This paper reviews some of the problems limiting broad manufacturing implementation of chemical mechanical polishing (CMP) as a planarization process for interlevel dielectrics. We examine the mechanism whereby polish rates tend to decrease as the polish pad ages, and propose an explanation based on slurry transport. We review a simple theory which provides an understanding in terms of basic mechanical principles of how CMP produces its planarizing effect. Finally, we demonstrate a method capable of providing a quantitative measure of planarity.
Chemical mechanical polishing (CMP) is rapidly becoming the process of choice for planarizing dielectrics in very large scale integrated circuits. In addition, it is being used at an increasing rate in the removal of metals in order to define conducting levels. In the case of dielectric CMP, planarization ability is dictated by the mechanical aspects of polishing such as pad rigidity, polishing pressure and speed of the polishing platen, while inherent removal rate of the dielectric material is generally a function of the polishing chemistry. Polishing rate of both, dielectric and metallic films can be significantly increased by changing the nature of the dispersed abrasive in the slurry and that of the dispersing agent. However, such changes have profound implications to the surface quality, planarity, and cleaning of the polished surface. In addition, the polishing pad plays an important role in manufacturability of metal CMP processes. This work reviews the chemistry of polishing slurries containing silica, ceria and alumina abrasives for dielectric and metal CMP. Also, the contribution of the polishing pad to CMP processes is explained. The need for balancing the chemical and mechanical aspects of polishing in order to achieve overall planarization and pattern definition is demonstrated.
Chemical mechanical polishing (CMP) technology has successfully met the stringent requirements of ultraplanarized surfaces in semiconductor manufacture. Commonly, polyurethane based pads have been used to achieve this level of planarization. Recent studies have shown that the material properties of polishing pads used in the CMP process strongly influence the ability to reduce topography. In addition, past work has shown that in the absence of pad regeneration, polishing rate drops dramatically with polishing time. This decrease in material removal rate is believed to coincide with deterioration of the pad surface due to “cold flow” and/or “caking” of the pad material. This study attempts to correlate the intrinsic polymer properties and cellular structure of the pad material to CMP process indices like polishing rate and planarity. For example, the drop off in removal rate as a function of time can be attributed to the mechanical response of polyurethanes under conditions of critical shear. Moreover, planarity achieved is a function of pad stiffness - which itself is dependant upon intrinsic polymer stiffness and cell density.
A chemical mechanical polishing (CMP) process for copper damascene has been developed and characterized on a second generation, multiple platen polishing tool.
Chemical Mechanical Polishing (CMP) is becoming a mainstream technology for the planarization of dielectrics at various process levels. Widely different types of glass films are now routinely processed using CMP techniques. In this work, the polish rates using an aqueous silica based slurry for thermally grown Si02, plasma deposited SiC2, and boro-phospho-silicate glasses have been compared. A polishing mechanism based on the concentration of water in the glass is proposed. It is also shown that the presence of phosphorous changes the polishing mechanism compared to undoped glasses and the rate increase due to phosphorous is much greater than that due to boron.
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