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Updates of Iowa State University

Updates of Iowa State University . S. Dumpala , S. Broderick and K. Rajan Oct-22, 2013 . Summary . Comparison of plasma and thermal oxidation with hyperthermal oxidation Literature review on sub oxide species analysis for thermal oxidation of silicon and comparison with APT results

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Updates of Iowa State University

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  1. Updates of Iowa State University S. Dumpala, S. Broderick and K. Rajan Oct-22, 2013

  2. Summary • Comparison of plasma and thermal oxidation with hyperthermal oxidation • Literature review on sub oxide species analysis for thermal oxidation of silicon and comparison with APT results • FIM – Attempts

  3. Hyper thermal, Plasma and Thermal Oxidation Plasma Oxidation ReaxFF Simulation Si+4 The concentrations of Si+1 (Si2O), Si+2 (SiO) in the interfacial region II and concentration of Si4+ (SiO2) in the bulk region III for the plasma oxidation match with hyperthermal one. In the thermal case, the concentration of Si4+ (SiO2) in region III is much lower. “In thermal oxidation regime, the oxide thickness remains constant and is equal to native-oxide thickness- U. Khalilov et.al.” - The observed trend is in agreement with no significant increase of Si4+ Thermal Oxidation

  4. Sub Oxide Species - Thermal Oxidation Significance of SiOx • Theoretical work demonstrated the role of sub oxide species on electronic properties (band gap profiles) of interface and leakage currents [1] • [1]. B.H. Kim, et.al. J. App.Phys., 113, 2013 • Theoretical models shown that sub stoichiometry effects phonon frequency shifts (Transverse optical, Longitudinal optical) apart from the compressive stress factor [2,3]. • [2]. A. Roy, et.al. Phys. Rev B, 67, 2003 • [3]. H. Ono, . J. App.Phys., 84, 1998 • Studies of SiOx – Thermal Oxidation • Synchrotron radiation photoemission • spectroscopy (PES) studies showed that • amounts of Si+2, Si+3 increases with T • (700 – 1000 C), while Si+1 remains • constant [4]. • [4]. Z.H. Lu, J. Vac. Sci. Technol. B., 13(4), 1995 • This is attributed to structural relaxation • to relieve long-range uniaxial strain (thermodynamic factor) • Another model predicts the change of distribution of sub stoichiometry near interface with increasing T from 550 to 700 C, and also predicts that sub oxide rich layer at higher temperature to be thicker [2]

  5. Effect of Temperature on Growth Mechanism • APT results experimentally prove the increase in the interfacial width and change of • sub oxide distribution and growth mechanism that agree with ReaxFF simulations • Thermal oxidation VsHyperthermal and Plasma oxidation (change of concentration of SiOx, and range of temperature)

  6. Field Ion Microscopy (FIM) • Preliminary attempts of FIM experiments were conducted using Tungsten tip Experimental result Schematic Image Experimental image of 110-oriented hemispherical 𝑊 tip subjected to field evaporation (image-force model without polarization component) at 30 K using Ne gas Schematic FIM images of 110-oriented hemispherical 𝑊 tip (radius 8 nm) subjected to field evaporation (image-force model without polarization component) at 77 K [1] Challenges • The temperature of stage and image quality • Software and equipment related issues

  7. Attempts of FIM on Si tips of Maryland 250 V Ar bombarded – 50 Monolayer Sample (Video clip of FIM Acquisition) • Initial results were obtained, but could not collect enough data • Tips tried studying were fractured • Images need to be analyzed • Bare Si need to be studied to estimate the damage

  8. Future • Plan to acquire better FIM images and analyze the results • Oxidation of Si paper is being written up –Tentative Title : “Effect of growth temperature on oxidation of Si and interfacial sub oxide species analysis via Atom Probe Tomography” • New Aluminum needles for Ar bombardment studies for Jarred are being ordered • Simulation results of Ar bombardment effects on Aluminum

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