The Role of Arginine as a Complexing Agent in Copper CMP
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0914-F12-03
The Role of Arginine as a Complexing Agent in Copper CMP Surya Sekhar Moganty, and Ramanathan Srinivasan Chemical Engineering, Indian Institute of Technology Madras, Particle Science Laboratory, Chennai, Tamil Nadu, 600036, India ABSTRACT: Copper Chemical Mechanical Polishing was characterized in hydrogen peroxide and L arginine based basic slurries. CMP and etch rate experiments were conducted to understand the complexing role of arginine in peroxide based slurries. Both polish and etch rate were studied for hydrogen peroxide concentration 0 to 10 vol% with 1 wt% L-arginine. The relative roles played by the both the chemicals were elucidated by electrochemical techniques.
INTRODUCTION: Multi level interconnects (MLM) are being used in the present day microelectronic chip to meet the performance driven demands. Copper has become the material of choice for the MLM combined with low–k materials to reduce the RC delay losses. Damascene technology introduced by IBM, is used to make these multi level copper interconnects. Chemical Mechanical Planarization (CMP) is the only choice to obtain the damascene copper interconnects in sub micro level [1-3]. In spite of its usage in large scale, copper CMP requires great attentions towards understanding it at a fundamental level to acquire the desired control over the process. Typically, Chemical Mechanical Polishing requires polishing slurry consisting of abrasive material (for erosion) and Chemicals (for corrosion) for removing the overburden copper to facilitate globally planarized structures. Most of the slurries used for Cu CMP are acidic. Hydrogen peroxide is one of the commonly used oxidizing agents in CMP slurries. It requires a complexing agent to enhance the removal rate. Glycine has been studied as the compatible complexing agent in peroxide based slurries in neutral and acidic pH regions [4-7]. Nitric acid based slurries have also been studied with various inhibiting agents [8-9]. The disadvantage of acidic slurries is the possible corrosion of the polishing equipment. Fewer studies have been conducted with slurries in alkaline pH range, where equipment corrosion is less likely to be a problem [10]. However, alkaline pH region is favorable for the SiO2 polishing [10]. This will lead to poor selectivity unless the oxide polish is suppressed. The amino acid L-Arginine is known to suppress the SiO2 removal rate even in basic pH values [11]. In this work, Cu CMP with slurries containing L-Arginine as complexing agent and peroxide as oxidizer is characterized. Polish and etch rate data is used to understand the effect of the additive. Interactions of the peroxide and arginine with the copper surface were characterized by the electrochemical techniques viz., potentiodynamic polarization experiments, Open Circuit Potential (OCP) and impedance measurements.
EXPERIMENTAL: CMP Experiments: The polishing experiments were performed by using a Struer’s LaboPol5- LaboPlo3 polisher. The samples were of electrochemical grade copper disks of 25.4 mm diameter. Polishing
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