Ta-Doped SnO2 as a reduction–resistant oxide electrode for DRAM capacitors

Noble metal oxides, such as RuO2, have received attention as capacitor electrodes in dynamic random access memories (DRAMs). Noble metal oxides generally have a high work function compared to noble metals and enhance the crystallinity of dielectric materials grown on them, resulting in a lower leakage current and higher dielectric constants. Despite these advantages, noble metal oxides are easily reduced during the dielectric film, such as TiO2, growth on top or by annealing under a forming gas atmosphere, degrading the capacitor performance. In this work, Ta-doped SnO2 is suggested as a potential capacitor electrode for DRAMs. Ta-Doped SnO2 films have a high work function, comparable to that of RuO2, and induce the formation of a high-temperature phase with a high dielectric constant, namely rutile TiO2, at low temperatures. More importantly, the Ta-doped SnO2 films show suitable structural and chemical stabilities, even after annealing at 400 °C under a forming gas atmosphere. RuO2 films, on the other hand, turn into a mixture of RuO2 and Ru after annealing under the same conditions. These findings suggest that Ta-doped SnO2 could serve as capacitor electrodes in next-generation DRAMs.

[1]  C. Hwang,et al.  Interface Engineering for Extremely Large Grains in Explosively Crystallized TiO2 Films Grown by Low-Temperature Atomic Layer Deposition , 2017 .

[2]  J. F. Conley,et al.  Atomic Layer Deposition of Ruthenium and Ruthenium Oxide Using a Zero-Oxidation State Precursor , 2017 .

[3]  D. Jeong,et al.  Control of the initial growth in atomic layer deposition of Pt films by surface pretreatment , 2015, Nanotechnology.

[4]  C. Hwang,et al.  Novel high-κ dielectrics for next-generation electronic devices screened by automated ab initio calculations , 2015 .

[5]  Alexander G. Agrios,et al.  Transparent conducting aerogels of antimony-doped tin oxide. , 2014, ACS applied materials & interfaces.

[6]  T. Yagi,et al.  Thermophysical properties of SnO_2-based transparent conductive films: Effect of dopant species and structure compared with In_2O_3-, ZnO-, and TiO_2-based films , 2014 .

[7]  C. Hwang,et al.  Atomic Layer Deposition of SrTiO3 Films with Cyclopentadienyl-Based Precursors for Metal–Insulator–Metal Capacitors , 2013 .

[8]  Doo Seok Jeong,et al.  Titanium dioxide thin films for next-generation memory devices , 2013 .

[9]  C. Hwang,et al.  Impact of bimetal electrodes on dielectric properties of TiO2 and Al-doped TiO2 films. , 2012, ACS applied materials & interfaces.

[10]  C. Hwang,et al.  Study on Initial Growth Behavior of RuO2 Film Grown by Pulsed Chemical Vapor Deposition: Effects of Substrate and Reactant Feeding Time , 2012 .

[11]  J. Roh,et al.  Ru Films from Bis(ethylcyclopentadienyl)ruthenium Using Ozone as a Reactant by Atomic Layer Deposition for Capacitor Electrodes , 2012 .

[12]  C. Hwang,et al.  Improvement in the leakage current characteristic of metal-insulator-metal capacitor by adopting RuO2 film as bottom electrode , 2011 .

[13]  C. Hwang,et al.  Growth of RuO2 Thin Films by Pulsed-Chemical Vapor Deposition Using RuO4 Precursor and 5% H2 Reduction Gas , 2010 .

[14]  Sang Woon Lee,et al.  Capacitors with an Equivalent Oxide Thickness of <0.5 nm for Nanoscale Electronic Semiconductor Memory , 2010 .

[15]  T. Hitosugi,et al.  Fabrication of highly conductive Ta-doped SnO2 polycrystalline films on glass using seed-layer technique by pulse laser deposition , 2010 .

[16]  P. Ágoston,et al.  Intrinsic n-type behavior in transparent conducting oxides: a comparative hybrid-functional study of In2O3, SnO2, and ZnO. , 2009, Physical review letters.

[17]  J. Aarik,et al.  Epitaxial growth of high-κ TiO[sub 2] rutile films on RuO[sub 2] electrodes , 2009 .

[18]  Cheol Seong Hwang,et al.  Al‐Doped TiO2 Films with Ultralow Leakage Currents for Next Generation DRAM Capacitors , 2008 .

[19]  J. Roh,et al.  Modified atomic layer deposition of RuO2 thin films for capacitor electrodes , 2007 .

[20]  Cheol Seong Hwang,et al.  Transformation of the Crystalline Structure of an ALD TiO2 Film on a Ru Electrode by O3 Pretreatment , 2006 .

[21]  C. Hwang,et al.  High dielectric constant TiO2 thin films on a Ru electrode grown at 250 °C by atomic-layer deposition , 2004 .

[22]  Haydn H D Chen,et al.  Microstructural evolution and electrical property of Ta-doped SnO2 films grown on Al2O3(0001) by metalorganic chemical vapor deposition , 2002 .

[23]  Sang Woo Lee,et al.  Electrical properties of Ta-doped SnO2 thin films prepared by the metal–organic chemical-vapor deposition method , 2001 .

[24]  R. Lamb,et al.  Ruthenium oxide and strontium ruthenate electrodes for ferroelectric thin-films capacitors , 2000 .