Chul-Hwan Lee

Stack friendly all-oxide 3D RRAM using GaInZnO peripheral TFT realized over glass substrates

This paper reports on new concept consisting of all-oxide-based device component for future high density non-volatile data storage with stackable structure. We demonstrate a GaInZnO (GIZO) thin film transistors (TFTs) integrated with 1D (CuO/InZnO)-1R (NiO) (one diode-one resistor) structure oxide memory node element. RRAM (Resistance Random Access Memory) has provided advantages in fabrication which have made these works possible. Therefore we also suggest methods and techniques for improving the distribution in bi-stable resistance characteristics of the NiO memory node. In order to fabricate stack structures, all device fabrication steps must be possible at low temperatures. The benefits provided by low temperature processes are demonstrated by our devices fabricated over glass substrates. Our paper shows the device characteristics of each individual component as well as the characteristics of combined select transistor with 1D-1R cell. XPS analysis of NiO RRAM resistance layer deposited by ALD confirms similar conclusions to previous reports of the importance of metallic Ni content in sputtered NiO for bistable resistance switching. Also we herein propose a generalized stacked-memory structure to minimize on-chip real estate to maximize integrated density.

Analysis on data retention time of nano-scale DRAM and its prediction by probing the tail cell leakage current

Characteristics of the data retention time (tRET) of nano-scale DRAM have been described. In addition, new approaches to enhance tRET and their properties have been analyzed. To optimize the process, we developed the tRET-modeling methodology, which has a good agreement with experimental data. The key feature of the methodology is an indirect probing of the tail leakage current by fitting the leakage model to reproduce the measured characteristics of the retention. The model shows the GIDL current is a major factor determining tRET of 80nm RCAT technology.