalls of the microvias were metallized by electroless copper plating in advance to deposit a 2-3 μm thick layer of copper before the filling plating.TSVs were formed by a deep reactive ion etching (DRIE) process (i.e., the Bosch process). The thickness of the isolation layer (i.e., SiO 2 ) in the TSVs formed by thermal oxidation was approximately 1-3 × 10 3 Å. The barrier layer was a TiN film with a thickness of 500 Å, which was conformably deposited by atomic layer deposition (ALD) for 600 cycles. The seed layer was depo...

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High-Aspect-Ratio Copper-Via-Filling for Three-Dimensional Chip Stacking

Cited by 107 publications

References 10 publications

Communication—Conical TSV Filling within 30 Seconds

Communication—Conical TSV Filling within 30 Seconds

Polyquaternium-2: A New Levelling Agent for Copper Electroplating from Acidic Sulphate Bath

Microvia Filling with Nickel-Tungsten Alloy to Decrease the Coefficient of Thermal Expansion of Electronic Circuit Interconnections

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