Preventing of Dewetting Effects for Inorganic–Organic Hybrid Polymers Applied in Sequentially Buildup (SBU) Technology Without Surface Pretreatments

Upon processing waveguide structures by using the ORMOCER materials ORMOCORE as core material, and a mixture of ORMOCORE and ORMOCER-III (refractive index tuning agent) as cladding material, dewetting effects of the core layer from the cladding layer were observed. A similar phenomenon was observed for a mixture of ORMOCORE and ORMOCLAD which was used as comparative refractive index tuning material. In order to use these material combinations for large-area panel (LAP) processing, a pretreatment or activation of surfaces is necessary but hard to realize. However, the addition of small amounts of ORMOCER-III or ORMOCLAD, respectively, to the core layer material, prevented the dewetting phenomenon. The objective of this, however, is to minimize the content of refractive index tuning agent in the core layer by retaining a good wetting behavior during multilayer processing. Wet film stability tests and contact angle measurements of these ORMOCER systems in various compositions on another ORMOCER surface of a specific cladding material composition were performed on a hotplate. Furthermore, contact angles of droplets formed by deionized water, formamide, and di-iodomethane on cured surfaces of these ORMOCER systems in a wide range of compositions were characterized, and surface tensions were calculated. By adding 0.1 wt% of ORMOCER-III or 5 wt% ORMOCLAD, respectively, to the pure ORMOCORE solution, the dewetting phenomenon was eliminated, while simultaneously the refractive index was affected only to a minor degree and no changes in the optical loss could be detected. It was shown that by adding ORMOCER-III or ORMOCLAD to pure ORMOCORE, the surface tension of the compound system was reduced. In comparison to silanization or gasplasma treatment to overcome dewetting effects in microelectronics multilayer processing, the investigated mixing method eliminates process steps and thus costs, and opens new process routes for LAP processing