Plasma Surface Modification for Selective Hydrophobic Control

2007 International Semiconductor Conference, 2007

The main objective of this study is theoretical and experimental investigation of the surfaces modification of SU8, PDMS, SiO2 and Si by plasma RF treatment. Physical-chemical reactions at room temperature can be used for the modifications of the surfaces in plasma, by modifying the contact angle, superficial polymerization, or by creating of hydrophilic regions and/or hydrophobic on the surfaces in contact with plasma. The argon-plasma annealing was used for generate the hydrophilic surfaces, and plasma of CF4 or CF4 with O2 has been used for creation of the hydrophobic surfaces.

Pure and Applied Chemistry, 1985

Surface treatment of' materials by plasma techniques depends essentially on the chemical properties of the boundary layers: plasma gas and solid surface. The first part of the paper presents the evolution of a non equilibrium plasma boundary layer and the molecule excitation correlated with its reactivity. Its applications to nitriding of the transition metals and silicon by NH3 low pressure plasma indicates the role of the vibrational excitation during the surface treatment.The second part analyzes the properties of radicals and molecules in terms of polarizability and Lewis acid base reactivity. Plasma polymerization and etching are essentially developed for polymer surface treatments. In fine heat transfer and plasma chemical reactivity in a high pressure plasma torch for surface treatment of metal and silicon permit the understanding of the surface treatment of liquid or solid at high temperaturesfor nitriding or refining.

Materials Research, 2002

Low-temperature plasma treatment has been used in the last years as a useful tool to modify the surface properties of different materials, in special of polymers. In the present work low temperature plasma was used to treat the surface of asymmetric porous substrates of polysulfone (PSf) membranes. The main purpose of this work was to study the influence of the exposure time and the power supplied to argon plasma on the permeability properties of the membranes. Three rf power levels, respectively 5, 10 and 15 W were used. Treatment time ranged from 1 to 50 min. Reduction of single gas permeability was observed with Ar plasma treatments at low energy bombardment (5 W) and short exposure time (20 min). Higher power and/or higher plasma exposition time causes a degradation process begins. The chemical and structural characterization of the membranes before and after the surface modification was done by AFM, SEM and XPS.

2007

Engineered surfaces with controlled hydrophilic/ hydrophobic character have been fabricated by tailoring the substrate topography and chemistry. In this method, the substrate to be treated was first coated by a photoresist, which was then surface-roughened using SF 6 plasma etching. The resulting rough texture was then transferred to the underlying silicon surface by over-etching of the photoresist. At this point, the topographically modified surface was modified chemically by controlled deposition of a thin polymer layer using plasma processing. In this way, both the surface texture and the surface chemistry could be varied independently, producing surfaces with variable wetting character, including super-hydrophilicity and super-hydrophobicity, depending on the choice of plasma polymer deposited. Chemical characterization demonstrates a correlation between the surface chemistry and the wettability of the samples after etching. The surface elementary composition contained more C-F groups as the measured contact angle increased, indicating that the change of wettability is due to both the roughness and the surface energy of the deposited photoresist. In the case of materials deposited on the plasma-treated rough surfaces, the strengthening of the wetting character is only due to the created surface roughness, as XPS analyses showed no significant chemical difference as compared to the flat polymer.

Plasmas and polymers, 2001

Tailoring of polymers for multifaceted applications is an increasing field, whereby most often the surface properties must be adjusted. Therefore, the coating of common polymers by plasma polymerization is a promising way to modify the surface and meet the demands. Beside the tuning of the required surface properties, good adhesion and stability of the films is essential. This work investigates the plasma deposition of pp-HMDSO films on PC and PC/ABS to generate stable, hydrophobic surfaces. By examining the plasma conditions-deposition rate, energy range, and surface topography-ultrathin, stable films with advancing contact angles up to 110 • and receding angles exceeding 90 • can be designed. Storage of the siloxane films for 1 year in air at ambient conditions exhibits almost no aging. Thus, these films are superior to fluorocarbon films deposited for comparison.

Langmuir, 2006

In this article, we describe a method to create rough features on silicon surfaces by reactive etching of a photoresist layer. The roughness and, consequently, the wettability of the surfaces can be modified by modifying the duration of plasma etching. Hydrophobic materials deposited on the rough silicon surface can be modified until a superhydrophobic behavior is obtained, whereas hydrophilic materials become more hydrophilic. The elaboration technique described herein offers an inexpensive and rapid method for the creation of tunable roughness on silicon surfaces with large areas.

Materials Today: Proceedings, 2020

This paper presents the results of the study and analysis of the surface of hydrophobic films deposited by a plasma jet of atmospheric pressure. The surface roughness was obtained by using nanoparticles synthesized in a plasma jet of atmospheric pressure in mixtures of argon and methane gas. The dependence of the contact angle on the discharge power and the time of sample surface treatment was determined. SEM and optical images of hydrophobic samples were also obtained.

Applied Surface Science, 2006

Surface properties of polycarbonate (PC), polypropylene (PP), polyethylene terephthalate (PET) samples treated by microwave-induced argon plasma have been studied with contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scanned electron microscopy (SEM). It is found that plasma treatment modified the surfaces both in composition and roughness. Modification of composition makes polymer surfaces tend to be highly hydrophilic, which mainly depended on the increase of ratio of oxygen-containing group as same as other papers reported. And this experiment further revealed that C O bond is the key factor to the improvement of the hydrophilicity of polymer surfaces. Our SEM observation on PET shown that the roughness of the surface has also been improved in micron scale and it has influence on the surface hydrophilicity. #

Surface and Interface Analysis, 2010

For the fabrication of microfluidic devices based on SU-8, the wetting properties of the polymer surface need to be adjusted. We investigated the effects of wet chemical and plasma processes with respect to wetting properties, surface roughness, and surface chemistry.

Journal of Vacuum Science & Technology A

Recently developed atmospheric pressure plasma jet (APPJ) is considered as a novel and efficient technique for uneven surfaces processing and APPJ array effectively expands the treatment area of a single APPJ. In this paper, a two-dimensional (2D) APPJ array in Ar/tetramethylsilane (TMS) is used to improve the surface hydrophobicity of polymethyl methacrylate (PMMA) by depositing polymerized silicalike clusters on the jet-PMMA interface. The electrical and optical characteristics of the 2D Ar/TMS APPJ array are measured to optimize experimental conditions. The wettability of jet-PMMA interface is assessed by measuring water contact angle, which increases from 65°to a maximum value of 115°after 240 s plasma treatment at 0.04% TMS content. Scanning electron microscopy is used to investigate the micro-and nanoscale surface morphology of PMMA after plasma treatment, and it is found that there are clusters of particles with diameters of hundreds of nanometers attached on the PMMA surface. The changes of the chemical composition and chemical bonding on the PMMA surface are further analyzed using Fourier transform infrared and x-ray photoelectron spectroscopies. It is found that the silicon-containing groups, such as Si-CH 3 , Si-H, and Si-O-Si, replace oxygen-containing hydrophilic polar groups (C-O and C=O), reduce the surface polarity, decrease the surface tension, and increase the surface hydrophobicity. For the intensive peak of Si-O-Si in FTIR spectra, the improvement of hydrophobicity of the PMMA surface is caused by the hydrophobic polymerized Si-O-Si thin film. The results demonstrate that the APPJ array as a novel atmospheric pressure plasma device provides an efficient way to modify large uneven material surfaces.