Finite element method simulation of the molding process for thermal nano-imprint lithography

Area of Science:

• Materials Science
• Mechanical Engineering
• Nanotechnology

Background:

• Thermal nano-imprint lithography (NIL) is a key technique for micro- and nanofabrication.
• Understanding polymer deformation under imprinting stress is critical for process optimization.
• Polymethyl methacrylate (PMMA) is a widely used resist material in NIL.

Purpose of the Study:

• To numerically study the deformation of viscoelastic PMMA during NIL.
• To analyze the stress distribution within the PMMA resist during imprinting.
• To identify potential defects like micro-gap formation.

Main Methods:

• Numerical simulation using the finite element method (FEM).
• Modeling the imprinting of a rigid SiO2 stamp with a rectangular line pattern into PMMA.
• Analysis of viscoelastic material behavior under applied stress.

Main Results:

• Asymmetric von Mises stress distribution observed around the imprinted line.
• Stress concentration identified at the sidewall near the structure's centerline.
• Formation of a micro-gap between the replicated structure and the mold wall.

Conclusions:

• The squeezing flow in PMMA contributes to asymmetric stress during NIL.
• Stress concentration and micro-gap formation are significant outcomes of the imprinting process.
• FEM simulations provide valuable insights into NIL process mechanics for PMMA.