Use of anionic surfactants for selective polishing of silicon dioxide over silicon nitride films using colloidal silica-based slurries

Penta, Naresh K.; Amanapu, H. P.; Peethala, B.; Babu, S. V.

doi:10.1016/j.apsusc.2013.07.057

Cited by 27 publications

(9 citation statements)

References 36 publications

(41 reference statements)

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“…Furthermore, the adsorption mechanism of the surfactant on silica surfaces is also similar to that on other mineral oxide surfaces, and the zeta potential of the surface will be positive [25]. An anionic surfactant does not adsorb on a negative hydrophilic substrate as electrostatic repulsion does not favour adsorption [25,28]. However, the adsorption kinetics of a surfactant molecule on a hydrophilic surface at pH > 6 is significantly faster and the final adsorbed amount is greater for a cationic surfactant than for an anionic surfactant [23].…”

Section: Resultsmentioning

confidence: 96%

Electroosmotic Flow in Free Liquid Films: Understanding Flow in Foam Plateau Borders

Sheik

Trybała

Starov

et al. 2018

Colloids and Interfaces

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Liquid flow in foams mostly proceeds through Plateau borders where liquid content is the highest. A sufficiently thick (~180 µm) free liquid film is a reasonable model for understanding of electrokinetic phenomena in foam Plateau borders. For this purpose, a flow cell with a suspended free liquid film has been designed for measurement of electrokinetic flow under an imposed electric potential difference. The free liquid film was stabilised by either anionic (sodium lauryl sulfate (NaDS)) or cationic (trimethyl(tetradecyl) ammonium bromide (TTAB)) surfactants. Fluid flow profiles in a stabilised free liquid film were measured by micron-resolution particle image velocimetry (µ-PIV) combined with a confocal laser scanning microscopy (CLSM) setup. Numerical simulations of electroosmotic flow in the same system were performed using the Finite Element Method. The computational geometry was generated by CLSM. A reasonably good agreement was found between the computed and experimentally measured velocity profiles. The features of the flow profiles and the velocity magnitude were mainly determined by the type of surfactant used. Irrespective of the surfactants used, electroosmotic flow dominated in the midfilm region, where the film is thinnest, while backflow due to pressure build-up developed near the glass rods, where the film is thickest.

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Section: Resultsmentioning

confidence: 96%

Electroosmotic Flow in Free Liquid Films: Understanding Flow in Foam Plateau Borders

Sheik

Trybała

Starov

et al. 2018

Colloids and Interfaces

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“…Some of the additives reported to yield high selectivity, relatively speaking, in silica based slurries are: cerium nitrate and acetic acid, 56 triethanol amine, 57 surfactants such as ammonium lauryl sulfate, ammonium dodecylbenzenesulfonate, and dodecylbenzenesulfonic acid or triethanolamine dodecylbenzenesulfonate. 58 Penta et al, 59 investigated the removal of oxide and nitride films in slurries with 10 wt% silica in the pH range of 2 to10 containing anionic surfactants such as sodium dodecyl sulfate (SDS), dodecyl benzene sulfonic acid (DBSA), dodecyl phosphate (DDP) and sodium lauryl sarcosine (SLS). When the pH was between 2 to 4, the nitride polishing rate was suppressed to <1 nm/min without affecting oxide removal rates.…”

Section: High Selectivity Slurriesmentioning

confidence: 99%

Shallow Trench Isolation Chemical Mechanical Planarization: A Review

Ramanathan

Dandu

Babu

2015

ECS J. Solid State Sci. Technol.

