Development of a Suite of Computational Models for the Design of Ultralow-k SiCOH-based Materials
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Development of a Suite of Computational Models for the Design of Ultralow-k SiCOHbased Materials Alexandra Cooper1 and Paulette Clancy2 1,2 School of Chemical and Biomolecular Engineering, Olin Hall, Cornell University, Ithaca, NY 14853 ABSTRACT A computational model of amorphous SiCOH materials is described that will facilitate studies of SiCOH behavior under different thermal and mechanical stresses. This involved developing an atomic-scale model of an SiCOH thin film, which exhibited structural, mechanical and electrical properties in agreement with experimental studies. We developed a unique process for computationally creating the structure of SiCOH films. We created an algorithm for introducing and estimating porosity in the system, which provides detailed information about the system’s pore size distribution on multiple length scales. We used Density Functional Theory (DFT) to develop a simple correlation that calculates the dielectric constant of a large SiCOH structure based only on its atomic composition and volume. Finally, we confirmed the mechanical properties of the model using established Molecular Dynamics techniques. We verified that essential electronic and mechanical properties of the model structure reproduce experimental data for a representative SiCOH material within acceptable accuracy. We find the mechanical properties are significantly weakened by the presence of pendant carbon groups. INTRODUCTION In order to facilitate the continued shrinking of device sizes in next-generation processors, it will be necessary to develop an ultra-low dielectric constant (ULK) material with the ability to reduce capacitance crosstalk between highly compact transistor channels, and with the mechanical and thermal stability to withstand the chip manufacturing process. The development of a ULK material has focused on using chemical vapor deposition (CVD) to create porous films of amorphous SiCOH. [1-2] Introducing porosity into materials with low dielectric constants, like SiCOH, decreases the film density, and therefore the total number of dipoles present in the film. As the number of dipoles decreases, so does the dielectric constant. The increased porosity in these films can be problematic, however, as it weakens the mechanical strength of the material, creating significant integration challenges. The carbon content lowers the dielectric constant, but also weakens the material by creating defects in the Si-O bond network. The goal of our research is to use computer simulation techniques to better understand key SiCOH properties like structure, porosity, dielectric behavior, and mechanical strength, and then to use this information to predict methods of treating the material which will lower the dielectric constant with minimal weakening of the mechanical strength. Interestingly, there are no papers in the literature that provide all these elements (structure, porosity, dielectric constant and mechanical properties) for a chosen SiCOH class material.
THEORY Sample SiCOH structures were created using a uniqu
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