Phenylacetates and their use in radiation sensitive compositions

#The present invention relates to novel phenylacetates, to compositions containing said compounds, to a process for the formation of images which comprises the use of these esters and to the use of said esters as dissolution inhibitors and of said compositions as positive resists.

#For the preparation of aqueous developable photoresists it is known to mix a film-forming resin which is soluble in aqueous or aqueous-alkaline solutions with a dissolution inhibitor that greatly reduces the solubility of the mixture in an aqueous-alkaline developer. A photochemical reaction causes the dissolution inhibitor to undergo change such that, for example by the depolymerisation, acetal cleavage, orthoester cleavage or formation of a carboxylic acid from an o-quinonediazide, the photoresist is again readily soluble at the exposed areas in the developer.

#Known dissolution inhibitors for positive photoresists are typically 1,2-naphthoquinonediazides (q.v. J. Kosar in "Light-Sensitive Systems", John Wiley & Sons, New York 1965, pages 339-352) in novolak resins. 1,2-Naphthoquinonediazides are photoactive and act at unexposed areas of the photoresist as dissolution inhibitors. However, they absorb very strongly in the DUV range (DUV: deep ultra-violet; range from 200 to 300 nm) and thus find only very limited utility in DUV lithography.

#2.5 g of the dissolution inhibitor of Example B, 7.5 g of Resin M.RTM. P4HS [poly(4-hydroxystyrene) obtained from Maruzen Oil Comp., Japan] and 0.5 g of triphenylsulfonium trifluoromethanesulfonate are dissolved in 25 ml of cyclopentanone. This solution is filtered through a 0.5 .mu.m filter and applied to a silicon wafer having a diameter of 76.2 mm. A homogeneous film is produced on the silicon wafer by spin coating at 3000 rpm. After drying for 60 seconds at 90.degree. C. on a hot plate the film has a thickness of 0.9 .mu.m. A mask is placed on the resist film by vacuum contact. The resist is then exposed through a narrow band filter with light of 254 nm wavelength. The exposure energy is 5 mJ/cm.sup.2. The resist film is heated for 60 seconds at 80.degree. C. on a hot plate and thereafter developed for 120 seconds in MF 312 [aqueous solution of tetramethylammonium hydroxide obtained from Shipley] diluted with 3 parts of water, whereupon the exposed zones dissolve in the developer (positive resist), giving 0.75 .mu.m lines with an almost vertical wall profile.

#1 g of the dissolution inhibitor of Example C, 7.5 g of Resin M.RTM. P4HS and 0.1 g of triphenylsulfonium trifluoromethanesulfonate are dissolved in 20 ml of cyclopentanone. The solution is coated on to a silicon wafer as described in Example 1 to give a 1 .mu.m film. This film is exposed through a mask with light of 254 nm wavelength at an exposure energy of 4 mJ/cm.sup.2 and then heated for 60 seconds at 90.degree. C. The latent images so obtained are developed for 140 seconds in MF 312 diluted with 4 parts of water. Submicron structures of marked resolution with high edge steepness are obtained.

#2 g of the dissolution inhibitor of Example F, 6 g of Resin M.RTM. P4HS and 0.2 g of triphenylsulfoniumtrifluoromethanesulfonate are dissolved in 15 ml of cyclopentanone. The solution is coated on to a silicon wafer as described in Example 1 to give a 0.9 .mu.m film. This film is exposed through a mask with light of 254 nm wavelength at an exposure energy of 7 mJ/cm.sup.2 and then heated for 60 seconds at 90.degree. C. The latent images so obtained are developed for 140 seconds in MF 312 diluted with 4 parts of water. Submicron structures of marked resolution with high edge steepness are obtained.