Patterning Of Metal Thin Films Research Articles

Out-of-plane surface patterning by subsurface processing of polymer substrates with focused ion beams.

This work explores a new technique for the out-of-plane patterning of metal thin films prefabricated on the surface of a polymer substrate. This technique is based on an ion-beam-induced material modification in the bulk of the polymer. Effects of subsurface and surface processes on the surface morphology have been studied for three polymer materials: poly(methyl methacrylate), polycarbonate, and polydimethylsiloxane, by using focused ion beam irradiation with He+, Ne+, and Ga+. Thin films of a Pt60Pd40 alloy and of pristine Au were used to compare the patterning of thin films with different microstructures. We show that the height of Pt60Pd40 thin films deposited onto poly(methyl methacrylate) and polycarbonate substrates can be patterned by He+ ion beams with ultrahigh precision (nanometers) while preserving in-plane features, at the nanoscale, of the pre-deposited films. Ion irradiation of the Au-coated samples results in delamination, bulging, and perforation of the Au film, which is attributed to the accumulation of gases from radiolysis at the film–substrate interface. The irradiation with Ne+ and Ga+ ions destroys the films and roughens the surface due to dominating sputtering processes. A very different behavior, resulting in the formation of complex, multiscale 3D patterns, is observed for polydimethylsiloxane samples. The roles of the metal film structure, elastic properties of the polymer substrate, and irradiation-induced mechanical strain in the patterning process are elaborated and discussed.

Modelling of a vacuum metallization patterning method for organic electronics

The high throughput roll-to-roll patterning of metal thin films could be used to create organic functional devices. In this paper we present research into the compatibility of an in-vacuum selective metallization technique, which uses a sacrificial oil to define the metal electrode pattern for functional devices. The exact mechanism of the sacrificial oil masking, pattern definition and oil vaporization, due to the radiant heating from the thermal evaporation source, is described from previous research and experimental findings. The thermal modelling of this process develops further the requirements for the masking oil. It is found that in this particular system the oil thickness must be 1.63±0.31μm to match the radiative energy, and not be evaporated prior to leaving the metallization zone or to remain, as excess, after metallization is complete. The temperatures required are low and compatible with heat sensitive functional organic materials. The definition of the metal pattern edges is found to be like the liquid oil but thermal modelling still supports the theory of the oil vapor having the largest masking effect and concludes that the pattern definition quality does not depend on the sacrificial oil masking or vaporization effects but on the flexography patterning.

Thermal Process of Drilling for Metal Thin Films Using Femtosecond Laser

The femtosecond laser drilling for metal thin film is theoretically investigated in this paper. Femtosecond laser patterning of metal thin films is of technological significance because the fabrication of electrodes or metallization lines is a key process commonly required in the manufacturing of modern electronic devices. A femtosecond pulsed laser has a temporally short pulse that does not cause significant heat conduction in the material. This property of femtosecond laser pulse drilling makes sub-micron machining achievable with laser irradiation. Considering vaporization as the mechanism of the material removal, this paper employs two-temperature model to analyze the thermal process for femtosecond laser drilling of metal thin film. The variations of the drilling rate and squared diameter with laser fluence are compared with the available experimental data. This study also analytically validates that the drilling depth per pulse is governed by the optical penetration depth for low laser fluences and the squared crater diameter is linearly in proportion to the logarithm of laser fluence.

Optically-controlled digital electrodeposition of thin-film metals for fabrication of nano-devices

Precise micro-scale patterning of metal thin-films with semiconductor materials is a critical step in the fabrication of any micro-devices. Conventional metal patterning methods such as photolithography, laser-induced direct printing techniques, and micro-contact printing methods all have different disadvantages such as high capital equipment cost and low throughput efficiency. In this article, an optically-controlled digital electrodeposition (ODE) method for direct patterning of metal thin-films on a semiconductor substrate has been demonstrated. This method allows for dynamic patterning of custom micro-scale silver structures with high conductivity of 2 × 107 S/m in large scale within 10 seconds and could reach a smallest line width of 2.7 μm. The entire process is performed at room temperature and atmospheric pressure conditions, while requiring no photolithographic steps or metal nanoparticle inks. Utilizing this direct structural formation technique, a bottom-up protocol for rapidly assembling nanowire-based field-effect transistors has been demonstrated, which shows that this novel technique could potentially become an alternative, low-cost and flexible technology for fabricating integrated nano-devices.

Direct nano-scale patterning of Ag films using hard X-ray induced oxidation.

The morphological change of silver nano-particles (AgNPs) exposed to an intense synchrotron X-ray beam was investigated for the purpose of direct nano-scale patterning of metal thin films. AgNPs irradiated by hard X-rays in oxygen ambient were oxidized and migrated out of the illuminated region. The observed X-ray induced oxidation was utilized to fabricate nano-scale metal line patterns using sectioned WSi2/Si multilayers as masks. Lines with a width as small as 21 nm were successfully fabricated on Ag films on silicon nitride. Au/Ag nano-lines were also fabricated using the proposed method.

Excimer Laser Projection Photoablation Patterning of Metal Thin Films for Fabrication of Microelectronic Devices and Displays

A nonlithographic process is demonstrated for patterning Al, Cr, Cu, Ni, Ti, and W thin films, which are widely used in microelectronic and display fabrication. A projection photoablation process using 248-nm-deep ultraviolet radiation from a KrF excimer laser was used to pattern a polyimide film coated on a SiN layer deposited on glass. The photoablation-patterned polyimide film was used as a sacrificial layer in a lift-off patterning process for the metal films, which resulted in clean metal patterns with fine line-edge definition being fabricated after lift-off. This process provides a simpler and more economical patterning technique compared to conventional lithography methods, eliminating the developing and etching steps.

An alternative method for selective metal deposition onto flexible materials

Abstract In this article, a cost effective and simple method called line patterning is used for patterning of metal thin films deposited onto flexible substrates. Silver, gold and copper thin films have been deposited onto plastic substrates such as polyester, overhead transparency, polyimide and polyether imide and patterned via line patterning method. It was observed that the all metal thin films were electrically conductive and highly adhesive. Morphology of chemically deposited thin metal films was tested using scanning electron microscopy. Room temperature DC conductivities, current densities and power dissipation of these metal films have been investigated.

Masterless Soft Lithography: Patterning UV/Ozone−Induced Adhesion on Poly(dimethylsiloxane) Surfaces

A novel microreactor-based photomask capable of effecting high resolution, large area patterning of UV/ozone (UVO) treatments of poly(dimethylsiloxane) (PDMS) surfaces is described. This tool forms the basis of two new soft lithographic patterning techniques that significantly extend the design rules of decal transfer lithography (DTL). The first technique, photodefined cohesive mechanical failure, fuses the design rules of photolithography with the contact-based adhesive transfer of PDMS in DTL. In a second powerful variation, the UVO masks described in this work enable a masterless soft lithographic patterning process. This latter method, UVO-patterned adhesive transfer, allows the direct transfer of PDMS-based polymer microstructures from a slab of polymer to silicon and other material surfaces. Both methods exploit the improved process qualities that result from the use of a deuterium discharge lamp to affect the UVO treatment to pattern complex, large area PDMS patterns with limiting feature sizes extending well below 1 microm (> or = 0.3 microm). The use of these structures as resists is demonstrated for the patterning of metal thin films. A time-of-flight secondary ion mass spectroscopy study of the process provides new insights into the mechanisms that contribute to the chemistry responsible for the interfacial adhesion of DTL transfers.