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IBM Journal of Research and Development  
Volume 21, Number 2, Page 143 (1977)
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Parameters Affecting the Electron Beam Sensitivity of Poly(methyl methacrylate)

by E. Gipstein, A. C. Ouano, D. E. Johnson, O. U. Need,III
Poly(methyl methacrylate), PMMA, is used as a model polymer to determine quantitatively the effect of molecular weight, molecular weight distribution, and tacticity on electron beam sensitivity. The heterotactic, syndiotactic, and isotactic stereoforms of PMMA were synthesized with molecular weights ranging from 104 to 107 and dispersivities from 1.2 to about 10. The G-values as determined by gamma radiation are about 1.3 and are independent of the three parameters. However, the solubility rate of PMMA is very dependent on the tacticity, and the relative solubility rates are in the order syndiotactic < heterotactic ≪ isotactic. The weight-average molecular weight ratio was found to give a better correlation with solubility rate ratio than the number-average molecular weight ratio. The molecular size of the developer solvent was shown to have a much greater effect on the solubility rate than the molecular weight of the resist. An optimal developer solvent for PMMA can be systematically selected from a homologous series of n-alkyl acetates which enhance the resist sensitivity.
Related Subjects: Beams, charged particle; Materials; Polymers