Browsing by Author "Ng, Dedy"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Interfacial forces in chemical-mechanical polishing(2009-05-15) Ng, DedyThe demand for microelectronic device miniaturization requires new concepts and technology improvement in the integrated circuits fabrication. In last two decades, Chemical-Mechanical Polishing (CMP) has emerged as the process of choice for planarization. The process takes place at the interface of a substrate, a polishing pad, and an abrasive containing slurry. This synergetic process involves several forces in multi-length scales and multi-mechanisms. This research contributes fundamental understanding of surface and interface sciences of microelectronic materials with three major objectives. In order to extend the industrial impact of this research, the chemical-mechanical polishing (CMP) is used as a model system for this study. The first objective of this research is to investigate the interfacial forces in the CMP system. For the first time, the interfacial forces are discussed systematically and comparatively so that key forces in CMP can be pinpointed. The second objective of this research is to understand the basic principles of lubrication, i.e., fluid drag force that can be used to monitor, evaluate, and optimize CMP processes. New parameters were introduced to include the change of material properties during CMP. Using the experimental results, a new equation was developed to understand the principle of lubrication behind the CMP. The third objective is to study the synergy of those interfacial forces with electrochemistry. The electro-chemical-mechanical polishing (ECMP) of copper was studied. Experiments were conducted on the tribometer in combination with a potentiostat. Friction coefficient was used to monitor the polishing process and correlated with the wear behavior of post-CMP samples. Surface characterization was performed using AFM, SEM, and XPS techniques. Results from experiments were used to generate a new wear model, which provided insight from CMP mechanisms. The ECMP is currently the newest technique used in the semiconductor industries. This research is expected to contribute to the CMP technology and improve its process performance. This dissertation consists of six chapters. The first chapter covers the introduction and background information of surface forces and CMP. The motivation and objectives are discussed in the second chapter. The three major objectives which include approaches and expected results are covered in the next three chapters. Finally chapter VI summarizes the major discovery in this research and provides some recommendations for future work.Item Nanoparticles removal in post-CMP (Chemical-Mechanical Polishing) cleaning(Texas A&M University, 2006-10-30) Ng, DedyResearch was performed to study the particle adhesion on the wafer surface after the chemical-mechanical polishing (CMP) process. The embedded particles can be abrasive particles from the slurry, debris from pad material, and particles of film being polished. Different methods of particle removal mechanism were investigated in order to find out the most effective technique. In post-CMP cleaning, surfactant was added in the solution. Results were compared with cleaning without surfactant and showed that cleaning was more effective with the combined interaction of the mechanical effort from the brush sweeping and the chemistry of the surfactant in the solution (i.e., tribochemical interaction). Numerical analysis was also performed to predict the particle removal rate with the addition of surfactants. The van der Waals forces present in the wafer-particle interface were calculated in order to find the energy required to remove the particle. Finally, the adhesion process was studied by modeling the van der Waals force as a function of separation distance between the particle and the surface. The successful adaptation of elasticity theory to nanoparticle-surface interaction brought insight into CMP cleaning mechanisms. The model tells us that it is not always the case that as the separation distance is decreased, the attraction force will be increased. The force value estimated can be used for slurry design and CMP process estimation.