Hydrophobic/hydrophilic surface modification within buried air channels

Abstract

Recently, a method for fabricating air channels using a photodefinable sacrificial material (Unity 2203P) with acid-catalyzed degradation at low temperature was reported [J. P. Jayachandran et al. J Microelectromech. Syst. 12, 147 (2003)]. The acid is created via a ‘photoacid’ generator (PAG) either photolytically (when exposed to UV irradiation) or thermolytically (when heated to the decomposition temperature of the PAG). This approach to the fabrication of micro air-channel structures using low-temperature decomposable sacrificial materials has applications to air-gap formation for electrical/optical interconnects, microelectromechanical systems, microfluidics, and microreactors. In this study, the surface characteristics of the silica surface after the decomposition of Unity 2203P was explored. It was found that the surface inside the air-channel after low-temperature Unity 2203P decomposition was hydrophilic and was then converted to hydrophobic after higher-temperature treatment. The modification of the silicon surface using silane-based chemistries and a method for creating alternating hydrophobic/hydrophilic textures within a buried air channel has been demonstrated. Trifluoropropyl dimethylchlorosilane was the most effective surface treatment for creating hydrophobic channels. The hydrophobic/hydrophilic nature of the silicon surfaces is shown by the contact angle measurements and x-ray photoelectron spectroscopy analyses.

Photodefinable Epoxycyclohexyl Polyhedral Oligomeric Silsesquioxane

“…Treatment with trimethyl methoxysilane, phenyldimethyl ethoxysilane, and triflouropropyl dimethylchlorosilane yielded contact angles of 68°, 68°, and 83°, respectively. 17 The elastic modulus and hardness of POSS were studied using nanoindentation. A 5 lm thick film was measured using a Berkovich tip after PEB.…”

Photo-definable microchannels made with spin-on polymers and short sacrificial etch times

“…This technique creates microchannels that etch according to a linear relationship with respect to time, independent of actual channel geometry (Metz et al 2004;Salas-Vernis et al 2004). One major drawback of this method is the high temperature required to diffuse the sacrificial layers through the SiO 2 layer, which renders this process incompatible with microfabrication techniques that require low temperatures.…”

From microchannels to nanochannels in a bilayer resist

“…Microfluidics devices have been fabricated using a variety of methods, ranging from thermal decomposition of buried patterned channels [1][2][3], to fabricating trenches via plasma etch or hot embossing and covering with a plastic [4] or filling with a polymer film [5]. This paper describes an alternative to these methods by using a bilayer resist in an inverted configuration normally used for T and Γ gate fabrication [6].…”