Lithography chemical amplification

The advantage of this approach is not only the free choice of surface stractures which can be created, the material contrast which can be realized by the combination of chemical lithography and amplification with SIP, but also the potential to bridge the gap in structural feature sizes ranging from the microscopic to the nano-scopic scale. Since the feature sizes reported are still limited to the features of the mask used, direct writing with a focused e-beam should result in patterned polymer brushes of features matching the size of the immobilized macromolecule. 

Note 2 The term chemical amplification is commonly used in photoresist lithography employing a photo-acid generator or photo-base generator. 

Chemical amplification type positive resist compositions provided in Table 1 were prepared by Takemoto [4] and were suitable for excimer laser lithography using ArF and KrF lasers. 

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. 

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. 

The very first chemical amplification resist designed for use in bilayer lithography employed Si-containing polyphthalaldehyde as a top layer resin,... 

The above-mentioned linewidth information is generally obtained by using a non-destructive top-down SEM. However, since the three-dimensional profile is what counts in lithography, cross-sectional SEM can provide the most important information. Chemical amplification resists tend to exhibit a foot in the case of positive systems and notching in negative systems when imaged on nitride substrates such as silicon nitride and titanium nitride, which can be examined only by cross-sectional SEM. 

Fig. 178 Scanning electron micrographs of sub-100 nm features printed in chemical amplification resists 60 nm line/space patterns by phase shifting 157 nm lithography [511], 70 nm line/space patterns by X-ray lithography [513], and 70 nm line/space patterns by EUV lithography [514]...

CHEMICAL AMPLIFICATION COATINGS/ TOPCOATS IMPRINT LITHOGRAPHY ... 

With F2 excimer laser lithography at 157 nm, even polymers based on aerylates and norbonenes are too opaque to be of any useful value in resist appheations. Therefore, fluorocarbons and silanol polymers are the two main classes of polymers that have reasonable transparency at this wavelength. Again, like their 193-nm and 248-nm counterparts, the 157-nm resists employ chemical amplification in their imaging mechanism, for quite similar reasons. 

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). 

The postexposure-based techniques are grouped into three broad categories, namely, reflow-based. shrink techniques, chemical-based shrink techniques, and plasma-assisted shrink techniques. The reflow-based shrink techniques comprise thermally induced reflow and electron-beam heating-induced reflow of patterned resist features. The chemical-based shrink techniques comprise those techniques that either increase or decrease the sidewall thickness of already patterned resist features, thus effectively altering their critical dimension. Examples of chemical-based shrink techniques that result in an increase in the sidewall of the patterned features include techniques based on RELACS (resolution enhancement of lithography assisted by chemical shrink) and CARL (chemical amplification of resist lines).Examples of chemical-base shrink techniques that result in decrease... 

S. Birkle, Chemical amplification of resist lines a novel sub half micron bilayer resist technique for NUV and deep UV lithography, Proc. SPIE 1262, 528 (1990) M. Sebald, H. Berthold, M. Beyer, R. Leuschner, Ch. Ndlscher, U. Scheler, R. Sezi, H. Ahne, and S. Birkel, Application aspects of the Si CARL bilayer process, Proc. SPIE 1466, 227 237 (1991) R. Leuschner, M. Beyer, H. Bomdorfer, E. Kiihn, Ch. Nolscher, M. Sebald, and R. Sezi, CARL resist A technology for optical quarter micron resolution and below, in Proc. SPE Reg. Tech. Conf. Photopolym., Ellenville, NY, pp. 215 224(1991). 

Table 9.5 Chemical amplification resists applicable in 193 nm lithography...

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