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The Effects of Hardness Variation on a CMP Model of Copper thin Films

Published online by Cambridge University Press:  31 January 2011

Joseph Bonivel ,
Yusuf Williams ,
Sarah Blitz ,
Micheal Kuo  and
Ashok Kumar
Joseph Bonivel
Affiliation:
[email protected], University of South Florida, College of Engineering, 4202 E. Fowler Avenue, Tampa, Florida, 33620, United States, 813-974-4101
Yusuf Williams
Affiliation:
[email protected], University of South Florida, Mechanical Engineering, Tampa, Florida, United States
Sarah Blitz
Affiliation:
[email protected], Carnegie Mellon University, Mechanical Engineering, Pittsburgh, Pennsylvania, United States
Micheal Kuo
Affiliation:
[email protected], Carnegie Mellon University, Mechanical Engineering, Pittsburgh, Pennsylvania, United States
Ashok Kumar
Affiliation:
[email protected], University of South Florida, Mechanical Engineering, Tampa, Florida, United States
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Abstract

With the rapid change of materials systems and decreased feature size, thin film microstructure and mechanical properties have become critical parameters for microelectronics reliability. An example of a major driver of this new technology is the data storage community who is pushing for 1 Terabit/square inch on its magnetic disk hard drives. This requires inherent knowledge of the mechanical properties of materials and in depth understanding of the tribological phenomena involved in the manufacturing process. Chemical mechanical polishing (CMP) is a semi-conductor manufacturing process used to remove or planarize ultra-thin metallic, dielectric, or barrier films (copper) on silicon wafers. The material removal rate (MRR), which ultimately effects the surface topography, corresponding to CMP is given by the standard Preston Equation, which contains the load applied, the velocity of the pad, the Preston coefficient which includes chemical dependencies, and the hardness of the material. Typically the hardness, a bulk material constant, is taken as a constant throughout the wafer and thereby included in the Preston coefficient. Through metallurgy studies, on the micro and nano scale, it has been proven that the hardness is dependent upon grain size and orientation. This research served to first relate the crystallographic orientation to a specific hardness value and secondly use the hardness variation in the previously developed particle augmented mixed-lubrication (PAML) model to simulate the surface topography and MRR during CMP. Recent test and results show that currently there is no empirical formula to relate the crystallographic orientation and thereby a critically resolved shear stress (CRSS) to a specific hardness value. The second part of this investigation utilized the variation in hardness values from the initial study and incorporated these results into the PAML numerical model that incorporates all the physics of chemical mechanical polishing (CMP). Incorporation of the variation of hardness resulted in a surface topography with a difference in roughness (Ra) from the bulk constant hardness value of 60 nm. The material removal rate (MRR) of the process differs by 2.17 μm3/s.

Keywords

CMPcrystallographic structurehardness
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1157: Symposium E – Science and Technology of Chemical Mechanical Planarization (CMP) , 2009 , 1157-E08-06
Copyright
Copyright © Materials Research Society 2009

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