In this paper, we address the most important issues related to realisation of μ-wave and mm-wave circuits containing power devices in the novel technology of Quasi-Monolithic Integration Technology (QMIT). A finite element simulator (2D and 3D), a scanning probe microscopy (SPM), a nanometer surface profiler (DEKTAK) and a Peltier element (PE) have been used to optimise the standard structure of QMIT with respect to these issues and limitations in fabrication process. The first important issue is the thermal resistance of QMIT structure. Using a 2D finite element method, the effects of the most important parameters on thermal resistance such as the distance between active device and substrate (W), the thermal conductivity of glue (kepoxy) and use of a heat spreader to decrease thermal resistance have been investigated in detail. The second important issue is the induced thermal stress in QMIT structure which results from differences in thermal expansion coefficient of materials involved. A 3D finite element simulator, a scanning probe microscopy (SPM) measurements and a nanometer surface profiler (DEKTAK) accompanied with a Peltier element (PE) have been used to simulate and measure the thermal stress distribution in QMIT standard structure. Then, the effect of the most important parameters such as W, baking temperature of epoxy and material properties of epoxy have been described in detail.

Keywords