Development and Optimization of Slurry for Ru CMP
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0991-C10-04
Development and Optimization of Slurry for Ru CMP In-Kwon Kim1, Tae-Young Kwon1, Jin-Goo Park1, and Hyung-Soon Park2 1 Division of Materials and Chemical Engineering, Hanyang University, 1271 Sa-dong, Ansan, 426-791, Korea, Democratic People's Republic of 2 Memory Research & Development Division, Hynix semiconductor Inc., San 136-1, Ami-Ri, Bubal-eub, Icheon-Si, 467-701, Korea, Democratic People's Republic of
ABSTRACT In this study, Ruthenium (Ru) chemical mechanical planarization (CMP) slurry was studied and developed to apply it for the formation of Ru bottom electrode in DRAM capacitor. An acidic chemical was chosen as both oxidant and etchant. The effects of the chemical on polishing and etching behavior were investigated as functions of chemical concentration and pHs. The static etch rate of Ru increased with an increase in chosen chemical concentration. Also, thin Ru oxide was generated in chemical solution. The highest etching and removal rate were obtained in slurry of pH 6. However, Ru over etching was generated due to the high etch rate of Ru, and then good planarity was not obtained. In slurry of pH 6, the plarnarity and isolation of each capacitor was acquired successfully because Ru over etching was prevented due to low etch rate of Ru,. INTRODUCTION In the DRAM technology, the conventional capacitor has a semiconductor (poly silicon) bottom electrode which is called metal insulator semiconductor (MIS) capacitor. However, conventional poly-Si bottom electrode cannot satisfy the requirement of electrical properties and compatibility with high k materials. For this reason, metal insulator metal (MIM) capacitor has been investigated [1-2]. Noble metals can be used as bottom electrodes of capacitors because they have high work function, and thus high barrier for leakage current. In addition, they are chemically very stable. Among novel metals, Ru (ruthenium) has been suggested as an alternative bottom electrode due to its excellent electrical performance such as a low leakage of current and compatibility to the high dielectric constant materials [3]. Also, Ru film have been investigated as a Cu diffusion barrier metal for Cu interconnection due to good electrical conductivity, immiscibility with Cu, and good adhesion property to Cu layer [4-5]. Dry etching technology has been widely used to isolate and planarize Ru bottom electrode [6]. However, the dry etching method generates several problems such as Ru excessive recess or a loss of oxide. Also, these problems cause a current leakage or loss of capacitance. Therefore, chemical mechanical planarization (CMP) process has been suggested to planarize and isolate the bottom electrode [7]. Even though there are great needs on development of Ru CMP slurry, not much studies were carried out due to the its noble properties against chemicals. In this research, the static etch rate, passivation film thickness and wettability were measured as functions of slurry chemical concentrations. The effects of chemicals on polishing behavior were investigated as
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