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c 2.1, H20) (lit.3 [a]22D -86.9°(c 2.1, H20)).

a-(Trifluoromethyl)styrene (Q = 0.43, e = 0.90) does not undergo radical homopolymerization. Anionic polymerization fails to produce appreciable amounts of polymer even in bulk at -78 °C in spite of its high e value. The resistance to anionic polymerization is primarily due to side reactions involving addition-elimination sequences (Sn2') when initiators are nucleophilic enough to add to the 3-carbon of TFMST. Weaker anionic initiators such as pyridine and potassium terf-butoxide that effectively induce polymerization of methyl a-(trifluoromethyl)acrylate (Q = 0.74, e = 2.5) do not react with TFMST. Reactions of TFMST with several anionic initiators are described in detail.

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Palladium‐catalyzed coupling of acid chlorides with organotin reagents: Ethyl ( E )‐4‐(4‐nitrophenyl)‐4‐oxo‐2‐butenoate reactant: 70.7 g (0.22 mol) of tributyltin chloride intermediate: tributylethynylstannane reactant: 23.1 g (0.079 mol) of tributyltin hydride intermediate: (E)‐1,2‐bis(tributylstannyl)ethylene intermediate: ethyl (E)‐3‐(tributylstannyl)propenoate product: ethyl (E)‐4‐(4‐nitrophenyl)‐4‐oxo‐2‐butenoate byproduct: ethyl (Z)‐3‐(tributylstannyl)propenoate

Polyphthalaldehyde (PPA) inhibits dissolution of novolac resins in aqueous base very efficiently. When an onium salt cationic photoinitiator such as triarylsulfonium or diaryliodonium metal halides is added lo the polymer mixture, PPA is completely reverted to the starting monomer by reaction with radiochemically generated acid and removed from the exposed area upon postbake, thereby recovering the intrinsic base solubility of the novolac resin. PPA as a polymeric dissolution inhibitor used in conjunction with onium salts provides aqueous-base-developable, high-contrast, positive resist systems very sensitive to deep UV radiation (full development at 2 mJ/cm2). The system offers stable development processes due to the induction effect and high contrast.Polyphthalaldehyde (PPA) derivatives depolymerize completely to starting monomers by reaction with radiochemically generated acids to provide extremely sensitive self-developing (1, 2) and thermally developable (3, 4) resist systems. The high sensitivity is a result of two stages of chemical amplification--acid-catalyzed acetal bond cleavage and subsequent depolymerization. Sensitive positive resist materials based on efficient main chain scission tend to suffer from poor plasma resistance which precludes their use in a device fabrication. One approach to practical utilization of these sensitive materials is to incorporate silicon in PPA which renders the highly sensitive material resistant to oxygen plasma so that the thermally imaged Sicontaining PPA serves as an etch mask for pattern transfer in the bilayer scheme (4). A similar approach has been taken to provide electron-beam-sensitive poly(olefin sulfones) with some practical utility other than mask making by incorporating Si into the structure (5).Another approach toward the design of sensitive positive resist systems with high dry etch resistance has been to mix poly(olefin sulfones) with novolac resins, thereby combining the high radiation sensitivity of the polymeric dissolution inhibitor with the high dry etch resistance of the base-soluble matrix resin (6-8). This concept of utilizing a polymeric dissolution inhibitor instead of diazonaphthoquinone has allowed extension of attractive features of diazonaphthoquinone/novolac photoresists --namely, high dry etch resistance and aqueous base development to provide high resolution, to electron beam lithography.As the circuit density in microelectronic devices becomes higher and higher, an increasing interest in lithography technologies based on short wavelength exposures has arisen because the resolution is directly proportional to the exposing wavelength. However, the diazonaphthoquinone novolac resists do not perform adequately as a single-layer resist when exposed to deep UV radiation (9) and poly(olefin sulfones) are not sensitive to UV radiations above 200 nm, though it has been reported that the charge transfer complex between polysulfone and a novolac resin renders such composite resists sensitive to deep UV radiation (i0).We have found that PPA inhibit...

Poly(4-trimethylsilylphthalaldehyde) sensitized with triphenylsulfonium triflate develops to the substrate upon postbake. The sensitivity is very high owing to chemical amplification. The resist system does not self-develop during exposure but the development is achieved simply by heating the image-wise exposed resist. The thermally developed resist image serves as an oxygen RIE barrier for the pattern transfer in the bilayer resist scheme, providing a new positive-tone all dry process.

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