Method to integrate dc & rf phase change switches into high-speed sige bicmos

A method of integrating a phase change switch (PCS) into a Bipolar (Bi)/Complementary Metal Oxide Semiconductor (CMOS) (BiCMOS) process, comprising:

• providing a base structure including BiCMOS circuitry on a semiconductor substrate;
• forming on the base structure a contact window layer that is a dielectric and having metal through-plugs that contact the BiCMOS circuitry;
• constructing the PCS on the contact window layer over a PCS region of the semiconductor substrate that is adjacent to the BiCMOS circuitry, wherein constructing includes:
• forming a metal through-plug in the contact window layer over the PCS region;
• forming a phase change region over the metal through-plug;
• forming ohmic contacts that are spaced-apart on the phase change region, wherein the phase change region is configured to operate as an in-line switch connected between the ohmic contacts and that is controlled by heat applied to the phase change region, and wherein the metal through-plug is configured to generate the heat responsive to a control signal applied to the metal through-plug;
• and
• forming, on the contact window layer and the PCS, a stack of alternating patterned metal layers and dielectric layers having metal through-plugs to interconnect the patterned metal layers, such that the stack connects a first of the ohmic contacts to the BiCMOS circuitry and provides respective connections to a second of the ohmic contacts and to the metal through-plug.