Narrow molecular weight distribution (w
<1.1) poly (methyl methyacrylate) [PMMA] with low molecular weight (w
<200 000) has been evaluated as an electron resist. It is shown that sensitivity and contrast of these narrow distribution resists can be altered by prebaking either above or below the glass transition temperature. Sensitivity of narrow distribution PMMA resists prebaked below the glass transition temperature (Tg
) can be a factor of 5 greater than the same resist prebaked above Tg
. Sensitivity improvement is shown to be caused by solvent trapped in the network of narrow distribution resists prebaked below Tg
. Trapped solvent preswells the polymer network so that small perturbations to the molecular weight distribution of the PMMA cause it to become soluble in developer. Low molecular weight broad distribution resists similarly prepared are readily soluble in the developer and do not exhibit improved sensitivity in usable lithographic images. When narrowly fractionated PMMA is baked above Tg
, the sensitivity is found to be slightly different from broad distribution material, and the contrast is significantly improved. Electron beam exposure of these narrow distribution PMMA resists baked below and above Tg
has produced 2000 and 800 Å period gratings, respectively.