BACKGROUND

The present disclosure relates to network fabrication and, in particular, to double-sided, high-density radio frequency (RF)/direct current (DC) network fabrication on a metal substrate.

The ability of systems and processes to create double-sided, high-density networks has been traditionally limited by several factors. In general, planarity of dielectric surfaces has been difficult to achieve because dielectric planarity is typically dependent on lamination/extrusion processes that often produce depression on one side of a substrate and protrusions on the other side of the substrate. This topology tends to lead to extensive patterning defects at photolithography stages. In addition, metal coverage of through-substrate coaxial vias is difficult to achieve because through-hole metallization can be marginally effective. This is often due to limited throwing power of metal deposition processes.

Attempts to overcome these factors have included processes whereby a plasma etch is applied to the protrusions to minimize the bump and multiple extrusion/lamination cycles were attempted with substrate flipping. While these realized improvements in terms of reducing the depression and protrusion formation, they did not eliminate depressions and protrusions entirely. Meanwhile, dielectric via metallization was attempted using two-step sputter deposition processes to deposit metal from both sides of the substrate.

SUMMARY

According to an aspect of the disclosure, a conductive network fabrication process is provided and includes filling a hole formed in a substrate with dielectric material, laminating films of the dielectric material on either side of the substrate, opening a through-hole through the dielectric material at the hole, depositing a conformal coating of dielectric material onto an interior surface of the through-hole and executing seed layer metallization onto the conformal coating in the through-hole to form a seed layer extending continuously along an entire length of the through-hole.

In accordance with additional or alternative embodiments, the dielectric material filling the hole is flush with substrate surfaces and interior and exterior surfaces of each of the films are substantially flat.

In accordance with additional or alternative embodiments, the through-hole is a high-aspect ratio through-hole.

In accordance with additional or alternative embodiments, the opening of the through-hole includes lasing.

In accordance with additional or alternative embodiments, the depositing of the conformal coating includes atomic layer deposition (ALD) of alumina.

In accordance with additional or alternative embodiments, the executing of the seed layer metallization includes high power impulse magnetron sputtering (HiPIMS).

In accordance with additional or alternative embodiments, the HiPIMS is executed sequentially at opposite sides of the substrate.

In accordance with additional or alternative embodiments, a thickness of the seed layer is about 10× a thickness of the conformal coating.

In accordance with additional or alternative embodiments, a thickness of at least the seed layer is substantially uniform along the entire length of the through-hole.

In accordance with additional or alternative embodiments, the method further includes forming network conductors on exterior surfaces of the films in electrical communication with the seed layer.

According to an aspect of the disclosure, a conductive network fabrication process is provided and includes filling holes formed in a substrate with liquid crystal polymer (LCP), laminating films of LCP on either side of the substrate, lasing through-holes through the LCP at each of the holes, depositing, by atomic layer deposition (ALD), conformal coatings of alumina onto interior surfaces of each of the through-holes and executing high power impulse magnetron sputtering (HiPIMS) to form, on the conformal coatings, seed layers extending continuously along entire lengths of each of the through-holes.

In accordance with additional or alternative embodiments, the LCP in the holes is flush with substrate surfaces and interior and exterior surfaces of each of the films of LCP are substantially flat.

In accordance with additional or alternative embodiments, the through-holes are high-aspect ratio through-holes.

In accordance with additional or alternative embodiments, the HiPIMS is executed sequentially at opposite sides of the substrate.

In accordance with additional or alternative embodiments, thicknesses of the seed layers are about 10× thicknesses of the conformal coatings.

In accordance with additional or alternative embodiments, thicknesses of at least the seed layers are substantially uniform along the entire lengths of each of the through-holes.

In accordance with additional or alternative embodiments, the method further includes forming network conductors on exterior surfaces of the films in electrical communication with the seed layers.

According to an aspect of the disclosure, a double-sided, high-density radio frequency (RF)/direct current (DC) network is provided and includes a substrate defining holes, liquid crystal polymer (LCP) lining each of the holes and forming substantially flat films on opposite surfaces of the substrate, the LCP defining through-holes at each of the holes, conformal coatings of alumina respectively disposed on the LCP in each of the through-holes and seed layers respectively disposed on the conformal coatings to respectively extend continuously along entire lengths of the through-holes.

In accordance with additional or alternative embodiments, the through-holes are high-aspect ratio through-holes and thicknesses of at least the seed layers are substantially uniform along the entire lengths of the through-holes.

In accordance with additional or alternative embodiments, network conductors are provided on exterior surfaces of the films in electrical communication with the seed layers.

Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with the advantages and the features, refer to the description and to the drawings.

