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Cheng-Yi Liu, Professor

Cheng-Yi Liu - Professor
劉正毓 教授
 |             Ph.D. in Materials Science and Engineering, University of California, Los Angeles (UCLA), USA
Ext.: 34228
Office: Engineering Building 4, E3-220-1
Lab: Optoelectronic Materials Laboratory, E3-218
Email:  chengyi@cc.ncu.edu.tw
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Professor Cheng-Yi Liu Photo

Research Interests

Self-Assembled Low-Temperature Solder Paste, Advanced Packaging Technology, Metal Surface Treatment & Lead-Free Solder, Nanotwinned Copper Electroplating Technology, Thermal Management Materials Development, Reliability Testing Research, Light-Emitting Diodes (LED), Transparent Conductive Films.

Research Projects:

The semiconductor and optoelectronic industries are booming in Taiwan, and advanced packaging has become a vital component of Taiwan's economic lifeline. To establish a high-tech "Green Silicon Island," it is crucial to further enhance semiconductor and optoelectronic technologies. We understand that advancements in materials are often key to technological progress, and many significant technologies are built upon the emergence of new cutting-edge materials. Therefore, the main direction of this laboratory is the research and development of semiconductor packaging and optoelectronic materials, along with related research on processes and reliability.

[Image of vertical LED structure]
  1. Thin-GaN LED Process Technology Development: Includes wafer bonding, laser lift-off, and metal layer electroplating processes, followed by final LED optical measurements to obtain luminous efficiency.
  2. Flip-Chip LED Packaging: Targeting flip-chip packaging structures to develop a superior heat dissipation system, which includes a substrate with good thermal conductivity and effective heat dissipation pathways.
  3. Nanotwinned Copper Electroplating Technology: By developing (111) nanotwinned copper electroplating processes, we fabricate nanotwinned copper films. Due to the reduction of internal high-energy defect density, electron scattering and signal transmission impedance are effectively reduced, allowing current and signals to pass smoothly through the conductor. This achieves high frequency with low loss, high mechanical strength, low resistivity, high electromigration resistance, and good thermal stability, while maintaining excellent reliability. [Image of nanotwinned copper microstructure]
  4. Low-Temperature Cu-Cu Direct Bonding Technology: Utilizing various copper microstructures developed in the laboratory, we can produce copper grains suitable for rapid interfacial growth, realizing low-temperature, low-pressure Cu-Cu direct bonding technology.
  5. Self-Assembled Low-Temperature Solder Paste Development: Our laboratory has developed a self-positioning solder paste. When filled between the chip and the substrate, conductive paths form between the metal contacts of the chip and substrate during heating. The liquid paste surrounding the conductive paths gradually cures during the heating process, finally completing the underfill protection of the solder joints. This single step completes the general flip-chip packaging process.
  6. Electromigration Research in Flip-Chip Bumps: Through appropriate experimental design, we obtain Z* values for Cu-Sn and Ni-Sn alloys with different Cu and Ni additions to establish teaching models. Simultaneously, we establish equipment and methods for measuring the basic properties of intermetallic compounds (IMCs), conducting comprehensive research on the electromigration resistance of IMCs themselves and their wettability with solder, as well as studying the effects of electromigration on the interfacial reactions between solder and IMCs. [Image of flip chip packaging structure]
  7. High-k Polymer/Metal Powder Composite Capacitor Materials: Increasing the k-value of polymer/metal powder materials and finding the optimal metal doping density and size to achieve high-dielectric capacitor materials compatible with PCBs. In academic research, we investigate the detailed mechanisms of dielectric constant enhancement due to metal powder doping.
  8. Nano Metal (Alloy) Particles/Powders: By adjusting material types, concentrations, temperature, and time in the reaction system, we tune the aspect ratio of substances to endow products with different physical properties. Due to their one-dimensional characteristics, they are often mixed with polymers and sintered into reticulated films. The formed cross-linked network maintains good conductivity after stretching, high porosity allows for high light transmission and facilitates mass transfer, and the 3D structure of the film enhances material adhesion.

Publications

  1. Lee, Yun-Fong, et al. "Low temperature Cu–Cu direct bonding in air ambient by ultrafast surface grain growth." Royal Society Open Science 11.9 (2024): 240459.

  2. Li, Bao-Jhen, et al. "High transparent and conductive ZnO/Ag/ZnO film structure." Materials Today Communications (2024): 109201.

  3. Hsu, Ya-Hui, et al. "Effect of expelling P content on Ni (P) dissolution and reaction with SnAgCu (Ni)." Journal of Materials Science: Materials in Electronics 35.10 (2024): 678.

  4. Tsai, Chieh-Pu, et al. "Single-grain Sn-rich micro-bump by reducing Sn undercooling with heterogeneous nucleation." Materials Letters 357 (2024): 135729.

