Development of coaxial shield via in silicon carrier for high frequency application

Abstract

System-in-package (SiP) based on silicon carriers is a fast emerging technology that offers system design flexibility and integration of heterogeneous technologies. One of the key technologies enabler for silicon carrier is through wafer interconnects. The development of SiP will require the devices with different functionality operating at high frequency to be densely packed on the silicon substrate. However, silicon substrate is usually of low resistivity, when a high frequency signal is transmitted vertically through the substrate via, significant signal attenuation can occur that leads to substrate crosstalk and poor RF performance. In this paper, a novel coaxial shielded via in silicon carrier is presented for high frequency applications. Electrical modeling was carried out to obtain the required geometries for optimum performance. The coaxial shield via is able to suppress undesirable substrate crosstalk between vertical interconnects as well as provide excellent RF performance. The detailed fabrication process is also presented. A negative tone SU-8 photoresist is used as the dielectric for the coaxial shield via structure. A test vehicle is fabricated on 8-inch, 10 ·cm resistivity silicon wafer with a target of achieving a transmission coefficient, S 21 of greater than -0.5 dB at 40 GHz. SU-8 dielectric of approximately 112 µm thickness was deposited on the via sidewall of a 300 µm diameter through wafer via holes, and the via-holes filled with copper using bottom up electroplating approach to achieve a radius ratio, n of 4.

Electro-Thermal and Thermal-Stress Coupling Optimization Design for Coaxial Through Silicon Via

“…With the increase of integration, the high frequency transmission loss and the ability of antielectromagnetic interference is an urgent challenge [13][14][15]. Due to the advantages of self-shielding and control of electromagnetic interference, coaxial TSV (CTSV) can effectively reduce the signal transmission loss and coupling noise, and has good high-frequency signal transmission performance [16,17].…”

Electrical Characterization of Through-Silicon-via-Based Coaxial Line for High-Frequency 3D Integration (Invited Paper)

“…Therefore, coaxial shield TSVs have been designed for high-speed signal transmission [9] and used as an efficient vertical transition in flip-chip structures [10]. The basic configuration of a coaxial shield TSV has a central signal conductor surrounded by an outside concentric ground shell, which can consequently suppress undesirable substrate crosstalk [11] and effectively reduce the losses caused by radiation and coupling when it is used for transmitting microwave signals [12,13]. It has been validated that compared to the common signal-ground (S-G) paired TSVs, such type of coaxial TSVs can offer better signal integrity and show better electrical performance at high frequencies [7].…”

Low-loss shielded through-silicon vias filled with multi-walled carbon nanotube bundle

“…However, the silicon substrate noise will degrade the performance of the system when a high frequency signal is transmitted vertically through the TSV. To improve the performance, the coaxial through-silicon via (C-TSV) has been proposed [1]. Much research on the electrical model and characterization of C-TSV has been conducted.…”