I. Introduction
Terahertz (THz) monolithic microwave integrated circuits (MMICs) are developed quickly these years [1]–[2]. With the MMICs operating at terahertz frequencies, the package of the MMIC meets some problems for the high-impedance character of traditional gold wire bonding transition. For the double-heterojunction-bipolar-transistor (DHBT) MMIC process in Nanjing Electronic Devices Institute (NEDI), the scribing way need a safe distance to the pad of the MMIC, as a consequence, the gold wire will no shorter than 100um. At the same time, the number of the bonded gold wire is limited for the pad area of the circuit. In some strict condition, the signal pad is only , and there is only space for a single 25um diameter gold wire. All the strict limits heavily decrease the performance of gold wire bonding transition in this type MMIC process as the simulation results shown in fig. 1.