The uncontrolled development of nanoscale roughness during plasma exposure of polymer surfaces is a major issue in the field of semiconductor processing. In this paper, we investigated the question of a possible relationship between the formation of nanoscale roughening and the simultaneous introduction of a nanometer-thick, densified surface layer that is formed on polymers due to plasma damage. Polystyrene films were exposed to an Ar discharge in an inductively coupled plasma reactor with controllable substrate bias and the properties of the modified surface layer were changed by varying the maximum Ar + ion energy. The modified layer thickness, chemical, and mechanical properties were obtained using real-time in situ ellipsometry, x-ray photoelectron spectroscopy, and modeled using molecular dynamics simulation. The surface roughness after plasma exposure was measured using atomic force microscopy, yielding the equilibrium dominant wavelength and amplitude A of surface roughness. The comparison of measured surface roughness wavelength and amplitude data with values of and A predicted from elastic buckling theory utilizing the measured properties of the densified surface layer showed excellent agreement both above and below the glass transition temperature of polystyrene. This agreement strongly supports a buckling mechanism of surface roughness formation.

Dependence of photoresist surface modifications during plasma-based pattern transfer on choice of feedgas composition: Comparison of C 4 F 8 -and C F 4 -based dischargesPlasma-polymer interactions are important for the purpose of etching, deposition, and surface modification in a wide range of different fields. An Ar discharge from an inductively coupled plasma reactor was used to determine the factors in a simple plasma that control etch and surface roughness behavior for three styrene-based and three ester-based model polymers. The authors compared the etch behavior of polymers in Ar plasma discharges with low and high energy ions by changing the substrate bias, compared cooled and elevated substrate temperature conditions, and compared fully plasma-exposed conditions and vacuum ultraviolet ͑vuv͒-only conditions by employing a magnesium fluoride window to prevent ion bombardment in the vuv-only case. It was found that ions, vuv radiation, and temperature all had significant impact on the etch behavior of polymers. The dependence of polymer structure on etch and surface roughness was also compared. Polymers with styrene and ester side groups were compared and polymers with ␣-hydrogen and with ␣-methyl were compared. It was found that for styrene-based polymers, there was a large difference in material removal between ␣-hydrogen ͓poly͑4-methylstyrene͒͑P4MS͔͒ and ␣-methyl ͓poly͑␣-methylstyrene͒ ͑P␣MS͔͒ structures. This difference was highly temperature dependent, and the ceiling temperature of the polymers was found to be the most important property to consider. Below the ceiling temperature, the amount of material removed in P4MS and P␣MS was the same, but above it there was a dramatic material loss in P␣MS not seen in P4MS. For the ester-based polymers, it was established that oxygen depletion occurred before any other mechanism and the most important factor to consider was oxygen content in the polymer. By using in situ ellipsometry, it was also found that at temperatures below the ceiling temperature modification by vuv radiation of P␣MS created a slightly denser layer at the surface with higher index of refraction. This effect was not seen in P4MS. It was observed that in general, low energy ions contributed to material removal by physical sputtering at the polymer surface and the amount of material removal increased with oxygen content in the polymer. vuv radiation caused bulk depolymerization and oxygen depletion reactions that were highly polymer structure specific and temperature dependent. High energy ion bombardment was found to create an amorphous carbonlike damage layer with a thickness that was determined by the ion penetration depth. This damage layer could be characterized by ellipsometry. While for P4MS it was sufficient to model by ellipsometry the etch process using an ion-damaged layer on top of a bulk layer of unmodified polymer, the vuv effect needed to be added to the optical model in order to accurately characterize P␣MS. Finally, surface roughening of polymers only occurred under ion bomba...

Yttrium fluoride (YF3) and yttrium oxide (Y2O3) protective coatings prepared using an atmospheric plasma spraying technique were used to investigate the relationship between surface erosion behaviors and their nanoparticle generation under high-density plasma (1012–1013 cm−3) etching. As examined by transmission electron microscopy, the Y2O3 and YF3 coatings become oxyfluorinated after exposure to the plasma, wherein the yttrium oxyfluoride film formation was observed on the surface with a thickness of 5.2 and 6.8 nm, respectively. The difference in the oxyfluorination of Y2O3 and YF3 coatings could be attributed to Y–F and Y–O bonding energies. X-ray photoelectron spectroscopy analyses revealed that a strongly fluorinated bonding (Y–F bond) was obtained on the etched surface of the YF3 coating. Scanning electron microscopy and energy dispersive X-ray diffraction analysis revealed that the nanoparticles on the 12-inch wafer are composed of etchant gases and Y2O3. These results indicate that the YF3 coating is a more erosion-resistant material, resulting in fewer contamination particles compared with the Y2O3 coating.

In this study, yttrium fluoride (YF3) and yttrium oxide (Y2O3) coatings were prepared by an atmospheric plasma spraying technique and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). YF3 powders were sprayed at various plasma spraying powers of 9, 15, and 21 kW. The XRD result indicates that the YF3 coating shows preferred orientations and was well crystallized. The XPS results revealed a strong Y–F bond on the YF3 coating surface. A porosity value analysis showed that the porosity of the YF3 coating was lower than that of the Y2O3 coating. Moreover, the dielectric strength of the YF3 coating (22.65 kV/mm) was higher than that of the Y2O3 coating (14.42 kV/mm). This confirms that the YF3 coating exhibits a breakdown voltage of 4.97 kV, which is more than 1.5 times higher than that observed for the Y2O3 coating (3.29 kV). These results indicate that the YF3 coating has better mechanical and dielectric properties than the Y2O3 coating, indicating that the YF3 coating is a very attractive novel antiplasma and corrosion-resistant material.

Surface roughness development of photoresist (PR) films during low pressure plasma etching has been studied using real-time laser light scattering from photoresist materials along with ellipsometric and atomic force microscopy (AFM) characterization. We show that evolution of the intensity of light scattered from a film surface can be used to study the development of surface roughness for a wide range of roughness starting from subnanometer to few hundred nanometers. Laser light scattering in combination with ellipsometry and AFM is also used to study the reticulation mechanism of 193 and 248 nm PRs during argon plasma processing. We employ a three-layer model (modified layer, rough layer, and bulk film) of the modified PR surface (193 and 248 nm PRs) to simulate and understand the behavior of ellipsometric Ψ-Δ trajectories. Bruggeman’s effective medium approximation is employed to study the roughness that develops on the surface after reticulation. When the glass transition temperature of the organic materials is reached during Ar plasma processing, the PR films reticulate and roughness develops rapidly. Roughness development is more pronounced for 248 nm PR than for 193 nm PR. Simulation of Ψ-Δ shows that the growth of roughness is accompanied by strong expansion in the materials, which is stronger for 248 nm PR than 193 nm PR. The leading factors responsible for reticulation are found to be compressive stress that develops in the modified surface layer as it is created along with strong molecular chain motion and expansion of the material when the temperature is increased past the glass transition temperature. Reticulation leads to a significantly different surface morphology for 248 nm PR as compared to 193 nm PR and can be related to differences in molecular structure and composition leading to different responses when a modified surface layer is formed by ion bombardment accompanying plasma etching.