In this paper we describe the synthesis, characterization, and lithographic evaluations of novel positive photoresists based on hydroxy polyimides and polyamides containing 6‐F linking groups. The polymers were synthesized using solution condensation techniques and characterized using solution viscosity, GPC, FTIR, NMR, UV, TGA, and DSC. Tg's of these polymers range from 250 to 300°C. Both polyimides and polyamides are soluble in a variety of solvents commonly utilized for photoresist applications. When formulated with diazonaphthoquinone sensitizers, these polymers provide an improved high‐temperature resistant, aqueous base developable positive photoresist system with good photospeed, contrast, and resolution characteristics. High resolution relief images were obtained which are comparable to 1300 Series AZ type photoresists. No thermal deformation, loss in resolution or defects were noticed when relief patterns were annealed to 250°C. Additionally, the hydroxy polyamide based resists, when thermally annealed to 300°C, provide a photoresist system with even higher thermal stability (400 to 450°C) and excellent resistance to solvents. Also, the photoresist formulations have excellent storage stability at room temperature and can be processed like conventional positive photoresists using broad band UV radiation sources.
Starting from general arguments on the relation of polymer structure, transpareiicy at 248 nm, resin hydrophilicity and resist dissolution characteristics, binder systems for novel DUV resists are presented, and the results of their lithographic evaluation are discussed. Phenolic polymers studied include homo-and copolymers of 2-, 3,-and 4-hvdroxystyrenes and of their alkyl substituted derivatives for three-component systems, as well as 2-and 4-hydroxyphenylmethacrylates for use in two-component t-BOC'-type resists. As an alternative non-phenolic resin, the peiformance of a maleimide/styrene copolymer in a two-component system is discussed.
SynopsisLinear poly(dimethylsi1oxane diol) of about 650 D.P. was synthesized by hydrolytic condensation of dimethyldichlorosilane in a saturated solution of sodium chloride. The polymer was then compounded with various fillers, Cab-O-Sil, Dicalite, and titanium dioxide, and cured at room temperature in the presence of tin salt and tri-or tetrafunctional s h e . The tensile strength and elongation of the unfilled rubber were found to be 0.8 kg/cm2 and 320%, respectively. However, Dicalite White (100 phr)-reinforced elastomer showed a tensile strength of 40 kg/cm2. Crosslink density was determined from the swelling studies. Thermal aging at 150,200, and 25OOC was also studied.
Novolak resins provide the best overall performance for “g” and “i”‐line photoresists. There is a continuing need for advanced novolak designs that will provide improved lithographic, thermal, and etch characteristics that may be reproducibly synthesized. A novolak synthesis process was developed using the solution condensation technique. Cresol mixtures with m‐cresol and 3,5‐xylenol at specific ratios provide reproducible novolaks with controlled molecular weights. In order to achieve high thermal and etch performance, while retaining photospeed and resolution characteristics, three basic approaches were investigated: (1) increase in molecular weight, which produces novolaks with Tg ranging from 120 to 130°C with relatively slow dissolution rates; (2) incorporation of multi‐hydroxyphenols such as resorcinol to tailor the dissolution rate, resolution, thermal, etch, and adhesion characteristics; (3) partial esterification of multi‐hydroxy novolaks giving a Tg range of 140 to 150°C. Lithographic evaluation of the novolak resins was performed by formulating with a 2,1,4‐diazonaphthoquinone (DNQ) sensitizer. Results on resin synthesis, molecular weights, lithographic, thermal, and etch characteristics are discussed.
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