(Invited) SiGe BiCMOS Heterogeneous Integration Using Wafer Bonding Technologies

Abstract

Heterogeneous integration has been a very attractive research topic for the last decades. Due to the limitations for further device scaling the More-than-Moore approach based on heterogeneous integration has been pointed out as the key integration path for future smart system integration [1]. Temporary and permanent wafer bonding technologies are one of the key enabling technologies for heterogeneous integration. Temporary wafer bonding is a well-established bonding technique to provide a stable handling and fabrication of ultra-thin silicon wafers. Permanent wafer bonding with various electrical isolating or conductive bonding interfaces is applied for wafer-level heterogeneous device integration [2]. Making available both temporary and permanent wafer bonding technologies together with a high performance SiGe BiCMOS technology will pave the way for new applications like millimeter-wave packaging, 3D-integration and smart sensors to realize multi-functional and miniaturized systems. The potential of temporary and permanent wafer bonding techniques for heterogeneous integration of a high performance SiGe BiCMOS technology with additional devices and technology modules will be presented by three different application examples namely BiCMOS embedded Through-Silicon Vias (TSV), silicon interposer including substrate-integrated waveguides and BiCMOS embedded microfluidics. With respect to the different applications the potential and the main technology obstacles for SiGe BiCMOS temporary and permanent wafer bonding will be highlighted. While the temporary wafer bonding process with subsequent wafer thinning and thin wafer backside fabrication is mainly limited by the robustness of adhesives against high temperature and high vacuum process conditions, the permanent wafer bonding based on SiO2-SiO2 fusion bonding is mainly limited by the demanding surface requirements in terms of roughness and wafer bow which has been optimized to fulfill the requirements. By optimizing the SiGe BiCMOS technology both temporary and permanent wafer bonding together with subsequent semiconductor fabrication becomes feasible. In summary, the development of wafer bonding application together with an industrial-level BiCMOS process will be presented. By the use of temporary and permanent wafer bonding new applications in the area of heterogeneous integration becomes feasible making SiGe BiCMOS technologies more attractive for future smart system applications.