For several decades, chemical mechanical polishing (CMP) has been the most widely used planarization method in integrated circuits manufacturing. The final polishing results are affected by many factors related to the carrier structure, the polishing pad, the slurry, and the process parameters. As both chemical and mechanical actions affect the effectiveness of CMP, and these actions are themselves affected by many factors, the CMP mechanism is complex and has been a hot research area for many years. This review provides a basic description of the development, challenges, and key technologies associated with CMP. We summarize theoretical CMP models from the perspectives of kinematics, empirical, its mechanism (from the viewpoint of the atomic scale, particle scale, and wafer scale), and its chemical-mechanical synergy. Experimental approaches to the CMP mechanism of material removal and planarization are further discussed from the viewpoint of the particle wear effect, chemical-mechanical synergy, and wafer-pad interfacial interaction.

No abstract

The abrasive effect of particles is one of the basic mechanical actions in chemical mechanical polishing (CMP). In this paper, numerical simulations of particle sliding trajectories are performed to examine the influence of the kinematic parameters on the polishing uniformity of typical rotary-type CMP equipment. The trajectory simulations are carried out based on the kinematic analysis. The results reveal that the speed ratio α and the period ratio k T 0 , which represent the coupling relationships among the three basic motions of CMP, are the two major factors affecting the trajectory distribution. Further, a trajectory density parameter is proposed to quantitatively evaluate the global uniformity of the trajectory distributions and to optimize the kinematic parameters for better uniformity. The statistical results of the trajectory density analysis reveal that the trajectory of the wafer edge is denser than that of the wafer central area. To obtain better trajectory uniformity, some particular values of α and k T 0 , that is, α = 1 and k T 0 = 1, which imply that the basic motions have a special coupling relationship, should be excluded; the preferred kinematic parameter values for CMP are α = 0.91∼0.93 and k T 0 = 5∼7. This paper provides a basic guide to the kinematic parameter settings of CMP.

In this paper, a novel in-situ interfacial fluid pressure measurement system is developed for the practical chemical mechanical polishing (CMP) equipment, in which the pressure sensors are equidistantly embedded in the platen along the radial direction and sweep beneath the wafer surface during CMP. Interfacial fluid pressure mapping is realized for standard 12 blanket wafers at the down pressure of 0.5 ∼ 2.0 psi. The fluid pressure profiles from the leading edge to the trailing edge and the pressure contour maps of the fluid film across the whole wafer surface are constructed and displayed. Results reveal a large positive pressure region located near the wafer trailing edge and a small negative pressure region located near the leading edge, which is quite different from the negative dominated results of previous studies. The fluid pressure can support 15% ∼ 30% of the applied pressure. The down pressure has great effect on the fluid pressure due to the wafer's bend under the applied load. When the down pressure increases, the positive pressure region expands and slightly shifts toward the outer of the pad while the negative pressure region shrinks.Chemical mechanical polishing (CMP) is a necessary process step in the manufacture of multilevel Integrated Circuits (IC). During CMP process, the platen and the wafer carrier rotate in the same direction. Synchronously, the wafer carrier reciprocates along the radial direction of the platen. Polishing pressure is applied on the back surface of the wafer and presses the wafer on the pad, while the slurry is continually injected at the wafer/pad interface. With the combined action of the chemicals and the abrasive particles in the slurry, micro material removal and planarization of the wafer surface are realized. To improve the performance of IC device, copper and low-k materials are used for multilevel connection, which demands CMP to provide global planar polishing surface with low defect. Low downforce CMP is becoming the general trend to prevent damaging the soft copper and the low-k materials in industry. 1 CMP is a complex process as many polishing variables, such as the down pressure, the rotational speed and the slurry flow rate, affect the final polishing results (e.g., the within wafer nonuniformity). However, the process and the mechanism of such affecting of these polishing variables are not quite clear owing to the complex interactions between the wafer surface, the pad asperities, the particles, and the slurry at the wafer/pad interface. Early study found that, when polishing, a thin slurry film was formed at the wafer/pad interface, 2 and the fluid pressure was generated at the interface. Actually, the contact status of the interface is determined by the fluid lubrication effect and the downforce applied on the back surface of the wafer. Therefore, the fluid pressure affects the distribution of the contact stress of the wafer/pad interface directly, which acts as the mechanical action for the polishing. In addition, previous studies have revealed that the...

The receding contact line driven by Marangoni flow induces an immersed pressure gradient, and thus a sudden increase of tangential velocity in dynamic meniscus.