Amplification, chemical

Dry-Film Resists Based on Radical Photopolymerization. Photoinitiated polymerization (PIP) is widely practiced ia bulk systems, but special measures must be taken to apply the chemistry ia Hthographic appHcations. The attractive aspect of PIP is that each initiator species produced by photolysis launches a cascade of chemical events, effectively forming multiple chemical bonds for each photon absorbed. The gain that results constitutes a form of "chemical amplification" analogous to that observed ia silver hahde photography, and illustrates a path for achieving very high photosensitivities. 

One potential approach extends the idea of chemical amplification introduced in our preceding description of dry-film resists. In 1982, Ito and co-workers (37,38) recognized that if a photosensitizer producing an acidic product is photolyzed in a polymer matrix containing acid-labile groups, the acid will serve as a spatially localized catalyst for the formation or cleavage of chemical bonds. 

Stimulation of glycogen breakdown involves consumption of molecules of ATP at three different steps in the hormone-sensitive adenylyl cyclase cascade (Figure 15.19). Note that the cascade mechanism is a means of chemical amplification, because the binding of just a few molecules of epinephrine or glucagon results in the synthesis of many molecules of cyclic / MP, which, through the action of c/ MP-dependent protein kinase, can activate many more molecules of phosphorylase kinase and even more molecules of phosphorylase. For example, an extracellular level of 10 to 10 M epinephrine prompts the for-... 

While investigating the potential for an instrument to measure atmospheric dimethyl sulfide (DMS) [69], discussed below, Hills et al. investigated the possibility of adding H2 to the reaction cell to provide chemical amplification of the chemiluminescence signal via the catalytic chain reaction ... 

Three component, aqueous-base developable, positive-tone resists utilizing the chemical amplification principle have also recently been reported (81,82). In these systems, irradiation of a phenolic resin/inhibitor/acid generator resist generates an acid which upon mild heating, catalyzes either depolymerization or deblocking of a... 

Nonswelling Negative Resists Incorporating Chemical Amplification... 

A number of new resist materials which provide very high sensitivities have been developed in recent years [1-3]. In general, these systems owe their high sensitivity to the achievement of chemical amplification, a process which ensures that each photoevent is used in a multiplicative fashion to generate a cascade of successive reactions. Examples of such systems include the electron-beam induced [4] ringopening polymerization of oxacyclobutanes, the acid-catalyzed thermolysis of polymer side-chains [5-6] or the acid-catalyzed thermolytic fragmentation of polymer main-chains [7], Other important examples of the chemical amplification process are found in resist systems based on the free-radical photocrosslinking of acrylated polyols [8]. 

The seminal work on deep-UV resist materials which incorporate chemical amplification was started at IBM San Jose s Research Laboratory in 1979 when FrSchet and Willson first prepared poly(4-t-butyloxycarbonyloxy styrene) and end-capped copolymers of o-phthalaldehyde and 3-nitro-l,2-phthalic dicarboxaldehyde. 

Protons are regenerated with each addition Process incorporates chemical amplification... 

This basic approach to chemical amplification was subsequently extended by Ito et al. [3] through resist formulations incorporating appropriately chosen triaryl sulfonium or diaryliodonium salt. For example, end-capped poly(phthalaldehyde) used in combination with an onium salt photoacid generator is an excellent self-... 

A significant part of our recent work with imaging systems which incorporate chemical amplification has involved the design of polymers which can undergo thermally activated multiple main-chain cleavages as the result of a phototriggered process. 

In this paper we report on the use of trifluoro-methanesulfonates (Table 1) of 4-N, N-dimethylamino-benzenediazonium (Dl) and 4-methoxybenzene-diazonium (D2) as CEL dyes, negative working sensitizers, and photoacid generators for chemical amplification resist systems(11). 

Figure 12 Schematic representation of chemical amplification resist chemistry.

S. Uchiyama, H. Shimizu, and Y. Hasebe, Chemical amplification of uric acid sensor responses by dithiothreitol. Anal. Chem., 66, 1873-1876 (1994). 

The latest addition to this list of dry developing resist materials is a contribution from IBM s San Jose Research Laboratory (66-67) that evolved from efforts to design positive-tone resist materials that incorporate chemical amplification. These efforts were stimulated by the fact that the quantum yield of typical diazoquinones of the sort used in the formulation of positive photoresists is 0.2 to 0.3 thus, three or four photons are required to transform a single molecule of sensitizer. This places a fundamental limit on the photo-sensitivity of such systems. 

In order to circumvent this sensitivity limitation, the San Jose researchers sought to design resist materials that incorporate chemical amplification of the sort that characterizes the silver halide photographic emulsion system. In these systems a single photo event initiates a cascade of subsequent chemical reactions that ultimately result in the intended function. 

Ito, H. Willson, G., "Chemical Amplification in the Design of Dry Developing Resist Materials," SPE Regional Technical Conference, Ellenville, New York, Nov. 1982. 

Frechet, J. M. J. Ito, H. Willson, C. G. "Sensitive Deep UV Resist Incorporating Chemical Amplification," International Conference on Microlithography, Grenoble, France, Oct. 1982. 

Zhan, Z.-Y. J. Lynn, D. G. Chemical amplification through template-directed synthesis. J. Am. Chem. Soc. 1997,119,12420-12421. 

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