Thin-film multilayer processing substrates

Ordered polymer films made from poly benzthiazole (PBZT) and poly benzoxazole (PBO) can be used as substrates for multilayer printed circuit boards and advanced interconnects to fill the current need for high speed, high density packaging. Foster-Miller, Inc. has made thin substrates (0.002 in.) using biaxially oriented liquid crystal polymer films processed from nematic solutions. PBZT films were processed and laminated to make a substrate with dielectric constant of 2.8 at 1 MHz, and a controllable CTE of 3 to 7 ppm/°C. The films were evaluated for use in multilayer boards (MLBs) which require thin interconnect substrates with uniform controllable coefficient of thermal expansion (CTE), excellent dielectric properties, low moisture absorption, high temperature capability, and simple reliable processing methods. We found that ordered polymer films surpass the limitations of fiber reinforced resins and meet the requirements of future chip-to-chip interconnection. 

The same methods to introduce grain boundaries, i.e. bi-crystal substrates, step-edges and bi-epitaxial techniques, also apply to the other superconductors [14.52, 14.107-14.109], The details of the interfacial interactions between the substrates and the thin films need to be investigated in order to find the optimum conditions and geometries for each individual system. The chemical interactions must also be considered when integrating the superconductors into multilayer structures. Intermediate non-superconducting layers that are inert to the YBCO may react chemically with the other superconductors. It is also necessary to carefully consider the ex situ processes of the Tl- and Hg-based superconductors producing multilayer structures. 

Poly(ferrocenylsilane) polyions are readily processed to novel, fully organometallic multilayer thin films. Furthermore, these organometaUic polyions, featuring a hydrophobic backbone, enable one to make use of both electrostatic and hydrophobic interactions to fabricate self-organized patterns on templated substrates, with potential applications as aqueous pro-cessable ultrathin etch resists. 

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