“Towards a rational understanding of structure-dependent
efficiency of organic corrosion inhibitors for Cu CMP”
Murali Ramu
Materials Science and Engineering Program, Clarkson University, Potsdam, NY, USA
Abstract
Chemical mechanical planarization (CMP) is a crucial process in the back-end-of-line (BEOL) process of semiconductor manufacturing. The primary objective of CMP is to uniformly polish the copper (Cu) metal interconnects and barrier materials while minimizing defects like pitting, dissolution, and corrosion. A typical Cu CMP slurry contains an oxidizer that chemically converts the metal film into metal oxides for easy removal, abrasive particles that enhance the material removal through wear and abrasion, a passivating agent (corrosion inhibitor) to prevent excessive corrosion in recessed areas and a pH regulator. In this process, organic corrosion inhibitors play a critical role by protecting the Cu film from aggressive chemical attacks that could lead to undesirable dissolution. Benzotriazole (BTA) has been widely used as a prominent organic corrosion inhibitor in the semiconductor industry due to its ability to form a stable, protective film on Cu surfaces. This aromatic heterocyclic compound containing three nitrogen atoms in its ring provides excellent corrosion resistance. However, the high concentrations of BTA required to meet CMP performance standards have raised environmental concerns due to its persistence in wastewater, driving a search for more eco-friendly alternatives. Our study evaluates a range of organic corrosion inhibitor candidates as potential replacements for BTA in Cu CMP slurries. The corrosion behavior of these inhibitors was assessed using potentiodynamic polarization techniques in a slurry solution containing 3 wt% silica, 3wt% of Hydrogen peroxide, and 10mM of inhibitors at pH 10. The experimental results were complemented by Density Functional Theory (DFT) calculations, which provided insights into the molecular and electronic properties of the inhibitors. To predict inhibitor efficiency, a quantitative structure-property relationship (QSPR) model was developed using multiple linear regression analysis. The model revealed that inhibitor performance is influenced by several key factors, including the aromaticity of the molecule, electron-donating ability of heteroatoms (e.g., nitrogen, oxygen), Molecular structure features such as chain length, conjugated bonds, and ring systems. This integrated approach, combining experimental data with computational modeling, offers new insights into the design of environmentally friendly corrosion inhibitors for CMP processes.
Keywords: Chemical Mechanical Planarization, Cu CMP Slurry, Inhibitors, QSPR, Semiconductor
Monday, 11/04/2024 at 4:30 pm CAMP 176
Short bio:
Murali Ramu is a Ph.D. student in the Materials Science and Engineering Program at Clarkson University. He is conducting his research under the mentorship of Dr. Jihoon Seo, focusing on the field of Chemical Mechanical Planarization (CMP). Murali’s primary research emphasis lies in achieving a fundamental understanding of slurry behavior and the interactions of its components at the slurry-wafer interface. His work aims to advance CMP processes by investigating the chemical and mechanical mechanisms critical to the efficiency and precision required in semiconductor manufacturing.