Sensitivity cross-linking negative

Examples of such photochemical acid generators are shown in Chart 3.2. These onium salts, which are cationic photoinitiators originally developed for curing of epoxy resins (i09), can be used to formulate cross-linking negative resist materials (JOS), are very sensitive to electron beam and X-ray (JOS, 107, 108) radiation, and can be sensitized to longer wavelength radiation (JOS, 110, 111). 

After the absorption step, it appears that the cross-linking or degradation chemistries of X-ray and e-beam resists are similar. This is demonstrated in Figure 9 where the sensitivities of several polymer resists to both 20 keV electron beam exposures and Mo (5.41 A) X-rays are plotted. Both degrading (positive) and cross-linking (negative) polymers are included in this plot. 

Almost all polymers are more sensitive (require fewer exposure units) when exposed to ion beams than when they are exposed to e-beams. Polymers such as styrene and novolac, which are relatively insensitive to e-beams, have a much more sensitive response to ion beams. However, resist speed is important for focused ion beam lithography and several high speed resists have been found, Poly(2,2,2-trifluoroethyl a-chloroacrylate), a scissioning positive tone polymer, and two cross-linking negative tone polymers, poly(2,5-dichlorostyrene) and poly(4-bromostyrene), have been found to function at high speed as ion beam resists. ... 

Zenkl et al. [51] presented another approach to design saccharide-sensitive nanobeads. They prepared particles (0 380 nm) based on poly (/V- i sopropy I aery I am ide) cross-linked with phenylboronic acid moieties. In the presence of a saccharide (glucose or fructose) the particles reversibly swell due to the formation of negative charges. A FRET-indicator couple (fhiorescein/rhodamine) is used to monitor the... 

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