No abstract

The effect of the substituent on the palladium(II)-catalyzed addition polymerization of functionalized norbornene derivatives was examined. Endo-substituted norbornenes are polymerized more slowly than their corresponding exo isomers. The size of the substituent plays a role. However, the coordinating ability of the functionality plays an even bigger role in attenuating polymerization than its size. The formation of chelates upon the coordination of the endo-functionalized norbornene is responsible, in part, for the observed decrease in polymerization rate. A further, and even greater, reason for the diminution of activity of both the endo- and the exo-functionalized isomers is simply the coordination of the functionality to the metal center.

The copolymerization of ethene with norbornene derivatives, as well as their terpolymerization with 1-alkenes, using a series of neutral, square-planar nickel complexes containing anionic P∼O chelates is described. In copolymerizations, up to 50 mol % incorporation of norbornene, leading to an essentially alternating copolymer, is obtained. With norbornene derivatives bearing oxygen functionalities, the level of incorporation is lower, as are the reaction rates and polymer molecular weights. In the case of terpolymerization of ethene and norbornene with 1-alkenes, the polymer molecular weights tend to be low because of slower monomer insertion and additional chain-transfer pathways that are available following 1-alkene insertion. For the ethene/norbornene polymers synthesized, the glass transition temperature (T g) increases smoothly with increasing norbornene content. Solution-cast films of the polymers show good optical clarity.

The roles of ultraviolet/vacuum ultraviolet (UV/VUV) photons, Ar+ ion bombardment and heating in the roughening of 193nm photoresist have been investigated. Atomic force microscopy measurements show minimal surface roughness after UV/VUV-only or ion-only exposures at any temperature. Simultaneous UV/VUV, ion bombardment, and heating to surface temperatures of 60–100°C result in increased surface roughness, and is comparable to argon plasma-exposed samples. Ion bombardment creates a modified near-surface layer while UV/VUV radiation results in loss of carbon-oxygen bonds up to a depth of ∼100nm. Enhanced roughness is only observed in the presence of all three effects.

We have identified a synergistic roughening mechanism of 193 nm photoresist, where simultaneous ion bombardment, vacuum ultraviolet (VUV) radiation, and moderate substrate heating in a well‐characterized beam system results in a similar level of surface roughness observed during conditions typical of plasma etching. VUV radiation (147 nm) results in bulk modification of the photoresist polymer, witnessed by the loss of carbon–oxygen bonds through transmission FTIR. Ion bombardment (150 eV) results in the formation of a densified surface layer on the order of a few nanometers in depth. We have shown that elevated levels of roughness are observed only during simultaneous exposure and that sequential exposure is not sufficient to produce surface roughness. In addition, through the use of transmission FTIR we have shown that an etching synergy does not exist and that etch rates are nearly independent of temperature. We propose that the observed roughness could be due to the drastically different mechanical properties of the ion‐modified near‐surface region and VUV‐modified bulk photoresist, where the difference is exaggerated at elevated temperatures. A more complete understanding of plasma‐induced surface roughness will require further study, resulting in the improvement of existing pattern transfer technologies and possibly novel new technologies as well.