A Possibility of Crystalline Indium-Gallium-Zinc-Oxide to Very Large Scale Integration

We have found that an IGZO film can exhibit a c-axis orientation by extremely highly purifying the oxide semiconductor. We call this IGZO as CAAC (C-Axis Aligned Crystal). CAAC structure can be achieved even on an amorphous and concave-convex surface. The CAAC structure has a crystal morphology in which a crystal grain boundary is not observed. By virtue of the CAAC structure, an off current Ioff is on the order of yA/mu m (10(-24) A/mu m) even with a channel length of 0.45 mu m at a temperature of 85 degrees C. This can be used for an ideal four-terminal switching element of a voltage input type having an on/off ratio of 20 digits or greater. Also, the temperature characteristics of Vg-Id are stable at temperatures ranging from. -25 degrees C to 150 degrees C. We attempted to apply it to a normally-off CPU and FPGA with a small increase of F2 and a non-volatile memory without degradation.