He Seung Lee

High photo- and electroluminescence efficiencies of ladder-like structured polysilsesquioxane with carbazole groups

Ladder-like structured polysilsesquioxane with carbazole groups showed unexpected high photo- and electroluminescence efficiencies both in solution and solid states due to its rigid silicone ladder structures, which efficiently isolated the carbazole groups and thus suppressed their excimer formations by inter- and intramolecules.

Low Dielectric Materials for Microelectronics

Over the past half century, low dielectric materials have been intensively researched by ceramic and polymer scientists. However, these materials possess a vast myriad of electrical, thermal, chemical, and mechanical properties that are just as crucial as the name that classifies them. Therefore, in many cases, the applications of low dielectric constant materials are dictated by these other properties, and the choice of low dielectric material may have a tremendous effect on a device’s performance and lifetime.

Synthesis and characterization of fluoro-co-Phenyl silsesquioxane (FCPSQ) for low dielectric constant materials

A new type of low-k dielectric material, poly(tridecafluoro1,1,2,2,tetrahydrooctyl-co-phenylsilsesquioxane) (PFCPSQ) was synthesized by hydrolysis and condensation reaction of trimethoxysilyl monomers in the presence of a base catalyst in H2O/THF mixture solvent at 25°C. Chemical compositions, molecular weight, and structure of the obtained PFCPSQs were characterized using 1H NMR, 29Si NMR, FT-IR, and GPC. Dielectric values were examined by a HP-4190 system and a dielectric constant k of 1.92 was obtained.

Incompletely condensed POSS-based spin-on-glass networks for impeccable ultra low-k integration

Poly(methyl)silsesquioxane-based spin-on-glass resins incorporating both a cyclic precursor, 1,3,5,7-tetramethyl 1,3,5,7-tetrahydroxyl cyclosiloxane, and incompletely condensed methyl-substituted POSS were synthesized and their thermal, mechanical, and electrical properties were investigated as a function of the POSS loading content. By introducing incompletely condensed methyl-substituted POSS compounds at the molecular level as sol–gel precursors, exceptional thermal stability (>700 °C), good mechanical properties (elastic modulus >4.0 GPa), and an ultra-low dielectric constant (k = 1.8) were obtained. In addition to providing a new route towards fully poly(methyl)silsesquioxane-based spin-on-glass resins with the above properties, the realization of the application of integration circuits was evaluated to show that the ultra low-k, mechanically robust spin-on-glass materials were able to withstand harsh wet chemical and dry etching, as well as chemical mechanical planarization (CMP) processing.

Robust spin-on-glass poly(methyl)silsesquioxane-based low-k materials derived from a cyclic siloxane precursor

A series of organic–inorganic hybrid spin-on-glass polymethylsilsesquioxanes were synthesized utilizing a cyclic siloxane precursor, 1,3,5,7-tetramethyl-1,3,5,7-tetrahydroxyl cyclosiloxane (MT4-OH), copolymerized with methyltriethoxysilane (MTES) at various comonomer ratios. By selectively introducing this 2-D cyclic crosslinker, we were able to obtain spin-on-glass hybrimers with low dielectric constant (2.5–2.7), high nanoindentation modulus (5–10.5 GPa), with high thermal stability (>700 °C) without the use of porogens or additives. The use of the cyclic monomer MT4-OH greatly increased the mechanical properties, which allowed for impeccable reliability of a variety of patterns obtained through etching and chemical mechanical planarization processes, while maintaining optimal gap-filling properties. Due to the superior dielectric, mechanical, and integrated processing of these materials, these hybrids derived from MT4-OH may be utilized as next generation spin-on-glass low-dielectric constant materials.

Synthesis and Characterization of Azido-Substituted Ladder-like Polysilsesquioxanes and their Click Chemistry

A novel organic-inorganic hybrid-type ladder-like poly(benzylazide) silsesquioxane (LPBAzSQ) and ladder-like poly(propylazide) silsesquioxane (LPPAzSQ) were synthesized through azidation of ladder-like poly(p-chloromethyl)phenylsilsesquioxane (LPCMPSQ) and ladder-like poly(propylchloro)silsesquioxane (LPPCSQ). The ladder-like structure of the synthesized LPBAzSQ and LPPAzSQ compounds, full substitution of azide groups, and their click chemistry with various functional groups was characterized by 1H NMR, 13C NMR, 29Si NMR, FT-IR, GPC. This new approach for functionalization of ladder-like silsesquioxanes has allowed for insertion of polar functional groups that have yet be examined in silsesquioxane chemistry.

Physical Properties of Polymethylsilsesquioxane with UV-Curable Group for Low-Loss Optical Materials

Polymethylsilsesquioxane(PMSQ)s with photo-curable groups were prepared by copolymerization of alkoxysilanes. Poly(acryloyl-co-methylsilsesquioxane)(PAMSQ)s of various mole ratio acryloyl group (6 mol%, 12 mol%, 24 mol%, 48 mol%, 100 mol%) were obtained from copolymerization of methyltrimethoxylsilane and 3-(trimethoxysilyl)propyl acrylate. Optical and photonic curable properties were studied by near infrared region spectra, prism coupler, UV-visible spectra, and photo-DSC. The optical losses were below 0.002 dB/cm at 830, 1330, and 1550 nm, respectively. Optical loss was found to be independent of a molar ratio of functional group.