  5. Chang, Jui-Sheng, et al. "Abnormal Cu Grain Growth by External Stress on Electroplated Cu Films." JOM 76.6 (2024): 2711-2717.

  6. Nhi Phan, Le Yen, et al. "Detecting glucose in a cell culture medium by surface-enhanced Raman scattering on InGaN quantum wells." Optics Continuum 2.12 (2023): 2509-2515.

  7. Yen, Tzu-Hsuan, et al. "Enhancing capacitance of dielectric Si-oxide film by inserting indium-tin-oxide interlayer." Journal of Physics D: Applied Physics 56.33 (2023): 335101.

  8. Lai, Tse-Lin, et al. "Low-temperature PECVD silicon-nitride passivation for perovskite solar cell." Materials Chemistry and Physics 294 (2023): 126880.

  9. Yeh, C. Y., et al. "Development of growth model on interfacial intermetallic compound at circular Cu/Sn3.5Ag interface." Journal of Materials Science: Materials in Electronics 33.34 (2022): 25580-25588.

  10. Liu, C. Y., et al. "Wet-etching mechanism of a semi-sphere pattern on sapphire substrate." Materials Chemistry and Physics 281 (2022): 125863.

    Chou, Chia-Yueh, et al. "Mechanism and quantum efficiency of yellow emission at the organic-inorganic F8T2/p-GaN interface." Surfaces and Interfaces 29 (2022): 101799.

    151  Huang, Yen-YU, et al. "Low-Noise, Single-Polarized, and High-Speed Vertical-Cavity Surface-Emitting Lasers for Very Short Reach Data Communication." Journal of Lightwave Technology (2022): 3845-3854.

    150  Huang, B. R., et al. "Cu Sintering Process Modified by Adding a Low Temperature Liquid Sintering Step." JOM 74.4 (2022): 1730-1738.

    149  Liu, Cheng-Yi, et al. "Flexible multijunction solar cells embedded inside smart dust modules for outdoor applications to Smart Grids." Applied Energy 306 (2022): 117970.

    148  Khan, Zuhaib, et al. "High-Brightness, High-Speed, and Low-Noise VCSEL Arrays for Optical Wireless Communication." IEEE Access (2021): 2303-2317.

    147  Lin, Y. X., et al. "Effect of Ag Additives on the Consumption of a Cathode Cu Pad in a Cu/Sn3.5Ag/Cu Flip-Chip Structure Under Electromigration." Journal of Electronic Materials 50.12 (2021): 6584-6589.

    146  Liu, Cheng-Yi, et al. "Pd/Cu (220) interdiffusion under compressive stress." Materials Chemistry and Physics 271 (2021): 124882.

    145  Chou, C. Y., et al. "Morphological effect of patterned sapphire substrate on efficiency of white-light phosphor LED package." Optical Materials 119 (2021): 111297.

    144  Nguyen, Thi Anh Nguyet, et al. "Controlling the Electron Concentration for Surface-Enhanced Raman Spectroscopy." ACS Photonics 8.8 (2021): 2410-2416.

    143  Li, B. J., et al. "High-mobility ZnVxOy/ZnO conduction path in ZnO/V/ZnO multilayer structure." Journal of Applied Physics 130.7 (2021): 075302.

    142  Chen, Wei‐Hao, et al. "Plastic deformation of ZnO thin films through edge and screw dislocation movements." Journal of the American Ceramic Society 104.12 (2021): 6579-6588.

     

    141  Wu, C. Y., et al. "Study of galvanized Sn-finished Ag surface." Journal of Materials Science: Materials in Electronics 32.14 (2021): 18605-18615.

     

    140  Lee, Chia-Hung, et al. "Effect of De-Twinning on Tensile Strength of Nano-Twinned Cu Films." Nanomaterials 11.7 (2021): 1630.

    139  Huang, C. K., et al. "Measurement of internal electrical field across InGaN quantum wells in GaN LEDs." Materials Chemistry and Physics 265 (2021): 124514.

     

    138  Huang, Chun-Kai, et al. "Flip‐Chip Packaged Perovskite Solar Cells." Energy Technology 9.7 (2021): 2001129.

     

    137  Chien, Fan-Ching, et al. "Nanostructured InGaN Quantum Wells as a Surface-Enhanced Raman Scattering Substrate with Expanded Hot Spots." ACS Applied Nano Materials 4.3 (2021): 2614-2620.

     

    136  Wang, Jyun-Yang, et al. "Effect of Ag solutes on the solid-state Cu dissolution in the Sn3.5Ag." Journal of Materials Science: Materials in Electronics 32.1 (2021): 567-576.

     

    135  Wang, Jyun Yang, et al. "Effect of mixing glass frits on electrical property and microstructure of sintered Cu conductive thick film." Journal of the American Ceramic Society 104.4 (2021): 1707-1715.

