Dimitri Stoppel

Interconnection development for InP-HBT terahertz circuits Dimitri Stoppel

For frequencies above 300 GHz applications are still in the research state since commercially available systems are missing. This dissertation shows three key aspects in process development that are now part of a standard indium phosphide (InP) transferred-substrate process, paving the way for future terahertz projects and applications. The InP transferred-substrate process at Ferdinand-Braun-Institut (FBH) has proven to be a promising candidate for the respective semiconductor components. This particular process utilizes the wafer bonding technique, which allows transferring the active monolithic microwave integrated circuits (MMICs) onto a host substrate. Such host substrate can be either a passive substrate that is equipped with through-silicon vias (TSVs) or a BiCMOS wafer. Hetero-integrated approaches offer ideal conditions to fulfill the requirements of applications regarding complexity (BiCMOS) and large bandwidth (InP). Within this thesis, three topics are described in greater detail: benzocyclobutene (BCB) dry etch process development, nickel-chrome (NiCr) thin film resistor (TFRs) development and through-silicon vias implementation. Eventually, the newly developed plasma etch process has been successfully implemented into standard InP processing, with a fivefold increase in etch rate at maintained bias and anisotropy. Also, a method to suppress redeposition formation was shown. Successful circuit measurements with implemented NiCr resistors demonstrated the last step of TFR integration. A new approach with bottom contacted TFRs was successfully integrated. A laser-enabled TSV process was developed to serve as an effective and reliable way to circumvent parasitic parallel plate modes that occur at high operating frequency circuits.