Semiconductor interposers with layer stackup features

A system comprising:

• one or more semiconductor devices;
• and
• a package enclosing the one or more semiconductor devices, the package comprising an interposer electrically coupled to the one or more semiconductor devices, the interposer comprising:
• a core comprising a substrate and first vias through the substrate;
• a first stackup of layers over a first side of the core, the first stackup of layers comprising first redistribution layers and first dielectric layers, the first redistribution layers electrically coupled together using second vias through the first dielectric layers, the first stackup of layers forming a first stripline and a second stripline;
• and
• a second stackup of layers over a second side of the core opposite the first side, the second stackup of layers comprising second redistribution layers and second dielectric layers, the second redistribution layers electrically coupled together using third vias through the second dielectric layers, the second stackup of layers forming a third stripline.

A method comprising:

• obtaining a core comprising a substrate and first vias through the substrate;
• forming a first stackup of layers over a first side of the core, the first stackup of layers comprising first redistribution layers and first dielectric layers, the first redistribution layers electrically coupled together using second vias through the first dielectric layers, the first stackup of layers forming a first stripline and a second stripline;
• and
• forming a second stackup of layers over a second side of the core opposite the first side, the second stackup of layers comprising second redistribution layers and second dielectric layers, the second redistribution layers electrically coupled together using third vias through the second dielectric layers, the second stackup of layers forming a third stripline.