Chemical amplification, concept

Synthesis of polyphthalaldehyde, PBOCST, and early contributions to the chemical amplification concept by Professor Jean Frechet of the University of Ottawa are gratefully acknowledged. The authors thank S. MacDonald, R. Kwong and R. Cox for preparation of various diazonium salts, and J. Carothers, D. Mathias, C. Hrusa, and C. Cole for assistance in TGA, GPC, and 13C NMR measurements. The iodonium and sulfonium salts used in the preliminary stages of this work were generously provided by V. Lee. 

Chemical amplification positive resists the chemical amplification concept... 

While the chemical amplification concept has served the semiconductor industry... 

Advanced photoresists, such as 193 and 248 nm photoresists, are based on chemical amplification concept [7,8]. These chemically amplified photoresists generally consist of a base polymer, a photo-sensitive compound called photoacid generator (PAG), and sometimes a cross-linking... 

Major advances in radiation sensitivity have been achieved by applying the concept of chemical amplification to photolithography [252-254]. Chemical amplification is related to a cascade of chemical reactions that are initiated by a single photon. In fact, strategies based on chemical amplification have played a key role in the development of novel resist systems, as will be outlined in the following subsection. It is to be noted, that the chemical amplification concept has served the semiconductor industry as a workhorse for the past few decades. 

Thus, these new copolymers form the basis of a new, deep UV, thermally stable photoresist. This resist combines the high Tg and thermal stability of the styrene-N-(p-hydroxyphenyl)maleimide copolymer and the sensitivity of the chemical amplification design concept. 

A new interesting concept to further increase the sensitivity of chemical amplification resists has been proposed primarily for 193 nm lithography. An acid amplifier in resist film, inert to radiation, produces a large number of acid molecules by its catalytic reaction with a photochemically generated acid (Fig. 10) [93,94]. In many cases only weak sulfonic acids such asp-toluenesul-fonic acid (tosic acid, TsOH) are generated by this mechanism and an aromatic structure incorporated into acid amplifiers to promote acid cleavage increases 193 nm absorption. 

This is the second chemical amplification resist invented for use in semiconductor lithography. Invented by Willson, Frechet, and Ito, the resist on exposure spontaneously and uncontrollably depol ymerizes in an exothermic reaction that is sufficiently energetic to evaporate the monomer. These inventors were unaware of a 3M Corporation patent on a similar concept, G.H. Smith and J.A. Bonham, Photosolubilizable compositions and elements, U.S. Patent No. 3779,778 (1973). 

An interesting variation on the hilayer resist concept is the chemical amplification of resist lines (CARL) process, developed at Siemens (see Fig. 17.8). In the CARL process, a top imaging layer resist formulated from an alternating polymer of maleic anhydride and an appropriate monomer, depending on the... 

The design concept of chemical amplification is based on generation of a chemically stable catalytic species (commonly referred to as a photoacid and designated as a proton H, as illustrated in Fig. 17.22 for a resist system comprising a copolymer—poly(4-hydroxystyrene-co-4-t-butyloxycarbonyloxystrene)—in... 

The idea of using chemical amplification for the measurement of RO2 was first proposed by Stedman. It utilises the chain reaction of HO2 with NO followed by OH with CO. This initial concept was found to be difficult to calibrate ([12] and references therein). A calibrated chemical amplifier system was developed in this laboratory for the first time [13]. This system detects ROx le. the sum of RO2, HO2, RO and OH) which participate effectively in the NO/CO chain reaction. As... 

The chemical amplification process concept has been extended to some of the high phenolic polymers described earlier. For example, high resolution thermally stable images were obtained in both a positive and negative mode for copolymers of N-(p-hydroxyphenyl)maleimide and styrene. 

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