MSE MS Thesis Defense - Chinmay Honrao
The committee includes:
Dr. Rao Tummala (MSE) (advisor)
Dr. Richard Neu (MSE)
Dr. Raj Pulugurtha (ECE)
The title is: "Fine-pitch Cu-SnAg Die-to-Die and Die-to-Interposer
Interconnections using Advanced SLID Bonding"
Multi-chip integration with emerging technologies such as a 3D IC stack or
2.5D interposer is primarily enabled by the off-chip interconnections. The
I/O density, speed and bandwidth requirements for emerging mobile and
high-performance systems, are projected to drive the off-chip
interconnection pitch from chip-to-chip or chip-to-interposer to less than
20μm by 2015. Such a fine-pitch interconnection technology must overcome a
variety of electrical, mechanical, thermal, reliability performance,
manufacturability and cost challenges.
The need for finer pitch has shifted the interconnection focus from
traditional C4 solder ball technology to Copper pillar with solder cap.
However, the poor electrical and thermo-mechanical reliability with
fine-pitch solders still creates several challenges in meeting the
performance targets. The reliability constraints are mostly associated with
the residual solders in the interconnections. This research aims to study 30
micron pitch Cu-SnAg interconnections with improved electrical performance
by fast and complete conversion of solders to stable inter-metallics (IMCs)
using a novel Solid Liquid Diffusion (SLID) bonding approach. SLID bonding,
being a liquid state diffusion process, combined with a novel, multi-layered
copper-solder stack structure, leads to higher diffusion rates and a much
faster conversion of solder to IMCs. Moreover this assembly bonding is done
at a much lower temperature and pressure as compared to that used for Cu-Cu
A comprehensive approach based on modeling, copper-solder stack design,
test-structure fabrication and characterization is pursued to explore and
demonstrate this new class of SLID interconnections. The effect of
interconnection stack design, bonding parameters such as temperature,
pressure and time on the microstructural evolution is also studied.