PROJECT TITLE :

Failure Analysis of Nitrogen-Doped Ge2Sb2Te5 Phase Change Memory

ABSTRACT:

Section amendment memory (PCM) devices, consisting of nitrogen-doped Ge2Sb2Te5 (NGST) chalcogenide, are totally integrated in the 110-nm complementary metal-oxide-semiconductor technology. By combining high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS), we tend to totally analyze the initial fail cells. The direct results of structural observation and compositional analysis of the phase amendment cells are displayed. The initial fail cells, which are initially at the additional low-resistance state, can't be operated to high-resistance state when applying the traditional reset condition as most of the successfully reset cells. Hexagonal Ge2Sb2Te5 (GST) and TiTe2 phases are observed in the microstructure of the initial fail cells. The component analysis indicates that the atomic composition of the fail cells changes to nonstoichiometric phase. Titanium atoms incorporate into the GST-based mostly film, whereas tellurium and antimony atoms diffuse into the titanium nitride adhesive layer. The germanium atoms accumulate at the underside electrode. It is believed that section change materials, which bear terribly high thermal budget throughout back-end processing at 350°C or perhaps high at 400°C during the fabrication, will inevitably cause intrinsic problems in stability of the PCM devices. The irreversible modification of the NGST composition and these hexagonal GST and TiTe2 phases will directly end in the first failure of the PCM.