Methacrylate terpolymer resist

As seen in Tables V, VI and VII, a number of these methacrylate-based resist systems are available commercially. Some, like IBM s "terpolymer" resist,... 

Lin et al. (J77) replaced PMMA with IBM terpolymer resist (a terpol-ymer of MM A, methacrylic acid, and methacrylic anhydride developed as an electron beam resist), which has a higher thermal stability and a higher DUV sensitivity. 

A methacrylate terpolymer containing 35 mol% methacrylic acid units was mixed with diepoxides (Fig. 131) and triphenylsulfonium triflate and imaged in a negative mode by exposure to ArF excimer laser followed by development with 0.06% (weak) TMAH solution [383]. The aromatic epoxide was selected for imaging because the more transparent aliphatic epoxide was liquid and thus lowered the Tg of the resist film to an unacceptable level. The insolubilization mechanism was speculated to be crosslinking through acid-catalyzed esterification between the carboxylic acid and epoxide. 

The tynthetic flodbility and demonstrated performance (e.g., photospeed and contrast) of the positive PCB resists based on functional methaoylate polymers provided the incentive to extend the methaoylate terpotymer design concepts to the submicron lithography arena. The methacrylate terpolymers have been modified in attempts to provide thin film, high resolution resists suitable for exposure at 248 and 193 nm. This woric demonstrates that high performance and low materials cost are not mutually e lusive. 

Another intriguing aspect of the methacrylate terpolymer CA resist polymers is their airborne contaminant absorption properties relative to more conventional CA resist materials (9). N-methylpyrrolidone (NMP) has been reported to result in serious image degradation of CA positive resists when present in very low levels in the air in resist processing enviromnents ilO). This is a very serious problem, as NMP is ubiquitous in IC fabrication lines, where it is used in resist stripping operations and as a solvent for polymer dielectrics... 

Nitrile rubber (NBR), a copolymer of 1,3-butadiene with 20-40% acrylonitrile, is noted for its oil resistance. More than 150 million pounds are produced annually in the United States. Applications include fuel tanks, gasoline hoses, and creamery equipment. Nitrile resin is made by copolymerizing acrylonitrile with about 20-30% styrene or methyl methacrylate in the presence of NBR or SBR rubber to yield a blend of the graft terpolymer and homocopolymer. Applications include extruded and blow-molded containers for household, automotive, and other products as well as some nonbeverage foods (spices, vitamins, candy). 

In an effort to improve PMMA s photosensitivity further, methyl methacrylate has been copolymerized with higher percentages of the a-keto-oxime methacrylate and terpolymerized with varying amounts of methacrylonitrile. The resulting effects on resist properties, e.g., sensitivity, contrast and resolution, and plasma resistance, are reported here. The terpolymers are up to 85 times more sensitive than PMMA, and retain its high resolution characteristics. 

PVC, another widely used polymer for wire and cable insulation, crosslinks under irradiation in an inert atmosphere. When irradiated in air, scission predominates.To make cross-linking dominant, multifunctional monomers, such as trifunctional acrylates and methacrylates, must be added. Fluoropolymers, such as copol5miers of ethylene and tetrafluoroethylene (ETFE), or polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack, and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance. Ethylene propylene rubber (EPR) has also been used for wire and cable insulation. When blended with thermoplastic polyefins, such as low density polyethylene (LDPE), its processibility improves significantly. The typical addition of LDPE is 10%. Ethylene propylene copolymers and terpolymers with high PE content can be cross-linked by irradiation. ... 

In ASA terpolymer acrylic acid brings more flexibility and the material has very good mechanical properties and weather resistance. For these reasons ASA is extensively used in automotive industry and in the fabrication of various appliances. Even more frequently than acrylic acid itself, various acrylates are used in copolymers. Among these can be mentioned the copolymers of acrylic acid esters with methacrylic acid esters such as poly(methyl methacrylate-co-methyl acrylate), poly(methyl methacrylate-co-ethyl acrylate), poly(methyl methacrylate-co-butyl acrylate), poly(ethyl methacrylate-co-ethyl acrylate), poly(acrylonitrile-co-methyl acrylate), poly(alkyl acrylate-co-methyl methacrylates), and poly(alkyl acrylate-co-hydroxyethyl methacrylates) where alkyl can be methyl, ethyl, butyl, etc. Some literature information regarding thermal decomposition of copolymers including acrylic acid and acrylic acid esters is given in Table 6.7.8 [6],... 

A terpolymer of ter/-butyl methacrylate (TBMA), methyl methacrylate (MMA), and methacrylic acid (MAA) was initially developed as a chemically amplified thick laser resist for circuit board fabrication [ 180]. The terpolymer containing 1 wt% of di(ferf-butylphenyl)iodonium trifluoromethanesulfonate (triflate) has demonstrated excellent imaging at 193 nm when developed with a dilute (0.01 N) TMAH aqueous solution [181]. This terpolymer single layer resist was employed for exposure tool testing. 

Commercial ionomers are ethylene-methacrylic acid copolymers and terpolymers in which the carboxylic acid moiety is partially neutralized with sodium or zinc, to promote interchain ionic bonding. Ionomers exhibit excellent low temperature toughness, chemical resistance and adhesion. However they lack in stiffness and heat resistance. Hence ionomer blends with polyolefins such as polyethylene have been developed which, upon reinforcing with suitable fillers, seem to give a unique combination of high strength, excellent low temperature toughness, and moderate stiff-... 

Other strategies that have been reported for improving the sensitivity of PMMA resists include the introduction of substituents in the ester part of the PMMA and copolymerization with methacrylic acid, with acrylonitrile, and with methacrylic anhydride. In particular, Moreau et al. have described a resist based on the terpolymer of methacrylic acid, methacrylic anhydride, and methylmethacrylate (XXVI) that has demonstrated significantly faster speed than other resists based on PMMA, while maintaining desirable properties. 

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