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Electrical isolation of the billion or so active components in each integrated device is achieved using shallow trench isolation (STI) which requires chemical mechanical planarization (CMP) involving silicon dioxide removal at a high rate and stopping on an underlying silicon nitride film. Several colloidal slurries with various additives can yield the desired high rate selectivity between the oxide and nitride films during CMP while maintaining an acceptably low nitride rate. Here, many of such high selectivity STI CMP slurries described in the literature are reviewed along with the characteristics of the colloidal dispersions like the abrasives, additives, the interactions between them and with the films being planarized and the associated pH range in which the high selectivity is observed. The mechanisms proposed to explain the high reactivity of ceria with oxide, the role of additives in suppressing the nitride removal rate and resulting high selectivity are discussed. Reduction of a multitude of defects in post-CMP processed STI structures still remains an important challenge, especially as the feature sizes continue to shrink. Chemical mechanical planarization (CMP) is one of the important enabling processes in facilitating multilevel metallization (in some cases reaching up to 14 levels) and incorporation of novel gate and channel materials at the component level in modern semiconductor device manufacturing where its use has become widespread and ubiquitous.1-6 Here, we review recent advances and remaining challenges in one specific application of CMP, the shallow trench isolation (STI) process. STI is a method of electrically isolating active areas using trenches created in the Si substrate around the active elements and filling it with an insulating dielectric, such as silicon dioxide or silicon oxy-nitride or silicon carbonitride.7-11 Process details of the STI structures are available in numerous publications. There are a multitude of techniques available for oxide deposition and even though the resulting oxides have very different properties, for simplicity we do not distinguish between them in this review. For completeness and ease of reference, a schematic representation of the STI process is given in Figure 1. While the trenches are being filled, silicon dioxide also deposits over unwanted areas on the entire wafer (since selective deposition in trenches only is not possible) creating an uneven topography. The excess and unwanted oxide has to be completely removed and CMP has proven to be the only viable and robust global and local planarization capable process technology.Here, as shown in Figure 1, presence of a very thin silicon nitride stop layer (deposited on another thin pad oxide layer to control film stress) is an essential and integral part of the process. This nitride stop layer prevents any damage during planarization to the all-important epitaxially grown surface underneath and is itself removed by a wet etch process subsequent to the overburden oxide removal. Since the integrity of the...

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“…For ionic surfactants on similarly charged interfaces, electrostatic interactions do not favor adsorption as the surfactants are electrostatically repelled. , Due to electrostatic repulsion, the adsorption of ionic surfactants onto similarly charged surfaces is related to the van der Waals and/or hydrophobic interactions between the surfactant tail and the solid surface. At lower concentrations, surfactants may adsorb vertically, where the molecule is perpendicular to the interface, with the hydrophilic head oriented toward the bulk, or if the hydrophobic interactions are strong enough to overcome electrostatic repulsion, the surfactant can adsorb laterally.…”

Section: Resultsmentioning

confidence: 99%

Stability of Two-Dimensional Liquid Foams under Externally Applied Electric Fields

et al. 2022

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Liquid foams are highly complex systems consisting of gas bubbles trapped within a solution of surfactant. Electroosmotic effects may be employed to induce fluid flows within the foam structure and impact its stability. The impact of external electric fields on the stability of a horizontally oriented monolayer of foam (2D foam) composed of anionic, cationic, non-ionic, and zwitterionic surfactants was investigated, probing the effects of changing the gas–liquid and solid–liquid interfaces. Time-lapse recordings were analyzed to investigate the evolution of foam over time subject to varying electric field strengths. Numerical simulations of electroosmotic flow of the same system were performed using the finite element method. Foam stability was affected by the presence of an external electric field in all cases and depended on the surfactant type, strength of the electric field, and the solid material used to construct the foam cell. For the myristyltrimethylammonium bromide (MTAB) foam in a glass cell, the time to collapse 50% of the foam was increased from ∼25 min under no electric field to ∼85 min under an electric field strength of 2000 V/m. In comparison, all other surfactants trialed exhibited faster foam collapse under external electric fields. Numerical simulations provided insight as to how different zeta potentials at the gas–liquid and solid–liquid interfaces affect fluid flow in different elements of the foam structure under external electric fields, leading to a more stable or unstable foam.

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Use of anionic surfactants for selective polishing of silicon dioxide over silicon nitride films using colloidal silica-based slurries

Cited by 27 publications

References 36 publications

Electroosmotic Flow in Free Liquid Films: Understanding Flow in Foam Plateau Borders

Electroosmotic Flow in Free Liquid Films: Understanding Flow in Foam Plateau Borders

Shallow Trench Isolation Chemical Mechanical Planarization: A Review

Stability of Two-Dimensional Liquid Foams under Externally Applied Electric Fields

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