Research Description
I. Electronic materials
Our research interest is in Si-based and diffusion-driven materials science for modern microelectronic, opto-electronic, bio-sensor, and MEMS devices. Our major research areas are (1) Lead (Pb)-free solder metallurgy for electronic and optical packaging technology, (2) Advanced materials reliability problems of microelectronic devices, especially concerning the flip chip technology and three-dimensional intergrated circuit (3D IC) technolgoy, and (3) Interfacial reaction and reliability problems of Cu wirebound tehcnology for electronic vehicles applications.
●Pb-free solder metallurgy: We study the wetting reaction and solid state aging for different Pb-free solder joint with thin film
under-bump-metallization. The Pb-free solders include eutectic SnAg, SnAgCu, SnCu, SnZn.
●Advanced materials reliability problems of microelectronic devices:
Reliability of first level interconnect in the microelectronic package industry has been a concern for a long time. Recently,
new reliability issues have appeared due to higher demand of greater functionality in the product. As the product performance increases, the number of input/output contact pads on a chip increases, and the diameter of solder bump decreases, the current density in the contact area of a solder bump increases very rapidly. Electromigration has been recognized to be a reliability issue in flip chip solders joints due to the formation of pancake-type void at the cathode contact on the die side. In addition, when joining the chip to the substrate, thermal stress is developed on the solder joint due to thermal coefficient mismatch. When a
temperature gradient exists across a solder joint due to joule heating, thermomigration tends to occur too. These effects have become serious reliability issues, especially when they are combined.
Since high density packaging is needed and the technology is moving towards denser I/O array, smaller feature size, and higher power, packing technology is moving from 2D IC to 3D IC. Different chips in the 3D IC technology are connected by micro bumps and vertical interconnects. The size of micro bumps is 20um to 30um. With the reduction of bump sizes, electromigration will be an important issue. Furthermore, Joule heating will be serious in 3D IC. In order to effectively remove heat, a temperature gradient will be established across the packages. If a difference of 2 oC across a micro-bump of 20um in diameter, the temperature gradient will be 1000 oC /cm, which will cause serious thermomigration failure. Therefore, the importance on both electromigration and thermomigration in the micro bumps for 3D IC will become more important.
The advanced materials reliability problems due to a combined action among chemical, mechanical, thermal and electrical forces in flip chip and 3D IC technology will be systematically studied, including microstructural evolution, phase transformation, their corresponding mechanism, and kinectic theroy.
●Cu interconnect technology: Our research emphasizes the fabrication, microstructure, properties of Cu nano thin films uitlized in the semiconductor industries. The mechanical properties and electromigration on the Cu nano thin films will be investigated.
●Cu wirebonding technology: Our research emphasizes the interfacial reaction and their corresponding reliability problems.
●Pb-free solder metallurgy: We study the wetting reaction and solid state aging for different Pb-free solder joint with thin film
under-bump-metallization. The Pb-free solders include eutectic SnAg, SnAgCu, SnCu, SnZn.
●Advanced materials reliability problems of microelectronic devices:
Reliability of first level interconnect in the microelectronic package industry has been a concern for a long time. Recently,
new reliability issues have appeared due to higher demand of greater functionality in the product. As the product performance increases, the number of input/output contact pads on a chip increases, and the diameter of solder bump decreases, the current density in the contact area of a solder bump increases very rapidly. Electromigration has been recognized to be a reliability issue in flip chip solders joints due to the formation of pancake-type void at the cathode contact on the die side. In addition, when joining the chip to the substrate, thermal stress is developed on the solder joint due to thermal coefficient mismatch. When a
temperature gradient exists across a solder joint due to joule heating, thermomigration tends to occur too. These effects have become serious reliability issues, especially when they are combined.
Since high density packaging is needed and the technology is moving towards denser I/O array, smaller feature size, and higher power, packing technology is moving from 2D IC to 3D IC. Different chips in the 3D IC technology are connected by micro bumps and vertical interconnects. The size of micro bumps is 20um to 30um. With the reduction of bump sizes, electromigration will be an important issue. Furthermore, Joule heating will be serious in 3D IC. In order to effectively remove heat, a temperature gradient will be established across the packages. If a difference of 2 oC across a micro-bump of 20um in diameter, the temperature gradient will be 1000 oC /cm, which will cause serious thermomigration failure. Therefore, the importance on both electromigration and thermomigration in the micro bumps for 3D IC will become more important.
The advanced materials reliability problems due to a combined action among chemical, mechanical, thermal and electrical forces in flip chip and 3D IC technology will be systematically studied, including microstructural evolution, phase transformation, their corresponding mechanism, and kinectic theroy.
●Cu interconnect technology: Our research emphasizes the fabrication, microstructure, properties of Cu nano thin films uitlized in the semiconductor industries. The mechanical properties and electromigration on the Cu nano thin films will be investigated.
●Cu wirebonding technology: Our research emphasizes the interfacial reaction and their corresponding reliability problems.
|
|
|
|
II. Energy materials (Cooperate with Prof. J.J. Kai & Dr. H.F. Lee)
We also conduct exploratory research on energy materials, including dye-sensitized solar cell, and nuclear materials. The research areas for dye-sensitized solar cells mianly focuses on the fabrication and material selection, including the following topics,
● Enhance efficiency and stability of DSSC by introducing thin films
● Electrolyte modification
● Flexible dye-sensitized solar cells
● Enhance efficiency and stability of DSSC by introducing thin films
● Electrolyte modification
● Flexible dye-sensitized solar cells
|
|
