Nonequilibrium Nitrogen Spike Annealing for Crystallization Enhancement Achieves High Mobility and Reliability in IGO TFTs

Abstract

Poly-crystallized In-Ga-O (IGO) semiconductor has the potential for application in high-density memory and back end of line (BEOL) integration with CPU. Since the development of In₂O₃-based multi-cation oxides, i.e., IGZO, such material is very difficult to be poly-crystallized under the limitation of BEOL temperature. Here, a novel Nitrogen-Spike Annealing (NSA) method is demonstrated, this nonequilibrium annealing process utilizes a transient high temperature to induce crystallization while reducing the overall thermal budget. During NSA, the O atoms are more intended to bond with Ga, resulting in a more rigid framework that stabilizes the O atoms. The crystal orientation of the NSA treated IGO film is more concentrated compared with the conventional equilibrium annealed one. Furthermore, poly-IGO thin-film transistors (TFTs) with high crystallinity and more centered crystal orientation are demonstrated through material characterization. Electrical characteristics revealed that the poly-IGO TFT exhibits high mobility of ≈86.2 cm² V s⁻¹ and enhanced reliability after NSA treatment. These findings will advance the design and improvement of oxide semiconductor memory applications.