Demonstration of crystalline IGZO transistor with high thermal stability for memory applications

Abstract

Highly ordered crystalline InGaZnO (c-IGZO) TFTs have been demonstrated in subsequent processes above 550 °C compatible with memory applications. Notably, c-IGZO featured strong immunity to high temperature and hydrogen-containing processes unlike amorphous IGZO (a-IGZO) where agglomeration occurs. The c-IGZO TFTs with optimized process in this study show a higher on-current ($\mathrm{I}_{\mathrm{o}\mathrm{n}}$) at a similar $\mathrm{V}_{\mathrm{t}\mathrm{h}}$ of −1 V, and $\mathrm{I}_{\mathrm{off}}$ of $1.82\times 10^{-18}$ A/$\mu$m compared with a-IGZO TFTs. In addition, striking enhancement in the short channel margin and $\mathrm{V}_{\mathrm{th}}$ stability over a-IGZO was achieved. With thin gate-oxide (50 Å), the improved device performance was realized such as S.S. $\times$ 0.41, DIBL $\times$ 0.18, and $\mathrm{I}_{\mathrm{on}}$× 76.5 compared with a-IGZO TFT at $\mathrm{T}_{\mathrm{ox}}$ 100 Å.