Poly-4-vinylphenol resistance

Ito and coworkers (86-87) recently described a new DUV resist system that has high sensitivity, does not suffer swelling during development, and may be used either as a positive or negative system. The new resist is based on a formulation consisting of t-butyloxycarbonyl (t-BOC) protected poly(vinylphenol) 88 (Figure 50) and an onium salt sensitizer. Exposure... 

Some data deal with the stabilizing efficiency of polymers and copolymers bearing a stabilizing functionality. Three isomeric poly(vinylphenols) provided a better resistance to oxidation than the corresponding monomers (the o-hydroxy isomer provided the best protection). All tested poly(vinylphenols) were however slightly inferior to 2,6-di-rerr-butyl-4-methylphenol [330]. The presence of the... 

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. 

The "Mannich" adduct synthesized from the condensation of formaldehyde, 2-(methylamino)ethanol and poly-4-vinylphenol as shown in Structure I, has been evaluated as a function of molecular weight versus corrosion resistance as measured by salt spray and humidity tests on Bonderite 1000, an iron phosphate conversion coating. The molecular weight of the polymer was varied from approximately = 2,900 to 60,000. The corrosion resistance results were essentially equivalent over the molecular weight range evaluated. 

On zinc phosphate conversion coatings, the "Mannich" derivatives of poly-4-vinylphenol have demonstrated performance equivalent to chromic chromate systems in salt spray, humidity, and physical testing. In addition. Table III illustrates results observed with automotive body paint systems evaluated by the "scab" or "cycle" test which causes failure more typical of actual end use conditions than do salt spray evaluations. Again, results equivalent to chromic-chromate post-treatments were obtained. In addition, the humidity resistance and adhesion tests were essentially equivalent to the chromium controls. 

A modification of these systems involving replacement of poly (4-vinylphenol) with poly(methyl isopropenyl ketone) (PMIPK) was reported by Nakane and co-workers (41). Although PMIPK is a positive-acting singlecomponent resist in the deep UV, it functions as a negative resist when mixed with an aromatic bisazide such as 2,6 di(4-azidobenzylidene)-4-... 

A novel, nonswelling DUV resist was developed by Iwayanagi et al. (77). This resist, known as MRS (micro resist for shorter wavelengths), consists of poly(p-vinylphenol) (structure 3.11), an alkaline-soluble phenolic resin, and an azide (structure 3.10). 

The decrease in solubility upon exposure in this type of resist was first ascribed to the formation of a secondary amine generated from nitrene insertion into C-H bonds of the polymer (see Scheme 3.6) (88). However, gel permeation chromatographic analyses revealed that the molecular weight of poly(p-vinylphenol) increased upon irradiation in the presence of the azide. Hydrogen abstraction from the polymer by nitrene and subsequent polymer... 

Another example is thermally depolymerizable polycarbonates that are sensitized with onium salt cationic photoinitiators (139). As discussed previously (Section 3.2.3), one of the positive-negative resists based on polystyrene with pendant tertiary butyl carbonate protecting groups undergoes acid-catalyzed thermolysis to generate poly( p-vinylphenol), carbon dioxide, and isobutene. Therefore, if the tertiary butyl carbonate moiety is incorporated in the polymer backbone as a repeating unit, such polymers will... 

Wijdenes and Geomini (170) examined the effects of the phenolic resin composition, its molecular weight distribution, solvent composition, and prebake temperature on the interfacial layer formation. They found that combined use of poly(p-vinylphenol) (structure 3.10) as matrix resin and cyclohexanone as the casting solvent in the diazoquinone resist formulation minimizes mixing of the two layers and yields a capped PCM structure without any plasma treatment. 

DUV exposure of poly( p-substituted styrenes), such as poly( p-chloro-styrene), poly( p-chloromethylstyrene), and poly( p-hydroxystyrene) [poly(p-vinylphenol)] (structure 3.11), in air leads to photocross-linking and photooxidation. Consequently, DUV hardening is applicable to resists based on these polymers as well as novolac-based resists (168, 169). 

A negative deep-UV resist composed of poly( p-vinylphenol) and a bisazide has been developed (5). A limitation has been that a high percentage of bisazide (20 wt%) to resin is required such that a resist film of 1 jam thickness is virtually opaque in the 200-300 nm region. Consequently, undercut profiles are typically observed after development and the processing conditions have to be carefully controlled to maintain line-width and reproducibility (2). Other negative resists such as novolac resin with a bisazide (15-20 wt%) (9), an acidic resin with a bisazide (30 wt%) 10) and poly(methyl methacrylate) with a bisazide (20-25 wt%) 11) also suffer because of the poor cross-linking efficiency of the bisazide. 

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