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Electron‐beam lithography of chlorinated polystyrenes with narrow molecular weight distributions
Author(s) -
Feit Eugene D.,
Stillwagon Larry E.
Publication year - 1980
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760201604
Subject(s) - materials science , polymer , monomer , electron beam lithography , resist , polymerization , lithography , molar mass distribution , yield (engineering) , polymer chemistry , benzene , chlorine , analytical chemistry (journal) , nanotechnology , chemistry , composite material , organic chemistry , optoelectronics , layer (electronics) , metallurgy
Polystyrenes with narrow molecular weight distributions have been chlorinated with only slight broadening of molecular weight distributions to yield materials that are five to six times more sensitive to electron‐beam irradiation. The chlorinated polystyrenes are useful negative resists for electron‐beam lithography. At molecular weights of 3‐4 × 10 5 g/mole, their threshold sensitivities to 20 keV electrons are 1‐2μC/cm 2 . Their lithographic contrasts are ≥ 1.5; in fact, > 2.0 for the narrowest molecular weight distributions. They compare favorably in these regards to polystyrenes of similar molecular weight characteristics. Lithographic relief images that are 80% of the original thickness of the polymer film can be formed at three to four times the threshold dose. The degree of chlorination ranged from 0.65‐0.76 Cl/monomer unit. The infrared spectra of the chlorinated materials resemble the spectrum for poly(4‐chlorostyrene). Elemental analysis indicated, however that some addition of chlorine had occurred. More extensive chlorination or chlorination of the higher molecular weight starting materials broadened the molecular weight distributions. The chlorinated material, a kind of poly(4‐chlorostyrene‐costyrene), is less sensitive than poly(4‐chlorostyrenc) prepared by addition polymerization by almost a factor of four.