Study on Stress Distribution and Its Impact on Reliability of SiO₂-Based Inorganic Chiplet Gap Filling

Area of Science:

• Materials Science
• Mechanical Engineering
• Semiconductor Manufacturing

Background:

• Inorganic gap filling using silicon dioxide (SiO2) via plasma-enhanced chemical vapor deposition (PECVD) is crucial for 2.5D and 3D chiplet integration, offering an alternative to Epoxy Mold Compound (EMC).
• SiO2 fillers present reliability challenges, including cracking and peeling, due to their inorganic nature.
• Quantitative characterization and modeling of microscale mechanical properties, thermal stress, and fracture risk in SiO2 fillers are lacking.

Purpose of the Study:

• To develop a comprehensive route for quantitative characterization of the mechanical behavior of inorganic gap fillers.
• To establish a finite element method (FEM) model for predicting the thermomechanical reliability of the gap filling process.
• To investigate the impact of filler thickness on stress distribution and fracture risk.

Main Methods:

• Combined nanoindentation and three-point bending tests for microscale mechanical characterization.
• Finite Element Method (FEM) modeling to simulate thermomechanical stress and predict fracture risk.
• Raman spectroscopy for experimental validation of the FEM model.

Main Results:

• A novel method for quantitative microscale mechanical characterization of SiO2 fillers was established.
• An FEM model was developed and validated using Raman spectroscopy, demonstrating reliable predictive ability for thermomechanical reliability.
• The study revealed the significant impact of filler thickness on stress distribution within the gap-filled structures.

Conclusions:

• The developed microscale characterization and FEM modeling approach overcomes limitations of traditional methods for inorganic gap filling in advanced packaging.
• This research provides crucial support for process optimization and structural design in high-density 2.5D/3D chiplet integration.
• The findings enhance the understanding of inorganic filling process reliability, crucial for the advancement of heterogeneous integration technologies.