Flexible CMOS chip converted by a novel chip transformation process

In this Letter, the authors report a flexible CMOS chip converted by a novel chip transformation process. To realise a truly flexible CMOS chip, a two-step etching process was employed in the transformation process: (i) vapour etching to remove inter-dielectric layers followed by polymer encapsulation and (ii) plasma etching to remove the substrate of the chip. The I–V results measured after the chip transformation process show a voltage variance of <0.8% compared to the rigid chip. The bending test also revealed very small changes (0.6%) under strain conditions. Their results offer a viable route to use the foundry-fabricated CMOS chip for flexible chips; thus, a high-performance flexible chip can be realised. This technology will enable us to utilise various foundry-processed chips for future flexible applications such as health and environment monitoring, advanced mobile communication systems, and wearable electronics via a simple post-transformation process.