During a typical microelectromechanical systems device fabrication process, a polysilicon top layer has to be polished with a slurry that yields a high polysilicon removal rate ( 0.5μm∕min or more) and a high selectivity over the underlying silicon dioxide and silicon nitride layers (50:1) . In this work, polysilicon polish rates as high as 550nm∕min and selectivity over silicon dioxide and nitride of ∼130 and ∼260 , respectively, have been achieved using colloidal silica and calcined ceria-based slurries containing arginine or lysine mono hydrochloride, at 4psi down pressure. At 8psi , polysilicon polish rates close to 900nm∕min and selectivities over both oxide and nitride that are close to 300 have been achieved. ξ potential, infrared spectroscopy, and contact angle data are used to explain the role of the amino acid additives in achieving the desired removal rate selectivities of polysilicon over silicon dioxide and silicon nitride.

Chemical mechanical polishing ͑CMP͒ of metal and dielectric films was performed using mixed abrasive slurries ͑MAS͒. MAS containing alumina and silica particles dispersed in deionized water were evaluated as second step slurries for Cu damascene polishing. It was demonstrated that MAS with proper selection of constituents and composition of abrasive particles can yield desired slurry/CMP characteristics. Based on the results of transmission electron microscope and particle size analysis of the abrasives in these MAS, possible reasons for the improved CMP performance are discussed.Chemical mechanical polishing ͑CMP͒ has emerged as a viable technique for planarizing metal and dielectric films for the fabrication of microelectronic devices. CMP is used to remove the overburden Cu from damascene structures and to achieve global planarization. Polishing of materials like Ta and tantalum nitride ͑TaN͒, used as a liner layer for Cu to serve as both an adhesion promoter and as a diffusion barrier in damascene patterning, has also gained importance in the recent years. Due to the vastly different mechanical and chemical properties of Cu and the barrier layer ͑Ta or TaN͒, these layers are polished sequentially in two separate steps. The main concerns in this patterning process are dishing of Cu lines and erosion of nearby areas. 1 Minimization of these phenomena in a damascene CMP process requires that the polishing be highly selective to Ta or TaN during the second step polishing. In addition, the film surface after CMP must be free of defects such as pits, microscratches, and particles.Typical slurries contain two phases, namely, liquid and solid phases even though some abrasive free slurries have been recently proposed. 2 Liquid phase consists of deionized ͑DI͒ water with additives like oxidizers, complexing agents, inhibiting agents, and surfactants. 3 Solid phase consists of abrasives, which are typically metal oxides, e.g., alumina, silica, ceria, etc. In single abrasive slurries ͑SAS͒, the solid phase consists of only one type of abrasive particle. Despite widespread use of SAS at all levels of metallization, polish rate selectivity, surface finish, and slurry stability still remain as major challenges. 4 Mixed abrasive slurries ͑MAS͒ consist of a mixture of at least two types of abrasive particles, which can be chosen from inorganic ͑alumina, silica, ceria, etc.͒ or organic ͑poly-meric resins͒ groups. 5 It has been observed that some of the problems associated with the use of SAS can be easily controlled by using MAS with proper composition and choice of constituents of the solid phase. In this paper, slurries containing alumina and silica particles dispersed in DI water at pH 4 have been studied for the second step Cu damascene polishing process. The modified abrasives in MAS are evaluated with respect to their particle size, surface morphology, and surface potential/charge. Arguments are presented to account for the improved CMP characteristics of these particles. ExperimentalChemical mechanical polishing.-Polish...

We report on the use of mixed abrasive slurries ͑MAS͒ containing alumina and ceria abrasives for chemical mechanical planarization ͑CMP͒ of silicon dioxide and silicon nitride films for shallow trench isolation applications, extending an earlier investigation of alumina/silica MAS for the CMP of copper and tantalum films. These slurries show a polish rate selectivity between oxide and nitride films that is as high as 65 and show an excellent surface quality even without additives. Analysis of dried slurry particles using transmission electron microscopy indicates formation of a sheath of smaller ceria particles around larger alumina particles. Possible explanations and supportive arguments for the improved performance of MAS during CMP are presented based on the particle-particle and particle-film interactions.Chemical mechanical planarization ͑CMP͒ is widely accepted as an effective technique for meeting current ͑2002͒ and near future planarization requirements of the semiconductor industry. 1 Damascene and dual-damascene processing, coupled with CMP, have successfully implemented copper ͑Cu͒ interconnects in integrated circuit ͑IC͒ fabrication, 2 leading to greatly reduced resistancecapacitance ͑RC͒ delays and superior chip performance. Another important application of CMP occurs in the use of shallow trench isolation ͑STI͒ for device isolation. STI offers better dimensional control ͑trench and width͒ and greater packing density 3,4 relative to the earlier isolation achieved by local oxidation of silicon ͑LOCOS͒. Better planarity is achieved due to the elimination of local encroachment of field oxide. 5 In STI, isolation trenches are plasma etched in the silicon substrate using a thin nitride mask layer, which simultaneously acts as a stop and a capping layer. The trenches are overfilled with chemical vapor deposited ͑CVD͒ oxide. 4 As in dualdamascene patterning, the overburden oxide is removed using CMP while removing as little of the nitride as possible. Finally, the nitride is etched using hot phosphoric acid and active devices are fabricated in the exposed silicon areas. It is critical to minimize microscratching, particulate adhesion, and overpolishing during STI CMP. 4 Introduction of a thin nitride film combined with a ceria-based, highly selective CMP process for overburden oxide removal can eliminate the need for overpolish. 6,7 These highly selective ceria-based slurries, however, can generate microscratches and hence performance must be improved further for an effective application to STI CMP.Thus, an important area of current research in CMP continues to be the development of slurries that can eliminate or minimize the problems associated with the conventional CMP process. 8,9 Typically, a slurry consists of two phases, namely, liquid and solid phases. Liquid phase consists primarily of deionized ͑DI͒ water with several additives like oxidizers, complexing agents, inhibiting agents, and surfactants. Solid phase is comprised of abrasives, which are usually inorganic oxides, e.g., alumina, silica, cer...

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