Ultra‐Flexible Monolithic 3D Complementary Metal‐Oxide‐Semiconductor Electronics

Flexible electronics based on complementary metal‐oxide‐semiconductor (CMOS) technology have enabled a smart soft world. However, the trade‐off among flexibility, density, and electrical performance has been a long‐lasting unresolved issue. Here, a monolithic three‐dimensional (M3D) CMOS design is proposed to address this problem and realize ultra‐flexible electronics with high electronic‐performance and integration. This design utilizes vertically stacked p‐type carbon nanotube transistors and n‐type indium gallium zinc oxide ones, which share common gates and drains, saving the inter tier vias required in the traditional M3D structure to reduce routing and improve flexibility. With this design, CMOS logic gates, multi‐stage circuits, ring oscillators (ROs) and memory modules, are demonstrated. This design enables circuits to save up to 45% of area compared with their planar counterparts. Particularly, inverters exhibit a record‐high gain of 191, and 55‐stage ROs can operate well even after bending at a 500‐µm radius for 50 cycles, exhibiting the highest flexibility among the reported ones. The ultra‐flexible and high‐integration RO enables a wearable light recorder to collect harmful blue light shining into human eyes by simply attaching the circuits on a contact lens. This integration method provides possibilities for developing complex‐function wearable electronics. A monolithic three‐dimensional (M3D) design is proposed to construct ultra‐flexible complementary metal‐oxide‐semiconductor electronics with high electrical‐performance and integration by stacking n‐ and p‐type transistors vertically and saving inter tier vias used in conventional M3D structure. The ultra‐flexible and high‐integration circuits enable a wearable light recorder to collect the harmful blue light illuminated into human eyes by attaching the circuits on a contact lens.