Thermal Reflow Simulation for PMMA Structures with Nonuniform Viscosity Profile

Area of Science:

• Materials Science
• Computational Modeling
• Nanotechnology

Background:

• Polymethyl methacrylate (PMMA) is widely used in microelectronics fabrication.
• Accurate simulation of thermal reflow is crucial for controlling 3D structure formation.
• Existing models often overlook the impact of nonuniform viscosity in exposed PMMA.

Purpose of the Study:

• To develop a novel numerical approach for simulating the thermal reflow of e-beam-exposed PMMA.
• To incorporate the nonuniform viscosity profile of PMMA into surface evolution modeling.
• To validate the simulation method for predicting reflow in complex microstructures.

Main Methods:

• Utilized numerical "soapfilm" modeling of surface evolution via the "Surface Evolver" software.
• Calculated PMMA viscosity profiles by simulating molecular weight distribution using Monte-Carlo methods and empirical formulas.
• Determined the relationship between PMMA viscosity and surface vertex mobility through analytical and numerical reflow simulations.

Main Results:

• Established a precise, proportional relationship between the inverse mobility of PMMA surface vertices and PMMA viscosity.
• Validated the "soapfilm" modeling approach against analytical and numerical simulations for uniform PMMA gratings.
• Demonstrated the capability of the developed method to simulate thermal reflow in complex, nonuniform structures.

Conclusions:

• The "soapfilm" modeling approach is highly applicable for simulating polymer thermal reflow, even with nonuniform viscosity.
• The developed method enables predictable reflow, facilitating its use in 3D microfabrication processes.
• This simulation technique offers a powerful tool for designing and optimizing micro/nanofabrication processes involving PMMA thermal reflow.