dr. Xu Liu

1. Reliability Analysis of Cu Sintered Die-Attach for SiC Power Devices: Mechanical, Electrical, and Thermal Evaluation
   Xu Liu; Shaogang Wang; Dong Hu; Chenshan Gao; Qianming Huang; Huaiyu Ye; Paddy French; Guoqi Zhang;
   In IEEE 74th Electronic Components and Technology Conference (ECTC),
   Denver, Colorado, IEEE, IEEE, May 2024.

2. Reliability Analysis of Cu Sintered Die-Attach for SiC Power Devices: Mechanical, Electrical, and Thermal Evaluation
   Xu Liu; Shaogang Wang; Dong Hu; Chenshan Gao; Qianming Huang; Huaiyu Ye; Paddy French; Guoqi Zhang;
   In IEEE 74th Electronic Components and Technology Conference (ECTC) in Denver, Colorado, from May 28 to May 31, 2024,
   2024.

3. Transient thermal measurement on nano-metallic sintered die-attach joints using a thermal test chip
   R. Sattari; Dong Hu; Xu Liu; H. van Zeijl; S. Vollebregt; GuoQi Zhang;
   Applied Thermal Engineering,
   Volume 221, pp. 119503, 2023. DOI: 10.1016/j.applthermaleng.2022.119503

4. Reverse Recovery Optimization of Multiepi Superjunction MOSFET Based on Tunable Doping Profile
   Ke Liu; Chunjian Tan; Shizhen Li; Wucheng Yuan; Xu Liu; Guoqi Zhang; Paddy French; Huaiyu Ye; Shaogang Wang;
   Electronics,
   Volume 12, Issue 2977, 2023. DOI: https://doi.org/10.3390/electronics12132977
   
   Keywords: ...

   superjunction; MOSFET; doping profile; reverse recovery; body diode.
   
   
   Abstract: ...

   This paper proposes and simulates research on the reverse recovery characteristics of two novel superjunction (SJ) MOSFETs by adjusting the doping profile. In the manufacturing process of the SJ MOSFET using multilayer epitaxial deposition (MED), the position and concentration of each Boron bubble can be adjusted by designing different doping profiles to adjust the resistance of the upper half P-pillar. A higher P-pillar resistance can slow down the sweep out speed of hole carriers when the body diode is turned off, thus resulting in a smoother reverse recovery current and reducing the current recovery rate (dir/dt) from a peak to zero. The simulation results show that the reverse recovery peak current (Irrm) of the two proposed devices decreased by 5% and 3%, respectively, compared to the conventional SJ. Additionally, the softness factor (S) increased by 64% and 55%, respectively. Furthermore, this study also demonstrates a trade-off relationship between static and reverse recovery characteristics with the adjustable doping profile, thus providing a guideline for actual application scenarios.

5. Rapid Fabrication of High-Performance Flexible Pressure Sensors Using Laser Pyrolysis Direct Writing
   Shaogang Wang; Qihang Zong; Huiru Yang; Chunjian Tan; Qianming Huang; Xu Liu; Guoqi Zhang; Paddy French; Huaiyu Ye;
   Applied Materials and Interfaces,
   2023. DOI: https://doi.org/10.1021/acsami.3c04290
   
   Keywords: ...

   flexible pressure sensor, UV laser, laser direct writing, continuous laser pyrolysis, PDMS, micro-truncated pyramid.
   
   
   Abstract: ...

   The fabrication of flexible pressure sensors with low cost, high scalability, and easy fabrication is an essential driving force in developing flexible electronics, especially for high-performance sensors that require precise surface microstructures. However, optimizing complex fabrication processes and expensive microfabrication methods remains a significant challenge. In this study, we introduce a laser pyrolysis direct writing technology that enables rapid and efficient fabrication of high-performance flexible pressure sensors with a microtruncated pyramid array. The pressure sensor demonstrates exceptional sensitivities, with the values of 3132.0, 322.5, and 27.8 kPa−1 in the pressure ranges of 0−0.5, 0.5−3.5, and 3.5−10 kPa, respectively. Furthermore, the sensor exhibits rapid response times (loading: 22 ms, unloading: 18 ms) and exceptional reliability, enduring over 3000 pressure loading and unloading cycles. Moreover, the pressure sensor can be easily integrated into a sensor array for spatial pressure distribution detection. The laser pyrolysis direct writing technology introduced in this study presents a highly efficient and promising approach to designing and fabricating high-performance flexible pressure sensors utilizing micro-structured polymer substrates.

6. Study on Sintering Mechanism and Mechanical Properties of Nano-Cu based on Molecular Dynamics Simulation
   Cheng Qian; Dong Hu; Xu Liu; Xuejun Fan; Guoqi Zhang; Jiajie Fan;
   In 24th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE),
   2023. DOI: 10.1109/EuroSimE56861.2023.10100810

7. Reliability Analysis on Ag and Cu Nanoparticles Sintered Discrete Power Devices with Various Frontside and Backside Interconnects
   Dong Hu; Xu Liu; Sten Vollebregt; Jiajie Fan; Guoqi Zhang; Ali Roshanghias; Xing Liu; Thomas Basler; Emiel De Bruin;
   In Proc. of Electronic Components and Technology Conference (ECTC),
   2023.

8. Pressure-assisted Cu sintering for SiC Die-attachment application
   Xu Liu;
   PhD thesis, Delft University Technology, 2023. DOI: 10.4233/uuid:291baefe-c4b9-46ea-b250-a6c8f4e6ece8

9. Low Leakage and High Forward Current Density Quasi-Vertical GaN Schottky Barrier Diode With Post-Mesa Nitridation
   X. Kang; Y. Sun; Y. Zheng; K. Wei; H. Wu; Y. Zhao; Xu Liu; GuoQi Zhang;
   IEEE Transactions on Electron Devices,
   Volume 68, Issue 3, pp. 1369-1373, 2021. DOI: 10.1109/TED.2021.3050739

10. A DFT Model Study about Structure Sensitivity for Benzotriazole Adsorption on Copper Surfaces and Nano Cluster
    Weihong Zhang; Quan Zhou; Honghao Tang; Xu Liu; Huaiyu Ye; Sau Wee Koh; GuoQi Zhang;
    In 2020 21st International Conference on Electronic Packaging Technology (ICEPT),
    Guangzhou, China, IEEE, pp. 1-4, Aug 2020. DOI: 10.1109/ICEPT50128.2020.9202975

11. Study on the effect of mixing proportion of micro- and nano-copper particles on sintering properties
    Xu Liu; Quan Zhou; Qipeng Liu; Honghao Tang; Chenshan Gao; Bin Xie; Sau Wee Koh; Huaiyu Ye; GuoQi Zhang;
    In 2020 21st International Conference on Electronic Packaging Technology (ICEPT),
    pp. 1-5, 2020. DOI: 10.1109/ICEPT50128.2020.9201937

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