Photoinduced acid

Figure 4.28. Molecular structures and photoinduced reactions of common photoresists. Shown (top) is the positive tone resist containing the active diazonapthoquinone (DNQ) chromophore group. Chemical amplification (CAM) reactions are illustrated in (i)-(iii). Reaction (i) represents photoinduced acid generation step (ii) is an acid-catalyzed deprotection mechanism (positive tone resist) and step (iii) is an acid-catalyzed crosslinking mechanism (negative tone resist).

Figure 3.79. Protonation of 43e2 caused by irradiation of triarylsulfonium hexafluor-oantimonate as photoinduced acid generator [118].

Figure 3.80. Two-photon induced dual-channel fluorescence image formation within a photosensitive polymer film containing 43e2 and triarylsulfonium hexafluoroantimonate as photoinduced acid generator. (From Ref. [118] with permission of the American Chemical Society.)...

Scheme 7.32 Photoinduced acid-catalyzed deprotection, followed by base-catalyzed deacetylation during development.

One of the most important ester-protected polyhydroxystyrene-based resist copolymers, ESCAP (environmentally stable chemically amplified photoresist), developed at IBM, is based on the random copolymerization of 4-hydroxystyrene with tert-butyl acrylate (XXX).On exposure, this resist copolymer is converted to a copolymer of 4-hydroxystyrene with acrylic acid through photoinduced acid-catalyzed deprotection of the tert-butyl group (see Scheme 7.34). Because this resist system can be annealed at temperatures near its Tg in a process that hlls up the free volumes (voids in the resist matrix), thus preventing the out-diffusion of photoacids from the matrix and in-diffusion of airborne bases into the resist, neutralization reactions between the photoacids and bases in the resist matrix (otherwise known as poisoning) are reduced, thus allowing... 

The deprotection kinetics of alicyclic polymer resist systems designed for 193 nm lithography was examined using JR and fluorescence spectroscopic techniques. A kinetic model was developed that simulates the deprotection of the resists fairly well. A new, simple, and reliable method for monitoring photoinduced acid generation in polymer films and in solutions of the kind used in 193 nm and deep-UV lithography was developed. This technique could find application in the study of diffusional processes in thin polymer films. 

Figure 7 shows the effect of acid generating unit fraction on the polysiloxane formation rate. The polysiloxane formation rate decreased in the order 2c > 2b > 2a, if the photolysis degrees of the NIS units in the polymers were same (4.5 mol%). The higher the concentration of the photoinduced acids at the surface, the larger the polysiloxane formation rate. 

In this paper, we report the syndiesis and characterization of photocrosslinkable polymers bearing thermally degradable property 10, 11). The concept of the present system is shown in Figure 1. On irradiation network formation takes place by the photoinduced-acid catalyzed reactions of the crosslinkable moieties. A thermal treatment of the crosslinked polymers induces the cleavage of the network linkages. Based on this concept, we have... 

Polymer films containing the photoacid generator FITS were irradiated at 254 nm and insoluble fraction in THF was studied. FITS was photolyzed to generate p-toluenesulfonic acid. The photoinduced-acid initiated cationic polymerization of epoxy units in the side chain to generate networks (Figure 4). Insoluble fractions for the polymers were 60-90%, except for... 

Figwre Photoinduced-acid catalyzed crosslinking and thermal degradation... 

We have synthesized a novel methacrylate monomer (MOBH) which has an epoxy moiety and a tertiary ester linkage in a molecule. Homopolymer of MOBH and copolymers of MOBH with tert-butyl methacrylate, tert-butoxystyrene, cyclohexyl styrenesulfonate, neopentyl styrenesulfonste or phenyl styrenesulfonate were obtained by the conventional radical photopolymerization. Polymer films containing photoacid generators (PAG) became insoluble in tetrahydrofuran on UV irradiation because of the photoinduced-acid catalyzed crosslinking reaction of epoxy units. 

Novel Anafytic Method of Photoinduced Acid Generation and Evidence of Photosensitization via Matrix Resin... 

Figure 6. Time profiles of photoinduced acid generation of TBI with and without PHS matrix...

There was no HBr production from the PMMA film containing TBI and HMM. HMM did not hinder the photoinduced acid generation. 

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