Newly Developed Abrasive-Free Copper CMP Slurry Based on Electrochemical Analysis
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0991-C03-01
Newly Developed Abrasive-Free Copper CMP Slurry Based on Electrochemical Analysis Jin Amanokura1, Katsumi Mabuchi2, Takafumi Sakurada1, Yutaka Nomura1, Masanobu Habiro1, and Haruo Akahoshi2 1
Hitachi Chemical Co., Ltd., Hitachi, Japan
2
Hitachi Ltd., Hitachi, Japan
ABSTRACT In order to reduce microscratches and obtain minimized dishing and erosion, we have developed new abrasive-free Cu CMP slurries. During the development of these slurries, some electrochemical examination was performed. The most effective knowledge was obtained through the analysis using rotary Cu disk electrode under pressure. On the basis of these studies, new abrasive-free Cu CMP slurries with a high removal rate and excellent planarity were designed and developed. The mechanism of reducing dishing and erosion was also discussed. INTRODUCTION Since the first announcement of introducing Cu interconnections to high speed ULSIs in 1997 [1], many semiconductor manufacturers began to develop Cu interconnections by applying chemical mechanical polishing (CMP) methods [2,3]. In the beginning of these research activities, conventional Cu slurries for CMP were applied, and many issues were introduced to be settled [4]. An outline of the problems is summarized in Figure 1. These problems should be solved from the viewpoints of both mechanical abrasion with abrasive powders and chemical reaction on Cu film. From these two viewpoints, abrasive-free polishing (AFP) solutions have been proposed, developed, and applied to the CMP of Cu interconnections [5-7], achieving a high Cu removal rate and excellent topography performance in LSI manufacturing. In addition, a new two-step CMP process, that is to polish Cu and barrier films in turn, has been proposed, and the process combined with AFP solutions has finally solved the problems [8]. For the first-step CMP, a slurry having high removal selectivity of Cu over barrier metal is required to obtain a stop-on-barrier characteristic. For the second-step CMP, a slurry with controllable selectivity for barrier metal over interlayer dielectric and Cu metal is required to minimize dishing and erosion. In order to realize the two-step process, we have successfully developed a new AFP solution for the first-step CMP and also a slurry for barrier metal with practically controllable selectivity for the second-step CMP [9]. Figure 2 shows the difference between the two types of polishing models. For the AFP, it is intended that Cu complex can be removed only by polishing pad shear force. For the conventional abrasive CMP, abrasive powders are necessary to remove the hard copper oxide layer formed at the Cu surface [10].
Cu interconnection technology will require a higher Cu removal rate and higher topography performance. International technology roadmap for semiconductor for future design rule (45nm node) indicates, for example, a topography target of less than 300 angstrom for intermediate Cu lines. To meet the high performance trends, we have been developing new AFP solutions based on the electrochemica
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