Photoresist composition for deep ultraviolet lithography

Abstract

The present invention relates to a photoresist composition comprising a photoacid generator and at least one novel polymer comprising at least one unit as described by structure 1, where, either (i) R1 is an aliphatic cyclic unit of a polymer, R2 is selected from H, F, (C1-C8)alkyl, (C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl, and (CR3R4)p(CO)OR5, and Rf is selected from F, H, (C1-C8)alkyl, or a fully or partially fluorinated alkyl, and cyclofluoroalkyl, or (ii) R1 and R2 combine to form an aliphatic cyclic unit of a polymer, and Rf is selected from F, H, (C1-C8)alkyl and a fully or partially fluorinated alkyl, and cyclofluoroalkyl, or (ii) R1 and Rf combine to form an aliphatic cyclic unit of a polymer, and R2 is selected from H, F, (C1-C8)alkyl, (C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl, and (CR3R4)p(CO)OR5; and, R3 and R4 are independently H, F, (C1-C8)alkyl, (C1-C8)fluoroalkyl, cycloalkyl, cyclofluoroalkyl, (CR3R4)p(CO)OR5, R3 and R4 may combine to form an alkylspirocyclic or a fluoroalkylspirocyclic group, X is selected from (C1-C8)alkylene, (C1-C8)fluoroalkylene, O(C1-C8)alkylene, O(C1-C8)fluoroalkylene, cycloalkyl and fluorinatedcycloalkyl, R5 is H or an acid labile group, m=0-1, and p=1-4. The invention also relates to a process for imaging the photoresist composition of the present invention.

Description

[0001] The present invention relates to a novel photoresist composition that is particularly useful in the field of microlithography, and especially useful for imaging positive patterns in the production of semiconductor devices. The photoresist resin composition comprises a polymer or a mixture of polymers in which fluoro-alcohol moieties on an aliphatic cyclic fluorinated polymer are fully or partially protected with an alkyloxycarbonylalkyl (AOCA) protecting group, a photoactive component, and optionally, a base additive. The resin of the novel photoresist has high transparency in the deep ultraviolet (uv) region, and such a composition is especially useful for exposure at 193 nanometers (nm) and 157 nm. The invention further relates to a process for imaging the novel photoresist.BACKGROUND OF INVENTION[0002] Photoresist compositions are used in microlithography processes for making miniaturized electronic components such as in the fabrication of computer chips and integrated cir...

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Benefits of technology

[0012] The inventors of this application have found that, surprisingly, aliphatic cyclic polymers can have their fluoroalcohol moieties easily functionalized with an alkyloxycarbonylalkyl(AOCA) group and that this group provides these types of resins with surprising advantages for photoresist applications.

[0015] The present inventors have found that when the AOCA group is used to protect fluoroalcohol moieties it is unexpectedly found to possess higher stability towards thermal cleavage than the t-BOC group or the MOM protecting group. Generally, from a photoresist standpoint, such an increase in thermal stability of the protected fluoroalcohol imparted by use of AOCA, particularly the BOCME group, is desirable as it increases thermal processing latitude and shelf life. Also, from a synthetic standpoint, such a increase in thermal stability is desirable as it helps to increase the yield of protected fluoroalcohol polymers, whether they are made by protection of pre-formed fluoroalcohol polymers or through polymerization of monomers containing a fluoroalcohol bearing polymer protected by AOCA groups. Surprisingly, despite its high thermal stability, the BOCME protecting group, in particular, can be easily removed by photoreleased acid in the exposed resist areas, requiring standard post-exposure bake temperatures to affect cleavage (1100 C-130.degree. C.). It has also been found by the applicants that the functionalization of perfluoroalcohols with AOCA groups results in higher contrast photoresist systems than using tert-butyl carboxylates of photoresist resins containing norbornene-5-carboxylic acid repeat units.

Problems solved by technology

U.S. Pat. No. 5,843,624 discloses polymers for photoresist that are obtained by free radical polymerization of maleic anhydride and unsaturated cyclic monomers, but the presence of maleic anhydride makes these polymers insufficiently transparent at 157 nm.

These materials give acceptable absorbance at 157 nm, but due to their lower alicyclic content as compared to the fluoro-norbornene polymer, have lower plasma etch resistance.

However, an important limitation to any of these approaches is the availability of a suitable protecting group for fluoroalcohols.

These protecting groups on the perfluoroalcohol moiety are relatively unstable and often undergo partial or complete deprotection during polymerization.

The difficulty in protecting the fluoroalcohol functionality, and the resultant loss of the unexposed photoresist film, has meant that the acid labile functionality can often only be attached to either a methacrylate, acrylate, or norbornenecarboxylic acid repeat unit (which are deleterious to transparency at 157 nm) or to a dissolution inhibitor additive (WO 00 / 67072, WO 00 / 17712 Hoang V. Tran et al Macromolecules 35, 6539, 2002).

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