Fabrication and testing of thin silicon interposers with multilevel frontside and backside metallization and Cu-filled TSVs

Lueck, Matthew; Malta, Dean; Huffman, Alan; Gregory, Chris; Butler, Marianne; Lannon, John; Temple, Dorota

doi:10.1109/ectc.2013.6575589

Cited by 10 publications

(6 citation statements)

References 8 publications

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“…Si was the initial material used for interposers because of its coefficient of thermal expansion (CTE) match to the Si chip and the familiarity of wafer fabrication facilities in Si processing. 1,2 Recently, glass has gained attention as a candidate interposer material. [3][4][5][6] The CTE of borosilicate glass, 3.2, is reasonably close to that of Si, 2.9, and a wide range of CTE's is available by changing the glass composition.…”

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confidence: 99%

“…10,11 Models have been developed to explain the preferential plating at the bottoms of 'blind' features through the interplay of "accelerators" such as SPS and suppressors such as PEG. [12][13][14] In the case of Si, through vias (TSV) have been generated by first filling vias as blind vias, then thinning the back side of the wafer by CMP until the bottoms of the filled vias are intersected, thereby producing filled TSVs 2 or by first sealing one end of the TSVs then filling them as blind vias. 1 In the case of glass, where through-holes may be formed directly into the glass without the need for mechanical thinning, it is our intent to develop Cu plating processes to fill these holes as TGVs (open on both ends) instead of as blind vias.…”

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confidence: 99%

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Superconformal Filling of High Aspect Ratio through Glass Vias (TGV) for Interposer Applications Using TNBT and NTBC Additives

Ogutu

Fey

Dimitrov

2015

J. Electrochem. Soc.

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Cu superconformal filling of through glass vias (TGV) of aspect ratios (AR) 6:1 and 10:1 for glass interposer applications is achieved by DC electroplating in the presence of the additives tetranitroblue tetrazolium Cl − (TNBT) and nitroblue tetrazolium Cl − (NTBC) in acidic CuSO 4 / Cl − formulations. Filling takes place by the so-called 'butterfly' mechanism that nucleates hemispherical or X-shaped Cu plugs in the centers of TGV's while keeping the thickness on external surfaces low. Holes of AR 6:1 are filled in 3 h at 2.5 mA.cm −2 , using a bath composed of 40 ppm TNBT, 80 ppm Cl − , 0.88 M CuSO 4 , and 0.3 M CH 3 COOH under stagnant conditions. Increasing [TNBT] to 80 ppm and [Cl − ] to 120 ppm in the presence of 0.3 M CH 3 COOH allows filling of 10:1 AR holes in 12.5 h at 1.0 mA.cm −2 while maintaining thin surface plating. In the case of NTBC, 6:1 holes are filled in 4-5 h at 2.5-4.0 mA.cm −2 , and 10:1 holes are filled in 12-13 h at 1.0 to 1.5 mA.cm −2 in a slowly stirred bath containing 0.88 M CuSO 4 , 80 ppm Cl − , 0.6 M H 2 SO 4, and 45-50 ppm NTBC. Optimization of bath composition is necessary to avoid void-formation in the holes. Effects of composition on overvoltage and Cu surface topography are discussed.

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confidence: 99%

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confidence: 99%

Superconformal Filling of High Aspect Ratio through Glass Vias (TGV) for Interposer Applications Using TNBT and NTBC Additives

Ogutu

Fey

Dimitrov

2015

J. Electrochem. Soc.

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“…In recent years interest has developed in the use of interposers in microelectronics packaging to accommodate increasing packaging density. [1][2][3] Silicon has been favored because of its match to the coefficient of thermal expansion (CTE) of integrated circuit chips and its compatibility with fabrication processes in integrated circuit manufacturing facilities. More recently interest has been shown in the use of glass as an interposer material for several reasons including its low cost, availability in large sizes including flexible rolls, high dielectric strength, lack of need for a barrier layer (as for Si), adjustable CTE, and prospects for higher frequency operation.…”

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confidence: 99%

Fast and Cost-Effective Superconformal Filling of High Aspect Ratio through Glass Vias Using MTT Additive

Fey¹,

Li²,

Dimitrov³

2017

J. Electrochem. Soc.

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Cu superconformal filling of through glass vias (TGV) of aspect ratios (AR) 6 and 10 for glass interposer applications is achieved at greatly reduced times of about 1 h and 4 h, respectively, compared to about 3 h and 12 h in the past. The DC electroplating is carried out in the presence of the additive thiazolyl blue tetrazolium bromide (MTT) in acidic (pH 2 to 4) copper methane sulfonate (CuMSA)/Cl− formulations. The applied plating conditions enable the ‘butterfly’ mechanism that nucleates hemispherical or X-shaped Cu plugs in the TGV's centers while keeping the thickness on external surfaces low. Plugs are formed in AR 6 TGV's in as little as 12 min, after which the plating can be viewed as the filling of double-sided blind vias. Issues with imperfections trapped in the plugs have been addressed by decreasing the current around the time of plug formation, then increasing it for the rest of the process. In order to fill AR 10 holes much longer times at lower current density are needed. Larger diameter AR 4 TGV's have been also successfully filled with Cu. Lab scale quantities of MTT are 8 to 14 times less expensive than the competing additives NTBC and TNBT, respectively.

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“…Further details of the interposer fabrication and testing are provided in other publications. [14,15] …”

Section: Tsv Processing and Interposer Fabricationmentioning

confidence: 99%

Characterization and modeling of copper TSVs for silicon interposers

Malta

Gregory

Lueck

et al. 2013

2013 IEEE 63rd Electronic Components and Technology Conference

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Silicon interposers enable advanced package architectures through the integration of multiple die and passive components onto a single silicon substrate, while offering high interconnect density and low thermal expansion mismatch. This paper will describe the processing and characterization of copper-filled through silicon vias (TSVs) for Si interposers and related three-dimensional wafer-level packaging (3D-WLP) applications. To evaluate potential reliability concerns, the thermomechanical behavior of Cu-filled TSVs was characterized experimentally over a range of TSV dimensions and also modeled using finite element analysis. The paper will include discussion of the correlation between the experimental observations and modeling data obtained for the TSV structures. Demonstrations of functional Si interposer substrates are also reported, based on three different design variations of TSV diameter and substrate thickness, respectively: 25 × 100m, 50 × 200m, and 80 × 300m. Finally, alternative TSV structures, based on Cu-lined vias with polymer filled cores, are demonstrated as a possible approach to reducing the thermomechanical concerns for Cu-filled TSVs in Si interposer or 3D-WLP substrates

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Fabrication and testing of thin silicon interposers with multilevel frontside and backside metallization and Cu-filled TSVs

Cited by 10 publications

References 8 publications

Superconformal Filling of High Aspect Ratio through Glass Vias (TGV) for Interposer Applications Using TNBT and NTBC Additives

Superconformal Filling of High Aspect Ratio through Glass Vias (TGV) for Interposer Applications Using TNBT and NTBC Additives

Fast and Cost-Effective Superconformal Filling of High Aspect Ratio through Glass Vias Using MTT Additive

Characterization and modeling of copper TSVs for silicon interposers

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