A study of the reliability of MOSFETs in two stacked thin chips for 3D system in package

RF wireless communication systems consist of many different components, analog/digital CMOS, passive components, sensors. The fabrication processes of these components are so different. System in package (SiP) can mount different chips fabricated by different processes in a package. Hence, SiP is effective, especially for wireless communication systems. On SiP, thinning of stacked chip thickness is required for better heat radiation and thinner packaging height (Ikeda, A. et al., Proc. IEEE Int. Conf. on Microelectronic Test Structures, p.161-4, 2004). For highly reliable SiP, we investigated MOSFET characteristics on a thinned wafer for two stacked chips bonded by flip chip Au-Au bump interconnection.