Effect of Temperature on Defect Generation during Copper Chemical Mechanical Planarization
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Effect of Temperature on Defect Generation during Copper Chemical Mechanical Planarization Subrahmanya Mudhivarthi a, b, Parshuram Zantyea, b, Ashok Kumara, b, and JeungYeop Shimc a
b
Department of Mechanical Engineering, Nanomaterials and Nanomaunfacturing Research Center, c Department of Chemical Engineering, University of South Florida, Tampa, FL 33620
ABSTRACT Chemical Mechanical Planarization (CMP) is the process of choice for planarization of the constituent layers of the Multi Level Metallization schemes in modern Integrated Circuits. Besides having a lot of advantages, copper CMP process still needs significant process control to eliminate defects such as delamination, microscratches, dishing, erosion etc. In this research, effect of heat generated at the interface on the generation of CMP defects has been investigated. CMP of blanket and patterned samples has been carried out at two conditions of pressure x velocity values with varying slurry temperature. Post CMP metrology is carried out using Atomic force microscopy (AFM) in order to characterize the variation in scratch depth, dishing profile and non-uniformity in step coverage. Pictures of the patterned samples polished at different temperatures are captured using Optical Microscopy (OM) to study the dishing and dissolution of copper lines in greater detail. The primary goal of this study was to gain deeper understanding of the effect of heat generation and rise in temperature at the pad-wafer-slurry interface on CMP induced defectivity. INTRODUCTION Chemical Mechanical Planarization (CMP) process has evolved into one of the most significant and integral processes in IC manufacturing process. CMP of copper layer is one of the main processes of the damascene (non-traditional) structure fabrication [1,2]. The copper thin film layer (overburden) is planarized and removed subsequently by synergistic chemical and mechanical processes. In a typical copper CMP process, the chemically modified copper surface is mechanically abraded and the slurry dissolves the removed copper debris avoiding re-deposition of the removed metal onto wafer surface [2]. In the past decade, significant research has been carried out on copper CMP process and effects of many process parameters were investigated. However, a relatively less researched and less understood facet of copper CMP is the effect of heat generation at the interface on the overall CMP process performance. CMP attributes that are prone to get affected by heat generation at the interface during the process of copper CMP are: precise control of removal rate (causing over polish) and surface defects like dishing of copper lines, surface scratches etc. The slurry interaction with copper surface and polishing pad properties which directly affect CMP performance are highly sensitive to temperature. Models, theories and experimental investigations have been carried out in the recent past
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to ascertain the effect of temperature on the CMP removal rate [3-5]. Also, research to estimate the pad, slurry an
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