(81d) Optimal Reaction Design of Alkoxy Silane Copolymers Using Design of Experiment Methods

Silicone-based copolymers such as polysiloxane and polysilsesquioxane have unique properties that make them well-suited for many industrial applications such as encapsulation and packaging of electronic components, anti-microbial coatings, and microelectronics^1,2. They are particularly used in multi-layer lithography, a type of fabrication process for integrated circuits that provides increased resolution and sensitivity compared to other methods, and which relies on silicon-containing polymers to enable sharp pattern transfer. Integrated circuit applications require materials with very precise and tight quality specifications. To obtain these specifications, a good quantitative understanding of the molecular structures and properties of organosilicon polymers³, which undergo structural changes during processing³, is needed. Thus, understanding how defects in molecular domains influence the properties of the silicon-containing copolymers enables high-quality and controlled production scheme.

In this study, we applied the design of experiment methods (DOE) to gain a systematic understanding of the effect of different factors such as acid catalyst concentration, water to alkoxy silanes ratio, alkoxy silane monomers ratio, and condenser flow rate on the copolymer physical properties and structural chemistry. Here, poly(MTMS-co-TEOS), with the range of weight average molecular weight of 3000-6000 gmole^-1, was synthesized. The effect of reaction parameters and their interactions were studied through using different characterization methods such as TGA-IR, AFM-IR, NMR spectroscopies to achieve the optimal reaction condition for manufacturing products within the specification limits. It was found that increasing the ratio of condensation rate to hydrolysis rate and using a high ratio of trimethoxymethylsilane (MTMS) to tetraethoxysilane (TEOS) monomers induce a transition in the molecular structure and favors formation of random and cage structures, which can be attributed to defects, to linear ones. Moreover, we found out that acid addition rate has the strong influence on the formation of defects. We concluded that the formation of random and cage structures can be suppressed through increasing the condensation rate, improving the mixing rate, and controlling the addition rate of the acid catalyst.

References:

(1) Okoroanyanwu, Uzodinma. "Chemistry and lithography." Bellingham, WA: SPIE, 2010.

(2) Schmid, H., and B. Michel. "Siloxane polymers for high-resolution, high-accuracy soft lithography." Macromolecules 33.8 (2000): 3042-3049.

(3) Reichmanis, Elsa, et al. "Organosilicon polymers for microlithographic applications." Advances in chemistry 224 (1990): 265-281.