sábado, 22 de mayo de 2010

Hybrid materials for microelectronics

Organically modified resins retain important roles in electrical component coatings such as resistors and molding compounds, as well as spin-on dielectrics in microelectronic interlayer and multilayer dielectric and planarization applications.

Simply methyl or hydride substitution of alkoxysilanes allowed the development of commercial products such as:
Glass-Rock1 by Owens–Illinois, for sealing cathode-ray tubes; Techneglas1 by NEC, for dielectric applications, Accu-Spin1 by Honeywell, for spin-on glass applications, etc. However, although numerous commercial hybrid-based products in electronics merit mention, only several representative examples will be detailed.

To demonstrate the feasibility of ORMOCER1s for use as an MCM L/D material, a substrate for a Pentium2 multi-chip module (MCM) with a BGA interface was realized. The substrate of that demonstrator consists of a metal interconnection separated by ORMOCER1 dielectrics on top of a FR-4 laminate including power and ground planes.

Two sputtered aluminium layers were used for the signal interconnection. The signal layers were separated from each other and from the power plane by 6 mm thick spin-coated ORMOCER1 layers in which via-holes were defined by direct photo-patterning. The FR-4 laminate was provided with micro-vias and through hole vias connecting to a 1.27 mm pitch, ball grid array underneath.

In Fig. 14(a), from right to left, the different steps of sequentially built-up (SBU) processing are given: Cu-metallised FR-
4-substrate (ground plane), first ORMOCER1 layer with power plane, second ORMOCER1 layer with first signal plane, third ORMOCER1 layer with second signal plane, and finally a Pentium2 chip set was also mounted on the substrate. This example shows the possibilities offered by low temperature curing of hybrid materials to achieve compact low cost devices by integration of the MCM substrate with the package.

As these hybrids show beside good dielectric and processing properties also high optical transmission, opto-electrical (o/e) and opto-electronic applications were done. The concept enabled by ORMOCER1 technology aims at very low cost and comprises high density electrical interconnects and optical waveguides integrated in three layers of ORMOCER1s.


An optoelectronic-MCM-L/D demonstrator is depicted (an electro-optical board, laminate with a hybrid in SBU-technology on top as well as a 5-channel optical transmitter and a 5-channel optical receiver). The thin film layers have been put on top of an FR-4 laminate with microvias. The laminate is furnished with a ball grid array (BGA) underneath, eliminating the need of any extra package.

The advantage of tuning the hybrid's flexibility and adhesion properties allows their use on flexible substrates, even as optical waveguides. Fig. 15 shows ORMOCER1 waveguides in which the hybrid coating is deposited on a flexible foil.

The chemistry of these hybrid polymers is based on the 1 : 1 polycondensation (alkoxolation) of diphenyl silanediol and silicon trialkoxides with methacryl and/or epoxy respectively cyclohexylepoxy functionalities. The ''water-free'' alkoxolation reaction causes condensates nearly free of residual SiOH, essential for low optical loss in the near infrared around 1550 nm. The high aryl content is chosen to get also a low-loss window in the NIR around 1310 nm. This easy chemistry therefore offers a perfect fit for implementation as an optical waveguide material in systems like transmitters and receivers in medium and long distance telecommunication, thermooptical switches and couplers etc., as the laser-sources as well as the glass-fibres work in these low-loss windows. Having a low permittivity e around 3.5 that composition could also be in parallel used as dielectrics. Because of the methacryl group such systems are photo-definable i.e. they can be used in photolithography, projection lithography as well as all kinds of UV-laser technology.

Dielectric ORMOCER1-hybrid polymers offer perfect media for high resolution photolithography because: (i) the precursor oligomers of the siloxane part have a small size around 1–5 nm, and (ii) the chemical cross-linking during mask-aligning (UV-polymerisation based patterning) is strongly sterically hindered by the oligomers which cause a fast break-down of radical polymerisation avoiding parasitic reactions into the mask-shaded areas. In general, their chemistry is based on the polycondensation of phenylfunctionalized silanols with tetraalkoxysilane as well as some percentage of zirconium alkoxides. As reactive cross-linking species such as silanes with methacryl groups (UV-polymerisation) and epoxy groups (thermal postcuring) can be used. Recent publications give information about the use of ORMOCER1 hybrids for 2-photon-polymerisation within femto-laser technology. It allows by careful choice of photoinitiators very high resolution for e.g. build-up of photonic crystals. Here, an additional benefit of hybrids: the mechanical stability allows the build-up of very fine structures ,100 nm.

Asignatura: CRF
Fuente: www.rsc.org/materials Journal of Materials Chemistry
Ver: http://nanocompositescrf.blogspot.com/


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