Solution chemistry effects on cracking and damage evolution during chemical-mechanical planarization
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Patrick Leduc Commissariat al’E´nergie Atomique - LETI (CEA-LETI), Minatec, 38054 Grenoble Cedex 9, France
Daniel W. McKenzie Department of Materials Science and Engineering, Stanford University, Stanford, California 94305
Thierry Farjot Commissariat al’E´nergie Atomique - LETI (CEA-LETI), Minatec, 38054 Grenoble Cedex 9, France
Gerard Passemard STMicroelectronics, 38926 Crolles Cedex, France
Sylvain Maitrejean Commissariat al’E´nergie Atomique - LETI (CEA-LETI), Minatec, 38054 Grenoble Cedex 9, France
Reinhold H. Dauskardta) Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (Received 4 February 2010; accepted 10 June 2010)
We describe progress in understanding the effect of simulated chemical-mechanical planarization (CMP) slurry chemistry on the evolution of defects and formation of damage that occurs during CMP processing. Specifically, we demonstrate the significant effect of aqueous solution chemistry on accelerating crack growth in porous methylsilsesquioxane (MSSQ) films. In addition, we show that the same aqueous solutions can diffuse rapidly into the highly hydrophobic nanoporous MSSQ films containing interconnected porosity. Such diffusion has deleterious effects on both dielectric properties and the acceleration of defect growth rates. Crack propagation rates were measured in several CMP solutions, and the resulting crack growth behavior was used to qualitatively predict the extent of damage during CMP. These predictions are compared with damage formed during actual CMP processes in identical chemistries. We discuss the effects of both the high and low crack growth rate regimes, including the presence of a crack growth threshold, on the predicted CMP damage. Finally, implications for improved CMP processing were considered. I. INTRODUCTION
Chemical-mechanical planarization (CMP) is an important processing step for state-of-the-art microelectronics devices and will likely remain so for the foreseeable future. Despite its critical necessity in multiple steps of the fabrication process, damage during CMP can significantly lower process yield, particularly when porous dielectric materials are incorporated into the device structure. These materials are highly susceptible to the diffusion of chemically active species encountered during CMP and accelerated cracking in CMP environments.1–6 However, despite the fact that the environmentally accelerated cracking of these dielectrics has been well documented and explained down to the molecular level, little has been done to correlate these environmental a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0249
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http://journals.cambridge.org
J. Mater. Res., Vol. 25, No. 10, Oct 2010 Downloaded: 26 Mar 2015
effects with accumulated damage during actual CMP processes at the wafer scale. This study intends to bridge that gap and argue that optimization of CMP processes for the mechanical integrity of novel dielectrics can and should begin from the fundamental
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