High Performance Cu-doped SiO₂ ReRAM by a Novel Chemical Soak Method

Abstract

In this paper, a novel chemical soak method is proposed to fabricate a Cu-doped SiO 2 ReRAM device. This method can easily fabricate a lightly Cu-doped SiO 2 film and effectively improve the reliability of the conventional Cu-doped SiO 2 ReRAM device. A reproducible bipolar switching characteristic with set/reset voltage (ca. 2.5 V/ -0.7 V) is performed in this device and the electrical conduction in HRS and LRS are related to Poole-Frenkel and Ohmic conduction, respectively. Excellent performance in terms of high on/off ratio (~10 6 ), narrow range distribution of set and reset voltages, stable data retention, and up to 110 times switching cycles has been achieved by this novel chemical soak method for Cu-doped SiO 2 ReRAM device. IntroductionRecently, ReRAM (Resistive Random Access Memory) has been researched extensively as a promising candidate for the next-generation nonvolatile memory. Cu-doped SiO 2 as a resistive layer for ReRAM application has been reported to show the resistive switching behavior (1). The switching mechanism has also been proposed by the migration and accumulation of copper ions from copper electrode into the resistive layer (1-2). After several times of set/reset operations, the increment of copper ions concentration in resistive layer results in a hardly ruptured metallic filament under reset process. Thus, the concentration of copper ions in the resistive layer plays an important role in electrical properties, especially for reliability characteristics. In addition, there are many research for Cu-doped SiO 2 ReRAM device (1, 3-5), while the endurance characteristic is a lack of investigation.In this study, a novel chemical soak method is provided to fabricate a Cu-doped SiO 2 ReRAM device. Results showed that this novel chemical soak process is promising to fabricate a high performance Cu-doped SiO 2 ReRAM device. ExperimentalA new technique introduced copper into SiO 2 films by soaking the film in copper sulfate solution is successfully demonstrated in this paper. The chemical solution consists of ECS Transactions, 41 (3) 469-473 (2011) 10.1149/1.3633063 © The Electrochemical Society 469 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 131.215.174.8 Downloaded on 2015-06-27 to IPcopper sulfate pentahydrate and DI water. Thereamong, the molarity of copper sulfate pentahydrate is 0.4 M. The copper sulfate solution was stirred and heated to 65 o C on hot plate; meanwhile, the temperature of solution was monitored by thermograph. Samples were fabricated on prepared SiO 2 /Si-sub wafers. Firstly, a 200-nm thick TaN metal layer as the bottom electrode was deposited on the SiO 2 /Si-sub wafer by using sputtering. Then a 20-nm thick SiO 2 film was deposited by PECVD as the resistive layer for ReRAM devices. Subsequently, samples were soaked in the copper sulfate solution at 65 o C for 15 min and baked at 250 o C for 30 min in an oven for eliminating residual moisture. Finally, a 200-nm thick top TaN electrode was d...

Modeling of Diffusion and Incorporation of Interstitial Oxygen Ions at the TiN/SiO2 Interface

“…The processing and handling benefits are derived from the abundance of SiO 2 expertise in the CMOS technology, particularly in the growth and electrical characterization of SiO 2 films. The SiO 2 based devices are divided into two main types: those based upon the inter-diffusion of metal ions, such as via electrochemical metalisation, [19][20][21][22][23][24][25][26] and valence change memory (VCM) where a CF is formed as a result of reduction under bias application. 1,2,[5][6][7][8]17 In VCM the CF is made up of oxygen vacancies, dependent upon material and mode of operation either V O or O i are suggested to be the mobile species during forming.…”

“…The processing and handling benefits are derived from the abundance of SiO 2 expertize in the complementary metal–oxide–semiconductor technology, particularly in the growth and electrical characterization of SiO 2 films. The SiO 2 -based devices are divided into two main types: those based upon the interdiffusion of metal ions, such as via electrochemical metalization, − and valence change memory (VCM) where a CF is formed as a result of the reduction under bias application. ,,− , In VCM, the CF is made up of oxygen vacancies, dependent upon the material and mode of operation either V O or O i are suggested to be the mobile species during forming . Forming has been kinetically modeled in a range of other materials giving some valuable insights into the energy barriers and time scales. − SiO 2 has only been of limited interest to the ReRAM community as the dielectric breakdown of stoichiometric SiO 2 requires high bias application, as evidenced by its role as a gate oxide.…”