Advantages of the New Generation Quasi-Monolithic Integration Technology (QMIT)

Fabrication process and advantages of the new generation quasi-monolithic integration technology are presented. The novel fabrication process gives excellent advantages such as extremely low thermal resistance, and a much lower thermal stress than the earlier QMIT concept [1]. This highly improves the packaging lifetime and electrical characteristics of the active devices. The fabrication process is simple and compatible with fabrication of high-Q passive elements. In comparison to the old concept of QMIT, elimination of air-bridges in this technology not only reduces the parasitics but also enables the fabrication of the rest of the circuit after measuring the microwave characteristics of the embedded active devices. This makes very accurate microwave and millimetrewave designs possible. Using the new fabrication process, microwave and millimetrewave circuits (with both coplanar and microstrip lines) containing power devices have for the first time been realised

Quasi-Monolithic integration technology (QMIT) for power applications

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

Improvements of Thermal Resistance and Thermal Stress in Quasi-Monolithic Integration Technology (QMIT) with a New Fabrication Process

Static heat transfer and thermal stress analysis for the new generation quasi-monolithic integration technology (NGQMIT) is presented using a three-dimensional finite element simulator. Effects of different factors and parameters such as the gap between the silicon sidewalls and GaAs-chip (Wg), temperature dependent materials properties, isotropic material properties and backside gold metallization thickness or diamond-filled polyimide are described. It is shown that thermal resistances of 11 °C/W and 8.5 °C/W are possible using 200 µm electroplated gold heat-spreader and diamond-filled polyimide on the backside of the active device, respectively. This promises successful realization of the high frequency circuits containing power active devices using the novel QMIT. In comparison to the earlier fabrication process [1-2], eight times improvement in thermal stress is achieved. This extremely improves lifetime of the packaging. The results of thermal stress simulation are compared with white-light interferomety measurement

Quasi-monolithic integration technology for flexible and reliable design of microwave and millimeterwave circuits

No abstract available

GRACE-derived ice-mass loss spread over Greenland

The Gravity Recovery and Climate Experiment (GRACE) monthly satellite data is used to examine the extent and magnitude of Greenland ice sheet melting for 2003-2012. We show that the well documented Greenland ice mass loss in the southern region spread to northwest Greenland in the period from2007 to 2010 and 2010 to 2012 by estimating ice mass variability over time in Greenland. The ice-mass melting is estimated to –183±11 Gt/yr. This estimation means that Greenland is still losing much more ice than gained, and continuing to contribute to global sea level rise in a warming world. Unlike other recent studies, our method employs a non-isotropic filter. A nonisotropic filter is used to decorrelate the GRACE data, since the GRACE noise structure has a non-isotropic nature