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.
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.
The present authors have studied a novel system of deep UV photoresist based on thermally crosslinkable photoacid generators(TCL-PAG), which have two or three crosslinking groups on the same molecule that can be crosslinked to a binder resin of chemically modified poly (p-hydroxystyrene), referred to as PHST hereinafter, in the stage of prebaking via the reaction of their phenolic hydroxyl groups on the polymer chain with the crosslinking groups of TCL-PAG. Upon exposure and subsequent PEB, the crosslinkage with acetal structures is cleaved by photogenerated acids to give an unprotected phenol resin, alcohol and acetaldehyde. We investigated some structural effects on resolution, photospeed, line edge roughness and other functional properties of the resulting resists with different size of the protecting groups in a combination with different types of PAGs and bases added. KrF steppers of Nikon (NA:0.45) and ASML(NA:0.7) were used in the lithographic test with binary test masks. Various types of partially protected PHST derivatives were synthesized with different protecting groups to control the dissolution rate and the activation energy of the base resins. The resist pattern quality can be enhanced by using our new PAG system based on the thermal crosslinking mechanism. A combination of the acetal and carbonate protecting groups onto the PHS base resin with the TCL-PAG can also enhance the resist performance so that a minimum resolution of 130 nm with KrF exposure could be obtained.