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Spontaneous N incorporation into the Si(100) surface

Spontaneous N incorporation into the Si(100) surface. ◎ Introduction - Si oxynitride as gate dielectrics - Review of previous results ◎ Experiments - MEIS & PLS U7 experimental chamber ◎ Results and Discussion - N 1 s core-level spectra - MEIS result of NO/Si(100)

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Spontaneous N incorporation into the Si(100) surface

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  1. Spontaneous N incorporationinto the Si(100) surface ◎ Introduction - Si oxynitride as gate dielectrics - Review of previous results ◎ Experiments - MEIS & PLS U7 experimental chamber ◎ Results and Discussion - N 1s core-level spectra - MEIS result of NO/Si(100) - Stable geometry for N-incorporation by calculation ◎ Conclusion J. W. Kim, Y. D. Chung, C. N. Hwang, H. W. Yeom* (Yonsei University) K. J. Kong, D. Y. Ahn, B. D. Yu (University of Seoul) Y. H. Ha, D. W. Moon (Korea Research Institute of Standards & Science) ASSRC & IPAP, Yonsei Univ.

  2. Importance of N incorporation in silicon (oxy)nitride • Application to gate dielectrics • Initial formation of Silicon nitride and N-rich layer at SiOxNy/Si interface Gusev, IBM J. Res. Devel. (1999) ASSRC & IPAP, Yonsei Univ.

  3. Previous Results of NO, NH3/Si(100) H H H H N N * Complete dissociative adsorption of NO at RT and formation of Nitride at elevated temperatures N O O N Si Si RT * Sucessive dissociation of N-H as temperature goes up H N H H H H H N N 500~700 K Si Si Si anneal RT Questions about the dissociated N species : Chemical configuration, depth population, energetically favorable geometries ASSRC & IPAP, Yonsei Univ.

  4. Experiments - HRPES (PLS U7) & MEIS (KRISS) Anal. chamber Sample manipulator (5-axis motion) Prep. chamber SES200 analyzer H+ beam Load lock 5-axis Sample manipulator Photon • H+ energy : ~ 100 keV • Toroidal electrostatic energy • analyzer with 2-axis motion • Unique soft X-ray undulator beam • line in PLS • Total resolution : 350 meV for N 1s ASSRC & IPAP, Yonsei Univ.

  5. PES Results : NO, NH3 /Si(100) – N 1s core levels NSi3 hυ = 500 eV hυ = 450 eV ASSRC & IPAP, Yonsei Univ.

  6. MEIS Results : NO/Si(100) Location of each element in N-Si3 species Energy (keV) ASSRC & IPAP, Yonsei Univ.

  7. Calculations of initial adsorption geometry and its energy • Density-functional theory (DFT) in the local density approximation (LDA) • Norm-conserving pseudopotential of Troullier and Martins • Plane wave basis set with Ecut = 50 Ry • Iterative scheme for minimization of total energy • p(2 x 2) surface unit cell with 9 Si layers + 5 vacuum layers • Fully relaxed geometry by Hellman-Feynman forces ASSRC & IPAP, Yonsei Univ.

  8. Stable N-incorporation geometry: three-fold Hexagonal Center (-0.25 eV) Substitution of down Si dimer (-0.59 eV) ASSRC & IPAP, Yonsei Univ.

  9. Stable N-incorporation geometry: four-fold BR down (-0.57 eV) D-down (-0.05 eV) 1.92 1.91 1.78 1.78 ASSRC & IPAP, Yonsei Univ.

  10. Conclusion • N atoms incorporate into the subsurface Si layers spontaneouslyafter N-O dissociation or N-H bond breaking from initial adsorption of NO and NH3. • Chemical configuration (N-Si3) and depth population (3rd or 4th layer) of the stable N atom are proved by PES & MEIS experimentally. • Subsurface incorporation is stabilized by a few possible geometries which are suggested by ab initio LDA calculation. : Hexagonal center or Substitution of down Si dimer • This unusual behavior of N-incorporation successfully explains initial nitridation & the N-rich layer formation on the oxynitride/Si interface. http://ipap.yonsei.ac.kr/~assl/ ASSRC & IPAP, Yonsei Univ.

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