Teck Guan Lim

Compact Wideband Equivalent-Circuit Model for Electrical Modeling of Through-Silicon Via

This paper presents a compact wideband equivalent circuit model for electrical modeling of through-silicon vias (TSVs) in 3-D stacked integrated circuits and packaging. Rigorous closed form formulas for the resistance and inductance of TSVs are de rived from the magneto-quasi-static theory with a Fourier-Bessel expansion approach, whereas analytical formulas from static solutions are used to compute the capacitance and conductance. The equivalent-circuit model can capture the important parasitic effects of TSVs, including the skin effect, proximity effect, lossy effect of silicon, and semiconductor effect. Therefore, it yields accurate results comparable to those with 3-D full-wave solvers.

TSV Technology for Millimeter-Wave and Terahertz Design and Applications

The through silicon via (TSV) technology provides a promising option to realize a compact millimeter-wave (mmW) and terahertz (THz) system with high performance. As the fundamental elements in this system, transmission lines (T-lines) and interconnects are very important and therefore studied in this paper. A TSV-based substrate integrated waveguide (SIW) is also characterized. The results show that, the T-lines and interconnects are viable at frequencies lower than ~150 GHz whereas SIW can operate relatively well up to 300 GHz. In addition, two mmW components, i.e., a hairpin filter and a patch antenna, are designed by the TSV technology. Results of all the above passive components indicate that the low-resistivity silicon is the main cause of the total loss. Afterwards, two novel TSV-based topologies are proposed to efficiently integrate an antenna with active circuits for the mmW and THz applications.

Through Silicon Via interposer for millimetre wave applications

A novel Through Silicon Via (TSV) structure to mitigate the high electrical loss at high frequency is presented here. At low frequency, the loss for the TSV is caused mainly by the material loss of the Silicon (Si) substrate due to its low resistivity. However, at millimetre wave (mmWave) frequency range, especially above 50GHz, in addition to the insertion loss, the return loss due to impedance mismatched becomes significant. These losses become a serious setback for the Si Interposer for the mmWave applications. To overcome these losses, polymer cavity formed in the Si substrate with TSV is developed. The polymer has lower loss tangent and lower dielectric constant than Si. These properties can help to reduce the insertion loss and the return loss. Depending on the requirement, multiple set of TSV can be formed on the polymer cavity to provide higher interconnect density. From the simulation results, the new polymer cavity TSV at 100GHz have an insertion loss and return loss of ∼0.2dB and less than −25dB, respectively. On the other hand, conventional high resistivity TSV has an insertion loss and return loss of ∼1.4dB and more than −10dB, respectively, at the same frequency. For higher frequency range, the performance of the polymer cavity TSV is approximately consistent, but the conventional TSV deteriorated drastically. In this paper, the design, fabrication process and the measurement results are presented. The prototype polymer cavity TSV via-line-via test vehicle has a measured insertion loss of less than 1dB and a return loss of better than −10dB through the frequency range up to 110Gz.

Embedded Wafer Level Packaging for 77-GHz Automotive Radar Front-End With Through Silicon Via and its 3-D Integration

In this paper, a 77-GHz automotive radar sensor transceiver front-end module is packaged with a novel embedded wafer level packaging (EMWLP) technology. The bare transceiver die and the pre-fabricated through silicon via (TSV) chip are reconfigured to form a molded wafer through a compression molding process. The TSVs built on a high resistivity wafer serve as vertical interconnects, carrying radio-frequency (RF) signals up to 77 GHz. The RF path transitions are carefully designed to minimize the insertion loss in the frequency band of concern. The proposed EMWLP module also provides a platform to design integrated passive components. A substrate-integrated waveguide resonator is implemented with TSVs as the via fences, and it is later used to design a second-order 77-GHz high performance bandpass filter. Both the resonator and the bandpass filter are fabricated and measured, and the measurement results match with the simulation results very well.

High Quality and Low Loss Millimeter Wave Passives Demonstrated to 77-GHz for SiP Technologies Using Embedded Wafer-Level Packaging Platform (EMWLP)

With the increasing demand for system integration to cater to continuously increasing number of I/Os as well as higher operating frequencies, reconfigured wafer-level packaging, or embedded WLP (EMWLP) is emerging as a promising technology for integration. This platform allows integrated passives to be designed in the redistribution layers using the mold compound as a substrate, which significantly improves the passives performance compared to those of on-chip. In this paper, we present low loss passives on EMWLP platform demonstrated in a 5.5-GHz band pass filter targeted for wireless local area network (WLAN) applications. To ascertain the feasibility of designing for low loss millimeter wave passives on EMWLP, transmission lines were designed and their loss characteristics investigated up to 110 GHz, which are reported here. Subsequently we demonstrate for the first time a narrowband low loss 77-GHz band pass filter on EMWLP platform, with a good correlation obtained between simulation and measurement results. In addition, a temperature dependence characterization was performed on the 77-GHz filter, with little variation in the measured filter characteristics observed.

