Resists chemical amplification

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.

Various PAGs have been synthesized specifically for use in chemical amplification resists, reflecting their important impact on lithographic performance (Fig. 7) [13,30]. The choice of PAG depends on a number of factors such as the nature of radiation, quantum efficiency of acid generation, solubility, miscibility with resin, thermal and hydrolytic stability, plasticization effect, toxicity, strength and size of generated acid, impact on dissolution rates, cost, etc. In... 

Photochemically generated acid must diffuse in resist film to catalyze desired reactions and to provide a gain mechanism for amplification. However, excessive diffusion (into the unexposed areas) destroys the linewidth control and eventually the resolution. Thus, as the minimum feature size becomes smaller and smaller, the control of acid diffusion plays a more important and difficult role. Therefore, investigation of acid diffusion in chemical amplification resist film is one of the most active areas of research today. A number of experimental procedures to measure acid diffusion length have been reported [67-88] ... 

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. 

Acetals and ketals have attracted a great deal of attention recently as protecting groups of PHOST due to their lower activation energies of deprotection than fBOC and terf-butyl esters. While the majority of chemical amplification resists require PEB to accelerate acid-catalyzed reactions, deprotection of ac-... 

PHOST is the resin for deep UV lithography as much as novolac resins are for near UV lithography. All the advanced 248 nm chemical amplification resists, both positive and negative, are built on this structure at least in part. PHOST provides aqueous base developability, which is mandatory in today s semiconductor manufacturing, dry etch resistance, and high deep UV transmission. Because of its very important and unique role in chemical amplification resists and also in order to facilitate better understanding of the subsequent sections, this phenolic polymer is separately described. 

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