EDA² | ISEDA 2024

Session Details

Technical Session 8

Multi-Physics Analysis and Simulation

Session Chair: Hongliang Lv, Xidian University

Recent progress and prospects of GaN-on-Si RF technology: high performance device, CMOS-compatible fabrication process, and III-V/CMOS integration

Invited Speaker: Xiaohua Ma, Xidian University

Abstract: GaN-based RF power technology possess the advantages of high frequency, high output power, and high efficiency, making it essential for national defense and wireless communication base station applications. While the next-generation wireless communication will operate at higher frequency with wider bandwidth and multi-mode communication than what they are now, this work puts forward that broadband and high-efficiency GaN-based RF technology can be used for terminal equipment as well as base station applications. This innovation will remarkably reduce the desired RF chips and their power consumption compared with the commonly used stack-chips method. In this work, we achieve high-efficiency GaN-based enhancement-mode RF devices suitable for terminal equipment by solving some critical issues involving design, CMOS-compatible process, and theory. We believe this work will make great contribution to the development of GaN RF technology for the next-generation wireless communication terminals or individual combat equipment in the future.

Electromagnetics-Centric Multi-Physics Simulation Algorithms and Applications

Invited Speaker: Huanhuan Zhang, Xidian University

Abstract: Multi-physics field coupling refers to the physical phenomenon where two or more physical fields (such as electromagnetic, thermal, mechanical, acoustic, etc.) interact and mutually influence each other within a system. This phenomenon is commonly found in nature and practical engineering applications. For instance, the increase in integration density and power density of high-speed radio frequency integrated circuits can lead to issues such as circuit temperature rise and structural deformation, posing challenges to thermal management and structural reliability. Similarly, high-power microwave devices may experience heating due to material losses during operation, causing changes in material electrical parameters and structural deformation, significantly impacting the reliability and stability of the device's electrical performance. In the case of high-power phased-array radar antennas, improper thermal design can result in thermal deformation of the antenna array, deviation in the positions of radiating units, and deviations in electromagnetic metrics such as radiation patterns and gain from the design requirements.
Addressing these issues urgently requires the cross-fusion of electromagnetic computation technology with other physical field computation technologies, conducting research on electromagnetics, circuits, thermal, and mechanics multi-physics field simulation techniques. This report first introduces multi-physics simulation algorithms centered around electromagnetics, detailing the equations for each physical field, boundary conditions, numerical solving methods, multi-physics field coupling mechanisms, parallel acceleration techniques, etc. It explains how to efficiently and accurately analyze multi-physics field coupling problems using limited computational resources. Subsequently, the report introduces the application of the multi-physics simulation programs developed in-house in complex engineering fields such as integrated circuits, microwave devices, antennas, and more.

Multi-physics Simulation of the Electromigration for Reliability Prediction

Invited Speaker: Xiaoyan Liu, Peking University

Abstract: The electromigration (EM) reliability of interconnects becomes more and more challenging in high-density integration [1]. EM is a typical multi-physics effect of the current driven degradation that forms void due to the mass transport in interconnects. It’s strong temperature dependence and sensitive to the process integration including line dimension, interface, grain size, and the complex stress distribution of multilayer interconnect. Usually the time-to-failure (TTF) of EM is projected by the empirical prediction equations [2]. However, the conventional empirical equation would overestimate the time-to-failure (TTF) of EM due to not taking some microscopic physical effects into consideration especially in advanced technology nodes. Hence the method to predict EM degradation accuracy and efficient is important to the robust IC design. We developed a 3D KMC simulator [3] to simulate the EM behaviors in multi-layer interconnects based on the microscopic mechanisms during EM including the metal ions activation, hopping and aggregation processes [4-6]. The effects of e-wind, hydrostatic stress and SHE on EM are implemented in the simulator. The microscopic mechanism of EM includes the physical processes of metal ions activation, hopping and aggregation. The hopping directions are dominated by the e-wind which can be hindered by the stress- and electric field-induced back flow. The electrical properties of interconnects are calculated by the developed 3D-resistor network. The initial parameter input depends on the simulated metal material, structure and size. Once the ions distribution is changed, the potential and current would be updated. The simulator visualizes the void microscopic evolution and investigates the resistance-time degradation during EM as well as the prediction of TTF. The simulation results are agreed with the measured [7] resistance-time curves and cumulative failure distribution respectively.
Based on the simulation method, we further developed a physics-based compact model [8] to predict the EM failure of interconnects. The proposed model includes the physical mechanisms of microscopic movements including the metal ions migration and vacancies generation, and describes resistance evolution of metal lines corresponding to the microscopic movements. The modeling resistance evolution of metal lines reveals the resistance changes undergo the three stages: the vacancies accumulation, void formation and full void growth, which agree well with the experimental data [7] and our EM simulation [3]. The impacts of different interconnect structures on EM degradation including aspect ratio and grain size can be analyzed. The recovery effect and time-to-failure (TTF) of EM can be calculated by considering different interconnect structures, operation schemes and temperature. And the EM lifetime of interconnects can be predicted under DC and pulse operation by considering the recovery effect. The model can be used to analyze the EM lifetime under both DC and pulse operation conditions, and find the failure location in multilayer interconnects.
The simulation method and the compact model we developed, provide the powerful tool for assessment of the interconnect structure and prediction EM reliability in large-scale integrated circuits, especially for the advanced technology nodes.

Quantum Transport and Drift-Diffusion Transport Simulation of Advanced Electronic/Optoelectronic Devices

Invited Speaker: Wenchao Chen, Zhejiang University

Abstract: As the integration density keeps increasing, the elevated temperature due to self-heating intensifies the thermal stress effects on the transistor. The thermal stress can affect the band structure of the semiconductor material, and further induce the variations of device characteristics. A comprehensive Multiphysics modeling and simulation of the self-heating induced thermal stress effects on quantum transport in virous advanced semiconductor devices will be discussed.
On the other hand, drift-diffusion transport and quantum corrected drift-diffusion simulation methods also play important roles for semiconductor devices in 3D ICs. The simulation methods for treating coexistence of quantum effect and drift-diffusion methods will also be presented and discussed.
Analysis of Multiphysics effects on device performance and reliability will be discussed.

Design and Optimization of Water Droplet Interconnect Structures for Millimeter-Wave Band Applications

Presenter: Ruixin Liu, Xidian University

Abstract: The arrival of the 5G era has led to the widespread use of millimeter waves. However, discontinuities in the vertical interconnect structure within the millimeter wave band can lead to significant impedance mismatch issues, resulting in serious loss problems. In this paper, a droplet-shaped vertical interconnect transition structure based on HTCC substrate is designed to reduce loss. Optimizing the parameters of pads and anti-pads, as well as the structure itself, by analyzing parasitic capacitances. Finally, the implementation of a rectangular anti-pad structure achieves impedance matching. Simulation results show that the return loss is less than 22 dB and insertion loss is less than 0.18 dB in the range of 28-33 GHz, which provides excellent transmission performance and can be used for the design of millimeter-band components.