This dissertation presents a series of studies relating to pad-wafer and brush-wafer contact characterization in planarization and post-planarization processes. These are also evaluated with the purposes of minimizing environmental impact and reducting cost of ownership.Firstly, a new method using spectral analysis based on real-time raw friction data is developed to quantify the total amount of mechanical interaction in the brush-fluid-wafer interface in terms of stick-slip phenomena in post-planarization scrubbing. This new method is remarkable from the standpoint of its potential to eliminate having to perform a multitude of experiments needed for constructing and interpreting Stribeck curves, and its application to processes where Stribeck curves fail to yield any useful data. Moreover, this method is applied to investigate the effect of brush roller design on scrubbing process and to analyze behaviors of eccentric brushes.In order to study pad-wafer contact in planarization processes, a mechanical characterization method (incremental loading test) is developed and applied to analyze different types of pads and pad surfaces subjected to various treatments. Along with optical interferometry and theoretical analysis, flow resistance due to pad land area topography can be estimated.The greatest contribution of this dissertation involves development of real pad-wafer contact area measurement technique using confocal microscopy. The real pad-wafer contact area is a difficult property to measure in planarization, yet it is a key feature to further understand the process. A custom-made sample holder with a sapphire window and a miniature load cell is used to collect confocal images at controlled values of down force.At last, the two newly developed techniques (incremental loading test and real pad-wafer contact area measurement using confocal microscopy) together with dual emission UV enhanced fluorescence imaging are utilized to investigate conditioning effects in planarization process.

This dissertation presents a series of studies related to the slurry mean residence time analysis and the pad-wafer contact characterization in Chemical Mechanical Planarization (CMP). The purpose of these studies is to further understand the fundamentals of CMP and to explore solutions to some of CMP's challenges. Mean residence time (MRT) is a widely used term that is mostly seen in classical chemical engineering reactor analysis. In a CMP process, the wafer-pad interface can be treated as a closed system reactor, and classical reactor theory can be applied to the slurry flow through the region. Slurry MRT represents the average time it takes for fresh incoming slurry to replace the existing slurry in the region bound between the pad and the wafer. Understanding the parameters that have an impact on MRT, and therefore removal rate, is critical to maintain tight specifications in the CMP process. In this dissertation, we proposed a novel slurry injection system (SIS) which efficiently introduced fresh slurry into the pad-wafer interface to reduce MRT. Results indicated that SIS exhibited lower slurry MRT and dispersion numbers but higher removal rates than the standard pad center slurry application by blocking the spent slurry and residual rinse water from re-entering the pad-wafer interface during polishing. Another study in this dissertation dealt with the effect of pad groove width on slurry MRT in the pad-wafer interface as well as slurry utilization efficiency (η). Three concentrically grooved pads with different groove widths were tested at different polishing pressures to experimentally determine the corresponding MRT using the residence time distribution (RTD) technique. Results showed that MRT and η increased significantly when the groove width increased from 300 to 600μm. On the other hand, when the groove width increased further to 900μm, MRT continued to increase while n remained constant. Results also indicated that MRT was reduced at a higher polishing pressure while η did not change significantly with pressure for all three pads. In the last study of this dissertation, the effect of pad surface micro-texture on removal rate during tungsten CMP was investigated. Two different conditioner discs ("Disc A" and "Disc B") were employed to generate different pad surface micro-textures during polishing. Results showed that "Disc B" generated consistently lower removal rates and coefficients of friction than "Disc A". To fundamentally elucidate the cause(s) of such differences, pad surface contact area and topography were analyzed using laser confocal microscopy. The comparison of the pad surface micro-texture analysis on pad surfaces conditioned by both discs indicated that "Disc A" generated a surface having a smaller abruptness (λ) and more solid contact area which resulted in a higher removal rate. In contrast, "Disc B" generated many large near-contact areas as a result of fractured and collapsed pore walls.