Effect of Ion Implant Modification on Electrical Properties of MTM Antifuse a-Si Films

Based on the basic theories of Poole Frenkel (P-F) emission, Fowler Nordheim (F-N) tunnel and Ohmic transport models, the linear relationship between breakdown voltage (BV) and leakage, I-V and accelerated stress test (AST) characteristics of a-Si dielectric layers are analyzed by the manufactured metal-to-metal (MTM) anti-fuse cells in details. The effects of different ion implant conditions on the amorphization degree of a-Si films are characterized by X-Ray diffraction (XRD). Meanwhile, the influence of annealing and ion implant process on the electrical properties of a-Si thin films are studied. Lastly, it is found that the implantation of E15 Si, Ar and SiF3 ions can promote the further amorphization of a-Si films, effectively improve the BV uniformity, reduce the leakage current and enhance the reliability of MTM anti-fuse cells. Especially, SiF3 ion implantation can reduce the leakage current of MTM anti-fuse cells by two orders of magnitude, which is mainly attributed to a-Si conductive band being greatly elevated by strong negative F ions, and it results in the increase of the potential barrier of a-Si/metal interface. Therefore, it can be further proved that SiF3 ion implant process may promote modification of a-Si films.