Defect and microstructural evolution in thermally cycled Cu through-silicon vias

Marro, James; Okoro, Chukwudi; Obeng, Yaw S.; Richardson, Kathleen

doi:10.1016/j.microrel.2014.05.007

Cited by 17 publications

(12 citation statements)

References 23 publications

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“…This difference in annealing temperature has significant impact on the grain sizes. In our study, the grains are expected to be stable, fully grown and in the micrometer size range, as reported in our earlier studies with similar annealing temperature [25][26][27]. On the other hand, due to the low annealing temperature of 150°C, the grain sizes in the studies performed by [6] are expected to be mainly in the sub-micrometer range in accordance with the microstructural analysis study of Cu TSVs by [8,28].…”

Section: Discussionsupporting

confidence: 89%

“…Additionally, our earlier study [25] and that of Kong et al [32] show that void formation and growth in Cu TSVs increase with the peak cycling/annealing temperature. Studies reported by Shaw et al [33] show that void density in Cu dramatically increases for annealing temperatures above 400°C.…”

Section: Discussionmentioning

confidence: 52%

“…This drop in the 3-lm diameter Cu TSV sample is attributed to the possible presence of defects such as voids and cracks at the center of the Cu TSV, where they act as stress-relieving centers [3,25]. The exact cause of such defects is unknown at the moment, as they may be pre-existing, meaning that they were formed during the electro deposition process, or that they were initiated as a result of the high temperature treatment at 420°C for 30 min [25].…”

Section: Discussionmentioning

confidence: 99%

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Experimental measurement of the effect of copper through-silicon via diameter on stress buildup using synchrotron-based X-ray source

Okoro

Levine

et al. 2015

J Mater Sci

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In this work, the effect of copper through-silicon via (TSV) interconnect diameter on stress buildup in Cu TSVs was experimentally determined using a synchrotron-based X-ray microdiffraction technique. A single chip with different Cu TSV diameters (3, 5, and 8 lm), all having the same depth and processing conditions was studied. Prior to the measurements, the chip was annealed at 420°C (30 min), leading to microstructurally stable Cu TSVs. The mean measured hydrostatic stresses were (190 ± 25) MPa (3 lm diameter), (138 ± 19) MPa (5 lm diameter), and (209 ± 26) MPa (8 lm diameter), respectively. No clear relationship between the measured stress and Cu TSV diameter was observed. This trend is attributed to the operation of stress relaxation mechanisms in the polycrystalline Cu TSVs, which includes plastic deformation, grain boundary sliding, void formation/growth, and rate-controlled dislocation motion, which are often neglected in reported finite element analysis studies. Additionally, this study highlights that the thermo-mechanical behavior of Cu TSVs is significantly influenced by their thermal history.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 52%

Section: Discussionmentioning

confidence: 99%

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Experimental measurement of the effect of copper through-silicon via diameter on stress buildup using synchrotron-based X-ray source

Okoro

Levine

et al. 2015

J Mater Sci

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“…Understanding and tuning of these attributes in blanket films is the first step towards fabricating advanced geometries, such as through silicon vias (TSV) [DISSERTATION]. Correlation of such process parameters with film attributes is required to enable improved reliability and electrical performance of Cu in microelectronics [29]. …”

Section: Introductionmentioning

confidence: 99%

The influence of pulse plating frequency and duty cycle on the microstructure and stress state of electroplated copper films

et al. 2017

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In this work we studied the impact of pulse electroplating parameters on the cross-sectional and surface microstructures of blanket copper films using electron backscattering diffraction and x-ray diffraction. The films evaluated were highly (111) textured in the direction perpendicular to the film surface. The degree of preferential orientation was found to decrease with longer pulse on-times, due to strain energy driven growth of other grain orientations. Residual biaxial stresses were also measured in the films and higher pulse frequencies during deposition led to smaller biaxial stresses in the films. Film stress was also found to correlate with the amount of twinning in the copper film cross-sections. This has been attributed to the twins’ thermal stability and mechanical properties.

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“…5–9 While desirable highly textured Cu has been achieved in low aspect ratio features, 10–12 only randomly oriented microstructures have been found in high aspect ratio vias. 2,13,14 …”

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confidence: 99%

The Impact of Organic Additives on Copper Trench Microstructure

Marro

Okoro

Obeng

et al. 2017

J. Electrochem. Soc.

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Organic additives are typically used in the pulse electrodeposition of copper (Cu) to prevent void formation during the filling of high aspect ratio features. In this work, the role of bath chemistry as modified by organic additives was investigated for its effects on Cu trench microstructure. Polyethylene glycol (PEG), bis(3-sulfopropyl) disulfide (SPS), and Janus green b (JGB) concentrations were varied in the Cu electrodeposition bath. Results indicated a correlation between the JGB/SPS ratio and the surface roughness and residual stresses in the Cu. Electron backscattering diffraction (EBSD) and transmission Kikuchi diffraction (TKD) were used to study the cross-sectional microstructure in the trenches. Finer grain morphologies appeared in trenches filled with organic additives as compared to additive-free structures. Cu trench (111) texture also decreased with increasing organic additive concentrations due to more pronounced influence of sidewall seed layers on trench features. Twin density in the microstructure closely tracked calculated stresses in the Cu trenches. A comprehensive microstructural analysis was conducted in this study, on an area of focus that has garnered little attention from the literature, yet can have a major impact on microelectronic reliability.

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Defect and microstructural evolution in thermally cycled Cu through-silicon vias

Cited by 17 publications

References 23 publications

Experimental measurement of the effect of copper through-silicon via diameter on stress buildup using synchrotron-based X-ray source

Experimental measurement of the effect of copper through-silicon via diameter on stress buildup using synchrotron-based X-ray source

The influence of pulse plating frequency and duty cycle on the microstructure and stress state of electroplated copper films

The Impact of Organic Additives on Copper Trench Microstructure

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