A flexible stress sensor using a sub-10μm silicon chip technology

Here, we present a flexible sensor based on a stack of two ultra-thin IC-chips, exploiting the excellent chip thickness control in Chipfilm™ technology. The sensor consists of an almost stress-compensated bottom chip and a stress-sensitive top chip that are in good mechanical and thermal contact. Moreover, for the first time, we demonstrate that the chip thickness can be reduced to 10 μm, with the bulk Si body measuring only 7 μm, thus allowing for flexible chipstacks measuring only 20 μm in height. Furthermore, we demonstrate a self-aligned Through-Silicon Via (TSV) process in Chipfilm™ enabling 3D integration of such ultra-thin flexible chip pairs.