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Wu W.,CAS Institute of Microelectronics | Wu W.,Innovation Center for MicroNanoelectronics and Integrated System | Mao H.,CAS Institute of Microelectronics | Han X.,CAS Institute of Microelectronics | And 2 more authors.
Nanotechnology | Year: 2016

This work presents arrays of heterogeneous nanopillars stacked with Si bodies and SiO2 heads for biomedical applications. Novel crossed and overlapped spacer techniques are proposed to fabricate the nanopillar arrays in controllable dimensions. For the nanopillars in the arrays, the minimum spacing, body diameter and head tip-radius reach 100 nm, 23 nm and 11 nm, respectively. The maximum height is 1.2 μm. In addition, because of hydrophilic/hydrophobic selectivity between the SiO2 heads and Si bodies, localized nanoliter water-droplet condensing, fluorescein solution extraction and protein capturing are observed on the SiO2 pillar heads. These experiments demonstrate the great potential of heterogeneous nanopillars in biomedical applications. © 2016 IOP Publishing Ltd.

Song Z.,Tsinghua National Laboratory for Information Sciences and Technology | Wu D.,Tsinghua National Laboratory for Information Sciences and Technology | Zhu H.,Tsinghua University | Liu L.,Tsinghua National Laboratory for Information Sciences and Technology | And 2 more authors.
Microelectronic Engineering | Year: 2015

A void-free bonding interface is critical to yield and reliability for high-quality wafer bonding. Although adhesive bonding using polymers as the bonding interface material is inherently able to restrain void-formation, for the wafers with uneven patterns like metal interconnects and alignment marks, void-free bonding is still challenging. This paper reports the void-formation in uncured and partially-cured benzocyclobutene (BCB) adhesive for bonding wafers with patterns. Experimental results show that uncured and partially-cured BCB has different behaviors in void-formation, and four types of voids, namely center voids, flower voids, micro voids, and floccules voids, are founded and their formation mechanisms are investigated. By optimizing bonding parameters for uncured BCB bonding, the center voids and flower voids are avoided and void-free bonding can be obtained. For partially-cured BCB, the micro voids and floccules voids tend to appear for uneven wafer surfaces. A reflow pretreatment at 140. °C for 2. h before curing process is beneficial to reducing the void areas. © 2014.

Huang C.,Tsinghua University | Pan L.,Tsinghua University | Liu R.,Fudan University | Wang Z.,Tsinghua National Laboratory for Information Sciences and Technology | Wang Z.,Innovation Center for MicroNanoelectronics and Integrated System
IEEE Transactions on Components, Packaging and Manufacturing Technology | Year: 2014

Through-silicon vias (TSVs) using benzocyclobutene (BCB)-liners as the insulator have the potential for reducing the TSV capacitances and the thermal expansion stresses. This paper reports the assessments of BCB-liner TSVs with respect to thermal and electrical properties. The C-V and I-V characteristics are measured at room temperature and at an elevated temperature as high as 125 °C to characterize the electrical properties of capacitance and leakage current at different temperatures. Some C-V and I-V features associated with BCB-liners are discussed and the mechanisms are analyzed. Thermal cycling between-65 °C and 150 °C is performed, and the C-V and I-V characteristics are measured before and after thermal cycling to evaluate the thermomechanical stability of the BCB-liners, and the results show that the C-V and I-V properties are improved after thermal cycling. These preliminary results on the electrical and thermal properties of BCB-liner TSVs show that they have good thermal stability. © 2014 IEEE.

Shao L.,Peking University | Shao L.,Harvard University | Zheng M.,Peking University | Zheng M.,Beth Israel Deaconess Medical Center | And 3 more authors.
Applied Physics Letters | Year: 2015

Ions in electrolytes have been proposed to resemble carriers in solid semiconductors over decades. Recently, nanofluidic devices have been demonstrated to phenomenologically mimic semiconductor devices by modulating ion concentrations near the interface of electrolytes and solids. However, the link between the ion transportation in nanofluidics and the solid semiconductor is still missing. This letter proposes an electrolyte doping scheme by introducing charged nanoparticles as dopers, which holds potential in modulating ion concentration in a bulk sense. These nanoparticles show a strong modulation of ion concentrations, and thus bridge the ion transportation in nanofluidics with the well-established semiconductor physics. Ionic diodes based on the present electrolyte doping picture are theoretically and experimentally demonstrated. The current-voltage characteristics are scrutinized by the depletion approximation. © 2015 AIP Publishing LLC.

Song Z.,Tsinghua University | Tan Z.,Tsinghua University | Liu L.,Tsinghua University | Wang Z.,Tsinghua University | And 2 more authors.
Microsystem Technologies | Year: 2015

Due to the flowability of benzocyclobutene (BCB) and the unavoidable shear components of the bonding force applied by bonding facilities, it is quite challenging to achieve void-free BCB adhesive bonding with simultaneous high post-bonding alignment accuracy. To solve this problem, this paper reports a compensation method for alignment errors to achieve simultaneous void-free and accurate wafer bonding using soft-baked BCB. By characterizing the wafer shift induced bonding force, it is found that the wafer shift is a systematic error associate with the bonders but independent of the wafers. Upon this investigation, a compensation method presetting a pre-bonding alignment shift opposite to the post-bonding shift is proposed to compensate the bonding induced wafer shift. Using this method, void-free bonding with soft-baked BCB has been achieved, and the alignment errors are improved significantly from around 35–40 μm to around 3 μm. Test results show that the average bonding strength of soft-baked BCB is about 26.4 % higher than that of partially-cured BCB. The preliminary results demonstrate the efficacy of the proposed compensation method, which has potential to improve the alignment accuracy of BCB bonding for three-dimensional integration, MEMS, and microsensors. © 2014, Springer-Verlag Berlin Heidelberg.

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