Hui Min Lee

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.

Two-Dimensional Discontinuous Galerkin Time-Domain Method for Modeling of Arbitrarily Shaped Power-Ground Planes

This paper presents a two-dimensional discontinuous Galerkin time-domain (2-D DGTD) method for modeling arbitrarily shaped power-ground planes in high-speed electronics. The DGTD method has advantage over the finite-difference time-domain method in handling complex geometries, and allows high-order spatial discretization for improved accuracy. Its explicit time-stepping scheme also reduces computational cost compared to the implicit finite element time-domain method. The proposed method is validated against both measurement and commercial software to demonstrate its accuracy and efficiency.

Different designs of TSVs for 3D IC: Signal integrity analysis with cascaded scattering matrix

Through silicon vias (TSV) are critical vertical interconnects in 3D IC. We comparatively studied the signal integrity of different designs of TSVs both existing and new in a single die up to 20 GHz. For TSVs in multiple die stacking, we proposed to use the cascaded scattering matrix approach for their signal integrity analysis. The results are validated against those from full-path simulation. Compared to full-path simulation by a full-wave approach, the cascaded approach reduces simulation time and memory usage.

Multi-physics modeling of through-silicon vias with equivalent-circuit approach

Multi-physics modeling offers rich opportunities for studying the properties of through-silicon vias (TSV). Results of a TSV study with the theories of electromagnetics, semiconductor physics, and thermal physics are presented. Equivalent circuit models are used to draw together the three different theories to perform the TSV modeling. Moreover, a single TSV is examined for high-speed signal transmission with surface waves. Some pertinent questions are posed regarding multi-physics modeling of TSVs.

Power integrity modeling and measurement of TSV-based 3D IC system with application to the analysis of seven-chip stack

This paper presents power integrity modeling and measurement of through-silicon via (TSV)-based 3D IC system. To leverage the accuracy of a full-wave approach and shorter computational time of a circuit approach, a hybrid full-wave and circuit approach is proposed to model each individual chip consisting of TSVs, on-chip power grids and decoupling capacitors. A cascaded scattering matrix approach is used to model the 3D IC system by combining the results for individual chips, packages and boards. The hybrid modeling approach is demonstrated on a 7-chip stack consisting of 6 via-last and 1 via-middle chips. Modeling results show good correlation with measurement from 0.1 GHz to 20.1 GHz. Power integrity analysis is performed to show the effects of TSVs and vertical natural capacitors (VNCAPs) on the power distribution network in individual chips and the 7-chip stack. The passive VNCAPs in the 7-chip stack are also compared with active capacitors based on measurement. Finally, both modeling and measurement results for a prototype consisting of the 7 stacked chips mounted on a BGA substrate and a PCB are presented. This is probably the first comprehensive power integrity modeling, measurement and analysis of such a complete TSV-based 3D IC system at both chip and board levels.

A compact common-mode noise suppression filter for high speed differential signals using defected ground structure

A wideband and compact microstrip filter for common-mode electromagnetic (EM) noise suppression in high speed circuit well beyond GHz is presented in this paper. The noise reduction is realized by using specific etched slots in ground metallic plane as defected ground structure (DGS). The effect of the DGS on the characteristics of the investigated filter is examined. It is proved that the common-mode noise can be reduced by more than 15dB at center frequency of 8.4 GHz with a bandwidth from 5.4 GHz to 11.4 GHz. The differential signal is unaffected. The filter size is comparably small to the wavelength interested and the fractional bandwidth of the stop band is 71%. It is also proved the proposed approach is more efficient and effective for the EM noise reduction after comparison with other conventional filters. The proposed simple method for increasing microstrip line insertion loss for the sake of EM noise suppression can be used extensively in microwave filter design.

Impact of TSV induced thermo-mechanical stress on semiconductor device performance

Evaluation of the impact caused by Through-Silicon Vias (TSV) induced thermo-mechanical stress on device performance is becoming important due to the close proximity between TSVs and the semiconductor devices in 3D integration. From the literatures, there exist discrepancies between theory, simulated and experimental results presented. For accurate predictions, we simulated stress build-up by taking the full CMOS process flow into consideration. We considered the interaction between TSV, stressors such as tensile stress liner and Shallow Trench Isolation (STI) and device channel. From the results, it was found that the nMOSFET Ion variation is less than 2% at Keep Out Zone (KOZ) of 1 μm due to TSV induced stress while the Ion variation is about 30% due to the tensile stress liner. Hence, the impact of TSV induced stress on nMOSFET performance is insignificant compared to that of tensile stress liner in the device.

Common-mode filter using cavity-backed defected ground structure for multilayer PCB

A simple but effective common-mode noise suppression filter using cavity-backed defected ground structure (DGS) is proposed for the application of multilayer printed circuit board (PCB). This filter adds a substrate-filled metallic cavity beneath a conventional DGS. Due to the shielding effect of the cavity, the back-radiation of the DGS can be significantly reduced, while the filtering behavior of the DGS is retained in the resonant frequency band. The frequency responses and design parameters of the proposed filter are analyzed via full-wave simulation. An equivalent circuit model is also built based on the simulation result to understand the filtering behavior. It shows that an improved signal integrity (SI) is obtained with good EMI performance for a multilayer PCB.

Effective resistance approach for DC analysis of power grid on through-silicon interposer (TSI)

This paper reports an effective resistance approach with an accurate closed-form formula for fast static IR drop analysis of the power grid on a Through-Silicon Interposer (TSI). Numerical validation of the approach is performed against the SPICE simulation.

Effective modeling of multidirectional CFRP panels based on characterizing unidirectional samples for studying the lightning direct effect

The electrical conductivity of a carbon fiber reinforced plastic (CFRP) panel is highly anisotropic due to its varied fiber orientations. This paper presents an effective modeling method for studying the lightning direct effect on a multidirectional CFRP panel based on an electrical conductivity characterization of unidirectional samples. The characterization using 4-probe method is done with a simple measurement setup. The measured DC conductivity is validated by comparing the samples behavior in AC regime (lightning spectrum) obtained from measurement and simulation. It is subsequently used in the modeling of a 32-layer multidirectional CFRP panel excited by a lightning current. Simulation results show that the proposed method is able to effectively model multidirectional CFRP panels, which might be useful to studying the current-carrying capacity of CFRP panels under lightning strikes.