Deep UV Laser Source Research Articles

Shrinkage Control of Photoresist for Large‐Area Fabrication of Sub‐30 nm Periodic Nanocolumns

A method to fabricate large-area arrays of nanocolumns without a deep-UV laser source is reported. This method allows high-yield fabrication of 3 x 3 cm(2) arrays of sub-30 nm nanocolumns made of bottom antireflection layer coating (BARC) by combining displacement Talbot lithography (DTL) using a monochromatic UV beam (365 nm wavelength) with plasma etching techniques. DTL is used to manufacture an initial pattern of periodic photo-resist nanocolumns with a diameter of similar or equal to 110 nm. N-2 plasma can transfer this pattern at a 1: 1 ratio to BARC nanocolumns. It is found that reactive O-2/N-2 plasma etching on the other hand can shrink the BARC nanocolumns to sub-30 nm dimensions. The shrink-etching process can be reproducibly controlled by tuning the gas flow ratio and the etching time. It is highly remarkable that the verticality of these BARC nanocolumns remains during O-2/N-2 plasma shrink etching. Combining the etching of O-2/N-2 plasma with N-2 plasma allows to produce BARC nanocolumns over the entire diameter range from 110 to sub-30 nm. The fabrication approach enables large-footprint fabrication of size-tunable periodic nanostructures that have many potential applications in photonics, electronics, biosensors, smart surfaces, catalysis, and biomedical analysis

Femtosecond-Laser-Coupled Near-Field Scanning Optical Microscopy Patterning Using Self-Assembled Monolayers

Investigations into the fabrication of nanoscale patterns on gold substrates via direct scanning near-field lithography were carried out. A laser beam is scanned over the workpiece where the pattern formation is desired by near-field scanning optical microscopy (NSOM). A pipette-type nanoprobe having a 100 nm aperture at its apex is used with the NSOM and a frequency-doubled Ti:sapphire femtosecond laser at a wavelength of 395 nm as the illumination source to prevent pulse dispersion of the femtosecond laser pulse. Self-assembled monolayers (SAMs) formed by the adsorption of alkanethiols onto the gold substrate are employed as very thin photoresists. The process underlying photopatterning of SAMs on gold is well-known at the phenomenological level. Alkanethiolates formed by the adsorption of alkanethiols are oxidized to alkylsulfonates upon exposure to UV light in the presence of air. Specifically, it is known that deep-UV light of wavelength less than 200 nm is necessary for oxidation to occur. The results show that an ultrafast laser can replace a deep-UV laser source for the photopatterning of thin organic films. Femtosecond-laser photolithography may be applied to create the patterning of a surface chemical structure or a three-dimensional nanostructure by combination with suitable etching methods.

펨토초레이저와 자기조립박막을 이용한 나노스케일 패터닝

Standard positive photoresist techniques were adapted to generate nano-scale patterns of gold substrate using self-assembled monolayers (SAMs) and femtosecond laser. SAMs formed by the adsorption of alkanethiols onto gold substrate are employed as very thin photoresists, Alkanethiolates formed by the adsorption of alkanethiols are oxidized on exposure to UV light in the presence of air to alkylsulfonates. Specifically, it is known that deep UV light of wavelength less than 200nm is necessary for oxidation to occur. In this study, ultrafast laser of wavelength 800nm and pulse width 200fs is applied for photolithography. Results show that ultrafast laser of visible range wavelength can replace deep UV laser source for photo patterning using thin organic films. Femtosecond laser coupled near-field scanning optical microscopy facilitates not only the patterning of surface chemical structure, but also the creation of three-dimensional nano-scale structures by combination with suitable etching methods.

Sub-micron scale patterning using femtosecond laser and self-assembled monolayers interaction

Standard positive photoresist techniques were adapted to generate sub-micron scale patterns of gold substrate using self-assembled monolayers (SAMs) and femtosecond laser. Self-assembled monolayers formed by the adsorption of alkanethiols onto gold substrate are employed as very thin photoresists. The process underlying photopatterning of SAMs on gold is well-known at the phenomenological level. Alkanethiolates formed by the adsorption of alkanethiols are oxidized on exposure to UV light in the presence of air to alkylsulfonates. Specifically, it is known that deep UV light of wavelength less than 200 nm is necessary for oxidation to occur. In this study, solid state femtosecond laser of wavelength 800 nm is applied for photolithography. The results show that ultrafast laser of near infrared (NIR) range wavelength can replace deep UV laser source for photopatterning using thin organic films. The essential basis of our approach is the photochemical excitation of specific reactions in a particular functional group (in this case a thiolate sulfur atom) distributed with monolayer coverage on a solid surface. Femtosecond laser photolithography could be applied to fabricate the patterning of surface chemical structure and the creation of three-dimensional nanostructures by combination with suitable etching methods.