Orientational order control, thin films

Processes which employ combinations of these strategies have proved to be much more effective at yielding uniform long-range ordered patterns than single strategies. Table 1 describes the methods used to control the microdomain orientation of a variety of thin film block copolymers [41,42,66-108],... 

Crystallization amounts by nature to the self-assembly of very large, boundaryless supramolecular species. Its control is a goal of major importance in order to be able to generate solid-state materials of specific structural and physical properties (see also Sections 7.1, 7.2, 9.4.4 [7.39-7.42, 9.105, 9.245]). Supramolecular effects play a crucial role. Directional growth of materials may be induced by a template and involve molecular recognition [9.246], occurring by epitaxy [9.247] or on oriented thin films [9.248]. 

Olszowka V, Kuntermann V, Boker A (2008) Control of orientational order in block copolymer thin films by electric fields a combinatorial approach. Macromolecules 41 5515-5518... 

Various experimental routes towards surface modification have been utilized in order to control the microphase separation in thin films, as well as to achieve large-area patterns with desirable orientation relative to the film plane [2, 19, 21, 51]. 

Table 1 Summary of block copolymers studied in order to control microdomain orientations in thin film states...

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. 

Figure 2). Orientation of the films is used to tailor and control the CTE, and the low dielectric thin film layers provide more controlled impedance and reduced crosstalk than other substrate materials. In addition to MLBs, ordered polymer films can be used to advantage in multichip molecules where silicon chips are directly bonded to the interconnect substrate. The very low permeability of PBO and PBZT films will protect the chips from moisture. Flexible circuitry is another promising application area for these films. 

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