Evaluation and Modeling of Novel Groove Pad Designs on Inter-layer Dielectric and Copper Chemical Mechanical Planarization

Abstract

The present dissertation includes several studies that describe the effects of novel groovedesigns on the tribological, thermal and kinetic characteristics of ILD and copper CMP. A novelIPL-FMC 200-mm polisher, in which friction force could be obtained in two directions, was introduced and compared to lab-scale (IPL 100-mm) polisher during ILD CMP. Results showed that scaling the ILD process from 100 to 200 mm caused a transition from a mechanically-limited regime, in which it was still possible to detect thermal effects, to a higher degree of mechanical limitation where it was no longer possible to detect thermal effects.Other studies in this dissertation were related to the evaluation and modeling of novel groove designs for copper CMP optimization. Novel groove designs were divided into two groups: (1) Logarithmic-Spiral and (2) Concentric Slanted. These novel groove designs were evaluated under several operating conditions, such as wafer load, sliding velocity and slurry flow rate. This work resulted in the identification of one novel groove design from each group, which resulted in high Copper RR. The observed RR behavior was attributed to two possible scenarios. Firstly, it was believed that these novel groove designs produced a more effective control of the transport of slurry into, and the discharge of spent slurry and debris out of, the pad-wafer interface. Secondly, the variations in slurry film thickness at the pad-wafer interface generated by the different groove designs evaluated, appeared to affect the degree of contact between the pad and the wafer; hence the mechanical (pad asperities-wafer contact) and chemical(rise in temperature) contributions of the system. A novel 3-Step copper removal model wasapplied to copper CMP. The model predicted remarkably well the removal rate behavior during copper polishing for different pad groove designs. The model allowed us to perform an analysis of the effect of groove designs on the chemical and mechanical contribution of the system.