ALD of Manganese Silicate Roy G. Gordon,1,2* Lu Sun,2 Qiang Chen,3 Jin-Seong Park4 and Sang Bok Kim1 1Department of Chemistry and Chemical Biology 2School of Engineering and Applied Sciences Harvard University, Cambridge, MA, USA 3Beijing Institute of Graphic Communication, Beijing, China 4Hanyang University, Seoul, Korea *Email: gordon@chemistry.harvard.edu Harvard University Outline Potential Applications of Manganese Silicate ALD Process for Manganese Oxide, MnO ALD Process for Manganese Silicate Properties of Manganese Silicate Harvard University 2 Potential Applications of MnSixOy Copper wires in computer chips could use MnSixOy as a „ barrier to diffusion of copper, water and oxygen „ adhesion promoter between copper and insulators „ nucleating layer for vapor deposition of copper Harvard University 3 Manganese Precursors NN Mn NN manganese(II) bis(N,N’-diisopropylpentamidinate) melting point: 60 °C boiling point: 120 °C / 0.02 torr NN Mn NN manganese(II) bis(N,N’-di-tert-butylacetamidinate) melting point: 107 °C boiling point: 100 °C/ 0.07 torr Harvard University 4 Saturation Curve for Manganese Oxide Saturated for doses > 10-5 moles/cycle Thickness per cycle (A/cycle) 1.2 200oC Co-reactant: water 1.0 0.8 0.6 NN 0.4 Mn NN 0.2 0.0 0 4 8 12 16 20 24 28 Mn-ipr (Pmole/cycle) Harvard University 5 Saturation Curve for Manganese Oxide Saturated for doses > 10-5 moles/cycle Thickness per cycle (A/cycle) Refractive Index 1.0 3.0 0.8 2.5 2.0 0.6 1.5 0.4 N N Mn 1.0 N GrowthNrate 0.2 @200oC/85oC or 95oC 0.5 Refractive Index 0.0 0.0 0 5 10 15 20 25 Pmole/cycle (10-6 mole/cycle) Harvard University 6 Thickness per Cycle for Manganese Oxide nearly constant from 200 to 340 oC 1.0 2.5 0.8 2.0 Thickness per cycle (A/cycle) Refractive Index 0.6 1.5 0.4 1.0 NN Mn 0.2 NN Refractive Index growth rate # of cycle = 1000 95oC*3, H O*2 2 0.5 0.0 0.0 200 240 280 320 360 Deposition temperature Harvard University 7 Rutherford Backscattering Spectroscopy => Stoichiometry MnO Adding O2 cycles => MnO2 Data Simulation Mn Co-reactant: water A.U. C substrate O 0 200 400 600 800 1000 Channel (eV) Harvard University 8 X-Ray Photoelectron Spectroscopy < 1% C or N impurities Mn (2p3) : 641.9 eV O (1s) : 530.9 eV carbon-free : about 285 eV (after sputtering 1 min) Mn 2p3 O 1s Intensity (A.U.) 0 Harvard University 200 400 600 800 Binding Energy (eV) 1000 9 XRD shows polycrystalline MnO 250oC MnO Cubic structure Intensity (A. U.) MnO(111) MnO(200) MnO(220) 20 30 40 50 60 2T Harvard University 10 Precursors for Silicon and Oxygen H O O Si O O H O O Si O O tris-tert-butoxysilanol (TBS) melting point: 63 - 65 °C boiling point: 205 - 210 °C/ 760 torr tris-tert-pentoxysilanol (TPS) melting point: < 20 °C boiling point: 96-99 °C/ 2-3 torr Harvard University 11 ALD Conditions for Manganese Silicate Substrate: SiO2/Si UV ozone cleaning: 2 min Drying at 350°C: 1 hour Mn amidinate source =105°C Si/O source (TPS)=120°C T(substrate)= 350°C Cycle times (s): 1/30/4/30 (Mn(amd)/purge/TPS/purge) growth per cycle = 0.43 nm thickness (nm) 20 15 10 5 0 0 10 20 30 40 50 cycles High growth per cycle due to a catalytic mechanism similar to that of aluminum-catalyzed silica: Dennis Hausmann, Jill Becker, Shenglong Wang, Roy G. Gordon, Science 298, 402 (2002) Harvard University 12 Saturation Curve for MnSixOy vs. Silicate Precursor Growth rate (nm/cycle) 0.55 0.50 0.45 0.40 0.35 0.30 0 2 4 6 8 10 12 14 16 18 TPS doses Harvard University 13 TEM => Amorphous Structure MnSixOy (35nm) glue Si Harvard University 14 STEM EDX Mapping of Elements Mn Si O Harvard University 15 Composition by Rutherford Backscattering Spectroscopy Cycles Mn Si O 1015at/cm^2 1015at/cm^2 1015at/cm^2 Mn:Si:O 10 2.32 6.2 24 1 : 2.7 : 10 20 5.56 15 47 1 : 2.7 : 8 50 15.4 41 117 1 : 2.7 : 7.6 Stoichiometry ~ MnSi2.7O7.6 so Mn is oxidized to Mn4+ Harvard University 16 Cu diffusion test anneal samples in N2 for 1h at 450 C, use Ni etchant to remove Cu film, then EDX Cu 200 nm MnSixOy 10 nm SiO2 8 nm Si Cu SiO2 Si 200 nm 8 nm visible appearance Harvard University 17 CV tests after electric field at room temperature Cu 200 nm MnSixOy 15 nm SiO2 60 nm Si Cu SiO2 Si 200 nm 60 nm 10V for 1min 12V for 1min 15V for 1min 10V for 1min 12V for 1min 15V for 1min Harvard University 18 Effectiveness of MnSixOy as a Cu Diffusion Barrier Composition SiO2 MnSi2.7O7.6 MnO Structure amorphous amorphous polycrystalline Cu Barrier no yes no Diffusion Pathway open tetrahedral network paths blocked by Mn ions grain boundaries Harvard University 19 Acknowledgements Precursors supplied by Dow Chemical, Sigma-Aldrich and Strem Chemical The work was supported as part of the Center for the Next Generation of Materials by Design, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science Facilities at Harvard’s Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Infrastructure Network (NNIN), previously supported by the U. S. National Science Foundation Harvard University 20