Novolac cresol/phenol

A cresol novolac resin has been synthesized which exhibits a much greater dissolution-inhibiting effect than in various commercially available novolac or phenolic resins. Using this resin, a positive electron beam resist was prepared and its exposure characteristics were examined. A tetramethylammonium hydroxide aqueous solution was used as the developer. The sensitivity reaches 3xl0 6 C/cm2 without post-exposure baking. It was found that the sensitivity to double exposure was much higher than that to single exposure with the same total dose. A similar phenomenon was also... 

Phenol and cresol epoxy novolacs Cresol epoxy novolacs [37382-79-9]... 

There are many types of epoxide resin the Atlas for the Coating Industry, produced by the Federation of Societies for Coating Technology, cites 47 IR spectra of different resins [77]. Some typical example structures are provided below for Novolac-type phenol (and Novolac-type o-cresol) epoxides, aromatic glycidyl ester-type epoxides, alicyclic epoxides (18-4), and polyalcohol glycidyl epoxides (polyglycol and polyol based). The IR spectra of some epoxides are show in Fig. 54. 

Figure 8 Chemical formulae of phenolic resins used to prepare epoxy-phenolic adhesives based on Gunei Kagaku phenol novolac 61, Dow Chemical OCN ortho-cxQsoX novolac 62, Mitsui Toatsu para-xylene-modified phenol novolac 63, phenolic ortho-ortho-vtsoX of para-cresol 64, and poly (para-hydroxy styrene) 65.

This class of compounds is one of the most important adhesive groups with applications ranging from consumer to aerospace markets. Epoxies are thermosets and are cross-linked during the cure cycle. The chemical stmcmre for a simple epoxy (ethylene oxide) in its unhardened state is shown in Figure 5.2. All epoxy compounds contain two or more of these groups. Epoxy resins form adducts with vinyl, acrylic, and polyester resins producing compounds such as phenol novolac, cresol novolac, bis-[4(2,3-epoxy propyoxy) phenyl] methane, and phenol hydrocarbon novalac [53]. 

Epoxy novolac resins are produced by glycidation of the low-molecular-weight reaction products of phenol (or cresol) with formaldehyde. Highly cross-linked systems are formed that have superior performance at elevated temperatures. 

I ovolac Synthesis and Properties. Novolac resins used in DNQ-based photoresists are the most complex, the best-studied, the most highly engineered, and the most widely used polymers in microlithography. Novolacs are condensation products of phenoHc monomers (typically cresols or other alkylated phenols) and formaldehyde, formed under acid catalysis. Figure 13 shows the polymerization chemistry and polymer stmcture formed in the step growth polymerization (31) of novolac resins. 

While phenol is the most common monomer for novolac manufacture, it is far more common to see incorporation of other phenolic materials with novolacs than with resoles. Cresols, xylenols, resorcinol, catechols, bisphenols, and a variety of phenols with longer alkyl side chains are often used. While most resoles are made with a single phenolic monomer, two or more phenolic materials are often seen in novolac formulae. These additional monomers may be needed to impart special flow characteristics under heat, change a glass transition temperature, modify cure speed, or to adjust solubility in the application process among others. 

For positive resists, mixtures of 1,2-naphthoquinone diazides with phenolic resins, mainly the polymer from 3-cresol and formaldehyde (Novolac), are used. 

Biernath et al. concluded that phenolic novolac and epoxidized cresol novolac cure reactions using triphenylphosphine as the catalyst had a short initiation period wherein the concentration of phenolate ion increased, followed by a (steady-state) propagation regime where the number of reactive phenolate species was constant.85 The epoxy ring opening was reportedly first order in the steady-state regime. 

The literature on basic- and acid-catalyzed alkylation of phenol and of its derivatives is wide [1,2], since this class of reactions finds industrial application for the synthesis of several intermediates 2-methylphenol as a monomer for the synthesis of epoxy cresol novolac resin 2,5-dimethylphenol as an intermediate for the synthesis of antiseptics, dyes and antioxidants 2,6-dimethylphenol used for the manufacture of polyphenylenoxide resins, and 2,3,6-trimethylphenol as a starting material for the synthesis of vitamin E. The nature of the products obtained in phenol methylation is affected by the surface characteristics of the catalyst, since catalysts having acid features address the electrophilic substitution in the ortho and para positions with respect to the hydroxy group (steric effects in confined environments may however affect the ortho/para-C-alkylation ratio), while with basic catalysts the ortho positions become the... 

Positive-Tone Photoresists based on Dissolution Inhibition by Diazonaphthoquinones. The intrinsic limitations of bis-azide—cyclized rubber resist systems led the semiconductor industry to shift to a class of imaging materials based on diazonaphthoquinone (DNQ) photosensitizers. Both the chemistry and the imaging mechanism of these resists (Fig. 10) differ in fundamental ways from those described thus far (23). The DNQ acts as a dissolution inhibitor for the matrix resin, a low molecular weight condensation product of formaldehyde and cresol isomers known as novolac (24). The phenolic structure renders the novolac polymer weakly acidic, and readily soluble in aqueous alkaline solutions. In admixture with an appropriate DNQ the polymer s dissolution rate is sharply decreased. Photolysis causes the DNQ to undergo a multistep reaction sequence, ultimately forming a base-soluble carboxylic acid which does not inhibit film dissolution. Immersion of a pattemwise-exposed film of the resist in an aqueous solution of hydroxide ion leads to rapid dissolution of the exposed areas and only very slow dissolution of unexposed regions. In contrast with crosslinking resists, the film solubility is controlled by chemical and polarity differences rather than molecular size. 

