Department of Chemical Engineering at the University of Texas at Austin go to home page university of texas at austin college of engineering U T direct
John G. Ekerdt
Dick Rothwell Endowed Chair in Chemical Engineering


Photo of John G. Ekerdt
Office: CPE 4.468 Mailing Address:
Phone: (512) 471-4689 The University of Texas at Austin
Fax: (512) 471-7060 Department of Chemical Engineering
Email: ekerdt@che.utexas.edu 1 University Station C0400
UT Mail: C0400 Austin, TX 78712-0231

ChE 372 Course Web Site

Presentation Made to Prospective Graduate Students Spring 2008

Focus:
Surface and interface reaction kinetics, and the chemistry of electronic materials growth.

Figure 1 (click image to enlarge):X-ray photoelectron spectroscopy (XPS) is one of many techniques used to study surface chemical reactions. Here, XP spectra are shown on the left for 1 monolayer (ML) of Ge on SiO2. The sample is annealed in stages and examined with XPS. Temperature programmed desorption (TPD) is used to follow surface reactions. The TPD spectra on the right were recorded following 1 ML Ge adsorption. Figure 2 (click image to enlarge): A model illustrating the reactions probed in Figure 1. At particle growth conditions (700 – 900 K) Ge adatoms have a difficult time accumulating on the surface because they react with the SiO2 and form volatile GeO. Particles are very difficult to grow because adatom density is too low and this prevents critical cluster nucleation.

Research:

The focus of my research is on electronic materials chemistry, and surface and interface reaction kinetics. The research programs are highly interdisciplinary and involve collaborations with faculty in chemistry, physics, and electrical engineering. Using the tools of surface science we probe how molecules adsorb and interact at surfaces, how ultrathin continuous films (<2-3 nm thick) are formed and how they bind to a substrate so the film stays continuous with thermal cycling, how nanoparticles of semiconductors form and evolve during chemical vapor deposition, and how force materials into an amorphous state.

The research on silicon alloy nanoparticle growth chemistry on dielectric surfaces seeks to understand how to grow nanoparticles of a particular diameter and density, and how to precisely position these nanoparticles on the surface. We have shown how to uncouple the nucleation stages from the particle growth stages and achieve particle densities in excess of 10 12/cm 2 and with a narrow size distribution, and we have shown the different reactions and reaction kinetics that Si and Ge adatoms have on various dielectric surfaces. This chemical insight is combined with self-assembly methods to precisely position 5 to 10 nm Ge particles on wafer surfaces in chemical vapor deposition processes, and to study the kinetics of nanoparticle growth.

The research on copper diffusion barriers investigates the scaling limits in ultrathin films to establish the minimum thickness at which materials retain their intrinsic properties and function as needed and to understand how these materials function as a barrier. Metal alloy films that can be used as conductive copper diffusion barriers, such as the ruthenium-phosphorus alloy, are studied. We are exploring the chemistry and reactions to enable chemical vapor deposition of these materials and applying this understanding to grow and test the materials properties of ultrathin films. We explore alloying components such as phosphorus and boron to form metastable, amorphous metal films with ruthenium and cobalt. The studies focus on reactions to enhance nucleation and the role of dopants in directing the growth of nearly amorphous metal films.

The research on dielectric films is exploring the nonoxidic dielectric, boron carbonitride, and hafnia and zirconia-based dielectrics. Boron carbonitride affords a wide range of properties by changing the relative amounts of boron, carbon, and nitrogen in the film through precursor chemistry and growth reactions. We are studying the potential of boron carbonitride to passivate semiconductor surfaces through manipulation of the interface bonding and interface states, and its potential to function as a diffusion barrier with ultra low-k dielectric materials. Studies with hafnia and zirconia are exploring the thermodynamic stability of the various phases and the role of aliovalent ions in changing the crystallization temperature and stabilizing the amorphous phase.

Selected Publications

  • Chemical Vapor Deposition of Amorphous Ruthenium-Phosphorus Alloy Films, (J. Shin, A. Waheed, W. A. Winkenwerder, H-W. Kim, K. Agapiou, R. A. Jones, G. S. Hwang, and J. G. Ekerdt), Thin Solid Films 515, 5298-5307 (2007).

  • Chemical routes to ultra thin films for copper barriers and liners (J. Shin, H-W. Kim, G. S. Hwang, J. G. Ekerdt), Surfaces and Coatings Technology 201, 9256-9257 (2007).

  • Experimental and Theoretical Investigation on Surfactant Segregation in Imprint Lithography, (K. Wu, X. Wang, E. K. Kim, C. G. Willson and J. G. Ekerdt) Langmuir 23(3), 1166-1170 (2007).

  • Sealing Ultra Low k Porous Dielectrics with Thin Boron Carbo-Nitride Films, (W. J. Ahearn, P. Ryan Fitzpatrick, and John G. Ekerdt) Journal of Vacuum Science and Technology A 25, 570-574 (2007).

  • Investigation of Volmer-weber growth mode kinetics for germanium nanoparticles on hafnia (S. S. Coffee and J. G. Ekerdt) J. Applied Physics 102, 1149129-(1-7) (2007).

  • Directed nucleation of ordered nanoparticle arrays on amorphous surfaces, (S. S. Coffee, S. K. Stanley, and J. G. Ekerdt), Journal Vacuum Science and Technology B 24, 1913-1917 (2006).

  • Ge interactions on HfO 2 surfaces and kinetically-driven patterning of Ge nanocrystals on HfO 2, (S. K. Stanley, S. V. Joshi, S. K. Banerjee, and J. G. Ekerdt) Journal of Vacuum Science and Technology A 24, 78-83 (2006).

 

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