Selective Atomic Layer Deposition of Zirconium Oxide on Copper Patterned Silicon Substrates

1. Selective Atomic Layer Deposition of Zirconium Oxide on Copper Patterned Silicon Substrates Jaya Parulekar, Illinois Institute of Technology SatheesSelvaraj, University of Illinois at Chicago Christos Takoudis, University of Illinois at Chicago NSF REU: UIC August 1st, 2013

2. Motivation • Applications in microelectronics and nanoelectronics • Semiconductors, transistors, memory and fuel cells • Challenges • Need for transistor gates made with high dielectric constant materials • Need to achieve a precise level of thickness for gate dielectric layers to prevent problems, such as leakage • Need to selectively deposit layers on to specific surfaces

3. Atomic Layer Deposition (ALD) Process by which thin films are deposited on surface of substrates at the Ångström level Precursors are injected one at a time in a sequential and self-limiting manner

4. Schematic of ALD design Metal Precursor Reactor Furnace Silicon wafer Nitrogen Quartz tube Substrate loading port Vacuum pump LN2 cold trap Ethanol Nitrogen Activated switching valve

5. ALD Reactor

6. Selective atomic layer deposition (SALD) Selectively depositing films on patterned substrates Molecular masking and self-assembled monolayers are techniques for SALD, but are inefficient More efficient and practical method: SALD based on surface physics and chemistry of different materials

7. Work from previous studies Growth of HfO2 was observed on silicon immediately Not observed on copper after 25 cycles Growth on copper after 50, but not to the extent of silicon Figure fromQ. Tao, C. Takoudis, and G. Jursich, Appl. Phys. Lett. 96, 192105 (2010)

8. Work from previous studies Increased amounts of Hf and O and decreased amounts of Si from 0 to 50 ALD cycles indicate HfO2 film growth HfO2 deposition for copper is not observed until after more than 25 ALD cycles Table fromQ. Tao, C. Takoudis, and G. Jursich, Appl. Phys. Lett. 96, 192105 (2010)

9. Reduction of copper oxide to metallic copper Method to achieve purely SALD As the number of cycles increases, the copper surface undergoes oxidation and deposition is observed. Challenge: selecting a reducing agent powerful and practical enough to ensure deposition of metal oxide Reducing Agent selected: Ethanol

10. Accomplishments and Open Challenges Adding a reactant line to supply ethanol to the ALD reactor E-beam deposition of 200 nm metallic copper on silicon substrate Chose zirconium precursor, (Tris(dimethylamino)cyclopentadienyl zirconium).

11. Accomplishments and Open Challenges • Difficulty in measuring film thickness on copper with ellipsometer • Four point probe to measure sheet resistance

12. Accomplishments and Open Challenges Ran trials on silicon wafers at 10, 15, 20, 25, 50, 75, 100, 150, and 200 cycles XPS on silicon wafers treated with ethanol and zirconium precursor Determined H2O oxidant line is unnecessary

13. Results Obtained Linearity is observed, indicating ALD has occurred on silicon substrate *Carried out at 200 °C and base pressure of 500 mTorr

14. Results Obtained O 1s Zr 3d Zr 3p C 1s Si 2p O KVV Zr 4p Zr 3s

15. Future Work XPS for copper patterned wafers Four point probe analysis Submitting for potential publication in reference journal

16. Acknowledgements • The National Science Foundation: REU program • EEC-NSF Grant #1062943 • Additional National Science Foundation support • CBET-NSF Grant #1346282 • Air Liquide for supply of precursor • Professor Christos Takoudis and Dr. Gregory Jursich • SatheesSelvaraj, Graduate Student • The Advanced Materials Research lab • Fellow REU participants

17. References [1] O. Engstrom, B. Raeissi, S. Hall, O. Buiu, M.C. Lemme, H.D.B. Gottlob, P.K. Hurley, K. Cherkaoui, Solid State Electron. 51 (2007) 622. [2] J.W. Long, B. Dunn, D. R. Rolison, and H.S. White, Chem. Rev. 104. 4463 (2004) [3] X. Jiang, H. Huang, F.B. Prinz, and S.F. Bent, Chem. Mater, 20, 3897, (2008) [4] R. Xu, Q. Tao, Y. Yang, C.Takoudis, Thin Solid Films, 520 (2012) 6752–6756 [5] Q. Tao, C. Takoudis, and G. Jursich, Appl. Phys. Lett. 96, 192105 (2010) [6] X.R. Jiang and S.F. Bent, J. Phys Chem. 113 17613 (2009) [7] Elam, J. W.; Zinovev, A.; Han, C. Y.; Wang, H. H.; Welp, U.; Hryn, J. N.; Pellin, M. J. Thin Solid Films, 515, 1664 (2006) [8] G. Dey, S.D. Elliot. J. Phys. Chem. A, 116 (35), pp 8893–8901 (2012) [9] Z. Li, A. Rathu, R.G. Gordon. Journal of the Electrochemical Society. 153 (11) C787-C794 (2006) [10] B.S. Lim, A. Rathu, R.G. Gordon, Nature Materials: Harvard University, 2, pp 749-754 (2003) [11] P. J. Soininen, K.-E. Elers, V. Saanila, S. Kaipio, T. Sajavaara, and S. Haukka, J. Electrochem. Soc. 152, (2), G122-G125(2005) [12] A.P. Premkumar, N.S. Prakash, F. Gaillard, N. Bahlawane, Materials Chemistry and Physics 125 (3) pp 757-762 (2011) [13] A. Satta, D. Shamiryan, M.R. Baklanov, C.M. Whelan, Q.T. Le, G.P. Beyer, A. Vantomme, K. Maex, J. Electrochem. Soc. 150, 5, G300-G306 (2003) [14] J. A.T. Norman, M. Perez, S. E. Schulz, T. Waechtler, Microelectron. Eng. 85, 2159-2163 (2008) [15] K. L. Chavez, D. W. Hess, J. Electrochem. Soc. 148. 11. G640-G643 (2001)