Demonstration of Direct Coupled Optical/Electrical Circuit Board

We report the development of a low cost, simple optical/electrical circuit board (OECB) using multimode polymer waveguide on FR4 printed circuit board (PCB). The design of this OECB uses only a 45deg-ended waveguide to couple and decouple the optical signal directly between the optical devices and the waveguide. The 45deg mirror is formed using excimer laser process on a multimode waveguide with temperature stability at reflow temperature. The optical waveguide is attached to a diced channel in the FR4 PCB using adhesive to form a completely planar circuit. This allows the laser diode and the photodiode to be assembled directly above the input and output of the waveguide using precision flip chip technology, which provides good alignment accuracy. This helps to increase the mechanical reliability of the circuit and minimize assembly requirements. Most importantly, all the electronic and optoelectronic devices used are commercially available components. In the paper, we report the details of the design, simulation result, and the testing results.

Demonstration of high quality and low loss millimeter wave passives on embedded wafer level packaging platform (EMWLP)

With the increasing demand for system integration to cater for continuously increasing I/Os as well as higher operating frequencies, EMWLP is emerging as a promising technology for integration. This platform allows integrated passives to be designed in the redistribution layers using the mold compound as a substrate, which significantly improves the passives performance compared to those of on-chip. In this paper, we present the results of high quality passives on EMWLP platform that are benchmarked against high resistivity silicon (HiRSi). The passives were then demonstrated in two band pass filters targeted to operate in the IEEE 802.11a band, with electrical performances comparable to that of commercial IPDs. Using the same platform, the measured loss characteristics of transmission lines up to 110 GHz is reported. We also demonstrate for the first time a low loss narrowband 77-GHz band pass filter on EMWLP platform, with a good correlation obtained between simulation and measurement results.

77-GHz Automotive Radar Sensor System With Antenna Integrated Package

In this paper, a 3-D integrated 77-GHz automotive radar front-end is presented. Embedded wafer level packaging (EMWLP) technology is proposed to eliminate the use of wire bonding, which not only introduces significant radio frequency loss, but also occupies large footprint for high-pin count die. The transceiver bare die is embedded in a reconfigured molded wafer with compression molding process. Double-sided multiple redistribution layers are formed to fan-out the transceiver input/output signals and through mold via is employed to realize the vertical interconnection. With these promising features, the EMWLP technology can be extended to a 3-D integration. A substrate integrated waveguide slot antenna is integrated on top of the EMWLP module and a lens is used to enhance the antenna directivity. The performance of the fully integrated radar front-end is tested and the measurement results show good package performance with RF loss around 5 dB for most of the samples. Temperature cycling reliability test was also performed by letting the fully integrated prototype goes through 1000 temperature cycles with JEDEC standard. The measured package loss spread across samples after 1000 cycles of TC test is about 13 dB, which is mainly due to the antenna warpage affecting the RF paths signal integrity.

Demonstration of High Frequency Data Link on FR4 Printed Circuit Board Using Optical Waveguides

We report the development of a low cost, simple optical circuit board (OECB) using large core multi mode polymer waveguide on FR4 printed circuit board (PCB). The design of this OECB uses only a 45deg-ended waveguide to couple and decouple the optical signal directly between the optical devices and the waveguide. The 45deg mirror is formed using excimer laser process on a multi mode waveguide with temperature stability at reflow temperature. The optical waveguide is attached to a diced channel in the FR4 PCB using adhesive to form a completely planar circuit. This allows the laser diode and the photodiode to be assembled directly above the input and output of the waveguide using precision flip chip technology, which provides good alignment accuracy. This helps to increase the mechanical reliability of the circuit and minimize assembly requirements. Most importantly, all the electronic and optoelectronic devices used are commercially available components, the FR4 PCB fabrication process is standard process, the component assembly process is normal reflow process and the method is amenable for manufacturing. In the present publication, we report the details of the design, assembly process, high accuracy optical device attachment, performance characterization and testing results.

Enhancement of Silicon-Based Inductor Q-Factor Using Polymer Cavity

A simple low-cost post-complementary metal-oxide-semiconductor-compatible process to enhance the performance of the planar spiral inductor in standard silicon (Si) substrate is demonstrated. In this process, the high loss and high permittivity of Si which reduces the inductors performance is replaced by a lower loss and lower permittivity thick polymer material. In this way, a measured high Q-factor of more than 37 and a high self-resonance frequency of 25 GHz are achieved for a 1.7-nH inductor. Using this newly developed process, the performance of the inductor can be further improved by optimizing the design.