Resist imaging experiments

We have also performed preliminary imaging experiments usin E-beam exposure, these experiments indicate that the 80 20 copolymer is a sensitive E-beam resist material which requires an exposure dose of < ljiC/cm. Further experiments involving both E-beam and X-ray exposure are in progress. 

Typical resist images obtained after a mid UV-exposure with an UV3 Perkin Elmer Exposure System are shown in Figure 5 using the m-c resol-benzaldehyde Novolak and the diester photoactive compound. The experiments were not carried out under optimum conditions, and the exposure dose at 313 nm was 500 mJ/cm2. Although this resist system was not the fastest one at this wavelength region, it clearly provides usable patterns. 

In a typical experiment, polyphthalaldehyde was dissolved in bis-(2-methoxyethyl) ether or cyclohexanone, to which was added the onium salt at 10 wt% to the polymer. Films spin coated on Si wafers were baked at 100°C for 10 minutes and then image-wise exposed. Optical micrographs of the resist images generated upon UV, e-beam, and x-ray radiations are exhibited in Figures 7a, b, and c, respectively. 

Resist films were spin-cast onto Si wafers for imaging experiments, NaQ plates for IR studies, and quartz discs for UV measurements and then baked at 80-130 °C for 2 min. The deep UV exposure sterns employed in these studies... 

Experiments indicate that ions are almost two orders of magnitude more efficient than 20 keV electrons 54). This is because the energy of the ions is more completely absorbed in the resist layer. The high sensitivity can be a problem, however, for very high resolution because of inherent noise fluctuations created by the small number of ions needed to expose an image element (55). At an exposure dose of 10 8 C/cm2, only 6 ions will expose a 0.1 /urn x 0.1 /urn element resulting in an exposure uncertainty of 40%. This is not satisfactory. 

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