     

    134  Chen, Wei-Hao, et al. "Conductive and Transparent Properties of ZnO/Cu/ZnO Sandwich Structure." Journal of electronic materials 50.3 (2021): 779-785.

     

    133  Lai, Wei-Han, et al. "Formation mechanism of self-formed triangular pyramidal patterns on sapphire substrate." Crystal Growth & Design 20.7 (2020): 4811-4817.

     

    132  Shi, Jin-Wei, et al. "High-power and single-mode VCSEL arrays with single-polarized outputs by using package-induced tensile strain." Optics Letters 45.17 (2020): 4839-4842.

    131  Huang, Che-Hsuan, et al. "Research on a Novel GaN-Based Converted Mini-LED Backlight Module via a Spectrum-Decouple System." IEEE Access 8 (2020): 138823-138833.
    130  Chou, Chia-Yueh, et al. "High-dielectric-constant silicon nitride thin films fabricated by radio frequency sputtering in Ar and Ar/N2 gas mixture." Thin Solid Films 709 (2020): 138198.
    129  Tang, Y. K., et al. "Effect of eutectic reaction between depositing atoms and substrate elements on morphological evolution of Sn–Bi–Sn multilayer deposition." Materials Chemistry and Physics (2020): 122960.
    128  Cheng, Cheng, et al. "Effect of annealing atmosphere (CO and N2 gas flow) on surface morphology and crystal quality of AlN buffer layer." Ceramics International (2020).
    127  Wu, C. Y., et al. "Effect of Chemical Additives in the Plating Bath on Surface Corrosion Resistance of Ni (P)." Journal of Electronic Materials 49.1 (2020): 26-33
    126  Wang, J. Y., et al. "Kinetics of Ni solid-state dissolution in Sn and Sn3.5Ag alloys." Journal of Alloys and Compounds 797 (2019): 684-691.
    125  Lin, Chia-Hua, et al. "Fabrication of p-type TiO2 and transparent p-TiO2/n-ITO pn junctions." AIP Advances 9.4 (2019): 045229.
    124  Liao, Ching‐Han, et al. "Experiment and Theoretical Calculation of the Surface Space Charge Region Effect on Photocurrent Generation of SnO2 Bilayer Photodiode Devices." Advanced Electronic Materials 5.4 (2019): 1800679.
    123  Chang, Pai-Jung, et al. "Fabrication of Aluminum Nitride Thermal Substrate and Low-Temperature Die-Bonding Process for High Power LED." Journal of Electronic Materials 48.1 (2019): 194-200.
    122  Yang, Bo‐Xuan, et al. "Fully Solution‐Processed Low‐Voltage Driven Transparent Oxide Thin Film Transistors." physica status solidi (a) 215.24 (2018): 1800192.
    121  Lee, Po-Ming, et al. "Photocurrent generation in SnO2 thin film by surface charged chemisorption O ions." Applied Surface Science 442 (2018): 398-402.
    120  Chen, Y. H., et al. "Mechanism of Ag sulfurization resistance improvement by alloying solutes in Ag-based alloy films." Journal of Applied Physics 123.24 (2018): 245305.
    119  Tang, Y. K., et al. "Die-Bonding of LED Chips on Ag/Cu Substrate Using Sn/Zn/Bi/Sn and Sn/Bi/Zn/Bi/Sn Bonding Systems." Journal of Electronic Materials 47.1 (2018): 77-83.
    118  Sun, Hui, et al. "p-type conductive NiOx: Cu thin films with high carrier mobility deposited by ion beam assisted deposition." Ceramics International 44.3 (2018): 3291-3296.
    117  Wu, Y. J., et al. "Organic/inorganic F8T2/GaN light emitting heterojunction." Organic Electronics 49 (2017): 64-68.
    116  Lin, E. J., et al. "Effect of Cu solubility on electromigration in Sn (Cu) micro joint." Journal of Applied Physics 122.9 (2017): 095702.
    115  Lin, E. J., et al. "Effect of interfacial dissolution on electromigration failures at metals interface." Journal of Materials Science: Materials in Electronics 28.20 (2017): 15149-15153.
    114  Liao, Ching-Han, et al. "Growth Direction Control of ZnO Nanorods on the Edge of Patterned Indium–Tin Oxide/Aluminum-Doped Zinc Oxide Bilayers." Crystal Growth & Design 17.6 (2017): 3100-3106.
    113  Huang, S. W., et al. "Fabrication of nano-cavity patterned sapphire substrate using self-assembly meshed Pt thin film on c-plane sapphire substrate." Thin Solid Films 628 (2017): 127-131.
    112  Tang, Y. K., et al. "LED Die-Bonded on the Ag/Cu Substrate by a Sn-BiZn-Sn Bonding System." Journal of Electronic Materials 45.12 (2016): 6171-6176.
