Chemically amplified resist process

Recently, nonionic acid precursors based on nitrobenzyl ester photochemistry have been developed for chemically amplified resist processes (78-80). These ester based materials (Figure 8) exhibit a number of advantages over the onium salt systems. Specifically, the esters are easily synthesized, are soluble in a variety organic solvents, are nonionic in character, and contain no potential device contaminants such as arsenic or antimony. In addition, their absorption characteristics are well suited for deep-UV exposure. 

Advanced Chemically Amplified Resist Process Using Non-Ammonia Generating Adhesion Promoter... 

We developed a non-ammonia generating adhesion promoter, isopropenoj trimethylsilane (IPTMS), in place of HMDS and its application to chemically amplified resist process was successful (4). However, the adhesion capability of the promoter has been an issue. The short treatment time of adhesion promoter in a gas phase is stron y necessary for actual device production in terms of throughput. 

Figure 1. Schematic representation of a generalized chemically amplified resist process.

A typical chemically amplified resist process involves conversion of the PAG molecule to a strong add upon absorption of a photon and the rate of this reaction is fast, with the extent of reaction being governed by the quantum effidenty of the particular add generator and exposure energy. The add effects the desired reaction with a characteristic rate, which is a function of the add concentration, the temperature and the diffusion rate of the add in the polymer matrix (84-86). The diffusion rate in turn, depends on the add structure, the... 

The chemically amplified resists reported here for deep-UV applications require a post-exposure thermal treatment process step to effect the deprotection reaction. This step has proven to be critical, and in order to understand the processing considerations it is instructive to discuss, qualitatively, the various primary and secondary reactions that occur with these systems during both exposure and PEB, ie ... 

The process control of the post-exposure bake that is required for chemically amplified resist systems deserves special attention. Several considerations are apparent from the previous fundamental discussion. In addition for the need to understand the chemical reactions and kinetics of each step, it is important to account for the diffusion of the acid. Not only is the reaction rate of the acid-induced deprotection controlled by temperature but so is the diffusion distance and rate of diffusion of acid. An understanding of the chemistry and chemical kinetics leads one to predict that several process parameters associated with the PEB will need to be optimized if these materials are to be used in a submicron lithographic process. Specific important process parameters include ... 

Both the DESIRE and DTSI processes might be good decisions for modern technology, but closely related with either DNQ/novolac or chemically amplified resists. The limited choice of materials to be used as the photoresist component and skin formation is the main drawbacks of the DTSI technology. The problems arisen could be party solved by the TFI approach realization in the form of the selective surface graft-polymerization. 

The industry roadmap specifies the need for chemically amplified resists that provide lithographic performance suitable to sustain their extension to 20 nm dimensional regime [522]. The ultimate resolution of 0.3 nm has been demonstrated by moving atoms at will with a scanning tunneling microscope [523] but the process is too slow to be economically feasible (one atom/min or... 

T. Kozawa and S. Tagawa, Basic aspects of acid generation processes in chemically amplified resists for electron beam hthography, Proc. SPIE 5753, 361 367 (2005) T. Kozawa and... 

T. Iwamoto, M. Akita, T. Kozawa, Y. Yamamoto, D. Werst, D.A. Trifunac, and D. Alexander, Radi ation and photochemistry of onium salts acid generators in chemically amplified resists, Proc. SPIE 3999, 204 213 (2000) A. Nakano, K. Okamoto, Y. Yamamoto, T. Kozawa, S. Tagawa, T. Kai, H. Nemoto, and T. Shimokawa, Deprotonation mechanism of poly(4 hydroxystyrene) and its deriva tives, Proc. SPIE 5753, 1034 1039 (2005) T. Kozawa, A. Saeki, and S. Tagawa, Modeling and simulation of chemically amplified electron beam, x ray, and EUV resist processes, J. Vac. Sci. Technol. B 22(6), 3522 3524 (2004) T. Kozawa, A. Saeki, A. Nakano, Y. Yoshida, and S. Tagawa, Relation between spatial resolution and reaction mechanism of chemically amplified resists for electron beam hthography, J. Vac. Sci. Technol. B 21(6), 3149 3152 (2003). 

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