Thermal and microwave characterization of GaAs to Si metal-bonded structures

Abstract

Isothermal solidification metal waferbonding is well suited to heterogeneously integrate high-speed/high-power density RF and microwave devices with standard CMOS technology. It is capable of forming efficient electrical and thermal interconnects as well as bonded-microstrip waveguide structures. Accurate means of characterizing the electrical, thermal, and microwave properties of these structures are necessary to enable heterogeneous monolithic microwave integrated circuits (HMMICs). This article describes a bond layer thermal conductivity measurement method, a bond-metal microstrip microwave waveguide characterization method, and the fabrication method developed to support the measurement structures. As a result, an In-Pd bond alloy thermal conductivity of 2.51 W/(m K) was measured for GaAs devices bonded to Si. Also, an optimized bonded-microstrip waveguide was simulated based upon measured microwave results of the measurement structure, projecting a 0.56 dB/mm loss, a microwave index of 2.91, and a characteristic impedance of 41.3+6i Ω at 15 GHz, thus advocating this approach as a means of realizing high power HMMICs.