The epoxy novolac resins are synthesized by reaction of phenolic or cresol novolacs with epichlorohydrin in the same fashion as the bisphenol A resins. The number of epoxy groups per molecule is dependent on the number of hydroxyls in the phenol novolac molecule and to the extent to which they are reacted. Complete epoxidation can be accomplished, but this will lead to steric factors, which could limit the useful size of the cured polymer. Thus, selective epoxidation is often practiced.9... 

Epoxy novolac resins are polyglycidyl ethers of a novolac resin. They are prepared by reacting epichlorohydrin with a novolac resin (see Chap. 2). The most common epoxy novolacs are based on medium-MW molecules with phenol and o-cresol novolacs. They generally have significantly different properties from DGEB A epoxies because of the presence of the phenolic structure. 

Trimethylsilylmethylphenol and o-cresol were obtained from Petrarch Systems, Inc. and Aldrich Chem. Co. Inc., respectively. Silylated novolac (Sl-novolac) resins were prepared by condensation polymerization of p-trimethylsilylmethyl phenol, o-cresol and formaldehyde. Poly(2-methyl-l-pentene-sulfone) (PMPS) was prepared as described in the literature (12). 

The epoxy-cresol—novolaks resins are prepared by glyci-dylation of o-cresol-formaldehyde condensates in the same manner as phenol-novolak resins, o-cresol-formaldehyde condensates are prepared under acidic conditions with HCHO-o-cresol ratios of less than unity. The o-cresol novolacs of commercial significance possesses degrees of polymerization, n, of 1.7-4.4 and the epoxide functionality of the resultant glycidylated resins varies from 2.7 to 5.4. Softening points (Durrain s) of the products are 35-99°C [31]. 

These resins (Resole or Novolac) are used as curing agents or hardeners for epoxy molding compounds for electronics applications such as computer components. 0-cresol-formaldehyde resins have heen also used to modify phenol-formaldehyde resins, and in laminates. 

Epoxy resins based on glycidylation of bisphenols, cresol and phenol novolacs, polycarboxylic acids, polyols, amines, and aminophenols have been long known. Epoxidized linear and cyclic olefins have also been used as specialty epoxy resins. More recently, glycidylated heterocycles have been introduced, initially as specialty resins promising improved resistance to weathering. One heterocycle in particular, the hydantoin ring, has become of particular interest as an epoxy substrate (J ). 

Ho et al (1996) examined polyol or polysiloxane thermoplastic polyurethanes (TPUs) as modifiers in cresol-formaldehye novolac epoxy resins cured with phenolic novolac resin for computer-chip encapsulation. A stable sea-island dispersion of TPU particles was achieved by the epoxy ring-opening with isocyanate groups of the urethane prepolymer to form an oxazolidone. The flexural modulus was reduced by addition of TPU and also the Tg was increased due to the rigid oxazolidone structure. Mayadunne et al (1999) extended this work to a series of phenol- and naphthol-based aralkyl epoxy resins. 

All samples were prepared from a commercially available epoxy cresol novolac-phenol formaldehyde novolac-tertia-ry amine based molding compound. Pelletized preforms were heated to 85°C in a RF preheater prior to being transfer molded at 180°C/68 atm. for 90 sec. Molded samples were cooled in air to room temperature and stored in a desiccated environment until testing or subsequent thermal treatment. Post mold curing, PMC, was accomplished in a gravity oven at 175°C for a period of 4 hours. Samples without post mold curing are designated by NPMC. 

Ea, above and below Tg. Three case studies illustrate the range of applicability of the bending beam setup and factors contributing to the stress state. The first is a comparison of two polymers for interlayer dielectrics PMDA-ODA (pyromellitic acid dianhydride - oxydiamine) and a bis-benzocyclobutene. The second is of a neat epoxy resin commonly used for microelectronics encapsulation (epoxidized ortho-cresol novolac cured with a phenolic novolac). The third is a screen-printable polyimide coating used for protection of the integrated-circuit chip. An outline of our stress model is sketched, and example results are presented. 

For electronic applications, 4-hydroxymethyl-3,5-dibromo-2,6-dimethyl-phenol was reacted with cresol novolac to form the m-bromo phenol containing cresol novolac which is then epoxidized to the corresponding epoxy resin (12V. 

SEC study of epoxy novolac polymers, such a low molecular weight peak was assigned to a phenol- or cresol-like residue (5). Considering the molecular... 

Cresol-formaldehyde, phenol-formaldehyde, and chlorinated cresol-formaldehyde novolac resins all undergo photo-oxidation upon UV-irradiation in air. The change of the carbon core level signals is shown in Fig. 8. The new IR band at about 1720 cm-, corresponding to formation of a carbonyl group, is also found after photo-oxidation of novolac resin. These oxidized layers of the novolac film are limited to a very shallow superficial surface only about 500 A thick, even after long deep UV irradiation, as discussed below in reference to photostabilization of resist images. 

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