Deep-UV resist system

Copolymer Approach to Design of Sensitive Deep-UV Resist Systems with High Thermal Stability and Dry Etch Resistance... 

In this paper, we report an alternative approach to the design of deep UV resist systems combining the desired properties, which involves copolymerization of methacrylic ester with styrenic comonomer and the use of the acid-catalyzed deprotection chemistry. 

ITOETAL. Copolymer Approach to Design of Deep- UV Resist Systems... 

H. Ito and E. Flores, Evaluation of onium salt cationic photoinitiators as novel dissolution inhibitor for novolac resin, J. Electrochem. Soc. 135,2322 (1988) H. Ito, Aqueous base developable deep UV resist systems based on novel monomeric and polymeric dissolution inhibitors, Proc. SPIE 920, 33 (1988). T. Aral, T. Sakamizu, K. Katoh, M. Hashimoto, and H. Shiraishi, A sensitive positive resist for 0.1 p,m electron beam direct writing hthography, J. Photopolym. Sci. Technol. 10, 625 (1997). 

S.A.M. Hesp, N. Hayashi, andT. Ueno, Tetrahydropyranyl and furanyl protectedpolyhydroxystyr ene in chemical amphfication systems, J. Appl. Polym. Sci. 42, 877 (1991) N. Hayashi, L. Schlegel, T. Ueno, H. Shiraishi, and T. Iwayanagj, Polyvinylphenols protected with tetrahydropyranyl group in chemical amplification positive deep UV resist systems, Proc. SPIE 1466, 377 (1991). 

Deep-UV resists comprised of matrix polymers and a 2,6-dinitrobenzyl tosylate photoactive acid generator have been described and compared to previously reported onium salt systems. Although these resists exhibited lower sensitivity than onium salt-based materials, the contrast and processibility are superior. The use of a matrix polymer capable of radiation-induced chain scission improves the sensitivity and allows the 2,6-dinitrobenzyl tosylate acid generator to more nearly... 

As for negative deep UV resist, O Toole et al. have exhibited half-micron pattern resolution in 0.5 micron film thickness using the new resist and PIE process (10). The pattern profiles, however, were re-entrant, due to the large photo absorption and the applications to single-layer-resist system have not been presented (11). 

Figure 15. Uncapped resist image obtained with a two-layer deep-UV PCM system. The 0.85-um wide PMMA lines were 1.9-fim thick separated by 2.4 ixm. A 0.2-um AZ1350J PCM was used.

Figure 16. Capped resist image obtained with an identical two-layer deep-UV PCM system as in Figure 13. The AZ layer was 0.3-fim thick on...

Various materials have been examined for use as deep UV resists poly(methyl methacrylate) (PMMA) (1), poly(methyl isopropenyl ketone) (PMIPK) fS.7L and the novolak-Meldrum s acid solution inhibition system (S). Each however has a problem related to sensitivity and/or resolution. While PMMA is insensitive to light of X > 230 nm because of its weak absorption, its high resolution properties make it an attractive starting point for the design of a resist that will perform well in the 230-280 region. The photochemical properties of PMMA could be modified by the incorporation of a small percentage of photolabile groups so as to have both the desired sensitivity and base polymer properties. 

These vinyl systems were chosen also because they function as high-resolution electron beam resists and deep UV resists at X<300 nm. 

A copolymer approach can provide more flexibility to the resist design because all the necessary functions do not have to reside on one component. Today s advanced positive deep UV resists are exclusively based on this concept with 4-hydroxystyrene as one component. However, early copolymer systems and some of the 193-nm resists consisted of lipophilic components only. Incorporation of 4-acetoxystyrene to poly(4- er -butoxycarbonyloxystyrene sulfone) has already been mentioned. This section deals with copolymer resists composed of lipophilic comonomers first and then the currently dominant hydroxystyrene copolymers. Co- and terpolymers for ArF excimer laser lithography will be described in a separate section. 

A chemically amplified deep UV photoresist system based on acetal chemistiy is reported. Acetal-protected pol vinylphenols) were prepared either by free radical polymerization of the monomers or chemical modification of poly(vinylphenol). In the presence of an add as a catalyst, the polymers thermally decomposed to aqueous base soluble po vinylphenol) and some small molecules. Therefore, the resists were formulated with the acetal-protected polymers and a photoadd generator such as triphei lsulfonium hex-afluoroantimonate. Positive-tone image could be resolved 1 exposing the resist film in deep UV region, post-baking, and developing in tetramethylam-monium hydroxide solutions. 

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