3-Oximino-2-butanone methacrylate

Poly(methyl methacrylate-co-3-oximino-2-butanone methacrylate-co-methacrylonitrile)... 

Poly(methyl methacryIate-co-3-oximino-2-butanone methacrylate) (P(M-OM) and poly(methyl methacrylate-co-3-oximino-2-butanone-methacrylate-co-methacrylonitrile) (P(M-OM-CN)) were dissolved in methoxyethyl acetate (10% solution). Where appropriate, the specified amount of sensitizer was added to the solutions before coating onto a silicon substrate with a Headway Research spinner. Films were prebaked at 120 C for 60 min. 

The incorporation of small percentages (<10%) of 3-oximino-2-butanone methacrylate (4) into poly(methyl methacrylate) (PMMA) (Scheme I) results in a four fold increase in polymer sensitivity in the range of 230-260 nm flO.l 11. Presumably, the moderately labile N-O bond is induced to cleave, leading to decarboxylation and main chain scission (Scheme II). The sensitivity is further enhanced by the addition of external sensitizers. Also, preliminary results indicated that terpolymerization with methacrylonitrile would effect an additional increase. These results complement those of Stillwagon (12) who had previously shown that copolymerization of methyl methacrylate with methacrylonitrile increased the polymer s sensitivity to electron beam irradiation. The mole fraction of the comonomers was kept low in order to insure retention of the high resolution properties of PMMA (3.41. 

Sensitivity. Typical absorption spectra of the copolymer, poly(methyl methacrylate-co-3-oximino-2-butanone methacrylate) (P(M-OM)), are shown in Figure 1, and Table... 

The effect of varying the concentration of the 3-oximino-2-butanone methacrylate moiety was studied next. From the above results, it appears that the optimum nitrile concentration is roughly 15 to 22%. We chose to fix the methacrylonitrile mole fraction at the lower value in order to least perturb the solubility characteristics of the polymer. 

The photosensitivity of PMMA is significantly enhanced by the incorporation of 10 to 40 mole% 3-oximino-2-butanone methacrylate. Terpolymerization with methacrylonitrile increases that sensitivity still further, P(M-OM-CN) (69 16 15) being 85 times more sensitive than PMMA on exposure to the full output of a 1000 watt mercury lamp. Upon addition of external sensitizers, this sensitivity may be increased by an additional factor of 2 to 3. The high resolution characteristics of PMMA have been retained and the polymers in question show good plasma resistance. 

Figure 6. Mole percent methyl methacrylate incorporated in poly(methyl)meth-acrylate-co-3-oximino-2-butanone methacrylate) copolymers as a function of monomer feed composition determined by Raman spectroscopy. Key -----------ideality...

Table 3.2 summarizes a variety of the methyl methacrylate (MMA) copolymers developed as DUV resists. Chandross et al. 41, 61), Wilkins et al. (58), and Reichmanis et al. (59, 60) reported that incorporation of 3-oximino-2-butanone methacrylate into the PMMA structure [P(MMA-OM)] improves both the absorption characteristics of the polymer in the 220-260-... 

One-component positive resists are essentially copolymers or terpolymers derived from PMMA. Copolymer strnctnres are chosen in order to increase the low value of the absorption coefficient of PMMA at 215 nm. Comonomers are selected either to absorb in the 230-280 nm range or becanse they contain a photosensitive chromophoric group. Poly(methyl methacrylate-co-3-oximino-2-butanone methacrylate-co-methacrylonitrile), p(PMMA-OM-MAN) (Figure 6.11), sensitised with t-butyl benzoic acid requires an exposnre dose of less than 30 mj/cm [18]. 

Copolymerization of trimethylsilyl methacrylate and 3-oximino-2-butanone methacrylate yields copolymers (18) with improved sensitivity to deep UV light, while maintaining good resistance to oxygen plasma. 

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