| The chemical mechanical polishing (CMP) process has become a primary planarization technique required for the manufacture of advanced integrated circuit (IC) devices. As the feature size of IC chips shrinks down to 0.18 μm and below, the role of CMP as a robust planarization process becomes increasingly important.; In this dissertation, mechanical aspects of the material removal mechanism in CMP are investigated analytically and experimentally as part of a fundamental study on CMP. The role of consumables, which include the polishing pad and abrasive particles in the slurry, in CMP performance is evaluated, and tribological characteristics (lubrication, friction, and wear) of CMP are also analyzed. To evaluate the role of slurry, the influence of chemistry of the slurry on the mechanical aspects of the material removal mechanism is examined. The mechanical and chemical contributions to material removal are studied to determine the key mechanism of material removal in CMP.; From this study, it is shown that the material removal rate of the wafers is inversely proportional to the pad density and proportional to the pad compressibility and surface roughness. This is due to the fact that the material removal for a wafer in CMP is closely related to the actual pad contact area of the wafer. This is an indication of the probability of abrasives contacting the wafer surface. The material removal rate of silicon wafers is also proportional to the friction force between the workpiece and the polishing pad.; The effect of the slurry film thickness variation on CMP performance, defined in terms of material removal, planarization, surface defects, and surface roughness, is significant. From the Stribeck curve, the lubrication condition under the wafer in CMP is closer to boundary or elasto-hydrodynamic lubrication than to hydrodynamic lubrication.; It is also shown that the chemically reacted silicon layer causes the extension of the brittle/ductile transition depth, and the brittle cutting behavior transition point becomes less distinctive. The chemically reacted ‘ductile’ layer is proposed to be the origin of the scratch/defect-free surface after CMP.; The material removal of CMP is more than the sum of the removal due to the mechanical and the chemical polishing effects. The test results verify the important effect of the combination of chemical and mechanical action to achieve high material removal in CMP. This supports the theory that there is a synergy effect that amplifies material removal only when the chemical and mechanical components act concurrently in CMP. |
