Chang-Ho Noh

Photochemical Deposition of Ni – Cu Patterns onto Conducting Substrates Employing TiO2 – Pd2 + Layers

The metal photopatterning process employing a thin film of amorphous TiO 2 doped with Pd 2+ and oxalic acid has been developed. The exposure of this photolayer to UV light is believed to yield Pd(I) stabilized in a titanium oxide matrix, while subsequent washing results in formation of Pd nanoparticles through disproportionation. The Pd centers at the exposed areas are capable of inducing electroless nickel plating yielding the adhesive nickel pattern. The electroless copper deposition over patterned Ni allows generation of metal patterns with a resistivity of 4-12 μΩ cm and a resolution of 7 μm on the conducting substrates (indium-tin oxide glass, Si).

Low-Temperature Fabrication of Zinc Oxide Micropatterns Using Selective Electroless Deposition

Zinc oxide ZnO micropatterns were synthesized site-selectively on photocatalytically activated regions of TiO2 in an aqueous solution of zinc nitrate and dimethylamine-borane at 55°C by an electroless deposition process. The as-deposited ZnO micropatterns showed a polycrystalline wurtzite structure with a thickness of approximately 0.1 m. The ZnO micropatterns emitted ultraviolet light at 380 nm due to the recombination of bound excitons and broad visible-light luminescence 500-800 nm .

A novel patterning method of low-resistivity metals

A new metal patterning process using photocatalyst was developed to reduce the number of chemical processing steps and to obtain high resolution. Films of amorphous TiO2 and water-soluble polyvinyl alcohol were used as photocatalytic layers. UV light was illuminated through a photomask onto the photocatalytic layers. Pd(II) in an aqueous solution was reduced to Pd(0) by the exposed TiO2 and deposited on the exposed regions. Selective electroless Ni/Cu plating on the Pd patterns showed high resolution metal patterns. Process parameters such as exposure dose and postexposure time delay were optimized to confirm the feasibility of this method. It was established that high resolution metal patterns of low resistivity with good adhesion were formed only at a small process steps without using high cost materials and equipments. Selective growth of carbon nanotubes on the Ni patterns was carried out by plasma-enhanced chemical vapor deposition. It’s expected that this methods will have several benefits for fabricating the microelectronic devices, especially in the large size flat panel display.

Selective Electroless Deposition Using Photoinduced Oxidation of Sn(II) Compounds on Surface-Modified Polyimide Layers

This paper describes an electroless deposition method for fabricating microscale metal patterns on polyimide surfaces. This method uses the selective deposition of catalytic Pd seeds via the photoinduced oxidation of Sn(II) compounds. The preparation process requires three steps: a first step in which the adsorption of Sn(II) compounds occurs on the surface of the polyimide film through ion exchange reactions, a second step in which the photoinduced oxidation of the Sn(II) compounds with atmospheric oxygen occurs in ultraviolet light (UV) irradiated areas, and a third step comprising the deposition of Pd 2+ ions in nonirradiated areas, which are simultaneously reduced.

Fluorocarbon-based single-layer resist for 157-nm lithography

We have designed and synthesized a number of unique polymer systems composed of acrylate and styrene even though it had moderate transparency. Our first model of 157nm photoresist was based on a (alpha) trifluoromethylacrylate and styrene bearing a pendent hexafluoroisopropanol with pentafluoroisopropyl t-butyl carbonate (PFITBC) as the transparent enhancer and acid labile compound. PFITBC was obtained from perfluorinated enolate with di-t-butyl carbonate with high yield. All of the absorbance of our system ranged over 3.0~3.4micrometers -1 for base resin, which corresponded to a resist thickness of 110~125 nm at the optical density of 0.4. We have formulated several resists based on these polymers and these formulations have shown high resolution and contrast at 248 nm. We were able to obtain 240nm 1:1 image when exposed at 248 nm by a Nikon stepper with 0.45NA. To overcome the weak etch resistance with thin thickness film, we investigated the vapor phase silylation treatment (SILYAL) in which the treated pattern was more persistent against the O2 plasma and turned to smoother surface. DMSMDA with Bi(DMA)MS of 30-40 wt% showed not only good control resist flow but also the improvement of line-edge roughness. Our results suggested that a facile approach to fluorine incorporated resin with SILYAL process can accelerate the 157nm lithography.