Carbon Based Materials Synthesis and Characterization for 3D Integrated Electronics
Doctoral thesis, 2017

3D IC packaging technology extends Moore’s law and shifts the IC field into a new generation of smaller, but more powerful devices. Interconnection and thermal management as two critical parts of 3D IC integration packaging, are facing harsh challenges due to the miniaturization of IC devices. This thesis focuses on improving the heat dissipation effect and interconnect performance for 3D IC integration packaging by developing carbon based nanomaterials. Thermal management has been identified by the semiconductor industry as one of the major technological bottlenecks to hinder the further miniaturization of 3D IC devices, particularly in high power devices. The first part of thesis presents a comprehensive thermal management solution including nanocomposite thermal interface material (Nano-TIM), hexagonal boron nitride (hBN) heat spreader and graphene-CNT (G-CNT) hybrid heatsink to address heat issue existing in high power IC devices. To decrease the thermal interface resistance, a smart Nano-TIM is developed through combining a silver-coated nanofiber network and an indium matrix. The matrix contributes to the heat conduction, while the nanofiber network defines the geometry and improves the mechanical performance. The thermal and mechanical performance of Nano-TIM is demonstrated in die attach applications in IC packaging. In addition to improve thermal interface resistance by Nano-TIM, an hBN heat spreader was synthesized by liquid exfoliation method to spread and dilute the heat energy generated in power chip for further cooling. This spreader potentially broadened the heat spreader application scenario in IC packaging due to its insulating performance. Moreover, in order to dissipate heat energy from IC microsystem, a 3D carbon based heat sink consisted of CNTs and graphene was synthesized using CVD method. The carbon based heat sink combining 1D CNTs with 2D graphene extended the excellent thermal property to three dimensions through covalent bonding. In the second part of thesis, it is devoted to the development of CNT-based through silicon vias (TSVs) for interconnects in 3D IC packaging. Vertically aligned carbon nanotubes (VA-CNTs) with different structures were synthesized by the thermal chemical vapor deposition (TCVD) method. In order to address the incompatibility with IC manufacturing processes and relatively lower electrical conductivity than metal, a series of processes including tape assisted transfer, filling solder balls into hollow structures and electroplating Cu into CNTs bundles were developed. Accordingly, different types of CNT-based TSVs were fabricated: densified VA-CNT TSV, VA-CNT-Solder TSV and VA-CNT-Cu TSV. The electrical conductivity performance of the TSVs was measured using the four-probe method. Among these different kinds of TSVs, VA-CNT-Cu TSV exhibits the best conductivity, around the same order of magnitude as copper. Meanwhile, the CTE of this kind of TSV is as low as that of silicon substrate, which can effectively decrease thermal stress of the interface between via and substrate. In addition, to broaden the TSV application scenario, a flexible CNT interconnect system was integrated to demonstrate potential carbon based application in future wearable microelectronics.   In addition, CNT-G material was developed for carbon based supercapacitors application, thanks to the huge surface area and high electrical conductivity of the CNT-G hybrid material. The results indicate a superior rate capability of the CNT-G material. This carbon hybrid material exhibited a great promise for supercapacitor applications particularly in high current density. In summary, integrating the Nano-TIM, heat spreader and G-CNT heatsink together offered a comprehensive thermal management solution for 3D IC microsystem using carbon based materials. Carbon based TSV technology further shortens interconnection path and enhanced 3D IC integration. To some extent, these findings offer a potential solution for the further miniaturization of 3D IC microsystem.



electrical resistivity


thermal resistance

3D IC integration





Kollektorn, MC2 Building
Opponent: Prof. Christopher Bailey, University of Greenwich


Shuangxi Sun

Chalmers, Microtechnology and Nanoscience (MC2), Electronics Material and Systems Laboratory

Vertically aligned CNT-Cu nano-composite material for stacked through-silicon-via interconnects

Nanotechnology,; Vol. 27(2016)p. Art no335705-

Journal article

A flexible and stackable 3D interconnect system using growth-engineered carbon nanotube scaffolds

Flexible and Printed Electronics,; Vol. 2(2017)

Journal article

Tape-Assisted Transfer of Carbon Nanotube Bundles for Through-Silicon-Via Applications

Journal of Electronic Materials,; Vol. 44(2015)p. 2898-2907

Journal article

Cooling hot spots by hexagonal boron nitride heat spreaders

2015 65th IEEE Electronic Components and Technology Conference, ECTC 2015, San Diego, United States, 26-29 May 2015,; (2015)p. 1658-1663

Paper in proceedings

Shuangxi Sun, K. Majid Samani, Yifeng Fu, Tao Xu, Lilei Ye, Maulik Satwara, Kjell Jeppson, Torbjörn Nilsson, Litao Sun, Johan Liu, Covalent bonding improved thermal transport at CNT-graphene interface

Shuangxi Sun, Qi Li(Equal first author), Yifeng Fu, Per Lundgren, Peng Su, Peter Enoksson, Johan Liu, A seamless CNT and graphene hybrid supercapacitor

This thesis addresses integration of carbon-based material into microsystems to meet current challenges of electronic performance and heat cooling. We developed a few advanced procedures for the realization of carbon-based material for microelectronics application. These include growth, densification, transfer, metal coating and integration of CNT and graphene based materials. We also combined these processes with microelectronics packaging technology for applications as: (1) thermal interface material, (2) micro heatsink and heat spreader, (3) through silicon via, (4) microsupercapacitor.

We succeeded in fabricating nanocomposite thermal interface material (Nano-TIM) through penetrating nanofiber network by melting indium. This material can effectively decrease thermal resistance of heat flow path in microelectronics devices. Moreover, carbon nanotube and graphene was synthesized together through covalent bonds to be used as micro heatsink for evaporating the condense heat energy in the electronic devices. In addition, “hexagonal boron nitride, “white” graphene, was used to fabricate heat spreader to dilute the hot spot energy of power chip. Finally, we offer a comprehensive cooling solution for high power device by integrating these materials.

Apart from cooling solutions, improving electronics performance is another focus in this thesis. We developed different through silicon vias (TSV) technologies to improve the interconnect performance in IC device. These different type of TSV including CNT TSV, CNT-metal composite TSV and flexible TSV, can respectively applied in different scenario, like wearable electronics and all carbon electronics, etc. Besides, considering the huge surface area and high electrical conductivity of CNT and graphene hybrid material, this hybrid structure was also used for carbon based mcirosupercapacitors application. This carbon hybrid material exhibited a great promise for microsupercapacitor applications particularly in high current density application.

Finally, I wish these technologies presented in this thesis can be a useful step for the further miniaturization of IC microsystem.

Driving Forces

Sustainable development

Innovation and entrepreneurship

Areas of Advance

Nanoscience and Nanotechnology (SO 2010-2017, EI 2018-)


Materials Science

Subject Categories

Energy Engineering

Materials Chemistry

Electrical Engineering, Electronic Engineering, Information Engineering

Nano Technology

Composite Science and Engineering


Chalmers Materials Analysis Laboratory

Nanofabrication Laboratory



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: Ny serie nr 4258


Chalmers University of Technology

Kollektorn, MC2 Building

Opponent: Prof. Christopher Bailey, University of Greenwich

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