A series of new polymers for 193 nm single layer resist based on maleic anhydride/cycloolefin systems with minimum amount of acrylate units were synthesized. In order to minimize the acrylate content, the cycloolefin moiety of the polymers was functionalized with side groups designed to either promote adhesion to silicon substrate and/or impart the imaging functionality. All polymers were prepared by free-radical polymerization in moderate to high yields (30-75%) and were characterized by variety of techniques (NMR, lit, DSC, TGA, GPC, UV). The initial lithographic evaluation of the new resists was carried out. It was found that acrylates can be successfully replaced with appropriately substituted cycloolefms to provide good resolution. The etch resistance of the new materials generally improves with increase in cycloolefin content. The Onishi and Kunz type plots will be discussed.
Through a series of statistical design experiments we optimized the lithographic performance of a 193 rim single layer resist based on a norbomene-maleic anhydride matrix resin. Several interesting findings were found including that having the PEB temperature higher than the SB temperature improved the performance of the resist. The polymer composition was found to strongly influence the lithographic performance of the resist. Variables that we examined included acrylate loading and blocking level. By optimizing the composition of the polymer, we have obtained resists with high etch resistance, square profiles and 0. 130 micron dense line ultimate resolution in 0.5 micron thick films. The resist formulations are compatible with industry standard 0.262 N TMAH. During exposure the resist does not suffer from the outgassing of volatile species (less than 2 molecules/cm2 x sec).
A novel material, bis(4-t-butylphenyl)iodonium cyclamate, an alkylaminosulfonate salt capable of photogenerating a zwitterion sulfamic acid is shown to have utility in 248 and 193 nm single layer chemically amplified resists. Specifically, bis(4-tbutylphenyl)iodonium cyclamate may be employed as a self-leveled photoacid generator (PAG) in resists in which protecting groups with a low activation energy are present. Alternatively, in resins protected with high activation groups, this material serves the role of a low volatility, low diffusion photodecomposable base used in conjunction with a super-acid PAG. In both types of resists, bis(4-tbutylphenyl)iodomum cyclamate reduces resist line slimming and T-topping by respectively reducing acid diffusion and its depletion at the resist surface. The above mentioned advantages of reduced line slimming and post-exposure bake delay (PED)' stability are accomplished both in the case of the low and high activation energy resists without the need for an additional amine component. Finally, formulation of the low activation energy resist with the cyclamate PAG suppresses film thickness loss during exposure thus reducing outgassing off volatiles.
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