Negative-acting resists polymers

Fig. 4. Chemistry of poly(vinyl cinnamate) negative-acting resist. Initial light absorption by the photosensitizer is followed by energy transfer to produce a pendant cinnamate group in a triplet electronic state. This combines with a second cinnamate on another polymer chain, forming a polymer—polymer...

Fig. 5. Chemistry of cyclized mbbei—bis-a2ide negative acting resist, (a) Preparation of cyclized mbber resin from polyisoprene (b) photochemistry of aromatic bis-a2ide sensiti2ers. The primary photoproduct is a highly reactive nitrene which may combine with molecular oxygen to form oxygenated products, or may react with the resin matrix by addition or insertion to form polymer—polymer linkages.

By general convention, the sensitivity, S, is related to the thickness, d, of the resist layer measured after exposure and development, and is obtained from exposure characteristic curves, as are illustrated in Fig. 9.3. In the case of positively functioning resists, S = corresponds to the exposure light dose required to completely remove the irradiated polymer from the substrate, i.e. the dose at which the normalized thickness of the resist layer is equal to zero, dirr/do=0. In the case of negatively acting resists, the sensitivity is reported as S = or... 

We have successfully employed the trimethylsilylmethyl appendage to effect oxygen RIE resistance in both positive and negative acting electron-beam resist systems (10,11). The relatively compact nature of this substituent allows the preparation of glassy polymers useful for lithographic applications. The preparation and characterization of select trimethylsilylmethyl substituted resists will be presented in addition to a study of their radiation chemistry and lithographic properties. 

The radiation chemistry of resist polymers is governed by two main processes, namely, backbone scission and cross-linking. Whether the polymer will act as a positive or negative resist resin under lithographic imaging depends on whether backbone scissioning or the cross-linking process is dominant. ... 

FIGURE 16.3 Normalized film thickness plotted against log (dose) to produce typical sensitivity curves for (a) a positive- and (b) a negative-acting polymer resist. 

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