Resist materials norbornenes

Perfluoroacetal or perfluoroketal polymethacrylates containing norbornene substituents and having improved transparency were prepared and were suitable for use in photolithography with far-ultraviolet light at a wavelength of 180 nm or shorter. These materials are particularly useful in the formation of a fine resist patterns. 

Elastomers or rubbers are flexible materials that are mainly used in tires, hoses, and seals as adhesives or as impact modifiers of thermoplastics. They exhibit high resistance to impact, even at low temperatures at which materials increase their rigidity. Eor some of the applications (e.g., tires or hoses), these materials have to be slightly crosslinked once they are formed into the desired shape in order to impart them dimensional stability, since otherwise they tend to slowly flow. Elastomers are polymers that are used above their glass-transition temperature (Tg). Some examples of common elastomers are polybutadiene, which is used as an impact modifier of rigid plastics SBR (copolymer of styrene and butadiene), mainly used in tires EPDM (copolymer of ethylene, propylene, and a diene monomer, usually norbornene) NBR (copolymer of acrylonitrile and butadiene) and so on. 

The copolymers of ethylene with norbornene produced with metallocene catalysts [199] are interesting thermoplastic materials characterized by high glass transition temperatures, good chemical and thermal resistance and excellent transparency [200,201]. The properties of these copolymers depend on the comonomer composition, the distribution of the comonomers and the chain stereoregularity. 

COMA polymers (Fig. 17), synthesized by conventional radical polymerization, have a 1 1 alternating structure, a consequence of the preference for each radical to react exclusively with the other monomer. As a rnle, the products are high Tg materials for example poly(norbornene-co-maleic anhydride) has a Tg > 300°C. The polymerization allows the incorporation of small amoimts of other vinyl monomers (e.g. acrylic acid) without disruption of the alternating structure (117). Substituted norbornenes can be included in the pol5mierization mixture to incorporate acid-labile functionality, to modify polymer polarity, and to improve film adhesion (118). Cholate dissolution inhibitors can be added in the formulated resist to further modify functional properties (119). 

At a norbornene content of 50 mol%, the Tg of a statistically random or alternating E/NB copolymer is about 150 °C. A material with 75 mol% norbornene has a Tg of about 200 °C. Alternating copolymers are semicrystalline if the norbornene content is above 37 mol%. They feature TgS of 100-130 °C and T s of 270-320 °C. Alternating copolymers have an even greater solvent resistance than statistical copolymers, although they are still transparent owing to the small size of their crystalline regions (5 nm). 

The literature describes several cases of the copolymerization of ethylene with cyclopentene [31b], cyclo-heptene [31b], norbornene [31c], 2-methylnorbornene [31c], dicyclopentadiene [31d], dimethanooctahydro-naphthalene [31a,e], and 2-methyldimethanooctahy-dronaphthalene [31a]. When chiral catalysts were employed (e.g., ethylenebis(indenyl)zirconium dichloride associated with methylaluminoxane), the activity was much higher than that of the achiral catalyst. In addition, the ehiral catalyst increased the polymer stereoselectivity and the amount of the cycloolefin incorporated into the copolymer. Materials having exeellent transpareney, thermal stability, and ehemical resistance—properties that are useful for optical disks—may be produced efficiently by this method. 

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