Search

Vinyl polymers containing pendant acetal groups were synthesized using (2,2-dimethyl-l,3-dioxolan-4-yl)methyl acrylate (DMA) and (2,2-dimethyl-l,3-dioxo-lan-4-yl)methyl methacrylate (DMM), and were evaluated as negative electron beam (EB) resists. It was found that the EB sensitivity of polymers containing acetal groups in the side chain was higher than that of polymers containing acetal groups in the main chain. A high sensitivity of 3.6 × 10−8 C/cm2 was observed. Copolymers of DMA or DMM with styrene were also synthesized in order to improve the durability for dry etching process. It was found that the copolymers had an excellent dry etching durability and were adaptable to EB lithography.

Homopolyamides and copolyamides containing a variety of reactive and/or stabilizing groups, such as double bonds, epoxy groups, or naphthalene moieties, were synthesized using 3-amino perhydroazepine (APA) as a diamine monomer. These polymers were evaluated as electron beam (EB) resists, in order to investigate the relationship between EB sensitivity and chemical structure of the polyamides. It was found that polyamides containing double bonds were easily crosslinked by the EB exposure and that the sensitivity of a polyamide containing double bonds in the side chain was higher than that of a polyamide containing double bonds in the main chain. The sensitivity of a polyamide containing epoxy groups was lower than that of the above. Copolymer from APA, 77 mol % of trans-3-hexenedioyl chloride (HC) and 23 mol % of 2,6-naphthalenedioyl chloride (NC) had the same EB sensitivity as that of the homopolymer from APA and HC. The polyamides had excellent dry etching durability and were adaptable to EB lithography.

Poly(lactam thioether) was synthesized from tetrahydro-1,4-thiazepine-5(4H)-one by a ring opening reaction under various conditions and was evaluated as positive electron beam(EB) resist. It was found that poly(lactam thioether) was easily decomposed by EB irradiation. The decomposition by EB exposure may be attributed to cleavage of CS bonds in the polymer chains. The sensitivity of poly(lactam thioether) was influenced by prebake temperature, molecular weight, and developer, a high sensitivity of 5.3 × 10−6 coulomb/cm2 was observed with a good resolution of less than 1 μm. Poly(lactam thioether) showed a high sensitivity and a high resolution, and is suitable as a positive EB resist.

Polyamides containing double bonds or epoxy groups were synthesized and evaluated as electron beam (EB) resists, in order to find the relationship between electron beam sensitivity and chemical structure of the polyamides. It was found that polyamides containing double bonds, which have good solubility, are easily crosslinked by the electron beam exposure. The sensitivity of a polyamide with 70 mol% of the repeat units containing double bonds was equivalent to that of a 100% unsaturated polyamide which contained double bonds of 100% molar ratios, and thus it is not necessary that the polyamide be a homopolymer of unsaturated repeating units. The polyamides have good physical properties, and are adaptable to dry etching processes.

Polymer complex of poly (4-vinylpyrldine) and malonic acid was investigated as a new type of electron beam (EB) resist for dry development, as malonic acid was decomposed by EB irradiation. It was found that the polymer complex could be developed with O2 plasma etching and that the positive resist patterns with high resolution could be obtained. The mechanism for this lithography process was studied by means of IR and ESCA spectra.

Polyamidethioethers were synthesized and evaluated as positive electron beam (EB) resists, The polyamidethioethers decomposed easily with EB exposure. At high doses (indicating low sensitivity), crosslinking reactions occurred for polyamidethioethers having C-S bonds produced by Michael addition, but the other polyamidethioethers did not crosslink. The C-S bonds produced by Michael addition may influence crosslinking rather than decomposition. The sensitivity of oxidized polyamidethioether was higher than that of the nonoxidized polymer with no change in resolution. The oxidized polyamidethioether had a high sensitivity and a high resolution, and is adaptable as a positive EB resist.