    111  Liu, C. Y., et al. "Study of Sn and SnAgCu Solders Wetting Reaction on Ni/Pd/Au Substrates." Journal of Electronic Materials 45.12 (2016): 6079-6085.
    110  Chung, C. C., C. T. Yang, and C. Y. Liu. "Anelasticity of GaN Epitaxial Layer in GaN LED." Materials Research Express 3.10 (2016): 105026.
    109  Lu, Chien-Chun, et al. "Effects of nighttime lights by LED and fluorescent lighting on human melatonin." Journal of Ambient Intelligence and Humanized Computing 7.6 (2016): 837-844.
    108  Lu, Chien-Chun, et al. "The efficiency and reliability improvement by utilizing quartz airtight packaging of UVC LEDs." IEEE Transactions on Electron Devices 63.8 (2016): 3143-3146.
    107  Lee, Po-Ming, et al. "Experimental observation and computer simulation of Al/Sn substitution in p-type aluminum nitride-doped tin oxide thin film." The Journal of Physical Chemistry C 120.8 (2016): 4211-4218.
    106  Chen, Y. H., et al. "Sulfurization Study on the Ag and Ag-Pd Reflectors for GaN-Based LEDs." Journal of Electronic Materials 45.1 (2016): 191-196.
    105  Liu, Wei Chih, et al. "Study of Al− Cu compounds as soldering bond pad for high-power device packaging." Microelectronics Reliability 55.12 (2015): 2549-2553.
    104  Lee, Po-Ming, et al. "Observation of Ni3+ acceptor in P-type Ni (P): SnO2." Applied Surface Science 337 (2015): 33-37.
    103  Li, Xu-Fong, et al. "Fabrication of patterned sapphire substrate and effect of light emission pattern on package efficiency." Optical Materials Express 5.8 (2015): 1784-1791.
    102  Huang, S. W., et al. "Etching three-dimensional pattern on sapphire substrate by dynamic self-masking alunogen compound." ECS Solid State Letters 4.6 (2015): R35.
    101  Villamagua, Luis, et al. "Change in the electrical conductivity of SnO2 crystal from n-type to p-type conductivity." Chemical Physics 452 (2015): 71-77.
    100  Wu, Y. J., et al. "Preparation of V-doped AZO thin films and ZnO nanorods on V-doped AZO thin films by hydrothermal process." Journal of Sol-Gel Science and Technology 73.3 (2015): 647-654.
    99    Wu, Yen-Ju, et al. "Local electronic structures and polarity of ZnO nanorods grown on GaN substrates." The Journal of Physical Chemistry C 119.9 (2015): 5122-5128.
    98    Wu, Y. J., et al. "Study of p-type AlN-doped SnO2 thin films and its transparent devices." Applied Surface Science 328 (2015): 262-268.
    97    Hsieh, Chih-Yi, et al. "Transparent p-AlN: SnO2/n-SnO2 tunnel diode." Applied Physics Express 7.9 (2014): 092201.
    96    Sun, Ching-Cherng, et al. "Packaging efficiency in phosphor-converted white LEDs and its impact to the limit of luminous efficacy." Journal of Solid State Lighting 1.1 (2014): 19.
    95    Lin, Yi Chin, et al. "Internal quantum efficiency enhancement by relieving compressive stress of GaN-based LED." IEEE Photonics Technology Letters 26.18 (2014): 1793-1796.
    94    Liu, W. C., et al. "An electroless-Ag reflector developed for high-brightness white LEDs." Journal of electronic materials 43.12 (2014): 4602-4609.
    93    Su, Chien-Hao, et al. "Kinetic analysis of spontaneous whisker growth on pre-treated surfaces with weak oxide." Journal of electronic materials 43.9 (2014): 3290-3295.
    92    Liu, C. Y., et al. "Back-fill Sn flux against current-stressing at cathode micro Cu/Sn interface." ECS Solid State Letters 3.2 (2013): P17.
    91    Liu, C. Y., et al. "Epitaxial Cu–Sn bulk crystals grown by electric current." Acta materialia 61.15 (2013): 5713-5719.
    90    Li, Xu Feng, et al. "Nanomeshed Pt (Au) Transparent Contact to p-GaN of Light-Emitting Diode." Journal of electronic materials 43.1 (2014): 166-169.
    89    Hu, Y. J., et al. "Interfacial Reactions Between Columnar or Layered Ni (P) Layers and Sn-Ag-Cu Solder." Journal of electronic materials 43.1 (2014): 277-283.
    88    Hu, Y. J., et al. "Effect of Metal Bond-Pad Configurations on the Solder Microstructure Development of Flip-Chip Solder Joints." Journal of electronic materials 43.1 (2014): 170-175.
    87    Liu, Yen-Shuo, et al. "Mechanism of conductivity degradation of AZO thin film in high

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