p-[Bi~(trimethylsilyl)methyllisopropenylbenzene (BSIB) was prepared by reaction of a,pdimethylstyrene (DMST) with lithium diisopropylamide (LDA) and trimethylsilyl chloride (TMSCI). Anionic polymerization of BSIB with sec-butyllithium (BuLi) or living lithium a-methylstyrene oligomers at -50 OC in THF gave polymers with the predicted molecular weights and narrow molecular weight distributions. When the temperature of the polymerization mixture was increased up to 20 "C after the monomer was almost completely consumed, the polymer formed disappeamd almost completely, indicating the anionic polymerization of BSIB to be a living equilibrium system. The ceiling temperature of BSIB in the anionic polymerization was 1.2 f 0.9 "C,
To induce degradabilities in polymers in response to environmental conditions, endmodification reactions of poly(a-methylstyrene) (PMS) derivatives were carried out. 2-Phenylallyl halide derivatives such as 2-phenylallyl bromide, 2-@-tolyl)allyl bromide, and a-trifluoromethylstyrene were found to be suitable end-modification agents. For example, the o-2-phenylallyl-PMS derivative was prepared with almost quantitative functionali1.y by the reaction of the living PMS derivative with 2-phenylallyl bromide. In a similar way, o3,3-difluoro-2-phenylallyl-and o-2-(4-tolyl)allyl-PMS derivatives were synthesized. Based on thermogravimetric analysis, the onset of the degradation temperature of the endmodified PMS derivatives decreased in the following order: o-hydrogen-> w-3,3-difluoro-2-phenylallyl-> o-2-phenylallyl-> o-2-@-tolyl)allyl-PMS. Actually, the onset temperature of w-2-@-tolyl)allyl-PMS derivatives was 50 "C lower than that of o-H-PMS derivatives. These results indicate that the active species is produced effectively at the endunsaturated bond, which initiates depolymerization of the polymer at rather low temperatures. Therefore, it is concluded that a 2-phenylallyl substituent at the end of the PMS chain induces effective degradation through a radical mechanism.
Several types of poly(si1amine)s were prepared and their structure-characteristics relationships were investigated. When a phenyl ring in the organosilyl unit and/or a cyclic structure in the amino unit was introduced, the glass transition temperatures were increased significantly in order to increase film formability. From the thermogravimetric analysis of the poly(silamine)s, it was found that the thermal decomposition of poly(si1amine)s starts at ca. 380-400°C. On electron-beam irradiation of the poly(si1amine) films, degradation of the polymer took place. On the basis of these results, poly(si1amine)s can be one of the candidates for new positive-type polymeric resists.
Hitachi Chemical DuPont MicroSystems (HDMS) is a supplier of photosensitive negative-tone polyimides (PI) and positive-tone poly(benzoxazole)s (PBO) for use as protection layers in semiconductor ICs or as dielectrics for re-distribution layers in Fan-in or Fan-out wafer level packages. These materials offer an easy manufacturing process as well as ensuring high reliability in semiconductor packages. Recently, design rules and structures for next generation packages are advancing in order to achieve higher end multi-functionality. In accordance with this trend, next generation PIs and PBOs need to be developed to address new challenges that include lithographic properties, in-process compatibility and end-use properties and, in this paper, the latest material sets developed by HDMS will be introduced for advanced packaging applications. The 1 st material set is a low stress photosensitive PI designed especially as a protection layer in advanced process node semiconductor ICs where warpage reduction and better protection capability for fragile low-k layers are needed. The 2 nd and 3 rd material sets are designed as low temperature curable photosensitive PI and PBO for use as dielectrics in Fan-out wafer level package to provide good applicability with future device designs as well as high package reliability by improving resolution, cured film properties, adhesion, insulation reliability, and others.
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