To improve the performance and functionality of electronics devices, beside scaling transistor gate length and high mobility transistors, 3D stacking lowers the interconnect length, combines different technologies and nods to finally obtain a high-performance device. Interconnects in 3D staking are made by direct metal to metal bonding or solder-based bonding. Solder based bonding offers fast and high throughput bonding for bonding two different chips which may have different technologies, different die sizes and different functionalities. During solder bonding an IMC layer made which may have reliability concerns specially when the size of connections and joints are small.
The goal of this PhD thesis is to study the properties of IMC layers when bump sizes are in few microns range and propose a good working system for high density interconnects.
The properties to be studied include:
- IMC growth rate at solid state and molten phases
- IMC grain evolution with scaling bump dimension
- Electrical and mechanical properties of IMCs when bump dimeter is shrinking
- Reliability properties such as electromigration with bump scaling
To understand the IMC phase evolution and wettability, phase field and molecular dynamic simulations might be needed as well.
The PhD candidate should be familiar with material science and different analyses techniques. Practical know-how of techniques such as SEM, XPS, Auger, contact angle measurements, TEM, AFM, EBSD is an asset. Experience with electrical measurements to study the electrical properties of different UBM and solder materials is a plus-point.
Required background: Engineering Technology, Engineering Science and material Science,
Type of work: 10% literature, 20% modeling, 70% experimental
Supervisor: Ingrid De Wolf
Daily advisor: Jaber Derakhshandeh
The reference code for this position is 2020-032. Mention this reference code on your application form.
Chinese nationals who wish to apply for the CSC scholarship, should use the following code when applying for this topic: CSC2020-16.