Poly negative tone images

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 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. 

These results confirm the potential of poly (p-formyloxystyrene) as a useful resist material combining such interesting properties as ability to be imaged in both positive or negative tone, ease of preparation, and activity in the deep UV, with a moderate sensitivity and good contrast. 

Figure 7 shows photo-images obtained with the composite resist made of poly(2-methyl-l-pentene sulfone) and Varcum positive tone patterns are shown on the left, and negative tone patterns on the right. The resists films were spin-coated onto silicon wafers from an AZ-thinner solution of poly(2-methyl-l-pentene sulfone) (16.5 wt% in solid) and Varcum, and prebaked at 100°C for 20 min. The UV exposures were carried out with a medium pressure mercury lamp with a dose of 200 mJ/cm2 of 254 nm light it can be reduced to 100 mJ/cm2 for full development. 

Ito, C.G. Willson, and J.M.J. Frechet, New UV resists with negative orpositive tone, Digest of Technical Papers, 1982 SPE Symp. on VLSI Technology, p. 6 (1982) C.G. Willson, H. Ito, J.M.J. Frechet, T.G. Tessier, and F.M. Houlihan, Approaches toward the design of radiation sensitive poly meric imaging systems with improved sensitivity and resolution, J. Electrochem. Soc. 133, 181 (1986). 

---