Atomistic Simulation of Polycrystalline Copper: Mechanical and Electromigration Reliability Analysis

Title: Atomistic Simulation of Polycrystalline Copper: Mechanical and Electromigration Reliability Analysis

Overview: This six-month internship/MSc Project focuses on the creation of a numerical model for a polycrystalline copper structure and the determination of its properties which have a potential to improve its mechanical and electromigration reliability. The polycrystalline structure will be generated using both Molecular Dynamics (MD) methods and Coincident Site Lattice (CSL) theory. Furthermore some extended crystal defects, like dislocations, relevant for investigation will be added.

Objective: The polycrystalline structures created by CSL methods will serve as training data for Machine Learning (ML) optimization of the interatomic potential used in MD simulations. Density Functional Theory (DFT) and Non-Equilibrium Green’s Function (NEGF) formalism will be employed to calculate the effective electromigration valence (Z*) of the numerically created polycrystalline copper. The possibility of determining the elasticity tensor and yield stress for a polycrystalline structure by a combination of DFT and MD will be investigated.  A prerequisite to performing simulations for calculating yield stress is setting of different dislocation types, which will also be performed utilizing MD methods.

Tasks: The planned work is organized into three main tasks, each with associated subtasks. All tasks will be performed using an atomistic simulation tool that includes DFT, Semi Empirical Methods, Force Field Methods (MD), and Machine-Learned Force Fields.

Task 1: Generation and Optimization of Grain Boundary Structure

• 1.1: Set up the polycrystalline structure using the CSL method.
• 1.2: Generate a polycrystalline structure using the MD method.
• 1.3: Optimize the MD potential using ML.
  
  Task 2: Calculation of Effective Valence and Mechanical Properties of Polycrystalline Copper
• 2.1: Calculate the electron density of atomic structures created in Task 1.
• 2.2: Calculate the effective valence Z* by utilizing different analytical approaches in combination with electron density determined in Task 2.1.
• 2.3: Calculate the elasticity tensor for the polycrystalline structures created in Task 1.
• 2.4: Calculate the yield stress using the polycrystalline structures created in Task 1 for different dislocation types and configurations.
  
  Task 3: Presentation of Results and Reporting
• 3.1: Present the obtained results at an internal IMEC meeting.
• 3.2: Write a 20-page report at the end of the internship.
  
   
  
  Scientific supervision:
• Prof. Hajdin Ceric (Technical University Vienna) and Dr. Houman Zahedmanesh imec