Negative tone image

Figure 3. Negative tone image made from poly-MAGME. Contact ptinted at 254 nm, using catalyst III. The SEM shows 2 y lines and 4 y spaces.

The developed resist patterns were heated at 200°C for 1 hour in a convection oven. Scanning electron microscopy shows no thermal deformation in the negative tone images (Figure 10). The positive tone images lost thickness consistent with thermolysis of the t-BOC side chain but also do not show evidence of thermal flow deformation. 

Figure 10. Scanning electron micrographs of negative tone images before (left) and after (right) heating in air at 200 C. for 30 min.

The SEMs shown in Figure 3.29 were made from a single wafer of poly( p-formyloxystyrene) that had been exposed on a Perkin-Elmer M500 scanner in the UV-2 mode and then broken in half One half was developed in a polar solvent to generate a positive-tone image, whereas the other was developed in a nonpolar solvent to produce a negative-tone image. 

Figure 7. Deep UV polymer patterns obtained with a matrix resist of poly(2-methyl-l-pentene sulfone) and Varcum resin positive tone images on the left and negative tone images on the right.

Poly[4-(2-hydroxy-2-propyl)styrene] undergoes acid-catalyzed dehydration to yield a stable tertiary benzylic carbocation, which then eliminates a p-pro-ton to form a pendant olefinic structure (Fig. 119) [353]. This intramolecular dehydration reaction converts the hydrophilic alcohol to a highly lipophilic olefin and allows negative tone imaging with a polar alcohol as a developer. 

Commercially available water soluble copolymers of maleic anhydride with ethylene and methyl vinyl ether (presumably partially hydrolyzed to vicinal carboxylic acids) and triphenylsulfonium triflate were dissolved in water as a casting solvent. Spin-cast films were baked at 130 °C for 10 s, exposed to 254 nm radiation, and postexposure-baked at 130 °C for 40 s. Development with pure water provided negative tone images, presumably due to acid-catalyzed dehydration between vicinal carboxylic acids to form less polar anhydride, as was demonstrated for polarity reversal (4.3.1). However, a copolymer of maleic acid with methyl vinyl ether failed to provide any negative images,... 

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