Endurance Characteristics of Amorphous-InGaZnO Transparent Flash Memory With Gold Nanocrystal Storage Layer

Abstract

The amorphous indium–gallium–zinc-oxide (a-IGZO) thin-film transistor (TFT)-based nonvolatile transparent Flash memory devices were fabricated with gold (Au) nanocrystal storage layer. The performance and the reliability of transparent memory devices have been characterized by experiment and technology computer-aided design simulation. This memory device shows a large-enough memory window <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\Delta V = \hbox{4.7} \ \hbox{V}$</tex></formula> at the program/erase (P/E) voltage <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${V_{ \rm PGM}/V_{\rm ERS}} = \hbox{35}/-\hbox{35} \ \hbox{V}$</tex></formula> for the P/E time <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${T_{\rm PGM}/ T_{\rm ERS}} = \hbox{3/25} \ \hbox{s}$</tex></formula> . The memory window was kept almost the same after 1050 P/E cycles; however, the center voltage of the memory window <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(V_{C})$</tex></formula> was shifted in a negative direction. The cycling effect was explained by the change in the density of states (DOS) and the acceptor-like interface-trap density <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$D_{\rm itA}(E)$</tex></formula> in the a-IGZO channel layer with increasing P/E cycles. The main mechanism for the change in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$V_{C}$</tex></formula> was found to be the accelerated injection of holes into the gate insulator due to the energy band bending during the erase operation.