G. Bahar Basim

Role of interaction forces in controlling the stability and polishing performance of CMP slurries.

Chemical mechanical polishing (CMP) is an essential step in metal and dielectric planarization in multilayer microelectronic device fabrication. In the CMP process it is necessary to minimize the extent of surface defect formation while maintaining good planarity and optimal material removal rates. These requirements are met through the control of chemical and mechanical interactions during the polishing process by engineering the slurry chemistry, particulate properties, and stability. In this study, the performance of surfactant-stabilized silica CMP slurries at high pH and high ionic strengths are investigated with particular emphasis on the particle-particle and particle-substrate interactions. It is shown that for the design of consistently high performing slurries, stability of abrasive particles must be achieved under the dynamic processing conditions of CMP while maintaining sufficient pad-particle-wafer interactions.

Strategies for Optimal Chemical Mechanical Polishing (CMP) Slurry Design

Abstract Chemical mechanical polishing (CMP) has become the preferred route for achieving wafer‐level global planarization in microelectronics device manufacturing. However, the micro‐ to molecular‐level mechanisms that control its performance and optimization are not well understood. In CMP, complex slurry chemistries react with the first few atomic layers on the wafer surfaces forming a chemically modified film. This film is subsequently mechanically abraded by nanosized slurry particles to achieve local and global planarity for multi‐level metalization. For optimal CMP performance, high material removal rates with minimal surface defectivity are required. This can be achieved by controlling the extent of interparticle and particle–substrate interactions, which are facilitated through the manipulation of the slurry composition, solution chemistry, as well as operational parameters. Interparticle interactions must be engineered to maintain slurry stability to minimize the number and extent of surface defects during polishing while maintaining adequate removal rates. The fundamental considerations, which are necessary for the development of high performance CMP slurries, are discussed in this article through model silica CMP systems.

Tailoring Silica Nanotribology for CMP Slurry Optimization: Ca2+ Cation Competition in C12TAB Mediated Lubrication

Self-assembled surfactant structures at the solid/liquid interface have been shown to act as nanoparticulate dispersants and are capable of providing a highly effective, self-healing boundary lubrication layer in aqueous environments. However, in some cases in particular, chemical mechanical planarization (CMP) applications the lubrication imparted by self-assembled surfactant dispersants can be too strong, resulting in undesirably low levels of wear or friction disabling material removal. In the present investigation, the influence of calcium cation (Ca(2+)) addition on dodecyl trimethylammonium bromide (C(12)TAB) mediated lubrication of silica surfaces is examined via normal and lateral atomic force microscopy (AFM/LFM), benchtop polishing experiments and surface adsorption characterization methods. It is demonstrated that the introduction of competitively adsorbing cations that modulate the surfactant headgroup surface affinity can be used to tune friction and wear without compromising dispersion stability. These self-healing, reversible, and tunable tribological systems are expected to lead to the development of smart surfactant-based aqueous lubrication schemes, which include designer polishing slurries and devices that take advantage of pressure-gated friction response phenomena.

Self-Cleaning Ability Quantization of Textiles with Degussa P-25

This study proposes a systematic quantification of effectiveness of the Degussa P-25 titania particles used as a benchmark in photocatalytic applications to standardize ability of self-cleaning textile applications and to compare activity of developing new self-cleaning textiles. To quantify photocatalytic efficiency of P-25, textile production was performed in a harmony with textile manufacturing by combining finishing process and coating procedure. The results of the study suggest that the textiles treated with P-25 particles produced without a secondary treatment were effectively coated and their stain discoloration ability was also validated with solid color spectrometer.

A Modeling Study on the Layout Impact of With-In-Die Thickness Range for STI CMP

Chemical Mechanical Planarization process has a proven track record as an effective method for planarizing the wafer surface at multiple points of the semiconductor manufacturing flow. One of the most challenging aspects of the CMP process, particularly in applications like Shallow Trench Isolation (STI), is the difference in relative removal rates of the different materials that are being polished. A certain amount of over-polish is required to clear oxide on top of the nitride, however, this over-polish may also lead to significant problems like dishing and erosion (introducing additional topography after the film has been planarized). This work formulates a methodology to predict how this additional topography is modulated by incoming layout properties introducing a parameter to accurately characterize line and space width on a layout with random geometric shapes. A real-life example is presented on a STI process with a methodology that is generic to any CMP process. To the first order lower densities, lower nitride and higher oxide widths lead to more material loss and thus lower step-height. The second order interactions between density-nitride width and nitride-oxide width also have a statistically significant impact on step-height.