172-nm Vacuum Ultraviolet Light Research Articles

Hexagonally Arranged Nanopore Film Fabricated via Selective Etching by 172-nm Vacuum Ultraviolet Light Irradiation

Highly ordered nanopore arrays were successfully fabricated using poly(ethylene oxide) (PEO) and polymethacrylate with azobenzene mesogen in side chains [PMA(Az)] block copolymer film based on irradiation of 172-nm vacuum ultraviolet (VUV) light. The block copolymer forms a highly ordered microphase-separated film with perpendicularly oriented PEO cylinders just by thermal annealing through a self-assembling process. We found that the etching rate of the PEO homopolymer was much higher than that of the PMA(Az) homopolymer at a chamber pressure of 102 Pa of atmosphere under VUV irradiation. The etching rate of the PEO component in the two systems of microphase separation and macrophase separation of the homopolymer blend crucially depended on the feature size of phase separation. In the PEO selective etching process of the block copolymer film, the water-contact angle of the film dramatically increased due to elimination of hydrophilic PEO. The resulting nanopore array film will be useful for low-density target materials.

A Photo-Desmear Method for Via Residue Removal Using a VUV Light Source

The desmear process of removing via residue after laser drill in substrate manufacturing is a critical step for reliability and electrical performance. Cost effective and environmentally clean desmear processes are industry-wide objectives, as the current wet desmear process results in significant chemical waste and regular bath replacement. Here, we evaluated an effective photo desmear method targeting a low total cost of ownership and negligible environmental impact. This method achieves residue and silica free via bottoms with the use of 172nm vacuum ultraviolet light (VUV) photo-chemical ashing followed by water clean. Studies of organic molecular photochemical decomposition by short wavelength UV light are widely reported and have been applied for purposes such as surface cleaning and improving wettability and are naturally extendable to via residue removal. Scanning electron microscope (SEM) and energy dispersed X-ray spectroscopy (EDX) reveal that the application of VUV desmear results in residue free microvia without negatively affecting via shape or the dielectric surface. In addition, the surface remains highly wettable, which aids downstream copper plating. The high reaction rate, absence of wet chemistry, and creation of surfaces amenable for subsequent copper plating make this dry desmear process a strong candidate for future applications in substrate manufacturing.

Evaluation of Changes in Chemical Structures of Poly (methyl-methacrylate) using 172nm Vacuum Ultraviolet light

Evaluation of Changes in Chemical Structures of Poly (methyl-methacrylate) using 172nm Vacuum Ultraviolet light

Controlled Cell Adhesion onto Photochemically Micropatterned Perfluoroalkyl Isocyanate Monolayer on Oxidized Aluminum

Abstract A superhydrophobic surface of a perfluoroalkyl isocyanate (RF-NCO) layer on oxidized aluminum (BWAlAl2O3) was photolithographed using masked 172-nm vacuum ultraviolet light to fabricate a superhydrophobic/superhydrophilic micropattern. Cell-adhesion experiments revealed complete cell repellency on the superhydrophobic region of the RF-NCO layer and cell adhesiveness on the superhydrophilic region of BWAlAl2O3 surface.

Photooxidation of plasma polymerized polydimethylsiloxane film by 172nm vacuum ultraviolet light irradiation in dilute oxygen

Plasma polymerized polydimethylsiloxane films irradiated under different partial pressures of oxygen with a 172nm vacuum ultraviolet light were investigated in order to clarify the roles of molecular oxygen and photons in photooxidation. The thickness, densities, surface roughness, elemental compositions, and molecular structures of the irradiated and unirradiated films were examined by using glazing incidence x-ray reflectivity, Rutherford backscattering, infrared, and x-ray absorption (XAS) spectroscopies. Photooxidation is hardly promoted by irradiation in a high vacuum of 1×10−4Pa, though photodesorption of the methyl group and formation of Si–H bonds were observed. Silica films thicker than 140nm were formed at room temperature by irradiating them in low pressure oxygen gases. The degree of oxidation was smaller for the oxygen pressure of 10kPa than for 83Pa. Si K-edge XAS was performed to clarify the change of coordination environment of silicon by photooxidation in dilute oxygen flow containing less than 5ppm of molecular oxygen.

Area-selective assembly of high crystalline tin-doped–indium–oxide particles onto monolayer template

Well-defined microstructures of tin-doped–indium–oxide (ITO) were successfully fabricated on a monoalyer template through an electrostatic interaction in aqueous media without any chemical and physical etching processes. Highly oriented amino-terminated self-assembled monolayers (SAMs) were formed on the SiO2∕Si substrate in a vapor of 12.5vol% solution of N-(6-aminohexyl)-3-aminopropyltrimethoxysilane [H2N(CH2)6NH(CH2)3Si(OCH3)3, AHAPS] diluted with absolute toluene. A chemical template of AHAPS–SAM was photolithographycally prepared using 172nm vacuum ultraviolet light under a reduced pressure of 10Pa for 30min through a photomask. The fabricated chemical template composed of AHAPS- and SiOH-covered regions served, respectively, as electrostatically repulsive and attractive areas to provide a monolayer template for the area-selective assembly of ITO particles. The ITO particles assembled preferentially onto the silanol regions through the electrostatic interaction, while their assembly was prevented on the amino-terminated regions because of the electrostatic repulsion between the particle’s surface and the terminated amino groups. The resistivity of the ITO particulate film formed on silanol region was measured to be 4.0×10−3Ωcm.

The hydrophilization of polystyrene substrates by 172-nm vacuum ultraviolet light.

This paper describes the photochemical surface modification of polystyrene (PS) substrates using vacuum ultraviolet (VUV) light 172 nm in wavelength. We have particularly focused on the effects of atmospheric pressure during VUV irradiation on the obtained surface's wettability and the stability of the wettability, in addition to its chemical structure, morphology, and photooxidation rate. Samples were photoirradiated with VUV light under pressures of 10, 10(3), or 10(5) Pa. Although, in each case, the originally hydrophobic PS surface became highly hydrophilic, the final water-contact angle and photooxidation rate depended on the atmospheric pressure. The samples treated at 10 Pa were less wettable than those prepared at 10(3) and 10(5) Pa due to the shortage of oxygen molecules in the atmosphere. The minimum water-contact angles of the samples treated at 10, 10(3), and 10(5) Pa were about 8 degrees, 0 degrees, and 0 degrees, respectively. With the samples prepared at 10 and 10(3) Pa, photooxidation reactions proceeded in the topmost region closest to the surface, while at 10(5) Pa photooxidation was found to be greatly enhanced in the deeper regions, as evidenced by angle-resolved X-ray photoelectron spectroscopy. Photoetching rates were determined through atomic force microscope observation of microstructured PS samples prepared by a simple mesh-contact method. As estimated from AFM images of the latticed microstructures obtained, the rates of samples prepared at 10(3) and 10(5) Pa were about 1.5 and 1.3 nm/min, respectively. However, no photoetched features were observable on the sample surface prepared at 10 Pa. Hydrophilic stability also varied greatly depending on atmospheric pressure. The hydrophilicity of samples treated at 10 and 10(3) Pa gradually decreased as they were exposed to air. On the other hand, the sample surface prepared at 10(5) Pa showed excellent hydrophilicity even after being left in air for 30 days.