The Effects of Friction and Temperature in the Chemical-Mechanical Planarization Process

Area of Science:

• Materials Science
• Chemical Engineering
• Semiconductor Manufacturing

Background:

• Chemical-mechanical planarization (CMP) is crucial for wafer surface polishing, combining chemical and mechanical actions.
• Mechanical parameters, particularly friction force (F) and generated heat, significantly influence the material removal rate (MRR) in CMP.
• Colloidal silica (SiO2) abrasives in CMP slurry increase both F and MRR, affecting wafer non-uniformity (WNU).

Purpose of the Study:

• To investigate the correlation between friction, temperature, and material removal in selective layer CMP.
• To understand the impact of colloidal silica (SiO2) concentration on CMP performance and defect generation.
• To develop an empirical model for material removal amount (MRA) based on friction energy (E).

Main Methods:

• Monitoring friction force (F) and using infrared (IR) sensors to measure process temperature.
• Correlating calculated wafer non-uniformity (WNU) with the friction coefficient (COF).
• Evaluating friction energy (E) to determine the chemical contribution and deriving an empirical model for MRA.

Main Results:

• Both F and MRR increase with higher SiO2 concentrations, while temperature also rises.
• A non-linear (Prestonian) behavior of MRR was observed with varying pressure distributions, improving planarization and uniformity.
• An empirical model for MRA was derived and validated, showing improved selective layer removal with increased SiO2 nanoparticle concentration.

Conclusions:

• Controlling F and slurry stability is vital for high-quality CMP and defect prevention.
• Friction energy (E) and temperature are key indicators of CMP performance and chemical contribution.
• The study provides insights into optimizing CMP processes by managing abrasive concentration and understanding friction-temperature-MRR relationships.